Sirtuin Inhibitors Research Articles

Protective Effects of SIRT2 Inhibition on Cardiac Fibrosis.

A primary factor in the pathogenesis of aging is oxidative stress, with cardiac inflammation and fibrosis being contributed to by increased oxidative stress as organisms age. Oxidative stress enhances the cardiac fibrotic signaling pathway, with reactive oxygen species inducing cardiac fibrosis through increased expression of the profibrotic factor transforming growth factor-beta 1 (TGF-β1). Furthermore, Wnt/β-catenin signaling pathway is implicated in interstitial fibrosis, which is associated with TGF-β. Sirtuin 2 (SIRT2) is expressed in heart tissue, with protective effects in pathological cardiac hypertrophy. We aimed to investigate the mechanisms of cardiac fibrosis in D-Galactose (D-Gal)-induced accelerated aging, focusing on TGF-β1, β-catenin, and SIRT2. A total of 30 young male Sprague-Dawley rats were randomly divided into 4 groups: control group, D-Gal group, D-Gal + 4% dimethyl sulfoxide (DMSO) group, and D-Gal + the SIRT2 inhibitor (AGK2) group. After 10 weeks, the rats were sacrificed, and their hearts were removed. SIRT2 expression levels were measured by western blot and gene expression levels of TGF-β1 and β-catenin by quantitative real-time polymerase chain reaction. Transforming growth factor-beta 1 (TGF-β1) mRNA expression in heart tissue was higher in the D-Gal group compared to all other groups. β-catenin mRNA expression was higher in the D-Gal group than in the D-Gal + AGK2 group. SIRT2 protein expression was higher in the D-Gal + DMSO group compared to the control group. Sirtuin 2 expression was lower in the D-Gal + AGK2 group compared to the D-Gal and D-Gal + DMSO groups. Sirtuin 2 inhibition attenuates fibrosis, as evidenced by the downregulation of TGF-β1 and β-catenin. Thus, targeting SIRT2 may represent a potential therapeutic strategy for diseases characterized by cardiac fibrosis in the future.

Stem Cell Therapy Modulates Molecular Cues of Vasogenic Edema Following Ischemic Stroke: Role of Sirtuin-1 in Regulating Aquaporin-4 Expression.

Conventional post-stroke edema management strategies are limitedly successful as in multiple cases of hemorrhagic transformation is being reported. Clinically, acute-ischemic-stroke (AIS) intervention by endovascular mesenchymal stem cells (MSCs) have shown benefits by altering various signaling pathways. Our previous studies have reported that intra-arterial administration of 1*105 MSCs (IA-MSCs) were beneficial in alleviating post-stroke edema by modulating PKCδ/MMP9/AQP4 axis and helpful in preserving the integrity of blood-brain-barrier (BBB). However, the role of mitochondrial dysfunction and ROS generation post-AIS cannot be overlooked in context to the alteration of the BBB integrity and edema formation through the activation of inflammatory pathways. The anti-inflammatory activity of IA-MSCs in stroke has been reported to be regulated by sirtuin-1 (SIRT-1). Hence, the relationship between SIRT-1 and AQP4 towards regulation of post-stroke edema needs to be further explored. Therefore, the present study deciphers the molecular events towards AQP4 upregulation, mitochondrial dysfunction and BBB disruption in context to the modulation of SIRT-1/PKCδ/NFκB loop by IA-MSCs administration. Ovariectomized SD rats were subjected to focal ischemia. SIRT-1 activator, SIRT-1 inhibitor, NFkB inhibitor and IA-MSCs were administered at optimized dose. At 24h of reperfusion, behavioral tests were performed, and brains were harvested following euthanasia for molecular studies. IA-MSCs downregulated AQP4, PKCδ and NFkB expression, and upregulated SIRT-1 expression. SIRT-1 upregulation renders mitochondrial protection via reduction of oxidative stress resulting in BBB protection. IA-MSCs can modulate SIRT-1 mediated AQP4 expression via mitochondrial ROS reduction and modification of NFkB transcriptional regulation.

Sirtuin-1 Regulates Mitochondrial Calcium Uptake Through Mitochondrial Calcium Uptake 1 (MICU1)

Mitochondria play a central role in cell biological processes, functioning not only as producers of ATP but also as regulators of Ca2+ signaling. Mitochondrial calcium uptake occurs primarily through the mitochondrial calcium uniporter channel (mtCU), with the mitochondrial calcium uptake subunits 1, 2, and 3 (MICU1, MICU2, and MICU3) serving as the main regulatory components. Dysregulated mitochondrial calcium uptake is a hallmark of cellular degeneration. Sirtuin 1 (SIRT1), a key regulator of cellular metabolism, plays a critical role in aging and various neurodegenerative conditions. By blocking SIRT1 using EX527 or shSIRT1, we observed mitochondrial structural fragmentation as well as intensified and prolonged mitochondrial calcium overload. Our study revealed a direct interaction between SIRT1 and MICU1. Notably, SIRT1 inhibition resulted in reduced MICU1 expression, hence led to mitochondrial calcium overload, illustrating the unconventional role of SIRT1 in governing mitochondrial function.

SIRT2 and ALDH1A1 as critical enzymes for astrocytic GABA production in Alzheimer’s disease

BackgroundAlzheimer’s Disease (AD) is a neurodegenerative disease with drastically altered astrocytic metabolism. Astrocytic GABA and H2O2 are associated with memory impairment in AD and synthesized through the Monoamine Oxidase B (MAOB)-mediated multi-step degradation of putrescine. However, the enzymes downstream to MAOB in this pathway remain unidentified.MethodsUsing transcriptomics analysis, we identified two candidate enzymes, Aldehyde Dehydrogenase 1 family member A1 (ALDH1A1) and Sirtuin 2 (SIRT2) for the steps following MAOB in the astrocytic GABA production pathway. We used immunostaining, metabolite analysis and electrophysiology, both in vitro and in vivo, to confirm the participation of these enzymes in astrocytic GABA production. We checked for the presence of SIRT2 in human AD patients as well as the mouse model APP/PS1 and finally, we selectively ablated SIRT2 in the astrocytes of APP/PS1 mice to observe its effects on pathology.ResultsImmunostaining, metabolite analysis, and electrophysiology recapitulated the participation of ALDH1A1 and SIRT2 in GABA production. Inhibition of SIRT2 reduced the production of astrocytic GABA but not H2O2, a key molecule in neurodegeneration. Elevated expression of these enzymes was found in hippocampal astrocytes of AD patients and APP/PS1 mice. Astrocyte-specific gene-silencing of SIRT2 in APP/PS1 mice restored GABA production and partially improved memory function.ConclusionsOur study is the first to identify the specific role of SIRT2 in reactive astrogliosis and determine the specific pathway and metabolic step catalyzed by the enzyme. We determine the partial, yet significant role of ALDH1A1 in this process, thereby highlighting 2 new players the astrocytic GABA production pathway. Our findings therefore, offer SIRT2 as a new tool to segregate GABA from H2O2 production, aiding future research in neurodegenerative diseases.Graphical

BCL6 Alleviates Hepatic Ischemia/Reperfusion Injury Via Recruiting SIRT1 to Repress the NF-κB/NLRP3 Pathway.

Hepatic ischemia/reperfusion (I/R) injury (HIRI) is an intrinsic phenomenon observed in the process of various liver surgeries. Unfortunately, there are currently few options available to prevent HIRI. Accordingly, we aim to explore the role and key downstream effects of B-cell lymphoma 6 (BCL6) in hepatic I/R (HIR). BCL6 expression levels were measured in I/R liver tissue and primary hepatocytes stimulated by hypoxia/reoxygenation (H/R). Moreover, we ascertained the BCL6 effect on HIR in vivo using liver-specific BCL6 knockout mice and adenovirus-BCL6-infected mice. RNA-sequencing, luciferase, chromatin immunoprecipitation, and interactome analysis were combined to identify the direct target and corresponding molecular events contributing to BCL6 function. DNA pull-down was applied to identify upstream of BCL6 in the H/R challenge. HIR represses BCL6 expression in vivo and in vitro. Hepatic BCL6 overexpression attenuates inflammation and apoptosis after I/R injury, whereas BCL6 deficiency aggravates I/R-induced liver injury. RNA-sequencing showed that BCL6 modulated nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 inflammasome signaling in HIRI. Mechanistically, BCL6 deacetylated nuclear factor kappa-B p65 lysine 310 by recruiting sirtuin 1 (SIRT1), thereby inhibiting the nuclear factor kappa-B/nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 pathway. Moreover, overexpression of SIRT1 blocked the detrimental effects of BCL6 depletion. Moreover, EX 527, a SIRT1 inhibitor, vanished protection from BCL6 overexpression. Furthermore, transcription factor 7 was found to mediate the transcription regulation of BCL6 on H/R challenge. Our results provide the first evidence supporting BCL6 as an important protective agent of HIR. This suggests a potential therapeutic approach for HIR.

Angong Niuhuang Pill pretreatment alleviates cerebral ischemia-reperfusion injury by inhibiting excessive autophagy through the SIRT1-H4K16ac axis

Ethnopharmacological relevanceCerebral ischemia-reperfusion injury (CIRI) is an important pathological process in stroke treatment. Angong Niuhuang Pill (ANP), originating from Wenbing Tiaobian, has been shown to have neuroprotective effects, but its mechanism in alleviating CIRI remains unclear. Aim of the studyThis study aimed to elucidate the mechanism by which ANP alleviates CIRI using acetylomics and proteomics. Materials and methodsThe CIRI model was established using middle cerebral artery occlusion (MCAO). Neurological deficit scoring, TTC staining, regional cerebral blood flow (rCBF) measurement, and TUNEL staining were used to assess the neuroprotective effects of ANP pretreatment on CIRI. Acetylomics and proteomics analyses were performed to identify the potential mechanisms by which ANP reduces CIRI. Finally, the role of SIRT1-H4K16ac-mediated autophagy in the neuroprotective effects of ANP was validated by using a SIRT1 inhibitor, EX527. ResultsANP pretreatment markedly lowered neurological deficit scores and cerebral infarct volumes, increased rCBF, and reduced apoptosis. Acetylomics and proteomics results suggested that ANP regulated autophagy at the transcriptional level by modulating H4K16ac. Immunofluorescence and western blot analyses confirmed that ANP promoted the accumulation of sirtuin 1 (SIRT1). Specifically, ANP pretreatment reduced H4K16ac levels, decreased LC3B-II/I ratios, upregulated SQSTM1/p62, and suppressed the expression of ATG5 and ATG7. The ability of EX527 to counteract these effects underscored the importance of the SIRT1-H4K16ac pathway in mediating the protective action of ANP against CIRI. ConclusionsANP provides neuroprotection by modulating the SIRT1-H4K16ac pathway, thereby preventing the excessive autophagy triggered by CIRI.

Design, synthesis, and biological evaluation of novel 3-naphthylthiophene derivatives as potent SIRT2 inhibitors for the treatment of myocardial fibrosis.

SIRT2 (sirtuin2) is a NAD+-dependent deacetylase implicated in fibrosis and inflammation of the liver, kidney, and heart. In this study, we designed and synthesized a series of 3-naphthylthiophene derivatives and evaluated their inhibitory activity against the SIRT2 enzyme. Among them, Z18 demonstrated outstanding SIRT2 inhibitory activity and selectivity. It significantly inhibited both the proliferation of cardiac fibroblasts (CFs) and the activity and expression of SIRT2 in CFs. Moreover, compound Z18 effectively suppressed TGF-β1-induced increases in α-SMA and CoL-1A1 protein expression, as well as hydroxyproline levels. Pharmacological mechanism tests demonstrated that Z18 inhibited SIRT2, thereby suppressing the TGF-β1-induced autocrine production of TGF-β1 and the phosphorylation of Smad2/3 in CFs. In MTT assays, Z18 exhibited a significant inhibitory effect on the proliferation of CFs induced by TGF-β1. In vivo, Z18 effectively ameliorated TAC- and ISO-induced declines in cardiac function, histopathological morphological changes, and collagen deposition. It also inhibited SIRT2 activity and reduced the expression of α-SMA and p-Smad2/3. In hepatorenal toxicity assays, Z18 exhibited an excellent safety profile. These results support the further development of the selective SIRT2 inhibitor Z18 as a potential lead compound for the treatment of myocardial fibrosis.

The curious case of mitochondrial sirtuin in rewiring breast cancer metabolism: Mr Hyde or Dr Jekyll?

Mammalian sirtuins are class III histone deacetylases involved in the regulation of multiple biological processes including senescence, DNA repair, apoptosis, proliferation, caloric restriction, and metabolism. Among the mammalian sirtuins, SIRT3, SIRT4, and SIRT5 are localized in the mitochondria and collectively termed the mitochondrial sirtuins. Mitochondrial sirtuins are NAD+-dependent deacetylases that play a central role in cellular metabolism and function as epigenetic regulators by performing post-translational modification of cellular proteins. Several studies have identified the role of mitochondrial sirtuins in age-related pathologies and the rewiring of cancer metabolism. Mitochondrial sirtuins regulate cellular functions by contributing to post-translational modifications, including deacetylation, ADP-ribosylation, demalonylation, and desuccinylation of diverse cellular proteins to maintain cellular homeostasis. Here, we review and discuss the structure and function of the mitochondrial sirtuins and their role as metabolic regulators in breast cancer. Altered breast cancer metabolism may promote tumor progression and has been an essential target for therapy. Further, we discuss the potential role of targeting mitochondrial sirtuin and its impact on breast cancer progression using sirtuin inhibitors and activators as anticancer agents.

Activation of SIRT1 by SRT1720 alleviates dyslipidemia, improves insulin sensitivity and exhibits liver-protective effects in diabetic rats on a high-fat diet: New insights into the SIRT1/Nrf2/NFκB signaling pathway.

Insulin resistance and diabetes are associated with non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) conditions, which are distinguished by metabolic dysfunction, oxidative stress and inflammation. Sirtuin 1 (SIRT1), a NAD+-dependent deacetylase, is fundamental in regulating metabolic pathways, reducing inflammation, and improving antioxidant defenses. This is the first study to investigate the effects of SRT1720, a SIRT1 activator, in diabetic rats on a high-fat diet. SRT1720 significantly lowered fasting blood glucose and insulin levels and enhanced glucose tolerance and HOMA-IR and QUICKI scores, indicating increased insulin sensitivity. The treatment also reduced total cholesterol, triglycerides, and LDL levels, showing amelioration of dyslipidemia. Moreover, SRT1720 lowered markers of liver fibrosis, including TGF-β, TIMP-1, Col1a1, and hydroxyproline, and decreased inflammation by reducing NFκB activity and pro-inflammatory cytokines (TNF-α and IL-6). Furthermore, SRT1720 augmented Nrf2 activity and HO-1 levels. Consequently, the SRT1720's protective role improved liver function and histology and prolonged rats' survival. These functions were suppressed by the co-administration of the SIRT1 inhibitor EX527, confirming that the beneficial effects of SRT1720 are SIRT1-dependent. Correlation analyses uncovered that increased SIRT1 activity was strongly associated with decreased oxidative stress, inflammation, insulin resistance, and fibrosis markers. To conclude, our results find that SRT1720 represents a promising therapeutic strategy for managing Type 2 diabetes in NAFLD or NASH patients possibly through the modulation of the SIRT1/Nrf2/NFκB signaling pathwa. SRT1720 could potentially halt or reverse the progression of these conditions and associated complications and merits further investigations.

Ellagic acid prevents ovariectomy-induced bone loss and attenuates oxidative damage of osteoblasts by activating SIRT1.

Oxidative stress has been implicated as a causative factor for the development and progression of osteoporosis(OP). Ellagic acid (EA), a natural polyphenol, presents anti-oxidative and anti-inflammatory properties. However, EA's role and molecular mechanism in osteoblasts have not yet been elucidated. In this study, exogenous supplementation with EA restored the osteoporotic bone defects in ovariectomized (OVX)-induced osteoporotic mice. Also, EA inhibited the H2O2-induced apoptosis of primary osteoblasts, prevented the production of reactive oxygen species, and restored the bone-forming potential of osteoblasts. Furthermore, EA was revealed to activate Sirtuin1 (SIRT1) and its downstream Nrf2/Heme Oxygenase 1 (HO-1) signaling pathway, and EX527 (a SIRT1 inhibitor) partially counteracted the effect of EA on bone loss. The findings suggest that EA protects against osteoporotic bone loss by activating SIRT1 and its downstream Nrf2/HO-1 signaling pathway, providing novel insights into the potential of EA as a treatment agent for osteoporosis-related bone metabolism diseases.

Gentiopicroside Alleviates Atherosclerosis by Suppressing Reactive Oxygen Species-Dependent NLRP3 Inflammasome Activation in Vascular Endothelial Cells via SIRT1/Nrf2 Pathway.

To evaluate the protective effects of gentiopicroside (GPS) against reactive oxygen species (ROS)-induced NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in endothelial cells, aiming to reduce atherosclerosis. Eight-week-old male ApoE-deficient mice were randomly divided into 2 groups (n=10 per group): the vehicle group and the GPS treatment group. Both groups were fed a high-fat diet for 16 weeks. GPS (40 mg/kg per day) was administered by oral gavage to the GPS group, while the vehicle group received an equivalent volume of the vehicle solution. At the end of the treatment, blood and aortic tissues were collected for assessments of atherosclerosis, lipid profiles, oxidative stress, and molecular expressions related to NLRP3 inflammasome activation, ROS production, and apoptosis. Additionally, in vitro experiments on human aortic endothelial cells treated with oxidized low-density lipoprotein (ox-LDL) were conducted to evaluate the effects of GPS on NLRP3 inflammasome activation, pyroptosis, apoptosis, and ROS production, specifically examining the role of the sirtuin 1 (SIRT1)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. SIRT1 and Nrf2 inhibitors were used to confirm the pathway's role. GPS treatment significantly reduced atherosclerotic lesions in the en face aorta (P<0.01), as well as in the thoracic and abdominal aortic regions, and markedly decreased sinus lesions within the aortic root (P<0.05 or P<0.01). Additionally, GPS reduced oxidative stress markers and proinflammatory cytokines, including interleukin (IL)-1 β and IL-18, in lesion areas (P<0.05, P<0.01). In vitro, GPS inhibited ox-LDL-induced NLRP3 activation, as evidenced by reduced NLRP3 (P<0.01), apoptosis-associated speck-like protein containing a CARD, cleaved-caspase-1, and cleaved-gasdermin D expressions (all P<0.01). GPS also decreased ROS production, apoptosis, and pyroptosis, with the beneficial effects being significantly reversed by SIRT1 or Nrf2 inhibitors. GPS exerts an antiatherogenic effect by inhibiting ROS-dependent NLRP3 inflammasome activation via the SIRT1/Nrf2 pathway.

Ethyl Lactate Ameliorates Hepatic Steatosis and Acute-on-Chronic Liver Injury in Alcohol-Associated Liver Disease by Inducing Fibroblast Growth Factor 21.

Aberrant upregulation of hepatic lipogenesis induced by chronic and excessive alcohol consumption is a critical driver of the progression of alcohol-associated liver disease (ALD), however, no effective approaches inhibiting lipogenesis are currently available for treating ALD patients. Moreover, little is known about whether and how nonethanol ingredients in alcoholic beverages regulate the pathogenesis of ALD. Here the discovery of a small molecule that activates the production and secretion of fibroblast growth factor 21 (FGF21) is reported. It is shown that the activator ethyl lactate, a nonethanol ingredient found in distilled liquors, ameliorates alcoholic hepatosteatosis, inflammation and acute-on-chronic liver injury by stimulating FGF21. In response to chronic-plus-binge ethanol feeding or fasting, ethyl lactate mimics lipogenesis lowering effects by stimulating FGF21 production through the NAD+-dependent deacetylase sirtuin 1 (SIRT1) signaling pathway. These ethyl lactate-mediated beneficial effects are abolished by inhibition of SIRT1 through injection of EX527. Importantly, FGF21 deficiency in hepatocytes blocks the downregulation of lipogenesis by ethyl lactate and exacerbates alcoholic steatosis, inflammation and liver injury. The regulatory mechanism is discussed during the pathophysiological conditions and suggests new lines of research into the therapeutic use of a foodborne small molecule ethyl lactate.

SIRT2 Inhibition by AGK2 Promotes Perinuclear Cytoskeletal Organisation and Reduces Invasiveness of MDA-MB-231 Triple-Negative Breast Cancer Cells in Confined In Vitro Models.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype characterised by the absence of targetable hormone receptors and increased metastatic rates. As nuclear softening strongly contributes to TNBC's enhanced metastatic capacity, increasing the nuclear stiffness of TNBC cells may present a promising therapeutic avenue. Previous evidence has demonstrated the ability of Sirtuin 2 (SIRT2) inhibition to induce cytoskeletal reorganisation, a key factor in regulating nuclear mechanics. Thus, our study aimed to investigate the effect of SIRT2 inhibition on the nuclear mechanics and migratory behaviour of TNBC cells. To achieve this, SIRT2 was pharmacologically inhibited in MDA-MB-231 cells using AGK2, a SIRT2-specific inhibitor. Although SIRT2 inhibition had no effect on LINC complex composition, the AGK2-treated MDA-MB-231 cells displayed more prominent perinuclear organisations of acetylated α-tubulin, vimentin, and F-actin. Additionally, the nuclei of the AGK2-treated MDA-MB-231 cells exhibited greater resistance to collapse under osmotic shock. Scratch-wound assays also revealed that SIRT2 inhibition led to polarity defects in the MDA-MB-231 cells, while in vitro space-restrictive invasion assays highlighted their reduced migratory capacity upon AGK2 treatment. Taken together, our findings suggest that SIRT2 inhibition promotes a perinuclear cytoskeletal organisation in MDA-MB-231 cells, which enhances their nuclear rigidity and impedes their invasion through confined spaces in vitro.

2-hydroxy-3-methyl anthraquinone promotes apoptosis and inhibits invasion of human hepatocellular carcinoma cells by targeting nicotinamide adenine dinucleotide-dependent protein deacetylase sirtuin-1/cellular tumor antigen p53 signaling pathway.

To investigate the anti-liver cancer effect of 2-hydroxy-3-methyl anthraquinone (HMA) and the specific mechanism based on nicotinamide adenine dinucleotide-dependent protein deacetylase sirtuin-1 (SIRT1)/cellular tumor antigen p53 (p53) pathway. Cell counting kit-8 method was used to observe the effect of HMA on the activity of human hepatocellular carcinoma cells (HepG2) cells. At 72 h and 80 μL HMA, the apoptosis rate of HepG2 cells in each group was measured by flow cytometry. Transwell was used to assay for cell invasion. The protein expression levels of SIRT1, p53, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), caspase-9 (CASP9) and caspase-3 (CASP3) were detected by Western Blot. HMA significantly inhibited the proliferation of HepG2 cells, The half inhibiting concentration (IC50) of the HMA at 24, 48 and 72 h were examined and it were 126.3, 98.6, and 80.55 μM, respectively. Compared with the control group, the apoptosis rate of HMA, Selisistat (EX527), and HMA+ EX527 groups enhanced, while the apoptosis rate of SRT1720 diminished, demonstrating that inhibition of SIRT1 can lead to apoptosis of HepG2 cells. HMA+ EX527 group had the highest apoptosis rate, the lowest expression of SIRT1 and Bcl-2, and the highest expression of p53, Bax, CASP9 and CASP3. The number of invasions of HepG2 was significantly reduced after HMA and EX527 intervened. Western blot shows HMA could inhibit SIRT1, promote the expression of p53, and decrease the ratio of Bcl-2/Bax. HMA induced apoptosis in HepG2 cells, while inhibiting proliferation and invasion. The mechanism of HMA against HCC may be related to the SIRT1/p53 pathway.

Tanshinone IIA, a component of Salvia miltiorrhiza Bunge, attenuated sepsis-induced liver injury via the SIRT1/Sestrin2/HO-1 signaling pathway

Ethnopharmacological relevanceAs a traditional Chinese medicine, Salvia miltiorrhiza Bunge has been widely used to treat ischemic and inflammation-related diseases for more than 2000 years. S. miltiorrhiza Bunge has hepatoprotective effects, but the underlying mechanism is not fully understood. ObjectiveTo verify the effect of tanshinone IIA (Tan IIA), the main fat-soluble component of S. miltiorrhiza Bunge, on liver damage induced by sepsis/LPS-induced inflammation and further explore the underlying mechanisms. Materials and methodsMice were administered Tan IIA 2 h before cecal ligation and puncture (CLP). Liver damage was evaluated by hematoxylin-eosin staining and changes in related serum factor levels. The expression of silent information regulator sirtuin 1 (SIRT1), Sestrin2, HO-1 and inflammatory cytokines was examined by immunohistochemistry or western blotting. LPS was used to induce the inflammatory response in vitro, and the activity of the related signaling pathway in response to Tan IIA was detected by western blotting. The SIRT1 inhibitor EX-527 and small interfering RNAs (siRNAs) were employed to determine the key roles of SIRT1 and Sestrin2 in Tan IIA's function. ResultsWe found that Tan IIA significantly improved the pathological changes and function of the liver, and alleviated liver damage in CLP mice. Additionally, SIRT1, Sestrin2, and HO-1 expression was significantly elevated after Tan IIA treatment compared with that in the CLP group both in vivo and in vitro, and Tan IIA treatment additionally suppressed pro-inflammatory cytokine release. However, inhibition of either SIRT1 or Sestrin2 remarkably abrogated the protective effects of Tan IIA. Most importantly, Sestrin2 appeared to function downstream of SIRT1 based on their expression changes after EX-527 or siRNA treatment. ConclusionTan IIA inhibited sepsis/LPS-induced inflammation through the SIRT1/Sestrin2/HO-1 pathway, thereby protecting against sepsis-induced liver injury (SLI). This study suggests that Tan IIA has therapeutic potential against SLI and that the SIRT1/Sestrin2/HO-1 signaling pathway might be a viable target for SLI treatment.

Dapagliflozin and Sirtuin-1 interaction and mechanism for ameliorating atrial fibrillation in a streptozotocin-induced rodent diabetic model.

The incidence of atrial fibrillation (AF) increases with age and is particularly high in individuals with diabetes. Sodium-glucose cotransporter-2 inhibitors (SGLT2i), such as dapagliflozin, show promise in treating heart failure (HF) and reducing the risk of AF. Sirtuin 1 (SIRT1), a key enzyme in metabolic regulation, may be influenced by SGLT2i and play a role in the development of AF. This study investigates the relationship between dapagliflozin therapy and atrial tachyarrhythmia in diabetic cardiomyopathy, with a focus on the role of SIRT1. A streptozotocin (STZ)-induced diabetes mellitus (DM) rat model was used to assess AF across four groups: sham, STZ, STZ with dapagliflozin, and STZ with dapagliflozin + sirtinol (a SIRT1 inhibitor). Additionally, HL-1 cardiomyocytes were cultured under high glucose (HG) conditions and treated with dapagliflozin, with or without sirtinol. In the rat model, dapagliflozin improved atrial fibrosis and reduced AF inducibility and duration-effects that were partially reversed by sirtinol. These findings suggest that dapagliflozin may alleviate cardiac fibrosis and atrial arrhythmia by modulating SIRT1. In HL-1 cells under HG conditions, dapagliflozin reduced apoptosis, restored autophagy and mitophagy, and improved calcium channel activity. However, sirtinol negated these protective effects. Dapagliflozin helped normalize autophagy, mitophagy, and calcium handling, while sirtinol diminished its protective effects, highlighting the key role of SIRT1 in regulating calcium handling under HG conditions. Overall, SIRT1 plays a protective role in diabetic cardiomyopathy by reducing apoptosis, regulating autophagy and mitophagy, and modulating calcium channel activity. Dapagliflozin reduces AF duration and inducibility in the STZ model, likely through SIRT1 upregulation and calcium channel modulation.

Liver-gut axis signaling regulates circadian energy metabolism in shift workers.

Circadian rhythm is critical to maintaining the whole-body metabolic homeostasis of an organism. Chronic disruption of circadian rhythm by shift work is an important risk factor for metabolic diseases. Fibroblast growth factor 15/19 (FGF15/19), a key component in the liver-gut axis, potently suppresses bile acid (BA) synthesis and improves insulin sensitivity. FGF15/19 emerges as a novel pharmaceutical target for prevention and treatment of metabolic diseases. The nicotinamide adenine dinucleotide (NAD+)-dependent sirtuin 1 (SIRT1) deacetylase plays an important role in the maintenance of hepatic homeostasis by linking hepatic metabolism to circadian rhythm. Here, our clinical study identified that circadian rhythmicity and levels of plasma FGF19 and BA profiling, and cellular NAD+-dependent SIRT1 signaling were disturbed in night shift (NS, n = 10) compared to day shift (DS, n = 12) nurses. Our invitro data showed that recombinant FGF19 protein rescued cellular circadian rhythm disrupted by SIRT1 inhibitors. Furthermore, we determined the effect of FGF15 on circadian rhythm and hepatic metabolism in wild-type (WT), Fgf15 knockout (KO), and Fgf15 transgenic (TG) mice. The expressions of circadian-controlled genes (CCGs) involved in SIRT1 signaling, BA and lipid metabolism, and inflammation were disrupted in Fgf15 KO compared to WT and/or Fgf15 TG mice. Moreover, systemic FGF15 deficiency led to the circadian disturbance of NAD+-dependent SIRT1 signaling and significant reduction during nighttime in mice. These findings suggest that FGF15/19 regulates the circadian energy metabolism, which warrants further studies as a putative prognostic biomarker and pharmaceutical target for preventing against metabolic diseases associated with chronic shift work.

Disruption of PCSK9 Suppresses Inflammation and Attenuates Abdominal Aortic Aneurysm Formation.

Abdominal aortic aneurysm (AAA) is a chronic vascular inflammatory disease without effective medications. PCSK9 (proprotein convertase subtilisin/kexin 9), a serine protease from the proprotein convertase family, has recently been associated with AAA in human genome-wide association studies. However, its role in AAA is unknown. Transcriptional and histological expression of PCSK9 was examined in AAA tissues and healthy controls. The impact of PCSK9 deletion and inhibition on AAA formation was assessed in mice with hyperlipidemia and Ang II (angiotensin II) overproduction. AAA lesion morphology was assessed by tissue staining. MMP (matrix metalloproteinase) activity was evaluated by gelatin zymography, and leukocyte-vessel wall interaction was monitored by intravital microscopy. RNA sequencing was used to characterize the downstream signaling of PCSK9. PCSK9 expression was upregulated and colocalized with macrophages in human and mouse AAAs. Pcsk9 deletion attenuated AAA formation, improved survival, and decreased systemic inflammation, without altering circulating cholesterol levels. Pcsk9 deficiency reduced aortic infiltration of macrophages and elastin degradation, without affecting vascular smooth muscle cell apoptosis and proliferation. Mechanistically, PCSK9 was essential in leukocyte-endothelium adhesion and expression of proinflammatory cytokines and MMP9 by macrophages. RNA sequencing of stimulated macrophages revealed that Pcsk9 deficiency upregulated histone deacetylase SIRT1 (sirtuin-1) and suppressed NF-κB (nuclear factor-κB) inflammatory signaling. SIRT1 inhibition attenuated the proinflammatory actions of PCSK9. Furthermore, administration of PCSK9 small interfering RNA or antibody constrained AAA formation/progression and inhibited vascular inflammation. PCSK9 critically mediates macrophage inflammation and elastin degradation, promoting AAA formation. PCSK9 inhibitors bear a promise to curtail AAA, beyond being used as cholesterol-lowering drugs.

Stem cell factor-mediated upregulation of SIRT1 protects melanin-deprived keratinocytes against UV-induced DNA damage in individuals with vitiligo.

Despite the loss of melanocytes, individuals with vitiligo have a significantly lower risk of developing skin malignancies compared to ethnicity-matched controls. The study investigated the molecular mechanisms that protect skin cells (keratinocytes) from UV-B-induced DNA damage in individuals with vitiligo. The study found that upregulation of stem cell factor (SCF) signaling significantly reduced γ-H2AX positivity and cyclobutane pyrimidine dimer formation and improved mitochondrial health (elongated mitochondria, reduced reactive oxygen species [ROS] and lipid peroxidation) in keratinocytes upon UV-B exposure. Interestingly, SCF treatment also reduced lipid droplet accumulation and triacylglyceride levels by upregulating lipoprotein lipase (LPL). Further, siLPL increased DNA damage and lipid droplet (LD) accumulation, while NO-1886, an LPL agonist, reversed both, suggesting a direct link between lipid metabolism and DNA damage. Downregulation of NAD-dependent deacetylase sirtuin1 (SIRT1) with siRNA or with Ex-527, a pharmacological inhibitor of SIRT1, diminished the protective effects mediated by SCF and NO-1886, suggesting SIRT1 to be the final effector protein in the SCF-LPL-SIRT1 signaling axis. Analysis of clinical samples of vitiligo corroborated the upregulation of SCF and LPL in lesional epidermis. In conclusion, our study demonstrates a novel SCF-LPL-SIRT1 signaling axis that confers protection to vitiligo keratinocytes from the harmful effects of UV-B radiation.

Network pharmacology and molecular docking insights into Sirtuin-2 inhibitors (AK-7 and AGK-2): A synergistic strategy for COPD treatment

ObjectiveIn the present study network pharmacology analysis of AGK-2 and AK-7 (SIRT-2 inhibitors) were performed to elucidate their mechanism in regulating COPD pathogenesis. MethodsDifferent database (Swiss Target Prediction, GeneCards and DisGeNet) were used for predicting targets of compound and disease. Drug-Target network was constructed using Cytoscape while functional enrichment and pathway analyses were performed using STRING database. ShinnyGo database was utilized for Annotation, Visualization, and Integrated Discovery, along with Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG). Molecular docking was performed to assess the binding affinities of AGK-2 and AK-7 to key proteins. ResultsAK-7 and AGK2 revealed 43 and 41 targets while 3392 targets related to COPD were found. Protein-protein interaction (PPI) network revealed 43 nodes and 133 edges for AK-7 and 41 nodes and 110 edges for AGK-2. Enrichment analysis highlighted distinct involvement of AGK-2 and AK-7 in various aspects of respiratory physiology including molecular signaling and neuronal secretions. AGK-2 revealed to influence pathways as EGFR and Ras/Raf/MAPK, while AK-7 targeted pathways like nitric oxide synthatase and tuberculosis, as well as regulating calcium signaling and neuro-immune interactions associated with COPD. Finally molecular docking revealed that AGK-2 showed good binding affinity with MAPK14 and STAT3. Whereas AK-7 with CASP3 and CXCL8. The findings highlight potency of AGK-2 and AK-7 in modulating inflammation, reactive oxygen species, and neuroimmune interactions, suggesting their efficacy in COPD management through SIRT-2 regulation. ConclusionThe study offers novel insights into the potential of SIRT-2 inhibitors to modulate disease mechanisms at a molecular level.