Fisetin disrupts mitochondrial homeostasis via superoxide dismutase 2 acetylation in pancreatic adenocarcinoma.

Pancreatic adenocarcinoma (PDAC) is one of the most lethal malignant tumors with an urgent need for precision medicine strategies. The present study seeks to assess the antitumor effects of fisetin, and characterize its impact on PDAC. Multi-omic approaches include proteomic, transcriptomic, and metabolomic analyses. Further validation includes the assessment of mitochondria-derived reactive oxygen species (mtROS), mitochondrial membrane potential, as well as ATP generation. Molecular docking, immunoprecipitation, and proximity ligation assay were used to detect the interactions among fiseitn, superoxide dismutase 2 (SOD2), and sirtuin 2 (SIRT2). We showed that fisetin disrupted mitochondrial homeostasis and induced SOD2 acetylation in PDAC. Further, we produced site mutants to determine that fisetin-induced mtROS were dependent on SOD2 acetylation. Fisetin inhibited SIRT2 expression, thus blocking SOD2 deacetylation. SIRT2 overexpression could impede fisetin-induced SOD2 acetylation. Additionally, untargeted metabolomic analysis revealed an acceleration of folate metabolism with fisetin. Collectively, our findings suggest that fisetin disrupts mitochondrial homeostasis, eliciting an important cancer-suppressive role; thus, fisetin may serve as a promising therapeutic for PDAC.

Novel insights into autophagy in gastrointestinal pathologies, mechanisms in metabolic dysfunction-associated fatty liver disease and acute liver failure.

In this editorial, we comment on three articles published in a recent issue of World Journal of Gastroenterology. There is a pressing need for new research on autophagy's role in gastrointestinal (GI) disorders, and also novel insights into some liver conditions, such as metabolic dysfunction-associated fatty liver disease (MAFLD) and acute liver failure (ALF). Despite advancements, understanding autophagy's intricate mechanisms and implications in these diseases remains incomplete. Moreover, MAFLD's pathogenesis, encompassing hepatic steatosis and metabolic dysregulation, require further elucidation. Similarly, the mechanisms underlying ALF, a severe hepatic dysfunction, are poorly understood. Innovative studies exploring the interplay between autophagy and GI disorders, as well as defined mechanisms of MAFLD and ALF, are crucial for identifying therapeutic targets and enhancing diagnostic and treatment strategies to mitigate the global burden of these diseases.

Solanum melongena L. Extract Promotes Intestinal Tight Junction Re-Assembly via SIRT-1-Dependent Mechanisms.

Tight junction disruption can lead to pathogenesis of various diseases without therapeutic strategy to recover intestinal barrier integrity. The main objective of this study is to demonstrate the effect of Solanum melongena L. extract (SMLE) on intestinal tight junction recovery and its underlying mechanism. Intestinal barrier function is attenuated by Ca2+ depletion. SMLE treatment increased TER value across T84 cell monolayers. Permeability assay reveals that Ca2+ depletion promotes 4-kDa FITC-dextran permeability, but not 70-kDa FITC-dextran. SMLE suppresses the rate of 4-kDa FITC-dextran permeability, indicating that SMLE inhibits paracellular leak pathway permeability. SMLE-mediated TER increase and leak pathway suppression are abolished by neither calcium/calmodulin-dependent protein kinase kinase ß (CaMKKß) inhibitor nor AMP-activated protein kinase (AMPK) inhibitor. Furthermore, mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) inhibitors have no effects on SMLE-mediated TER increase and leak pathway suppression. Interestingly, SMLE is unable to enhance TER value and diminish leak pathway permeability in T84 cell monolayers pre-treated with sirtuin-1 (SIRT-1) inhibitor. Immunofluorescence staining reveals that SMLE enhances re-assembly of tight junction proteins, including occludin and ZO-1 to intercellular space but this effect is abolished by SIRT-1 inhibitor. These data suggest that SMLE promotes intestinal tight junction re-assembly via SIRT-1-dependent manner.

SIRT1-driven mechanism: sevoflurane's interference with mESC neural differentiation via PRRX1/DRD2 cascade.

Investigating the sevoflurane-induced perturbation in the differentiation of mouse embryonic stem cells (mESCs) into neural stem cells (mNSCs), our study delineates a novel SIRT1/PRRX1/DRD2/PKM2/NRF2 axis as a key player in this intricate process. Sevoflurane treatment hindered mESC differentiation, evidenced by altered expression patterns of pluripotency and neural lineage markers. Mechanistically, sevoflurane downregulated Sirt1, setting in motion a signaling cascade. Sevoflurane may inhibit PKM2 dimerization and NRF2 signaling pathway activation by inhibiting the expression of SIRT1 and its downstream genes Prrx1 and DRD2, ultimately inhibiting mESCs differentiation into mNSCs. These findings contribute to our understanding of the molecular basis of sevoflurane-induced neural toxicity, presenting a potential avenue for therapeutic intervention in sevoflurane-induced perturbation in the differentiation of mESCs into mNSCs by modulating the SIRT1/PRRX1/DRD2/PKM2/NRF2 axis.

Expression analysis and biological regulation of silencing regulatory protein 6 (SIRT6) in cutaneous squamous cell carcinoma

Abstract Background Cutaneous squamous cell carcinoma (CSCC) is one of the most common types of skin cancer worldwide. Therefore, the identification of biomarkers associated with CSCC progression could aid in the early detection of high-risk squamous cell carcinoma and the development of novel therapeutic strategies. Objective This study aimed to investigate the expression patterns of silent mating type Information Regulation 2 homolog 6 (SIRT6) in CSCC and its clinical significance. Methods The protein expression level of SIRT6 in tissues was detected by immunohistochemistry, and the correlation between SIRT6 expression and clinicopathological parameters in CSCC patients was analyzed. The relative expression of SIRT6 in CSCC cell lineage and tissue specimens was determined by western blotting and PCR. The effect of SIRT6 silencing on cell proliferation was evaluated using cell counting kit 8. Wound healing, transwell method, and flow cytometry were used to investigate the migration, invasion, and cell cycle distribution/apoptosis of CSCC cells after SIRT6 silencing, respectively. Western blot was used to detect the expression of EMT (Epithelial-Mesenchymal Transition), cycle, apoptosis, and other related proteins. Results The high expression of SIRT6 was correlated with the location of cancer tissue and Broder staging in CSCC patients. Knockdown of SIRT6 inhibited the proliferation, migration, invasion and EMT of CSCC cells, and promoted their apoptosis, with cells blocked in G1 phase. Study limitations No animal experiments were conducted to further verify the results. Conclusion Decreased expression of SIRT6 can inhibit the occurrence and development of CSCC.

Emodin alleviates cholestatic liver injury by modulating Sirt1/Fxr signaling pathways.

Emodin (EMO) has the effect of anti-cholestasis induced by alpha-naphthylisothiocyanate (ANIT). But its mechanism is still unclear. The farnesoid X receptor (Fxr) is the master bile acid nuclear receptor. Recent studies have reported that Sirtuin 1 (Sirt1) can regulate the activities of Fxr. The purpose of the current study was to investigate the mechanism of EMO against ANIT-induced liver injury based on Sirt1/Fxr signaling pathway. The ANIT-induced cholestatic rats were used with or without EMO treatment. Serum biochemical indicators, as well as liver histopathological changes were examined. The genes expressions of Sirt1, Fxr, Shp, Bsep and Mrp2 were detected. The expressions of Sirt1, Fxr and their downstream related genes were investigated in vitro. The results showed that EMO significantly alleviated ANIT-induced liver injury in rats, and increased Sirt1, Fxr, Shp, Bsep and Mrp2 gene expression in liver, while decreased the expression of Cyp7a1. EMO significantly activated Fxr, while Sirt1 inhibitor and Sirt1 gene silencing significantly reduced Fxr activity in vitro. Collectively, EMO in the right dose has a protective effect on liver injury induced by ANIT, and the mechanism may be through activation of Fxr by Sirt1, thus regulating bile acid metabolism, and reducing bile acid load in hepatocytes.

Activity of DNA Repair Systems in the Cells of Long-Lived Rodents and Bats.

Damages of various origin accumulated in the genomic DNA can lead to the breach of genome stability, and are considered to be one of the main factors involved in cellular senescence. DNA repair systems in mammalian cells ensure effective damage removal and repair of the genome structure, therefore, activity of these systems is expected to be correlated with high maximum lifespan observed in the long-lived mammals. This review discusses current results of the studies focused on determination of the DNA repair system activity and investigation of the properties of its key regulatory proteins in the cells of long-lived rodents and bats. Based on the works discussed in the review, it could be concluded that the long-lived rodents and bats in general demonstrate high efficiency in functioning and regulation of DNA repair systems. Nevertheless, a number of questions around the study of DNA repair in the cells of long-lived rodents and bats remain poorly understood, answers to which could open up new avenues for further research.

Frataxin Loss Promotes Angiotensin II-Induced Endothelial-to-Mesenchymal Transition.

BACKGROUND: The metabolic flexibility of endothelial cells is linked to their phenotypic plasticity. Frataxin is critical in determining the iron metabolism and fate of endothelial cells. This study aimed to investigate frataxin-mediated metabolic remodeling during the endothelial-to-mesenchymal transition (EndoMT). METHODS AND RESULTS: Endothelial cell-specific frataxin knockout and frataxin mutation mice were subjected to angiotensin II to induce hypertension. EndoMT and cardiac fibrosis were assessed using histological and protein expression analyses. Fatty acid oxidation (FAO) in microvascular endothelial cells was measured using a Seahorse XF96 analyzer. We showed that inhibition of FAO accompanies angiotensin II-induced EndoMT. Frataxin knockout mice promote EndoMT, associated with increased cardiac fibrosis following angiotensin II infusion. Angiotensin II reduces frataxin expression, which leads to mitochondrial iron overload and subsequent carbonylation of sirtuin 3. In turn, carbonylated sirtuin 3 contributes to the acetylated frataxin at lysine 189, making it more prone to degradation. The frataxin/sirtuin 3 feedback loop reduces hydroxyl-CoA dehydrogenase α subunit-mediated FAO. Additionally, silymarin is a scavenger of free radicals, restoring angiotensin II-induced reduction of FAO activity and sirtuin 3 and frataxin expression, improving EndoMT both in vitro and in vivo. Furthermore, frataxin mutation mice showed suppressed EndoMT and improved cardiac fibrosis. CONCLUSIONS: The frataxin/sirtuin 3 feedback loop has the potential to attenuate angiotensin II-induced EndoMT by improving FAO.

Sirtuin 3-activated superoxide dismutase 2 mediates fluoride-induced osteoblastic differentiation in vitro and in vivo by down-regulating reactive oxygen species.

Skeletal fluorosis is a chronic metabolic bone disease caused by long-term excessive fluoride intake. Abnormal differentiation of osteoblasts plays an important role in disease progression. Research on the mechanism of fluoride-mediated bone differentiation is necessary for the prevention and treatment of skeletal fluorosis. In the present study, a rat model of fluorosis was established by exposing it to drinking water containing 50 mg/L F-. We found that fluoride promoted Runt-related transcription factor 2 (RUNX2) as well as superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) expression in osteoblasts of rat bone tissue. In vitro, we also found that 4 mg/L sodium fluoride promoted osteogenesis-related indicators as well as SOD2 and SIRT3 expression in MG-63 and Saos-2 cells. In addition, we unexpectedly discovered that fluoride suppressed the levels of reactive oxygen species (ROS) and mitochondrial reactive oxygen species (mtROS) in osteoblasts. When SOD2 or SIRT3 was inhibited in MG-63 cells, fluoride-decreased ROS and mtROS were alleviated, which in turn inhibited fluoride-promoted osteogenic differentiation. In conclusion, our results suggest that SIRT3/SOD2 mediates fluoride-promoted osteoblastic differentiation by down-regulating reactive oxygen species.

The SIRT7-nucleolus connection in cancer: ARF enters the fray.

The nucleolar enzyme sirtuin 7 (SIRT7) promotes cancer progression in certain malignancies, likely in part by controlling ribosome biosynthesis. Recently, we discovered that SIRT7 destabilizes the cyclin dependent kinase inhibitor 2A (CDKN2A, known as ARF) within the nucleolus, aiding cancer progression. We propose that targeting nucleolar SIRT7 offers promise for new anti-cancer therapies.

Discovery and characterization of a new class of NAD+-independent SIRT1 activators.

The activity of sirtuin 1 (SIRT1, a member of the NAD+-dependent deacetylases family) decreases during aging as NAD+ levels naturally decline, thus increasing the risk of several age-associated diseases. Several sirtuin-activating compounds (STACs) have been developed to counteract the age-associated reduction in SIRT1 activity, and some of them are currently under development in clinical trials. STACs induce SIRT1 activation, either through allosteric activation of the enzyme in the presence of NAD+, or by increasing NAD+ levels by inhibiting its degradation or by supplying a key precursor in biosynthesis. In this study, we have identified (E)-2'-des-methyl sulindac analogues as a novel class of STACs that act also in the absence of NAD+, a peculiar behavior demonstrated through enzymatic and mass spectrometry experiments, both in vitro and in cell lines. The activation of the SIRT1 pathway was confirmed in vivo through gene expression and metabolomics analysis. Our data suggest that these compounds could serve as candidate leads for a novel therapeutic strategy aimed at addressing a key metabolic deficiency that may contribute to metabolic and age-associated diseases.

X-Box binding protein 1 downregulates SIRT6 to promote injury in pancreatic ductal epithelial cells.

OBJECTIVE: Acute pancreatitis (AP) stands as a frequent cause for clinical emergency hospital admissions. The X-box binding protein 1 (XBP1) was found to be implicated in pancreatic acinar cell apoptosis. The objective is to unveil the potential mechanisms governed by XBP1 and SIRT6 in the context of AP. METHODS: Caerulein-treated human pancreatic duct epithelial (HPDE) cells to establish an in vitro research model. The levels and regulatory role of SIRT6 in the treated cells were evaluated, including its effects on inflammatory responses, oxidative stress, apoptosis, and endoplasmic reticulum stress. The relationship between XBP1 and SIRT6 was explored by luciferase and ChIP experiments. Furthermore, the effect of XBP1 overexpression on the regulatory function of SIRT6 on cells was evaluated. RESULTS: Caerulein promoted the decrease of SIRT6 and the increase of XBP1 in HPDE cells. Overexpression of SIRT6 slowed down the secretion of inflammatory factors, oxidative stress, apoptosis level, and endoplasmic reticulum stress in HPDE cells. However, XBP1 negatively regulated SIRT6, and XBP1 overexpression partially reversed the regulation of SIRT6 on the above aspects. CONCLUSION: Our study illuminates the role of XBP1 in downregulating SIRT6 in HPDE cells, thereby promoting cellular injury. Inhibiting XBP1 or augmenting SIRT6 levels holds promise in preserving cell function and represents a potential therapeutic avenue in the management of AP.

Shiitake mushroom powder supplementation increase antioxidative activity in dogs.

Introduction: The prevalence of age-related diseases, including obesity (a lipid metabolism disorder), increases with the increase in a dog's lifespan. Most of age-related diseases are associated with oxidative stress by excessive production of reactive oxygen species (ROS) from impaired mitochondrial functions. Safe and effective supplements with antioxidative and anti-inflammatory activities are required to prevent obesity and associated complications. Shiitake mushroom exhibit various functions including antioxidant activity. We investigated the effect of shiitake powder supplementation in healthy dogs. Methods: Shiitake powder was supplemented at a dose of 800 mg/kg body weight/day for 4 weeks. The dose was set as 0.60-0.65 mg/kg/day of eritadenine, a hypocholesterolemic factor. Results: The body weight and body condition score of the dogs did not change after shiitake supplementation. In contrast, plasma total cholesterol concentrations decreased and superoxide dismutase activity and leukocyte sirtuin1 mRNA expression increased significantly in the dogs that received the supplement. Discussion: Oral administration of shiitake powder increased antioxidative activity. The supplement may be useful in ameliorating the signs of age-related diseases, including obesity, in dogs.

Preventing loss of sirt1 lowers mitochondrial oxidative stress and preserves C2C12 myotube diameter in an in vitro model of cancer cachexia.

Cancer cachexia is a multifactorial syndrome associated with advanced cancer that contributes to mortality. Cachexia is characterized by loss of body weight and muscle atrophy. Increased skeletal muscle mitochondrial reactive oxygen species (ROS) is a contributing factor to loss of muscle mass in cachectic patients. Mice inoculated with Lewis lung carcinoma (LLC) cells lose weight, muscle mass, and have lower muscle sirtuin-1 (sirt1) expression. Nicotinic acid (NA) is a precursor to nicotinamide dinucleotide (NAD+) which is exhausted in cachectic muscle and is a direct activator of sirt1. Mice lost body and muscle weight and exhibited reduced skeletal muscle sirt1 expression after inoculation with LLC cells. C2C12 myotubes treated with LLC-conditioned media (LCM) had lower myotube diameter. We treated C2C12 myotubes with LCM for 24 h with or without NA for 24 h. C2C12 myotubes treated with NA maintained myotube diameter, sirt1 expression, and had lower mitochondrial superoxide. We then used a sirt1-specific small molecule activator SRT1720 to increase sirt1 activity. C2C12 myotubes treated with SRT1720 maintained myotube diameter, prevented loss of sirt1 expression, and attenuated mitochondrial superoxide production. Our data provides evidence that NA may be beneficial in combating cancer cachexia by maintaining sirt1 expression and decreasing mitochondrial superoxide production.

Relationship between Serum Sirtuin 1 and Growth Hormone/Insulin-like Growth Factor 1 Concentrations in Children with Growth Hormone Deficiency and Idiopathic Short Stature.

Sirtuin 1 (SIRT1) inhibits growth hormone (GH) intracellular signaling for the insulin-like growth factor 1 (IGF-1) synthesis via the janus kinase (JAK)/signal transducer and activator of transcription proteins (STATs) pathway. The aim of this study was to compare SIRT1 concentrations in children with GH deficiency (GHD) and so-called idiopathic short stature (ISS, non-GH deficient), in order to determine the possible impact of changes in serum SIRT1 concentrations on the GH-IGF-1 axis. The study group included 100 short-stature children: 38 with GHD and 62 with ISS (maxGH in two stimulation tests <10 and ≥10 ng/mL, respectively). The control group consisted of 47 healthy, normal-height children. For each child, the concentrations of SIRT1, IGF-1 and insulin-like growth factor-binding protein 3 (IGFBP-3) were determined and the IGF-1/IGFBP-3 molar ratio was calculated. The level of SIRT1 was significantly higher in both groups of short children than in the controls (p < 0.0001), but there were no differences between GHD and ISS (mean ± SD: 0.89 ± 0.45 for ISS; 1.24 ± 0, 86 for GHD; and 0.29 ± 0.21 for controls). A significant negative correlation was found between SIRT1 and height standard deviation score (SDS), IGF-1 and IGF-1/IGFBP-3, but not between SIRT1 and maxGH. Elevated SIRT1 levels may serve as one of the mechanisms through which the secretion of IGF-1 is reduced in children with short stature; however, further research is required to confirm this issue.

Insight into the cardioprotective effects of melatonin: shining a spotlight on intercellular Sirt signaling communication.

Cardiovascular diseases (CVDs) are the leading causes of death and illness worldwide. While there have been advancements in the treatment of CVDs using medication and medical procedures, these conventional methods have limited effectiveness in halting the progression of heart diseases to complete heart failure. However, in recent years, the hormone melatonin has shown promise as a protective agent for the heart. Melatonin, which is secreted by the pineal gland and regulates our sleep-wake cycle, plays a role in various biological processes including oxidative stress, mitochondrial function, and cell death. The Sirtuin (Sirt) family of proteins has gained attention for their involvement in many cellular functions related to heart health. It has been well established that melatonin activates the Sirt signaling pathways, leading to several beneficial effects on the heart. These include preserving mitochondrial function, reducing oxidative stress, decreasing inflammation, preventing cell death, and regulating autophagy in cardiac cells. Therefore, melatonin could play crucial roles in ameliorating various cardiovascular pathologies, such as sepsis, drug toxicity-induced myocardial injury, myocardial ischemia-reperfusion injury, hypertension, heart failure, and diabetic cardiomyopathy. These effects may be partly attributed to the modulation of different Sirt family members by melatonin. This review summarizes the existing body of literature highlighting the cardioprotective effects of melatonin, specifically the ones including modulation of Sirt signaling pathways. Also, we discuss the potential use of melatonin-Sirt interactions as a forthcoming therapeutic target for managing and preventing CVDs.

Understanding the molecular crossroads in acute liver failure: A pathway to new therapies.

In this editorial we comment on the article published in a recent issue of the World Journal of Gastroenterology. Acute liver failure (ALF) is a critical condition characterized by rapid hepatocellular injury and organ dysfunction, and it often necessitates liver transplant to ensure patient survival. Recent research has elucidated the involvement of distinct cell death pathways, namely ferroptosis and pyroptosis, in the pathogenesis of ALF. Ferroptosis is driven by iron-dependent lipid peroxidation, whereas pyroptosis is an inflammatory form of cell death; both pathways contribute to hepatocyte death and exacerbate tissue damage. This comprehensive review explores the interplay between ferroptosis and pyroptosis in ALF, highlighting the role of key regulators such as silent information regulator sirtuin 1. Insights from clinical and preclinical studies provide valuable perspectives on the dysregulation of cell death pathways in ALF and the therapeutic potential of targeting these pathways. Collaboration across multiple disciplines is essential for translating the experimental insights into effective treatments for this life-threatening condition.

The role of deacetylase SIRT1 in allergic diseases.

The silent information regulator sirtuin 1 (SIRT1) protein is an NAD+-dependent class-III lysine deacetylase that serves as an important post-transcriptional modifier targeting lysine acetylation sites to mediate deacetylation modifications of histones and non-histone proteins. SIRT1 has been reported to be involved in several physiological or pathological processes such as aging, inflammation, immune responses, oxidative stress and allergic diseases. In this review, we summarized the regulatory roles of SIRT1 during allergic disorder progression. Furthermore, we highlight the therapeutic effects of targeting SIRT1 in allergic diseases.

Inhibition of SIRT1 relieves hepatocarcinogenesis via alleviating autophagy and inflammation.

Imbalanced Sirtuin 1 (SIRT1) levels may lead to liver diseases through abnormal regulation of autophagy, but the roles of SIRT1-regulated autophagy in hepatocellular carcinoma are still controversial. In this study, we found that SIRT1 mRNA and protein levels were upregulated in hepatocellular carcinoma, and high SIRT1 expression hinted an advanced stage and a poor prognosis. The differentially expressed proteins were significantly elevated in autophagy, cellular response to stress, and immune signaling pathways. In a thioacetamide-induced hepatocellular carcinoma mouse model, we found that SIRT1 expression was highly increased with increased autophagy and excessive macrophage inflammatory response. Next, we established a Hepa 1-6 cells and macrophage co-culture system in vitro to model the alteration of tumor microenvironment, and found that the medium from CCl4-treated or SIRT1-overexpressing Hepa 1-6 cells triggered the polarization of macrophage M1, and the culture medium derived from M1 macrophage promoted Hepa 1-6 cells growth and intracellular oxidative stress. The progression of liver fibrosis in the CCl4-induced liver fibrosis mouse model showed that inhibition of SIRT1 alleviated inflammatory response and ameliorated liver fibrosis. These findings suggest that SIRT1-regulated autophagy and inflammation are oncogenic in hepatocarcinogenesis.

Epigenetically Rewiring Metabolic Genes via SIRT6 Orchestrates MSC Fate Determination.

SIRT6 owns versatile types of enzymatic activities as a multitasking protein, including ribosyltransferase and deacetylase ones. To investigate the epigenetic regulations of SIRT6 on MSC fate determination via histone deacetylation, we utilized allosteric small molecules specifically controlling its histone 3 deacetylation activities. Results showed that enhanced deacetylation of SIRT6 promoted the ossific lineage commitment of MSC and finally achieved anabolic effects on hard tissues. Mechanistically, H3K9ac and H3K56ac, governed by SIRT6, in MSC orchestrated the transcriptions of crucial metabolic genes, mediating MSC fate determination. Most importantly, our data evidenced that modulating the epigenetic regulations of SIRT6, specifically via enhancing its deacetylation of H3K9ac and H3K56ac, was a promising choice to treat bone loss diseases and promote dentine regeneration. In this study, we revealed the specific roles of SIRT6's histone modification in MSC fate determination. These findings endow us with insights on SIRT6 and the promising therapeutic choices through SIRT6's epigenetic functions for hard tissues regeneration.