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

Abstract

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.

Figure 1.

Human HaCaT keratinocytes were treated with various concentrations of IL-17 for 24 h. Gene expression levels of (A) FLG and (B) IVL; protein levels of (C) FLG and (D) IVL. *P<0.05; **P<0.01; ***P<0.001 (n=4). FLG, filaggrin; IVL, involucrin; IL-17, interleukin-17.

Figure 2.

Effects of the IL-4 and IL-17 cytokines on the gene expression levels of (A) FLG and (B) IVL. *P<0.05; **P<0.01 (n=4). FLG, filaggrin; IVL, involucrin; IL, interleukin.

Figure 3.

P38 and ERK inhibitors inhibit the IL-17-mediated reduction of FLG and IVL. Phosphorylation levels of (A) P38 and (B) ERK were assessed using western blot analysis following treatment with IL-17 (100 ng/ml). (C) IL-17-induced reduction in the expression of FLG was partially inhibited by P38 and ERK inhibitors at the gene and protein levels. (D) IL-17-induced reduction in the expression of IVL was partially inhibited by P38 and ERK inhibitors. These results are representative of three experiments performed in triplicate. Band intensities were quantified and data are presented as the mean ± standard deviation. ***P<0.001, compared with the control group. FLG, filaggrin; IVL, involucrin; IL-17, interleukin-17; ERK, extracellular signal-regulated kinase; P-/phospho-, phosphorylated.