Pubertal exposure to Microcystin-LR arrests spermatogonia proliferation by inducing DSB and inhibiting SIRT6 dependent DNA repair in vivo and in vitro.

The reproduction toxicity of pubertal exposure to Microcystin-LR (MC-LR) and the underlying mechanism needs to be further investigated. In the current study, pubertal male ICR mice were intraperitoneally injected with 2 µg/kg MC-LR for four weeks. Pubertal exposure to MC-LR decreased epididymal sperm concentration and blocked spermatogonia proliferation. In-vitro studies found MC-LR inhibited cell proliferation of GC-1 cells and arrested cell cycle in G2/M phase. Mechanistically, MC-LR exposure evoked excessive reactive oxygen species (ROS) and induced DNA double-strand break in GC-1 cells. Besides, MC-LR inhibited DNA repair by reducing PolyADP-ribosylation (PARylation) activity of PARP1. Further study found MC-LR caused proteasomal degradation of SIRT6, a monoADP-ribosylation enzyme which is essential for PARP1 PARylation activity, due to destruction of SIRT6-USP10 interaction. Additionally, MG132 pretreatment alleviated MC-LR-induced SIRT6 degradation and promoted DNA repair, leading to the restoration of cell proliferation inhibition. Correspondingly, N-Acetylcysteine (NAC) pre-treatment mitigated the disturbed SIRT6-USP10 interaction and SIRT6 degradation, causing recovered DNA repair and subsequently restoration of cell proliferation inhibition in MC-LR treated GC-1 cells. Together, pubertal exposure to MC-LR induced spermatogonia cell cycle arrest and sperm count reduction by oxidative DNA damage and simultaneous SIRT6-mediated DNA repair failing. This study reports the effect of pubertal exposure to MC-LR on spermatogenesis and complex mechanism how MC-LR induces spermatogonia cell proliferation inhibition.

A NAD(P)H oxidase mimic for catalytic tumor therapy via a deacetylase SIRT7-mediated AKT/GSK3ß pathway.

Nicotinamide adenine dinucleotide (NADH) and its phosphorylated form, NADPH, are essential cofactors that play critical roles in cell functions, influencing antioxidation, reductive biosynthesis, and cellular pathways involved in tumor cell apoptosis and tumorigenesis. However, the use of nanomaterials to consume NAD(P)H and thus bring an impact on signaling pathways in cancer treatment remains understudied. In this study, we employed a salt template method to synthesize a carbon-coated-cobalt composite (C@Co) nanozyme, which exhibited excellent NAD(P)H oxidase (NOX)-like activity and mimicked the reaction mechanism of natural NOX. The C@Co nanozyme efficiently consumed NAD(P)H within cancer cells, leading to increased production of reactive oxygen species (ROS) and a reduction in mitochondrial membrane potential. Meanwhile, the generation of the biologically active cofactor NAD(P)+ promoted the expression of the deacetylase SIRT7, which in turn inhibited the serine/threonine kinase AKT signaling pathway, ultimately promoting apoptosis. This work sheds light on the influence of nanozymes with NOX-like activity on cellular signaling pathways in tumor therapy and demonstrates their promising antitumor effects in a tumor xenograft mouse model. These findings contribute to a better understanding of NAD(P)H manipulation in cancer treatment and suggest the potential of nanozymes as a therapeutic strategy for cancer therapy.

Biodegradable Zn-5Dy Alloy with Enhanced Osteo/Angio-Genic Activity and Osteointegration Effect via Regulation of SIRT4-Dependent Mitochondrial Function.

Zinc (Zn)-dysprosium (Dy) binary alloys are promising biodegradable bone fracture fixation implants owing to their attractive biodegradability and mechanical properties. However, their clinical application is a challenge for bone fracture healing, due to the lack of Zn-Dy alloys with tailored proper bio-mechanical and osteointegration properties for bone regeneration. A Zn-5Dy alloy with high strength and ductility and a degradation rate aligned with the bone remodeling cycle is developed. Here, mechanical stability is further confirmed, proving that Zn-5Dy alloy can resist aging in the degradation process, thus meeting the mechanical requirements of fracture fixation. In vitro cellular experiments reveal that the Zn-5Dy alloy enhances osteogenesis and angiogenesis by elevating SIRT4-mediated mitochondrial function. In vivo Micro-CT, SEM-EDS, and immunohistochemistry analyses further indicate good biosafety, suitable biodegradation rate, and great osteointegration of Zn-5Dy alloy during bone healing, which also depends on the upregulation of SIRT4-mediated mitochondrial events. Overall, the study is the first to report a Zn-5Dy alloy that exerts remarkable osteointegration properties and has a strong potential to promote bone healing. Furthermore, the results highlight the importance of mitochondrial modulation and shall guide the future development of mitochondria-targeting materials in enhancing bone fracture healing.

SIRT3 Activation a Promise in Drug Development? New Insights into SIRT3 Biology and Its Implications on the Drug Discovery Process.

Sirtuins catalyze deacetylation of lysine residues with a NAD+-dependent mechanism. In mammals, the sirtuin family is composed of seven members, divided into four subclasses that differ in substrate specificity, subcellular localization, regulation, as well as interactions with other proteins, both within and outside the epigenetic field. Recently, much interest has been growing in SIRT3, which is mainly involved in regulating mitochondrial metabolism. Moreover, SIRT3 seems to be protective in diseases such as age-related, neurodegenerative, liver, kidney, heart, and metabolic ones, as well as in cancer. In most cases, activating SIRT3 could be a promising strategy to tackle these health problems. Here, we summarize the main biological functions, substrates, and interactors of SIRT3, as well as several molecules reported in the literature that are able to modulate SIRT3 activity. Among the activators, some derive from natural products, others from library screening, and others from the classical medicinal chemistry approach.

Design, synthesis, and biological screening of a series of pyrazolo [1,5-a]quina-zoline derivatives as SIRT6 activators.

SIRT6 has emerged as a novel therapeutic target for a variety of diseases. In this study, a total of 102 pyrazolo [1,5-a]quinazoline derivatives were designed and synthesized. The result revealed that 2-methyl-N-(4-phenoxy-phenyl)pyrazolo [1,5-a]quinazoline-5-amine (21q) was the most active compound by structure-activity relationship study, which significantly enhanced SIRT6 defatty-acylation activity with an EC1.5 value of 1.85±0.41 µM and EC50 value of 11.15±0.33 µM. The biological activity of 21q was further verified by differential scanning fluorimetry assay (DSF) and surface plasmon resonance assay (SPR). Molecular docking showed that the pyrazolo [1,5-a]quinazoline of 21q formed a hydrogen bond with Val115 and four π- π interactions with Phe64, Phe82 and Phe86. 21q can significantly improve the thermal stability of SIRT6 protein and inhibit the PI3K/Akt signaling pathway in mouse embryonic fibroblasts (MEFs), thereby inhibiting the proliferation of MEFs. Collectively, we discovered a new potent SIRT6 activator, which can be taken as a lead compound for later studies.

Profiling the regulatory interplay of BET bromodomains and Sirtuins in cancer cell lines.

Alterations in epigenetic marking, due to changes in expression or activity of epigenetic regulators, may affect cancer development and progression and thus, targeting epigenetic regulators provides potential avenues for cancer treatment. Bromodomain and extra terminal domain (BET) proteins, epigenetic readers recognizing histone acetylation, and Sirtuins (SIRT1-7), histone deacetylases or erasers, affect the chromatin acetylation status, and thus have a vital role in transcriptional regulation of a variety of cancer-related genes. Here, the effects of three BET inhibitors on SIRT expression were screened in a broad set of cancer cell lines to study the potential interplay of these distinct epigenetic factors in gene regulation. We show that BET inhibitors have distinct effects on SIRTs and their target gene expression in cancer cell lines derived from several solid tumour cancers. This functional link may open further avenues for epigenetic combination therapies for different cancers.

Sodium valproate increases activity of the sirtuin pathway resulting in beneficial effects for spinocerebellar ataxia-3 in vivo.

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3) is a fatal neurodegenerative disease that impairs control and coordination of movement. Here we tested whether treatment with the histone deacetylase inhibitor sodium valproate (valproate) prevented a movement phenotype that develops in larvae of a transgenic zebrafish model of the disease. We found that treatment with valproate improved the swimming of the MJD zebrafish, affected levels of acetylated histones 3 and 4, but also increased expression of polyglutamine expanded human ataxin-3. Proteomic analysis of protein lysates generated from the treated and untreated MJD zebrafish also predicted that valproate treatment had activated the sirtuin longevity signaling pathway and this was confirmed by findings of increased SIRT1 protein levels and sirtuin activity in valproate treated MJD zebrafish and HEK293 cells expressing ataxin-3 84Q, respectively. Treatment with resveratrol (another compound known to activate the sirtuin pathway), also improved swimming in the MJD zebrafish. Co-treatment with valproate alongside EX527, a SIRT1 activity inhibitor, prevented induction of autophagy by valproate and the beneficial effects of valproate on the movement in the MJD zebrafish, supporting that they were both dependent on sirtuin activity. These findings provide the first evidence of sodium valproate inducing activation of the sirtuin pathway. Further, they indicate that drugs that target the sirtuin pathway, including sodium valproate and resveratrol, warrant further investigation for the treatment of MJD and related neurodegenerative diseases.

Mechanism of Action of Ketogenic Diet Treatment: Impact of Decanoic Acid and Beta-Hydroxybutyrate on Sirtuins and Energy Metabolism in Hippocampal Murine Neurons.

The ketogenic diet (KD), a high-lipid and low-carbohydrate diet, has been used in the treatment of epilepsy, neurodegenerative disorders, inborn errors of metabolism and cancer; however, the exact mechanism/s of its therapeutic effect is not completely known. We hypothesized that sirtuins (SIRT)-a group of seven NAD-dependent enzymes and important regulators of energy metabolism may be altered under KD treatment. HT22 hippocampal murine neurons were incubated with two important KD metabolites-beta-hydroxybutyrate (BHB) (the predominant ketone body) and decanoic acid (C10), both accumulating under KD. Enzyme activity, protein, and gene expressions of SIRT 1-4, enzyme capacities of the mitochondrial respiratory chain complexes (MRC), citrate synthase (CS) and gene expression of monocarboxylate transporters were measured in control (untreated) and KD-treated cells. Incubation with both-BHB and C10 resulted in significant elevation of SIRT1 enzyme activity and an overall upregulation of the MRC. C10 incubation showed prominent increases in maximal activities of complexes I + III and complex IV of the MRC and ratios of their activities to that of CS, pointing towards a more efficient functioning of the mitochondria in C10-treated cells.

Effects of Sirt3­autophagy and resveratrol activation on myocardial hypertrophy and energy metabolism.

The aim of the present study was to examine the role of sirtuin 3 (Sirt3)­autophagy in regulating myocardial energy metabolism and inhibiting myocardial hypertrophy in angiotensin (Ang) II­induced myocardial cell hypertrophy. The primary cultured myocardial cells of neonatal Sprague Dawley rats were used to construct a myocardial hypertrophy model induced with Ang II. Following the activation of Sirt3 by resveratrol (Res), Sirt3 was silenced using small interfering (si)RNA­Sirt3, and the morphology of the myocardial cells was observed under an optical microscope. Reverse transcription­polymerase chain reaction was used to detect the mRNA expression of the following myocardial hypertrophy markers; atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), Sirt3, medium­chain acyl­CoA dehydrogenase (MCAD) and pyruvate kinase (PK). Western blot analysis was used to detect the protein expression of Sirt3, light chain 3 (LC3) and Beclin1. Ang II may inhibit the protein expression of Sirt3, LC3 and Beclin1. Res, an agonist of Sirt3, may promote the protein expression of Sirt3, LC3 and Beclin1. Res inhibited the mRNA expression of ANP and BNP, and reversed the Ang II­induced myocardial cell hypertrophy. The addition of siRNA­Sirt3 decreased the protein expression of Sirt3, LC3 and Beclin1, increased the mRNA expression of ANP and BNP, and weakened the inhibitory effect of Res on myocardial cell hypertrophy. Res promoted the mRNA expression of MCAD, inhibited the mRNA expression of PK, and reversed the influence of Ang II on myocardial energy metabolism. siRNA­Sirt3 intervention significantly decreased the effect of Res in eliminating abnormal myocardial energy metabolism. In conclusion, Sirt3 may inhibit Ang II­induced myocardial hypertrophy and reverse the Ang II­caused abnormal myocardial energy metabolism through activation of autophagy.

Sirtuin modulators: where are we now? A review of patents from 2015 to 2019.

In recent years, sirtuins (SIRTs) gained an increasing consideration because of their multiple key roles in several biological settings such as the regulation of transcription, energetic metabolism, cell cycle progression, and cytodifferentiation, apoptosis, neuro- and cardio-protection, inflammation, cancer onset and progression. Since there is mounting evidence in favor of potential therapeutic applications of SIRT modulators in various age-related disorders, the search about them is quite active. Areas covered: This review includes the patents regarding SIRT modulators released from 2015 to 2019 and provides an overview of the most relevant SIRT modulators.Expert opinion: Despite the knowledge about this family of broad-spectrum protein lysine deacylases has recently massively increased, there are still open questions, first of all, the exact nature of their involvement in various age-related conditions. The search for isoform-specific SIRT activators and inhibitors is still at its infancy, a limited number of patents describing them has been released, and not many clinical trials are ongoing. However, it is extremely likely that the successes obtained in the structural elucidation and structure-based design approaches that very recently have led to potent and specific SIRT modulators will pave the way for the development of further compounds selective for every single isoform.

Molecular docking and mechanisms of fusaric acid induced mitochondrial sirtuin aberrations in glycolytically and oxidatively poised human hepatocellular carcinoma (HepG2) cells.

Fusaric acid (FA) is a ubiquitous yet neglected mycotoxin. The toxicity of FA is associated with mitochondrial dysfunction and oxidative stress. Sirtuins (SIRTs) are key mediators of cell stress responses through deacetylation of antioxidant, mitochondrial maintenance and energy metabolism proteins. Dietary bioactive compounds have profound effects on SIRT activity, however little is known regarding common foodborne toxins and SIRTs. In this study the interaction of FA with mitochondrial SIRTs - SIRT3 and SIRT5, were firstly studied by molecular docking. Thereafter we substantiated the in silico findings by investigating the effect of FA on expression profiles of SIRT3 and SIRT5, and transcriptional and post-transcriptional regulators, PGC-1α and miRNA-30c using western blots and qPCR in vitro. FA was predicted to bind to the active site of SIRT3 and SIRT5 having implications for biological activity. Furthermore, protein expression of SIRT3 and SIRT5 was down-regulated despite elevated mRNA levels. Further experimentation revealed post-transcriptional regulation of both SIRTs as evidenced by elevated miRNA-30c despite induction of PGC-1α. This study highlights the potential of a diet contaminated with FA to dysregulate mitochondrial specific proteins that can lead to initiation and progression of sirtuin related diseases including cancer and insulin resistance.

Inhibition of SIRT1/2 upregulates HSPA5 acetylation and induces pro-survival autophagy via ATF4-DDIT4-mTORC1 axis in human lung cancer cells.

Sirtuins have emerged as a promising novel class of anti-cancer drug targets. Inhibition of SIRT1 and SIRT2 induces apoptosis in cancer cells and they play multifaceted roles in regulating autophagy. In the present study, we found that salermide, a SIRT1/2-specific inhibitor or small interfering RNAs (siRNAs) to block SIRT1/2 expression could induce autophagy in human NSCLC cells. Moreover, SIRT1/2 inhibition increased the expression levels of ATF4 and DDIT4 and downregulated p-RPS6KB1 and p-EIF4EBP1, two downstream molecules of mTORC1. Moreover, ATF4 or DDIT4 knockdown attenuated salermide-induced autophagy, suggesting that SIRT1/2 inhibition induced autophagy through the ATF4-DDIT4-mTORC1 axis. Mechanistically, SIRT1/2 inhibition led to HSPA5 acetylation and dissociation from EIF2AK3, leading to ER stress response and followed by upregulation of ATF4 and DDIT4, triggering autophagy. Silencing of the autophagic gene ATG5 in lung cancer cells resulted in increased apoptotic cell death induced by SIRT1/2 inhibition. Our data show that inhibition of SIRT1/2 induces pro-survival autophagy via acetylation of HSPA5 and subsequent activation of ATF4 and DDIT4 to inhibit the mTOR signaling pathway in NSCLC cells. These findings suggest that combinatorial treatment with SIRT1/2 inhibitors and pharmacological autophagy inhibitors is an effective therapeutic strategy for cancer therapy.

Depletion of SIRT7 sensitizes human non-small cell lung cancer cells to gemcitabine therapy by inhibiting autophagy.

Anti-metabolic therapy, as a major chemotherapy, is an important option in the treatment of lung cancer. However, tumor resistance to cytotoxic chemotherapy has become more common. It has been reported that autophagy is one of the processes contributing to such resistance. In our study, we find that SIRT7 protein level elevated dramatically in response to an anti-metabolic drug-gemcitabine treatment. Moreover, autophagy induced by gemcitabine in non-small cell lung cancer cells is SIRT7-dependent. Furthermore, depletion of SIRT7 promoted Gemcitabine-induced cell death. Our report also shows that SIRT7 knockdown markedly improves the anti-tumor activity of gemcitabine treatment in mice. These results suggest that SIRT7-elicits an autophagic response that plays a protective role against cell death and the SIRT7-inhibition has a potential to improve the efficacy of anti-metabolic therapy in non-small cell lung cancer cells.

The sirtuin family members SIRT1, SIRT3 and SIRT6: Their role in vascular biology and atherogenesis.

The sirtuins, silent mating-type information regulation 2 (SIRTs), are a family of nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases with important roles in regulating energy metabolism and senescence. Activation of SIRTs appears to have beneficial effects on lipid metabolism and antioxidants, prompting investigation of the roles of these proteins in atherogenesis. Although clinical data are currently limited, the availability and safety of SIRT activators such as metformin and resveratrol provide an excellent opportunity to conduct research to better understand the role of SIRTs in human atherosclerosis. Encouraging observations from preclinical studies necessitate rigorous large, prospective, randomized clinical trials to determine the roles of SIRT activators on the progression of atherosclerosis and ultimately on cardiac outcomes, such as myocardial infarction and mortality.

Effect of 6-gingerol on AMPK- NF-κB axis in high fat diet fed rats.

OBJECTIVES: Adenosine monophosphate (AMP)-activated protein kinase (AMPK) plays a central role in metabolic homeostasis and regulation of inflammatory responses through attenuation of nuclear factor kappa-B (NF-κB), Thus AMPK may be a promising pharmacologic target for the treatment of various chronic inflammatory diseases. We examined the effect of 6-gingerol, an active ingredient of ginger on AMPK-NF-κB pathway in high fat diet (HFD) rats in comparison to fish oil. METHODS: Protein levels of AMPK-α1 and phosphorylated AMPK-α1 were measured by western blot while Sirtuin 6 (Sirt-6), resistin and P65 were estimated by RT-PCR, TNF-α was determined by ELISA, FFAs were estimated chemically as well as the enzymatic determination of the metabolic parameters. RESULTS: 6-Gingerol substantially enhanced phosphorylated AMPK-α1 more than fish oil and reduced the P65 via upregulation of Sirt-6 and downregulation of resistin, and resulted in attenuation of the inflammatory molecules P65, FFAs and TNF-α more than fish oil treated groups but in an insignificant statistical manner, those effects were accompanied by a substantial hypoglycemic effect. CONCLUSION: Gingerol treatment effectively modulated the state of inflammatory privilege in HFD group and the metabolic disorders via targeting the AMPK-NF-κB pathway, through an increment in the SIRT-6 and substantial decrement in resistin levels.

Sirtuins and nonalcoholic fatty liver disease.

Mammalian sirtuins are seven members belonging to the silent information regulator 2 family, a group of Class III histone/protein deacetylases. Sirtuins (SIRT 1-7) have different subcellular localization and function and they regulate cellular protein function through various posttranslational modifications. SIRT1 and 3, the most studied sirtuins, use the product of cellular metabolism nicotinamide adenine dinucleotide as a cofactor to post-translationally deacetylate cellular proteins and consequently link the metabolic status of the cell to protein function. Sirtuins have been shown to play a key role in the development and rescue of various metabolic diseases including non-alcoholic fatty liver disease (NAFLD). NAFLD is currently the most chronic liver disease due mainly to high-calorie consumption and lower physical activity. No pharmacological approach is available to treat NAFLD, the current recommended treatment are lifestyle modification such as weight loss through calorie restriction and exercise. Recent studies have shown downregulation of sirtuins in human as well as animal models of NAFLD indicating an important role of sirtuins in the dynamic pathophysiology of NAFLD. In this review, we highlight the recent knowledge on sirtuins, their role in NAFLD and their unique potential role as novel therapeutic target for NAFLD treatment.

Brief Communication: SIR-2.1-dependent lifespan extension of Caenorhabditis elegans by oxyresveratrol and resveratrol.

Resveratrol (RES) has been studied for its effects on the lifespan extension of Caenorhabditis elegans, but controversy still remains on its mechanism related with SIR-2. In this study, longevity assay was performed to confirm SIR-2-dependent lifespan extension of C. elgeans with RES and oxyresveratrol (OXY), an isomer of hydroxylated RES using loss-of-function mutants of C. elegans including sir-2.1 mutant. The results showed that OXY and RES significantly (P < 0.05) extended the lifespan of C. elegans compared with the control. OXY and RES also significantly (P < 0.05) increased the mRNA expression levels of sir-2.1 and aak-2 in a dose-dependent manner and increased the protein expression levels of SIR-2.1. OXY and RES treatment extended the lifespan in daf-16 loss-of-function mutants, which suggested that lifespan extension was not occurring via the activation of DAF-16. However, OXY and RES failed to extend the lifespan in loss-of-function mutants of sir-2.1 and aak-2 Therefore, OXY and RES extend the lifespan of C. elegans by overexpression of SIR-2.1, which is related to lifespan extension through calorie restriction and the AMP-activated protein kinase (AMPK) pathway, although this process is independent of the FOXO/DAF-16 pathway.

Mediterranean Way of Drinking and Longevity.

The relation between alcohol consumption and mortality is a J-shaped curve in most of the many studies published on this topic. The Copenhagen Prospective Population Studies demonstrated in the year 2000 that wine intake may have a beneficial effect on all cause mortality that is additive to that of alcohol. Wine contains various poliphenolic substances which may be beneficial for health and in particular flavonols (such as myricetin and quercetin), catechin and epicatechin, proanthocyanidins, anthocyanins, various phenolic acids and the stilbene resveratrol. In particular, resveratrol seems to play a positive effect on longevity because it increases the expression level of Sirt1, besides its antioxidant, anti-inflammatory and anticarcinogenic properties. Moderate wine drinking is part of the Mediterranean diet, together with abundant and variable plant foods, high consumption of cereals, olive oil as the main (added) fat and a low intake of (red) meat. This healthy diet pattern involves a "Mediterranean way of drinking," that is a regular, moderate wine consumption mainly with food (up to two glasses a day for men and one glass for women). Moderate wine drinking increases longevity, reduces the risk of cardiovascular diseases and does not appreciably influence the overall risk of cancer.

Protective effects of sirtuins in cardiovascular diseases: from bench to bedside.

Sirtuins (Sirt1-Sirt7) comprise a family of nicotinamide adenine dinucleotide (NAD(+))-dependent enzymes. While deacetylation reflects their main task, some of them have deacylase, adenosine diphosphate-ribosylase, demalonylase, glutarylase, and desuccinylase properties. Activated upon caloric restriction and exercise, they control critical cellular processes in the nucleus, cytoplasm, and mitochondria to maintain metabolic homeostasis, reduce cellular damage and dampen inflammation-all of which serve to protect against a variety of age-related diseases, including cardiovascular pathologies. This review focuses on the cardiovascular effects of Sirt1, Sirt3, Sirt6, and Sirt7. Most is known about Sirt1. This deacetylase protects from endothelial dysfunction, atherothrombosis, diet-induced obesity, type 2 diabetes, liver steatosis, and myocardial infarction. Sirt3 provides beneficial effects in the context of left ventricular hypertrophy, cardiomyopathy, oxidative stress, metabolic homeostasis, and dyslipidaemia. Sirt6 is implicated in ameliorating dyslipidaemia, cellular senescence, and left ventricular hypertrophy. Sirt7 plays a role in lipid metabolism and cardiomyopathies. Most of these data were derived from experimental findings in genetically modified mice, where NFκB, Pcsk9, low-density lipoprotein-receptor, PPARγ, superoxide dismutase 2, poly[adenosine diphosphate-ribose] polymerase 1, and endothelial nitric oxide synthase were identified among others as crucial molecular targets and/or partners of sirtuins. Of note, there is translational evidence for a role of sirtuins in patients with endothelial dysfunction, type 1 or type 2 diabetes and longevity. Given the availability of specific Sirt1 activators or pan-sirtuin activators that boost levels of the sirtuin cofactor NAD⁺, we anticipate that this field will move quickly from bench to bedside.

Characterization of Trypanosoma cruzi Sirtuins as Possible Drug Targets for Chagas Disease.

Acetylation of lysine is a major posttranslational modification of proteins and is catalyzed by lysine acetyltransferases, while lysine deacetylases remove acetyl groups. Among the deacetylases, the sirtuins are NAD(+)-dependent enzymes, which modulate gene silencing, DNA damage repair, and several metabolic processes. As sirtuin-specific inhibitors have been proposed as drugs for inhibiting the proliferation of tumor cells, in this study, we investigated the role of these inhibitors in the growth and differentiation of Trypanosoma cruzi, the agent of Chagas disease. We found that the use of salermide during parasite infection prevented growth and initial multiplication after mammalian cell invasion by T. cruzi at concentrations that did not affect host cell viability. In addition, in vivo infection was partially controlled upon administration of salermide. There are two sirtuins in T. cruzi, TcSir2rp1 and TcSir2rp3. By using specific antibodies and cell lines overexpressing the tagged versions of these enzymes, we found that TcSir2rp1 is localized in the cytosol and TcSir2rp3 in the mitochondrion. TcSir2rp1 overexpression acts to impair parasite growth and differentiation, whereas the wild-type version of TcSir2rp3 and not an enzyme mutated in the active site improves both. The effects observed with TcSir2rp3 were fully reverted by adding salermide, which inhibited TcSir2rp3 expressed in Escherichia coli with a 50% inhibitory concentration (IC50) ± standard error of 1 ± 0.5 µM. We concluded that sirtuin inhibitors targeting TcSir2rp3 could be used in Chagas disease chemotherapy.