A SIRT3/AMPK/autophagy network orchestrates the protective effects of trans-resveratrol in stressed peritoneal macrophages and RAW 264.7 macrophages

SIRT3 promotes lipophagy and chaperon-mediated autophagy to protect hepatocytes against lipotoxicity

Lipophagy is a lysosomal lipolytic pathway that complements the actions of cytosolic neutral lipases. Chaperon-mediated autophagy (CMA) triggers lipid droplets (LDs) breakdown, to initiate lipolysis via either cytosolic lipases or macroautophagy. SIRT3, a mitochondrial NAD⁺-dependent deacetylase, regulates the acetylation status and activity of many substrates involving in energy metabolism. However, the role of SIRT3 in regulating lipophagy is controversial. The current study showed that SIRT3 expression was decreased and the macroautophagy flux was blocked in the primary hepatocytes from high-fat diet fed mice and P/O (palmitic acid and oleic acid mixture) treated AML12 mouse hepatocytes, compared with the corresponding controls. SIRT3 overexpression promoted macroautophagy in LDs from P/O-treated hepatocytes through activating AMP-activated protein kinase (AMPK) and unc-51-like kinase 1, to boost LDs digestion. Gain of SIRT3 expression stimulated the formation of lysosome-associated membrane protein 2A (LAMP-2A)-heat shock cognate 71 kDa protein (HSC70)-perilipin-2 (PLN2) complex, to promote CMA process and reduce the stability of LDs in hepatocytes. Moreover, SIRT3 reduced the expression of stearoyl-CoA desaturase 1, to suppress lipogenesis. In addition, SIRT3 overexpression promoted LDs dispersion on detyrosinated microtubules, and directly deacetylated long-chain acyl-CoA dehydrogenase to enhance mitochondrial energetics. Taken together, SIRT3 ameliorates lipotoxicity in hepatocytes, which might be a potential target for the treatment of nonalcoholic fatty liver disease.

Modulation of Autophagy for Controlling Immunity

Autophagy is an essential process that maintains physiological homeostasis by promoting the transfer of cytoplasmic constituents to autophagolysosomes for degradation. In immune cells, the autophagy pathway plays an additional role in facilitating proper immunological functions. Specifically, the autophagy pathway can participate in controlling key steps in innate and adaptive immunity. Accordingly, alterations in autophagy have been linked to inflammatory diseases and defective immune responses against pathogens. In this review, we discuss the various roles of autophagy signaling in coordinating immune responses and how these activities are connected to pathological conditions. We highlight the therapeutic potential of autophagy modulators that can impact immune responses and the mechanisms of action responsible.

SIRT3 diminishes inflammation and mitigates endotoxin-induced acute lung injury

Acute lung injury (ALI) is characterized by exuberant proinflammatory responses and mitochondrial dysfunction. However, the link between mitochondrial dysfunction and inflammation in ALI is not well understood. In this report, we demonstrate a critical role for the mitochondrial NAD+-dependent deacetylase, sirtuin-3 (SIRT3), in regulating macrophage mitochondrial bioenergetics, ROS formation, and proinflammatory responses. We found that SIRT3 expression was significantly diminished in lungs of mice subjected to LPS-induced ALI. SIRT3-deficient mice (SIRT3-/-) develop more severe ALI compared with wild-type controls (SIRT3+/+). Macrophages obtained from SIRT3-/- mice show significant alterations in mitochondrial bioenergetic and redox homeostasis, in association with a proinflammatory phenotype characterized by NLRP3 inflammasome activation. The SIRT3 activator viniferin restored macrophage bioenergetic function in LPS-treated macrophages. Viniferin also reduced NLRP3 activation and the production of proinflammatory cytokines, effects that were absent in SIRT3-/- macrophages. In-vivo administration of viniferin reduced production of inflammatory mediators TNF-α, MIP-2, IL-6, IL-1β, and HMGB1, and diminished neutrophil influx and severity of endotoxin-mediated ALI; this protective effect of vinferin was abolished in SIRT3-/- mice. Taken together, our results show that the induction/activation of SIRT3 may serve as a new therapeutic strategy in ALI by modulating cellular bioenergetics, controlling inflammatory responses, and reducing the severity of lung injury.

SIRT-3 Modulation by Resveratrol Improves Mitochondrial Oxidative Phosphorylation in Diabetic Heart through Deacetylation of TFAM

Background and Purpose: Mitochondrial dysfunction remains the crucial cause for many heart diseases including diabetic cardiomyopathy (DCM). Sirtuin-3 (SIRT-3) is a protein deacetylase localized in the mitochondria and regulates mitochondrial function. Being a noteworthy mitochondrial protein deacetylase enzyme, the role of SIRT-3 in DCM is yet to be explored. Experimental Approach: Diabetes mellitus (Type-I, T1DM) was induced using streptozotocin (STZ, 50 mg/kg) in male Sprague Dawley (SD) rats. Rats with >200 mg/dL blood glucose levels were then divided randomly into two groups, DIA and DIA + RESV, where vehicle and resveratrol (25 mg/kg/day) were administered orally in both groups, respectively. Cardiac oxidative stress, fibrosis, and mitochondrial parameters were evaluated. H9c2 cells were transfected with SIRT-3 siRNA and shRNA, and ORF plasmid for silencing and overexpression, respectively. Key Results: After eight weeks, diabetic rat heart showed reduced cardiac cell size, increased oxidative stress and reduction of the activities of enzymes involved in mitochondrial oxidative phosphorylation (OXPHOS). There was reduced expression and activity of SIRT-3 and mitochondrial transcription factor (TFAM) in diabetic heart. Reduced SIRT-3 expression is also correlated with increased acetylation, decreased mitochondrial DNA (mtDNA) binding activity of TFAM, and reduced transcription of mitochondrial DNA encoded genes. Administration of resveratrol prevented the decrease in SIRT-3 and TFAM activity, which was corresponding to the reduced acetylation status of TFAM. Silencing SIRT-3 using siRNA in H9C2 cells showed increased acetylation of TFAM. Conclusion and Implications: Together our data shows that resveratrol activates SIRT-3, regulates the acetylation status of TFAM and preserves the mitochondrial function along with cellular size in diabetic rat heart.

Caffeine Protects Skin from Oxidative Stress-Induced Senescence through the Activation of Autophagy

Skin cells are vulnerable to oxidative stress-induced senescence, which may lead to abnormal aging or aging-related disorders. Therefore, strategies that can ameliorate oxidative stress-induced senescence are expected to protect skin from damage, holding the promise of treating skin diseases in the clinic. This study aims to investigate whether caffeine, a well-known purine alkaloid, is able to prevent skin from oxidative stress-induced senescence, and to explore the underlying molecular mechanisms.

Methods: A free radical inducer 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) was used to induce oxidative stress and cellular senescence in both transformed skin cells and in normal human epidermal keratinocytes (NHEKs). Ultraviolet (UV) irradiation was established as the in vivo oxidative stress model in mouse skin tissues. Cellular senescence was determined by SA β-galactosidase staining, immunofluorescence and western blotting. Activation of autophagy was confirmed by western blotting, immunofluorescence, and transmission electron microscopy. Reactive oxygen species (ROS) detection by commercial kits, gene knockdown by RNA interference (RNAi) and receptor activation/inactivation by agonist/antagonist treatment were applied in mechanistic experiments.

Results: We report that AAPH induced senescence in both transformed skin cells and in NHEKs. Similarly, UV irradiation induced senescence in mouse skin tissues. Remarkably, low dose of caffeine (<10 μM) suppressed cellular senescence and skin damage induced by AAPH or UV. Mechanistically, caffeine facilitated the elimination of ROS by activating autophagy. Using a combination of RNAi and chemical treatment, we demonstrate that caffeine activates autophagy through a series of sequential events, starting from the inhibition of its primary cellular target adenosine A2a receptor (A2AR) to an increase in the protein level of Sirtuin 3 (SIRT3) and to the activation of 5' adenosine monophosphate-activated protein kinase (AMPK). Oral administration of caffeine increased the protein level of SIRT3, induced autophagy, and reduced senescence and tissue damage in UV-irradiated mouse skin. On the other hand, co-administration with autophagy inhibitors attenuated the protective effect of caffeine on UV-induced skin damage in mice.

Conclusion: The results reveal that caffeine protects skin from oxidative stress-induced senescence through activating the A2AR/SIRT3/AMPK-mediated autophagy. Our study not only demonstrated the beneficial effect of caffeine using both in vitro and in vivo models, but also systematically investigated the underlying molecular mechanisms. These discoveries implicate the potential of caffeine in the protection of skin disease.

Honokiol protects pulmonary microvascular endothelial barrier against lipopolysaccharide-induced ARDS partially via the Sirt3/AMPK signaling axis

AIMS

Acute respiratory distress syndrome (ARDS) is characterized by acute hypoxemia with diffuse alveolar damage and increased pulmonary microvascular permeability. Honokiol (HKL), the principal active ingredient of Chinese herb magnolia officinalis, protected the lung of experimental ARDS models via attenuation of inflammation and oxidative stress. However, whether HKL has protective effects against the dysfunction of pulmonary microvascular endothelial barrier and the potential mechanisms remain unclear.

MAIN METHODS

In the present study, we examined the levels of plasma Angiopoietin-2 (Ang-2) in ARDS patients, explored the effects of HKL on the vascular endothelial barrier at the ARDS animal and cell levels.

KEY FINDINGS

Our data showed that compared with the healthy controls, circulating Ang-2 level was higher in the patients with ARDS, and were usually supposed to be positively related to the severity of ARDS. Moreover, HKL effectively inhibited lung inflammatory injury and microvascular leakage, and improved ARDS mice survival. HKL also inhibited the expression of Ang-2, ICAM-1 and VCAM-1, and restored the expression of Sirt3, β-Catenin and VE-Cadherin. Furthermore, HKL improved ECs survival and inhibited the apoptosis of ECs. The inhibition of Ang-2 expression in vitro by HKL is accompanied by the upregulation of Sirt3 and AMPK phosphorylation.

SIGNIFICANCE

Our data demonstrated that HKL protected pulmonary microvascular endothelial barrier against LPS-induced ARDS at least in part through activating the Sirt3/AMPK signaling and inhibiting the Ang-2 expression. Thus, our findings show that the activation of Sirt3 signaling is a potential mechanism for the protective effects of HKL on vascular barrier.

Promoting the clearance of neurotoxic proteins in neurodegenerative disorders of ageing

Neurodegenerative disorders of ageing (NDAs) such as Alzheimer disease, Parkinson disease, frontotemporal dementia, Huntington disease and amyotrophic lateral sclerosis represent a major socio-economic challenge in view of their high prevalence yet poor treatment. They are often called 'proteinopathies' owing to the presence of misfolded and aggregated proteins that lose their physiological roles and acquire neurotoxic properties. One reason underlying the accumulation and spread of oligomeric forms of neurotoxic proteins is insufficient clearance by the autophagic-lysosomal network. Several other clearance pathways are also compromised in NDAs: chaperone-mediated autophagy, the ubiquitin-proteasome system, extracellular clearance by proteases and extrusion into the circulation via the blood-brain barrier and glymphatic system. This article focuses on emerging mechanisms for promoting the clearance of neurotoxic proteins, a strategy that may curtail the onset and slow the progression of NDAs.

The role of autophagy induction in the mechanism of cytoprotective effect of resveratrol

We aimed at studying the potential mechanisms in the preventive effect of resveratrol on serum deprivation induced caspase 3 activation on non-transformed cells.

METHODS

Apoptosis was induced by serum deprivation in primary mouse embryonic fibroblasts. Caspase 3 activation, reactive oxygen species production and depolarization of the mitochondrial membrane were measured by fluorescence methods. The involvement of intracellular receptors and autophagy in the effect of resveratrol were analyzed by using specific agonists and antagonists. The role of autophagy was further examined by Western Blot analysis of its protein markers, LC3-II and p62 as well as by acridine orange staining of acidic vacuoles.

RESULTS

We found that neither aromatic hydrocarbon receptors nor estrogen receptors play an important role in the cytoprotective effect of resveratrol. Reactive oxygen species production was not significantly altered by either serum deprivation or resveratrol treatment. In the presence of serum deprivation resveratrol however, induced a significant depolarization in mitochondrial membrane potential. The autophagy inhibitor, chloroquine not only eliminated the preventive effect of resveratrol, but also turned it to deleterious suggesting the prominent role of autophagy induction in the cytoprotective effect. Resveratrol did not alter LC3-II expression, but facilitated p62 degradation in serum deprived cells, suggesting its ability to augment the late phase of autophagy and thus promote the autophagic flux.

CONCLUSION

We have demonstrated that resveratrol can protect primary fibroblasts against serum deprivation induced apoptosis by provoking mild mitochondrial stress and consequent up-regulation of autophagic flux.

SIRT3 Protects Rotenone-induced Injury in SH-SY5Y Cells by Promoting Autophagy through the LKB1-AMPK-mTOR Pathway

SIRT3 is a class III histone deacetylase that modulates energy metabolism, genomic stability and stress resistance. It has been implicated as a potential therapeutic target in a variety of neurodegenerative diseases, including Parkinson’s disease (PD). Our previous study demonstrates that SIRT3 had a neuroprotective effect on a rotenone-induced PD cell model, however, the exact mechanism is unknown. In this study, we investigated the underlying mechanism. We established a SIRT3 stable overexpression cell line using lentivirus infection in SH-SY5Y cells. Then, a PD cell model was established using rotenone. Our data demonstrate that overexpression of SIRT3 increased the level of the autophagy markers LC3 II and Beclin 1. After addition of the autophagy inhibitor 3-MA, the protective effect of SIRT3 diminished: the cell viability decreased, while the apoptosis rate increased; α-synuclein accumulation enhanced; ROS production increased; antioxidants levels, including SOD and GSH, decreased; and MMP collapsed. These results reveal that SIRT3 has neuroprotective effects on a PD cell model by up-regulating autophagy. Furthermore, SIRT3 overexpression also promoted LKB1 phosphorylation, followed by activation of AMPK and decreased phosphorylation of mTOR. These results suggest that the LKB1-AMPK-mTOR pathway has a role in induction of autophagy. Together, our findings indicate a novel mechanism by which SIRT3 protects a rotenone-induced PD cell model through the regulation of autophagy, which, in part, is mediated by activation of the LKB1-AMPK-mTOR pathway.

Mitophagy regulates macrophage phenotype in diabetic nephropathy rats

Imbalance of M1/M2 macrophages phenotype activation is a key point in diabetic nephropathy (DN). Macrophages mainly exhibit M1 phenotype, which contributes to the inflammation and fibrosis in DN. Studies indicate that autophage plays an important role in M1/M2 activation. However, the effect of mitophage on M1/M2 macrophage phenotype transformation in DN is unknown. This study investigates the role of mitophage on macrophage polarization in DN. In vivo experiments show that macrophages are exhibited to M1 phenotype and display a lower level of mitophagy in the kidney of streptozocin (STZ)-induced diabetic rats. Additionally, inducible nitric oxide synthase (iNOS) expression is positive correlated with the P62 expression, while negative correlated with LC3. Electronic microscope analysis shows mitochondria swelling, crista decrease and lysosome reduction in DN rats compared with NC rats. In vitro, RAW264.7 macrophages switch to M1 phenotype under high glucose conditions. Mitophagy is downregulated in such high glucose induced M1 macrophages. Furthermore, macrophages tend to switch to the M1 phenotype, expressing higher iNOS and TNF-α when impair mitophagy by 3-MA. Rapamycin, an activator of mitophagy, signifcantly blocks high-glucose induced M1 makers (iNOS and TNF-α) expression, meanwhile enhances M2 makers (MR and Arg-1) expression. These results demonstrate that mitophage participates in the regulation of M1/M2 macrophage phenotype in diabetic nephropathy.

Dosis Facit Sanitatem-Concentration-Dependent Effects of Resveratrol on Mitochondria

The naturally occurring polyphenol, resveratrol (RSV), is known for a broad range of actions. These include a positive impact on lifespan and health, but also pro-apoptotic anti-cancer properties. Interestingly, cell culture experiments have revealed a strong impact of RSV on mitochondrial function. The compound was demonstrated to affect mitochondrial respiration, structure and mass of mitochondria as well as mitochondrial membrane potential and, ultimately, mitochondria-associated cell death pathways. Notably, the mitochondrial effects of RSV show a very strict and remarkable concentration dependency: At low concentrations, RSV (<50 μM) fosters cellular antioxidant defense mechanisms, activates AMP-activated protein kinase (AMPK)- and sirtuin 1 (SIRT1)-linked pathways and enhances mitochondrial network formation. These mechanisms crucially contribute to the cytoprotective effects of RSV against toxins and disease-related damage, in vitro and in vivo. However, at higher concentrations, RSV (>50 μM) triggers changes in (sub-)cellular Ca²⁺ homeostasis, disruption of mitochondrial membrane potential and activation of caspases selectively yielding apoptotic cancer cell death, in vitro and in vivo. In this review, we discuss the promising therapeutic potential of RSV, which is most probably related to the compound’s concentration-dependent manipulation of mitochondrial function and structure.

Tenovin-6 inhibits proliferation and survival of diffuse large B-cell lymphoma cells by blocking autophagy

Diffuse large B-cell lymphoma (DLBCL) is one of the most aggressive non-Hodgkin lymphomas. It is curable but one-third of cases are refractory to therapy or relapse after initial response highlighting the urgent need for developing novel therapeutic approaches. Targeting sirtuins, particularly SIRT1 by genetic approaches or using pharmaceutical inhibitor tenovin-6, has shown promising therapeutic potential in various hematopoietic malignancies. However, it remains unknown whether these approaches are effective for DLBCL. In this study, we have found that tenovin-6 potently inhibits the proliferation and survival of DLBCL cells. Surprisingly, specific knockdown of SIRT1/2/3 has no effect on DLBCL. Mechanistically, tenovin-6 increases the level of microtubule-associated protein 1 light chain 3B (LC3B)-II in a SIRT1/2/3- and p53-independent manner in DLBCL cell lines. Tenovin-6-mediated increase of LC3B-II is through inhibition of classical autophagy pathway. Furthermore, inhibition of the autophagy pathway by using other inhibitors or by knocking down key genes in the pathway impairs cell proliferation and survival of DLBCL cells. These results indicate that targeting the autophagic pathway could be a novel therapeutic strategy for DLBCL and that precaution should be taken to interpret data where tenovin-6 was used as an inhibitor of sirtuins.

Could Sirtuin Activities Modify ALS Onset and Progression?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a complex etiology. Sirtuins have been implicated as disease-modifying factors in several neurological disorders, and in the past decade, attempts have been made to check if manipulating Sirtuin activities and levels could confer benefit in terms of neuroprotection and survival in ALS models. The efforts have largely focused on mutant SOD1, and while limited in scope, the results were largely positive. Here, the body of work linking Sirtuins with ALS is reviewed, with discussions on how Sirtuins and their activities may impact on the major etiological mechanisms of ALS. Moving forward, it is important that the potentially beneficial effect of Sirtuins in ALS disease onset and progression are assessed in ALS models with TDP-43, FUS, and C9orf72 mutations.

The Ketone Metabolite β-Hydroxybutyrate Attenuates Oxidative Stress in Spinal Cord Injury by Suppression of Class I Histone Deacetylases

The ketone metabolite β-hydroxybutyrate (βOHB), is reported to be neuroprotective after spinal cord injury (SCI) in rats, but the underlying mechanism remains unknown. The present study aims to investigate effects of βOHB on suppression of oxidative stress and inhibition of class I histone deacetylases (HDACs) in in vivo and in vitro models. Rats were fed with ketogenic diet (KD) or standard diet (SD) for 3 weeks. A C5 hemi-contusion injury was applied to these animals on the 14th day of experiment, and spinal cord samples were harvested on the 1st, 3rd and 7th days after SCI, respectively. The blood ketone levels were significantly higher in the KD groups. KD reduced oxidative stress markers and reactive oxygen species (ROS) products, downregulated the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)2 and NOX4, and upregulated the expression of forkhead box group O (FOXO)3a, mitochondrial superoxide dismutase (MnSOD), and catalase after SCI. The in vitro study, performed on PC12 cells, indicated that βOHB inhibited H₂O₂-induced ROS production, decreased NOX2 and NOX4 protein levels, and upregulated FOXO3a, MnSOD, and catalase levels in a dose-dependent manner, which was consistent with the in vivo results. The ketone metabolite βOHB inhibited HDAC1, HDAC2, and HDAC3 activity, but not HDAC8 in SCI rats and PC12 cells. Depletion of HDAC1 or HDAC2 with small interfering RNA (siRNA) attenuated H₂O₂-induced ROS production and protein carbonylation and elevated FOXO3a protein levels, meanwhile reducing NOX2 and NOX4 protein expression in PC12 cells. Our results indicate that the ketone metabolite βOHB attenuates oxidative stress in SCI by inhibition of class I HDACs, and selected suppression of HDAC1 or HDAC2 regulates FOXO3a, NOX2, and NOX4 expression. Therefore, the ketone metabolite βOHB may be a novel promising therapeutic agent for SCI.

Green Tea Polyphenols, Mimicking the Effects of Dietary Restriction, Ameliorate High-Fat Diet-Induced Kidney Injury via Regulating Autophagy Flux

Epidemiological and experimental studies reveal that Western dietary patterns contribute to chronic kidney disease, whereas dietary restriction (DR) or dietary polyphenols such as green tea polyphenols (GTPs) can ameliorate the progression of kidney injury. This study aimed to investigate the renal protective effects of GTPs and explore the underlying mechanisms. Sixty Wistar rats were randomly divided into 6 groups: standard diet (STD), DR, high-fat diet (HFD), and three diets plus 200 mg/kg(bw)/day GTPs, respectively. After 18 weeks, HFD group exhibited renal injuries by increased serum cystatin C levels and urinary N-acetyl-β-d-glucosaminidase activity, which can be ameliorated by GTPs. Meanwhile, autophagy impairment as denoted by autophagy-lysosome related proteins, including LC3-II, Beclin-1, p62, cathepsin B, cathepsin D and LAMP-1, was observed in HFD group, whereas DR or GTPs promoted renal autophagy activities and GTPs ameliorated HFD-induced autophagy impairment. In vitro, autophagy flux suppression was detected in palmitic acid (PA)-treated human proximal tubular epithelial cells (HK-2), which was ameliorated by epigallocatechin-3-gallate (EGCG). Furthermore, GTPs (or EGCG) elevated phosphorylation of AMP-activated protein kinase in the kidneys of HFD-treated rats and in PA-treated HK-2 cells. These findings revealed that GTPs mimic the effects of DR to induce autophagy and exert a renal protective effect by alleviating HFD-induced autophagy suppression.

Crosstalk of ROS/RNS and autophagy in silibinin-induced apoptosis of MCF-7 human breast cancer cells in vitro

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play important roles in regulating cell survival and death. Silibinin is a natural polyphenolic flavonoid isolated from milk thistle with anti-tumor activities, but it was found to induce cytoprotective ROS/RNS in human breast cancer MCF-7 cells. Furthermore, treatment with silibinin down-regulates ERα expression in MCF-7 cells, and inducing both autophagy and apoptosis. In this study we explored the relationship between ER-associated pathways and RNS/ROS in MCF-7 cells. We also investigated the molecular mechanisms underlying the reciprocal regulation between ROS/RNS levels and autophagy in the death signaling pathways in silibinin-treated MCF-7 cells. Silibinin (100-300 μmol/L) dose-dependently increased ROS/RNS generation in MCF-7 cells (with high expression of ERα and low expression of ERβ) and MDA-MB-231 cells (with low expression of ERα and high expression of ERβ). Scavenging ROS/RNS significantly enhanced silibinin-induced death of MCF-7 cells, but not MDA-MB231 cells. Pharmacological activation or blockade of ERα in MCF-7 cells significantly enhanced or decreased, respectively, silibinin-induced ROS/RNS generation, whereas activation or block of ERβ had no effect. In silibinin-treated MCF-7 cells, exposure to the ROS/RNS donators decreased the autophagic levels, whereas inhibition of autophagy with 3-MA significantly increased ROS/RNS levels. We further showed that increases in ROS/RNS generation, ERα activation or autophagy down-regulation had protective roles in silibinin-treated MCF-7 cells. Under a condition of ERα activation, scavenging ROS/RNS or stimulating autophagy enhanced the cytotoxicity of silibinin. These results demonstrate the existence of two conflicting pathways in silibinin-induced death of MCF-7 cells: one involves the down-regulation of ERα and thereby augmenting the pro-apoptotic autophagy downstream, leading to cell death; the other involves the up-regulation of pro-survival ROS/RNS; and that the generation of ROS/RNS and autophagy form a negative feedback loop whose balance is regulated by ERα.

Sirt3 deficiency exacerbates diabetic cardiac dysfunction: Role of Foxo3A-Parkin-mediated mitophagy

Diabetic cardiomyopathy (DCM) is often associated with suppressed cardiac autophagy, mitochondrial structural and functional impairment. Sirtuin-3 (Sirt3) has been reported to play a crucial role in mitochondrial homeostasis and confers a protective role against the onset and development of DCM although the precise mechanism(s) remains elusive. Here we hypothesized that Sirt3 exerts cardioprotection against DCM by activating Parkin-mediated mitophagy, en route to preserved mitochondrial homeostasis and suppressed cardiomyocyte apoptosis. Adult male wild-type (WT) and Sirt3 knockout (Sirt3KO) mice were treated with streptozotocin (STZ) or vehicle for 3months prior to assessment of echocardiographic property, interstitial fibrosis, cardiomyocyte apoptosis, mitochondrial morphology, cardiac autophagy and cell signaling molecules. Our findings revealed that STZ-induced diabetes mellitus prompted cardiac dysfunction, interstitial fibrosis, cardiomyocyte apoptosis and mitochondrial injury, accompanied with suppressed autophagy and mitophagy, the effects of which were aggravated by Sirt3KO. To the contrary, Sirt3 overexpression in vitro activated autophagy and mitophagy, inhibited mitochondrial injury and cardiomyocyte apoptosis, the effects of which were attenuated by autophagy inhibition using 3-MA. Moreover, deacetylation of Foxo3A and expression of Parkin were decreased by Sirt3KO, while these effects were facilitated by Sirt3OE in diabetic and high glucose settings. Taken together, our data suggested that suppressed Sirt3-Foxo3A-Parkin signaling mediated downregulation of mitophagy may play a vital role in the development of diabetic cardiomyopathy. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure edited by Dr. Jun Ren & Yingmei Zhang.

WITHDRAWN: Resveratrol increases microRNA-130a expression to promote angiogenesis and improve heart functions in mice after myocardial infarction

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Autophagy and mitochondrial dysfunction in adjuvant-arthritis rats treatment with resveratrol

Resveratrol is a polyphenol derivatives which exhibits a pro-apoptotic effect in a variety of human cancers by triggering mitochondria apoptosis pathway and autophagy. However, there are scarcely reports on its apoptosis-promoting effect in abnormal proliferation fibroblast-like synoviocytes (FLSs). In this study, we investigated the underlying mechanism and apoptosis-inducing effects of resveratrol on the abnormal proliferation of FLSs in adjuvant-arthritis (AA) rats. Since using resveratrol for 12 days resulted in a significant decreasing the swelling degree of the paw, reducing malondialdehyde (MDA) content and enhancing superoxide dismutase (SOD) activity, antioxidant capacity, glutathione peroxidase and glutathione reductase ratio in AA rats. Moreover, we found that 5 μMH₂O₂ could increase cells viability, Beclin1, LC3A/B, MnSOD, SIRT3 protein expression in FLSs. But, resveratrol could reverse these effects by changing mitochondrial membrane potential (Δψm) to promote mitochondrial reactive oxygen species (mtROS) generation in 5 μMH₂O₂-treatment FLSs. These results suggest that oxidative stress existed in AA rats. Resveratrol could suppress oxidative stress in AA rats and increase mtROS production by reducing autophagy protein Beclin1, LC3A/B and oxidative stress protein MnSOD to promoted the apoptosis of FLSs. Thus, targeting of mtROS may be a crucial mechanism of resveratrol confers patients with rheumatoid arthritis.