Dubey R K, Gillespie D G, Mi Z, Jackson E K
Department of Medicine, University of Pittsburgh Medical Center, PA 15213-2582, USA.
Hypertension. 1998 Jan;31(1 Pt 2):516-21. doi: 10.1161/01.hyp.31.1.516.
Adenosine inhibits rat vascular smooth muscle cell (SMC) growth. However, the effects of adenosine on human vascular SMC proliferation and synthesis of extracellular matrix proteins, such as collagen, are unknown. The objective of this study was to characterize the effects of exogenous and endogenous (SMC-derived) adenosine on human aortic SMC proliferation and collagen synthesis. Growth-arrested SMCs were stimulated with 2.5% fetal calf serum (FCS) in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), and with agents that increase endogenous adenosine levels, including erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), dipyridamole, and iodotubericidin. All of these agents inhibited in a concentration-dependent manner FCS-induced SMC proliferation as assessed by DNA synthesis (3H-thymidine incorporation) and cell counting, as well as collagen synthesis (3H-proline incorporation). EHNA, dipyridamole, and iodotubericidin increased extracellular levels of adenosine by 1.7-fold to 18-fold when added separately to SMCs, and EHNA+iodotubericidin and EHNA+iodotubericidin+dipyridamole increased extracellular adenosine levels by more than 392-fold. Both KF17837 (selective A2 antagonist) and DPSPX (A1/A2 antagonist), but not DPCPX (selective A1 antagonist), blocked the antimitogenic effects of 2-chloroadenosine, EHNA, and dipyridamole on DNA and collagen synthesis, suggesting the involvement of A2A and/or A2B, but excluding the participation of A1, receptors. The lack of effect of CGS21680 (selective A2A agonist), excluded involvement of A2A receptors and suggested a major role for A2B receptors. A comparison of the inhibitory potencies of 2-chloroadenosine, N6-cyclopentyladenosine (selective A1 agonist), NECA (A1/A2 agonist), and MECA (A1/A2 agonist) were consistent with an A2B receptor subtype mediating the inhibitory effects of adenosine on human aortic SMC proliferation. In conclusion, human aortic SMCs synthesize adenosine, and exogenous as well as endogenous (SMC-derived) adenosine inhibits SMC proliferation and collagen synthesis via activation of A2B receptors.
腺苷可抑制大鼠血管平滑肌细胞（SMC）的生长。然而，腺苷对人血管SMC增殖以及细胞外基质蛋白（如胶原蛋白）合成的影响尚不清楚。本研究的目的是明确外源性和内源性（SMC源性）腺苷对人主动脉SMC增殖和胶原蛋白合成的影响。在有和没有腺苷、2-氯腺苷（稳定的腺苷类似物）的情况下，用2.5%胎牛血清（FCS）刺激生长停滞的SMC，并使用能提高内源性腺苷水平的药物，包括erythro-9-(2-羟基-3-壬基)腺嘌呤（EHNA）、双嘧达莫和碘结核菌素。通过DNA合成（3H-胸腺嘧啶核苷掺入）、细胞计数以及胶原蛋白合成（3H-脯氨酸掺入）评估，所有这些药物均以浓度依赖性方式抑制FCS诱导的SMC增殖。当分别添加到SMC中时，EHNA、双嘧达莫和碘结核菌素可使细胞外腺苷水平提高1.7倍至18倍，而EHNA+碘结核菌素以及EHNA+碘结核菌素+双嘧达莫可使细胞外腺苷水平提高超过392倍。KF17837（选择性A2拮抗剂）和DPSPX（A1/A2拮抗剂），而非DPCPX（选择性A1拮抗剂），可阻断2-氯腺苷、EHNA和双嘧达莫对DNA和胶原蛋白合成的抗增殖作用，提示A2A和/或A2B受体参与其中，但排除了A1受体的参与。CGS21680（选择性A2A激动剂）无作用，排除了A2A受体的参与，并提示A2B受体起主要作用。比较2-氯腺苷、N6-环戊基腺苷（选择性A1激动剂）、NECA（A1/A2激动剂）和MECA（A1/A2激动剂）的抑制效力，与A2B受体亚型介导腺苷对人主动脉SMC增殖的抑制作用一致。总之，人主动脉SMC可合成腺苷，外源性以及内源性（SMC源性）腺苷通过激活A2B受体抑制SMC增殖和胶原蛋白合成。
