Melatonin elicits protective effects on OGD/R‑insulted H9c2 cells by activating PGC‑1α/Nrf2 signaling

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

DT-010 Exerts Cardioprotective Effects by Regulating the Crosstalk between the AMPK/PGC-1α Pathway and ERp57

The AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) pathway performs a crucial role in energy metabolism and mitochondrial network. Our previous study found that DT-010, a novel danshensu (DSS) and tetramethylpyrazine (TMP) conjugate, had significant cardioprotective properties in vitro and in vivo. We also reported that ERp57 served as a major target of DSS using the chemical proteomics approach. In this article, we focus on exploring the interrelationship between the regulation of the AMPK/PGC-1α pathway and promoting ERp57 expression induced by DT-010 in tert-butylhydroperoxide- (t-BHP-) induced H9c2 cell injury. The results showed that DT-010 activated the AMPK/PGC-1α pathway and increased ERp57 protein expression. Importantly, the above phenomenon as well as the mitochondrial function can be partially reversed by siRNA-mediated ERp57 suppression. Meanwhile, silencing AMPK significantly inhibited the ERp57 expression induced by DT-010. In addition, molecular docking and kinase assay in vitro revealed that DT-010 had no direct regulation effects on AMPK activity. Taken together, DT-010 exerted cardioprotective effects by regulating the crosstalk of AMPK/PGC-1α pathway and ERp57, representing a potential therapeutic agent for ischemic heart disease.

Oxygen-Glucose Deprivation/Reperfusion-Induced Sirt3 Reduction Facilitated Neuronal Injuries in an Apoptosis-Dependent Manner During Prolonged Reperfusion

Cerebral ischemia is a major cause of morbidity and permanent disability. To date, no treatments for cerebral ischemia/reperfusion injury can be effectively administered beyond 4-6 h after the ischemic insult. Our study aimed to clarify the significance of Sirt3 during acute cerebral ischemia and explore Sirt3-targeted therapy for ischemic injuries. Upon establishing the oxygen-glucose deprivation/reperfusion (OGD/R) cell model, changes of Sirt3 protein levels and the effects of Sirt3 overexpression on primary hippocampal neurons were detected at indicated time points. Moreover, mitochondrial damage was observed in neurons upon OGD/R injury. The results showed that compared with the normoxia group, Sirt3 protein was significantly decreased in hippocampal neurons exposed to 1 h of OGD followed by 12 h of reperfusion. In addition, the reduction of Sirt3 protein levels contributed to OGD/R-induced neuronal injuries, a higher ratio of neuronal apoptosis, and extensive production of reactive oxygen species (ROS). However, all neuronal injuries were partly rescued by Sirt3 overexpression induced by lentivirus transfection. Mitochondrial morphologies were significantly impaired after OGD/R, but partly salvaged by Sirt3 overexpression. We further explored whether pharmacologically activating Sirt3 is protective for neurons, and found that treatment with honokiol (a Sirt3 agonist) after OGD exposure activated Sirt3 during reperfusion and significantly alleviated OGD/R-induced neuronal injuries. Because mitochondrial functions are essential for neuronal survival, the current results indicate that Sirt3 may be an efficient target to suppress ischemic injuries via maintenance of mitochondrial homeostasis. Our current findings shed light on a novel therapeutic strategy against subacute ischemic injuries.

Quercetin Protects H9c2 Cardiomyocytes against Oxygen-Glucose Deprivation/Reoxygenation-Induced Oxidative Stress and Mitochondrial Apoptosis by Regulating the ERK1/2/DRP1 Signaling Pathway

Reperfusion of blood flow during ischemic myocardium resuscitation induces ischemia/reperfusion (I/R) injury. Oxidative stress has been identified as a major cause in this process. Quercetin (QCT) is a member of the flavonoid family that exerts antioxidant effects. The aim of this study was to investigate the preventive effects of QCT on I/R injury and its underlying mechanism. To this end, H9c2 cardiomyocytes were treated with different concentrations of QCT (10, 20, and 40 μM) and subsequently subjected to oxygen-glucose deprivation/reperfusion (OGD/R) administration. The results indicated that OGD/R-induced oxidative stress, apoptosis, and mitochondrial dysfunction in H9c2 cardiomyocytes were aggravated following 40 μM QCT treatment and alleviated following the administration of 10 and 20 μM QCT prior to OGD/R treatment. In addition, OGD/R treatment inactivated ERK1/2 signaling activation. The effect was mitigated using 10 and 20 μM QCT prior to OGD/R treatment. In conclusion, these results suggested that low concentrations of QCT might alleviate I/R injury by suppressing oxidative stress and improving mitochondrial function through the regulation of ERK1/2-DRP1 signaling, providing a potential candidate for I/R injury prevention.

Melatonin reshapes the mitochondrial network and promotes intercellular mitochondrial transfer via tunneling nanotubes after ischemic-like injury in hippocampal HT22 cells

Mitochondrial dysfunction is considered one of the hallmarks of ischemia/reperfusion injury. Mitochondria are plastic organelles that undergo continuous biogenesis, fusion, and fission. They can be transferred between cells through tunneling nanotubes (TNTs), dynamic structures that allow the exchange of proteins, soluble molecules, and organelles. Maintaining mitochondrial dynamics is crucial to cell function and survival. The present study aimed to assess the effects of melatonin on mitochondrial dynamics, TNT formation, and mitochondria transfer in HT22 cells exposed to oxygen/glucose deprivation followed by reoxygenation (OGD/R). The results showed that melatonin treatment during the reoxygenation phase reduced mitochondrial reactive oxygen species (ROS) production, improved cell viability, and increased the expression of PGC1α and SIRT3. Melatonin also preserved the expression of the membrane translocase proteins TOM20 and TIM23, and of the matrix protein HSP60, which are involved in mitochondrial biogenesis. Moreover, it promoted mitochondrial fusion and enhanced the expression of MFN2 and OPA1. Remarkably, melatonin also fostered mitochondrial transfer between injured HT22 cells through TNT connections. These results provide new insights into the effect of melatonin on mitochondrial network reshaping and cell survival. Fostering TNTs formation represents a novel mechanism mediating the protective effect of melatonin in ischemia/reperfusion injury.

Macrophages induce the expression of lncRNA ATB via the secretion of TGF-β to relieve ischemia-reperfusion injury in cardiomyocytes

Cardiac ischemia-reperfusion can cause severe damage to cardiomyocytes. Previous studies have revealed that TGF-β can alleviate ischemia-reperfusion injury in cardiomyocytes by inducing the expression of long non-coding RNA (lncRNA) activated by TGF-β (ATB). However, M2 macrophages can secrete a large amount of TGF-β. However, whether M2 macrophages alleviate the ischemia-reperfusion-induced injury of cardiomyocytes by secreting TGF-β is unclear. In the present study, macrophages and cardiomyocytes were cultured under oxygen-glucose deprivation/reoxygenation (OGD/R) conditions to simulate ischemia-reperfusion injury. M2-type macrophage markers (IL-10, Arginase-1 and IL-13) were validated using reverse transcription-quantitative PCR and western blotting. Subsequently, the culture medium of M2-type macrophages was collected for the treatment of cardiomyocytes, which were cultured under OGD/R conditions. The levels of inflammatory factors and oxidase enzymes were detected with ELISA. The apoptotic rates of cardiomyocytes were detected by flow cytometry. The expression of cell apoptosis-related proteins and the phosphorylation levels of NF-κB were analyzed by western blotting. The expression levels of specific inflammatory cytokines and the levels of malondialdehyde and lactate dehydrogenase were suppressed in cardiomyocytes following treatment with culture medium derived from M2-type macrophages, which were cultured under OGD/R conditions. Furthermore, OGD/R-induced apoptosis of cardiomyocytes was also relieved following treatment of the cells with macrophage medium. It was found that M2-type macrophages could secrete TGF-β and that the culture medium of M2-type macrophages could activate the expression of lncRNA ATB in cardiomyocytes. TGF-β secreted by M2 macrophages relieved the inflammatory response, oxidative stress and apoptosis of cardiomyocytes by inducing the expression of lncRNA ATB.

Melatonin Act as an Antidepressant via Attenuation of Neuroinflammation by Targeting Sirt1/Nrf2/HO-1 Signaling

Physical or psychological stress can cause an immunologic imbalance that disturbs the central nervous system followed by neuroinflammation. The association between inflammation and depression has been widely studied in recent years, though the molecular mechanism is still largely unknown. Thus, targeting the signaling pathways that link stress to neuroinflammation might be a useful strategy against depression. The current study investigated the protective effect of melatonin against lipopolysaccharide (LPS)-induced neuroinflammation and depression. Our results showed that LPS treatment significantly induced depressive-like behavior in mice. Moreover, LPS-treatment enhanced oxidative stress, pro-inflammatory cytokines including TNFα, IL-6, and IL-1β, NF-κB phosphorylation, and glial cell activation markers including GFAP and Iba-1 in the brain of mice. Melatonin treatment significantly abolished the effect of LPS, as indicated by improved depressive-like behaviors, reduced cytokines level, reduced oxidative stress, and normalized LPS-altered Sirt1, Nrf2, and HO-1 expression. However, the melatonin protective effects were reduced after luzindole administration. Collectively, it is concluded that melatonin receptor-dependently protects against LPS-induced depressive-like behaviors via counteracting LPS-induced neuroinflammation.