Baicalin Inhibits NLRP3 Inflammasome Activity Via the AMPK Signaling Pathway to Alleviate Cerebral Ischemia-Reperfusion Injury.

Baicalin has been reported to have ameliorative effects on nerve-induced hypoxic ischemia injury; however, its role in the NLRP3 inflammasome-dependent inflammatory response during cerebral ischemia-reperfusion remains unclear. To investigate the molecular mechanisms involved in baicalin alleviating cerebral ischemia-reperfusion injury, we investigated the AMPK signaling pathway which regulates NLRP3 inflammasome activity. SD rats were treated with baicalin at doses of 100 mg/kg and 200 mg/kg, respectively, after middle cerebral artery occlusion at 2 h and reperfusion for 24 h (MCAO/R). MCAO/R treatment significantly increased cerebral infarct volume, changed the ultrastructure of nerve cells, and activated the NLRP3 inflammasome, manifesting as significantly increased expression of NLRP3, ASC, cleaved caspase-1, IL-1ß, and IL-18. Our results demonstrated that baicalin treatment effectively reversed these phenomena in a dose-dependent manner. Additionally, inhibition of NLRP3 expression was found to promote the neuroprotective effects of baicalin on cortical neurons. Furthermore, baicalin remarkably increased the expression of p-AMPK following oxygen glucose deprivation/reperfusion (OGD/R). The expression of the NLRP3 inflammasome was also increased when the AMPK pathway was blocked by compound C. Taken together, our findings reveal that baicalin reduces the activity of the NLRP3 inflammasome and consequently inhibits cerebral ischemia-reperfusion injury through activation of the AMPK signaling pathway.

[Forest fire management in the United States]. / 美国林火管理概况及分析.

With the intensification of climate change and human activities, megafires frequently occur, with serious impacts on ecosystems, atmospheric environment, and human health. The United States has accumulated a large amount of practical experience in forest fire management. A comprehensive review of the framework of forest fire management in the United States can provide an inspiring reference for forest fire prevention in China. Starting from the process of historical evolution of forest fire policy, we systematically introduced the four stages of policy evolution and the characteristics of each stage in the US. Moreover, a comprehensive analysis of forest fire management situation in the US from four aspects was conducted, including the management of combustible fuels, administrative responsibility, fire suppression and forest fire management research support. We summarized relevant literature and proposed improvement strategies for future combustibles management, policy politics and fire fighting in the United States. Through the comprehensive analysis of forest fire management in the United States, we put forward some inspiring opinions on forest fire management in China to promote the establishment of a sound forest fire management system with Chinese characteristics.

Renin-angiotensin system activation and imbalance of matrix metalloproteinase-9/tissue inhibitor of matrix metalloproteinase-1 in cold-induced stroke.

AIMS: In the present study, we investigated the roles of renin-angiotensin system (RAS) activation and imbalance of matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in cold-induced stroke during chronic hypertension, as well as the protective effects of captopril and recombinant human TIMP-1 (rhTIMP-1). MAIN METHODS: Rats were randomly assigned to sham; 2-kidney, 2-clip (2K-2C); 2K-2C + captopril, and 2K-2C + rhTIMP-1 groups. After blood pressure values had stabilized, each group was randomly divided into an acute cold exposure (ACE) group (12-h light at 22 °C/12-h dark at 4 °C) and a non-acute cold exposure (NACE) group (12-h light/12-h dark at 22 °C), each of which underwent three cycles of exposure. Captopril treatment was administered via gavage (50 mg/kg/d), while rhTIMP-1 treatment was administered via the tail vein (60 µg/kg/36 h). KEY FINDINGS: In the 2K-2C group, angiotensin II (AngII) and MMP-9 levels increased in both the plasma and cortex, while no such changes in TIMP-1 expression were observed. Cold exposure further upregulated AngII and MMP-9 levels and increased stroke incidence. Captopril and rhTIMP-1 treatment inhibited MMP-9 expression and activation and decreased stroke incidence in response to cold exposure. SIGNIFICANCE: The present study is the first to demonstrate that cold exposure exacerbates imbalance between MMP-9 and TIMP-1 by activating the RAS, which may be critical in the initiation of stroke during chronic hypertension. In addition, our results suggest that captopril and rhTIMP-1 exert protective effects against cold-induced stroke by ameliorating MMP-9/TIMP-1 imbalance.

Baicalin inhibiting cerebral ischemia/hypoxia-induced neuronal apoptosis via MRTF-A-mediated transactivity.

Baicalin has been shown to provide the neuroprotective effect by alleviating cerebral ischemia injury. However, little's known about the underlying mechanism. Here, a cerebral artery occlusion (MACO)/reperfusion rat model and rat primary cortical neuron culture exposed to hydrogen peroxide (H2O2) were established to evaluate the effect of baicalin on ischemia-induced neuronal apoptosis. We found baicalin can significantly less neurological deficit and reduced infarct volume in vivo. And it efficiently inhibited neuronal apoptosis in vivo and vitro, which was especially characterized by the enhancing of transcription and expression of myeloid cell leukemia-1 (MCL-1) and B-cell lymphoma-2 (BCL-2) in a dose-dependent manner. Furthermore, Baicalin markedly increased myocardin-related transcription factor-A (MRTF-A) level either in ischemic hemisphere or in primary cortical neuron cultures, whiles the anti-apoptosis effect of baicalin was significantly inhibited by transfected with the small interfering RNA of MRTF-A (MRTF-A siRNA) in primary cortical neuron cultures. The luciferase assays also indicated baicalin enhanced the transactivity of MCL-1 and BCL-2 promoter by activating the key CArG box (CC [A/T] 6GG) element, which was reduced by MRTF-A siRNA, suggesting MRTF-A may participate the anti-apoptosis effect of baicalin, and MRTF-A was involved in the transcriptional activity of MCL-1 and BCL-2 that was induced by baicalin. LY294002 (phosphatidylinositol-3 kinase (PI3K) inhibitor) and PD98059 (extracellular signal regulates kinase-1/2 (ERK1/2) inhibitor) obviously reduced baicalin-induced MRTF-A expression and transactivity and expression of MCL-1 and BCL-2, which further abolished the anti-apoptotic effect of baicalin on neuronal apoptosis. Taken together, our data provided the evidence demonstrating the neuroprotective effect of baicalin partially due to MRTF-A-mediated transactivity and expression of MCL-1 and BCL-2 by triggering the CArG box, which might be controlled by the activation of PI3K and ERK1/2.

Baicalin protects PC-12 cells from oxidative stress induced by hydrogen peroxide via anti-apoptotic effects.

PRIMARY OBJECTIVE: To examine the neuroprotection of baicalin, a flavonoid compound derived from the dried root of Scutellaria baicalensis Georgi, on neurons. RESEARCH DESIGN: A rat PC12 cell line was used to study the neuroprotection and possible mechanisms of baicalin on H2O2-induced neuron damage. METHODS: Three anti- and one pro-apoptosis genes in PC12 cells were examined. Cell apoptosis was induced by H2O2 and apoptotic rate was obtained by flow cytometry. MTT for cell viability, immunofluorescence microscopy for promoter activity and western blot for gene expression were also employed. RESULTS: Data of MTT reduction assay and flow cytometry revealed that viability loss and apoptotic rate were reduced by pre-treatment of PC12 cells with baicalin for 24 hours. Baicalin was also found to increase SOD, GSH-Px activities and to decrease MDA level. Results from Western blot and immunofluorescence microscopy showed baicalin increased the expressions of survivin, Bcl-2 and p-STAT3 and decreased caspase-3 expression which were attenuated by AG-490. CONCLUSIONS: The results point to the possibility of the neuroprotective effects of baicalin on neuronal apoptosis induced by oxidative stress and indicate that activation of the JAK/STAT signalling pathway might involve the anti-apoptotic effect of baicalin.

Coexistence of hyperlipidemia and acute cerebral ischemia/reperfusion induces severe liver damage in a rat model.

AIM: To investigate the correlation of hyperlipemia (HL) and acute cerebral ischemia/reperfusion (I/R) injury on liver damage and its mechanism. METHODS: Rats were divided into 4 groups: control, HL, I/R and HL+I/R. After the induction of HL via a high-fat diet for 18 wk, middle cerebral artery occlusion was followed by 24 h of reperfusion to capture I/R. Serum alanine transaminase (ALT) and aspartate aminotransferase (AST) were analyzed as part of liver function tests and liver damage was further assessed by histological examination. Hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. The expression of genes related to apoptosis (caspase-3, bcl-2) was assayed by immunohistochemistry and Western blotting. Serum tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) and liver mitochondrial superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and Ca(2+) levels were measured to determine inflammatory and oxidative/antioxidative status respectively. Microsomal hydroxylase activity of the cytochrome P450 2E1 (CYP2E1)-containing enzyme was measured with aniline as the substrate, and CYP2E1 expression in the liver tissue and microsome was determined by immunohistochemistry and Western blotting respectively. RESULTS: HL alone induced by high-fat diet for 18 wk resulted in liver damage, indicated by histopathological analysis, and a considerable increase in serum ALT (25.13 ± 16.90 vs 9.56 ± 1.99, P < 0.01) and AST levels (18.01 ± 10.00 vs 11.33 ± 4.17, P < 0.05) compared with control. Moreover, HL alone induced hepatocyte apoptosis, which was determined by increased TUNEL-positive cells (4.47 ± 0.45 vs 1.5 ± 0.22, P < 0.01), higher caspase-3 and lower bcl-2 expression. Interestingly, compared with those in control, HL or I/R groups, massive increases of serum ALT (93.62 ± 24.00 vs 9.56 ± 1.99, 25.13 ± 16.90 or 12.93 ± 6.14, P < 0.01) and AST (82.32 ± 26.92 vs 11.33 ± 4.17, 18.01 ± 10.00 or 14.00 ± 6.19, P < 0.01) levels in HL+I/R group were observed suggesting severe liver damage, which was confirmed by liver histology. In addition, HL combined with I/R also caused significantly increased hepatocyte apoptosis, as evidenced by increased TUNEL-positive cells (6.20 ± 0.29 vs 1.5 ± 0.22, 4.47 ± 0.45 or 1.97 ± 0.47, P < 0.01), elevated expression of caspase-3 and lower expression of bcl-2. Furthermore, when compared to HL or I/R alone, HL plus I/R enhanced serum TNF-α, IL-1, liver mitochondrial MDA and Ca(2+) levels, suppressed SOD and GSH-Px in liver mitochondria, and markedly up-regulated the activity (11.76 ± 2.36 vs 4.77 ± 2.31 or 3.11 ± 1.35, P < 0.01) and expression (3.24 ± 0.38 vs 1.98 ± 0.88 or 1.72 ± 0.58, P < 0.01) of CYP2E1 in liver. CONCLUSION: The coexistence of HL and acute cerebral I/R induces severe liver damage, suggesting that cerebral ischemic stroke would exaggerate the damage of liver caused by HL. This effect is possibly due to enhanced CYP2E1 induction which further promotes oxidative damage, inflammation and hepatocyte apoptosis.

Myocardin-related transcription factor-A promoting neuronal survival against apoptosis induced by hypoxia/ischemia.

MRTF-A, known as one of the myocardin-related transcription factors, is widely found in newborn rat cortical or hippocampus neurons as well as in adult rat forebrain. Recent studies indicate that MRTF-A elevates SRF-driven transcription and enhances its stimulation by neurotrophic factor (BDNF). However, the mechanism underlying the contribution of the MRTF-A to neuronal survival is not completely understood. In this study, we investigated the effect of MRTF-A on neuronal apoptosis and its underlying mechanism. First of all, our study demonstrated that MRTF-A expression decreased obviously in rats' brains during the early period of cerebral ischemia-reperfusion. In order to estimate the effect of MRTF-A on neuronal apoptosis in vitro, we used an established experimental paradigm in which MRTF-A protected cortical neurons against both hypoxia-trophic deprivation and hydrogen peroxide-induced apoptosis. Obviously, over-expression of wild-type MRTF-A in cortical neurons inhibited apoptosis rate and enhanced anti-apoptotic gene-MCL-1. In contrast, co-expression of MRTF-A and the small interfering RNA of MRTF-A (siRNA) reversed the effect of neuroprotection and the upregulation on MCL-1 expression afforded by MRTF-A. Our study also determined whether the effect of MRTF-A up-regulating on MCL-1 expression is correlated to MRTF-A-enhancing CArG box transcription. The result showed that over-expression of wild-type MRTF-A upregulated the transcription activity of MCL reporter gene via driving the binding-domain CArG box in MCL-1 promoter, which was also reversed by co-expression of MRTF-A siRNA. In addition, we also found that BDNF neuroprotection on apoptosis induced by hypoxia-trophic withdrawal was not only inhibited by LY29004 and PD98059 but also partially blocked by transfection of dominant-negative MRTF-A in cortical neurons via enhancing the expression of anti-apoptotic gene-MCL-1, suggesting a downstream neuroprotective mechanism to BDNF neuroprotection on apoptosis.