Collagen peptides from soft-shelled turtle induce calpain-1 expression and regulate inflammatory cytokine expression in HaCaT human skin keratinocytes

Abstract

Collagen peptides (CPs), derived by hydrolyzing collagen with chemicals or enzymes, are often used as functional materials, due to their various bioactivities and high bioavailability. A previous study by our group reported that collagen from soft-shelled turtle, Pelodiscus sinensis, induces keratinocytes to undergo epithelial-mesenchymal transition and facilitates wound healing. Therefore, CPs derived from soft-shelled turtle collagen may have useful effects on the skin. In the present study, the functional effects of CPs on human skin were examined by analyzing CP-treated human keratinocytes with a shotgun liquid chromatography/mass spectrometry-based global proteomic approach. A semi-quantitative method based on spectral counting was applied and 211 proteins that exhibited >2-fold changes in expression after CP treatment were successfully identified. Based on a Gene Ontology analysis, the functions of these proteins were indicated to be closely linked with protein processing. In addition, CP treatment significantly increased the expression of calpain-1, a calcium-dependent intracellular cysteine protease. Furthermore, CP-treated keratinocytes exhibited elevated interleukin (IL)-1α and IL-8 expression and reduced IL-6 expression. CPs also induced the expression of proteins implicated in cell-cell adhesion and the skin barrier. Therefore, CPs from soft-shelled turtle may provide significant benefits for maintaining the biological environment of the skin, and may be useful as components of pharmaceuticals and medical products.