Potential efficacy of imiquimod on immunity-related cytokines in murine skin in vivo and in human Langerhans cells in vitro

Introduction Imiquimod, an immune-response modifier, has been proven to be clinically effective in the treatment of viral infections and skin cancers, but its mechanism of action remains poorly understood. This study aimed to assess the effects of imiquimod on the expression of three immunity-related cytokines, TNF-a, IL-1 beta, and IL-6. Materials and methods Female BALB/C mice were treated for seven days with topical 1% imiquimod cream; they were then killed and skin samples were snap-frozen. In the in vitro studies, both purified LCs and HaCaT cells were incubated with 5 mu g/ml imiquimod for four hours. In all samples, the mRNA levels of TNF-a, IL-1 beta, and IL-6 were then detected by reverse transcription polymerase chain reaction, and the secretion levels were determined by an enzyme-linked immunosorbent assay. Results Imiquimod upregulated the mRNA and protein expression levels of TNF-a, IL-1 beta, and IL-6 in the skin of imiquimod-treated BALB/C mice and in human LCs, compared with untreated controls (P < 0.05). However, there was no significant difference in the expression of these cytokines in imiquimod-treated and untreated HaCaT cells. Conclusions These findings indicate that imiquimod increased the expression of TNF-a, IL-1 beta, and IL-6 in skin and that the target cell of imiquimod may be the LCs but is unlikely to be the epidermal keratinocytes.