Mupirocin blocks imiquimod-induced psoriasis-like skin lesion by inhibiting epidermal isoleucyl-tRNA synthetase.

BACKGROUND: The Isoleucyl-tRNA synthetase (IARS) catalyzes isoleucine to the corresponding tRNA, maintaining the accuracy of gene translation. Its role in psoriasis has been not investigated so far. In this study, we aimed to investigate the mechanisms underlying the efficacy of IARS inhibitor, mupirocin, treatment for psoriasis. METHODS: The expression of IARS was determined by immunofluorescence, Western blot and qRT-PCR in normal healthy control- and psoriatic human skin. An imiquimod (IMQ) -induced psoriasis-like skin disease model was used to study the phenotypes changed by an IARS inhibitor, mupirocin (MUP). Endotypes were analyzed by RNA-seq, R&D Luminex multi-factor technique, ELISA, immunofluorescence and flow cytometry. Additionally, the effect of MUP on epidermal keratinocytes (KCs) were conducted in-vitro in primary cultured human KCs. RESULTS: We found the expression of IARS was higher in psoriatic skin than in healthy controls. In IMQ-induced psoriasis-like C57BL/6 J mouse model, MUP reversed IMQ-induced keratinocytes proliferation, expression of inflammatory cytokines and infiltration of immune cells. Furthermore, in cultured human keratinocytes, MUP inhibited proliferation, but promoted apoptosis, which may be related with STAT3 signaling pathway. CONCLUSION: Our finding of blocking the infiltration of immune cells by inhibiting the formation of IARS, could be one mechanism to explain the effect of MUP in the treatment of psoriasis. Developing strategies targeting suppression IARS should open new perspectives for the treatment of psoriasis. Video Abstract.