Correlation of HSP70 Expression and Cell Viability Following Thermal Stimulation of Aortic Endothelial Cells

The goal of this study was to determine the kinetics of HSP70 expression and variations in cell viability resulting from thermal preconditioning of the heart. Experiments were conducted to determine combinations of elevated temperatures and brief heating durations that could produce enhanced HSP70 levels while maintaining high cell viability. Bovine aortic endothelial cells were heated with a water bath at temperatures ranging from 44–50°C and periods of 1–30 min consistent with anticipated protocols for cardiac preconditioning prior to surgery. Western blot and cell adhesion analysis in culture following heating were employed to determine HSP70 level and cell viability respectively. The results demonstrate that HSP70 expression and cell viability are not maximized simultaneously. To ensure cell viability greater than 90% required a heating protocol for which HSP70 expression was less than its maximum level. HSP70 expression increments from 2.3 to 3.6 times the value of the control can be achieved for thermal stimulation protocols varying from T = 46°C for 10 min to T = 50°C for 1 min while maintaining a cell viability of 90% or greater. An Arrhenius injury model was fit to the cell damage data yielding values for scaling and activation energy terms of A = 1.4×10⁶⁶ s⁻¹ and E_a = 4.1×10⁵ J/mole.