Altered Hippocampal BDNF Cleavage In A Rat Model Of Vascular Dementia

BackgroundVD is an acquired persistent syndrome, characterized by a decline in global brain functioning, such as memory deterioration, cognitive impairment and emotional and behavioral disorders. During the last century, life expectancy has increased worldwide, leading to an increase in the prevalence of vascular dementia(VD). This epidemic growth in dementia is of great concern for society. As the pathogenesis of VD is not clear and no drug has yet been approved for the treatment of VD, research in VD has become the current research hot spot. BDNF is a neurotrophin that is widely expressed in the mammalian brain and that is closely related to learning and memory. BDNF is synthesized as the precursor protein pro-BDNF, and is stored in secretory vesicles, from where it can be released in an activity-dependent manner or constitutive secretion. Pro-BDNF is then proteolytically cleaved via two distinct processing pathways to either truncated BDNF whose biological role is not identified, or to the mBDNF form. Studies show that there were changes of BDNF expression in brain after cerebral ischemia and that all the three BDNF forms were related to cognition impairment. But the changes of these three BDNF is unknown in VD. So in this study, we investigate the changes of pro-BDNF, mature BDNF, truncated BDNF in hippocampal of vascular dementia rats and observe the relation between the changes and cofnitionPart one Changes of the level of Pro-BDNF, Mature BDNF and Truncated BDNF in Hippocampal Neuron after Oxygen-glucose Deprivation Objective:Establish the model of oxygen- glucose deprivation on hippocampal neuron cultured in vitro, to investigate the changes of pro-BDNF, mature BDNF, truncated BDNF in vascular dementia. Methods:In vitro primary culture was conducted on the neurons in hippocampus area of newborn SD rats within 24 hours. The damaged neuron model which was ischemic and hypoxic was established by oxygen- glucose deprivation. The survival of cells suffered by OGD was examined by MTT assay. Western blotting method was used to test pro-BDNF, mature BDNF, truncated BDNF level. Results:1. Compared with the control group : the cell activity were decreased significantly( P < 0. 05). With prolonged of OGD, the cell activity were decreased more significantly( P < 0. 05).2. Compared with sham operated group, the mBDNF of model group increased at 30 min, and then reduced gradually with the extension of ischemia time(F = 10.496,P = 0.000),and the truncated BDNF in model group significantly reduced after OGD injury(F = 31.641,P = 0.000), and pro-BDNF significantly increased at 30 min, 6h, and 12 h, reduced at 24h(F = 16.246,P = 0.000). Conclusions:The cell activity decreased afer OGD injury, and the longer of the injury last, the lower of the cell activity is?Pro-BDNF, mature BDNF, truncated BDNF in Hippocampal Neuron after Oxygen-glucose Deprivation changed differently?Maybe the change of proportion of three isoforms BDNF associated with cognitive dysfunction of Va D.Part two Changes of Pro-BDNF, Mature BDNF, Truncated BDNF in Hippocampal of Model Rats of Vascular Dementia Objective:To investigate the changes of pro-BDNF, mature BDNF, truncated BDNF in hippocampal of vascular dementia rats and observe the relation between the changes and cofnition. Methods:A total of 120 healthy male Sprague-Dawley rat, aged 6 months, verge of weight 350 g were randomly divided into model group and sham-operated group. The model of chronic cerebral ischemia was established by permanent occlusion of the bilateral common carotid arteries(2VO) in rats, while the sham-operated group accepted the same operation except occlusion of the bilateral common carotid arteries. Both model group and sham-operated group rats were randomly divided into 2 weeks, 4 weeks, 8 weeks, 12 weeks sub-group, and the behavior of the rats in each group was evaluated by the Morris water maze to select the successful modeling, then the brains were collected for immunohistochemistry and western blotting to detect the changes of pro- BDNF, mature BDNF, truncated BDNF in the hippocampus. Results:1. The results of VD model: There were 65 rats being established in model group rats ans 55 rats in sham-operated group. 16 rats in model group and 4 rats of sham-operated group were died.2. Behavior observation:the escape latency of rat in model group was extended significantly compared with sham operated group(P < 0.05). With prolonged ischemia, the escape latency of model group rats inscreased more significantly(P < 0.05).3. Compared with sham operated group, the total BDNF of model group reduced gradually with the extension of ischemia time,and the truncated BDNF in model group significantly reduced in 4 week, 8 week and 12 weeks(P < 0.05), and pro-BDNF significantly reduced in 8 week and 12 weeks(P < 0.05), and mature BDNF significantly reduced 12 weeks(P < 0.05). With prolonged ischemia, pro-BDNF in model group decreased slowly, and truncated BDNF in model group decreased significantly in 2 week and 4 week but gentle downslope after 4 week, and mature BDNF altered significantly after 8 week. Conclusions:Pro-BDNF, mature BDNF, truncated BDNF in hippocampal of chronic cerebral ischemia rat changed differently, and the change of proportion of three isoforms BDNF associated with cognitive dysfunction.