Polydatin protects cardiomyocytes against myocardial infarction injury by activating Sirt3

Programmed death of cardiomyocytes in cardiovascular disease and new therapeutic approaches

Cardiovascular diseases (CVDs) have a complex pathogenesis and pose a major threat to human health. Cardiomyocytes have a low regenerative capacity, and their death is a key factor in the morbidity and mortality of many CVDs. Cardiomyocyte death can be regulated by specific signaling pathways known as programmed cell death (PCD), including apoptosis, necroptosis, autophagy, pyroptosis, and ferroptosis, etc. Abnormalities in PCD can lead to the development of a variety of cardiovascular diseases, and there are also molecular-level interconnections between different PCD pathways under the same cardiovascular disease model. Currently, the link between programmed cell death in cardiomyocytes and cardiovascular disease is not fully understood. This review describes the molecular mechanisms of programmed death and the impact of cardiomyocyte death on cardiovascular disease development. Emphasis is placed on a summary of drugs and potential therapeutic approaches that can be used to treat cardiovascular disease by targeting and blocking programmed cell death in cardiomyocytes.

Polydatin and Nicotinamide Rescue the Cellular Phenotype of Mitochondrial Diseases by Mitochondrial Unfolded Protein Response (mtUPR) Activation

Primary mitochondrial diseases result from mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA) genes, encoding proteins crucial for mitochondrial structure or function. Given that few disease-specific therapies are available for mitochondrial diseases, novel treatments to reverse mitochondrial dysfunction are necessary. In this work, we explored new therapeutic options in mitochondrial diseases using fibroblasts and induced neurons derived from patients with mutations in the GFM1 gene. This gene encodes the essential mitochondrial translation elongation factor G1 involved in mitochondrial protein synthesis. Due to the severe mitochondrial defect, mutant GFM1 fibroblasts cannot survive in galactose medium, making them an ideal screening model to test the effectiveness of pharmacological compounds. We found that the combination of polydatin and nicotinamide enabled the survival of mutant GFM1 fibroblasts in stress medium. We also demonstrated that polydatin and nicotinamide upregulated the mitochondrial Unfolded Protein Response (mtUPR), especially the SIRT3 pathway. Activation of mtUPR partially restored mitochondrial protein synthesis and expression, as well as improved cellular bioenergetics. Furthermore, we confirmed the positive effect of the treatment in GFM1 mutant induced neurons obtained by direct reprogramming from patient fibroblasts. Overall, we provide compelling evidence that mtUPR activation is a promising therapeutic strategy for GFM1 mutations.

SIRT3: A potential therapeutic target for liver fibrosis

Sirtuin3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase located in the mitochondria, which mainly regulates the acetylation of mitochondrial proteins. In addition, SIRT3 is involved in critical biological processes, including oxidative stress, inflammation, DNA damage, and apoptosis, all of which are closely related to the progression of liver disease. Liver fibrosis characterized by the deposition of extracellular matrix is a result of long termed or repeated liver damage, frequently accompanied by damaged hepatocytes, the recruitment of inflammatory cells, and the activation of hepatic stellate cells. Based on the functions and pharmacology of SIRT3, we will review its roles in liver fibrosis from three aspects: First, the main functions and pharmacological effects of SIRT3 were investigated based on its structure. Second, the roles of SIRT3 in major cells in the liver were summarized to reveal its mechanism in developing liver fibrosis. Last, drugs that regulate SIRT3 to prevent and treat liver fibrosis were discussed. In conclusion, exploring the pharmacological effects of SIRT3, especially in the liver, may be a potential strategy for treating liver fibrosis.

SIRT3 Activation a Promise in Drug Development? New Insights into SIRT3 Biology and Its Implications on the Drug Discovery Process

Sirtuins catalyze deacetylation of lysine residues with a NAD+-dependent mechanism. In mammals, the sirtuin family is composed of seven members, divided into four subclasses that differ in substrate specificity, subcellular localization, regulation, as well as interactions with other proteins, both within and outside the epigenetic field. Recently, much interest has been growing in SIRT3, which is mainly involved in regulating mitochondrial metabolism. Moreover, SIRT3 seems to be protective in diseases such as age-related, neurodegenerative, liver, kidney, heart, and metabolic ones, as well as in cancer. In most cases, activating SIRT3 could be a promising strategy to tackle these health problems. Here, we summarize the main biological functions, substrates, and interactors of SIRT3, as well as several molecules reported in the literature that are able to modulate SIRT3 activity. Among the activators, some derive from natural products, others from library screening, and others from the classical medicinal chemistry approach.

Mitochondrial sirtuins: Energy dynamics and cancer metabolism

Mitochondria are pivotal for energy regulation and are linked to cancer. Mitochondrial sirtuins, (Sirtuin) SIRT3, SIRT4, and SIRT5, play crucial roles in cancer metabolism. This review explores their impact on cellular processes, with a focus on the NAD+ interplay and the modulation of their enzymatic activities. The varied roles of SIRT3, SIRT4, and SIRT5 in metabolic adaptation and cancer are outlined, emphasizing their tumor suppressor or oncogenic nature. We propose new insights into sirtuin biology, and cancer therapeutics, suggesting an integrated proteomics and metabolomics approach for a comprehensive understanding of mitochondrial sirtuins in cancer.

Melatonin protects against myocardial ischemia-reperfusion injury by inhibiting excessive mitophagy through the Apelin/SIRT3 signaling axis

Excessive or uncontrolled mitophagy may result in a drastic shortage of healthy mitochondrial for ATP supply after reperfusion, leading to irreversible myocardial damage. Melatonin, a hormone produced by the pineal gland, has been proven to ameliorate myocardial ischemia-reperfusion (I/R) injury via regulating mitophagy. However, its underlying mechanism has not been fully elucidated. The present study focused on the role of mitophagy in the cardioprotective effects of melatonin by using the myocardial I/R rat model. The rats were pretreated with or without the apelin inhibitor ML221, the sirtuin 3 (SIRT3) inhibitor 3-TYP and then subjected to I/R injury, with melatonin administrated 10 min before reperfusion. The effects of melatonin on myocardial infarct size, biomarkers of myocardial injury, oxidative stress, and mitochondrial function were detected, and the expression of apelin, SIRT3, and mitophagy-related proteins were also measured. Excessive mitophagy was activated after I/R injury and was correlated with oxidative stress and mitochondrial dysfunction. Melatonin pretreatment ameliorated myocardial injury by decreasing oxidative stress, restoring mitochondrial function, and inhibiting excessive mitophagy. However, ML221 or 3-TYP disrupted these beneficial effects of melatonin on I/R injury. Taken together, these results suggest that melatonin pretreatment ameliorates myocardial I/R injury through regulating the apelin/SIRT3 pathway to inhibit excessive mitophagy.

A review on SIRT3 and its natural small molecule activators as a potential Preventive and therapeutic target

Sirtuins (SIRTs) were originally characterized by yeast Sir2 as a lifespan regulator that is conserved in all three structural domains of bacteria, archaea and eukaryotes and belong to histone deacetylases consisting of seven members (SIRT1-SIRT7). Surprisingly, SIRTs have been shown to play important regulatory roles in almost all cellular functions, including mitochondrial biogenesis, oxidative stress, inflammation, cell growth, energy metabolism, neural function, and stress resistance. Among the SIRT members, sirtuin 3 (SIRT3) is one of the most important deacetylases that regulates the mitochondrial acetylation and plays a role in pathological processes, such as metabolism, DNA repair, oxidative stress, apoptosis and ferroptosis. Therefore, SIRT3 is considered as a potential target for the treatment of a variety of pathological diseases, including metabolic diseases, neurodegenerative diseases, age-related diseases and others. Furthermore, the isolation, screening, and development of SIRT3 signaling agonists, especially from natural products, have become a widely investigated objective. This paper describes the structure of SIRT3 protein, discusses the pathological process of SIRT3-mediated acetylation modification, and reviews the role of SIRT3 in diseases, SIRT3 activators and its related disease studies.

SIRT3 regulates mitochondrial function: A promising star target for cardiovascular disease therapy

Dysregulation of mitochondrial homeostasis is common to all types of cardiovascular diseases. SIRT3 regulates apoptosis and autophagy, material and energy metabolism, mitochondrial oxidative stress, inflammation, and fibrosis. As an important mediator and node in the network of mechanisms, SIRT3 is essential to many activities. This review explains how SIRT3 regulates mitochondrial homeostasis and the tricarboxylic acid cycle to treat common cardiovascular diseases. A novel description of the impact of lifestyle factors on SIRT3 expression from the angles of nutrition, exercise, and temperature is provided.

Doxorubicin-Induced Cardiac Senescence Is Alleviated Following Treatment with Combined Polyphenols and Micronutrients through Enhancement in Mitophagy

Oxidative stress and impaired mitophagy are the hallmarks of cardiomyocyte senescence. Specifically, a decrease in mitophagic flux leads to the accumulation of damaged mitochondria and the development of senescence through increased ROS and other mediators. In this study, we describe the preventive role of A5+, a mix of polyphenols and other micronutrients, in doxorubicin (DOXO)-induced senescence of H9C2 cells. Specifically, H9C2 cells exposed to DOXO showed an increase in the protein expression proteins of senescence-associated genes, p21 and p16, and a decrease in the telomere binding factors TRF1 and TRF2, indicative of senescence induction. Nevertheless, A5+ pre-treatment attenuated the senescent-like cell phenotype, as evidenced by inhibition of all senescent markers and a decrease in SA-β-gal staining in DOXO-treated H9C2 cells. Importantly, A5+ restored the LC3 II/LC3 I ratio, Parkin and BNIP3 expression, therefore rescuing mitophagy, and decreased ROS production. Further, A5+ pre-treatment determined a ripolarization of the mitochondrial membrane and improved basal respiration. A5+-mediated protective effects might be related to its ability to activate mitochondrial SIRT3 in synergy with other micronutrients, but in contrast with SIRT4 activation. Accordingly, SIRT4 knockdown in H9C2 cells further increased MnSOD activity, enhanced mitophagy, and reduced ROS generation following A5+ pre-treatment and DOXO exposure compared to WT cells. Indeed, we demonstrated that A5+ protects H9C2 cells from DOXO-induced senescence, establishing a new specific role for A5+ in controlling mitochondrial quality control by restoring SIRT3 activity and mitophagy, which provided a molecular basis for the development of therapeutic strategies against cardiomyocyte senescence.

Melatonin Restores Autophagic Flux by Activating the Sirt3/TFEB Signaling Pathway to Attenuate Doxorubicin-Induced Cardiomyopathy

Doxorubicin (DOX) chemotherapy in cancer patients increases the risk of the occurrence of cardiac dysfunction and even results in congestive heart failure. Despite the great progress of pathology in DOX-induced cardiomyopathy, the underlying molecular mechanisms remain elusive. Here, we investigate the protective effects and the underlying mechanisms of melatonin in DOX-induced cardiomyopathy. Our results clearly show that oral administration of melatonin prevented the deterioration of cardiac function caused by DOX treatment, which was evaluated by left ventricular ejection fraction and fractional shortening as well as cardiac fibrosis. The ejection fraction and fractional shortening in the DOX group were 49.48% and 25.5%, respectively, while melatonin treatment increased the ejection fraction and fractional shortening to 60.33 and 31.39 in wild-type mice. Cardiac fibrosis in the DOX group was 3.97%, while melatonin reduced cardiac fibrosis to 1.95% in wild-type mice. Sirt3 is a mitochondrial deacetylase and shows protective effects in diverse cardiovascular diseases. Therefore, to test whether Sirt3 is a key factor in protection, Sirt3 knockout mice were used, and it was found that the protective effects of melatonin in DOX-induced cardiomyopathy were partly abolished. Further analysis revealed that Sirt3 and its downstream molecule TFEB were downregulated in response to DOX treatment, while melatonin administration was able to significantly enhance the expressions of Sirt3 and TFEB. Our in vitro study demonstrated that melatonin enhanced lysosomal function by increasing the Sirt3-mediated increase at the TFEB level, and the accumulation of autolysosomes induced by DOX treatment was attenuated. Thus, autophagic flux disrupted by DOX treatment was restored by melatonin supplementation. In summary, our results demonstrate that melatonin protects the heart against DOX injury by the restoration of autophagic flux via the activation of the Sirt3/TFEB signaling pathway.

Role of SIRT3 in mitochondrial biology and its therapeutic implications in neurodegenerative disorders

Sirtuin 3 (SIRT3), a mitochondrial deacetylase expressed preferentially in high-metabolic-demand tissues including the brain, requires NAD⁺ as a cofactor for catalytic activity. It regulates various processes such as energy homeostasis, redox balance, mitochondrial quality control, mitochondrial unfolded protein response (UPRmt), biogenesis, dynamics and mitophagy by altering protein acetylation status. Reduced SIRT3 expression or activity causes hyperacetylation of hundreds of mitochondrial proteins, which has been linked with neurological abnormalities, neuro-excitotoxicity and neuronal cell death. A body of evidence has suggested, SIRT3 activation as a potential therapeutic modality for age-related brain abnormalities and neurodegenerative disorders.

The role of autophagy in cardiovascular disease: Cross-interference of signaling pathways and underlying therapeutic targets

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic proteins and organelles, which realizes the metabolic needs of cells and the renewal of organelles. Autophagy-related genes (ATGs) are the main molecular mechanisms controlling autophagy, and their functions can coordinate the whole autophagic process. Autophagy can also play a role in cardiovascular disease through several key signaling pathways, including PI3K/Akt/mTOR, IGF/EGF, AMPK/mTOR, MAPKs, p53, Nrf2/p62, Wnt/β-catenin and NF-κB pathways. In this paper, we reviewed the signaling pathway of cross-interference between autophagy and cardiovascular diseases, and analyzed the development status of novel cardiovascular disease treatment by targeting the core molecular mechanism of autophagy as well as the critical signaling pathway. Induction or inhibition of autophagy through molecular mechanisms and signaling pathways can provide therapeutic benefits for patients. Meanwhile, we hope to provide a unique insight into cardiovascular treatment strategies by understanding the molecular mechanism and signaling pathway of crosstalk between autophagy and cardiovascular diseases.

Therapeutically important bioactive compounds of the genus Polygonum L. and their possible interventions in clinical medicine

OBJECTIVES

Increasing literature data have suggested that the genus Polygonum L. possesses pharmacologically important plant secondary metabolites. These bioactive compounds are implicated as effective agents in preclinical and clinical practice due to their pharmacological effects such as anti-inflammatory, anticancer, antidiabetic, antiaging, neuroprotective or immunomodulatory properties among many others. However, elaborate pharmacological and clinical data concerning the bioavailability, tissue distribution pattern, dosage and pharmacokinetic profiles of these compounds are still scanty.

KEY FINDINGS

The major bioactive compounds implicated in the therapeutic effects of Polygonum genus include phenolic and flavonoid compounds, anthraquinones and stilbenes, such as quercetin, resveratrol, polydatin and others, and could serve as potential drug leads or as adjuvant agents. Data from in-silico network pharmacology and computational molecular docking studies are also highly helpful in identifying the possible drug target of pathogens or host cell machinery.

SUMMARY

We provide an up-to-date overview of the data from pharmacodynamic, pharmacokinetic profiles and preclinical (in-vitro and in-vivo) investigations and the available clinical data on some of the therapeutically important compounds of genus Polygonum L. and their medical interventions, including combating the outbreak of the COVID-19 pandemic.

SZC-6, a small-molecule activator of SIRT3, attenuates cardiac hypertrophy in mice

Sirtuin3 (SIRT3), a class III histone deacetylase, is implicated in various cardiovascular diseases as a novel therapeutic target. SIRT3 has been proven to be cardioprotective in a model of Ang II-induced cardiac hypertrophy. However, a few small-molecule compounds targeting deacetylases could activate SIRT3. In this study, we generated a novel SIRT3 activator, 3-(2-bromo-4-hydroxyphenyl)-7-hydroxy-2H-chromen-2-one (SZC-6), through structural optimization of the first SIRT3 agonist C12. We demonstrated that SZC-6 directly bound to SIRT3 with Kd value of 15 μM, and increased SIRT3 deacetylation activity with EC50 value of 23.2 ± 3.3 µM. In neonatal rat cardiomyocytes (NRCMs), pretreatment with SZC-6 (10, 20, 40 µM) dose-dependently attenuated isoproterenol (ISO)-induced hypertrophic responses. Administration of SZC-6 (20, 40 and 60 mg·kg-1·d-1, s.c.) for 2 weeks starting from one week prior ISO treatment dose-dependently reversed ISO-induced impairment of diastolic and systolic cardiac function in wild-type mice, but not in SIRT3 knockdown mice. We showed that SZC-6 (10, 20, 40 µM) dose-dependently inhibited cardiac fibroblast proliferation and differentiation into myofibroblasts, which was abolished in SIRT3-knockdown mice. We further revealed that activation of SIRT3 by SZC-6 increased ATP production and rate of mitochondrial oxygen consumption, and reduced ROS, improving mitochondrial function in ISO-treated NRCMs. We also found that SZC-6 dose-dependently enhanced LKB1 phosphorylation, thereby promoting AMPK activation to inhibit Drp1-dependent mitochondrial fragmentation. Taken together, these results demonstrate that SZC-6 is a novel SIRT3 agonist with potential value in the treatment of cardiac hypertrophy partly through activation of the LKB1-AMPK pathway.

Polydatin Inhibits Hepatocellular Carcinoma Cell Proliferation and Sensitizes Doxorubicin and Cisplatin through Targeting Cell Mitotic Machinery

Polydatin (PD) is a natural compound with anticancer activities, but the underlying mechanisms remain largely unclear. To understand how PD inhibited hepatocellular carcinoma (HCC), we studied PD treatments in HCC HepG2 and SK-HEP1 cells, and normal liver HL-7702 cells. PD selectively blocked the proliferation of HCC cells but showed low toxicity in normal cells, while the effects of doxorubicin (DOX) and cisplatin (DDP) on HCC and normal liver cells were opposite. In the cotreatment studies, PD synergistically improved the inhibitory activities of DOX and DDP in HCC cells but alleviated their toxicity in HL-7702 cells. Furthermore, RNA-seq studies of PD-treated HepG2 cells revealed multiple altered signaling pathways. We identified 1679 Differentially Expressed Genes (DEGs) with over a 2.0-fold change in response to PD treatment. Integrative analyses using the DEGs in PD-treated HepG2 cells and DEGs in a TCGA dataset of HCC patients revealed five PD-repressed DEGs regulating mitotic spindle midzone formation. The expression of these genes showed significantly positive correlation with poor clinical outcomes of HCC patients, suggesting that mitotic machinery was likely a primary target of PD. Our findings improve the understanding of PD's anticancer mechanisms and provide insights into developing effective clinical approaches in HCC therapies.

Mitochondrial Dysfunction and Therapeutic Perspectives in Cardiovascular Diseases

High mortality rates due to cardiovascular diseases (CVDs) have attracted worldwide attention. It has been reported that mitochondrial dysfunction is one of the most important mechanisms affecting the pathogenesis of CVDs. Mitochondrial DNA (mtDNA) mutations may result in impaired oxidative phosphorylation (OXPHOS), abnormal respiratory chains, and ATP production. In dysfunctional mitochondria, the electron transport chain (ETC) is uncoupled and the energy supply is reduced, while reactive oxygen species (ROS) production is increased. Here, we discussed and analyzed the relationship between mtDNA mutations, impaired mitophagy, decreased OXPHOS, elevated ROS, and CVDs from the perspective of mitochondrial dysfunction. Furthermore, we explored current potential therapeutic strategies for CVDs by eliminating mtDNA mutations (e.g., mtDNA editing and mitochondrial replacement), enhancing mitophagy, improving OXPHOS capacity (e.g., supplement with NAD+, nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), and nano-drug delivery), and reducing ROS (e.g., supplement with Coenzyme Q10 and other antioxidants), and dissected their respective advantages and limitations. In fact, some therapeutic strategies are still a long way from achieving safe and effective clinical treatment. Although establishing effective and safe therapeutic strategies for CVDs remains challenging, starting from a mitochondrial perspective holds bright prospects.

Polydatin: Pharmacological Mechanisms, Therapeutic Targets, Biological Activities, and Health Benefits

Polydatin is a natural potent stilbenoid polyphenol and a resveratrol derivative with improved bioavailability. Polydatin possesses potential biological activities predominantly through the modulation of pivotal signaling pathways involved in inflammation, oxidative stress, and apoptosis. Various imperative biological activities have been suggested for polydatin towards promising therapeutic effects, including anticancer, cardioprotective, anti-diabetic, gastroprotective, hepatoprotective, neuroprotective, anti-microbial, as well as health-promoting roles on the renal system, the respiratory system, rheumatoid diseases, the skeletal system, and women's health. In the present study, the therapeutic targets, biological activities, pharmacological mechanisms, and health benefits of polydatin are reviewed to provide new insights to researchers. The need to develop further clinical trials and novel delivery systems of polydatin is also considered to reveal new insights to researchers.

In Vitro and in Silico Investigation of DNA Interaction, Topoisomerase I and II Inhibitory Properties of Polydatin

Polydatin or piceid, is the 3-O-glucoside of resveratrol and is found abundantly in grapes, peanuts, wine, beer, and cacao products. Although anticancer activity of polydatin was reported before, and potential antiproliferative mechanisms of polydatin have been proposed, its direct effects on DNA and inhibitory potential against topoisomerase enzymes have remained unknown. In this study we aimed to reveal the link between polydatin's effects on DNA and DNA-topoisomerases and its antiproliferative promise. For this purpose, we evaluated the effects of polydatin on DNA and DNA topoisomerase using in vitro and in silico techniques. Polydatin was found to protect DNA against Fenton reaction-induced damage while not showing any hydrolytic nuclease effect. Further, polydatin inhibited topoisomerase II but not topoisomerase I. According to molecular docking studies, polydatin preferably showed minor groove binding to DNA where the stilbene moiety was important for binding to the DNA-topoisomerase II complex. As a result, topoisomerase II inhibition might be another anticancer mechanism of polydatin.

Polydatin attenuates chronic alcohol consumption-induced cardiomyopathy through a SIRT6-dependent mechanism

Polydatin has attracted much attention as a potential cardioprotective agent against ischemic heart disease and diabetic cardiomyopathy. However, the effect and mechanism of polydatin supplementation on alcoholic cardiomyopathy (ACM) are still unknown. This study aimed to determine the therapeutic effect of polydatin against ACM and to explore the molecular mechanisms with a focus on SIRT6-AMP-activated protein kinase (AMPK) signaling and mitochondrial function. The ACM model was established by feeding C57/BL6 mice with an ethanol Lieber-DeCarli diet for 12 weeks. The mice received polydatin (20 mg kg^-1) or vehicle treatment. We showed that polydatin treatment not only improved cardiac function but also reduced myocardial fibrosis and dynamin-related protein 1 (Drp-1)-mediated mitochondrial fission, and enhanced PTEN-induced putative kinase 1 (PINK1)-Parkin-dependent mitophagy in alcohol-treated myocardium. Importantly, these beneficial effects were mimicked by SIRT6 overexpression but abolished by the infection of recombinant serotype 9 adeno-associated virus (AAV9) carrying SIRT6-specific small hairpin RNA. Mechanistically, alcohol consumption induced a gradual decrease in the myocardial SIRT6 level, while polydatin effectively activated SIRT6-AMPK signaling and modulated mitochondrial dynamics and mitophagy, thus reducing oxidative stress damage and preserving mitochondrial function. In summary, these data present new information regarding the therapeutic actions of polydatin, suggesting that the activation of SIRT6 signaling may represent a new approach for tackling ACM-related cardiac dysfunction.

Activated Drp1 regulates p62-mediated autophagic flux and aggravates inflammation in cerebral ischemia-reperfusion via the ROS-RIP1/RIP3-exosome axis

BACKGROUND

Cerebral ischemia-reperfusion injury (CIRI) refers to a secondary brain injury that can occur when the blood supply to the ischemic brain tissue is restored. However, the mechanism underlying such injury remains elusive.

METHODS

The 150 male C57 mice underwent middle cerebral artery occlusion (MCAO) for 1 h and reperfusion for 24 h, Among them, 50 MCAO mice were further treated with Mitochondrial division inhibitor 1 (Mdivi-1) and 50 MCAO mice were further treated with N-acetylcysteine (NAC). SH-SY5Y cells were cultured in a low-glucose culture medium for 4 h under hypoxic conditions and then transferred to normal conditions for 12 h. Then, cerebral blood flow, mitochondrial structure, mitochondrial DNA (mtDNA) copy number, intracellular and mitochondrial reactive oxygen species (ROS), autophagic flux, aggresome and exosome expression profiles, cardiac tissue structure, mitochondrial length and cristae density, mtDNA and ROS content, as well as the expression of Drp1-Ser616/Drp1, RIP1/RIP3, LC3 II/LC3 I, TNF-α, IL-1β, etc., were detected under normal or Drp1 interference conditions.

RESULTS

The mtDNA content, ROS levels, and Drp1-Ser616/Drp1 were elevated by 2.2, 1.7 and 2.7 times after CIRI (P < 0.05). However, the high cytoplasmic LC3 II/I ratio and increased aggregation of p62 could be reversed by 44% and 88% by Drp1 short hairpin RNA (shRNA) (P < 0.05). The low fluorescence intensity of autophagic flux and the increased phosphorylation of RIP3 induced by CIRI could be attenuated by ROS scavenger, NAC (P < 0.05). RIP1/RIP3 inhibitor Necrostatin-1 (Nec-1) restored 75% to a low LC3 II/LC3 I ratio and enhanced 2 times to a high RFP-LC3 after Drp1 activation (P < 0.05). In addition, although CIRI-induced ROS production caused no considerable accumulation of autophagosomes (P > 0.05), it increased the packaging and extracellular secretion of exosomes containing p62 by 4 - 5 times, which could be decreased by Mdivi-1, Drp1 shRNA, and Nec-1 (P < 0.05). Furthermore, TNF-α and IL-1β increased in CIRI-derived exosomes could increase RIP3 phosphorylation in normal or oxygen-glucose deprivation/reoxygenation (OGD/R) conditions (P < 0.05).

CONCLUSIONS

CIRI activated Drp1 and accelerated the p62-mediated formation of autophagosomes while inhibiting the transition of autophagosomes to autolysosomes via the RIP1/RIP3 pathway activation. Undegraded autophagosomes were secreted extracellularly in the form of exosomes, leading to inflammatory cascades that further damaged mitochondria, resulting in excessive ROS generation and the blockage of autophagosome degradation, triggering a vicious cycle.

The Double-Edged Sword of SIRT3 in Cancer and Its Therapeutic Applications

Reprogramming of cellular energy metabolism is considered an emerging feature of cancer. Mitochondrial metabolism plays a crucial role in cancer cell proliferation, survival, and metastasis. As a major mitochondrial NAD⁺-dependent deacetylase, sirtuin3 (SIRT3) deacetylates and regulates the enzymes involved in regulating mitochondrial energy metabolism, including fatty acid oxidation, the Krebs cycle, and the respiratory chain to maintain metabolic homeostasis. In this article, we review the multiple roles of SIRT3 in various cancers, and systematically summarize the recent advances in the discovery of its activators and inhibitors. The roles of SIRT3 vary in different cancers and have cell- and tumor-type specificity. SIRT3 plays a unique function by mediating interactions between mitochondria and intracellular signaling. The critical functions of SIRT3 have renewed interest in the development of small molecule modulators that regulate its activity. Delineation of the underlying mechanism of SIRT3 as a critical regulator of cell metabolism and further characterization of the mitochondrial substrates of SIRT3 will deepen our understanding of the role of SIRT3 in tumorigenesis and progression and may provide novel therapeutic strategies for cancer targeting SIRT3.

Polydatin Attenuates Intra-Uterine Growth Retardation-Induced Liver Injury and Mitochondrial Dysfunction in Weanling Piglets by Improving Energy Metabolism and Redox Balance

The present study investigated the potential of polydatin to protect against liver injury and the mitochondrial dysfunction of weanling piglets suffering from intra-uterine growth retardation (IUGR). Thirty-six normal birth weight weanling piglets and an equal number of IUGR littermates were given a basal diet with or without polydatin (250 mg/kg) from 21 to 35 d of age. Plasma and liver samples were collected to measure biochemistry parameters at 35 d of age. IUGR caused hepatic apoptosis, mitochondrial dysfunction, and oxidative damage, along with a lower efficiency of energy metabolism and inferior antioxidant ability. Polydatin decreased apoptotic rate, improved the features of mitochondrial damage, inhibited mitochondrial swelling and superoxide anion formation, and preserved mitochondrial membrane potential in the liver. Concurrently, polydatin promoted mitochondrial biogenesis, increased sirtuin 1 activity, and upregulated the expression levels of several genes related to mitochondrial function and fitness. Polydatin also facilitated mitochondrial oxidative metabolism with a beneficial outcome of increased energy production. Furthermore, polydatin mitigated the IUGR-induced reduction in manganese superoxide dismutase activity and prevented the excessive accumulation of oxidative damaging products in the liver. These findings indicate that polydatin confers protection against hepatic injury and mitochondrial dysfunction in the IUGR piglets by improving energy metabolism and redox balance.

Emerging Roles of SIRT3 in Cardiac Metabolism

The heart is a highly metabolically active organ that predominantly utilizes fatty acids as an energy substrate. The heart also derives some part of its energy by oxidation of other substrates, including glucose, lactose, amino acids and ketones. The critical feature of cardiac pathology is metabolic remodeling and loss of metabolic flexibility. Sirtuin 3 (SIRT3) is one of the seven mammalian sirtuins (SIRT1 to SIRT7), with NAD⁺ dependent deacetylase activity. SIRT3 is expressed in high levels in healthy hearts but downregulated in the aged or diseased hearts. Experimental evidence shows that increasing SIRT3 levels or activity can ameliorate several cardiac pathologies. The primary deacetylation targets of SIRT3 are mitochondrial proteins, most of which are involved in energy metabolism. Thus, SIRT3 improves cardiac health by modulating cardiac energetics. In this review, we discuss the essential role of SIRT3 in regulating cardiac metabolism in the context of physiology and pathology. Specifically, we summarize the recent advancements that emphasize the critical role of SIRT3 as a master regulator of cardiac metabolism. We also present a comprehensive view of all known activators of SIRT3, and elaborate on their therapeutic potential to ameliorate energetic abnormalities in various cardiac pathologies.

Sirtuin 3: Emerging therapeutic target for cardiovascular diseases

Acetylation is one of the most important methods of modification that lead to a change in the function of proteins. In humans, metabolic enzymes commonly undergo acetylation, which regulates the activities of metabolic enzymes and metabolic pathways. Sirtuin 3 (SIRT3) is a prominent deacetylase that participates in mitochondrial metabolism, redox balance, and mitochondrial dynamics by regulating mitochondrial protein acetylation, thereby protecting mitochondria from damage. Normal mitochondrial function is essential for maintaining the metabolism and function of the heart. Therefore, mitochondrial dysfunction caused by SIRT3 consumption and defects leads to the development of a variety of cardiovascular diseases. A comprehensive understanding of the role of SIRT3 in cardiovascular disease is critical for developing new therapeutic strategies. Herein, we summarize the function of SIRT3 in mitochondria, the complex mechanisms mediating cardiovascular diseases, and the potential value of SIRT3 small-molecule agonists in future clinical treatments.

Polydatin: A Critical Promising Natural Agent for Liver Protection via Antioxidative Stress

Polydatin, one of the natural active small molecules, was commonly applied in protecting and treating liver disorders in preclinical studies. Oxidative stress plays vital roles in liver injury caused by various factors, such as alcohol, viral infections, dietary components, drugs, and other chemical reagents. It is reported that oxidative stress might be one of the main reasons in the progressive development of alcohol liver diseases (ALDs), nonalcoholic liver diseases (NAFLDs), liver injury, fibrosis, hepatic failure (HF), and hepatocellular carcinoma (HCC). In this paper, we comprehensively summarized the pharmacological effects and potential molecular mechanisms of polydatin for protecting and treating liver disorders via regulation of oxidative stress. According to the previous studies, polydatin is a versatile natural compound and exerts significantly protective and curative effects on oxidative stress-associated liver diseases via various molecular mechanisms, including amelioration of liver function and insulin resistance, inhibition of proinflammatory cytokines, lipid accumulation, endoplasmic reticulum stress and autophagy, regulation of PI3K/Akt/mTOR, and activation of hepatic stellate cells (HSCs), as well as increase of antioxidant enzymes (such as catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), superoxide dismutase (SOD), glutathione reductase (GR), and heme oxygenase-1 (HO-1)). In addition, polydatin acts as a free radical scavenger against reactive oxygen species (ROS) by its phenolic and ethylenic bond structure. However, further clinical investigations are still needed to explore the comprehensive molecular mechanisms and confirm the clinical treatment effect of polydatin in liver diseases related to regulation of oxidative stress.

Sirtuins Modulation: A Promising Strategy for HIV-Associated Neurocognitive Impairments

HIV-Associated neurocognitive disorder (HAND) is one of the major concerns since it persists in 40% of this population. Nowadays, HAND neuropathogenesis is considered to be caused by the infected cells that cross the brain-blood barrier and produce viral proteins that can be secreted and internalized into neurons leading to disruption of cellular processes. The evidence points to viral proteins such as Tat as the causal agent for neuronal alteration and thus HAND. The hallmarks in Tat-induced neurodegeneration are endoplasmic reticulum stress and mitochondrial dysfunction. Sirtuins (SIRTs) are NAD+-dependent deacetylases involved in mitochondria biogenesis, unfolded protein response, and intrinsic apoptosis pathway. Tat interaction with these deacetylases causes inhibition of SIRT1 and SIRT3. Studies revealed that SIRTs activation promotes neuroprotection in neurodegenerative diseases such Alzheimer's and Parkinson's disease. Therefore, this review focuses on Tat-induced neurotoxicity mechanisms that involve SIRTs as key regulators and their modulation as a therapeutic strategy for tackling HAND and thereby improving the quality of life of people living with HIV.

Standpoints in mitochondrial dysfunction: Underlying mechanisms in search of therapeutic strategies

Mitochondrial dysfunction has been defined as a reduced efficiency of mitochondria to produce ATP given by a loss of mitochondrial membrane potential, alterations in the electron transport chain (ETC) function, with increase in reactive oxygen species (ROS) generation and decrease in oxygen consumption. During the last decades, mitochondrial dysfunction has been the focus of many researchers as a convergent point for the pathophysiology of several diseases. Numerous investigations have demonstrated that mitochondrial dysfunction is detrimental to cells, tissues and organisms, nevertheless, dysfunctional mitochondria can signal in a particular way in response to stress, a characteristic that may be useful to search for new therapeutic strategies with a common feature. The aim of this review addresses mitochondrial dysfunction and stress signaling as a promising target for future drug development.

Old dog, new tricks: Polydatin as a multitarget agent for current diseases

Polydatin (PD) is a natural single-crystal product that is primarily extracted from the traditional plant Polygonum cuspidatum Sieb. et Zucc. Early research showed that PD exhibited a variety of biological activities. PD has attracted increasing research interest since 2014, but no review comprehensively summarized the new findings. A great gap between its biological activities and drug development remains. It is necessary to summarize new findings on the pharmacological effects of PD on current diseases. We propose that PD will most likely be used in cardiac and cerebral ischaemia/reperfusion-related diseases and atherosclerosis in the future. The present work classified these new findings according to diseases and summarized the main effects of PD via specific mechanisms of action. In summary, we found that PD played a therapeutic role in a variety of diseases, primarily via five mechanisms: antioxidative effects, antiinflammatory effects, regulation of autophagy and apoptosis, maintenance of mitochondrial function, and lipid regulation.

Protective effect of Pulsatilla saponin A on acute myocardial infarction via miR-24-3p/p16

The effect of Pulsatilla saponin A (PsA) on acute myocardial infarction (AMI) was unknown. This study targeted to examine the roles of PsA on hypoxia-triggered toxicity to H9c2 cells and reveal the potential mechanism. H9c2 cells were maintained under a hypoxic environment for 12 h to construct the AMI cell model and the cells were pretreated by PsA. Hypoxia triggered toxicity to H9c2 cells and the anti-toxicity effect of PsA was evaluated by CCK8, TUNEL, and Western blot. The levels of miR-24-3p and p16 in H9c2 cells, AMI group tissues, and their respective controls were assessed using qRT-PCR. The dual-luciferase assay was applied to verify the targeting mechanism of miR-24-3p on p16. Then the effects of miR-24-3p inhibitor or/and si-p16 on H9c2 cells treated with PsA under hypoxia were detected by CCK8, TUNEL, and Western blot. Flow cytometry was executed to determine the cell cycle. Hypoxia decreased viability and proliferation and increased apoptosis of H9c2 cells, which were ameliorated by PsA pretreatment. The level of miR-24-3p was diminished, but p16 expression was elevated in hypoxia-treated cells and AMI group tissues. MiR-24-3p could sponge p16 in hypoxia-treated cells. Furthermore, the impact of applying miR-24-3p inhibitor on PsA and hypoxia-treated cells could be reversed by si-p16. PsA relieved hypoxia-triggered cell toxicity via miR-24-3p/p16 axis. These findings provided some fresh insights into the potential therapeutic effects of the application of PsA in AMI.

Melatonin postconditioning ameliorates anoxia/reoxygenation injury by regulating mitophagy and mitochondrial dynamics in a SIRT3-dependent manner

Ischaemia/reperfusion (I/R) injury is accompanied by excessive mitochondrial autophagy (mitophagy) and an imbalance in mitochondrial dynamics. Melatonin has been reported to alleviate I/R injury by regulating mitophagy and mitochondrial dynamics. However, the underlying mechanism associated with this activity is not fully understood. The goal of the present study was to investigate whether and how melatonin administration at the beginning of reoxygenation exerts protective effects by regulating mitophagy and mitochondrial dynamics. H9c2 cells were transfected with sirtuin 3 (SIRT3)-targeting siRNA and then subjected to anoxia/reoxygenation (A/R) injury, with melatonin (150 μM) administered at the onset of reoxygenation. Biomarkers related to cellular apoptosis, oxidative stress, mitochondrial function, mitophagy and mitochondrial dynamics were assessed, and the expression and activity of SIRT3 was also measured. Mitochondrial fission and mitophagy were activated after A/R injury and were accompanied by cellular apoptosis, oxidative stress, and mitochondrial dysfunction. However, melatonin postconditioning inhibited excessive mitochondrial fission and mitophagy, promoted mitochondrial fusion, restored mitochondrial function and reduced cellular apoptosis, and the mitophagy inhibitor 3-methyladenine (3-MA) also attenuated A/R-induced apoptosis. Moreover, the A/R-induced decreases in SIRT3 and manganese superoxide dismutase (SOD2) activities were ameliorated by melatonin. However, SIRT3 silencing abolished the beneficial effects of melatonin, eliminated the inhibitory effects of melatonin on mitochondrial fission and mitophagy, and reversed the melatonin-induced increase in SOD2 activity. These results indicate that melatonin postconditioning protects H9c2 cells from A/R injury by inhibiting excessive mitophagy and maintaining the balance of mitochondrial fission and fusion in a SIRT3-dependent manner.

Predictive Value of Sirtuins in Acute Myocardial Infarction - Bridging the Bench to the Clinical Practice

Acute myocardial infarction (AMI) is a non-transmissible condition with high prevalence, morbidity, and mortality. Different strategies for the management of AMI are employed worldwide, but its early diagnosis remains a major challenge. Many molecules have been proposed in recent years as predictive agents in the early detection of AMI, including troponin (C, T, and I), creatine kinase MB isoenzyme, myoglobin, heart-type fatty acid-binding protein, and a family of histone deacetylases with enzymatic activities named sirtuins. Sirtuins may be used as predictive or complementary treatment strategies and the results of recent preclinical studies are promising. However, human clinical trials and data are scarce, and many issues have been raised regarding the predictive values of sirtuins. The present review summarizes research on the predictive value of sirtuins in AMI. We also briefly summarize relevant clinical trials and discuss future perspectives and possible clinical applications.

Soluble Epoxide Hydrolase in Aged Female Mice and Human Explanted Hearts Following Ischemic Injury

Myocardial infarction (MI) accounts for a significant proportion of death and morbidity in aged individuals. The risk for MI in females increases as they enter the peri-menopausal period, generally occurring in middle-age. Cytochrome (CYP) 450 metabolizes N-3 and N-6 polyunsaturated fatty acids (PUFA) into numerous lipid mediators, oxylipids, which are further metabolised by soluble epoxide hydrolase (sEH), reducing their activity. The objective of this study was to characterize oxylipid metabolism in the left ventricle (LV) following ischemic injury in females. Human LV specimens were procured from female patients with ischemic cardiomyopathy (ICM) or non-failing controls (NFC). Female C57BL6 (WT) and sEH null mice averaging 13–16 months old underwent permanent occlusion of the left anterior descending coronary artery (LAD) to induce myocardial infarction. WT (wild type) mice received vehicle or sEH inhibitor, trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (tAUCB), in their drinking water ad libitum for 28 days. Cardiac function was assessed using echocardiography and electrocardiogram. Protein expression was determined using immunoblotting, mitochondrial activity by spectrophotometry, and cardiac fibre respiration was measured using a Clark-type electrode. A full metabolite profile was determined by LC–MS/MS. sEH was significantly elevated in ischemic LV specimens from patients, associated with fundamental changes in oxylipid metabolite formation and significant decreases in mitochondrial enzymatic function. In mice, pre-treatment with tAUCB or genetic deletion of sEH significantly improved survival, preserved cardiac function, and maintained mitochondrial quality following MI in female mice. These data indicate that sEH may be a relevant pharmacologic target for women with MI. Although future studies are needed to determine the mechanisms, in this pilot study we suggest targeting sEH may be an effective strategy for reducing ischemic injury and mortality in middle-aged females.

SIRT3 as a potential therapeutic target for heart failure

Heart failure causes significant morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with heart failure are exceptionally complex. Despite recent advances in heart failure research, treatment outcomes remain poor. The sirtuin family member sirtuin-3 (SIRT3) is involved in several key biological processes, including ATP production, catabolism, and reactive oxygen species detoxification. In addition to its role in metabolism, SIRT3 regulates cell death and survival and has been implicated in the pathogenesis of cardiovascular diseases. Emerging evidence also shows that SIRT3 can protect cardiomyocytes from hypertrophy, ischemia-reperfusion injury, cardiac fibrosis, and impaired angiogenesis. In this review article, we summarize the recent advances in SIRT3 research and discuss the role of SIRT3 in heart failure. We also discuss the potential use of SIRT3 as a therapeutic target in heart failure.

Arachis hypogaea resveratrol synthase 3 alters the expression pattern of UDP-glycosyltransferase genes in developing rice seeds

The resveratrol-producing rice (Oryza sativa L.) inbred lines, Iksan 515 (I.515) and Iksan 526 (I.526), developed by the expression of the groundnut (Arachis hypogaea) resveratrol synthase 3 (AhRS3) gene in the japonica rice cultivar Dongjin, accumulated both resveratrol and its glucoside, piceid, in seeds. Here, we investigated the effect of the AhRS3 transgene on the expression of endogenous piceid biosynthesis genes (UGTs) in the developing seeds of the resveratrol-producing rice inbred lines. Ultra-performance liquid chromatography (UPLC) analysis revealed that I.526 accumulates significantly higher resveratrol and piceid in seeds than those in I.515 seeds and, in I.526 seeds, the biosynthesis of resveratrol and piceid reached peak levels at 41 days after heading (DAH) and 20 DAH, respectively. Furthermore, RNA-seq analysis showed that the expression patterns of UGT genes differed significantly between the 20 DAH seeds of I.526 and those of Dongjin. Quantitative real-time PCR (RT-qPCR) analyses confirmed the data from RNA-seq analysis in seeds of Dongjin, I.515 and I.526, respectively, at 9 DAH, and in seeds of Dongjin and I.526, respectively, at 20 DAH. A total of 245 UGTs, classified into 31 UGT families, showed differential expression between Dongjin and I.526 seeds at 20 DAH. Of these, 43 UGTs showed more than 2-fold higher expression in I.526 seeds than in Dongjin seeds. In addition, the expression of resveratrol biosynthesis genes (PAL, C4H and 4CL) was also differentially expressed between Dongjin and I.526 developing seeds. Collectively, these data suggest that AhRS3 altered the expression pattern of UGT genes, and PAL, C4H and 4CL in developing rice seeds.

Control over Polymorph Formation of Polydatin in Binary Solvent System and Structural Characterization

Polydatin is a natural product used for anti-oxidant, anti-inflammatory and anti-tumor purposes, and often added in medicine, nutraceutical, cosmetics, and dietary supplement. Polymorphism is a key feature of solid-state pharmaceutical products. Polymorphic modifications may exhibit different physical and chemical properties. Here we report two different polymorphs, and the amorphous form of Polydatin. Polymorphs were prepared in binary solvent system. The crystal structures of the two forms were revealed for the first time. The structure and 3D packing were determined with single crystal X-ray diffraction analysis. The batch consistency and stability were identified with Powder X-ray diffraction analysis. Various functional groups present in the polymorphs were analyzed with fourier transform infrared spectroscopic method. The thermal properties were investigated with DSC and TGA. HPLC-MS was used for the pharmacokinetic study. Results show that form B has the faster absorption, and can be maintained in animal bodies for a longer time than form A.

Protective Effect of Polydatin on Jejunal Mucosal Integrity, Redox Status, Inflammatory Response, and Mitochondrial Function in Intrauterine Growth-Retarded Weanling Piglets

Intrauterine growth retardation (IUGR) delays the gut development of neonates, but effective treatment strategies are still limited. This study used newborn piglets as a model to evaluate the protective effect of polydatin (PD) against IUGR-induced intestinal injury. In total, 36 IUGR piglets and an equal number of normal birth weight (NBW) littermates were fed either a basal diet or a PD-supplemented diet from 21 to 35 days of age. Compared with NBW, IUGR induced jejunal damage and barrier dysfunction of piglets, as indicated by observable bacterial translocation, enhanced apoptosis, oxidative and immunological damage, and mitochondrial dysfunction. PD treatment decreased bacterial translocation and inhibited the IUGR-induced increases in circulating diamine oxidase activity (P = 0.039) and D-lactate content (P = 0.004). The apoptotic rate (P = 0.024) was reduced by 35.2% in the PD-treated piglets, along with increases in villus height (P = 0.033) and in ratio of villus height to crypt depth (P = 0.049). PD treatment promoted superoxide dismutase (P = 0.026) and glutathione S-transferase activities (P = 0.006) and reduced malondialdehyde (P = 0.015) and 8-hydroxy-2′-deoxyguanosine accumulation (P = 0.034) in the jejunum. The PD-treated IUGR piglets showed decreased jejunal myeloperoxidase activity (P = 0.029) and tumor necrosis factor alpha content (P = 0.035) than those received a basal diet. PD stimulated nuclear sirtuin 1 (P = 0.028) and mitochondrial citrate synthase activities (P = 0.020) and facilitated adenosine triphosphate production (P = 0.009) in the jejunum of piglets. Furthermore, PD reversed the IUGR-induced declines in mitochondrial DNA content (P = 0.048), the phosphorylation of adenosine monophosphate-activated protein kinase alpha (P = 0.027), and proliferation-activated receptor gamma coactivator 1 alpha expression (P = 0.033). Altogether, the results indicate that PD may improve jejunal integrity, mitigate mucosal oxidative and immunological damage, and facilitate mitochondrial function in IUGR piglets.

Autophagy and cardiac diseases: Therapeutic potential of natural products

The global incidence of cardiac diseases is expected to increase in the coming years, imposing a substantial socioeconomic burden on healthcare systems. Autophagy is a tightly regulated lysosomal degradation mechanism important for cell survival, homeostasis, and function. Accumulating pieces of evidence have indicated a major role of autophagy in the regulation of cardiac homeostasis and function. It is well established that dysregulation of autophagy in cardiomyocytes is involved in cardiac hypertrophy, myocardial infarction, diabetic cardiomyopathy, and heart failure. In this sense, autophagy seems to be an attractive therapeutic target for cardiac diseases. Recently, multiple natural products/phytochemicals, such as resveratrol, berberine, and curcumin have been shown to regulate cardiomyocyte autophagy via different pathways. The autophagy-modifying capacity of these compounds should be taken into consideration for designing novel therapeutic agents. This review focuses on the role of autophagy in various cardiac diseases and the pharmacological basis and therapeutic potential of reported natural products in cardiac diseases by modifying autophagic processes.

Polydatin alleviates parkinsonism in MPTP-model mice by enhancing glycolysis in dopaminergic neurons

Parkinson's disease (PD) is a common neurodegenerative disease. Damage to energy metabolism and reduced adenosine triphosphate (ATP) levels in dopaminergic neurons are common features of PD. Previous studies suggested that the occurrence of PD often affects glucose metabolism and ATP production in the brain, and increased glycolysis or ATP production protects dopaminergic neuronal degeneration in the brain of PD patients. These systems may provide new potential therapeutic targets for the prevention of PD. The present study investigated the inhibitory action of polydatin (PLD) on early dopaminergic neuronal degeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The results showed that PLD protected against MPTP-induced early dopaminergic neuronal degeneration. PLD reduced the MPTP-induced loss of dopaminergic neurons in substantia nigra and striatum, inhibited the occurrence of neural apoptosis, and restored motor function in mice. PLD also increased the continuous activity duration and rhythm amplitude in mice during the circadian activity test. PLD improved glucose metabolism in the brain and restored ATP production levels. These observations suggest that PLD attenuates MPTP-induced early PD-like symptoms, and its mechanism of action may be associated with the promotion of glucose metabolism in neurons.

Mitochondrial Sirtuin 3: New emerging biological function and therapeutic target

Sirtuin 3 (SIRT3) is one of the most prominent deacetylases that can regulate acetylation levels in mitochondria, which are essential for eukaryotic life and inextricably linked to the metabolism of multiple organs. Hitherto, SIRT3 has been substantiated to be involved in almost all aspects of mitochondrial metabolism and homeostasis, protecting mitochondria from a variety of damage. Accumulating evidence has recently documented that SIRT3 is associated with many types of human diseases, including age-related diseases, cancer, heart disease and metabolic diseases, indicating that SIRT3 can be a potential therapeutic target. Here we focus on summarizing the intricate mechanisms of SIRT3 in human diseases, and recent notable advances in the field of small-molecule activators or inhibitors targeting SIRT3 as well as their potential therapeutic applications for future drug discovery.

Melatonin Attenuates Anoxia/Reoxygenation Injury by Inhibiting Excessive Mitophagy Through the MT2/SIRT3/FoxO3a Signaling Pathway in H9c2 Cells

Purpose

Autophagy caused by ischemia/reperfusion (I/R) increases the extent of cardiomyocyte damage. Melatonin (Mel) diminishes cardiac injury through regulating autophagy and mitochondrial dynamics. However, illustrating the specific role of mitophagy in the cardioprotective effects of melatonin remains a challenge. The aim of our research was to investigate the impact and underlying mechanisms of melatonin in connection with mitophagy during anoxia/reoxygenation (A/R) injury in H9c2 cells.

Methods

H9c2 cells were pretreated with melatonin with or without the melatonin membrane receptor 2 (MT2) antagonist 4-P-PDOT, the MT2 agonist IIK7 and the sirtuin 3 (SIRT3) inhibitor 3-TYP for 4 hours and then subjected to A/R injury. Cell viability, cellular apoptosis, necrosis levels and oxidative markers were assessed. The expression of SIRT3 and forkhead box O3a (FoxO3a), mitochondrial function and the levels of mitophagy-related proteins were also evaluated.

Results

A/R injury provoked enhanced mitophagy in H9c2 myocytes. In addition, increased mitophagy was correlated with decreased cellular viability, increased oxidative stress and mitochondrial dysfunction in H9c2 cells. However, melatonin pretreatment notably increased cell survival and decreased cell apoptosis and oxidative response after A/R injury, accompanied by restored mitochondrial function. The inhibition of excessive mitophagy is involved in the cardioprotective effects of melatonin, as shown by the decreased expression of the mitophagy-related molecules Parkin, Beclin1, and BCL2-interacting protein 3-like (BNIP3L, best known as NIX) and decreased light chain 3 II/light chain 3 I (LC3 II/LC3 I) ratio and upregulation of p62 expression. Moreover, the decreased expression of SIRT3 and FoxO3a in A/R-injured H9c2 cells was abrogated by melatonin, but these beneficial effects were attenuated by the MT2 antagonist 4-P-PDOT or the SIRT3 inhibitor 3-TYP and enhanced by the MT2 agonist IIK7.

Conclusion

These results indicate that melatonin protects H9c2 cells during A/R injury through suppressing excessive mitophagy by activating the MT2/SIRT3/FoxO3a pathway. Melatonin may be a useful candidate for alleviating myocardial ischemia/reperfusion (MI/R) injury in the future, and the MT2 receptor might become a therapeutic target.

Interplay between NADH oxidation by complex I, glutathione redox state and sirtuin-3, and its role in the development of insulin resistance

Metabolic diseases are characterized by high NADH/NAD⁺ ratios due to excessive electron supply, causing defective mitochondrial function and impaired sirtuin-3 (SIRT-3) activity, the latter driving to oxidative stress and altered fatty acid β-oxidation. NADH is oxidized by the complex I in the electron transport chain, thereby factors inhibiting complex I like acetylation, cardiolipin peroxidation, and glutathionylation by low GSH/GSSG ratios affects SIRT3 function by increasing the NADH/NAD⁺ ratio. In this review, we summarized the evidence supporting a role of the above events in the development of insulin resistance, which is relevant in the pathogenesis of obesity and diabetes. We propose that maintenance of proper NADH/NAD⁺ and GSH/GSSG ratios are central to ameliorate insulin resistance, as alterations in these redox couples lead to complex I dysfunction, disruption of SIRT-3 activity, ROS production and impaired β-oxidation, the latter two being key effectors of insulin resistance.

Polydatin protects H9c2 cells from hypoxia-induced injury via up-regulating long non-coding RNA DGCR5

Polydatin (PD), a monocrystalline polyphenolic drug mainly found in the roots of Polygonum cuspidatum, has various pharmacological activities. Long non-coding RNAs (lncRNA) DiGeorge syndrome critical region gene 5 (DGCR5) was found to participate in the suppression of multiple cancers. Here, we proposed to study the effect of PD on myocardial infarction (MI) by inducing DGCR5. CCK-8 assay was performed to detect the viability of H9c2 cells. Flow cytometry was utilized to test apoptosis of H9c2 cells. These results determined the optimal concentration and effect time of hypoxia as well as PD. Si-DGCR5 was transfected into cells and the expression level was determined by qRT-PCR. Western blot was utilized to evaluate the expression of apoptosis-related proteins, Bcl-2, Bax, and cleaved-caspase-3, as well as autophagy-associated proteins including Beclin-1, p62, and LC3-II/LC3-I. As a result, PD efficiently attenuated hypoxia-induced apoptosis and autophagy in H9c2 cells. The expression of DGCR5 was down-regulated by hypoxia and up-regulated by PD. Besides, knocking-down the expression of DGCR5 inhibited the protection of PD in H9c2 cells. In addition, PD up-regulated the accumulation of DGCR5, DGCR5 decreased the expression of Bcl-2 and p62, raised the expression of Bax and cleaved-caspase-3, and the proportion of LC3-II/LC3-I. PD stimulated the PI3K/AKT/mTOR and MEK/ERK signaling pathways via up-regulating the expression of DGCR5. Our data demonstrated that PD reduced cell apoptosis and autophagy induced by hypoxia in cardiomyocytes. Moreover, PD activated PI3K/AKT/mTOR and MEK/ERK signaling pathways by up-regulating the expression of DGCR5.

MiR-421 inhibition protects H9c2 cells against hypoxia/reoxygenation-induced oxidative stress and apoptosis by targeting Sirt3

BACKGROUND

MicroRNAs (miRNAs) are involved in myocardial ischemia-reperfusion injury. miRNA-421 (miR-421) plays a significant role in the initiation of apoptosis and myocardial infarction. However, the molecular regulation of miR-421 in myocardial ischemia-reperfusion injury requires further elucidation.

METHODS

An in vitro hypoxia/reoxygenation model was established, and the expression levels of miR-421 and Sirtuin-3 (Sirt3) in H9c2 cells were quantified using quantitative real-time polymerase chain reaction. Flow cytometry was employed to measure the effects of miR-421 on myocardial apoptosis induced by hypoxia/reoxygenation. The activity of lactate dehydrogenase and superoxide dismutase and levels of malondialdehyde were measured. The binding sites of miR-421 on Sirt3 were predicted using TargetScan software. A luciferase reporter assay was used to validate the direct targeting of Sirt3 with miR-421. Protein expression levels of Sirt3 and its downstream proteins were evaluated using Western blot analysis.

RESULTS

Exposure of H9c2 cells to hypoxia/reoxygenation led to increased apoptosis, levels of malondialdehyde and lactate dehydrogenase, and decreased levels of superoxide dismutase. miR-421 knockdown resulted in decreased apoptosis, levels of lactate dehydrogenase and malondialdehyde, and increased superoxide dismutase levels in H9c2 cells. Hypoxia/reoxygenation significantly decreased the relative expression levels of Sirt3. Down-regulation of Sirt3 resulted from overexpression of miR-421, which directly targeted Sirt3. Knockdown of miR-421 up-regulated Sirt3 expression, inhibited activation of the Jun N-terminal kinase/activator protein 1 pathway and caspase 9/3-dependent cell death.

CONCLUSION

The miR-421-Sirt3-Jun N-terminal kinase/activator protein 1 axis is a novel molecular mechanism that accommodates hypoxia/reoxygenation-induced oxidative stress and apoptosis and provides a new direction for the study and treatment of hypoxia/reoxygenation.

Halofuginone protects against advanced glycation end products‑induced injury of H9C2 cells via alleviating endoplasmic reticulum stress‑associated apoptosis and inducing autophagy

Advanced glycation end products (AGEs) have been reported to serve an important role in the stiffening of cardiac tissues and myocardial cell injury. Serious myocardial cell injury can result in various heart diseases with high mortality. Halofuginone (HF), which possesses marked anti-inflammatory and antifibrotic effects, has recently been applied to inhibit the effects of cardiac stress. The present study aimed to investigate the potential effects of HF and its underlying mechanism in the treatment of AGEs-induced H9C2 cardiomyocyte damage. The western blot results of the present study demonstrated that HF may reduce the expression levels of myocardial injury markers, including myoglobin, creatine kinase MB and cardiac troponin I. In addition, flow cytometric analysis indicated that the production of reactive oxygen species (ROS) was significantly decreased by HF. Additionally, endoplasmic reticulum (ER) stress was suppressed in response to treatment with HF, as observed by low expression levels of ER stress-associated proapoptotic proteins (CCAAT/enhancer-binding protein homologous protein and cleaved caspase-12); overexpression of prosurvival proteins (growth arrest and DNA damage-inducible protein GADD34 and binding immunoglobulin protein) was also reported. Furthermore, the expression levels of microtubule-associated proteins 1A/1B light chain 3B (LC3)II/LC3I and Beclin 1 were elevated, whereas P62 expression levels were reduced following treatment with HF. These findings, together with immunofluorescence staining of LC3, indicated that HF may induce autophagy. Finally, the protective effects of HF on AGEs-treated H9C2 cells were reversed following treatment with the inhibitor 3-methyladenine, as indicated by inhibition of autophagy, and increases in apoptosis, ROS production and the ER stress response. Collectively, the findings of the present study suggested that the protective effects of HF against AGEs-induced myocardial cell injury may be associated with the induction of autophagy and amelioration of ROS-mediated ER stress and apoptosis. These findings may contribute to the development of a novel therapeutic method to inhibit the progression of myocardial cell injury.

Polydatin Regulates the Apoptosis and Autophagy of Fibroblasts Obtained from Patients with Ankylosing Spondylitis

The development of ankylosing spondylitis (AS) occurs due to excessive proliferation of fibroblasts. Polydatin, a monomeric compound isolated from a traditional Chinese medicine Polygonum cuspidatum, exhibits anti-inflammatory and anti-arthritic effects. However, the mechanisms underlying the regulatory effects of polydatin on the proliferation, apoptosis and autophagy of fibroblasts obtained from patients with AS remain unclear. The aim of this study was to investigate the therapeutic effects of polydatin on symptoms associated with AS. Multiple cellular and molecular biology experiments were performed in the present study, such as cell viability assay, Western blotting, flow cytometry, monodansylcadaverine (MDC) staining and immunofluorescence assays. In the present study, the results revealed that polydatin induced the apoptosis of fibroblasts isolated from patients with AS by upregulating the expression of active caspase-3 and Bax, and downregulating the expression of Bcl-2. Meanwhile, polydatin was revealed to enhance the autophagy of fibroblasts by increasing the expression levels of LC3II, Beclin 1 and Atg5. The results of MDC and immunofluorescence assays further demonstrated that polydatin significantly induced the formation of autophagosomes in fibroblasts. Furthermore, polydatin-induced apoptosis and autophagy were markedly inhibited following treatment with the autophagy inhibitor, 3-methyladenine (3-MA). In conclusion, the results of the present study indicated that polydatin induces the apoptosis and autophagy of fibroblasts obtained from patients suffering from AS, and that polydatin may represent a therapeutic agent for the future treatment of patients with AS.

Emerging role of SIRT3 in mitochondrial dysfunction and cardiovascular diseases

As a nicotinamide adenine dinucleotide (NAD)⁺-dependent protein deacetylase, SIRT3 is highly expressed in tissues with high metabolic turnover and mitochondrial content. It has been demonstrated that SIRT3 plays a critical role in maintaining normal mitochondrial biological function through reversible protein lysine deacetylation. SIRT3 has a variety of substrates that are involved in mitochondrial biological processes such as energy metabolism, reactive oxygen species production and clearance, electron transport chain flux, mitochondrial membrane potential maintenance, and mitochondrial dynamics. In the suppression of SIRT3, functional deficiencies of mitochondria contribute to the development of various cardiovascular disorders. Activation of SIRT3 may represent a promising therapeutic strategy for the improvement of mitochondrial function and the treatment of relevant cardiovascular disorders. In the current review, we discuss the emerging roles of SIRT3 in mitochondrial derangements and subsequent cardiovascular malfunctions, including cardiac hypertrophy and heart failure, ischemia-reperfusion injury, and endothelial dysfunction in hypertension and atherosclerosis.

SIRT3 Regulation Under Cellular Stress: Making Sense of the Ups and Downs

Sirtuin 3 (SIRT3) is an NAD+ dependent deacetylase that resides primarily in mitochondria and functions to maintain mitochondrial homeostasis under stress. SIRT3 expression has been observed to change under a number of different stresses in multiple tissues and model systems. Inconsistencies in the literature with regards to how and when SIRT3 protein levels change indicates that the mechanism of SIRT3 regulation is multi-faceted. Alterations in SIRT3 have been observed in experimental models of cellular stress, however, the effect these changes have on mitochondrial health remain unknown. Neurons are highly dependent on proper mitochondrial function for their survival. SIRT3 dynamics and function have been studied using models of genotoxic, metabolic, and oxidative stresses, although it remains unclear how SIRT3 is being regulated under these conditions. A closer look into SIRT3 regulation under stress conditions in various model systems will help incorporate the many SIRT3 regulatory mechanisms at play in disease states. In this review, we describe the observations that have been made about SIRT3 protein modulation under basic stress conditions. We then point out consistencies and contradictions in these observations and what they mean. Lastly, we present the observations made in the complicated neuronal stress of stroke. We hope that this review will help consolidate the ambiguous SIRT3 literature and provide a framework for investigation of SIRT3 regulation during stress response.