Retinol, at concentrations greater than the physiological limit, induces oxidative stress and apoptosis in human dermal fibroblasts

We have investigated the dose (in the range of muM) and time-dependent effects of four different retinoids (retinol, retinal, retinoic acid and retinol palmitate) on human dermal fibroblasts cultivated in vitro. Retinol and retinal, at a concentration of 20 muM, caused cell damage as evaluated by lactate dehydrogenase activity released into the culture medium. The oxidised glutathione (GSSG)/reduced glutathione (GSH) ratio and malondialdehyde production indicated that 20 muM of retinol provoked oxidative stress in the cultivated human fibroblasts. In the first 8 h after retinol treatment the levels of p53 and Bax proteins as well as caspase 3 activity increased, suggesting apoptotic cell death during the first hours of treatment. If the retinol treatment exceeded 18-24 h we observed necrotic cell death. Vitamin E and coenzyme Q(10) had a protective effect against oxidative stress generated by retinol. Both antioxidant molecules reduced retinol uptake, and in the case of vitamin E the expression of CRABP-II mRNA was induced, providing a plausible explanation for its protective effect.