SURVIVAL OF HUMAN EPIDERMAL-KERATINOCYTES AFTER SHORT-DURATION HIGH-TEMPERATURE - SYNTHESIS OF HSP70 AND IL-8

Thermal injury by short pulses (1-30 s) of relatively high temperature (50-68 degrees C) was investigated in normal human epidermal keratino cytes (NHEK). NHEK were cultured on plastic coverslips and dipped in m edium held at various temperatures. Survival assessed by methylthiazol tetrazolium reduction assay at 6 days postheating demonstrated an inv erse time-temperature relationship that indicated that most cells coul d survive after a 1-s, 60 degrees C exposure or a 30-s, 55 degrees C e xposure. Arrhenius plots of the data indicated major transition points for cell injury at 50 and 60 degrees C. Heat shock protein 70 (HSP70) and interleukin-8 (IL-8) were both induced by elevation of temperatur e between 50 and 60 degrees C for as short a time as 1 s. HSP70 synthe sis stimulated by short, high pulses of heat appeared to induce thermo tolerance. These results demonstrate that brief exposure to relatively high temperature can induce HSP70 and IL-8 synthesis in keratinocytes .