Ming M, Wu J, Lachance S, Delalandre A, Carrière S, Chan J S
University of Montreal, Maisonneuve-Rosemont Hospital Research Center, Montreal, Canada.
Hypertension. 1995 Jan;25(1):105-9. doi: 10.1161/01.hyp.25.1.105.
We have previously reported that addition of 8-bromocyclic AMP enhances the stimulatory effect of dexamethasone on the expression of the angiotensinogen gene in mouse hepatoma cells in vitro. Isoproterenol is known to stimulate the synthesis of hepatic intracellular cyclic AMP via beta-adrenergic receptors. To study the possible effect of beta-adrenergic receptors on the expression of the angiotensinogen gene in mouse hepatoma cells, we transiently transfected them with a fusion gene with the 5'-flanking region of the angiotensinogen gene linked to a bacterial chloramphenicol acetyltransferase coding sequence as a reporter, pOCAT (ANG N-1498/+18). The addition of isoproterenol (10(-9) to 10(-5) mol/L) alone had no stimulatory effect on the expression of pOCAT (ANG N-1498/+18). In the presence of dexamethasone (10(-6) mol/L), however, isoproterenol enhanced the stimulatory effect on the dexamethasone on the expression of pOCAT (ANG N-1498/+18). The enhancing effect of isoproterenol was inhibited by the presence of propranolol (beta 1- and beta 2-adrenergic receptor antagonist) and ICI 118,551 (beta 2-adrenergic receptor antagonist) but not by the presence of atenolol (beta 1-adrenergic receptor antagonist). Furthermore, the addition of Rp-cAMP (an inhibitor of protein kinase A I and II) blocked the enhancing effect of isoproterenol. These studies demonstrated that isoproterenol enhances the stimulatory effect of dexamethasone on the expression of the angiotensinogen gene in mouse hepatoma cells via beta 2-adrenergic receptor and cyclic AMP-dependent protein kinase pathways. Our data may be important in understanding the molecular mechanism(s) of the stimulatory effect of catecholamines/glucocorticoid-induced expression of the angiotensinogen gene in the liver.
我们之前曾报道，添加8-溴环磷酸腺苷（8-bromocyclic AMP）可增强地塞米松对体外培养的小鼠肝癌细胞血管紧张素原基因表达的刺激作用。已知异丙肾上腺素可通过β-肾上腺素能受体刺激肝内细胞内环磷酸腺苷的合成。为研究β-肾上腺素能受体对小鼠肝癌细胞血管紧张素原基因表达的可能影响，我们用一个融合基因瞬时转染这些细胞，该融合基因包含血管紧张素原基因的5'侧翼区，与一个细菌氯霉素乙酰转移酶编码序列相连作为报告基因，即pOCAT (ANG N-1498/+18)。单独添加异丙肾上腺素（10⁻⁹至10⁻⁵ mol/L）对pOCAT (ANG N-1498/+18)的表达没有刺激作用。然而，在地塞米松（10⁻⁶ mol/L）存在的情况下，异丙肾上腺素增强了地塞米松对pOCAT (ANG N-1498/+18)表达的刺激作用。异丙肾上腺素的增强作用被普萘洛尔（β1和β2肾上腺素能受体拮抗剂）和ICI 118,551（β2肾上腺素能受体拮抗剂）抑制，但不受阿替洛尔（β1肾上腺素能受体拮抗剂）的抑制。此外，添加Rp-环磷酸腺苷（蛋白激酶A I和II的抑制剂）可阻断异丙肾上腺素的增强作用。这些研究表明，异丙肾上腺素通过β2肾上腺素能受体和环磷酸腺苷依赖性蛋白激酶途径增强地塞米松对小鼠肝癌细胞血管紧张素原基因表达的刺激作用。我们的数据对于理解儿茶酚胺/糖皮质激素诱导肝脏血管紧张素原基因表达的刺激作用的分子机制可能具有重要意义。
