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The dysfunction of type II alveolar epithelial cells (AECIIs), mainly manifested by apoptosis, has emerged as a major component of idiopathic pulmonary fibrosis (IPF) pathophysiology. A pivotal mechanism leading to AECIIs apoptosis is mitochondrial dysfunction. Recently, interleukin (IL)‐17A has been demonstrated to have a pro‐fibrotic role in IPF, though the mechanism is unclear. In this study, we report enhanced expression of IL‐17 receptor A (IL‐17RA) in AECIIs in lung samples of IPF patients, which may be related to the accumulation of mitochondria in AECIIs of IPF. Next, we investigated this relationship in bleomycin (BLM)‐induced PF murine model. We found that IL‐17A knockout (IL‐17A−/−) mice exhibited decreased apoptosis levels of AECIIs. This was possibly a result of the recovery of mitochondrial morphology from the improved mitochondrial dynamics of AECIIs, which eventually contributed to alleviating lung fibrosis. Analysis of in vitro data indicates that IL‐17A impairs mitochondrial function and mitochondrial dynamics of mouse primary AECIIs, further promoting apoptosis. PTEN‐induced putative kinase 1 (PINK1)/Parkin signal‐mediated mitophagy is an important aspect of mitochondria homeostasis maintenance. Our data demonstrate that IL‐17A inhibits mitophagy and promotes apoptosis of AECIIs by decreasing the expression levels of PINK1. We conclude that IL‐17A exerts its pro‐fibrotic effects by inducing mitochondrial dysfunction in AECIIs by disturbing mitochondrial dynamics and inhibiting PINK1‐mediated mitophagy, thereby leading to apoptosis of AECIIs.

The present study aimed to explore how semaglutide can help protect the heart from injury caused by hypoxia/reoxygenation (H/R) and to reveal the underlying mechanism. Briefly, AC16 cardiomyocytes were subjected to 8 h of hypoxia followed by 12 h of reoxygenation to simulate H/R. The cells were divided into the following five groups: Normoxia, H/R, H/R + semaglutide, H/R + semaglutide + rapamycin (autophagy inducer), and H/R + semaglutide + 3-methyladenine (3-MA; autophagy inhibitor) groups. Cell viability was examined using a Cell Counting Kit-8 assay, ATP levels were examined using a bioluminescent detection kit, reactive oxygen species (ROS) production was detected using a ROS Assay Kit, and monomeric red fluorescent protein (mRFP)-green fluorescent protein (GFP)-LC3 was assessed using tandem mRFP-GFP fluorescence microscopy, while autophagosomes were observed using transmission electron microscopy. Furthermore, the protein expression levels of autophagy markers (LC3, p62 and Beclin1) and regulators of mitochondrial autophagy [PTEN-induced putative kinase protein-1 (PINK1) and Parkin] were examined using western blot analysis. In AC16 cells, exposure to hypoxia followed by reoxygenation led to an increase in oxidative stress. This condition also induced an increase in autophagy activity, as evidenced by an increase in the number of autophagosomes, elevated LC3-II/LC3-I ratio, and upregulation of p62, Beclin1, PINK1 and Parkin expression compared with those in cells cultured under normoxia. Notably, treatment with semaglutide or rapamycin effectively reversed the H/R-induced oxidative stress, enhanced the changes in autophagy activity, autophagosome levels and elevated LC3BII/LC3BI ratio, and increased the expression levels of Beclin1, PINK1, Parkin and p62 expression. Notably, the use of 3-MA exhibited distinct effects under the same conditions; it exacerbated oxidative stress, decreased autophagy activity and reduced the LC3BII/LC3BI ratio. In conclusion, semaglutide was found to reduce oxidative stress caused by H/R and to increase autophagy via the ROS/PINK1/Parkin/p62 pathway. The present study offers a novel understanding of how semaglutide may protect the heart, and suggests its potential use in the treatment of myocardial ischemia/reperfusion injury.

Background Dysregulation of both mitochondrial biogenesis and mitophagy is critical to sustain oncogenic signaling pathways. However, the mechanism of mitophagy in promoting hepatocellular carcinoma (HCC) progression remains poorly understood. In this study, we investigated the clinical significance and biological involvement of mitochondrial inner membrane protein STOML2 in HCC. Methods STOML2 was identified by gene expression profiles of HCC tissues and was measured in tissue microarray and cell lines. Gain/loss-of-function experiment was applied to study the biological function of STOML2 in HCC. Flow cytometry, Western blotting, laser confocal microscopy, transmission electron microscopy, and co-immunoprecipitation were used to detect and analyze mitophagy. ChIP and luciferase reporter assay were conducted to evaluate the relationship between STOML2 and HIF-1α. The sensitivity to lenvatinib was assessed in HCC both in vitro and in vivo. Results Increased expression of STOML2 was found in HCC compared with paired peritumoral tissues. It was more significant in HCC with metastasis and correlated with worse overall survival and higher probability of recurrence after hepatectomy. Upregulation of STOML2 accelerated HCC cells colony formation, migration and invasion. Mechanically, TCGA dataset-based analysis showed enrichment of autophagy-related pathways in STOML2 highly-expressed HCC. Next, STOML2 was demonstrated to interact and stabilize PINK1 under cellular stress, amplify PINK1-Parkin-mediated mitophagy and then promote HCC growth and metastasis. Most interestingly, HIF-1α was upregulated and transcriptionally increased STOML2 expression in HCC cells under the treatment of lenvatinib. Furthermore, higher sensitivity to lenvatinib was found in HCC cells when STOML2 was downregulated. Combination therapy with lenvatinib and mitophagy inhibitor hydroxychloroquine obtained best efficacy. Conclusions Our findings suggested that STOML2 could amplify mitophagy through interacting and stabilizing PINK1, which promote HCC metastasis and modulate the response of HCC to lenvatinib. Combinations of pharmacologic inhibitors that concurrently block both angiogenesis and mitophagy may serve as an effective treatment for HCC.

AbstractDendritic cells (DCs) are vital antigen-presenting cells (APCs) in the immune system, whose apoptosis is closely related to the development of sepsis. Mitophagy is one of the necessary forms of selective autophagy that removes damaged or dysfunctional mitochondria to regulate immunity and inflammation. However, its effect on the apoptosis of DC in sepsis remains unknown. Here, we showed that sepsis activated the apoptosis and mitophagy of DC, and mitophagy had an anti-apoptotic effect on sepsis-induced DC apoptosis. In this study, we used cecal ligation and puncture (CLP) to simulate the pathophysiological state of sepsis. Apoptosis and mitophagy of DC were significantly enhanced in CLP mice compared with controls, and in the Pink1-KO (Pink1-knockout) mice CLP model, the level of apoptosis in DC was further increased while the level of mitophagy was decreased. In addition, more severe mitochondrial dysfunction was exhibited in DC of Pink1-KO mice CLP model compared to wild-type (WT) mice. The results suggest that Pink1/Parkin-mediated mitophagy is activated during sepsis and has an anti-apoptotic effect on DC, which regulates immune functions.

Melatonin (N-acetyl-5-methoxytryptamine; MT) has been shown to have a protective effect against sepsis-induced renal injury, however, the mechanisms underlying the function of MT remain to be elucidated. Therefore, in the present study, the potential mechanisms underlying the preventive role of MT in sepsis-induced renal injury were investigated. Hematoxylin and eosin staining was used to detect the effect of MT on the reduction of renal tissue damage, and immunohistochemistry (IHC), ELISA and western blot analysis were performed to determine the influence of MT on the protein expression of PTEN-induced putative kinase 1 (PINK1), nucleotide-oligomerization binding domain and leucine-rich repeat pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC1), interleukin (IL)-18, IL-1β, IL-6 and cleaved caspase-1. Finally, a TUNEL assay was used to compare the rate of apoptosis of renal tissues among the sham, cecal ligation and puncture (CLP), and CLP + MT groups. The extent of tissue damage in the CLP group was the highest and the extent of tissue damage in the sham group was the lowest. The IHC and western blot analysis showed that the sham group had the highest protein level of PINK1, whereas the CLP group had the lowest protein level of PINK1. By contrast, the sham group had the lowest protein level of NLRP, whereas the CLP group had the highest level of NLRP3. Furthermore, CLP treatment enhanced the protein expression of ASC1 and cleaved caspase-1, whereas the administration of MT reduced the protein expression of ASC1 and cleaved caspase-1 to a certain degree. Finally, the apoptotic rate was found to be the highest in the CLP group and the lowest in the sham group. Taken together, in evaluating the therapeutic effect of MT on sepsis-induced renal injury, the results of the present study showed that MT alleviated sepsis-induced renal injury by regulating the expression of PINK1, Parkin1, NLRP3, ASC and cleaved caspase-1 in rats.

ABSTRACT Background Mer tyrosine kinase (Mertk) regulating mitochondrial function of liver sinusoidal endothelial cells (LSECs) in metabolic dysfunction‐associated steatohepatitis (MASH) remains unclear. Methods Mertk/p‐Mertk, PINK1, and ERK/p‐ERK expression in steatotic LSECs and livers of MASH mice were studied. Mitochondrial functions were assessed via immunofluorescence, Western blot, and qPCR. C‐Kit+‐bone marrow cells (BMCs)sh‐Mertk were bone marrow transplanted (BMT) to MASH mice to evaluate its effect. Results Ov‐Mertk would markedly stimulate ERK, and ERK further suppress downstream PINK1. Higher levels of Mertk/p‐Mertk and lower levels of PINK1 were confirmed in steatotic LSECs and MASH mice livers. Steatotic LSECssh‐Mertk exhibited intact mitophagy, integral mitochondrial membrane potential, reduced reactive oxygen productions and upregulation of the PINK1 pathway. BMT of C‐Kit+‐BMCssh‐Mertk could equivalently protect mitochondrial functions and ameliorate lipid accumulation in MASH mice. Conclusion Mertk negatively regulates PINK1‐mediated mitophagy in LSECs through the p‐ERK signaling pathway, thereby accelerating MASH progression. Therefore, LSECs deficient of Mertk should be a novel therapy for reversing PINK1‐related mitophagy and MASH.

With overall food intake among the general population as high as ever, metabolic syndrome (MetS) has become a global epidemic and is responsible for many serious lifethreatening diseases, especially heart failure. In multiple metabolic disorders, maintaining a dynamic balance of mitochondrial number and function is necessary to prevent the overproduction of reactive oxygen species (ROS), which has been proved to be one of the important mechanisms of cardiomyocyte injury due to the mismatching of oxygen consumption and mitochondrial population and finally to heart failure. Mitophagy is a process that eliminates damaged or redundant mitochondria. It is mediated by a series of signaling molecules, including PINK, parkin, BINP3, FUNDC1, CTSD, Drp1, Rab9 and mTOR. Meanwhile, increasing evidence also showed that the interaction between ferroptosis and mitophagy interfered with mitochondrial homeostasis. This review will focus on these essential molecules and pathways of mitophagy and cell homeostasis affected by hypoxia and other stimuli in metabolic heart diseases. Keywords: mitophagy, metabolic heart diseases, metabolic syndrome, PTEN induced putative kinase, PINK, parkin, Bcl-2/E1B19kDa-interacting protein, BNIP3, FUN14 domaincontaining protein 1, FUNDC1, ferroptosis

Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) is a gatekeeper of mitochondrial quality control. The present study was aimed to examine whether PINK1 possesses a protective function against gentamicin (GM)-induced sensory hair cell (HC) damage . The formation of parkin particles (a marker revealing the activation of PINK1 pathway which is a substrate of PINK1 and could signal depolarized mitochondria for clearance) and autophagy were determined by immunofluorescence staining. The expressions of PINK1, LC3B, cleaved-caspase 3 and p53 were measured by Western blotting. The levels of reactive oxygen species (ROS) and apoptosis were respectively evaluated by DCFH-DA staining, Annexin V Apoptosis Detection Kit and TUNEL staining. Cell viability was tested by a CCK8 kit. We found that treatment of 400 μM GM elicited the formation of ROS, which, in turn, led to PINK1 degradation, parkin recruitment, autophagy formation, an increase of p53 and cleaved-caspase 3 in HEI-OC1 cells and murine HCs. In contrast, co-treatment with ROS scavenger N-acetyl-L-cysteine (NAC) inhibited parkin recruitment, alleviated autophagy and p53 pathway-related damaged-cell elimination. Moreover, PINK1 interference contributed to a decrease of autophagy but an increase of p53 level in HEI-OC1 cells in response to GM stimulus. Findings from this work indicate that PINK1 alleviates the GM-elicited ototoxicity via induction of autophagy and resistance the increase of p53 in HCs.

The PTEN induced putative kinase 1 (PINK1) mutation is the second most common cause of autosomal recessive adolescent Parkinson's disease (PD). Furthermore, mitochondrial disorders and oxidative stress are important mechanisms in the pathogenesis of PD. Numerous members of the Wnt family have been found to be associated with neurodegenerative diseases. Therefore, the present study investigated the role of the Wnt2 gene in PINK1B9 transgenic flies, which is a PD model, and its underlying mechanism. It was identified that overexpression of Wnt2 reduced the abnormality rate of PD transgenic Drosophila and improved their flight ability, while other intervention groups had no significant effect. Furthermore, an increase in ATP concentration normalized mitochondrial morphology, and increased the mRNA expression levels of NADH-ubiquinone oxidoreductase chain 1 (ND1), ND42, ND75, succinate dehydrogenase complex subunits B, Cytochrome b and Cyclooxygenase 1, which are associated with Wnt2 overexpression. Moreover, overexpression of Wnt2 in PD transgenic Drosophila resulted in the downregulation of reactive oxygen species and malondialdehyde production, and increased manganese superoxide dismutase (MnSOD), while glutathione was not significantly affected. It was found that overexpression of Wnt2 did not alter the protein expression of β-catenin in PINK1B9 transgenic Drosophila, but did increase the expression levels of PPARG coactivator 1α (PGC-1α) and forkhead box sub-group O (FOXO). Collectively, the present results indicated that the Wnt2 gene may have a protective effect on PD PINK1B9 transgenic Drosophila. Thus, it was speculated that the reduction of oxidative stress and the restoration of mitochondrial function via Wnt2 overexpression may be related to the PGC-1α/FOXO/MnSOD signaling pathway in PINK1 mutant transgenic Drosophila.

Mitophagy mediated by the recessive Parkinson’s disease genes PINK1 and Parkin responds to mitochondrial damage to preserve mitochondrial function. In the pathway, PINK1 is the damage sensor, probing the integrity of the mitochondrial import pathway, and activating Parkin when import is blocked. Parkin is the effector, selectively marking damaged mitochondria with ubiquitin for mitophagy and other quality-control processes. This selective mitochondrial quality-control pathway may be especially critical for dopamine neurons affected in Parkinson’s disease, in which the mitochondrial network is widely distributed throughout a highly branched axonal arbor. Here we review the current understanding of the role of PINK1–Parkin in the quality control of mitophagy, including sensing of mitochondrial distress by PINK1, activation of Parkin by PINK1 to induce mitophagy, and the physiological relevance of the PINK1–Parkin pathway. Narendra and Youle review the current understanding of the role of PINK1–Parkin in the quality control of mitophagy, highlighting the underlying mechanisms and physiological relevance of the pathway, as well as its role in neuroprotection.