Samokovlisky A, Rimon G, Danon A
Department of Clinical Pharmacology, The Corob Center for Health Sciences, Ben-Gurion University, Beer Sheva, Israel.
Eur J Pharmacol. 1999 Aug 6;378(2):203-11. doi: 10.1016/s0014-2999(99)00461-6.
Bovine aortic endothelial cells produce prostacyclin as their major arachidonic acid metabolite. cAMP, in turn, is the second messenger for prostacyclin. In the present study, we investigated the effects of cAMP-elevating agents on prostacyclin production by bovine aortic endothelial cells. Treatment of resting bovine aortic endothelial cells with cAMP-elevating agents inhibited prostacyclin production and cyclooxygenase activity, without affecting arachidonic acid release. No change was detected in cyclooxygenase-1 protein expression. The specific inhibitor of protein kinase A, Rp-cAMPS (adenosine 3',5'-cyclic monophosphorothioate, Rp-isomer, triethylammonium salt), and the phosphatase inhibitor, okadaic acid, both suppressed cAMP-induced inhibition, suggesting that this inhibition is mediated by a phosphorylation-dephosphorylation cascade, which is possibly protein kinase A-dependent. In lipopolysaccharide-treated cyclooxygenase-2 expressing bovine aortic endothelial cells, where cyclooxygenase-1 activity was selectively inhibited, dibutyryl cAMP failed to inhibit cyclooxygenase-2 activity. Cyclooxygenase-2 protein was induced upon treatment with dibutyryl cAMP and further induction of cyclooxygenase-2 protein was effected by IBMX (3-isobutyl-1-methyl-xanthine) and dibutyryl cAMP in bacterial lipopolysaccharide-stimulated cells. These results suggest that increased cellular cAMP selectively inhibits cyclooxygenase-1 activity without altering cyclooxygenase-1 protein expression, and at the same time, up-regulates cyclooxygenase-2 protein. This complex regulation of cyclooxygenase activity and protein expression by cAMP may represent a prostacyclin-induced autoregulatory mechanism in bovine aortic endothelial cells.
牛主动脉内皮细胞产生前列环素作为其主要的花生四烯酸代谢产物。反过来，环磷酸腺苷（cAMP）是前列环素的第二信使。在本研究中，我们研究了升高cAMP的药物对牛主动脉内皮细胞产生前列环素的影响。用升高cAMP的药物处理静息的牛主动脉内皮细胞可抑制前列环素的产生和环氧化酶活性，而不影响花生四烯酸的释放。未检测到环氧化酶-1蛋白表达的变化。蛋白激酶A的特异性抑制剂Rp-cAMPS（腺苷3',5'-环磷硫酰酯，Rp-异构体，三乙铵盐）和磷酸酶抑制剂冈田酸均抑制了cAMP诱导的抑制作用，表明这种抑制作用是由磷酸化-去磷酸化级联介导的，这可能依赖于蛋白激酶A。在表达环氧化酶-2的经脂多糖处理的牛主动脉内皮细胞中，环氧化酶-1的活性被选择性抑制，二丁酰cAMP未能抑制环氧化酶-2的活性。用二丁酰cAMP处理可诱导环氧化酶-2蛋白表达，在细菌脂多糖刺激的细胞中，3-异丁基-1-甲基黄嘌呤（IBMX）和二丁酰cAMP可进一步诱导环氧化酶-2蛋白表达。这些结果表明，细胞内cAMP增加可选择性抑制环氧化酶-1的活性，而不改变环氧化酶-1蛋白的表达，同时上调环氧化酶-2蛋白。cAMP对环氧化酶活性和蛋白表达的这种复杂调节可能代表了牛主动脉内皮细胞中前列环素诱导的一种自调节机制。
