Purification and characterization of HSP-inducers from Eupatorium lindleyanum

The expression of heat shock proteins (HSPs), particularly HSP70, provides resistance to stressors. We recently reported that ultraviolet (UV)-induced melanin production and skin damage were suppressed in transgenic mice expressing HSP70 and that an extract of Eupatorium lindleyanum induces the expression of HSP70 in cells. Here we report the purification of eupalinolide A and B (EA and EB) from E. lindleyanum, and describe their actions as HSP-inducers. EA and EB both induced the expression of HSP70 in cells at concentrations that did not significantly affect cell viability. Treatment of cells with EA or EB activated heat shock factor 1 (HSF1), while the artificial suppression of HSF1 expression diminished the EA- or EB-mediated induction of HSP70 expression. Furthermore, EB inhibited the interaction between HSF1 and HSP90, which is known to inhibit the activity of HSF1. These findings suggest that EA and EB induce the expression of HSP70 via the activation of HSF1 by inhibiting the interaction between HSF1 and HSP90. EA and EB both induced the expression of HSP70 synergistically with other stressors. Furthermore, pre-treatment of cells with EA or EB suppressed melanin production and stressor-induced apoptosis. These effects were suppressed by the artificial suppression of HSP70 expression. In vivo, the percutaneous administration of EB induced the expression of HSP70 and suppressed UVB radiation-induced damage, inflammatory responses and melanin production in the skin. These results suggest that EA and EB could be beneficial for use in cosmetics and medicines as a consequence of their inhibitory action on UV-induced skin damage and melanin production.