Prostaglandins stimulate the stress-induced synthesis of hsp27 and alpha B crystallin

The effects were examined of various prostaglandins (prostaglandin A(1), A(2), J(2), E-2, and D-2) on the stress-induced accumulation of hsp27 and alpha B crystallin in C6 rat glioma cells. The levels of hsp27 and alpha B crystallin, which were determined by specific immunoassays, were low in cells in confluent cultures. The levels of the two proteins increased after exposure of cells to heat (42 degrees C for 30 min) or arsenite (50 mu M for 1 h). Cells exposed to 10 mu M each of prostaglandin A(1), A(2), or J(2) for 1 h resulted in stimulation of the binding to the heat shock element (HSE) of heat shock transcription factor (HSF). However, there was no phosphorylation-dependent mobility shift of HSF1 and no subsequent increase in the transcription and translation for hsp27, alpha B crystallin, and hsp70. When cells were exposed to arsenite in the presence of 10-40 mu M prostaglandin, the accumulation of hsp27 and alpha B crystallin in cells was enhanced markedly. The levels of hsp70 also increased in cells that had been treated with arsenite in the presence of a prosta glandin, as estimated by Western blot analysis. Northern blot analysis revealed that the expression of messenger RNAs (mRNAs) for hsp27, alpha B crystallin, and hsp70 was enhanced in cells that had been exposed to arsenite in the presence of each prostaglandin. Similar stimulatory effects of prostaglandins also were observed in the case of the heat-induced responses of hsp27, alpha B crystallin, and hsp70. Gel mobility shift assays revealed that each prostaglandin prolonged the arsenite-induced binding of HSF to HSE. These results suggest that the pharmacological dose of prostaglandins stimulates the stress-induced synthesis of stress proteins via activation of the HSF. (C) 1997 Wiley-Liss, Inc.