Megyesi J, Di Mari J, Udvarhelyi N, Price P M, Safirstein R
Department of Internal Medicine, University of Texas Medical Branch at Galveston, USA.
Kidney Int. 1995 Nov;48(5):1451-8. doi: 10.1038/ki.1995.434.
The response of the kidney to ischemic injury includes increased DNA synthesis, which is preceded by rapid and brief expression of the c-fos proto-oncogene. While the timing of these two events would suggest that c-Fos participates in an immediate-early gene program leading to proliferation, no direct test of this hypothesis exists. The purpose of these studies was (1) to determine whether c-fos is expressed as part of a typical immediate-early (IE) gene response, which would require co-expression of c-jun and sensitivity to cycloheximide, and (2) to determine whether the cells expressing c-Fos are the same as those undergoing DNA synthesis. Northern analysis was performed on renal mRNA at different times following release of a 50 minute period of renal hilar clamping. c-jun and c-fos mRNA were rapidly and briefly expressed following renal ischemia and their expression was superinduced by cycloheximide in a manner typical of an immediate-early gene response. 3H-thymidine autoradiography performed on semi-thin sections from intravascularly perfusion fixed kidneys 24 hours following induction of ischemia showed labeled nuclei in cells lining the damaged proximal tubules of the outer stripe of the outer medulla, as well as proximal tubules in the cortex and interstitial cells throughout the kidney. However, immunohistochemical localization of c-Fos and c-Jun protein occurred predominantly in nuclei of the thick ascending limb, distal tubule and collecting duct cells. The studies demonstrate that c-fos and c-jun are expressed following renal ischemia as a typical immediate-early gene response, but they are expressed in cells that do not enter the cell cycle. The failure of the cells to enter the cell cycle may depend on the co-expression of jun-B and jun-D, which suppress the mitogenic activity of c-Jun in other cells. The data suggest that the IE response following renal ischemia is part of the stress response, which is antiproliferative rather than proliferative. The role of the stress response during renal ischemia and the fate of the cells undergoing it are unknown.
肾脏对缺血性损伤的反应包括DNA合成增加，这之前c-fos原癌基因会有快速且短暂的表达。虽然这两个事件的发生时间表明c-Fos参与了导致增殖的早期即刻基因程序，但尚无对这一假说的直接验证。这些研究的目的是：（1）确定c-fos是否作为典型的早期即刻（IE）基因反应的一部分而表达，这需要c-jun的共表达以及对放线菌酮敏感；（2）确定表达c-Fos的细胞是否与进行DNA合成的细胞相同。在肾蒂钳夹50分钟后不同时间，对肾mRNA进行Northern分析。肾缺血后c-jun和c-fos mRNA快速且短暂表达，并且它们的表达以典型的早期即刻基因反应方式被放线菌酮超诱导。在缺血诱导24小时后，对经血管内灌注固定的肾脏半薄切片进行3H-胸腺嘧啶放射自显影，结果显示在外髓质外带受损近端小管的内衬细胞、皮质中的近端小管以及整个肾脏的间质细胞中存在标记的细胞核。然而，c-Fos和c-Jun蛋白的免疫组化定位主要出现在厚壁升支、远曲小管和集合管细胞的细胞核中。这些研究表明，肾缺血后c-fos和c-jun作为典型的早期即刻基因反应而表达，但它们在不进入细胞周期的细胞中表达。细胞未能进入细胞周期可能取决于jun-B和jun-D的共表达，它们会抑制其他细胞中c-Jun的促有丝分裂活性。数据表明，肾缺血后的IE反应是应激反应的一部分，该应激反应是抗增殖而非增殖性的。肾缺血期间应激反应的作用以及经历该反应的细胞的命运尚不清楚。
