Activation Of SIRT1 Signaling Research Articles

Resveratrol alleviates enterotoxigenic Escherichia coli K88-induced damage by regulating SIRT-1 signaling in intestinal porcine epithelial cells.

This study found that resveratrol pretreatment attenuated porcine intestinal epithelial cell damage caused by enterotoxigenic Escherichia coli (ETEC) K88 in vitro and the protective effects of resveratrol were associated with SIRT-1 signaling. ETEC K88 is a main intestinal pathogen for post-weaning diarrhea (PWD) in piglets. With the strict ban on antibiotics in animal feed, people are seeking effective antibiotic substitutes to protect the intestinal system against harmful pathogenic bacteria. This study was conducted to evaluate the effects of resveratrol, a natural plant polyphenol, on ETEC K88-induced cellular damage in porcine enterocytes and underlying mechanisms. Intestinal porcine epithelial cell line 1 (IPEC-1) cells, pretreated with or without resveratrol (30 μM, 4 h), were challenged with ETEC K88 (MOI = 1 : 10) for 3 h. The results showed that ETEC K88 infection induced severe damage and dysfunction in IPEC-1 cells, as evidenced by a reduced cell viability, decreased tight junctions, mitochondrial dysfunction, and autophagy. It is noteworthy that IPEC-1 cells pre-treated with resveratrol improved their capacity for resistance to most of these abnormal phenotypes caused by ETEC K88 infection. Furthermore, we found that the activation of SIRT-1 signaling was associated with the benefits of resveratrol, as demonstrated by EX-527, an inhibitor of SIRT-1, which reversed most of the protective effects of resveratrol. In conclusion, these results indicated that resveratrol could protect intestinal epithelial cells against ETEC K88 infection by activating SIRT-1 signaling. These findings provide new insights into the role of resveratrol in maintaining intestinal physiological functions.

Urolithin A prevents streptozotocin-induced diabetic cardiomyopathy in rats by activating SIRT1

This study examined the cardiac anti-cardiomyopathy (DC) protective effect of urolithin A in streptozotocin (STZ)-treated rats and investigated if this protection involves activation of SIRT1 signaling. Diabetes was induced first STZ (65 mg/kg, i.p.) before starting the experiments. Adult male rats (n = 8/group) were treated for 8 weeks as control (non-diabetic), control + urolithin A (2.5 mg/kg/i.p.), STZ, STZ + urolithin A, and STZ + urolithin A + Ex-527 (1 mg/kg/i.p.) (a SIRT1 inhibitor). With no effect on fasting glucose and insulin levels, urolithin A improved left ventricular (LV) function and structure and reduced heart weight and serum levels of cardiac markers in STZ-treated rats. Also, it prevented collagen deposition, reduced mRNA levels of Bax, cleaved caspaspe3, collagen 1A1, transforming growth factor-β1 (TGF-β1), and Smad3 but enhanced those of Bcl2 in the LVs of diabetic rats. However, urolithin A suppressed the generation of reactive oxygen species (ROS), activated the nuclear factor erythroid 2–related factor 2 (Nrf2), and increased the levels of manganese superoxide dismutase (MnSOD) and total glutathione (GSH) in the LVs of the non-diabetic and diabetic rats, In parallel, it suppressed the cardiac activity of NF-nuclear factor-kappa beta p65 (κB p65) and reduced levels of tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Coincided with these events, urolithin A promoted higher activity, mRNA, and total/nuclear protein levels of SIRT1 and lowered the levels of acetyl-FOXO1, Nrf2, NF-κB, and p53. All these benefits of urolithin A were prevented by Ex-527. In conclusion, urolithin A protects against DC by activating SIRT signaling.

Resveratrol Ameliorates Aortic Calcification in Ovariectomized Rats via SIRT1 Signaling.

Postmenopausal women are at an increased risk of vascular calcification which is defined as the pathological deposition of minerals in the vasculature, and is strongly linked with increased cardiovascular disease risk. Since estrogen-replacement therapy is associated with increased cancer risk, there is a strong need for safer therapeutic approaches. In this study we aimed to investigate the protective and therapeutic effects of the phytoestrogen resveratrol against vascular calcification in ovariectomized rats, a preclinical model of postmenopause. Furthermore, we aimed to compare the effects of resveratrol to those of estrogen and to explore the mechanisms underpinning those effects. Treatment with resveratrol or estrogen ameliorated aortic calcification in ovariectomized rats, as shown by reduced calcium deposition in the arterial wall. Mechanistically, the effects of resveratrol and estrogen were mediated via the activation of SIRT1 signaling. SIRT1 protein expression was downregulated in the aortas of ovariectomized rats, and upregulated in rats treated with resveratrol or estrogen. Moreover, resveratrol and estrogen reduced the levels of the osteogenic markers: runt-related transcription factor 2 (RUNX2), osteocalcin and alkaline phosphatase (ALP) which have been shown to play a role during vascular calcification. Additionally, the senescence markers (p53, p16 and p21) which were also reported to play a role in the pathogenesis of vascular calcification, were reduced upon treatment with resveratrol and estrogen. In conclusion, the phytoestrogen resveratrol may be a safer alternative to estrogen, as a therapeutic approach against the progression of vascular calcification during postmenopause.

Resveratrol improved hippocampal neurogenesis following lead exposure in rats through activation of SIRT1 signaling.

Lead (Pb) poses a potential environmental risk factor for cognitive dysfunction during early life and childhood. Resveratrol is considered a promising antioxidant with respect to the prevention of cognitive deficits and act as a potent SIRT1 agonist. Herein, this study aims to investigate the profile of neurogenesis markers following Pb exposure and to determine the regulatory role of resveratrol in this process. We confirmed firstly the protective effects of resveratrol against Pb-induced impairments of hippocampal neurogenesis in Male SD rats. Pb exposure early in life caused the altered expression of Ki-67, NeuN, caspase-3 and SIRT1 signaling, thereby resulting in spatial cognitive impairment of adolescent rats. As expected, resveratrol reduced cognitive damage and promoted neurogenesis in Pb-induced injury by regulation of SIRT1 pathway. Collectively, our study establishes the efficacy of resveratrol as a neuroprotective agent and provides a strong rationale for further studies on SIRT1-mediated mechanisms of neuroprotective functions.

Human Neural Stem Cell-Conditioned Medium Inhibits Inflammation in Macrophages Via Sirt-1 Signaling Pathway In Vitro and Promotes Sciatic Nerve Injury Recovery in Rats.

Chronic persistent inflammation is thought to impede axon regeneration and cause demyelinating disease also with neuropathic pain, leading to more severe dysfunction after peripheral nerve injury. Increasing evidence indicates that neural stem cells (NSCs) have immunomodulatory effects, and previous studies have shown that many of the beneficial effects attributed to stem cell therapy may exert their therapeutic effects through paracrine mechanisms. In this research, the repairing effect of NSC-conditioned medium (NSC-CM) on sciatic nerve injury and its mechanism of repair were further explored. The present research showed that NSC-CM promoted histopathological and functional recovery after crush injury in rats, and what counts is that NSC-CM inhibited the inflammation of sciatic nerve in the late stage of injury. NSC-CM significantly downregulated the infiltration of proinflammatory factors [tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and IL-1β] as well as decreased the CD68 inflammatory macrophages infiltrating in the sciatic nerve. In addition, to study the effect of NSC-CM on the inflammatory state of macrophages in vitro, lipopolysaccharide (LPS) was used to induce the proinflammation of macrophages. The results showed that NSC-CM decreased the expression of macrophage proinflammatory-related proteins (IL-6, IL-1β, TNF-α, inducible nitric oxide synthase) induced by LPS. The activation of Sirt-1 signaling in macrophages effectively countered the proinflammation induced by LPS in the presence of NSC-CM. Using Sirt-1-specific inhibitor EX527 partially weakened the anti-inflammatory effect of NSC-CM. Altogether, this study demonstrated for the first time that NSC-CM promotes functional recovery after sciatic nerve crush injury in vivo and also inhibits the inflammation in activated macrophages by activating Sirt-1 signaling pathway in vitro.

Melatonin protects against thoracic aortic aneurysm and dissection through SIRT1-dependent regulation of oxidative stress and vascular smooth muscle cell loss.

Melatonin functions as an endogenous protective molecule in multiple vascular diseases, whereas its effects on thoracic aortic aneurysm and dissection (TAAD) and underlying mechanisms have not been reported. In this study, TAAD mouse model was successfully induced by β-aminopropionitrile fumarate (BAPN). We found that melatonin treatment remarkably prevented the deterioration of TAAD, evidenced by decreased incidence, ameliorated aneurysmal dilation and vascular stiffness, improved aortic morphology, and inhibited elastin degradation, macrophage infiltration, and matrix metalloproteinase expression. Moreover, melatonin blunted oxidative stress damage and vascular smooth muscle cell (VSMC) loss. Notably, BAPN induced a decrease in SIRT1 expression and activity of mouse aorta, whereas melatonin treatment reversed it. Further mechanistic study demonstrated that blocking SIRT1 signaling partially inhibited these beneficial effects of melatonin on TAAD. Additionally, the melatonin receptor was involved in this phenomenon. Our study is the first to report that melatonin exerts therapeutic effects against TAAD by reducing oxidative stress and VSMC loss via activation of SIRT1 signaling in a receptor-dependent manner, thus suggesting a novel therapeutic strategy for TAAD.

Neuroprotective Effect of Resveratrol via Activation of Sirt1 Signaling in a Rat Model of Combined Diabetes and Alzheimer’s Disease

BackgroundAlzheimer’s disease (AD) and diabetes mellitus (DM) often coexist in patients because having one of these conditions increases risk for the other. These two diseases share several pathophysiological mechanisms, such as specific inflammatory signaling pathways, oxidative stress, and cell apoptosis. It is still unclear exactly which mechanisms associated with DM are responsible for increased AD risk. Studies have found that even transient elevation of brain Aβ levels can allow T2DM to slightly disrupt the neural milieu in a way that encourages pathologies associated with the onset of memory deficits and AD. A recent study argues that a potential common pathogenetic mechanism underlying both DM and AD is evidenced by the cooccurrence of amyloid brain legions and deposits containing both tau and Aβ in pancreatic β cells. Given these links, an investigation detailing disease mechanisms as well as treatment options for patients with cooccurring DM and AD is urgently needed. The biological effects of resveratrol relevant to DM and AD treatment include its abilities to modulate oxidative stress and reduce inflammation. A rat model of DM and concomitant AD was created for this study using intraperitoneal injection of streptozotocin and hippocampal injection of Aβ1–40 to characterize resveratrol’s potential protective action.ResultsResveratrol significantly increased the Sirt1 expression, inhibited the memory impairment, the increased acetylcholinesterase, malondialdehyde, interleukin-1β and interleukin 6 levels, and the decreased levels of choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione in this rat model of diabetes and concomitant AD. The Sirt 1 inhibitor EX527 partially reversed the effects of resveratrol.ConclusionThis study suggests that resveratrol may have a neuroprotective action through activation of Sirt1 signaling in diabetes and AD with concurrent onset.

Sirt1 in the Regulation of Interferon Gamma in Severe Aplastic Anemia

Recent studies have indicated that Sirt1 plays critical roles in the suppression of inflammation, T cell activation, and differentiation of hematopoietic progenitor cells. Severe aplastic anemia (SAA) is an immune-mediated disease that is characterized by elevated cytotoxic lymphocytes and type 1 cytokines. As a negative effector cytokine, interferon gamma (IFNγ) takes part in aplastic anemia through its inhibitory effect on hematopoiesis. In this study, we investigated the role of Sirt1 in the regulation of IFNγ in patients with SAA. A significant decrease in relative SIRT1 (p< 0.05) and increase in IFNG (p< 0.05) expression levels was observed in the sorted CD8+T cells of SAA patients compared to the controls. There was a significant negative correlation (r = –0.53, p < 0.05) between SIRT1 and IFNG expression in SAA patients. SRT3025, a Sirt1 activator, was shown to significantly reduce IFNγ (p < 0.01) and elevate Sirt1 (p < 0.05) expression in the CD8+T cells of SAA patients, and also showed a therapeutic role in an aplastic anemia mouse model. In conclusion, the defective Sirt1 may be correlated to the abnormal IFNγ expression in SAA patients, and activation of Sirt1 signaling may help improve the inflammatory status of SAA.

Melatonin protects mouse granulosa cells against oxidative damage by inhibiting FOXO1-mediated autophagy: Implication of an antioxidation-independent mechanism

Oxidative stress has been described as a prime driver of granulosa cell (GCs) death during follicular atresia. Increasing evidence suggests potential roles of melatonin in protecting GCs from oxidative injury, though the underlying mechanisms remain largely undetermined. Here we first proposed that the inhibition of autophagy through some novel regulators contributes to melatonin-mediated GCs survival under conditions of oxidative stress. Oxidant-induced loss of GCs viability was significantly reduced after melatonin administration, which was correlated with attenuated autophagic signals upon oxidative stimulation both in vivo and in vitro. Compared with melatonin treatment, suppression of autophagy displayed similar preventive effect on GCs death during oxidative stress, but melatonin provided no additional protection in GCs pretreated with autophagy inhibitors. Notably, we found that melatonin-directed regulation of autophagic death was independent of its antioxidation/radical scavenging ability. Further investigations identified FOXO1 as a critical downstream effector of melatonin in promoting GCs survival from oxidative stress-induced autophagy. Specifically, suppression of FOXO1 via the melatonin-phosphatidylinositol 3-kinase (PI3K)-AKT axis not only improved GCs resistance to oxidative stress, but also abolished the autophagic response, from genes expression to the formation of autophagic vacuoles. Moreover, the activation of SIRT1 signaling was required for melatonin-mediated deacetylation of FOXO1 and its interaction with ATG proteins, as well as the inhibition of autophagic death in GCs suffering oxidative stress. These findings reveal a brand new mechanism of melatonin in defense against oxidative damage to GCs by repressing FOXO1, which may be a potential therapeutic target for anovulatory disorders.

Sirt1 Activation by Post-ischemic Treatment With Lumbrokinase Protects Against Myocardial Ischemia-Reperfusion Injury.

Lumbrokinase is used as an oral supplement to support and maintain healthy cardiovascular function, and to treat cardiovascular diseases in clinical for more than 10 years. Up until now, the mechanism of the cardioprotective effects of post-ischemic treatment with lumbrokinase has remained unclear. We therefore investigated the signaling pathways involved in the amelioration of myocardial ischemia-reperfusion (I-R) injury in rats treated with lumbrokinase 20 min after myocardial ischemia. Compared to vehicle-treated rats, post-ischemic treatment with lumbrokinase was associated with significant reductions in myocardial I-R-induced arrhythmias and myocardial damage, and an improvement in cardiac function. Moreover, lumbrokinase significantly upregulated levels of silent information regulator 1 (Sirt1). In addition, lumbrokinase significantly increased manganese-dependent superoxide dismutase expression, decreased Cleaved-Caspase-3 expression, and induced deacetylation of FoxO1. On the other hand, lumbrokinase also significantly downregulated levels of succinate dehydrogenase, cytochrome c oxidase, nuclear factor kappa B (NF-κB) and elevated levels of microtubule-associated protein light chain 3. Notably, the cardioprotective effects of lumbrokinase were abolished by administration of the specific Sirt1 inhibitor EX527. These findings demonstrate that post-ischemic treatment with lumbrokinase attenuates myocardial I-R injury through the activation of Sirt1 signaling, and thus enhances autophagic flux and reduces I-R-induced oxidative damage, inflammation and apoptosis.

Natural mineral-rich water ingestion by ovariectomized fructose-fed Sprague-Dawley rats: effects on sirtuin 1 and glucocorticoid signaling pathways.

Prevention or induction of metabolic disorders and obesity depend on estrogen signaling and/or exogenous factors, such as mineral content in diet. The protective effects of a Portuguese natural mineral-rich water against the induction of metabolic syndrome in fructose-fed male Sprague-Dawley rats have been reported. The present study was designed to assess the impact of this mineral-rich water on fructose-fed estrogen-deficient female Sprague-Dawley rats. Ovariectomized rats had access to tap (TWO) or mineral-rich (MWO) waters, with and without 10% fructose (10-wk treatment). A sham-operated (tap water supplied) group was included and each of the five groups included six rats. Plasma biochemical and metabolic parameters were evaluated by routine clinical measurements. Western blotting was used to assess hepatic protein expression of sirtuins (Sirt) 1 and 3, phosphorylated AMP-activated protein kinase-α (p-AMPKα), peroxisome proliferator-activated receptor gamma coactivator-1-α (PGC1α), glucocorticoid receptor, and 11beta-hydroxysteroid dehydrogenase type 1 (11βHSD1). Ovariectomy increased plasma total cholesterol (46%/P < 0.05), but had no significant effects on hepatic protein expression. Fructose intake by ovariectomized rats increased PGC1α and 11βHSD1 (fructose in tap water [TWFO] vs TWO: 65%/P < 0.05 and 38%/P = 0.05, respectively) as well as glucocorticoid receptor (TWFO and fructose in natural mineral-rich water [MWFO] vs TWO and MWO: 107%/P = 0.05 and 182%/P < 0.05, respectively). Mineral-rich water ingestion exerted an increasing shape on Sirt1 (MWO vs TWO: 76%/P < 0.05; MWFO vs TWFO: 76%/P = 0.06), PGC1α (MWO vs TWO: 77%/P < 0.01), p-AMPKα (MWO vs TWO: 152%/P = 0.01; MWFO vs TWFO: 107%/P = 0.01), and 11βHSD1 (MWO vs TWO: 91%/P = 0.05; MWFO vs TWFO: 47%/P = 0.05). Mineral-rich water ingestion may have a prime role on the activation of Sirt1 signaling and the modulation of glucocorticoid signaling in the postmenopause.

Treadmill exercise decreases amyloid-β burden possibly via activation of SIRT-1 signaling in a mouse model of Alzheimer's disease

Accumulation of amyloid-β (Aβ) correlates significantly with progressive cognitive deficits, a main symptom of Alzheimer's disease (AD). Although treadmill exercise reduces Aβ levels, the molecular mechanisms underlying the effects are not fully understood. We hypothesize that treadmill exercise decreases Aβ production and alleviates cognitive deficits by activating the non-amyloidogenic pathway via SIRT-1 signaling. Treadmill exercise improved cognitive deficits and alleviated neurotoxicity. Most importantly, treadmill exercise increased SIRT-1 level, which subsequently resulted in increased ADAM-10 level by down-regulation of ROCK-1 and upregulation of RARβ, ultimately facilitating the non-amyloidogenic pathway. Treadmill exercise-induced activation in SIRT-1 level also elevated PGC-1α level and reduced BACE-1 and C-99 level, resulting in inhibition of the amyloidogenic pathway. Treadmill exercise may thus inhibit Aβ production via upregulation of SIRT-1, which biases amyloid precursor protein processing toward the non-amyloidogenic pathway. This study provides novel and valuable insight into the molecular mechanisms possibly by which treadmill exercise reduces Aβ production.

Resveratrol alleviates sepsis‑induced myocardial injury in rats by suppressing neutrophil accumulation, the induction of TNF‑α and myocardial apoptosis via activation of Sirt1.

Sepsis is a severe inflammatory response to systemic infection that frequently affects the myocardium. Previous studies have suggested that resveratrol (RESV) is protective in sepsis. The present study aimed to investigate the role of sirtuin 1 (Sirt1) signaling in the protective effect of intraperitoneally administered RESV against sepsis‑induced myocardial injury. Cecal ligation and puncture, or a sham operation, were performed in male Sprague‑Dawley rats, and the levels of tumor necrosis factor (TNF)‑α and myeloperoxidase (MPO) were assessed by ELISA and an MPO activity kit, respectively. The extent of myocardial apoptosis was assessed by TUNEL staining. The protein expression levels of Sirt1, acetylated (Ac)‑Forkhead box O1 (FoxO1), B cell lymphoma 2 apoptosis regulator (Bcl‑2) and Bcl‑2 associated protein X apoptosis regulator (Bax) were detected by western blot analysis. RESV was demonstrated to attenuate myocardial apoptosis and decrease the production of TNF‑α and MPO. Additionally, RESV upregulated the expression of Sirt1 and Bcl‑2, and downregulated the expression of Ac‑FoxO1 and Bax. The protective effects of RESV were abolished by EX527, a Sirt1 inhibitor. RESV has therefore been demonstrated to attenuate myocardial injury in sepsis by decreasing neutrophil accumulation, TNF‑α expression, and myocardial apoptosis via activation of Sirt1 signaling. These results suggest a novel therapeutic strategy for the clinical treatment of sepsis.

Melatonin prevents acute kidney injury in severely burned rats via the activation of SIRT1.

Acute kidney injury (AKI) is a common complication after severe burns. Melatonin has been reported to protect against multiple organ injuries by increasing the expression of SIRT1, a silent information regulator that regulates stress responses, inflammation, cellular senescence and apoptosis. This study aimed to investigate the protective effects of melatonin on renal tissues of burned rats and the role of SIRT1 involving the effects. Rat severely burned model was established, with or without the administration of melatonin and SIRT1 inhibitor. The renal function and histological manifestations were determined to evaluate the severity of kidney injury. The levels of acetylated-p53 (Ac-p53), acetylated-p65 (Ac-p65), NF-κB, acetylated-forkhead box O1 (Ac-FoxO1), Bcl-2 and Bax were analyzed to study the underlying mechanisms. Our results suggested that severe burns could induce acute kidney injury, which could be partially reversed by melatonin. Melatonin attenuated oxidative stress, inflammation and apoptosis accompanied by the increased expression of SIRT1. The protective effects of melatonin were abrogated by the inhibition of SIRT1. In conclusion, we demonstrate that melatonin improves severe burn-induced AKI via the activation of SIRT1 signaling.

Isoflavones Derived from Soy Beans Prevent MuRF1-Mediated Muscle Atrophy in C2C12 Myotubes through SIRT1 Activation

Proinflammatory cytokines are factors that induce ubiquitin-proteasome-dependent proteolysis in skeletal muscle, causing muscle atrophy. Although isoflavones, as potent antioxidative nutrients, have been known to reduce muscle damage during the catabolic state, the non-antioxidant effects of isoflavones against muscle atrophy are not well known. Here we report on the inhibitory effects of isoflavones such as genistein and daidzein on muscle atrophy caused by tumor necrosis factor (TNF)-α treatment. In C2C12 myotubes, TNF-α treatment markedly elevated the expression of the muscle-specific ubiquitin ligase MuRF1, but not of atrogin-1, leading to myotube atrophy. We found that MuRF1 promoter activity was mediated by acetylation of p65, a subunit of NFκB, a downstream target of the TNF-α signaling pathway; increased MuRF1 promoter activity was abolished by SIRT1, which is associated with deacetylation of p65. Of interest, isoflavones induced expression of SIRT1 mRNA and phosphorylation of AMP kinase, which is well known to stimulate SIRT1 expression, although there was no direct effect on SIRT1 activation. Moreover, isoflavones significantly suppressed MuRF1 promoter activity and myotube atrophy induced by TNF-α in C2C12 myotubes. These results suggest that isoflavones suppress myotube atrophy in skeletal muscle cells through activation of SIRT1 signaling. Thus, the efficacy of isoflavones could provide a novel therapeutic approach against inflammation-related muscle atrophy.