Sirtuin 3-activated superoxide dismutase 2 mediates fluoride-induced osteoblastic differentiation in vitro and in vivo by down-regulating reactive oxygen species.

Skeletal fluorosis is a chronic metabolic bone disease caused by long-term excessive fluoride intake. Abnormal differentiation of osteoblasts plays an important role in disease progression. Research on the mechanism of fluoride-mediated bone differentiation is necessary for the prevention and treatment of skeletal fluorosis. In the present study, a rat model of fluorosis was established by exposing it to drinking water containing 50 mg/L F-. We found that fluoride promoted Runt-related transcription factor 2 (RUNX2) as well as superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) expression in osteoblasts of rat bone tissue. In vitro, we also found that 4 mg/L sodium fluoride promoted osteogenesis-related indicators as well as SOD2 and SIRT3 expression in MG-63 and Saos-2 cells. In addition, we unexpectedly discovered that fluoride suppressed the levels of reactive oxygen species (ROS) and mitochondrial reactive oxygen species (mtROS) in osteoblasts. When SOD2 or SIRT3 was inhibited in MG-63 cells, fluoride-decreased ROS and mtROS were alleviated, which in turn inhibited fluoride-promoted osteogenic differentiation. In conclusion, our results suggest that SIRT3/SOD2 mediates fluoride-promoted osteoblastic differentiation by down-regulating reactive oxygen species.

Frataxin Loss Promotes Angiotensin II-Induced Endothelial-to-Mesenchymal Transition.

BACKGROUND: The metabolic flexibility of endothelial cells is linked to their phenotypic plasticity. Frataxin is critical in determining the iron metabolism and fate of endothelial cells. This study aimed to investigate frataxin-mediated metabolic remodeling during the endothelial-to-mesenchymal transition (EndoMT). METHODS AND RESULTS: Endothelial cell-specific frataxin knockout and frataxin mutation mice were subjected to angiotensin II to induce hypertension. EndoMT and cardiac fibrosis were assessed using histological and protein expression analyses. Fatty acid oxidation (FAO) in microvascular endothelial cells was measured using a Seahorse XF96 analyzer. We showed that inhibition of FAO accompanies angiotensin II-induced EndoMT. Frataxin knockout mice promote EndoMT, associated with increased cardiac fibrosis following angiotensin II infusion. Angiotensin II reduces frataxin expression, which leads to mitochondrial iron overload and subsequent carbonylation of sirtuin 3. In turn, carbonylated sirtuin 3 contributes to the acetylated frataxin at lysine 189, making it more prone to degradation. The frataxin/sirtuin 3 feedback loop reduces hydroxyl-CoA dehydrogenase α subunit-mediated FAO. Additionally, silymarin is a scavenger of free radicals, restoring angiotensin II-induced reduction of FAO activity and sirtuin 3 and frataxin expression, improving EndoMT both in vitro and in vivo. Furthermore, frataxin mutation mice showed suppressed EndoMT and improved cardiac fibrosis. CONCLUSIONS: The frataxin/sirtuin 3 feedback loop has the potential to attenuate angiotensin II-induced EndoMT by improving FAO.

ANXA1sp modulates the protective effect of Sirt3-induced mitophagy against sepsis-induced myocardial injury in mice.

AIM: Sepsis-induced myocardial injury (SIMI) may be associated with insufficient mitophagy in cardiomyocytes, but the exact mechanism involved remains unknown. Sirtuin 3 (Sirt3) is mainly found in the mitochondrial matrix and is involved in repairing mitochondrial function through means such as the activation of autophagy. Previously, we demonstrated that the annexin-A1 small peptide (ANXA1sp) can promote Sirt3 expression in mitochondria. In this study, we hypothesized that the activation of Sirt3 by ANXA1sp induces mitophagy, thereby providing a protective effect against SIMI in mice. METHODS: A mouse model of SIMI was established via cecal ligation and puncture. Intraperitoneal injections of ANXA1sp, 3TYP, and 3MA were administered prior to modeling. After successful modeling, IL-6, TNF-α, CK-MB, and CTn-I levels were measured; cardiac function was assessed using echocardiography; myocardial mitochondrial membrane potential, ROS, and ATP production were determined; myocardial mitochondrial ultrastructure was observed using transmission electron microscopy; and the expression levels of Sirt3 and autophagy-related proteins were detected using western blotting. RESULTS: ANXA1sp significantly reduced serum IL-6, TNF-α, CK-MB, and CTn-I levels; decreased myocardial ROS production; increased mitochondrial membrane potential and ATP synthesis; and improved myocardial mitochondrial ultrastructure in septic mice. Furthermore, ANXA1sp promoted Sirt3 expression and activated the AMPK-mTOR pathway to induce myocardial mitophagy. These protective effects of ANXA1sp were reversed upon treatment with the Sirt3 blocker, 3-TYP. CONCLUSION: ANXA1sp can reverse SIMI, and the underlying mechanism may be related to the activation of the AMPK-mTOR pathway following upregulation of Sirt3 by ANXA1sp, which, in turn, induces autophagy.

Activation of Sirtuin3 by honokiol ameliorates alveolar epithelial cell senescence in experimental silicosis via the cGAS-STING pathway.

BACKGROUND: Silicosis, characterized by interstitial lung inflammation and fibrosis, poses a significant health threat. ATII cells play a crucial role in alveolar epithelial repair and structural integrity maintenance. Inhibiting ATII cell senescence has shown promise in silicosis treatment. However, the mechanism behind silica-induced senescence remains elusive. METHODS: The study employed male C57BL/6 N mice and A549 human alveolar epithelial cells to investigate silicosis and its potential treatment. Silicosis was induced in mice via intratracheal instillation of crystalline silica particles, with honokiol administered intraperitoneally for 14 days. Silica-induced senescence in A549 cells was confirmed, and SIRT3 knockout and overexpression cell lines were generated. Various analyses were conducted, including immunoblotting, qRT-PCR, histology, and transmission electron microscopy. Statistical significance was determined using one-way ANOVA with Tukey's post-hoc test. RESULTS: This study elucidates how silica induces ATII cell senescence, emphasizing mtDNA damage. Notably, honokiol (HKL) emerges as a promising anti-senescence and anti-fibrosis agent, acting through sirt3. honokiol effectively attenuated senescence in ATII cells, dependent on sirt3 expression, while mitigating mtDNA damage. Sirt3, a class III histone deacetylase, regulates senescence and mitochondrial stress. HKL activates sirt3, protecting against pulmonary fibrosis and mitochondrial damage. Additionally, HKL downregulated cGAS expression in senescent ATII cells induced by silica, suggesting sirt3's role as an upstream regulator of the cGAS/STING signaling pathway. Moreover, honokiol treatment inhibited the activation of the NF-κB signaling pathway, associated with reduced oxidative stress and mtDNA damage. Notably, HKL enhanced the activity of SOD2, crucial for mitochondrial function, through sirt3-mediated deacetylation. Additionally, HKL promoted the deacetylation activity of sirt3, further safeguarding mtDNA integrity. CONCLUSIONS: This study uncovers a natural compound, HKL, with significant anti-fibrotic properties through activating sirt3, shedding light on silicosis pathogenesis and treatment avenues.

Quantitative analysis of the lysine acetylome reveals the role of SIRT3-mediated HSP60 deacetylation in suppressing intracellular Mycobacterium tuberculosis survival.

Protein acetylation and deacetylation are key epigenetic modifications that regulate the initiation and development of several diseases. In the context of infection with Mycobacterium tuberculosis (M. tb), these processes are essential for host-pathogen interactions and immune responses. However, the specific effects of acetylation and deacetylation on cellular functions during M. tb infection are not fully understood. This study employed Tandem Mass Tag (TMT) labeling for quantitative proteomic profiling to examine the acetylproteome (acetylome) profiles of noninfected and M. tb-infected macrophages. We identified 715 acetylated peptides from 1,072 proteins and quantified 544 lysine acetylation sites (Kac) in 402 proteins in noninfected and M. tb-infected macrophages. Our research revealed a link between acetylation events and metabolic changes during M. tb infection. Notably, the deacetylation of heat shock protein 60 (HSP60), a key chaperone protein, was significantly associated with this process. Specifically, the deacetylation of HSP60 at K96 by sirtuin3 (SIRT3) enhances macrophage apoptosis, leading to the elimination of intracellular M. tb. These findings underscore the pivotal role of the SIRT3-HSP60 axis in the host immune response to M. tb. This study offers a new perspective on host protein acetylation and suggests that targeting host-directed therapies could be a promising approach for tuberculosis immunotherapy. IMPORTANCE: Protein acetylation is crucial for the onset, development, and outcome of tuberculosis (TB). Our study comprehensively investigated the dynamics of lysine acetylation during M. tb infection, shedding light on the intricate host-pathogen interactions that underlie the pathogenesis of tuberculosis. Using an advanced quantitative lysine proteomics approach, different profiles of acetylation sites and proteins in macrophages infected with M. tb were identified. Functional enrichment and protein-protein network analyses revealed significant associations between acetylated proteins and key cellular pathways, highlighting their critical role in the host response to M. tb infection. Furthermore, the deacetylation of HSP60 and its influence on macrophage-mediated clearance of M. tb underscore the functional significance of acetylation in tuberculosis pathogenesis. In conclusion, this study provides valuable insights into the regulatory mechanisms governing host immune responses to M. tb infection and offers promising avenues for developing novel therapeutic interventions against TB.

Effect of 3-nitropropionic acid on sirtuin gene expression in Sirt3 deficient mice.

Huntington's disease (HD) is an autosomal inherited progressive neurodegenerative disorder which is caused by the CAG trinucleotide repeat in the huntingtin gene. The mutation induces mitochondrial dysfunction in neurons, which leads to striatal neuronal loss. The efficacy of the available therapies is limited, thus acquisition of more data about the pathomechanism of HD and development of new strategies is urgent. Sirtuins (Sirt1-7) belong to the histone deacetylase family, and interestingly they have been associated with HD, however, their role in HD is still not fully understood. To clarify the role of sirtuins in HD, we utilized a 3-nitropropionic acid (3-NP) induced HD model and assessed alterations in gene expression using RT-PCR. Moreover, we studied the extension of neurodegeneration in the striatum, and behavioural changes. Furthermore, we involved Sirt3 knockout (Sirt3KO) mice to investigate the impact of Sirt3 deficiency in the expression of the other sirtuins. Our results showed that with 3-NP treatment, the mRNA level of Sirt2,5,7 changed significantly in wild-type (WT) mice, whereas in Sirt3KO animals there was no change. Interestingly, Sirt3 deficiency did not exacerbate 3-NP-mediated striatal neuronal loss, while Sirt3KO animals showed higher mortality than WT littermates. However, the absence of Sirt3 did not affect the behaviour of animals. Finally, we demonstrated that the changes in the expression of sirtuins are age- and sex- dependent. According to our findings, there is evidence that Sirt3 has a major impact on the regulation of other sirtuin isoforms, survival and neuroprotection. However, this neuroprotective effect does not manifest in the behaviour.

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.

Plasma Proteomics Identifies B2M as a Regulator of Pulmonary Hypertension in Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Pulmonary hypertension (PH) represents an important phenotype in heart failure with preserved ejection fraction (HFpEF). However, management of PH-HFpEF is challenging because mechanisms involved in the regulation of PH-HFpEF remain unclear. METHODS: We used a mass spectrometry-based comparative plasma proteomics approach as a sensitive and comprehensive hypothesis-generating discovery technique to profile proteins in patients with PH-HFpEF and control subjects. We then validated and investigated the role of one of the identified proteins using in vitro cell cultures, in vivo animal models, and independent cohort of human samples. RESULTS: Plasma proteomics identified high protein abundance levels of B2M (ß2-microglobulin) in patients with PH-HFpEF. Interestingly, both circulating and skeletal muscle levels of B2M were increased in mice with skeletal muscle SIRT3 (sirtuin-3) deficiency or high-fat diet-induced PH-HFpEF. Plasma and muscle biopsies from a validation cohort of PH-HFpEF patients were found to have increased B2M levels, which positively correlated with disease severity, especially pulmonary capillary wedge pressure and right atrial pressure at rest. Not only did the administration of exogenous B2M promote migration/proliferation in pulmonary arterial vascular endothelial cells but it also increased PCNA (proliferating cell nuclear antigen) expression and cell proliferation in pulmonary arterial vascular smooth muscle cells. Finally, B2m deletion improved glucose intolerance, reduced pulmonary vascular remodeling, lowered PH, and attenuated RV hypertrophy in mice with high-fat diet-induced PH-HFpEF. CONCLUSIONS: Patients with PH-HFpEF display higher circulating and skeletal muscle expression levels of B2M, the magnitude of which correlates with disease severity. Our findings also reveal a previously unknown pathogenic role of B2M in the regulation of pulmonary vascular proliferative remodeling and PH-HFpEF. These data suggest that circulating and skeletal muscle B2M can be promising targets for the management of PH-HFpEF.

Simultaneous targeting of peripheral and brain tumors with a therapeutic nanoparticle to disrupt metabolic adaptability at both sites.

Brain metastasis of advanced breast cancer often results in deleterious consequences. Metastases to the brain lead to significant challenges in treatment options, as the blood-brain barrier (BBB) prevents conventional therapy. Thus, we hypothesized that creation of a nanoparticle (NP) that distributes to both primary tumor site and across the BBB for secondary brain tumor can be extremely beneficial. Here, we report a simple targeting strategy to attack both the primary breast and secondary brain tumors utilizing a single NP platform. The nature of these mitochondrion-targeted, BBB-penetrating NPs allow for simultaneous targeting and drug delivery to the hyperpolarized mitochondrial membrane of the extracranial primary tumor site in addition to tumors at the brain. By utilizing a combination of such dual anatomical distributing NPs loaded with therapeutics, we demonstrate a proof-of-concept idea to combat the increased metabolic plasticity of brain metastases by lowering two major energy sources, oxidative phosphorylation (OXPHOS) and glycolysis. By utilizing complementary studies and genomic analyses, we demonstrate the utility of a chemotherapeutic prodrug to decrease OXPHOS and glycolysis by pairing with a NP loaded with pyruvate dehydrogenase kinase 1 inhibitor. Decreasing glycolysis aims to combat the metabolic flexibility of both primary and secondary tumors for therapeutic outcome. We also address the in vivo safety parameters by addressing peripheral neuropathy and neurobehavior outcomes. Our results also demonstrate that this combination therapeutic approach utilizes mitochondrial genome targeting strategy to overcome DNA repair-based chemoresistance mechanisms.

Sirtuin 3 ameliorates inflammatory bowel disease via inhibiting intestinal inflammation and oxidative stress.

Sirtuin 3 involved in development of various diseases, but its role in inflammatory bowel disease is still unknown. We used inflammatory bowel disease biopsies, colitis animal model, and vitro cells RAW264.7 to study the role of Sirtuin 3 in the pathophysiology of inflammatory bowel disease. Sirtuin 3 negatively correlated with intestinal TNF-α. Sirt3 was less pronounced in pediatric and adult inflammatory bowel disease patients compared with corresponding control group. Sirtuin 3 activator Honokiol suppressed dextran sulfate sodium induced colonic manifestations, while Sirt3 inhibitor caused opposite results. Honokiol inhibited colonic oxidative stress by and reduced intestinal permeability. Honokiol repressed inflammatory response by reducing macrophage infiltration, pro-inflammatory cytokines TNF-α, IL-1ß, and IL-6 levels, and inhibiting activation of NF-κB p65 in the colitis mice. However, Sirt3 inhibitor amplified colonic oxidative stress and inflammatory response. In vitro study, Sirt3 inhibitor or siRNA Sirtuin 3 activated NF-κB p65 and enhanced TNF-α, IL-1ß, and IL-6 secretion from LPS stimulated RAW264.7, while Honokiol remarkably attenuated these pro-inflammatory cytokines secretion. Finally, knockdown of Sirt3 in Caco-2 cells enhanced TNF-α induced intestinal barrier integrity injury. Sirtuin 3 negatively regulates inflammatory bowel disease progression via reducing colonic inflammation and oxidative stress. Sirtuin 3 is a promising therapeutic target in clinical application for inflammatory bowel disease therapy.

Gene Expression Profiling Reveals Fundamental Sex-Specific Differences in SIRT3-Mediated Redox and Metabolic Signaling in Mouse Embryonic Fibroblasts.

Sirt-3 is an important regulator of mitochondrial function and cellular energy homeostasis, whose function is associated with aging and various pathologies such as Alzheimer's disease, Parkinson's disease, cardiovascular diseases, and cancers. Many of these conditions show differences in incidence, onset, and progression between the sexes. In search of hormone-independent, sex-specific roles of Sirt-3, we performed mRNA sequencing in male and female Sirt-3 WT and KO mouse embryonic fibroblasts (MEFs). The aim of this study was to investigate the sex-specific cellular responses to the loss of Sirt-3. By comparing WT and KO MEF of both sexes, the differences in global gene expression patterns as well as in metabolic and stress responses associated with the loss of Sirt-3 have been elucidated. Significant differences in the activities of basal metabolic pathways were found both between genotypes and between sexes. In-depth pathway analysis of metabolic pathways revealed several important sex-specific phenomena. Male cells mount an adaptive Hif-1a response, shifting their metabolism toward glycolysis and energy production from fatty acids. Furthermore, the loss of Sirt-3 in male MEFs leads to mitochondrial and endoplasmic reticulum stress. Since Sirt-3 knock-out is permanent, male cells are forced to function in a state of persistent oxidative and metabolic stress. Female MEFs are able to at least partially compensate for the loss of Sirt-3 by a higher expression of antioxidant enzymes. The activation of neither Hif-1a, mitochondrial stress response, nor oxidative stress response was observed in female cells lacking Sirt-3. These findings emphasize the sex-specific role of Sirt-3, which should be considered in future research.

Effects of electroacupuncture on Sirt3/NLRP3/GSDMD signaling pathway in the substantia nigra of midbrain of rats with Parkinson's disease. / ç”µé’ˆå¯¹å¸•é‡‘æ£®ç— å¤§é¼ ä¸­è„‘é»‘è´¨Sirt3/NLRP3/GSDMD信号通路的影响.

OBJECTIVES: To observe the effects on tyrosine hydroxylase (TH), α-synaptic nucleoprotein (α-syn), sirtuin 3 (Sirt3), NOD-like receptor 3 (NLRP3) and gasdermin-D (GSDMD) in the substantia nigra of midbrain after electroacupuncture (EA) at "Fengfu"(GV16), "Taichong" (LR3) and "Zusanli" (ST36) in rats of Parkinson's disease (PD), so as to explore the mechanism of EA in treatment of PD. METHODS: SD rats were randomly divided into control, model and EA groups, with 10 rats in each group. The PD model was established by injecting rotenone into the neck and back, lasting 28 days. In the EA group, EA was applied to GV16, LR3 and ST36, 30 min each time, once daily, consecutively for 28 days. The open-field test was adopted to detect the total distance of autonomic movement of rats, and the pole climbing test was used to detect the body coordination ability of rats. In the substania nigra of midbrain, the positive expression of TH was determined using immunohistochemistry, the mRNA expression levels of α - syn, Sirt3, NLRP3 and GSDMD were detected by quantitative real-time fluorescence PCR, and the protein expression levels of NLRP3, apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) and cysteinyl aspartate specific proteinase (Caspase)-1 were detected by Western blot. RESULTS: Compared with the control group, the total distance of autonomous movement was decreased (P<0.01) in the model group, and the score of pole climbing experiment was increased (P<0.01)；in the midbrain substantia nigra the positive expression of TH was decreased (P<0.01)；the mRNA expression level of Sirt3 was decreased (P<0.01), and those of α-syn, NLRP3 and GSDMD were increased (P<0.01)；while the protein expression levels of NLRP3, ASC and Caspase-1 were increased (P<0.01). When compared with the model group, the total distance of autonomous movement in open field experiment was increased (P<0.01) in the EA group and the score of pole climbing experiment was lower (P<0.05)；in the midbrain substantia nigra the positive expression of TH was increased (P<0.01)；the mRNA expression level of Sirt3 in the midbrain substantia nigra was increased (P<0.01), and those of α-syn, NLRP3 and GSDMD were reduced (P<0.01)；while the protein expression levels of NLRP3, ASC and Caspase-1 decreased (P<0.01, P<0.05). CONCLUSIONS: EA at "GV16" "LR3" and "ST36" can repair the neuronal injury, clear the abnormal accumulation of α-syn in the substania nigra of midbrain, and ameliorate mitochondrial damage in PD rats, which may be obtained by regulating Sirt3/NLRP3/GSDMD signaling pathway, so as to delay the occurrence and development of Parkinson's disease.

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.

Sirtuin 3 regulates astrocyte activation by reducing Notch1 signaling after status epilepticus.

Sirtuin3 (Sirt3) is a nicotinamide adenine dinucleotide enzyme that contributes to aging, cancer, and neurodegenerative diseases. Recent studies have reported that Sirt3 exerts anti-inflammatory effects in several neuropathophysiological disorders. As epilepsy is a common neurological disease, in the present study, we investigated the role of Sirt3 in astrocyte activation and inflammatory processes after epileptic seizures. We found the elevated expression of Sirt3 within reactive astrocytes as well as in the surrounding cells in the hippocampus of patients with temporal lobe epilepsy and a mouse model of pilocarpine-induced status epilepticus (SE). The upregulation of Sirt3 by treatment with adjudin, a potential Sirt3 activator, alleviated SE-induced astrocyte activation; whereas, Sirt3 deficiency exacerbated astrocyte activation in the hippocampus after SE. In addition, our results showed that Sirt3 upregulation attenuated the activation of Notch1 signaling, nuclear factor kappa B (NF-κB) activity, and the production of interleukin-1ß (IL1ß) in the hippocampus after SE. By contrast, Sirt3 deficiency enhanced the activity of Notch1/NF-κB signaling and the production of IL1ß. These findings suggest that Sirt3 regulates astrocyte activation by affecting the Notch1/NF-κB signaling pathway, which contributes to the inflammatory response after SE. Therefore, therapies targeting Sirt3 may be a worthy direction for limiting inflammatory responses following epileptic brain injury.

SIRT3 alleviates high glucose-induced chondrocyte injury through the promotion of autophagy and suppression of apoptosis in osteoarthritis progression.

A growing amount of epidemiological evidence proposes diabetes mellitus (DM) to be an independent risk factor for osteoarthritis (OA). Sirtuin 3 (SIRT3), which is mainly located in mitochondria, belongs to the family of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases and is involved in the physiological and pathological processes of cell regulation. The aim of this study was to investigate the effects of SIRT3 on diabetic OA and underlying mechanisms in the prevention of type 2 DM (T2DM)-induced articular cartilage damage. High-fat and high-sugar diets combined with streptozotocin (STZ) injection were used for establishing an experimental T2DM rat model. The destabilization of medial meniscus (DMM) surgery was applied to induce the rat OA model. Primary rat chondrocytes were cultivated with a concentration of gradient glucose. Treatment with intra-articular injection of SIRT3 overexpression lentivirus was achieved in vivo, and intervention with SIRT3 knockdown was performed using siRNA transfection in vitro. High glucose content was found to activate inflammatory response, facilitate apoptosis, downregulate autophagy, and exacerbate mitochondrial dysfunction in a dose-dependent manner in rat chondrocytes, which can be deteriorated by SIRT3 knockdown. In addition, articular cartilage damage was found to be more severe in T2DM-OA rats than in DMM-induced OA rats, which can be mitigated by the intra-articular injection of SIRT3 overexpression lentivirus. Targeting SIRT3 is a potential therapeutic strategy for the alleviation of diabetic OA.

Sirt3 Regulates Proliferation and Progesterone Production in Leydig Cells via Suppression of Reactive Oxygen Species.

Sirt3 is a mitochondrial protein deacetylase functioning in energy metabolism, regulation of intracellular reactive oxygen species (ROS) levels, and aging. Although Sirt3 loss has negative effects on fertility of oocytes during in vitro fertilization and on progesterone production in granulosa cells, Sirt3's function in Leydig cells remains unclear. Therefore, we investigated Sirt3 activity in Leydig cells, focusing on androgen production. To do so, we performed immunohistochemistry to confirm Sirt3 localization in gonads and observed strong Sirt3 immunostaining in Leydig cells of human testes and of Sirt3+/+ and Sirt3+/- mouse testes, while Sirt3-/- mouse testis tissue was negative. In human ovary, hilus cells were strongly Sirt3-positive, theca cells showed weak positivity, and granulosa cells showed very weak or almost no immunostaining. Next, we used the murine Leydig tumor cell line MA-10 as a model. We overexpressed Sirt3 but observed no changes in proliferation, expression of Star, Cyp11a1 (p450scc gene), and Hsd3b, or progesterone production in MA-10 cells. Sirt3 knockdown significantly reduced proliferation, suppressed expressions of steroidogenic enzymes and of transcription factors Ad4bp (Sf-1 gene) and Gata4, and decreased progesterone production. Sirt3 knockdown in MA-10 cells also increased intracellular ROS levels based on CM-H2DCFDA fluorescence dye analysis and increased the proportion of both early and late apoptotic (necrotic) cells based on Annexin V/7AAD assays. These results indicate that Sirt3 has a potential function in androgen production in Leydig cells by regulating intracellular ROS levels.

Role of Argininosuccinate Synthase 1 -Dependent L-Arginine Biosynthesis in the Protective Effect of Endothelial Sirtuin 3 Against Atherosclerosis.

Atherosclerosis is initiated with endothelial cell (EC) dysfunction and vascular inflammation under hyperlipidemia. Sirtuin 3 (SIRT3) is a mitochondrial deacetylase. However, the specific role of endothelial SIRT3 during atherosclerosis remains poorly understood. The present study aims to study the role and mechanism of SIRT3 in EC function during atherosclerosis. Wild-type Sirt3f/f mice and endothelium-selective SIRT3 knockout Sirt3f/f; Cdh5Cre/+ (Sirt3EC-KO) mice are injected with adeno-associated virus (AAV) to overexpress PCSK9 and fed with high-cholesterol diet (HCD) for 12 weeks to induce atherosclerosis. Sirt3EC-KO mice exhibit increased atherosclerotic plaque formation, along with elevated macrophage infiltration, vascular inflammation, and reduced circulating L-arginine levels. In human ECs, SIRT3 inhibition resulted in heightened vascular inflammation, reduced nitric oxide (NO) production, increased reactive oxygen species (ROS), and diminished L-arginine levels. Silencing of SIRT3 results in hyperacetylation and deactivation of Argininosuccinate Synthase 1 (ASS1), a rate-limiting enzyme involved in L-arginine biosynthesis, and this effect is abolished in mutant ASS1. Furthermore, L-arginine supplementation attenuates enhanced plaque formation and vascular inflammation in Sirt3EC-KO mice. This study provides compelling evidence supporting the protective role of endothelial SIRT3 in atherosclerosis and also suggests a critical role of SIRT3-induced deacetylation of ASS1 by ECs for arginine synthesis.

Context-dependent role of SIRT3 in cancer.

Sirtuin 3 (SIRT3), an NAD+-dependent deacetylase, plays a key role in the modulation of metabolic reprogramming and regulation of cell death, as well as in shaping tumor phenotypes. Owing to its critical role in determining tumor-type specificity or the direction of tumor evolution, the development of small-molecule modulators of SIRT3, including inhibitors and activators, is of significant interest. In this review, we discuss recent studies on the oncogenic or tumor-suppressive functions of SIRT3, evaluate advances in SIRT3-targeted drug discovery, and present potential avenues for the design of small-molecule modulators of SIRT3 for cancer therapy.

Sirtuin 3 is required for the dexmedetomidine-mediated alleviation of inflammation and oxidative stress in nephritis.

INTRODUCTION: Although sirtuin 3 (SIRT3) is known to be involved in dexmedetomidine (DEX)-mediated alleviation of renal ischemia and reperfusion injury, the influence of the association between DEX and SIRT3 on nephritis development remains unclear. In this study, the role of SIRT3 in DEX-mediated amelioration of inflammation and oxidative stress in nephritis as well as the possible underlying mechanism were explored in vivo and in vitro. METHODS: An animal model of glomerulonephritis was generated by injecting mice with interferon-alpha (IFNα)-expressing adenoviruses, and periodic acid-Schiff staining was then used to reveal pathogenicity-related changes in the renal tissue. Additionally, human embryonic kidney cells (HEK293) and renal mesangial cells (RMCs) were treated with IFNα to establish cell models of inflammation in vitro. RESULTS: DEX administration alleviated glomerulonephritis in the animal model and upregulated SIRT3 expression in the renal tissue. SIRT3 knockdown inhibited the renoprotective effects of DEX against nephritis. IFNα induced inflammation, oxidative stress, and apoptosis in the RMCs and HEK293 cells and reduced their growth, as evidenced by the evaluation of cytokine levels (enzyme-linked immunosorbent assay), reactive oxygen species generation, catalase and superoxide dismutase activities, nuclear factor-erythroid factor 2-related factor 2/heme oxygenase-1 signal transduction, apoptotic cell proportion, and cell viability. In addition to promoting SIRT3 expression, DEX inhibited IFNα-induced inflammation, oxidative stress, and apoptosis in these cells and promoted their viability. SIRT3 knockdown partially reversed the beneficial effects of DEX on RMCs and HEK293 cells. CONCLUSIONS: Our results suggest that DEX exhibits renoprotective activity during nephritis progression, protecting renal cells against inflammatory injury by promoting SIRT3 expression.

Remote Ischemic Conditioning Mediates Cardio-protection After Myocardial Ischemia/Reperfusion Injury by Reducing 4-HNE Levels and Regulating Autophagy via the ALDH2/SIRT3/HIF1α Signaling Pathway.

Remote ischemic conditioning (RIC) can be effectively applied for cardio-protection. Here, to clarify whether RIC exerts myocardial protection via aldehyde dehydrogenase 2 (ALDH2), we established a myocardial ischemia/reperfusion (I/R) model in C57BL/6 and ALDH2 knockout (ALDH2-KO) mice and treated them with RIC. Echocardiography and single-cell contraction experiments showed that RIC significantly improved myocardial function and alleviated I/R injury in C57BL/6 mice but did not exhibit its cardioprotective effects in ALDH2-KO mice. TUNEL, Evan's blue/triphenyl tetrazolium chloride, and reactive oxygen species (ROS) assays showed that RIC's effect on reducing myocardial cell apoptosis, myocardial infarction area, and ROS levels was insignificant in ALDH2-KO mice. Our results showed that RIC could increase ALDH2 protein levels, activate sirtuin 3 (SIRT3)/hypoxia-inducible factor 1-alpha (HIF1α), inhibit autophagy, and exert myocardial protection. This study revealed that RIC could exert myocardial protection via the ALDH2/SIRT3/HIF1α signaling pathway by reducing 4-HNE secretion.