664 Pro-energetics creatine and nicotinamide prevent stress-induced senescence in human dermal fibroblasts

Senescence is the process by which cells irreversibly avoid dividing without undergoing cell death and enter a state of irreversible growth arrest. Fibroblast senescence associated with aging is known to contribute to the increased incidence of non-melanoma skin cancer in the aged population. To that end, agents that can inhibit fibroblast senescence could be protective. Senescence can be induced by various cellular stressors such as DNA damage, oncogenic activation and oxidative stress. Hydrogen peroxide (H2O2), ultraviolet light, tert-butyl hydroperoxide, and hyperoxia are pro-oxidative stressors which are used experimentally to induce premature senescence. The present studies were designed to test if the pro-energetics creatine and nicotinamide can block H2O2-induced senescence in primary cultures of human fibroblasts in vitro. Short-term exposure of fibroblasts with H2O2 followed by a three day incubation resulted in senescence as denoted by increased b-galactosidase (b-gal) staining, increased P21 expression, decreased insulin-like growth factor-1 and increased expression of pro-inflammatory cytokines IL-6, IL-8 and TNFa. Pretreatment with creatine and nicotinamide blocked experimental senescence as measured by normalization of all these parameters associated with experimental senescence. Of interest, post-treatment with creatine or nicotinamide following H2O2 had no effect on oxidant-induced senescence. Creatine and nicotinamide pre-treatment also blocked H2O2-mediated increased levels of reactive oxygen species, providing a potential mechanism for their protective effects. These studies suggest that creatine and nicotinamide could have clinical use in preventing fibroblast senescence