IL-22-mediated microRNA-124-3p/GRB2 axis regulates hyperproliferation and inflammatory response of keratinocytes in psoriasis

Psoriasis is an inflammatory dermatosis that features overproliferation and inflammatory reaction of keratinocytes. A study reported that IL-22 is involved in the pathogenesis of psoriasis by mediating miR-124 to regulate the expression of fibroblast growth factor receptor 2 in keratinocytes. A microRNA may target multiple target genes. Therefore, we speculate that miR-124-3p may also target other downstream genes to affect IL -22-induced keratinocyte function. A possible target gene of miR-124-3p, growth factor receptor-bound protein 2 (GRB2), was screened by analyzing the target gene databases. GRB2 expression was elevated and miR-124-3p expression was decreased in psoriatic lesions compared to psoriatic adjacent normal skins and healthy controls. We performed the following cell experiments in the IL-22-stimulated HaCaT cell model. In keratinocytes transfected with the miR-124-3p mimics, GRB2 expression was significantly lower. We analyzed the regulation of keratinocyte proliferation by GRB2 and miR-124-3p. High levels of GRB2 promoted keratinocyte proliferation and expression of Ki67, PCNA, and K16, which were inhibited by low expression of GRB2. In addition, we found that the effect of GRB2 inhibitors on the proliferation and inflammatory response of keratinocytes was dose-dependent. Finally, we investigated the influence of GRB2 on inflammatory mediators in keratinocytes with the ELISA. After low expression of GRB2, the mRNA expression and secretion of the pro-inflammatory factor were suppressed. When both GRB2 and miR-124-3p were overexpressed, the cellular overproliferation and inflammation caused by GRB2 overexpression were significantly reversed by miR-124-3p. In summary, IL-22-mediated miR-124-3p regulates keratinocyte hyperproliferation and inflammatory response by suppressing GRB2 expression in psoriasis.