Alpha-lipoic acid upregulates SIRT1-dependent PGC-1α expression and protects mouse brain against focal ischemia

Acupuncture modulates the AMPK/PGC-1 signaling pathway to facilitate mitochondrial biogenesis and neural recovery in ischemic stroke rats

Aims

The main objective of this study was to investigate the role and mechanism of acupuncture on anti-nerve injury in the acute phase by regulating mitochondrial energy metabolism via monophosphate-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) axis in rat ischemic stroke.

Main methods

Middle cerebral artery occlusion (MCAO) was established by middle cerebral artery occlusion/reperfusion. One-week of acupuncture was performed during the acute phase of ischemic stroke. The neurological function and brain tissue integrity were evaluated. Mitochondrial function (intracellular ATP level and the activity of mitochondrial respiratory chain complex I) and the level of NADH oxidase (NOX) were detected by enzymatic chemistry. Next, the potential molecular mechanisms were explored by western blotting, fluorescence quantitative PCR and immunohistochemistry method.

Key findings

(1) Acupuncture treatment for MCAO/R rats showed a significant improvement in the infarcted tissue accompanied by functional recovery in Zea-Longa score and balance beam score outcomes, motor function performances. (2) Acupuncture increased the levels of ATP and mitochondrial respiratory chain complex I, decreased the NOX levels in cerebral ischemia established by suture-occluded method. (3) Acupuncture reduced the necrosis dissolution of neuronal cells and meningeal edema, while promoting angiogenesis. (4) Quantitative immunohistochemical staining results showed acupuncture can increase the expression of AMPK, p-AMPK and the mitochondrial transcription factor PGC-1α, NRF2, TFAM and uncoupling protein 2 (UCP2). Meanwhile, acupuncture treatment up-regulated the expression of the corresponding protein. (5) Subsequently, acupuncture enhanced AMPK phosphorylation as well as the expression of PGC-1α, NRF2, TFAM and UCP2, implicated in mitochondrial synthesis and cellular apoptosis. (6) Finally, injections of AMPK antagonists and activators confirmed AMPK as a therapeutic target for the anti-nerve damage effects of acupuncture.

Significance

Acupuncture intervention relieved ischemic stroke progression in MCAO rats by promoting energy metabolism and mitochondrial biogenesis in the brain and alleviating neuronal apoptosis, which was mediated by eliciting AMPK/PGC-1α axis, among them AMPK is a therapeutic target.

Intranasal Delivery of Mitochondria Attenuates Brain Injury by AMPK and SIRT1/PGC-1α Pathways in a Murine Model of Photothrombotic Stroke

Ischemic stroke is one of the major causes of morbidity and mortality worldwide. Mitochondria play a vital role in the pathological processes of cerebral ischemic injury, but its transplantation and underlying mechanisms remain unclear. In the present study, we examined the effects of mitochondrial therapy on the modulation of AMPK and SIRT1/PGC-1α signaling pathway, oxidative stress, and NLRP3 inflammasome activation after photothrombotic ischemic stroke (pt-MCAO). The adult male mice were subjected to the pt-MCAO in which the proximal-middle cerebral artery was exposed with a 532-nm laser beam for 4 min by retro-orbital injection of a photosensitive dye (Rose Bengal: 15 mg/kg) before the laser light exposure and isolated mitochondria (100 μg protein) were administered intranasally at 30 min, 24 h, and 48 h following post-stroke. After 72 h, mice were tested for neurobehavioral outcomes and euthanized for infarct volume, brain edema, and molecular analysis. First, we found that mitochondria therapy significantly decreased brain infarct volume and brain edema, improved neurological dysfunction, attenuated ischemic stroke-induced oxidative stress, and neuroinflammation. Second, mitochondria treatment inhibited NLRP3 inflammasome activation. Finally, mitochondria therapy accelerated p-AMPKα(Thr172) and PGC-1α expression and resorted SIRT1 protein expression levels in pt-MCAO mice. In conclusion, our results demonstrate that mitochondria therapy exerts neuroprotective effects by inhibiting oxidative damage and inflammation, mainly dependent on the heightening activation of the AMPK and SIRT1/PGC-1α signaling pathway. Thus, intranasal delivery of mitochondria might be considered a new therapeutic strategy for ischemic stroke treatment.

Neuroprotective effect of, a flavonoid, sudachitin in mice stroke model

A flavonoid, sudachitin, has been reported to show some beneficial health effects, including as an anti-inflammatory in LPS-stimulated macrophages, as well as improving glucose and lipid metabolism in mice fed a high-fat diet. In this study, we investigated the neuroprotective effect of sudachitin in the transient middle cerebral artery occlusion (tMCAO) mouse model. After daily pre-treatment of vehicle or sudachitin (5 or 50 mg/kg) for 14 days, mice (n = 76) were subjected to a sham operation or tMCAO for 45 min, and on the following days, they were treated daily with vehicle or sudachitin. The administration of sudachitin significantly reduced (p < 0.05) cerebral infarct volume and attenuated apoptosis, 5 days after tMCAO. Neurological impairment improved, the expression of an oxidative stress marker, 4-HNE, decreased, and the Sirt1/PGC-1α pathway was activated 5 days after tMCAO in the sudachitin-treated group. This is the first report to demonstrate the neuroprotective effect of sudachitin in cerebral ischemia/reperfusion injury mice model, probably by activating the Sirt1/PGC-1α axis. Sudachitin may be a promising supplement or therapeutic agent for reducing injury caused by ischemic strokes.

Transcutaneous electrical acupoint stimulation attenuated neuroinflammation and oxidative stress by activating SIRT1-induced signaling pathway in MCAO/R rat models

BACKGROUND

Silent information regulator 1 (SIRT1) plays a beneficial role in cerebral ischemic injury. Previous reports have demonstrated that transcutaneous electrical acupoint stimulation (TEAS) exerts a beneficial effect on ischemic stroke; however, whether SIRT1 participates in the underlying mechanism for the neuroprotective effects of TEAS against ischemic brain damage has not been confirmed.

METHODS

The rat models of middle cerebral artery occlusion/reperfusion (MCAO/R) were utilized in the current experiment. After MCAO/R surgery, rats in TEAS, EC and EX group received TEAS intervention with or without the injection of EX527, the SIRT1 inhibitor. Neurological deficit scores, infarct volume, hematoxylin eosin (HE) staining and apoptotic cell number were measured. The results of RNA sequencing were analyzed to determine the differential expression changes of genes among sham, MCAO and TEAS groups, in order to investigate the possible pathological processes involved in cerebral ischemia and explore the protective mechanisms of TEAS. Moreover, oxidative stress markers including MDA, SOD, GSH and GSH-Px were measured with assay kits. The levels of the proinflammatory cytokines, such as IL-6, IL-1β and TNF-α, were detected by ELISA assay, and Iba-1 (the microglia marker protein) positive cells was measured by immunofluorescence (IF). Western blot and IF were utilized to examine the levels of key molecules in SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways.

RESULTS

TEAS significantly decreased brain infarcted size and apoptotic neuronal number, and alleviated neurological deficit scores and morphological injury by activating SIRT1. The results of RNA-seq and bioinformatic analysis revealed that oxidative stress and inflammation were the key pathological mechanisms, and TEAS alleviated oxidative injury and inflammatory reactions following ischemic stroke. Then, further investigation indicated that TEAS notably attenuated neuronal apoptosis, neuroinflammation and oxidative stress damage in the hippocampus of rats with MCAO/R surgery. Moreover, TEAS intervention in the MCAO/R model significantly elevated the expressions of SIRT1, FOXO3a, CAT, BRCC3, NLRP3 in the hippocampus. Furthermore, EX527, as the inhibitor of SIRT1, obviously abolished the anti-oxidative stress and anti-neuroinflammatory roles of TEAS, as well as reversed the TEAS-mediated elevation of SIRT1, FOXO3a, CAT and reduction of BRCC3 and NLRP3 mediated by following MCAO/R surgery.

CONCLUSIONS

In summary, these findings clearly suggested that TEAS attenuated brain damage by suppressing apoptosis, oxidative stress and neuroinflammation through modulating SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways following ischemic stroke, which can be a promising treatment for stroke patients.

Safranal acts as a neurorestorative agent in rats with cerebral ischemic stroke via upregulating SIRT1

Safranal is an active ingredient of saffron (Crocus sativus L.). Its neuroprotective role in ischemic stroke (IS) through reducing oxidative stress damage has been widely reported. However, the neurorestorative mechanisms of safranal are still in the preliminary stage of exploration. the present study is aimed to discuss the effects of safranal on the recovery of neural function after IS. A middle cerebral artery occlusion/reperfusion (MCAO/R) rat model and an oxygen-glucose deprivation/reoxygenation (OGD/R) model in rat brain microvascular endothelial cells (RBMEC) were established to explore the effects of safranal on IS in vivo and in vitro. It was found that safranal dramatically reduced infarct size and Nissl's body loss in rats subjected to MCAO/R. Safranal also promoted neuron survival, stimulated neurogenesis, induced angiogenesis and increased SIRT1 expression in vivo and in vitro. Silencing of SIRT1 reversed the above effects of safranal on OGD/R-induced RBMEC. The present study indicated that safranal was a promising compound to exert neurorestorative effect in IS via upregulating SIRT1 expression. These results offer insight into developing new mechanisms in the recovery of neural function after safranal treatment of IS.

Modified rougan decoction attenuates hepatocyte apoptosis through ameliorating mitochondrial dysfunction by upregulated SIRT1/PGC-1α signaling pathway

The modified rougan decoction (MRGD) compound formula has been proven a certain ability to relieve lipopolysaccharide-enrofloxacin (LPS-ENR)-induced liver oxidant injury in chickens. Recent advances have shown that mitochondrial dysfunction affects the development of many diseases, leading to increased interest in exploring its effects. Using LPS-ENR-injured in vivo and in vitro to further evaluate the effects of MRGD on mitochondrial structure and function, and emphasized further investigation of its molecular mechanism. After LPS-ENR treatment, the levels of inflammation and apoptosis markers were increased, along with higher mitochondrial injury. Results showed that MRGD reduced inflammatory factors expression and inhibited the nuclear translocation of NF-κB P65, reducing the inflammatory response in vivo and in vitro. Additionally, MRGD pretreatment inhibited mitochondrial dysfunction, mitochondrial oxidative stress, and mitochondrial pathway apoptosis by maintaining mitochondrial structure and function. Moreover, treatment with the inhibitor EX527 showed that MRGD promoted mitochondrial biogenesis ability through the SIRT1/PGC-1α pathway and interfered with mitochondrial dynamics, and activate Nrf2. In summary, MRGD played a key role in promoting mitochondrial function and thus alleviating hepatocyte apoptosis in vivo and in vitro at least in part.

Sirtuins: Promising Therapeutic Targets to Treat Ischemic Stroke

Stroke is a major cause of mortality and disability globally, with ischemic stroke (IS) accounting for over 80% of all stroke cases. The pathological process of IS involves numerous signal molecules, among which are the highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent enzymes known as sirtuins (SIRTs). SIRTs modulate various biological processes, including cell differentiation, energy metabolism, DNA repair, inflammation, and oxidative stress. Importantly, several studies have reported a correlation between SIRTs and IS. This review introduces the general aspects of SIRTs, including their distribution, subcellular location, enzyme activity, and substrate. We also discuss their regulatory roles and potential mechanisms in IS. Finally, we describe the current therapeutic methods based on SIRTs, such as pharmacotherapy, non-pharmacological therapeutic/rehabilitative interventions, epigenetic regulators, potential molecules, and stem cell-derived exosome therapy. The data collected in this study will potentially contribute to both clinical and fundamental research on SIRTs, geared towards developing effective therapeutic candidates for future treatment of IS.

Alpha-lipoic acid activates AMPK to protect against oxidative stress and apoptosis in rats with diabetic peripheral neuropathy

PURPOSE

To investigate the AMPK pathway-mediated effect of alpha-lipoic acid (ALA) on the dorsal root ganglia (DRGs) of rats with diabetic peripheral neuropathy (DPN) and to attempt to elucidate the underlying mechanism.

METHODS

Sprague-Dawley rats (n = 15) were randomly divided into three groups. The control group was fed a standard diet, and the other groups were fed a high-carbohydrate/high-fat diet. Diabetes was established by a single streptozotocin (STZ) (30 mg/kg) injection, and control rats were injected with an equal volume of citrate buffer. ALA (60 mg/kg/day) was administered for 12 weeks. The nerve conduction velocity (NCV) of the sciatic nerve was measured. Glutathione (GSH) and malondialdehyde (MDA) concentrations in serum were measured with the thiobarbituric acid method and biochemistry. Pathological changes in the rat DRGs were observed. AMPK, phospho-AMPK (p-AMPK), nuclear factor erythroid-2-related factor 2 (Nrf2), phospho-nuclear factor erythroid-2-related factor 2 (p-Nrf2), heme oxygenase 1 (HO-1), quinone oxidoreductase 1 (NQO1), Forkhead box O3 (FoxO3a), phospho-Forkhead box O3 (p-FoxO3a), and Bcl-2 interacting mediator of cell death (Bim) expression levels were assessed by immunohistochemistry and western blotting.

RESULTS

ALA improved the motor NCV (MNCV) and sensory NCV (SNCV) of rats with DPN and reduced their mechanical pain threshold. ALA increased serum GSH concentrations and decreased serum MDA concentrations. Additionally, AMPK was activated by ALA. Nrf2, p-Nrf2, HO-1, and NQO1 expression was upregulated, while FoxO3a, p-FoxO3a, and Bim expression was downregulated. ALA reduced oxidative stress and apoptosis in DRG.

CONCLUSION

ALA alleviates DPN and improves peripheral nerve function. ALA reduces oxidative stress by activating Nrf2 through AMPK and inhibits FoxO3a and Bim thereby reducing neuronal apoptosis.

Syringin exerts anti-inflammatory and antioxidant effects by regulating SIRT1 signaling in rat and cell models of acute myocardial infarction

INTRODUCTION

This study aimed to investigate the role of syringin in improving heart function during myocardial ischemia/reperfusion (I/R) and to determine whether the sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator 1 alpha (SIRT1/PGC-1α) pathway contributes to this cardioprotective effect in vivo and in vitro.

METHODS

H9c2 cells were incubated with H₂ O₂ for 12 h. The effect of syringin was assessed by measuring cell viability; the apoptotic rate; Keap1/NRF2/HO-1 activation; and the levels of proinflammatory cytokines, oxidative products, and antioxidative enzymes. In addition, SIRT1 was silenced via short hairpin RNA (shRNA)-SIRT1 transfection to evaluate its involvement in syringin-mediated protection. Syringin rescued cells from H₂ O₂ -induced reductions in viability, antioxidative enzyme levels, and NRF2/HO-1 activation; likewise, syringin inhibited apoptosis, inflammation, and oxidative stress. We also created a rat model of I/R by ligating the left anterior descending coronary artery for 30 min, followed by reperfusion for 12 min. Syringin was then intraperitoneally injected, and the effect on infarct size and cardiac function was examined after 7 days. NRF2/HO-1 activity and the levels of myocardial proinflammatory cytokines, oxidative products, and antioxidative enzymes were measured.

RESULTS

In comparison to the untreated I/R group, the syringin treatment group exhibited improved cardiac function and reduced cardiac lesion and infarct size. Syringin administration also markedly reduced the levels of proinflammatory cytokines and reactive oxygen species and promoted antioxidative enzyme expression and NRF2/HO-1 pathway activation.

CONCLUSIONS

Syringin may serve a protective role in animal and cell models of I/R by improving cardiac function, inhibiting the inflammatory response, and activating the antioxidative response.

LncRNA MALAT1 improves cerebral ischemia-reperfusion injury and cognitive dysfunction by regulating miR-142-3p/SIRT1 axis

PURPOSE

To investigate the regulation and related mechanisms of MALAT1 in cerebral ischemia- reperfusion (CI/R) injury.

MATERIALS AND METHODS

72 mice were divided into sham group (n=24), MCAO group (n=24), MCAO+pcDNA-NC group (n=12) and MCAO+MALAT1 group (n=12). At 12 h, 24 h and 48 h after reperfusion, 6 mice were randomly selected from the sham group and the MCAO group to detect the expression of MALAT1, miR-142-3p and SIRT1 in brain tissue. All mice were scored for neurobehavioral after 48 h of reperfusion. After the completion of the scoring, 6 mice were randomly selected from each group and brain tissue was obtained for TTC analysis. The remaining mice of each group were kept on the Morris water maze test after 3 days of feeding. TTC staining and cerebral infarct volume determination. The infarct size of each brain slice was calculated using Image J image analysis software. OGD/R model PC12 cells were prepared according to simulating CI/R injury in vitro. MALAT1 was cloned into the pcDNA3.1 to construct a MALAT1 overexpression vector with the empty vector NC as a control. Plasmid or oligonuceotides were transfected into PC12 cells. The content of TNF-α, IL-1β, IL-6, the content of reactive oxygen species (ROS), malondialdehyde (MDA) in brain tissue was detected. The activity of superoxide dismutase (SOD), catalase (CAT) activity was measured.

RESULTS

MALAT1 was down-regulated in a time-dependent manner in CI/R-damaged mouse cerebral cortex and OGD/R-induced PC12 cells, accompanied by an increase in the expression of miR-142-3p and a decrease in sirtuin 1 (SIRT1) expression. Overexpression of MALAT1 inhibited OGD/R-induced cell necrosis and apoptosis and promoted cell proliferation. Overexpression of MALAT1 reduced the levels of TNF-α, IL-6, IL-1β, ROS and MDA and increased the activities of SOD and CAT in OGD/R-injured PC12 cells. MALAT1 negatively regulated the expression of miR-142-3p, and SIRT1 was a target gene of miR-142-3p. The expression of SIRT1 induced by MALAT1 overexpression was obviously abolished by the introduction of miR-142-3p mimic. MALAT1 overexpression can exert its role by regulating the miR-142-3p/SIRT1 axis. Besides, overexpression of MALAT1 improved cerebral infarction, neurological impairment and cognitive dysfunction in CI/R mice.

CONCLUSION

MALAT1 mediates SIRT1 expression by acting as a ceRNA of miR-142-3p to improve CI/R injury.

Abbreviations: CAT: catalase; CI/R: cerebral ischemia-reperfusion; IL-1β: interleukin-1β; IL-6: interleukin-6; lncRNA: long-chain non-coding RNA; MALAT1: metastasis-associated lung adenocarcinoma transcript1; MCAO: middle cerebral artery occlusion; MDA: malondialdehyde; OGD/R: oxygen-glucose deprivation and reoxygenation; ROS: reactive oxygen species; SIRT1: sirtuin 1; SOD: superoxide dismutase; TNF-α: tumour necrosis factor-alpha.

Role of NAD+ and FAD in Ischemic Stroke Pathophysiology: An Epigenetic Nexus and Expanding Therapeutic Repertoire

The redox coenzymes viz., oxidized β-nicotinamide adenine dinucleotide (NAD⁺) and flavin adenine dinucleotide (FAD) by way of generation of optimal reducing power and cellular energy currency (ATP), control a staggering array of metabolic reactions. The prominent cellular contenders for NAD⁺ utilization, inter alia, are sirtuins (SIRTs) and poly(ADP-ribose) polymerase (PARP-1), which have been significantly implicated in ischemic stroke (IS) pathogenesis. NAD⁺ and FAD are also two crucial epigenetic enzyme-required metabolites mediating histone deacetylation and poly(ADP-ribosyl)ation through SIRTs and PARP-1 respectively, and demethylation through FAD-mediated lysine specific demethylase activity. These enzymes and post-translational modifications impinge on the components of neurovascular unit, primarily neurons, and elicit diverse functional upshots in an ischemic brain. These could be circumstantially linked with attendant cognitive deficits and behavioral outcomes in post-stroke epoch. Parsing out the contribution of NAD⁺/FAD-synthesizing and utilizing enzymes towards epigenetic remodeling in IS setting, together with their cognitive and behavioral associations, combined with possible therapeutic implications will form the crux of this review.

Natural Compounds for SIRT1-Mediated Oxidative Stress and Neuroinflammation in Stroke: A Potential Therapeutic Target in the Future

Stroke is a fatal cerebral vascular disease with a high mortality rate and substantial economic and social costs. ROS production and neuroinflammation have been implicated in both hemorrhagic and ischemic stroke and have the most critical effects on subsequent brain injury. SIRT1, a member of the sirtuin family, plays a crucial role in modulating a wide range of physiological processes, including apoptosis, DNA repair, inflammatory response, and oxidative stress. Targeting SIRT1 to reduce ROS and neuroinflammation might represent an emerging therapeutic target for stroke. Therefore, we conducted the present review to summarize the mechanisms of SIRT1-mediated oxidative stress and neuroinflammation in stroke. In addition, we provide a comprehensive introduction to the effect of compounds and natural drugs on SIRT1 signaling related to oxidative stress and neuroinflammation in stroke. We believe that our work will be helpful to further understand the critical role of the SIRT1 signaling pathway and will provide novel therapeutic potential for stroke treatment.

Redox Active α-Lipoic Acid Differentially Improves Mitochondrial Dysfunction in a Cellular Model of Alzheimer and Its Control Cells

Introduction: Alpha lipoic acid (ALA) is a sulphur-containing organic compound, derived from octanoic acid, and an important cofactor for mitochondrial respiratory enzymes. It has strong antioxidant properties that improve mitochondrial function. We investigated if ALA improves mitochondrial dysfunction in a cellular model of Alzheimer’s disease (AD). Methods: SH-SY5Y-APP₆₉₅ cells were used as a model for an early stage of AD. Vector-transfected SH-SY5Y-MOCK cells served as controls. Using these cells, we investigated mitochondrial respiration (OXPHOS), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) production, and citrate synthase activity (CS) in cells treated with ALA. Cells were treated for 24 h with different concentrations of ALA and with or without the complex I inhibitor rotenone. Results: Incubation with ALA showed a significant increase in ATP levels in both SH-SY5Y-APP₆₉₅ and SH-SY5Y-MOCK cells. MMP levels were elevated in SH-SY5Y-MOCK cells, treatment with rotenone showed a reduction in MMP, which could be partly alleviated after incubation with ALA in SH-SY5Y-MOCK cells. ALA treatment showed significant differences in respiration chain complex activities in SH-SY5Y-MOCK cells. Citrate synthase activity was unaffected. ROS levels were significantly lower in both cell lines treated with ALA. Conclusions: ALA increased the activity of the different complexes of the respiratory chain, and consequently enhanced the MMP, leading to increased ATP levels indicating improved mitochondrial function. ALA only marginally protects from additional rotenone-induced mitochondrial stress.

Modulation of autophagy by melatonin via sirtuins in stroke: From mechanisms to therapies

Sirtuins perform an important effect on the neural cell fate following stroke. Several mechanisms that have been correlated with stroke are oxidative stress, apoptosis, necrosis and autophagy. Autophagy is usually regarded as unitary of the neural cell survival mechanisms. Recently, the importance of the sirtuins effect on autophagy by antioxidant agents for stroke treatment mentioned in various studies. One of these agents is melatonin. Melatonin can modulate autophagy by changing on sirtuin pathways. Melatonin and its metabolites adjust various sirtuins pathways related to apoptosis, proliferation, metastases, autophagy and inflammation in case of stroke. In this review, we will discuss about the modulation of autophagy by melatonin via sirtuins in stroke.

Neuromodulatory Mechanisms of a Memory Loss-Preventive Effect of Alpha-Lipoic Acid in an Experimental Rat Model of Dementia

This study evaluates some of the neuromodulatory mechanisms of the memory loss preventive effect of alpha-lipoic acid (ALA) in a scopolamine (Sco)-induced rat model of Alzheimer's disease (AD) type dementia. Our results confirmed that Sco administration induces significant memory impairment, worsens exploratory behaviour and habituation, increases acetylcholinesterase (AChE) activity, and induces pathological monoamine content changes in the prefrontal cortex and hippocampus. ALA administration largely prevented Sco-induced memory impairment. It also improved exploratory behaviour and preserved habituation, and it decreased AChE activity, reversing it to control group levels, and corrected aberrant monoamine levels in the prefrontal cortex and hippocampus. According to the data available, this is the first time that ALA-induced changes in AChE and monoamine levels in the prefrontal cortex and hippocampus (brain structures related to learning and memory) have been demonstrated in a Sco-induced rat model of AD type dementia.

Alpha-Lipoic Acid Attenuates MPTP/MPP+-Induced Neurotoxicity: Roles of SIRT1-Dependent PGC-1α Signaling Pathways

Accumulated oxidative damage plays key roles in the pathogenesis of Parkinson's disease (PD). Silent mating type information regulation 2 homolog 1 (SIRT1), a class III histone deacetylase, can directly activate peroxisome proliferator-activated receptor-c coactivator-1α (PGC-1α) and attenuate oxidative stress. Alpha-lipoic acid (ALA) is a natural antioxidant that has been demonstrated to protect PC12 cells against 1-methyl-4-phenylpyridinium (MPP⁺). However, the underlying mechanisms related to changes in cell signaling cascades are not fully understood. In the present study, the neuroprotective effect of ALA and the potential role of ALA in the SIRT1 pathway was investigated in vitro and in a mouse model of PD. A Cell Counting Kit-8 (CCK-8) assay was performed to detect the SY5Y-SH cell viability. Immunohistochemistry, quantitative real-time polymerase chain reaction and western blot assays were used to evaluate the expression of tyrosine hydroxylase (TH), SIRT1, and PGC-1α in vivo and in vitro. Intracellular reactive oxygen species (ROS) production and tissue SOD and MDA were detected by the corresponding assay kits. The results showed that ALA notably prevented oxidative stress and neurotoxicity in vivo and in vitro against 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)/MPP⁺. Furthermore, ALA significantly increased the expression of SIRT1 and PGC-1α in vivo and in vitro in MPTP/MPP⁺-induced models, which was reversed by the SIRT1 inhibitor EX527. These results suggested that ALA prevented oxidative stress and that neurotoxicity was involved in the upregulation of SIRT1 and PGC-1α in PD mice.

Hydroxysafflor Yellow A and Anhydrosafflor Yellow B Protect Against Cerebral Ischemia/Reperfusion Injury by Attenuating Oxidative Stress and Apoptosis via the Silent Information Regulator 1 Signaling Pathway

Hydroxysafflor yellow A (HSYA) and anhydrosafflor yellow B (AHSYB) are the main water-soluble compounds in Carthamus tinctorius L. However, studies on the effect of AHSYB on cerebral ischemia/reperfusion (I/R) injury and the therapeutic effect of HSYA by regulating silent information regulator 1 (SIRT1) pathway remain obscure. In this study, we investigated whether the neuroprotective effects of HSYA and AHSYB on oxygen-glucose deprivation/reoxygenation in primary-cultured hippocampal neuronal cells and the middle cerebral artery occlusion and reperfusion model in rats are associated with the regulation of the SIRT1 pathway. In vitro, HSYA and AHSYB increased cell viability, depressed oxidation properties, and reduced neuronal cell apoptosis. In vivo results showed that HSYA and AHSYB effectively reduced infarct volume, improved neurological function, suppressed apoptosis, and decreased the oxidative stress reaction. Besides, RT-PCR and Western blot analysis showed that HSYA and AHSYB increased the mRNA and protein expressions of the main factors in the SIRT1 pathway, including SIRT1, forkhead box O (FOXO) 1, and peroxisome proliferator–activated receptor coactivator 1α (PGC1α), decreased the expression of Bax, and increased the expression of Bcl-2. The results from immunohistochemistry also showed that the expressions of SIRT1, FOXO1, and PGC1α were increased after treatment with HSYA and AHSYB. Furthermore, the neuroprotective effects of HSYA and AHSYB were abolished by EX527 (SIRT1–specific inhibitor). These results indicated that HSYA and AHSYB should be developed into potential drugs for treating cerebral I/R injury via the SIRT1 pathway. Although HSYA and AHSYB have different chemical structures, both of them exert similar neuroprotective properties against I/R injury in vitro and in vivo, which means that AHSYB is also a non-negligible component in safflower.

Histone Deacetylases and Their Isoform-Specific Inhibitors in Ischemic Stroke

Cerebral ischemia is the second leading cause of death in the world and multimodal stroke therapy is needed. The ischemic stroke generally reduces the gene expression due to suppression of acetylation of histones H3 and H4. Histone deacetylases inhibitors have been shown to be effective in protecting the brain from ischemic damage. Histone deacetylases inhibitors induce neurogenesis and angiogenesis in damaged brain areas promoting functional recovery after cerebral ischemia. However, the role of different histone deacetylases isoforms in the survival and death of brain cells after stroke is still controversial. This review aims to analyze the data on the neuroprotective activity of nonspecific and selective histone deacetylase inhibitors in ischemic stroke.

SIRT1/PGC-1α signaling activation by mangiferin attenuates cerebral hypoxia/reoxygenation injury in neuroblastoma cells

Ischemia reperfusion injury (IRI) is associated with poor prognoses in the setting of ischemic brain diseases. Silence information regulator 1 (SIRT1) is a member of the third class of nicotinamide adenine dinucleotide (NAD+)-dependent sirtuins. Recently, the role of SIRT1/peroxisome proliferators-activated receptor-γ coactivator 1α (PGC-1α) pathway in organ (especially the brain) protection under various pathological conditions has been widely investigated. Mangiferin (MGF), a natural C-glucosyl xanthone polyhydroxy polyphenol, has been shown to be beneficial to several nervous system diseases and the protective effects of MGF can be achieved through the regulation of SIRT1 signaling. This study is designed to investigate the protective effects of MGF treatment in the setting of cerebral IRI and to elucidate the potential mechanisms. We first evaluated the toxicity of MGF and chose the safe concentrations for the following experiments. MGF exerted obvious neuroprotection against hypoxia/reoxygenation (HR)-induced injury, indicated by restored cell viability and cell morphology, decreased lactate dehydrogenase (LDH) release and reactive oxygen species generation. MGF also restored the protein expressions of SIRT1, PGC-1α, Nrf2, NQO1, HO-1, NRF1, UCP2, and Bcl2 down-regulated by HR treatment. However, SIRT1 siRNA could reverse MGF-induced neuroprotection and decrease the expressions of molecules mentioned above. Taken together, our findings suggest that MGF treatment exerts neuroprotection against HR injury via activating SIRT1/PGC-1α signaling. These findings may provide a theoretical basis for the exploitation of MGF as a potential neuroprotective drug candidate, which may be beneficial for the ischemic stroke patients in clinic.

miR-124-3p targeted SIRT1 to regulate cell apoptosis, inflammatory response, and oxidative stress in acute myocardial infarction in rats via modulation of the FGF21/CREB/PGC1α pathway

To investigate whether miR-124-3p influences cell apoptosis, inflammatory response, and oxidative stress in rats with acute myocardial infarction (AMI) by mediating the SIRT1/FGF21/CREB/PGC1α pathway. A dual-luciferase reporter gene assay was performed to verify the relationship between miR-124-3p and SIRT1. AMI rats were established via coronary artery ligation after injection with agomiR-124-3p, antagomiR-124-3p, and/or SIRT1 siRNA, and triphenyltetrazolium chloride (TTC), HE, and TUNEL stainings were performed. Bio-Plex rat cytokine assays were performed to determine proinflammatory factor levels. qRT-PCR and Western blotting were used to examine the mRNA and protein expression, respectively. The activity levels of antioxidant enzymes in myocardial tissues were also measured. miR-124-3p was confirmed to target SIRT1 in the H9C2 cells. AMI rats exhibited increased miR-124-3p expression and decreased SIRT1 expression in myocardial tissues. HE staining showed a disorganized cell arrangement and inflammatory cell infiltration in the myocardial tissues of the AMI rats, which was more severe in the rats injected with SIRT1 and agomiR-124-3p but was ameliorated in those treated with antagomiR-124-3p. Moreover, the AMI rats in the antagomiR-124-3p group presented with a reduction in infarct area with an increase in antioxidant enzyme activity, Bcl-2 expression, and activation of the FGF21/CREB/PGC1α pathway, as well as a decrease in cell apoptosis rate, Bax and Caspase-3 expression, and levels of proinflammatory factors, effects that were reversed by si-SIRT1. Inhibiting miR-124-3p expression may activate the FGF21/CREB/PGC1α pathway to reduce cell apoptosis, alleviate the inflammatory response, and attenuate oxidative stress in AMI rats by targeting SIRT1. Graphical abstract.

Danggui-Shaoyao-San (DSS) Ameliorates Cerebral Ischemia-Reperfusion Injury via Activating SIRT1 Signaling and Inhibiting NADPH Oxidases

Danggui-Shayao-San (DSS) is a famous Traditional Chinese Medicine formula that used for treating pain disorders and maintaining neurological health. Recent studies indicate that DSS has neuroprotective effects against ischemic brain damage but its underlining mechanisms remain unclear. Herein, we investigated the neuroprotective mechanisms of DSS for treating ischemic stroke. Adult male Sprague-Dawley (S.D.) rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus 22 h of reperfusion. Both ethanol extract and aqueous extract of DSS (12 g/kg) were orally administrated into the rats at 30 min prior to MCAO ischemic onset. We found that 1) ethanol extract of DSS, instead of aqueous extract, reduced infarct sizes and improved neurological deficit scores in the post-ischemic stroke rats; 2) Ethanol extract of DSS down-regulated the expression of the cleaved-caspase 3 and Bax, up-regulated bcl-2 and attenuated apoptotic cell death in the ischemic brains; 3) Ethanol extract of DSS decreased the production of superoxide and peroxynitrite; 4) Ethanol extract of DSS significantly down-regulated the expression of p67^phox but has no effect on p47^phox and iNOS statistically. 5) Ethanol extract of DSS significantly up-regulated the expression of SIRT1 in the cortex and striatum of the post-ischemic brains; 6) Co-treatment of EX527, a SIRT1 inhibitor, abolished the DSS’s neuroprotective effects. Taken together, DSS could attenuate oxidative/nitrosative stress and inhibit neuronal apoptosis against cerebral ischemic-reperfusion injury via SIRT1-dependent manner.

Epigenetics Mechanisms in Ischemic Stroke: A Promising Avenue?

Stroke has emerged as the second most common cause of mortality worldwide and is a major public health problem. It is a multi-factorial disease and genetics plays an important role in its pathophysiology, however, mechanisms of genome involvement in the disease remain unclear. Both genetic and epigenetic mechanisms could play a role in the development of stroke disease. Although epigenetic characteristics may also be heritable, they can be modified during the lifetime under different environmental exposure in response to lifestyle. Recent studies provide clear evidence that epigenetic factors play an important role in the pathological mechanisms leading to an elevated risk of cardiovascular diseases and stroke. Epigenetic changes are reversible therefore; studying epigenetic factors may serve as a marker for disease progression, biomarker for disease diagnosis, and development of novel targets for therapeutic intervention. Identifying the factors which predispose the risk of stroke provides information for the mechanism of stroke and the design of new drug targets where epigenetic modifications play a significant role. Epigenetic modifications play an essential role in a large variety of multifactorial diseases. This review will focus on the evidence that epigenetic mechanisms play a crucial role in the pathophysiology of ischemic stroke.

The Beneficial Roles of SIRT1 in Neuroinflammation-Related Diseases

Sirtuins are the class III of histone deacetylases whose deacetylate of histones is dependent on nicotinamide adenine dinucleotide (NAD+). Among seven sirtuins, SIRT1 plays a critical role in modulating a wide range of physiological processes, including apoptosis, DNA repair, inflammatory response, metabolism, cancer, and stress. Neuroinflammation is associated with many neurological diseases, including ischemic stroke, bacterial infections, traumatic brain injury, Alzheimer's disease (AD), and Parkinson's disease (PD). Recently, numerous studies indicate the protective effects of SIRT1 in neuroinflammation-related diseases. Here, we review the latest progress regarding the anti-inflammatory and neuroprotective effects of SIRT1. First, we introduce the structure, catalytic mechanism, and functions of SIRT1. Next, we discuss the molecular mechanisms of SIRT1 in the regulation of neuroinflammation. Finally, we analyze the mechanisms and effects of SIRT1 in several common neuroinflammation-associated diseases, such as cerebral ischemia, traumatic brain injury, spinal cord injury, AD, and PD. Taken together, this information implies that SIRT1 may serve as a promising therapeutic target for the treatment of neuroinflammation-associated disorders.

α-Lipoic Acid Maintains Brain Glucose Metabolism via BDNF/TrkB/HIF-1α Signaling Pathway in P301S Mice

The microtubule-associated protein tau is closely correlated with hypometabolism in Alzheimer’s disease (AD). α-lipoic acid (LA), which is a naturally occurring cofactor in mitochondrial, has been shown to have properties that can inhibit the tau pathology and neuronal damage in our previous research. However, if LA affects glucose metabolism when it reverses tau pathology remains unclear, especially concerning the potential mechanism. Therefore, we make a further study using the P301S mouse model (a tauopathy and AD mouse model which overexpressing fibrillary tau) to gain a clear idea of the aforementioned problems. Here, we found chronic LA administration significantly increased glucose availability by elevating glucose transporter 3 (GLUT3), GLUT4, vascular endothelial growth factor (VEGF) protein and mRNA level, and heme oxygenase-1 (HO-1) protein level in P301S mouse brains. Meanwhile, we found that LA also promoted glycolysis by directly upregulating hexokinase (HK) activity, indirectly by increasing proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and DNA repair enzymes (OGG1/2 and MTH1). Further, we found the underlying mechanism of restored glucose metabolism might involve in the activation of brain-derived neurotrophic factor (BDNF)/tyrosine Kinase receptor B (TrkB)/hypoxia-inducible factor-1α (HIF-1α) signaling pathway by LA treatment.

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.

Mitochondrial Dysfunction and Alpha-Lipoic Acid: Beneficial or Harmful in Alzheimer's Disease?

Alzheimer's disease (AD) is a neurodegenerative disorder characterised by impairments in the cognitive domains associated with orientation, recording, and memory. This pathology results from an abnormal deposition of the β-amyloid (Aβ) peptide and the intracellular accumulation of neurofibrillary tangles. Mitochondrial dysfunctions play an important role in the pathogenesis of AD, due to disturbances in the bioenergetic properties of cells. To date, the usual therapeutic drugs are limited because of the diversity of cellular routes in AD and the toxic potential of these agents. In this context, alpha-lipoic acid (α-LA) is a well-known fatty acid used as a supplement in several health conditions and diseases, such as periphery neuropathies and neurodegenerative disorders. It is produced in several cell types, eukaryotes, and prokaryotes, showing antioxidant and anti-inflammatory properties. α-LA acts as an enzymatic cofactor able to regulate metabolism, energy production, and mitochondrial biogenesis. In addition, the antioxidant capacity of α-LA is associated with two thiol groups that can be oxidised or reduced, prevent excess free radical formation, and act on improvement of mitochondrial performance. Moreover, α-LA has mechanisms of epigenetic regulation in genes related to the expression of various inflammatory mediators, such PGE2, COX-2, iNOS, TNF-α, IL-1β, and IL-6. Regarding the pharmacokinetic profile, α-LA has rapid uptake and low bioavailability and the metabolism is primarily hepatic. However, α-LA has low risk in prolonged use, although its therapeutic potential, interactions with other substances, and adverse reactions have not been well established in clinical trials with populations at higher risk for diseases of aging. Thus, this review aimed to describe the pharmacokinetic profile, bioavailability, therapeutic efficacy, safety, and effects of combined use with centrally acting drugs, as well as report in vitro and in vivo studies that demonstrate the mitochondrial mechanisms of α-LA involved in AD protection.

Inhibition of PI3Kγ by AS605240 Protects tMCAO Mice by Attenuating Pro-Inflammatory Signaling and Cytokine Release in Reactive Astrocytes

The intense and prolonged inflammatory response after ischemic stroke significantly contributes to the secondary neural injury. PI3Kγ, which is involved in the regulation of vascular permeability, chemotactic leukocyte migration and microglia activation, is a key target for intervention in the inflammatory response. In this study, we identified the protective effect of the PI3Kγ inhibitor AS605240 against stroke-related injury in the mouse model of transient intraluminal middle cerebral artery occlusion (tMCAO). The results showed that administration of AS605240 could improve the neurological function score, reduce the infarct size and decrease astrocyte activation in the tMCAO mice after injury. The inhibitory effect of AS605240 on microglia activation is relatively clear. Therefore, in this study, the effects of AS605240 on astrocytes were studied in cell cultures. IL-6 and its soluble receptor were used to construct the astrocyte activation model. AS605240 treatment significantly reduced the astrocyte activation markers and the morphological changes of cells. We also identified 13 inflammatory factors whose expression was significantly upregulated by IL-6/sIL-6R and significantly inhibited by AS605240 at the protein level, and seven of those factors were verified at the mRNA level. These results indicated that specific inhibition of PI3Kγ could reduce astrocyte activation induced by inflammation, which might aid the repair and remodeling of neurons in the later stage after ischemic stroke.

Deacetylation of NAT10 by Sirt1 promotes the transition from rRNA biogenesis to autophagy upon energy stress

Anabolism and catabolism are tightly regulated according to the cellular energy supply. Upon energy stress, ribosomal RNA (rRNA) biogenesis is inhibited, and autophagy is induced. However, the mechanism linking rRNA biogenesis and autophagy is unclear. Here, we demonstrate that the nucleolar protein NAT10 plays a role in the transition between rRNA biogenesis and autophagy. Under normal conditions, NAT10 is acetylated to activate rRNA biogenesis and inhibit autophagy induction. Mechanistic studies demonstrate that NAT10 binds to and acetylates the autophagy regulator Che-1 at K228 to suppress the Che-1-mediated transcriptional activation of downstream genes Redd1 and Deptor under adequate energy supply conditions. Upon energy stress, NAT10 is deacetylated by Sirt1, leading to suppression of NAT10-activated rRNA biogenesis. In addition, deacetylation of NAT10 abolishes the NAT10-mediated transcriptional repression of Che-1, leading to the release of autophagy inhibition. Collectively, we demonstrate that the acetylation status of NAT10 is important for the anabolism-catabolism transition in response to energy stress, providing a novel mechanism by which nucleolar proteins control rRNA synthesis and autophagy in response to the cellular energy supply.

Triptolide Improves Cognitive Dysfunction in Rats with Vascular Dementia by Activating the SIRT1/PGC-1α Signaling Pathway

Tripterygium Wilfordii Hook F has been exploited as a treatment for several diseases due to its neuroprotective, anti-tumor, and anti-inflammatory effects. Triptolide is one of its key bioactive compounds. Currently, the role of triptolide in cognitive dysfunction remains unclear. Here, the role of triptolide on cognitive dysfunction was investigated using chronic cerebral hypoperfusion-induced vascular dementia (VD) rat model. SD rats were administrated with Triptolide (5 μg/kg) for 6 weeks after undergoing permanent bilateral common carotid artery occlusion. The results show that triptolide treatment conferred neuroprotective effects in VD rats. Intraperitoneal injection of triptolide attenuated oxidative stress, learning and memory deficits, and neuronal apoptosis in the hippocampi. Moreover, triptolide enhanced the expression of SIRT1, PGC-1α, ZO-1, Claudin-5, and decreased the serum levels of NSE and S100B significantly. It also improved CCH-induced learning and memory deficits, and this is attributed to its capacity to promote SIRT1/PGC-1α signaling, confer antioxidant effects, and inhibit neuronal apoptosis. These findings indicate that triptolide may be an effective therapeutic agent for vascular cognitive dysfunction.

Photobiomodulation and Coenzyme Q10 Treatments Attenuate Cognitive Impairment Associated With Model of Transient Global Brain Ischemia in Artificially Aged Mice

Disturbances in mitochondrial biogenesis and bioenergetics, combined with neuroinflammation, play cardinal roles in the cognitive impairment during aging that is further exacerbated by transient cerebral ischemia. Both near-infrared (NIR) photobiomodulation (PBM) and Coenzyme Q10 (CoQ10) administration are known to stimulate mitochondrial electron transport that potentially may reverse the effects of cerebral ischemia in aged animals. We tested the hypothesis that the effects of PBM and CoQ10, separately or in combination, improve cognition in a mouse model of transient cerebral ischemia superimposed on a model of aging. We modeled aging by 6-week administration of D-galactose (500 mg/kg subcutaneous) to mice. We subsequently induced transient cerebral ischemia by bilateral occlusion of the common carotid artery (BCCAO). We treated the mice with PBM (810 nm transcranial laser) or CoQ10 (500 mg/kg by gavage), or both, for 2 weeks after surgery. We assessed cognitive function by the Barnes and Lashley III mazes and the What-Where-Which (WWWhich) task. PBM or CoQ10, and both, improved spatial and episodic memory in the mice. Separately and together, the treatments lowered reactive oxygen species and raised ATP and general mitochondrial activity as well as biomarkers of mitochondrial biogenesis, including SIRT1, PGC-1α, NRF1, and TFAM. Neuroinflammatory responsiveness declined, as indicated by decreased iNOS, TNF-α, and IL-1β levels with the PBM and CoQ10 treatments. Collectively, the findings of this preclinical study imply that the procognitive effects of NIR PBM and CoQ10 treatments, separately or in combination, are beneficial in a model of transient global brain ischemia superimposed on a model of aging in mice.

Pretreatment with Tilianin improves mitochondrial energy metabolism and oxidative stress in rats with myocardial ischemia/reperfusion injury via AMPK/SIRT1/PGC-1 alpha signaling pathway

Mitochondrial energy metabolism and oxidative stress play a crucial role in ameliorating myocardial ischemia/reperfusion injury (MIRI). Tilianin has been reported to have a significant protection for mitochondrion in MIRI. However, the underlying mechanisms remain unknown. This study investigated whether Tilianin regulates mitochondrial energy metabolism and oxidative stress in MIRI via AMPK/SIRT1/PGC-1 alpha signaling pathway. The MIRI model was established by 30 min of coronary occlusion followed by 2 h of reperfusion in rats. The results revealed that Tilianin significantly reduced myocardial infarction, improved the pathological morphology of myocardium, markedly increased the contents of ATP and NAD⁺, decreased ADP and AMP contents and the ratio of AMP/ATP, reduced the level of ROS and MDA, enhanced SOD activity, evidently increased the levels of AMPK, SIRT1 and PGC-1 alpha mRNA, up-regulated the expressions of AMPK, pAMPK, SIRT1, PGC-1alpha, NRF1, TFAM and FOXO1 proteins. However, these effects were respectively abolished by Compound C (a specific AMPK inhibitor) and EX-527 (a specific SIRT1 inhibitor). Taken together, this study found that Tilianin could attenuate MIRI by improving mitochondrial energy metabolism and reducing oxidative stress via AMPK/SIRT1/PGC-1 alpha signaling pathway.

Protective effects of ex-527 on cerebral ischemia-reperfusion injury through necroptosis signaling pathway attenuation

Necroptosis, a novel type of programmed cell death, is involved in ischemia-reperfusion-induced brain injury. Sirtuin 1 (Sirt1), as a well-known member of histone deacetylase class III, plays pivotal roles in inflammation, metabolism, and neuron loss in cerebral ischemia. We explored the relationship between Sirt1 and the necroptosis signaling pathway and its downstream events by administration of ex-527, as a selective and potent inhibitor of Sirt1, and necrostatin-1 (nec-1), as a necroptosis inhibitor, in an animal model of focal cerebral ischemia. Our data showed different patterns of sirt1 and necroptosis critical regulators, including receptor-interacting protein kinase 3 and mixed lineage kinase domain-like protein gene expressions in the prefrontal cortex and the hippocampus after ischemia-reperfusion. We found that ex-527 microinjection reduces the infarction volume of ischemic brains and improves the survival rate, but not stroke-associated neurological deficits. Additionally, treatment with ex-527 effectively abolished the elevation of the critical regulators of necroptosis, whereas necroptosis inhibition through nec-1 microinjection did not influence Sirt1 expression levels. Our data also demonstrated that the ex-527 relieves ischemia-induced perturbation of necroptosis-associated metabolic enzymes activity in downstream. This study provides a new approach to the possible neuroprotective potential of ex-527 orchestrated by necroptosis pathway inhibition to alleviate ischemia-reperfusion brain injury.

The Role of Sirt1 in Ischemic Stroke: Pathogenesis and Therapeutic Strategies

Silent mating type information regulation 2 homolog 1 (Sirt1), a nicotine adenine dinucleotide (NAD⁺)-dependent enzyme, is well-known in playing a part in longevity. Ischemic stroke is a major neurological disorder and is a leading cause of death and adult disability worldwide. Recently, many studies have focused on the role of Sirt1 in ischemic stroke. Numerous studies consider Sirt1 as a protective factor and investigate the signaling pathways involved in the process under ischemic stress. However, the answer to whether upregulation of Sirt1 improves the outcome of stroke is still a controversy. In this review, we discuss the role and mechanisms of Sirt1 in the setting of ischemic stroke.

Impact of curcumin on sirtuins: A review

Curcumin is a bioactive phytochemical that modulates several physiological and cellular processes leading to therapeutic effects against different diseases. Sirtuins are highly conserved nicotine adenine dinucleotide-dependent proteins that regulate the activity of target enzymes and transcription factors by deacetylation. Curcumin possesses both antioxidant and anti-inflammatory properties and has been shown to increase sirtuin-1 (SIRT1) by activating small molecules. Upregulation of SIRT1 by curcumin has been reported to confer protective effects against a range of neurological disorders including glutamate excitotoxicity, β-amyloid-induced cell death in cortical neurons, cerebral ischemic damage, and stroke. Activation of AMPK and SIRT1 by curcumin has also been noted to mediate the protective effects of curcumin against ischemia/reperfusion injury, cardiac fibrosis, diabetes, and lipid metabolism abnormalities. These protective effects of SIRT1 activation are partly mediated by the deacetylation of p53 and reduction of apoptosis. In this review, we summarize the role of SIRT1 in mediating the pharmacological effects of curcumin in several diseases.

Rux largely restores lungs in Iraq PM-exposed mice, Up-regulating regulatory T-cells (Tregs)

Background Military personnel post-deployment to Iraq and Afghanistan have noted new-onset respiratory illness. This study's primary objective was to further develop an animal model of Iraq Afghanistan War Lung Injury (IAW-LI) and to test a novel class of anti-injury drug called RuX. Methods Particulate Matter (PM) samples were obtained in Iraq then characterized by spectromicroscopy. C57BL/6 mice underwent orotracheal instillation with PM, followed by drinkable treatment with RuX. Lung histology, inspiratory capacity (FlexiVent), thymic/splenic regulatory T cell (Treg) number, and whole-lung genomics were analyzed. Results Tracheal instillation of Iraq PM led to lung septate thickening and lymphocytic inflammation. PM-exposed mice had suppression of thymic/splenic regulatory T-cells (Tregs). Drinking RuX after PM exposure attenuated the histologic lung injury response, improved lung inspiratory capacity, and increased Tregs. Pooled whole lung genomics suggest differences among gene expression of IL-15 among control, PM, and PM + RuX groups. Conclusions RuX, a ruthenium and alpha-lipoic acid complex, attenuates lung injury by improving histology and inspiratory capacity via upregulation of Tregs in Iraq PM-exposed C57BL/6. Plausible genomic effects may involve IL-15 whole lung gene expression.

Exposure to Alumina Nanoparticles in Female Mice During Pregnancy Induces Neurodevelopmental Toxicity in the Offspring

Alumina nanoparticles (AlNP) have been shown to accumulate in organs and penetrate biological barriers which lead to toxic effects in many organ systems. However, it is not known whether AlNP exposure to female mice during pregnancy can affect the development of the central nervous system or induce neurodevelopmental toxicity in the offspring. The present study aims to examine the effect of AlNP on neurodevelopment and associated underlying mechanism. ICR strain adult female mice were randomly divided into four groups, which were treated with normal saline (control), 10 μm particle size of alumina (bulk-Al), and 50 and 13 nm AlNP during entire pregnancy period. Aluminum contents in the hippocampus of newborns were measured and neurodevelopmental behaviors were tracked in the offspring from birth to 1 month of age. Furthermore, oxidative stress and neurotransmitter levels were measured in the cerebral cortex of the adolescents. Our results showed that aluminum contents in the hippocampus of newborns in AlNP-treated groups were significantly higher than those in bulk-Al and controls. Moreover, the offspring delivered by AlNP-treated female mice displayed stunted neurodevelopmental behaviors. Finally, the offspring of AlNP-treated mice demonstrated significantly increased anxiety-like behavior with impaired learning and memory performance at 1 month of age. The underlying mechanism could be related to increased oxidative stress and decreased neurotransmitter levels in the cerebral cortex. We therefore conclude that AlNP exposure of female mice during pregnancy can induce neurodevelopmental toxicity in offspring.

Anti-inflammatory and anti-apoptotic effects of the combination of Ligusticum chuanxiong and Radix Paeoniae against focal cerebral ischaemia via TLR4/MyD88/MAPK/NF-κB signalling pathway in MCAO rats

Objective

This study was performed to assess the anti-inflammatory and anti-apoptotic effects of the combination of Ligusticum chuanxiong and Radix Paeoniae (XS) on focal cerebral ischaemic stroke.

Methods

MCAO rats were used to evaluate the effect of XS on stroke. Cerebral water content was measured, and the levels of IFN-γ, IL-1β, IL-6 and IL-12 in serum and brain were assessed by ELISA kits. Protein expressions including p-p38, p-38, TLR-4, p-ERK, ERK, TLR-5, NF-κBp65, Myd88, Caspase-3 and Caspase-12 were examined by WB and IHC. Q-PCR was applied to examine IL-1β and IL-6 mRNA levels in the rat brain of each group.

Key findings

XS treatment remarkedly decreased the levels of IFN-γ, IL-1β, IL-6 and IL-12 in serum and brain tissues of MCAO rats. In the ischaemic brain, the expressions of TLR-4, TLR-5, p-p38, p-ERK, Myd88, NF-κBp65, Caspase-3 and Caspase-12 were increased significantly, while the treatment attenuated the activated expressions by MCAO. XS also downregulated Caspase-3 and Caspase-12 expressions. IL-1β and IL-6 mRNA levels in MCAO brain tissue were decreased by XS treatment.

Conclusions

XS could protect MCAO rats by anti-inflammation and anti-apoptosis through TLR4/MyD88/MAPK/NF-κB signalling pathway. Furthermore, the combination has a more meaningful improvement on focal cerebral ischaemic stroke.

Emerging Roles of Sirtuins in Ischemic Stroke

Ischemic stroke is one of the leading causes of death worldwide. It is characterized by a sudden disruption of blood flow to the brain causing cell death and damage, which will lead to neurological impairments. In the current state, only one drug is approved to be used in clinical setting and new therapies that confer ischemic neuroprotection are desperately needed. Several targets and pathways have been indicated to be neuroprotective in ischemic stroke, among which the sirtuin family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases has emerged as important modulators of several processes in the normal physiology and pathological conditions such as stroke. Recent studies have identified some members of the sirtuin family are able to ameliorate the devastating consequences of ischemic stroke by conferring neuroprotection by means of reducing neuronal cell death, oxidative stress, and neuroinflammation whereas some sirtuins are found to be detrimental in the pathophysiology of ischemic stroke. This review summarizes implications of sirtuins in ischemic stroke and the experimental evidences that demonstrate the potential of sirtuin modulators as neuroprotective therapy for ischemic stroke.

SIRT1 plays a neuroprotective role in traumatic brain injury in rats via inhibiting the p38 MAPK pathway

Traumatic brain injury (TBI) is a major cause of disability and death in patients who experience a traumatic injury. Mitochondrial dysfunction is one of the main factors contributing to secondary injury in TBI-associated brain damage. Evidence of compromised mitochondrial function after TBI has been, but the molecular mechanisms underlying the pathogenesis of TBI are not well understood. Silent information regulator family protein 1 (SIRT1), a member of the NAD⁺-dependent protein deacetylases, has been shown to exhibit neuroprotective activities in animal models of various pathologies, including ischemic brain injury, subarachnoid hemorrhage and several neurodegenerative diseases. In this study, we investigated whether SIRT1 also exert neuroprotective effect post-TBI, and further explored the possible regulatory mechanisms involved in TBI pathogenesis. A lateral fluid-percussion (LFP) brain injury model was established in rats to mimic the insults of TBI. The expression levels of SIRT1, p-p38, cleaved caspase-9 and cleaved caspase-3 were all markedly increased and reached a maximum at 12 h post-TBI. In addition, mitochondrial function was impaired, evidenced by the presence of swollen and irregularly shaped mitochondria with disrupted and poorly defined cristae, a relative increase of the percentage of neurons with low ΔΨm, the opening of mPTP, and a decrease in neuronal ATP content, especially at 12 h post-TBI. Pretreatment with the SIRT1 inhibitor sirtinol (10 mg/kg, ip) induced p-p38 activation, exacerbated mitochondrial damage, and promoted the activation of the mitochondrial apoptosis pathway. In contrast, pretreatment with the p38 inhibitor SB203580 (200 μg/kg, ip) significantly attenuated post-TBI-induced expression of both cleaved caspase-9 and cleaved caspase-3 and mitochondrial damage, whereas it had no effects on SIRT1 expression. Together, these results reveal that the 12 h after TBI may be a crucial time at which secondary damage occurs; the activation of SIRT1 expression and inhibition of the p38 MAPK pathway may play a neuroprotective role in preventing secondary damage post-TBI. For this reason, both SIRT1 and p38 are likely to be important targets to prevent secondary damage post-TBI.

Bakuchiol attenuates myocardial ischemia reperfusion injury by maintaining mitochondrial function: the role of silent information regulator 1

Ischemia reperfusion (IR) injury (IRI) is associated with poor prognoses in the settings of both cardiac surgery and ischemic heart disease and causes mitochondrial oxidative stress and cell death. Silent information regulator 1 (SIRT1), a member of the histone deacetylase family, exerts anti-IRI effects. Bakuchiol (BAK), an analog of resveratrol and a monoterpene phenol isolated from the seeds of Psoralea corylifolia (Leguminosae), protects tissues from injury. This study was designed to investigate the protective effects of BAK treatment in the setting of myocardial IRI and to elucidate the potential mechanism of those effects. Prior to induction of IR, isolated rat hearts or cardiomyocytes were exposed to BAK in either the absence or presence of the SIRT1 inhibitors Sirtinol and SIRT1 siRNA. BAK exerted cardioprotective effects, as evidenced by the improvements noted in cardiac function following ischemia, attenuated myocardial apoptosis, and changes in several biochemical parameters (including increases in the level of the anti-apoptotic protein Bcl2, decreases in the level of the pro-apoptotic protein Bax, and decreases in the cleaved Caspase 3 level). However, Sirtinol and SIRT1 siRNA each blocked BAK-induced cardioprotection by inhibiting SIRT1 signaling. Additionally, BAK significantly increased the activities of mitochondrial succinate dehydrogenase, cytochrome c oxidase, and mitochondrial superoxide dismutase and decreased the production of malondialdehyde. These findings suggested that BAK significantly attenuated IR-induced mitochondrial oxidative damage. However, Sirtinol and SIRT1 siRNA abolished BAK-dependent mitochondrial function. In summary, our results demonstrate that BAK treatment attenuates IRI by attenuating IR-induced mitochondrial oxidative damage via the activation of SIRT1/PGC-1α signaling.

Adiponectin Protects against Glutamate-Induced Excitotoxicity via Activating SIRT1-Dependent PGC-1α Expression in HT22 Hippocampal Neurons

Glutamate- (Glu-) induced excitotoxicity plays a critical role in stroke. This study aimed to investigate the effects of APN on Glu-induced injury in HT22 neurons. HT22 neurons were treated with Glu in the absence or the presence of an APN peptide. Cell viability was assessed using the MTT assay, while cell apoptosis was evaluated using TUNEL staining. Levels of LDH, MDA, SOD, and GSH-Px were detected using the respective kits, and ROS levels were detected using dichlorofluorescein diacetate. Western blot was used to detect the expression levels of silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), cleaved caspase-3, Bax, and Bcl-2. In addition to the western blot, immunofluorescence was used to investigate the expression levels of SIRT1 and PGC-1α. Our results suggest that APN peptide increased cell viability, SOD, and GSH-Px levels and decreased LDH release, ROS and MDA levels, and cell apoptosis. APN peptide upregulated the expression of SIRT1, PGC-1α, and Bcl-2 and downregulated the expression of cleaved caspase-3 and Bax. Furthermore, the protective effects of the APN peptide were abolished by SIRT1 siRNA. Our findings suggest that APN peptide protects HT22 neurons against Glu-induced injury by inhibiting neuronal apoptosis and activating SIRT1-dependent PGC-1α signaling.

Sirtuin 1 activation protects against early brain injury after experimental subarachnoid hemorrhage in rats

Increasing evidence indicates that sirtuin 1 (SIRT1) is implicated in a wide range of cellular functions, such as oxidative stress, inflammation and apoptosis. The aim of this study was to investigate the change of SIRT1 in the brain after subarachnoid hemorrhage (SAH) and its role on SAH-induced early brain injury (EBI). In the first set of experiments, rats were randomly divided into sham group and SAH groups at 2, 6, 12, 24, 48 and 72 h. The expression of SIRT1 was evaluated by western blot analysis, immunohistochemistry and immunofluorescence. In another set of experiments, SIRT1-specific inhibitor (sirtinol) and activator (activator 3) were exploited to study the role of SIRT1 in SAH-induced EBI. It showed that the protein level of SIRT1 was markedly elevated at the early stage of SAH and peaked at 24 h after SAH. The expression of SIRT1 could be observed in neurons and microglia, and the enhanced SIRT1 was mainly located in neurons after SAH. Administration of sirtinol inhibited the expression and activation of SIRT1 pathways after SAH, while activator 3 enhanced the expression and activation of SIRT1 pathways after SAH. In addition, inhibition of SIRT1 could exacerbate forkhead transcription factors of the O class-, nuclear factor-kappa B- and p53-induced oxidative damage, neuroinflammation and neuronal apoptosis, leading to aggravated brain injury after SAH. In contrast, activator 3 treatment could reduce forkhead transcription factors of the O class-, nuclear factor-kappa B-, and p53-induced oxidative damage, neuroinflammation and neuronal apoptosis to protect against EBI. These results suggest that SIRT1 plays an important role in neuroprotection against EBI after SAH by deacetylation and subsequent inhibition of forkhead transcription factors of the O class-, nuclear factor-kappa B-, and p53-induced oxidative, inflammatory and apoptotic pathways. SIRT1 might be a new promising molecular target for SAH.

Unified theory of Alzheimer's disease (UTAD): implications for prevention and curative therapy

The aim of this review is to propose a Unified Theory of Alzheimer's disease (UTAD) that integrates all key behavioural, genetic and environmental risk factors in a causal chain of etiological and pathogenetic events. It is based on three concepts that emanate from human's evolutionary history: (1) The grandmother-hypothesis (GMH), which explains human longevity due to an evolutionary advantage in reproduction by trans-generational transfer of acquired knowledge. Consequently it is argued that mental health at old-age must be the default pathway of humans' genetic program and not development of AD. (2) Therefore, mechanism like neuronal rejuvenation (NRJ) and adult hippocampal neurogenesis (AHN) that still function efficiently even at old age provide the required lifelong ability to memorize personal experiences important for survival. Cumulative evidence from a multitude of experimental and epidemiological studies indicate that behavioural and environmental risk factors, which impair productive AHN, result in reduced episodic memory performance and in reduced psychological resilience. This leads to avoidance of novelty, dysregulation of the hypothalamic-pituitary-adrenal (HPA)-axis and cortisol hypersecretion, which drives key pathogenic mechanisms of AD like the accumulation and oligomerization of synaptotoxic amyloid beta, chronic neuroinflammation and neuronal insulin resistance. (3) By applying to AHN the law of the minimum (LOM), which defines the basic requirements of biological growth processes, the UTAD explains why and how different lifestyle deficiencies initiate the AD process by impairing AHN and causing dysregulation of the HPA-axis, and how environmental and genetic risk factors such as toxins or ApoE4, respectively, turn into disease accelerators under these unnatural conditions. Consequently, the UTAD provides a rational strategy for the prevention of mental decline and a system-biological approach for the causal treatment of AD, which might even be curative if the systemic intervention is initiated early enough in the disease process. Hence an individualized system-biological treatment of patients with early AD is proposed as a test for the validity of UTAD and outlined in this review.

Combination of Ligusticum chuanxiong and Radix Paeoniae ameliorate focal cerebral ischemic in MCAO rats via endoplasmic reticulum stress-dependent apoptotic signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Combination of Ligusticum chuanxiong and Radix Paeoniae (XS) is highly effective in the treatment for focal cerebral ischemic, but the underlying mechanism is not clear. This study was conducted to evaluate the combinative effects of XS on MCAO rats and explore the underlying mechanisms.

MATERIALS AND METHODS

MCAO rats were used to evaluate the protective effect of Ligusticum chuanxiong (CX), Radix Paeoniae Rubra (CS) and their combination (XS) on ameliorating focal cerebral ischemic. Cerebral ischemia deficits and infarct size were performed by 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (H-E) staining. Activities of SOD, CAT and GSH-Px, as well as levels of LPO and MDA were detected by commercial kits while ELISA kits for the content of plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator (PA). Immunohistochemistry (IHC) and western blot analysis (WB) were carried out to examine the protein expressions including PKR-like endoplasmic reticulum kinase (PERK), cytoplasmic of glucose regulated protein 78 (GRP78), X box-binding protein-1 (XBP-1), activating transcription factor-6 (ATF-6), C/EBP-homologous protein (CHOP), metalloprotease-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), Bcl-2 associated X protein (Bax), and porcineB-cellleukemia/lymphoma-2 (Bcl-2) in brain tissues. Reverse transcription polymerase chain reaction (RT-PCR) and Quantitative PCR (Q-PCR) were applied to examine vascular endothelial growth factor (VEGF) and N-methyl-d-aspartate receptors (NMDAR1) mRNA levels.

RESULTS

CX, CS and their combination (XS) could reduce cerebral ischemia deficits and infarct size of MCAO rats. They increased SOD, CAT and GSH-Px activities, and reduced MDA and LPO levels in serum, markedly. A significant decrease of endoplasmic reticulum stress-related factors PERK, XBP-1, ATF-6 and CHOP protein expression levels while an increase of GRP78 and MVD expression by the treatment of CX, CS and XS. It could also be observed that their treatment could reduce apoptotic damage of brain tissues by up-regulating Bax level and down-regulating Bcl-2 level. Furthermore, the levels of MMP-9 and PAI-1 in serum and tissues of rats were down-regulated remarkably while TIMP-1 and PA levels were up-regulated. VEGF mRNA level was up-regulated dramatically whereas NMDAR1 was reduced. Importantly, the combination of CX and CS, namely XS, has a more meaningful improvement on focal cerebral ischemic than CX or CS alone.

CONCLUSION

All these revealed that the combined XS exerted more remarkable protective effects than alone. XS could inhibit neuronal apoptosis by attenuating ER-stress-dependent apoptotic signaling and protected the blood-brain barrier. These findings might supply beneficial hints for the synergy of CX and CS, and provide the basis for rationality of XS preparation and deserve further clinical investigations.