Today's H2S ... Thought of the Day !H2S protects against stress-induced cellular senescence by initiating antioxidant responses and inhibition of mitochondrial ROS production. Others demonstrated that H2S induced the S-sulfhydration of MEK1, leading to PARP-1 activation and DNA damage repair, protecting cells from senescence. Caloric restriction, reported to decelerate the biological aging process, maintained normal H2S levels, reduced oxidative stress-induced cellular senescence and promoted cellular cyto-protective systems. In addition, deficiency of CSE in mouse embryonic fibroblasts led to early development of cellular senescence, under-scoring the regulative role of H2S signaling in senescence."