| Alzheimer's disease (AD) is the most common cause of dementia. Mechanisms of its pathogenesis are not clear. And there is no effective treatment for it. P-amyloid protein(Aβ).deposition around neuron is a core pathology, which can cause the symptom of dementia, as well as other pathologies. In addition to senile plaque and neurofibrillary tangle, decreasing dendritic spine plasticity is also one of the key pathologies of AD. Spine plasticity is decided by the dynamic of Actin cytoskeleton. This procession is mediated by the actin binding protein activation by Phosphatidylinositol 4,5-bisphosphate (PIP2). Myristoylated alanine-rich C-kinase substrate (MARCKS), is a rich and important membrane protien in brain, which connect neuron signal with dendritic spine plasticity. MARCKS can bind to PIP2 and f-actin separately with its effecter domain. When phorsphorlated by PKC or interacted with Ca2+, MARCKS can leave membrane, at the same time, PIP2 and f-actin can be released. F-actin binding proteins can be activated, which can induce the f-actin depended dendritic spine plasticity. So, This PhD project aims to clarify the mechanism of the MARCKS alteration and the dendritic spine plasticity alteration mediated by it in AD animal model, as well as the mechanism of Chinese medicine effects.Objective:1. Establish and assess the validity of dementia model induced by AP protein intracranial injection, which is used for the research of Alzheimer's disease.2. Observe the alteration of MARCKS mRNA and drebrin, which is a marker protein of dendritic spine plasticity, in hippocampus of old dementia rats induced by P-amyloid(Aβ)(1-40). Observe the effect of Fu Fang Cong Rong Yi Zhi capsule on the alteration of MARCKS mRNA and drebrin level in hippocampus of the dementia animal model.4. Implore AD pathology in Chinese medicine on the base of this research.Methods:1. Establish the dementia old rat model induced byβ-amyloid protein intracerebroventrical injection. Face validity was assessed by behavior test, pathological; predictive validity was assessed by the effect of cholinesterase inhibitor on learning and membrane function improvement; construct validity was assessed by mechanism of the mechanism of Aβinducing dementia.2. Animals were assigned randomly to young group, old group, sham operation group, model group, donepezil group and Chinese medicine group. Model, west and Chinese medicine group received Aβ(1-40) intracerebroventrical injection to build dementia animal model, and then Chinese and west medicine group received Fu Fang Cong Rong Yi Zhi capsule and donepezil for 14 days, respectively. Observe changes of behavior, Aβ(1-40), MARCKS mRNA and drebrin by morris test, RT-PCR, ELISA test and westernblotting respectively.Results:1. Face validity was supported:the model could mimic the memory impairments of Alzheimer's disease, Predictive validity was supported:cholinesterase inhibitor could improve the learning and memory function of the model; Construct validity was supported:The pathological changes induced by Aβ(1-40) were correspondent with the amyloid hypothesis of AD.2. Learning and memory function of model group was decreased, compared with young group. Learning and memory function of Chinese and donepezil group were better than model group. MARCKS mRNA of model group was increased significantly, compared with young group, old group and sham operation group (P<0.01). Drebrin level of model group is decreased significantly, compared with young group, old group and sham operation group(P<0.01). MARCKS mRNA of Chinese medicine was increased significantly (P<0.01), campared with model group. There is no difference between drebrin level of Chinese medicine group, donepezil group and that of model group.Conclusion:1. This model could be used as an effective protocol for us to understand the neurobiology of AD and new therapy for it.2. Aβ(1-40) can increase the level of MARCKS m RNA, decrease the level of drebrin in old rat hippocampus, as well as decrease the learning and memory function of old rats. So MARKS may play a key role in the process of neuroplasticity reduction caused by Aβ(1-40). Fu Fang Cong Rong Yi Zhi capsule with the effect of benefiting kidney and liver, clearing toxin and improving blood vessel, which is based on the hypothesis "toxin damaging luo of brain" can reduce the level of MARCKS mRNA in hippocampus of old dementia rats caused by Aβ(1-40), through which it can improve the learning and memory function of the dementia old rats. Whether this medicine can increase the dendritic spine plasticity through this pathway, needs to be researched more deeply.3. Implore the pathology of AD in Chinese medicine, it is discovered that Aβhad the character of damaging of brain and marrow internal toxin, so it belongs to internal toxin, internal toxin damaging brain and marrow is also the pathology of the disease. Membrane is the most easily damaged by oxidation. Membrane is the important pathway for Qi circulation, which can be belonged to the definition of "luo" in Chinese medicine. The Chinese medicine hypothesis of "toxin damaging brain vessel" is an important pathology of AD. |
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