Current role of mammalian sirtuins in DNA repair

Pioglitazone ameliorates sepsis-associated encephalopathy through SIRT1 signaling pathway

Sepsis is a severe immune response to an infection. It is associated with multiple organ dysfunction syndrome (MODs) along with systemic and neuronal inflammatory response. This study focused on the acute neurologic dysfunction associated with sepsis by exploring the role of PPARγ/SIRT1 pathway against sepsis. We studied the role of this axis in ameliorating sepsis-associated encephalopathy (SAE) and its linked neurobehavioral disorders by using pioglitazone (PIO). This PPARγ agonist showed neuroprotective actions in neuroinflammatory disorders. Sepsis was induced in mice by LPS (10 mg/kg). Survival rate and MODs were assessed. Furthermore, behavioral deficits, cerebral oxidative, inflammatory, and apoptotic markers, and the cerebral expression level of SIRT1 were determined. In this study, we observed that PIO attenuated sepsis-induced cerebral injury. PIO significantly enhanced survival rate, attenuated MODs, and systemic inflammatory response in septic mice. PIO also promoted cerebral SIRT1 expression and reduced cerebral activation of microglia, oxidative stress, HMGB, iNOS, NLRP3 and caspase-3 along with an obvious improvement in behavioral deficits and cerebral pathological damage induced by LPS. Most of the neuroprotective effects of PIO were abolished by EX-527, a SIRT1 inhibitor. These results highlight that the neuroprotective effect of PIO in SAE is mainly SIRT1-dependent.

The dual role of sirtuins in cancer: biological functions and implications

Sirtuins are pivotal in orchestrating numerous cellular pathways, critically influencing cell metabolism, DNA repair, aging processes, and oxidative stress. In recent years, the involvement of sirtuins in tumor biology has garnered substantial attention, with a growing body of evidence underscoring their regulatory roles in various aberrant cellular processes within tumor environments. This article delves into the sirtuin family and its biological functions, shedding light on their dual roles-either as promoters or inhibitors-in various cancers including oral, breast, hepatocellular, lung, and gastric cancers. It further explores potential anti-tumor agents targeting sirtuins, unraveling the complex interplay between sirtuins, miRNAs, and chemotherapeutic drugs. The dual roles of sirtuins in cancer biology reflect the complexity of targeting these enzymes but also highlight the immense therapeutic potential. These advancements hold significant promise for enhancing clinical outcomes, marking a pivotal step forward in the ongoing battle against cancer.

Cannabidiol Mitigates Lipopolysaccharide-Induced Pancreatic Pathology: A Promising Therapeutic Strategy

Background: Lipopolysaccharides (LPSs) are a component of certain types of bacteria and can induce an inflammatory response in the body, including in the pancreas. Cannabidiol (CBD), a nonpsychoactive compound found in cannabis, has been shown to have anti-inflammatory effects and may offer potential therapeutic benefits for conditions involving inflammation and damage. The aim of this study was to investigate any potential preventative effects of CBD on experimental LPS-induced pancreatic pathology in rats. Materials and Methods: Thirty-two rats were randomly divided into four groups as control, LPS (5 mg/kg, intraperitoneally [i.p.]), LPS+CBD, and CBD (5 mg/kg, i.p.) groups. Six hours after administering LPS, the rats were euthanized, and blood and pancreatic tissue samples were taken for biochemical, polymerase chain reaction (PCR), histopathological, and immunohistochemical examinations. Results: The results indicated that LPS decreased serum glucose levels and increased lipase levels. It also caused severe hyperemia, increased vacuolization in endocrine cells, edema, and slight inflammatory cell infiltrations at the histopathological examination. Insulin and amylin expressions decreased during immunohistochemical analyses. At the PCR analysis, Silent Information Regulator 2 homolog 1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha expressions decreased and tumor protein p53 expressions increased in the LPS group. CBD improved the biochemical, PCR, histopathological, and immunohistochemical results. Conclusions: The findings of the current investigation demonstrated that LPS damages both the endocrine and exocrine pancreas. However, CBD demonstrated marked ameliorative effects in the pancreas in LPS induced rat model pancreatitis.

Selective inhibition of SIRT2: A disputable therapeutic approach in cancer therapy

Sirtuin 2 (SIRT2) is involved in a wide range of processes, from transcription to metabolism to genome stability. Dysregulation of SIRT2 has been associated with the pathogenesis and progression of different diseases, such as cancer and neurodegenerative disorders. In this context, targeting SIRT2 activity by small molecule inhibitors is a promising therapeutic strategy for treating related conditions, particularly cancer. This review summarizes the regulatory roles and molecular mechanisms of SIRT2 in cancer and the attempts to evaluate potential antitumor activities of SIRT2-selective inhibitors by in vitro and in vivo testing, which are expected to deepen our understanding of the role of SIRT2 in tumorigenesis and progression and may offer important clues or inspiration ideas for developing SIRT2 inhibitors with excellent affinity and selectivity.

DNA methylation extends lifespan in the bumblebee Bombus terrestris

Epigenetic alterations are a primary hallmark of ageing. In mammals, age-related epigenetic changes alter gene expression profiles, disrupt cellular homeostasis and physiological functions and, therefore, promote ageing. It remains unclear whether ageing is also driven by epigenetic mechanisms in invertebrates. Here, we used a pharmacological hypomethylating agent (RG108) to evaluate the effects of DNA methylation (DNAme) on lifespan in an insect-the bumblebee Bombus terrestris. RG108 extended mean lifespan by 43% and induced the differential methylation of genes involved in hallmarks of ageing, including DNA damage repair and chromatin organization. Furthermore, the longevity gene sirt1 was overexpressed following the treatment. Functional experiments demonstrated that SIRT1 protein activity was positively associated with lifespan. Overall, our study indicates that epigenetic mechanisms are conserved regulators of lifespan in both vertebrates and invertebrates and provides new insights into how DNAme is involved in the ageing process in insects.

Evaluation of potential aging biomarkers in healthy individuals: telomerase, AGEs, GDF11/15, sirtuin 1, NAD+, NLRP3, DNA/RNA damage, and klotho

Aging is a natural process of gradual decrease in physical and mental capacity. Biological age (accumulation of changes and damage) and chronological age (years lived) may differ. Biological age reflects the risk of various types of disease and death from any cause. We selected potential biomarkers of aging - telomerase, AGEs, GDF11 and 15 (growth differentiation factor 11/15), sirtuin 1, NAD+ (nicotinamide adenine dinucleotide), inflammasome NLRP3, DNA/RNA damage, and klotho to investigate changes in their levels depending on age and sex. We included 169 healthy volunteers and divided them into groups according to age (under 35; 35-50; over 50) and sex (male, female; male and female under 35; 35-50, over 50). Markers were analyzed using commercial ELISA kits. We found differences in values depending on age and gender. GDF15 increased with age (under 30 and 35-50 p < 0.002; 35-50 and over 50; p < 0.001; under 35 and over 50; p < 0.001) as well as GDF11 (35-50 and over 50; p < 0.03; under 35 and over 50; p < 0.02), AGEs (under 30 and 35-50; p < 0.005), NLRP3 (under 35 over 50; p < 0.03), sirtuin 1 (35-50 and over 50; p < 0.0001; under 35 and over 50; p < 0.004). AGEs and GDF11 differed between males and females. Correlations were identified between individual markers, markers and age, and markers and sex. Markers that reflect the progression of biological aging vary with age (GDF15, GDF11, AGEs, NLRP3, sirtuin) and sex (AGEs, GDF11). Their levels could be used in clinical practice, determining biological age, risk of age-related diseases and death of all-causes, and initiating or contraindicating a therapy in the elderly based on the patient's health status.

Life-Cycle-Dependent Toxicities of Mono- and Bifunctional Alkylating Agents in the 3R-Compliant Model Organism C. elegans

Caenorhabditis elegans (C. elegans) is gaining recognition and importance as an organismic model for toxicity testing in line with the 3Rs principle (replace, reduce, refine). In this study, we explored the use of C. elegans to examine the toxicities of alkylating sulphur mustard analogues, specifically the monofunctional agent 2-chloroethyl-ethyl sulphide (CEES) and the bifunctional, crosslinking agent mechlorethamine (HN2). We exposed wild-type worms at different life cycle stages (from larvae L1 to adulthood day 10) to CEES or HN2 and scored their viability 24 h later. The susceptibility of C. elegans to CEES and HN2 paralleled that of human cells, with HN2 exhibiting higher toxicity than CEES, reflected in LC50 values in the high µM to low mM range. Importantly, the effects were dependent on the worms' developmental stage as well as organismic age: the highest susceptibility was observed in L1, whereas the lowest was observed in L4 worms. In adult worms, susceptibility to alkylating agents increased with advanced age, especially to HN2. To examine reproductive effects, L4 worms were exposed to CEES and HN2, and both the offspring and the percentage of unhatched eggs were assessed. Moreover, germline apoptosis was assessed by using ced-1p::GFP (MD701) worms. In contrast to concentrations that elicited low toxicities to L4 worms, CEES and HN2 were highly toxic to germline cells, manifesting as increased germline apoptosis as well as reduced offspring number and percentage of eggs hatched. Again, HN2 exhibited stronger effects than CEES. Compound specificity was also evident in toxicities to dopaminergic neurons-HN2 exposure affected expression of dopamine transporter DAT-1 (strain BY200) at lower concentrations than CEES, suggesting a higher neurotoxic effect. Mechanistically, nicotinamide adenine dinucleotide (NAD+) has been linked to mustard agent toxicities. Therefore, the NAD+-dependent system was investigated in the response to CEES and HN2 treatment. Overall NAD+ levels in worm extracts were revealed to be largely resistant to mustard exposure except for high concentrations, which lowered the NAD+ levels in L4 worms 24 h post-treatment. Interestingly, however, mutant worms lacking components of NAD+-dependent pathways involved in genome maintenance, namely pme-2, parg-2, and sirt-2.1 showed a higher and compound-specific susceptibility, indicating an active role of NAD+ in genotoxic stress response. In conclusion, the present results demonstrate that C. elegans represents an attractive model to study the toxicology of alkylating agents, which supports its use in mechanistic as well as intervention studies with major strength in the possibility to analyze toxicities at different life cycle stages.

NAD+: A key metabolic regulator with great therapeutic potential for myocardial infarction via Sirtuins family

Myocardial infarction (MI) is one of the complex phenotypes of coronary artery disease, which results from the interaction of multiple genetic and environmental factors. Nicotinamide Adenine Dinucleotide (NAD+) is an important cofactor regulating metabolic homeostasis and a rate-limiting substrate for sirtuin (SIRT) deacetylase. Numerous NAD+ studies have shown that it can be used as an anti-MI treatment. However, there have been few systematic reviews of the overall role of NAD+ in treating MI. MI, which has long been a global health problem, still lacks effective treatment till now, and the discovery of NAD+ provides a new perspective on its adjuvant treatment. This review summarizes the role of NAD+ signaling in SIRTs in alleviating MI.

Bioinformatic analysis of SIRT7 sequence and structure

Sirtuins are highly conserved proteins that perform very important functions in different cellular processes. Notably, SIRT7 is the least studied human sirtuin, but it is known to be involved in a wide variety of processes in both health and disease. In this way, SIRT7 activity-regulating molecules could be beneficial for the treatment of relevant diseases such as cardiovascular and bone diseases, where SIRT7 levels are reduced, or obesity and cancer, where they are increased. In this work, using bioinformatic methods, the sequence and structure of SIRT7 orthologs in a wide variety of organisms were analyzed. Thus, the catalytic domain was found to be quite conserved (83.23% identity) and key residues such as D118, Y119, R120, D170, H187, N189, C198, C225, C228, V273, G298, F239 and V237 were identified. Furthermore, a phylogenetic tree was constructed where SIRT7 orthologs from mammals, birds, reptiles, amphibians, fish, insects, and arachnids were found to cluster in different groups. Finally, predicted three-dimensional structures showed a classic structure of the central catalytic region of most sirtuins, while the flanking N- and C-terminal regions were unique to each phylogenetic group. All this helps to understand a little more how SIRT7 works and gives clues for the future design and development of small molecules that benefit human and animal health.Communicated by Ramaswamy H. Sarma.

The Impact of NAD Bioavailability on DNA Double-Strand Break Repair Capacity in Human Dermal Fibroblasts after Ionizing Radiation

Nicotinamide adenine dinucleotide (NAD) serves as a substrate for protein deacetylases sirtuins and poly(ADP-ribose) polymerases, which are involved in the regulation of DNA double-strand break (DSB) repair molecular machinery by various mechanisms. However, the impact of NAD bioavailability on DSB repair remains poorly characterized. Herein, using immunocytochemical analysis of γH2AX, a marker for DSB, we investigated the effect of the pharmacological modulation of NAD levels on DSB repair capacity in human dermal fibroblasts exposed to moderate doses of ionizing radiation (IR). We demonstrated that NAD boosting with nicotinamide riboside did not affect the efficiency of DSB elimination after the exposure of cells to IR at 1 Gy. Moreover, even after irradiation at 5 Gy, we did not observe any decrease in intracellular NAD content. We also showed that, when the NAD pool was almost completely depleted by inhibition of its biosynthesis from nicotinamide, cells were still able to eliminate IR-induced DSB, though the activation of ATM kinase, its colocalization with γH2AX and DSB repair capacity were reduced in comparison to cells with normal NAD levels. Our results suggest that NAD-dependent processes, such as protein deacetylation and ADP-ribosylation, are important but not indispensable for DSB repair induced by moderate doses of IR.

DNA Damage-Mediated Neurotoxicity in Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease around the world; however, its pathogenesis remains unclear so far. Recent advances have shown that DNA damage and repair deficiency play an important role in the pathophysiology of PD. There is growing evidence suggesting that DNA damage is involved in the propagation of cellular damage in PD, leading to neuropathology under different conditions. Here, we reviewed the current work on DNA damage repair in PD. First, we outlined the evidence and causes of DNA damage in PD. Second, we described the potential pathways by which DNA damage mediates neurotoxicity in PD and discussed the precise mechanisms that drive these processes by DNA damage. In addition, we looked ahead to the potential interventions targeting DNA damage and repair. Finally, based on the current status of research, key problems that need to be addressed in future research were proposed.

Improvement of oocyte quality through the SIRT signaling pathway

Background

Oocyte quality is one of the major deciding factors in female fertility competence.

Methods

PubMed database was searched for reviews by using the following keyword "oocyte quality" AND "Sirtuins". The methodological quality of each literature review was assessed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 statement.

Main Findings

Oxidative stress has been recognized as the mechanism attenuating oocyte quality. Increasing evidence from animal experiments and clinical studies has confirmed the protective roles of the sirtuin family in improving oocyte quality via an antioxidant effect.

Conclusion

The protective roles in the oocyte quality of the sirtuin family have been increasingly recognized.

SIRT1 in the cardiomyocyte counteracts doxorubicin-induced cardiotoxicity via regulating histone H2AX

AIMS

Cardiotoxicity by doxorubicin predicts worse prognosis of patients. Accumulation of damaged DNA has been implicated in doxorubicin-induced cardiotoxicity. SIRT1, an NAD+-dependent histone/protein deacetylase, protects cells by deacetylating target proteins. We investigated whether SIRT1 counteracts doxorubicin-induced cardiotoxicity by mediating Ser139 phosphorylation of histone H2AX, a critical signal of the DNA damage response.

METHODS AND RESULTS

Doxorubicin (5 mg/kg per week, x4) was administered to mice with intact SIRT1 (Sirt1f/f) and mice that lack SIRT1 activity in cardiomyocytes (Sirt1f/f;MHCcre/+). Reductions in left ventricular fractional shortening and ejection fraction by doxorubicin treatment were more severe in Sirt1f/f;MHCcre/+ than in Sirt1f/f. Myocardial expression level of type-B natriuretic peptide was 2.5-fold higher in Sirt1f/f;MHCcre/+ than in Sirt1f/f after doxorubicin treatment. Sirt1f/f;MHCcre/+ showed larger fibrotic areas and higher nitrotyrosine levels in the heart after doxorubicin treatment. Although doxorubicin-induced DNA damage evaluated by TUNEL staining was enhanced in Sirt1f/f;MHCcre/+, the myocardium from Sirt1f/f;MHCcre/+ showed blunted Ser139 phosphorylation of H2AX by doxorubicin treatment. In H9c2 cardiomyocytes, SIRT1 knockdown attenuated Ser139 phosphorylation of H2AX, increased DNA damage, and enhanced caspase-3 activation under doxorubicin treatment. Immunostaining revealed that acetylation level of H2AX at Lys5 was higher in hearts from Sirt1f/f;MHCcre/+. In H9c2 cells, acetyl-Lys5-H2AX level was increased by SIRT1 knockdown and reduced by SIRT1 overexpression. Ser139 phosphorylation in response to doxorubicin treatment was blunted in a mutant H2AX with substitution of Lys5 to Gln (K5Q) that mimics acetylated lysine compared with that in wild-type H2AX. Expression of K5Q-H2AX as well as S139A-H2AX, which cannot be phosphorylated at Ser139, augmented doxorubicin-induced caspase-3 activation. Treatment of mice with resveratrol, a SIRT1 activator, attenuated doxorubicin-induced cardiac dysfunction, which was associated with a reduction in acetyl-Lys5-H2AX level and a preserved phospho-Ser139-H2AX level.

CONCLUSION

These findings suggest that SIRT1 counteracts doxorubicin-induced cardiotoxicity by mediating H2AX phosphorylation through its deacetylation in cardiomyocytes.

Cell-Free Production and Regeneration of Cofactors

Cofactors, such as adenosine triphosphate, nicotinamide adenine dinucleotide, and coenzyme A, are involved in nearly 50% of enzymatic reactions and widely used in biocatalytic production of useful chemicals. Although commercial production of cofactors has been mostly dependent on extraction from microbial cells, this approach has a theoretical limitation to achieve a high-titer, high-yield production of cofactors owing to the tight regulation of cofactor biosynthesis in living cells. Besides the cofactor production, their regeneration is also a key challenge to enable continuous use of costly cofactors and improve the feasibility of enzymatic chemical manufacturing. Construction and implementation of enzyme cascades for cofactor biosynthesis and regeneration in a cell-free environment can be a promising approach to these challenges. In this chapter, we present the available tools for cell-free cofactor production and regeneration, the pros and cons, and how they can contribute to promote the industrial application of enzymes.

EhSir2c, a Sir2 homolog from the human pathogen Entamoeba histolytica interacts with a DNA repair protein, EhRAD23: Protein-protein interaction, docking and functional study

Chromosome segregation is a crucial phenomenon in the cell cycle and defects in genome segregation result in an abnormality in various cellular events. Unlike higher eukaryotes, chromosome segregation and a number of cell cycle events are unusual in the protozoan parasite Entamoeba histolytica (E. histolytica). Characterization of Sir2 proteins from E. histolytica may reveal its unique cellular events as they play role in diverse cellular processes including chromosome segregation. E. histolytica has four homologs of Sir2 proteins. EhSir2a and EhSir2b show sequence similarity towards eukaryotic Sir2 homologs, whereas EhSir2c and EhSir2d are more like prokaryotic sirtuins. Using both computational and experimental methods, EhSir2c has been characterized in this study. The three-dimensional structure of EhSir2c is predicted by homology modelling. The protein interactors of EhSir2c have been identified by yeast-two-hybrid screening against the cDNA library of E. histolytica. We have identified a novel interactor, EhRAD23 which is a homolog of UV excision repair protein RAD23. The interaction of EhSir2c and EhRAD23 was validated by pull-down assay. UV-C irradiation up-regulates the relative expression of EhSir2c, suggesting the necessity of EhSir2c in UV-induced stress in this parasite.Communicated by Ramaswamy H. Sarma.

Why Is Longevity Still a Scientific Mystery? Sirtuins-Past, Present and Future

The sirtuin system consists of seven highly conserved regulatory enzymes responsible for metabolism, antioxidant protection, and cell cycle regulation. The great interest in sirtuins is associated with the potential impact on life extension. This article summarizes the latest research on the activity of sirtuins and their role in the aging process. The effects of compounds that modulate the activity of sirtuins were discussed, and in numerous studies, their effectiveness was demonstrated. Attention was paid to the role of a caloric restriction and the risks associated with the influence of careless sirtuin modulation on the organism. It has been shown that low modulators' bioavailability/retention time is a crucial problem for optimal regulation of the studied pathways. Therefore, a detailed understanding of the modulator structure and potential reactivity with sirtuins in silico studies should precede in vitro and in vivo experiments. The latest achievements in nanobiotechnology make it possible to create promising molecules, but many of them remain in the sphere of plans and concepts. It seems that solving the mystery of longevity will have to wait for new scientific discoveries.

Fueling genome maintenance: On the versatile roles of NAD+ in preserving DNA integrity

NAD⁺ is a versatile biomolecule acting as a master regulator and substrate in various cellular processes, including redox regulation, metabolism, and various signaling pathways. In this article, we concisely and critically review the role of NAD⁺ in mechanisms promoting genome maintenance. Numerous NAD⁺-dependent reactions are involved in the preservation of genome stability, the cellular DNA damage response, and other pathways regulating nucleic acid metabolism, such as gene expression and cell proliferation pathways. Of note, NAD⁺ serves as a substrate to ADP-ribosyltransferases, sirtuins, and potentially also eukaryotic DNA ligases, all of which regulate various aspects of DNA integrity, damage repair, and gene expression. Finally, we critically analyze recent developments in the field as well as discuss challenges associated with therapeutic actions intended to raise NAD⁺ levels.

SIRT7 in the aging process

Aging is the result of the accumulation of a wide variety of molecular and cellular damage over time. This has been associated with a number of features termed hallmarks of aging, including genomic instability, loss of proteostasis, telomere attrition, dysregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and impaired intercellular communication. On the other hand, sirtuins are enzymes with an important role in aging and life extension, of which humans have seven paralogs (SIRT1 to SIRT7). SIRT7 is the least studied sirtuin to date, but it has been reported to serve important functions, such as promoting ribosomal RNA expression, aiding in DNA damage repair, and regulating chromatin compaction. Several studies have established a close relationship between SIRT7 and age-related processes, but knowledge in this area is still scarce. Therefore, the purpose of this review was to analyze how SIRT7 is associated with each of the hallmarks of aging, as well as with some of age-associated diseases, such as cardiovascular diseases, obesity, osteoporosis, and cancer.

Natural Bioactive Compounds Targeting Histone Deacetylases in Human Cancers: Recent Updates

Cancer is a complex pathology that causes a large number of deaths worldwide. Several risk factors are involved in tumor transformation, including epigenetic factors. These factors are a set of changes that do not affect the DNA sequence, while modifying the gene’s expression. Histone modification is an essential mark in maintaining cellular memory and, therefore, loss of this mark can lead to tumor transformation. As these epigenetic changes are reversible, the use of molecules that can restore the functions of the enzymes responsible for the changes is therapeutically necessary. Natural molecules, mainly those isolated from medicinal plants, have demonstrated significant inhibitory properties against enzymes related to histone modifications, particularly histone deacetylases (HDACs). Flavonoids, terpenoids, phenolic acids, and alkaloids exert significant inhibitory effects against HDAC and exhibit promising epi-drug properties. This suggests that epi-drugs against HDAC could prevent and treat various human cancers. Accordingly, the present study aimed to evaluate the pharmacodynamic action of different natural compounds extracted from medicinal plants against the enzymatic activity of HDAC.

Role of the Synergistic Interactions of Environmental Pollutants in the Development of Cancer

There is a growing awareness that the large number of environmental pollutants we are exposed to on a daily basis are causing major health problems. Compared to traditional studies that focus on individual pollutants, there are relatively few studies on how pollutants mixtures interact. Several studies have reported a relationship between environmental pollutants and the development of cancer, even when pollutant levels are below toxicity reference values. The possibility of synergistic interactions between different pollutants could explain how even low concentrations can cause major health problems. These intricate that molecular interactions can occur through a wide variety of mechanisms, and our understanding of the physiological effects of mixtures is still limited. The purpose of this paper is to discuss recent reports that address possible synergistic interactions between different types of environmental pollutants that could promote cancer development. Our literature studies suggest that key biological pathways are frequently implicated in such processes. These include increased production of reactive oxygen species, activation by cytochrome P450, and aryl hydrocarbon receptor signaling, among others. We discuss the need to understand individual pathological vulnerability not only in relation to basic genetics and gene expression, but also in terms of measurable exposure to contaminants. We also mention the need for significant improvements in future studies using a multitude of disciplines, such as the development of high-throughput study models, better tools for quantifying pollutants in cancer patients, innovative pharmacological and toxicological studies, and high-efficiency computer analysis, which allow us to analyze the molecular mechanisms of mixtures.

Ferulic acid and berberine, via Sirt1 and AMPK, may act as cell cleansing promoters of healthy longevity

Ferulic acid, a bacterial metabolite of anthocyanins, seems likely to be a primary mediator of the health benefits associated with anthocyanin-rich diets, and has long been employed in Chinese cardiovascular medicine. In rodent studies, it has exerted wide-ranging antioxidant and anti-inflammatory effects, the molecular basis of which remains rather obscure. However, recent studies indicate that physiologically relevant concentrations of ferulic acid can boost expression of Sirt1 at mRNA and protein levels in a range of tissues. Sirt1, a class III deacetylase, functions to detect a paucity of oxidisable substrate, and in response works in various ways to promote cellular survival and healthful longevity. Sirt1 promotes ‘cell cleansing’ and cell survival by boosting autophagy, mitophagy, mitochondrial biogenesis, phase 2 induction of antioxidant enzymes via Nrf2, and DNA repair—while inhibiting NF-kB-driven inflammation, apoptosis, and cellular senescence, and boosting endothelial expression of the protective transcription factor kruppel-like factor 2. A deficit of the latter appears to mediate the endothelial toxicity of the SARS-CoV-2 spike protein. Ferulic acid also enhances the activation of AMP-activated kinase (AMPK) by increasing expression and activity of its activating kinase LKB1—whereas AMPK in turn amplifies Sirt1 activity by promoting induction of nicotinamide phosphoribosyltranferase, rate-limiting for generation of Sirt1’s obligate substrate NAD+. Curiously, AMPK acts by independent mechanisms to potentiate many of the effects mediated by Sirt1. Hence, it is proposed that ferulic acid may exert complementary or synergistic health-promoting effects when used in conjunction with clinically useful AMPK activators, such as the nutraceutical berberine. Additional nutraceuticals which might have potential for amplifying certain protective effects of ferulic acid/berberine are also discussed.

Coenzyme Q10 deficiency can be expected to compromise Sirt1 activity

For reasons that remain unclear, endogenous synthesis and tissue levels of coenzyme Q10 (CoQ10) tend to decline with increasing age in at least some tissues. When CoQ10 levels are sufficiently low, this compromises the efficiency of the mitochondrial electron transport chain, such that production of superoxide by site 2 increases and the rate of adenosine triphosphate production declines. Moreover, CoQ10 deficiency can be expected to decrease activities of Sirt1 and Sirt3 deacetylases, believed to be key determinants of health span. Reduction of the cytoplasmic and mitochondrial NAD⁺/NADH ratio consequent to CoQ10 deficit can be expected to decrease the activity of these deacetylases by lessening availability of their obligate substrate NAD⁺. The increased oxidant production induced by CoQ10 deficiency can decrease the stability of Sirt1 protein by complementary mechanisms. And CoQ10 deficiency has also been found to lower mRNA expression of Sirt1. An analysis of the roles of Sirt1/Sirt3 in modulation of cellular function helps to rationalise clinical benefits of CoQ10 supplementation reported in heart failure, hypertension, non-alcoholic fatty liver disease, metabolic syndrome and periodontal disease. Hence, correction of CoQ10 deficiency joins a growing list of measures that have potential for amplifying health protective Sirt1/Sirt3 activities.

G protein-coupled receptors that influence lifespan of human and animal models

Humanity has always sought to live longer and for this, multiple strategies have been tried with varying results. In this sense, G protein-coupled receptors (GPCRs) may be a good option to try to prolong our life while maintaining good health since they have a substantial participation in a wide variety of processes of human pathophysiology and are one of the main therapeutic targets. In this way, we present the analysis of a series of GPCRs whose activity has been shown to affect the lifespan of animal and human models, and in which we put a special interest in describing the molecular mechanisms involved. Our compilation of data revealed that the mechanisms most involved in the role of GPCRs in lifespan are those that mimic dietary restriction, those related to insulin signaling and the AMPK and TOR pathways, and those that alter oxidative homeostasis and severe and/or chronic inflammation. We also discuss the possibility of using agonist or antagonist drugs, depending on the beneficial or harmful effects of each GPCR, in order to prolong people's lifespan and healthspan.

Overexpression of RNA-binding bacterial chaperones in rice leads to stay-green phenotype, improved yield and tolerance to salt and drought stresses

Genes encoding bacterial cold shock proteins A (CspA, 213 bp) and B (CspB, 216 bp) were isolated from Escherichia coli strain K12, which showed 100% homology with gene sequences isolated from other bacterial species. In silico domain, analysis showed eukaryotic conserved cold shock domain (CSD) and ribonuclease-binding domain (RBD) indicating that they bind to RNA and are involved in temperature stress tolerance. Overexpression of these two genes in E. coli resulted in higher growth in presence of 200 mM NaCl and 300 mM mannitol. Western blot confirmed the translational products of the two genes. Seedlings of indica rice were transformed with Agrobacterium tumefaciens containing pCAMBIA1301 CspA and CspB genes. Transgene integration was confirmed by β-glucuronidase (GUS) histochemical assay, polymerase chain reaction (PCR) amplification, and gene copy number by Southern blotting. Chlorophyll, proline, Na⁺ , and K⁺ contents were higher in transgenics exposed to 150 mM NaCl and drought (imposed by withholding water) stresses during floral initiation stage. Catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (GPX) activities increased, while malondialdehyde (MDA) content was low in transgenics. Transgenics displayed increased root, shoot, and panicle lengths, root dry mass, and a distinct stay-green (SGR) phenotype. Higher transcript levels of CspA, CspB, SGR, chlorophyllase, isopentenyl adenine transferase 1 (IPT1), 9-cis-epoxycarotenoid dioxygenase (NCED), SOD, and sirtuin 1 (SIRT1) genes were observed in transgenics compared to wild type plants (WT) under multiple stresses. Present work indicates that bacterial chaperone proteins are capable of imparting SGR phenotype, salt and drought stress tolerance alongside grain improvement.

Targeted antioxidant delivery modulates mitochondrial functions, ameliorates oxidative stress and preserve sperm quality during cryopreservation

Mitochondria are vital organelles with a multifaceted role in cellular bioenergetics, biosynthesis, signaling and calcium homeostasis. During oxidative phosphorylation, sperm mitochondria generate reactive oxygen species (ROS) at physiological levels mediating signaling pathways essential for sperm fertilizing competence. Moreover, sperm subpopulation with active mitochondria is positively associated with sperm motility, chromatin and plasma membrane integrity, and normal morphology. However, the osmotic and thermal stress, and intracellular ice crystal formation generate excess ROS to cause mitochondrial dysfunction, potentiating cryoprotectant-induced calcium overload in the mitochondrial matrix. It further stimulates the opening of mitochondrial permeability transition pores (mPTP) to release pro-apoptotic factors from mitochondria and initiate apoptotic cascade, with a decrease in Mitochondrial Membrane Potential (MMP) and altered sperm functions. To improve the male reproductive potential, it is essential to address challenges in semen cryopreservation, precisely the deleterious effects of oxidative stress on sperm quality. During semen cryopreservation, the supplementation of extended semen with conventional antioxidants is extensively reported. However, the outcomes of supplementation to improve semen quality are inconclusive across different species, which is chiefly attributed to the unknown bioavailability of antioxidants at the primary site of ROS generation, i.e., mitochondria. Increasing evidence suggests that the targeted delivery of antioxidants to sperm mitochondria is superior in mitigating oxidative stress and improving semen freezability than conventional antioxidants. Therefore, the present review comprehensively describes mitochondrial-targeted antioxidants, their mechanism of action and effects of supplementation on improving semen cryopreservation efficiency in different species. Moreover, it also discusses the significance of active mitochondria in determining sperm fertilizing competence, cryopreservation-induced oxidative stress and mitochondrial dysfunction, and its implications on sperm fertility. The potential of mitochondrial-targeted antioxidants to modulate mitochondrial functions and improve semen quality has been reviewed extensively.

Sirtuin 1 in Endothelial Dysfunction and Cardiovascular Aging

Sirtuin 1 (SIRT1) is a histone deacetylase belonging to the family of Sirtuins, a class of nicotinamide adenine dinucleotide (NAD+)-dependent enzymes with multiple metabolic functions. SIRT1 localizes in the nucleus and cytoplasm, and is implicated in the regulation of cell survival in response to several stimuli, including metabolic ones. The expression of SIRT1 is associated with lifespan and is reduced with aging both in animal models and in humans, where the lack of SIRT1 is regarded as a potential mediator of age-related cardiovascular diseases. In this review, we will summarize the extensive evidence linking SIRT1 functional and quantitative defects to cellular senescence and aging, with particular regard to their role in determining endothelial dysfunction and consequent cardiovascular diseases. Ultimately, we outline the translational perspectives for this topic, in order to highlight the missing evidence and the future research steps.

Dietary Supplementation of Olive Mill Waste Water Polyphenols in Rabbits: Evaluation of the Potential Effects on Hepatic Apoptosis, Inflammation and Metabolism through RT-qPCR Approach

Agro-industrial processing for the production of food or non-food products generates a wide range of by-products and residues rich in bioactive compounds including polyphenols. The concentration of these by-products is sometimes higher than in the original raw material as in the case of olive mill waste water (OMWW), one of the main by-products of olive oil extraction. Polyphenols are secondary plant metabolites that regulate the expression of specific inflammatory genes, transcriptional factors and pro/anti-apoptotic molecules, thus modulating the signaling pathways essential for cell health and homeostasis. The liver plays a key role in regulating homeostasis by responding to dietary changes in order to maintain nutritional and physiological states. In this study a nutrigenomic approach was adopted, which focuses on the effects of diet-health-gene interactions and the modulation of cellular processes, in order to evaluate the expression of the genes (AGER, BAX, COX2, IL1B, PPARA, PPARG, SIRT1, TNFA) involved in these interactions in the livers of rabbits fed with a diet supplemented with OMWW (POL) or without supplements (control, CTR). The RT-qPCR analysis showed the down-regulation of SIRT1, TNFA, AGER, BAX and PPARA transcripts in the POL group compared to the CTR group. These results show that OMWW dietary supplementation prevents cell death and tissue deterioration in rabbits.

Factors Regulating the Activity of LINE1 Retrotransposons

LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer. Altered activity of L1 retrotransposons for some pathologies is associated with epigenetic changes and defects in the genes involved in their repression. This review discusses the molecular genetic mechanisms of the retrotransposition and regulation of the activity of L1 elements. The contribution of various factors controlling the expression and distribution of L1 elements in the genome occurs at all stages of the retrotransposition. The regulation of L1 elements at the transcriptional, post-transcriptional and integration into the genome stages is described in detail. Finally, this review also focuses on the evolutionary aspects of L1 accumulation and their interplay with the host regulation system.

Characterization of Histone Deacetylase Mechanisms in Cancer Development

Over decades of studies, accumulating evidence has suggested that epigenetic dysregulation is a hallmark of tumours. Post-translational modifications of histones are involved in tumour pathogenesis and development mainly by influencing a broad range of physiological processes. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are pivotal epigenetic modulators that regulate dynamic processes in the acetylation of histones at lysine residues, thereby influencing transcription of oncogenes and tumour suppressor genes. Moreover, HDACs mediate the deacetylation process of many nonhistone proteins and thus orchestrate a host of pathological processes, such as tumour pathogenesis. In this review, we elucidate the functions of HDACs in cancer.

SIRT2 promotes murine melanoma progression through natural killer cell inhibition

SIRT2, an NAD+-dependent histone deacetylase, has been shown to play a pivotal role in various physiological processes, however, its role in cancer is currently controversial. In recent years, SIRT2 has been described as both a tumor suppressor and oncogene with divergent expression and function in various malignancies. Using murine allograft melanoma models, our results suggest increased systemic expression of SIRT2 promotes tumor progression. In this study, SIRT2-overexpressing mice exhibited enhanced tumor growth and larger tumor volumes compared to their wild-type littermates. Mechanistically, systemic overexpression of SIRT2 reduces the number of tumor-infiltrating natural killer (NK) cells and suppresses NK cell function and proliferation within the tumor microenvironment (TME). Furthermore, despite the enhancing effect of NK cell depletion on tumor volume and growth rate in wild-type littermate mice, this effect was diminished in SIRT2-overexpressing mice. Lastly, pharmacological inhibition of SIRT2 increases NK cell tumor infiltration and suppresses allograft melanoma tumor growth. The findings of this study identify a dynamic functional interaction between systemic SIRT2 and NK cell activity, which controls melanoma tumor progression. Given the recent renewed interest in NK-cell-mediated immunotherapy response, SIRT2 could present a new opportunity to mediate immunotherapy response and resistance.

NAD+-mediated regulation of mammalian base excision repair

The enzymes of the base excision repair (BER) pathway form DNA lesion-dependent, transient complexes that vary in composition based on the type of DNA damage. These protein sub-complexes facilitate substrate/product handoff to ensure reaction completion so as to avoid accumulation of potentially toxic DNA repair intermediates. However, in the mammalian cell, additional signaling molecules are required to fine-tune the activity of the BER pathway enzymes and to facilitate chromatin/histone reorganization for access to the DNA lesion for repair. These signaling enzymes include nicotinamide adenine dinucleotide (NAD⁺) dependent poly(ADP-ribose) polymerases (PARP1, PARP2) and class III deacetylases (SIRT1, SIRT6) that comprise a key PARP-NAD-SIRT axis to facilitate the regulation and coordination of BER in the mammalian cell. Here, we briefly describe the key nodes in the BER pathway that are regulated by this axis and highlight the cellular and organismal variation in NAD⁺ bioavailability that can impact BER signaling potential. We discuss how cellular NAD⁺ is required for BER to maintain genome stability and to mount a robust cellular response to DNA damage. Finally, we consider the dependence of BER on the PARP-NAD-SIRT axis for BER protein complex assembly.

mTOR as a senescence manipulation target: A forked road

Cellular senescence, cancer and aging are highly interconnected. Among many important molecular machines that lie at the intersection of this triad, the mechanistic (formerly mammalian) target of rapamycin (mTOR) is a central regulator of cell metabolism, proliferation, and survival. The mTOR signaling cascade is essential to maintain cellular homeostasis in normal biological processes or in response to stress, and its dysregulation is implicated in the progression of many disorders, including age-associated diseases. Accordingly, the pharmacological implications of mTOR inhibition using rapamycin or others rapalogs span the treatment of various human diseases from immune disorders to cancer. Importantly, rapamycin is one of the only known pan-species drugs that can extend lifespan. The molecular and cellular mechanisms explaining the phenotypic consequences of mTOR are vast and heavily studied. In this review, we will focus on the potential role of mTOR in the context of cellular senescence, a tumor suppressor mechanism and a pillar of aging. We will explore the link between senescence, autophagy and mTOR and discuss the opportunities to exploit senescence-associated mTOR functions to manipulate senescence phenotypes in age-associated diseases and cancer treatment.

Sirtuin GdSir2.4 participates in the regulation of rRNA transcription in the Giardia duodenalis parasite

Giardia duodenalis is a parasite of great medical interest due to the number of infections it causes worldwide each year. Although research on epigenetic mechanisms in this protist has only begun recently, epigenetic regulation has already been shown to have important roles in encystation, antigenic variation, and resistance to antibiotics in Giardia. In this work, we show that a Giardia ortholog of Sir2, GdSir2.4, is involved in the silencing of rRNA expression. Our results demonstrate that GdSir2.4 localizes to the nucleolus, and its binding to the intergenic spacer region of the rDNA is associated with the deacetylation of the chromatin in this region. Given the importance of the regulation of rRNA expression to maintain adequate levels of ribosomes and genomic stability within the cells, GdSir2.4 can be considered a target to create new therapeutic agents against this parasite.

Human SIRT2 and SIRT3 deacetylases function in DNA homologous recombinational repair

SIRT2 and SIRT3 protein deacetylases maintain genome integrity and stability. However, their mechanisms for maintaining the genome remain unclear. To examine the roles of SIRT2 and SIRT3 in DSB repair, I-SceI-based GFP reporter assays for HR, single-strand annealing (SSA) and nonhomologous end joining (NHEJ) repair were performed under SIRT2- or SIRT3-depleted conditions. SIRT2 or SIRT3 depletion inhibited HR repair equally to RAD52 depletion, but did not affect SSA and NHEJ repairs. SIRT2 or SIRT3 depletion disturbed the recruitment of RAD51 to DSB sites, an essential step for RAD51-dependent HR repair, but not directly through RAD52 deacetylation. SIRT2 or SIRT3 depletion decreased the colocalization of γH2AX foci with RPA1, and thus, they might be involved in initiating DSB end resection for the recruitment of RAD51 to DSB sites at an early step in HR repair. These results show the novel underlying mechanism of the SIRT2 and SIRT3 functions in HR for genome stability.

Impairment of sirtuin 1-mediated DNA repair is involved in bisphenol A-induced aggravation of macrophage inflammation and atherosclerosis

Bisphenol A (BPA), an environmental pollutant, has received considerable attention worldwide for its hazardous effects of promoting atherosclerosis and increasing the risk of cardiovascular diseases (CVDs). However, the mechanisms involved are unclear. We aimed to investigate the mechanisms underlying BPA-aggravated atherosclerosis and potential preventive treatments. Four-week-old male Ldlr^-/- C57BL/6 mice were administered 250 μg/L BPA via drinking water for 30 weeks with or without a Western diet and/or resveratrol (RESV) for 12 weeks. Chronic BPA exposure significantly aggravated atherosclerosis, enhanced the production of inflammatory cytokines but not lipid levels, promoted macrophage infiltration into plaque areas. Moreover, peritoneal macrophages isolated from BPA-exposed mice exhibited a more pro-inflammatory phenotype in response to cholesterol crystal treatment than those from control mice. The comet assay revealed that the DNA repair capacity of BPA-exposed macrophages was impaired, and western blotting showed that sirtuin 1 and Nijmegen breakage syndrome 1 (NBS1) expression was reduced. However, restoring sirtuin 1 by RESV administration significantly blocked the BPA-induced decrease in NBS1 and subsequently attenuated the BPA-induced impairment of DNA repair and apoptosis, as indicated by phosphorylated H2AX expression and staining and PARP expression. Moreover, RESV administration significantly ameliorated BPA-aggravated NOD-like receptor pyrin domain 3 and caspase 1 activation and interleukin-1β production, which were abolished by NBS1 knockdown. Furthermore, RESV administration prevented BPA-induced aggravation of atherosclerosis. Our findings indicate that impairment of sirtuin 1-mediated DNA repair is involved in BPA-induced aggravation of macrophage inflammation and atherosclerosis and that RESV might be a promising preventive and therapeutic agent for BPA-related CVDs.

Hit-to-lead optimization on aryloxybenzamide derivative virtual screening hit against SIRT

Sirtuins (SIRTs) are a class of nicotinamide adenine dinucleotide (NAD⁺)-dependent protein histone deacetylases (HDACs) that are evolutionarily conserved from bacteria to mammals. This group of enzymes catalyses the reversible deacetylation of lysine residues in the histones or non-histone substrates using NAD⁺ as a cosubstrate. Numerous studies have demonstrated that the aberrant enzymatic activity of SIRTs has been linked to various diseases like diabetes, cancer, and neurodegenerative disorders. Previously, we performed a pharmacophore-based virtual screening campaign and an aryloxybenzamide derivative (1) displaying SIRT1/2 inhibitory effect was identified as a hit compound. In the current study, the hit-to-lead optimization on the hit compound was explored in order to improve the SIRT binding and inhibition. Fourteen compounds, ten of which were new, have been synthesized and subjected to in vitro biological evaluation for their inhibitory activity against SIRT1-3. By the structural modifications performed, a significant improvement was observed in selective SIRT1 inhibition for ST01, ST02, and ST11 compared to that of the hit compound. The highest SIRT2 inhibitory activity was observed for ST14, which was designed according to compatibility with pharmacophore model developed for SIRT2 inhibitors and thus, providing the interactions required with key residues in SIRT2 active site. Furthermore, ST01, ST02, ST11, and ST14 were subjected to in vitro cytotoxicity assay against MCF-7 human breast cancer cell line to determine the influence of the improvement in SIRT1/2 inhibition along with the structural modifications on the cytotoxic properties of the compounds. The cytotoxicity of the compounds was found to be correlated with their SIRT inhibitory profiles indicating the effects of SIRT1/2 inhibition on cancer cell viability. Overall, this study provides structural insights for further inhibitor improvement.

Development of Second Generation Activity-Based Chemical Probes for Sirtuins

NAD⁺ (nicotinamide adenine dinucleotide)-dependent protein deacylases, namely, the sirtuins, are important cell adaptor proteins that alter cell physiology in response to low calorie conditions. They are thought to mediate the beneficial effects of calorie restriction to extend longevity and improve health profiles. Novel chemical probes are highly desired for a better understanding of sirtuin’s roles in various biological processes. We developed a group of remarkably simple activity-based chemical probes for the investigation of active sirtuin content in complex native proteomes. These probes harbor a thioacyllysine warhead, a diazirine photoaffinity tag, as well as a terminal alkyne bioorthogonal functional group. Compared to their benzophenone-containing counterparts, these new probes demonstrated improved labeling efficiency and sensitivity, shortened irradiation time, and reduced background signal. They were applied to the labeling of individual recombinant proteins, protein mixtures, and whole cell lysate. These cell permeable small molecule probes also enabled the cellular imaging of sirtuin activity change. Taken together, our study provides new chemical biology tools and future drug discovery strategies for perturbing the activity of different sirtuin isoforms.

Sirtuins and Their Implications in Neurodegenerative Diseases from a Drug Discovery Perspective

Sirtuins are class III histone deacetylase (HDAC) enzymes that target both histone and non-histone substrates. They are linked to different brain functions and the regulation of different isoforms of these enzymes is touted to be an emerging therapy for the treatment of neurodegenerative diseases (NDs), including Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). The level of sirtuins affects brain health as many sirtuin-regulated pathways are responsible for the progression of NDs. Certain sirtuins are also implicated in aging, which is a risk factor for many NDs. In addition to SIRT1-3, it has been suggested that the less studied sirtuins (SIRT4-7) also play critical roles in brain health. This review delineates the role of each sirtuin isoform in NDs from a disease centric perspective and provides an up-to-date overview of sirtuin modulators and their potential use as therapeutics in these diseases. Furthermore, the future perspectives for sirtuin modulator development and their therapeutic application in neurodegeneration are outlined in detail, hence providing a research direction for future studies.

Natural Compounds That Target DNA Repair Pathways and Their Therapeutic Potential to Counteract Cancer Cells

Resistance to current cancer treatments is an important problem that arises through various mechanisms, but one that stands out involves an overexpression of several factors associated with DNA repair. To counteract this type of resistance, different drugs have been developed to affect one or more DNA repair pathways, therefore, to test different compounds of natural origin that have been shown to induce cell death in cancer cells is paramount. Since natural compounds target components of the DNA repair pathways, they have been shown to promote cancer cells to be resensitized to current treatments. For this and other reasons, natural compounds have aroused great curiosity and several research projects are being developed around the world to establish combined treatments between them and radio or chemotherapy. In this work, we summarize the effects of different natural compounds on the DNA repair mechanisms of cancer cells and emphasize their possible application to re-sensitize these cells.

NAD+ metabolism: pathophysiologic mechanisms and therapeutic potential

Nicotinamide adenine dinucleotide (NAD+) and its metabolites function as critical regulators to maintain physiologic processes, enabling the plastic cells to adapt to environmental changes including nutrient perturbation, genotoxic factors, circadian disorder, infection, inflammation and xenobiotics. These effects are mainly achieved by the driving effect of NAD+ on metabolic pathways as enzyme cofactors transferring hydrogen in oxidation-reduction reactions. Besides, multiple NAD+-dependent enzymes are involved in physiology either by post-synthesis chemical modification of DNA, RNA and proteins, or releasing second messenger cyclic ADP-ribose (cADPR) and NAADP+. Prolonged disequilibrium of NAD+ metabolism disturbs the physiological functions, resulting in diseases including metabolic diseases, cancer, aging and neurodegeneration disorder. In this review, we summarize recent advances in our understanding of the molecular mechanisms of NAD+-regulated physiological responses to stresses, the contribution of NAD+ deficiency to various diseases via manipulating cellular communication networks and the potential new avenues for therapeutic intervention.

The Role of Resveratrol in Mammalian Reproduction

Resveratrol is one of the most investigated natural polyphenolic compounds and is contained in more than 70 types of plants and in red wine. The widespread interest in this polyphenol derives from its antioxidant, anti-inflammatory and anti-aging properties. Several studies have established that resveratrol regulates animal reproduction. However, the mechanisms of action and the potential therapeutic effects are still unclear. This review aims to clarify the role of resveratrol in male and female reproductive functions, with a focus on animals of veterinary interest. In females, resveratrol has been considered as a phytoestrogen due to its capacity to modulate ovarian function and steroidogenesis via sirtuins, SIRT1 in particular. Resveratrol has also been used to enhance aged oocyte quality and as a gametes cryo-protectant with mainly antioxidant and anti-apoptotic effects. In males, resveratrol enhances testes function and spermatogenesis through activation of the AMPK pathway. Furthermore, resveratrol has been supplemented to semen extenders, improving the preservation of sperm quality. In conclusion, resveratrol has potentially beneficial effects for ameliorating ovarian and testes function.

SIRT1/SIRT3 Modulates Redox Homeostasis during Ischemia/Reperfusion in the Aging Heart

Ischemia/reperfusion (I/R) injury is the central cause of global death in cardiovascular diseases, which is characterized by disorders such as angina, stroke, and peripheral vascular disease, finally causing severe debilitating diseases and death. The increased rates of morbidity and mortality caused by I/R are parallel with aging. Aging-associated cardiac physiological structural and functional deterioration were found to contribute to abnormal reactive oxygen species (ROS) production during I/R stress. Disturbed redox homeostasis could further trigger the related signaling pathways that lead to cardiac irreversible damages with mitochondria dysfunction and cell death. It is notable that sirtuin proteins are impaired in aged hearts and are critical to maintaining redox homeostasis via regulating substrate metabolism and inflammation and thus preserving cardiac function under stress. This review discussed the cellular and functional alterations upon I/R especially in aging hearts. We propose that mitochondria are the primary source of reactive oxygen species (ROS) that contribute to I/R injury in aged hearts. Then, we highlight the cardiomyocyte protection of the age-related proteins Sirtuin1 (SIRT1) and Sirtuin1 (SIRT3) in response to I/R injury, and we discuss their modulation of cardiac metabolism and the inflammatory reaction that is involved in ROS formation.

Pioglitazone alleviates cisplatin nephrotoxicity by suppressing mitochondria-mediated apoptosis via SIRT1/p53 signalling

Pioglitazone (PIO) attenuates cisplatin nephrotoxicity whereas the underlying mechanism remains unknown. Apoptosis is associated with mitochondrial dysfunction and SIRT1 activation can decrease cell apoptosis in cisplatin nephrotoxicity. Therefore, we explored whether the protective effect of PIO in cisplatin nephrotoxicity is achieved by suppressing mitochondria‐mediated apoptosis through SIRT1/p53 signalling regulation. Cell viability, apoptosis, survival rate, renal pathology and function were examined. Moreover, we also analysed the expression of SIRT1, Acetyl‐p53, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), mitochondrial permeability transition pore (mPTP) opening, adenosine triphosphate (ATP) and apoptosis‐related protein in vivo and in vitro. Pioglitazone treatment significantly increased cell viability, promoted SIRT1‐p53 interaction, upregulated Bcl‐2 expression, activated SIRT1 and elevated mitochondrial ATP synthesis after cisplatin treatment. However, PIO decreased the generation of ROS, opening of mPTP, dissipation of MMP and translocation of cytochrome c after cisplatin treatment. Pioglitazone also reduced the activation of caspase‐3 and caspase‐9, lowered the ratio of Bax/Bcl‐2, attenuated kidney pathological damage and dysfunction, down‐regulated the expression of Acetyl‐p53, PUMA‐α and Bax and abated cell apoptosis after cisplatin treatment. The SIRT1 inhibitor, EX527, clearly reversed the protective effects of PIO. These results implied PIO attenuated cisplatin nephrotoxicity by suppressing mitochondria‐mediated apoptosis through regulating SIRT1/p53 signalling.

Review: The plant sirtuins

The sirtuin family of intracellular enzymes are able to catalyze a unique β-nicotinamide adenine dinucleotide (β-NAD⁺)-dependent N^ε-acyl-lysine deacylation reaction on histone and non-histone protein substrates. Since 2000, the sirtuin family members have been identified in both prokaryotes and eukaryotes; tremendous accomplishments have also been achieved on the mechanistic and functional (pharmacological) understanding of the sirtuin-catalyzed deacylation reaction. Among the eukaryotic organisms, past research has been focused more on the yeast and mammalian sirtuins than on the plant sirtuins, however, the very presence of sirtuins in various plant species and the functional studies on plant sirtuins published thus far attest to the importance of this particular subfamily of eukaryotic sirtuins in regulating the growth and development of plants and their responses to biotic and abiotic stresses. In this review, an integrated and updated account will be presented on the biochemical, cellular, and functional profiles of all the plant sirtuins identified thus far. It is hoped that this article will also set a stage for expanded efforts in the identification, characterization, and functional interrogation of plant sirtuins; and the development and exploration of their chemical modulators (activators and inhibitors) in plant research and agriculture.

NAD+ in sulfur mustard toxicity

Sulfur mustard (SM) is a toxicant and chemical warfare agent with strong vesicant properties. The mechanisms behind SM-induced toxicity are not fully understood and no antidote or effective therapy against SM exists. Both, the risk of SM release in asymmetric conflicts or terrorist attacks and the usage of SM-derived nitrogen mustards as cancer chemotherapeutics, render the mechanisms of mustard-induced toxicity a highly relevant research subject. Herein, we review a central role of the abundant cellular molecule nicotinamide adenine dinucleotide (NAD⁺) in molecular mechanisms underlying SM toxicity. We also discuss the potential beneficial effects of NAD⁺ precursors in counteracting SM-induced damage.

Noninvasive quantification of SIRT1 expression-activity and pharmacologic inhibition in a rat model of intracerebral glioma using 2-[18F]BzAHA PET/CT/MRI

Background

Several studies demonstrated that glioblastoma multiforme progression and recurrence is linked to epigenetic regulatory mechanisms. Sirtuin 1 (SIRT1) plays an important role in glioma progression, invasion, and treatment response and is a potential therapeutic target. The aim of this study is to test the feasibility of 2-[¹⁸F]BzAHA for quantitative imaging of SIRT1 expression–activity and monitoring pharmacologic inhibition in a rat model of intracerebral glioma.

Methods

Sprague Dawley rats bearing 9L (N = 12) intracerebral gliomas were injected with 2-[¹⁸F]BzAHA (300–500 µCi/animal i.v.) and dynamic positron-emission tomography (PET) imaging was performed for 60 min. Then, SIRT1 expression in 9L tumors (N = 6) was studied by immunofluorescence microscopy (IF). Two days later, rats with 9L gliomas were treated either with SIRT1 specific inhibitor EX-527 (5 mg/kg, i.p.; N = 3) or with histone deacetylases class IIa specific inhibitor MC1568 (30 mg/kg, i.p.; N = 3) and 30 min later were injected i.v. with 2-[¹⁸F]BzAHA. PET-computerized tomography-magnetic resonance (PET/CT/MR) images acquired after EX-527 and MC1568 treatments were co-registered with baseline images.

Results

Standard uptake values (SUVs) of 2-[¹⁸F]BzAHA in 9L tumors measured at 20 min post-radiotracer administration were 1.11 ± 0.058 and had a tumor-to-brainstem SUV ratio of 2.73 ± 0.141. IF of 9L gliomas revealed heterogeneous upregulation of SIRT1, especially in hypoxic and peri-necrotic regions. Significant reduction in 2-[¹⁸F]BzAHA SUV and distribution volume in 9L tumors was observed after administration of EX-527, but not MC1568.

Conclusions

PET/CT/MRI with 2-[¹⁸F]BzAHA can facilitate studies to elucidate the roles of SIRT1 in gliomagenesis and progression, as well as to optimize therapeutic doses of novel SIRT1 inhibitors.