Hemistepsin A protects human keratinocytes against hydrogen peroxide-induced oxidative stress through activation of the Nrf2/HO-1 signaling pathway.

Hemistepsin A, a sesquiterpene lactone compound isolated from Hemistepta lyrata, has been identified a variety of pharmacological actions including anti-hepatotoxic, anti-inflammatory and anti-cancer activities. Nevertheless, the antioxidant effects of hemistepsin A and the underlying mechanisms have not been investigated properly. Therefore, in the present study, we investigated the protective effect of hemistepsin A against oxidative stress in HaCaT human keratinocytes. The results demonstrated that hemistepsin A suppressed 500 μM hydrogen peroxide (H2O2)-induced cytotoxicity and DNA damage by blocking ROS accumulation. 10 μM Hemistepsin A also prevented apoptosis by preventing the mitochondrial dysfunction and the cytosolic release of cytochrome c, reducing the rate of Bax/Bcl-2 expression, and decreasing the activation of caspase-9 and caspase-3, suggesting that hemistepsin A protected cells from H2O2-induced mitochondria-mediated apoptosis. In addition, hemistepsin A markedly promoted the activation of nuclear factor-erythroid-2-related factor 2 (Nrf2), which was associated with the enhanced expression and activity of heme oxygenase-1 (HO-1) in the presence of 500 μM H2O2. However, inhibiting the expression of HO-1 by artificially blocking the expression of Nrf2 or HO-1 using siRNA significantly eliminated the protective effect of hemistepsin A, indicating that hemistepsin A activates the Nrf2/HO-1 signaling pathway in HaCaT cells to protect against oxidative stress. Therefore, these results suggest that hemistepsin A may be useful as a potential therapeutic agent against various oxidative stress-related skin diseases.