The aim of this study was to investigate whether nicotinamide (NCT) was able to exert anti-inflammatory as well as non-melanoma skin cancer (NMSC) chemoprevention properties by modulating the cutaneous expression of cyclooxygenase (COX-2) after ultraviolet (UV)-irradiation. For this purpose, immortalized human keratinocytes were pre-incubated with different doses of NCT (0.1, 2.5 and 10mM) for 2h and irradiated in PBS with UVB 10 and 60 mJ/cm2. COX-2 gene expression was assessed after 6 and 24h, whereas protein levels were measured in cell lysates 24h after irradiation. Our results showed that NCT, at all tested concentrations, strongly down-regulated COX-2 mRNA and protein levels 24h after irradiation with UVB 10 mJ/cm2. Irradiation with UVB 60 mJ/cm2 resulted in a lower COX-2 increase, nevertheless NCT was able to reduce its expression. Taken together, these data addict another important tessera to the complex mosaic of vitamin B3 action mechanism, confirming our hypothesis that NCT efficacy against UV-induced skin damages could occur through COX-2 modulation.

Scientific rationale underlying the use of nicotinamide in actinic keratosis