MECHANISM OF SUGAR CATARACT FORMATION IN LENS CELLS

描述：（研究者的摘要）。 牛晶状体上皮细胞 （BLEC）暴露于高半乳糖血症或高血糖条件下可提供 方便的生理替代品来检查机制 参与白内障的形成和糖尿病的早期发病 体内细胞培养模型的并发症。 具体的角色是 高环境糖分在糖尿病并发症发生中的作用尚不清楚 但不能忽视醛糖还原酶的施用 抑制剂可以预防或逆转上述“并发症”。 然而， 任何通过多元醇讨论糖尿病并发症发生的模型 积累还必须考虑到许多组织不积累 山梨醇达到足够高的水平以发挥渗透作用。 因此，任何解释都必须为参与提供机制基础 醛糖还原酶反应，但也从低的角度讨论这一点 累积多元醇的浓度。 本研究将整合 “多元醇”假说与“肌醇耗尽”假说 方式更适用于发现糖尿病人晶状体的情况。 本拨款提案的具体目标是确定：(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暴露于高血糖 条件。 (2)是否因还原而导致谷胱甘肽耗竭 谷胱甘肽合成酶的活性促进肌醇减少 吸收和 Na -K -ATP 酶活性降低，(3) 如果改变 Na - 膜通透性或 Na - K - ATP 酶活性降低的结果 细胞内钠的积累导致 细胞外水和肌醇摄取减少，（4）如果 肌醇摄取减少和/或 Na -K -ATP 酶活性干扰 正常的磷酸肌醇周转导致释放受损 第二信使 lns(1,4,5)P3 和二酰基甘油 (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 -ATP 酶活性的稳定性。 (6) 是否 高血糖暴露会导致脂质代谢功能失调 减少前列腺素产物的形成，并且（7）如果抑制 高血糖条件介导的 PGH 合酶活性增强 替代花生四烯酸氧化代谢物，特别是 12 (R)-HETE，一种已知的 Na -K -ATP 酶抑制剂。 因此，生化缺陷 在这些相互关联的水平中的任何一个都可能有助于 白内障形成或糖尿病并发症的发生。 此外，我们的 工作假设不依赖于高浓度的细胞内 多元醇解释与高血糖相关的水流入 暴露，而是假设细胞内钠的积累 导致离子失衡以及细胞水合作用和肿胀。 镜头 上皮细胞系统将为确定 持续高半乳糖血症导致的生化缺陷或 高血糖和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.