IMPAIRED GALLBLADDER CONTRACTION WITH GALLSTONES

胆结石导致胆囊收缩受损

• 批准号: 2391324
• 负责人: JOSE BEHAR
• 金额: $ 24.28万
• 依托单位: RHODE ISLAND HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1980
• 资助国家: 美国
• 起止时间: 1980-09-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2391324
• 关键词: G protein; biological signal transduction; calcium flux; cellular pathology; cholecystokinin; cholelithiasis; cholesterol; dietary lipid; disease /disorder prevention /control; gallbladder; guanosine triphosphate; human tissue; inositol phosphates; membrane activity; muscle contraction; muscle relaxation; nutrition related tag; protein kinase C; receptor binding; receptor coupling; receptor sensitivity; second messengers; smooth muscle; squirrel

Gallbladder stasis due to a defective muscle contraction is thought to play a permissive role in gallstone formation and growth and may be a major contributing factor in the recurrence of gallstones. This defective gallbladder contraction in humans and prairie dogs is associated with excess bile cholesterol and is characterized by a reduced response to receptor-dependent ligands such as CCK-8 and acetylcholine. CCK-8 does not fully activate available intracellular pathways of defective muscle cells that appear to be functionally normal. The contraction of control muscle cells induced by low concentrations of CCK-8 is mediated by PKC, whereas that induced by high concentrations is calmodulin dependent. In contrast, the contraction of defective muscle cells induced by all CCK-8 concentrations can only utilize the PKC pathway. The magnitude of contraction of these defective muscle cells is normalized when membrane receptors are circumvented by directly activating G proteins with GTPgammas or by utilizing second messengers such as IP3 and DAG or by calmodulin. These data suggest that the defect may lie in the signal transduction across the plasma membrane possibly due to excessive incorporation of cholesterol which could affect its lipid milieu and transmembrane proteins. This hypothesis is supported by our preliminary findings: 1) that normal muscle cells incubated with cholesterol-rich liposomes increased their cholesterol:phospholipid (Ch:P1) ratio in the plasma membrane and develop a defective contraction in response to CCK which is normalized when treated with GTPgammas; and, 2) that the abnormal Ch:P1 ratio and defective contraction of muscle cells from gallbladders with cholesterol stones are normalized after incubation with cholesterol-free liposomes. We therefore propose to investigate in control and defective muscle cells from human and prairie dog gallbladders: 1) the direct role of cholesterol in the pathogenesis of the defective muscle contraction and relaxation; 2) the generation of second messengers that mediate contraction and relaxation induced by receptor-dependent ligands and by agonists that circumvent membrane receptors; 3) the changes of the plasma membrane of control and defective muscle cells before and after incubation with cholesterol-rich and cholesterol-free liposomes by measuring its cholesterol:phospholipid ratio and membrane fluidity; 4) the functional abnormalities of membrane receptors in these defective muscle cells by measuring ligand binding, receptor-G protein coupling and receptor activation of G proteins; and, 5) whether these cholesterol associated muscle abnormalities are reversible in vitro after incubation with cholesterol-free liposomes and in vivo after cholesterol-free or low cholesterol diets.

由于肌肉收缩缺陷导致胆囊瘀滞被认为是起作用的 在胆结石形成和生长中起许可作用，可能是一个主要因素 是胆结石复发的重要因素。这个有缺陷的 人类和土拨鼠的胆囊收缩与 胆汁胆固醇过多，其特点是对胆汁胆固醇的反应降低 受体依赖性配体，例如 CCK-8 和乙酰胆碱。 CCK-8 没有 完全激活有缺陷的肌肉细胞的可用细胞内通路 看起来功能正常。控制肌的收缩 低浓度 CCK-8 诱导的细胞是由 PKC 介导的，而 高浓度诱导的钙调素依赖性。 相比之下， 所有 CCK-8 诱导的有缺陷的肌肉细胞收缩 浓度只能利用 PKC 途径。的大小 当膜出现时，这些有缺陷的肌肉细胞的收缩就会正常化 通过用 GTPgamma 直接激活 G 蛋白来绕过受体 或利用第二信使如 IP3 和 DAG 或钙调蛋白。 这些数据表明缺陷可能在于信号转导 穿过质膜可能是由于过量掺入 胆固醇可能会影响其脂质环境和跨膜蛋白。 我们的初步研究结果支持了这一假设：1）正常情况下 与富含胆固醇的脂质体一起孵育的肌肉细胞增加了 质膜中胆固醇：磷脂 (Ch:P1) 的比例并发育 对 CCK 反应的收缩缺陷在治疗后恢复正常 与 GTPgamma； 2) 异常的 Ch:P1 比率和缺陷 胆囊肌肉细胞因胆固醇结石而收缩 用无胆固醇脂质体孵育后标准化。 因此，我们建议研究对照和有缺陷的肌肉细胞 来自人类和土拨鼠胆囊：1）胆固醇的直接作用 肌肉收缩和舒张缺陷的发病机制； 2） 介导收缩和松弛的第二信使的产生 由受体依赖性配体和规避的激动剂诱导 膜受体； 3)控制质膜的变化 有缺陷的肌肉细胞与富含胆固醇的孵化前后 和无胆固醇脂质体通过测量其胆固醇：磷脂 比率和膜流动性； 4）膜的功能异常 通过测量配体结合来识别这些有缺陷的肌肉细胞中的受体， 受体-G 蛋白偶联和 G 蛋白受体激活；以及，5) 这些胆固醇相关的肌肉异常是否可逆 体外与无胆固醇脂质体孵育后和体内 无胆固醇或低胆固醇饮食。