UVB-induced IL-18 production in human keratinocyte cell line NCTC 2544 through NF-kappaB activation

In the present study, we investigated the implication of NF-kappaB in the production of pro-inflammatory cytokine IL-18 by human keratinocytes stimulated by UVB. We demonstrated that NCTC 2544 keratinocyte cell line irradiated by UVB enhanced the IL-18 mRNA and protein secretion under its bioactive form. Overexpression of IL-18 by UVB irradiation was accompanied by NF-kappaB transcription factor activation using specific IL-18 gene sequence corresponding to NF-kappaB DNA binding site. The relationship between these transcription factors and IL-18 expression was confirmed using curcumin and PDTC, two inhibitors of NF-kappaB. Our results show that UVB and curcumin or PDTC co-treatment led to a down-regulation of IL-18 expression associated with an inhibition of NF-kappaB DNA binding. Hence, our results demonstrated that this transcription factor is implicated in biologically active IL-18 production by human keratinocytes irradiated by UVB.