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-1β (IL1β) in the hippocampus after SE. By contrast, Sirt3 deficiency enhanced the activity of Notch1/NF-κB signaling and the production of IL1β. 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.

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 ameliorates diabetes-associated cognitive dysfunction via regulating mitochondria-associated ER membranes

BACKGROUND

Diabetes is associated with an increased risk of cognitive decline and dementia. These diseases are linked with mitochondrial dysfunction, most likely as a consequence of excessive formation of mitochondria-associated membranes (MAMs). Sirtuin3 (SIRT3), a key mitochondrial NAD⁺-dependent deacetylase, is critical responsible for mitochondrial functional homeostasis and is highly associated with neuropathology. However, the role of SIRT3 in regulating MAM coupling remains unknown.

METHODS

Streptozotocin-injected diabetic mice and high glucose-treated SH-SY5Y cells were established as the animal and cellular models, respectively. SIRT3 expression was up-regulated in vivo using an adeno-associated virus in mouse hippocampus and in vitro using a recombinant lentivirus vector. Cognitive function was evaluated using behavioural tests. Hippocampus injury was assessed using Golgi and Nissl staining. Apoptosis was analysed using western blotting and TUNEL assay. Mitochondrial function was detected using flow cytometry and confocal fluorescence microscopy. The mechanisms were investigated using co-immunoprecipitation of VDAC1-GRP75-IP3R complex, fluorescence imaging of ER and mitochondrial co-localisation and transmission electron microscopy of structural analysis of MAMs.

RESULTS

Our results demonstrated that SIRT3 expression was significantly reduced in high glucose-treated SH-SY5Y cells and hippocampal tissues from diabetic mice. Further, up-regulating SIRT3 alleviated hippocampus injuries and cognitive impairment in diabetic mice and mitigated mitochondrial Ca²⁺ overload-induced mitochondrial dysfunction and apoptosis. Mechanistically, MAM formation was enhanced under high glucose conditions, which was reversed by genetic up-regulation of SIRT3 via reduced interaction of the VDAC1-GRP75-IP3R complex in vitro and in vivo. Furthermore, we investigated the therapeutic effects of pharmacological activation of SIRT3 in diabetic mice via honokiol treatment, which exhibited similar effects to our genetic interventions.

CONCLUSIONS

In summary, our findings suggest that SIRT3 ameliorates cognitive impairment in diabetic mice by limiting aberrant MAM formation. Furthermore, targeting the activation of SIRT3 by honokiol provides a promising therapeutic candidate for diabetes-associated cognitive dysfunction. Overall, our study suggests a novel role of SIRT3 in regulating MAM coupling and indicates that SIRT3-targeted therapies are promising for diabetic dementia patients.

Cardioprotective effect of ultrasound-targeted destruction of Sirt3-loaded cationic microbubbles in a large animal model of pathological cardiac hypertrophy

Pathological cardiac hypertrophy occurs in response to numerous increased afterload stimuli and precedes irreversible heart failure (HF). Therefore, therapies that ameliorate pathological cardiac hypertrophy are urgently required. Sirtuin 3 (Sirt3) is a main member of histone deacetylase class III and is a crucial anti-oxidative stress agent. Therapeutically enhancing the Sirt3 transfection efficiency in the heart would broaden the potential clinical application of Sirt3. Ultrasound-targeted microbubble destruction (UTMD) is a prospective, noninvasive, repeatable, and targeted gene delivery technique. In the present study, we explored the potential and safety of UTMD as a delivery tool for Sirt3 in hypertrophic heart tissues using adult male Bama miniature pigs. Pigs were subjected to ear vein delivery of human Sirt3 together with UTMD of cationic microbubbles (CMBs). Fluorescence imaging, western blotting, and quantitative real-time PCR revealed that the targeted destruction of ultrasonic CMBs in cardiac tissues greatly boosted Sirt3 delivery. Overexpression of Sirt3 ameliorated oxidative stress and partially improved the diastolic function and prevented the apoptosis and profibrotic response. Lastly, our data revealed that Sirt3 may regulate the potential transcription of catalase and MnSOD through Foxo3a. Combining the advantages of ultrasound CMBs with preclinical hypertrophy large animal models for gene delivery, we established a classical hypertrophy model as well as a strategy for the targeted delivery of genes to hypertrophic heart tissues. Since oxidative stress, fibrosis and apoptosis are indispensable in the evolution of cardiac hypertrophy and heart failure, our findings suggest that Sirt3 is a promising therapeutic option for these diseases. STATEMENT OF SIGNIFICANCE: : Pathological cardiac hypertrophy is a central prepathology of heart failure and is seen to eventually precede it. Feasible targets that may prevent or reverse disease progression are scarce and urgently needed. In this study, we developed surface-filled lipid octafluoropropane gas core cationic microbubbles that could target the release of human Sirt3 reactivating the endogenous Sirt3 in hypertrophic hearts and protect against oxidative stress in a pig model of cardiac hypertrophy induced by aortic banding. Sirt3-CMBs may enhance cardiac diastolic function and ameliorate fibrosis and apoptosis. Our work provides a classical cationic lipid-based, UTMD-mediated Sirt3 delivery system for the treatment of Sirt3 in patients with established cardiac hypertrophy, as well as a promising therapeutic target to combat pathological cardiac hypertrophy.

Ozanimod-Dependent Activation of SIRT3/NF-κB/AIM2 Pathway Attenuates Secondary Injury After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is characterized by poor prognosis and high mortality rates. To date, satisfactory therapeutic approaches for ICH remain limited, so it is urgently needed to develop a safer and more effective prescription. Secondary inflammatory response has been acknowledged as an aggravating factor to neurological deterioration after ICH. As a component of inflammasome sensors, absent in melanoma 2 (AIM2) plays an important role in the neuroinflammation process. Here, ozanimod, a novel selective sphingosine 1-phosphate receptor modulator, has gained much attention, which alleviates the resultant neuroinflammation and improves functional recovery derived from ICH. In this study, ozanimod improved neurological functions of ICH mice via reduction of hematoma size. Furthermore, both microglial and AIM2 inflammasome activations were reversed by ozanimod, which are confirmed by the downregulation of related inflammatory proteins and cytokines (IL-1β, IL-6, and TNF-α), coupled with the upregulation of SIRT3, by leveraging the Western blot and enzyme-linked immunosorbent assay. Additionally, we find that ozanimod decreases nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) expression. Notably, in vitro cell experiments induced by lipopolysaccharide confirms that the anti-inflammatory effect of ozanimod could be abolished by the SIRT3 inhibitor. In conclusion, these results indicate that ozanimod mitigates ICH-induced secondary inflammatory responses by modulating AIM2 inflammasome mediated by SIRT3/NF-κB/AIM2 pathway. This demonstrates ozanimod orchestrates ICH-induced neuroinflammation and could be a targeted therapy for improving prognosis of ICH.

Effects of resveratrol supplementation on cardiac remodeling in hypertensive patients: a randomized controlled clinical trial

Resveratrol (RES) has been demonstrated to be protective in the cardiovascular system in animal studies, but the evidence is limited in humans. The purpose of the study was to evaluate the effect of RES supplementation on cardiac remodeling in patients with hypertension. Eighty Subjects were randomly divided into RES group (plus RES 400 mg/d in addition to conventional therapy, n = 43) and control group (conventional therapy, n = 37). The main outcomes of the study were changes within cardiac-remodeling parameters. Secondary outcomes were changes in anthropometric parameters, arterial stiffness parameters and mechanism indices. There was no statistically significant difference between the RES group and control group in terms of baseline characteristics. After 6 months, the RES group had smaller left atrial, lower E/e', higher left ventricular global longitudinal strain and lower biomarkers indicating cardiac fibrosis (expressed by decreases in procollagen type I C-peptide and galectin-3) compared to the control group. However, there was no significant difference in left ventricular structure between the two groups. Although the RES group showed a significant decrease in brachial-ankle pulse wave velocity compared to the pre-intervention value, the difference between the RES and the control groups was not obvious. What's more, compared with the control group, the serum levels of sirtuin3, superoxide dismutase and klotho were significantly increased in the RES group. In conclusion, RES supplementation can alleviate left atrial remodeling, improve left ventricular diastolic function and may alleviate cardiac fibrosis in hypertensive patients, and could be used as an adjunct to conventional therapies of hypertensive heart disease.

Sirtuin 3 and mitochondrial permeability transition pore (mPTP): A systematic review

Mitochondrial permeability transition pore (mPTP) is a channel that opens at the inner mitochondrial membrane under conditions of stress. Sirtuin 3 (Sirt3) is a mitochondrial deacetylase known to play a major role in stress resistance and a regulatory role in cell death. This systematic review aims to elucidate the role of Sirt3 in mPTP inhibition. Electronic databases, including PubMed, EMBASE, Web of Science and Cochrane Library were searched up to May 2020. Original studies that investigated the relationship between Sirt3 and mPTP were included. Two reviewers independently extracted data on study characteristics, methods and outcomes. A total of 194 articles were found. Twenty-nine articles, which met criteria were included in the systematic review. Twenty-three studies provided evidence of the inhibitory effect of Sirt3 on the mPTP aperture. This review summarizes up-to-date evidence of the protective and inhibitory role of Sirt3 through deacetylating Cyclophilin D (CypD) on the mPTP aperture. Furthermore, we discuss the implications of this effect in disease.

Microbubble drug conjugate and focused ultrasound blood brain barrier delivery of AAV-2 SIRT-3

BACKGROUND

Delivery of viral vectors as gene therapies to treat neurodegenerative diseases has been hampered by the inability to penetrate the blood brain barrier (BBB) and invasive or non-targeted delivery options prone to inducing immune responses. MR guided focused ultrasound (MR-g-FUS) and microbubbles have demonstrated safe, temporary, targeted BBB permeabilization clinically.

METHODS

We developed clinically scalable, microbubble drug conjugates (MDCs) for the viral gene therapy, AAV.SIRT3-myc [adeno-associated virus expressing myc-tagged SIRT3], which has previously been shown to have disease modifying effects in animal models of Parkinson's disease (PD). The lipid shells of the perfluorocarbon gas MDCs were covalently conjugated to antibodies with binding specificity to AAVs. Following systemic (iv) delivery of AAV.SIRT3-myc MDCs, MR-g-FUS was used to deliver SIRT3-myc to brain regions affected in PD. SIRT3-myc expression was determined post mortem, using immunohistochemistry.

RESULTS

An in vitro, SH-SY5Y cell culture model was used to show that the localized destruction of MDCs using ultrasound exposures within biological safety limits dissociated AAV2-GFP (green fluorescent protein) from the MDCs in the targeted area while maintaining their transduction capacity. In rats, MR-g-FUS resulted in BBB permeabilization in the striatum and substantia nigra (SNc). SIRT3-myc was expressed in the striatum, but not the SNc.

CONCLUSION

These studies demonstrate that MDCs combined with MR-g-FUS are an effective method for delivery of viral vector gene therapies, such as AAV.SIRT3, to brain regions affected in PD. This technology may prove useful as a disease-modifying strategy in PD and other neurodegenerative disorders.

The Protective Effects of Mogroside V Against Neuronal Damages by Attenuating Mitochondrial Dysfunction via Upregulating Sirtuin3

Mitochondrial dysfunction and oxidative stress are thought to play a dominant role in the pathogenesis of Parkinson's disease (PD). Mogroside V (MV), extracted from Siraitia grosvenorii, exhibits antioxidant-like activities. The aim of this study was to investigate the function of MV in neuroprotection in PD and to reveal its mechanism of action. To that end, we firstly set up mice models of PD with unilateral striatum injection of 0.25 mg/kg rotenone (Rot) and co-treated with 2.5 mg/kg, 5 mg/kg, and 10 mg/kg MV by gavage. Results showed that Rot-induced motor impairments and dopaminergic neuronal damage were reversed by treatment of 10 mg/kg MV. Then, we established cellular models of PD using Rot-treated SH-SY5Y cells, which were divided into six groups, including control, Rot, and co-enzyme Q10 (CQ10), as well as MV groups, MV25, MV50, and MV100 treated with 25 μM, 50 μM, and 100 μM MV doses, respectively. Results demonstrated that MV effectively attenuates Rot neurotoxicity through a ROS-related intrinsic mitochondrial pathway. MV reduced overproduction of reactive oxygen species (ROS), recovered the mitochondrial membrane potential (MMP), and increased the oxygen consumption rate and adenosine triphosphate (ATP) production in a dose-dependent manner. Hence, treatment with MV led to a reduction in the number of apoptotic cells, as reflected by Annexin-V/propidium iodide co-staining using flow cytometry and TdT-mediated dUTP Nick-End Labeling (TUNEL) assay. In addition, the Sirtuin3 (SIRT3) protein level and activity were decreased upon exposure to Rot both in substantia nigra (SN) of mice and SH-SY5Y cells. SIRT3 impairment hyperacetylated a key mitochondrial antioxidant enzyme, superoxide dismutase 2 (SOD2). MV alleviates SIRT3 and SOD2 molecular changes. However, after successfully inhibiting SIRT3 by its specific inhibitor 3-1H-1, 2, 3-triazol-4-yl pyridine (3TYP), MV was not able to reduce ROS levels, reverse abnormal MMP, or decrease apoptotic cells. Motor impairments and dopaminergic neuronal injury in the SN were alleviated with the oral administration of MV in Rot-treated PD mice, indicating a relationship between protection against defective motility and preservation of dopaminergic neurons. Therefore, we conclude that MV can alleviate Rot-induced neurotoxicity in a PD model, and that SIRT3 may be an important regulator in the protection of MV.

Quercetin Attenuates Cardiac Hypertrophy by Inhibiting Mitochondrial Dysfunction Through SIRT3/PARP-1 Pathway

Cardiac hypertrophy is an important characteristic in the development of hypertensive heart disease. Mitochondrial dysfunction plays an important role in the pathology of cardiac hypertrophy. Recent studies have shown that sirtuin 3 (SIRT3)/poly (ADP-ribose) polymerase-1 (PARP-1) pathway modulation inhibits cardiac hypertrophy. Quercetin, a natural flavonol agent, has been reported to attenuate cardiac hypertrophy. However, the molecular mechanism is not completely elucidated. In this study, we aimed to explore the mechanism underlying the protective effect of quercetin on cardiac hypertrophy. Spontaneously hypertensive rats (SHRs) were treated with quercetin (20 mg/kg/d) for 8 weeks to evaluate the effects of quercetin on blood pressure and cardiac hypertrophy. Additionally, the mitochondrial protective effect of quercetin was assessed in H9c2 cells treated with Ang II. SHRs displayed aggravated cardiac hypertrophy and fibrosis, which were attenuated by quercetin treatment. Quercetin also improved cardiac function, reduced mitochondrial superoxide and protected mitochondrial structure in vivo. In vitro, Ang II increased the mRNA level of hypertrophic markers including atrial natriuretic factor (ANF) and β-myosin heavy chain (β-MHC), whereas quercetin ameliorated this hypertrophic response. Moreover, quercetin prevented mitochondrial function against Ang II induction. Importantly, mitochondrial protection and PARP-1 inhibition by quercetin were partly abolished after SIRT3 knockdown. Our results suggested that quercetin protected mitochondrial function by modulating SIRT3/PARP-1 pathway, contributing to the inhibition of cardiac hypertrophy.

A potential role of Sirtuin3 and its target enzyme activities in patients with ovarian endometrioma

OBJECTIVE

Sirtuin3 (SIRT3) is a NAD⁺-dependent major mitochondrial deacetylase. In this study, we aimed to investigate SIRT3 levels and their target enzyme activities, including glutamate dehydrogenase (GDH), succinate dehydrogenase (SDH), and manganese superoxide dismutase (MnSOD), also to determine the antioxidant capacity and oxidative stress in tissue, mitochondria and serum samples in ovarian endometrioma patients.

METHODS

We collected serum and endometrioma tissue samples from 30 patients. In the control group, we collected serum and eutopic endometrial tissue samples from 26 women without endometriosis.

RESULTS

SIRT3 levels were significantly decreased in endometrioma tissue samples compared to the control group. There was no statistically significant difference in SIRT3 levels between patient and control serum samples. Furthermore, there was a decrease in GDH and SDH enzyme activities in both endometrioma tissue homogenate and mitochondria. MnSOD activity was decreased in tissue homogenate but increased in mitochondria and there was no difference in serum. While total SOD activity was decreased, CuZnSOD activity was increased in both tissue and serum samples. Besides these, total antioxidant capacity and advanced oxidation protein products (AOPP) levels were decreased in endometrioma tissue and mitochondria, but there was no difference in serum.

CONCLUSIONS

Our results suggested that decreased levels of SIRT3 in endometrioma may be an important factor in the weakening of mitochondrial energy metabolism and antioxidant defense in endometriosis. We think that SIRT3 deficiency may be an important factor underlying the pathogenesis of endometriosis. More detailed studies are needed to reveal the relationship between SIRT3 and metabolism and oxidative stress in ovarian endometrioma.

Sirtuin3 rs28365927 functional variant confers to the high risk of non-alcoholic fatty liver disease in Chinese Han population

Background

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial condition associated with aging, insulin resistance, metabolic syndrome, genetic factors and more. Although genetic traits are among the most important risks factors for NAFLD, the understanding of their influence is still quite limited. The present study aimed at identifying novel single nucleotide polymorphisms (SNPs) that may confer a risk for NAFLD in the Han Chinese population.

Methods

Based on the “two-hit hypothesis”, candidate SNPs, including Sirtuin3 rs28365927, were genotyped by MassARRAY in B-type ultrasonography-proven NAFLD patients (n = 292) and healthy controls (n = 387).

Results

In a model analysis of individuals matched based on gender and age that compared 223 NAFLD and 223 non-NAFLD patients, the rs28365927 GA + AA genotype was a significant risk factor for the development of NAFLD in a dominant model. Rs28365927 was significantly associated with a higher NAFLD risk in both an additive model (A vs G) and genotypic model (GA vs GG). Among the NAFLD patients, serum levels of total bilirubin (TBIL), DBIL direct bilirubin (DBIL) and glutamic-pyruvic transaminase (ALT) in rs28365927 A allele carriers (GA + AA) were 11.1, 14.7 and 41.5% higher, respectively, than in non-carriers (GG). Furthermore, among the NAFLD patients, the carriers of Rs28365927 allele A were positively correlated with higher ALT levels.

Conclusion

Sirtuin3 rs28365927 functional variant confers to the high risk of non-alcoholic fatty liver disease in Chinese Han population. The rs28365927 A allele significantly increased the ALT levels of NAFLD patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01520-x.

Protective role of sirtuin3 against oxidative stress and NLRP3 inflammasome in cholesterol accumulation and foam cell formation of macrophages with ox-LDL-stimulation

Sirtuin3 (SIRT3) is involved in reactive oxygen species (ROS), cell metabolism, apoptosis and inflammation. However, the exact role of SIRT3 in macrophages during pathophysiological process of atherosclerosis remains unclear. The present study was to investigate the possible effects and mechanisms of SIRT3 on lipid uptake and foam cells transforming in oxidized low-density lipoprotein (ox-LDL)-stimulated macrophages. Compared with wild-type (WT) mice, SIRT3 deficiency further increased foam cell formation and cellular cholesterol accumulation, exacerbated oxidative stress, impaired mitochondrial permeability potential, decreased optic atrophy 1 (OPA1) but enhanced dynamin-related protein 1 (DRP1) expression, and promoted NLR family pyrin domain-containing protein 3 (NLRP3) activation in ox-LDL-stimulated macrophages from SIRT3 knockout (KO) mice. Dihydromyricetin (DMY), a potential compound to enhance SIRT3 expression, significantly inhibited cellular cholesterol accumulation, suppressed foam cell formation, improved mitochondrial function, attenuated oxidative stress, and alleviated NLRP3 activation in ox-LDL-stimulated macrophages. Moreover, above protective effects of DMY was unavailable in macrophages from SIRT3 KO mice. Collectively, the study demonstrated the protective role of SIRT3 against oxidative stress and NLRP3 inflammasome in cholesterol accumulation and foam cell formation of macrophages with ox-LDL-stimulation, which is beneficial to provide novel strategy for atherosclerosis prevention and treatment.

NIPSNAP protein family emerges as a sensor of mitochondrial health

Since their discovery over two decades ago, the molecular and cellular functions of the NIPSNAP family of proteins (NIPSNAPs) have remained elusive until recently. NIPSNAPs interact with a variety of mitochondrial and cytoplasmic proteins. They have been implicated in multiple cellular processes and associated with different physiologic and pathologic conditions, including pain transmission, Parkinson's disease, and cancer. Recent evidence demonstrated a direct role for NIPSNAP1 and NIPSNAP2 proteins in regulation of mitophagy, a process that is critical for cellular health and maintenance. Importantly, NIPSNAPs contain a 110 amino acid domain that is evolutionary conserved from mammals to bacteria. However, the molecular function of the conserved NIPSNAP domain and its potential role in mitophagy have not been explored. It stands to reason that the highly conserved NIPSNAP domain interacts with a substrate that is ubiquitously present across all species and can perhaps act as a sensor for mitochondrial health.

Sirt3-mediated mitophagy regulates AGEs-induced BMSCs senescence and senile osteoporosis

Senile osteoporosis (SOP) is widely regarded as one of the typical aging-related diseases due to a decrease in bone mass and the destruction in microarchitecture. The inhibition of mitophagy can promote bone marrow mesenchymal stem cells (BMSCs) senescence, and increasing studies have shown that interventions targeting BMSCs senescence can ameliorate osteoporosis, exhibiting their potential for use as therapeutic strategies. Sirtuin-3 (Sirt3) is an essential mitochondria metabolic regulatory enzyme that plays an important role in mitochondrial homeostasis, but its role in bone homeostasis remains largely unknown. This study seeks to investigate whether advanced glycation end products (AGEs) accumulation aggravated BMSCs senescence and SOP, and explored the mechanisms underlying these effects. We observed that AGEs significantly aggravated BMSCs senescence, as well as promoted mitochondrial dysfunction and inhibited mitophagy in a concentration-dependent manner. In addition, this effect could be further strengthened by Sirt3 silencing. Importantly, we identified that the reduction of Sirt3 expression and the mitophagy were vital mechanisms in AGEs-induced BMSCs senescence. Furthermore, overexpression of Sirt3 by intravenously injection with recombinant adeno-associated virus 9 carrying Sirt3 plasmids (rAAV-Sirt3) significantly alleviated BMSCs senescence and the formation of SOP in SAMP6. In conclusion, our data demonstrated that Sirt3 protects against AGEs-induced BMSCs senescence and SOP. Targeting Sirt3 to improve mitophagy may represent a potential therapeutic strategy for attenuating AGEs-associated SOP.

SIRT2 and SIRT3 expression correlates with redox imbalance and advanced clinical stage in patients with multiple myeloma

OBJECTIVES

Sirtuins comprise seven family elements (SIRT1-7) involved in various cell signalling pathways comprising cancer inhibition and tumorigenesis. The present study aims to evaluate SIRT2 and SIRT3 gene expression and potential redox reactions in patients with multiple myeloma (MM) at onset and its correlation with disease status, extent and presence of organ damage secondary to myeloma.

DESIGN & METHODS

Total RNA was extracted from 17 MM patients and 10 controls to assess gene expression using real-time PCR. The NAD+/NADH ratio as well as the levels of glutathione peroxidase (GPx) and hydrogen peroxide (HP) in peripheral blood mononuclear cells (PBMCs) were determined using established biochemical assays.

RESULTS

SIRT2 and SIRT3 expression is reduced in MM patients compared to healthy controls. Correlational analysis demonstrated that SIRT2 reduction is associated with advanced clinical stage and with more advanced bone lesions than in the remaining patients. SIRT3 expression is correlated with lytic bone lesions. Biochemical analysis indicated an imbalance of oxidative stress biomarkers with low concentrations of the antioxidant enzyme GPx, low amounts of NAD + and higher concentrations of pro-oxidant enzyme HP in PBMCs of MM patients compared to controls. Moreover, MM patients with bone lesions had lower concentrations of NAD + and GPx in PBMCs than patients without signs of bone disease. In addition, MM patients had higher quantities of intracellular HP than controls.

CONCLUSIONS

Our results demonstrate that SIRT2 and SIRT3 are downregulated in MM and that lower concentrations correlate with an advanced stage of disease and redox imbalance. We conclude that SIRT2 and SIRT3 together with oxidative stress biomarkers, may be useful for improved risk stratification of MM patients.

Ginsenoside Rg1 attenuates isoflurane/surgery-induced cognitive disorders and sirtuin 3 dysfunction

Isoflurane/surgery (I/S) may induce neurocognitive disorders, but detailed mechanisms and appropriate treatment remain largely unknown. This experiment was designed to determine whether ginsenoside Rg1 could attenuate I/S-induced neurocognitive disorders and Sirtuin3 (Sirt3) dysfunction. C57BL/6J male mice received 1.4% isoflurane plus abdominal surgery for 2 h. Ginsenoside Rg1 10 mg/kg was intraperitoneally given for 8 days before surgery. Neurocognitive function was assessed by the Barnes Maze test. Levels of reactive oxygen species (ROS), oxygen consumption rate (OCR), mitochondrial membrane potential (MMP), expression and deacetylation activity of Sirt3 in the hippocampus tissues were measured. Results showed that I/S induced hippocampus-dependent learning and memory impairments, with increased ROS levels, and reduced OCR, MMP, and expression and deacetylation activity of Sirt3 in hippocampus tissues. Ginsenoside Rg1 treatment before I/S intervention significantly ameliorated learning and memory performance, reduced ROS levels and improved the OCR, MMP, expression and deacetylation activity of Sirt3. In conclusion, this experiment demonstrates that ginsenoside Rg1 treatment can attenuate I/S-induced neurocognitive disorders and Sirt3 dysfunction.

Glycyrrhizic acid protects juvenile epileptic rats against hippocampal damage through activation of Sirtuin3

Glycyrrhizic acid (GA) and Sirtuin3 (Sirt3) were both found to be involved in epilepsy (EP), but their interaction was rarely studied. Herein, we aim to investigate the underlying mechanism of GA with the interaction of Sirt3 in juvenile EP rats. The EP model in juvenile rats was established by lithium chloride-pilocarpine and treated with different concentrations of GA, GA + DMSO or GA + 3-TYP [a selective inhibitor of Sirtuin3 (Sirt3)]. The expression of Sirt3, mitochondrial autophagy-related genes (C-III core 1, COX IV, LC3-I, LC3-II), apoptosis-related genes (Bcl-2, Bax, Caspase-3), glutathione (GSH), superoxide dismutase (SOD), malondialchehyche (MDA) and reactive oxygen species (ROS) as well as mitochondrial membrane potential were subsequently detected. The juvenile EP rats treated with GA showed increased level of C-III core 1 and COX IV, increased LC3-I/LC3-II, GSH and SOD, decreased MDA, increased expression of Sirt3, and Bcl-2, and decreased expression of Bax and Caspase-3. However, inhibition of Sirt3 caused reverse results. Collectively, GA could alleviate hippocampal pathological damage, promote mitochondrial autophagy and reduce oxidative stress in juvenile EP rats through activation of Sirt3. Understanding of these mechanisms may allow devising of novel therapeutics for pediatric EP.

Sirt3 modulates fatty acid oxidation and attenuates cisplatin-induced AKI in mice

Fatty acid oxidation (FAO) dysfunction is one of the important mechanisms of renal fibrosis. Sirtuin 3 (Sirt3) has been confirmed to alleviate acute kidney injury (AKI) by improving mitochondrial function and participate in the regulation of FAO in other disease models. However, it is not clear whether Sirt3 is involved in regulating FAO to improve the prognosis of AKI induced by cisplatin. Here, using a murine model of cisplatin-induced AKI, we revealed that there were significantly FAO dysfunction and extensive lipid deposition in the mice with AKI. Metabolomics analysis suggested reprogrammed energy metabolism and decreased ATP production. In addition, fatty acid deposition can increase reactive oxygen species (ROS) production and induce apoptosis. Our data suggested that Sirt3 deletion aggravated FAO dysfunction, resulting in increased apoptosis of kidney tissues and aggravated renal injury. The activation of Sirt3 by honokiol could improve FAO and renal function and reduced fatty acid deposition in wide-type mice, but not Sirt3-defective mice. We concluded that Sirt3 may regulate FAO by deacetylating liver kinase B1 and activating AMP-activated protein kinase. Also, the activation of Sirt3 by honokiol increased ATP production as well as reduced ROS and lipid peroxidation through improving mitochondrial function. Collectively, these results provide new evidence that Sirt3 is protective against AKI. Enhancing Sirt3 to improve FAO may be a potential strategy to prevent kidney injury in the future.

Mitochondria Lysine Acetylation and Phenotypic Control

Mitochondria have a central role in cellular metabolism and reversible post-translational modifications regulate activity of mitochondrial proteins. Thanks to advances in proteomics, lysine acetylation has arisen as an important post-translational modification in the mitochondrion. During acetylation an acetyl group is covalently attached to the epsilon amino group in the side chain of lysine residues using acetyl-CoA as the substrate donor. Therefore the positive charge is neutralized, and this can affect the function of proteins thereby regulating enzyme activity, protein interactions, and protein stability. The major deacetylase in mitochondria is SIRT3 whose activity regulates many mitochondrial enzymes. The method of choice for the analysis of acetylated proteins foresees the combination of mass spectrometry-based proteomics with affinity enrichment techniques. Beyond the identification of lysine-acetylated proteins, many studies are moving towards the characterization of acetylated patterns in different diseases. Indeed, modifications in lysine acetylation status can directly alter mitochondrial function and, therefore, be linked to human diseases such as metabolic diseases, cancer, myocardial injury and neurodegenerative diseases. Despite the progress in the characterization of different lysine acetylation sites, additional studies are needed to differentiate the specific changes with a significant biological relevance.

Duodenal-Jejunal Bypass Surgery Stimulates the Expressions of Hepatic Sirtuin1 and 3 and Hypothalamic Sirtuin1

Background

Sirtuins mediate metabolic responses to nutrient availability and slow aging and accompanying decline in health. This study was designed to assess the expressions of sirtuin1 (SIRT1) and sirtuin3 (SIRT3) in the liver and hypothalamus after duodenal-jejunal bypass (DJB) surgery in rats.

Methods

A total of 38 rats were randomly assigned to either sham group (n=8) or DJB group (n=30). DJB group was again divided into three groups according to the elapsed time after surgery (10 weeks, DJB10; 16 week, DJB16; 28 week, DJB28). The mRNA and protein expressions of SIRT1 and SIRT3 in the liver and hypothalamus were measured by reverse transcription polymerase chain reaction, Western blot, and immunohistochemistry analyses. NAD⁺/NADH ratio was also measured.

Results

We found increased mRNA and protein expression levels of SIRT1 in the liver of DJB16 and DJB28 groups compared with those of sham group. The mRNA and protein expressions of SIRT3 in the liver of DJB group increased proportionally to the elapsed time after DJB surgery. The mRNA expression levels of SIRT1 in the hypothalamus increased in DJB16 and DJB28 groups and protein expression levels of SIRT1 in the hypothalamus increased in DJB10, DBJ16, and DJB28 groups compared with sham group. We observed that mRNA and protein levels of SIRT3 in the hypothalamus of DJB group were not changed.

Conclusion

This study proves that DJB increases SIRT1 and SIRT3 expressions in the liver and SIRT1 expression in the hypothalamus. These results suggest the possibility of sirtuins being involved in bypass surgery-induced metabolic changes.

Pyrroloquinoline quinine protects HK-2 cells against high glucose-induced oxidative stress and apoptosis through Sirt3 and PI3K/Akt/FoxO3a signaling pathway

High glucose(HG)-induced oxidative stress and apoptosis in renal tubular epithelial cells play an important role in the pathogenesis of diabetic nephropathy. Pyrroloquinoline quinine (PQQ), a new B vitamin, has been demonstrated to be important in antioxidant and anti-apoptotic effects. However, its effect on HK-2 cells and the potential mechanism are rarely investigated. In this study, we investigated that PPQ had protective effects against HG-induced oxidative stress damage and apoptosis in vitro model of diabetic nephropathy. PPQ at 10, 100, 500, 1000 and 10000 nM could protect HK-2 cell from HG-induced inhibition. The protective effects of PQQ were associated with increasing the level of antioxidants(SOD2, CAT), inhibition of reactive oxygen species(ROS) production, and dependent modulation of Bcl-2 family proteins. PPQ significantly upregulated the protein and mRNA expression of Sirtuin3(Sirt3) in HG-induced HK-2 cells. PPQ also reduced apoptosis in HG-induced HK-2 cells by the PI3K/Akt/FoxO3a signal pathway. As down-regulated sirt3 or inhibitory the activity of PI3K/Akt/FoxO3a pathway, the protective effects of PPQ were weakened. In conclusion, our data suggest that PPQ achieves the protective effects through PI3K/Akt/FoxO3a pathway and dependent modulation of Sirt3.

SIRT3 activator honokiol ameliorates surgery/anesthesia-induced cognitive decline in mice through anti-oxidative stress and anti-inflammatory in hippocampus

AIMS

Increasing evidence indicates that neuroinflammatory and oxidative stress play two pivotal roles in cognitive impairment after surgery. Honokiol (HNK), as an activator of Sirtuin3 (SIRT3), has potential multiple biological functions. The aim of these experiments is to evaluate the effects of HNK on surgery/anesthesia-induced cognitive decline in mice.

METHODS

Adult C57BL/6 mice received a laparotomy under sevoflurane anesthesia and HNK or SIRT3 inhibitor (3-TYP) treatment. Cognitive function and locomotor activity of mice were evaluated using fear conditioning test and open field test on postoperative 1 and 3 days. Neuronal apoptosis in CA1 and CA3 area of hippocampus was examined using TUNEL assay. And Western blot was applied to measure the expression of pro-inflammatory cytokines and SIRT3/SOD2 signaling-associated proteins in hippocampus. Meanwhile, SIRT3 positive cells were calculated by immunohistochemistry. The mitochondrial membrane potential, malondialdehyde (MDA), and mitochondrial radical oxygen species (mtROS) were detected using standard methods.

RESULTS

Honokiol attenuated surgery-induced memory loss and neuronal apoptosis, decreased neuroinflammatory response, and ameliorated oxidative damage in hippocampus. Notably, surgery/anesthesia induced an obviously decrease in hippocampal SIRT3 expression, whereas the HNK increased SIRT3 expression and thus decreased the acetylation of superoxide dismutase 2 (SOD2). However, 3-TYP treatment inhibited the HNK's rescuing effects.

CONCLUSIONS

These results suggested that activation of SIRT3 by honokiol may attenuate surgery/anesthesia-induced cognitive impairment in mice through regulation of oxidative stress and neuroinflammatory in hippocampus.

Berberine Reduces Pyruvate-driven Hepatic Glucose Production by Limiting Mitochondrial Import of Pyruvate through Mitochondrial Pyruvate Carrier 1

BACKGROUND

Mitochondrial pyruvate import via mitochondrial pyruvate carrier (MPC) is a central step in hepatic gluconeogenesis. Berberine inhibits hepatic gluconeogenesis, but the mechanism is incompletely understood. This study aims to investigate whether berberine could reduce excessive hepatic glucose production (HGP) by limiting mitochondrial import of pyruvate through MPC1.

METHODS

High-fat diet (HFD) feeding augmented HGP. The effects of berberine on hepatic fatty acid oxidation, sirtuin3 (SIRT3) induction and mitochondrial pyruvate carrier 1 (MPC1) function were examined.

FINDINGS

HFD feeding increased hepatic acetyl coenzyme A (acetyl CoA) accumulation with impaired pyruvate dehydrogenase (PDH) activity and increased pyruvate carboxylase (PC) induction. Berberine reduced acetyl CoA accumulation by limiting fatty acid oxidation and prevented mitochondrial pyruvate shift from oxidation to gluconeogenesis through carboxylation. Upon pyruvate response, SIRT3 binded to MPC1 and stabilized MPC1 protein via deacetylation modification, facilitating mitochondrial import of pyruvate. Berberine preserved the acetylation of MPC1 by suppression of SIRT3 induction and impaired MPC1 protein stabilization via protein degradation, resultantly limiting mitochondrial pyruvate supply for gluconeogenesis.

INTERPRETATION

Berberine reduced acetyl CoA contents by limiting fatty acid oxidation and increased MPC1 degradation via preserving acetylation, thereby restraining HGP by blocking mitochondrial import of pyruvate. These findings suggest that limitation of mitochondrial pyruvate import might be a therapeutic strategy to prevent excessive hepatic glucose production.

Preventing muscle wasting by osteoporosis drug alendronate in vitro and in myopathy models via sirtuin-3 down-regulation

BACKGROUND

A global consensus on the loss of skeletal muscle mass and function in humans refers as sarcopenia and cachexia including diabetes, obesity, renal failure, and osteoporosis. Despite a current improvement of sarcopenia or cachexia with exercise training and supportive therapies, alternative and specific managements are needed to discover for whom are unable or unwilling to embark on these treatments. Alendronate is a widely used drug for osteoporosis in the elderly and postmenopausal women. Osteopenic menopausal women with 6 months of alendronate therapy have been observed to improve not only lumbar bone mineral density but also handgrip strength. However, the effect and mechanism of alendronate on muscle strength still remain unclear. Here, we investigated the therapeutic potential and the molecular mechanism of alendronate on the loss of muscle mass and strength in vitro and in vivo.

METHODS

Mouse myoblasts and primary human skeletal muscle-derived progenitor cells were used to assess the effects of low-dose alendronate (0.1-1 μM) combined with or without dexamethasone on myotube hypertrophy and myogenic differentiation. Moreover, we also evaluated the effects of low-dose alendronate (0.5 and 1 mg/kg) by oral administration on the limb muscle function and morphology of mice with denervation-induced muscle atrophy and glycerol-induced muscle injury.

RESULTS

Alendronate inhibited dexamethasone-induced myotube atrophy and myogenic differentiation inhibition in mouse myoblasts and primary human skeletal muscle-derived progenitor cells. Alendronate significantly abrogated dexamethasone-up-regulated sirtuin-3 (SIRT3), but not SIRT1, protein expression in myotubes. Both SIRT3 inhibitor AKG7 and SIRT3-siRNA transfection could also reverse dexamethasone-up-regulated atrogin-1 and SIRT3 protein expressions. Animal studies showed that low-dose alendronate by oral administration ameliorated the muscular malfunction in mouse models of denervation-induced muscle atrophy and glycerol-induced muscle injury with a negative regulation of SIRT3 expression.

CONCLUSIONS

The putative mechanism by which muscle atrophy was improved with alendronate might be through the SIRT3 down-regulation. These findings suggest that alendronate can be a promising therapeutic strategy for management of muscle wasting-related diseases and sarcopenia.

Cardiac and placental mitochondrial characterization in a rabbit model of intrauterine growth restriction

BACKGROUND

Intrauterine growth restriction (IUGR) is associated with cardiovascular remodeling persisting into adulthood. Mitochondrial bioenergetics, essential for embryonic development and cardiovascular function, are regulated by nuclear effectors as sirtuins. A rabbit model of IUGR and cardiovascular remodeling was generated, in which heart mitochondrial alterations were observed by microscopic and transcriptomic analysis. We aimed to evaluate if such alterations are translated at a functional mitochondrial level to establish the etiopathology and potential therapeutic targets for this obstetric complication.

METHODS

Hearts and placentas from 16 IUGR-offspring and 14 controls were included to characterize mitochondrial function.

RESULTS

Enzymatic activities of complexes II, IV and II + III in IUGR-hearts (-11.96 ± 3.16%; -15.58 ± 5.32%; -14.73 ± 4.37%; p < 0.05) and II and II + III in IUGR-placentas (-17.22 ± 3.46%; p < 0.005 and -29.64 ± 4.43%; p < 0.001) significantly decreased. This was accompanied by a not significant reduction in CI-stimulated oxygen consumption and significantly decreased complex II SDHB subunit expression in placenta (-44.12 ± 5.88%; p < 0.001). Levels of mitochondrial content, Coenzyme Q and cellular ATP were conserved. Lipid peroxidation significantly decreased in IUGR-hearts (-39.02 ± 4.35%; p < 0.001), but not significantly increased in IUGR-placentas. Sirtuin3 protein expression significantly increased in IUGR-hearts (84.21 ± 31.58%; p < 0.05) despite conserved anti-oxidant SOD2 protein expression and activity in both tissues.

CONCLUSIONS

IUGR is associated with cardiac and placental mitochondrial CII dysfunction. Up-regulated expression of Sirtuin3 may explain attenuation of cardiac oxidative damage and preserved ATP levels under CII deficiency.

GENERAL SIGNIFICANCE

These findings may allow the design of dietary interventions to modulate Sirtuin3 expression and consequent regulation of mitochondrial imbalance associated with IUGR and derived cardiovascular remodeling.

Role of Sirtuin3 in high glucose-induced apoptosis in renal tubular epithelial cells

The apoptosis of renal tubular epithelial cells contributes to the pathogenesis of diabetic nephropathy. High glucose-induced mitochondrial oxidative stress is considered to be an important mediator for renal tubular cell apoptosis. Sirtuin3(Sirt3), a kind of mitochondria-localized nicotinamide adenine dinucleotide(NAD⁺)-dependent protein deacetylase, has been reported to regulate the generation of ROS in mitochondria through regulating acetylation level and activity of several key mitochondrial enzymes. In this study, we investigated the role of Sirt3 on high glucose-induced apoptosis in HK-2 cells. High glucose decreased the protein and mRNA expression of Sirt3 in a time-dependent manner, along with increased cell apoptosis in HK-2 cells. Furthermore, high glucose-induced oxidative stress and apoptosis were reversed by Sirt3 overexpression or antioxidant treatment. Meanwhile, we also found that overexpression of Sirt3 or antioxidant could regulate the activity of Akt/FoxO signaling pathway associated with cell apoptosis in diabetic nephropathy. In conclusion, our data suggest that Sirt3 overexpression antagonize high glucose-induced apoptosis by controlling ROS accumulation and ROS-sensitive Akt/FoxO signaling pathway in HK-2 cells.

Expression of SIRT1 and SIRT3 varies according to age in mice

Sirtuins (SIRTs) are involved in multiple cellular processes including those related to aging, cancer, and a variety of cellular functions including cell cycle progression, DNA repair, and cellular proliferation. SIRTs have been shown to extend the yeast life span, although there is presently little known about SIRT expression in the organs of mice. In the present study, we were especially interested in identifying differences in SIRT expression between young mice and aged mice. Specifically, we investigated the expression of SIRT1 and SIRT3 in the kidney, lung, skin, adipose tissue, and spleens of 6-month-old and 24-month-old mice using immunohistochemical staining. Compared with that in younger mice, the expression of SIRT1 in 24-month-old rats was increased in kidney, lung, and spleen tissue, while that of SIRT3 was decreased in adipose, kidney, and lung tissue. The results of our study suggest that aging is associated with altered patterns of expression of SIRT1 and SIRT3. In addition, we noted that the expression patterns of SIRT1 and SIRT3 varied by organ. Taken together, the results of this study suggest the possibility that SIRTs may be involved in diseases associated with aging.