SIRT3 deacetylates and activates OPA1 to regulate mitochondrial dynamics during stress

Mitochondrial quality control dysfunction in osteoarthritis: Mechanisms, therapeutic strategies & future prospects

Osteoarthritis (OA) is a prevalent chronic joint disease characterized by articular cartilage degeneration, pain, and disability. Emerging evidence indicates that mitochondrial quality control dysfunction contributes to OA pathogenesis. Mitochondria are essential organelles to generate cellular energy via oxidative phosphorylation and regulate vital processes. Impaired mitochondria can negatively impact cellular metabolism and result in the generation of harmful reactive oxygen species (ROS). Dysfunction in mitochondrial quality control mechanisms has been increasingly linked to OA onset and progression. This review summarizes current knowledge on the role of mitochondrial quality control disruption in OA, highlighting disturbed mitochondrial dynamics, impaired mitochondrial biogenesis, antioxidant defenses and mitophagy. The review also discusses potential therapeutic strategies targeting mitochondrial Quality Control in OA, offering future perspectives on advancing OA therapeutic strategies.

Insights into the post-translational modifications in heart failure

Heart failure (HF), as the terminal manifestation of multiple cardiovascular diseases, causes a huge socioeconomic burden worldwide. Despite the advances in drugs and medical-assisted devices, the prognosis of HF remains poor. HF is well-accepted as a myriad of subcellular dys-synchrony related to detrimental structural and functional remodelling of cardiac components, including cardiomyocytes, fibroblasts, endothelial cells and macrophages. Through the covalent chemical process, post-translational modifications (PTMs) can coordinate protein functions, such as re-localizing cellular proteins, marking proteins for degradation, inducing interactions with other proteins and tuning enzyme activities, to participate in the progress of HF. Phosphorylation, acetylation, and ubiquitination predominate in the currently reported PTMs. In addition, advanced HF is commonly accompanied by metabolic remodelling including enhanced glycolysis. Thus, glycosylation induced by disturbed energy supply is also important. In this review, firstly, we addressed the main types of HF. Then, considering that PTMs are associated with subcellular locations, we summarized the leading regulation mechanisms in organelles of distinctive cell types of different types of HF, respectively. Subsequently, we outlined the aforementioned four PTMs of key proteins and signaling sites in HF. Finally, we discussed the perspectives of PTMs for potential therapeutic targets in HF.

The role of SIRT3 in homeostasis and cellular health

Mitochondria are responsible for maintaining cellular energy levels, and play a major role in regulating homeostasis, which ensures physiological function from the molecular to whole animal. Sirtuin 3 (SIRT3) is the major protein deacetylase of mitochondria. SIRT3 serves as a nutrient sensor; under conditions of mild metabolic stress, SIRT3 activity is increased. Within the mitochondria, SIRT3 regulates every complex of the electron transport chain, the tricarboxylic acid (TCA) and urea cycles, as well as the mitochondria membrane potential, and other free radical scavengers. This article reviews the role of SIRT3 in regulating homeostasis, and thus physiological function. We discuss the role of SIRT3 in regulating reactive oxygen species (ROS), ATP, immunological function and mitochondria dynamics.

Sirtuin 3 in renal diseases and aging: From mechanisms to potential therapies

The longevity protein sirtuins (SIRTs) belong to a family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases. In mammals, SIRTs comprise seven members (SIRT1-7) which are localized to different subcellular compartments. As the most prominent mitochondrial deacetylases, SIRT3 is known to be regulated by various mechanisms and participate in virtually all aspects of mitochondrial homeostasis and metabolism, exerting significant impact on multiple organs. Notably, the kidneys possess an abundance of mitochondria that provide substantial energy for filtration and reabsorption. A growing body of evidence now supports the involvement of SIRT3 in several renal diseases, including acute kidney injury, chronic kidney disease, and diabetic nephropathy; notably, these diseases are all associated with aging. In this review, we summarize the emerging role of SIRT3 in renal diseases and aging, and highlights the intricate mechanisms by which SIRT3 exerts its effects. In addition, we highlight the potential therapeutic significance of modulating SIRT3 and provide valuable insights into the therapeutic role of SIRT3 in renal diseases to facilitate clinical application.

SIRTUIN 5 ALLEVIATES EXCESSIVE MITOCHONDRIAL FISSION VIA DESUCCINYLATION OF ATPASE INHIBITORY FACTOR 1 IN SEPSIS-INDUCED ACUTE KIDNEY INJURY

ABSTRACT

Sepsis-induced acute kidney injury (SAKI) poses a significant clinical challenge with high morbidity and mortality. Excessive mitochondrial fission has been identified as the central pathogenesis of sepsis-associated organ damage, which is also implicated in the early stages of SAKI. Sirtuin 5 (SIRT5) has emerged as a central regulator of cellular mitochondrial function; however, its role in the regulation of sepsis-induced excessive mitochondrial fission in kidney and the underlying mechanism remains unclear. In this study, SAKI was modeled in mice through cecal ligation and puncture, and in human renal tubular epithelial (HK-2) cells stimulated with lipopolysaccharide (LPS), to mimic the cell SAKI model. Our findings revealed that septic mice with a SIRT5 knockout exhibited shortened survival times and elevated levels of renal injury compared to wild-type mice, suggesting the significant involvement of SIRT5 in SAKI pathophysiology. Additionally, we observed that SIRT5 depletion led to increased renal mitochondrial fission, while the use of a mitochondrial fission inhibitor (Mdivi-1) reversed the detrimental effects caused by SIRT5 depletion, emphasizing the pivotal role of SIRT5 in preventing excessive mitochondrial fission. In vitro experiments demonstrated that the overexpression of SIRT5 effectively mitigated the adverse effects of LPS on HK-2 cells viability and mitochondrial fission. Conversely, downregulation of SIRT5 decreased HK-2 cells viability and exacerbated LPS-induced mitochondrial fission. Mechanistically, the protective function of SIRT5 may be in part, ascribed to its desuccinylating action on ATPase inhibitory factor 1. In conclusion, this study provides novel insights into the underlying mechanisms of SAKI, suggesting the possibility of identifying future drug targets in terms of improved mitochondrial dynamics by SIRT5.

Sex-related differences in SIRT3-mediated mitochondrial dynamics in renal ischemia/reperfusion injury

The prevalence of renal ischemia/reperfusion injury (IRI) in premenopausal women is considerably lower than that in age-matched men. This suggests that sex-related differences in mitochondrial function and homeostasis may contribute to sexual dimorphism in renal injury, though the mechanism remains unclear. Mouse model of unilateral left renal IRI with contralateral kidney enucleation, Ovariectomy in female mice, and a human embryonic kidney (HEK) cell model of hypoxia-reoxygenation were used to study how estrogen affects the sexual dimorphism of renal IRI through SIRT3 in vitro and in vivo, respectively. Here, we demonstrate differential expression of renal SIRT3 may induce sexual dimorphism in IRI using the renal IRI model. Higher SIRT3 level in female mice was associated with E2-induced protection of renal tubular epithelium, reduced mitochondrial reactive oxygen species (ROS), and IRI resistance. In hypoxia-reoxygenated HEK cells, SIRT3 knockdown increased oxidative stress, shifted the interconnected mitochondrial network toward fission, exacerbated hypoxia/reoxygenation-induced endoplasmic reticulum stress (ERS), and abolished the protective effects of E2 on IRI. Mechanistically, the SIRT3 level is E2-dependent and that E2 increases the SIRT3 protein level via estrogen receptor. SIRT3 targeted an i-AAA protease, yeast mitochondrial AAA metalloprotease (YME1L1), and hydrolyzed long optic atrophy 1 (L-OPA) to short-OPA1 (S-OPA1) by deacetylating YME1L1, regulating mitochondrial dynamics toward fusion to reduce oxidative stress and ERS. These findings explored the mechanism by how estrogen alleviates renal IRI and providing a basis for potential therapeutic interventions targeting SIRT3.

Sirt3-Mediated Opa1 Deacetylation Protects Against Sepsis-Induced Acute Lung Injury by Inhibiting Alveolar Macrophage Pro-Inflammatory Polarization

Aims: Mitochondrial dynamics in alveolar macrophages (AMs) are associated with sepsis-induced acute lung injury (ALI). In this study, we aimed to investigate whether changes in mitochondrial dynamics could alter the polarization of AMs in sepsis-induced ALI and to explore the regulatory mechanism of mitochondrial dynamics by focusing on sirtuin (SIRT)3-induced optic atrophy protein 1 (OPA1) deacetylation. Results: The AMs of sepsis-induced ALI showed imbalanced mitochondrial dynamics and polarization to the M1 macrophage phenotype. In sepsis, SIRT3 overexpression promotes mitochondrial dynamic equilibrium in AMs. However, 3-(1H-1, 2, 3-triazol-4-yl) pyridine (3TYP)-specific inhibition of SIRT3 increased the mitochondrial dynamic imbalance and pro-inflammatory polarization of AMs and further aggravated sepsis-induced ALI. OPA1 is directly bound to and deacetylated by SIRT3 in AMs. In AMs of sepsis-induced ALI, SIRT3 protein expression was decreased and OPA1 acetylation was increased. OPA1 acetylation at the lysine 792 amino acid residue (OPA1-K792) promotes self-cleavage and is associated with an imbalance in mitochondrial dynamics. However, decreased acetylation of OPA1-K792 reversed the pro-inflammatory polarization of AMs and protected the barrier function of alveolar epithelial cells in sepsis-induced ALI. Innovation: Our study revealed, for the first time, the regulation of mitochondrial dynamics and AM polarization by SIRT3-mediated deacetylation of OPA1 in sepsis-induced ALI, which may serve as an intervention target for precision therapy of the disease. Conclusions: Our data suggest that imbalanced mitochondrial dynamics promote pro-inflammatory polarization of AMs in sepsis-induced ALI and that deacetylation of OPA1 mediated by SIRT3 improves mitochondrial dynamic equilibrium, thereby ameliorating lung injury.

SIRT3 Negatively Regulates TFH-Cell Differentiation in Cancer

Follicular helper T (TFH) cells are essential for inducing germinal center (GC) reactions to mediate humoral adaptive immunity in tumors; however, the mechanisms underlying TFH-cell differentiation remain unclear. In this study, we found that the metabolism sensor sirtuin 3 (SIRT3) is critical for TFH-cell differentiation and GC formation during tumor development and viral infection. SIRT3 deficiency in CD4+ T cells intrinsically enhanced TFH-cell differentiation and GC reactions during tumor development and viral infection. Mechanistically, damaged oxidative phosphorylation (OXPHOS) compensatively triggered the NAD+-glycolysis pathway to provide a cellular energy supply, which was necessary for SIRT3 deficiency-induced TFH-cell differentiation. Blocking NAD+ synthesis-glycolysis signaling or recovering OXPHOS activities reversed the TFH-cell differentiation induced by SIRT3 deficiency. Moreover, the mTOR and hypoxia-inducible factor 1α (HIF1α) signaling axis was found to be responsible for TFH-cell differentiation induced by SIRT3 deficiency. HIF1α directly interacted with and regulated the activity of the transcription factor Bcl6. Thus, our findings identify a cellular energy compensatory mechanism, regulated by the mitochondrial sensor SIRT3, that triggers NAD+-dependent glycolysis during mitochondrial OXPHOS injuries and an mTOR-HIF1α-Bcl6 pathway to reprogram TFH-cell differentiation. These data have implications for future cancer immunotherapy research targeting SIRT3 in T cells.

Gastrodin regulates the expression of renin-angiotensin system-SIRT3 and proinflammatory mediators in reactive astrocytes via activated microglia

Gastrodin, an anti-inflammatory herbal agent, is known to suppress microglia activation. Here, we investigated whether it would exert a similar effect in reactive astrocytes and whether it might act through the renin-angiotensin system (RAS) and sirtuin 3 (SIRT3). Angiotensinogen (ATO), angiotensin-converting enzyme (ACE), angiotensin II type 1 (AT1) and type 2 (AT2) receptor and SIRT3 expression was detected in TNC-1 astrocytes treated with BV-2 microglia conditioned medium (CM) with or without gastrodin and lipopolysaccharide (LPS) pre-treatment by RT-PCR, immunofluorescence and western blotting analysis. Expression of C3 (A1 astrocyte marker), S100A10 (A2 astrocyte marker), proinflammatory cytokines and neurotrophic factors was then evaluated. The results showed a significant increase of ATO, ACE, AT1, SIRT3, C3, proinflammatory cytokines and neurotrophic factors expression in TNC-1 astrocytes incubated in CM + LPS when compared with cells incubated in the CM, but AT2 and S100A10 expression was reduced. TNC-1 astrocytes responded vigorously to BV-2 CM treated with gastrodin + LPS as compared with the control. This was evident by the decreased expression of the abovementioned protein markers, except for AT2 and S100A10. Interestingly, SIRT3, IGF-1 and BDNF expression was enhanced, suggesting that gastrodin inhibited the expression of RAS and proinflammatory mediators but promoted the expression of neurotrophic factors. And gastrodin regulated the phenotypic changes of astrocytes through AT1. Additionally, azilsartan (a specific inhibitor of AT1) inhibited the expression of C3 and S100A10, which remained unaffected in gastrodin and azilsartan combination treatment. These findings provide evidence that gastrodin may have a therapeutic effect via regulating RAS-SIRT3.

SIRT3 facilitates mitochondrial structural repair and functional recovery in rats after ischemic stroke by promoting OPA1 expression and activity

BACKGROUND

Optical atrophy 1 (OPA1), a protein accountable for mitochondrial fusion, facilitates the restoration of mitochondrial structure and function following cerebral ischemia/reperfusion (I/R) injury. The OPA1-conferred mitochondrial protection involves its expression and activity, which can be improved by SIRT3 in non-cerebral ischemia. Nevertheless, it remains obscure whether SIRT3 enhances the expression and activity of OPA1 after cerebral I/R injury.

METHODS

Mature male Sprague Dawley rats were intracranially injected with adeno-associated viral-Sirtuin-3(AAV-SIRT3) and AAV-sh_OPA1, followed by a 90-min temporary blockage of the middle cerebral artery and subsequent restoration of blood flow. Cultured cortical neurons of rats were transfected with LV-SIRT3 or LV-sh_OPA1 before a 2-h oxygen-glucose deprivation and reoxygenation. The rats and neurons were subsequently treated with a selective OPA1 activity inhibitor (MYLS22). The interaction between SIRT3 and OPA1 was assessed by molecular dynamics simulation technology and co-immunoprecipitation. The expression, function, and specific protective mechanism of SIRT3 were examined by various analyses.

RESULTS

SIRT3 interacted with OPA1 in the rat cerebral cortex before and after cerebral I/R. After cerebral I/R damage, SIRT3 upregulation increased the OPA1 expression, which enhanced deacetylation and OPA1 activity, thus alleviating cerebral infarct volume, neuronal apoptosis, oxidative pressure, and impairment in mitochondrial energy production; SIRT3 upregulation also improved neuromotor performance, repaired mitochondrial ultrastructure and membrane composition, and promoted the mitochondrial biogenesis. These neuroprotective effects were partly reversed by OPA1 expression interference and OPA1 activity inhibitor MYLS22.

CONCLUSION

In rats, SIRT3 enhances the expression and activity of OPA1, facilitating the repair of mitochondrial structure and functional recovery following cerebral I/R injury. These findings highlight that regulating SIRT3 may be a promising therapeutic strategy for ischemic stroke.

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Pharmacological Activation of SIRT3 Modulates the Response of Cancer Cells to Acidic pH

Cancer cells modulate their metabolism, creating an acidic microenvironment that, in turn, can favor tumor progression and chemotherapy resistance. Tumor cells adopt strategies to survive a drop in extracellular pH (pHe). In the present manuscript, we investigated the contribution of mitochondrial sirtuin 3 (SIRT3) to the adaptation and survival of cancer cells to a low pHe. SIRT3-overexpressing and silenced breast cancer cells MDA-MB-231 and human embryonic kidney HEK293 cells were grown in buffered and unbuffered media at pH 7.4 and 6.8 for different times. mRNA expression of SIRT3 and CAVB, was measured by RT-PCR. Protein expression of SIRT3, CAVB and autophagy proteins was estimated by western blot. SIRT3-CAVB interaction was determined by immunoprecipitation and proximity ligation assays (PLA). Induction of autophagy was studied by western blot and TEM. SIRT3 overexpression increases the survival of both cell lines. Moreover, we demonstrated that SIRT3 controls intracellular pH (pHi) through the regulation of mitochondrial carbonic anhydrase VB (CAVB). Interestingly, we obtained similar results by using MC2791, a new SIRT3 activator. Our results point to the possibility of modulating SIRT3 to decrease the response and resistance of tumor cells to the acidic microenvironment and ameliorate the effectiveness of anticancer therapy.

Advances in SIRT3 involvement in regulating autophagy-related mechanisms

The silencing regulatory factor 2-like protein 3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD+) dependent deacetylase located primarily in the mitochondria. This protein plays an important role in oxidative stress, energy metabolism, and autophagy in multicellular organisms. Autophagy (macroautophagy) is primarily a cytoprotective mechanism necessary for intracellular homeostasis and the synthesis, degradation, and recycling of cellular products. Autophagy can influence the progression of several neural, cardiac, hepatic, and renal diseases and can also contribute to the development of fibrosis, diabetes, and many types of cancer. Recent studies have shown that SIRT3 has an important role in regulating autophagy. Therefore in this study, we aimed to perform a literature review to summarize the role of SIRT3 in the regulation of cellular autophagy. The findings of this study could be used to identify new drug targets for SIRT3-related diseases. Methods: A comprehensive literature review of the mechanism involved behind SIRT3 and autophagy-related diseases was performed. Relevant literature published in Pubmed and Web of Science up to July 2023 was identified using the keywords "silencing regulatory factor 2-like protein 3", "SIRT3" and "autophagy".

SIRT6 in Regulation of Mitochondrial Damage and Associated Cardiac Dysfunctions: A Possible Therapeutic Target for CVDs

Cardiovascular diseases (CVDs) can be described as a global health emergency imploring possible prevention strategies. Although the pathogenesis of CVDs has been extensively studied, the role of mitochondrial dysfunction in CVD development has yet to be investigated. Diabetic cardiomyopathy, ischemic-reperfusion injury, and heart failure are some of the CVDs resulting from mitochondrial dysfunction Recent evidence from the research states that any dysfunction of mitochondria has an impact on metabolic alteration, eventually causes the death of a healthy cell and therefore, progressively directing to the predisposition of disease. Cardiovascular research investigating the targets that both protect and treat mitochondrial damage will help reduce the risk and increase the quality of life of patients suffering from various CVDs. One such target, i.e., nuclear sirtuin SIRT6 is strongly associated with cardiac function. However, the link between mitochondrial dysfunction and SIRT6 concerning cardiovascular pathologies remains poorly understood. Although the Role of SIRT6 in skeletal muscles and cardiomyocytes through mitochondrial regulation has been well understood, its specific role in mitochondrial maintenance in cardiomyocytes is poorly determined. The review aims to explore the domain-specific function of SIRT6 in cardiomyocytes and is an effort to know how SIRT6, mitochondria, and CVDs are related.

Nicotinamide riboside attenuates myocardial ischemia-reperfusion injury via regulating SIRT3/SOD2 signaling pathway

Ischemic heart disease invariably leads to devastating damage to human health. Nicotinamide ribose (NR), as one of the precursors of NAD+ synthesis, has been discovered to exert a protective role in various neurological and cardiovascular disorders. Our findings demonstrated that pretreatment with 200 mg/kg NR for 3 h significantly reduced myocardial infarct area, decreased levels of CK-MB and LDH in serum, and improved cardiac function in the rats during myocardial ischemia-reperfusion (I/R) injury. Meanwhile, 0.5 mM NR also effectively increased the viability and decreased the LDH release of H9c2 cells during OGD/R. We had provided evidence that NR pretreatment could decrease mitochondrial reactive oxygen species (mtROS) production and MDA content, and enhance SOD activity, thereby mitigating mitochondrial damage and inhibiting apoptosis during myocardial I/R injury. Further investigations revealed that NR increased NAD+ content and upregulated SIRT3 protein expression in myocardium. Through using of SIRT3 small interfering RNA and the SIRT3 deacetylase activity inhibitor 3-TYP, we had confirmed that the cardioprotective effect of NR on cardiomyocytes was largely dependent on the inhibition of mitochondrial oxidative stress via SIRT3-SOD2 axis. Overall, our study suggested that exogenous supplementation with NR mitigated mitochondrial damage and inhibited apoptosis during myocardial I/R injury by reducing mitochondrial oxidative stress via SIRT3-SOD2-mtROS pathway.

The protective effects of orexin-A in alleviating cell senescence against interleukin-1β (IL-1β) in chondrocytes

Osteoarthritis (OA) is one of the most important causes of global disability, and dysfunction of chondrocytes is an important risk factor. The treatment of OA is still a challenge. Orexin-A is a hypothalamic peptide, and its effects in OA are unknown. In this study, we found that exposure to interleukin-1β (IL-1β) reduced the expression of orexin-2R, the receptor of orexin-A in TC-28a2 chondrocytes. Importantly, the senescence-associated β-galactosidase (SA-β-gal) staining assay demonstrated that orexin-A treatment ameliorates IL-1β-induced cellular senescence. Importantly, the presence of IL-1β significantly reduced the telomerase activity of TC-28a2 chondrocytes, which was rescued by orexin-A. We also found that orexin-A prevented IL-1β-induced increase in the levels of Acetyl-p53 and the expression of p21. It is shown that orexin-A mitigates IL-1β-induced reduction of sirtuin 3 (SIRT3). Silencing of SIRT3 abolished the protective effects of orexin-A against IL-1β-induced cellular senescence. These results imply that orexin-A might serve as a promising therapeutic agent for OA.

Mitochondrial dysfunction: mechanisms and advances in therapy

Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.

Mitochondrial Dysfunction: A Roadmap for Understanding and Tackling Cardiovascular Aging

Cardiovascular aging is a progressive remodeling process constituting a variety of cellular and molecular alterations that are closely linked to mitochondrial dysfunction. Therefore, gaining a deeper understanding of the changes in mitochondrial function during cardiovascular aging is crucial for preventing cardiovascular diseases. Cardiac aging is accompanied by fibrosis, cardiomyocyte hypertrophy, metabolic changes, and infiltration of immune cells, collectively contributing to the overall remodeling of the heart. Similarly, during vascular aging, there is a profound remodeling of blood vessel structure. These remodeling present damage to endothelial cells, increased vascular stiffness, impaired formation of new blood vessels (angiogenesis), the development of arteriosclerosis, and chronic vascular inflammation. This review underscores the role of mitochondrial dysfunction in cardiac aging, exploring its impact on fibrosis and myocardial alterations, metabolic remodeling, immune response remodeling, as well as in vascular aging in the heart. Additionally, we emphasize the significance of mitochondria-targeted therapies in preventing cardiovascular diseases in the elderly.

Sirtuins in kidney health and disease

Sirtuins (SIRTs) are putative regulators of lifespan in model organisms. Since the initial discovery that SIRTs could promote longevity in nematodes and flies, the identification of additional properties of these proteins has led to understanding of their roles as exquisite sensors that link metabolic activity to oxidative states. SIRTs have major roles in biological processes that are important in kidney development and physiological functions, including mitochondrial metabolism, oxidative stress, autophagy, DNA repair and inflammation. Furthermore, altered SIRT activity has been implicated in the pathophysiology and progression of acute and chronic kidney diseases, including acute kidney injury, diabetic kidney disease, chronic kidney disease, polycystic kidney disease, autoimmune diseases and renal ageing. The renoprotective roles of SIRTs in these diseases make them attractive therapeutic targets. A number of SIRT-activating compounds have shown beneficial effects in kidney disease models; however, further research is needed to identify novel SIRT-targeting strategies with the potential to treat and/or prevent the progression of kidney diseases and increase the average human healthspan.

Design, Synthesis, and In Vivo Evaluation of Isosteviol Derivatives as New SIRT3 Activators with Highly Potent Cardioprotective Effects

Cardiovascular diseases (CVDs) persist as the predominant cause of mortality, urging the exploration of innovative pharmaceuticals. Mitochondrial dysfunction stands as a pivotal contributor to CVDs development. Sirtuin 3 (SIRT3), a prominent mitochondrial deacetylase known for its crucial role in protecting mitochondria against damage and dysfunction, has emerged as a promising therapeutic target for CVDs treatment. Utilizing isosteviol, a natural ent-beyerene diterpenoid, 24 derivatives were synthesized and evaluated in vivo using a zebrafish model, establishing a deduced structure-activity relationship. Among these, derivative 5v exhibited significant efficacy in doxorubicin-induced cardiomyopathy in zebrafish and murine models. Subsequent investigations revealed that 5v selectively elevated SIRT3 expression, leading to the upregulation of SOD2 and OPA1 expression, effectively preventing mitochondrial dysfunction, mitigating oxidative stress, and preserving cardiomyocyte viability. As a novel structural class of SIRT3 activators with robust therapeutic effects, 5v emerges as a promising candidate for further drug development.

TRPV4 Activator-Containing CMT-Hy Hydrogel Enhances Bone Tissue Regeneration In Vivo by Enhancing Mitochondrial Health

Treating different types of bone defects is difficult, complicated, time-consuming, and expensive. Here, we demonstrate that transient receptor potential cation channel subfamily V member 4 (TRPV4), a mechanosensitive, thermogated, and nonselective cation channel, is endogenously present in the mesenchymal stem cells (MSCs). TRPV4 regulates both cytosolic Ca2+ levels and mitochondrial health. Accordingly, the hydrogel made from a natural modified biopolymer carboxymethyl tamarind CMT-Hy and encapsulated with TRPV4-modulatory agents affects different parameters of MSCs, such as cell morphology, focal adhesion points, intracellular Ca2+, and reactive oxygen species- and NO-levels. TRPV4 also regulates cell differentiation and biomineralization in vitro. We demonstrate that 4α-10-CMT-Hy and 4α-50-CMT-Hy (the hydrogel encapsulated with 4αPDD, 10 and 50 nM, TRPV4 activator) surfaces upregulate mitochondrial health, i.e., an increase in ATP- and cardiolipin-levels, and improve the mitochondrial membrane potential. The same scaffold turned out to be nontoxic in vivo. 4α-50-CMT-Hy enhances the repair of the bone-drill hole in rat femur, both qualitatively and quantitatively in vivo. We conclude that 4α-50-CMT-Hy as a scaffold is suitable for treating large-scale bone defects at low cost and can be tested for clinical trials.

Role of mitochondria in doxorubicin-mediated cardiotoxicity: From molecular mechanisms to therapeutic strategies

This comprehensive review delves into the pivotal role of mitochondria in doxorubicin-induced cardiotoxicity, a significant complication limiting the clinical use of this potent anthracycline chemotherapeutic agent. Doxorubicin, while effective against various malignancies, is associated with dose-dependent cardiotoxicity, potentially leading to irreversible cardiac damage. The review meticulously dissects the molecular mechanisms underpinning this cardiotoxicity, particularly focusing on mitochondrial dysfunction, a central player in this adverse effect. Central to the discussion is the concept of mitochondrial quality control, including mitochondrial dynamics (fusion/fission balance) and mitophagy. The review presents evidence linking aberrations in these processes to cardiotoxicity in doxorubicin-treated patients. It elucidates how doxorubicin disrupts mitochondrial dynamics, leading to an imbalance between mitochondrial fission and fusion, and impairs mitophagy, culminating in the accumulation of dysfunctional mitochondria and subsequent cardiac cell damage. Furthermore, the review explores emerging therapeutic strategies targeting mitochondrial dysfunction. It highlights the potential of modulating mitochondrial dynamics and enhancing mitophagy to mitigate doxorubicin-induced cardiac damage. These strategies include pharmacological interventions with mitochondrial fission inhibitors, fusion promoters, and agents that modulate mitophagy. The review underscores the promising results from preclinical studies while advocating for more extensive clinical trials to validate these approaches in human patients. In conclusion, this review offers valuable insights into the intricate relationship between mitochondrial dysfunction and doxorubicin-mediated cardiotoxicity. It underscores the need for continued research into targeted mitochondrial therapies as a means to improve the cardiac safety profile of doxorubicin, thereby enhancing the overall treatment outcomes for cancer patients.

Regulation of PM2.5 on mitochondrial damage in H9c2 cells through miR-421/SIRT3 pathway and protective effect of miR-421 inhibitor and resveratrol

Fine particulate matter (PM2.5) exposure is associated with cardiovascular disease (CVD) morbidity and mortality. Mitochondria are sensitive targets of PM2.5, and mitochondrial dysfunction is closely related to the occurrence of CVD. The epigenetic mechanism of PM2.5-triggered mitochondrial injury of cardiomyocytes is unclear. This study focused on the miR-421/SIRT3 signaling pathway to investigate the regulatory mechanism in cardiac mitochondrial dynamics imbalance in rat H9c2 cells induced by PM2.5. Results illustrated that PM2.5 impaired mitochondrial function and caused dynamics homeostasis imbalance. Besides, PM2.5 up-regulated miR-421 and down-regulated SIRT3 gene expression, along with decreasing p-FOXO3a (SIRT3 downstream target gene) and p-Parkin expression and triggering abnormal expression of fusion gene OPA1 and fission gene Drp1. Further, miR-421 inhibitor (miR-421i) and resveratrol significantly elevated the SIRT3 levels in H9c2 cells after PM2.5 exposure and mediated the expression of SOD2, OPA1 and Drp1, restoring the mitochondrial morphology and function. It suggests that miR-421/SIRT3 pathway plays an epigenetic regulatory role in mitochondrial damage induced by PM2.5 and that miR-421i and resveratrol exert protective effects against PM2.5-incurred cardiotoxicity.

Late pregnancy maternal naringin supplementation affects the mitochondria in the cerebellum of Wistar rat offspring via sirtuin 3 and AKT

Dietary polyphenol consumption is associated with a wide range of neuroprotective effects by improving mitochondrial function and signaling. Consequently, the use of polyphenol supplementation has been investigated as an approach to prevent neurodevelopmental diseases during gestation; however, the data obtained are still very inconclusive, mostly because of the difficulty of choosing the correct doses and period of administration to properly prevent neurodegenerative diseases without undermining normal brain development. Thus, we aimed to evaluate the effect of naringin supplementation during the third week of gestation on mitochondrial health and signaling in the cerebellum of 21-day-old offspring. The offspring born to naringin-supplemented dams displayed higher mitochondrial mass, membrane potential, and superoxide content in the cerebellum without protein oxidative damage. Such alterations were associated with dynamin-related protein 1 (DRP1) and phosphorylated AKT (p-AKT) downregulation, whereas the sirtuin 3 (SIRT3) levels were strongly upregulated. Our findings suggest that high dietary polyphenol supplementation during gestation may reduce mitochondrial fission and affect mitochondrial dynamics even 3 weeks after delivery via SIRT3 and p-AKT. Although the offspring born to naringin dams did not present neurobehavioral defects, the mitochondrial alterations elicited by naringin may potentially interfere during neurodevelopment and need to be further investigated.

Mitochondrial and Nuclear DNA Variants in Amyotrophic Lateral Sclerosis: Enrichment in the Mitochondrial Control Region and Sirtuin Pathway Genes in Spinal Cord Tissue

Amyotrophic Lateral Sclerosis (ALS) is a progressive disease with prevalent mitochondrial dysfunctions affecting both upper and lower motor neurons in the motor cortex, brainstem, and spinal cord. Despite mitochondria having their own genome (mtDNA), in humans, most mitochondrial genes are encoded by the nuclear genome (nDNA). Our study aimed to simultaneously screen for nDNA and mtDNA genomes to assess for specific variant enrichment in ALS compared to control tissues. Here, we analysed whole exome (WES) and whole genome (WGS) sequencing data from spinal cord tissues, respectively, of 6 and 12 human donors. A total of 31,257 and 301,241 variants in nuclear-encoded mitochondrial genes were identified from WES and WGS, respectively, while mtDNA reads accounted for 73 and 332 variants. Despite technical differences, both datasets consistently revealed a specific enrichment of variants in the mitochondrial Control Region (CR) and in several of these genes directly associated with mitochondrial dynamics or with Sirtuin pathway genes within ALS tissues. Overall, our data support the hypothesis of a variant burden in specific genes, highlighting potential actionable targets for therapeutic interventions in ALS.

SIRT3 rs11246020 Polymorphism Associated Postprandial Triglyceride Dysmetabolism

Purpose

Energy metabolism is regulated by SIRT3, no research has been done on the connection between lipid metabolism in the oral fat test and SIRT3 polymorphism. Thus, we conducted a case-control study to investigate the connection between postprandial lipid and SIRT3 polymorphism.

Patients and Methods

402 non-obese Chinese subjects were enrolled and their postprandial lipid response to oral fat tolerance test (OFTT) was observed to understand the relationship between rs11246020 gene and postprandial triglyceride metabolism.

Results

In a binary logic regression model, a protective effect of the T allele of the rs11246020 SIRT3 for postprandial hypertriglyceridemia was shown (OR=0.417, 95% CI = 0.219-0.794, p=0.008). Compared to the CC genotype, individuals with the TT+CT variant of the rs11246020 SIRT3 gene demonstrated significantly lower levels of homeostasis model assessment of insulin resistance (HOMA-IR) (p=0.04), postprandial plasma glucose (PPG) (p=0.037), fasting plasma glucose (FPG) (p=0.02), and 4-hour triglyceridemia (Tg) (p=0.032).

Conclusion

The C allele of rs11246020 SIRT3 gene may be a risk factor to increased possibility of postprandial triglyceridemia after an oral fat test, which involved in the mechanism of glucose and insulin metabolism.

Role of mitochondria in doxorubicin-mediated cardiotoxicity: from molecular mechanisms to therapeutic strategies

This comprehensive review delves into the pivotal role of mitochondria in doxorubicin-induced cardiotoxicity, a significant complication limiting the clinical use of this potent anthracycline chemotherapeutic agent. Doxorubicin, while effective against various malignancies, is associated with dose-dependent cardiotoxicity, potentially leading to irreversible cardiac damage. The review meticulously dissects the molecular mechanisms underpinning this cardiotoxicity, particularly focusing on mitochondrial dysfunction, a central player in this adverse effect. Central to the discussion is the concept of mitochondrial quality control (MQC), including mitochondrial dynamics (fusion/fission balance) and mitophagy. The review presents evidence linking aberrations in these processes to cardiotoxicity in doxorubicin-treated patients. It elucidates how doxorubicin disrupts mitochondrial dynamics, leading to an imbalance between mitochondrial fission and fusion, and impairs mitophagy, culminating in the accumulation of dysfunctional mitochondria and subsequent cardiac cell damage. Furthermore, the review explores emerging therapeutic strategies targeting mitochondrial dysfunction. It highlights the potential of modulating mitochondrial dynamics and enhancing mitophagy to mitigate doxorubicin-induced cardiac damage. These strategies include pharmacological interventions with mitochondrial fission inhibitors, fusion promoters, and agents that modulate mitophagy. The review underscores the promising results from preclinical studies while advocating for more extensive clinical trials to validate these approaches in human patients. In conclusion, this review offers valuable insights into the intricate relationship between mitochondrial dysfunction and doxorubicin-mediated cardiotoxicity. It underscores the need for continued research into targeted mitochondrial therapies as a means to improve the cardiac safety profile of doxorubicin, thereby enhancing the overall treatment outcomes for cancer patients.

The human OPA1delTTAG mutation induces adult onset and progressive auditory neuropathy in mice

Dominant optic atrophy (DOA) is one of the most prevalent forms of hereditary optic neuropathies and is mainly caused by heterozygous variants in OPA1, encoding a mitochondrial dynamin-related large GTPase. The clinical spectrum of DOA has been extended to a wide variety of syndromic presentations, called DOAplus, including deafness as the main secondary symptom associated to vision impairment. To date, the pathophysiological mechanisms underlying the deafness in DOA remain unknown. To gain insights into the process leading to hearing impairment, we have analyzed the Opa1delTTAG mouse model that recapitulates the DOAplus syndrome through complementary approaches combining morpho-physiology, biochemistry, and cellular and molecular biology. We found that Opa1delTTAG mutation leads an adult-onset progressive auditory neuropathy in mice, as attested by the auditory brainstem response threshold shift over time. However, the mutant mice harbored larger otoacoustic emissions in comparison to wild-type littermates, whereas the endocochlear potential, which is a proxy for the functional state of the stria vascularis, was comparable between both genotypes. Ultrastructural examination of the mutant mice revealed a selective loss of sensory inner hair cells, together with a progressive degeneration of the axons and myelin sheaths of the afferent terminals of the spiral ganglion neurons, supporting an auditory neuropathy spectrum disorder (ANSD). Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism. In addition, we evidenced an early increase in Sirtuin 3 level and in Beclin1 activity, and subsequently an age-related mtDNA depletion, increased oxidative stress, mitophagy as well as an impaired autophagic flux. Together, these results support a novel role for OPA1 in the maintenance of inner hair cells and auditory neural structures, addressing new challenges for the exploration and treatment of OPA1-linked ANSD in patients.

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.

Senescent hearts from male Ts65Dn mice exhibit preserved function but altered size and nicotinamide adenine dinucleotide pathway signaling

Down syndrome (DS) is associated with congenital heart defects at birth, but cardiac function has not been assessed at older ages. We used the Ts65Dn mouse, a model of DS, to quantify heart structure and function with echocardiography in 18-mo male Ts65Dn and wild-type (WT) mice. Heart weight, nicotinamide adenine dinucleotide (NAD) signaling, and mitochondrial (citrate synthase) activity were investigated, as these pathways may be implicated in the cardiac pathology of DS. The left ventricle was smaller in Ts65Dn versus WT, as well as the anterior wall thickness of the left ventricle during both diastole (LVAW_d; mm) and systole (LVAW_s; mm) as assessed by echocardiography. Other functional metrics were similar between groups including left ventricular area end systole (mm2), left ventricular area end diastole (mm2), left ventricular diameter end systole (mm), left ventricular diameter end diastole (mm), isovolumetric relaxation time (ms), mitral valve atrial peak velocity (mm/s), mitral valve early peak velocity (mm/s), ratio of atrial and early peak velocities (E/A), heart rate (beats/min), ejection fraction (%), and fractional shortening (%). Nicotinamide phosphoribosyltransferase (NAMPT) protein expression, NAD concentration, and tissue weight were lower in the left ventricle of Ts65Dn versus WT mice. Sirtuin 3 (SIRT3) protein expression and citrate synthase activity were not different between groups. Although cardiac function was generally preserved in male Ts65Dn, the altered heart size and bioenergetic disturbances may contribute to differences in aging for DS.

Qishen granule attenuates doxorubicin-induced cardiotoxicity by protecting mitochondrial function and reducing oxidative stress through regulation of Sirtuin3

ETHNOPHARMACOLOGICAL RELEVANCE

Doxorubicin (DOX) is one of the most potent chemotherapy drugs available today. However, the adverse effect of cardiotoxicity limits its clinical application. New approaches are being investigated for the treatment of doxorubicin-induced cardiotoxicity (DIC). Doxorubicin is enriched in mitochondria and it could induce imbalance of protein modification, including acetylation of mitochondria proteins, thereby inducing DIC. Restoration of mitochondria function is an effective way to attenuate DIC. The formula for traditional Chinese medicine Granules of Qishen (QSG) was derived from the classic formula "Zhen-Wu-Tang" which has been extensively used in the treatment of myocardial infarction. It consists of six traditional Chinese medicines, including Astragalus membranaceus var. mongholicus (Bunge) P.K.Hsiao (Fabaceae), Salvia miltiorrhiza Bunge (Lamiaceae), Lonicera japonica Thunb. (Caprifoliaceae), Aconitum carmichaelii Debeaux (Ranunculaceae), Scrophularia ningpoensis Hemsl. (Scrophulariaceae), and Glycyrrhiza uralensis Fisch. (Fabaceae). QSG is a potential anti-DIC formula. A better understanding of the effectiveness and pharmacological mechanisms of QSG will aid in the prevention and treatment of DIC.

AIM OF THE STUDY

The purpose of this research was to explore the effectiveness of QSG in the treatment of DIC and to explore whether QSG could protect mitochondrial function and reduce oxidative damage by activating Sirtuin3(SIRT3)/Acetylated-superoxide dismutase 2(Ac-SOD2) signaling pathway.

MATERIALS AND METHODS

DOX was injected into mice through the tail vein to construct a mouse model of DOX-induced cardiotoxicity to explore the therapeutic effect of QSG in animals. Meanwhile, the H9C2 cell model was used to study the mechanism of QSG. The cardiac function was evaluated by echocardiography, hematoxylin-eosin (H&E) staining and measurement of serum levels of creatine kinase isoenzymes (CK-MB) and lactate dehydrogenase (LDH). Oxidative damage was evaluated by 2',7'-dichlorodihydro fluorescein diacetate (DCFH-DA) staining and Mito-SOX Red staining. Levels of total superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured by following the instructions of commercially available kits. In order to detect the changes in mitochondrial membrane potential, cells were stained using the mitochondrial membrane potential detection kit (JC-1). Western blot analysis was applied to detect protein expressions of SIRT3, Ac-SOD2, Acetylation Lysine (Ac-Lys), Bax and Bcl-2. H9C2 cells were treated with SIRT3 inhibitor, in order to determine if QSG had effects via the SIRT3/Ac-SOD2 pathway.

RESULTS

In vivo studies showed that QSG ameliorated doxorubicin-induced damage of cardiac function in DIC mice model. The ejection fraction (EF) and fractional shortening (FS) were all up-regulated by QSG treatment. QSG decreased MDA levels and increased SOD activity. Meanwhile, doxorubicin induced high level of protein acetylation and QSG restored the acetylated protein back to normal levels. In particular, QSG upregulated expression of SIRT3 and downregulated Ac-SOD level. In vitro study demonstrated that QSG restored mitochondrial membrane potential, increased ATP level and reduced mitochondrial ROS production. When H9C2 cells were co-incubated with SIRT3 inhibitor, the efficacies of QSG on mitochondrial function were abrogated. Meanwhile, the regulative effects of QSG on SIRT3/Ac-SOD2 pathway were also abolished.

CONCLUSION

This study demonstrates that QSG is effective in treating DIC. QSG ameliorates oxidative damage and protects mitochondrial function partly by restoring protein acetylation level and by activating the SIRT3/Ac-SOD2 pathway.

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.

Cardioprotective Action of a Novel Synthetic 19,20-EDP Analog Is Sirt Dependent

ABSTRACT

Mounting evidence suggests that cytochrome P450 epoxygenase-derived metabolites of docosahexaenoic acid, called epoxydocosapentaenoic acids (EDPs), limit mitochondrial damage after cardiac injury. In particular, the 19,20-EDP regioisomer has demonstrated potent cardioprotective action. Thus, we investigated our novel synthetic 19,20-EDP analog SA-22 for protection against cardiac ischemia-reperfusion (IR) injury. Isolated C57BL/6J mouse hearts were perfused through Langendorff apparatus for 20 minutes to obtain baseline function, followed by 30 minutes of global ischemia. Hearts were then treated with vehicle, 19,20-EDP, SA-22, or SA-22 with the pan-sirtuin inhibitor nicotinamide or the SIRT3-selective inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP) at the start of 40 minutes reperfusion (N = 5-8). We assessed IR injury-induced changes in recovery of myocardial function, using left ventricular developed pressure and systolic and diastolic pressure change. Tissues were assessed for electron transport chain function, SIRT1 and SIRT3, optic atrophy type 1, and caspase-1. We also used H9c2 cells in an in vitro model of hypoxia/reoxygenation injury (N = 3-6). Hearts perfused with SA-22 had significantly improved postischemic left ventricular developed pressure, systolic and diastolic recovery (64% of baseline), compared with vehicle control (15% of baseline). In addition, treatment with SA-22 led to better catalytic function observed in electron transport chain and SIRT enzymes. The protective action of SA-22 resulted in reduced activation of pyroptosis in both hearts and cells after injury. Interestingly, although nicotinamide cotreatment worsened functional outcomes, cell survival, and attenuated sirtuin activity, it failed to completely attenuate SA-22-induced protection against pyroptosis, possibly indicating EDPs exert cytoprotection through pleiotropic mechanisms. In short, these data demonstrate the potential of our novel synthetic 19,20-EDP analog, SA-22, against IR/hypoxia-reoxygenation injury and justify further development of therapeutic agents based on 19,20-EDP.

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.

A review for the correlation between optic atrophy 1-dependent mitochondrial fusion and cardiovascular disorders

Mitochondrial dynamics homeostasis is sustained by continuous and balanced fission and fusion, which are determinants of morphology, abundance, biogenesis and mitophagy of mitochondria. Optic atrophy 1 (OPA1), as the only inner mitochondrial membrane fusion protein, plays a key role in stabilizing mitochondrial dynamics. The disturbance of mitochondrial dynamics contributes to the pathophysiological progress of cardiovascular disorders, which are the main cause of death worldwide in recent decades and result in tremendous social burden. In this review, we describe the latest findings regarding OPA1 and its role in mitochondrial fusion. We summarize the post-translational modifications (PTMs) for OPA1 and its regulatory role in mitochondrial dynamics. Then the diverse cell fates caused by OPA1 expression during cardiovascular disorders are discussed. Moreover, cardiovascular disorders (such as heart failure, myocardial ischemia/reperfusion injury, cardiomyopathy and cardiac hypertrophy) relevant to OPA1-dependent mitochondrial dynamics imbalance have been detailed. Finally, we highlight the potential that targeting OPA1 to impact mitochondrial fusion may be used as a novel strategy against cardiovascular disorders.

Sirtuin3 ensures the metabolic plasticity of neurotransmission during glucose deprivation

Neurotransmission is an energetically expensive process that underlies cognition. During intense electrical activity or dietary restrictions, the glucose level in the brain plummets, forcing neurons to utilize alternative fuels. However, the molecular mechanisms of neuronal metabolic plasticity remain poorly understood. Here, we demonstrate that glucose-deprived neurons activate the CREB and PGC1α transcriptional program, which induces expression of the mitochondrial deacetylase Sirtuin 3 (Sirt3) both in vitro and in vivo. We show that Sirt3 localizes to axonal mitochondria and stimulates mitochondrial oxidative capacity in hippocampal nerve terminals. Sirt3 plays an essential role in sustaining synaptic transmission in the absence of glucose by providing metabolic support for the retrieval of synaptic vesicles after release. These results demonstrate that the transcriptional induction of Sirt3 facilitates the metabolic plasticity of synaptic transmission.

Sirtuins, a key regulator of ageing and age-related neurodegenerative diseases

Sirtuins are Nicotinamide Adenine Dinucleotide (NAD+) dependent class ІΙΙ histone deacetylases enzymes (HDACs) present from lower to higher organisms such as bacteria (Sulfolobus solfataricus L. major), yeasts (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), humans (Homo sapiens sapiens), even in plants such as rice (Oryza sativa), thale cress (Arabidopsis thaliana), vine (Vitis vinifera L.) tomato (Solanum lycopersicum). Sirtuins play an important role in the regulation of various vital cellular functions during metabolism and ageing. It also plays a neuroprotective role by modulating several biological pathways such as apoptosis, DNA repair, protein aggregation, and inflammatory processes associated with ageing and neurodegenerative diseases. In this review, we have presented an updated Sirtuins and its role in ageing and age-related neurodegenerative diseases (NDDs). Further, this review also describes the therapeutic potential of Sirtuins and the use of Sirtuins inhibitor/activator for altering the NDDs disease pathology.

SIRT4 is a regulator of human skeletal muscle fatty acid metabolism influencing inner and outer mitochondrial membrane-mediated fusion

OBJECTIVE

The mitochondrial phenotype, governed by the balance of fusion-fission, is a key determinant of energy metabolism. The inner and outer mitochondrial membrane (IMM) fusion proteins optic atrophy 1 (OPA1) and Mitofusin 1 and 2 (Mfn1/2) play an important role in this process. Recent evidence also shows that Sirtuin 4 (SIRT4), located within the mitochondria, is involved in the regulation of fatty acid oxidation. The purpose of this study was to determine if SIRT4 expression regulates inner and outer mitochondrial-mediated fusion and substrate utilization within differentiated human skeletal muscle cells (HSkMC).

MATERIAL AND METHODS

SIRT4 expression was knocked down using small interfering RNA (siRNA) transfection in differentiated HSkMC. Following knockdown, mitochondrial respiration was determined by high-resolution respirometry (HRR) using the Oroboros Oxygraph O2k. Live cell confocal microscopy, quantified using the Mitochondrial Network Analysis (MiNA) toolset, was used to examine mitochondrial morphological change. This was further examined through the measurement of key metabolic and mitochondrial morphological regulators (mRNA and protein) induced by knockdown.

RESULTS

SIRT4 knockdown resulted in a significant decrease in LEAK respiration, potentially explained by a decrease in ANT1 protein expression. Knockdown further increased oxidative phosphorylation and protein expression of key regulators of fatty acid metabolism. Quantitative analysis of live confocal imaging of fluorescently labelled mitochondria following SIRT4 knockdown supported the role SIRT4 plays in the regulation of mitochondrial morphology, as emphasized by an increase in mitochondrial network branches and junctions. Measurement of key regulators of mitochondrial dynamics illustrated a significant increase in mitochondrial fusion proteins Mfn1, OPA1 respectively, indicative of an increase in mitochondrial size.

CONCLUSIONS

This study provides evidence of a direct relationship between the mitochondrial phenotype and substrate oxidation in HSkMC. We identify SIRT4 as a key protagonist of energy metabolism via its regulation of IMM and OMM fusion proteins, OPA1 and Mfn1. SIRT4 knockdown increases mitochondrial capacity to oxidize fatty acids, decreasing LEAK respiration and further increasing mitochondrial elongation via its regulation of mitochondrial fusion.

Inhibiting mir-34a-5p regulates doxorubicin-induced autophagy disorder and alleviates myocardial pyroptosis by targeting Sirt3-AMPK pathway

Doxorubicin (DOX) is a commonly used chemotherapy drug widely applied in various cancers such as breast cancer, leukemia, and sarcomas. However, its usage is limited by cardiotoxicity. Additionally, the cardiac toxicity of DOX accumulates with dose and duration, making it imperative to identify therapeutic targets for DOX-induced cardiomyopathy (DIC). It has been reported that miRNAs are involved in the progression of DIC. Mir-34a-5p has been identified as an early diagnostic marker for DIC. While studies have shown the involvement of mir-34a-5p in DIC apoptosis, it has not been validated in animal models, nor has the potential improvement of DIC by inhibiting mir-34a-5p been confirmed. Autophagy and pyroptosis are key factors in the development of DIC and can serve as therapeutic targets for its treatment. In this study, we found that mir-34a-5p was upregulated in the heart after DOX treatment and that the inhibition of mir-34-5p reduced autophagy and pyroptosis in DIC. We also found that the inhibition of mir-34a-5p inhibited pyroptosis by regulating autophagy and reducing mitochondrial reactive oxygen species. Moreover, we identified Sirtuin3 (Sirt3) as a target gene of mir-34a-5p using a double-luciferase reporter assay. overexpression Sirt3 reduced pyroptosis by alleviating autophagy. Our research findings suggest that inhibiting mir-34a-5p has a beneficial role in alleviating autophagy and pyroptosis in DIC. This provides therapeutic prospects for treating DIC.

Targeting Mitochondrial Dysfunction and Oxidative Stress to Prevent the Neurodegeneration of Retinal Ganglion Cells

The imbalance of redox homeostasis contributes to neurodegeneration, including that related to the visual system. Mitochondria, essential in providing energy and responsible for several cell functions, are a significant source of reactive oxygen and/or nitrogen species, and they are, in turn, sensitive to free radical imbalance. Dysfunctional mitochondria are implicated in the development and progression of retinal pathologies and are directly involved in retinal neuronal degeneration. Retinal ganglion cells (RGCs) are higher energy consumers susceptible to mitochondrial dysfunctions that ultimately cause RGC loss. Proper redox balance and mitochondrial homeostasis are essential for maintaining healthy retinal conditions and inducing neuroprotection. In this respect, the antioxidant treatment approach is effective against neuronal oxidative damage and represents a challenge for retinal diseases. Here, we highlighted the latest findings about mitochondrial dysfunction in retinal pathologies linked to RGC degeneration and discussed redox-related strategies with potential neuroprotective properties.

Pectolinarigenin Improves Oxidative Stress and Apoptosis in Mouse NSC-34 Motor Neuron Cell Lines Induced by C9-ALS-Associated Proline-Arginine Dipeptide Repeat Proteins by Enhancing Mitochondrial Fusion Mediated via the SIRT3/OPA1 Axis

Amyotrophic lateral sclerosis (ALS) is considered a fatal progressive degeneration of motor neurons (MN) caused by oxidative stress and mitochondrial dysfunction. There are currently no treatments available. The most common inherited form of ALS is the C9orf72 mutation (C9-ALS). The proline-arginine dipeptide repeat protein (PR-DPR) produced by C9-ALS has been confirmed to be a functionally acquired pathogenic factor that can cause increased ROS, mitochondrial defects, and apoptosis in motor neurons. Pectolinarigenin (PLG) from the traditional medicinal herb Linaria vulgaris has antioxidant and anti-apoptotic properties. I established a mouse NSC-34 motor neuron cell line model expressing PR-DPR and confirmed the neuroprotective effect of PLG. The results showed that ROS production and apoptosis caused by PR-DPR could be improved by PLG treatment. In terms of mechanism research, PR-DPR inhibited the activity of the mitochondrial fusion proteins OPA1 and mitofusin 2. Conversely, the expression of fission protein fission 1 and dynamin-related protein 1 (DRP1) increased. However, PLG treatment reversed these effects. Furthermore, I found that PLG increased the expression and deacetylation of OPA1. Deacetylation of OPA1 enhances mitochondrial fusion and resistance to apoptosis. Finally, transfection with Sirt3 small interfering RNA abolished the neuroprotective effects of PLG. In summary, the mechanism by which PLG alleviates PR-DPR toxicity is mainly achieved by activating the SIRT3/OPA1 axis to regulate the balance of mitochondrial dynamics. Taken together, the potential of PLG in preclinical studies for C9-ALS drug development deserves further evaluation.

Intermittent fasting promotes adipocyte mitochondrial fusion through Sirt3-mediated deacetylation of Mdh2

Fat deposition and lipid metabolism are closely related to the morphology, structure and function of mitochondria. The morphology of mitochondria between fusion and fission processes is mainly regulated by protein posttranslational modification. Intermittent fasting (IF) promotes high expression of Sirtuin 3 (Sirt3) and induces mitochondrial fusion in high-fat diet (HFD)-fed mice. However, the mechanism by which Sirt3 participates in mitochondrial protein acetylation during IF to regulate mitochondrial fusion and fission dynamics remains unclear. This article demonstrates that IF promotes mitochondrial fusion and improves mitochondrial function in HFD mouse inguinal white adipose tissue. Proteomic sequencing revealed that IF increased protein deacetylation levels in HFD mice and significantly increased Sirt3 mRNA and protein expression. After transfecting with Sirt3 overexpression or interference vectors into adipocytes, we found that Sirt3 promoted adipocyte mitochondrial fusion and improved mitochondrial function. Furthermore, Sirt3 regulates the JNK-FIS1 pathway by deacetylating malate dehydrogenase 2 (MDH2) to promote mitochondrial fusion. In summary, our study indicates that IF promotes mitochondrial fusion and improves mitochondrial function by upregulating the high expression of Sirt3 in HFD mice, promoting deacetylation of MDH2 and inhibiting the JNK-FIS1 pathway. This research provides theoretical support for studies related to energy limitation and animal lipid metabolism.

Mitochondria-Melanocyte cellular interactions: An emerging mechanism of vitiligo pathogenesis

Mitochondria has emerged as a potential modulator of melanocyte function other than just meeting its cellular ATP demands. Mitochondrial DNA defects are now an established cause of maternal inheritance diseases. Recent cellular studies have highlighted the mitochondrial interaction with other cellular organelles that lead to disease conditions such as in Duchenne muscular dystrophy, where defective mitochondria was found in melanocytes of these patients. Vitiligo, a depigmentory ailment of the skin, is another such disorder whose pathogenesis is now found to be associated with mitochondria. The complete absence of melanocytes at the lesioned site in vitiligo is a fact; however, the precise mechanism of this destruction is still undefined. In this review we have tried to discuss and link the emerging facts of mitochondrial function or its inter- and intra-organellar communications in vitiligo pathogenesis. Mitochondrial close association with melanosomes, molecular involvement in melanocyte-keratinocyte communication and melanocyte survival are new paradigm of melanogenesis that could ultimately account for vitiligo. This definitely adds the new dimensions to our understanding of vitiligo, its management and designing of future mitochondrial targeted therapy for vitiligo.

p53 contributes to cardiovascular diseases via mitochondria dysfunction: A new paradigm

Cardiovascular diseases (CVDs) are leading causes of global mortality; however, their underlying mechanisms remain unclear. The tumor suppressor factor p53 has been extensively studied for its role in cancer and is also known to play an important role in regulating CVDs. Abnormal p53 expression levels and modifications contribute to the occurrence and development of CVDs. Additionally, mounting evidence underscores the critical involvement of mitochondrial dysfunction in CVDs. Notably, studies indicate that p53 abnormalities directly correlate with mitochondrial dysfunction and may even interact with each other. Encouragingly, small molecule inhibitors targeting p53 have exhibited remarkable effects in animal models of CVDs. Moreover, therapeutic strategies aimed at mitochondrial-related molecules and mitochondrial replacement therapy have demonstrated their advantageous potential. Therefore, targeting p53 or mitochondria holds immense promise as a pioneering therapeutic approach for combating CVDs. In this comprehensive review, we delve into the mechanisms how p53 influences mitochondrial dysfunction, including energy metabolism, mitochondrial oxidative stress, mitochondria-induced apoptosis, mitochondrial autophagy, and mitochondrial dynamics, in various CVDs. Furthermore, we summarize and discuss the potential significance of targeting p53 or mitochondria in the treatment of CVDs.

Outcomes of hypothalamic oxytocin neuron-driven cardioprotection after acute myocardial infarction

Altered autonomic balance is a hallmark of numerous cardiovascular diseases, including myocardial infarction (MI). Although device-based vagal stimulation is cardioprotective during chronic disease, a non-invasive approach to selectively stimulate the cardiac parasympathetic system immediately after an infarction does not exist and is desperately needed. Cardiac vagal neurons (CVNs) in the brainstem receive powerful excitation from a population of neurons in the paraventricular nucleus (PVN) of the hypothalamus that co-release oxytocin (OXT) and glutamate to excite CVNs. We tested if chemogenetic activation of PVN-OXT neurons following MI would be cardioprotective. The PVN of neonatal rats was transfected with vectors to selectively express DREADDs within OXT neurons. At 6 weeks of age, an MI was induced and DREADDs were activated with clozapine-N-oxide. Seven days following MI, patch-clamp electrophysiology confirmed the augmented excitatory neurotransmission from PVN-OXT neurons to downstream nuclei critical for parasympathetic activity with treatment (43.7 ± 10 vs 86.9 ± 9 pA; MI vs. treatment), resulting in stark improvements in survival (85% vs. 95%; MI vs. treatment), inflammation, fibrosis assessed by trichrome blue staining, mitochondrial function assessed by Seahorse assays, and reduced incidence of arrhythmias (50% vs. 10% cumulative incidence of ventricular fibrillation; MI vs. treatment). Myocardial transcriptomic analysis provided molecular insight into potential cardioprotective mechanisms, which revealed the preservation of beneficial signaling pathways, including muscarinic receptor activation, in treated animals. These comprehensive results demonstrate that the PVN-OXT network could be a promising therapeutic target to quickly activate beneficial parasympathetic-mediated cellular pathways within the heart during the early stages of infarction.

Sirtuins as Potential Targets for Neuroprotection: Mechanisms of Early Brain Injury Induced by Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a prevalent cerebrovascular disease with significant global mortality and morbidity rates. Despite advancements in pharmacological and surgical approaches, the quality of life for SAH survivors has not shown substantial improvement. Traditionally, vasospasm has been considered a primary contributor to death and disability following SAH, but anti-vasospastic therapies have not demonstrated significant benefits for SAH patients' prognosis. Emerging studies suggest that early brain injury (EBI) may play a crucial role in influencing SAH prognosis. Sirtuins (SIRTs), a group of NAD + -dependent deacylases comprising seven mammalian family members (SIRT1 to SIRT7), have been found to be involved in neural tissue development, plasticity, and aging. They also exhibit vital functions in various central nervous system (CNS) processes, including cognition, pain perception, mood, behavior, sleep, and circadian rhythms. Extensive research has uncovered the multifaceted roles of SIRTs in CNS disorders, offering insights into potential markers for pathological processes and promising therapeutic targets (such as SIRT1 activators and SIRT2 inhibitors). In this article, we provide an overview of recent research progress on the application of SIRTs in subarachnoid hemorrhage and explore their underlying mechanisms of action.

Mitochondrial Cristae Morphology Reflecting Metabolism, Superoxide Formation, Redox Homeostasis, and Pathology

Significance: Mitochondrial (mt) reticulum network in the cell possesses amazing ultramorphology of parallel lamellar cristae, formed by the invaginated inner mitochondrial membrane. Its non-invaginated part, the inner boundary membrane (IBM) forms a cylindrical sandwich with the outer mitochondrial membrane (OMM). Crista membranes (CMs) meet IBM at crista junctions (CJs) of mt cristae organizing system (MICOS) complexes connected to OMM sorting and assembly machinery (SAM). Cristae dimensions, shape, and CJs have characteristic patterns for different metabolic regimes, physiological and pathological situations. Recent Advances: Cristae-shaping proteins were characterized, namely rows of ATP-synthase dimers forming the crista lamella edges, MICOS subunits, optic atrophy 1 (OPA1) isoforms and mitochondrial genome maintenance 1 (MGM1) filaments, prohibitins, and others. Detailed cristae ultramorphology changes were imaged by focused-ion beam/scanning electron microscopy. Dynamics of crista lamellae and mobile CJs were demonstrated by nanoscopy in living cells. With tBID-induced apoptosis a single entirely fused cristae reticulum was observed in a mitochondrial spheroid. Critical Issues: The mobility and composition of MICOS, OPA1, and ATP-synthase dimeric rows regulated by post-translational modifications might be exclusively responsible for cristae morphology changes, but ion fluxes across CM and resulting osmotic forces might be also involved. Inevitably, cristae ultramorphology should reflect also mitochondrial redox homeostasis, but details are unknown. Disordered cristae typically reflect higher superoxide formation. Future Directions: To link redox homeostasis to cristae ultramorphology and define markers, recent progress will help in uncovering mechanisms involved in proton-coupled electron transfer via the respiratory chain and in regulation of cristae architecture, leading to structural determination of superoxide formation sites and cristae ultramorphology changes in diseases. Antioxid. Redox Signal. 39, 635-683.

Mitochondrial Dynamics and Cristae Shape Changes During Metabolic Reprogramming

Significance: The architecture of the mitochondrial network and cristae critically impact cell differentiation and identity. Cells undergoing metabolic reprogramming to aerobic glycolysis (Warburg effect), such as immune cells, stem cells, and cancer cells, go through controlled modifications in mitochondrial architecture, which is critical for achieving the resulting cellular phenotype. Recent Advances: Recent studies in immunometabolism have shown that the manipulation of mitochondrial network dynamics and cristae shape directly affects T cell phenotype and macrophage polarization through altering energy metabolism. Similar manipulations also alter the specific metabolic phenotypes that accompany somatic reprogramming, stem cell differentiation, and cancer cells. The modulation of oxidative phosphorylation activity, accompanied by changes in metabolite signaling, reactive oxygen species generation, and adenosine triphosphate levels, is the shared underlying mechanism. Critical Issues: The plasticity of mitochondrial architecture is particularly vital for metabolic reprogramming. Consequently, failure to adapt the appropriate mitochondrial morphology often compromises the differentiation and identity of the cell. Immune, stem, and tumor cells exhibit striking similarities in their coordination of mitochondrial morphology with metabolic pathways. However, although many general unifying principles can be observed, their validity is not absolute, and the mechanistic links thus need to be further explored. Future Directions: Better knowledge of the molecular mechanisms involved and their relationships to both mitochondrial network and cristae morphology will not only further deepen our understanding of energy metabolism but may also contribute to improved therapeutic manipulation of cell viability, differentiation, proliferation, and identity in many different cell types. Antioxid. Redox Signal. 39, 684-707.

Mitochondrial dysfunction at the crossroad of cardiovascular diseases and cancer

A large body of evidence indicates the existence of a complex pathophysiological relationship between cardiovascular diseases and cancer. Mitochondria are crucial organelles whose optimal activity is determined by quality control systems, which regulate critical cellular events, ranging from intermediary metabolism and calcium signaling to mitochondrial dynamics, cell death and mitophagy. Emerging data indicate that impaired mitochondrial quality control drives myocardial dysfunction occurring in several heart diseases, including cardiac hypertrophy, myocardial infarction, ischaemia/reperfusion damage and metabolic cardiomyopathies. On the other hand, diverse human cancers also dysregulate mitochondrial quality control to promote their initiation and progression, suggesting that modulating mitochondrial homeostasis may represent a promising therapeutic strategy both in cardiology and oncology. In this review, first we briefly introduce the physiological mechanisms underlying the mitochondrial quality control system, and then summarize the current understanding about the impact of dysregulated mitochondrial functions in cardiovascular diseases and cancer. We also discuss key mitochondrial mechanisms underlying the increased risk of cardiovascular complications secondary to the main current anticancer strategies, highlighting the potential of strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction and tumorigenesis. It is hoped that this summary can provide novel insights into precision medicine approaches to reduce cardiovascular and cancer morbidities and mortalities.

Mechanisms of Modulation of Mitochondrial Architecture

Mitochondrial network architecture plays a critical role in cellular physiology. Indeed, alterations in the shape of mitochondria upon exposure to cellular stress can cause the dysfunction of these organelles. In this scenario, mitochondrial dynamics proteins and the phospholipid composition of the mitochondrial membrane are key for fine-tuning the modulation of mitochondrial architecture. In addition, several factors including post-translational modifications such as the phosphorylation, acetylation, SUMOylation, and o-GlcNAcylation of mitochondrial dynamics proteins contribute to shaping the plasticity of this architecture. In this regard, several studies have evidenced that, upon metabolic stress, mitochondrial dynamics proteins are post-translationally modified, leading to the alteration of mitochondrial architecture. Interestingly, several proteins that sustain the mitochondrial lipid composition also modulate mitochondrial morphology and organelle communication. In this context, pharmacological studies have revealed that the modulation of mitochondrial shape and function emerges as a potential therapeutic strategy for metabolic diseases. Here, we review the factors that modulate mitochondrial architecture.