Hormesis is an adaptive response to a variety of oxidative stresses that renders
cells resistant to harmful doses of stressing agents. Caffeic acid (CaA) is an
important antioxidant that has protective effects against DNA damage caused by
reactive oxygen species (ROS). However, whether CaA-induced protection is a hormetic
effect remains unknown, as is the molecular mechanism that is involved. We found that
a low concentration (10 μM) of CaA increased human liver L-02 cell viability,
attenuated hydrogen peroxide (H2O2)-mediated decreases in cell
viability, and decreased the extent of H2O2-induced DNA
double-strand breaks (DSBs). In L-02 cells exposed to H2O2, CaA
treatment reduced ROS levels, which might have played a protective role. CaA also
activated the extracellular signal-regulated kinase (ERK) signal pathway in a
time-dependent manner. Inhibition of ERK by its inhibitor U0126 or by its specific
small interfering RNA (siRNA) blocked the CaA-induced improvement in cell viability
and the protective effects against H2O2-mediated DNA damage.
This study adds to the understanding of the antioxidant effects of CaA by identifying
a novel molecular mechanism of enhanced cell viability and protection against DNA
damage.
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