Yuhai Wang

Sirt3 Protects Cortical Neurons against Oxidative Stress via Regulating Mitochondrial Ca2+ and Mitochondrial Biogenesis

Oxidative stress is a well-established event in the pathology of several neurobiological diseases. Sirt3 is a nicotinamide adenine nucleotide (NAD+)-dependent protein deacetylase that regulates mitochondrial function and metabolism in response to caloric restriction and stress. This study aims to investigate the role of Sirt3 in H2O2 induced oxidative neuronal injury in primary cultured rat cortical neurons. We found that H2O2 treatment significantly increased the expression of Sirt3 in a time-dependent manner at both mRNA and protein levels. Knockdown of Sirt3 with a specific small interfering RNA (siRNA) exacerbated H2O2-induced neuronal injury, whereas overexpression of Sirt3 by lentivirus transfection inhibited H2O2-induced neuronal damage reduced the generation of reactive oxygen species (ROS), and increased the activities of endogenous antioxidant enzymes. In addition, the intra-mitochondrial Ca2+ overload, but not cytosolic Ca2+ increase after H2O2 treatment, was strongly attenuated after Sirt3 overexpression. Overexpression of Sirt3 also increased the content of mitochondrial DNA (mtDNA) and the expression of mitochondrial biogenesis related transcription factors. All these results suggest that Sirt3 acts as a prosurvival factor playing an essential role to protect cortical neurons under H2O2 induced oxidative stress, possibly through regulating mitochondrial Ca2+ homeostasis and mitochondrial biogenesis.

Sirt3 attenuates hydrogen peroxide-induced oxidative stress through the preservation of mitochondrial function in HT22 cells

Sirtuins (Sirt) are a family of phylogenetically conserved nicotinamide adenine nucleotide (NAD(+))-dependent protein deacetylases, among which Sirt3 resides primarily in the mitochondria and serves as a stress responsive deacetylase, playing a role in protecting cells from damage under stress conditions. The present study aimed to investigate the role of Sirt3 in hydrogen peroxide (H(2)O(2))-induced oxidative neuronal injury in HT22 mouse hippocampal cells. Treatment with H(2)O(2) increased the expression of Sirt3 in a dose- and time-dependent manner, and the knockdown of Sirt3 using specific small interfering RNA (siRNA) exacerbated the H(2)O(2)-induced neuronal injury. The overexpression of Sirt3 induced by lentiviral transfection significantly reduced the generation of reactive oxygen species (ROS) and lipid peroxidation following injury, whereas the activities of endogenous antioxidant enzymes were not affected. Further experiments revealed that the H(2)O(2)-induced inhibition of mitochondrial complex activity and adenosine triphosphate (ATP) synthesis, the decrease in mitochondrial Ca(2+) buffering capacity and mitochondrial swelling were all partly reversed by Sirt3. Furthermore, the overexpression of Sirt3 attenuated the release of cytochrome c, the increase in the Bax/Bcl-2 ratio, as well as caspase-9/caspase-3 activity induced by H(2)O(2), and eventually inhibited apoptotic neuronal cell death. These results suggest that Sirt3 acts as a prosurvival factor, playing an essential role in protecting HT22 cells under H(2)O(2)-induced oxidative stress, possibly by inhibiting ROS accumulation and the activation of the mitochondrial apoptotic pathway.

Sirt3 confers protection against neuronal ischemia by inducing autophagy: involvement of the AMPK-mTOR pathway.

Abstract Sirtuin3 (Sirt3) is a member of the silent information regulator 2 (Sir2) family of proteins located in mitochondria that influences almost every major aspect of mitochondrial biology, including ATP generation and reactive oxygen species (ROS) production. Our previous study showed that Sirt3 exerts protective effects against oxidative stress in neuronal cells. In this study, we investigated the role of Sirt3 in neuronal ischemia using an oxygen and glucose deprivation (OGD) model. Sirt3 was up‐regulated by OGD and overexpression of Sirt3 through lentivirus transfection significantly reduced OGD‐induced lactate dehydrogenase (LDH) release and neuronal apoptosis. These effects were accompanied by reduced hydrogen dioxide (H2O2) production, enhanced ATP generation and preserved mitochondrial membrane potential (MMP). The results of immunocytochemistry and electron microscopy showed that Sirt3 increased autophagy in OGD‐injured neurons, which was also confirmed by the increased expression of Beclin‐1 as well as LC3‐I to LC3‐II conversion. In addition, the autophagy inhibitor 3‐MA and bafilomycin A1 partially prevented the effects of Sirt3 on LDH release and apoptosis after OGD. The results of western blotting showed that overexpression of Sirt3 in cortical neurons markedly increased the phosphorylation of AMPK, whereas the phosphor‐mTOR (p‐mTOR) levels decreased both in the presence and absence of OGD insult. Furthermore, pre‐treatment with the AMPK inhibitor compound C partially reversed the protective effects of Sirt3. Taken together, these findings demonstrate that Sirt3 protects against OGD insult by inducing autophagy through regulation of the AMPK‐mTOR pathway and that Sirt3 may have therapeutic value for protecting neurons from cerebral ischemia. Graphical abstract Figure. No Caption available. HighlightsOverexpression of Sirt3 attenuates OGD‐induced neuronal injury.Sirt3 preserves mitochondrial function and cellular bioenergetics.Sirt3 promotes autophagy following neuronal ischemia.Autophagy contributes to the neuroprotective effect of Sirt3.Sirt3‐induced protection is mediated by the AMPK‐mTOR pathway.

Sirt1-Sirt3 axis regulates human blood-brain barrier permeability in response to ischemia

Sirtuin1 (Sirt1) and Sirtuin3 (Sirt3) are two well-characterized members of the silent information regulator 2 (Sir2) family of proteins. Both Sirt1 and Sirt3 have been shown to play vital roles in resistance to cellular stress, but the interaction between these two sirtuins has not been fully determined. In this study, we investigated the role of Sirt1-Sirt3 axis in blood-brain barrier (BBB) permeability after ischemia in vitro. Human brain microvascular endothelial cells and astrocytes were co-cultured to model the BBB in vitro and oxygen and glucose deprivation (OGD) was performed to mimic ischemia. The results of transepithelial electrical resistance (TEER) showed that suppression of Sirt1 via siRNA or salermide significantly decreased BBB permeability, whereas Sirt3 knockdown increased BBB permeability. In addition, Sirt1 was shown to regulate Sirt3 expression after OGD through inhibiting the AMPK-PGC1 pathway. Application of the AMPK inhibitor compound C partially prevented the effects of Sirt1-Sirt3 axis on BBB permeability after OGD. The results of flow cytometry and cytochrome c release demonstrated that Sirt1 and Sirt3 exert opposite effects on OGD-induced apoptosis. Furthermore, suppression of Sirt1 was shown to attenuate mitochondrial reactive oxygen species (ROS) generation, which contribute to the Sirt1-Sirt3 axis-induced regulation of BBB permeability and cell damage. In summary, these findings demonstrate that the Sirt1-Sirt3 axis might act as an important modulator in BBB physiology, and could be a therapeutic target for ischemic stroke via regulating mitochondrial ROS generation.

Endoscope-Assisted Keyhole Technique for Hypertensive Cerebral Hemorrhage in Elderly Patients: A Randomized Controlled Study in 184 Patients.

AIM Hypertensive cerebral hemorrhage (HCH) is a potentially life-threatening cerebrovascular disease with high mortality. In case of a massive hematoma, surgical drainage is a crucial treatment. The aim of the present study was to assess the efficacy of the endoscope-assisted keyhole technique in elderly patients with intracerebral hematoma who needed a flap craniotomy as traditional treatment. MATERIAL AND METHODS One hundred-eighty-four elderly patients with HCH, who had craniotomy indications after conservative treatment for 6-24 hours after onset, were randomly divided into two groups. In the craniotomy group, traditional hematoma drainage was performed. In the keyhole group, an endoscope-assisted keyhole technique was used. Anesthesia time, blood loss, hematoma drainage rate, and complications were compared. The clinical primary outcome was the six-month efficacy rate (defined by the activities of daily living (ADL) score). RESULTS Anesthesia time was longer in the craniotomy group (3.43 ± 0.65 vs. 1.53 ± 0.52 h, P < 0.01), and blood losses were more important (256 ± 129 vs. 96 ± 39 ml P < 0.01). There was no difference in hematoma drainage rate between the two groups (77.25 ± 13.44 vs. 83.52 ± 27.51% P > 0.05). Complications, including tracheotomy (P < 0.01), pulmonary infection (P < 0.01) and hypoproteinemia (P < 0.05) were more frequent in the craniotomy group. There was no difference in the occurrence of other complications, including revision surgery digestive tract ulcer and epilepsy. Proportion of patients with good prognosis (ADL I-III) was larger in the keyhole group (P < 0.05). CONCLUSION In elderly HCH patients with an indication for hematoma drainage, better outcomes were achieved using an endoscope-assisted keyhole technique.

Surgical management of traumatic interhemispheric subdural hematoma.

AIM To review our experience in the surgical treatment of TISH, and to analyze prognostic factors. MATERIAL AND METHODS Clinical and imaging data, surgical modalities, and outcomes of 21 patients with TISH who were treated with microsurgery were analyzed retrospectively. Prognostic factors for outcome were analyzed by univariate analysis. RESULTS Long-term follow up with outcome assessment according to the Glasgow Outcome Scale (GOS) showed good recovery in 16 cases, moderate disability in two cases, severe disability in one case, and death in two cases. During surgery the origin of bleeding could be identified in all 21 cases. A rupture of the distal anterior cerebral artery or veins in the interhemispheric fissure was seen more frequently in patients with whole interhemispheric fissure hematoma, while hemorrhage from brain tissue laceration was seen more frequently in patients with more localized hematomas. The outcome in patients with an identified rupture of a vessel was better than in those with cortical laceration. Preoperative GCS score and thickness of the interhemispheric hematoma were correlated with outcome (P=0.001 and P=0.004, respectively). CONCLUSION Outcome after surgical treatment for TISH can be good, and careful surgical planning and microsurgical techniques to preserve venous drainage are essential.

Controlled decompression for the treatment of severe head injury: a preliminary study.

AIM Fast direct decompression surgery for treatment of severe head injury often results in intraoperative and postoperative complications. Controlled decompression may help prevent these complications. This preliminary study aims to compare the effects of controlled and conventional decompression in patients with severe head injury. MATERIAL AND METHODS A total of 128 patients with severe head injury were included. Patients were allocated to receive either controlled decompression surgery (n = 64) or conventional decompressive craniectomy (n = 64). Controlled decompression comprised controlled ventricular drainage and controlled hematoma evacuation. The occurrence of delayed hematoma, acute brain swelling, and postoperative cerebral infarction were recorded. RESULTS Significantly lower proportion of patients in the controlled decompression group had intraoperative acute brain swelling compared to patients in the decompressive craniectomy group (9.4% vs 26.6%, P = 0.011). Intraoperative acute encephalocele occurred in 3 of 13 patients (23.1%) who had delayed hematoma in the controlled decompression group compared with 11 of 18 patients (61.1%) in the decompressive craniectomy group. There was no significant between group difference in the incidence of delayed hematoma or postoperative cerebral infarction. CONCLUSION Controlled decompression may reduce or delay intraoperative acute brain swelling by delaying hematoma formation in patients with severe head injury.

Glutamate-induced rapid induction of Arc/Arg3.1 requires NMDA receptor-mediated phosphorylation of ERK and CREB

Arc/Arg3.1 is a unique immediate early gene whose expression is highly dynamic and correlated with various forms of synaptic plasticity. Many previous reports highlight the complexity of mechanisms that regulate Arc/Arg3.1 expression in neurons. In the present study, the expression and regulation of Arc/Arg3.1 after glutamate treatment in primary cultured cortical neurons were investigated. We found that both Arc/Arg3.1 mRNA and Arc/Arg3.1 protein dynamically increased within 24h after glutamate treatment. The results of immunostaining showed that abundant amounts of Arc/Arg3.1 protein are presented in both soma and dendrites. The glutamate-induced increase in Arc/Arg3.1 protein levels was partially prevented by the NMDAR inhibitor DL-AP5, but not the AMPAR inhibitor NBQX. The results of calcium imaging showed that glutamate induced significant increases in intracellular calcium levels in a NMDAR-dependent manner. However, the intracellular calcium chelator BAPTA-AM had no effect on glutamate-induced upregulation of Arc/Arg3.1 protein, and alteration of cytosolic calcium ion homeostasis with A23187 and TG did not change Arc/Arg3.1 protein levels. In addition, the phosphorylation of ERK and CREB, two downstream factors of NMDAR signaling, markedly increased after glutamate exposure. Blocking ERK and CREB activation via selective inhibitors partially prevented the glutamate-induced elevation of Arc/Arg3.1 protein levels. Combined observations support a NMDAR-mediated and calcium-independent mechanism by which glutamate increases Arc/Arg3.1 expression in cortical neurons.

Increased Levels of Pro-Inflammatory and Anti-Inflammatory Cellular Responses in Parkinson’s Disease Patients: Search for a Disease Indicator

Background Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder and it arises when most of the dopaminergic neurons of substantia nigra region die. Several mechanisms have been postulated as the causative event in PD pathology, and neuroinflammation is most crucial among them. Material/Methods We analyzed T-helper 17 (Th17) cells and myeloid-derived suppressor cells (MDSCs) from 80 PD patients to assess inflammatory processes and to find a cost-effective means to evaluate PD prognosis. Results We found significantly increased numbers of Th17 cells and MDSCs count in peripheral circulation in PD patients compared with controls (p<0.001). A positive correlation was found between Th17 cells and MDSCs in PD patients (r=0.421, p<0.05). Conclusions Our results show the effector role of Th17 cells and MDSCs in PD pathology and shows their utility as effective biomarkers for PD diagnosis.

Atorvastatin ameliorates early brain injury after subarachnoid hemorrhage via inhibition of AQP4 expression in rabbits

The therapeutic effects of atorvastatin on early brain injury (EBI), cerebral edema and its association with aquaporin 4 (AQP4) were studied in rabbits after subarachnoid hemorrhage (SAH) using western blot analysis and the dry-wet method. Seventy-two healthy male New Zealand rabbits weighing between 2.5 and 3.2 kg were randomly divided into three groups: the SAH group (n=24), sham-operated group (n=24) and the SAH + atorvastatin group (n=24). A double SAH model was employed. The sham-operated group were injected with the same dose of saline solution, the SAH + atorvastatin group received atorvastatin 20 mg/kg/day after SAH. All rabbit brain samples were taken at 72 h after the SAH model was established successfully. Brain edema was detected using the dry-wet method after experimental SAH was induced; AQP4 and caspase-3 expression was measured by western blot analysis, and neuronal apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) staining at 72 h after SAH. The results indicated that brain edema and injury appeared soon after SAH, while brain edema and EBI were ameliorated and increased behavior scores were noted after prophylactic use of atorvastatin. Compared with the SAH group, the level of AQP4 and the cerebral content of water was significantly decreased (P<0.01) by atorvastatin, and TUNEL staining and studying the expression of caspase-3 showed that the apoptosis of neurons was reduced markedly both in the hippocampus and brain cortex by atorvastatin. The results suggest that atorvastatin ameliorated brain edema and EBI after SAH, which was related to its inhibition of AQP4 expression. Our findings provide evidence that atorvastatin is an effective and well-tolerated approach for treating SAH in various clinical settings.