Heat shock protein expression in adenosine triphosphate depleted renal epithelial cells

Abstract

Background: In this study, the putative interactions between apoptosis and heat shock proteins disturbed as a result of ATP depletion were investigated as a hypoxia model.

Methods: The direct cellular damages were assessed by the release of LDH from the cytoplasm of the human tubular epithelial cells (HK-2 cells) following ATP depletion. The Bcl-2/Bax mRNA expression ratio, used as an index to assess to what extent apoptosis contributed to tubular cell damage, and the expressions of HSP 90, 72 and 27 in relation to the Bcl-2/Bax ratio in the ischemic model, as parameters of their functional contributions to tubule cell damage, were also studied. Heat preconditioning (HS) was performed at 43 degrees C in a temperature-regulated water bath for 1 h.

Results: The release of LDH due to ATP depletion was not significantly increased in HK-2 cells compared to the control, but was slightly increased in heat preconditioned cells compared to non heat preconditioned cells, but the difference was not statistically significant (6.33 +/- 0.57 U/L vs. 8.67 +/- 2.52 U/L, p>0.05). The Bcl-2/ Bax mRNA expression ratio increased progressively from the control to the heat preconditioned and ATP depleted cells (control; 100%, ATP depletion; 154 +/- 6%, heat preconditioning; 212 +/- 6%, heat preconditioning and ATP depletion; 421 +/- 8%). No contribution of heat preconditioning and ATP depletion was observed on the expressions of HSP90 and HSP27. However, HSP72 expression was prominent by ATP depletion, especially after heat preconditioning.

Conclusion: There may be a possibility that the preservation of cytolytic damage and an increase in the Bcl-2/Bax mRNA expression ratio is related to the increase of HSP72 in ATP depletion as a hypoxia model.

Figure 1.

HSP72 (upper panel) and GAPDH (lower panel) expressions prior to and after heat preconditioning under ATP depletion. (ATPD, ATP depletion; HS, heat preconditioning).

Figure 2.

Western blotting for HSP90 (A), HSP72 (B) and HSP27 (C). (MM, Molecular marker; ATPD, 12 h after ATP depletion; HS+ATPD, 12 h after ATP depletion + heat preconditioning)