MECHANISM OF SUGAR CATARACT FORMATION IN LENS CELLS

描述：(调查员摘要)。牛晶状体上皮细胞 暴露在高半乳糖或高血糖条件下的(BLEC)提供 用于检查机制的方便的生理替代物 参与白内障的形成和糖尿病的早期发病 体内细胞培养模型中的并发症。在其中扮演的确切角色 高环境糖在糖尿病并发症发病中的作用尚不清楚 但也不能忽视对醛糖还原酶的管理 抑制剂可预防或逆转上述“并发症”。然而， 任何通过多元醇讨论糖尿病并发症发病的模型 蓄积还必须考虑到许多组织不会蓄积 山梨醇的含量足够高，足以起到渗透作用。 因此，任何解释都必须为参与其中提供机制基础。 但也要从低的角度来讨论这一点 聚合醇的浓度。这项研究将整合 “多元醇”假说与“肌醇消耗”假说 方式更适用于发现糖尿病人晶状体的情况。 这项拨款建议的具体目的是确定：(1) 谷胱甘肽合成酶活性降低的机制 培养的牛晶状体上皮细胞对高血糖的暴露 条件。(2)减少是否导致谷胱甘肽耗竭 谷胱甘肽合成酶活性促进肌醇减少 摄取和Na-K-ATPase活性降低，(3)如果 Na-K-ATPase活性降低或膜通透性降低 在细胞内钠的积累中导致大量的 细胞外水分和肌醇摄取的减少，(4)如果 肌醇摄取和/或Na-K-ATPase活性下降干扰 正常的磷脂酰肌醇周转导致磷脂的释放受损 第二信使，LNS(L，4，5)P3和二酰甘油(DAG)，(5)如果 细胞内释放的DAG减少对蛋白激酶产生不利影响 C(PKC)活性进一步破坏Na-K-ATPase活性。(6)是否 高血糖暴露会导致脂代谢紊乱和 减少前列腺素产物的形成，以及(7)如果抑制 高血糖条件下的PGH合成酶活性增强 替代花生四烯酸含氧代谢物，特别是12 (R)-HETE，已知的Na-K-ATPase抑制剂。因此，生化缺陷 在这些相互关联的任何一个层面上都可能有助于 白内障的形成或糖尿病并发症的发病。而且，我们的 工作假说不依赖于高浓度的细胞内 用多元醇解释与高血糖相关的水流入 而是假设细胞内钠的积累 导致离子失衡和细胞水合和肿胀。镜头 上皮细胞系统将提供一个有用的模型来确定 持续的高半乳糖血症或 高血糖与醛糖还原酶抑制剂的调节。

DESCRIPTION: (Investigator's Abstract). Bovine lens epithelial cells (BLECs) exposed to hypergalactosemic or hyperglycemic conditions provide a convenient physiological surrogate with which to examine the mechanisms involved in cataract formation and the early onset of diabetic complications in an in vivo cell culture model. The precise role in which high ambient sugars play in the onset of diabetic complications is obscure but cannot be overlooked as the administration of aldose reductase inhibitors prevent or reverse the aforementioned "complications". However, any model which discusses the onset of diabetic complications via polyol accumulation must also consider that many tissues do not accumulate sorbitol to an adequately high enough level to exert an osmotic effect. Hence any explanation must provide a mechanistic basis for the involvement of the aldose reductase reaction but also discuss this in terms of low concentration of accumulated polyols. This study will integrate the "polyol" hypothesis with the "myo-inositol depletion" hypothesis in a manner more applicable to the situation found in the diabetic human lens. The specific aims of this grant proposal are to determine: (1) the mechanism of reduction in activity of glutathione synthetase as mediated by exposure of cultured bovine lens epithelial cells to hyperglycemic conditions. (2) whether glutathione depletion resulting from the reduction in activity of glutathione synthetase promotes decreased myo-inositol uptake and a reduction in Na+-K+-ATPase activity, (3) if an alteration in Na+-membrane permeability or a reduction in Na+-K+-ATPase activity results in an accumulation of intracellular sodium which leads to an influx of extracellular water and a decrease in myo-inositol uptake, (4) if a decrease in myo-inositol uptake and/or Na+-K+-ATPase activity disturbs normal phosphoinositide turnover resulting in the compromised release of the second messengers, lns(l,4,5)P3 and diacylglycerol (DAG), (5) if a decrease in released intracellular DAG adversely affects protein kinase C(PKC) activity further destabilizing Na+-K+-ATPase activity. (6) whether hyperglycemic exposure leads to dysfunctional lipid metabolism and decreased prostaglandin product formation, and (7) if the suppression of PGH synthase activity as mediated by hyperglycemic conditions, augments alternative arachidonate oxygenated metabolites, in particular, 12 (R)-HETE, a known inhibitor of Na+-K+-ATPase. Hence, a biochemical deficit at any one of these interrelated levels could potentially contribute to cataract formation or the onset of diabetic complications. Moreover, our working hypothesis does not rely on a high concentration of intracellular polyol to explain the influx of water associated with hyperglycemic exposure, but rather assumes that the accumulation of intracellular sodium leads to ionic imbalance and cell hydration and swelling. The lens epithelial cell system will provide a useful model for determining the biochemical deficits resulting from sustained hypergalactosemia or hyperglycemia and regulation by aldose reductase inhibitors.