Thorin-Trescases N, Ono Y, Tremblay J, Hamet P, Orlov S N
Research Center, Centre hospitalier de l'Université de Montréal - Hôtel-Dieu, Montréal, Québec, Canada.
J Vasc Res. 2000 Nov-Dec;37(6):477-84. doi: 10.1159/000054080.
This study examined the contribution of cAMP signaling to the modulation of vascular smooth muscle cell (VSMC) proliferation by adenosine. At a concentration of 1 mM, adenosine inhibited [(3)H]-thymidine uptake, measured as the initial rate of isotope influx, by 10-fold. Diminution of [(3)H]-thymidine uptake by adenosine was independent of the presence of A(1)- and A(2)-receptor antagonists, indicating that adenosine competes with thymidine for plasma membrane transporter-binding sites. Considering these results, in order to estimate [(3)H]-thymidine DNA labeling, VSMCs were preincubated with adenosine for 48 h, and adenosine was then omitted during the subsequent 2 h of incubation in [(3)H]-thymidine-containing medium. In serum-depleted VSMCs, preincubation with 100 microM or 1,000 microM adenosine augmented DNA synthesis by approximately 6- and 3-fold, respectively, whereas the increment of DNA synthesis triggered by serum was decreased in the presence of adenosine by 20-30%. Both cAMP production and inhibition of DNA synthesis by adenosine in serum-supplied cells were independent of the presence of the A(1)-antagonist 1,2-dipropyl-8-cyclopentylxanthine (DPCPX), but were abolished by the A(2)-antagonist 1,3-dimethyl-7-propylxanthine (DMPX). In contrast, the activation of DNA synthesis in serum-depleted cells by adenosine was decreased in the presence of DPCPX and DMPX by approximately 30 and 40%, respectively. Both in serum-supplied and -depleted VSMCs, dose-dependent elevation of cAMP production with an adenylate cyclase activator, forskolin, reduced DNA synthesis by up to 40-60%. Thus, our results show that in addition to suppressing thymidine uptake, adenosine depresses the DNA synthesis triggered by serum-derived growth factors and stimulates DNA synthesis in serum-depleted cells. These data also suggest that the inhibition of DNA synthesis is mediated by cAMP production where the activation of DNA synthesis is independent of cAMP signaling.
本研究检测了环磷酸腺苷（cAMP）信号传导在腺苷对血管平滑肌细胞（VSMC）增殖调节中的作用。在浓度为1 mM时，腺苷抑制了以同位素流入初始速率衡量的[³H] - 胸腺嘧啶核苷摄取，抑制程度达10倍。腺苷对[³H] - 胸腺嘧啶核苷摄取的减少与A₁和A₂受体拮抗剂的存在无关，这表明腺苷与胸腺嘧啶核苷竞争质膜转运体结合位点。考虑到这些结果，为了评估[³H] - 胸腺嘧啶核苷DNA标记，VSMC先与腺苷预孵育48小时，然后在随后含[³H] - 胸腺嘧啶核苷的培养基中孵育2小时期间去除腺苷。在血清缺乏的VSMC中，用100 μM或1000 μM腺苷预孵育分别使DNA合成增加约6倍和3倍，而在腺苷存在下，血清引发的DNA合成增加量减少了20 - 30%。在血清供应的细胞中，腺苷产生cAMP以及抑制DNA合成均与A₁拮抗剂1,2 - 二丙基 - 8 - 环戊基黄嘌呤（DPCPX）的存在无关，但被A₂拮抗剂1,3 - 二甲基 - 7 - 丙基黄嘌呤（DMPX）消除。相反，在DPCPX和DMPX存在下，腺苷对血清缺乏细胞中DNA合成的激活作用分别降低了约30%和40%。在血清供应和血清缺乏的VSMC中，用腺苷酸环化酶激活剂福司可林使cAMP产生呈剂量依赖性升高，DNA合成最多减少40 - 60%。因此，我们的结果表明，除了抑制胸腺嘧啶核苷摄取外，腺苷还抑制由血清衍生生长因子引发的DNA合成，并刺激血清缺乏细胞中的DNA合成。这些数据还表明，DNA合成的抑制是由cAMP产生介导的，而DNA合成的激活与cAMP信号传导无关。
