Curcumin, a major component of turmeric, a seasoning commonly used in Indian food, and a known antioxidant, anti-inflammatory and anti-carcinogenic agent, is a potent stimulator of the stress-induced expression of Hsp27, alphaB crystallin and Hsp70. When C6 rat glioma cells were exposed to arsenite (100 microM for 1 h), CdCl2 (100 microM for 1 h) or heat (42 degrees C for 30 min) in the presence of 3-10 microM curcumin, induction of the synthesis of all three proteins was markedly stimulated, as detected by specific immunoassays, Western blot analysis and Northern blot analysis. A gel mobility shift assay revealed that curcumin prolonged the stress-induced activation of the heat shock element-binding (HSE-binding) activity of heat shock transcription factor (Hsf) in the cultured cells. The stimulatory effect of curcumin on the responses to stress was also observed in BRL-3A rat liver cells and Swiss 3T3 mouse fibroblasts. Induction of Hsp27, alphaB crystallin and Hsp70 in the liver and adrenal glands of heat-stressed (42 degrees C for 20 min) rats was also enhanced by prior injection of curcumin (20 mg/kg body weight). As curcumin is a potent inhibitor of arachidonic acid metabolism, it is suggested that the mechanism of the stimulation by curcumin of the stress responses might be similar to that of salicylate, indomethacin and nordihydroguaiaretic acid.