SIRT1 deacetylase protects against neurodegeneration in models for Alzheimer's disease and amyotrophic lateral sclerosis

Role of Sirtuins in Modulating Neurodegeneration of the Enteric Nervous System and Central Nervous System

Neurodegeneration of the central and enteric nervous systems is a common feature of aging and aging-related diseases, and is accelerated in individuals with metabolic dysfunction including obesity and diabetes. The molecular mechanisms of neurodegeneration in both the CNS and ENS are overlapping. Sirtuins are an important family of histone deacetylases that are important for genome stability, cellular response to stress, and nutrient and hormone sensing. They are activated by calorie restriction (CR) and by the coenzyme, nicotinamide adenine dinucleotide (NAD+). Sirtuins, specifically the nuclear SIRT1 and mitochondrial SIRT3, have been shown to have predominantly neuroprotective roles in the CNS while the cytoplasmic sirtuin, SIRT2 is largely associated with neurodegeneration. A systematic study of sirtuins in the ENS and their effect on enteric neuronal growth and survival has not been conducted. Recent studies, however, also link sirtuins with important hormones such as leptin, ghrelin, melatonin, and serotonin which influence many important processes including satiety, mood, circadian rhythm, and gut homeostasis. In this review, we address emerging roles of sirtuins in modulating the metabolic challenges from aging, obesity, and diabetes that lead to neurodegeneration in the ENS and CNS. We also highlight a novel role for sirtuins along the microbiota-gut-brain axis in modulating neurodegeneration.

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

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

The Potential of Resveratrol to Act as a Caloric Restriction Mimetic Appears to Be Limited: Insights from Studies in Mice

Caloric restriction (CR) has been shown repeatedly to prolong the lifespan in laboratory animals, with its benefits dependent on molecular targets forming part of the nutrient signaling network, including the NAD-dependent deacetylase silent mating type information regulation 2 homologue 1 (SIRT1). It has been hypothesized that the stilbene resveratrol (RSV) may counteract age- and obesity-related diseases similarly to CR. In yeast and worms, RSV-promoted longevity also depended on SIRT1. While it remains unclear whether RSV can prolong lifespans in mammals, some studies in rodents supplemented with RSV have reported lowered body weight (BW) and fat mass, improved insulin sensitivity, lowered cholesterol levels, increased fitness, and mitochondrial biogenesis. Molecular mechanisms possibly leading to such changes include altered gene transcription and activation of SIRT1, AMP-activated kinase (AMPK), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A). However, some mouse models did not benefit from RSV treatment to the same extent as others. We conducted a literature search on PubMed (15 April, 2020) for trials directly comparing RSV application to CR feeding in mice. In most studies retrieved by this systematic PubMed search, mice supplemented with RSV did not show significant reductions of BW, glucose, or insulin. Moreover, in some of these studies, RSV and CR treatments affected molecular targets differently and/or findings on RSV and CR impacts varied between trials. We discuss those RSV-induced changes in gene transcription hypothesized to partly counteract age-related alterations. Although there may be a moderate effect of RSV supplementation on parameters such as insulin sensitivity toward a more CR-like profile in mice, data are inconsistent. Likewise, RSV supplementation trials in humans report controversial findings. While we consider that RSV may, under certain circumstances, moderately mimic some aspects of CR, current evidence does not fully support its use to prevent or treat age- or obesity-related diseases.

SIRT1 mediates improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway

OBJECTIVES

Clinically, there is no effective therapy for postoperative cognitive dysfunction (POCD). Inflammation after surgery is closely associated with POCD.

METHODS

In this study, we explored the role of sirtuin 1 (SIRT1) in POCD. POCD in mice was induced by cardiac surgery. The mRNA and protein levels of related genes were determined by real-time polymerase chain reaction and western blot, respectively. Plasma concentrations of inflammatory factors were measured using an ELISA kit. Novel object and novel location recognition tests were carried out to measure recognition ability. The Morris water maze (MWM) test was performed to measure learning and memory ability.

RESULTS

There was a clear decrease in SIRT1 expression after POCD. The SIRT1 activator SRT1720 promoted recognition, learning, and memory ability of mice with POCD. Moreover, SRT1720 treatment greatly inhibited plasma inflammatory cytokine levels and TLR4 and P65 protein expression in the hippocampus of POCD mice. The effect of SRT1720 on POCD was in a TLR4-dependent manner.

CONCLUSIONS

SIRT1 mediates the improvement of cardiac surgery-induced postoperative cognitive dysfunction via the TLR4/NF-κB pathway.

SIRT1 Inhibits High Shear Stress-Induced Apoptosis in Rat Cortical Neurons

INTRODUCTION

Sirtuin1 (SIRT1), one of NAD+-dependent protein deacetylases, is proved to be neuroprotective in aging diseases, but its effect on neuronal apoptosis has not been clarified. To investigate the role of SIRT1 in inhibiting neuronal apoptosis, SIRT1 was interfered or overexpressed in cortical neurons.

METHODS

We exerted overloading laminar shear stress with 10 dyn/cm2 for 4, 8, and 12 h on neurons to cause cortical neuronal apoptosis, and the apoptosis percentage was tested by TUNEL assay. The adenovirus plasmids containing SIRT1 RNA interference or SIRT1 wild type gene were transfected into neurons before shear stress loading. SIRT1 mRNA and protein level were tested by Real-time PCR, immunofluorescence and western blots assay.

RESULTS

SIRT1 was primarily expressed in nucleus of cortical neurons, and its mRNA level was significantly increased after 4 h stimulation. SIRT1 RNAi cortical neurons had higher TUNEL positive cells, while SIRT1 overexpression significantly decreased the percentage of died cells induced by shear stress compared to control group.

CONCLUSIONS

SIRT1 plays a neuroprotective role in shear stress induced apoptosis and could be as potential pharmacological targets against neuronal degeneration in future.

Effects of berberine hydrochloride on methamphetamine-induced anxiety behaviors and relapse in rats

Objective(s):

This research aimed at evaluating the effect of berberine hydrochloride on anxiety-related behaviors induced by methamphetamine (METH) in rats, assessing relapse and neuroprotective effects.

Materials and Methods:

27 male Wistar rats were randomly assigned into groups of Control, METH-withdrawal (METH addiction and subsequent withdrawal), and METH addiction with berberine hydrochloride oral treatment (100 mg/kg/per day) during the three weeks of withdrawal. Two groups received inhaled METH self-administration for two weeks (up to 10 mg/kg). The elevated plus maze (EPM) test and open field test (OFT) were carried out one day after the last berberine treatment and relapse was assessed by conditional place preference (CPP) test. TUNEL assay and immunofluorescence staining for NF-κB, TLR4, Sirt1, and α-actin expression in the hippocampus were tested.

Results:

After 3 weeks withdrawal, berberine hydrochloride decreased locomotor activity and reduced anxiety-related behaviors in comparison with the METH-withdrawal group (P<0.001). The obtained results from CPP showed that berberine significantly reduced relapse (P<0.01). Significantly decrease in activation of TLR4, Sirt1, and α-actin in METH-withdrawal group was found and the percentage of TLR4, Sirt1, and α-actin improved in berberine-treated group (P<0.001). A significant activity rise of NF-κB of cells in the METH-withdrawal group was detected compared to berberine-treated and control groups (P<0.001).

Conclusion:

Treatment with berberine hydrochloride via modulating neuroinflammation may be considered as a potential new medication for the treatment of METH addiction and relapse. The histological assays supported the neuroprotective effects of berberine in the hippocampus.

Tauopathies: Deciphering Disease Mechanisms to Develop Effective Therapies

Tauopathies are neurodegenerative diseases characterized by the pathological accumulation of microtubule-associated protein tau (MAPT) in the form of neurofibrillary tangles and paired helical filaments in neurons and glia, leading to brain cell death. These diseases include frontotemporal dementia (FTD) and Alzheimer's disease (AD) and can be sporadic or inherited when caused by mutations in the MAPT gene. Despite an incredibly high socio-economic burden worldwide, there are still no effective disease-modifying therapies, and few tau-focused experimental drugs have reached clinical trials. One major hindrance for therapeutic development is the knowledge gap in molecular mechanisms of tau-mediated neuronal toxicity and death. For the promise of precision medicine for brain disorders to be fulfilled, it is necessary to integrate known genetic causes of disease, i.e., MAPT mutations, with an understanding of the dysregulated molecular pathways that constitute potential therapeutic targets. Here, the growing understanding of known and proposed mechanisms of disease etiology will be reviewed, together with promising experimental tau-directed therapeutics, such as recently developed tau degraders. Current challenges faced by the fields of tau research and drug discovery will also be addressed.

Potential Role of Phosphoglycerol Dihydroceramide Produced by Periodontal Pathogen Porphyromonas gingivalis in the Pathogenesis of Alzheimer's Disease

Background

Among different types of sphingolipids produced by human cells, the possible engagement of ceramide species in the pathogenesis of Alzheimer's disease (AD) has attracted recent attention. While ceramides are primarily generated by de novo synthesis in mammalian cells, only a limited number of bacterial species, produce ceramides, including phosphoglycerol dihydroceramide (PGDHC) that is produced by the key periodontal pathogen Porphyromonas gingivalis. Emerging evidence indicates that virulence factors produced by P. gingivalis, such as lipopolysaccharide and gingipain, may be engaged in the initiation and/or progression of AD. However, the potential role of PGDHC in the pathogenesis of AD remains unknown. Therefore, the aim of this study was to evaluate the influence of PGDHC on hallmark findings in AD.

Material and Methods

CHO-7WD10 and SH-SY-5Y cells were exposed to PGDHC and lipopolysaccharide (LPS) isolated from P. gingivalis. Soluble Aβ42 peptide, amyloid precursor protein (APP), phosphorylated tau and senescence-associated secretory phenotype (SASP) factors were quantified using ELISA and Western blot assays.

Results

Our results indicate that P. gingivalis (Pg)-derived PGDHC, but not Pg-LPS, upregulated secretion of soluble Aβ42 peptide and expression of APP in CHO-7WD10 cells. Furthermore, hyperphosphorylation of tau protein was observed in SH-SY-5Y cells in response to PGDHC lipid. In contrast, Pg-LPS had little, or no significant effect on the tau phosphorylation induced in SH-SY-5Y cells. However, both PGDHC and Pg-LPS contributed to the senescence of SH-SY5Y cells as indicated by the production of senescence-associated secretory phenotype (SASP) markers, including beta-galactosidase, cathepsin B (CtsB), and pro-inflammatory cytokines TNF-α, and IL-6. Additionally, PGDHC diminished expression of the senescence-protection marker sirtuin-1 in SH-SY-5Y cells.

Conclusions

Altogether, our results indicate that P. gingivalis-derived PGDHC ceramide promotes amyloidogenesis and hyperphosphorylation, as well as the production of SASP factors. Thus, PGDHC may represent a novel class of bacterial-derived virulence factors for AD associated with periodontitis.

The role of sirt1 in the retinal ganglion cells cultured by high glucose

OBJECTIVE

To observe the effect of sirt1 on retinal ganglion cells (RGC) with high glucose culture and to explore the role of sirt1 in the development of diabetic retinopathy. Method RGC was infected by sirt1 lentivirus overexpression vector pLV5-sirt1 and interference vector pLV3-si-sirt1. The normal control group and control virus vector group were set up at the same time. After 48 h of infection, the viability of RGC was detected by CCK8 kit, the apoptosis rate was detected by FCM analysis, and the protein expression of p53, FOXO3a, NF-κ B, caspase-3 was detected by Western blot.

RESULTS

After RGC were infected with lentivirus, the cell viability of lentivirus overexpression vector pLV5-sirt1 was significantly higher than that of the high glucose group and the sirt1 overexpression control group, while the cell viability of interference vector pLV3-si-sirt1 was significantly lower than that of the high glucose group and the sirt1 interference control group (P < 0.05). At the same time, the apoptosis rate of RGC cells infected by lentivirus overexpression vector pLV5-sirt1 was lower than that of the high glucose group and the control virus vector group, while the apoptosis rate of the interference vector pLV3-si-sirt1 cells was significantly higher than that of the high glucose group and the control virus vector group (P < 0.05). The results of Western blotting showed that the expression of p53, FOXO3a, NF-κ B and caspase-3 in RGC cells decreased significantly after infection with pLV5-sirt1 compared with the high glucose group and the control virus vector group, while the expression of p53, FOXO3a, NF-κB and caspase-3 in RGC cells increased significantly after infection with pLV3-si-sirt1 (P < 0.05).

CONCLUSION

Sirt1 can inhibit the apoptosis of RGCs through regulating the expression of some apoptotic cytokinessome, and it can be used as a candidate gene for the biotherapy of retinal diseases.

Non-Coding RNAs as Sensors of Oxidative Stress in Neurodegenerative Diseases

Oxidative stress (OS) results from an imbalance between the production of reactive oxygen species and the cellular antioxidant capacity. OS plays a central role in neurodegenerative diseases, where the progressive accumulation of reactive oxygen species induces mitochondrial dysfunction, protein aggregation and inflammation. Regulatory non-protein-coding RNAs (ncRNAs) are essential transcriptional and post-transcriptional gene expression controllers, showing a highly regulated expression in space (cell types), time (developmental and ageing processes) and response to specific stimuli. These dynamic changes shape signaling pathways that are critical for the developmental processes of the nervous system and brain cell homeostasis. Diverse classes of ncRNAs have been involved in the cell response to OS and have been targeted in therapeutic designs. The perturbed expression of ncRNAs has been shown in human neurodegenerative diseases, with these changes contributing to pathogenic mechanisms, including OS and associated toxicity. In the present review, we summarize existing literature linking OS, neurodegeneration and ncRNA function. We provide evidences for the central role of OS in age-related neurodegenerative conditions, recapitulating the main types of regulatory ncRNAs with roles in the normal function of the nervous system and summarizing up-to-date information on ncRNA deregulation with a direct impact on OS associated with major neurodegenerative conditions.

Mir-141-3p Regulates Apoptosis and Mitochondrial Membrane Potential via Targeting Sirtuin1 in a 1-Methyl-4-Phenylpyridinium in vitro Model of Parkinson's Disease

Objectives

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the loss of midbrain dopaminergic neurons in the substantia nigra. The present study investigated miR-141-3p/sirtuin1 (SIRT1) activity in a 1-methyl-4-phenylpyridinium- (MPP+-) induced PC12-cell model of PD.

Methods

PC12 cells were exposed to MMP+ following induction of differentiation by nerve growth factor (NGF). miR-141-3p and SIRT1 expressions were examined using RT-qPCR and western blot. Cell viability was evaluated using the MTT assay. Apoptosis percentage, reactive oxygen species (ROS) production, and mitochondrial membrane potential (Δψm) were evaluated using flow cytometry. Expression of Nuclear factor-kappa B- (NF-κB-) related proteins was determined by western blot. Bioinformatic analysis, RT-qPCR, and luciferase reporter assay were used to confirm the interaction between miR-141-3p and SIRT1.

Results

miR-141-3p was upregulated, and SIRT1 was downregulated in MPP+-treated PC12 cells. MPP+ treatment also upregulated nitric oxide synthase 1 (Nos1) and α-synuclein. miR-141-3p induced apoptosis, oxidative stress, mitochondrial dysfunction, and downregulated the SIRT1 mRNA expression. The luciferase reporter assay showed that SIRT1 was the target of miR-141-3p. SIRT1 transfection attenuated apoptosis, ROS production and maintained Δψm. SIRT1 also downregulated Nos1, tumor necrosis factor-α (TNF-α), interleukin 1 beta (IL-1β), interleukin 6(IL-6) and upregulated B cell lymphoma 2 (Bcl-2) protein. In addition, SIRT1 activator resveratrol blocked the effects of miR-141-3p mimic on Nos1, α-synuclein, and mitochondrial membrane potential. SIRT1 inhibitor sirtinol reversed the biological effects of miR-141-3p.

Conclusion

Increased miR-141-3p induced apoptosis, oxidative stress, and mitochondrial dysfunction in MPP+-treated PC12 cells by directly targeting the SIRT1 expression. Our study provided a potential therapeutic strategy for PD.

Advancements in therapeutic drugs targeting of senescence

Aging leads to a high burden on society, both medically and economically. Cellular senescence plays an essential role in the initiation of aging and age-related diseases. Recent studies have highlighted the therapeutic value of senescent cell deletion in natural aging and many age-related disorders. However, the therapeutic strategies for manipulating cellular senescence are still at an early stage of development. Among these strategies, therapeutic drugs that target cellular senescence are arguably the most highly anticipated. Many recent studies have demonstrated that a variety of drugs exhibit healthy aging effects. In this review, we summarize different types of drugs promoting healthy aging – such as senolytics, senescence-associated secretory phenotype (SASP) inhibitors, and nutrient signaling regulators – and provide an update on their potential therapeutic merits. Taken together, our review synthesizes recent advancements in the therapeutic potentialities of drugs promoting healthy aging with regard to their clinical implications.

Mechanisms of Aging and the Preventive Effects of Resveratrol on Age-Related Diseases

Aging gradually decreases cellular biological functions and increases the risk of age-related diseases. Cancer, type 2 diabetes mellitus, cardiovascular disease, and neurological disorders are commonly classified as age-related diseases that can affect the lifespan and health of individuals. Aging is a complicated and sophisticated biological process involving damage to biochemical macromolecules including DNA, proteins, and cellular organelles such as mitochondria. Aging causes multiple alterations in biological processes including energy metabolism and nutrient sensing, thus reducing cell proliferation and causing cellular senescence. Among the polyphenolic phytochemicals, resveratrol is believed to reduce the negative effects of the aging process through its multiple biological activities. Resveratrol increases the lifespan of several model organisms by regulating oxidative stress, energy metabolism, nutrient sensing, and epigenetics, primarily by activating sirtuin 1. This review summarizes the most important biological mechanisms of aging, and the ability of resveratrol to prevent age-related diseases.

Microbiota modulation as preventative and therapeutic approach in Alzheimer's disease

The gut microbiota coevolves with its host, and numerous factors like diet, lifestyle, drug intake and geographical location continuously modify its composition, deeply influencing host health. Recent studies demonstrated that gut dysbiosis can alter normal brain function through the so-called gut-brain axis, a bidirectional communication network between the central nervous system and the gastrointestinal tract, thus playing a key role in the pathogenesis of neurodegenerative disorders, such as Alzheimer's disease (AD). In this perspective, in the constant search for novel treatments in AD, the rational modulation of gut microbiota composition could represent a promising approach to prevent or delay AD onset or to counteract its progression. Preclinical and human studies on microbiota modulation through oral bacteriotherapy and faecal transplantation showed anti-inflammatory and antioxidant effects, upregulation of plasma concentration of neuroprotective hormones, restoration of impaired proteolytic pathways, amelioration of energy homeostasis with consequent decrease of AD molecular hallmarks and improvement of behavioural and cognitive performances. In this review, we dissect the role of gut microbiota in AD and highlight recent advances in the development of new multitarget strategies for microbiota modulation to be used as possible preventative and therapeutic approaches in AD.

NAD+ metabolism: pathophysiologic mechanisms and therapeutic potential

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

A conserved mechanism of sirtuin signalling through steroid hormone receptors

SIRT1 and orthologous sirtuins regulate a universal mechanism of ageing and thus determine lifespan across taxa; however, the precise mechanism remains vexingly polemical. They also protect against many metabolic and ageing-related diseases by dynamically integrating several processes including autophagy, proteostasis, calorie restriction, circadian rhythmicity and metabolism. These sirtuins are therefore important drug targets particularly because they also transduce allosteric signals from sirtuin-activating compounds such as resveratrol into increased healthspan in evolutionarily diverse organisms. While many of these functions are apparently regulated by deacetylation, that mechanism may not be all-encompassing. Since gonadal signals have been shown to regulate ageing/lifespan in worms and flies, the present study hypothesized that these sirtuins may act as intermediary factors for steroid hormone signal transduction. Accordingly, SIRT1 and its orthologues, Sir2 and Sir-2.1, are shown to be veritable nuclear receptor coregulators that classically coactivate the oestrogen receptor in the absence of ligand; coactivation was further increased by 17β-oestradiol. Remarkably in response to the worm steroid hormone dafachronic acid, SIRT1 reciprocally coactivates DAF-12, the steroid receptor that regulates nematode lifespan. These results suggest that steroid hormones may co-opt and modulate a phyletically conserved mechanism of sirtuin signalling through steroid receptors. Hence, it is interesting to speculate that certain sirtuin functions including prolongevity and metabolic regulation may be mechanistically linked to this endocrine signalling pathway; this may also have implications for understanding the determinative role of gonadal steroids such as oestradiol in human ageing. At its simplest, this report shows evidence for a hitherto unknown deacetylation-independent mechanism of sirtuin signalling.

Two boron-containing compounds affect the cellular viability of SH-SY5Y cells in an in vitro amyloid-beta toxicity model

Boron is a naturally occurring trace element found in organic and inorganic complexes. Boron-containing compounds are required for living organisms for diverse metabolic functions, including nitrogen fixation in microorganisms, cell wall stability in plants, and bone and carbohydrate metabolism in animals. The number of studies about the effect of boron in biological model systems is very limited; so far, there has been no study on the correlation between boron and amyloid-beta toxicity. Here, we investigated the possible effects of 2 boron-containing compounds—sodium borate decahydrate and boric acid—against amyloid-beta toxicity. In our in vitro amyloid-beta toxicity model, we showed that these 2 compounds increase the survival of the SH-SY5Y cells. Furthermore, boron in these 2 forms increases the expression of Sirt1, which has protective functions against cellular stress. The compounds also change the expressions of GSK-3α/β; by doing so, boron may contribute to the stimulation of intracellular prosurvival pathways. This is the first experimental study indicating the prosurvival effect of boron in an amyloid-beta toxicity model.

Compounds that extend longevity are protective in neurodegenerative diseases and provide a novel treatment strategy for these devastating disorders

While aging is the greatest risk factor for the development of neurodegenerative disease, the role of aging in these diseases is poorly understood. In the inherited forms of these diseases, the disease-causing mutation is present from birth but symptoms appear decades later. This indicates that these mutations are well tolerated in younger individuals but not in older adults. Based on this observation, we hypothesized that changes taking place during normal aging make the cells in the brain (and elsewhere) susceptible to the disease-causing mutations. If so, then delaying some of these age-related changes may be beneficial in the treatment of neurodegenerative disease. In this review, we examine the effects of five compounds that have been shown to extend longevity (metformin, rapamycin, resveratrol, N-acetyl-l-cysteine, curcumin) in four of the most common neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis). While not all investigations observe a beneficial effect of these compounds, there are multiple studies that show a protective effect of each of these lifespan-extending compounds in animal models of neurodegenerative disease. Combined with genetic studies, this suggests the possibility that targeting the aging process may be an effective strategy to treat neurodegenerative disease.

Enhancement of Hippocampal Plasticity by Physical Exercise as a Polypill for Stress and Depression: A Review

Generation of newborn neurons that form functional synaptic connections in the dentate gyrus of adult mammals, known as adult hippocampal neurogenesis, has been suggested to play critical roles in regulating mood, as well as certain forms of hippocampus-dependent learning and memory. Environmental stress suppresses structural plasticity including adult neurogenesis and dendritic remodeling in the hippocampus, whereas physical exercise exerts opposite effects. Here, we review recent discoveries on the potential mechanisms concerning how physical exercise mitigates the stressrelated depressive disorders, with a focus on the perspective of modulation on hippocampal neurogenesis, dendritic remodeling and synaptic plasticity. Unmasking such mechanisms may help devise new drugs in the future for treating neuropsychiatric disorders involving impaired neural plasticity.

Impact of circadian and diurnal rhythms on cellular metabolic function and neurodegenerative diseases

The 24-h rotational period of the earth has driven evolution of biological systems that serve to synchronize organismal physiology and behavior to this predictable environmental event. In mammals, the circadian (circa, "about" and dia, "a day") clock keeps 24-h time at the organismal and cellular level, optimizing biological function for a given time of day. The most obvious circadian output is the sleep-wake cycle, though countless bodily functions, ranging from hormone levels to cognitive function, are influenced by the circadian clock. Here we discuss the regulation of metabolic pathways by the circadian clock, discuss the evidence implicating circadian and sleep disruption in neurodegenerative diseases, and suggest some possible connections between the clock, metabolism, and neurodegenerative disease.

Minutes of PPAR-γ agonism and neuroprotection

Peroxisome proliferator-activated receptor gamma (PPAR-γ) is one of the ligand-activated transcription factors which regulates a number of central events and considered as a promising target for various neurodegenerative disease conditions. Numerous reports implicate that PPAR-γ agonists have shown neuroprotective effects by regulating genes transcription associated with the pathogenesis of neurodegeneration. In regards, this review critically appraises the recent knowledge of PPAR-γ receptors in neuroprotection in order to hypothesize potential neuroprotective mechanism of PPAR-γ agonism in chronic neurological conditions. Of note, the PPAR-γ's interaction dynamics with PPAR-γ coactivator-1α (PGC-1α) has gained significant attention for neuroprotection. Likewise, a plethora of studies suggest that the PPAR-γ pathway can be actuated by the endogenous ligands present in the CNS and thus identification and development of novel agonist for the PPAR-γ receptor holds a vow to prevent neurodegeneration. Together, the critical insights of this review enlighten the translational possibilities of developing novel neuroprotective therapeutics targeting PPAR-γ for various neurodegenerative disease conditions.

Amarogentin from Gentiana rigescens Franch Exhibits Antiaging and Neuroprotective Effects through Antioxidative Stress

In the present study, the replicative lifespan assay of yeast was used to guide the isolation of antiaging substance from Gentiana rigescens Franch, a traditional Chinese medicine. A compound with antiaging effect was isolated, and the chemical structure of this molecule as amarogentin was identified by spectral analysis and compared with the reported data. It significantly extended the replicative lifespan of K6001 yeast at doses of 1, 3, and 10 μM. Furthermore, amarogentin improved the survival rate of yeast under oxidative stress by increasing the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), and these enzymes' gene expression. In addition, this compound did not extend the replicative lifespan of sod1, sod2, uth1, and skn7 mutants with K6001 background. These results suggested that amarogentin exhibited antiaging effect on yeast via increase of SOD2, CAT, GPx gene expression, enzyme activity, and antioxidative stress. Moreover, we evaluated antioxidant activity of this natural products using PC12 cell system, a useful model for studying the nervous system at the cellular level. Amarogentin significantly improved the survival rate of PC12 cells under H₂O₂-induced oxidative stress and increased the activities of SOD and SOD2, and gene expression of SOD2, CAT, GPx, Nrf2, and Bcl-x1. Meanwhile, the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) of PC12 cells were significantly reduced after treatment of the amarogentin. These results indicated that antioxidative stress play an important role for antiaging and neuroprotection of amarogentin. Interestingly, amarogentin exhibited neuritogenic activity in PC12 cells. Therefore, the natural products, amarogentin from G. rigescens with antioxidant activity could be a good candidate molecule to develop drug for treating neurodegenerative diseases.

Mitochondrial Dysfunction, Neurogenesis, and Epigenetics: Putative Implications for Amyotrophic Lateral Sclerosis Neurodegeneration and Treatment

Amyotrophic lateral sclerosis (ALS) is a progressive and devastating multifactorial neurodegenerative disorder. Although the pathogenesis of ALS is still not completely understood, numerous studies suggest that mitochondrial deregulation may be implicated in its onset and progression. Interestingly, mitochondrial deregulation has also been associated with changes in neural stem cells (NSC) proliferation, differentiation, and migration. In this review, we highlight the importance of mitochondrial function for neurogenesis, and how both processes are correlated and may contribute to the pathogenesis of ALS; we have focused primarily on preclinical data from animal models of ALS, since to date no studies have evaluated this link using human samples. As there is currently no cure and no effective therapy to counteract ALS, we have also discussed how improving neurogenic function by epigenetic modulation could benefit ALS. In support of this hypothesis, changes in histone deacetylation can alter mitochondrial function, which in turn might ameliorate cellular proliferation as well as neuronal differentiation and migration. We propose that modulation of epigenetics, mitochondrial function, and neurogenesis might provide new hope for ALS patients, and studies exploring these new territories are warranted in the near future.

SIRT1 relieves Necrotizing Enterocolitis through inactivation of Hypoxia-inducible factor (HIF)-1a

Necrotizing enterocolitis (NEC) is a major cause of mortality and morbidity in newborns, characterized by inflammatory intestinal necrosis. Sirtuin-1 (SIRT1), a NAD-dependent deacetylase, is involved in multiple biological functions. It has been reported that SIRT1 was downregulated in NEC tissues. However, the precise role of SIRT1 in NEC progress remains unknown. In this study, we found that SIRT1 was decreased in serum samples of NEC patients, associated with an inflammation response. an in vitro model was established by using LPS-induced NEC-like cell in this study. The results indicate that overexpression of SIRT1 inhibited the cell apoptosis induced by LPS. Besides, overexpression of SIRT1 suppressed the high expression of proinflammatory factors (IL-6, IL-8, and TNF-α), the decrease of transepithelial electrical resistance (TEER), and the decline expression of tight junction proteins (ZO-1, ZO-2, and Claudin-4) induced by LPS in Caco-2 cells. What is more, serum HIF-1α was increased in NEC patients. SIRT1 overexpression suppressed the expression and activity of HIF-1a, while knockdown of SIRT1 made the opposite effect. In summary, this study indicates that overexpression of SIRT1 alleviates the inflammation response and intestinal epithelial barrier dysfunction through regulating the expression and inactivation of HIF-1a.

Trans-Cinnamaldehyde Alleviates Amyloid-Beta Pathogenesis via the SIRT1-PGC1α-PPARγ Pathway in 5XFAD Transgenic Mice

Abnormal amyloid-β (Aβ) accumulation is the most significant feature of Alzheimer’s disease (AD). Among the several secretases involved in the generation of Aβ, β-secretase (BACE1) is the first rate-limiting enzyme in Aβ production that can be utilized to prevent the development of Aβ-related pathologies. Cinnamon extract, used in traditional medicine, was shown to inhibit the aggregation of tau protein and Aβ aggregation. However, the effect of trans-cinnamaldehyde (TCA), the main component of cinnamon, on Aβ deposition is unknown. Five-month-old 5XFAD mice were treated with TCA for eight weeks. Seven-month-old 5XFAD mice were evaluated for cognitive and spatial memory function. Brain samples collected at the conclusion of the treatment were assessed by immunofluorescence and biochemical analyses. Additional in vivo experiments were conducted to elucidate the mechanisms underlying the effect of TCA in the role of Aβ deposition. TCA treatment led to improvements in cognitive impairment and reduced Aβ deposition in the brains of 5XFAD mice. Interestingly, the levels of BACE1 were decreased, whereas the mRNA and protein levels of three well-known regulators of BACE1, silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1α (PGC1α), and PPARγ, were increased in TCA-treated 5XFAD mice. TCA led to an improvement in AD pathology by reducing BACE1 levels through the activation of the SIRT1-PGC1α-PPARγ pathway, suggesting that TCA might be a useful therapeutic approach in AD.

Brd2 haploinsufficiency extends lifespan and healthspan in C57B6/J mice

Aging in mammals is the gradual decline of an organism's physical, mental, and physiological capacity. Aging leads to increased risk for disease and eventually to death. Here, we show that Brd2 haploinsufficiency (Brd2+/-) extends lifespan and increases healthspan in C57B6/J mice. In Brd2+/- mice, longevity is increased by 23% (p<0.0001), and, relative to wildtype animals (Brd2+/+), cancer incidence is reduced by 43% (p<0.001). In addition, relative to age-matched wildtype mice, Brd2 heterozygotes show healthier aging including: improved grooming, extended period of fertility, and lack of age-related decline in kidney function and morphology. Our data support a role for haploinsufficiency of Brd2 in promoting healthy aging. We hypothesize that Brd2 affects aging by protecting against the accumulation of molecular and cellular damage. Given the recent advances in the development of BET inhibitors, our research provides impetus to test drugs that target BRD2 as a way to understand and treat/prevent age-related diseases.

AMPK-SIRT1-PGC1α Signal Pathway Influences the Cognitive Function of Aged Rats in Sevoflurane-Induced Anesthesia

To understand the effect of AMP-activated protein kinase (AMPK)-SIRT1 (silent information regulator 1)-PPARγ coactivator-1α (PGC1α) signaling pathway on the cognitive function of sevoflurane-anesthetized aged rats. Aged rats were divided into Normal group, Sevo group (Sevoflurane anesthesia), Sevo + AICAR (the AMPK activator) group, Sevo + EX527 group (the AMPK inhibitor), and Sevo + AICAR + EX527 group. The cognitive function of rats was determined by the Morris water maze. Hippocampal neuronal apoptosis was evaluated by TUNEL and Fluoro-Jade C (FJC) staining, and the expression of cleaved caspase-3 was detected by immunohistochemistry. ROS, SOD, and MDA levels and the fluorescence intensity of GFAP in the hippocampus were assayed. The mitochondrial membrane potential (MMP), mitochondrial mass, ATP level, and the expression of AMPK-SIRT1-PGC1α were determined by the corresponding methods. Rats in the Sevo group manifested significant extension in the escape latency, with fewer platform crossings; and meanwhile, the apoptotic rate, the number of FJC-positive cells, and the fluorescence intensity of GFAP of neurons were elevated, with up-regulation of cleaved caspase-3. Moreover, the level of MDA and ROS was increased evidently, with significant down-regulation of SOD activity, ATP, mitochondrial mass and MMP levels, and AMPK, SIRT1 and PGC-1α protein expressions. However, sevoflurane-induced changes above were improved after the administration of AICAR, and EX527 could reverse AICAR-induced improvements in Sevo-anesthetized aged rats. Activating AMPK-SIRT1-PGC1α pathway can improve the cognitive function and mitigate the neuronal injury in Sevo-anesthetized aged rats by antagonizing the oxidative stress and maintaining the mitochondrial function.

Changes in PGC-1α/SIRT1 Signaling Impact on Mitochondrial Homeostasis in Amyloid-Beta Peptide Toxicity Model

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive impairment that increasingly afflicts the elderly population. Soluble oligomers (AβOs) has been implicated in AD pathogenesis: however, the molecular events underlying a role for Aβ are not well understood. We studied the effects of AβOs on mitochondrial function and on key proteins that regulate mitochondrial dynamics and biogenesis in hippocampal neurons and PC-12 cells. We find that AβOs treatment caused a reduction in total Mfn1 after a 2 h exposure (42 ± 11%); while DRP1 increased at 1 and 2 h (205 ± 22% and 198 ± 27%, respectively), correlating to changes in mitochondrial morphology. We also observed that SIRT1 levels were reduced after acute and chronic AβOs treatment (68 ± 7% and 77 ± 6%, respectively); while PGC-1α levels were reduced with the same time treatments (68 ± 8% and 67 ± 7%, respectively). Interestingly, we found that chronic treatment with AβOs increased the levels of pSIRT1 (24 h: 157 ± 18%), and we observed changes in the PGC-1α and p-SIRT1 nucleus/cytosol ratio and SIRT1-PGC-1α interaction pattern after chronic exposure to AβOs. Our data suggest that AβOs induce important changes in the level and localization of mitochondrial proteins related with the loss of mitochondrial function that are mediated by a fast and sustained SIRT1/PGC-1α complex disruption promoting a “non-return point” to an irreversible synaptic failure and neuronal network disconnection.

Nicotinamide mononucleotide administration after sever hypoglycemia improves neuronal survival and cognitive function in rats

Hypoglycemia-induced brain injury is a potential complication of insulin therapy in diabetic patients. Severe hypoglycemia triggers a cascade of events in vulnerable neurons that may lead to neuronal death and cognitive impairment even after glucose normalization. Oxidative stress and the activation of poly (ADP-ribose) polymerase-1 (PARP-1) are key events in this cascade. The production of reactive oxygen species (ROS) induces DNA damage and the consequent PARP-1 activation, which depletes NAD⁺ and ATP, resulting in brain injury. One of the key precursors of NAD⁺ is nicotinamide mononucleotide (NMN), which is converted to NAD⁺ and reduces production of ROS. Here we investigated whether NMN could reduce brain injury after severe hypoglycemia. We used a rat model of insulin-induced severe hypoglycemia and injected NMN (500 mmg/kg, i.p., one week) following 30 min of severe hypoglycemia, at the time of glucose administration. One week after severe hypoglycemia, hippocampal long-term potentiation (LTP), an electrophysiogic assay of synaptic plasticity, was examined and neuronal damage was assessed by Hematoxylin-Eosin staining. ROS accumulation, PARP-1 activation, NAD⁺ and ATP levels in hippocampus were also measured. Cognitive function was assessed using the Morris water maze 6 weeks after severe hypoglycemia. The addition of NMN reduced neuron death by 83 ± 3% (P < 0.05) after severe hypoglycemia. The hippocampal LTP was significantly reduced by severe hypoglycemia but showed recovery in the NMN addition group. NMN treatment also attenuated the severe hypoglycemia-induced spatial learning and memory impairment. Mechanically, we showed that NMN administration decreased ROS accumulation, suppressed PARP-1 activation, and restored levels of NAD⁺ and ATP in hippocampus. All these protective effects were reversed by 3-acetylpyridine (3-AP), which generates inactive NAD⁺. In summary, NMN administration following severe hypoglycemia could ameliorate neuronal damage and cognitive impairment caused by severe hypoglycemia. These results suggest that NMN may be a promising therapeutic drug to prevent hypoglycemia-induced brain injury.

SIRT1 Regulation in Ageing and Obesity

Ageing and obesity have common hallmarks: altered glucose and lipid metabolism, chronic inflammation and oxidative stress are some examples. The downstream effects of SIRT1 activity have been thoroughly explored, and their research is still in expanse. SIRT1 activation has been shown to regulate pathways with beneficiary effects on 1) ageing and obesity-associated metabolic disorders such as metabolic syndrome, insulin resistance and type-II diabetes with, 2) chronic inflammatory processes such as arthritis, atherosclerosis and emphysema, 3) DNA damage and oxidative stress with impact on neurodegenerative diseases, cardiovascular health and some cancers. This knowledge intensified the interest in uncovering the mechanisms regulating the expression and activity of SIRT1. This review focuses on the upstream regulatory mechanisms controlling SIRT1, and how this knowledge could potentially contribute to the development of therapeutic interventions.

Neuroprotective Properties of Resveratrol and Its Derivatives-Influence on Potential Mechanisms Leading to the Development of Alzheimer's Disease

The lack of effective Alzheimer's disease treatment is becoming a challenge for researchers and prompts numerous attempts to search for and develop better therapeutic solutions. Compounds that affect several routes of the neurodegeneration cascade leading to the development of disease are of particular interest. An example of such substances is resveratrol and its synthetic and natural derivatives, which have gained popularity in recent years and show promise as a possible new therapeutic option in the approach to Alzheimer's disease treatment. In this article, the state of the art evidence on the role of resveratrol (RSV) in neuroprotection is presented; research results are summarized and the importance of resveratrol and its derivatives in the treatment of Alzheimer's disease are underlined. It also focuses on various modifications of the resveratrol molecule that should be taken into account in the design of future research on drugs against Alzheimer's disease.

Mitochondrial biogenesis as a therapeutic target for traumatic and neurodegenerative CNS diseases

Central nervous system (CNS) diseases, both traumatic and neurodegenerative, are characterized by impaired mitochondrial bioenergetics and often disturbed mitochondrial dynamics. The dysregulation observed in these pathologies leads to defective respiratory chain function and reduced ATP production, thereby promoting neuronal death. As such, attenuation of mitochondrial dysfunction through induction of mitochondrial biogenesis (MB) is a promising, though still underexplored, therapeutic strategy. MB is a multifaceted process involving the integration of highly regulated transcriptional events, lipid membrane and protein synthesis/assembly and replication of mtDNA. Several nuclear transcription factors promote the expression of genes involved in oxidative phosphorylation, mitochondrial import and export systems, antioxidant defense and mitochondrial gene transcription. Of these, the nuclear-encoded peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is the most commonly studied and is widely accepted as the 'master regulator' of MB. Several recent preclinical studies document that reestablishment of mitochondrial homeostasis through increased MB results in inhibited injury progression and increased functional recovery. This perspective will briefly review the role of mitochondrial dysfunction in the propagation of CNS diseases, while also describing current research strategies that mediate mitochondrial dysfunction and compounds that induce MB for the treatment of acute and chronic neuropathologies.

Expression Levels of SMAD Specific E3 Ubiquitin Protein Ligase 2 (Smurf2) and its Interacting Partners Show Region-specific Alterations During Brain Aging

Aging occurs due to a combination of several factors, such as telomere attrition, cellular senescence, and stem cell exhaustion. The telomere attrition-dependent cellular senescence is regulated by increased levels of SMAD specific E3 ubiquitin protein ligase 2 (smurf2). With age smurf2 expression increases and Smurf2 protein interacts with several regulatory proteins including, Smad7, Ep300, Yy1, Sirt1, Mdm2, and Tp53, likely affecting its function related to cellular aging. The current study aimed at analyzing smurf2 expression in the aged brain because of its potential regulatory roles in the cellular aging process. Zebrafish were used because like humans they age gradually and their genome has 70% similarity. In the current study, we demonstrated that smurf2 gene and protein expression levels altered in a region-specific manner during the aging process. Also, in both young and old brains, Smurf2 protein was enriched in the cytosol. These results imply that during aging Smurf2 is regulated by several mechanisms including post-translational modifications (PTMs) and complex formation. Also, the expression levels of its interacting partners defined by the STRING database, tp53, mdm2, ep300a, yy1a, smad7, and sirt1, were analyzed. Multivariate analysis indicated that smurf2, ep300a, and sirt1, whose proteins regulate ubiquitination, acetylation, and deacetylation of target proteins including Smad7 and Tp53, showed age- and brain region-dependent patterns. Our data suggest a likely balance between Smurf2- and Mdm2-mediated ubiquitination, and Ep300a-mediated acetylation/Sirt1-mediated deacetylation, which most possibly affects the functionality of other interacting partners in regulating cellular and synaptic aging and ultimately cognitive dysfunction.

Molecular Pathogenesis and Interventional Strategies for Alzheimer's Disease: Promises and Pitfalls

Alzheimer's disease (AD) is a debilitating disorder characterized by age-related dementia, which has no effective treatment to date. β-Amyloid depositions and hyperphosphorylated tau proteins are the main pathological hallmarks, along with oxidative stress, N-methyl-d-aspartate (NMDA) receptor-mediated excitotoxicity, and low levels of acetylcholine. Current pharmacotherapy for AD only provides symptomatic relief and limited improvement in cognitive functions. Many molecules have been explored that show promising outcomes in AD therapy and can regulate cellular survival through different pathways. To have a vivid approach to strategize the treatment regimen, AD physiopathology should be better explained considering diverse etiological factors in conjunction with biochemical disturbances. This Review attempts to discuss different disease modification approaches and address the novel therapeutic targets of AD that might pave the way for new drug discovery using the well-defined targets for therapy of the disease.

Sirtuins transduce STACs signals through steroid hormone receptors

SIRT1 protects against several complex metabolic and ageing-related diseases (MARDs), and is therefore considered a polypill target to improve healthy ageing. Although dietary sirtuin-activating compounds (dSTACs) including resveratrol are promising drug candidates, their clinical application has been frustrated by an imprecise understanding of how their signals are transduced into increased healthspan. Recent work indicates that SIRT1 and orthologous sirtuins coactivate the oestrogen receptor/ER and the worm steroid receptor DAF-12. Here they are further shown to ligand-independently transduce dSTACs signals through these receptors. While some dSTACs elicit ER subtype-selectivity in the presence of hormone, most synergize with 17β-oestradiol and dafachronic acid respectively to increase ER and DAF-12 coactivation by the sirtuins. These data suggest that dSTACs functionally mimic gonadal steroid hormones, enabling sirtuins to transduce the cognate signals through a conserved endocrine pathway. Interestingly, resveratrol non-monotonically modulates sirtuin signalling, suggesting that it may induce hormesis, i.e. “less is more”. Together, the findings suggest that dSTACs may be informational molecules that use exploitative mimicry to modulate sirtuin signalling through steroid receptors. Hence dSTACs’ intrinsic oestrogenicity may underlie their proven ability to impart the health benefits of oestradiol, and also provides a mechanistic insight into how they extend healthspan or protect against MARDs.

Impact of neural stem cell-derived extracellular vesicles on mitochondrial dysfunction, sirtuin 1 level, and synaptic deficits in Alzheimer's disease

Small extracellular vesicles (EVs), including exosomes, play multiple physiological roles. In neurodegenerative diseases, EVs can be pivotal in dispersing neuropathogenic proteins. This study investigates the role of neural stem cell (NSC)-derived EVs in a transgenic (Tg) mouse model of Alzheimer's disease (AD). Five weeks following treatment on 9-month-old APP/PS1 mice, the effects of NSC-derived EVs on cognitive behavior, mitochondrial function, sirtuin1 (SIRT1), synaptic function and morphology, quantification of amyloid-β (Aβ) level, and inflammatory response were investigated. The results showed that mice in the Tg-NSCs-ev group exhibited significant improvement in cognitive performance compared with Tg-Veh group. Furthermore, the expression of mitochondrial function-related factors (peroxisome proliferator-activated receptor-γ coactivator-1α [PGC1α], nuclear respiratory factor 1 and 2 [NRF1 and 2], and fission 1 [Fis1]), SIRT1 as well as synaptic proteins (growth-associated protein 43 [GAP43], synaptophysin [SYP], post-synaptic density 95 [PSD95] and microtubule-associated protein 2 [MAP2]) were significantly higher in the Tg-NSCs-ev group, when compared with the Tg-Veh group. In addition, oxidative damage markers (anti-4-Hydroxynonenal [4-HNE] and anti-3 nitrotyrosine [3-NT]), inflammatory cytokines and the microglial marker (Iba1) were significantly lower in the Tg-NSCs-ev group, compared to the Tg-Veh group. Moreover, synaptic morphology was distinctly improved in the Tg-NSCs-ev group, whereas the Aβ level was not altered. Our study provides novel evidences that NSC-derived EVs enhanced mitochondrial function, SIRT1 activation, synaptic activity, decreased inflammatory response, and rescued cognitive deficits in AD like mice.

Muscarinic Toxin 7 Signals Via Ca2+/Calmodulin-Dependent Protein Kinase Kinase β to Augment Mitochondrial Function and Prevent Neurodegeneration

Mitochondrial dysfunction is implicated in a variety of neurodegenerative diseases of the nervous system. Peroxisome proliferator–activated receptor-γ coactivator-1α (PGC-1α) is a regulator of mitochondrial function in multiple cell types. In sensory neurons, AMP-activated protein kinase (AMPK) augments PGC-1α activity and this pathway is depressed in diabetes leading to mitochondrial dysfunction and neurodegeneration. Antimuscarinic drugs targeting the muscarinic acetylcholine type 1 receptor (M₁R) prevent/reverse neurodegeneration by inducing nerve regeneration in rodent models of diabetes and chemotherapy-induced peripheral neuropathy (CIPN). Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ) is an upstream regulator of AMPK activity. We hypothesized that antimuscarinic drugs modulate CaMKKβ to enhance activity of AMPK, and PGC-1α, increase mitochondrial function and thus protect from neurodegeneration. We used the specific M₁R antagonist muscarinic toxin 7 (MT7) to manipulate muscarinic signaling in the dorsal root ganglia (DRG) neurons of normal rats or rats with streptozotocin-induced diabetes. DRG neurons treated with MT7 (100 nM) or a selective muscarinic antagonist, pirenzepine (1 μM), for 24 h showed increased neurite outgrowth that was blocked by the CaMKK inhibitor STO-609 (1 μM) or short hairpin RNA to CaMKKβ. MT7 enhanced AMPK phosphorylation which was blocked by STO-609 (1 μM). PGC-1α reporter activity was augmented up to 2-fold (p < 0.05) by MT7 and blocked by STO-609. Mitochondrial maximal respiration and spare respiratory capacity were elevated after 3 h of exposure to MT7 (p < 0.05). Diabetes and CIPN induced a significant (p < 0.05) decrease in corneal nerve density which was corrected by topical delivery of MT7. We reveal a novel M₁R-modulated, CaMKKβ-dependent pathway in neurons that represents a therapeutic target to enhance nerve repair in two of the most common forms of peripheral neuropathy.

SIRT1 Decreases Emotional Pain Vulnerability with Associated CaMKIIα Deacetylation in Central Amygdala

Emotional disorders are common comorbid conditions that further exacerbate the severity and chronicity of chronic pain. However, individuals show considerable vulnerability to the development of chronic pain under similar pain conditions. In this study on male rat and mouse models of chronic neuropathic pain, we identify the histone deacetylase Sirtuin 1 (SIRT1) in central amygdala as a key epigenetic regulator that controls the development of comorbid emotional disorders underlying the individual vulnerability to chronic pain. We found that animals that were vulnerable to developing behaviors of anxiety and depression under the pain condition displayed reduced SIRT1 protein levels in central amygdala, but not those animals resistant to the emotional disorders. Viral overexpression of local SIRT1 reversed this vulnerability, but viral knockdown of local SIRT1 mimicked the pain effect, eliciting the pain vulnerability in pain-free animals. The SIRT1 action was associated with CaMKIIα downregulation and deacetylation of histone H3 lysine 9 at the CaMKIIα promoter. These results suggest that, by transcriptional repression of CaMKIIα in central amygdala, SIRT1 functions to guard against the emotional pain vulnerability under chronic pain conditions. This study indicates that SIRT1 may serve as a potential therapeutic molecule for individualized treatment of chronic pain with vulnerable emotional disorders.SIGNIFICANCE STATEMENT Chronic pain is a prevalent neurological disease with no effective treatment at present. Pain patients display considerably variable vulnerability to developing chronic pain, indicating individual-based molecular mechanisms underlying the pain vulnerability, which is hardly addressed in current preclinical research. In this study, we have identified the histone deacetylase Sirtuin 1 (SIRT1) as a key regulator that controls this pain vulnerability. This study reveals that the SIRT1-CaMKIIaα pathway in central amygdala acts as an epigenetic mechanism that guards against the development of comorbid emotional disorders under chronic pain, and that its dysfunction causes increased vulnerability to the development of chronic pain. These findings suggest that SIRT1 activators may be used in a novel therapeutic approach for individual-based treatment of chronic pain.

The effects simultaneous inhibition of dipeptidyl peptidase-4 and P2X7 purinoceptors in an in vivo Parkinson's disease model

Loss of dopaminergic neurons following Parkinson's disease (PD) diminishes quality of life in patients. The present study was carried out to investigate the protective effects of simultaneous inhibition of dipeptidyl peptidase-4 (DPP-4) and P2X7 purinoceptors in a PD model and explore possible mechanisms. The 6-hydroxydopamine (6-OHDA) was used as a tool to establish PD model in male Wister rats. The expressions of SIRT1, SIRT3, mTOR, PGC-1α, PTEN, P53 and DNA fragmentation were evaluated by ELISA assay. Behavioral impairments were determined using apomorphine-induced rotational and narrow beam tests. Dopamine synthesis and TH-positive neurons were detected by tyrosine hydroxylase (TH) immunohistochemistry. Neuronal density was determined by Nissl staining. OHDA-lesioned rats exhibited behavioral impairments that reversed by BBG, lin and lin + BBG. We found significant reduced levels of SIRT1, SIRT3, PGC-1α and mTOR in both mid brain and striatum from OHDA-lesioned rats that reversed by BBG, lin and lin + BBG. Likewise, significant increased levels of PTEN and P53 were found in both mid brain and striatum from OHDA-lesioned rats that was reversed by BBG, lin and lin + BBG. TH-positive neurons and neuronal density were markedly reduced OHDA-lesioned rats that reversed by BBG, lin and lin + BBG. Collectively, our results showed protective effects of simultaneous inhibition of DPP-4 and P2X7 purinoceptors in a rat model of PD can be linked to targeting SIRT1/SIRT3, PTEN-mTOR pathways. Moreover, our findings demonstrated that simultaneous inhibition of DPP-4 and P2X7 purinoceptors might have stronger effect on mitochondrial biogenesis compared to only one.

Lipid Droplet-Derived Monounsaturated Fatty Acids Traffic via PLIN5 to Allosterically Activate SIRT1

Lipid droplets (LDs) provide a reservoir for triacylglycerol storage and are a central hub for fatty acid trafficking and signaling in cells. Lipolysis promotes mitochondrial biogenesis and oxidative metabolism via a SIRT1/PGC-1α/PPARα-dependent pathway through an unknown mechanism. Herein, we identify that monounsaturated fatty acids (MUFAs) allosterically activate SIRT1 toward select peptide-substrates such as PGC-1α. MUFAs enhance PGC-1α/PPARα signaling and promote oxidative metabolism in cells and animal models in a SIRT1-dependent manner. Moreover, we characterize the LD protein perilipin 5 (PLIN5), which is known to enhance mitochondrial biogenesis and function, to be a fatty-acid-binding protein that preferentially binds LD-derived monounsaturated fatty acids and traffics them to the nucleus following cAMP/PKA-mediated lipolytic stimulation. Thus, these studies identify the first-known endogenous allosteric modulators of SIRT1 and characterize a LD-nuclear signaling axis that underlies the known metabolic benefits of MUFAs and PLIN5.

Discovering the genes mediating the interactions between chronic respiratory diseases in the human interactome

The molecular and clinical features of a complex disease can be influenced by other diseases affecting the same individual. Understanding disease-disease interactions is therefore crucial for revealing shared molecular mechanisms among diseases and designing effective treatments. Here we introduce Flow Centrality (FC), a network-based approach to identify the genes mediating the interaction between two diseases in a protein-protein interaction network. We focus on asthma and COPD, two chronic respiratory diseases that have been long hypothesized to share common genetic determinants and mechanisms. We show that FC highlights potential mediator genes between the two diseases, and observe similar outcomes when applying FC to 66 additional pairs of related diseases. Further, we perform in vitro perturbation experiments on a widely replicated asthma gene, GSDMB, showing that FC identifies candidate mediators of the interactions between GSDMB and COPD-associated genes. Our results indicate that FC predicts promising gene candidates for further study of disease-disease interactions.

Antioxidant Alternatives in the Treatment of Amyotrophic Lateral Sclerosis: A Comprehensive Review

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that produces a selective loss of the motor neurons of the spinal cord, brain stem and motor cortex. Oxidative stress (OS) associated with mitochondrial dysfunction and the deterioration of the electron transport chain has been shown to be a factor that contributes to neurodegeneration and plays a potential role in the pathogenesis of ALS. The regions of the central nervous system affected have high levels of reactive oxygen species (ROS) and reduced antioxidant defenses. Scientific studies propose treatment with antioxidants to combat the characteristic OS and the regeneration of nicotinamide adenine dinucleotide (NAD+) levels by the use of precursors. This review examines the possible roles of nicotinamide riboside and pterostilbene as therapeutic strategies in ALS.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

Multiscale landscape of molecular mechanism of SIRT1 activation by STACs

Sirtuins are a family of highly conserved NAD-dependent deacetylase that are involved in multiple biological processes in both prokaryotes and eukaryotes. Many sirtuin-activating compounds (STACs) have been reported for SIRT1, which is the best-characterized sirtuin. However, the molecular mechanism of SIRT1 activation by STACs remains controversial. Here, we developed a multiscale simulation model to explore this mechanism. By quantifying the free energy landscape for the closed conformation of a SIRT1-FdL peptide-resveratrol complex, we found a positive correlation between the barrier height of the active free energy basin and the experimentally determined fluctuations in the rate of SIRT1 deacetylation by resveratrol. In addition, by monitoring dynamics, we found that the open conformation of a SIRT1-p53-STAC-1 complex had a faster rate of conformational change than the closed structure. We also determined the structural properties of each thermodynamic or dynamic state and found that two potential activating factors, the stability of FdL peptide (the p53 peptide substrate including an AMC fluorophore group) binding and the stability of the SIRT1 conformation, were weakly correlated under certain conditions. These results address the controversial question of whether the AMC fluorophore group and native hydrophobic residues have similar roles in the SIRT1 activation process. Finally, we captured the global landscape of the transition, including less stable and more stable states, and proposed a global physical landscape for the mechanism of SIRT1 activation by STACs.

Role of Post-translational Modifications in Alzheimer's Disease

The global burden of Alzheimer's disease (AD) is growing. Valiant efforts to develop clinical candidates for treatment have continuously met with failure. Currently available palliative treatments are temporary and there is a constant need to search for reliable disease pathways, biomarkers and drug targets for developing diagnostic and therapeutic tools to address the unmet medical needs of AD. Challenges in drug-discovery efforts raise further questions about the strategies of current conventional diagnosis; drug design; and understanding of disease pathways, biomarkers and targets. In this context, post-translational modifications (PTMs) regulate protein trafficking, function and degradation, and their in-depth study plays a significant role in the identification of novel biomarkers and drug targets. Aberrant PTMs of disease-relevant proteins could trigger pathological pathways, leading to disease progression. Advancements in proteomics enable the generation of patterns or signatures of such modifications, and thus, provide a versatile platform to develop biomarkers based on PTMs. In addition, understanding and targeting the aberrant PTMs of various proteins provide viable avenues for addressing AD drug-discovery challenges. This review highlights numerous PTMs of proteins relevant to AD and provides an overview of their adverse effects on the protein structure, function and aggregation propensity that contribute to the disease pathology. A critical discussion offers suggestions of methods to develop PTM signatures and interfere with aberrant PTMs to develop viable diagnostic and therapeutic interventions in AD.

Neuroprotective Effect of Resveratrol via Activation of Sirt1 Signaling in a Rat Model of Combined Diabetes and Alzheimer's Disease

Background

Alzheimer’s disease (AD) and diabetes mellitus (DM) often coexist in patients because having one of these conditions increases risk for the other. These two diseases share several pathophysiological mechanisms, such as specific inflammatory signaling pathways, oxidative stress, and cell apoptosis. It is still unclear exactly which mechanisms associated with DM are responsible for increased AD risk. Studies have found that even transient elevation of brain Aβ levels can allow T2DM to slightly disrupt the neural milieu in a way that encourages pathologies associated with the onset of memory deficits and AD. A recent study argues that a potential common pathogenetic mechanism underlying both DM and AD is evidenced by the cooccurrence of amyloid brain legions and deposits containing both tau and Aβ in pancreatic β cells. Given these links, an investigation detailing disease mechanisms as well as treatment options for patients with cooccurring DM and AD is urgently needed. The biological effects of resveratrol relevant to DM and AD treatment include its abilities to modulate oxidative stress and reduce inflammation. A rat model of DM and concomitant AD was created for this study using intraperitoneal injection of streptozotocin and hippocampal injection of Aβ1–40 to characterize resveratrol’s potential protective action.

Results

Resveratrol significantly increased the Sirt1 expression, inhibited the memory impairment, the increased acetylcholinesterase, malondialdehyde, interleukin-1β and interleukin 6 levels, and the decreased levels of choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione in this rat model of diabetes and concomitant AD. The Sirt 1 inhibitor EX527 partially reversed the effects of resveratrol.

Conclusion

This study suggests that resveratrol may have a neuroprotective action through activation of Sirt1 signaling in diabetes and AD with concurrent onset.

Chemical and pharmacological research on the polyphenol acids isolated from Danshen: A review of salvianolic acids

Danshen, the dried root of Salvia miltiorrhiza Bge, is a common medicinal herb in Traditional Chinese Medicine, which has been used for the treatment of a number of diseases for thousands of years. More than 2000 years ago, the Chinese early pharmacy monograph "Shennong Materia Medica" recorded that Danshen could be used for the treatment of gastrointestinal diseases, cardiovascular diseases, certain gynecological diseases, etc. Since then, Danshen has been widely used clinically in many different prescriptions for many different diseases, especially for the treatment of cardiovascular diseases. Nowadays, many pharmacological studies about the water-soluble components from Danshen have been reported, especially salvianolic acids. It turned out that salvianolic acids showed strong anti-lipid peroxidation and anti-thrombic activities, and among them, SalAA and SalAB were the most potent. This review focused on the achievements in research of salvianolic acids regarding their bioactivities and pharmacological effects. These studies not only shed light on the water-soluble active components of Danshen and their mechanisms at the molecular level, but also provided theoretical information for the development of new medicines from Danshen for the treatment of cardiovascular and cerebrovascular diseases, inflammatory diseases, metabolic diseases, etc.

Relationship of Wine Consumption with Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD), the most threatening neurodegenerative disease, is characterized by the loss of memory and language function, an unbalanced perception of space, and other cognitive and physical manifestations. The pathology of AD is characterized by neuronal loss and the extensive distribution of senile plaques and neurofibrillary tangles (NFTs). The role of environment and the diet in AD is being actively studied, and nutrition is one of the main factors playing a prominent role in the prevention of neurodegenerative diseases. In this context, the relationship between dementia and wine use/abuse has received increased research interest, with varying and often conflicting results. Scope and Approach: With this review, we aimed to critically summarize the main relevant studies to clarify the relationship between wine drinking and AD, as well as how frequency and/or amount of drinking may influence the effects. Key Findings and Conclusions: Overall, based on the interpretation of various studies, no definitive results highlight if light to moderate alcohol drinking is detrimental to cognition and dementia, or if alcohol intake could reduce risk of developing AD.

Butein, isoliquiritigenin, and scopoletin attenuate neurodegeneration via antioxidant enzymes and SIRT1/ADAM10 signaling pathway

Neuronal cell death is a key feature of neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. Plant polyphenols, namely butein, isoliquiritigenin, and scopoletin, have been shown to exhibit various biological activities including anti-inflammatory, antimicrobial, and antioxidant activities. Herein, butein, isoliquiritigenin, and scopoletin were explored for their neuroprotective properties against oxidative stress-induced human dopaminergic SH-SY5Y cell death. The cells exposed to hydrogen peroxide (H₂O₂) revealed a reduction in cell viability and increases in apoptosis and levels of reactive oxygen species (ROS). Interestingly, pretreatment of SH-SY5Y cells with 5 μM of butein, isoliquiritigenin, or scopoletin protected against the cell death induced by H₂O₂, and decreased the levels of apoptotic cells and ROS. In addition, the levels of SIRT1, FoxO3a, ADAM10, BCL-2, and antioxidant enzymes (catalase and SOD2) were maintained in the cells pretreated with butein, isoliquiritigenin, or scopoletin before H₂O₂ treatment compared to cells without pretreatment and the reference (resveratrol). Molecular docking analysis revealed that the interactions between the activator-binding sites of SIRT1 and the phenolic compounds were similar to those of resveratrol. Taken together, the data suggest that these polyphenolic compounds could be potential candidates for prevention and/or treatment of neurodegeneration.

Neuronal cells exposed to H₂O₂ may undergo increase ROS, reduction in cell viability and cell death. Butein, isoliquiritigenin, and scopoletin ameliorated H₂O₂-induced neurotoxicity by reducing ROS, balancing antioxidants and activating SIRT1-FoxO3a-ADAM10 pathway.