Sirtuins in Neuroendocrine Regulation and Neurological Diseases

The impact of nicotine smoking on spondyloarthritis and rheumatoid arthritis

OBJECTIVE

Nicotine has major side effects on human health through numerous mechanisms, one of which is the alteration of the immune system and its genetic components. Such alteration can be a predisposing factor for autoimmune diseases such as spondyloarthritis (SpA) and rheumatoid arthritis (RA). This review aims to shed light on the effects of nicotine smoking on the pathophysiology, clinical presentation, and management of SpA and RA.

METHODS

This review looked into the studies, excluding case reports and series, which were cited by PubMed/MEDLINE.

RESULTS

Patients with established autoimmune conditions may have a different underlying pathophysiology and disease course when exposed to nicotine through cigarette smoking. Through the involvement of several cytokines, endothelial dysfunction, and epigenetic mechanisms, the severity of SpA is more prominent in smokers. The global health status, pain, and fatigue are worse in SpA patients. The evidence on the effect of nicotine smoking on the treatment of SpA is still limited. Nicotine can contribute to RA via the disruption of cellular regulatory activity, inflammatory responses, morphological, physiological, biochemical, and enzymatic responses. As such, smokers with RA have higher disease activity and are more likely to be seropositive through the citrullination of peptides. In addition, these patients are at risk of achieving a suboptimal response to tumor necrosis factor inhibitors.

CONCLUSIONS

Cigarette smoking can substantially affect the pathophysiology and clinical presentation of patients with SpA and RA. The impact of nicotine on the management of these diseases still needs to be further studied.

Development and Characterization of a Novel Carbon-11 Labeled Positron Emission Tomography Radiotracer for Neuroimaging of Sirtuin 1 with Benzoxazine-Based Compounds

Introduction

Sirtuins (SIRTs) comprise a group of histone deacetylase enzymes crucial for regulating metabolic pathways and contributing significantly to various disease mechanisms. Sirtuin 1 (SIRT1), among the seven known mammalian homologs, is extensively investigated and understood, playing a key role in neurodegenerative disorders and cancer. This study focuses on potential as a therapeutic target for conditions such as Parkinson's disease (PD), Huntington's disease (HD), and Alzheimer's disease (AD).

Methods

Utilizing positron emission tomography (PET) as a noninvasive molecular imaging modality, we aimed to expedite the validation of a promising sirtuin 1 inhibitor for clinical trials. However, the absence of a validated sirtuin 1 PET radiotracer impedes clinical translation. We present the development of [11C]1, and 11C-labeled benzoxazine-based derivative, as a lead imaging probe. The radiosynthesis of [11C]1 resulted in a radiochemical yield of 31 ± 4%.

Results

Baseline studies demonstrated that [11C]1 exhibited excellent blood-brain barrier (BBB) penetration capability, with uniform accumulation throughout various brain regions. Self-blocking studies revealed that introducing an unlabeled compound 1, effectively blocking sirtuin 1, led to a substantial reduction in whole-brain uptake, emphasizing the in vivo specificity of [11C]1 for sirtuin 1.

Discussion

The development of [11C]1 provides a valuable tool for noninvasive imaging investigations in rodent models with aberrant sirtuin 1 expression. This novel radiotracer holds promise for advancing our understanding of sirtuin 1's role in disease mechanisms and may facilitate the validation of sirtuin 1 inhibitors in clinical trials.

AMPK/PGC-1α and p53 modulate VDAC1 expression mediated by reduced ATP level and metabolic oxidative stress in neuronal cells

Voltage-dependent anion channel 1 (VDAC1) is a pore protein located in the outer mitochondrial membrane. Its channel gating mediates mitochondrial respiration and cell metabolism, and it has been identified as a critical modulator of mitochondria-mediated apoptosis. In many diseases characterized by mitochondrial dysfunction, such as cancer and neurodegenerative diseases, VDAC1 is considered a promising potential therapeutic target. However, there is limited research on the regulatory factors involved in VDAC1 protein expression in both normal and pathological states. In this study, we find that VDAC1 protein expression is up-regulated in various neuronal cell lines in response to intracellular metabolic and oxidative stress. We further demonstrate that VDAC1 expression is modulated by intracellular ATP level. Through the use of pharmacological agonists and inhibitors and small interfering RNA (siRNA), we reveal that the AMPK/PGC-1α signaling pathway is involved in regulating VDAC1 expression. Additionally, based on bioinformatics predictions and biochemical verification, we identify p53 as a potential transcription factor that regulates VDAC1 promoter activity during metabolic oxidative stress. Our findings suggest that VDAC1 expression is regulated by the AMPK/PGC-1α and p53 pathways, which contributes to the maintenance of stress adaptation and apoptotic homeostasis in neuronal cells.

Transcriptomic profiles of brains in juvenile Atlantic cod (Gadus morhua) exposed to pharmaceuticals and personal care products from a wastewater treatment plant discharge

Pharmaceuticals and personal care products (PPCPs) are frequently detected in marine environments, posing a threat to aquatic organisms. Our previous research demonstrated the occurrence of neuroactive compounds in effluent and sediments from a wastewater treatment plant (WWTP) in a fjord North of Stavanger, the fourth-largest city in Norway. To better understand the influence of PPCP mixtures on fish, Atlantic cod (Gadus morhua) were caged for one month in 3 locations: site 1 (reference), site 2 (WWTP discharge), and site 3 (6.7 km west of discharge). Transcriptomic profiling was conducted in the brains of exposed fish and detection of PPCPs in WWTP effluent and muscle fillets were determined. Caffeine (47.8 ng/L), benzotriazole (10.9 ng/L), N,N-diethyl-meta-toluamide (DEET) (5.6 ng/L), methyl-1H-benzotriazole (5.5 ng/L), trimethoprim (3.4 ng/L), carbamazepine (2.1 ng/L), and nortriptyline (0.4 ng/L) were detected in the WWTP effluent. Octocrylene concentrations were observed in muscle tissue at all sites and ranged from 53 to 193 ng/g. Nervous system function and endocrine system disorders were the top enriched disease and function pathways predicted in male and female fish at site 2, with the top shared canonical pathways involved with estrogen receptor and Sirtuin signaling. At the discharge site, predicted disease and functional responses in female brains were involved in cellular assembly, organization, and function, tissue development, and nervous system development, whereas male brains were involved in connective tissue development, function, and disorders, nervous system development and function, and neurological disease. The top shared canonical pathways in females and males were involved in fatty acid activation and tight junction signaling. This study suggests that pseudopersistent, chronic exposure of native juvenile Atlantic cod from this ecosystem to PPCPs may alter neuroendocrine and neuron development.

Effects of Dimerization on the Deacylase Activities of Human SIRT2

Human sirtuin isoform 2 (SIRT2) is an NAD+-dependent enzyme that functions as a lysine deacetylase and defatty-acylase. Here, we report that SIRT2 readily dimerizes in solution and in cells and that dimerization affects its ability to remove different acyl modifications from substrates. Dimerization of recombinant SIRT2 was revealed with analytical size exclusion chromatography and chemical cross-linking. Dimerized SIRT2 dissociates into monomers upon binding long fatty acylated substrates (decanoyl-, dodecanoyl-, and myristoyl-lysine). However, we did not observe dissociation of dimeric SIRT2 in the presence of acetyl-lysine. Analysis of X-ray crystal structures led us to discover a SIRT2 double mutant (Q142A/E340A) that is impaired in its ability to dimerize, which was confirmed with chemical cross-linking and in cells with a split-GFP approach. In enzyme assays, the SIRT2(Q142A/E340A) mutant had normal defatty-acylase activity and impaired deacetylase activity compared with the wild-type protein. These results indicate that dimerization is essential for optimal SIRT2 function as a deacetylase. Moreover, we show that SIRT2 dimers can be dissociated by a deacetylase and defatty-acylase inhibitor, ascorbyl palmitate. Our finding that its oligomeric state can affect the acyl substrate selectivity of SIRT2 is a novel mode of activity regulation by the enzyme that can be altered genetically or pharmacologically.

Dihydrokaempferol attenuates LPS-induced inflammation and apoptosis in WI-38 cells

BACKGROUND

Globally, pneumonia has been associated as a primary cause of mortality in children aged less than 5 years. Dihydrokaempferol (DHK) has been proposed for being correlated with the process of various diseases. Nevertheless, whether DHK has a role in the progression of infantile pneumonia remains unclear. This study aimed at exploring whether DHK was involved in the progression of infantile pneumonia.

METHODS

Human fibroblast cells WI-38 were treated with lipopolysaccharide (LPS). The viability of WI-38 cells was measured via Cell counting kit-8. Reverse transcription-quantitative polymerase chain reaction was used to evaluate the levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α). Western blot analysis revealed the protein levels of IL-1β, IL-6, TNF-α, Bax, and cleaved-caspase 3. Flow cytometry was applied for exploring the apoptosis of WI-38 cells. The concentrations of IL-1β, IL-6, and TNF-α were assessed via enzyme-linked-immunosorbent serologic assay.

RESULTS

DHK modulated the viability of WI-38 cells in infantile pneumonia. Furthermore, we identified that DHK treatment inversely changed LPS induction-mediated elevation on the levels of inflammation biomarkers. Besides, DHK counteracted LPS-induced production of reactive oxygen species (ROS) in WI-38 cells. DHK also decreased LPS-induced elevation of WI-38 cells apoptosis and mediated the levels of apoptosis-associated indexes. Moreover, modulating sirtuin-1 (SIRT1) protein level was lowered by the induction of LPS, and was reversed by DHK treatment. In addition, DHK counteracted LPS induction-mediated elevation of p-p65 and phosphorylated inhibitor of nuclear factor kappa-B kinase subunit alpha (p-IκBα) protein levels.

CONCLUSION

DHK alleviated LPS-induced WI-38 cells inflammation injury in infantile pneumonia through SIRT1/NF-κB pathway. The results shed light on the implications of DHK on the prevention and treatment of infantile pneumonia.

Role of SIRT1 Gene Polymorphisms and Serum Levels in Patients with Multiple Sclerosis

AIM

The purpose of this work was to investigate the prevalence of SIRT1 rs3818292, rs3758391, and rs7895833 single nucleotide polymorphisms and SIRT1 serum levels associated with multiple sclerosis (MS) in the Lithuanian population.

METHODS

A total of 250 MS patients and 250 healthy controls were included in the study. Genotyping was performed using the RT-PCR method. Statistical analysis was performed using "IBM SPSS version 29.0". The serum SIRT1 level was determined by the ELISA method.

RESULTS

We found that rs3818292 was associated with increased odds of developing MS under the dominant (p = 0.007) and allelic genetic (p = 0.004) models. rs3758391 was associated with increased odds of developing under the co-dominant (p < 0.001), overdominant (p < 0.001), dominant (p < 0.001), and allelic (p = 0.002) genetic models. rs7895833 was associated with increased odds of developing MS under co-dominant (p < 0.001), overdominant (p < 0.001), dominant (p < 0.001), and allelic (p < 0.001) genetic models. Additional sex-differentiated analysis within females revealed that the rs3758391 was associated with an increased odds ratio for the occurrence of MS among the co-dominant (p = 0.006), dominant (p = 0.002), and allelic (p = 0.001). rs7895833 was associated with an increased odds ratio for the development of MS under the co-dominant (p < 0.001), overdominant (p < 0.001), dominant (p < 0.001), and allelic (p < 0.001) genetic models. Age-differentiated analysis showed that rs3758391 was associated with an increased odds ratio for the development of MS in younger patients under the codominant (p = 0.002), overdominant (p = 0.003), and dominant (p = 0.004) genetic models. rs7895833 was associated with an increased odds ratio for the occurrence of MS under the overdominant genetic model (p = 0.013). In elderly patients, rs3818292 was associated with an increased odds ratio for the occurrence of MS under the dominant (p = 0.008) and allelic (p = 0.009) genetic models. rs7895833 was associated with an increased odds ratio for the occurrence of MS under the codominant (p = 0.011 and p = 0.012), dominant (p = 0.001), and allelic (p < 0.001) genetic models. We also found that serum SIRT1 levels were statistically significantly different between MS patients and control group subjects (p < 0.001). In addition, comparison of SIRT1 levels between study groups and genotypes showed that rs3818292 AA (p = 0.001), rs3758391 CT (p < 0.001), and rs7895833 AA (p = 0.002) and AG (p = 0.004) had higher SIRT1 levels in the control group than in the MS group. All results were provided after strict Bonferroni correction.

CONCLUSIONS

Genetic variations in SIRT1 rs3818292, rs3758391, and rs7895833 are associated with multiple sclerosis, with possible differences in gender and age, as well as lower serum SIRT1 levels.

LXA4 attenuates perioperative neurocognitive disorders by suppressing neuroinflammation and oxidative stress

Perioperative neurocognitive disorder (PND) is a common complication that increases morbidity and mortality in elderly patients undergoing surgery. Abnormal microglia activation causes neuroinflammation and contributes to the development of PND. Growing evidence shows that lipoxin A4 (LXA4), a lipid mediator, possesses potent anti-inflammatory activities. In this study, we investigated whether LXA4 exerted a protective effect against surgery-induced neurocognitive deficits and explored the underlying mechanisms. Mice were subjected to laparotomy under sevoflurane anesthesia to establish an animal model of PND. LXA4 (15 μg/kg/d, ip) was administered three days prior surgery. We showed that LXA4 significantly alleviated surgery-induced cognitive impairments, attenuated neuroinflammation and microglial activation in hippocampus. In BV2 microglial cells treated with LPS (100 ng/mL), pre-application of LXA4 (100 nΜ) significantly inhibited M1 polarization and promoted M2 polarization, and decreased the levels of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and increased the levels of anti-inflammatory cytokine (IL-10). LXA4 also mitigated LPS-regulated expression of HO-1, NOX2, and SOD1, elevated SOD activity, and attenuated ROS production. Furthermore, we revealed that LXA4 increased the expression of SIRT1 and decreased the protein level of acetylated NF-κB p65. SIRT1 inhibitor EX-527 abolished the anti-inflammatory and antioxidant response effects of LXA4 in BV2 microglial cells. Hence, LXA4 is a potential therapeutic agent for surgery-induced neuroinflammation, oxidative stress, and cognitive deficit, and the effect of LXA4 is probably mediated by the activation of the SIRT1/NF-κB signaling pathway in microglia.

Lactate Improves Long-term Cognitive Impairment Induced By Repeated Neonatal Sevoflurane Exposures Through SIRT1-mediated Regulation of Adult Hippocampal Neurogenesis and Synaptic Plasticity in Male Mice

Repeated neonatal exposures to sevoflurane induce long-term cognitive impairment that has been reported to have sex-dependent differences. Exercise promotes learning and memory by releasing lactate from the muscle. The study tested the hypothesis that lactate may improve long-term cognitive impairment induced by repeated neonatal exposures to sevoflurane through SIRT1-mediated regulation of adult hippocampal neurogenesis and synaptic plasticity. C57BL/6 mice of both genders were exposed to 3% sevoflurane for 2 h daily from postnatal day 6 (P6) to P8. In the intervention experiments, mice received lactate at 1 g/kg intraperitoneally once daily from P21 to P41. Behavioral tests including open field (OF), object location (OL), novel object recognition (NOR), and fear conditioning (FC) tests were performed to assess cognitive function. The number of 5-Bromo-2'- deoxyuridine positive (BrdU+) cells and BrdU+/DCX+ (doublecortin) co-labeled cells, expressions of brain-derived neurotrophic factor (BDNF), activity-regulated cytoskeletal-associated protein (Arc), early growth response 1 (Egr-1), SIRT1, PGC-1α and FNDC5, and long-term potentiation (LTP) were evaluated in the hippocampus. Repeated exposures to sevoflurane induced deficits in OL, NOR and contextual FC tests in male but not female mice. Similarly, adult hippocampal neurogenesis, synaptic plasticity-related proteins and hippocampal LTP were impaired after repeated exposures to sevoflurane in male but not female mice, which could rescue by lactate treatment. Our study suggests that repeated neonatal exposures to sevoflurane inhibit adult hippocampal neurogenesis and induce defects of synaptic plasticity in male but not female mice, which may contribute to long-term cognitive impairment. Lactate treatment rescues these abnormalities through activation of SIRT1.

Histone modifications in embryo implantation and placentation: insights from mouse models

Embryo implantation and placentation play pivotal roles in pregnancy by facilitating crucial maternal-fetal interactions. These dynamic processes involve significant alterations in gene expression profiles within the endometrium and trophoblast lineages. Epigenetics regulatory mechanisms, such as DNA methylation, histone modification, chromatin remodeling, and microRNA expression, act as regulatory switches to modulate gene activity, and have been implicated in establishing a successful pregnancy. Exploring the alterations in these epigenetic modifications can provide valuable insights for the development of therapeutic strategies targeting complications related to pregnancy. However, our current understanding of these mechanisms during key gestational stages remains incomplete. This review focuses on recent advancements in the study of histone modifications during embryo implantation and placentation, while also highlighting future research directions in this field.

Resveratrol inhibits LPS-induced apoptosis in bovine mammary epithelial cells: the role of PGC1α-SIRT3 axis

Resveratrol (Res) is a bioactive dietary component and alleviates apoptosis in multiple cell types. However, its effect and mechanism on lipopolysaccharide (LPS)-induced bovine mammary epithelial cells (BMEC) apoptosis, which commonly happens in dairy cows with mastitis, is unknown. We hypothesized that Res would inhibit LPS-induced apoptosis in BMEC through SIRT3, a NAD + -dependent deacetylase activated by Res. To test the dose-response effect on apoptosis, 0-50 μM Res were incubated with BMEC for 12 h, followed by 250 μg/mL LPS treatment for 12 h. To investigate the role of SIRT3 in Res-mediated alleviation of apoptosis, BMEC were pretreated with 50 μM Res for 12 h, then incubated with si-SIRT3 for 12 h and were finally treated with 250 μg/mL LPS for 12 h. Res dose-dependently promoted the cell viability and protein levels of Bcl-2 (Linear P < 0.001) but decreased protein levels of Bax, Caspase-3 and Bax/Bcl-2 (Linear P < 0.001). TUNEL assays indicated that cellular fluorescence intensity declined with the rising doses of Res. Res also dose-dependently upregulated SIRT3 expression, but LPS had the opposite effect. SIRT3 silencing abolished these results with Res incubation. Mechanically, Res enhanced the nuclear translocation of PGC1α, the transcriptional cofactor for SIRT3. Further molecular docking analysis revealed that Res could directly bind to PGC1α by forming a hydrogen bond with Tyr-722. Overall, our data suggested that Res relieved LPS-induced BMEC apoptosis through the PGC1α-SIRT3 axis, providing a basis for further in vivo investigations of applying Res to relieve mastitis in dairy cows.

How Many Sirtuin Genes Are Out There? Evolution of Sirtuin Genes in Vertebrates With a Description of a New Family Member

Studying the evolutionary history of gene families is a challenging and exciting task with a wide range of implications. In addition to exploring fundamental questions about the origin and evolution of genes, disentangling their evolution is also critical to those who do functional/structural studies to allow a deeper and more precise interpretation of their results in an evolutionary context. The sirtuin gene family is a group of genes that are involved in a variety of biological functions mostly related to aging. Their duplicative history is an open question, as well as the definition of the repertoire of sirtuin genes among vertebrates. Our results show a well-resolved phylogeny that represents an improvement in our understanding of the duplicative history of the sirtuin gene family. We identified a new sirtuin gene family member (SIRT3.2) that was apparently lost in the last common ancestor of amniotes but retained in all other groups of jawed vertebrates. According to our experimental analyses, elephant shark SIRT3.2 protein is located in mitochondria, the overexpression of which leads to an increase in cellular levels of ATP. Moreover, in vitro analysis demonstrated that it has deacetylase activity being modulated in a similar way to mammalian SIRT3. Our results indicate that there are at least eight sirtuin paralogs among vertebrates and that all of them can be traced back to the last common ancestor of the group that existed between 676 and 615 millions of years ago.

Nicotinamide n-Oxide Attenuates HSV-1-Induced Microglial Inflammation through Sirtuin-1/NF-κB Signaling

HSV-1 is a typical neurotropic virus that infects the brain and causes keratitis, cold sores, and occasionally, acute herpes simplex encephalitis (HSE). The large amount of proinflammatory cytokines induced by HSV-1 infection is an important cause of neurotoxicity in the central nervous system (CNS). Microglia, as resident macrophages in CNS, are the first line of defense against neurotropic virus infection. Inhibiting the excessive production of inflammatory cytokines in overactivated microglia is a crucial strategy for the treatment of HSE. In the present study, we investigated the effect of nicotinamide n-oxide (NAMO), a metabolite mainly produced by gut microbe, on HSV-1-induced microglial inflammation and HSE. We found that NAMO significantly inhibits the production of cytokines induced by HSV-1 infection of microglia, such as IL-1β, IL-6, and TNF-α. In addition, NAMO promotes the transition of microglia from the pro-inflammatory M1 type to the anti-inflammatory M2 type. More detailed studies revealed that NAMO enhances the expression of Sirtuin-1 and its deacetylase enzymatic activity, which in turn deacetylates the p65 subunit to inhibit NF-κB signaling, resulting in reduced inflammatory response and ameliorated HSE pathology. Therefore, Sirtuin-1/NF-κB axis may be promising therapeutic targets against HSV-1 infection-related diseases including HSE.

SIRT1 activation attenuates microglia-mediated synaptic engulfment in postoperative cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a debilitating neurological complication in surgical patients. Current research has focused mainly on microglial activation, but less is known about the resultant neuronal synaptic changes. Recent studies have suggested that Sirtuin-1 (SIRT1) plays a critical role in several different neurological disorders via its involvement in microglial activation. In this study, we evaluate the effects of SIRT1 activation in a POCD mouse model.

MATERIALS AND METHODS

Exploratory laparotomy was performed in mice aged 12-14 months under sevoflurane anesthesia to establish our animal POCD model. Transcriptional changes in the hippocampus after anesthesia and surgery were evaluated by RNA sequencing. SIRT1 expression was verified by Western Blot. Mice were treated with SIRT1 agonist SRT1720 or vehicle after surgery. Changes in microglia morphology, microglial phagocytosis, presence of dystrophic neurites, and dendritic spine density were evaluated. Cognitive performance was evaluated using the Y maze and Morris water maze (MWM).

RESULTS

Sirtuin-1 expression levels were downregulated in POCD. Exposure to anesthesia and surgery lead to alteration in microglia morphology, increased synaptic engulfment, dendritic spine loss, and cognitive deficits. These effects were alleviated by SRT1720 administration.

CONCLUSION

This study suggests an important neuroprotective role for SIRT1 in POCD pathogenesis. Increasing SIRT1 function represents a promising therapeutic strategy for prevention and treatment of POCD.

Mesenchymal Stem Cell-Derived Exosomes Ameliorate Delayed Neurocognitive Recovery in Aged Mice by Inhibiting Hippocampus Ferroptosis via Activating SIRT1/Nrf2/HO-1 Signaling Pathway

Delayed neurocognitive recovery (dNCR) is a prevalent perioperative neurological complication in older patients and has common characteristics such as acute cognitive dysfunction, impaired memory, and inattention. Mesenchymal stem cell-derived exosomes (MSCs-Exo) are enclosed by a lipid bilayer contain proteins, DNA, miRNA, and other components, which are important mediators of intercellular communication. It has been reported that exosomes could play an important role in the treatment of neurodegenerative diseases, nerve injury, and other neurological diseases. In this study, we examined the effects of MSCs-Exo on dNCR aged mice after exploratory laparotomy and evaluated their potential regulatory mechanisms. We found that MSCs-Exo treatment ameliorated cognitive impairment in dNCR aged mice. MSCs-Exo inhibit hippocampus ferroptosis and increase the expression of silent information regulator 1 (SIRT1), factor nuclear factor-erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) in dNCR aged mice. Interestingly, the above effects of MSCs-Exo on dNCR aged mice were abolished by SIRT1 selective inhibitor EX-527. In conclusion, these findings indicated that MSCs-Exo can ameliorate cognitive impairment by inhibiting hippocampus ferroptosis in dNCR aged mice via activating SIRT1/Nrf2/HO-1 signaling pathway, providing a potential avenue for the treatment of dNCR.

Role of Sirtuins in Physiology and Diseases of the Central Nervous System

Silent information regulators, sirtuins (SIRTs), are a family of enzymes which take part in major posttranslational modifications of proteins and contribute to multiple cellular processes, including metabolic and energetic transformations, as well as regulation of the cell cycle. Recently, SIRTs have gained increased attention as the object of research because of their multidirectional activity and possible role in the complex pathomechanisms underlying human diseases. The aim of this study was to review a current literature evidence of SIRTs' role in the physiology and pathology of the central nervous system (CNS). SIRTs have been demonstrated to be crucial players in the crosstalk between neuroinflammation, neurodegeneration, and metabolic alterations. The elucidation of SIRTs' role in the background of various CNS diseases offers a chance to define relevant markers of their progression and promising candidates for novel therapeutic targets. Possible diagnostic and therapeutic implications from SIRTs-related investigations are discussed, as well as their future directions and associated challenges.

Activating SIRT-1 Signalling with the Mitochondrial-CoQ10 Activator Solanesol Improves Neurobehavioral and Neurochemical Defects in Ouabain-Induced Experimental Model of Bipolar Disorder

Bipolar disorder (BD) is a chronic mental illness characterized by mood fluctuations that range from depressive lows to manic highs. Several studies have linked the downregulation of SIRT-1 (silent mating type information regulation-2 homologs) signaling to the onset of BD and other neurological dysfunctions. This research aimed to look into the neuroprotective potential of Solanesol (SNL) in rats given ICV-Ouabain injections, focusing on its effect on SIRT-1 signaling activation in the brain. Ouabain, found in hypothalamic and medullary neurons, is an endogenous inhibitor of brain Na⁺/K⁺ ATPase. The inhibition of brain Na⁺/K⁺ ATPase by Ouabain may also result in changes in neurotransmission within the central nervous system. SNL is a Solanaceae family active phytoconstituent produced from the plant Nicotiana tabacum. SNL is used as a precursor for the production of CoQ10 (Coenzyme Q10), a powerful antioxidant and neuroprotective compound. In the current study, lithium (Li), an important mood stabilizer drug, was used as a control. This study looked at the neuroprotective potential of SNL at dosages of 40 and 80 mg/kg in ICV-OUA injections that caused BD-like neurobehavioral and neurochemical defects in Wistar rats. Wistar rats were placed into eight groups (n = 6) and administered 1 mM/0.5 µL ICV-OUA injections for three days. Neurochemical assessments were done in rat brain homogenates, CSF, and blood plasma samples at the end of the experiment protocol schedule. Long-term SNL and lithium administration have been shown to decrease the number of rearing and crossings and reduce time spent in the center, locomotor activities, and immobility time. Solansesol treatment gradually raises the amount of Na⁺/K⁺ ATPase, limiting the severity of behavioural symptoms. These findings also revealed that SNL increases the levels of SIRT-1 in CSF, blood plasma, and brain homogenate samples. Moreover, in rat brain homogenates and blood plasma samples, SNL modulates apoptotic markers such as Caspase-3, Bax (pro-apoptotic), and Bcl-2 (anti-apoptotic). Mitochondrial-ETC complex enzymes, including complex-I, II, IV, V, and CoQ10, were also restored following long-term SNL treatment. Furthermore, SNL lowered inflammatory cytokines (TNF-α, IL-1β) levels while restoring neurotransmitter levels (serotonin, dopamine, glutamate, and acetylcholine) and decreasing oxidative stress markers. Histological examinations also validated Solanesol’s protective effect. As a result, our findings suggest that SNL, as a SIRT-1 signalling activator, may be a promising therapeutic approach for BD-like neurological dysfunctions.

Specific epigenetic regulators serve as potential therapeutic targets in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a disorder observed mostly in older human beings, is characterised by chronic and progressive lung scarring leading to an irreversible decline in lung function. This health condition has a dismal prognosis and the currently available drugs only delay but fail to reverse the progression of lung damage. Consequently, it becomes imperative to discover improved therapeutic compounds and their cellular targets to cure IPF. In this regard, a number of recent studies have targeted the epigenetic regulation by histone deacetylases (HDACs) to develop and categorise antifibrotic drugs for lungs. Therefore, this review focuses on how aberrant expression or activity of Classes I, II and III HDACs alter TGF-β signalling to promote events such as epithelial-mesenchymal transition, differentiation of activated fibroblasts into myofibroblasts, and excess deposition of the extracellular matrix to propel lung fibrosis. Further, this study describes how certain chemical compounds or dietary changes modulate dysregulated HDACs to attenuate five faulty TGF-β-dependent profibrotic processes, both in animal models and cell lines replicating IPF, thereby identifying promising means to treat this lung disorder.

Selective Upregulation of SIRT1 Expression in Retinal Ganglion Cells by AAV-Mediated Gene Delivery Increases Neuronal Cell Survival and Alleviates Axon Demyelination Associated with Optic Neuritis

Optic neuritis (ON), the most common ocular manifestation of multiple sclerosis, is an autoimmune inflammatory demyelinating disease also characterized by degeneration of retinal ganglion cells (RGCs) and their axons, which commonly leads to visual impairment despite attempted treatments. Although ON disease etiology is not known, changes in the redox system and exacerbated optic nerve inflammation play a major role in the pathogenesis of the disease. Silent information regulator 1 (sirtuin-1/SIRT1) is a ubiquitously expressed NAD+-dependent deacetylase, which functions to reduce/prevent both oxidative stress and inflammation in various tissues. Non-specific upregulation of SIRT1 by pharmacologic and genetic approaches attenuates RGC loss in experimental ON. Herein, we hypothesized that targeted expression of SIRT1 selectively in RGCs using an adeno-associated virus (AAV) vector as a delivery vehicle is an effective approach to reducing neurodegeneration and preserving vision in ON. We tested this hypothesis through intravitreal injection of AAV7m8.SNCG.SIRT1, an AAV2-derived vector optimized for highly efficient SIRT1 transgene transfer and protein expression into RGCs in mice with experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis that recapitulates optic neuritis RGC loss and axon demyelination. Our data show that EAE mice injected with a control vehicle exhibit progressive alteration of visual function reflected by decreasing optokinetic response (OKR) scores, whereas comparatively, AAV7m8.SNCG.SIRT1-injected EAE mice maintain higher OKR scores, suggesting that SIRT1 reduces the visual deficit imparted by EAE. Consistent with this, RGC survival determined by immunolabeling is increased and axon demyelination is decreased in the AAV7m8.SNCG.SIRT1 RGC-injected group of EAE mice compared to the mouse EAE counterpart injected with a vehicle or with control vector AAV7m8.SNCG.eGFP. However, immune cell infiltration of the optic nerve is not significantly different among all EAE groups of mice injected with either vehicle or AAV7m8.SNCG.SIRT1. We conclude that despite minimally affecting the inflammatory response in the optic nerve, AAV7m8-mediated SIRT1 transfer into RGCs has a neuroprotective potential against RGC loss, axon demyelination and vison deficits associated with EAE. Together, these data suggest that SIRT1 exerts direct effects on RGC survival and function.

SIRT1: A promising therapeutic target for chronic pain

Chronic pain remains an unresolved problem. Current treatments have limited efficacy. Thus, novel therapeutic targets are urgently required for the development of more effective analgesics. An increasing number of studies have proved that sirtuin 1 (SIRT1) agonists can relieve chronic pain. In this review, we summarize recent progress in understanding the roles and mechanisms of SIRT1 in mediating chronic pain associated with peripheral nerve injury, chemotherapy‐induced peripheral neuropathy, spinal cord injury, bone cancer, and complete Freund's adjuvant injection. Emerging studies have indicated that SIRT1 activation may exert positive effects on chronic pain relief by regulating inflammation, oxidative stress, and mitochondrial dysfunction. Therefore, SIRT1 agonists may serve as potential therapeutic drugs for chronic pain.

A Review of ApoE4 Interference Targeting Mitophagy Molecular Pathways for Alzheimer's Disease

Alzheimer's disease (AD) is one of the major worldwide causes of dementia that is characterized by irreversible decline in learning, memory loss, and behavioral impairments. Mitophagy is selective autophagy through the clearance of aberrant mitochondria, specifically for degradation to maintain energy generation and neuronal and synaptic function in the brain. Accumulating evidence shows that defective mitophagy is believed to be as one of the early and prominent features in AD pathogenesis and has drawn attention in the recent few years. APOE ε4 allele is the greatest genetic determinant for AD and is widely reported to mediate detrimental effects on mitochondria function and mitophagic process. Given the continuity of the physiological process, this review takes the mitochondrial dynamic and mitophagic core events into consideration, which highlights the current knowledge about the molecular alterations from an APOE-genotype perspective, synthesizes ApoE4-associated regulations, and the cross-talk between these signaling, along with the focuses on general autophagic process and several pivotal processes of mitophagy, including mitochondrial dynamic (DRP1, MFN-1), mitophagic induction (PINK1, Parkin). These may shed new light on the link between ApoE4 and AD and provide novel insights for promising mitophagy-targeted therapeutic strategies for AD.

Resveratrol and neuroprotection: an insight into prospective therapeutic approaches against Alzheimer's disease from bench to bedside

Alzheimer's disease (AD) is the most common cause of dementia and cognitive impairment; yet, there is currently no treatment. A buildup of Aβ, tau protein phosphorylation, oxidative stress, and inflammation in AD is pathogenic. The accumulation of amyloid-beta (Aβ) peptides in these neurocognitive areas is a significant characteristic of the disease. Therefore, inhibiting Aβ peptide aggregation has been proposed as the critical therapeutic approach for AD treatment. Resveratrol has been demonstrated in multiple studies to have a neuroprotective, anti-inflammatory, and antioxidant characteristic and the ability to minimize Aβ peptides aggregation and toxicity in the hippocampus of Alzheimer's patients, stimulating neurogenesis and inhibiting hippocampal degeneration. Furthermore, resveratrol's antioxidant effect promotes neuronal development by activating the silent information regulator-1 (SIRT1), which can protect against the detrimental effects of oxidative stress. Resveratrol-induced SIRT1 activation is becoming more crucial in developing novel therapeutic options for AD and other diseases that have neurodegenerative characteristics. This review highlighted a better knowledge of resveratrol's mechanism of action and its promising therapeutic efficacy in treating AD. We also highlighted the therapeutic potential of resveratrol as an AD therapeutic agent, which is effective against neurodegenerative disorders.

Regulation of SIRT1 and Its Roles in Inflammation

The silent information regulator sirtuin 1 (SIRT1) protein, a highly conserved NAD⁺-dependent deacetylase belonging to the sirtuin family, is a post-translational regulator that plays a role in modulating inflammation. SIRT1 affects multiple biological processes by deacetylating a variety of proteins including histones and non-histone proteins. Recent studies have revealed intimate links between SIRT1 and inflammation, while alterations to SIRT1 expression and activity have been linked to inflammatory diseases. In this review, we summarize the mechanisms that regulate SIRT1 expression, including upstream activators and suppressors that operate on the transcriptional and post-transcriptional levels. We also summarize factors that influence SIRT1 activity including the NAD⁺/NADH ratio, SIRT1 binding partners, and post-translational modifications. Furthermore, we underscore the role of SIRT1 in the development of inflammation by commenting on the proteins that are targeted for deacetylation by SIRT1. Finally, we highlight the potential for SIRT1-based therapeutics for inflammatory diseases.

Sirtuin-1 - Mediated NF-κB Pathway Modulation to Mitigate Inflammasome Signaling and Cellular Apoptosis is One of the Neuroprotective Effects of Intra-arterial Mesenchymal Stem Cell Therapy Following Ischemic Stroke

AIM

Stroke results in long term serious disability that affect millions across the globe. Several clinical and preclinical studies have reinforced the therapeutic use of stem cells in stroke patients to enhance their quality of life. Previous studies from our lab have demonstrated that 1*10⁵ allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) when given intraarterially (IA) render neuroprotection by modulating the expression of inflammasomes. Sirtuins are a class of important deacylases having a significant role in cellular functioning. Sirtuin-1 (SIRT-1) is an important enzyme essential for regulating cellular metabolism, which is reduced following an ischemic episode. The present study aims to unviel the role of MSCs in regulating the brain SIRT-1 levels following stroke and the involvement of SIRT-1 in regulating inflammasome signaling to reduce cellular apoptosis towards rendering neuroprotection.

MATERIALS AND METHODS

6 h post-reversible middle cerebral artery occlusion (MCAo), ovariectomized Sprague Dawley (SD) rats were infused intraarterially with 1*10⁵ MSCs. 24 h after MCAo animals were examined for functional and behavioral outcomes. Brains were collected for assessing size of infarct and neuronal morphology. Molecular and immunofluroscence studies were also performed for assessing changes in gene and protein expressions. Extent of apoptosis was also determined in different groups. Inhibition study with SIRT-1 specific inhibitor EX-527 was also performed.

RESULTS

A reduction in infarct size and improvement in motor functional and behavioral outcomes following infusion of MSCs IA at 6 h post-stroke was observed. Increase in average neuronal density and neuronal length was also seen. Increased expression of SIRT-1, BDNF and concomitant reduction in the expression of different inflammatory and apoptotic markers in the brain cortical regions were observed following MSCs treatment.

CONCLUSION

Our study provides a preliminary evidence that post-stroke IA MSCs therapy regulates SIRT-1 to modulate NF-κB pathway to mitigate inflammasome signaling and cellular apoptosis. This study using IA approach for administering MSCs is highly relevant clinically. Our study is the first to report that neuroprotective effects of IA MSCs in rodent focal ischemia is mediated by SIRT-1 regulation of inflammasome signaling.

Dietary Supplements in Chemotherapy-Induced Peripheral Neuropathy: A New Hope?

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the main and most prevalent side effects of chemotherapy, significantly affecting the quality of life of patients and the course of chemotherapeutic treatment. Nevertheless, despite its prevalence, the management of the CIPN is considered particularly challenging, with this condition often being perceived as very difficult or even impossible to prevent with currently available agents. Therefore, it is imperative to find better options for patients diagnosed with this condition. While the search for the new agents must continue, another opportunity should be taken into consideration—repurposing of the already known medications. As proposed, acetyl-L-carnitine, vitamins (group B and E), extracts of medical plants, including goshajinkigan, curcumin and others, unsaturated fatty acids, as well as the diet composed of so-called “sirtuin-activating foods”, could change the typical way of treatment of CIPN, improve the quality of life of patients and maintain the continuity of chemotherapy. This review summarizes currently available data regarding mentioned above agents and evaluates the rationale behind future research focused on their efficacy in CIPN.

Role of nutraceuticals on neurodegenerative diseases: neuroprotective and immunomodulant activity

Neurodegeneration is a degenerative process characterized by the progressive loss of the structure and function of neurons that involves several immune cells. It is the primary cause of dementia and other several syndromes, known as neurodegenerative diseases. These disorders are age-related and it is estimated that by 2040 there will be approximately 81.1 million people suffering from these diseases. In addition to the traditional pharmacological therapy, in recent years nutraceuticals, naturally based compounds with a broad spectrum of biological effects: anti-aging, antioxidants, hypoglycaemic, hypocholesterolemic, anticancer, anxiolytic, antidepressant, etc., assumed an important role in counteracting these pathologies. In particular, several compounds such as astaxanthin, baicalein, glycyrrhizin, St. John's wort, and Ginkgo biloba L. extracts show particular neuroprotective and immunomodulatory abilities, involving several immune cells and some neurotransmitters that play a critical role in neurodegeneration, making them particularly useful in improving the symptoms and progression of neurodegenerative diseases.

Role of Klotho as a Modulator of Oxidative Stress Associated with Ovarian Tissue Cryopreservation

Ovarian tissue cryopreservation is the only option for preserving fertility in adult and prepubertal cancer patients who require immediate chemotherapy or do not want ovarian stimulation. However, whether ovarian tissue cryopreservation can ameliorate follicular damage and inhibit the production of reactive oxygen species in cryopreserved ovarian tissue remains unclear. Oxidative stress is caused by several factors, such as UV exposure, obesity, age, oxygen, and cryopreservation, which affect many of the physiological processes involved in reproduction, from maturation to fertilization, embryonic development, and pregnancy. Here, freezing and thawing solutions were pre-treated with N-acetylcysteine (NAC) and klotho protein upon the freezing of ovarian tissue. While both NAC and klotho protein suppressed DNA fragmentation by scavenging reactive oxygen species, NAC induced apoptosis and tissue damage in mouse ovarian tissue. Klotho protein inhibited NAC-induced apoptosis and restored cellular tissue damage, suggesting that klotho protein may be an effective antioxidant for the cryopreservation of ovarian tissue.

Sirtuin Modulators in Cellular and Animal Models of Human Diseases

Sirtuins use NAD⁺ to remove various acyl groups from protein lysine residues. Through working on different substrate proteins, they display many biological functions, including regulation of cell proliferation, genome stability, metabolism, and cell migration. There are seven sirtuins in humans, SIRT1-7, each with unique enzymatic activities, regulatory mechanisms, subcellular localizations, and substrate scopes. They have been indicated in many human diseases, including cancer, neurodegeneration, microbial infection, metabolic and autoimmune diseases. Consequently, interests in development of sirtuin modulators have increased in the past decade. In this brief review, we specifically summarize genetic and pharmacological modulations of sirtuins in cancer, neurological, and cardiovascular diseases. We further anticipate this review will be helpful for scrutinizing the significance of sirtuins in the studied diseases.

SIRT7 Acts as a Guardian of Cellular Integrity by Controlling Nucleolar and Extra-Nucleolar Functions

Sirtuins are key players for maintaining cellular homeostasis and are often deregulated in different human diseases. SIRT7 is the only member of mammalian sirtuins that principally resides in the nucleolus, a nuclear compartment involved in ribosomal biogenesis, senescence, and cellular stress responses. The ablation of SIRT7 induces global genomic instability, premature ageing, metabolic dysfunctions, and reduced stress tolerance, highlighting its critical role in counteracting ageing-associated processes. In this review, we describe the molecular mechanisms employed by SIRT7 to ensure cellular and organismal integrity with particular emphasis on SIRT7-dependent regulation of nucleolar functions.

High-Throughput Screening Identifies Ascorbyl Palmitate as a SIRT2 Deacetylase and Defatty-Acylase Inhibitor

Small-molecule inhibitors of the human sirtuin SIRT2 are being developed because of their therapeutic potential in a variety of diseases. Here, we developed a high-throughput screen to identify novel SIRT2 inhibitors using a fluorescent SIRT2 probe, 1-aminoanthracene (AMA). AMA has high fluorescence when bound to SIRT2, and its fluorescence reduces >10-fold when it is displaced from SIRT2 by other ligands. We used this property of AMA to screen a library of known bioactive compounds for SIRT2 binding and discovered two known pharmaceutical compounds that bind SIRT2 with K_d values in the low μM range, ascorbyl palmitate and pictilisib. Both compounds inhibit the deacetylase and defatty-acylase activities of SIRT2. While pictilisib has selectivity for SIRT2, ascorbyl palmitate also inhibits the enzymatic activities of SIRT1 and SIRT6. Finally, we show that ascorbyl palmitate inhibits SIRT2 deacetylase and defatty-acylase activities in cells, and SIRT2 inhibition by ascorbyl palmitate contributes to the cytotoxicity of the compound. Our work discovered novel SIRT2 deacylase inhibitors and presents a screening approach that can be applied on a larger scale.

A review study on the modulation of SIRT1 expression by miRNAs in aging and age-associated diseases

Sirtuin-1 (SIRT1) as a NAD + -dependent Class III protein deacetylase, involves in longevity and various cellular physiological processes. SIRT1 via deacetylating transcription factors regulates cell growth, inflammation, metabolism, hypoxic responses, cell survival, senescence, and aging. MicroRNAs (miRNAs) are short non-coding RNAs that modulate the expression of target genes in a post-transcriptional manner. Recent investigations have exhibited that miRNAs have an important role in regulating cell growth, development, stress responses, tumor formation and suppression, cell death, and aging. In the present review, we summarize recent findings about the roles of miRNAs in regulating SIRT1 and SIRT1-associated signaling cascade and downstream effects, like apoptosis and aging. Here we introduce and discuss how activity and expression of SIRT1 are modulated by miRNAs and further review the therapeutic potential of targeting miRNAs for age-associated diseases that involve SIRT1 dysfunction. Although at its infancy, research on the roles of miRNAs in aging and their function through modulating SIRT1 may provide new insights in deciphering the key molecular pathways related to aging and age-associated disorders.

QKI 6 ameliorates CIRI through promoting synthesis of triglyceride in neuron and inhibiting neuronal apoptosis associated with SIRT1-PPARγ-PGC-1α axis

BACKGROUND

The stroke induced by ischemia of brain remains high incidence and death rate. The study wanted to confirm the effects of Quaking 6 (QKI 6) on the protection role in neurons of rat model of cerebral ischemia/reperfusion injury (CIRI).

MATERIAL AND METHODS

The rat model with CIRI induced by middle cerebral artery occlusion was well established and rat neurons were isolated to characterize the effects of QKI 6 mediated by sirtuin 1 (SIRT1) on synthesis of triglyceride in neuron and neuronal apoptosis via activation of SIRT1-peroxisome proliferater-activated receptor (PPAR)γ- peroxisome proliferator-activated receptor coactivator (PGC)-1α signaling pathway.

RESULTS

The expression levels of SIRT1 or QKI 6, and acetylation level of QKI 6 were decreased in neurons of rat model with CIRI. QKI 6 deacetylated and mediated by SIRT1 that contributed to suppressing the progression of neuronal apoptosis in rat through promoting synthesis of triglyceride in vivo and in vitro via SIRT1-PPARγ-PGC-1α signaling pathway, then inhibiting CIRI.

CONCLUSIONS

Our results demonstrated SIRT1 deacetylates QKI 6, the RNA-binding protein, that affects significantly the synthesis of triglyceride in neurons of CIRI rat model. Moreover, it activated transcription factor peroxisome proliferator-activated receptorγ coactivator-1α (PGC-1α) through post-transcriptional regulation of the expression of PPARγ, and further enhanced synthesis of triglyceride, thereby restrained the progression of neural apoptosis and CIRI.

Sirtuins: Potential Therapeutic Targets for Defense against Oxidative Stress in Spinal Cord Injury

Spinal cord injury (SCI) is one of the most incapacitating neurological disorders. It involves complex pathological processes that include a primary injury and a secondary injury phase, or a delayed stage, which follows the primary injury and contributes to the aggravation of the SCI pathology. Oxidative stress, a key pathophysiological event after SCI, contributes to a cascade of inflammation, excitotoxicity, neuronal and glial apoptosis, and other processes during the secondary injury phase. In recent years, increasing evidence has demonstrated that sirtuins are protective toward the pathological process of SCI through a variety of antioxidant mechanisms. Notably, strategies that modulate the expression of sirtuins exert beneficial effects in cellular and animal models of SCI. Given the significance and novelty of sirtuins, we summarize the oxidative stress processes that occur in SCI and discuss the antioxidant effects of sirtuins in SCI. We also highlight the potential of targeting sirtuins for the treatment of SCI.

Hypothalamic GHR-SIRT1 Axis in Fasting

Many aspects of physiological functions are controlled by the hypothalamus, a brain region that connects the neuroendocrine system to whole-body metabolism. Growth hormone (GH) and the GH receptor (GHR) are expressed in hypothalamic regions known to participate in the regulation of feeding and whole-body energy homeostasis. Sirtuin 1 (SIRT1) is the most conserved mamma-lian nicotinamide adenine dinucleotide (NAD⁺)-dependent protein deacetylase that plays a key role in controlling life span and sensing nutrient availability in the hypothalamus in response to caloric restriction. However, the interaction between GHR signaling and SIRT1 in the hypothal-amus is not established. In the arcuate nucleus (ARC) of the hypothalamus, the anorexigenic proopiomelanocortin (POMC)-expressing neurons and the orexigenic agouti-related protein (AgRP)-expressing neurons are the major regulators of feeding and energy expenditure. We show that in the ARC, the majority of GHR-expressing neurons also express SIRT1 and respond to fasting by upregulating SIRT1 expression. Accordingly, hypothalamic upregulation of SIRT1 in response to fasting is blunted in animals with GHR deletion in the AgRP neurons (AgRP^EYFPΔGHR). Our data thus reveal a novel interaction between GH and SIRT1 in responses to fasting.

Histone Deacetylases Regulation by δ-Opioids in Human Optic Nerve Head Astrocytes

Purpose

We determined whether δ-opioid receptor agonist (SNC-121) regulates acetylation homeostasis via controlling histone deacetylases (HDACs) activity and expression in optic nerve head (ONH) astrocytes.

Methods

ONH astrocytes were treated with SNC-121 (1 µM) for 24 hours. The HDAC activity was measured using HDAC-specific fluorophore-conjugated synthetic substrates, Boc-Lys(Ac)-AMC and (Boc-Lys(Tfa)-AMC). Protein and mRNA expression of each HDAC was determined by Western blotting and quantitative real-time PCR. IOP in rats was elevated by injecting 2.0 M hypertonic saline into the limbal veins.

Results

Delta opioid receptor agonist, SNC-121 (1 µM), treatment increased acetylation of histone H3, H2B, and H4 by 128 ± 3%, 45 ± 1%, and 68 ± 2%, respectively. The addition of Garcinol, a histone-acetyltransferase inhibitor, fully blocked SNC-121–induced histone H3 acetylation. SNC-121 reduced the activities of class I and IIb HDACs activities significantly (17 ± 3%) and this decrease in HDACs activities was fully blocked by a selective δ-opioid receptors antagonist, naltrindole. SNC-121 also decrease the mRNA expression of HDAC-3 and HDAC-6 by 19% and 18%, respectively. Furthermore, protein expression of HDAC 1, 2, 3, and 6 was significantly (P < 0.05) decreased by SNC-121 treatment. SNC-121 treatment also reduced lipopolysaccharide-induced TNF-α production from ONH astrocytes and glial fibrillary acidic protein immunostaining in the optic nerve of ocular hypertensive animals.

Conclusions

We provided evidence that δ-opioid receptor agonist activation increased histone acetylation, decrease HDACs class I and class IIb activities, mRNA, and protein expression, lipopolysaccharide-induced TNF-α production in ONH astrocytes. Our data also demonstrate that SNC-121 treatment decrease glial fibrillary acidic protein immunostaining in the optic nerves of animals with ocular hypertension.

Sirtuins, a potential target in Traumatic Brain Injury and relevant experimental models

Traumatic brain injury (TBI) can simply be defined as a violent external injury to the head causing brain dysfunction. The primary injury occurs immediately on impact whereas the secondary injury begins minutes to months after impact. TBI affects a vast majority of population worldwide yet, there isn't any therapeutic intervention available. Sirtuins (SIRTs) are important regulator proteins found in humans. In several neurodegenerative diseases, SIRTs have proven its neuroprotective actions. Owing to the pathophysiological similarities in these diseases and TBI, SIRTs may serve as a potential target for therapeutic intervention in TBI. This review aims to describe the relevance of SIRTs as a potential pharmacological target in TBI. Also, the experimental animal model of TBI explored to understand the role of SIRTs in TBI have been discussed.

Tantalizing role of p53 molecular pathways and its coherent medications in neurodegenerative diseases

Neurodegenerative diseases are incongruous, commonly age-related disorders characterized by progressive neuronal loss, comprising the most prevalent being Alzheimer's disease, Parkinson's disease, and Huntington's disease. Perilous health states are anticipated following the neurodegeneration. Their etiology remains largely ambiguous, while various mechanisms are ascribed to their pathogenesis. A recommended conception is regarding the role of p53, as a transcription factor regulating numerous cellular pathways comprising apoptosis. Neuronal fates are a feasible occurrence that contributes to all neurodegenerative diseases. In this work, we review the research investigated the potential role of p53 in the pathogenesis of these diseases. We put special emphasis on intricate We not only describe aberrant changes in p53 level/activity observed in CNS regions affected by particular diseases but, most importantly, put special attention to the complicated reciprocal tuning connections prevailing between p53 and molecules considered in pathological hallmarks of these disorders. Natural and synthetic medications regulating p53 expression are regarded as well.

Biochemical mechanism and biological effects of the inhibition of silent information regulator 1 (SIRT1) by EX-527 (SEN0014196 or selisistat)

The human sirtuin silent information regulator 1 (SIRT1) is a NAD⁺-dependent deacetylase enzyme. It deacetylates many protein substrates, including histones and transcription factors, thereby controlling many physiological and pathological processes. Several synthetic inhibitors and activators of SIRT1 have been developed, and some therapeutic applications have been explored. The indole EX-527 and its derivatives are among the most potent and selective SIRT1 inhibitors. EX-527 has been often used as a pharmacological tool to explore the effect of SIRT1 inhibition in various cell types. Its therapeutic potential has, therefore, been evaluated in animal models for several pathologies, including cancer. It has also been tested in phase II clinical trial for the treatment of Huntington’s disease (HD). In this review, we will provide an overview of the literature on EX-527, including its mechanism of inhibition and biological studies.

A Review of APOE Genotype-Dependent Autophagic Flux Regulation in Alzheimer's Disease

Autophagy is a basic physiological process maintaining cell renewal, the degradation of dysfunctional organelles, and the clearance of abnormal proteins and has recently been identified as a main mechanism underlying the onset and progression of Alzheimer's disease (AD). The APOE ɛ4 genotype is the strongest genetic determinant of AD pathogenesis and initiates autophagic flux at different times. This review synthesizes the current knowledge about the potential pathogenic effects of ApoE4 on autophagy and describes its associations with the biological hallmarks of autophagy and AD from a novel perspective. Via a remarkable variety of widely accepted signaling pathway markers, such as mTOR, TFEB, SIRT1, LC3, p62, LAMP1, LAMP2, CTSD, Rabs, and V-ATPase, ApoE isoforms differentially modulate autophagy initiation; membrane expansion, recruitment, and enclosure; autophagosome and lysosome fusion; and lysosomal degradation. Although the precise pathogenic mechanism varies for different genes and proteins, the dysregulation of autophagic flux is a key mechanism on which multiple pathogenic processes converge.

Protective effect of hydrogen sulfide on endothelial cells through Sirt1-FoxO1-mediated autophagy

Background

As a new member of the vasculoprotective gasotransmitter family, hydrogen sulfide (H₂S) functions similar to nitric oxide (NO) and carbon monoxide (CO). Endothelial cell (EC) death and autophagy enable cells to cope with the progression of cardiovascular diseases. However, the impacts and underlying mechanisms of H₂S in the autophagic process in ECs are not completely understood. Here, we investigated the effects of H₂S on autophagy in human vascular ECs.

Methods

Human umbilical vein endothelial cells (HUVECs) were exposed to different concentrations (0, 50, 100, 200, 500 and 1,000 µmol/L) GYY4137 (H₂S donor) for indicated times (0, 0.5, 1, 2, 4 and 8 h), with or without pre-treatment with the autophagy inhibitor 3-methyladenine (3-MA) or bafilomycin A1. HUVECs were transfected with sirtuin 1 (Sirt1) overexpression plasmids (PIRES-Sirt1), Sirt1-siRNAs or forkhead box O1 (FoxO1)-siRNA using Lipofectamine 2000. Cell autophagy was evaluated via Western blotting and fluorescence microscopy. Co-immunoprecipitation assay was used to measure acetylation level of FoxO1. The distribution of FoxO1 in the cytoplasm and nucleus was observed using Western blotting and immunofluorescence. Western blotting, flow cytometric analysis, and cell count kit-8 assay were conducted to evaluate the effect of H₂S on the oxidized low-density lipoprotein (Ox-LDL) induced apoptosis of HUVECs.

Results

Using both gain- and loss-of-function experiments, we showed that Sirt1-dependent activation of FoxO1, including its nuclear translocation and deacetylation, was critical for mediating H₂S-induced autophagy in ECs. Furthermore, H₂S-induced autophagy protected ECs from Ox-LDL-induced apoptosis by activating Sirt1.

Conclusions

These results suggest that Sirt1-mediated autophagy in ECs is a novel mechanism by which H₂S exerts vascular-protective actions.

Exosomal MicroRNAs in Military Personnel with Mild Traumatic Brain Injury: Preliminary Results from the Chronic Effects of Neurotrauma Consortium Biomarker Discovery Project

Chronic symptoms after mild traumatic brain injury (mTBI) are common among veterans and service members, and represent a significant source of morbidity, with those who sustain multiple mTBIs at greatest risk. Exosomal micro-RNAs (miRNAs), mediators of intercellular communication, may be involved in chronic TBI symptom persistence. Exosomal miRNA (exomiR) was extracted from 153 participants enrolled in the Chronic Effect of Neurotrauma Consortium (CENC) longitudinal study (no TBI, n = 35; ≥ 3 mTBIs (rTBI), n = 45; 1-2 mTBIs, n = 73). Analyses were performed with nCounter® Human miRNA Expression Panels and Ingenuity Pathway Analysis (IPA) for identification of gene networks associated with TBI. Generalized linear models were used to analyze the predictive value of exomiR dysregulation and remote neurobehavioral symptoms. Compared with controls, there were 17 dysregulated exomiRs in the entire mTBI group and 32 dysregulated exomiRs in the rTBI group. Two miRNAs, hsa-miR-139-5p and hsa-miR-18a-5p, were significantly differentially expressed in the rTBI and 1-2 mTBI groups. IPA analyses showed that these dysregulated exomiRs correlated with pathways of inflammatory regulation, neurological disease, and cell development. Within the rTBI group, exomiRs correlated with gene activity for hub-genes of tumor protein TP53, insulin-like growth factor 1 receptor, and transforming growth factor beta. TBI history and neurobehavioral symptom survey scores negatively and significantly correlated with hsa-miR-103a-3p expression. Participants with remote mTBI have distinct exomiR profiles, which are significantly linked to inflammatory and neuronal repair pathways. These profiles suggest that analysis of exosomal miRNA expression may provide novel insights into the underlying pathobiology of chronic TBI symptom persistence.

Modelling of pathogen-host systems using deeper ORF annotations and transcriptomics to inform proteomics analyses

The Zika virus is a flavivirus that can cause fulminant outbreaks and lead to Guillain-Barré syndrome, microcephaly and fetal demise. Like other flaviviruses, the Zika virus is transmitted by mosquitoes and provokes neurological disorders. Despite its risk to public health, no antiviral nor vaccine are currently available. In the recent years, several studies have set to identify human host proteins interacting with Zika viral proteins to better understand its pathogenicity. Yet these studies used standard human protein sequence databases. Such databases rely on genome annotations, which enforce a minimal open reading frame (ORF) length criterion. An ever-increasing number of studies have demonstrated the shortcomings of such annotation, which overlooks thousands of functional ORFs. Here we show that the use of a customized database including currently non-annotated proteins led to the identification of 4 alternative proteins as interactors of the viral capsid and NS4A proteins. Furthermore, 12 alternative proteins were identified in the proteome profiling of Zika infected monocytes, one of which was significantly up-regulated. This study presents a computational framework for the re-analysis of proteomics datasets to better investigate the viral-host protein interplays upon infection with the Zika virus.

Desoxyrhapontigenin attenuates neuronal apoptosis in an isoflurane-induced neuronal injury model by modulating the TLR-4/cyclin B1/Sirt-1 pathway

This study investigated the protective effect of desoxyrhapontigenin (DOP) against isoflurane (ISF)-induced neuronal injury in rats. Neuronal injury was induced in pups by exposing them to 0.75% ISF on postnatal day 7 with 30% oxygen for 6 h. The pups were treated with DOP 10 mg/kg, i.p., for 21 days after ISF exposure. The protective effect of DOP was estimated by assessing cognitive function using the neurological score and the Morris water maze. Neuronal apoptosis was assessed in the hippocampus using the TUNEL assay, and protein expression of caspase-3, Bax, and Bcl-2 was measured by Western blotting. The levels of cytokines and oxidative stress parameters were assessed by ELISA. Western blotting and RT-PCR were performed to measure the expression of NF-kB, TLR-4, Sirt-1, and cyclin B1 protein in the brain. The cognitive function and neurological function scores were improved in the DOP group compared with the ISF group. Moreover, DOP treatment reduced the number of TUNEL-positive cells and the expression of caspase-3, Bax, and Bcl-2 protein in the brains of rats with neuronal injury. The levels of mediators of inflammation and oxidative stress were reduced in the brain tissue of the DOP group. Treatment with DOP attenuated the protein expression of TLR-4, NF-kB, cyclin B1, and Sirt-1 in the brain tissue of rats with neuronal injury. In conclusion, DOP ameliorates neuronal apoptosis and improves cognitive function in rats with ISF-induced neuronal injury. Moreover, DOP treatment can prevent neuronal injury by regulating the TLR-4/cyclin B1/Sirt-1 pathway.

Synthesis of indole inhibitors of silent information regulator 1 (SIRT1), and their evaluation as cytotoxic agents

A series of achiral indole analogues of the selective sirtuin inhibitor EX-527 (a racemic, substituted 1,2,3,4 tetrahydrocarbazole) was designed to stabilize the bioactive conformation, and synthesized. These new indoles were evaluated against the isolated sirtuin enzymes SIRT1 and SIRT2, and against a panel of nine human cell lines. Structure-activity relationship studies demonstrated the influence of the substituent at position 3 of the indole. The most potent SIRT1 inhibitor 3h, bearing an isopropyl substituent, was as potent as EX-527, and more selective for SIRT1 over SIRT2. Compound 3g, bearing a benzyl substituent, inhibited both sirtuins at micromolar concentration and was more cytotoxic than EX-527 on several cancer cell lines.

Will Sirtuins Be Promising Therapeutic Targets for TBI and Associated Neurodegenerative Diseases?

Traumatic brain injury (TBI), a leading cause of morbidity worldwide, induces mechanical, persistent structural, and metabolic abnormalities in neurons and other brain-resident cells. The key pathological features of TBI include neuroinflammation, oxidative stress, excitotoxicity, and mitochondrial dysfunction. These pathological processes persist for a period of time after TBIs. Sirtuins are evolutionarily conserved nicotinamide-adenine dinucleotide (NAD+)-dependent deacetylases and mono-ADP-ribosyl transferases. The mammalian sirtuin family has seven members, referred to as Sirtuin (SIRT) 1-7. Accumulating evidence suggests that SIRT1 and SIRT3 play a neuroprotective role in TBI. Although the evidence is scant, considering the involvement of SIRT2, 4-7 in other brain injury models, they may also intervene in similar pathophysiology in TBI. Neurodegenerative diseases are generally accepted sequelae of TBI. It was found that TBI and neurodegenerative diseases have many similarities and overlaps in pathological features. Besides, sirtuins play some unique roles in some neurodegenerative diseases. Therefore, we propose that sirtuins might be a promising therapeutic target for both TBI and associated neurodegenerative diseases. In this paper, we review the neuroprotective effects of sirtuins on TBI as well as related neurodegeneration and discuss the therapeutic potential of sirtuin modulators.

Olive Leaf Polyphenols Attenuate the Clinical Course of Experimental Autoimmune Encephalomyelitis and Provide Neuroprotection by Reducing Oxidative Stress, Regulating Microglia and SIRT1, and Preserving Myelin Integrity

Numerous evidences suggest that plant polyphenols may have therapeutic benefits in regulating oxidative stress and providing neuroprotection in many neurodegenerative diseases, including multiple sclerosis (MS). However, these mechanisms are not yet completely understood. In this study, we investigated the effect of olive leaf polyphenols on oxidative stress through oxidation marker level and activity (TBARS, SOD, and GPX) and their protein expression (SOD1, SOD2, and GPX1), as well as the protein expression of Sirtuin 1 (SIRT1) and microglia markers (Iba-1, CD206, and iNOS) and myelin integrity (proteolipid protein expression) in the brain of rats with induced experimental autoimmune encephalomyelitis (EAE) and subjected to olive leaf therapy. Experiments were performed in male EAE DA rats, which were randomly divided into 2 main groups: EAE groups treated with the therapy of olive leaf (EAE+TOL) and untreated EAE control groups. The EAE treated groups consumed olive leaf tea instead of drinking water (ad libitum) from the beginning to the end of the experiment. In addition, olive leaf extract was injected intraperitoneally (i.p.) for the 10 continuous days and started on the 8^th day after EAE induction. The clinical course was monitored in both groups until the 30^th day after EAE induction. Our results demonstrated that TOL attenuated the clinical course of EAE; reduced the oxidative stress (by decreasing the concentration of MDA); upregulated antioxidant enzymes (SOD1, SOD2, and GPX1), SIRT1 (overall and microglial), and anti-inflammatory M2 microglia; downregulated proinflammatory M1 type; and preserved myelin integrity. These data support the idea that TOL may be an effective therapeutic approach for treating MS and other neurodegenerative diseases.

The effect of swimming exercise and diet on the hypothalamic inflammation of ApoE-/- mice based on SIRT1-NF-κB-GnRH expression

A high-fat diet and sedentary lifestyle could accelerate aging and hypothalamic inflammation. In order to explore the regulatory mechanisms of lifestyle in the hypothalamus, swimming exercise and diet control were applied in the high-fat diet ApoE-/- mice in our study. 20-week-old ApoE-/- mice fed with 12-week high-fat diet were treated by high-fat diet, diet control and swimming exercise. The results showed that hypothalamic inflammation, glial cells activation and cognition decline were induced by high-fat diet. Compared with the diet control, hypothalamic inflammation, glial cells activation and learning and memory impairment were effectively alleviated by swimming exercise plus diet control, which was related to the increasing expression of SIRT1, inhibiting the expression of NF-κB and raising secretion of GnRH in the hypothalamus. These findings supported the hypothesis that hypothalamic inflammation was susceptible to exercise and diet, which was strongly associated with SIRT1-NF-κB-GnRH expression in the hypothalamus.