Dubey R K, Gillespie D G, Mi Z, Jackson E K
Center for Clinical Pharmacology, Department of Medicine, University of Pittsburgh Medical Center, Pa 15213-2582, USA.
Circulation. 1997 Oct 21;96(8):2656-66. doi: 10.1161/01.cir.96.8.2656.
Because proliferation of cardiac fibroblasts participates in cardiac hypertrophy/remodeling associated with hypertension and myocardial infarction, it is important to elucidate factors regulating cardiac fibroblast proliferation. Adenosine, a nucleoside abundantly produced by cardiac cells, is antimitogenic vis-à-vis vascular smooth muscle cells; however, the effect of adenosine on cardiac fibroblast proliferation is unknown. The objective of this study was to characterize the effects of exogenous and endogenous (cardiac fibroblast-derived) adenosine on cardiac fibroblast proliferation.
Growth-arrested cardiac fibroblasts were stimulated with 2.5% FCS in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), or modulators of adenosine levels, including (1) erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; adenosine deaminase inhibitor); (2) dipyridamole (adenosine transport blocker); and (3) iodotubericidin (adenosine kinase inhibitor). All of these agents inhibited, in a concentration-dependent manner, FCS-induced cardiac fibroblast proliferation as assessed by DNA synthesis ([3H]thymidine incorporation) and cell counting. EHNA, dipyridamole, and iodotubericidin increased extracellular levels of adenosine by 2.3- to 5.6-fold when added separately to cardiac fibroblasts, and EHNA+iodotubericidin or EHNA+iodotubericidin+dipyridamole increased extracellular adenosine levels by >690-fold. Both KF17837 (selective A2 antagonist) and DPSPX (nonselective A2 antagonist) but not DPCPX (selective A1 antagonist) blocked the antimitogenic effects of 2-chloroadenosine, EHNA, and dipyridamole on DNA 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. This conclusion was confirmed by the rank order potencies of four adenosine analogues.
Cardiac fibroblasts synthesize adenosine, and exogenous and cardiac fibroblast-derived adenosine inhibits cardiac fibroblast proliferation via activation of A2B receptors. Cardiac fibroblast-derived adenosine may regulate cardiac hypertrophy and/or remodeling by modulating cardiac fibroblast proliferation.
由于心脏成纤维细胞的增殖参与了与高血压和心肌梗死相关的心脏肥大/重塑，因此阐明调节心脏成纤维细胞增殖的因素非常重要。腺苷是一种由心脏细胞大量产生的核苷，对血管平滑肌细胞具有抗有丝分裂作用；然而，腺苷对心脏成纤维细胞增殖的影响尚不清楚。本研究的目的是表征外源性和内源性（心脏成纤维细胞衍生的）腺苷对心脏成纤维细胞增殖的影响。
在有和没有腺苷、2-氯腺苷（稳定的腺苷类似物）或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心脏成纤维细胞，所述调节剂包括（1）赤藓红-9-（2-羟基-3-壬基）腺嘌呤（EHNA；腺苷脱氨酶抑制剂）；（2）双嘧达莫（腺苷转运阻滞剂）；和（3）碘结核菌素（腺苷激酶抑制剂）。通过DNA合成（[3H]胸苷掺入）和细胞计数评估，所有这些试剂均以浓度依赖性方式抑制胎牛血清诱导的心脏成纤维细胞增殖。当分别添加到心脏成纤维细胞中时，EHNA、双嘧达莫和碘结核菌素使细胞外腺苷水平增加2.3至5.6倍，而EHNA+碘结核菌素或EHNA+碘结核菌素+双嘧达莫使细胞外腺苷水平增加>690倍。KF17837（选择性A2拮抗剂）和DPSPX（非选择性A2拮抗剂）而非DPCPX（选择性A1拮抗剂）阻断了2-氯腺苷、EHNA和双嘧达莫对DNA合成的抗有丝分裂作用，提示A2A和/或A2B参与其中，但排除了A1受体的参与。CGS21680（选择性A2A激动剂）缺乏作用排除了A2A受体的参与，并提示A2B受体起主要作用。四种腺苷类似物的效价顺序证实了这一结论。
心脏成纤维细胞合成腺苷，外源性和心脏成纤维细胞衍生的腺苷通过激活A2B受体抑制心脏成纤维细胞增殖。心脏成纤维细胞衍生的腺苷可能通过调节心脏成纤维细胞增殖来调节心脏肥大和/或重塑。
