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Long-term radiofrequency radiation (RFR) exposure, which adversely affects organisms, deteriorates testicular functions. Misfolding or unfolding protein accumulation in the endoplasmic reticulum (ER) initiates an intracellular reaction known as ER stress (ERS), which activates the unfolded protein response (UPR) for proteostasis. Since both RFR exposure and ERS can cause male infertility, we hypothesized that RFR exposure causes ERS to adversely affect testicular functions in rats. To investigate role of ERS in mediating RFR effects on rat testis, we established five experimental groups in male rats: control, short-term 2100-megahertz (MHz) RFR (1-week), short-term sham (sham/1-week), long-term 2100-MHz RFR (10-week), and long-term sham (sham/10-week). ERS markers Grp78 and phosphorylated PERK (p-Perk) levels and ERS-related apoptosis markers Chop and caspase 12 were investigated by immunohistochemistry, immunoblotting, and quantitative real-time polymerase chain reaction (qPCR). Long-term RFR exposure increased Grp78, p-Perk, and Chop levels, while short-term RFR exposure elevated Chop and caspase 12 levels. Chop expression was not observed in spermatogonia and primary spermatocytes, which may protect spermatogonia and primary spermatocytes against RFR-induced ERS-mediated apoptosis, thereby allowing transmission of genetic material to next generations. While short and long-term RFR exposures trigger ERS and ERS-related apoptotic pathways, further functional analyses are needed to elucidate whether this RFR-induced apoptosis has long-term male infertility effects. Article Highlights: Long-term radiofrequency radiation in testis triggers endoplasmic reticulum stress. Short-term radiofrequency radiation causes apoptosis in testis. Spermatogonia and spermatocytes are not affected by short-term radiofrequency radiation. [ABSTRACT FROM AUTHOR]

Melatonin, as an endocrine neurotransmitter, can promote the development of the ovary. Meanwhile, it also has protective effect on the ovary as an antioxidant. Thyroid hormone (TH) is essential for normal human reproductive function. Many studies have shown that 3,5,3′-triiodothyronine (T3) regulates the development of ovarian granulosa cells. However, little is known about the specific mechanisms by which melatonin combines with T3 to regulate granulosa cell development. The aim of present study was to investigate the effects and the possible mechanisms of melatonin and T3 on ovarian granulosa cell development. In the present study, cell development and apoptosis were detected by CCK8, EdU and TUNEL, respectively. The levels of related proteins were analyzed by Western blotting. The results showed that oxidative stress (OS) and reactive oxygen species (ROS) were induced by H2O2 in granulosa cells, and cell apoptosis was also increased accompanied with the decreased cellular proliferation and viability. Melatonin protects granulosa cells from H2O2-induced apoptosis and OS by downregulating ROS levels, especially in the presence of T3. Co-treatment of cell with melatonin and T3 also promotes the expression of GRP78 and AMH, while inhibiting CHOP, Caspase-3, and P16. It was demonstrated that melatonin alone or in combination with T3 had positive effect on the development of granulosa cells. In addition, the AMPK/SIRT1 signaling pathway is involved in the process of melatonin/T3 promoting granulosa cell development. [ABSTRACT FROM AUTHOR]

Background: Long-term accumulation of misfolded proteins leads to endoplasmic reticulum (ER) stress in colorectal cancer (CRC). However, the precise pathways controlling the decision between survival and apoptosis in CRC are unclear. Therefore, in this study, we investigated the function and molecular mechanism of glucosidase I (GCS1) in regulating ER stress in CRC. Methods: A public database was used to confirm the expression level of GCS1 in CRC and normal tissues. Clinical samples from our center were used to confirm the mRNA and protein expression levels of GCS1. Cell proliferation, migration, invasion, and apoptosis assays revealed the biological role of GCS1. Immunohistochemical techniques were used to evaluate the expression of key proteins in subcutaneous implanted tumors in nude mice, which provided further evidence for the biological function of GCS1 in promoting cancer in vivo. The results of coimmunoprecipitation-mass spectrometry analysis and immunofluorescence colocalization analysis the interaction between GCS1 and GRP78. In addition, the mechanism of action of USP10, GRP78, and GCS1 at the post- translational level was investigated. Finally, a tissue microarray was used to examine the connection between GCS1 and GRP78 expression and intracellular localization of these proteins using immunohistochemistry and immunofluorescence. Results: The experimental results revealed that GCS1 was substantially expressed in CRC, with higher expression indicating a worse prognosis. Thus, GCS1 can enhance the proliferation and metastasis while inhibiting the apoptosis of CRC cells both in vivo and in vitro. Mechanistically, GCS1 binds to GRP78, recruits USP10 for deubiquitination of GRP78 to promote its degradation, and decreases ER stress-mediated apoptosis, increasing CRC cell proliferation and metastasis. Conclusions: In summary, GCS1 stimulates CRC growth and migration and reduces ER stress-mediated apoptosis via USP10-mediated deubiquitination of GRP78. Our findings identify a possible therapeutic target for CRC. [ABSTRACT FROM AUTHOR]

Background: Despite recent therapeutic advances, combating cancer resistance remains a formidable challenge. The 78-kilodalton glucose-regulated protein (GRP78), a key stress-inducible endoplasmic reticulum (ER) chaperone, plays a crucial role in both cancer cell survival and stress adaptation. GRP78 is also upregulated during SARS-CoV-2 infection and acts as a critical host factor. Recently, we discovered cardiac glycosides (CGs) as novel suppressors of GRP78 stress induction through a high-throughput screen of clinically relevant compound libraries. This study aims to test the possibility that agents capable of blocking stress induction of GRP78 could dually suppress cancer and COVID-19. Results: Here we report that oleandrin (OLN), is the most potent among the CGs in inhibiting acute stress induction of total GRP78, which also results in reduced cell surface and nuclear forms of GRP78 in stressed cells. The inhibition of stress induction of GRP78 is at the post-transcriptional level, independent of protein degradation and autophagy and may involve translational control as OLN blocks stress-induced loading of ribosomes onto GRP78 mRNAs. Moreover, the human Na+/K+-ATPase α3 isoform is critical for OLN suppression of GRP78 stress induction. OLN, in nanomolar range, enhances apoptosis, sensitizes colorectal cancer cells to chemotherapeutic agents, and reduces the viability of patient-derived colon cancer organoids. Likewise, OLN, suppresses GRP78 expression and impedes tumor growth in an orthotopic breast cancer xenograft model. Furthermore, OLN blocks infection by SARS-CoV-2 and its variants and enhances existing anti-viral therapies. Notably, GRP78 overexpression mitigates OLN-mediated cancer cell apoptotic onset and suppression of virus release. Conclusion: Our findings validate GRP78 as a target of OLN anti-cancer and anti-viral activities. These proof-of-principle studies support further investigation of OLN as a readily accessible compound to dually combat cancer and COVID-19. [ABSTRACT FROM AUTHOR]

Angiotensin-converting enzyme 2 (ACE2) is considered a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor of high importance, but due to its non-ubiquitous expression, studies of other proteins that may participate in virus internalisation have been undertaken. To date, many alternative receptors have been discovered. Their functioning may provide an explanation for some of the events observed in severe COVID-19 that cannot be directly explained by the model in which ACE2 constitutes the central point of infection. Diabetes mellitus type 2 (T2D) can induce severe COVID-19 development. Although many mechanisms associated with ACE2 can lead to increased SARS-CoV-2 virulence in diabetes, proteins such as basigin (CD147), glucose-regulated protein 78 kDa (GRP78), cluster of differentiation 4 (CD4), transferrin receptor (TfR), integrins α5β1/αvβ3, or ACE2 co-receptors neuropilin 2 (NRP2), vimentin, and even syalilated gangliosides may also be responsible for worsening the COVID-19 course. On the other hand, some others may play protective roles. Understanding how diabetes-associated mechanisms can induce severe COVID-19 via modification of virus receptor functioning needs further extensive studies. [ABSTRACT FROM AUTHOR]

Autophagy is the primary intracellular degradation system, and it plays an important role in many biological and pathological processes. Studies of autophagy involvement in developmental processes are important for understanding various processes. Among them are fibrosis, degenerative diseases, cancer development, and metastasis formation. Diabetic kidney disease is one of the main causes of chronic kidney disease and end-stage renal failure. The aim of this study was to investigate the immunohistochemical expression patterns of LC3B, LAMP2A, and GRP78 during different developmental stages of early-developing human kidneys and in samples from patients with type II diabetes mellitus. During the 7/8th DW, moderate expression of LC3B and LAMP2A and strong expression of GRP78 were found in the mesonephric glomeruli and tubules. In the 9/10th DW, the expression of LC3B and LAMP2A was even more pronounced in the mesonephric tubules. LC3B, LAMP2A, and GRP78 immunoreactivity was also found in the paramesonephric and mesonephric ducts and was stronger in the 9/10th DW compared with the 7/8th DW. In addition, the expression of LC3B, LAMP2A, and GRP78 also appeared in the mesenchyme surrounding the paramesonephric duct in the 9/10th DW. In the 15/16th DW, the expression of LC3B in the glomeruli was weak, that of LAMP2A was moderate, and that of GRP78 was strong. In the tubuli, the expression of LC3B was moderate, while the expression of LAMP2A and GRP78 was strong. The strongest expression of LC3B, LAMP2A, and GRP78 was observed in the renal medullary structures, including developing blood vessels. In postnatal human kidneys, the most extensive LC3B, LAMP2A, and GRP78 expression in the cortex was found in the epithelium of the proximal convoluted tubules, with weak to moderate expression in the glomeruli. The medullary expression of LC3B was weak, but the expression of LAMP2A and GRP78 was the strongest in the medullary tubular structures. Significantly lower expression of LC3B was found in the glomeruli of the diabetic patients in comparison with the nondiabetic patients, but there was no difference in the expression of LC3B in the tubule–interstitial compartment. The expression of LAMP2A was significantly higher in the tubule–interstitial compartments of the diabetic patients in comparison with the nondiabetic patients, while its expression did not differ in the glomeruli. Extensive expression of GRP78 was found in the glomeruli and the tubule–interstitial compartments, but there was no difference in the expression between the two groups of patients. These data give us new information about the expression of LC3B, LAMP2A, and GRP78 during embryonic, fetal, and early postnatal development. The spatiotemporal expression of LC3B, LAMP2A, and GRP78 indicates the important role of autophagy during the early stages of renal development. In addition, our data suggest a disturbance in autophagy processes in the glomeruli and tubuli of diabetic kidneys as an important factor in the pathogenesis of diabetic kidney disease. [ABSTRACT FROM AUTHOR]

Abstract Background Long-term accumulation of misfolded proteins leads to endoplasmic reticulum (ER) stress in colorectal cancer (CRC). However, the precise pathways controlling the decision between survival and apoptosis in CRC are unclear. Therefore, in this study, we investigated the function and molecular mechanism of glucosidase I (GCS1) in regulating ER stress in CRC. Methods A public database was used to confirm the expression level of GCS1 in CRC and normal tissues. Clinical samples from our center were used to confirm the mRNA and protein expression levels of GCS1. Cell proliferation, migration, invasion, and apoptosis assays revealed the biological role of GCS1. Immunohistochemical techniques were used to evaluate the expression of key proteins in subcutaneous implanted tumors in nude mice, which provided further evidence for the biological function of GCS1 in promoting cancer in vivo. The results of coimmunoprecipitation-mass spectrometry analysis and immunofluorescence colocalization analysis the interaction between GCS1 and GRP78. In addition, the mechanism of action of USP10, GRP78, and GCS1 at the post- translational level was investigated. Finally, a tissue microarray was used to examine the connection between GCS1 and GRP78 expression and intracellular localization of these proteins using immunohistochemistry and immunofluorescence. Results The experimental results revealed that GCS1 was substantially expressed in CRC, with higher expression indicating a worse prognosis. Thus, GCS1 can enhance the proliferation and metastasis while inhibiting the apoptosis of CRC cells both in vivo and in vitro. Mechanistically, GCS1 binds to GRP78, recruits USP10 for deubiquitination of GRP78 to promote its degradation, and decreases ER stress-mediated apoptosis, increasing CRC cell proliferation and metastasis. Conclusions In summary, GCS1 stimulates CRC growth and migration and reduces ER stress-mediated apoptosis via USP10-mediated deubiquitination of GRP78. Our findings identify a possible therapeutic target for CRC.

Abstract Background Despite recent therapeutic advances, combating cancer resistance remains a formidable challenge. The 78-kilodalton glucose-regulated protein (GRP78), a key stress-inducible endoplasmic reticulum (ER) chaperone, plays a crucial role in both cancer cell survival and stress adaptation. GRP78 is also upregulated during SARS-CoV-2 infection and acts as a critical host factor. Recently, we discovered cardiac glycosides (CGs) as novel suppressors of GRP78 stress induction through a high-throughput screen of clinically relevant compound libraries. This study aims to test the possibility that agents capable of blocking stress induction of GRP78 could dually suppress cancer and COVID-19. Results Here we report that oleandrin (OLN), is the most potent among the CGs in inhibiting acute stress induction of total GRP78, which also results in reduced cell surface and nuclear forms of GRP78 in stressed cells. The inhibition of stress induction of GRP78 is at the post-transcriptional level, independent of protein degradation and autophagy and may involve translational control as OLN blocks stress-induced loading of ribosomes onto GRP78 mRNAs. Moreover, the human Na+/K+-ATPase α3 isoform is critical for OLN suppression of GRP78 stress induction. OLN, in nanomolar range, enhances apoptosis, sensitizes colorectal cancer cells to chemotherapeutic agents, and reduces the viability of patient-derived colon cancer organoids. Likewise, OLN, suppresses GRP78 expression and impedes tumor growth in an orthotopic breast cancer xenograft model. Furthermore, OLN blocks infection by SARS-CoV-2 and its variants and enhances existing anti-viral therapies. Notably, GRP78 overexpression mitigates OLN-mediated cancer cell apoptotic onset and suppression of virus release. Conclusion Our findings validate GRP78 as a target of OLN anti-cancer and anti-viral activities. These proof-of-principle studies support further investigation of OLN as a readily accessible compound to dually combat cancer and COVID-19.

Abstract Glucose regulated protein 78 (GRP78) is a chaperone protein that is a central mediator of the unfolded protein response, a key cellular stress response pathway. GRP78 has been shown to be critically required for infection and replication of a number of flaviviruses, and to interact with both non-structural (NS) and structural flavivirus proteins. However, the nature of the specific interaction between GRP78 and viral proteins remains largely unknown. This study aimed to characterize the binding domain and critical amino acid residues that mediate the interaction of GRP78 to ZIKV E and NS1 proteins. Recombinant EGFP fused GRP78 and individual subdomains (the nucleotide binding domain (NBD) and the substrate binding domain (SBD)) were used as a bait protein and co-expressed with full length or truncated ZIKV E and NS1 proteins in HEK293T/17 cells. Protein–protein interactions were determined by a co-immunoprecipitation assay. From the results, both the NBD and the SBD of GRP78 were crucial for an effective interaction. Single amino acid substitutions in the SBD showed that R492E and T518A mutants significantly reduced the binding affinity of GRP78 to ZIKV E and NS1 proteins. Notably, the interaction of GRP78 with ZIKV E was stably maintained against various single amino acid substitutions on ZIKV E domain III and with all truncated ZIKV E and NS1 proteins. Collectively, the results suggest that the principal binding between GRP78 and viral proteins is mainly a classic canonical chaperone protein-client interaction. The blocking of GRP78 chaperone function effectively inhibited ZIKV infection and replication in neuronal progenitor cells. Our findings reveal that GRP78 is a potential host target for anti-ZIKV therapeutics.

Huanglian Jiedu Decoction (HLJDD) is a quintessential prescription renowned for its heat-clearing and detoxifying properties. It is primarily prescribed to counteract the syndrome characterized by the excessive heat of the Sanjiao fire. Notably, the hyperactivity of liver fire is frequently linked with hypertension, where wind fire and wind toxicity emerge as pivotal pathogenic factors. This study aimed to investigate the impact of HLJDD on the endoplasmic reticulum in spontaneously hypertensive rats (SHR), further delving into the interplay between endoplasmic reticulum stress (ERS) and myocardial remodeling and damage. Fifty SHR rats were stratified randomly into five cohorts: model, low-dose HLJDD, medium-dose HLJDD, high-dose HLJDD, and captopril groups. For comparison, a set of Wistar-Kyoto (WKY ) rats served as the baseline control group, with each group comprising 10 rats. While the model and control groups received equivalent volumes of normal saline via gavage, the other groups were administered the respective drug dosages through the same route daily for a span of 6 weeks. Upon the experiment's conclusion, metrics such as the heart mass index (HWI) and left ventricular mass index (LVWI) were assessed. Cardiac tissue anomalies were identified using H&E staining, while ERS-related protein and mRNA expression levels were ascertained via Western blotting analysis and qPCR. Moreover, TUNEL staining was employed to detect cardiomyocyte apoptosis. The findings indicated that increasing HLJDD concentrations corresponded with escalated HWI and LVWI in rat hearts (P < 0.05). There was a marked enhancement in myocardial structural integrity, accompanied by a notable reduction in collagen fibers. The mRNA and protein expressions of myocardial inositol-dependent enzyme 1α (IRE1α), X-box binding protein 1 (XBP1), glycoregulatory protein 78 (GRP78), and CCAAT enhancer binding protein homologous protein (CHOP) in the medium and high-dose groups saw significant declines (P < 0.05). These effects mirrored those observed in the captopril group. The study underscored HLJDD's efficacy in mitigating myocardial tissue damage in SHR. This therapeutic effect was potentially attributed to the downregulation of IRE1α, XBP1, GRP78, and CHOP, curbing excessive ERS, diminishing cardiomyocyte apoptosis, and thereby conferring cardioprotection. [ABSTRACT FROM AUTHOR]

Enteroviruses are the causative agents associated with several human and animal diseases, posing a significant threat to human and animal health. As one of the host immune defense strategies, innate immunity plays a crucial role in defending against invading pathogens, where the host utilizes a variety of mechanisms to inhibit or eliminate the pathogen. Here, we report a new strategy for the host to repress enterovirus replication by the 78 kDa glucose-regulated protein (GRP78), also known as heat shock protein family A member 5 (HSPA5). The GRP78 recognizes the EV-encoded RNA-dependent RNA polymerases (RdRPs) 3D protein and interacts with the nuclear factor kappa B kinase complex (CHUK) and subunit beta gene (IKBKB) to facilitate the phosphorylation and nuclear translocation of NF-κB, which induces the production of inflammatory factors and leads to a broad inhibition of enterovirus replication. These findings demonstrate a new role of GRP78 in regulating host innate immunity in response to viral infection and provide new insights into the mechanism underlying enterovirus replication and NF-κB activation. IMPORTANCE GRP78 is known as a molecular chaperone for protein folding and plays a critical role in maintaining protein folding and participating in cell proliferation, cell survival, apoptosis, and metabolism. However, the functions of GRP78 to participate in enterovirus genome replication and innate immune responses are rarely documented. In this study, we explored the functions of the EV-3D-interacting protein GRP78 and found that GRP78 inhibits enterovirus replication by activating NF-κB through binding to EV-F 3D and interacting with the NF-κB signaling molecules CHUK/IKBKB. This is the first report that GRP78 interacts with CHUK/IKBKB to activate the NF-κB signaling pathway, which leads to the expression of the proinflammatory cytokines and inhibition of enterovirus replication. These results demonstrate a unique mechanism of virus replication regulation by GRP78 and provide insights into the prevention and treatment of viral infections. [ABSTRACT FROM AUTHOR]

Glioma accounts for 80% of malignant central nervous system, with high incidence and extremely difficult to cure. However, for the role of ER stress apoptosis in tumor has caused great attention, the neuronal polarity molecule glycogen synthase kinase-3 β(GSK-3 β) endoplasmic network stress apoptosis pathway in tumor mechanism is a hot research in recent years, but for GSK-3 β ER stress apoptosis pathway in different levels of glioma research is extremely rare. In this experiment, we jointly explored the significance of GSK-3 β ER apoptosis pathway in different grades of glioma, which provided a strong basis for the precise treatment of glioma. 35 inpatients from December 2021 to December 2022 were enrolled into the different grades of glioma group and the normal control group. Tumor tissue was classified according to medical pathology. The other five normal brain tissues were obtained from the normal brain tissue of the fistula created in non-functional areas. One of the brain samples was stored for the apoptosis index (AI) of TUNEL (chromogenic method), and another part was stored in liquid nitrogen for the expression of GRP78, IRE 1, ATF 6, PERK, p-Tyr216-GSK-3 β, p-Ser 9-GSK-3 β, and Caspase-3. The AI values of different grades of glioma and normal control groups showed that the normal control, low-grade glioma and high-grade glioma groups were 8. 131 ± 0.234, 68.523 ± 1.392 and 22. 421 ± 0.236, respectively. The AI value was higher in the glioma group than in the normal controls (P < 0.05), while the AI value in the glioma group was negatively correlated with its malignancy (r = –0.725, P = 0.000). Western blot showed: compared with the normal control group, apoptosis initiation protein GRP78 expression, IRE 1, ATF 6, PERK decreased (P < 0.05); pathway key protein p-Ser 9-GSK-3 β increased, and p-Tyr216-GSK-3 β decreased (P < 0.05); pathway executive protein Caspase-3 increased (P < 0.05). However, the apoptosis initiation protein GRP78, IRE 1, ATF 6, PERK increased (P < 0.05); pathway key protein p-Ser 9-GSK-3 β decreased and p-Tyr216-GSK-3 β was increased (P < 0.05); pathway execution protein Caspase-3 expression decreased (P < 0.05). Conclusion: the AI value of low-grade glioma is higher than that of high-grade glioma, indicating that the progression of brain glioma may inhibit cell apoptosis. The increased apoptosis index and the expression changes of GSK-3 β ER stress cell apoptosis pathway in the glioma group indicate that the apoptosis pathway in GSK-3 β ER stress cells was initiated and executed in glioma. In low-grade glioma cells, there may be a mechanism to inhibit IRE 1, ATF 6, PERK, and p-Tyr216-GSK-3 β expression, which further promotes cell apoptosis and inhibited tumor progression. And with the progression of glioma, The expression of IRE 1, ATF 6, PERK, GRP78, and p-Tyr216-GSK-3 β was gradually increased, The expression of P-Ser 9-GSK-3 β, Caspase-3 was gradually decreased, It indicates that GRP78, IRE 1, ATF 6, PERK and p-Tyr216-GSK-3 β may be involved in the progression of glioma; Meanwhile, brain glioma cells may, by inhibiting the expression of P-Ser 9-GSK-3 β and the apoptosis executive protein Caspase-3, Further inhibited the apoptosis of brain glioma cells, promoted the progression of brain glioma. Inhibiting the expression of IRE 1, ATF 6, PERK, GRP78 and p‑Tyr216-GSK-3 β may be of great significance to inhibiting the progression of glioma, which provides a strong basis for guiding the precision treatment of clinical glioma. [ABSTRACT FROM AUTHOR]

Pediatric neuroblastomas (NBs) are heterogeneous, aggressive, therapy-resistant embryonal tumors that originate from cells of neural crest origin committed to the sympathoadrenal progenitor cell lineage. Stress- and drug-resistance mechanisms drive post-therapeutic relapse and metastatic progression, the characterization and inhibition of which are major goals in improving therapeutic responses. Stress- and drug-resistance mechanisms in NBs include alternative TrkAIII splicing of the neurotrophin receptor tropomyosin-related kinase A (NTRK1/TrkA), which correlates with post-therapeutic relapse and advanced-stage metastatic disease. The TrkAIII receptor variant exerts oncogenic activity in NB models by mechanisms that include stress-induced mitochondrial importation and activation. In this study, we characterize novel targetable and non-targetable participants in this pro-survival mechanism in TrkAIII-expressing SH-SY5Y NB cells, using dithiothreitol (DTT) as an activator and a variety of inhibitors by regular and immunoprecipitation Western blotting of purified mitochondria and IncuCyte cytotoxicity assays. We report that stress-induced TrkAIII misfolding initiates this mechanism, resulting in Grp78, Ca2+-calmodulin, adenosine ribosylating factor (Arf) and Hsp90-regulated mitochondrial importation. TrkAIII imported into inner mitochondrial membranes is cleaved by Omi/high temperature requirement protein A2 (HtrA2) then activated by a mechanism dependent upon calmodulin kinase II (CaMKII), alpha serine/threonine kinase (Akt), mitochondrial Ca2+ uniporter and reactive oxygen species (ROS), involving inhibitory mitochondrial protein tyrosine phosphatase (PTPase) oxidation, resulting in phosphoinositide 3 kinase (PI3K) activation of mitochondrial Akt, which enhances stress resistance. This novel pro-survival function for misfolded TrkAIII mitigates the cytotoxicity of mitochondrial Ca2+ homeostasis disrupted during integrated stress responses, and is prevented by clinically approved Trk and Akt inhibitors and also by inhibitors of 78kDa glucose regulated protein (Grp78), heat shock protein 90 (Hsp90), Ca2+-calmodulin and PI3K. This identifies Grp78, Ca2+-calmodulin, Hsp90, PI3K and Akt as novel targetable participants in this mechanism, in addition to TrkAIII, the inhibition of which has the potential to enhance the stress-induced elimination of TrkAIII-expressing NB cells, with the potential to improve therapeutic outcomes in NBs that exhibit TrkAIII expression and activation. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease in which the death of motor neurons leads to loss of muscle function. Additionally, cognitive and circadian disruptions are common in ALS patients, contributing to disease progression and burden. Most ALS cases are sporadic, and environmental exposures contribute to their aetiology. However, animal models of these sporadic ALS cases are scarce. The small vertebrate zebrafish is a leading organism to model neurodegenerative diseases; previous studies have proposed bisphenol A (BPA) or β-methylamino- l -alanine (BMAA) exposure to model sporadic ALS in zebrafish, damaging motor neurons and altering motor responses. Here we characterise the face and predictive validity of sporadic ALS models, showing their potential for the mechanistic study of ALS drugs. We phenotypically characterise the BPA and BMAA-induced models, going beyond motor activity and motor axon morphology, to include circadian, redox, proteostasis, and metabolomic phenotypes, and assessing their predictive validity for ALS modelling. BPA or BMAA exposure induced concentration-dependent activity impairments. Also, exposure to BPA but not BMAA induced motor axonopathy and circadian alterations in zebrafish larvae. Our further study of the BPA model revealed loss of habituation to repetitive startles, increased oxidative damage, endoplasmic reticulum (ER) stress, and metabolome abnormalities. The BPA-induced model shows predictive validity, since the approved ALS drug edaravone counteracted BPA-induced motor phenotypes, ER stress, and metabolic disruptions. Overall, BPA exposure is a promising model of ALS-related redox and ER imbalances, contributing to fulfil an unmet need for validated sporadic ALS models. [Display omitted] • We characterise face and predictive validity of zebrafish models of sporadic ALS (sALS). • Phenotypes of sALS models include behavioural impairments and axonopathy. • BPA-induced sALS model shows altered metabolism and increased ER/redox stress. • ALS drug edaravone counteracts sALS phenotypes, modulating ER stress and metabolism. [ABSTRACT FROM AUTHOR]

The existence of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) greatly limits the application of chemotherapy in glioma. To address this challenge, an optimal drug delivery system must efficiently cross the BBB/BBTB and specifically deliver therapeutic drugs into glioma cells while minimizing systemic toxicity. Here we demonstrated that glucose-regulated protein 78 (GRP78) and dopamine receptor D2 were highly expressed in patient-derived glioma tissues, and dopamine receptors were highly expressed on the BBB. Subsequently, we synthesized a novel "Y"-shaped peptide and compared the effects of different linkers on the receptor affinity and targeting ability of the peptide. A peptide-drug conjugate (pHA-AOHX-VAP-doxorubicin conjugate, pHA-AOHX-VAP-DOX) with a better affinity for glioma cells and higher solubility was derived for glioma treatment. pHA-AOHX-VAP-DOX could cross both BBB and BBTB via dopamine receptor and GRP78 receptor, and finally target glioma cells, significantly prolonging the survival time of nude mice bearing intracranial glioma. Furthermore, pHA-AOHX-VAP-DOX significantly reduced the toxicity of DOX and increased the maximum tolerated dose (MTD). Collectively, this work paves a new avenue for overcoming multiple barriers and effectively delivering chemotherapeutic agents to glioma cells while providing key evidence to identify potential receptors for glioma-targeted drug delivery. [Display omitted] • GRP78 and Dopamine receptor D2 were highly expressed on the cell surface of patient-derived glioma tissues. • A new "Y"-shaped targeting ligand (pHA-AOHX-VAP) was developed by optimizing the hydrophilic properties of the linker. • pHA-AOHX-VAP exhibited enhanced receptor affinity and glioma cell targeting ability. • A new peptide-drug conjugate pHA-AOHX-VAP-DOX demonstrated improved in vivo safety and remarkable anti-glioma efficacy. [ABSTRACT FROM AUTHOR]

Licochalcone A (LicA), a natural compound extracted from licorice root, has been shown to exert a variety of anticancer activities. Whether LicA has such effects on endometrial cancer (EMC) is unclear. This study aims to investigate the antitumor effects of LicA on EMC. Our results show that LicA significantly reduced the viability and induced apoptosis of EMC cells and EMC‐7 cells from EMC patients. LicA was also found to induce endoplasmic reticulum (ER) stress, leading to increased expression of ER‐related proteins (GRP78/PERK/IRE1α/CHOP) in EMC cell lines. Suppression of GRP78 expression in human EMC cells treated with LicA significantly attenuated the effects of LicA, resulting in reduced ER‐stress mediated cell apoptosis and decreased expression of ER‐ and apoptosis‐related proteins. Our findings demonstrate that LicA induces apoptosis in EMC cells through the GRP78‐mediated ER‐stress pathway, emphasizing the potential of LicA as an anticancer therapy for EMC. [ABSTRACT FROM AUTHOR]

The 78-kDa glucose regulated protein (GRP78) commonly upregulated in a wide variety of tumors is an important prognostic marker and a promising target for suppressing tumorigenesis and treatment resistance. While GRP78 is well established as a major endoplasmic reticulum (ER) chaperone with anti-apoptotic properties and a master regulator of the unfolded protein response, its new role as a regulator of oncoprotein expression is just emerging. MYC is dysregulated in about 70 % of human cancers and is the most commonly activated oncoprotein. However, despite recent advances, therapeutic targeting of MYC remains challenging. Here we identify GRP78 as a new target for suppression of MYC expression. Using multiple MYC-dependent cancer models including head and neck squamous cell carcinoma and their cisplatin-resistant clones, breast and pancreatic adenocarcinoma, our studies revealed that GRP78 knockdown by siRNA or inhibition of its activity by small molecule inhibitors (YUM70 or HA15) reduced c-MYC expression, leading to onset of apoptosis and loss of cell viability. This was observed in 2D cell culture, 3D spheroid and in xenograft models. Mechanistically, we determined that the suppression of c-MYC is at the post-transcriptional level and that YUM70 and HA15 treatment potently upregulated the eukaryotic translation inhibitor 4E-BP1, which targets eIF4E critical for c-MYC translation initiation. Furthermore, knock-down of 4E-BP1 via siRNA rescued YUM70-mediated c-MYC suppression. As YUM70 is also capable of suppressing N-MYC expression, this study offers a new approach to suppress MYC protein expression through knockdown or inhibition of GRP78.

Successful treatment of glioblastoma multiforme (GBM), an aggressive form of primary brain neoplasm, mandates the need to develop new therapeutic strategies. In this study, we investigated the potential of PBI-05204 in targeting GBM stem cells (GSCs) and the underlying mechanisms. Treatment with PBI-05204 significantly reduced both the number and size of tumor spheres derived from patient-derived GSCs (GBM9, GSC28 and TS543), and suppressed the tumorigenesis of GBM9 xenografts. Moreover, PBI-05204 treatment led to a significant decrease in the expression of CD44 and NANOG, crucial markers of progenitor stem cells, in GBM9 and GSC28 GSCs. This treatment also down-regulated GRP78 expression in both GSC types. Knocking down GRP78 expression through GRP78 siRNA transfection in GBM9 and GSC28 GSCs also resulted in reduced spheroid size and CD44 expression. Combining PBI-05204 with GRP78 siRNA further decreased spheroid numbers compared to GRP78 siRNA treatment alone. PBI-05204 treatment led to increased expression of pRIP1K and pRIP3K, along with enhanced binding of RIPK1/RIPK3 in GBM9 and GSC28 cells, resembling the effects observed in GRP78-silenced GSCs, suggesting that PBI-05204 induced necroptosis in these cells. Furthermore, oleandrin, a principle active cardiac glycoside component of PBI-05204, showed the ability to inhibit the self-renewal capacity in GSCs. These findings highlight the potential of PBI-05204 as a promising candidate for the development of novel therapies that target GBM stem cells.

Abstract Hostile microenvironment of cancer cells provoke a stressful condition for endoplasmic reticulum (ER) and stimulate the expression and secretion of ER chaperones, leading to tumorigenic effects. However, the molecular mechanism underlying these effects is largely unknown. In this study, we reveal that the last four residues of ER chaperones, which are recognized by KDEL receptor (KDELR), is required for cell proliferation and migration induced by secreted chaperones. By combining proximity-based mass spectrometry analysis, split venus imaging and membrane yeast two hybrid assay, we present that EGF receptor (EGFR) may be a co-receptor for KDELR on the surface. Prior to ligand addition, KDELR spontaneously oligomerizes and constantly undergoes recycling near the plasma membrane. Upon KDEL ligand binding, the interactions of KDELR with itself and with EGFR increase rapidly, leading to augmented internalization of KDELR and tyrosine phosphorylation in the C-terminus of EGFR. STAT3, which binds the phosphorylated tyrosine motif on EGFR, is subsequently activated by EGFR and mediates cell growth and migration. Taken together, our results suggest that KDELR serves as a bona fide cell surface receptor for secreted ER chaperones and transactivates EGFR-STAT3 signaling pathway.

The accumulation of misfolded and aggregated α-synuclein can trigger endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), leading to apoptotic cell death in patients with Parkinson's disease (PD). As the major ER chaperone, glucose-regulated protein 78 (GRP78/BiP/HSPA5) plays a key role in UPR regulation. GRP78 overexpression can modulate the UPR, block apoptosis, and promote the survival of nigral dopamine neurons in a rat model of α-synuclein pathology. Here, we explore the therapeutic potential of intranasal exogenous GRP78 for preventing or slowing PD-like neurodegeneration in a lactacystin-induced rat model. We show that intranasally-administered GRP78 rapidly enters the substantia nigra pars compacta (SNpc) and other afflicted brain regions. It is then internalized by neurons and microglia, preventing the development of the neurodegenerative process in the nigrostriatal system. Lactacystin-induced disturbances, such as the abnormal accumulation of phosphorylated pS129-α-synuclein and activation of the pro-apoptotic GRP78/PERK/eIF2α/CHOP/caspase-3,9 signaling pathway of the UPR, are substantially reversed upon GRP78 administration. Moreover, exogenous GRP78 inhibits both microglia activation and the production of proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), via the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway in model animals. The neuroprotective and anti-inflammatory potential of exogenous GRP78 may inform the development of effective therapeutic agents for PD and other synucleinopathies. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relation of clinicopathological characteristics and RCN1 and GRP78 expression levels in colorectal cancer, and explore their prognostic value. Methods: The expression of RCN1 and HSPA5 mRNA in colorectal cancer( CRC) was examined using the TCGA and UALCAN databases, and clinical samples were obtained for immunohistochemistry to confirm the expression of both. Then, the correlation with clinicopathological features and its prognostic value were analyzed. Results: According to a bioinformatics analysis, RCN1 and HSPA5 mRNA were both significantly overexpressed in CRC and had a positive correlation.The expression of RCN1 was correlated with N stage and TP53 mutations, the expression of HSPA5 was higher in mucinous adenocarcinomas. In CRC tissues, RCN1 and GRP78 protein were both strongly expressed and localized in the cytoplasm. GRP78 expression was significantly correlated with T stage. The Kaplan-Meier survival analysis curve indicates that patients with higher RCN1 expression had significantly shorter DFS than those with lower expression and a tendency toward shorter OS.According to COX regression analysis,DFS in CRC was found to be independently associated with tumor nerve invasion, TNM stage, and high RCN1 expression, Correlation analysis: RCN1 and GRP78 expression were positively associated in CRC. Conclusion: RCN1 is an independent risk factor for a poor prognosis in colorectal cancer (CRC) and has a positive correlation with GRP78 expression. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of Dab1 gene silencing on the immunoexpression of light chain 3 beta (Lc3b), glucose regulating protein 78 (Grp78), heat shock cognate 71 (Hsc70), mammalian target of rapamycin (mTOR) and lysosomal-associated membrane protein 2A (Lamp2a) in the lung tissue of developing yotari (Dab1−/−) and wild-type (wt) mice. The lung epithelium and mesenchyme of the embryos at gestational days E13.5 and E15.5 were examined using immunofluorescence and semi-quantitative methods. In the pulmonary mesenchyme and epithelium, Grp78 and Lc3b of moderate fluorescence reactivity was demonstrated in wt mice for both evaluated time points, while yotari mice exhibited only epithelial reactivity for the same markers. Mild punctate expression of Hsc70 was observed for both genotypes. A significant difference was present when analyzing mTOR expression, where wt mice showed strong perinuclear staining in the epithelium. According to our data, Dab1 gene silencing may result in autophagy abnormalities, which could then cause respiratory system pathologies via defective lung cell degradation by lysosome-dependent cell elimination. [ABSTRACT FROM AUTHOR]

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin–proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis. [ABSTRACT FROM AUTHOR]

The pathologic consequences of Coronavirus Disease-2019 (COVID-19) include elevated inflammation and dysregulated vascular functions associated with thrombosis. In general, disruption of vascular homeostasis and ensuing prothrombotic events are driven by activated platelets, monocytes, and macrophages, which form aggregates (thrombi) attached to the endothelium lining of vessel walls. However, molecular pathways underpinning the pathological interactions between myeloid cells and endothelium during COVID-19 remain undefined. Here, we tested the hypothesis that modulations in the expression of cellular receptors angiotensin-converting enzyme 2 (ACE2), CD147, and glucose-regulated protein 78 (GRP78), which are involved in homeostasis and endothelial performance, are the hallmark responses induced by SARS-CoV-2 infection. Cultured macrophages and lungs of hamster model systems were used to test this hypothesis. The results indicate that while macrophages and endothelial cells are less likely to support SARS-CoV-2 proliferation, these cells may readily respond to inflammatory stimuli generated by the infected lung epithelium. SARS-CoV-2 induced modulations of tested cellular receptors correlated with corresponding changes in the mRNA expression of coagulation cascade regulators and endothelial integrity components in infected hamster lungs. Among these markers, tissue factor (TF) had the best correlation for prothrombotic events during SARS-CoV-2 infection. Furthermore, the single-molecule fluorescence in situ hybridization (smFISH) method alone was sufficient to determine the peak and resolution phases of SARS-CoV-2 infection and enabled screening for cellular markers co-expressed with the virus. These findings suggest possible molecular pathways for exploration of novel drugs capable of blocking the prothrombotic shift events that exacerbate COVID-19 pathophysiology and control the disease. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relationship between serum leucine-rich alpha-2 glycoprotein 1 (LRG1), glucose-regulated protein 78 (GRP78) and secondary acute lung injury (ALI) in patients with emergency sepsis. Methods: 155 patients with emergency sepsis who were treated in the emergency intensive care unit (EICU) of our hospital from January 2021 to October 2022 were retrospectively selected as observation group, patients were divided into ALI group (43 cases) and non-ALI group (112 cases) according to whether secondary ALI occurred, and 100 healthy subjects in our hospital during the same period were selected as control group. The levels of serum LRG1 and GRP78 were detected by enzyme-linked immunosorbent assay kit. The influencing factors of secondary ALI in patients with emergency sepsis were analyzed by univariate and multivariate logistic regression. The predictive value of serum LRG1 and GRP78 levels for secondary ALI in patients with emergency sepsis were analyzed by receiver operating characteristic (ROC) curve was used to analyze. Results: Compared with control group, the levels of serum LRG1 and GRP78 in observation group were increased (P<0.05). Univariate analysis showed that, ALI secondary to emergency sepsis was related to sepsis grade, EICU time, mechanical ventilation, sepsis-related organ failure assessment (SOFA) score, blood lactic acid, LRG1 and GRP78 (P<0.05). Multivariate logistic regression analysis showed that, septic shock, prolonged EICU time and increased SOFO score, blood lactic acid, LRG1 and GRP78 were independent risk factors for secondary ALI in patients with emergency sepsis (P<0.05). ROC curve analysis showed that, the area under the curve (AUC) of serum LRG1 and GRP78 levels alone and in combination in predicting ALI secondary to emergency sepsis were 0.790, 0.782 and 0.884 respectively, and the AUC of combined prediction was the largest (P<0.05). Conclusion: The increase of serum LRG1 and GRP78 levels in patients with emergency sepsis is closely relate to secondary ALI, and the combination of serum LRG1 and GRP78 levels has a higher value in predicting secondary ALI in patients with emergency sepsis. [ABSTRACT FROM AUTHOR]

Hostile microenvironment of cancer cells provoke a stressful condition for endoplasmic reticulum (ER) and stimulate the expression and secretion of ER chaperones, leading to tumorigenic effects. However, the molecular mechanism underlying these effects is largely unknown. In this study, we reveal that the last four residues of ER chaperones, which are recognized by KDEL receptor (KDELR), is required for cell proliferation and migration induced by secreted chaperones. By combining proximity-based mass spectrometry analysis, split venus imaging and membrane yeast two hybrid assay, we present that EGF receptor (EGFR) may be a co-receptor for KDELR on the surface. Prior to ligand addition, KDELR spontaneously oligomerizes and constantly undergoes recycling near the plasma membrane. Upon KDEL ligand binding, the interactions of KDELR with itself and with EGFR increase rapidly, leading to augmented internalization of KDELR and tyrosine phosphorylation in the C-terminus of EGFR. STAT3, which binds the phosphorylated tyrosine motif on EGFR, is subsequently activated by EGFR and mediates cell growth and migration. Taken together, our results suggest that KDELR serves as a bona fide cell surface receptor for secreted ER chaperones and transactivates EGFR-STAT3 signaling pathway. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to analyze the effects of combined oral contraceptive active ingredients, Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone, on liver histopathological changes and endoplasmic reticulum stress levels. Material and Methods: In the study, 37 Balb/c female mice were used. Mice were randomly divided into the Control, Sham, Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone groups. The experimental groups were administered with gavage to 8-week-old female mice for 35 days. Kidney tissue sections were applied with Hematoxylin&Eosin, Orcein, Mallory's Azan, and Periodic Acid-Schiff to detect histopathological changes, and Chop and Grp78 were used to detect Endoplasm Reticulum Stress. Results: Significant loss of microvilli and a decrease in glycogen accumulation were observed in the apical part of some of the proximal tubules of animals in the Drospirenone and Ethinyl Estradiol+Drospirenone groups. The amount of collagen fiber stained with Mallory's Azan increased in the parietal layer of Bowman's capsule of the kidney tissues of the Drospirenone and Ethinyl Estradiol+Drospirenone applied groups, but no difference was observed in elastic fibers in all groups. The expression level of Grp78 and Chop proteins in the kidney tubules of female mice given Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone was significantly higher compared to the control group. Conclusion: In this study, it was shown that the expression of Grp78 and Chop markers detected in the mouse kidney increased as a result of Drospirenone, Ethinyl Estradiol and Ethinyl Estradiol + Drospirenone administration, thus causing kidney cell apoptosis by inducing ER-dependent death pathway activity. [ABSTRACT FROM AUTHOR]

Objective: To analyze the effect of allicin on the immunoreactivity of osteosarcoma (OS) cells and further explore whether its mechanism is related to the long non-coding Ribonucleic Acid (lncRNA) CBR3-AS1/miR-145-5p/GRP78 axis, so as to provide clinical evidence. Methods: The human OS cell line Saos-2 was treated with allicin at 25, 50, and 100 μmol/L, respectively, to observe changes in cell biological behaviors. Subsequently, CBR3-AS1 abnormal expression vectors were constructed and transfected into Saos-2 to discuss their influence on OS. Furthermore, the regulatory relationship between allicin and the CBR3-AS1/miR-145-5p/GRP78 axis was validated by rescue experiments. Finally, a nude mice tumorigenesis experiment was carried out to analyze the effects of allicin and CBR3-AS1/miR-145-5p/GRP78 axis on the growth of living tumors. Alterations in T-lymphocyte subsets were also detected to assess the effect of allicin on OS immunoreactivity. Results: With the increase of allicin concentration, Saos-2 activity decreased and apoptosis increased (P

Objective: To explore the efficacy and potential mechanisms of the ethanol extract of Abelmoschus manihot (L.) Medic in contrast-induced nephropathy (CIN). Methods: CIN rat models and human renal proximal tubular cells (HK-2) with iopromide-induced injury were employed to mimic CIN conditions. The effect of Abelmoschus manihot extract on the rat models and HK-2 cells was evaluated. In rat models, kidney function, histology, oxidative stress and apoptosis were determined. In HK-2 cells, cell viability, apoptosis, mitochondrial membrane potential, and endoplasmic reticulum stress were assessed. Results: Abelmoschus manihot extract significantly improved structural and functional impairments in the kidneys of CIN rats. Additionally, the extract effectively mitigated the decline in cellular viability and reduced iopromide-induced oxidative stress and lipid peroxidation. Mechanistic investigations revealed that Abelmoschus manihot extract prominently attenuated acute endoplasmic reticulum stress-mediated apoptosis by downregulating GRP78 and CHOP protein levels. Conclusions: Abelmoschus manihot extract can be used as a promising therapeutic and preventive agent in the treatment of CIN.

Abstract Backgroud Hypoadiponectinemia is the important cause of insulin resistance. Recent studies have shown that periodontitis is associated with hypoadiponectinemia. The purpose of this study was to investigate the effect of periodontitis-induced endoplasmic reticulum stress (ERS) in visceral adipocytes on hypoadiponectinemia. Methods Rat periodontitis models were established by local ligation with silk around the bilateral maxillary second molars. Porphyromonas gingivalis-lipopolysaccharid (P.g-LPS) was also used to stimulate the visceral adipocytes in vitro. The protein expression levels of glucose regulated protein 78 (GRP78), inositol-requiring protein 1α (IRE1α), protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6) and adiponectin were detected. IRE1α lentiviruses were transfected into visceral adipocytes in vitro, and an IRE1α inhibitor (KIRA6) was injected in epididymal adipose tissue of rats to detect and verify the effect of ERS on adiponectin expression in visceral adipocytes in vivo. Results Hypoadiponectinemia was observed in periodontitis rat, and the expression levels of ERS key proteins GRP78 and the phosphorylation levels of IRE1α (p-IRE1α)/IRE1α in visceral adipocytes were increased, while the expression levels of adiponectin protein were decreased. After KIRA6 injection into epididymal adipose tissue of rats with periodontitis, adiponectin levels in visceral adipocytes increased, and serum adiponectin levels recovered to a certain extent. The protein expression levels of GRP78 and p-IRE1α/IRE1α were increased and adiponectin protein expression was decreased in P.g-LPS-induced visceral adipocytes. Overexpression of IRE1α further inhibited adiponectin expression in P.g-LPS-stimulated visceral adipocytes, and conversely, IRE1α inhibition restored adiponectin expression. Conclusions Our findings suggest that periodontitis induces ERS in visceral adipocytes leading to hypoadiponectinemia. IRE1α is a key protein regulating adiponectin expression in visceral adipocytes.

Cardiomyocyte apoptosis is an important cause of trauma-induced secondary cardiac injury (TISCI), in which the endoplasmic reticulum stress (ERS)-mediated apoptosis signaling pathway is known to be first activated, but the mechanism remains unclear. In this study, rat models of traumatic injury are established by using the Noble-Collip trauma device. The expression of glucose-regulating protein 78 (GRP78, a molecular chaperone of the cardiomyocyte ER), acetylation modification of GRP78 and apoptosis of cardiomyocytes are determined. The results show that ERS-induced GRP78 elevation does not induce cardiomyocyte apoptosis in the early stage of trauma. However, with prolonged ERS, the GRP78 acetylation level is elevated, and the apoptosis of cardiomyocytes also increases significantly. In addition, in the early stage of trauma, the expression of histone acetyl-transferase (HAT) P300 is increased and that of histone deacetylase 6 (HDAC6) is decreased in cardiomyocytes. Inhibition of HDAC function could induce the apoptosis of traumatic cardiomyocytes by increasing the acetylation level of GRP78. Our present study demonstrates for the first time that post-traumatic protracted ERS can promote cardiomyocyte apoptosis by increasing the acetylation level of GRP78, which may provide an experimental basis for seeking early molecular events of TISCI.

Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anticancer properties. A recently developed SOT, 1‐[2‐cyano‐3,12‐dioxooleana‐1,9(11)‐dien‐28‐oyl]‐4(‐pyridin‐2‐yl)‐1H‐imidazole (CDDO‐2P‐Im or ‘2P‐Im’), exhibits enhanced activity and improved pharmacokinetics over CDDO‐Im, a previous generation SOT. However, the mechanisms leading to these properties are not defined. Here, we show the synergy of 2P‐Im and the proteasome inhibitor ixazomib in human multiple myeloma (MM) cells and 2P‐Im activity in a murine model of plasmacytoma. RNA sequencing and quantitative reverse transcription PCR revealed the upregulation of the unfolded protein response (UPR) in MM cells upon 2P‐lm treatment, implicating the activation of the UPR as a key step in 2P‐Im‐induced apoptosis. Supporting this hypothesis, the deletion of genes encoding either protein kinase R‐like endoplasmic reticulum kinase (PERK) or DNA damage‐inducible transcript 3 protein (DDIT3; also known as CHOP) impaired the MM response to 2P‐Im, as did treatment with ISRIB, integrated stress response inhibitor, which inhibits UPR signaling downstream of PERK. Finally, both drug affinity responsive target stability and thermal shift assays demonstrated direct binding of 2P‐Im to endoplasmic reticulum chaperone BiP (GRP78/BiP), a stress‐inducible key signaling molecule of the UPR. These data reveal GRP78/BiP as a novel target of SOTs, and specifically of 2P‐Im, and suggest the potential broader utility of this class of small molecules as modulators of the UPR.

Melatonin, as an endocrine neurotransmitter, can promote the development of the ovary. Meanwhile, it also has protective effect on the ovary as an antioxidant. Thyroid hormone (TH) is essential for normal human reproductive function. Many studies have shown that 3,5,3′-triiodothyronine (T3) regulates the development of ovarian granulosa cells. However, little is known about the specific mechanisms by which melatonin combines with T3 to regulate granulosa cell development. The aim of present study was to investigate the effects and the possible mechanisms of melatonin and T3 on ovarian granulosa cell development. In the present study, cell development and apoptosis were detected by CCK8, EdU and TUNEL, respectively. The levels of related proteins were analyzed by Western blotting. The results showed that oxidative stress (OS) and reactive oxygen species (ROS) were induced by H2O2 in granulosa cells, and cell apoptosis was also increased accompanied with the decreased cellular proliferation and viability. Melatonin protects granulosa cells from H2O2-induced apoptosis and OS by downregulating ROS levels, especially in the presence of T3. Co-treatment of cell with melatonin and T3 also promotes the expression of GRP78 and AMH, while inhibiting CHOP, Caspase-3, and P16. It was demonstrated that melatonin alone or in combination with T3 had positive effect on the development of granulosa cells. In addition, the AMPK/SIRT1 signaling pathway is involved in the process of melatonin/T3 promoting granulosa cell development.

Angiotensin-converting enzyme 2 (ACE2) is considered a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor of high importance, but due to its non-ubiquitous expression, studies of other proteins that may participate in virus internalisation have been undertaken. To date, many alternative receptors have been discovered. Their functioning may provide an explanation for some of the events observed in severe COVID-19 that cannot be directly explained by the model in which ACE2 constitutes the central point of infection. Diabetes mellitus type 2 (T2D) can induce severe COVID-19 development. Although many mechanisms associated with ACE2 can lead to increased SARS-CoV-2 virulence in diabetes, proteins such as basigin (CD147), glucose-regulated protein 78 kDa (GRP78), cluster of differentiation 4 (CD4), transferrin receptor (TfR), integrins α5β1/αvβ3, or ACE2 co-receptors neuropilin 2 (NRP2), vimentin, and even syalilated gangliosides may also be responsible for worsening the COVID-19 course. On the other hand, some others may play protective roles. Understanding how diabetes-associated mechanisms can induce severe COVID-19 via modification of virus receptor functioning needs further extensive studies.

Mesenchymal stem cells (MSCs) are a popular cell source for repairing the liver. Improving the survival rate and colonization time of MSCs may significantly improve the therapeutic outcomes of MSCs. Studies showed that 78‐kDa glucose‐regulated protein (GRP78) expression improves cell viability and migration. This study aims to examine whether GRP78 overexpression improves the efficacy of rat bone marrow‐derived MSCs (rBMSCs) in HS‐induced liver damage. Bone marrow was isolated from the femurs and tibias of rats. rBMSCs were transfected with a GFP‐labeled GRP78 expression vector. Flow cytometry, transwell invasion assay, scratch assay immunoblotting, TUNEL assay, MTT assay, and ELISA were carried out. The results showed that GRP78 overexpression enhanced the migration and invasion of rBMSCs. Moreover, GRP78‐overexpressing rBMSCs relieved liver damage, repressed liver oxidative stress, and inhibited apoptosis. We found that overexpression of GRP78 in rBMSCs inhibited activation of the NLRP3 inflammasome, significantly decreased the levels of inflammatory factors, and decreased the expression of CD68. Notably, GRP78 overexpression activated the Nrf‐2/HO‐1 pathway and inhibited the NF–κB pathway. High expression of GRP78 efficiently enhanced the effect of rBMSC therapy. GRP78 may be a potential target to improve the therapeutic efficacy of BMSCs. [ABSTRACT FROM AUTHOR]

Objective: In this study, the effects of Prunus laurocerasus fruit extract (PLE), which is known for its high levels of phenolic compounds and antioxidant efficiency, on doxorubicin (DXR)-induced cardiotoxicity were examined. Methods: Male Sprague-Dawley rats were randomly assigned to the Control, DXR, PLE500+DXR, and PLE1000+DXR groups (n=6). PLE was orally administered to the animals in the PLE500+DXR (500 mg/kg) and PLE1000+DXR (1000 mg/kg) groups for 2 weeks. DXR was injected (15 mg/kg, intraperitoneally) 2 days before sacrification in the DXR, PLE500+DXR, and PLE1000+DXR groups. At the end of the study period, serum troponin I levels, myocardial superoxide dismutase (SOD) and catalase (CAT) activities, malondialdehyde (MDA), glutathione (GSH), glucose-regulated protein (GRP)78, and pro-caspase 12 levels were measured. Results: In the DXR group, serum troponin I concentration significantly increased (p<0.001), however PLE treatment significantly reduced this DXR-induced increment (p<0.001 and p<0.05 in the PLE500+DXR and PLE1000+DXR groups, respectively). DXR-induced increase in myocardial MDA (p<0.001) significantly reduced in the PLE500+DXR (p<0.001) and PLE1000+DXR (p<0.001) groups. However, DXR-induced changes, such as GSH depletion (p<0.001), reduced CAT (p<0.001) and SOD (p<0.001) activities, increased GRP78 (p<0.01) and decreased pro-caspase 12 (p<0.001) levels, were not significantly affected by PLE treatment. Conclusion: The present results indicate that pretreatment with PLE reduced, but not completely prevented, cardiac damage induced by DXR. While a reduction in oxidative stress appears to play a role in the partial protective effect of PLE treatment, endoplasmic reticulum stress appears to have no role. Further research is necessary to understand the mechanisms of action underlying PLE treatment. [ABSTRACT FROM AUTHOR]

Objective(s): Exosomes are nanovesicular vehicles capable of transporting different cargoes. Based on their characteristics, exosomes are proposed as a class of vehicles for targeted delivery of therapeutics. We aimed to establish a HEK293T stable cell line capable of secreting GRP78-specific scFv-targeted exosomes. Methods: The pLEX-LAMP2b-GRP78 construct was developed by enzymatic replacement of DARPin in pLEX-LAMP2b-DARPin with a GRP78-specific scFv. pLEX-LAMP2b-GRP78 (or TurboGFP as control), psPAX2, and pMD2.G plasmids were co-transfected into HEK293T cells, and produced lentiviruses were harvested. Different multiplicities of infection (MOI; 10, 20, 30, 60, 120, and 240) were used for the transduction of HEK293T to select the most appropriate one as assessed by flow cytometry. Transduced HEK293T cells were subject to puromycin selection and the presence of the scFv was assessed in the established cell line at the DNA, transcript, and protein levels by PCR, RT-PCR, and Western blotting, respectively. Results: pLEX-LAMP2b-GRP78 was successfully developed. Co-transfection resulted in the expression of GFP by HEK293T in the control group 48 hours following transfection. The MOI of 60 was selected as 10% of cells were GFP+ 72 hours following transduction. Following puromycin selection, the presence of the integrated scFv DNA and transcript was confirmed. Moreover, Western blotting results confirmed the presence of the His-tagged scFv in the established cell line. Conclusions: HEK293T cells can be engineered for the production of targeted exosomes which could be applied for therapeutic purposes. Moreover, scFvs are potent targeting domains that could be leveraged for the development of targeted exosomes. [ABSTRACT FROM AUTHOR]

Objective: We aimed to evaluate the effects of combined oral contraceptive active ingredients ethinylestradiol, drospirenone, and ethinylestradiol+drospirenone for histopathological changes, and endoplasmic reticulum stress levels in the liver. Methods: In the study, 37 to 8-week-old Balb/c female mice were used. Mice were randomly divided into the control, sham, ethinylestradiol, drospirenone, and ethinylestradiol+drospirenone groups. Experimental groups were administered ethinylestradiol, drospirenone, and ethinylestradiol+drospirenone with gavage for 35 days. In liver tissue sections, histopathological changes were detected with hematoxylin&eosin, orcein, Mallory's Azan, and periodic acid-Schiff, and the presence of endoplasmic reticulum stress was detected by Chop and Grp78 immunostaining. Results: The ethinylestradiol+drospirenone group showed significant histopathological changes compared to the control group. Some degenerative changes were noted such as swelling and size differences in hepatocytes in the ethinylestradiol+drospirenone group. When compared to the control group, an increased collagen and elastic fibers density around the vena centralis was observed in the ethinylestradiol+drospirenone group. The expression level of Grp78 protein in female mice given ethinylestradiol+drospirenone was statistically significantly increased compared to the control group. The expression level of Chop protein was significantly increased in the ethinylestradiol, drospirenone, and ethinylestradiol+drospirenone groups. Conclusion: We concluded that the use of combined oral contraceptives increases endoplasmic reticulum stress in mouse liver tissue, and as a result, it may cause liver histopathological disorders by promoting cell death. [ABSTRACT FROM AUTHOR]

Backgroud: Hypoadiponectinemia is the important cause of insulin resistance. Recent studies have shown that periodontitis is associated with hypoadiponectinemia. The purpose of this study was to investigate the effect of periodontitis-induced endoplasmic reticulum stress (ERS) in visceral adipocytes on hypoadiponectinemia. Methods: Rat periodontitis models were established by local ligation with silk around the bilateral maxillary second molars. Porphyromonas gingivalis-lipopolysaccharid (P.g-LPS) was also used to stimulate the visceral adipocytes in vitro. The protein expression levels of glucose regulated protein 78 (GRP78), inositol-requiring protein 1α (IRE1α), protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6) and adiponectin were detected. IRE1α lentiviruses were transfected into visceral adipocytes in vitro, and an IRE1α inhibitor (KIRA6) was injected in epididymal adipose tissue of rats to detect and verify the effect of ERS on adiponectin expression in visceral adipocytes in vivo. Results: Hypoadiponectinemia was observed in periodontitis rat, and the expression levels of ERS key proteins GRP78 and the phosphorylation levels of IRE1α (p-IRE1α)/IRE1α in visceral adipocytes were increased, while the expression levels of adiponectin protein were decreased. After KIRA6 injection into epididymal adipose tissue of rats with periodontitis, adiponectin levels in visceral adipocytes increased, and serum adiponectin levels recovered to a certain extent. The protein expression levels of GRP78 and p-IRE1α/IRE1α were increased and adiponectin protein expression was decreased in P.g-LPS-induced visceral adipocytes. Overexpression of IRE1α further inhibited adiponectin expression in P.g-LPS-stimulated visceral adipocytes, and conversely, IRE1α inhibition restored adiponectin expression. Conclusions: Our findings suggest that periodontitis induces ERS in visceral adipocytes leading to hypoadiponectinemia. IRE1α is a key protein regulating adiponectin expression in visceral adipocytes. [ABSTRACT FROM AUTHOR]

Glucose-regulated protein 78 (GRP78) binds to and stabilizes melanocortin 4 receptor (MC4R), which activates protein kinase A (PKA) by regulating G proteins. GRP78 is primarily used as a marker for endoplasmic reticulum stress; however, its other functions have not been well studied. Therefore, in this study, we aimed to investigate the function of GRP78 during porcine embryonic development. The developmental quality of porcine embryos, expression of cell cycle proteins, and function of mitochondria were evaluated by inhibiting the function of GRP78. Porcine oocytes were activated to undergo parthenogenesis, and blastocysts were obtained after 7 days of in vitro culture. GRP78 function was inhibited by adding 20 μM HA15 to the in vitro culture medium. The inhibition in GRP78 function led to a decrease in G proteins release, which subsequently downregulated the cyclic adenosine monophosphate (cAMP)/PKA pathway. Ultimately, inhibition of GRP78 function induced the inhibition of CDK1 and cyclin B expression and disruption of the cell cycle. In addition, inhibition of GRP78 function regulated DRP1 and SIRT1 expression, resulting in mitochondrial dysfunction. This study provides new insights into the role of GRP78 in porcine embryonic development, particularly its involvement in the regulation of the MC4R pathway and downstream cAMP/PKA signaling. The results suggest that the inhibition of GRP78 function in porcine embryos by HA15 treatment may have negative effects on embryo quality and development. This study also demonstrated that GRP78 plays a crucial role in the functioning of MC4R, which releases the G protein during porcine embryonic development. [ABSTRACT FROM AUTHOR]

Infection of the central nervous system by the Japanese encephalitis virus (JEV) is characterized by extensive neuronal cell death and neuroinflammation. Several protein-coding genes and microRNAs are implicated in JEV-induced neuronal cell death. However, the global expression patterns and functional contributions of long non-coding RNAs (lncRNAs) during JEV-induced neuronal cell death have not been explored. Here, we profiled the transcriptome of the JEV-infected neuronal cell line and identified several lncRNAs whose expression is altered during JEV infection. We functionally characterized a lncRNA named JINR1 (JEV-induced non-coding RNA 1), which is evolutionarily conserved in primates. JINR1 induction during JEV infection is regulated by nuclear factor-kappa B (NF-κB). Depletion of JINR1 during infection reduces flavivirus replication, neuronal cell death, and the expression of genes involved in ER stress and neuroinflammation. Interestingly, GRP78 overexpression prevents the decrease in flavivirus replication due to JINR1 knockdown. JINR1 interacts with RBM10 and NF-κB to regulate the transcription of virus-induced genes. In addition, RBM10 and JINR1 form a feed-forward loop to reciprocally promote each other's expression by regulating NF-κB activity. Our results suggest the role of JINR1 in promoting flavivirus replication and flavivirusinduced neuronal cell death. [ABSTRACT FROM AUTHOR]

Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anticancer properties. A recently developed SOT, 1‐[2‐cyano‐3,12‐dioxooleana‐1,9(11)‐dien‐28‐oyl]‐4(‐pyridin‐2‐yl)‐1H‐imidazole (CDDO‐2P‐Im or '2P‐Im'), exhibits enhanced activity and improved pharmacokinetics over CDDO‐Im, a previous generation SOT. However, the mechanisms leading to these properties are not defined. Here, we show the synergy of 2P‐Im and the proteasome inhibitor ixazomib in human multiple myeloma (MM) cells and 2P‐Im activity in a murine model of plasmacytoma. RNA sequencing and quantitative reverse transcription PCR revealed the upregulation of the unfolded protein response (UPR) in MM cells upon 2P‐lm treatment, implicating the activation of the UPR as a key step in 2P‐Im‐induced apoptosis. Supporting this hypothesis, the deletion of genes encoding either protein kinase R‐like endoplasmic reticulum kinase (PERK) or DNA damage‐inducible transcript 3 protein (DDIT3; also known as CHOP) impaired the MM response to 2P‐Im, as did treatment with ISRIB, integrated stress response inhibitor, which inhibits UPR signaling downstream of PERK. Finally, both drug affinity responsive target stability and thermal shift assays demonstrated direct binding of 2P‐Im to endoplasmic reticulum chaperone BiP (GRP78/BiP), a stress‐inducible key signaling molecule of the UPR. These data reveal GRP78/BiP as a novel target of SOTs, and specifically of 2P‐Im, and suggest the potential broader utility of this class of small molecules as modulators of the UPR. [ABSTRACT FROM AUTHOR]

Aim: Glucose-regulated protein 78 (GRP78) is an endoplasmic reticulum located chaperone that plays a vital role during cellular stress. NS5A is one of the hepatitis C virus (HCV) non-structural proteins essential for replication. Materials & methods: Protein–protein docking was used to test the binding mode between GRP78 and HCV NS5A. Molecular dynamics simulations (MDSs) are performed on HCV NS5A, GRP78 and the HCV NS5A–GRP78 complex. Results: Docking and MDS reveal the ability of the GRP78 substrate-binding domain β to associate tightly with the HCV NS5A C142-C165 region. Conclusion: MDS reveals the potential of the C142-C165 region of the HCV NS5A to be used as a seed to develop a recognition inhibitor that counterparts the viral protein recognition by GRP78. Human cells contain a protein called GRP78. GRP78 is important to the ability of germs to cause infection because they can bind GRP78. We used a computer model to test how GRP78 binds to germs. This could be a target for future medicines and a useful way to stop infections. [ABSTRACT FROM AUTHOR]

Background: Cardiac hypertrophy (CH) is one of the contributing causes of morbidity and mortality. Hyperhomocysteinemia (HHcy) is one of the diseases which may predispose hyperlipidemia and CH. Linagliptin (Lina) and secoisolariciresinol diglucoside (SDG) are known to alleviate a variety of illnesses by reducing oxidative stress and inflammation. Aim: This study aimed to study the effect of HHcy on cardiac tissues, with a special focus on endoplasmic reticulum (ER) stress as a mainstay pathophysiological pathway. In addition, our study examined the protective effect of Lina, SDG, and their combination against HHcy-induced hyperlipidemia and CH in rats. Methods: Seventy-five male Sprague–Dawley rats were randomly divided into five groups, and for 60 days, the following regimen was administered: Group I: rats received distilled water; Group II: rats received methionine (MET) (2 g/kg/day, p.o.); groups III and IV: rats received Lina (3 mg/kg/day, p.o.) and SDG (20 mg/kg/ day, p.o.), respectively, followed by MET (2 g/kg/day, p.o.); Group V: rats received Lina and SDG, followed by MET (2 g/kg/day, p.o.). Results: Pretreatment with Lina, SDG, and their combination showed a significant decrease in serum levels of HHcy and an improved lipid profile compared to the MET group. Moreover, both drugs improved cardiac injury, as evidenced by the substantial improvement in ECG parameters, morphological features of the cardiac muscle, and reduced serum levels of cardiac markers. Additionally, Lina and SDG significantly attenuated cardiac oxidative stress, inflammation, and apoptosis. Furthermore, Lina, SDG, and their combination remarkably downregulated the enhanced expression of endoplasmic reticulum (ER) stress markers, GRP78, PERK, ATF-4, CHOP, NF-κB, and SREBP1c compared to the METgroup. Conclusion: Lina and SDG showed cardioprotective effects against HHcy-induced heart hypertrophy and hyperlipidemia in rats. [ABSTRACT FROM AUTHOR]

Background: Allergic asthma is a common respiratory disease that significantly impacts human health. Through in silico analysis of human lung RNASeq, we found that asthmatic lungs display lower levels of Isthmin-1 (ISM1) expression than healthy lungs. ISM1 is an endogenous anti-inflammatory protein that is highly expressed in mouse lungs and bronchial epithelial cells, playing a crucial role in maintaining lung homeostasis. However, how ISM1 influences asthma remains unclear. This study aims to investigate the potential involvement of ISM1 in allergic airway inflammation and uncover the underlying mechanisms. Methods: We investigated the pivotal role of ISM1 in airway inflammation using an ISM1 knockout mouse line (ISM1−/−) and challenged them with house dust mite (HDM) extract to induce allergic-like airway/lung inflammation. To examine the impact of ISM1 deficiency, we analyzed the infiltration of immune cells into the lungs and cytokine levels in bronchoalveolar lavage fluid (BALF) using flow cytometry and multiplex ELISA, respectively. Furthermore, we examined the therapeutic potential of ISM1 by administering recombinant ISM1 (rISM1) via the intratracheal route to rescue the effects of ISM1 reduction in HDM-challenged mice. RNA-Seq, western blot, and fluorescence microscopy techniques were subsequently used to elucidate the underlying mechanisms. Results: ISM1−/− mice showed a pronounced worsening of allergic airway inflammation and hyperresponsiveness upon HDM challenge. The heightened inflammation in ISM1−/− mice correlated with enhanced lung cell necroptosis, as indicated by higher pMLKL expression. Intratracheal delivery of rISM1 significantly reduced the number of eosinophils in BALF and goblet cell hyperplasia. Mechanistically, ISM1 stimulates adiponectin secretion by type 2 alveolar epithelial cells partially through the GRP78 receptor and enhances adiponectin-facilitated apoptotic cell clearance via alveolar macrophage efferocytosis. Reduced adiponectin expression under ISM1 deficiency also contributed to intensified necroptosis, prolonged inflammation, and heightened severity of airway hyperresponsiveness. Conclusions: This study revealed for the first time that ISM1 functions to restrain airway hyperresponsiveness to HDM-triggered allergic-like airway/lung inflammation in mice, consistent with its persistent downregulation in human asthma. Direct administration of rISM1 into the airway alleviates airway inflammation and promotes immune cell clearance, likely by stimulating airway adiponectin production. These findings suggest that ISM1 has therapeutic potential for allergic asthma. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the hypothesis that microparticles (MP) may be a source of autoantigens and drive disease progression in rheumatoid arthritis (RA) synovium. Methods: Synovial fluid (SF) was collected from the knee joints of 41 disease‐modifying anti‐rheumatic drug‐naive RA patients and 30 osteoarthritis (OA) patients. Samples were stained with either anti‐vimentin‐AlexaFluor‐488 or anti‐glucose‐regulated protein‐78‐Dylight‐488 (GRP78) and Annexin‐V‐allophycocyanin for flow cytometry analysis. RA and OA fibroblast‐like synoviocytes (FLS) were co‐cultured with respective SF‐derived MP in vitro for 24 h. Supernatant and cell‐free SF was assayed for pro‐inflammatory analytes by multiplex assays. Results: Elevated percentages of AnnexinV+ Vimentin+ MP (median 0.8, interquartile range [IQR] 1.30) and AnnexinV+ GRP78+ MP (median 0.3, IQR 0.28) were present in RA compared with OA patients. We observed that CXCL6 and CCL8 were secreted in excess by RA‐FLS stimulated with RA‐SF‐MP but not by stimulation with MP‐free RA‐SF. Conclusions: Microparticles express vimentin and GRP78 on their surface and stimulate synoviocytes to produce inflammatory molecules, thus sustaining local inflammation in the synovium in RA. [ABSTRACT FROM AUTHOR]

Abstract Background Osteoarthritis (OA) is a frequently encountered debilitating joint disorder. Whether plexin C1 (PLXNC1) is implicated in OA is far from being investigated despite its well-documented pro-inflammatory property in human diseases. The goal of this study is to expound the specific role of PLXNC1 in OA and elaborate the probable action mechanism. Methods Firstly, PLXNC1 expression in the cartilage tissues of patients with OA was examined with GEO database. In interleukin-1beta (IL-1β)-induced OA cell model, RT-qPCR and western blotting tested the expression of PLXNC1, glucose-regulating protein 78 (GRP78) and extracellular matrix (ECM) degradation-related factors. Cell viability and inflammation were respectively judged by CCK-8 assay and RT-qPCR. TUNEL and western blotting estimated cell apoptosis. The potential binding between PLXNC1 and GRP78 was corroborated by Co-IP assay. Western blotting also tested the expression of endoplasmic reticulum stress (ERS)-associated proteins. Results As it turned out, PLXNC1 expression was elevated in the cartilage tissues of patients with OA and IL-1β-treated chondrocytes. When PLXNC1 was depleted, the viability injury, inflammation, apoptosis and ECM degradation of chondrocytes exposed to IL-1β were obstructed. Besides, GRP78 bond to PLXNC1 in IL-1β-treated chondrocytes. The ascending GRP78 expression in the chondrocytes exposed to IL-1β was depleted after PLXNC1 was silenced. Meanwhile, the impacts of PLXNC1 deficiency on the viability, inflammatory response, apoptosis, ECM degradation as well as ERS in IL-1β-exposed chondrocytes were abolished by GRP78 up-regulation. Conclusion In summary, PLXNC1 silencing might interact with and down-regulate GRP78 to mitigate the apoptosis, inflammation, and ECM degradation of IL-1β-insulted chondrocytes in OA.