Wei-Na Yang

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.

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 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.

Puerarin attenuates learning and memory impairments and inhibits oxidative stress in STZ-induced SAD mice

Puerarin (PUE), an isoflavone purified from the root of Pueraria lobata (Chinese herb), has been reported to attenuate learning and memory impairments in the transgenic mouse model of Alzheimers disease (AD). In the present study, we tested PUE in a sporadic AD (SAD) mouse model which was induced by the intracerebroventricular injection of streptozotocin (STZ). The mice were administrated PUE (25, 50, or 100mg/kg/d) for 28 days. Learning and memory abilities were assessed by the Morris water maze test. After behavioral test, the biochemical parameters of oxidative stress (glutathione peroxidase (GSH-Px), superoxide dismutases (SOD), and malondialdehyde (MDA)) were measured in the cerebral cortex and hippocampus. The SAD mice exhibited significantly decreased learning and memory ability, while PUE attenuated these impairments. The activities of GSH-Px and SOD were decreased while MDA was increased in the SAD animals. After PUE treatment, the activities of GSH-Px and SOD were elevated, and the level of MDA was decreased. The middle dose PUE was more effective than others. These results indicate that PUE attenuates learning and memory impairments and inhibits oxidative stress in STZ-induced SAD mice. PUE may be a promising therapeutic agent for SAD.

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.

Treatment effects of tanshinone IIA against intracerebroventricular streptozotocin induced memory deficits in mice.

Our previous studies demonstrated that tanshinone IIA (tan IIA) has significant protective effects against the neurotoxicity induced by β-amyloid protein (Aβ) in cultured cortical neurons and PC12 cells. This study was designed to investigate the protective effects of tan IIA against memory deficits induced by streptozotocin (STZ) in a model of sporadic Alzheimers disease (AD). STZ was injected twice intracerebroventrically (3mg/kg ICV) on alternate days (day 1 and day 3) in mice. Daily treatment with tan IIA (20, 40, and 80mg/kg, i.g.) starting from the first dose of STZ for 28 days showed a dose dependent improvement in STZ induced memory deficits as assessed by Morris water maze (MWM) test. Nissl staining results confirmed the protective effects of tan IIA on cerebral cortical and hippocampal neurons damage induced by STZ. In addition, tan IIA markedly reduced STZ induced elevation in acetylcholinesterase (AChE) activity and malondialdehyde (MDA) level, and significantly inhibited STZ induced reduction in superoxide dismutases (SOD) and glutathione peroxidase (GSH-Px) activities in the parietal cortex and hippocampus. Moreover, tan IIA attenuated p38 mitogen activated protein kinase (MAPK) phosphorylation in the parietal cortex and hippocampus. These findings demonstrate that tan IIA prevents STZ induced memory deficits may be attributed to ameliorating neuronal damage, restoring cholinergic function, attenuating oxidative stress and blocking p38 MAPK signal pathway activation. Based on our previous studies, the present study provides further support for the potential use of tan IIA in the treatment of AD.

Aβ-HBc virus-like particles immunization without additional adjuvant ameliorates the learning and memory and reduces Aβ deposit in PDAPP mice.

β-Amyloid peptide (Aβ) immunization is regarded as a promising therapy to Alzheimers disease. The full length Aβ as antigen might induce meningoencephalitis adverse effect since the middle and C-terminal fragments of Aβ contain T cell epitopes. While N-terminal fragment of Aβ, containing B cell epitope, has weak or no immunogenicity. To improve the immunogenicity, in the previous study, we used HBv core antigen as carrier to make fusion protein containing 2 Aβ1-15. The fusion protein could form virus-like particles (VLPs) and had strong immunogenicity. The antisera prevented Aβ fiber formation and protected the PC12 cells against toxicity of Aβ. In the present study, we immunized 12-month old AD transgenic mice, PDAPP mice, to observe the therapeutic effect of immunization on behaviour and pathology. During immunization, the titer of anti-Aβ antibody reached to nearly 1:10(6) after 4th inoculation, and then maintained that level to the end of the experiment. After 6-month immunization, the behavioral changes of mice were tested by Morris Water Maze (MWM). The escape latency of immunized mice was shorter than control, and these mice entered platform quadrant more times. Immunohistochemistry results showed that Aβ-HBc VLPs immunized mice had less amyloid deposit with less microglia in cortex and hippocampus. In conclusion, Aβ-HBc VLPs ameliorated the learning and memory and reduced cerebral Aβ deposit in PDAPP mice.

The effects of valsartan on cognitive deficits induced by aluminum trichloride and d-galactose in mice

Abstract Objectives: Valsartan has been reported to reduce brain beta-amyloid protein levels and improve spatial learning in the Tg2576 transgenic mouse model of Alzheimers disease (AD). However, the exact mechanism of neuroprotective effects of valsartan has not been properly studied especially in cholinergic function and oxidative damage, the essential factors that undergo impairment in AD. Therefore, the present study examined the effects of valsartan on memory impairment, cholinergic dysfunction, and oxidative stress in aluminum trichloride (AlCl3) and d-galactose (d-gal)-induced experimental sporadic dementia of Alzheimers type. Methods: Valsartan was administered intragastrically (i.g.) (20 mg/kg/day) for 60 days after mice were given AlCl3 (10 mg/kg/day) and d-gal (150 mg/kg/day) intraperitoneally (i.p.) once daily for 90 days. Then, memory function was evaluated by Morris water maze test. Acetylcholinesterase (AChE), superoxide dismutases (SOD) and glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) level in cortex and hippocampus were also assessed with biochemical technique. Results: Chronic administration of valsartan not only improved learning and memory but also restored the elevation of AChE activity induced by AlCl3 and d-gal in cortex and hippocampus. In addition, valsartan significantly restored SOD and GSH-Px activities and reduced MDA level in cortex and hippocampus indicating attenuation of oxidative stress. Discussion: Our results indicate that valsartan prevents AlCl3- and d-gal-induced cognitive decline partly to restore cholinergic function and attenuate oxidative damage. These findings further support the potential of valsartan to be used in AD treatment.

Mitogen-activated protein kinase signaling pathways promote low-density lipoprotein receptor-related protein 1-mediated internalization of beta-amyloid protein in primary cortical neurons

Mounting evidence suggests that the pathological hallmarks of Alzheimers disease (AD) are caused by the intraneuronal accumulation of beta-amyloid protein (Aβ). Reuptake of extracellular Aβ is believed to contribute significantly to the intraneuronal Aβ pool in the early stages of AD. Published reports have claimed that the low-density lipoprotein receptor-related protein 1 (LRP1) mediates Aβ1-42 uptake and lysosomal trafficking in GT1-7 neuronal cells and mouse embryonic fibroblast non-neuronal cells. However, there is no direct evidence supporting the role of LRP1 in Aβ internalization in primary neurons. Our recent study indicated that p38 MAPK and ERK1/2 signaling pathways are involved in regulating α7 nicotinic acetylcholine receptor (α7nAChR)-mediated Aβ1-42 uptake in SH-SY5Y cells. This study was designed to explore the regulation of MAPK signaling pathways on LRP1-mediated Aβ internalization in neurons. We found that extracellular Aβ1-42 oligomers could be internalized into endosomes/lysosomes and mitochondria in cortical neurons. Aβ1-42 and LRP1 were also found co-localized in neurons during Aβ1-42 internalization, and they could form Aβ1-42-LRP1 complex. Knockdown of LRP1 expression significantly decreased neuronal Aβ1-42 internalization. Finally, we identified that p38 MAPK and ERK1/2 signaling pathways regulated the internalization of Aβ1-42 via LRP1. Therefore, these results demonstrated that LRP1, p38 MAPK and ERK1/2 mediated the internalization of Aβ1-42 in neurons and provided evidence that blockade of LRP1 or inhibitions of MAPK signaling pathways might be a potential approach to lowering brain Aβ levels and served a potential therapeutic target for AD.

The p38 mitogen-activated protein kinase signaling pathway is involved in regulating low-density lipoprotein receptor-related protein 1-mediated β-amyloid protein internalization in mouse brain.

Alzheimers disease (AD) is one of the most common neurodegenerative diseases. Recently, increasing evidence suggests that intracellular β-amyloid protein (Aβ) alone plays a pivotal role in the progression of AD. Therefore, understanding the signaling pathway and proteins that control Aβ internalization may provide new insight for regulating Aβ levels. In the present study, the regulation of Aβ internalization by p38 mitogen-activated protein kinases (MAPK) through low-density lipoprotein receptor-related protein 1 (LRP1) was analyzed in vivo. The data derived from this investigation revealed that Aβ1-42 were internalized by neurons and astrocytes in mouse brain, and were largely deposited in mitochondria and lysosomes, with some also being found in the endoplasmic reticulum. Aβ1-42-LRP1 complex was formed during Aβ1-42 internalization, and the p38 MAPK signaling pathway was activated by Aβ1-42 via LRP1. Aβ1-42 and LRP1 were co- localized in the cells of parietal cortex and hippocampus. Furthermore, the level of LRP1-mRNA and LRP1 protein involved in Aβ1-42 internalization in mouse brain. The results of this investigation demonstrated that Aβ1-42 induced an LRP1-dependent pathway that related to the activation of p38 MAPK resulting in internalization of Aβ1-42. These results provide evidence supporting a key role for the p38 MAPK signaling pathway which is involved in the regulation of Aβ1-42 internalization in the parietal cortex and hippocampus of mouse through LRP1 in vivo.