MDR1 IN HUMAN INTESTINE

MDR 1（多药耐药）是一种多功能的ATP依赖性泵， 从细胞质中运输各种不相关的物质， 细胞内积累。 MDR 1在许多正常的 包括肠上皮细胞的腔表面在内的组织， 数据表明，MDR 1起着对外源性物质屏障的部分作用。 我发现，有显着的个体差异，在 mdr 1 mRNA和蛋白在小肠中的表达。 而且我 已经表明，这种变化占了很大一部分， MDR 1底物的口服药代动力学的患者间差异， 环孢菌素A 我相信mdr 1表达的这种变化可能 影响MDR 1底物的口服清除率， 以前未被认识到的环境疾病的危险因素。 的 我要检验的第一个假设是肠道mdr 1的变异 表达主要是由于非遗传因素。 这种假设是 基于我的初步数据显示mdr 1在体外和体内都是可诱导的， 利福平在人体肠道内的作用。 在具体目标1中，我将确定 通过治疗在小肠和结肠中诱导mdr 1 mRNA和蛋白 用可疑的诱导物培养人肠外植体。 在特定 目标2，目标1中鉴定的诱导剂将通过以下方法进行体内试验： 在小肠和大肠活检组织中测量mdr 1的表达， 在4天无诱导剂饮食后从健康受试者通过内窥镜检查获得， 在用诱导剂短期治疗后再次进行。 肠外植体 将与诱导剂同时培养， 体内和体外结果的相关性。 我还将测试 饮食对健康大鼠肠道多药耐药基因表达的影响 志愿者的饮食中含有木炭烤牛肉，或者， 与保罗沃特金斯，葡萄柚汁（黄酮类化合物）。 mdr 1 mRNA水平 和蛋白质将在小肠和大肠活检中测定， 在研究入组时，在4天无诱导剂饮食后，以及在7天后， 测试饮食。 具体目标3将直接检验假设， 肠道mdr 1水平影响药物的吸收， 肠子 我将首先检查mdr 1表达水平是否影响 MDR 1底物的“吸收”阈值和速率， 环孢菌素A和长春碱，在培养的Caco-2细胞单层。 其次，我将确定是否在肠道的个体间变异， mdr 1表达与不同的口服药代动力学相关 他克莫司、咪达唑仑和炔雌醇（与Paul合作 Watkins和Alan Leichtman）。 我相信这些数据 研究将引导我对mdr 1的影响提出新的假设 外源性物质的吸收和环境风险的表达 疾病

MDR1 (multiple drug resistance) is a versatile ATP-dependent pump which transports a variety of unrelated substances from the cytoplasm to reduce their intracellular accumulation. MDR1 is expressed in many normal tissues including the luminal surface of intestinal epithelia where my data suggest that mdr1 functions as part of a barrier to xenobiotics. I have found there is significant interindividual variation in the expression of mdr1 mRNA and protein in the small bowel. Furthermore, I have shown this variability accounts for a significant portion of the interpatient differences in oral pharmacokinetics of the mdr1 substrate, cyclosporin A. I believe this variation in mdr1 expression is likely to affect the oral clearance of mdr1 substrates and may represent a previously unrecognized risk factor for environmental diseases. The first hypothesis I will test is that variation in intestinal mdr1 expression is largely due to non-genetic factors. This hypothesis is based on my preliminary data showing mdr1 is inducible in vitro and in vivo in human intestine by rifampin. In Specific Aim 1, I will identify inducers of mdr1 mRNA and protein in small bowel and colon by treating cultured human intestinal explants with suspected inducers. In Specific Aim 2, the inducers identified in Aim 1 will be tested in vivo by measuring mdr1 expression in small and large bowel biopsies obtained endoscopically from healthy subjects after a 4 day inducer free diet and again after short term treatment with an inducer. Intestinal explants from each subject will be simultaneously cultured with the inducer for correlation of in vivo and in vitro results. I will also test the effects of diet on intestinal mdr1 expression by placing healthy volunteers on diets containing charcoal broiled beef or, in collaboration with Paul Watkins, grapefruit juice (flavonoids). The level of mdr1 mRNA and protein will be determined in small and large bowel biopsies obtained at study entry, after a 4 day inducer free diet, and after 7 days on the test diet. Specific Aim 3 will directly test the hypothesis that the level of intestinal mdr1 influences the absorption of drugs in the intestine. I will first examine if the level of mdr1 expression affects the threshold and rate of "absorption" of the mdr1 substrates, cyclosporin A and vinblastine, across cultured Caco-2 cell monolayers. Second, I will determine whether interindividual variation in intestinal mdr1 expression correlates with the variable oral pharmacokinetics of tacrolimus, midazolam, and ethinyl estradiol (collaboration with Paul Watkins and Alan Leichtman). I am confident that the data from these studies will lead me to novel hypotheses regarding the effects of mdr1 expression on xenobiotic absorption and the risk of environmental diseases.