Experimental Studies Of Protective Effects Of Icariin On Brain Damages Induced By Ischemia/Reperfusion

Objective: With the social development and population aging, the morbidity of aging-related dementia sharply increased. Vascular dementia is one of the main types in aging dementia, which is common disease seriously influencing life qualify of old population in the world. It is well known that brain is very susceptible to hypo-glucose and hypoxia. Ischemic cerebral disease is the primary cause of vascular dementia. Because of the high morbidity of cerebrovascular diseases in our country, the vascular dementia is main responsible for aging dementia. Unfortunately, there is rarely effective remedy that can be used to reverse or prevent the pathological course up to date. Search for novel anti-ischemia neuroprotective drugs is very important for prevention or treatment of vascular dementia. Icariin, the major active component of traditional Chinese herb "Yinyanghuo", has been revealed that it possesses various important pharmacological effects, such as promoting cerebral blood flow, improving circulation, regulating immunity,affecting endocrine and anti-aging effect. There is a possibility that icariin may have a beneficial role for neurons in cerebral ischemia/reperfusion caused by accident. However, it has been little known about this effect as yet. In this study we investigate the protective effects of icariin on neurons injured by cerebral ischemia / reperfusion and further explore its possible protective mechanisms at the levels of entirety, cell, subcell, and molecular. Our object is to illustrate the mechanisms of icariin against cerebral ischemia /reperfusion injury and hope to find novel neuro- protective drug that can decrease the neuron damages induced by ischemia/ reperfusion. Methods: (1) In order to observe the protective effects of icariin on neurons treated by ischemia/ reperfusion in vitro and investigate its protection mechanisms, primary culture cerebral cortical neurons of Wistar rats were studied during the different period of oxygen-glucose deprivation / reperfusion with oxygen and glucose. MTT assay was used to determine cell viability,and the activity of lactate dehydrogenase (LDH) leaked from neurons, pathological changes of neurons and cell apoptosis were measured, as well as concentration of intracellular free calcium were also evaluated,respectively. (2) The mice model of transient cerebral ischemia/reperfusion was made by bilateral occlusion of common carotid arteries and ischemic hypotension for 20 min before reperfusion to investigate the protective effects of icariin on mice injured by transient cerebral ischemia/ reperfusion in vivo. The changes of mice behavioral (locomotive activity, passive learning and memory ability and spatial learning and memory ability) and pathological changes were detected, respectively. And to further investigate the possible mechanisms of icariin, based on the results above the total anti-oxidant capacity, the activity of superoxide dismutase (SOD), the content of malondialdehyde (MDA), the activity of acetylcholinesterase (AchE), the activity of choline acetyltransferse (ChAT), and the changes of ultrastructure in brain tissue were measured, respectively. (3) The injury model of mitochondria induced by oxygen free radical was made by ferrous sulfate/ ascorbic acid (Fe2+/VitC) in vitro. To investigate the protective effects of icariin, the swelling and the activities of complexⅠ-Ⅳ, as well as the content of MDA of mitochondria injured bydifferent concentration Fe2+/VitC were measured,respectively. (4) In order to investigate the effects of cerebral ischemia/ reperfusion on the expression of cytochrome C oxidase subunit Ⅱ (COⅡ) mRNA and the effects of icariin, the mice model of transient cerebral ischemia/ reperfusion was made by similar method above. The changes of the expression of COⅡ mRNA were measured at different reperfusion time points by RT – PCR . Results: (1) During the different period of oxygen-glucose deprivation (4, 6, 8h) or oxygen-glucose deprivation (6h)/ reperfusion with oxygen and glucose (3, 12, 24h) incubation in...