The influence of dexamethasone on Hsp70 level and association with glucocorticoid receptor in the liver of unstressed and heat-stressed rats

Summary: The aim of the present study was to examine the influence of dexamethasone on the levels of heat shock protein Hsp70 and glucocorticoid hormones receptor, as well as on the interaction of these two proteins in the liver cytosol and nuclei of unstressed and rats exposed to whole body hyperthermic stress. The results, obtained by quantitative immunoblotting, have shown that dexamethasone provoked a reduction of Hsp70 basal level and an increase in its stress-induced level in the nuclei, supporting the idea that this hormone may be a factor included in the regulation of Hsp70 level both under normal and stress conditions. The cytosolic reduction and nuclear elevation of the glucocorticoid hormones receptor level by dexamethasone were also observed. Coimmunopurification of Hsp70 and glucocorticoid hormones receptor has revealed that the changes of cytosolic and nuclear levels of the two examined proteins resulted in the changes of their interaction within the respective cellular compartments. Thus, 41 °C heat stress, was shown to cause at least two-fold elevation of Hsp70/GR ratio within the glucocorticoid hormones receptor heterocomplexes both in the presence and in the absence of dexamethasone. The results support the view that glucocorticoid hormones signaling pathway and heat shock system are interrelated.