Yi-Hua Qian

The herbal medicine Dipsacus asper Wall extract reduces the cognitive deficits and overexpression of β-amyloid protein induced by aluminum exposure

Excess aluminum (Al) exposure impairs neurocognitive function in humans and animals. Epidemiologic studies have shown a potential link between chronic Al exposure and Alzheimers disease. In the present study, we sought to evaluate the protective effects of the herbal medicine Dipsacus asper extract against the cognitive impairment and overexpression of hippocampal beta-amyloid protein (Abeta) induced by chronic Al exposure in rats. Vitamin E (VE) was used as a positive control. Following exposure to 0.3% aluminum chloride (AlCl(3)) solution for 90 days in their drinking water, animals displayed a striking decrease (>80%) in step-through latency in the passive avoidance task and a significant increase (123%) in the number of Abeta immunoreactive cells in the hippocampus compared to controls. Al-exposed animals were then randomly assigned to receive vehicle, Dipsacus asper extract (4 g/kg), or VE (40 mg/kg) treatment up to 5 months. Both Dipsacus asper extract and VE significantly ameliorated animals performance impairment in the passive avoidance task and suppressed the overexpression of hippocampal Abeta immunoreactivity. The effects of Dipsacus asper extract, but not VE, increased with time of treatment. The present results suggest that Dipsacus asper extract may possess therapeutic effects against Alzheimers disease.

The protective effects of tanshinone IIA on neurotoxicity induced by β-amyloid protein through calpain and the p35/Cdk5 pathway in primary cortical neurons.

The characteristic pathological change of Alzheimers disease (AD) include deposits of β-amyloid protein (Aβ) in brain, neurofibrillary tangles (NFTs), as well as a few neuronal loss. Evidence shows that Aβ causes calcium influx and induces the cleavage of p35 into p25. Furthermore, the binding of p25 to cyclin-dependent kinase 5 (Cdk5) constitutively activates Cdk5. The p25/Cdk5 complex then hyperphosphorylates tau. Tanshinone IIA (tanIIA), a natural product extracted from Chinese herbal medicine Salvia miltiorrhiza BUNGE, has been reported to exert antioxidative activity. However, its neuroprotective activity remains unclear. The present study determined whether tanIIA protects neurons against Aβ(25-35)-induced cytotoxicity and detected the association of this protective effect with calpain and the p35/Cdk5 pathway. The results showed that tanIIA protected neurons against the neurotoxicity of Aβ(25-35), increased the viability of neurons, decreased expression of phosphorylated tau in neurons induced by Aβ(25-35), improved the impairment of the cell ultrastructure (such as nuclear condensation and fragmentation, and neurofibril collapse). Further more, we found that tanIIA maintained the normal expression of p35 on peripheral membranes, and decreased p25 expression in the cytoplasm. TanIIA also inhibited the translocation of Cdk5 from the nucleus into the cytoplasm of primary neurons induced by Aβ(25-35). These data suggested that tanIIA possessed neuroprotective action and the protection may involve in calpain and the p35/Cdk5 pathway.

Neuroprotective effects of ebselen are associated with the regulation of Bcl-2 and Bax proteins in cultured mouse cortical neurons.

There is little information available on the mechanisms underlying the neuroprotective actions of the organoselenium compound ebselen. In this study, we sought to determine the relationship between alterations in the expression of Bcl-2 and Bax proteins and intracellular levels of calcium and the protective effects of ebselen with a concentration range of 0.01-20 microM against glutamate toxicity in cultured mouse cortical neurons. Pretreatment with ebselen at moderate doses (4-12 microM), but not at lower or higher doses, significantly improved glutamate-induced suppression of cell viability. Pretreatment with ebselen (8 microM) also prevented apoptotic alterations, completely reversed the suppression of Bcl-2 expression, and significantly inhibited Bax overexpression, but did not alter elevated intracellular concentrations of calcium induced by glutamate. Pre-, co-, and post-treatment with ebselen (8 microM) had similar potency in improving the decreased viability of glutamate-exposed cells. These results indicate that the neuroprotective effects of ebselen at low doses are associated with the regulation of Bcl-2 and Bax proteins but appear to be independent of glutamate-mediated elevation of intracellular calcium, suggesting that different mechanisms are involved in the actions of low and high dose regimens. Ebselen may be an effective agent used for early treatment of acute brain injuries.

The effects of perindopril on cognitive impairment induced by d-galactose and aluminum trichloride via inhibition of acetylcholinesterase activity and oxidative stress

Preclinical and clinical studies indicate involvement of renin angiotensin system (RAS) in memory functions. However, exact role of RAS in cognition is still ambiguous. The present study investigated the effects of perindopril on dementia of Alzheimers type induced by d-galactose (d-gal) and aluminum trichloride (AlCl3). Perindopril, an angiotensin converting enzyme inhibitor, was administered intragastrically (0.5mg/kg/day) for 60days after mice were given d-gal (150mg/kg/day) and AlCl3 (10mg/kg/day) intraperitoneally for 90days. Then, memory function was evaluated by Morris water maze test. The biochemical studies were conducted in cerebral cortex and hippocampus of mouse brain after the behavioral studies. d-Gal and AlCl3 caused significant memory impairment along with significant elevation of acetylcholinesterase (AChE) activity in cerebral cortex and hippocampus. Further, a significant reduction of superoxide dismutases (SOD) and glutathione peroxidase (GSH-Px) activities, and elevation of malondialdehyde (MDA) level in cerebral cortex and hippocampus were observed. Perindopril not only improved cognitive impairment but also restored the elevation of AChE activity induced by d-gal and AlCl3. In addition, perindopril significantly increased SOD and GSH-Px activities, reduced MDA level in cerebral cortex and hippocampus. Taken together, the above findings indicate that perindopril improves learning and memorizing probably by restoring cholinergic function and attenuating oxidative damage.

Protective effect of ginsenoside Rb1 on β-amyloid protein(1-42)-induced neurotoxicity in cortical neurons

Abstract The effects of ginsenosides were thought to prevent neurodegenerative processes associated with aging. The accumulation of β-amyloid protein (Aβ) within the brain is one of the pathological hallmarks of Alzheimers disease (AD). There is no one effective treatment of AD. To investigate the effects of ginsenoside Rb1 (GRb1) on neuronal damage induced by Aβ and potential mechanisms of the effects of GRb1 in vitro, morphological observation and biochemical analysis combining primary cultured neurons were adopted. A positive control was pre-treated with Trolox. Neurons that were treated with Aβ 1-42 (2 μM) were shrunken perikaryon with loss of neurite processes; the survival rate of neurons decreased almost to 50% (p<0.01). Lactate dehydrogenase (LDH) release, malondialdehyde (MDA) product and superoxide dismutase (SOD) activity level all increased obviously (p<0.01 or p<0.05). However, neurons pre-treated with GRb1 (0.1, 1 and 10 μM) or Trolox (10 μM) had a survival rate increase compared with neurons treated with Aβ alone; LDH release and MDA product decreased distinctly, and the increase in SOD activity in Aβ-treated neurons was attenuated evidently (p<0.01 or p<0.05). Thus, we conclude that GRb1 exerted neuroprotection obviously. GRb1 protected neurons against the toxicity of Aβ, most likely through an antioxidant pathway. GRb1 could be useful neuroprotective agents of AD.

Retrovirus delivered neurotrophin-3 promotes survival, proliferation and neuronal differentiation of human fetal neural stem cells in vitro.

Poor survival and insufficient neuronal differentiation are the main obstacles to neural stem cell (NSC) transplantation therapy. Genetic modification of NSCs with neurotrophins is considered a promising approach to overcome these difficulties. In this study, the effects on survival, proliferation and neuronal differentiation of human fetal NSCs (hfNSCs) were observed after infection by a neurotrophin-3 (NT-3) recombinant retrovirus. The hfNSCs, from 12-week human fetal brains formed neurospheres, expressed the stem cell marker nestin and differentiated into the three main cell types of the nervous system. NT-3 recombinant retrovirus (Retro-NT-3) infected hfNSCs efficiently expressed NT-3 gene for at least 8 weeks, presented an accelerated proliferation, and therefore produced an increased number of neurospheres and after differentiation in vitro, contained a higher percentage of neuronal cells. Eight weeks after infection, 37.9+/-4.2% of hfNSCs in the Retro-NT-3 infection group expressed the neuronal marker, this was significantly higher than the control and mock infection groups. NT-3 transduced hfNSCs also displayed longer protruding neurites compared with other groups. Combined these results demonstrate that NT-3 modification promote the survival/proliferation, neuronal differentiation and growth of neurites of hfNSCs in vitro. This study proposes recombinant retrovirus mediated NT-3 modification may provide a promising means to resolve the poor survival and insufficient neuronal differentiation of NSCs.

Protective effects of perindopril on d-galactose and aluminum trichloride induced neurotoxicity via the apoptosis of mitochondria-mediated intrinsic pathway in the hippocampus of mice

Perindopril, an angiotensin converting enzyme inhibitor, has been reported to improve learning and memory in a mouse or rat model of Alzheimers disease (AD) induced by injection of beta-amyloid protein. However, the exact mechanism of perindopril on the cognitive deficits is not fully understood. Our previous data have indicated that perindopril improves learning and memory in a mouse model of AD induced by D-galactose (D-gal) and aluminum trichloride (AlCl₃) via inhibition of acetylcholinesterase activity and oxidative stress. Whether perindopril also inhibit apoptosis to prevent cognitive decline remains unknown in mice. Therefore, the present study explored the protective effects of perindopril in the hippocampus of mice further. Perindopril (0.5 mg/kg/day) was administered intragastrically for 60 days after the mice were given a D-gal (150 mg/kg/day) and AlCl₃ (10 mg/kg/day) intraperitoneally for 90 days. Then the expression of Bcl-2, Bax, Fas, FasL, caspase-3, caspase-8 and caspase-9 were analyzed by RT-PCR and western blotting in the hippocampus. Perindopril significantly decreased caspase-3 and caspase-9 activities, and elevated Bcl-2/Bax ratio in the hippocampus. However, the expression of Fas, FasL and caspase-8 did not change in the hippocampus whether treatment with d-gal and AlCl₃ or perindopril. Taken together, the above findings indicated that perindopril inhibited apoptosis in the hippocampus may be another mechanism by which perindopril improves learning and memory functions in d-gal and AlCl₃ treated mice.

Dexamethasone Inhibits Camptothecin-Induced Apoptosis in C6-Glioma via Activation of Stat5/Bcl-xL Pathway

Dexamethasone (DX) induces apoptosis resistance in most solid malignant tumors during co-treatment with chemotherapy agents, such as camptothecin (CAM). In this study, we investigated the mechanism by which DX reduces chemotherapy efficiency in C6-glioma. DX reduced CAM-increased DNA fragmentation and caspase-3 activation. The DXs protection was negated by RU486, an antagonist of glucocorticoid receptor (GR). DX itself increased anti-apoptotic gene, Bcl-xL expression, and its transcription factor, signaling transducer and activator of transcription 5 (Stat5), DNA binding activity and phospho-Stat5 expression. DX blocked the CAM-decreased Bcl-xL and phospho-Stat5 expression, and Stat5 binding activity. RU486 negated DXs actions. To determine whether Stat5 regulates Bcl-xL expression in CAM-induced cell death, C6-glioma was infected with an adenovirus containing a constitutively activated Stat5-GFP (Ad-Stat5ca). Overexpression of Stat5ca increased Bcl-xL and decreased CAM-induced cell death compared to control adenovirus infected cells; whereas Stat5 siRNA decreased DX-induced Bcl-xL and increased cell death. Phospho-Stat5 expression was observed in the nuclear extract by co-immunoprecipitation with an anti-GR antibody, indicating that Stat5 and GR were interactive and formed a complex in the nuclei. These results suggest that DXs prevention from CAM-induced apoptosis and RU486s antagonism of DXs protection may be through Stat5/Bcl-xL signal pathway regulated by a GR.

The protective effects of tanshinone IIA on β-amyloid protein (1–42)-induced cytotoxicity via activation of the Bcl-xL pathway in neuron

The deposition of β-amyloid protein(Aβ) and loss of neurons within the brain are the pathologic hallmarks of Alzheimers disease (AD). Apoptosis is a crucial pathway in neuronal loss in AD. Tanshinone IIA (tanIIA) is one of ingredients of tanshinone which is the major component of the traditional Chinese herb Danshen. The present study explores the effects of tanIIA on Aβ(1-42)-induced cytotoxicity. Cultured cortical neurons that were treated with 4 μM Aβ(1-42) showed shrunken perikaryon with loss of neurite processes; the survival rate of neurons decreased almost to 57% and the apoptotic rate of neurons increased to 47%. In addition, the level of gene bcl-xl mRNA and Bcl-xL protein decreased significantly. These changes, however, were prevented by pretreatment of neurons with tanIIA for 24h before Aβ(1-42), which markedly increased neuron survival rate compared to neurons treated with Aβ(1-42) alone; the apoptotic rate of neurons decreased to 15%, and the decrease in level of gene bcl-xl mRNA and Bcl-xL protein in Aβ-treated neurons, were prevented. Thus, we conclude that tanIIA might serve as an obvious neuroprotection. TanIIA protected neurons against the Aβ-induced cytotoxicity most likely via activation of the Bcl-xL pathway.

Mitogen-activated protein kinase signaling pathways are involved in regulating α7 nicotinic acetylcholine receptor-mediated amyloid-β uptake in SH-SY5Y cells

Intraneuronal accumulation of beta-amyloid protein (Aβ) is an early pathological change in Alzheimers disease (AD). Recent studies demonstrate that α7 nicotinic acetylcholine receptor (α7nAChR) binds to soluble Aβ with a high affinity. In vitro and in vivo experiments also show that Aβ activates p38 MAPK and ERK1/2 signaling pathways via the α7nAChR. Interestingly, it has been reported that p38 MAPK and ERK1/2 signaling pathways affect the regulation of receptor-mediated endocytosis. These data suggest that MAPK signaling pathways maybe involved in the regulation of α7nAChR-mediated Aβ uptake. However, the evidence for this hypothesis is lacking. In the present study, we examined whether Aβ1-42 oligomers activate MAPK signaling pathways via α7nAChR, and assessed the role of MAPK signaling pathways in the regulation of Aβ1-42 uptake by α7nAChR. We confirm that undifferentiated SH-SY5Y cells are capable of taking up extracellular Aβ1-42. The internalization of Aβ1-42 accumulates in the endosomes/lysosomes and mitochondria. MAPK signaling pathways are activated by Aβ1-42 via α7nAChR. Aβ1-42 and α7nAChR are co-localized in SH-SY5Y cells and the expression of α7nAChR involves in Aβ1-42 uptake and accumulation in SH-SY5Y cells. Our data demonstrate that Aβ1-42 induces an α7nAChR-dependent pathway that relates to the activation of p38 MAPK and ERK1/2, resulting in internalization of Aβ1-42. Our findings suggest that α7nAChR and MAPK signaling pathways play an important role in the uptake and accumulation of Aβ1-42 in SH-SY5Y cells. Blockade of α7nAChR may have a beneficial effect by limiting intracellular accumulation of amyloid in AD brain and serves a potential therapeutic target for AD.