Expression and Regulation of Gap Junction Proteins in Human Cholangiocytes by Excretory-Secretory Products of Clonorchis sinensis and

Abstract

Clonorchis sinensis, the most prevalent parasite in Korea, has been reclassified as Group I bio-carcinogen for cholangiocarcinoma (CCA) in humans by IARC in 2009. In order to understand the mechanism of carcinogenesis of C. sinensis, the present study investigated cell proliferation and expression and regulation of gap junction proteins by stimulation with N-nitrosodimethylamine (NDMA) and/or excretory-secretory product of C. sinensis (ESP) in a human cholangiocyte line, H69. In cells exposed to NDMA and ESP, cellular proliferation and the proportion of cells in the G2/M phase increased to 37%. Moreover, the expression of the cell cycle protein E2F1 and the cell proliferation related proteins, ki67, and cytokeratin 19 were more than 30-fold increased when NDMA and ESP were added together. Especially, expression of gap-junction proteins (connexin 43 and connexin 26) and Cox-2 was increased while that of connexin 32 was reduced in the NDMA and ESP group. Connexin 43 silencing significantly suppressed expression of connexin 26 and Cox-2 in the same group. In conclusion, it is suggested that the connexin 43 plays a key role in regulation of inflammatory responses, which may cause cholangicarcinoma under stimulation by ESP of C. sinensis and NDMA.