Dubey R K, Gillespie D G, Mi Z, Suzuki F, Jackson E K
Center for Clinical Pharmacology, Department of Medicine, University of Pittsburgh Medical Center, PA 15213-2582, USA.
Hypertension. 1996 Mar;27(3 Pt 2):766-73. doi: 10.1161/01.hyp.27.3.766.
Several endogenous factors generated within the vessel wall have been implicated in contributing to the vascular remodeling process associated with hypertension and atherosclerosis. Furthermore, substances generated by smooth muscle cells (SMCs) are known to regulate SMC proliferation in an autocrine fashion. Adenosine is a vasodilator synthesized by SMCs, and exogenous adenosine inhibits SMC proliferation. However, whether adenosine produced endogenously has antimitogenic effects is not known. Hence, we evaluated the effects of SMC-derived adenosine on 2.5% fetal calf serum-induced proliferation of rat aortic SMCs. SMC proliferation was assayed by measurement of DNA synthesis ([3H]thymidine incorporation) and cell counting. To determine the effects of endogenous adenosine on SMC proliferation, we stimulated growth-arrested SMCs with 2.5% fetal calf serum in the presence and absence of modulators of adenosine levels, including (1) erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA; inhibits adenosine deaminase), (2) dipyridamole (blocks adenosine transport and inhibits phosphodiesterase), (3) dipyridamole plus EHNA, and (4) adenosine with or without EHNA. [3H]Thymidine incorporation and cell number were measured after 24 and 96 hours, respectively. EHNA and dipyridamole inhibited both FCS-induced DNA synthesis and cell proliferation in a concentration-dependent manner. Furthermore, extracellular (in medium) adenosine levels were significantly increased when cultured cells were treated with EHNA, and the inhibitory effects of dipyridamole as well as exogenous adenosine were enhanced in the presence of EHNA. Additionally, the inhibitory effects of dipyridamole and EHNA on DNA synthesis were significantly reduced in the presence of KF17837, an A2 adenosine receptor antagonist. These results indicate that SMC-derived adenosine can inhibit SMC proliferation. Hence, it is possible that a defect in localized adenosine synthesis within the vessel wall could contribute to vascular thickening and neointima formation.
血管壁内产生的几种内源性因素被认为与高血压和动脉粥样硬化相关的血管重塑过程有关。此外，已知平滑肌细胞（SMC）产生的物质以自分泌方式调节SMC增殖。腺苷是一种由SMC合成的血管舒张剂，外源性腺苷可抑制SMC增殖。然而，内源性产生的腺苷是否具有抗有丝分裂作用尚不清楚。因此，我们评估了SMC衍生的腺苷对2.5%胎牛血清诱导的大鼠主动脉SMC增殖的影响。通过测量DNA合成（[3H]胸腺嘧啶核苷掺入）和细胞计数来检测SMC增殖。为了确定内源性腺苷对SMC增殖的影响，我们在有和没有腺苷水平调节剂的情况下，用2.5%胎牛血清刺激生长停滞的SMC，这些调节剂包括：（1）盐酸erythro-9-（2-羟基-3-壬基）腺嘌呤（EHNA；抑制腺苷脱氨酶），（2）双嘧达莫（阻断腺苷转运并抑制磷酸二酯酶），（3）双嘧达莫加EHNA，以及（4）有或没有EHNA的腺苷。分别在24小时和96小时后测量[3H]胸腺嘧啶核苷掺入和细胞数量。EHNA和双嘧达莫以浓度依赖性方式抑制FCS诱导的DNA合成和细胞增殖。此外，当用EHNA处理培养细胞时，细胞外（培养基中）腺苷水平显著升高，并且在存在EHNA的情况下，双嘧达莫以及外源性腺苷的抑制作用增强。此外，在A2腺苷受体拮抗剂KF17837存在的情况下，双嘧达莫和EHNA对DNA合成的抑制作用显著降低。这些结果表明，SMC衍生的腺苷可以抑制SMC增殖。因此，血管壁内局部腺苷合成的缺陷可能导致血管增厚和新生内膜形成。
