Compound K inhibits MMP-1 expression through suppression of c-Src-dependent ERK activation in TNF-α-stimulated dermal fibroblast

Compound K (CK) is one of the major metabolites of ginsenosides exhibiting a variety of pharmacological properties such as anti-ageing, anti-oxidation and anti-inflammatory activities. However, the protective efficacy of CK in abnormal skin conditions with inflammatory responses was not examined. Here, we investigated the effects of CK on matrix metalloproteinase-1 (MMP-1) and type I procollagen production in tumor necrosis factor- (TNF-)-stimulated human skin fibroblasts HS68 cells and human skin equivalents. We found that CK suppressed MMP-1 secretion and increased the level of reduced type I procollagen secretion, caused by the inhibition of extracellular signal-regulated kinase (ERK) activation, but not p38 and c-Jun N-terminal kinase (JNK) activation in TNF--stimulated HS68 cells. Then, we focused on the involvement of the c-Src and epidermal growth factor receptor (EGFR) as upstream signalling molecules for ERK activation by TNF- in HS68 cells. CK suppressed the phosphorylation of c-Src/EGFR by TNF-, which led to the inactivation of downstream signalling molecules including AKT and MEK. In addition, CK suppressed AP-1 (c-jun and c-fos) phosphorylation as downstream transcription factors of active ERK for MMP-1 expression in TNF-stimulated HS68 cells. These results showed novel mechanisms by which CK inhibits TNF--induced MMP-1 expression through the inactivation of c-Src/EGFR-dependent ERK/AP-1 signalling pathway, resulting in the inhibition of collagen degradation in human fibroblast cells. Therefore, CK may be a promising protective agent for the treatment of inflammatory skin conditions such as skin ageing and atopic dermatitis.