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Objective To investigate the protective effect and possible mechanism of type Ⅱ alveolar epithelial cells (AEC-Ⅱ)-derived exosomal (Exos)-miR-21-5p (miR-21) on the regulation of epithelial sodium channels (ENaC) in hyperoxia-induced acute lung injury (HALI). Methods Sixty male C57BL/6J mice (6-8 weeks old) were subjected, and 20 of them were used to isolate AEC-Ⅱ using differential wall centrifugation, which were further cultured extract derived exosomes with density gradient centrifugation. Transmission electron microscopy was employed to identify the morphology of obtained exosomes. The 40 remaining mice were randomly divided into (n=10): normoxia (Control), hyperoxia (HALI), hyperoxia+Exo-miR-21 (HALI+miR-21), and hyperoxia+siPI3K+miR-21 groups. Except for the Control group, the other 3 groups were exposed to self-made hyperoxia chamber containing 95%O2 to establish rat model of HALI. In 72 h after exposure, RT-qPCR was performed to detect the miR-21 expression in lung tissue and in AEC-Ⅱ-derived exosomes. HE staining was performed to observe morphological changes in lung tissue and to score the pathology of lung injury, and the wet/dry mass ratio of lung tissue and alveolar fluid clearance (AFC) were calculated. Superoxide dismutase (SOD), malondialdehyde (MDA) and total antioxidant capacity (T-AOC) were measured by visible spectrophotometry. The levels of reactive oxygen species (ROS) were measured by fluorescence spectrophotometry. The protein levels PTEN, AKT, p-AKT, PI3K and α-ENaC, β-ENaC, γ-ENaC were detected by Western blotting. Dual luciferase reporter gene assay was conducted to verify the relationship between miR-21 and PTEN targeting. Results The vesicular material extracted from primary cultured AEC-Ⅱ was identified as exosomes, the expression level of miR-21 was significantly increased in the exosomes (P < 0.05), and PTEN was identified as the target gene of miR-21. Compared with the mice of the Control group, thickening pulmonary septum, massive infiltration of inflammatory cells and alveolar atrophy were observed, and pathological score of lung injury, lung wet/dry mass ratio, and protein levels of MDA and PTEN were elevated in the the HALI group, HALI+miR-21 group and HALI+siPI3K+miR-21 group (P < 0.05). The protein expression levels of SOD, T-AOC, AFC, miR-21 and p-Akt, α-ENaC, β-ENaC, γ-ENaC were reduced in the above 3 groups (P < 0.05), significantly in the HALI+siPI3K+miR-21 group. HE staining showed that no significant differences in thickening of pulmonary septum and inflammatory cell infiltration were observed between the HALI+miR-21 group and the HALI group, but milder alveolar atrophy was seen in the former group. What's more, the former group also got obviously reduced pathological score of lung injury, lower lung wet/dry mass ratio, and decreased MDA and PTEN expression (P < 0.05), but increased protein levels of SOD, T-AOC, AFC, miR-21 and p-Akt, α-ENaC, β-ENaC, γ-ENaC (P < 0.05) when compared with the latter group. Conclusion Exosomal miR-21 derived from AEC-Ⅱ targets PTEN to activate PI3K/AKT signaling pathway, and attenuates hyperoxic acute lung injury by regulating epithelial sodium channels. [Key words] type Ⅱ alveolar epithelial cells , exosomes , microRNA-21-5p, epithelial sodium channels , hyperoxic acute lung injury , PI3K/Akt signaling pathway ,

ALI(acute lung injury) is a severe respiratory dysfunction caused by various intrapulmonary and extrapulmonary factors. It is primarily characterized by oxidative stress and affects the integrity of the pulmonary barrier. In severe cases, ALI can progress to ARDS(acute respiratory distress syndrome), a condition that poses a serious threat to the lives of affected patients. To date, the etiological mechanisms underlying ALI remain elusive, and available therapeutic options are quite limited. AMPK(AMP-activated protein kinase), an essential serine/threonine protein kinase, performs a pivotal function in the regulation of cellular energy levels and cellular regulatory mechanisms, including the detection of redox signals and mitigating oxidative stress. Meanwhile, Nrf2(nuclear factor erythroid 2-related factor 2), a critical transcription factor, alleviates inflammation and oxidative responses by interacting with multiple signaling pathways and contributing to the modulation of oxidative enzymes associated with inflammation and programmed cell death. Indeed, AMPK induces the dissociation of Nrf2 from Keap1(kelch-like ECH-associated protein-1) and facilitates its translocation into the nucleus to trigger the transcription of downstream antioxidant genes, ultimately suppressing the expression of inflammatory cells in the lungs. Given their roles, AMPK and Nrf2 hold promise as novel treatment targets for ALI. This study aimed to summarise the current status of research on the AMPK/Nrf2 signaling pathway in ALI, encompassing recently reported natural compounds and drugs that can activate the AMPK/Nrf2 signaling pathway to alleviate lung injury, and provide a theoretical reference for early intervention in lung injury and future research on lung protection. [ABSTRACT FROM AUTHOR]

Oxygen therapy is a crucial medical intervention, but it is undeniable that it can lead to lung damage. The mTOR pathway plays a pivotal role in governing cell survival, including autophagy and apoptosis, two phenomena deeply entwined with the evolution of diseases. However, it is unclarified whether the mTOR pathway is involved in hyperoxic acute lung injury (HALI). The current study aims to clarify the molecular mechanism underlying the pathogenesis of HALI by constructing in vitro and in vivo models using H 2 O 2 and hyperoxia exposure, respectively. To investigate the role of mTOR, the experiment was divided into five groups, including normal group, injury group, mTOR inhibitor group, mTOR activator group, and DMSO control group. Western blotting, Autophagy double labeling, TUNEL staining, and HE staining were applied to evaluate protein expression, autophagy activity, cell apoptosis, and pathological changes in lung tissues. Our data revealed that hyperoxia can induce autophagy and apoptosis in Type II alveolar epithelial cell (AECII) isolated from the treated rats, as well as injuries in the rat lung tissues; also, H 2 O 2 stimulation increased autophagy and apoptosis in MLE-12 cells. Noticeably, the experiments performed in both in vitro and in vivo models proved that the mTOR inhibitor Rapamycin (Rapa) functioned synergistically with hyperoxia or H 2 O 2 to promote AECII autophagy, which led to increased apoptosis and exacerbated lung injury. On the contrary, activation of mTOR with MHY1485 suppressed autophagy activity, consequently resulting in reduced apoptosis and lung injury in H 2 O 2 -challenged MLE-12 cells and hyperoxia-exposed rats. In conclusion, hyperoxia caused lung injury via mTOR-mediated AECII autophagy., (© 2023. The Author(s).)

Septic myocardial injury is a common complication of severe sepsis, which occurs in about 50% of cases. Patients with this disease may experience varying degrees of myocardial damage. Annexin-A1 short peptide (ANXA1sp), with a molecular structure of Ac-Gln-Ala-Tyr, has been reported to exert an organ protective effect in the perioperative period by modulating sirtuin-3 (SIRT3). Whether it possesses protective activity against sepsis-induced cardiomyopathy is worthy of study. This study aimed to investigate whether ANXA1sp exerts its anti-apoptotic effect in septic myocardial injury in vitro and in vivo via regulating SIRT3. In this study, we established in vivo and in vivo models of septic myocardial injury based on C57BL/6 mice and primary cardiomyocytes by lipopolysaccharide (LPS) induction. Results showed that ANXA1sp pretreatment enhanced the seven-day survival rate, improved left ventricular ejection fraction (EF), left ventricular fractional shortening (FS), and cardiac output (CO), and reduced the levels of creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), and lactate dehydrogenase (LDH). Western blotting results revealed that ANXA1sp significantly increased the expression of SIRT3, Bcl-2, and downregulated Bax expression. TUNEL staining and flow cytometry results showed that ANXA1sp could attenuate the apoptosis rate of cardiomyocytes, whereas this anti-apoptotic effect was significantly attenuated after SIRT3 knockout. To sum up, ANXA1sp can alleviate LPS-induced myocardial injury by reducing myocardial apoptosis via SIRT3 upregulation., (©The Author(s) 2024. Open Access. This article is licensed under a Creative Commons CC-BY International License.)

Objective: To observe and verify the changes of transcriptome in hyperoxia-induced acute lung injury (HALI), and to further clarify the changes of pathways in HALI., Methods: Twelve healthy male C57BL/6J mice were randomly divided into normoxia group and HALI group according to the random number table, with 6 mice in each group. The mice in the normoxia group were fed normally in the room, and the mice in the HALI group was exposed to 95% oxygen to reproduce the HALI animal model. After 72 hours of hyperoxia exposure, the lung tissues were taken for transcriptome sequencing, and then Kyoto Encyclopedia of Genes and Genomes database (KEGG) pathway enrichment analysis was performed. The pathological changes of lung tissue were observed under light microscope after hematoxylin-eosin (HE) staining. Real-time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were used to verify the key molecules in the signal pathways closely related to HALI identified by transcriptomics analysis., Results: Transcriptomic analysis showed that hyperoxia induced 537 differentially expressed genes in lung tissue of mice as compared with the normoxia group including 239 up-regulated genes and 298 down-regulated genes. Further KEGG pathway enrichment analysis identified 20 most significantly enriched pathway entries, and the top three pathways were ferroptosis signaling pathway, p53 signaling pathway and glutathione (GSH) metabolism signaling pathway. The related genes in the ferroptosis signaling pathway included the up-regulated gene heme oxygenase-1 (HO-1) and the down-regulated gene solute carrier family 7 member 11 (SLC7A11). The related genes in the p53 signaling pathway included the up-regulated gene tumor suppressor gene p53 and the down-regulated gene murine double minute 2 (MDM2). The related gene in the GSH metabolic signaling pathway was up-regulated gene glutaredoxin 1 (Grx1). The light microscope showed that the pulmonary alveolar structure of the normoxia group was normal. In the HALI group, the pulmonary alveolar septum widened and thickened, and the alveolar cavity shrank or disappeared. RT-RCR and Western blotting confirmed that compared with the normoxia group, the mRNA and protein expressions of HO-1 and p53 in lung tissue of the HALI group were significantly increased [HO-1 mRNA (2 -ΔΔCt ): 2.16±0.17 vs. 1.00±0.00, HO-1 protein (HO-1/β-actin): 1.05±0.01 vs. 0.79±0.01, p53 mRNA (2 -ΔΔCt ): 2.52±0.13 vs. 1.00±0.00, p53 protein (p53/β-actin): 1.12±0.02 vs. 0.58±0.03, all P < 0.05], and the mRNA and protein expressions of Grx1, MDM2, SLC7A11 were significantly decreased [Grx1 mRNA (2 -ΔΔCt ): 0.53±0.05 vs. 1.00±0.00, Grx1 protein (Grx1/β-actin): 0.54±0.03 vs. 0.93±0.01, MDM2 mRNA (2 -ΔΔCt ): 0.48±0.03 vs. 1.00±0.00, MDM2 protein (MDM2/β-actin): 0.57±0.02 vs. 1.05±0.01, SLC7A11 mRNA (2 -ΔΔCt ): 0.50±0.06 vs. 1.00±0.00, SLC7A11 protein (SLC7A11/β-actin): 0.72±0.03 vs. 0.98±0.01, all P < 0.05]., Conclusions: HALI is closely related to ferroptosis, p53 and GSH metabolism signaling pathways. Targeting the key targets in ferroptosis, p53 and GSH metabolism signaling pathways may be an important strategy for the prevention and treatment of HALI.

Mitophagy is the selective degradation of damaged mitochondria, and it is of great significance to maintain the normal quantity and quality of mitochondria to ensure cell homeostasis and survival. Necroptosis is a type of programmed cell necrosis that can be induced by excessive mitophagy. Reactive oxygen species (ROS) are produced mainly by mitochondria and can damage mitochondria. Hyperoxic acute lung injury (HALI) is a serious complication of clinical oxygen therapy, and its pathogenesis is not clear. Existing studies have shown that mitophagy and necroptosis are involved in the occurrence of HALI. There are many mechanisms regulating mitophagy and necroptosis, including tumor necrosis factor-α (TNF-α), E3 ubiquitin protein ligase (PINK1/Parkin) protein pathway encoded by PTEN-induced kinase 1/PARK2 gene, phosphoglycerate mutase 5 (PGAM5), etc. PGAM5 has been proved to be a key factor linking mitophagy and necroptosis. Previous studies of our team found that the mechanism of microRNA-21-5p (miR-21-5p) alleviating HALI was related to its pGAM5-mediated inhibition of mitophagy, but the mechanism of PGAM5-mediated mitophagy and necroptosis remains unclear. Therefore, this paper reviews the targets of PGAM5-mediated mitophagy and necroptosis, in order to find clues of lung protection of pGAM5-mediated mitophagy and necroptosis in HALI, and provide theoretical basis for subsequent basic research.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by the destruction of the barrier function of alveolar epithelial cells and capillary endothelial cells and the recruitment of inflammatory cells, which leads to alveolar and interstitial edema, hyaline membrane formation and inflammatory infiltration of the lungs, etc. The mechanism is not completely defined. The current treatment plan focuses on comprehensive treatments such as ventilator support treatment, fluid management, and nutritional support, but the prognosis is still poor. Studies have shown that extracellular vesicle microRNA (miRNA) from different sources participate in regulating the function of epithelial cells, endothelial cells and phagocytes in different ways, thus aggravating or improving ALI, and have diagnostic, differential diagnosis and the therapeutic value. In this article, the mechanism, diagnostic and differerntial value of extracellular vesicle miRNA from different sources in ALI and the therapy of extracellular vesicle miRNA from stem cell in ALI are reviewed.