咬合支持丧失对伴有慢性脑缺血的认知功能损害的影响及机制研究

More and more studies confirm occlusal support loss as a risk factor for cognitive impairment in the aging population, but the mechanism is not very clear. Vascular risk factor is one of the very important factors in the process of cognitive impairment and dementia, wherein the nitric oxide signaling pathway plays an important role in its pathogenic process. The chewing movement can also affect blood flow in the brain. Our previous studies found that the loss of occlusal support affect the expression of nitric oxide and its synthase in brain, suggesting that the nitric oxide signaling pathway might play an important role in cognitive impairment caused by occlusal support loss. This project is intend to investigate the effect of occlusal support loss for development of cognitive dysfunction with chronic cerebral ischemia, the function and molecular mechanism of NO signaling pathway in this process by establishing the animal model of chronic cerebral ischemia and occlusal support loss, cognitive behavior, examining the cerebral blood flow, the expression and function of nitric oxide and its synthase, screening down-stream target gene by microarray annalysis, surveying the relationship of cognitive impairment with chronic cerebral ischemia and occlusal support loss in the old population. Through this study, we will discover neurophysiological mechanisms of cognitive impairment and occlusal support loss, reveal the biological mechanisms of effect of chewing movement on the function of brain, and provide the useful information for improving the life quality in old people.

越来越多的研究证实咬合支持丧失作为危险因素对认知功能损害的影响，但机制尚不明确。血管性危险因素是认知损害和痴呆进程中非常重要的因素之一，其中一氧化氮(NO)信号通路在其致病中起重要的作用。咀嚼运动也会影响脑部血流，同时，本课题组前期研究发现咬合支持丧失影响脑内NO及其合酶的表达，推测NO信号通路在咬合支持丧失造成的认知损害中起着重要的作用。本课题拟建立慢性脑缺血咬合支持丧失动物模型，通过建模后不同时间点的认知行为学测试、脑血流监测、NO及其合酶表达与功能检测、NO相关下游基因筛查等方法，以及老年人群伴有慢性脑缺血的认知功能损害与咬合支持相关性的观察，研究咬合支持丧失对伴有慢性脑缺血的认知功能损害发生发展的影响和NO信号通路在其中的作用及分子调控机制，探究咬合支持丧失对脑认知功能损害的神经生理学机制，为揭示咬合影响脑功能的生物学机制提供理论依据，以期改善老年人的生活质量。

越来越多的研究证实咬合支持丧失作为危险因素对认知功能损害的影响，但机制尚不明确。血管性危险因素是认知损害和痴呆进程中非常重要的因素之一，其中一氧化氮（NO）信号通路在其中作用显著。咀嚼运动会影响脑部血流，同时前期研究发现咬合支持丧失影响脑内NO及其合酶的表达，推测NO信号通路在咬合支持丧失造成的认知损害中起重要作用。本课题组通过建立咬合支持丧失伴慢性脑缺血大鼠模型，检测动物认知功能和脑内NO及其合酶的影响情况及其分子调控机制。选取3月龄大鼠分组，分别建立模型，术后8周进行Morris水迷宫实验显示慢性脑缺血伴咬合支持丧失大鼠认知功能损害。行为学结束后断头取海马组织，利用硝酸盐还原法、Western Blot和乙酰胆碱酶试剂盒分别对海马内NO、iNOS、eNOS及神经递质进行定量检测，发现咬合支持丧失会导致慢性脑缺血大鼠海马区一氧化氮含量以及一氧化氮合酶表达的进一步提高；脑神经递质乙酰胆碱以及胆碱乙酰转移酶含量进一步减少，和乙酰胆碱脂酶活性进一步提高。通过免疫组化分析发现：星形胶质细胞以及小胶质细胞被激活。另外应用PCR技术检测到导致慢性脑缺血大鼠海马区p38MAPK、NFκB、caspase-3mRNA水平表达的进一步提高。p38MAPK、NFκB、caspase-3信号通路炎性凋亡机制中表达上调，海马区一氧化氮含量及其合酶增加，进一步激活星形胶质细胞以及小胶质细胞使神经递质减少，最终导致咬合支持丧失会加重慢性脑缺血大鼠学习能力的下降。本研究提示提高人们对牙齿咬合支持功能重要性的认识，对于已有轻度血管性认知功能障碍的老年人群，修复缺失牙齿可能延缓其痴呆症状的加重。