Division of Translational Medicine, Department of Medicine, New York University School of Medicine, 550 First Avenue, MSB 255, New York, NY, 10016, USA,
Purinergic Signal. 2013 Dec;9(4):573-83. doi: 10.1007/s11302-013-9368-1. Epub 2013 Jun 8.
Adenosine is a potent endogenous anti-inflammatory and immunosuppressive metabolite that is a potent modulator of tissue repair. However, the adenosine A2A receptor (A2AR)-mediated promotion of collagen synthesis is detrimental in settings such as scarring and scleroderma. The signaling cascade from A2AR stimulation to increased collagen production is complex and obscure, not least because cAMP and its downstream molecules PKA and Epac1 have been reported to inhibit collagen production. We therefore examined A2AR-stimulated signaling for collagen production by normal human dermal fibroblasts (NHDF). Collagen1 (Col1) and collagen3 (Col3) content after A2AR activation by CGS21680 was studied by western blotting. Contribution of PKA and Epac was analyzed by the PKA inhibitor PKI and by knockdowns of the PKA-Cα, -Cβ, -Cγ, Epac1, and Epac2. CGS21680 stimulates Col1 expression at significantly lower concentrations than those required to stimulate Col3 expression. A2AR stimulates Col1 expression by a PKA-dependent mechanism since PKA inhibition or PKA-Cα and -Cβ knockdown prevents A2AR-mediated Col1 increase. In contrast, A2AR represses Col3 via PKA but stimulates both Col1 and Col3 via an Epac2-dependent mechanism. A2AR stimulation with CGS21680 at 0.1 μM increased Col3 expression only upon PKA blockade. A2AR activation downstream signaling for Col1 and Col3 expression proceeds via two distinct pathways with varying sensitivity to cAMP activation; more highly cAMP-sensitive PKA activation stimulates Col1 expression, and less cAMP-sensitive Epac activation promotes both Col1 and Col3 expression. These observations may explain the dramatic change in Col1:Col3 ratio in hypertrophic and immature scars, where adenosine is present in higher concentrations than in normal skin.
腺苷是一种有效的内源性抗炎和免疫抑制代谢物，是组织修复的有效调节剂。然而，在疤痕和硬皮病等情况下，腺苷 A2A 受体（A2AR）介导的胶原合成促进是有害的。从 A2AR 刺激到增加胶原产生的信号级联是复杂而模糊的，尤其是因为已经报道 cAMP 及其下游分子 PKA 和 Epac1 抑制胶原产生。因此，我们检查了正常人类真皮成纤维细胞（NHDF）中 A2AR 刺激胶原产生的信号。通过 Western blot 研究了 CGS21680 激活 A2AR 后胶原 1（Col1）和胶原 3（Col3）的含量。通过 PKA 抑制剂 PKI 和 PKA-Cα、-Cβ、-Cγ、Epac1 和 Epac2 的敲低分析了 PKA 和 Epac 的贡献。CGS21680 以显著低于刺激 Col3 表达所需的浓度刺激 Col1 表达。A2AR 通过依赖于 PKA 的机制刺激 Col1 表达，因为 PKA 抑制或 PKA-Cα 和 -Cβ 的敲低可防止 A2AR 介导的 Col1 增加。相比之下，A2AR 通过 PKA 抑制 Col3，但通过依赖于 Epac2 的机制刺激 Col1 和 Col3。用 0.1μM 的 CGS21680 刺激 A2AR 仅在 PKA 阻断时增加 Col3 表达。Col1 和 Col3 表达的 A2AR 下游信号转导通过两条具有不同 cAMP 激活敏感性的不同途径进行；更高度 cAMP 敏感的 PKA 激活刺激 Col1 表达，而较少 cAMP 敏感的 Epac 激活促进 Col1 和 Col3 表达。这些观察结果可能解释了在肥大和未成熟疤痕中 Col1：Col3 比值的剧烈变化，其中腺苷的浓度高于正常皮肤。
