MAPK and PI3K/Akt Signalling Pathways Potentially Modulate the Enhancing Effect of Black Tea Extracts on Endo180 Expression and Collagen Internalisation

Abstract

As the skin ages, collagen denatures into fragments that accumulate in the dermal matrix. Endo180 allows these fragments to reenter cells and be used for collagen recombination. While several studies have reported on the efficacy of green tea on skin health, studies on black tea have been limited. The aim of this study was to reveal the effects of black tea on skin health and the associated mechanisms. We estimated collagen internalisation using fluorescence-labelled gelatin and measured Endo180 expression following treatment with black tea extract (BTE). BTE at a concentration of 10 ug/ml increased Endo180 mRNA and protein expression by 1.67-fold $\left(p=0.006\right)$ and 1.46-fold $\left(p=0.010\right)$, respectively. In addition, collagen internalisation was increased by 1.29-fold $\left(p=0.001\right)$ in human skin fibroblasts compared with the untreated control group. These effects were reversed by five inhibitors of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathways to the same levels as those of the untreated control group. These results suggest that BTE enhances collagen internalisation and upregulates Endo180 expression via the MAPK and PI3K/Akt signalling pathways in HDFs and that black tea could be used as a functional food for improving skin health.