Knock-down of filaggrin influences the mitogen-activated protein kinases signaling pathway in normal human epidermal keratinocytes

Abstract

Background: Filaggrin is an essential structural protein of the stratum corneum binding to the keratin intermediate filaments to form a dense protein-lipid matrix. However, the function of filaggrin in epidermal terminal differentiation is not completely understood. Aim: To evaluate the effects of filaggrin on normal human epidermal keratinocytes (NHEKs) and to investigate the relevant mechanisms. Methods: Short hairpin RNA (shRNA) technology was used to knock-down filaggrin in normal human epidermal keratinocytes (NHEKs). Western blot and real-time quantitative PCR (qRT-PCR) were performed to detect expression of filaggrin, differentiation-related proteins and MAPK-related proteins. Results: Filaggrin was successfully knocked down in NHEKs (99% efficiency). We found that the lack of filaggrin significantly decreased the expression of some differentiation-related proteins, including Cytokeratin 5 protein, Cytokeratin 14 protein, ST14 protein and SPRR3 protein (P<0.05). In addition, filaggrin knock-down significantly decreased expression of p-p38, p-ERK1/2, p-JNK, p-Akt, and p-NF-κB in NHEKs. Conclusion: Our study shows that filaggrin regulates epidermal terminal differentiation and impairs MAPK signaling pathway in normal human epidermal keratinocytes.