Zager Richard A, Johnson Ali, Hanson Sherry, dela Rosa Vivian
Department of Medicine, University of Washington, and Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
Kidney Int. 2002 May;61(5):1674-83. doi: 10.1046/j.1523-1755.2002.00316.x.
Renal cortical/proximal tubule cholesterol accumulation, with preferential localization within plasma membrane "detergent resistant microdomains" (DRMs: rafts/caveolae), is a hallmark of the maintenance phase of acute renal failure (ARF). This study addressed two related issues: (1) Are maintenance-phase cholesterol increases accompanied by an up-regulation of caveolin, a DRM/caveolar-associated cholesterol binding protein? (2) Is DRM cholesterol/caveolin homeostasis acutely altered during the induction phase of ARF?
Mouse kidneys were subjected to ischemia +/- reperfusion (I/R) followed by assessment of cholesterol DRM partitioning. Acute cell injury effects on potential caveolin release from isolated proximal tubules or into urine also were assessed. Finally, renal cortical/isolated proximal tubule caveolin levels were determined 18 hours after I/R or myoglobinuric ARF.
Acute ischemia causes a rapid shift of cholesterol into cortical DRMs (>22%). Cholesterol migration into DRMs also was observed in ATP-depleted cultured proximal tubule (HK-2) cells. Acute hypoxic or toxic tubule injury induced plasma membrane caveolin release (Western blot). By the maintenance phase of ARF, marked renal cortical/proximal tubule caveolin increases resulted.
Acute proximal tubular injury damages caveolar/DRM structures, as determined by cholesterol maldistribution and caveolin release. Post-injury, there is a dramatic up-regulation of renal cortical/proximal tubule caveolin, suggesting an increased caveolar mass. These findings indicate, to our knowledge for the first time, that dysregulation of caveolae/raft microdomain expression is a correlate of, and potential participant in, the induction and maintenance phases of ischemic and toxic forms of experimental ARF.
肾皮质/近端小管胆固醇蓄积，且优先定位于质膜“抗去污剂微区”（DRMs：脂筏/小窝）内，是急性肾衰竭（ARF）维持期的一个标志。本研究探讨了两个相关问题：（1）维持期胆固醇增加是否伴随着小窝蛋白（一种与DRM/小窝相关的胆固醇结合蛋白）的上调？（2）在ARF诱导期，DRM胆固醇/小窝蛋白的稳态是否会急性改变？
对小鼠肾脏进行缺血加/减再灌注（I/R），随后评估胆固醇在DRM中的分配情况。还评估了急性细胞损伤对从分离的近端小管释放到尿液中的潜在小窝蛋白的影响。最后，在I/R或肌红蛋白尿性ARF 18小时后测定肾皮质/分离的近端小管中小窝蛋白的水平。
急性缺血导致胆固醇快速转移至皮质DRMs（>22%）。在ATP耗竭的培养近端小管（HK-2）细胞中也观察到胆固醇向DRMs迁移。急性缺氧或毒性小管损伤诱导质膜小窝蛋白释放（蛋白质印迹法）。到ARF维持期时，肾皮质/近端小管中小窝蛋白显著增加。
急性近端小管损伤破坏了小窝/DRM结构，这由胆固醇分布不均和小窝蛋白释放所确定。损伤后，肾皮质/近端小管中小窝蛋白显著上调，提示小窝质量增加。据我们所知，这些发现首次表明小窝/脂筏微区表达失调是实验性ARF缺血性和中毒性形式诱导期及维持期的一个相关因素和潜在参与者。
