P38/ERK MAPK signaling pathways are involved in the regulation of filaggrin and involucrin by IL‑17.

Atopic dermatitis (AD) is characterized by a defective skin barrier, which increases the penetration of allergens and pathogens through the skin. The role of interleukin (IL)‑17, a pro‑inflammatory cytokine, in the pathogenesis of AD remains to be elucidated. The present study aimed to examine the effects of IL‑17 on skin barrier proteins in the HaCaT cell line. The expression levels of filaggrin (FLG) and involucrin (IVL) were evaluated by reverse transcription‑quantitative polymerase chain reaction and western blot analyses of the HaCaT cells following IL‑17 simulation. The role of IL‑17 was further examined by using small molecule inhibitors of extracellular signal‑regulated kinase (ERK) and P38. Treatment of the HaCaT cells with IL‑17 resulted in reduced expression levels of FLG and IVL at the mRNA and protein levels. In addition, the gene expression levels of FLG and IVL were significantly reduced in the HaCaT cells by IL‑4. Treatment with the mitogen‑activated protein kinase (MAPK) inhibitors, SB203580 and PD98059, significantly inhibited the effects of IL‑17 on the gene and protein expression levels of FLG and IVL. Finally, the protein levels of phosphorylated ERK and P38 were significantly increased following IL‑17 stimulation. Taken together, the results revealed that IL‑17 reduced the expression of FLG and IVL in HaCaT cells, and this effect involved the P38/ERK MAPK signaling pathways.