Cytokine modulation of retinoic acid-inducible gene-I (RIG-I) expression in human epidermal keratinocytes.
BACKGROUND: Retinoic acid-inducible gene-I (RIG-I) is a member of the DExH/D box family proteins and designated as a putative RNA helicase, which plays various roles in gene expression and cellular functions in response to a variety of RNA viruses. OBJECTIVE: The present study was designed to investigate the effects of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha on RIG-I expression in human keratinocytes, and the expression of RIG-I in skin lesions of psoriasis vulgaris, in which IFN-gamma and TNF-alpha are considered to be involved in its pathogenesis. METHODS: The mRNA and protein expression of RIG-I was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. Immunohistochemical staining of RIG-I was examined on psoriatic skin section. RESULTS: The levels of RIG-I mRNA and protein were upregulated in HaCaT keratinocytes in the presence of IFN-gamma or TNF-alpha. Immunohistochemically, RIG-I was detected in the cytoplasm of the spinous and basal layers of psoriatic skin. CONCLUSION: Our results suggest that RIG-I might operate not only as a RNA helicase but also as a mediator of the cytokine network in the inflammatory skin diseases, such as psoriasis vulgaris.