c-Kit+ progenitor smooth muscle cells (P-SMCs) can develop into SMCs that contribute to injury-induced neointimal thickening. Here, we investigated whether adenosine reduces P-SMC migration and proliferation and whether this contributes to adenosine's inhibitory actions on neointima formation. In human P-SMCs, 2-chloroadenosine (stable adenosine analogue) and BAY60-6583 (A2B agonist) inhibited P-SMC proliferation and migration. Likewise, increasing endogenous adenosine by blocking adenosine metabolism with erythro-9-(2-hydroxy-3-nonyl) adenine (inhibits adenosine deaminase) and 5-iodotubercidin (inhibits adenosine kinase) attenuated P-SMC proliferation and migration. Neither N6-cyclopentyladenosine (A1 agonist), CGS21680 (A2A agonist), nor N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (A3 agonist) affected P-SMC proliferation or migration. 2-Chloroadenosine increased cyclic AMP, reduced Akt phosphorylation (activates cyclin D expression), and reduced levels of cyclin D1 (promotes cell-cycle progression). Moreover, 2-chloroadenosine inhibited expression of Skp2 (promotes proteolysis of p27Kip1) and upregulated levels of p27Kip1 (negative cell-cycle regulator). A2B receptor knockdown prevented the effects of 2-chloroadenosine on cyclic AMP production and P-SMC proliferation and migration. Likewise, inhibition of adenylyl cyclase and protein kinase A rescued P-SMCs from the inhibitory effects of 2-chloroadenosine. The inhibitory effects of adenosine were similar in male and female P-SMCs. In vivo, peri-arterial (rat carotid artery) 2-chloroadenosine (20 μmol/L for 7 days) reduced neointimal hyperplasia by 64.5% (P<0.05; intima/media ratio: control, 1.4±0.02; treated, 0.53±0.012) and reduced neointimal c-Kit+ cells. Adenosine inhibits P-SMC migration and proliferation via the A2B receptor/cyclic AMP/protein kinase A axis, which reduces cyclin D1 expression and activity via inhibiting Akt phosphorylation and Skp2 expression and upregulating p27kip1 levels. Adenosine attenuates neointima formation in part by inhibiting infiltration and proliferation of c-Kit+ P-SMCs.

中文翻译：

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腺苷，通过 A 2B 受体，抑制人类 (P-SMC) 祖细胞平滑肌细胞生长

c-Kit+ 祖平滑肌细胞 (P-SMC) 可以发育成 SMC，导致损伤诱导的新内膜增厚。在这里，我们研究了腺苷是否减少 P-SMC 迁移和增殖，以及这是否有助于腺苷对新内膜形成的抑制作用。在人 P-SMC 中，2-氯腺苷（稳定腺苷类似物）和 BAY60-6583（A2B 激动剂）抑制 P-SMC 增殖和迁移。同样，通过用 erythro-9-(2-hydroxy-3-nonyl) 腺嘌呤（抑制腺苷脱氨酶）和 5-iodotubercidin（抑制腺苷激酶）阻断腺苷代谢来增加内源性腺苷，减弱 P-SMC 增殖和迁移。N6-环戊基腺苷（A1 激动剂）、CGS21680（A2A 激动剂）和 N6-(3-iodobenzyl)-adenosine-5' -N-甲基脲酰胺（A3 激动剂）影响 P-SMC 增殖或迁移。2-氯腺苷增加环 AMP，减少 Akt 磷酸化（激活细胞周期蛋白 D 表达），并降低细胞周期蛋白 D1 水平（促进细胞周期进程）。此外，2-氯腺苷抑制 Skp2 的表达（促进 p27Kip1 的蛋白水解）并上调 p27Kip1（负细胞周期调节剂）的水平。A2B 受体敲低阻止了 2-氯腺苷对环 AMP 产生和 P-SMC 增殖和迁移的影响。同样，腺苷酸环化酶和蛋白激酶 A 的抑制使 P-SMC 免受 2-氯腺苷的抑制作用。腺苷的抑制作用在男性和女性 P-SMC 中相似。在体内，动脉周围（大鼠颈动脉）2-氯腺苷（20 μmol/L 持续 7 天）使新生内膜增生减少 64。5%（P<0.05；内膜/中膜比率：对照，1.4±0.02；治疗，0.53±0.012）和减少的新内膜 c-Kit+ 细胞。腺苷通过 A2B 受体/环 AMP/蛋白激酶 A 轴抑制 P-SMC 迁移和增殖，从而通过抑制 Akt 磷酸化和 Skp2 表达以及上调 p27kip1 水平来降低细胞周期蛋白 D1 的表达和活性。腺苷通过抑制 c-Kit+ P-SMC 的浸润和增殖来部分减弱新内膜的形成。