Expression of microRNA-184 in keratinocytes represses argonaute 2.

Interleukin-22 (IL-22) is a proinflammatory cytokine that has been associated with the pathogenesis of inflammatory skin disorders. However, the impact of IL-22 on microRNA (miRNA) expression in epidermal keratinocytes is unknown. Here we show that IL-22 induces miR-184 in reconstituted human epidermis (RHE) and in the HaCaT keratinocyte cell line. Exposure to IL-22 increased miR-184 expression 8- and 15-fold in RHE and HaCaT cells, respectively. Oncostatin M, an unrelated proinflammatory cytokine, also raised miR-184 expression in RHE and HaCaT keratinocytes. Pharmacologic and genetic inhibition demonstrated that cytokine-induced expression of miR-184 was mediated by signal transducer and activation of transcription 3 (STAT3). Argonaute 2 (AGO2), a member of the RNA-induced silencing complex (RISC), is a predicted miR-184 target. Using protein, messenger RNA and reporter analyses, we found that miR-184 regulates the expression of AGO2. We conclude that cytokine-induced miR-184 attenuates AGO2 expression in keratinocytes.