全反式维甲酸通过γ-氨基丁酸途径促进小鼠胚胎腭板间充质细胞的凋亡

维甲酸(RA)是一种能够诱导腭裂发生的致畸物．研究显示γ-氨基丁酸(GABA)在腭板的发育过程中发挥重要作用．而GABA是否参与了RA诱导的腭裂发生还不清楚．本研究以小鼠胚胎腭板间充质细胞(MEPM)为研究对象，观察全反式维甲酸(atRA)(0.2、0.67、2.0和 6.7 μmol/L)对MEPM细胞增殖和凋亡的影响，并探讨GABA信号通路在其中的可能作用．结果显示，atRA(2.0 μmol/L和6.7 μmol/L)显著性抑制了MEPM的增殖，并促进了细胞凋亡．atRA(0.67、2.0和 6.7 μmol/L)显著性降低了GABA合成的关键酶谷氨酸脱羧酶(GAD67)mRNA和蛋白质的表达，但对γ-氨基丁酸A型受体-β3(GABAAR-β3)mRNA和蛋白质的表达没有影响．1.0 μmol/L的GABA逆转了atRA(6.7 μmol/L)对MEPM细胞增殖和凋亡的影响．以上结果表明，atRA通过下调GAD67的表达，减少GABA的产生，抑制MEPM的增殖和促进MEPM的凋亡，从而可能影响腭板的发育，诱导腭裂形成．

All-trans Retinoic Acid Promotes Cell Apoptosis Through Gamma Amino Butyric Acid Pathway in Murine Embryonic Palate Mesenchymal Cells

Retinoic acid (RA) is a teratogen which can induce cleft palate. Recent studies suggested that gamma amino butyric acid (GABA) was involved in the development of palate. If the GABA signal pathway participates the cleft palate induced by RA remains to be elucidated. In the present study, we investigated the effect of all-trans retinoic acid (atRA) (0.2, 0.67, 2.0 and 6.7 μmol/L) on cell proliferation and apoptosis, and then examined the role of gamma amino butyric acid (GABA) signaling pathway in regulation of cell proliferation and apoptosis by atRA in murine embryonic palate mesenchymal (MEPM) cells. Results showed that atRA (2 μmol/L and 6.7 μmol/L ) significantly inhibited cell proliferation and increased apoptosis. The mRNA and protein expression of glutamic acid decarboxylase 67 (GAD 67) which was a key enzyme in synthesis of GABA were significantly down regulated by atRA (0.67, 2.0 μmol/L and 6.7 μmol/L). But the mRNA and protein expression of GABAAR-β3 were shown no obvious change compared with the control group. When GABA (1.0 μmol/L) was added to cell culture system, the effect of atRA (6.7 μmol/L) on the proliferation and apoptosis of MEPM cells was reversed. In conclusion, all-trans retinoic acid inhibits cell proliferation and promotes cell apoptosis through gamma amino butyric acid pathway in murine embryonic palate mesenchymal cells.