SOD2 Acetylation Research Articles

Abstract P354: Endothelial Sirt3 deficiency and SOD2 acetylation voids female protection from hypertension

The prevalence of hypertension in early adulthood among women is 3-times lower than in men; but with aging hypertension rate increases in women much steeper, and hypertensive vascular and kidney damage is significantly higher in women. Gender-specific aspects of hypertension are poorly understood and clinical studies did not show protection by estrogen hormone therapy. We found that human hypertension is linked to hyperacetylation of critical antioxidant and metabolic mitochondrial enzymes superoxide dismutase (SOD2) and long-chain acyl dehydrogenase (LCAD) due to vascular deficiency of mitochondrial deacetylase Sirt3. We hypothesized that endothelial Sirt3 depletion leads to the loss of female protective cardiovascular phenotype and exacerbates hypertension in female compared with male mice due to hyperacetylation of mitochondrial proteins. Indeed, infusion of angiotensin II in wild-type female mice showed protection of vascular metabolism, endothelial nitric oxide and lower blood pressure compared with male littermates which was coupled with reduced acetylation of mitochondrial LCAD and SOD2 in female mice. Endothelial specific Sirt3 knockout female mice showed increased mitochondrial acetylation, exacerbated angiotensin II-induced hypertension and higher blood pressure compared with male mice which models human hypertension. Hypertension is linked to SOD2 acetylation (Circ Res. 2020;126(4):439-452) which leads to SOD2 inactivation and vascular oxidative stress. We found that endothelial specific acetylation mimetic SOD2-K68Q knock-in female mice lost antihypertensive phenotype and had higher blood pressure compared with angiotensin II-infused male mice. These studies demonstrate critical role of mitochondrial acetylation in endothelial dysfunction and hypertension suggesting that female antihypertensive phenotype can be associated with reduced mitochondrial acetylation protecting mitochondrial and endothelial functions. It is conceivable that pharmacological targeting of mitochondrial metabolism and acetylation can rescue female cardiovascular protection and improve treatment of endothelial dysfunction and hypertension.

Mitochondrial impairment, decreased sirtuin activity and protein acetylation in dorsal root ganglia in Friedreich Ataxia models

Friedreich ataxia (FA) is a rare, recessive neuro-cardiodegenerative disease caused by deficiency of the mitochondrial protein frataxin. Mitochondrial dysfunction, a reduction in the activity of iron-sulfur enzymes, iron accumulation, and increased oxidative stress have been described. Dorsal root ganglion (DRG) sensory neurons are among the cellular types most affected in the early stages of this disease. However, its effect on mitochondrial function remains to be elucidated. In the present study, we found that in primary cultures of DRG neurons as well as in DRGs from the FXNI151F mouse model, frataxin deficiency resulted in lower activity and levels of the electron transport complexes, mainly complexes I and II. In addition, altered mitochondrial morphology, indicative of degeneration was observed in DRGs from FXNI151F mice. Moreover, the NAD+/NADH ratio was reduced and sirtuin activity was impaired. We identified alpha tubulin as the major acetylated protein from DRG homogenates whose levels were increased in FXNI151F mice compared to WT mice. In the mitochondria, superoxide dismutase (SOD2), a SirT3 substrate, displayed increased acetylation in frataxin-deficient DRG neurons. Since SOD2 acetylation inactivates the enzyme, and higher levels of mitochondrial superoxide anion were detected, oxidative stress markers were analyzed. Elevated levels of hydroxynonenal bound to proteins and mitochondrial Fe2+ accumulation was detected when frataxin decreased. Honokiol, a SirT3 activator, restores mitochondrial respiration, decreases SOD2 acetylation and reduces mitochondrial superoxide levels. Altogether, these results provide data at the molecular level of the consequences of electron transport chain dysfunction, which starts negative feedback, contributing to neuron lethality. This is especially important in sensory neurons which have greater susceptibility to frataxin deficiency compared to other tissues.

Abstract P3199: Role Of Acetylation In Regulating Mitochondrial Dysfunction In The Aged Heart

Cardiac mitochondrial dysfunction is a critical contributor to the pathogenesis of aging. Cardiac muscle is an extremely high energy demanding tissue, necessitating properly functioning mitochondria to meet this demand for contractile function. As such, complete control of mitochondrial function is indispensable to maintain cardiac efficiency. Lysine acetylation is a post-translational modification of proteins that has been shown to regulate several metabolic and biochemical processes in the mitochondria. The goal of this study is to understand the role of mitochondrial lysine acetylation in regulating mitochondrial processes in the aged heart. We observed an increased propensity towards a pro-acetylation profile resulting in increased acetylation of several cardiac mitochondrial proteins involved in metabolism, redox milieu and electron transport chain complexes in aging which was attenuated in our cardiac GCN5L1 knockout old animal. Based upon these findings, we hypothesize that mitochondrial acetyltransferase GCN5L1 has a critical role in regulating the function of mitochondrial proteins in the aged heart. Using immunoprecipitation assay, we observed an age-associated increase in acetylation of several key fatty acid oxidation and glucose oxidation proteins. This increased acetylation correlated with decreased activity of several fatty acid oxidation proteins, including short- and long-chain acyl-CoA dehydrogenase. Several mitochondrial proteins involved in mitochondrial fatty acid import and electron transport chain complexes were hyperacetylated in aging. These proteins largely exhibited increased acetylation levels in response to age that was attenuated by cardiac-specific GCN5L1 knockout. Lastly, we observed an age-associated increase in GCN5L1-mediated acetylation of the antioxidant enzyme manganese superoxide dismutase (SOD2) at lysine site K122. Acetylation of SOD2 at the K122 site has been shown to inhibit SOD2 activity. Based upon our findings, we conclude that age-associated increases in GCN5L1 expression results in derangements in cardiac fuel substrate utilization, electron transport chain complex function, and mediation of reactive oxygen species-associated damage.

SIRT1 regulates osteoblast senescence through SOD2 acetylation and mitochondrial dysfunction in the progression of Osteoporosis caused by Cadmium exposure

Environmental Cadmium (Cd) is a toxicant with widespread exposure, documented adverse effects on bone homeostasis, and makes the onset of osteoporosis (OP), one of the age-related chronic diseases an enormous burden to modern societies worldwide. Aging is the largest risk factor for a multitude of age-related diseases and osteoblasts senescence reduces bone formation and is a key factor for osteoporosis. Despite anti-aging molecules the nuclear silent information regulator of transcription 1 (SIRT1) actions in chondrocytes and bone cells are critical for normal skeletal development and homeostasis, much less is known about the role of SIRT1 in osteoporosis. Here, we aim to demonstrate that SIRT1 mediates osteoblasts' senescence response to OP caused by Cd. The senescent osteoblasts accumulation and their viability were analyzed after Cd exposure. To explore the effects and mechanism of SIRT1 in Cd-induced osteoblastic senescence, we generated SIRT1-overexpressed osteoblast and SIRT1 conditional overexpression in the rat femur. Meanwhile, the OP rat model was established by removing bilateral ovaries. We found decreased SIRT1 expression and senescent osteoblasts accumulation after Cd exposure. Meanwhile, Cd exposure increased P53, P16INK4a, and P21CIPI proteins level, triggered DNA damage response (DDR) through the phosphorylation of ATM and H2AX, and caused mitochondrial dysfunction by the increased acetylation of SOD2 and excessive mitophagy. SIRT1 overexpression attenuated DDR and mitochondrial dysfunction and downregulated the increase of hall makers senescence caused by Cd in osteoblasts. We found overexpression of osteoblastic SIRT1 protects against Cd-induced senescence, which is likely driven by ATM-mediated DDR and SOD2ace-mediated mitochondrial dysfunction. Our study demonstrates the mechanism of SIRT1 in mediating bone homeostasis via senescence. Further mechanistic studies using specific SIRT1 mutations elucidating how SIRT1 modulates bone cell senescence, will provide new therapeutic strategies for human osteoporosis.

Promising anti-ovarian aging herbal formulation He's Yangchao promotes in vitro maturation of oocytes from advanced maternal age mice

Ethnopharmacological relevanceMarveled at the discovery of artemisinin, the world's expectations for traditional Chinese medicine are rising. He's Yangchao formula (HSYC) is a traditional Chinese herbal formula with the effects of tonifying kidney and essence, and reconciling yin and yang. It has been clinically proven to have anti-ovarian aging effects. Age is the primary cause of diminished ovarian reserve and assisted reproductive failure in women, whether HSYC has the potential to improve in vitro maturation of oocytes from advanced maternal age (AMA) mice has yet to be determined. Aim of the studyThis study aims to evaluate the efficacy and possible mechanism of HSYC in promoting in vitro maturation of oocytes from AMA mice. Materials and methodsThe GV oocytes were obtained from young and aged mice. The GV oocytes from young mice were cultured in drops of M16 medium, and the GV oocytes from AMA mice were randomly divided four groups: Vehicle group (cultured in 90% M16 medium +10% blank serum), Low HSYC group (cultured in 90% M16 medium + 10% Low HSYC-medicated serum), High-HSYC group (cultured in 90% M16 medium +10% High HSYC-medicated serum), and Quercetin group (cultured in M16 medium supplemented with 10 μM quercetin). The rates of first polar body extrusion, reactive oxygen species (ROS), intracellular calcium, and mitochondrial membrane potential levels in each groups were observed. In addition, expression levels of mitochondrial function, autophagy, DNA damage, and antioxidant-related proteins were assessed. ResultsSupplementation of HSYC in vitro alleviated age-associated meiotic progression defects in maternally aged oocytes. Importantly, HSYC supplementation eliminated the age-related ROS accumulation to suppress DNA damage and autophagy during the in vitro maturation of maternally aged oocytes. Meanwhile, the mitochondrial function was improved after HSYC treatment, as manifested by higher mitochondrial membrane potential and lower Ca2+ levels. Furthermore, we found that HSYC supplementation during in vitro maturation of maternally aged oocytes upregulated the expression level of SIRT3, a crucial protein in regulating mitochondrial function. Consistently, the expression levels of the SOD2, PCG1α, and TFAM were increased, while the SOD2 acetylation level was decreased, which further proved its antioxidant function. ConclusionsHSYC supplementation promotes in vitro maturation of oocytes from AMA mice mainly via improving mitochondrial function and alleviating oxidative stress. The mechanism may be related to the regulation of SIRT3-dependent deacetylation of the SOD2 pathway.

Metabolism-based targeting of MYC via MPC-SOD2 axis-mediated oxidation promotes cellular differentiation in group 3 medulloblastoma

Group 3 medulloblastoma (G3 MB) carries the worst prognosis of all MB subgroups. MYC oncoprotein is elevated in G3 MB tumors; however, the mechanisms that support MYC abundance remain unclear. Using metabolic and mechanistic profiling, we pinpoint a role for mitochondrial metabolism in regulating MYC. Complex-I inhibition decreases MYC abundance in G3 MB, attenuates the expression of MYC-downstream targets, induces differentiation, and prolongs male animal survival. Mechanistically, complex-I inhibition increases inactivating acetylation of antioxidant enzyme SOD2 at K68 and K122, triggering the accumulation of mitochondrial reactive oxygen species that promotes MYC oxidation and degradation in a mitochondrial pyruvate carrier (MPC)-dependent manner. MPC inhibition blocks the acetylation of SOD2 and oxidation of MYC, restoring MYC abundance and self-renewal capacity in G3 MB cells following complex-I inhibition. Identification of this MPC-SOD2 signaling axis reveals a role for metabolism in regulating MYC protein abundance that has clinical implications for treating G3 MB.

A Genetically Heterogeneous Rat Model with Divergent MitochondrialGenomes.

We generated a genetically heterogenous rat model by a 4-way cross strategy using 4 inbred strains (Brown Norway [BN], Fischer 344 [F344], Lewis [LEW], and Wistar Kyoto [KY]) to provide investigators with a highly genetically diverse rat model from commercially available inbred rats. We made reciprocal crosses between males and females from the 2 F1 hybrids to generate genetically heterogeneous rats with mitochondrial genomes from either the BN (OKC-HETB, a.k.a "B" genotype) or WKY (OKC-HETW a.k.a "W" genotype) parental strains. These two mitochondrial genomes differ at 94 nucleotides, more akin to human mitochondrial genome diversity than that available in classical laboratory mouse strains. Body weights of the B and W genotypes were similar. However, mitochondrial genotype antagonistically affected grip strength and treadmill endurance in females only. In addition, mitochondrial genotype significantly affected multiple responses to a high-fat diet (HFD) and treatment with 17α-estradiol. Contrary to findings in mice in which males only are affected by 17α-estradiol supplementation, female rats fed a HFD beneficially responded to 17α-estradiol treatment as evidenced by declines in body mass, adiposity, and liver mass. Male rats, by contrast, differed in a mitochondrial genotype-specific manner, with only B males responding to 17α-estradiol treatment. Mitochondrial genotype and sex differences were also observed in features of brain-specific antioxidant response to a HFD and 17α-estradiol as shown by hippocampal levels of Sod2 acetylation, JNK, and FoxO3a. These results emphasize the importance of mitochondrial genotype in assessing responses to putative interventions in aging processes.

POLYDATIN AMELIORATES TRAUMATIC BRAIN INJURY-INDUCED SECONDARY BRAIN INJURY BY INHIBITING NLRP3-INDUCED NEUROINFLAMMATION ASSOCIATED WITH SOD2 ACETYLATION.

Traumatic brain injury (TBI) is a kind of disease with high morbidity, mortality, and disability, and its pathogenesis is still unclear. Research shows that nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) activation in neurons and astrocytes is involved in neuroinflammatory cascades after TBI. What is more, polydatin (PD) has been shown to have a protective effect on TBI-induced neuroinflammation, but the mechanisms remain unclear. Here, we speculated that PD could alleviate TBI-induced neuroinflammatory damage through the superoxide dismutase (SOD2)-NLRP3 signal pathway, and SOD2 might regulate NLRP3 inflammasome activation. The model of lateral fluid percussion for in vivo and cell stretching injury for in vitro were established to mimic TBI. NLRP3 chemical inhibitor MCC950, SOD2 inhibitor 2-methoxyestradiol, and PD were administered immediately after TBI. As a result, the expression of SOD2 acetylation (SOD2 Ac-K122), NLRP3, and cleaved caspase-1 were increased after TBI both in vivo and in vitro , and using SOD2 inhibitor 2-methoxyestradiol significantly promoted SOD2 Ac-K122, NLRP3, and cleaved caspase-1 expression, as well as exacerbated mitochondrial ROS (mtROS) accumulation and mitochondrial membrane potential (MMP) collapse in PC12 cells. However, using NLRP3 inhibitor MCC950 significantly inhibited cleaved caspase-1 activation after TBI both in vivo and in vitro ; meanwhile, MCC950 inhibited mtROS accumulation and MMP collapse after TBI. More importantly, PD could inhibit the level of SOD2 Ac-K122, NLRP3, and cleaved caspase-1 and promote the expression of SOD2 after TBI both in vivo and in vitro. Polydatin also inhibited mtROS accumulation and MMP collapse after stretching injury. These results indicated that PD inhibited SOD2 acetylation to alleviate NLRP3 inflammasome activation, thus acting a protective role against TBI neuroinflammation.

Abstract 15464: Mitochondrial Function of Adventitial Fibroblasts in Pulmonary Hypertension is Regulated Through Sirt3 Deacetylase Activity

Introduction: Pulmonary hypertension (PH) is a heterogeneous and life-threatening cardiopulmonary disorder in which mitochondrial dysfunction drive pathogenesis. Although metabolic changes in PH draw attention of extensive investigation, the underlying mechanisms remain unclear. Hypothesis: Decreased Sirt3 mitochondrial deacetylase activity leads to increased mitochondrial enzyme acetylation level and mitochondrial dysfunction in pulmonary artery adventitial fibroblast cells isolated from IPAH patients (PH-Fibs). Methods: 1) qPCR and western blot to examine Sirt3 gene and protein levels in PH-Fibs and CO-Fibs, 2) western blotting of isolated mitochondrial protein acetylation level to examine the Sirt3 deacetylase activity, 3) immunostaining of mitochondrial SOD2 (direct target of Sirt3) acetylation level in lung tissues from PAH patients to examine Sirt3 deacetylase activity in vivo, 4) respiratory analysis and fluorescent lifetime imaging microscopy (FLIM) to analyze the glycolytic and mitochondrial function in cells, 5) overexpressing Sirt3 and supplement NAD + to investigate the therapeutic potential of regulating mitochondrial enzyme acetylation level and mitochondrial function in PH-Fibs. Results: PH-Fibs have decreased Sirt3 mRNA and protein levels compared to CO-Fibs. NAD + , a Sirt3 co-factor, is also decreased in PH-Fibs. Increased mitochondrial protein pan-acetylation levels and mitochondrial specific Sirt3 target (MnSOD2) were identified in cultured PH-Fibs, as well as lung vasculatures of IPAH patients, indicating the decreased mitochondrial deacetylase activity of Sirt3 in vitro and in vivo. We demonstrated increased glycolytic capacity and impaired mitochondrial function in PH-Fibs compared to CO-Fibs. Finally, by overexpressing Sirt3 level and at the same time increase NAD + availability, we proved that Sirt3 and NAD + can serve as therapeutic methods to synergistically improve mitochondrial function by regulating mitochondrial enzyme acetylation level in PH-Fibs. Conclusions: This study demonstrated that the mitochondrial deacetylase activity of Sirt3 as a critical mechanism regulating mitochondrial protein acetylation and mitochondrial function of fibroblast cells in IPAH patients.

Irisin Promotes Osteogenesis by Modulating Oxidative Stress and Mitophagy through SIRT3 Signaling under Diabetic Conditions.

Advanced glycation end products (AGEs) accumulate in the bone tissue of patients with diabetes mellitus, resulting in oxidative stress, poor bone healing, or regeneration. Irisin, a novel exercise-induced myokine, is involved in the regulation of bone metabolism. However, the effects of irisin on adipose-derived stem cell (ASC) osteogenic differentiation and bone healing under diabetic conditions remain poorly understood. ASCs were obtained from inguinal fat of Sprague-Dawley rats and treated with different concentrations of AGEs and irisin. Cell proliferation, apoptosis, and osteogenic differentiation abilities of ASCs were detected. To explore the regulatory role of sirtuin 3 (SIRT3), ASCs were transfected with lentivirus-mediated SIRT3 overexpression or knockdown vectors. Next, we investigated mitochondrial functions, mitophagy, and mitochondrial biogenesis in different groups. Moreover, SOD2 acetylation and potential signaling pathways were assessed. Additionally, a diabetic rat model was used to evaluate the effect of irisin on bone healing in calvarial critical-sized defects (CSDs) in vivo. Our results showed that irisin incubation mitigated the inhibitory effects of AGEs on ASCs by increasing cell viability and promoting osteogenesis. Moreover, irisin modulated mitochondrial membrane potential, intracellular ROS levels, mitochondrial O2·− status, ATP generation, complex I and IV activities, mitophagy, and mitochondrial biogenesis via a SIRT3-mediated pathway under AGEs exposure. Furthermore, in calvarial CSDs of diabetic rats, transplantation of gels encapsulating irisin-pretreated ASCs along with irisin largely enhanced bone healing. These findings suggest that irisin attenuates AGE-induced ASC dysfunction through SIRT3-mediated maintenance of oxidative stress homeostasis and regulation of mitophagy and mitochondrial biogenesis. Thus, our studies shed new light on the role of irisin in promoting the ASC osteogenesis and targeting SIRT3 as a novel therapeutic intervention strategy for bone regeneration under diabetic conditions.

Sirt3-Sod2-mROS-Mediated Manganese Triggered Hepatic Mitochondrial Dysfunction and Lipotoxicity in a Freshwater Teleost.

Exposure to excessive manganese (Mn) is toxic to humans and animals. However, the toxic effects and mechanisms of excessive Mn influencing the vertebrates have been highly overlooked. In the present study, dietary Mn overload significantly increased hepatic lipid and Mn contents, decreased superoxide dismutase 2 (Sod2) activity, increased the Sod2 acetylation level, and induced mitochondrial dysfunction; Mn induced mitochondrial dysfunction through Mtf1/sirtuin 3 (Sirt3)-mediated acetylation of Sod2 at the sites K55 and K70. Meanwhile, mitochondrial oxidative stress was involved in Mn-induced lipotoxicity. Mechanistically, Mn-induced lipotoxicity was via oxidative stress-induced Hsf1 nucleus translocation and its DNA binding capacity to the regions of a peroxisome proliferator-activated receptor g (pparg) promoter, which in turn induced the transcription of lipogenic-related target genes. For the first time, our study demonstrated that Mn-induced hepatic lipotoxicity via a mitochondrial oxidative stress-dependent Hsf1/Pparg pathway and Mtf1/sirt3-mediated Sod2 acetylation participated in mitochondrial dysfunction. Considering that lipid metabolism and lipotoxicity are widely used as the biomarkers for environmental assessments of pollutants, our study provided innovative and important insights into Mn toxicological and environmental evaluation in aquatic environments.

Regulation of NAD Metabolism in Diastolic Dysfunction Induced by Metabolic Stress

Patients of heart failure with preserved ejection fraction (HFpEF) have diastolic dysfunction. Intervention targeting mechanisms of diastolic dysfunction is lacking, leading to a growing population of patients with HFpEF. Diabetes and obesity are key risk factors of HFpEF. NAD depletion is associated with heart failure, diabetes and obesity, and is due to NAD redox imbalance, suppressed synthesis and/or activated consumption pathways. Here, we used mouse models manipulating NAD redox balance and hydrolysis to determine their roles in metabolic cardiomyopathy. Cardiac Ndufs4‐KO mice (cKO) have lowered cardiac NAD/NADH ratio, normal baseline function, geometry and energetics. Chronic diabetic stress induced by streptozotocin (STZ) or diet‐induced obesity (DIO) in wild type (WT) mice promoted diastolic dysfunction, which was further exacerbated in cKO mice with latent cardiac NAD redox imbalance. Elevated oxidative stress by SOD2 acetylation and increased TnI‐S150 phosphorylation by energetic deficiency in diabetic cKO hearts led to exacerbated diastolic dysfunction. Elevation of cardiac NAD levels normalized NAD/NADH ratio, ameliorated these pathogenic mechanisms and diastolic dysfunction in metabolically stressed mice. These results supported the causal role of NAD redox imbalance in metabolic cardiomyopathy.Next, we tested whether deficiency of SARM1, an intracellular NAD hydrolase, will ameliorate diastolic dysfunction induced by metabolic stresses. WT and total SARM1‐KO mice were challenged with diabetic stress or DIO. These metabolic stresses led to a decline in diastolic function, which was improved in SARM1‐KO mice. DIO also promoted cardiac hypertrophy that was ameliorated by SARM1 deficiency. To determine that the improvement of diastolic function by SARM1 deficiency was not due to a reversal of systemic metabolic state, a comprehensive plasma metabolomic analyses was performed. Hyperglycemia was similar in diabetic WT and SARM1‐KO plasma. Metabolomic analyses showed significant changes in 58 out of 298 aqueous metabolites and in 26 out of 85 lipid species measured, when comparing non‐diabetic WT to diabetic WT plasma. When comparing the 84 metabolites with diabetic changes from diabetic WT and diabetic SARM1‐KO plasma, only one of the lipid metabolites (PC 16:0/16:0) showed a mild further decrease in SARM1‐KO plasma. The metabolomic data suggest that WT and SARM1‐KO hearts experienced similar metabolic stress, and that the improvement of diastolic dysfunction by SARM1 deficiency was due to the reversal of cardiac pathogenic mechanisms.To determine how SARM1 deficiency affected cardiac NAD metabolism, transcript levels of genes in NAD metabolic pathways were assessed. Expressions of Bst1 and Cd38 NAD hydrolases did not change in SARM1‐KO hearts, suggesting that SARM1 deficiency did not induce compensatory changes in expression of the other NAD hydrolases. SARM1‐KO hearts showed lower expressions in several other NAD consuming genes (e.g. Sirtuins) and NAD synthesis genes (e.g. Nmnats). Cardiac fibrosis, pro‐fibrotic genes (e.g. ctgf) and Nppb expression were induced in diabetic WT hearts and were suppressed by SARM1 deficiency. In summary, our data support the critical roles of NAD redox imbalance and SARM1 in diastolic dysfunction induced by metabolic stress.

Polydatin improves intestinal barrier injury after traumatic brain injury in rats by reducing oxidative stress and inflammatory response via activating SIRT1-mediated deacetylation of SOD2 and HMGB1

To investigate the protective effect against intestinal mucosal injury in rats following traumatic brain injury (TBI) and explore the underlying mechanism. SD rat models of TBI were established by fluid percussion injury (FPI), and the specimens were collected at 12, 24, 48, and 72 h after TBI. Another 15 rats were randomly divided into shamoperated group (n=5), TBI with saline treatment (TBI+NS) group (n=5), and TBI with PD treatment (TBI+PD) group (treated with 30 mg/kg PD after TBI; n=5). Body weight gain and fecal water content of the rats were recorded, and after the treatments, the histopathology of the jejunum was observed, and the levels of D-lactic acid (D-LAC), diamine oxidase (DAO), ZO-1, claudin-5, and reactive oxygen species (ROS) were detected. Lipid peroxide (LPO) and superoxide dismutase (SOD) 2 content, jejunal pro-inflammatory factors (IL-6, IL-1β, and TNF- α), Sirt1 activity, SOD2 and HMGB1 acetylation level were also determined after the treatments. The rats showed significantly decreased body weight and fecal water content and progressively increased serum levels of D-LAC and DAO after TBI (P < 0.05) with obvious jejunal injury, significantly decreased expression levels of ZO-1 and claudin-5, lowered SOD2 and Sirt1 activity (P < 0.05), increased expression levels of LPO, ROS, and pro-inflammatory cytokines, and enhanced SOD2 and HMGB1 acetylation levels (P < 0.05). Compared with TBI+NS group, the rats in TBI+PD group showed obvious body weight regain, increased fecal water content, reduced jejunal pathologies, decreased D-LAC and DAO levels (P < 0.05), increased ZO-1, claudin-5, SOD2 expression levels and Sirt1 activity, and significantly decreased ROS, LPO, pro-inflammatory cytokines, and acetylation levels of SOD2 and HMGB1 (P < 0.05). PD alleviates oxidative stress and inflammatory response by activating Sirt1-mediated deacetylation of SOD2 and HMGB1 to improve intestinal mucosal injury in TBI rats.

Weighted Gene Co-Expression Network Analysis Identifies ANGPTL4 as a Key Regulator in Diabetic Cardiomyopathy via FAK/SIRT3/ROS Pathway in Cardiomyocyte.

BackgroundDiabetic cardiomyopathy (DbCM) is characterized by initial impairment of left ventricular relaxation followed by contractile dysfunction. Despite intensive research, the exact mechanism remains so far unsolved.MethodsWe constructed weighted gene co-expression network analysis (WGCNA) to screen gene modules that were closely related with DbCM based on the GSE5606 dataset, which contained expression data of the cardiac left ventricle in a rodent model of streptozotocin (STZ)-induced DbCM. Then, the most related hub gene, angiopoietin-like 4 (ANGPTL4), was selected for functional ex vivo and in vitro assays. In our experiments, STZ-induced diabetic mice (C57BL/6J) and human cardiomyocytes (AC16) were used to study the functional roles and potential mechanisms of ANGPTL4 in DbCM.ResultsWGCNA analysis revealed the yellow and green modules were most correlated with DbCM, and identified ANGPTL4 as one of the most significantly upregulated hub genes (ANGPTL4, ACOT1, DECR1, HMGCS2, and PDK4). Consistent with the bioinformatic analysis, the amount of ANGPTL4 was significantly upregulated in diabetic mouse heart. DbCM group, compared with the control group, had increased phosphorylation of focal adhesion kinase (FAK), reduced SIRT3 expression, increased SOD2 acetylation, upregulated NADPH oxidase activation, elevated reactive oxygen species (ROS) produciton, and enhanced apoptosis in the diabetic mouse heart. Moreover, ANGPTL4 induced apoptosis via FAK/SIRT3/ROS pathway in human cardiomyocytes (AC16) under high glucose condition in vitro.These effects were abrogated by treatment of two independent siRNA for ANGPTL4, whereas exogenous recombinant ANGPLT4 protein treatment exacerbated those effects in AC16.ConclusionWe found ANGPTL4, ACOT1, DECR1, HMGCS2, and PDK4 were significantly increased in diabetic heart. ANGPTL4 could promote cardiac apoptosis via a FAK/SIRT3/ROS dependent signaling pathway in DbCM.

NAD + Redox Imbalance Exacerbates Diabetic Cardiomyopathy via Enhanced Troponin I Phosphorylation, Impaired Energetics and Prolonged Cardiac Relaxation

Diabetes is a major risk factor of heart failure. Diabetes and heart failure have been linked to NAD redox imbalance, whose role in the progression of diabetic cardiomyopathy (DCM) is far from established. Streptozotocin (STZ)-induced diabetes in C57BL/6 mice for 16 weeks promoted declines in systolic and diastolic function and lowered cardiac NAD/NADH ratio. We employed cardiac-specific Ndufs4-KO mice (cKO), which exhibit lowered cardiac NAD/NADH ratio with normal baseline function and energetics, to determine the role of NAD redox imbalance in DCM. Plasma metabolomic analysis showed similar diabetic stress in diabetic control and cKO mice. Systolic (fractional shortening) and diastolic (E’/A’ ratio; isovolumic relaxation time, IVRT) dysfunctions were further exacerbated in diabetic cKO mice in both male and female cohorts. Collagen levels and transcript analyses of fibrosis and extracellular matrix-dependent pathways did not show changes in diabetic cKO hearts, suggesting that the exacerbated cardiac dysfunction was likely due to cardiomyocyte dysfunction. We next analyzed protein acetylation-dependent pathways to account for the exacerbated decline of function in diabetic cKO hearts. NAD redox imbalance in diabetic cKO hearts promoted protein acetylation, including SOD2 acetylation (SOD2-K68Ac). This SOD2 acetylation inhibits its antioxidant function and we observed elevated protein oxidation levels in diabetic cKO hearts. To gain further insights how NAD redox imbalance may regulate cardiomyocyte function, phosphorylation levels of myosin binding protein C (MyBPC) and troponin I (TnI) were examined. MyBPC phosphorylation at S282 is suppressed in failing hearts and remained unchanged in diabetic cKO hearts. TnI phosphorylation at S150 (TnI-S150Pi) increases myofilament calcium sensitivity and prolongs calcium dissociation, while TnI-S23/24Pi decreases calcium sensitivity and accelerates calcium dissociation. In diabetic cKO hearts, levels of TnI-S150Pi were elevated while TnI-S23/24Pi remained unchanged. TnI-S150Pi is sensitive to AMPK, the master energy sensor, and we found that ATP levels decreased, and AMP/ATP ratio increased in diabetic cKO hearts. Elevation of cardiac NAD levels by nicotinamide phosphoribosyltransferase (NAMPT) normalized NAD redox balance and alleviated systolic and diastolic dysfunction. Importantly, elevated TnI-S150Pi, exacerbated diastolic dysfunction and prolonged IVRT in diabetic cKO hearts were all restored by NAMPT over-expression. The data collectively suggest that NAD redox imbalance promotes impairments in cellular energetics and diastolic function via enhancing TnI-S150Pi, and is a critical mediator of the progression of DCM.

Iron overload adversely effects bone marrow haematogenesis via SIRT-SOD2-mROS in a process ameliorated by curcumin

BackgroundIron overload, which is common in patients with haematological disorders, is known to have a suppressive effect on haematogenesis. However, the mechanism for this effect is still unclear. The antioxidant curcumin has been reported to protect against iron overload-induced bone marrow damage through an as-yet-unknown mechanism.MethodsWe established iron overload cell and mouse models. Mitochondrial reactive oxygen species (mROS) levels, autophagy levels and the SIRT3/SOD2 pathway were examined in the models and in the bone marrow of patients with iron overload.ResultsIron overload was shown to depress haematogenesis and induce mitochondrion-derived superoxide anion-dependent autophagic cell death. Iron loading decreased SIRT3 protein expression, promoted an increase in SOD2, and led to the elevation of mROS. Overexpression of SIRT3 reversed these effects. Curcumin treatment ameliorated peripheral blood cells generation, enhanced SIRT3 activity, decreased SOD2 acetylation, inhibited mROS production, and suppressed iron loading-induced autophagy.ConclusionsOur results suggest that curcumin exerts a protective effect on bone marrow by reducing mROS-stimulated autophagic cell death in a manner dependent on the SIRT3/SOD2 pathway.

Abstract 17069: NAD+Redox Imbalance in the Heart Exacerbates Diabetic Cardiomyopathy

Diabetes is a risk factor of heart failure and leads to cardiac dysfunction, a condition named diabetic cardiomyopathy (DCM). NAD redox imbalance is observed in diabetic tissues. However, whether NAD redox imbalance promotes cardiac dysfunction in DCM remains unknown. The objective of this study is to determine the causal role of NAD redox imbalance in DCM.Type 1 diabetes was induced in C57BL6 mice by streptozotocin (STZ) injections, and DCM was allowed to develop for 16 weeks. Diabetes-induced chronic stress led to systolic and diastolic cardiac dysfunction along with a lowered NAD/NADH ratio. The diabetogenic protocol was applied to control and cardiac-specific Ndufs4-KO mice (cKO), a mouse model with lowered cardiac NAD/NADH without baseline cardiac dysfunction. Analyses of blood glucose and &gt;200 metabolites in plasma showed no significant change in diabetic control and diabetic cKO mice, suggesting that their hearts experienced similar diabetic stress. Diabetic cKO hearts showed lowered NAD/NADH, aggravated contractile and relaxation dysfunction compared to the diabetic control hearts in both sexes. The data suggest that NAD redox imbalance exacerbated DCM. Collagen staining and transcript analyses of fibrosis-related genes showed no change in diabetic cKO hearts, signifying that the exacerbated dysfunction was due to cardiomyocyte dysfunction. A global protein acetylation was promoted in the diabetic cKO hearts with an increase in SOD2 acetylation levels at lysine-68 (SOD2-K68Ac) and enhanced protein oxidation. Diabetic cKO mice displayed enhanced levels of TnI S150 phosphorylation (TnI-S150Pi), but not phosphorylation of TnI-S23/24 or MyBPc-S282. These data suggest that enhanced oxidative stress and altered myofilament Ca 2+ sensitivity via TnI-S150Pi are responsible for the NAD redox imbalance-exacerbated DCM.To confirm the role of NAD redox imbalance in DCM, we elevated cardiac NAD levels in diabetic cKO mice by cardiac-specific expression of NAMPT. Expression of NAMPT in the heart improved cardiac systolic and diastolic function in diabetic cKO hearts. This was due to increased NAD/NADH ratio and reversed pathogenic mechanisms (lowered SOD2-K68Ac and TnI-S150Pi). This study supports the causal role of NAD redox imbalance in DCM.

Quercetin promotes in vitro maturation of oocytes from humans and aged mice

Maternal fertility declines irreversibly with aging, and advanced maternal age is mostly related to impaired oocyte quality. The flavonol compound quercetin is considered to be an anti-aging agent due to its cytoprotective actions as an antioxidant. However, its role and mechanisms on aged oocytes are unclear. In this study, the quercetin promotes in vitro maturation (IVM) and early embryonic development of oocytes from aged mice. It is extended these findings in human oocytes, showing that quercetin promotes the IVM rate by 19.6% and increases the blastocyst formation rate by 15.5% compared to untreated controls. The overall oocyte quality of aged mice is improved by quercetin treatment, assessed as spindle/chromosome morphology and cortical granule distribution. Mitochondria is the primary endogenous source of age-related oxidative stress, and an RNA-seq analysis of quercetin-treated oocytes reveals molecular insights including scavenged mitochondrial-ROS, reduced apoptosis, and improved autophagy. Further, this study demonstrates that quercetin reduces ROS via SIRT3-mediated acetylation of SOD2’s K68 residue. Thus, beyond demonstrating that quercetin confers beneficial mitochondria-related impacts in aged oocytes, this study illustrates a potential strategy to prevent or delay oocyte aging and to improve success rates of assisted human reproductive technologies (ART).

Caffeine Targets SIRT3 to Enhance SOD2 Activity in Mitochondria.

Caffeine is chemically stable and not readily oxidized under normal physiological conditions but also has antioxidant effects, although the underlying molecular mechanism is not well understood. Superoxide dismutase (SOD) 2 is a manganese-containing enzyme located in mitochondria that protects cells against oxidative stress by scavenging reactive oxygen species (ROS). SOD2 activity is inhibited through acetylation under conditions of stress such as exposure to ultraviolet (UV) radiation. Sirtuin 3 (SIRT3) is the major mitochondrial nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, which deacetylates two critical lysine residues (lysine 68 and lysine 122) on SOD2 and promotes its antioxidative activity. In this study, we investigated whether the antioxidant effect of caffeine involves modulation of SOD2 by SIRT3 using in vitro and in vivo models. The results show that caffeine interacts with SIRT3 and promotes direct binding of SIRT3 with its substrate, thereby enhancing its enzymatic activity. Mechanistically, caffeine bound to SIRT3 with high affinity (KD = 6.858 × 10–7 M); the binding affinity between SIRT3 and its substrate acetylated p53 was also 9.03 (without NAD+) or 6.87 (with NAD+) times higher in the presence of caffeine. Caffeine effectively protected skin cells from UV irradiation-induced oxidative stress. More importantly, caffeine enhanced SIRT3 activity and reduced SOD2 acetylation, thereby leading to increased SOD2 activity, which could be reversed by treatment with the SIRT3 inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP) in vitro and in vivo. Taken together, our results show that caffeine targets SIRT3 to enhance SOD2 activity and protect skin cells from UV irradiation-induced oxidative stress. Thus, caffeine, as a small-molecule SIRT3 activator, could be a potential agent to protect human skin against UV radiation.

Roles of NAD Metabolism in Diabetic Cardiomyopathy

Diabetes is a major risk factor of heart failure. Diabetes and heart failure have been linked to altered NAD metabolism, whose roles in the progression of diabetic cardiomyopathy (DC) are far from established. We induced diabetes in wild type C57BL6N mice (WT) by streptozotocin (STZ) injections. WT mice with chronic diabetic stress (fasting glucose ~600 mg/dl) for 16 weeks had gradual declines in systolic and diastolic function and lowered NAD/NADH ratio, while acute STZ treatment (1‐day) did not affect cardiac function and NAD pool. To determine whether NAD redox imbalance promotes DC, we employed cardiac‐specific Ndufs4‐KO mice (cKO), which exhibit lowered cardiac NAD/NADH ratio without overt dysfunction. While insulin depletion and hyperglycemia were similar in diabetic control and cKO mice stressed by the same diabetogenic protocol, systolic and diastolic dysfunctions were accelerated in diabetic cKO mice. We next determined how NAD metabolism is altered to accelerate DC. In addition to the NAD redox balance, NAD metabolism also involves metabolites and enzymes in the NAD consumption and synthesis pathways, coordinating the homeostasis of NAD. Targeted analyses of transcripts and metabolites involved in these pathways were performed using qPCR and quantitative LC‐MS/MS analyses. Of 22 genes measured, we identified that Nmrk mRNA levels were up‐regulated in diabetic cKO hearts, compared to diabetic control hearts. Of thirteen cardiac NAD metabolite levels surveyed, product metabolites of NMRK enzymatic reaction (i.e. NMN or NAMN) showed decreases in levels in diabetic cKO hearts. The transcript and metabolite data suggest a role of NMRK in DC. Histologically, cardiac fibrosis levels of diabetic control and cKO hearts were slightly elevated compared to non‐diabetic controls, but they were not different. The results suggest that the accelerated decline of cardiac function in diabetic cKO hearts is not be due to altered extracellular matrix environment. We next analyzed acetylation‐dependent pathways to account for the accelerated decline of function in diabetic cKO hearts. NAD redox imbalance in diabetic cKO hearts promoted protein acetylation, including SOD2 acetylation (SOD2‐K68Ac). SOD2 acetylation inhibits its antioxidant function and we observed elevated protein oxidation levels in diabetic cKO hearts. To gain further insights how NAD redox imbalance may regulate cardiomyocyte function, phosphorylation levels of myosin binding protein C (MyBPC) and troponin I (TnI) were examined. In diabetic cKO hearts, TnI phosphorylation was elevated while MyBPC phosphorylation remained unchanged, suggesting a regulation of cardiomyocyte contraction/relaxation by NAD‐dependent mechanisms. To normalize NAD redox imbalance, we elevated NAD levels in diabetic cKO mice with cardiac‐specific NAMPT overexpression. Cardiac NAMPT expression slowed the accelerated decline of systolic and diastolic functions in diabetic cKO hearts. Our results support that altered NAD metabolism is a critical determinant for the progression of DC and warrants further investigations.Support or Funding Information1. Scientist Development Grant, AHA2. Seed Funding, Presbyterian Health Foundation of Oklahoma City 1.