The Role Of Keratin 17 As An Autoantigen In The Pathogenesis Of Psoriasis

Psoriasis is a common and chronic autoimmune disease. It is now believed to be a mixed Th1/Th17 cells-mediated disease. Interleukin 17 (IL-17), the main cytokine produced by Th17 cells, involved in the T cell-mediated disorder including psoriasis. IL-17 and IFN-γare believed to play a key role in the pathogenesis of psoriasis. IL-17 signaling pathway includes JAK/STAT, NF-κB and MAPK. The level of Keratin 17 (K17) expression has been recognized as a hallmark of psoriasis. K17 and the M protein of streptococcus share an ALEEAN amino acid sequence, which may be a major target for autoreactive T cells in psoriasis. The expression of K17 can be up-regulated in vitro by IFN-γvia STAT1 pathway. The interactions among IFN-γ,K17 and T cells act in the pathogenic process of psoriasis. K17 is regarded as a candidate autoantigen in psoriasis. Our previous studies have confirmed there was the K17/ T cells/ cytokine autoimmune loop working in the pathogenic process of psoriasis.In this study, we investigated the regulation of K17 expression by IL-17 in HaCaT cells. We proposed that IL-17 enhanced K17 expression in a dose-dependent manner. Moreover, IL-17 induced K17 expression via STAT1 and STAT3 pathways. Therefore, IL-17 may be associated with development of psoriasis through up-regulation of K17 production. Our researches were attempted to provide a more completely understanding of the immunological basis and provide the experimental references for specific biologic therapy of psoriasis.Main experiment methods and results were as follows:A. HaCaT cells were cultured in Dulbecco's Modified Eagle's Minimal Essential Medium (DMEM) with 10% fetal bovine serum (FBS) under a humidified atmosphere containing 5% CO2 at 37°C.B. We investigated the capacity of IL-17 in inducing K17 expression at concentrations of 10, 50, 250 and 500U/mL for 24~72h and used IFN-γ-treated HaCaT cells at 250 U/mL as positive control.C. The level of K17 expression was evaluated by real time RT-PCR, ELISA, Western blot, immunofluorescence staining and confocal microscopy.D. IL-17 treated HaCaT cells at optimal concentraition.E. The levels of STAT1, STAT3, phospho-STAT1 and phospho-STAT3 were analyzed by real time RT-PCR, ELISA, Western blot, immunofluorescence staining and confocal microscopy.F. HaCaT cells were treated with fludarabine or piceatannol for 2h hen, the level of K17 expression was detected by real time RT-PCR, ELISA, Western blot, immunofluorescence staining and confocal microscopy.The results demonstrated that IL-17 could up-regulate K17 expression in a dose-depentend manner via STAT1 and STAT3 signaling pathways.In summary, our results show for the first time that in a new pathway on regulation K17 expression, IL-17 induces K17 expression in keratinocytes through STAT1 and STAT3-dependent mechanism. IL-17 is an important cytokine in K17/ T cells/ cytokine autoimmune loop working in psoriasis. Our findings will help to elucidate the role of keratin 17 as an autoantigen in the autoimmune loop. It further provides molecular and cellular mechanisms underlying the pathogenesis of psoriasis.