γ-氨基丁酸能活性增强可抑制甲胎蛋白信使核糖核酸表达及人肝癌细胞系HepG2的增殖活性。

Increased GABAergic activity inhibits alpha-fetoprotein mRNA expression and the proliferative activity of the HepG2 human hepatocellular carcinoma cell line.

作者信息

Zhang M, Gong Y, Assy N, Minuk G Y

机构信息

Department of Medicine, University of Manitoba, Winnipeg, Canada.

出版信息

J Hepatol. 2000 Jan;32(1):85-91. doi: 10.1016/s0168-8278(00)80193-2.

DOI:10.1016/s0168-8278(00)80193-2

PMID:10673071

Abstract

BACKGROUND/AIMS: Gamma aminobutyric acid (GABA) is a potent inhibitory neurotransmitter with growth regulatory properties. Recent data indicate that increased GABAergic activity inhibits hepatocyte proliferation in regenerating livers. In the present study, we aimed to investigate whether GABA inhibits the growth of malignant hepatocytes.

METHODS

Increasing concentrations of muscimol (0.05-50 microM), a specific GABA(A) receptor agonist, were added to HepG2 human hepatocellular carcinoma cells and alpha-fetoprotein (AFP) and albumin mRNA expression were determined for varying periods of time (maximum 24 h) thereafter. Cell proliferation was also documented after 48 h of exposure to muscimol.

RESULTS

Muscimol significantly (p<0.0001) decreased AFP mRNA expression (maximum decrease: 65% below baseline values) without affecting albumin mRNA expression. However, the effect on AFP mRNA was transient (maximum duration: 3-6 h) and not associated with changes in cell proliferation. Because preliminary data indicate that GABA(A) receptor activity is markedly downregulated in malignant hepatocytes, transfection studies were performed wherein HepG2 cells were cotransfected with GABA(A) receptor beta2 and beta2 subunit genes in a pCDM8 expression vector or vector alone followed by re-exposure to either muscimol (5 betaM) or saline. In this series of experiments, in addition to AFP mRNA inhibition being as extensive and more prolonged (maximum duration: 6-12 h) in muscimol-treated, GABA(A) receptor-transfected cells, proliferative activity was also significantly inhibited when compared to saline-treated GABA(A) receptor-transfected controls (p<0.01) and muscimol-treated cells transfected with vector alone (p<0.005).

CONCLUSION

The results of this study indicate that increased GABAergic activity inhibits AFP mRNA expression and cell proliferation in this malignant hepatocyte cell line.

摘要

背景/目的：γ-氨基丁酸（GABA）是一种具有生长调节特性的强效抑制性神经递质。最近的数据表明，GABA能活性增加会抑制再生肝脏中肝细胞的增殖。在本研究中，我们旨在调查GABA是否抑制恶性肝细胞的生长。

方法

将浓度递增的蝇蕈醇（0.05 - 50微摩尔），一种特异性GABA(A)受体激动剂，添加到HepG2人肝癌细胞中，随后在不同时间段（最长24小时）测定甲胎蛋白（AFP）和白蛋白mRNA的表达。在暴露于蝇蕈醇48小时后也记录细胞增殖情况。

结果

蝇蕈醇显著（p<0.0001）降低AFP mRNA表达（最大降幅：比基线值低65%），而不影响白蛋白mRNA表达。然而，对AFP mRNA的影响是短暂的（最长持续时间：3 - 6小时），且与细胞增殖变化无关。因为初步数据表明恶性肝细胞中GABA(A)受体活性明显下调，所以进行了转染研究，将HepG2细胞与pCDM8表达载体中的GABA(A)受体β2和β2亚基基因或单独的载体共转染，然后再次暴露于蝇蕈醇（5微摩尔）或生理盐水。在这一系列实验中，除了在经蝇蕈醇处理的、转染了GABA(A)受体的细胞中AFP mRNA抑制作用更广泛且持续时间更长（最长持续时间：6 - 12小时）外，与经生理盐水处理的转染了GABA(A)受体的对照细胞（p<0.01）和经蝇蕈醇处理的仅转染载体的细胞（p<0.005）相比，增殖活性也受到显著抑制。