Pyruvate maintains and enhances the pro-inflammatory response of microglia caused by glucose deficiency in early stroke.

Pro-inflammatory microglia mainly rely on glycolysis to maintain cytokine production during ischemia, accompanied by an increase in inducible nitric oxide synthase (iNOS) and monocarboxylate transporter 1 (MCT1). The role of energy metabolism in the pro-inflammatory response of microglia is currently unclear. In this study, we tested the response of microglia in mice after cerebral ischemia and simulated an energy environment in vitro using low glucose culture medium. The research results indicate that the expression levels of iNOS and arginase 1 (ARG1) increase in the ischemic mouse brain, but the upregulation of MCT1 expression is mainly present in iNOS positive microglia. In microglia exposed to low glucose conditions, iNOS and MCT1 levels increased, while ARG1 levels decreased. Under the same conditions, knocking down MCT1 in microglia leads to a decrease in iNOS levels, while overexpression of MCT1 leads to the opposite result. The use of NF-κB inhibitors reduced the expression levels of iNOS and MCT1 in microglia. In summary, our data indicate that pyruvate maintains and enhances the NF-κB regulated pro-inflammatory response of microglia induced by low glucose.

Cell apoptosis and proliferation in rat brains after intracerebral hemorrhage: role of Wnt/ß-catenin signaling pathway.

BACKGROUND/AIM: To investigate the role of Wnt/ß-catenin signaling pathway in cell apoptosis and proliferation in intracerebral hemorrhage (ICH) in rats. MATERIALS AND METHODS: The ICH rats were established by stereotaxic infusion of 50 µL autologous arterial blood into the right striatum. Pathological characteristics of brain tissue was assessed by hematoxylin and eosin and TUNEL staining, and the expressions of proliferating cell nuclear antigen (PCNA) and Wnt3a/ß-catenin/cyclin D1 were investigated by immunohistochemistry or reverse-transcription polymerase chain reaction. RESULTS: The number of apoptotic cells and PCNA-positive cells kept increasing from the day following the ICH induction and reached a peak on the 3rd and 14th days, respectively. Some of the PCNA-positive cells could coexpress neurofilament protein-200 or glial fibrillary acidic protein. Wnt3a, ß-catenin, cyclin D1, and PCNA mRNAs reached maximal expression levels on the 3rd, 7th, 7th, and 14th days, respectively. Moreover, the number of apoptotic cells was significantly positively correlated with the expressions of Wnt3a and ß-catenin mRNAs, and negatively correlated with the number of PCNA-positive cells. CONCLUSION: Our results suggest that the Wnt/ß-catenin signaling pathway is associated with cell apoptosis and expression of PCNA in the ICH rat brain and regulates the balance between cell apoptosis and proliferation.

Transplantation of neural stem cells overexpressing glial cell line-derived neurotrophic factor enhances Akt and Erk1/2 signaling and neurogenesis in rats after stroke.

BACKGROUND: Our previous studies have indicated that the beneficial effects of grafting neural stem cells (NSCs) overexpressing glial cell line-derived neurotrophic factor (GDNF) in rats after stroke. However, the underlying mechanisms are highly debatable. In this study, we investigated whether neurogenesis, Akt, and extracellular signal-regulated kinase 1/2 (Erk1/2) signaling were involved in this process. METHODS: Transient ischemic stroke were induced by occluding middle cerebral artery for 2 hours and reperfusion. At 3 days after reperfusion, GDNF/NSCs, NSCs, and vehicle were administered. Immunohistochemical staining was used to evaluate neurogenesis by nestin antibody; phosphorylation of Akt and Erk1/2 was investigated by Western blotting analysis. RESULTS: Transplantation of GDNF/NSCs and NSCs significantly increased nestin-positive cells compared to control group (vehicle) from 1 to 7 weeks after reperfusion, and GDNF/NSCs showed stronger effect than NSCs at 2 and 3 weeks after reperfusion. Meanwhile, enhanced phosphorylation level of Erk1/2 was observed in the GDNF/NSCs and NSCs groups compared with control group, and phosphorylation level of Erk1/2 in GDNF/NSCs group was remarkably higher than that of NSCs group at any given time. In contrast, expression of mitogen-activated protein kinase phosphatase-1 (MKP-1), known as inhibitor of Erk1/2 signaling, was significantly decreased in the GDNF/NSCs and NSCs groups compared with the control group. Moreover, much enhanced and prolonged phosphorylation level of Akt of GDNF/NSCs group was detected compared with control and NSCs group. CONCLUSION: Grafting GDNF/NSCs enhances neurogenesis and activates Akt and Erk1/2 signaling, that may provide the potential for GDNF/NSCs in stroke treatment.

Ginsenoside Rb1 regulates the expressions of brain-derived neurotrophic factor and caspase-3 and induces neurogenesis in rats with experimental cerebral ischemia.

AIM OF THE STUDY: Recent studies have revealed that ginsenoside Rb1 (GRb1) is neuroprotective for cerebral ischemia. However, the mechanism underlying of this function is unclear. We assessed whether this neuroprotective effect of GRb1 was mediated by the levels of brain-derived neurotrophic factor (BDNF), by the levels of caspase-3 proteins and by induced neurogenesis in rats following transient cerebral ischemia or not. MATERIALS AND METHODS: Cerebral ischemia was prepared by a 2 h occlusion of the middle cerebral artery and reperfusion, followed by infusion of GRb1 (40 mg/kg) and saline (GRb1 and ischemia groups, respectively). All rats were sacrificed at 3 and 12 h, 1, 2, 3, 5, and 10 days after reperfusion. Normal and sham-operated rats were used in control group. Modified Neurological Severity Scores (mNSS) test and hematoxylin and eosin staining were respectively performed to evaluate neurological function and histological feature. Immunohistochemistry was used to identify intrinsic neurogenesis by nestin antibody. Western blotting was used to detect BDNF and caspase-3 protein content. RESULTS: GRb1 infusion after cerebral ischemia significantly promoted recoveries of neurological functions at 3 and 5 days after reperfusion compared to ischemic rats. The number of nestin-positive cells was apparently increased after GRb1 infusion compared to ischemia rats at given time. Moreover, BDNF was significantly increased in GRb1-treated rats compared to ischemia rats at different time points. In contrast, GRb1 infusion after the onset of reperfusion, caspase-3 at a given time was significantly reduced compared to ischemia rats, but still significantly increased compared to control rats. CONCLUSIONS: Promotion of the neurogenesis and regulation of the expressions of BDNF and caspase-3 may be involved in GRb1-induced neuroprotection against cerebral ischemia.

[Effects of Ginsenoside RB1 on neural cell apoptosis and expressions of Bcl-2 and Bax in rats following subjected to cerebral ischemia-reperfusion].

OBJECTIVE: To observe the effects of Ginsenoside Rb1 (GRb1) on neuronal cell apoptosis and the expressions of Bcl-2 and Bax in rats after cerebral ischemia-reperfusion so as to investigate the neuroprotective mechanism of GRb1. METHDOS: The model of cerebral ischemia-reperfusion was established by occluding rat middle cerebral artery for 2 h. The rats were randomly divided into two groups: ischemia-reperfusion group (I/R group) and GRb1 treat group (GRb1 group). GRb1 (40 mg/kg, i.p.) was administered immediately to rats after the onset of reperfusion. Two groups were further subdivided 7 subgroups according to various reperfusion time (3 h, 12 h, 1 d, 2 d, 3 d, 5 d and 10 d, n=4 per time point). HE staining was used to observe histological features. TUNEL and immunohistochemical method were used to analyze the cell apoptosis and expressions of Bcl-2 and Bax, respectively. RESULTS: Compared with I/R group, GRb1 reduced pathological changes, and decreased the number of apoptotic neural cells (P<0.05 on 12 h, 1 d, 2 d and 3 d) and up-regulated the number of Bcl-2 positive cells (P<0.05 on 12 h, 1 d, 3 d, 5 d and 10 d), and meanwhile down-regulated the number of Bax positive cells (P<0.05 on 3 h, 12 h, 1 d, 2 d, 3 d, 5 d and 10 d) in the ipsilateral hemisphere. CONCLUSION: The neuroprotective effect of GRb1 on cerebral ischemia-reperfusion injury is related to inhibit neuronal apoptosis and to up-regulate the expression of Bcl-2 with down-regulating the expression of Bax.