Reversible Alteration in the Expression of the Gap Junctional Protein Connexin 32 During Tumor Promotion in Rat Liver and Its Role during Cell Proliferation

Abstract Non-alcoholic steatohepatitis (NASH) is a recognized risk factor for liver fibrosis and malignancies, and is associated with features of metabolic syndrome, such as obesity and insulin resistance (IR). We previously demonstrated that the disturbance of connexin 32 (Cx32), a gap junctional protein of hepatocytes, exacerbated NASH in Cx32 dominant-negative transgenic (Cx32ΔTg) rats fed methionine choline-deficient diet (MCDD). MCDD is well-established means of inducing NASH in rodents; however, the Cx32ΔTg-MCDD NASH model does not reproduce obesity and IR. In this study, we aimed to establish an improved NASH model. Eight-week-old male Cx32ΔTg and wild-type (Wt) rats received a high-fat diet (HFD) with dimethylnitrosamine (DMN) for 12 weeks. The HFD with DMN led to gains in body, liver, and visceral fat weights in both genotypes. IR was significantly greater in Cx32ΔTg than in Wt rats. Elevation of serum hepatic enzymes (AST, ALT), inflammatory cytokine expressions (Tnfα, Il-6, Tgf-β1, Il-1β, Timp2, and Col1a1), steatohepatitis, and fibrosis were significantly greater in Cx32ΔTg as compared with Wt rats. Regarding carcinogenesis, the number and area of glutathione S-transferase placental form (GST-P)-positive preneoplastic hepatic foci were significantly increased in Cx32ΔTg versus Wt rats. Moreover, activation of NF-κB and JNK contributed to the progression of NASH in Cx32ΔTg rats. These results suggest that Cx32 dysfunction promoted the progression of NASH, metabolic syndrome, and carcinogenesis. Therefore, the novel Cx32ΔTg–HFD–DMN NASH model may be a rapid and useful tool for evaluating the progression of NASH.

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The time course of gap-junctional protein connexin 32 expression in the pancreas after the induction of acute pancreatitis by caerulein in rats

Journal of Gastroenterology ◽

10.1007/s005350200100 ◽

2002 ◽

Vol 37 (8) ◽

pp. 633-639 ◽

Cited By ~ 2

Author(s):

Keiichiro Ogoshi ◽

Tetsuhide Ito ◽

Hisato Igarashi ◽

Yoshiyuki Arita ◽

Terumasa Hisano ◽

...

Keyword(s):

Acute Pancreatitis ◽

Time Course ◽

Connexin 32 ◽

Junctional Protein ◽

Gap Junctional

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Effects of cadmium on gap junctional intercellular communication in WB-F344 rat liver epithelial cells

Human & Experimental Toxicology ◽

10.1191/096032701718620855 ◽

2001 ◽

Vol 20 (11) ◽

pp. 577-583 ◽

Cited By ~ 16

Author(s):

S-H Jeong ◽

M-H Cho ◽

J-H Cho

Keyword(s):

Cell Proliferation ◽

Epithelial Cells ◽

Gap Junctions ◽

Cell Viability ◽

Gap Junction ◽

Intercellular Communication ◽

Tumor Promotion ◽

Gap Junctional Intercellular Communication ◽

Rat Liver Epithelial Cells ◽

Gap Junctional

Cadmium has been associated with a number of tumors but its role in tumor promotion has not been elucidated clearly or the results obtained from various studies have been conflicting. This study was designed to investigate the effects of cadmium on the gap junctional intercellular communication (GJIC), number of gap junctions per cell, and cell proliferation in WB-F344 rat liver epithelial cells from the viewpoint of tumor promotion. GJIC was monitored by counting the cells stained with Lucifer yellow CH dye, using the scrape-loading and dye-transfer method. The numbers of gap junctions per cell were visually quantitated after an indirect immunostaining for gap junction protein using an antibody to connexin 43. Cell proliferation was assayed by direct counting of the living cells using the trypan blue dye exclusion method. In the time course study, cells treated with 200 μM CdCl2 showed rapid and nearly complete inhibition of GJIC (approximately 14% of the control) and a decrease in the number of gap junctions per cell (approximately 21% of the control) at 30 min, and the decrease continued up to 4 h without any changes in the cell viability. Treatment with CdCl2 7.4-200 μM) for 4 h resulted in the decrease of GJIC and gap junction numbers per cell in a dose-response pattern without changes in the cell viability. In the long-term (14 days) exposure studies at doses of 0.01-7.4 μM CdCl2, an increase in cell proliferation was observed at low doses of 0.03-2.5 μM CdCl2, with GJIC also decreasing. These data demonstrate that cadmium inhibits GJIC, reduces the number of gap junctions per cell, and induces cell proliferation while decreasing the function of the gap junction.

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