Expression of hsp 90 in the human kidney and in proximal tubule cells exposed to heat, sodium arsenite and cadmium chloride

Abstract

The expression of heat shock protein (hsp) 90α and β mRNA and protein were determined in the human kidney and in human proximal tubule (HPT) cells exposed to lethal and sub-lethal concentrations of Cd +2 under both acute and extended conditions of exposure. Using immunohistochemical analysis, it was demonstrated that hsp 90 was widely distributed in the human adult and fetal kidney. Moderate to strong staining was observed in the straight portions of the distal and proximal tubules, the distal convoluted tubule, the collecting ducts and the parietal epithelium of Bowmans capsule in the glomerulus. Moderate staining was observed in the proximal convoluted tubule of the cortex and the thick loops of Henle within the medulla. In addition, the fetal kidney demonstrated strong staining of the blastema, the ‘S-shaped’ bodies, and the developing glomeruli. Analysis of hsp 90α and β mRNA expression in total RNA isolated from in situ microdissected proximal tubules or HPT cells demonstrated similar expression levels of both the α and β isoforms in this tubule segment. It was demonstrated that HPT cells exhibited the classic heat shock response when subjected to a physical (heat) or chemical stress (NaAsO 2). Heat stress, elevated temperature at 42.5 °C for 1 h, caused a modest increase in both hsp 90α and β mRNA and protein. Similar results were obtained when the cells were subjected to a classic chemical stress of exposure to 100 μM NaAsO 2 for 4 h. In contrast, acute exposure of HPT cells to 53.4 μM CdCl 2 for 4 h resulted in no consistent increase in hsp 90α and β mRNA or protein. Chronic exposure to Cd +2 likewise failed to increase either hsp 90 mRNA or protein expression, even at concentrations of Cd +2 that were lethal to the cells during the time course. This study shows that the HPT has a high basal expression of hsp 90, which is not induced by Cd +2 exposure.