Non-
alcoholic steatohepatitis (NASH) has the potential to lead to the development of
cirrhosis and
hepatocellular carcinoma (HCC).
Connexin (Cx) 32, a hepatocyte
gap-junction protein, plays a preventive role in hepatocarcinogenesis. However, the precise contribution of Cx32 in the development of NASH has not been established. In this study, we aimed to clarify the role of Cx32 and the chemopreventive effect of
luteolin, an
antioxidant flavonoid, on the progression of NASH and NASH-related hepatocarcinogenesis. Cx32 dominant negative transgenic (Cx32ΔTg) and wild-type (Wt) rats
at 10 weeks of age were given
diethylnitrosamine and fed
methionine-
choline-deficient diet (MCDD) or MCDD with
luteolin for 12 weeks. MCDD induced
steatohepatitis and
fibrosis along with increased inflammatory
cytokine expression and
reactive oxygen species in the liver. These effects were more severe in Cx32ΔTg rats as compared with Wt rats, and significantly suppressed by
luteolin in both genotypes. Concerning NASH-related hepatocarcinogenesis, the number of
glutathione S-transferase placental form (GST-P)-positive foci was greater in Cx32ΔTg versus Wt rats, and significantly reduced by
luteolin in Cx32ΔTg rats. Microarray analysis identified brain expressed, X-linked 1 (Bex1) as an upregulated gene in Cx32ΔTg rat liver. Quantitative RT-PCR and in situ hybridization revealed that increased Bex1
mRNA was localized in GST-P-positive foci in Cx32ΔTg rats, and the expression level was significantly decreased by
luteolin. Moreover, Bex1 knockdown resulted in significant growth inhibition of the rat HCC cell lines. These results show that Cx32 and
luteolin have suppressive roles in
inflammation,
fibrosis and hepatocarcinogenesis during NASH progression, suggesting a potential therapeutic application for NASH.