Curcumin's Biphasic Hormetic Response on Proteasome Activity and Heat-Shock Protein Synthesis in Human Keratinocytes
Abstract:?Curcumin (diferuloylmethane), is a component of the yellow powder prepared from the roots of Curcuma longa (Zingiberaceae), also known as tumeric or turmeric. It is widely cultivated and used as a food ingredient in tropical areas of Asia and Central America. Treatment of mid-passage human epidermal keratinocytes with curcumin resulted in a biphasic hormetic doseresponse with respect to proteasome activity. Curcumin treatment (up to 1 ?M for 24 h) increased chymotrypsin-like activity by 46% compared to that in untreated keratinocytes. However, higher concentrations of curcumin were inhibitory, and at 10 ?M the proteasome activity decreased to 46% of its initial value. Furthermore, the preincubation of human keratinocytes at 43C for 1 h, followed by 24-h treatment with 3 ?M curcumin, led to an increase in heat-shock protein (hsp70 and hsp90) levels by 24% and 19%, respectively, and the effect was sustained at concentrations up to 10 ?M. On the other hand, the level of the small hsp27 was unaffected by curcumin concentrations of 0.31 ?M, while it decreased by 34% at 10 ?M.
aging hormesis hormetin heat shock stress protein degradation