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Objective To explore the mechanism by which puerarin alleviates the cardiotoxicity induced by doxorubicin in myocardial cells. Methods Cells in the logarithmic growth phase were divided into normal control group, model group, low- (20 mmol·L-1), medium- (40 mmol·L-1) and high- (80 mmol·L-1) dose puerarin groups, and positive control group (captopril, 1 mmol·L-1). Except for the normal control group, the other groups were co-incubated with 5 mmol·L-1 doxorubicin. Cell viability was assessed using CCK-8 and lactate dehydrogenase (LDH) assays. ROS levels were detected using a ROS probe. Autophagy flux was detected by transfection with HBAD-mcherry-EGFP-LC3 adenovirus. Western Blot was used to measure the protein expression levels of Beclin-1, LC3, p62, p-AMPKα, and AMPKα. Lysosomal function was assessed using a lysosomal probe. Immunofluorescence was used to detect the relative intensity and co-localization of ASMase and LAMP1. Molecular docking analysis was performed to predict the binding capacity of PUE with ASMase. Differential gene expression was analyzed by gene set enrichment analysis. Results Compared to the normal control group, the model group showed reduced cell viability (P＜0.01), increased release levels of LDH and ROS (P＜0.05, P＜0.01), increased number of autophagosomes (P＜0.01), and decreased number of autophagic lysosomes (P＜0.05). Beclin-1 protein expression and LC3-II/LC3-I ratio decreased (P＜0.01), but p62 protein expression increased (P＜0.01). Fluorescence intensity of lysosome decreased (P＜0.01), whereas fluorescence intensity of ASMase increased (P＜ 0.01). Immunofluorescence co-localization of ASMase and LAMP1 increased (P＜0.01), the ratio of p-AMPKα/ AMPKα decreased (P＜0.05). Compared to the model group, the high-dose puerarin group showed a rebound in cell viability (P＜0.05). The medium- and high-dose puerarin groups showed a decreasing trend in LDH level (P＜0.05), and all puerarin groups showed a decreasing trend in ROS level (P＜0.01). The number of autophagosomes in high-dose puerarin group reduced (P＜0.01). The number of autophagic lysosomes in all puerarin groups increased (P＜0.05, P＜0.01). The high-dose puerarin group showed increased expression of Beclin-1 (P＜0.05) and LC3-II/LC3-I ratio, and decreased p62 expression (P＜0.01). All puerarin groups showed increased lysosomal fluorescence intensity (P＜0.05, P＜0.01). The medium- and high-dose puerarin groups showed a decrease in ASMase fluorescence intensity (P＜0.05), a reduction in the immunofluorescence co-localization of ASMase with LAMP1 (P＜0.01), and an increase in the p-AMPKα/AMPKα ratio (P＜0.01). Molecular docking analysis discovered puerarin showed a binding energy of -8.6 kcal·mol-1 with ASMase. Gene enrichment analysis indicated that the differentially expressed genes in the doxorubicin cardiotoxicity model were related to apoptosis, autophagy, and lysosomal function. Conclusion Puerarin can alleviate doxorubicin-induced cardiotoxicity in myocardial cells and protect myocardial cells by regulating autophagy through AMPK/ASMase, as well as restoring autophagic flux. [ABSTRACT FROM AUTHOR]

Background/Aims: After 9/11, multiple government agencies instituted programs aimed at developing medical radiation countermeasures (MRCs) for two syndromes lethal within weeks of a limited nuclear attack; the hematopoietic-acute radiation syndrome (H-ARS) and the higher-dose gastrointestinal-acute radiation syndrome (GI-ARS). While re-purposing drugs that enhance marrow repopulation treats H-ARS, no mitigator protects GI tract. Methods: We recently reported anti-ceramide 6B5 single-chain variable fragment (scFv) pre-treatment abrogates ongoing small intestinal endothelial apoptosis to rescue Lgr5+ stem cells, preventing GI-ARS lethality in C57B/L6J mice. Here, with US Department of Defense support, we provide evidence that humanized anti-ceramide scFv (CX-01) is a promising prophylactic MRC for first responders, who risk exposure upon entering a radiation-contaminated site. Results: CX-01, when delivered up to 90 min before irradiation, is highly-effective in preventing small intestinal endothelial apoptosis in mice and lethality in both sexes. Unexpectedly, females require an ~2-fold higher CX-01 dose than males for full protection. CX-01 is effective subcutaneously and intramuscularly, a property critical for battlefield use. Increasing the maximally-effective dose 5-fold does not extend duration of bioeffectiveness. Conclusion: While CX-01 prevents GI-ARS lethality, structural modification to extend half-life may be necessary to optimize first responder prophylaxis. [ABSTRACT FROM AUTHOR]

Abstract Recently, COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, caused > 6 million deaths. Symptoms included respiratory strain and complications, leading to severe pneumonia. SARS-CoV-2 attaches to the ACE-2 receptor of the host cell membrane to enter. Targeting the SARS-CoV-2 entry may effectively inhibit infection. Acid sphingomyelinase (ASMase) is a lysosomal protein that catalyzes the conversion of sphingolipid (sphingomyelin) to ceramide. Ceramide molecules aggregate/assemble on the plasma membrane to form “platforms” that facilitate the viral intake into the cell. Impairing the ASMase activity will eventually disrupt viral entry into the cell. In this review, we identified the metabolism of sphingolipids, sphingolipids' role in cell signal transduction cascades, and viral infection mechanisms. Also, we outlined ASMase structure and underlying mechanisms inhibiting viral entry 40 with the aid of inhibitors of acid sphingomyelinase (FIASMAs). In silico molecular docking analyses of FIASMAs with inhibitors revealed that dilazep (S = − 12.58 kcal/mol), emetine (S = − 11.65 kcal/mol), pimozide (S = − 11.29 kcal/mol), carvedilol (S = − 11.28 kcal/mol), mebeverine (S = − 11.14 kcal/mol), cepharanthine (S = − 11.06 kcal/mol), hydroxyzin (S = − 10.96 kcal/mol), astemizole (S = − 10.81 kcal/mol), sertindole (S = − 10.55 kcal/mol), and bepridil (S = − 10.47 kcal/mol) have higher inhibition activity than the candidate drug amiodarone (S = − 10.43 kcal/mol), making them better options for inhibition.

Recently, COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, caused > 6 million deaths. Symptoms included respiratory strain and complications, leading to severe pneumonia. SARS-CoV-2 attaches to the ACE-2 receptor of the host cell membrane to enter. Targeting the SARS-CoV-2 entry may effectively inhibit infection. Acid sphingomyelinase (ASMase) is a lysosomal protein that catalyzes the conversion of sphingolipid (sphingomyelin) to ceramide. Ceramide molecules aggregate/assemble on the plasma membrane to form "platforms" that facilitate the viral intake into the cell. Impairing the ASMase activity will eventually disrupt viral entry into the cell. In this review, we identified the metabolism of sphingolipids, sphingolipids' role in cell signal transduction cascades, and viral infection mechanisms. Also, we outlined ASMase structure and underlying mechanisms inhibiting viral entry 40 with the aid of inhibitors of acid sphingomyelinase (FIASMAs). In silico molecular docking analyses of FIASMAs with inhibitors revealed that dilazep (S = − 12.58 kcal/mol), emetine (S = − 11.65 kcal/mol), pimozide (S = − 11.29 kcal/mol), carvedilol (S = − 11.28 kcal/mol), mebeverine (S = − 11.14 kcal/mol), cepharanthine (S = − 11.06 kcal/mol), hydroxyzin (S = − 10.96 kcal/mol), astemizole (S = − 10.81 kcal/mol), sertindole (S = − 10.55 kcal/mol), and bepridil (S = − 10.47 kcal/mol) have higher inhibition activity than the candidate drug amiodarone (S = − 10.43 kcal/mol), making them better options for inhibition. [ABSTRACT FROM AUTHOR]

Cholesterol-rich membrane domains, also called lipid rafts (LRs), are specialized membrane domains that provide a platform for intracellular signal transduction. Membrane proteins often cluster in LRs that further aggregate into larger platform-like structures that are enriched in ceramides and are called ceramide-rich platforms (CRPs). The role of CRPs in the regulation of intestinal epithelial functions remains unknown. Down-regulated in adenoma (DRA) is an intestinal Cl−/HCO3− antiporter that is enriched in LRs. However, little is known regarding the mechanisms involved in the regulation of DRA activity. The air–liquid interface (ALI) was created by removing apical media for a specified number of days; from 12–14 days post-confluency, Caco-2/BBe cells or a colonoid monolayer were grown as submerged cultures. Confocal imaging was used to examine the dimensions of membrane microdomains that contained DRA. DRA expression and activity were enhanced in Caco-2/BBe cells and human colonoids using an ALI culture method. ALI causes an increase in acid sphingomyelinase (ASMase) activity, an enzyme responsible for enhancing ceramide content in the plasma membrane. ALI cultures expressed a larger number of DRA-containing platforms with dimensions >2 µm compared to cells grown as submerged cultures. ASMase inhibitor, desipramine, disrupted CRPs and reduced the ALI-induced increase in DRA expression in the apical membrane. Exposing normal human colonoid monolayers to ALI increased the ASMase activity and enhanced the differentiation of colonoids along with basal and forskolin-stimulated DRA activities. ALI increases DRA activity and expression by increasing ASMase activity and platform formation in Caco-2/BBe cells and by enhancing the differentiation of colonoids. [ABSTRACT FROM AUTHOR]

Background: DDP-based chemotherapy is one of the first-line treatment in GC. However, the therapeutic efficacy of DDP is limited due to side effects. Therefore, it is of great significance to develop novel adjuvants to synergize with DDP. We had demonstrated previously that rMV-Hu191 had antitumor activity in GC. Here we examined the synergism of rMV-Hu191 with DDP in vitro and in vivo. Methods: Cellular proliferation, the synergistic effect and cell apoptosis were evaluated by CCK-8 assay, ZIP analysis and flow cytometry, respectively. The protein levels and location of ASMase were monitored by western blot and immunofluorescence assay. shRNA and imipramine were used to regulate the expression and activity of ASMase. MβCD was administrated to disrupt lipid rafts. Mice bearing GC xenografts were used to confirm the synergism in vivo. Results: From our data, combinational therapy demonstrated synergistic cytotoxicity both in resistant GC cell lines from a Chinese patient and drug-nonresistant GC cell lines, and increased cell apoptosis, instead of viral replication. Integrity of lipid rafts and ASMase were required for rMV-Hu191- and combination-induced apoptosis. The ASMase was delivered to the lipid raft microdomains at the initial stage of rMV-Hu191 treatment. In vivo GC mice xenografts confirmed the synergism of combinational treatment, together with increased apoptosis and trivial side-effects. Conclusions: This is the first study to demonstrate that rMV-Hu191 combined with DDP could be used as a potential therapeutic strategy in GC treatment and the ASMase and the integrity of lipid rafts are required for the synergistic effects. [ABSTRACT FROM AUTHOR]

Macrophage inflammation and oxidative stress promote atherosclerosis progression. Naringenin is a naturally occurring flavonoid with antiatherosclerotic properties. Here, we elucidated the effects of naringenin on monocyte/macrophage endothelial infiltration and vascular inflammation. We found naringenin inhibited oxidized low-density lipoprotein (oxLDL)-induced pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α toward an M2 macrophage phenotype and inhibited oxLDL-induced TLR4 (Toll-like receptor 4) membrane translocation and downstream NF-κB transcriptional activity. Results from flow cytometric analysis showed that naringenin reduced monocyte/macrophage infiltration in the aorta of high-fat-diet-treated ApoE-deficient mice. The aortic cytokine levels were also inhibited in naringenin-treated mice. Further, we found that naringenin reduced lipid raft clustering and acid sphingomyelinase (ASMase) membrane gathering and inhibited the TLR4 and NADPH oxidase subunit p47phox membrane recruitment, which reduced the inflammatory response. Recombinant ASMase treatment or overexpression of ASMase abolished the naringenin function and activated macrophage and vascular inflammation. We conclude that naringenin inhibits ASMase-mediated lipid raft redox signaling to attenuate macrophage activation and vascular inflammation.

Background/Aims: Despite enormous effort, anti-angiogenic drugs have not lived up to the promise of globally-enhancing anti-cancer therapies. Clinically, anti-angiogenic drugs have been used to persistently suppress vascular endothelial growth factor (VEGF) in order to “normalize” dysfunctional neo-angiogenic microvasculature and prevent recruitment of endothelial progenitors. Recently, we showed that a 1h pre-treatment with anti-angiogenic drugs prior to ultra-high single dose radiotherapy and specific chemotherapies transiently de-represses acid sphingomyelinase (ASMase), leading to enhanced cancer therapy-induced, ceramidemediated vascular injury and tumor response. Here we formally decipher parameters of chemotherapy induction of endothelial sphingolipid signaling events and define principles for optimizing anti-angiogenic chemosensitization. Methods: These studies examine the antimetabolite chemotherapeutic gemcitabine in soft tissue sarcoma (STS), a clinically-relevant combination. Results: Initial studies address the theoretic problem that anti-angiogenic drugs such as bevacizumab, an IgG with a 3-week half-life, have the potential for accumulating during the 3-week chemotherapeutic cycles currently standard-of-care for STS treatment. We show that anti-angiogenic ASMase-dependent enhancement of the response of MCA/129 fibrosarcomas in sv129/BL6 mice to gemcitabine progressively diminishes as the level of the VEGFR2 inhibitor DC101, an IgG, accumulates, suggesting a short-acting anti-angiogenic drug might be preferable in multi-cycle chemotherapeutic regimens. Further, we show lenvatinib, a VEGFR2 tyrosine kinase inhibitor with a short half-life, to be superior to DC101, enhancing gemcitabine-induced endothelial cell apoptosis and tumor response in a multi-cycle treatment schedule. Conclusion: We posit that a single delivery of a short-acting anti-angiogenic agent at 1h preceding each dose of gemcitabine and other chemotherapies may be more efficacious for repeated sensitization of the ASMase pathway in multi-cycle chemotherapy regimens than current treatment strategies. [ABSTRACT FROM AUTHOR]

Background: Hexavalent chromium (Cr(VI)) is a common environmental pollutant. Cr(VI) exposure can lead to severe damage in the liver, but the preventive measures to diminish Cr(VI)-induced hepatotoxicity need further study. Acid sphingomyelinase (ASMase) is responsible for the production of ceramide via the hydrolysis of sphingomyelin. The present study was designed to investigate effects of desipramine (DES), as an ASMase inhibitor, on Cr(VI)-induced hepatotoxicity. Methods: L-02 hepatocytes were incubated with different concentrations of Cr(VI) for 24h, and ASMase activities and ceramide levels were measured. Moreover, the study investigated the role of DES played in ASMase activities and ceramide levels. Finally, effects of DES on mRNA and protein expressions of the components of mitochondrial permeability transition pore (PTP) and PTP opening were detected. Results: The ASMase activities and ceramide contents increased in L-02 hepatocytes treated with Cr(VI). The results demonstrated that apoptosis rates, ASMase activities and ceramide content decreased in groups treated with the combination of DES and Cr(VI) compared to Cr(VI) groups. Furthermore, DES inhibited Cr(VI)-induced mitochondrial PTP opening by intervening the mRNA and protein expressions of the components of mitochondrial PTP. Conclusions: DES may exert protective effects on Cr(VI)-induced hepatocellular apoptosis probably by inhibiting ceramide channel formation and mitochondrial PTP opening.

Ultraviolet (UV) irradiation accelerates formation of ceramide through hydrolysis of sphingomyelin and de novo synthesis. Here, we investigated the effects of ceramide on UV-induced matrix metalloproteinase-1 (MMP-1) expression in human dermal fibroblasts. Our results showed that acidic-sphingomyelinase (aSMase) and MMP-1 mRNA expression were increased by UV irradiation. Treatment of D609 (aSMase inhibitor) decreased the level of basal and UV-induced MMP-1 expression. On the other hand, basal and UV-induced MMP-1 expression was increased through induction of intracellular ceramide by D-MAPP, a ceramidase inhibitor. Our results also showed that MMP-1 protein expression was dose-dependently increased by C2-ceramide or SMase treatment. The activation of ceramide pathway by C2-ceramide enhanced phosphorylation of signal transducer and activators of transcription-1 (STAT-1), whereas ceramide-induced MMP-1 expression was potently prevented by piceatannol; Janus kinase (JAK1) inhibtor; and WHI-P131, a specific inhibitor of JAK3; but not by AG490, JAK 2 inhbitor, in human dermal fibroblasts. We also found that UV induced the phosphorylation of STAT-1, and UV-induced MMP-1 expression was significantly decreased by JAK1 inhibitor, piceatannol. Overall, we demonstrate that induction of intracellular ceramide by UV may activate MMP-1 gene expression via JAK1/STAT-1 pathway. Therefore, we suggest that targeted modulation of the ceramide signaling pathway may offer a novel therapeutic approach for inhibiting MMP-1 expression, which is a causing gene of skin aging.

Keratins are epithelial cell intermediate filament (IF) proteins that are expressed as pairs in a cell-differentiation-regulated manner. Hepatocytes express the keratin 8 and 18 pair (denoted K8/K18) of IFs, and a loss of K8 or K18, as in K8-null mice, leads to degradation of the keratin partner. We have previously reported that a K8/K18 loss in hepatocytes leads to altered cell surface lipid raft distribution and more efficient Fas receptor (FasR, also known as TNFRSF6)- mediated apoptosis. We demonstrate here that the absence of K8 or transgenic expression of the K8 G62C mutant in mouse hepatocytes reduces lipid raft size. Mechanistically, we find that the lipid raft size is dependent on acid sphingomyelinase (ASMase, also known as SMPD1) enzyme activity, which is reduced in absence of K8/K18. Notably, the reduction of ASMase activity appears to be caused by a less efficient redistribution of surface membrane PKCd toward lysosomes. Moreover, we delineate the lipid raft volume range that is required for an optimal FasR-mediated apoptosis. Hence, K8/ K18-dependent PKCd- and ASMase-mediated modulation of lipid raft size can explain the more prominent FasR-mediated signaling resulting from K8/K18 loss. The fine-tuning of ASMase-mediated regulation of lipid rafts might provide a therapeutic target for deathreceptor- related liver diseases. [ABSTRACT FROM AUTHOR]

Cancer therapies result in the killing of cancer cells but remain largely ineffective, with most patients dying of their disease. The methodology described here is a new image-guided cancer treatment under development that relies on physical methods to alter tumour biology. It enhances tumour responses to radiation significantly by synergistically destroying tumour blood vessels using microbubbles. It achieves tumour specificity by confining the ultrasonic fields that stimulate microbubbles to tumour location only. By perturbing tumour vasculature and activating specific genetic pathways in endothelial cells, the technique has been demonstrated to sensitise the targeted tissues to subsequent therapeutic application of radiation, resulting in significantly enhanced cell killing through a ceramide-dependent pathway initiated at the cell membrane. The treatment reviewed here destroys blood vessels, significantly enhancing the anti-vascular effect of radiation and improving tumour cure. The significant enhancement of localised tumour cell kill observed with this method means that radiation-based treatments can be potentially made more potent and lower doses of radiation utilised. The technique has the potential to have a profound impact on the practice of radiation oncology by offering a novel and safe means of reducing normal tissue toxicity while at the same time significantly increasing treatment effectiveness. [ABSTRACT FROM AUTHOR]

Background: Hexavalent chromium (Cr(VI)) is a common environmental pollutant. Cr(VI) exposure can lead to severe damage in the liver, but the preventive measures to diminish Cr(VI)-induced hepatotoxicity need further study. Acid sphingomyelinase (ASMase) is responsible for the production of ceramide via the hydrolysis of sphingomyelin. The present study was designed to investigate effects of desipramine (DES), as an ASMase inhibitor, on Cr(VI)-induced hepatotoxicity. Methods: L-02 hepatocytes were incubated with different concentrations of Cr(VI) for 24h, and ASMase activities and ceramide levels were measured. Moreover, the study investigated the role of DES played in ASMase activities and ceramide levels. Finally, effects of DES on mRNA and protein expressions of the components of mitochondrial permeability transition pore (PTP) and PTP opening were detected. Results: The ASMase activities and ceramide contents increased in L-02 hepatocytes treated with Cr(VI). The results demonstrated that apoptosis rates, ASMase activities and ceramide content decreased in groups treated with the combination of DES and Cr(VI) compared to Cr(VI) groups. Furthermore, DES inhibited Cr(VI)-induced mitochondrial PTP opening by intervening the mRNA and protein expressions of the components of mitochondrial PTP. Conclusions: DES may exert protective effects on Cr(VI)-induced hepatocellular apoptosis probably by inhibiting ceramide channel formation and mitochondrial PTP opening. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Sphingolipids are components of the lipid rafts in plasma membranes, which are important for proper function of podocytes, a key element of the glomerular filtration barrier. Research revealed an essential role of sphingolipids and sphingolipid metabolites in glomerular disorders of genetic and non-genetic origin. The discovery that glucocerebrosides accumulate in Gaucher disease in glomerular cells and are associated with clinical proteinuria initiated intensive research into the function of other sphingolipids in glomerular disorders. The accumulation of sphingolipids in other genetic diseases including Tay-Sachs, Sandhoff, Fabry, hereditary inclusion body myopathy 2, Niemann-Pick, and nephrotic syndrome of the Finnish type and its implications with respect to glomerular pathology will be discussed. Similarly, sphingolipid accumulation occurs in glomerular diseases of non-genetic origin including diabetic kidney disease (DKD), HIV-associated nephropathy, focal segmental glomerulosclerosis (FSGS), and lupus nephritis. Sphingomyelin metabolites, such as ceramide, sphingosine, and sphingosine-1-phosphate have also gained tremendous interest. We recently described that sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is expressed in podocytes where it modulates acid sphingomyelinase activity and acts as a master modulator of danger signaling. Decreased SMPDL3b expression in postreperfusion kidney biopsies from transplant recipients with idiopathic FSGS correlates with the recurrence of proteinuria in patients and in experimental models of xenotransplantation. Increased SMPDL3b expression is associated with DKD. The consequences of differential SMPDL3b expression in podocytes in these diseases with respect to their pathogenesis will be discussed. Finally, the role of sphingolipids in the formation of lipid rafts in podocytes and their contribution to the maintenance of a functional slit diaphragm in the glomerulus will be discussed. [ABSTRACT FROM AUTHOR]

Abstract: NSMase2 is associated to the plasma membrane, whereas ASMase is predominantly lysosomal; both hydrolyze sphingomyelin (SM) to ceramide and phosphocholine. Although SM accumulated in both ASMase−/− and fro/fro (NSMase2−/−) fibroblasts, the reduction of ceramides was more dramatic in fro/fro cells. ASMase mRNA, protein and enzyme activity were substantially elevated in fro/fro fibroblasts. In contrast, NSMase2 activity was unaffected in ASMase−/− fibroblasts. ASMase−/− cells showed normal cell cycling whereas fro/fro cells grew slowly and were arrested in G1/G0 and could be corrected by transfection with smpd3 gene. This suggests two distinct subcellular pathways for SM catabolism with distinct functions. [Copyright &y& Elsevier]

Abstract: Recent evidence suggests that ceramide regulates stress signaling via reorganization of the plasma membrane. The focus of this review will be to discuss the mechanism by which acid sphingomyelinase (ASMase)-generated ceramide initiates transmembrane signaling in the plasma membrane exoplasmic leaflet. In particular, we review the unique biophysical properties of ceramide that render it proficient in formation of signaling domains termed ceramide-rich platforms (CRPs), and the role of CRPs in the pathophysiology of various diseases. The biomedical significance of CRPs makes these structures an attractive therapeutic target. [Copyright &y& Elsevier]

Aging is associated with a decline in muscle force that exceeds loss of muscle mass, suggesting that factors other than sarcopenia affect age-related muscle weakness. Here, we investigate in situ muscle force and sarcoplasmic reticulum (SR) properties in gastrocnemius muscles of adult (6-8 months) and aged (24 months) rats. Despite minimal loss of muscle mass, peak tetanic force was significantly reduced (-28%) in aged muscles. Adjusting for differences in muscle cross-sectional area mitigated the age difference (-23%), but it remained significant. The SR calcium release function was also impaired (-17%) with aging, although calcium uptake was not, and SR-associated glycogen increased (+30%) with aging. Western blotting revealed age related increases in Grp78, serinepalmitoyltransferase and neutral sphingomyelinase, suggesting that age increased the stress response and ceramide metabolism in the SR. In contrast Parkin, a protein associated with autophagic signaling, was reduced in the aged SR. These findings are consistent with a hypothesis that age-related impairments of the SR, possibly due to impaired autophagy and/or altered membrane metabolism, contribute to age-related muscle weakness, independent of changes in muscle mass., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background & Aims: The pathogenesis of alcohol-induced liver disease (ALD) is poorly understood. Here, we examined the role of acid sphingomyelinase (ASMase) in alcohol induced hepatic endoplasmic reticulum (ER) stress, a key mechanism of ALD., Methods: We examined ER stress, lipogenesis, hyperhomocysteinemia, mitochondrial cholesterol (mChol) trafficking and susceptibility to LPS and concanavalin-A in ASMase(-)(/-) mice fed alcohol., Results: Alcohol feeding increased SREBP-1c, DGAT-2, and FAS mRNA in ASMase(+/+) but not in ASMase(-/-) mice. Compared to ASMase(+/+) mice, ASMase(-/-) mice exhibited decreased expression of ER stress markers induced by alcohol, but the level of tunicamycin-mediated upregulation of ER stress markers and steatosis was similar in both types of mice. The increase in homocysteine levels induced by alcohol feeding was comparable in both ASMase(+/+) and ASMase(-/-) mice. Exogenous ASMase, but not neutral SMase, induced ER stress by perturbing ER Ca(2+) homeostasis. Moreover, alcohol-induced mChol loading and StARD1 overexpression were blunted in ASMase(-/-) mice. Tunicamycin upregulated StARD1 expression and this outcome was abrogated by tauroursodeoxycholic acid. Alcohol-induced liver injury and sensitization to LPS and concanavalin-A were prevented in ASMase(-/-) mice. These effects were reproduced in alcohol-fed TNFR1/R2(-/-) mice. Moreover, ASMase does not impair hepatic regeneration following partial hepatectomy. Of relevance, liver samples from patients with alcoholic hepatitis exhibited increased expression of ASMase, StARD1, and ER stress markers., Conclusions: Our data indicate that ASMase is critical for alcohol-induced ER stress, and provide a rationale for further clinical investigation in ALD., (Copyright © 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Inflammation can be either beneficial or detrimental to the liver, depending on multiple factors. Mild (i.e., limited in intensity and destined to resolve) inflammatory responses have indeed been shown to exert consistent hepatoprotective effects, contributing to tissue repair and promoting the re-establishment of homeostasis. Conversely, excessive (i.e., disproportionate in intensity and permanent) inflammation may induce a massive loss of hepatocytes and hence exacerbate the severity of various hepatic conditions, including ischemia-reperfusion injury, systemic metabolic alterations (e.g., obesity, diabetes, non-alcoholic fatty liver disorders), alcoholic hepatitis, intoxication by xenobiotics and infection, de facto being associated with irreversible liver damage, fibrosis, and carcinogenesis. Both liver-resident cells (e.g., Kupffer cells, hepatic stellate cells, sinusoidal endothelial cells) and cells that are recruited in response to injury (e.g., monocytes, macrophages, dendritic cells, natural killer cells) emit pro-inflammatory signals including - but not limited to - cytokines, chemokines, lipid messengers, and reactive oxygen species that contribute to the apoptotic or necrotic demise of hepatocytes. In turn, dying hepatocytes release damage-associated molecular patterns that-upon binding to evolutionary conserved pattern recognition receptors-activate cells of the innate immune system to further stimulate inflammatory responses, hence establishing a highly hepatotoxic feedforward cycle of inflammation and cell death. In this review, we discuss the cellular and molecular mechanisms that account for the most deleterious effect of hepatic inflammation at the cellular level, that is, the initiation of a massive cell death response among hepatocytes., (Copyright © 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)