Neuroprotective effects of matrix metalloproteinases in cerebral ischemic rats by promoting activation and migration of astrocytes and microglia.

Matrix metalloproteinases (MMPs) cleave almost all components of the extracellular matrix (ECM) and cause acute neurovascular disruption and parenchymal destruction. Previously, MMPs inhibition was considered to be a therapeutic strategy in early stages of ischemia. This study was designed to investigate whether early MMPs inhibition could promote the recovery of cerebral ischemia. Male Sprague-Dawley rats underwent right middle cerebral artery occlusion (MCAO) for 1 h and reperfusion. The rats were divided into three groups: sham + vehicle (S + V) group, MCAO + vehicle (M + V) group, and MCAO + GM6001 (M + G) group. Infarct volume was assessed by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, and the expression of GFAP, IBA1, p-ERK, ERK, and MMP9 were evaluated by Western blot and immunofluorescence staining on 1, 4, 7, and 14 days after MCAO. Neuronal apoptosis was assessed by Fluoro-Jade C staining. The results showed that MMPs inhibition significantly increased the infarct volume and the expressions of GFAP and IBA1 in the M + V group were much higher than those in the M + G group; whereas the expression of p-ERK was upregulated in both the M + V and M + G groups. These findings suggest that MMPs promote the activation and migration of astrocytes and microglia to form protected zone in the penumbra and lessen the infarct volume after cerebral ischemic stroke.

Interactions between Sirt1 and MAPKs regulate astrocyte activation induced by brain injury in vitro and in vivo.

BACKGROUND: Astrocyte activation is a hallmark of traumatic brain injury resulting in neurological dysfunction or death for an overproduction of inflammatory cytokines and glial scar formation. Both the silent mating type information (Sirt1) expression and mitogen-activated protein kinase (MAPK) signal pathway activation represent a promising therapeutic target for several models of neurodegenerative diseases. We investigated the potential effects of Sirt1 upregulation and MAPK pathway pharmacological inhibition on astrocyte activation in vitro and in vivo. Moreover, we attempted to confirm the underlying interactions between Sirt1 and MAPK pathways in astrocyte activation after brain injury. METHODS: The present study employs an interleukin-1ß (IL-1ß) stimulated primary cortical astrocyte model in vitro and a nigrostriatal pathway injury model in vivo to mimic the astrocyte activation induced by traumatic brain injury. The activation of GFAP, Sirt1, and MAPK pathways were detected by Western blot; astrocyte morphological hypertrophy was assessed using immunofluorescence staining; in order to explore the neuroprotective effect of regulation Sirt1 expression and MAPK pathway activation, the motor and neurological function tests were assessed after injury. RESULTS: GFAP level and morphological hypertrophy of astrocytes are elevated after injury in vitro or in vivo. Furthermore, the expressions of phosphorylated extracellular regulated protein kinases (p-ERK), phosphorylated c-Jun N-terminal kinase (p-JNK), and phosphorylated p38 activation (p-p38) are upregulated, but the Sirt1 expression is downregulated. Overexpression of Sirt1 significantly increases the p-ERK expression and reduces the p-JNK and p-p38 expressions. Inhibition of ERK, JNK, or p38 activation respectively with their inhibitors significantly elevated the Sirt1 expression and attenuated the astrocyte activation. Both the overproduction of Sirt1 and inhibition of ERK, JNK, or p38 activation can alleviate the astrocyte activation, thereby improving the neurobehavioral function according to the modified neurological severity scores (mNSS) and balance latency test. CONCLUSIONS: Thus, Sirt1 plays a protective role against astrocyte activation, which may be associated with the regulation of the MAPK pathway activation induced by brain injury in vitro and in vivo.

Involvement of GSK3 and PP2A in ginsenoside Rb1's attenuation of aluminum-induced tau hyperphosphorylation.

Environmental agent aluminum, a well-known neurotoxin, has been proposed to play a role in the development of Alzheimer's disease (AD), and produced clinical and pathological features which were strikingly similar to those seen in AD brain, such as neurofibrillary tangles. Ginsenoside Rb1, highly abundant active component of ginseng, has been demonstrated to be neuroprotective against various neurotoxins. In this study we investigated the effect of Rb1 on aluminum-induced tau hyperphosphorylation in ICR mice. Mice were exposed to aluminum chloride (200 mg/kg/day) for 6 months followed by a post treatment of Rb1 (20 mg/kg/day) for another 4 months. Aluminum exposure induced the cognitive ability by Morris water maze, and upregulated the tau phosphorylation level at Ser396 accompanied by increasing p-GSK and decreasing PP2A level in motor, sensory cortex and hippocampal formation. Post treatment of Rb1 significantly improved the learning and memory and reduced the tau phosphorylation by reversing the p-GSK3 and PP2A level. Our results indicate that ginsenoside Rb1 protected mice against Al-induced toxicity. The possible mechanism may be its role in preventing tau hyperphosphorylation by regulating p-GSK3 and PP2A level, which implicate Rb1 as the potential preventive drug candidate for AD and other tau pathology-related neuronal degenerative diseases.

Treadmill exercise prevents decline in spatial learning and memory in APP/PS1 transgenic mice through improvement of hippocampal long-term potentiation.

Alzheimer's disease (AD) is a progressive neurodegenerative disease clinically characterized by learning and memory function deterioration. While it is well established that exercise can improve cognitive performance in AD, there have been few basic cellular and molecular mechanisms research performed to test the interaction between exercise and AD. In this study, we aimed at investigating whether treadmill exercise improves learning and memory function in APP/PS1 transgenic mouse model of Alzheimer's disease by enhancing long-term potentiation (LTP) and up-regulation of brain-derived neurotrophic factor (BDNF) mRNA expression. Our results show that, in comparison to wild type mice, transgenic mice were characterized by impaired learning and memory function, LTP deficits and increased BDNF mRNA levels. Treadmill exercise enhanced learning and memory function not only in wild type mice but also in APP/PS1 mice paralleled by LTP. However, BDNF has emerged as a crucial regulator of synaptic plasticity mechanisms underlying learning and memory in wild-type mice, but not in APP/PS1 mice. Hence, this investigation demonstrates that treadmill exercise is an effective therapeutic that alleviate learning and memory decline in APP/PS1 mouse model, and enhanced LTP maybe a cellular mechanism involved in neuropathological course of AD and cognitive improvement induced by exercise.

MCP-1, ICAM-1 and VCAM-1 are present in early aneurysmal dilatation in experimental rats.

Recent studies have suggested that inflammation actively participates in ascending aortic aneurysm formation. The aim of the present study was to evaluate the expression changes of adhesion molecules and MMPs in an experimental model of ascending aortic aneurysm induced by ascending aorta banding in Wistar rats. Twelve rats developed aortic dilation after ascending aorta banding treatment, while nine normal animals underwent surgery without banding were used as controls. Light microscope and scanning electron microscope showed that the wall of the ascending aorta became disorganized as well as infiltration by inflammatory cells in aneurysmal rats. By using immunohistochemical techniques, a significant increase in the immunostaining of MCP-1 was observed in the aneurysmal wall as compared to the normal aortic wall. Under similar experimental conditions, we also found that the immunostaining of ICAM-1 and VCAM-1 was markedly increased in the aneurysmal wall. In addition, gelatin zymographic analysis showed that the expression and activities of MMP-2 and MMP-9 were remarkably enhanced in the ascending aorta of ascending aortic aneurysmal rats as compared to normal rats. These results demonstrate that MCP-1, ICAM-1 and VCAM-1 are involved in the pathogenesis of ascending aortic aneurysm and an increase in the immunostaining and activity of MMP-2 and MMP-9 may promote the progression of ascending aortic aneurysm.

Ginsenoside Rb1 protects PC12 cells against ß-amyloid-induced cell injury.

Excessive accumulation of ß-amyloid (Aß) has been proposed as a pivotal event in the pathogenesis of Alzheimer's disease. Possible mechanisms underlying Aß-induced neuronal cytotoxicity include oxidative stress and apoptosis. Reactive oxygen species (ROS) have been proposed to be involved in the apoptotic mechanism of Aß-induced cytotoxicity. Ginsenoside Rb1 (GRb1), which is among the key compounds of ginsenoside, found in ginseng, may be a potent scavenger of ROS. To examine the potential protective effect of GRb1 in Aß25-35-induced cytotoxicity, cells were pre-treated with GRb1 for 24 h, and then Aß25-35 was added to the medium for an additional 24 h. Exposure to Aß led to the accumulation of ROS and lipid peroxidation, eventually causing a decrease in the Bcl-2/Bax ratio, caspase-3 activation, cell apoptosis and cell death. Pre-treatment with GRb1 not only inhibited Aß-induced ROS overproduction and lipid peroxidation, but also increased the Bcl-2/Bax ratio and attenuated caspase-3 activation, thereby improving cell survival. GRb1 may therefore act as a ROS scavenger, and such antioxidant properties may play a protective role against Aß-induced cell injury. Further exploration of GRb1 antioxidant properties may provide novel therapeutic strategies for the treatment of Alzheimer's disease.

[Gene expression profiles and proteomics analysis of the cell transfected with the mutant type of COOH-terminal deleted of hepatitis B virus X].

OBJECTIVE: To investigate the mechanism of the different biological impacts of HBx3'-40, an engineered deletion mutant lacking the last 40 C-terminal amino acids. METHOD: Human hepatocellular cells of the line Huh7 were transfected with HBx3'-40 or wtHBx (wild type HBx) constructs. An oligo cDNA microarray containing 21074 human genes and Ests was utilized to examine the different gene expression between HBx3'-40 and paired control wtHBx cells. A series of methods, including immobilized pH gradient two-dimensional polyacrylamide gel electrophoresis (2-DE), silver staining, and PDQuest 2-D analysis software were used to analyze the differential protein-spots between HBx3'-40 and wtHBx cells. Selected differential protein-spots were identified with peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time-of-fight mass spectrometry (MALDI-TOF-MS) and database searching. RESULTS: 165 (0.82%) candidate genes showing aberrant expression under HBx3'-40 induction were identified, of which 144 were up-regulated while 21 were down-regulated. Compared with wtHBx group, there were 135 +/- 13 differently protein spots in HBx3'-40 group by 2-DE. Of them, 7 significantly different protein spots were identified using mass spectrometry and computer matching with protein database. Most of the differently expressed genes and proteins were involved in transcription, oncogenes and tumor suppressor genes or protein, cell adhesion, signal transduction pathways, metabolisms, etc. CONCLUSION: The mutant HBx affects cell genes and proteins involved in various processes, especially in regulation of liver metabolism.