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

Long noncoding RNA KCNQ1OT1 aggravates cerebral infarction by regulating PTBT1/SIRT1 via miR-16-5p

Cerebral infarction (CI) is one of the leading causes of disability and death. LncRNAs are key factors in CI progression. Herein, we studied the function of long noncoding RNA KCNQ1OT1 in CI patient plasma samples and in CI models. Quantitative real-time PCR and Western blotting tested gene and protein expressions. The interactions of KCNQ1OT1/PTBP1 and miR-16-5p were analyzed using dual-luciferase reporter and RNA immunoprecipitation assays; MTT assays measured cell viability. Cell migration and angiogenesis were tested by wound healing and tube formation assays. Pathological changes were analyzed by triphenyltetrazolium chloride and routine staining. We found that KCNQ1OT1 and PTBP1 were overexpressed and miR-16-5p was downregulated in CI patient plasma and in oxygen-glucose deprived (OGD) induced mouse brain microvascular endothelial (bEnd.3) cells. KCNQ1OT1 knockdown suppressed pro-inflammatory cytokine production and stimulated angiogenic responses in OGD-bEnd.3 cells. KCNQ1OT1 upregulated PTBP1 by sponging miR-16-5p. PTBP1 overexpression or miR-16-5p inhibition attenuated the effects of KCNQ1OT1 knockdown. PTBP1 silencing protected against OGD-bEnd.3 cell injury by enhancing SIRT1. KCNQ1OT1 silencing or miR-16-5p overexpression also alleviated ischemic injury in a mice middle cerebral artery occlusion model. Thus, KCNQ1OT1 silencing alleviates CI by regulating the miR-16-5p/PTBP1/SIRT1 pathway, providing a theoretical basis for novel therapeutic strategies targeting CI.

Electroacupuncture improves cognitive function in a rat model of mild traumatic brain injury by regulating the SIRT-1/PGC-1α/mitochondrial pathway

BACKGROUND

Mild traumatic brain injury (mTBI) is a common neurological trauma that can lead to cognitive impairment. The sirtuin-1 (SIRT-1)/peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) pathway has been reported to have neuroprotective effects in rats with craniocerebral injury. We evaluated potential mechanisms underlying electroacupuncture-mediated recovery of cognitive function after mTBI, focusing on the SIRT-1/PGC-1α/mitochondrial pathway.

METHODS

We included forty 6-week-old male Sprague-Dawley rats in this study. Rats were randomly divided into four groups: controlled cortical impactor (CCI, n = 10), sham operation (sham, n = 10), electroacupuncture-treated CCI (CCI+EA, n = 10), and electroacupuncture-treated sham (sham+EA, n = 10) group. Randomization was performed by assigning a random number to each rat and using a random number table. The mTBI rat model was established using a controllable cortical impactor. Electroacupuncture therapy was performed on the back of rats, by inserting acupuncture needles to the specific acupoints and setting appropriate parameters for treatment. We evaluated spatial learning and memory functions with the Morris water maze test. We performed quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, adenosine triphosphate (ATP) determination, and mitochondrial respiratory chain complex I (MRCC I) determination on rat hippocampal tissue. We analyzed SIRT-1/PGC-1α expression levels and the results of mitochondrial function assays, and compared differences between groups using bilateral Student's t -tests.

RESULTS

Compared with the sham group, SIRT-1/PGC-1α expression was downregulated in the hippocampus of CCI group ( P <0.01). Although this expression was upregulated following electroacupuncture, it did not reach the levels observed in the sham group ( P <0.05). Compared with the sham group, MRCC I and ATP levels in the CCI group were significantly reduced, and increased after electroacupuncture ( P <0.01). In the Morris water maze, electroacupuncture reduced the incubation period of rats and increased average speed and number of crossing platforms ( P <0.05).

CONCLUSION

Electroacupuncture may improve cognitive function in the mTBI rat model by regulating the SIRT-1/PGC-1α/mitochondrial pathway.

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.

New Insights into Antioxidant Peptides: An Overview of Efficient Screening, Evaluation Models, Molecular Mechanisms, and Applications

Antioxidant peptides are currently a hotspot in food science, pharmaceuticals, and cosmetics. In different fields, the screening, activity evaluation, mechanisms, and applications of antioxidant peptides are the pivotal areas of research. Among these topics, the efficient screening of antioxidant peptides stands at the forefront of cutting-edge research. To this end, efficient screening with novel technologies has significantly accelerated the research process, gradually replacing the traditional approach. After the novel antioxidant peptides are screened and identified, a time-consuming activity evaluation is another indispensable procedure, especially in in vivo models. Cellular and rodent models have been widely used for activity evaluation, whilst non-rodent models provide an efficient solution, even with the potential for high-throughput screening. Meanwhile, further research of molecular mechanisms can elucidate the essence underlying the activity, which is related to several signaling pathways, including Keap1-Nrf2/ARE, mitochondria-dependent apoptosis, TGF-β/SMAD, AMPK/SIRT1/PGC-1α, PI3K/Akt/mTOR, and NF-κB. Last but not least, antioxidant peptides have broad applications in food manufacture, therapy, and the cosmetics industry, which requires a systematic review. This review introduces novel technologies for the efficient screening of antioxidant peptides, categorized with a new vision. A wide range of activity evaluation assays, encompassing cellular models, as well as rodent and non-rodent models, are provided in a comprehensive manner. In addition, recent advances in molecular mechanisms are analyzed with specific cases. Finally, the applications of antioxidant peptides in food production, therapy, and cosmetics are systematically reviewed.

The role of the SIRT1-BMAL1 pathway in regulating oxidative stress in the early development of ischaemic stroke

Oxidative stress is the primary cause of ischaemic stroke and is closely related to circadian rhythm. However, the mechanism by which circadian rhythm regulates oxidative stress in ischaemic stroke remains elusive. The Silent Information Regulator 1 (SIRT1) controls circadian rhythm by activating the transcription of the circadian clock core protein Basic Helix-Loop-Helix ARNT Like 1 (BMAL1) through deacetylation. Studies have shown that the SIRT1-BMAL1 pathway can regulate oxidative stress. To investigate its correlation with oxidative stress, we examined the expression levels and influencing factors of SIRT1-BMAL1 at different times in ischaemic stroke patients and analyzed their clinical indexes, oxidative stress, and inflammatory factor indicators. The expression levels of oxidative stress and inflammatory factor indicators, including malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-α), SIRT1, and BMAL1, were detected in ischaemic stroke patients within 4.5 h of onset and in non-stroke patients. Patients were divided into four subgroups based on onset time: subgroup 1 (0:00-05:59); subgroup 2 (06:00-11:59); subgroup 3 (12:00-17: 59); and subgroup 4 (18:00-23:59). Our results showed higher MDA, IL-6, and TNF-α levels, and lower SOD, SIRT1, and BMAL1 levels in ischaemic stroke patients compared to control patients (P < 0.05). Among the four subgroups, the content of MDA, IL-6, and TNF-α was highest in patients with ischaemic stroke onset from subgroup 2 (06:00-11:59), while the expression levels of SOD, BMAL1, and SIRT1 were lowest in patients with ischaemic stroke in subgroup 2. Additionally, myeloperoxidase (MPO) reached the highest value showing the same trends consistent with MDA, IL-6, and TNF-ɑ and opposite trends consistent with SOD, BMAL1, and SIRT1. However, triglycerides (TGs), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), immediate blood glucose, immediate diastolic blood pressure, immediate systolic blood pressure, and homocysteine (HCY) did not show any statistically significant circadian rhythm changes (P > 0.05). Our findings suggest that the SIRT1-BMAL1 pathway may be involved in early oxidative stress in ischaemic stroke, which may be related to MPO.

Icariin prevents methylmercury-induced experimental neurotoxicity: Evidence from cerebrospinal fluid, blood plasma, brain samples, and in-silico investigations

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that causes significant neurodegeneration. Methylmercury (MeHg+) is a neurotoxin that induces axonal neurodegeneration and motor nerve degeneration by destroying oligodendrocytes, degenerating white matter, inducing apoptosis, excitotoxicity, and reducing myelin basic protein (MBP). This study examines the inhibition of SIRT-1 (silence information regulator 1), Nrf-2 (nuclear factor E2-related factor 2), HO-1 (heme oxygenase 1), and TDP-43 (TAR-DNA-binding protein 43) accumulation in the context of ALS, as well as the modulation of these proteins by icariin (15 and 30 mg/kg, orally), a glycoside flavonoid with neuroprotective properties. Neuroprotective icariin activates SIRT-1, Nrf-2, and HO-1, mitigating inflammation and neuronal injury in neurodegenerative disorders. In-vivo and in-silico testing of experimental ALS models confirmed icariin efficacy in modulating these cellular targets. The addition of sirtinol 10 mg/kg, an inhibitor of SIRT-1, helps determine the effectiveness of icariin. In this study, we also examined neurobehavioral, neurochemical, histopathological, and LFB (Luxol fast blue) markers in various biological samples, including Cerebrospinal fluid (CSF), blood plasma, and brain homogenates (Cerebral Cortex, Hippocampus, Striatum, mid-brain, and Cerebellum). These results demonstrate that the administration of icariin ameliorates experimental ALS and that the mechanism underlying these benefits is likely related to regulating the SIRT-1, Nrf-2, and HO-1 signaling pathways.

Time-dependent dual effect of microglia in ischemic stroke

Stroke, the third leading cause of death and disability worldwide, is classified into ischemic or hemorrhagic, in which approximately 85% of strokes are ischemic. Ischemic stroke occurs as a result of arterial occlusion due to embolus or thrombus, with ischemia in the perfusion territory supplied by the occluded artery. The traditional concept that ischemic stroke is solely a vascular occlusion disorder has been expanded to include the dynamic interaction between microglia, astrocytes, neurons, vascular cells, and matrix components forming the "neurovascular unit." Acute ischemic stroke triggers a wide spectrum of neurovascular disturbances, glial activation, and secondary neuroinflammation that promotes further injury, ultimately resulting in neuronal death. Microglia, as the resident macrophages in the central nervous system, is one of the first responders to ischemic injury and plays a significant role in post-ischemic neuroinflammation. In this review, we reviewed the mechanisms of microglia in multiple stages of post-ischemic neuroinflammation development, including acute, sub-acute and chronic phases of stroke. A comprehensive understanding of the dynamic variation and the time-dependent role of microglia in post-stroke neuroinflammation could aid in the search for more effective therapeutics and diagnostic strategies for ischemic stroke.

Transplantation of Exercise-Induced Extracellular Vesicles as a Promising Therapeutic Approach in Ischemic Stroke

Clinical evidence affirms physical exercise is effective in preventive and rehabilitation approaches for ischemic stroke. This sustainable efficacy is independent of cardiovascular risk factors and associates substantial reprogramming in circulating extracellular vesicles (EVs). The intricate journey of pluripotent exercise-induced EVs from parental cells to the whole-body and infiltration to cerebrovascular entity offers several mechanisms to reduce stroke incidence and injury or accelerate the subsequent recovery. This review delineates the potential roles of EVs as prospective effectors of exercise. The candidate miRNA and peptide cargo of exercise-induced EVs with both atheroprotective and neuroprotective characteristics are discussed, along with their presumed targets and pathway interactions. The existing literature provides solid ground to hypothesize that the rich vesicles link exercise to stroke prevention and rehabilitation. However, there are several open questions about the exercise stressors which may optimally regulate EVs kinetic and boost brain mitochondrial adaptations. This review represents a novel perspective on achieving brain fitness against stroke through transplantation of multi-potential EVs generated by multi-parental cells, which is exceptionally reachable in an exercising body.

SIRT1 pathway in Parkinson's disease: a faraway snapshot but so close

Silent information regulator (SIRT) has distinctive enzymatic activities and physiological functions to control cell-cycle progression, gene expression, and DNA stability by targeting histone and non-histone proteins. SIRT1 enhances synaptic formation and synaptic activity, and therefore, can reduce the progression of various degenerative brain diseases including Parkinson's disease (PD). SIRT1 activity is decreased by aging with a subsequent increased risk for the development of degenerative brain diseases. Inhibition of SIRT1 promotes inflammatory reactions since SIRT1 inhibits transcription of nuclear factor kappa B (NF-κB) which also inhibits SIRT1 activation via activation of microRNA and miR-34a which reduce NAD synthesis. SIRT1 is highly expressed in microglia as well as neurons, and has antioxidant and anti-inflammatory effects. Therefore, this review aimed to find the possible role of SIRT1 in PD neuropathology. SIRT1 has neuroprotective effects; therefore, downregulation of SIRT1 during aging promotes p53 expression and may increase the vulnerability of neuronal cell deaths. PD neuropathology is linked with the sequence of inflammatory changes and the release of pro-inflammatory cytokines due to the activation of inflammatory signaling pathways. In addition, oxidative stress, inflammatory disorders, mitochondrial dysfunction, and apoptosis contribute mutually to PD neuropathology. Thus, SIRT1 and SIRT1 activators play a crucial role in the mitigation of PD neuropathology through the amelioration of oxidative stress, inflammatory disorders, mitochondrial dysfunction, apoptosis, and inflammatory signaling pathways.

Bone marrow mesenchymal stem cell-derived exosomal lncRNA KLF3-AS1 stabilizes Sirt1 protein to improve cerebral ischemia/reperfusion injury via miR-206/USP22 axis

BACKGROUND

Cerebral ischemia/reperfusion (I/R) is a pathological process that occurs in ischemic stroke. Bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exos) have been verified to relieve cerebral I/R-induced inflammatory injury. Hence, we intended to clarify the function of BMSC-Exos-delivered lncRNA KLF3-AS1 (BMSC-Exos KLF3-AS1) in neuroprotection and investigated its potential mechanism.

METHODS

To mimic cerebral I/R injury in vivo and in vitro, middle cerebral artery occlusion (MCAO) mice model and oxygen-glucose deprivation (OGD) BV-2 cell model were established. BMSC-Exos KLF3-AS1 were administered in MCAO mice or OGD-exposed cells. The modified neurological severity score (mNSS), shuttle box test, and cresyl violet staining were performed to measure the neuroprotective functions, while cell injury was evaluated with MTT, TUNEL and reactive oxygen species (ROS) assays. Targeted genes and proteins were detected using western blot, qRT-PCR, and immunohistochemistry. The molecular interactions were assessed using RNA immunoprecipitation, co-immunoprecipitation and luciferase assays.

RESULTS

BMSC-Exos KLF3-AS1 reduced cerebral infarction and improved neurological function in MCAO mice. Similarly, it also promoted cell viability, suppressed apoptosis, inflammatory injury and ROS production in cells exposed to OGD. BMSC-Exos KLF3-AS1 upregulated the decreased Sirt1 induced by cerebral I/R. Mechanistically, KLF3-AS1 inhibited the ubiquitination of Sirt1 protein through inducing USP22. Additionally, KLF3-AS1 sponged miR-206 to upregulate USP22 expression. Overexpression of miR-206 or silencing of Sirt1 abolished KLF3-AS1-mediated protective effects.

CONCLUSION

BMSC-Exos KLF3-AS1 promoted the Sirt1 deubiquitinating to ameliorate cerebral I/R-induced inflammatory injury via KLF3-AS1/miR-206/USP22 network.

A novel link between silent information regulator 1 and autophagy in cerebral ischemia-reperfusion

Cerebral ischemia is one of the leading causes of death and disability worldwide. Although revascularization via reperfusion combined with advanced anticoagulant therapy is currently a gold standard treatment for patients, the reperfusion itself also results in a serious dysfunction termed cerebral ischemia-reperfusion (I/R) injury. Silent information regulator 1 (sirtuin 1, SIRT1), is a classic NAD⁺-dependent deacetylase, which has been proposed as an important mediator in the alleviation of cerebral ischemia through modulating multiple physiological processes, including apoptosis, inflammation, DNA repair, oxidative stress, and autophagy. Recent growing evidence suggests that SIRT1-mediated autophagy plays a key role in the pathophysiological process of cerebral I/R injury. SIRT1 could both activate and inhibit the autophagy process by mediating different autophagy pathways, such as the SIRT1-FOXOs pathway, SIRT1-AMPK pathway, and SIRT1-p53 pathway. However, the autophagic roles of SIRT1 in cerebral I/R injury have not been systematically summarized. Here, in this review, we will first introduce the molecular mechanisms and effects of SIRT1 in cerebral ischemia and I/R injury. Next, we will discuss the involvement of autophagy in the pathogenesis of cerebral I/R injury. Finally, we will summarize the latest advances in the interaction between SIRT1 and autophagy in cerebral I/R injury. A good understanding of these relationships would serve to consolidate a framework of mechanisms underlying SIRT1's neuroprotective effects and provides evidence for the development of drugs targeting SIRT1.

Inhibition of microRNA-200c preserves astrocyte sirtuin-1 and mitofusin-2, and protects against hippocampal neurodegeneration following global cerebral ischemia in mice

Memory impairment remains a leading disability in survivors of global cerebral ischemia, occurring secondary to delayed neurodegeneration of hippocampal cornu ammonis-1 (CA1) neurons. MicroRNA-200c (miR-200c) is induced following ischemic stress and we have previously demonstrated that pre-treatment with anti-miR-200c is protective against embolic stroke in mice. In the present study we assessed the role of miR-200c on CA1 neurodegeneration, sirtuin-1 (SIRT1), and mitochondrial dynamic protein expression in a mouse model of transient global cerebral ischemia and in vitro in primary mouse astrocyte cultures after simulated ischemia. Mice were subjected to 10 min bilateral common carotid artery occlusion plus hypotension with 5% isoflurane. After 2 h recovery mice were treated with intravenous injection of either anti-miR-200c or mismatch control. Memory function was assessed by Barnes maze at post-injury days 3 and 7. Mice were sacrificed at post-injury day 7 for assessment of brain cell-type specific expression of miR-200c, SIRT1, and the mitochondrial fusion proteins mitofusin-2 (MFN2) and OPA1 via complexed fluorescent in situ hybridization and fluorescent immunohistochemistry. Global cerebral ischemia induced significant loss of CA1 neurons, impaired memory performance and decreased expression of CA1 SIRT1, MFN2, and OPA1. Post-injury treatment with anti-miR-200c significantly improved survival, prevented CA1 neuronal loss, improved post-injury performance in Barnes maze, and was associated with increased post-injury expression of CA1 SIRT1 and MFN2 in astrocytes. In vitro, primary mouse astrocyte cultures pre-treated with miR-200c inhibitor prior to oxygen/glucose deprivation preserved expression of SIRT1 and MFN2, and decreased reactive oxygen species generation, whereas pre-treatment with miR-200c mimic had opposite effects that could be reversed by co-treatment with SIRT1 activator. These results suggest that miR-200c regulates astrocyte mitochondrial homeostasis via targeting SIRT1, and that CA1 astrocyte mitochondria and SIRT1 represent potential post-injury therapeutic targets to preserve cognitive function in survivors of global cerebral ischemia.

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

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

The Neuroprotective Effects of Exosomes Derived from TSG101-Overexpressing Human Neural Stem Cells in a Stroke Model

Although tissue-type plasminogen activator was approved by the FDA for early reperfusion of occluded vessels, there is a need for an effective neuroprotective drug for stroke patients. In this study, we established tumor susceptibility gene (TSG)101-overexpressing human neural stem cells (F3.TSG) and investigated whether they showed enhanced secretion of exosomes and whether treatment with exosomes during reperfusion alleviated ischemia-reperfusion-mediated brain damage. F3.TSG cells secreted higher amounts of exosomes than the parental F3 cells. In N2A cells subjected to oxygen–glucose deprivation (OGD), treatment with exosomes or coculture with F3.TSG cells significantly attenuated lactate dehydrogenase release, the mRNA expression of proinflammatory factors, and the protein expression of DNA-damage-related proteins. In a middle cerebral artery occlusion (MCAO) rat model, treatment with exosomes, F3 cells, or F3.TSG cells after 2 h of occlusion followed by reperfusion reduced the infarction volume and suppressed inflammatory cytokines, DNA-damage-related proteins, and glial fibrillary acidic protein, and upregulated several neurotrophic factors. Thus, TSG101-overexpressing neural stem cells showed enhanced exosome secretion; exosome treatment protected against MCAO-induced brain damage via anti-inflammatory activities, DNA damage pathway inhibition, and growth/trophic factor induction. Therefore, exosomes and F3.TSG cells can affect neuroprotection and functional recovery in acute stroke patients.

Sirtuins 1 and 2 in the Acute Period After Photothrombotic Stroke: Expression, Localization and Involvement in Apoptosis

Sirtuins (SIRTs) are NAD+- dependent histone deacetylases. They are involved in a variety of biological pathways and are thought to be a promising target for treating several human disorders. Although evidence is piling up to support the neuroprotective role of SIRTs in ischemic stroke, the role of different sirtuin isoforms needs further investigation. We studied the effects of photothrombotic stroke (PTS) on the expression and localization of sirtuins SIRT1 and SIRT2 in neurons and astrocytes of the penumbra and tested the activity of their selective and non-selective inhibitors. SIRT1 levels significantly decreased in the penumbra cells nuclei and increased in their cytoplasm. This indicated a redistribution of SIRT1 from the nucleus to the cytoplasm after PTS. The expression and intracellular distribution of SIRT1 were also observed in astrocytes. Photothrombotic stroke caused a sharp increase in SIRT2 levels in the cytoplasmic fraction of the penumbra neurons. SIRT2 was not expressed in the penumbra astrocytes. SIRT1 and SIRT2 did not co-localize with TUNEL-positive apoptotic cells. Mice were injected with EX-527, a selective SIRT1 inhibitor; SirReal2, selective SIRT2 inhibitor or salermide, a nonspecific inhibitor of SIRT1 and SIRT2. These inhibitors did not demonstrate any change in the infarction volume or the apoptotic index, compared to the control samples. The studies presented indicate the involvement of these sirtuins in the response of brain cells to ischemia in the first 24 h, but the alterations in their expression and change in the localization of SIRT1 are not related to the regulation of penumbra cell apoptosis in the acute period after PTS.

Poly (ADP-ribose) polymerase: An Overview of Mechanistic Approaches and Therapeutic Opportunities in the Management of Stroke

Stroke is one of the leading causes of morbidity and mortality accompanied by blood supply loss to a particular brain area. Several mechanistic approaches such as inhibition of poly (ADP-ribose) polymerase, therapies against tissue thrombosis, and neutrophils lead to stroke's therapeutic intervention. Evidence obtained with the poly (ADP-ribose) polymerase (PARP) inhibition and animals having a deficiency of PARP enzymes; represented the role of PARP in cerebral stroke, ischemia/reperfusion, and neurotrauma. PARP is a nuclear enzyme superfamily with various isoforms, each with different structural domains and functions, and out of all, PARP-1 is the best-characterized member. It has been shown to perform multiple physiological as well as pathological processes, including its role in inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction. The enzyme interacts with NF-κB, p53, and other transcriptional factors to regulate survival and cell death and modulates multiple downstream signaling pathways. Clinical trials have also been conducted using PARP inhibitors for numerous disorders and have shown positive results. However, additional information is yet to be established for the therapeutic intervention of PARP inhibitors in stroke. These agents' utilization appears to be challenging due to their unknown potential long-term side effects. PARP activity increased during ischemia, but its inhibition provided significant neuroprotection. Despite the increased interest in PARP as a pharmacological modulator for novel therapeutic therapies, the current review focused on stroke and poly ADP-ribosylation.

Oxidative Stress in Ischemia/Reperfusion Injuries following Acute Ischemic Stroke

Recanalization therapy is increasingly used in the treatment of acute ischemic stroke. However, in about one third of these patients, recanalization is followed by ischemia/reperfusion injuries, and clinically to worsening of the neurological status. Much research has focused on unraveling the involved mechanisms in order to prevent or efficiently treat these injuries. What we know so far is that oxidative stress and mitochondrial dysfunction are significantly involved in the pathogenesis of ischemia/reperfusion injury. However, despite promising results obtained in experimental research, clinical studies trying to interfere with the oxidative pathways have mostly failed. The current article discusses the main mechanisms leading to ischemia/reperfusion injuries, such as mitochondrial dysfunction, excitotoxicity, and oxidative stress, and reviews the clinical trials with antioxidant molecules highlighting recent developments and future strategies.

Quercetin attenuates ischemia reperfusion injury by protecting the blood-brain barrier through Sirt1 in MCAO rats

The purpose of the present study was to examine the protective action and mechanisms of quercetin on the blood-brain barrier (BBB) in rats subjected to transient middle cerebral artery occlusion (tMCAO) and reperfusion. Quercetin (10, 30, 50 mg/kg) was intraperitoneally administered at the onset of reperfusion. The results showed that quercetin significantly reduced cerebral infarct volume, neurological deficit, BBB permeability and ROS generation via Sirt1/Nrf2/HO-1 signaling pathway. Moreover, EX527, a selective inhibitor of Sirt1, reversed these neuroprotective effects. Our findings indicate that quercetin has neuroprotective effects against cerebral ischemia-reperfusion injury by protecting BBB through Sirt1 signaling pathway in MCAO rats.

Calorie restriction or dietary restriction: how far they can protect the brain against neurodegenerative diseases?

Finding the correct nutritional intervention is one of the biggest challenges in treating patients with neurodegenerative diseases. In general, these patients develop strong metabolic alterations, resulting in lower treatment efficacy and higher mortality rates. However, there are still many open questions regarding the effectiveness of dietary interventions in neurodiseases. Some studies have shown that a reduction in calorie intake activates key pathways that might be important for preventing or slowing down the progression of such diseases. However, it is still unclear whether these neuroprotective effects are associated with an overall reduction in calories (hypocaloric diet) or a specific nutrient restriction (diet restriction). Therefore, here we discuss how commonly or differently hypocaloric and restricted diets modulate signaling pathways and how these changes can protect the brain against neurodegenerative diseases.

Diosmetin alleviated cerebral ischemia/reperfusion injury in vivo and in vitro by inhibiting oxidative stress via the SIRT1/Nrf2 signaling pathway

Cerebral ischemia/reperfusion (I/R) injury is caused by blood flow recovery after an ischemic stroke, and effective treatments targeting I/R injury are still insufficient. Oxidative stress is known to play a pivotal role in the pathogenesis of cerebral I/R injury. Previous studies have revealed that diosmetin could protect against oxidative stress in cerebral I/R injury, but the underlying mechanisms have not been fully revealed. The present study was undertaken to investigate the effects and mechanisms of action of diosmetin on cerebral I/R injury. In vivo, rats were orally gavaged with diosmetin for seven days, and middle cerebral artery occlusion (MCAO) was established to simulate cerebral I/R injury. The neurological deficit score, cerebral infarct volume, and cortical pathological lesions were measured. In vitro, PC12 cells were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R). To clarify the mechanism, the SIRT1 inhibitor EX527 and the small interfering RNA (siRNA) of SIRT1 were used to downregulate the SIRT1 protein level, respectively. The contents of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and malondialdehyde (MDA) were determined with commercial kits. The protein expressions of SIRT1, total Nrf2 (T-Nrf2), nucleus Nrf2 (N-Nrf2), NQO1 and HO-1 were measured by western blotting. The results showed that diosmetin pretreatment improved neurological outcomes, decreased the cerebral infarct volume and pathological lesions, and inhibited oxidative stress in cerebral I/R rats. In PC12 cells, diosmetin increased cell viability, reduced lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) level, and inhibited oxidative stress. Besides, diosmetin increased the protein expressions of SIRT1, T-Nrf2, N-Nrf2, NQO1 and HO-1 both in vivo and in vitro. However, administration of EX527 or silencing the SIRT1 gene with its siRNA eliminated the beneficial effects of diosmetin. Meanwhile, inhibition of SIRT1 decreased the levels of Nrf2 and the protein expressions of its downstream antioxidants NQO1 and HO-1. In conclusion, our data suggested that diosmetin could attenuate cerebral I/R injury by inhibiting oxidative stress via the SIRT1/Nrf2 signaling pathway.

Citicoline and COVID-19-Related Cognitive and Other Neurologic Complications

With growing concerns about COVID-19’s hyperinflammatory condition and its potentially damaging impact on the neurovascular system, there is a need to consider potential treatment options for managing short- and long-term effects on neurological complications, especially cognitive function. While maintaining adequate structure and function of phospholipid in brain cells, citicoline, identical to the natural metabolite phospholipid phosphatidylcholine precursor, can contribute to a variety of neurological diseases and hypothetically toward post-COVID-19 cognitive effects. In this review, we comprehensively describe in detail the potential citicoline mechanisms as adjunctive therapy and prevention of COVID-19-related cognitive decline and other neurologic complications through citicoline properties of anti-inflammation, anti-viral, neuroprotection, neurorestorative, and acetylcholine neurotransmitter synthesis, and provide a recommendation for future clinical trials.

LncRNA SNHG15 Promotes Oxidative Stress Damage to Regulate the Occurrence and Development of Cerebral Ischemia/Reperfusion Injury by Targeting the miR-141/SIRT1 Axis

Ischemic stroke is a kind of disease with high mortality and high disability, which brings a huge burden to the public health system (Hu et al. (2017)), and it poses a serious threat to the quality of life of patients. Cerebral ischemia/reperfusion injury is an important pathophysiological mechanism. This study aims to assess the mechanism of SNHG15 in the occurrence and development of cerebral ischemia/reperfusion injury of nerve cells and to investigate its potential value for diagnosis and treatment. SNHG15 targeted miRNA molecules and target genes were predicted with bioinformatics tools such as StarBase and TargetScan. The process of ischemic reperfusion in cerebral apoplexy in normal cultured and oxygen-glucose-deprived and reoxygenated neurons was simulated with RT-PCR and western blot technique. The expressions of SNHG15 and miR-141 were detected with qPCR, and the expressions of SIRT1 and p65, TNF-α, ROS, iNOS, and IL-6 were detected with western blot. Meanwhile, SNHG15 siRNAs and miR-141 mimics were transfected for SH-SY5Y, with western blot testing. And the expressions of miR-141, SIRT1, and p65, TNF-α, ROS, iNOS, and IL-6 were tested. According to the prediction with bioinformatics tools of StarBase and TargetScan, miR-141 is the target of lncSNHG15. In the luciferase reporter plasmid double-luciferase assay, miR-141 and SIRT1 were defined as the target relationship. In the oxygen-glucose-deprived reoxygenation model group, SNHG15 expression increased, miR-141 expression decreased, SIRT1 expression increased, and the expressions of p65, TNF-α, ROS, iNOS, and IL-6 decreased. In the SNHG15-siRNA-transfected oxygen-glucose-deprived reoxygenation cell model group, miR-141 expression increased, SIRT1 expression decreased, and the expressions of p65, TNF-α, and IL-6 increased compared with the si-NC group. In the miR-141-mimic-transfected oxygen-glucose-deprived reoxygenation cell model, SNHG15 expression decreased, SIRT1 expression decreased, and the expressions of p65, TNF-α, IL-1β, and IL-6 increased. In conclusion, SNHG15 expression increased during the process of oxygen-glucose-deprived reoxygenation, and the oxidative stress process was reduced by miR-141/SIRT1.

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.

Activation of GPR39 with TC-G 1008 attenuates neuroinflammation via SIRT1/PGC-1α/Nrf2 pathway post-neonatal hypoxic-ischemic injury in rats

Background

Hypoxic–ischemic encephalopathy (HIE) is a severe anoxic brain injury that leads to premature mortality or long-term disabilities in infants. Neuroinflammation is a vital contributor to the pathogenic cascade post-HIE and a mediator to secondary neuronal death. As a plasma membrane G-protein-coupled receptor, GPR39, exhibits anti-inflammatory activity in several diseases. This study aimed to explore the neuroprotective function of GPR39 through inhibition of inflammation post-hypoxic–ischemic (HI) injury and to elaborate the contribution of sirtuin 1(SIRT1)/peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α)/nuclear factor, erythroid 2 like 2(Nrf2) in G-protein-coupled receptor 39 (GPR39)-mediated protection.

Methods

A total of 206 10-day-old Sprague Dawley rat pups were subjected to HIE or sham surgery. TC-G 1008 was administered intranasally at 1 h, 25 h, 49 h, and 73 h post-HIE induction. SIRT1 inhibitor EX527, GPR39 CRISPR, and PGC-1α CRISPR were administered to elucidate the underlying mechanisms. Brain infarct area, short-term and long-term neurobehavioral tests, Nissl staining, western blot, and immunofluorescence staining were performed post-HIE.

Results

The expression of GPR39 and pathway-related proteins, SIRT1, PGC-1α and Nrf2 were increased in a time-dependent manner, peaking at 24 h or 48-h post-HIE. Intranasal administration of TC-G 1008 reduced the percent infarcted area and improved short-term and long-term neurological deficits. Moreover, TC-G 1008 treatment significantly increased the expression of SIRT1, PGC-1α and Nrf2, but downregulated the expressions of IL-6, IL-1β, and TNF-α. GPR39 CRISPR EX527 and PGC-1α CRISPR abolished GPR39’s neuroprotective effects post-HIE.

Conclusions

TC-G 1008 attenuated neuroinflammation in part via the SIRT1/PGC-1α/Nrf2 pathway in a neonatal rat model of HIE. TC-G 1008 may be a novel therapeutic target for treatment post-neonatal HIE injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02289-7.

Buyang Huanwu Decoction promotes neurogenesis via sirtuin 1/autophagy pathway in a cerebral ischemia model

Stroke is one of the main causes of disease-related mortality worldwide. Buyang Huanwu Decoction (BHD) has been used to protect against stroke and stroke-induced disability for several years in China. Studies have shown that BHD can relieve neuronal damage in rats with cerebral ischemia/reperfusion (I/R) injury. However, the mechanism remains unclear. A middle cerebral artery occlusion and reperfusion (MCAO-R) model was used in the present study. The animals were treated with BHD (5, 10 and 20 g/kg) or rapamycin. Infarct size and modified neurological severity score were calculated on day 5 following MCAO-R surgery. Cellular changes around the ischemic penumbra were revealed by hematoxylin and eosin and Nissl staining. The protein expression levels of nestin, brain-derived neurotrophic factor (BDNF), doublecortin on the X chromosome (DCX) and autophagy-related proteins (beclin 1, LC3-II and p62) in the peri-ischemic area of the brain were detected. The results demonstrated that post-surgical treatment with BHD reduced the brain infarct size and improved neurological deficits in MCAO-R rats. BHD protected against MCAO-R-induced neuronal impairment and promoted neurogenesis, increased the protein expression of nestin, BDNF and DCX and markedly enhanced autophagy by increasing beclin 1 and LC3-II and decreasing p62. Meanwhile, BHD promoted the expression of sirtuin 1 (SIRT1), an important regulator of autophagy. In conclusion, the present study suggested that post-surgical treatment with BHD could protect rat brains from I/R injury, potentially through the SIRT1/autophagy pathway.

Prasugrel anti-ischemic effect in rats: Modulation of hippocampal SUMO2/3-IкBα/Ubc9 and SIRT-1/miR-22 trajectories

The beneficial role of prasugrel, a P2Y12 receptor blocker, in several neurointerventional procedures has been reviewed clinically. Beyond its antiplatelet capacity, the potential neuroprotective mechanisms of prasugrel are poorly addressed experimentally. Relevant to the imbalance between neuro-inflammation and neuroprotective pathways in cerebral ischemia/reperfusion (I/R), our study evaluated the anti-ischemic potential of prasugrel treatment through tackling novel targets. Male Wistar rats were allocated into 2 sets; set 1 (I/R 60 min/3 days) to assess the neurological deficits/biochemical impact of prasugrel and set 2 (I/R 60 min/5 days) for evaluating short memory/morphological/immunoreactive changes. Each set comprised 4 groups designated as sham, sham + prasugrel, I/R, and I/R + prasugrel. Post-administration of prasugrel for 3 and 5 days reduced neurological deficit scores and improved the spontaneous activity/short term spatial memory using the Y-maze paradigm. On the molecular level, prasugrel turned off SUMO2/3-inhibitory kappa (Iκ)Bα, Ubc9 and nuclear factor kappa (NF-κ)B. Besides, it inhibited malondialdehyde (MDA) and inactivated astrocytes by downregulating the glial fibrillary acidic protein (GFAP) hippocampal immune-expression. Conversely, it activated its target molecule cAMP, protein kinase (PK)A, and cAMP response element-binding protein (CREB) to enhance the brain-derived nuclear factor (BDNF) hippocampal content. Additionally, cAMP/PKA axis increased the hippocampal content of deacetylator silent information regulator 1 (SIRT1) and the micro RNA (miR)-22 gene expression. The crosstalk between these paths partakes in preserving hippocampal cellularity. Accordingly, prasugrel, regardless inhibiting platelets activity, modulated other cellular components; viz., SUMO2/3-IκBα/Ubc9/NF-κB, cAMP/PKA related trajectories, CREB/BDNF and SIRT1/miR-22 signaling, besides inhibiting GFAP and MDA to signify its anti-ischemic potential.

Sirtuin 1 activated by SRT1460 protects against myocardial ischemia/reperfusion injury

BACKGROUND

Ischemia reperfusion usually results in certain degree of damage to the myocardium, which is called myocardial ischemia/reperfusion (I/R) injury.

OBJECTIVE

Previous studies have found that Sirt1 plays a critical role in I/R injury by protecting cardiac function. SRT1460 is the activator for Sirt1 that participates in the regulation of various diseases. However, whether SRT1460 has any effects on myocardial I/R injury needs further study.

METHODS

The I/R rat model and H/R H9C2 model were established to simulate myocardial I/R injury. The infarct area of the rat heart was examined through TTC staining. The EF and FS of rats were detected through echocardiography. The levels of CK-MB, LDH, MDA, SOD and CK in cardiac tissues, serum or H9C2 cells were measured using commercial kits. Cell viability was assessed through MTT assay. Apoptosis was determined through flow cytometry analysis. Sirt1 expression was measured through western blot.

RESULTS

Our work found that SRT1460 reduced the infarct area of the heart induced by myocardial I/R injury. In addition, SRT1460 was confirmed to ameliorate cardiac dysfunction induced by myocardial I/R injury. Further exploration discovered that SRT1460 weakened oxidative stress induced by myocardial I/R injury. Findings from in vitro assays demonstrated that SRT1460 relieved injury of H/R-treated H9C2 cells. Finally, rescue assays proved that Sirt1 knockdown reversed the protective effects of SRT1460 on the injury of H/R-treated H9C2 cells.

CONCLUSION

Sirt1 activated by SRT1460 protected against myocardial I/R injury. This discovery may offer new sights on the treatment of myocardial I/R injury.

miR-19a/b-3p promotes inflammation during cerebral ischemia/reperfusion injury via SIRT1/FoxO3/SPHK1 pathway

Background

Stroke affects 3–4% of adults and kills numerous people each year. Recovering blood flow with minimal reperfusion-induced injury is crucial. However, the mechanisms underlying reperfusion-induced injury, particularly inflammation, are not well understood. Here, we investigated the function of miR-19a/b-3p/SIRT1/FoxO3/SPHK1 axis in ischemia/reperfusion (I/R).

Methods

MCAO (middle cerebral artery occlusion) reperfusion rat model was used as the in vivo model of I/R. Cultured neuronal cells subjected to OGD/R (oxygen glucose deprivation/reperfusion) were used as the in vitro model of I/R. MTT assay was used to assess cell viability and TUNEL staining was used to measure cell apoptosis. H&E staining was employed to examine cell morphology. qRT-PCR and western blot were performed to determine levels of miR-19a/b-3p, SIRT1, FoxO3, SPHK1, NF-κB p65, and cytokines like TNF-α, IL-6, and IL-1β. EMSA and ChIP were performed to validate the interaction of FoxO3 with SPHK1 promoter. Dual luciferase assay and RIP were used to verify the binding of miR-19a/b-3p with SIRT1 mRNA.

Results

miR-19a/b-3p, FoxO3, SPHK1, NF-κB p65, and cytokines were elevated while SIRT1 was reduced in brain tissues following MCAO/reperfusion or in cells upon OGD/R. Knockdown of SPHK1 or FoxO3 suppressed I/R-induced inflammation and cell death. Furthermore, knockdown of FoxO3 reversed the effects of SIRT1 knockdown. Inhibition of the miR-19a/b-3p suppressed inflammation and this suppression was blocked by SIRT1 knockdown. FoxO3 bound SPHK1 promoter and activated its transcription. miR-19a/b-3p directly targeted SIRT1 mRNA.

Conclusion

miR-19a/b-3p promotes inflammatory responses during I/R via targeting SIRT1/FoxO3/SPHK1 axis.

Neuroprotective Effect of Astragaloside IV on Cerebral Ischemia/Reperfusion Injury Rats Through Sirt1/Mapt Pathway

Background: Ischemic stroke is a common disease with poor prognosis, which has become one of the leading causes of morbidity and mortality worldwide. Astragaloside IV (AS-IV) is the main bioactive ingredient of Astragali Radix (which has been used for ischemic stroke for thousands of years) and has been found to have multiple bioactivities in the nervous system. In the present study, we aimed to explore the neuroprotective effects of AS-IV in rats with cerebral ischemia/reperfusion (CIR) injury targeting the Sirt1/Mapt pathway. Methods: Sprague-Dawley rats (male, 250-280 g) were randomly divided into the Sham group, middle cerebral artery occlusion/reperfusion (MCAO/R) group, AS-IV group, MCAO/R + EX527 (SIRT1-specific inhibitor) group, and AS-IV + EX527 group. Each group was further assigned into several subgroups according to ischemic time (6 h, 1 d, 3 d, and 7 days). The CIR injury was induced in MCAO/R group, AS-IV group, MCAO/R + EX527 group, and AS-IV + EX527 group by MCAO surgery in accordance with the modified Zea Longa criteria. Modified Neurological Severity Scores (mNSS) were used to evaluate the neurological deficits; TTC (2,3,5-triphenyltetrazolium chloride) staining was used to detect cerebral infarction area; Western Blot was used to assess the protein levels of SIRT1, acetylated MAPT (ac-MAPT), phosphorylated MAPT (p-MAPT), and total MAPT (t-MAPT); Real-time Quantitative Polymerase Chain Reaction (qRT-PCR) was used in the detection of Sirt1 and Mapt transcriptions. Results: Compared with the MCAO/R group, AS-IV can significantly improve the neurological dysfunction (p < 0.05), reduce the infarction area (p < 0.05), raise the expression of SIRT1 (p < 0.05), and alleviate the abnormal hyperacetylation and hyperphosphorylation of MAPT (p < 0.05). While compared with the AS-IV group, AS-IV + EX527 group showed higher mNSS scores (p < 0.05), more severe cerebral infarction (p < 0.05), lower SIRT1 expression (p < 0.01), and higher ac-MAPT and p-MAPT levels (p < 0.05). Conclusion: AS-IV can improve the neurological deficit after CIR injury in rats and reduce the cerebral infarction area, which exerts neuroprotective effects probably through the Sirt1/Mapt pathway.

Sirt1 activator SRT2104 protects against oxygen-glucose deprivation/reoxygenation-induced injury via regulating microglia polarization by modulating Sirt1/NF-κB pathway

Cerebral ischemic/reperfusion injury is the most common neurological disorder and the second leading cause of death worldwide. Modulating microglia polarization from pro-inflammatory M1 phenotype to anti-inflammatory M2 state has been suggested as a potential therapeutic approach in the treatment of this injury. SRT2104, a novel activator of histone deacetylase Sirtuin-1 (Sirt1), has recently been shown to have anti-inflammation properties. However, the effect of SRT2104 on cerebral ischemic/reperfusion injury has not been elucidated. Here, we found that SRT2104 inhibited neuron and microglia death directly and indirectly through microglia condition medium from an oxygen glucose deprivation/reoxygenation (OGD/R) -induced cell injury models. Moreover, SRT2104 treatment modulated the microglia polarization shift from the M1 phenotype and skewed toward the M2 phenotype. Additionally, we found that SRT2104 could significant inhibit the activation of NF-κB and enhanced Sirt1 expression in microglia. Mechanism studies using the BV2 microglial cell line confirmed that knockdown Sirt1 significantly reduced the effect of SRT2104 on the activation of NF-κB pathway and microglial phenotype shift. Altogether, our result shows SRT2104 protect OGD/R-induced injury through shifting microglia phenotype, which may have potential in further studies as a novel neuroprotective agent for cerebral ischemic/reperfusion injury therapy.

FoxO1 and Wnt/β-catenin signaling pathway: Molecular targets of human amniotic mesenchymal stem cells-derived conditioned medium (hAMSC-CM) in protection against cerebral ischemia/reperfusion injury

Ischemia-reperfusion (I/R) injury has weakened the effects of available treatment options for ischemic stroke. Although conditioned medium obtained from human amniotic mesenchymal stem cells (hAMSC-CM) has been reported to exert protective effect against stroke, detailed knowledge about its possible molecular mechanisms is not still completely available. The present study was designed to investigate whether hAMSC-CM can modulate FoxO1 and Wnt/β-catenin signaling pathway after ischemic stroke to create neuroprotective effects. Middle cerebral artery occlusion (MCAO) model with male Wistar rats was used to evaluate the effects of hAMSC-CM on activities of FoxO1, Wnt/β-catenin signaling pathway, and endogenous antioxidant system and apoptotic cell death. The results demonstrated that induction of MCAO significantly reduced activities of FoxO1, Wnt/β-catenin signaling pathway, and endogenous antioxidant system and enhanced apoptotic cell death (P < 0.05). In addition, treatment by hAMSC-CM immediately after cerebral reperfusion resulted in significantly reduced infarct size and increased activities of FoxO1, Wnt/β-catenin signaling pathway, and restoring endogenous antioxidant system and suppressing apoptotic cell death (P < 0.05). Likewise, increased activity of Wnt/β-catenin signaling pathway resulted in suppressing the neuroinflammation by inhibiting the expression of TNF-α and increasing the expression of IL-10. These findings demonstrate that hAMSC-CM can be considered as an excellent candidate in the treatment of acute ischemic stroke in clinical routine.

Kaempferol protects against cadmium chloride-induced hippocampal damage and memory deficits by activation of silent information regulator 1 and inhibition of poly (ADP-Ribose) polymerase-1

The neuroprotective effect of Kaempferol against cadmium chloride (CdCl₂) -induced neurotoxicity is well reported. The silent information regulator 1 (SIRT1) and poly (ADP-Ribose) polymerase-1 (PARP1) are two related cellular molecules that can negatively affect the activity of each other to promote or inhibit cell survival, respectively. It is still largely unknown if the neurotoxicity of CdCl₂ or the neuroprotection of Kaempferol are mediated by modulating SIRT1 and/or PAPR1 activities. In this study, we tested the hypothesis that CdCl₂-induced memory deficit and hippocampal damage are associated with downregulation/inhibition of SIRT1 and activation of PAPR1, an effect that can be reversed by co-treatment with Kaempferol. Rats (n = 12/group) were divided into 4 groups as control, control + Kaempferol (50 mg//kg), CdCl₂ (0.5 mg/kg), and CdCl₂ + Kaempferol. All treatments were administered orally for 30 days daily. As compared to control rats, CdCl2 reduced rat's final body weights (21.8%) and their food intake (30%), induced oxidative stress and apoptosis in their hippocampi, and impaired their short and long-term recognition memory functions. Besides, the hippocampi of CdCl₂-treated rats had higher levels of TNF-α (197%), and IL-6 (190%) with a concomitant increase in nuclear activity and levels of NF-κB p65 (721% & 554%). Besides, they showed reduced nuclear activity (53%) and levels (74%) of SIRT1, higher nuclear activity and levels of PARP1 (292% & 138%), increased nuclear levels of p53 (870%), and higher acetylated levels of NF-κB p65 (513%), p53 (644%), PARP1 (696%), and FOXO-2 (149%). All these events were significantly reversed in the CdCl₂ + Kaempferol-treated rats. Of note, Kaempferol also increased levels of MnSOD (73.5%), and GSH (40%), protein levels of Bcl-2 (350%), and nuclear activity (67%) and levels (46%) of SIRT1 in the hippocampi of the control rats. In conclusion, Kaempferol ameliorates CdCl₂-induced memory deficits and hippocampal oxidative stress, inflammation, and apoptosis by increasing SIRT1 activity and inhibiting PARP1 activity.

Cycloastragenol upregulates SIRT1 expression, attenuates apoptosis and suppresses neuroinflammation after brain ischemia

Cycloastragenol (CAG) is the active form of astragaloside IV isolated from Astragalus Radix, which displays multiple pharmacological effects. Silent information regulator 1 (SIRT1), a class III histone deacetylase, has been shown to play an important role in neuroprotection against cerebral ischemia. In this study, we investigated whether CAG protected against ischemic brain injury and, if so, whether the beneficial effects were associated with the regulation of SIRT1 in the ischemic brain. Mice were subjected to 45 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. CAG (5, 10, 20 mg/kg) was injected intraperitoneally at the onset of reperfusion, 12 h later and then twice daily for up to three days. CAG dose-dependently reduced brain infarct volume, significantly ameliorated functional deficits, and prevented neuronal cell loss in MCAO mice. Meanwhile, CAG significantly reduced matrix metalloproteinase-9 activity, prevented tight junction degradation and subsequently ameliorated blood-brain barrier disruption. Moreover, CAG significantly upregulated SIRT1 expression in the ischemic brain but did not directly activate its enzymatic activity. Concomitant with SIRT1 upregulation, CAG reduced p53 acetylation and the ratio of Bax to Bcl-2 in the ischemic brain. CAG also inhibited NF-κB p65 nuclear translocation. As a result, CAG suppressed the mRNA expression of pro-inflammatory cytokines, including TNF-α and IL-1β, and inhibited the activation of microglia and astrocytes in the ischemic brain. Our findings suggest that CAG is neuroprotective against ischemic brain injury in mice and that its beneficial effect may involve SIRT1 upregulation and the inhibition of apoptosis and neuroinflammation in the ischemic brain.

SIRT1 Protects Against Apoptosis by Promoting Autophagy in the Oxygen Glucose Deprivation/Reperfusion-Induced Injury

Silent information regulator 1 (SIRT1) contributes to cellular regulation. Previous studies have reported SIRT1 to be abnormally expressed in the ischemic penumbra of cerebral ischemia/reperfusion (I/R) injury rat model. We investigated the effect of SIRT1 on oxygen and glucose deprivation/reperfusion (OGD/R) cell injury. Over-expressed or silenced SIRT1 pheochromocytoma 12 (PC12) cells were exposed to an in-vitro OGD/R injury. Western blot, TUNEL staining and immunofluorescence analyses were performed to assess apoptosis and autophagy. We found autophagy and apoptosis to be up-regulated and down-regulated, respectively, following the over-expression of SIRT1 in the OGD/R-induced PC12 cells. We also found the silencing of SIRT1 to culminate in the down-regulation and up-regulation of autophagy and apoptosis, respectively. On the basis of our results, we surmise that SIRT1 can promote autophagy and inhibit apoptosis in-vitro, and thus exhibit potential neuroprotection against OGD/R-induced injury. This could facilitate in the development of therapeutic approaches for cerebral I/R injury.

Sirtuin 1 Regulates Mitochondrial Biogenesis and Provides an Endogenous Neuroprotective Mechanism Against Seizure-Induced Neuronal Cell Death in the Hippocampus Following Status Epilepticus

Status epilepticus may decrease mitochondrial biogenesis, resulting in neuronal cell death occurring in the hippocampus. Sirtuin 1 (SIRT1) functionally interacts with peroxisome proliferator-activated receptors and γ coactivator 1α (PGC-1α), which play a crucial role in the regulation of mitochondrial biogenesis. In Sprague-Dawley rats, kainic acid was microinjected unilaterally into the hippocampal CA3 subfield to induce bilateral seizure activity. SIRT1, PGC-1α, and other key proteins involving mitochondrial biogenesis and the amount of mitochondrial DNA were investigated. SIRT1 antisense oligodeoxynucleotide was used to evaluate the relationship between SIRT1 and mitochondrial biogenesis, as well as the mitochondrial function, oxidative stress, and neuronal cell survival. Increased SIRT1, PGC-1α, and mitochondrial biogenesis machinery were found in the hippocampus following experimental status epilepticus. Downregulation of SIRT1 decreased PGC-1α expression and mitochondrial biogenesis machinery, increased Complex I dysfunction, augmented the level of oxidized proteins, raised activated caspase-3 expression, and promoted neuronal cell damage in the hippocampus. The results suggest that the SIRT1 signaling pathway may play a pivotal role in mitochondrial biogenesis, and could be considered an endogenous neuroprotective mechanism counteracting seizure-induced neuronal cell damage following status epilepticus.