Hesse Julia, Groterath Wiebke, Owenier Christoph, Steinhausen Julia, Ding Zhaoping, Steckel Bodo, Czekelius Constantin, Alter Christina, Marzoq Aseel, Schrader Jürgen
Department of Molecular Cardiology, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
Institute for Organic Chemistry and Macromolecular Chemistry, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
FASEB J. 2021 May;35(5):e21517. doi: 10.1096/fj.202002545R.
Myocardial infarction (MI) activates the epicardium to form epicardial stromal cells (EpiSC) that reside in the epicardial hypoxic microenvironment. Paracrine factors secreted by EpiSC were shown to modulate the injury response of the post-MI heart and improve cardiac function. We have previously reported that the expression of the angiogenic cytokines vascular endothelial growth factor A (VEGFA) and IL-6 is strongly upregulated in EpiSC by adenosine acting via the A receptor (A R). Since tissue hypoxia is well known to be a potent stimulus for the generation of extracellular adenosine, the present study explored the crosstalk of A R activation and hypoxia-hypoxia-inducible factor 1 alpha (HIF-1α) signaling in cultured EpiSC, isolated from rat hearts 5 days after MI. We found substantial nuclear accumulation of HIF-1α after A R activation even in the absence of hypoxia. This normoxic HIF-1α induction was PKC-dependent and involved upregulation of HIF-1α mRNA expression. While the influence of hypoxia on adenosine generation and A R signaling was only minor, hypoxia and A R activation cumulatively increased VEGFA expression. Normoxic A R activation triggered an HIF-1α-associated cell-protective metabolic switch and reduced oxygen consumption. HIF-1α targets and negative regulators PHD2 and PHD3 were only weakly induced by A R signaling, which may result in a sustained HIF-1α activity. The A R-mediated normoxic HIF-1α induction was also observed in cardiac fibroblasts from healthy mouse hearts, suggesting that this mechanism is also functional in other A R-expressing cell types. Altogether, we identified A R-mediated HIF-1α induction as novel aspect in the HIF-1α-adenosine crosstalk, which modulates EpiSC activity and can amplify HIF-1α-mediated cardioprotection.
心肌梗死（MI）可激活心外膜，使其形成驻留在心外膜低氧微环境中的心外膜基质细胞（EpiSC）。EpiSC分泌的旁分泌因子可调节心肌梗死后心脏的损伤反应并改善心脏功能。我们之前报道过，血管生成细胞因子血管内皮生长因子A（VEGFA）和白细胞介素6（IL-6）的表达在EpiSC中通过腺苷经由A受体（AR）作用而强烈上调。由于众所周知组织缺氧是细胞外腺苷生成的有力刺激因素，本研究探讨了在心肌梗死后5天从大鼠心脏分离的培养EpiSC中，AR激活与缺氧-缺氧诱导因子1α（HIF-1α）信号通路之间的相互作用。我们发现即使在没有缺氧的情况下，AR激活后HIF-1α也会大量在细胞核中积累。这种常氧下HIF-1α的诱导是蛋白激酶C（PKC）依赖性的，并且涉及HIF-1α mRNA表达的上调。虽然缺氧对腺苷生成和AR信号通路的影响较小，但缺氧和AR激活会累积增加VEGFA的表达。常氧下AR激活会触发与HIF-1α相关的细胞保护性代谢转换并减少耗氧量。HIF-1α的靶标及负调节因子脯氨酰羟化酶2（PHD2）和脯氨酰羟化酶3（PHD3）仅被AR信号通路微弱诱导，这可能导致HIF-1α活性持续存在。在健康小鼠心脏的心脏成纤维细胞中也观察到了AR介导的常氧下HIF-1α诱导，这表明该机制在其他表达AR的细胞类型中也起作用。总之，我们确定AR介导的HIF-1α诱导是HIF-1α-腺苷相互作用中的一个新方面，它可调节EpiSC的活性并能增强HIF-1α介导的心脏保护作用。
