Sirtuin deacetylases in neurodegenerative diseases of aging

SENP1-Sirt3 axis promotes cholesterol biosynthesis in tumor-associated macrophages to suppress anti-tumor immunity

Tumor-associated macrophages (TAMs) play a multifaceted role in the tumor microenvironment, notably by suppressing antitumor immune responses through immunosuppressive mechanisms. TAMs secrete a range of cytokines that simultaneously inhibit T cell function and foster a microenvironment that supports tumor progression and dissemination. Our study has delved into the intricate relationship between the metabolic reprogramming of TAMs and their impact on tumor progression. Mitochondrial metabolic reprogramming mediated by the SENP1-Sirt3 axis altered the dynamics and activity of tumor-infiltrating immune cells, including macrophages and CD8+ T lymphocytes. SENP1-Sirt3 axis increases the level of acetyl-CoA in macrophage mitochondria, which in turn promotes cholesterol biosynthesis in macrophages. The upregulation of cholesterol synthesis is a key factor in driving macrophage polarization towards the immunosuppressive M2 phenotype, which in turn supports tumor development. Notably, increased cholesterol levels contributed to a reduction in the number and activity of CD8+ T cells, which are essential for mounting an effective immune response against cancer cells. These findings suggest that targeting cholesterol biosynthesis in TAMs may be a promising strategy for cancer immunotherapy. SIGNIFICANCE: Activation of the SENP1-Sirt3 axis initiates mitochondrial metabolic reprogramming in tumor-associated macrophages (TAMs), leading to enhanced cholesterol and acetyl-CoA production, M2 macrophage polarization, and impaired CD8+ T cell anti-tumor responses.

The advances in acetylation modification in senescence and aging-related diseases

Aging is a process in which organisms or cells undergo a decline in their functions. Epigenetic modification changes have been recognized as a senescence hallmark in both natural aging and stimulation-induced senescence. An acetylation modification is a dynamic process, which plays a crucial role in the senescence process through DNA stability, metabolism, and signaling pathways. We summarized the role and regulatory pathways of acetylation modifications in senescence. Various cell fate-determining proteins regulate multiple cellular processes through acetylation modifications. These processes interact and coordinate with each other, forming an integrated regulatory network framework that collectively drives cellular senescence via multiple systemic mechanisms. Based on these findings, we proposed the "acetylation-network regulation-cellular senescence" model, to elaborate how acetylation contributes to senescence. We believe this insight could provide new directions and intervention strategies for senescence and aging-related diseases.

MCC950 mitigates SIRT3-NLRP3-driven inflammation and rescues post-stroke neurogenesis

Sustained activation of the SIRT3-NLRP3 inflammasome has been associated with worse outcomes after ischemic stroke. The objective of this study was to examine the potential mechanism by which the SIRT3-NLRP3 inflammasome affects neural stem and progenitor cells (NSPCs) after transient middle cerebral artery occlusion (tMCAO) in rats. Following tMCAO, significantly elevated levels of NLRP3, ASC, cleaved caspase 1, IL-1β, and IL-18 were observed in the ischemic subventricular zone. Moreover, tMCAO increased NLRP3 expression while decreasing SIRT3 levels, suggesting a connection between these two processes. Furthermore, we discovered that inflammation induced by the NLRP3 inflammasome impaired post-stroke hippocampal and subventricular neurogenesis, while nestin (a marker for NSPCs) and Sox2 (a marker for stem cell pluripotency) were downregulated after tMCAO. However, systemic administration of MCC950 reduced inflammatory signaling and effectively restored neurogenesis. Overall, our results suggest that protecting NSPCs and neurogenesis in the ischemically damaged brain by mitigating the impact of the SIRT3-NLRP3 inflammasome may be a feasible treatment strategy for ischemic stroke.

Neurodegeneration: Effects of calorie restriction on the brain sirtuin protein levels

BACKGROUND

Calorie restriction (CR) is suggested to activate protective mechanisms in neurodegenerative diseases (NDDs). Despite existing literature highlighting the protective role of Sirtuin (SIRT) proteins against age-related neurodegeneration (ND), no study has explored the total levels of SIRT 1, 3, and 6 proteins simultaneously in brain homogenates by ELISA following intermittent calorie restriction. Applying CR protocols in mice to induce stress, we aimed to determine whether ND would be more pronounced with ad libitum (AL) or with CR.

METHODS

Mice were randomly assigned to ad libitum (AL), Chronic CR (CCR), or Intermittent CR (ICR) groups at 10 weeks of baseline age (BL). SIRT 1, 3, and 6 protein levels were measured in the homogenized whole-brain supernatants of 49/50 weeks old mice by the ELISA method. Neuronal morphology was evaluated by the cresyl violet on the hippocampus. Neurodegeneration (ND) was assessed by the fluoro-jade and ImageJ was used for quantifications.

RESULTS

In the ICR group, SIRT1 levels were elevated compared to both the AL and BL groups. Similarly, the CCR group exhibited higher SIRT1 values compared to the AL and BL groups. While SIRT3 levels were higher in both the ICR and CCR groups compared to the AL and BL groups, this disparity did not reach statistical significance. SIRT6 levels were also higher in the ICR group compared to both the BL and AL groups, with the CCR group showing higher values compared to the BL and AL groups as well. Image quantification demonstrated significant neurodegeneration in the AL group compared to the CCR and ICR group, with no observed alterations in nerve cell morphology and number.

CONCLUSION

This study revealed that the levels of SIRT 1, SIRT 3, and SIRT 6 in brain tissue were notably elevated, and there was less evidence of ND at the 50-week mark in groups undergoing continuous calorie restriction and intermittent calorie restriction compared to baseline and ad libitum groups. Our findings illustrate that CR promotes increased SIRT expression in the mouse brain, thereby potentially mitigating neurodegeneration.

Molecular Sentinels: Unveiling the Role of Sirtuins in Prostate Cancer Progression

Prostate cancer (PCa) remains a critical global health challenge, with high mortality rates and significant heterogeneity, particularly in advanced stages. While early-stage PCa is often manageable with conventional treatments, metastatic PCa is notoriously resistant, highlighting an urgent need for precise biomarkers and innovative therapeutic strategies. This review focuses on the dualistic roles of sirtuins, a family of NAD+-dependent histone deacetylases, dissecting their unique contributions to tumor suppression or progression in PCa depending on the cellular context. It reveals their multifaceted impact on hallmark cancer processes, including sustaining proliferative signaling, evading growth suppressors, activating invasion and metastasis, resisting cell death, inducing angiogenesis, and enabling replicative immortality. SIRT1, for example, fosters chemoresistance and castration-resistant prostate cancer through metabolic reprogramming, immune modulation, androgen receptor signaling, and enhanced DNA repair. SIRT3 and SIRT4 suppress oncogenic pathways by regulating cancer metabolism, while SIRT2 and SIRT6 influence tumor aggressiveness and androgen receptor sensitivity, with SIRT6 promoting metastatic potential. Notably, SIRT5 oscillates between oncogenic and tumor-suppressive roles by regulating key metabolic enzymes; whereas, SIRT7 drives PCa proliferation and metabolic stress adaptation through its chromatin and nucleolar regulatory functions. Furthermore, we provide a comprehensive summary of the roles of individual sirtuins, highlighting their potential as biomarkers in PCa and exploring their therapeutic implications. By examining each of these specific mechanisms through which sirtuins impact PCa, this review underscores the potential of sirtuin modulation to address gaps in managing advanced PCa. Understanding sirtuins' regulatory effects could redefine therapeutic approaches, promoting precision strategies that enhance treatment efficacy and improve outcomes for patients with aggressive disease.

Structure-Guided Discovery of Subtype Selective SIRT6 Inhibitors with a β-Carboline Skeleton for the Treatment of Breast Cancer

SIRT6 promotes the progression of breast cancer by inducing drug resistance by reinforcing DNA damage repair mechanisms. This study utilized a combination of high-throughput virtual screening and FLUOR DE LYS assays. Hit 14 which features a novel β-carboline skeleton as a potent SIRT6 inhibitor was found. Subsequent structure-guided optimization led to the synthesis of 60 3,6,9-position modified derivatives based on the differences analysis of SIRTs family proteins. Of which, 10d inhibited the deacetylase activity of SIRT6, with an IC50 of 5.81 μM and more than 27 times subtype selectivity. Phe64, Met157, and Ser56 were identified as the key residues. Moreover, 10d suppressed breast cancer cell proliferation, migration, invasion, and induced apoptosis in MCF-7 cells by disrupting the DNA damage repair pathway. Additionally, 10d demonstrated a safe and effective antibreast cancer effect in vivo, presenting a promising strategy for the treatment of breast cancer by targeting SIRT6.

Role of SIRT1 in Potentially Toxic Trace Elements (Lead, Fluoride, Aluminum and Cadmium) Associated Neurodevelopmental Toxicity

The formation of the central nervous system is a meticulously planned and intricate process. Any modification to this process has the potential to disrupt the structure and operation of the brain, which could result in deficiencies in neurological growth. When neurotoxic substances are present during the early stages of development, they can be exceptionally dangerous. Prenatally, the immature brain is extremely vulnerable and is therefore at high risk in pregnant women associated with occupational exposures. Lead, fluoride, aluminum, and cadmium are examples of possibly toxic trace elements that have been identified as an environmental concern in the aetiology of a number of neurological and neurodegenerative illnesses. SIRT1, a member of the sirtuin family has received most attention for its potential neuroprotective properties. SIRT1 is an intriguing therapeutic target since it demonstrates important functions to increase neurogenesis and cellular lifespan by modulating multiple pathways. It promotes axonal extension, neurite growth, and dendritic branching during the development of neurons. Additionally, it contributes to neurogenesis, synaptic plasticity, memory development, and neuroprotection. This review summarizes the possible role of SIRT1 signalling pathway in potentially toxic trace elements -induced neurodevelopmental toxicity, highlighting some molecular pathways such as mitochondrial biogenesis, CREB/BDNF and PGC-1α/NRF1/TFAM.

The relationship between SIRT1 and inflammation: a systematic review and meta-analysis

Recent studies underscore the anti-inflammatory role of SIRT1; however, its levels during inflammatory states remain ambiguous. We synthesized relevant studies up to 20 March 2024 to evaluate the relationship between SIRT1 and inflammation, using data from three major databases. Employing a random-effects model, we analyzed both cross-sectional and longitudinal studies, calculating weighted mean differences (WMDs) for pooled effect sizes. Subgroup and sensitivity analyses, along with a risk of bias assessment, were also conducted. We reviewed 13 publications, encompassing 21 datasets and 2,028 participants. The meta-analysis indicated higher SIRT1 levels in inflammatory groups compared to control groups pre-adjustment (WMD, 3.18 ng/ml; 95% CI 2.30, 4.06 ng/ml; P<0.001; I²= 99.7%) and post-adjustment (WMD, 0.88 ng/ml; 95% CI 0.14, 1.62 ng/ml; P<0.001; I²= 99.5%). Notably, middle-aged patients with inflammation exhibited lower SIRT1 levels (WMD, -0.85 ng/ml; 95% CI -1.47, -0.22 ng/ml; P= 0.008; I²= 95.4%), while groups characterized by East Asian descent, plasma studies, autoimmune conditions, and musculoskeletal disorders showed higher levels. The findings suggest that inflammation generally upregulates SIRT1, potentially elucidating its role in immunobiological processes. However, the significant heterogeneity observed, partly due to the cross-sectional nature of some data, limits insights into the duration of disease progression, which remains highly variable.

Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission

Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep or circuit activity, posing major metabolic stress. Here, we demonstrate that the mammalian brain uses pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability, and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation, which, in turn, modulates mitochondrial pyruvate uptake. Our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in neurotransmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval-functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of neurotransmission in hippocampal terminals.

Novel Approach to Skin Anti-Aging: Boosting Pharmacological Effects of Exogenous Nicotinamide Adenine Dinucleotide (NAD+) by Synergistic Inhibition of CD38 Expression

Nicotinamide adenine dinucleotide (NAD+) is indispensable for the regulation of biological metabolism. Previous studies have revealed its role in aging and degenerative diseases, while crucially showing that supplementation with NAD+ or its precursors could ameliorate or reverse the progression of aging. Despite extensive evidence for the role and action of NAD+ in aging, its pharmacological activity on the skin, or even its mechanism, has not been elucidated. In this study, we established a novel approach to effectively utilize NAD+ for skin anti-aging by enhancing the pharmacological efficacy of exogenous NAD+ using a phytochemical complex consisting of quercetin, and enoxolone through inhibition of CD38. Through the comprehensive in vitro experiments based on human fibroblasts, we observed that exogenous NAD+ could exert protective effects against both extrinsic aging induced by ultraviolet light exposure and intrinsic aging. Additionally, we found that its effects were significantly boosted by quercetin and enoxolone. In this in-depth study, we demonstrated that these beneficial effects are mediated by improved sirtuin activation, autophagy, and mitochondrial functionality. Our approach is expected to verify the applicability of the topical application of NAD+ and offer more effective solutions for the unmet needs of patients and consumers who demand more effective anti-aging effects.

LINE-1 transposable element renaissance in aging and age-related diseases

Transposable elements (TEs) are essential components of eukaryotic genomes and subject to stringent regulatory mechanisms to avoid their potentially deleterious effects. However, numerous studies have verified the resurrection of TEs, particularly long interspersed nuclear element-1 (LINE-1), during preimplantation development, aging, cancer, and other age-related diseases. The LINE-1 family has also been implicated in several aging-related processes, including genomic instability, loss of heterochromatin, DNA methylation, and the senescence-associated secretory phenotype (SASP). Additionally, the role of the LINE-1 family in cancer development has also been substantiated. Research in this field has offered valuable insights into the functional mechanisms underlying LINE-1 activity, enhancing our understanding of aging regulation. This review provides a comprehensive summary of current findings on LINE-1 and their roles in aging and age-related diseases.

Sirtuin 5 (SIRT5) Suppresses Tumor Growth by Regulating Mitochondrial Metabolism and Synaptic Remodeling in Gliomas

Sirtuin 5 (SIRT5) is increasingly recognized as a key regulator of cellular metabolism, which is commonly dysregulated in cancer cells, resulting in enhanced proliferation and tumor progression. To investigate the clinicopathologic implications of SIRT5 dysregulation in glioblastoma, we performed comprehensive analyses of transcriptomic data and functional verifications using in vitro and in vivo glioblastoma models. We found that higher SIRT5 expression levels were associated with a favorable prognosis in glioma patients. Knockdown of SIRT5 significantly enhanced glioblastoma cell growth. Our data suggest its potential role in regulating mitochondrial metabolism in gliomas. Furthermore, SIRT5 is also significantly correlated with synaptic remodeling pathways. Our findings indicate a tumor-suppressive role for SIRT5 that extends beyond regulating cancer metabolism, by which it may function through modulating neuroplasticity. Understanding these cellular interactions provides nuanced insights into the multifaceted role of SIRT5 and the broader therapeutic implications of this for the development of novel treatment strategies.

The role of SIRT3 in homeostasis and cellular health

Mitochondria are responsible for maintaining cellular energy levels, and play a major role in regulating homeostasis, which ensures physiological function from the molecular to whole animal. Sirtuin 3 (SIRT3) is the major protein deacetylase of mitochondria. SIRT3 serves as a nutrient sensor; under conditions of mild metabolic stress, SIRT3 activity is increased. Within the mitochondria, SIRT3 regulates every complex of the electron transport chain, the tricarboxylic acid (TCA) and urea cycles, as well as the mitochondria membrane potential, and other free radical scavengers. This article reviews the role of SIRT3 in regulating homeostasis, and thus physiological function. We discuss the role of SIRT3 in regulating reactive oxygen species (ROS), ATP, immunological function and mitochondria dynamics.

Activation of SIRT1 by silibinin improved mitochondrial health and alleviated the oxidative damage in experimental diabetic neuropathy and high glucose-mediated neurotoxicity

BACKGROUND

Silibinin (SBN), a sirtuin 1 (SIRT1) activator, has been evaluated for its anti-inflammatory activity in many inflammatory diseases. However, its role in diabetes-induced peripheral neuropathy (DPN) remains unknown. The SIRT1 activation convalesces nerve functions by improving mitochondrial biogenesis and mitophagy.

METHODS

DPN was induced by streptozotocin (STZ) at a dose of 55 mg/kg, i.p. in the male SD rats whereas neurotoxicity was induced in Neuro2A cells by 30 mM (high glucose) glucose. Neurobehavioural (nerve conduction velocity and nerve blood flow) western blot, immunohistochemistry, and immunocytochemistry were performed to evaluate the protein expression and their cellular localisation.

RESULTS

Two-week SBN treatment improved neurobehavioural symptoms, SIRT1, PGC-1α, and TFAM expression in the sciatic nerve and HG insulted N2A cells. It has also maintained the mitophagy by up-regulating PARL, PINK1, PGAM5, LC3 level and provided antioxidant defence by upregulating Nrf2.

CONCLUSION

SBN has shown neuroprotective potential in DPN through SIRT1 activation and antioxidant mechanism.

Brain Slice Derived Nerve Fibers Grow along Microcontact Prints and are Stimulated by Beta-Amyloid(42)

BACKGROUND

Alzheimer's disease is characterized by extracellular beta-amyloid plaques, intraneuronal tau neurofibrillary tangles and excessive neurodegeneration. The mechanisms of neuron degeneration and the potential of these neurons to form new nerve fibers for compensation remain elusive. The present study aimed to evaluate the impact of beta-amyloid and tau on new formations of nerve fibers from mouse organotypic brain slices connected to collagen-based microcontact prints.

METHODS

Organotypic brain slices of postnatal day 8-10 wild-type mice were connected to established collagen-based microcontact prints loaded with polyornithine to enhance nerve fiber outgrowth. Human beta-amyloid(42) or P301S mutated aggregated tau was co-loaded to the prints. Nerve fibers were immunohistochemically stained with neurofilament antibodies. The physiological activity of outgrown neurites was tested with neurotracer MiniRuby, voltage-sensitive dye FluoVolt, and calcium-sensitive dye Rhod-4.

RESULTS

Immunohistochemical staining revealed newly formed nerve fibers extending along the prints derived from the brain slices. While collagen-only microcontact prints stimulated nerve fiber growth, those loaded with polyornithine significantly enhanced nerve fiber outgrowth. Beta-amyloid(42) significantly increased the neurofilament-positive nerve fibers, while tau had only a weak effect. MiniRuby crystals, retrogradely transported along these newly formed nerve fibers, reached the hippocampus, while FluoVolt and Rhod-4 monitored electrical activity in newly formed nerve fibers.

CONCLUSIONS

Our data provide evidence that intact nerve fibers can form along collagen-based microcontact prints from mouse brain slices. The Alzheimer's peptide beta-amyloid(42) stimulates this growth, hinting at a neuroprotective function when physiologically active. This "brain-on-chip" model may offer a platform for screening bioactive factors or testing drug effects on nerve fiber growth.

Sirtuins and Cellular Senescence in Patients with Idiopathic Pulmonary Fibrosis and Systemic Autoimmune Disorders

The sirtuin family is a heterogeneous group of proteins that play a critical role in many cellular activities. Several degenerative diseases have recently been linked to aberrant sirtuin expression and activity because of the involvement of sirtuins in maintaining cell longevity and their putative antiaging function. Idiopathic pulmonary fibrosis and progressive pulmonary fibrosis associated with systemic autoimmune disorders are severe diseases characterized by premature and accelerated exhaustion and failure of alveolar type II cells combined with aberrant activation of fibroblast proliferative pathways leading to dramatic destruction of lung architecture. The mechanisms underlying alveolar type II cell exhaustion in these disorders are not fully understood. In this review, we have focused on the role of sirtuins in the pathogenesis of idiopathic and secondary pulmonary fibrosis and their potential as biomarkers in the diagnosis and management of fibrotic interstitial lung diseases.

AAV-mediated upregulation of VDAC1 rescues the mitochondrial respiration and sirtuins expression in a SOD1 mouse model of inherited ALS

Mitochondrial dysfunction represents one of the most common molecular hallmarks of both sporadic and familial forms of amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder caused by the selective degeneration and death of motor neurons. The accumulation of misfolded proteins on and within mitochondria, as observed for SOD1 G93A mutant, correlates with a drastic reduction of mitochondrial respiration and the inhibition of metabolites exchanges, including ADP/ATP and NAD+/NADH, across the Voltage-Dependent Anion-selective Channel 1 (VDAC1), the most abundant channel protein of the outer mitochondrial membrane. Here, we show that the AAV-mediated upregulation of VDAC1 in the spinal cord of transgenic mice expressing SOD1 G93A completely rescues the mitochondrial respiratory profile. This correlates with the increased activity and levels of key regulators of mitochondrial functions and maintenance, namely the respiratory chain Complex I and the sirtuins (Sirt), especially Sirt3. Furthermore, the selective increase of these mitochondrial proteins is associated with an increase in Tom20 levels, the receptor subunit of the TOM complex. Overall, our results indicate that the overexpression of VDAC1 has beneficial effects on ALS-affected tissue by stabilizing the Complex I-Sirt3 axis.

Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission

Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep, intense circuit activity, or dietary restrictions, posing significant metabolic stress. Here, we demonstrate that the mammalian brain utilizes pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability within a neuron and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation which in turn modulates mitochondrial pyruvate uptake. Importantly, our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in synaptic transmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval, functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of synaptic transmission in hippocampal terminals.

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.

NAD+ affects differentially expressed genes-MBOAT2-SLC25A21-SOX6 in experimental autoimmune encephalomyelitis model

BACKGROUND

Nicotinamide adenine dinucleotide (NAD+) plays a key role in neuroinflammation and neurodegeneration and provides anti-inflammatory and neuroprotective effects in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE).

AIM

In this study, we aimed to investigate whether NAD+ affects differentially expressed genes (DEGs) in splenocytes of EAE mice to reveal candidate genes for the pathogenesis of MS.

METHODS

The EAE model was used to perform an intervention on NAD+ to investigate its potential as a protective agent in inflammation and demyelination. Transcriptome analysis of nerve tissue was carried out to gain better insights into NAD+ function. Effects of NAD+ on DEGs in the splenocytes of EAE mice were investigated to determine its anti-inflammatory effect.

RESULTS

NAD+ in EAE mice showed the clinical score was significantly improved (EAE 3.190 ± 0.473 vs. NAD+ 2.049 ± 0.715). DEGs (MBOAT2, SLC25A21, and SOX6) between the EAE and the EAE + NAD+ groups showed that SOX6 was significantly improved after NAD+ treatment compared with the EAE group, and other indicators were improved but did not reach statistical significance. NAD+ exhibited clinical scores in EAE mice, and key inflammation was ameliorated in EAE mice spleen after NAD+ intervention, while transcriptome analysis between EAE and EAE + NAD+ groups showed several DEGs in the underlying mechanism.

CONCLUSION

NAD+ on DEGs attenuates disease severity in EAE. Transcriptome analysis on nerve tissue reveals several protein targets in the underlying mechanisms. However, NAD+ does not significantly improve DEGs in the splenocytes of the EAE model.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Alternate-day fasting ameliorated anxiety-like behavior in high-fat diet-induced obese mice

Alternate-day fasting (ADF) has been reported to reduce body weight, neuroinflammation, and oxidative stress damage. However, it is not known whether ADF affects obesity-induced anxiety-like behavior. Here, male C57BL/6 mice were given an alternate fasting and high-fat diet (HFD) or standard chow diet (SD) every other day for 16 or 5 weeks. After the intervention, the degree of anxiety of the mice was evaluated by the open field test (OFT) and the elevated plus maze (EPM) test. Pathological changes in the hippocampus, the expression of Sirt1 and its downstream protein monoamine oxidase A (MAO-A) in the hippocampus, and the expression of 5-hydroxytryptamine (5-HT) were detected. Compared with HFD-fed mice, HFD-fed mice subjected to ADF for 16 weeks had a lower body weight but more brown adipose tissue (BAT), less anxiety behavior, and less pathological damage in the hippocampus, and lower expression of Sirt1 and MAO-A protein and higher 5-HT levels in the hippocampus could be observed. In addition, we noted that long-term ADF intervention could cause anxiety-like behavior in SD mice. Next, we changed the intervention time to 5 weeks. The results showed that short-term ADF intervention could reduce the body weight and increase the BAT mass of SD mice, but it did not affect anxiety. These results indicated that long-term ADF ameliorated obesity-induced anxiety-like behavior and hippocampal damage, but caused anxiety in normal-weight mice. Short-term ADF did not produce adverse emotional reactions in normal-weight mice. Here, we might provide new ideas for the treatment of obesity-induced anxiety.

Dysregulation of histone deacetylases in ocular diseases

Ocular diseases are a growing global concern and have a significant impact on the quality of life. Cataracts, glaucoma, age-related macular degeneration, and diabetic retinopathy are the most prevalent ocular diseases. Their prevalence and the global market size are also increasing. However, the available pharmacotherapy is currently limited. These diseases share common pathophysiological features, including neovascularization, inflammation, and/or neurodegeneration. Histone deacetylases (HDACs) are a class of enzymes that catalyze the removal of acetyl groups from lysine residues of histone and nonhistone proteins. HDACs are crucial for regulating various cellular processes, such as gene expression, protein stability, localization, and function. They have also been studied in various research fields, including cancer, inflammatory diseases, neurological disorders, and vascular diseases. Our study aimed to investigate the relationship between HDACs and ocular diseases, to identify a new strategy for pharmacotherapy. This review article explores the role of HDACs in ocular diseases, specifically focusing on diabetic retinopathy, age-related macular degeneration, and retinopathy of prematurity, as well as optic nerve disorders, such as glaucoma and optic neuropathy. Additionally, we explore the interplay between HDACs and key regulators of fibrosis and angiogenesis, such as TGF-β and VEGF, highlighting the potential of targeting HDAC as novel therapeutic strategies for ocular diseases.

Epithelial SIRT6 governs IL-17A pathogenicity and drives allergic airway inflammation and remodeling

Dysregulation of IL-17A is closely associated with airway inflammation and remodeling in severe asthma. However, the molecular mechanisms by which IL-17A is regulated remain unclear. Here we identify epithelial sirtuin 6 (SIRT6) as an epigenetic regulator that governs IL-17A pathogenicity in severe asthma. Mice with airway epithelial cell-specific deletion of Sirt6 are protected against allergen-induced airway inflammation and remodeling via inhibiting IL-17A-mediated inflammatory chemokines and mesenchymal reprogramming. Mechanistically, SIRT6 directly interacts with RORγt and mediates RORγt deacetylation at lysine 192 via its PPXY motifs. SIRT6 promotes RORγt recruitment to the IL-17A gene promoter and enhances its transcription. In severe asthma patients, high expression of SIRT6 positively correlates with airway remodeling and disease severity. SIRT6 inhibitor (OSS_128167) treatment significantly attenuates airway inflammation and remodeling in mice. Collectively, these results uncover a function for SIRT6 in regulating IL-17A pathogenicity in severe asthma, implicating SIRT6 as a potential therapeutic target for severe asthma.

Sirtuins, a key regulator of ageing and age-related neurodegenerative diseases

Sirtuins are Nicotinamide Adenine Dinucleotide (NAD+) dependent class ІΙΙ histone deacetylases enzymes (HDACs) present from lower to higher organisms such as bacteria (Sulfolobus solfataricus L. major), yeasts (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), humans (Homo sapiens sapiens), even in plants such as rice (Oryza sativa), thale cress (Arabidopsis thaliana), vine (Vitis vinifera L.) tomato (Solanum lycopersicum). Sirtuins play an important role in the regulation of various vital cellular functions during metabolism and ageing. It also plays a neuroprotective role by modulating several biological pathways such as apoptosis, DNA repair, protein aggregation, and inflammatory processes associated with ageing and neurodegenerative diseases. In this review, we have presented an updated Sirtuins and its role in ageing and age-related neurodegenerative diseases (NDDs). Further, this review also describes the therapeutic potential of Sirtuins and the use of Sirtuins inhibitor/activator for altering the NDDs disease pathology.

Exploring the mRNA and Plasma Protein Levels of BDNF, NT4, SIRT1, HSP27, and HSP70 in Multiple Sclerosis Patients and Healthy Controls

Multiple sclerosis (MS) is a chronic, autoimmune neurodegenerative disease affecting the central nervous system. It is a major cause of non-traumatic neurological disability among young adults in North America and Europe. This study focuses on neuroprotective genes (BDNF, NT4/5, SIRT1, HSP70, and HSP27). Gene expression and protein levels of these markers were compared between MS patients and healthy controls. Blood samples were collected from 42 patients with multiple sclerosis (MS) and 48 control subjects without MS. Quantitative real-time PCR was performed to measure the expression of specific genes. The samples were analyzed in duplicate, and the abundance of mRNA was quantified using the 2-ΔCt method. ELISA assay was used to measure the concentration of specific proteins in the plasma samples. The results show that a 3.5-fold decrease in the gene expression of BDNF corresponds to a 1.5-fold downregulation in the associated plasma protein concentration (p < 0.001). Similar trends were observed with NT-4 (five-fold decrease, slight elevation in protein), SIRT1 (two-fold decrease, two-fold protein decrease), HSP70 (four-fold increase, nearly two-fold protein increase), and HSP27 (four-fold increase, two-fold protein increase) (p < 0.001). This study reveals strong correlations between gene expression and protein concentration in MS patients, emphasizing the relevance of these neuroprotective markers in the disease.

Targeting Mitochondrial Sirtuins in Age-Related Neurodegenerative Diseases and Fibrosis

Aging is a natural and complex biological process that is associated with widespread functional declines in numerous physiological processes, terminally affecting multiple organs and tissues. Fibrosis and neurodegenerative diseases (NDs) often occur with aging, imposing large burdens on public health worldwide, and there are currently no effective treatment strategies for these diseases. Mitochondrial sirtuins (SIRT3-5), which are members of the sirtuin family of NAD+-dependent deacylases and ADP-ribosyltransferases, are capable of regulating mitochondrial function by modifying mitochondrial proteins that participate in the regulation of cell survival under various physiological and pathological conditions. A growing body of evidence has revealed that SIRT3-5 exert protective effects against fibrosis in multiple organs and tissues, including the heart, liver, and kidney. SIRT3-5 are also involved in multiple age-related NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Furthermore, SIRT3-5 have been noted as promising targets for antifibrotic therapies and the treatment of NDs. This review systematically highlights recent advances in knowledge regarding the role of SIRT3-5 in fibrosis and NDs and discusses SIRT3-5 as therapeutic targets for NDs and fibrosis.

Structure-Activity Relationship Studies of 2,4,5-Trisubstituted Pyrimidine Derivatives Leading to the Identification of a Novel and Potent Sirtuin 5 Inhibitor against Sepsis-Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (AKI) is a serious clinical problem without effective drugs. Inhibition of sirtuin 5 (SIRT5) has been confirmed to protect against AKI, suggesting that SIRT5 inhibitors might be a promising therapeutic approach for AKI. Herein, structural optimization was performed on our previous compound 1 (IC50 = 3.0 μM), and a series of 2,4,5-trisubstituted pyrimidine derivatives have been synthesized. The structure-activity relationship (SAR) analysis led to the discovery of three nanomolar level SIRT5 inhibitors, of which the most potent compound 58 (IC50 = 310 nM) was demonstrated to be a substrate-competitive and selective inhibitor. Importantly, 58 significantly alleviated kidney dysfunction and pathological injury in both lipopolysaccharide (LPS)- and cecal ligation/perforation (CLP)-induced septic AKI mice. Further studies revealed that 58 regulated protein succinylation and the release of proinflammatory cytokines in the kidneys of septic AKI mice. Collectively, these results highlighted that targeting SIRT5 has a therapeutic potential against septic AKI.

Discovery of Novel SIRT1/2 Inhibitors with Effective Cytotoxicity against Human Leukemia Cells

The sirtuin enzyme family members, SIRT1 and SIRT2, play both tumor-promoting and tumor-suppressing roles, depending on the context and experimental conditions. Compounds that inhibit either SIRT1 or SIRT2 show promising antitumor effects in several types of cancer models, both in vitro and in vivo. The simultaneous inhibition of SIRT1 and SIRT2 is helpful in treating cancer by completely blocking p53 deacetylation, leading to cell death. However, only a few SIRT1/2 dual inhibitors have been developed. Here, we report the discovery of a novel series of SIRT1/2 dual inhibitors via a rational drug design that involved virtual screening and a substructure search. Eleven of the derived compounds exhibited high inhibitory activities, with IC50 < 5 μM and high specificity for both SIRT1 and SIRT2. Compounds hsa55 and PS9 strongly induced apoptosis and showed antiproliferative effects against human leukemia cell lines, which could be due to their ability to increase of p53 and α-tubulin acetylation, as we observed in MOLM-13 cells. Therefore, the new scaffolds of these compounds and their efficacy in leukemia cell lines provide important clues for the further development of novel anti-leukemia drugs.

SIRT1/FOXO3-mediated autophagy signaling involved in manganese-induced neuroinflammation in microglia

Manganese (Mn), as one of the environmental risk factors for Parkinson's disease (PD), has been widely studied. Though autophagy dysfunction and neuroinflammation mainly are responsible for the causative issue of Mn neurotoxicity, the molecular mechanism of parkinsonism caused by Mn has not been explored clearly. The results of in vivo and in vitro experiments showed that overexposure to Mn caused neuroinflammation impairment and autophagy dysfunction, accompanied by the increase of IL-1β, IL-6, and TNF-α mRNA expression, and nerve cell apoptosis, microglia cell activation, NF-κB activation, poor neurobehavior performance. This is due to Mn-induced the downregulation of SIRT1. Upregulation of SIRT1 in vivo and in vitro could alleviate Mn-induced autophagy dysfunction and neuroinflammation, yet these beneficial effects were abolished following 3-MA administration. Furthermore, we found that Mn interfered with the acetylation of FOXO3 by SIRT1 in BV2 cells, leading to a decrease in the nuclear translocation of FOXO3, and its binding of LC3B promoter and transcription activity. This could be antagonized by the upregulation of SIRT1. Finally, it is proved that SIRT1/FOXO3-LC3B autophagy signaling involves in Mn-induced neuroinflammation impairment.

Role of SIRT3 in mitochondrial biology and its therapeutic implications in neurodegenerative disorders

Sirtuin 3 (SIRT3), a mitochondrial deacetylase expressed preferentially in high-metabolic-demand tissues including the brain, requires NAD⁺ as a cofactor for catalytic activity. It regulates various processes such as energy homeostasis, redox balance, mitochondrial quality control, mitochondrial unfolded protein response (UPRmt), biogenesis, dynamics and mitophagy by altering protein acetylation status. Reduced SIRT3 expression or activity causes hyperacetylation of hundreds of mitochondrial proteins, which has been linked with neurological abnormalities, neuro-excitotoxicity and neuronal cell death. A body of evidence has suggested, SIRT3 activation as a potential therapeutic modality for age-related brain abnormalities and neurodegenerative disorders.

24-Hydroxycholesterol Induces Tau Proteasome-Dependent Degradation via the SIRT1/PGC1α/Nrf2 Pathway: A Potential Mechanism to Counteract Alzheimer’s Disease

Considerable evidence indicates that cholesterol oxidation products, named oxysterols, play a key role in several events involved in Alzheimer’s disease (AD) pathogenesis. Although the majority of oxysterols causes neuron dysfunction and degeneration, 24-hydroxycholesterol (24-OHC) has recently been thought to be neuroprotective also. The present study aimed at supporting this concept by exploring, in SK-N-BE neuroblastoma cells, whether 24-OHC affected the neuroprotective SIRT1/PGC1α/Nrf2 axis. We demonstrated that 24-OHC, through the up-regulation of the deacetylase SIRT1, was able to increase both PGC1α and Nrf2 expression and protein levels, as well as Nrf2 nuclear translocation. By acting on this neuroprotective pathway, 24-OHC favors tau protein clearance by triggering tau ubiquitination and subsequently its degradation through the ubiquitin–proteasome system. We also observed a modulation of SIRT1, PGC1α, and Nrf2 expression and synthesis in the brain of AD patients with the progression of the disease, suggesting their potential role in neuroprotection. These findings suggest that 24-OHC contributes to tau degradation through the up-regulation of the SIRT1/PGC1α/Nrf2 axis. Overall, the evidence points out the importance of avoiding 24-OHC loss, which can occur in the AD brain, and of limiting SIRT1, PGC1α, and Nrf2 deregulation in order to prevent the neurotoxic accumulation of hyperphosphorylated tau and counteract neurodegeneration.

Piceatannol promotes neuroprotection by inducing mitophagy and mitobiogenesis in the experimental diabetic peripheral neuropathy and hyperglycemia-induced neurotoxicity

Piceatannol (PCN), a SIRT1 activator, regulates multiple oxidative stress mechanism and has anti-inflammatory potential in various inflammatory conditions. However, its role in Diabetic insulted peripheral neuropathy (DN) remains unknown. Oxidative stress and mitochondrial dysfunction are major contributing factors to DN. Myriad studies have proven that sirtuin1 (SIRT1) stimulation convalesce nerve functions by activating mitochondrial functions like mitochondrial biogenesis and mitophagy. Diabetic neuropathy (DN) was provoked by injecting streptozotocin (STZ) at a dose of 55 mg/kg, i.p to male Sprague Dawley (SD) rats. Mechanical, thermal hyperalgesia was evaluated by using water immersion, Vonfrey Aesthesiometer, and Randall Sellito Calipers. Motor, sensory nerve conduction velocity was measured using Power Lab 4sp system whereas The Laser Doppler system was used to evaluate nerve blood flow. To induce hyperglycemia for the in vitro investigations, high glucose (HG) (30 mM) conditions were applied to Neuro2a cells. At doses of 5 and 10 µM, PCN was examined for its role in SIRT1 and Nrf2 activation. HG-induced N2A cells, reactive oxygen exposure, mitochondrial superoxides and mitochondrial membrane potentials were restored by PCN exposure, and their neurite outgrowth was enhanced. Peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis was induced by increased SIRT1 activation by piceatannol. SIRT1 activation also enhanced Nrf2-mediated antioxidant signalling. Our study results inferred that PCN administration can counteract the decline in mitochondrial function and antioxidant activity in diabetic rats and HG-exposed N2A cells by increasing the SIRT1 and Nrf2 activities.

Epigenetic Modification Factors and microRNAs Network Associated with Differentiation of Embryonic Stem Cells and Induced Pluripotent Stem Cells toward Cardiomyocytes: A Review

More research is being conducted on myocardial cell treatments utilizing stem cell lines that can develop into cardiomyocytes. All of the forms of cardiac illnesses have shown to be quite amenable to treatments using embryonic (ESCs) and induced pluripotent stem cells (iPSCs). In the present study, we reviewed the differentiation of these cell types into cardiomyocytes from an epigenetic standpoint. We also provided a miRNA network that is devoted to the epigenetic commitment of stem cells toward cardiomyocyte cells and related diseases, such as congenital heart defects, comprehensively. Histone acetylation, methylation, DNA alterations, N6-methyladenosine (m⁶a) RNA methylation, and cardiac mitochondrial mutations are explored as potential tools for precise stem cell differentiation.

In-depth analysis of the Sirtuin 5-regulated mouse brain malonylome and succinylome using library-free data-independent acquisitions

Post-translational modifications (PTMs) dynamically regulate proteins and biological pathways, typically through the combined effects of multiple PTMs. Lysine residues are targeted for various PTMs, including malonylation and succinylation. However, PTMs offer specific challenges to mass spectrometry-based proteomics during data acquisition and processing. Thus, novel and innovative workflows using data-independent acquisition (DIA) ensure confident PTM identification, precise site localization, and accurate and robust label-free quantification. In this study, we present a powerful approach that combines antibody-based enrichment with comprehensive DIA acquisitions and spectral library-free data processing using directDIA (Spectronaut). Identical DIA data can be used to generate spectral libraries and comprehensively identify and quantify PTMs, reducing the amount of enriched sample and acquisition time needed, while offering a fully automated workflow. We analyzed brains from wild-type and Sirtuin 5 (SIRT5)-knock-out mice, and discovered and quantified 466 malonylated and 2211 succinylated peptides. SIRT5 regulation remodeled the acylomes by targeting 164 malonylated and 578 succinylated sites. Affected pathways included carbohydrate and lipid metabolisms, synaptic vesicle cycle, and neurodegenerative diseases. We found 48 common SIRT5-regulated malonylation and succinylation sites, suggesting potential PTM crosstalk. This innovative and efficient workflow offers deeper insights into the mouse brain lysine malonylome and succinylome.

Neuroprotective Actions of Different Exogenous Nucleotides in H2O2-Induced Cell Death in PC-12 Cells

Exogenous nucleotides (NTs) are considered conditionally essential nutrients, and the brain cannot synthesize NTs de novo. Therefore, the external supplementation of exogenous NTs is of great significance for maintaining normal neuronal metabolism and function under certain conditions, such as brain aging. This study, therefore, sets out to assess the neuroprotective effect of four kinds of single exogenous NTs and a mixture of the NTs, and to elucidate the potential mechanism. A rat pheochromocytoma cell line PC-12 was treated with different concentrations of exogenous NTs after 4 h of exposure to 200 µM H₂O₂. We found that the exogenous NTs exerted significant neuroprotection through decreasing neuron apoptosis and DNA damage, ameliorating inflammation and mitochondrial dysfunction, promoting cell viability, and augmenting antioxidant activity, and that they tended to up-regulate the NAD⁺/SIRTI/PGC-1α pathway involved in mitochondrial biogenesis. Among the different NTs, the neuroprotective effect of AMP seemed to be more prominent, followed by the NT mixture, NMN, and CMP. AMP also exhibited the strongest antioxidant activity in H₂O₂-treated PC-12 cells. UMP was excellent at inhibiting neuronal inflammation and improving mitochondrial function, while GMP offered major advantages in stabilizing mitochondrial membrane potential. The mixture of NTs had a slightly better performance than NMN, especially in up-modulating the NAD⁺/SIRTI/PGC-1α pathway, which regulates mitochondrial biogenesis. These results suggest that antioxidant activity, anti-inflammatory activity, and protection of mitochondrial function are possible mechanisms of the neuroprotective actions of exogenous NTs, and that the optimization of the mixture ratio and the concentration of NTs may achieve a better outcome.

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

Hyperglycemic Neurovasculature-On-A-Chip to Study the Effect of SIRT1-Targeted Therapy for the Type 3 Diabetes "Alzheimer's Disease"

Diabetes mellitus (DM) is closely related to Alzheimer's disease (AD), but individual cellular changes and the possibilities of recovery through molecular level regulation have not been investigated. Here, a neurovasculature-on-a-chip (NV chip) model is presented in which the perfusable brain microvasculature is surrounded by the neurons. Under hyperglycemic conditions, the brain microvasculature shows disruption of barrier function and reduced expression of junctional markers. The neurons show Tau pathology and amyloid-beta (Aß) accumulation. Endothelial cells and neurons in the NV chip show sirtuin 1 (SIRT1) downregulation under hyperglycemic conditions, suggesting SIRT1 as a key regulator of hyperglycemia-induced AD. The recovery of glucose levels rescue SIRT1 expression, suggesting that this type of intervention may rescue the progression of hyperglycemia-mediated AD. Furthermore, the short hairpin RNA (shRNA)-, clustered regularly interspaced short palindromic repeats (CRISPR)-, and pharmaceutics-mediated regulation of SIRT1 regulate the pathophysiology of the brain endothelium and neurons at the functional and molecular levels.

Walnut Oligopeptide Delayed Improved Aging-Related Learning and Memory Impairment in SAMP8 Mice

Aging-related learning and memory decline are hallmarks of aging and pose a significant health burden. The effects of walnut oligopeptides (WOPs) on learning and memory were evaluated in this study. Sixty SAMP8 mice were randomly divided into four groups (15 mice/group), including one SAMP8 age-control group and three WOP-treated groups. SAMR1 mice (n = 15) that show a normal senescence rate were used as controls. The SAMP8 and SAMR1 controls were administered ordinary sterilized water, while the WOP-intervention groups were administered 110, 220, and 440 mg/kg·bw of WOPs in water, respectively. The whole intervention period was six months. The remaining 15 SAMP8 (4-month-old) mice were used as the young control group. The results showed that WOPs significantly improved the decline in aging-related learning/memory ability. WOPs significantly increased the expression of BDNF and PSD95 and decreased the level of APP and Aβ1-42 in the brain. The mechanism of action may be related to an increase in the activity of antioxidant enzymes (SOD and GSH-Px), a reduction in the expression of inflammatory factors (TNF-α and IL-1β) in the brain and a reduction in oxidative stress injury (MDA). Furthermore, the expression of AMPK, SIRT-1, and PGC-1α was upregulated and the mitochondrial DNA content was increased in brain. These results indicated that WOPs improved aging-related learning and memory impairment. WOP supplementation may be a potential and effective method for the elderly.

dNAGLU Extends Life Span and Promotes Fitness and Stress Resistance in Drosophila

To identify new factors that promote longevity and healthy aging, we studied Drosophila CG13397, an ortholog of the human NAGLU gene, a lysosomal enzyme overexpressed in centenarians. We found that the overexpression of CG13397 (dNAGLU) ubiquitously, or tissue specifically, in the nervous system or fat body could extend fly life span. It also extended the life span of flies overexpressing human Aβ42, in a Drosophila Alzheimer's disease (AD) model. To investigate whether dNAGLU could influence health span, we analyzed the effect of its overexpression on AD flies and found that it improved the climbing ability and stress resistance, including desiccation and hunger, suggesting that dNAGLU improved fly health span. We found that the deposition of Aβ42 in the mushroom body, which is the fly central nervous system, was reduced, and the lysosomal activity in the intestine was increased in dNAGLU over-expressing flies. When NAGLU was overexpressed in human U251-APP cells, which expresses a mutant form of the Aβ-precursor protein (APP), APP-p.M671L, these cells exhibited stronger lysosomal activity and and enhanced expression of lysosomal pathway genes. The concentration of Aβ42 in the cell supernatant was reduced, and the growth arrest caused by APP expression was reversed, suggesting that NAGLU could play a wider role beyond its catalytic activity to enhance lysosomal activity. These results also suggest that NAGLU overexpression could be explored to promote healthy aging and to prevent the onset of neurodegenerative diseases, including AD.

Resveratrol: A potential therapeutic natural polyphenol for neurodegenerative diseases associated with mitochondrial dysfunction

Most polyphenols can cross blood-brain barrier, therefore, they are widely utilized in the treatment of various neurodegenerative diseases (ND). Resveratrol, a natural polyphenol contained in blueberry, grapes, mulberry, etc., is well documented to exhibit potent neuroprotective activity against different ND by mitochondria modulation approach. Mitochondrial function impairment is the most common etiology and pathological process in various neurodegenerative disorders, viz. Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. Nowadays these ND associated with mitochondrial dysfunction have become a major threat to public health as well as health care systems in terms of financial burden. Currently available therapies for ND are limited to symptomatic cures and have inevitable toxic effects. Therefore, there is a strict requirement for a safe and highly effective drug treatment developed from natural compounds. The current review provides updated information about the potential of resveratrol to target mitochondria in the treatment of ND.

Hydrogen Sulfide (H2S) Signaling as a Protective Mechanism against Endogenous and Exogenous Neurotoxicants

In view of the significant role of H₂S in brain functioning, it is proposed that H₂S may also possess protective effects against adverse effects of neurotoxicants. Therefore, the objective of the present review is to discuss the neuroprotective effects of H₂S against toxicity of a wide spectrum of endogenous and exogenous agents involved in the pathogenesis of neurological diseases as etiological factors or key players in disease pathogenesis. Generally, the existing data demonstrate that H₂S possesses neuroprotective effects upon exposure to endogenous (amyloid β, glucose, and advanced-glycation end-products, homocysteine, lipopolysaccharide, and ammonia) and exogenous (alcohol, formaldehyde, acrylonitrile, metals, 6-hydroxydopamine, as well as 1-methyl-4-phenyl- 1,2,3,6- tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenyl pyridine ion (MPP)) neurotoxicants. On the one hand, neuroprotective effects are mediated by S-sulfhydration of key regulators of antioxidant (Sirt1, Nrf2) and inflammatory response (NF-κB), resulting in the modulation of the downstream signaling, such as SIRT1/TORC1/CREB/BDNF-TrkB, Nrf2/ARE/HO-1, or other pathways. On the other hand, H₂S appears to possess a direct detoxicative effect by binding endogenous (ROS, AGEs, Aβ) and exogenous (MeHg) neurotoxicants, thus reducing their toxicity. Moreover, the alteration of H₂S metabolism through the inhibition of H₂S-synthetizing enzymes in the brain (CBS, 3-MST) may be considered a significant mechanism of neurotoxicity. Taken together, the existing data indicate that the modulation of cerebral H₂S metabolism may be used as a neuroprotective strategy to counteract neurotoxicity of a wide spectrum of endogenous and exogenous neurotoxicants associated with neurodegeneration (Alzheimer's and Parkinson's disease), fetal alcohol syndrome, hepatic encephalopathy, environmental neurotoxicant exposure, etc. In this particular case, modulation of H₂S-synthetizing enzymes or the use of H₂S-releasing drugs should be considered as the potential tools, although the particular efficiency and safety of such interventions are to be addressed in further studies.

Neuromodulating roles of estrogen and phytoestrogens in cognitive therapeutics through epigenetic modifications during aging

Estrogen (E2) plays important role in regulating hippocampal learning and memory. The decline of E2 after menopause affects learning and memory and increases the risk of neurodegenerative diseases like Alzheimer's disease (AD). Additionally, from the estrogen receptor (ER) mediated gene regulation; E2 also regulates gene expression at the transcriptional and posttranscriptional levels through epigenetic modifications. E2 recruits a number of proteins called co-regulators at the promoter region of genes. These co-regulators act as chromatin modifiers, alter DNA and histone modifications and regulate gene expression. Several studies show that E2 regulates learning and memory by altering chromatin at the promoters of memory-linked genes. Due to structural similarities with E2 and low side effects, phytoestrogens are now used as neuroprotective agents to recover learning and memory in animal models as well as human subjects during aging and different neurological disorders. Growing evidence suggests that apart from anti-oxidative and anti-inflammatory properties, phytoestrogens also act as epigenetic modifiers and regulate gene expression through epigenetic modifications. The epigenetic modifying properties of phytoestrogens are mostly studied in cancer cells but very little is known regarding the regulation of synaptic plasticity genes, learning and memory, and neurological disorders. In this article, we discuss the epigenetic modifying properties of E2 and the roles of phytoestrogens as epigenetic modifiers in the brain to recover and maintain cognitive functions.

SARS-CoV-2 virus NSP14 Impairs NRF2/HMOX1 activation by targeting Sirtuin 1

Most deaths from the COVID-19 pandemic are due to acute respiratory distress syndrome (ARDS)-related respiratory failure. Cytokine storms and oxidative stress are the major players in ARDS development during respiratory virus infections. However, it is still unknown how oxidative stress is regulated by viral and host factors in response to SARS-CoV-2 infection. Here, we found that activation of NRF2/HMOX1 significantly suppressed SARS-CoV-2 replication in multiple cell types by producing the metabolite biliverdin, whereas SARS-CoV-2 impaired the NRF2/HMOX1 axis through the action of the nonstructural viral protein NSP14. Mechanistically, NSP14 interacts with the catalytic domain of the NAD-dependent deacetylase Sirtuin 1 (SIRT1) and inhibits its ability to activate the NRF2/HMOX1 pathway. Furthermore, both genetic and pharmaceutical evidence corroborated the novel antiviral activity of SIRT1 against SARS-CoV-2. Therefore, our findings reveal a novel mechanism by which SARS-CoV-2 dysregulates the host antioxidant defense system and emphasize the vital role played by the SIRT1/NRF2 axis in host defense against SARS-CoV-2.

Comparative metabolomic analysis in plasma and cerebrospinal fluid of humans and in plasma and brain of mice following antidepressant-dose ketamine administration

Subanesthetic-dose racemic (R,S)-ketamine (ketamine) produces rapid, robust, and sustained antidepressant effects in major depressive disorder (MDD) and bipolar disorder (BD) and has also been shown to effectively treat neuropathic pain, complex regional pain syndrome, and post-traumatic stress disorder (PTSD). However, to date, its mechanism of action remains unclear. Preclinical studies found that (2 R,6 R;2 S,6 S)-hydroxynorketamine (HNK), a major circulating metabolite of ketamine, elicits antidepressant effects similar to those of ketamine. To help determine how (2 R,6 R)-HNK contributes to ketamine's mechanism of action, an exploratory, targeted, metabolomic analysis was carried out on plasma and CSF of nine healthy volunteers receiving a 40-minute ketamine infusion (0.5 mg/kg). A parallel targeted metabolomic analysis in plasma, hippocampus, and hypothalamus was carried out in mice receiving either 10 mg/kg of ketamine, 10 mg/kg of (2 R,6 R)-HNK, or saline. Ketamine and (2 R,6 R)-HNK both affected multiple pathways associated with inflammatory conditions. In addition, several changes were unique to either the healthy human volunteers and/or the mouse arm of the study, indicating that different pathways may be differentially involved in ketamine's effects in mice and humans. Mechanisms of action found to consistently underlie the effects of ketamine and/or (2 R,6 R)-HNK across both the human metabolome in plasma and CSF and the mouse arm of the study included LAT1, IDO1, NAD+, the nitric oxide (NO) signaling pathway, and sphingolipid rheostat.

Epigenetic repression of Wnt receptors in AD: a role for Sirtuin2-induced H4K16ac deacetylation of Frizzled1 and Frizzled7 promoters

Growing evidence supports a role for deficient Wnt signalling in Alzheimer's disease (AD). First, the Wnt antagonist DKK1 is elevated in AD brains and is required for amyloid-β-induced synapse loss. Second, LRP6 Wnt co-receptor is required for synapse integrity and three variants of this receptor are linked to late-onset AD. However, the expression/role of other Wnt signalling components remain poorly explored in AD. Wnt receptors Frizzled1 (Fzd1), Fzd5, Fzd7 and Fzd9 are of interest due to their role in synapse formation/plasticity. Our analyses showed reduced FZD1 and FZD7 mRNA levels in the hippocampus of human early AD stages and in the hAPP^NLGF/NLGF mouse model. This transcriptional downregulation was accompanied by reduced levels of the pro-transcriptional histone mark H4K16ac and a concomitant increase of its deacetylase Sirt2 at Fzd1 and Fzd7 promoters in AD. In vitro and in vivo inhibition of Sirt2 rescued Fzd1 and Fzd7 mRNA expression and H4K16ac levels at their promoters. In addition, we showed that Sirt2 recruitment to Fzd1 and Fzd7 promoters is dependent on FoxO1 activity in AD, thus acting as a co-repressor. Finally, we found reduced levels of SIRT2 inhibitory phosphorylation in nuclear samples from human early AD stages with a concomitant increase in the SIRT2 phosphatase PP2C. This results in hyperactive nuclear Sirt2 and favours Fzd1 and Fzd7 repression in AD. Collectively, our findings define a novel role for nuclear hyperactivated SIRT2 in repressing Fzd1 and Fzd7 expression via H4K16ac deacetylation in AD. We propose SIRT2 as an attractive target to ameliorate AD pathology.

Sirtuin 6 Protects Against Oxidative Stress and Vascular Dysfunction in Mice

Objective: Sirtuin deacetylases are major regulators of organismal aging, and while depletion of sirtuin 6 (SIRT6) in mice results in a profound progeroid phenotype, the role of SIRT6 in the regulation of vasomotor function is unknown. Thus, our objective was to test the hypothesis that reductions in SIRT6 elicit endothelial dysfunction in young, genetically altered mice.

Results and Approach: We used young (3 month old), littermate-matched, SIRT6 wild-type (WT), and SIRT6 heterozygous (HET) mice. SIRT6 expression (qRT-PCR) was reduced by 50% in HET mice. Carotid vessel responses to acetylcholine, sodium nitroprusside, U46619, and serotonin were examined in isolated organ chamber baths. Relaxation in response to acetylcholine (ACH) was impaired in HET mice compared to littermate-matched WT controls (67 ± 3% versus 76 ± 3%, respectively; p < 0.05), while responses to sodium nitroprusside were unchanged. Short-term incubation of carotid rings with the NAD(P)H oxidase inhibitor, apocynin, significantly improved in vessels from HET mice but not their WT littermates. Peak tension generated in response to either U46619 or serotonin was significantly blunted in HET mice compared to their WT littermates.

Conclusion: These data suggest that SIRT6 is a key regulator of vasomotor function in conduit vessels. More specifically, we propose that SIRT6 serves as a tonic suppressor of NAD(P)H oxidase expression and activation, as inhibition of NAD(P)H oxidase improved endothelial function in SIRT6 haploinsufficient mice. Collectively, SIRT6 activation and/or histone acetyltransferase inhibition may be useful therapeutic approaches to reduce endothelial dysfunction and combat age-associated cardiovascular disease.

Influence of psychostimulants and opioids on epigenetic modification of class III histone deacetylase (HDAC)-sirtuins in glial cells

Substance abuse affects the central nervous system (CNS) and remains a global health problem. Psychostimulants, such as cocaine and methamphetamine (METH), and opioids affect neuronal function and lead to behavioral impairments via epigenetic modification. Epigenetic changes occur via classical pathways, especially the class III histone deacetylase (HDAC)-sirtuin (SIRT) family, that act as cellular sensors to regulate energy homeostasis and coordinate cellular responses to maintain genome integrity. However, SIRT family (1-7)-associated neurodegeneration has not been elucidated in the context of energy metabolism. The present study examined the effects of psychostimulants, such as cocaine and METH, and opioids, such as morphine, on SIRT family (1-7) [class I, II, III and IV] expression and cellular translocation-mediated dysfunction in astrocytes and microglial cells. The "nootropic" drug piracetam played a preventative role against psychostimulant- and opioid-induced SIRT (1-7) expression in astrocytes. These results indicate that cocaine, METH, and morphine affected deacetylation and cellular function, and these changes were prevented by piracetam in astrocytes.

Profiling sirtuin activity using Copper-free click chemistry

The mammalian sirtuins are a group of posttranslational modification enzymes that remove acyl modifications from lysine residues in an NAD⁺-dependent manner. Although initially proposed as histone deacetylases (HDACs), they are now known to target other cellular enzymes and proteins as well. Sirtuin-catalyzed simple amide hydrolysis has profound biological consequences including suppression of gene expression, promotion of DNA damage repair, and regulation of glucose and lipid metabolism. Human sirtuins have been intensively pursued by both academia and industry as potential therapeutic targets for the treatment of diseases such as cancer and neurodegeneration. To gain a better understanding of their roles in various cellular events, innovative chemical probes are highly sought after. This current study focuses on the development of activity-based chemical probes (ABPs) for the profiling of sirtuin activity in biological samples. Cyclooctyne-containing and azido-containing probes were synthesized to enable the subsequent copper-free "click" conjugation to either a fluorophore or biotin. The two groups of structurally related ABPs demonstrated different labeling efficiency and selectivity: the cyclooctyne-containing probes failed to label recombinant sirtuins to any appreciable level, while the azido-containing ABPs showed good isoform selectivity. The azido-containing ABPs were further analyzed for their ability to label an individual sirtuin isoform in protein mixtures and cell lysates. These biocompatible ABPs allow the study of dynamic cellular protein activity change to become possible.