Modulation of gap junctional intercellular communication (GJIC) is a known cellular event associated with tumor promotion. We examined the anti-carcinogenic properties of the Korean cabbage extracts (DF-01, DF-02, DF-03, Seoul, GM-A, GM-B) on the inhibition of GJIC by hydrogen peroxide (H₂O₂) or phorbol ester (12-O-Tetradecanoylphorbol-13-acetate; TPA) in WB-F344 rat liver cell (WB cells). The cells were pre-incubated with Korean cabbage extracts within non-cytotoxic concentration for 24 h followed by co-treatment with extracts and H₂O₂ (750μM) or TPA (10 ng/ml) for 1 h. DF-01, DF-02, and DF-03 prevented the inhibition of GJIC by H₂O₂. Inhibition by TPA of GJIC was not prevented by any extracts. To find out the action mechanism of Korean cabbage extracts, western blot analysis was performed to show whether, DF-01 and DF-03 block connexin 43 hyperphosphorylation or inhibit extracellular signal-regulated protein kinases (ERK) 1/2 activation by H₂O₂ in WB cells. Korean cabbage extracts such as DF-01 and DF-03 prevented H₂O₂ induced GJIC inhibition through inactivation of ERK1/2 mitogen-activated protein (MAP) kinases. Therefore, it is suggested that the Korean cabbage extracts might have the potential chemopreventive effects by the inhibition of GJIC.

Keywords: Korean cabbage extracts, Gap junctional intercellular communication (GJIC), WB-F344 rat liver cells (WB cells), Connexin 43, Extracellular signal-regulated protein kinases (ERK) 1/2