PATH MECH /THERAPC STRAT /CELL MODELS /mtDNA MUTATIONS

MELAS是与mtDNA tRNALeu基因A3243G突变相关的最常见的线粒体疾病，以乳酸性酸中毒、中风、脑梗死和水肿为特征。MELAS患者脑卒中和水肿的发病机制尚不清楚。没有对病理生理学的正确理解，就不可能设计出合理的治疗方法。皮质血管中的线粒体功能障碍可能导致血脑屏障（BBB）的破坏。利用正常血脑屏障和MELAS血脑屏障体外模型，我们拟研究血脑屏障通透性功能、紧密连接、水通道和乳酸转运蛋白表达的变化，并将这些数据与呼吸链功能联系起来。我们有必要的野生型和突变细胞，我们已经证明了我们可以

MELAS is the most common mitochondrial disease associated with a A3243G mutation in the tRNALeu gene of the mtDNA, and characterized by lactic acidosis, strokes, cerebral infarction and edema. The pathogenesis of strokes and edema in MELAS patients is not understood. Without a proper understanding of the pathophysiology, it has not been possible to devise rational therapies. Mitochondrial dysfunction in the cortical blood vessels may perhaps cause a breakdown of the blood-brain barrier (BBB). Using in vitro models of normal and MELAS BBB, we propose to study alterations in permeability functions, expression of tight junctions, water channels and lactate transporters, and correlate the data with respiratory chain function. We have the necessary wild-type and mutant cells, and we have demonstrated that we can construct the normal BBB with tight junctions. Management of stroke in MELAS patients with steroids has been anecdotally effective. Glucocorticoids are effective in treatment of cerebral edema associated with brain tumors. But the mechanism by which they act is not clear. The in vitro BBB system is a dynamic model which can be manipulated to test the effect of steroids in regulating brain water content. We propose to study the effect of hydrocortisone, and its synthetic analog, dexamethasone, on paracellular permeability, using the MELAS BBB model. First, these studies will provide insights into the physiological mechanisms associated with the BBB. Secondly, they will reveal critical information regarding pathological changes in vascular permeability in MELAS due to mitochondrial dysfunction and energy shortage. The culture model will also allow us to evaluate the sequence of events leading to the increase in permeability. Finally, the in vitro model provides a flexible system to test therapeutic effectiveness of steroids in patients with this devastating illness.