Cukiernik Mark, Hileeto Denise, Downey Donal, Evans Terry, Khan Zia Ali, Karmazyn Morris, Chakrabarti Subrata
University of Western Ontario, Department of Pathology, Canada.
Diabetes Metab Res Rev. 2004 Jan-Feb;20(1):61-71. doi: 10.1002/dmrr.421.
The sodium hydrogen exchanger (NHE) is a transmembrane protein responsible for alkalinization and control of intracellular acidosis by the removal of hydrogen and the subsequent influx of sodium. Our investigation attempts to determine the role of NHE-1 in the pathogenesis of early retinal microangiopathy due to diabetes.
Diabetes was induced in male Sprague-Dawley rats with a single intravenous streptozotocin injection (65 mg/kg). To examine the duration-dependent changes in NHE-1 expression, retinas from 1-, 6- and 12-week diabetic animals were analyzed. To examine the functional consequences of NHE-1 inhibition in comparison with good blood glucose control, diabetic rats were randomly assigned to poorly controlled diabetic, well-controlled diabetic, poorly controlled diabetic with cariporide groups and were compared with nondiabetic controls after six weeks. Cariporide is an orally active inhibitor of NHE-1 (6000 ppm in rat chow). At the end of the treatment period, color Doppler ultrasound was used to determine the resistivity index (RI) of the central retinal artery. The mRNA expression of endothelin (ET) isoforms 1 and 3, inducible and endothelial nitric oxide synthase (iNOS and eNOS respectively) and NHE-1 were examined. NHE-1 distribution was localized with immunohistochemistry.
All diabetic animals showed hyperglycemia, increased glycated hemoglobin and lower body weight gain compared to nondiabetic controls. Diabetes caused an increased RI, indicative of retinal vasoconstriction, which was corrected by both cariporide treatment and good glucose control. NHE-1 was localized in the endothelium of the retinal microvasculature and the neuronal and glial components. NHE-1 mRNA expression was unchanged after 1 week and increased after 6 and 12 weeks of diabetes. Furthermore, a diabetes-induced upregulation of ET-1 and ET-3 mRNA expression after six weeks was corrected with cariporide treatment. NHE-1 inhibition of diabetic animals upregulated iNOS mRNA levels, although expression of eNOS and iNOS mRNA were not altered in poorly controlled diabetes. Improved blood glucose control with higher doses of insulin also corrected diabetes-induced increased RI by upregulating eNOS and iNOS mRNA expression.
The results of the study suggest that NHE-1 may be involved in the regulation of several vasoactive modulators that contribute to functional alterations in diabetic retinal microangiopathy.
钠氢交换体（NHE）是一种跨膜蛋白，通过去除氢离子并随后使钠离子内流，负责细胞内碱化和酸中毒的控制。我们的研究旨在确定NHE-1在糖尿病所致早期视网膜微血管病变发病机制中的作用。
通过单次静脉注射链脲佐菌素（65mg/kg）诱导雄性Sprague-Dawley大鼠患糖尿病。为了研究NHE-1表达的时间依赖性变化，对糖尿病1周、6周和12周的动物视网膜进行分析。为了研究与良好血糖控制相比，NHE-1抑制的功能后果，将糖尿病大鼠随机分为血糖控制不佳的糖尿病组、血糖控制良好的糖尿病组、服用卡立泊来德的血糖控制不佳糖尿病组，并在6周后与非糖尿病对照组进行比较。卡立泊来德是一种口服活性NHE-1抑制剂（在大鼠饲料中含量为6000ppm）。在治疗期结束时，使用彩色多普勒超声测定视网膜中央动脉的阻力指数（RI）。检测内皮素（ET）1和3亚型、诱导型一氧化氮合酶和内皮型一氧化氮合酶（分别为iNOS和eNOS）以及NHE-1的mRNA表达。通过免疫组织化学确定NHE-1的分布。
与非糖尿病对照组相比，所有糖尿病动物均表现出高血糖、糖化血红蛋白升高和体重增加减少。糖尿病导致RI升高，表明视网膜血管收缩，卡立泊来德治疗和良好的血糖控制均可纠正这一情况。NHE-1定位于视网膜微血管的内皮以及神经元和神经胶质成分中。糖尿病1周后NHE-1 mRNA表达未改变，但在糖尿病6周和12周后升高。此外，卡立泊来德治疗纠正了糖尿病6周后诱导的ET-1和ET-3 mRNA表达上调。糖尿病动物的NHE-1抑制上调了iNOS mRNA水平，尽管在血糖控制不佳的糖尿病中eNOS和iNOS mRNA的表达未改变。高剂量胰岛素改善血糖控制也通过上调eNOS和iNOS mRNA表达纠正了糖尿病诱导的RI升高。
研究结果表明，NHE-1可能参与了几种血管活性调节剂的调节，这些调节剂导致糖尿病视网膜微血管病变的功能改变。
