Dubey R K, Gillespie D G, Jackson E K
Department of Medicine, University of Pittsburgh Medical Center, Pa 15213-2582, USA.
Hypertension. 1998 Jan;31(1 Pt 2):296-302. doi: 10.1161/01.hyp.31.1.296.
The main purpose of this investigation was to evaluate whether the cyclic AMP-adenosine pathway, ie, the conversion of cAMP to AMP and, hence, to adenosine, is involved in the regulation of nitric oxide (NO) synthesis by vascular smooth muscle cells (SMCs). Treatment of confluent monolayers of SMCs with adenosine, 2-chloroadenosine (stable analog of adenosine), and agents that elevate endogenous (SMC-derived) adenosine (EHNA and iodotubericidin) increased nitrite/nitrate (stable metabolites of NO) levels in the medium and enhanced the conversion of 3H-L-arginine to 3H-L-citrulline by cytosolic extracts obtained from the pretreated SMCs. The stimulatory effects of adenosine were not mimicked by low (1 to 100 nmol/L) concentrations of CGS21680, an A2A receptor agonist, or CPA, a selective A1 receptor agonist. The stimulatory effects of 2-chloroadenosine and EHNA plus iodotubericidin were significantly inhibited by KF17837, a selective A2 receptor antagonist, and by DPSPX, an A1/A2 receptor antagonist, but not by DPCPX, a selective A1 receptor antagonist. DDA (adenylyl cyclase inhibitor) and Rp-cyclic AMP (protein kinase A inhibitor) did not block the effects of adenosine on NO synthesis. Incubation of SMCs with exogenous cyclic AMP, at concentrations previously shown to elevate levels ofadenosine in the medium, also increased nitrite/nitrate levels and 3H-L-citrulline formation, and the effects of cyclic AMP on NO synthesis were blocked by DPSPX and KF17837, but not by DPCPX. These findings provide evidence that exogenous and SMC-derived adenosine induce NO synthesis via A2B receptors linked to a pathway not involving adenylyl cyclase/protein kinase A. Moreover, extracellular cyclic AMP induces NO synthesis via conversion to adenosine and activation of A2B adenosine receptors. The cyclic AMP-adenosine pathway may be importantly involved in the vascular production of NO.
本研究的主要目的是评估环磷酸腺苷 - 腺苷途径，即cAMP转化为AMP并进而转化为腺苷，是否参与血管平滑肌细胞（SMC）对一氧化氮（NO）合成的调节。用腺苷、2 - 氯腺苷（腺苷的稳定类似物）以及能提高内源性（SMC衍生）腺苷的试剂（EHNA和碘结核菌素）处理汇合的SMC单层细胞，可增加培养基中亚硝酸盐/硝酸盐（NO的稳定代谢产物）水平，并增强从预处理的SMC中获得的胞质提取物将3H - L - 精氨酸转化为3H - L - 瓜氨酸的能力。低浓度（1至100 nmol/L）的A2A受体激动剂CGS21680或选择性A1受体激动剂CPA不能模拟腺苷的刺激作用。选择性A2受体拮抗剂KF17837和A1/A2受体拮抗剂DPSPX可显著抑制2 - 氯腺苷以及EHNA加碘结核菌素的刺激作用，但选择性A1受体拮抗剂DPCPX则无此作用。腺苷酸环化酶抑制剂DDA和蛋白激酶A抑制剂Rp - 环磷酸腺苷不能阻断腺苷对NO合成的影响。用先前已证明能提高培养基中腺苷水平的外源性环磷酸腺苷孵育SMC，也可增加亚硝酸盐/硝酸盐水平以及3H - L - 瓜氨酸的生成，且环磷酸腺苷对NO合成的作用可被DPSPX和KF17837阻断，但不能被DPCPX阻断。这些发现提供了证据，表明外源性和SMC衍生的腺苷通过与不涉及腺苷酸环化酶/蛋白激酶A的途径相连的A2B受体诱导NO合成。此外，细胞外环磷酸腺苷通过转化为腺苷并激活A2B腺苷受体来诱导NO合成。环磷酸腺苷 - 腺苷途径可能在血管NO生成中起重要作用。
