Abstract 374 HIF1-α induction via A<SUB>2B</SUB>R activation under normoxic conditions in post MI epicardial stromal cells and activated cardiac fibroblasts

Introduction: Myocardial infarction (MI) induces the activation of cardiac fibroblasts (aCF) and the de-novo formation of epicardial stromal cells (EpiSC). Both cell types are known to play a crucial role in the post MI healing process by secretion of paracrine factors. In a recent single cell transciptomics study of our group (Hesse et al. eLife 2021), EpiSC were found to express hypoxia-inducible factor 1 alpha (HIF1-α) and various glycolytic enzymes suggesting that the epicardium may be a hypoxic niche. Since tissue hypoxia is also well known to stimulate the extracellular formation of adenosine, the present study explored the crosstalk between A_2B receptor (A_2BR) activation and HIF1-α in cultured EpiSCs and aCFs obtained from infarcted hearts.

Methods: MI was induced in rat hearts by 50 min ischemia followed by reperfusion and 5 days after MI EpiSC were isolated according to a protocol recently reported by us (Owenier et al. Cardiovasc Res. 2020). Similar studies were also conducted in aCFs, isolated from mouse hearts 7 days after MI. Oxygen consumption and metabolic switches of the cells were analyzed by using the glycolytic rate assay with the Extracellular Flux Technology (Seahorse XFe96).

Results: Using the A_2BR-selective agonist BAY 60-6583 we found that even under normoxic conditions, A_2BR activation significantly increased HIF1-α mRNA expression in EpiSCs and aCFs. In addition, this activation was associated with a significant decrease in mitochondrial oxygen consumption. In aCFs, normoxic A_2BR activation similarly induced a HIF1-α-associated metabolic switch towards glycolysis. Both, the upregulation of HIF1-α mRNA together with the glycolytic switch and decreased oxygen consumption, were also observed in cardiac fibroblasts obtained from healthy mouse hearts.

Conclusion: Even under normoxic conditions, extracellular adenosine can induce HIF1-α in EpiSCs and aCFs, via A2BR activation. The resulting metabolic switch towards glycolysis may be cardioprotective and discloses a novel aspect in HIF1-α regulation.

Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5
HIF1-α induction via A_2BR activation under normoxic conditions in post MI epicardial stromal cells and activated cardiac fibroblasts
J. Steinhausen¹, J. Hesse¹, Z. Ding¹, C. Alter¹, J. Schrader¹
¹Institut für Molekulare Kardiologie, Universitätsklinikum Düsseldorf, Düsseldorf;
Introduction: Myocardial infarction (MI) induces the activation of cardiac fibroblasts (aCF) and the de-novo formation of epicardial stromal cells (EpiSC). Both cell types are known to play a crucial role in the post MI healing process by secretion of paracrine factors. In a recent single cell transciptomics study of our group (Hesse et al. eLife 2021), EpiSC were found to express hypoxia-inducible factor 1 alpha (HIF1-α) and various glycolytic enzymes suggesting that the epicardium may be a hypoxic niche. Since tissue hypoxia is also well known to stimulate the extracellular formation of adenosine, the present study explored the crosstalk between A_2B receptor (A_2BR) activation and HIF1-α in cultured EpiSCs and aCFs obtained from infarcted hearts. Methods: MI was induced in rat hearts by 50 min ischemia followed by reperfusion and 5 days after MI EpiSC were isolated according to a protocol recently reported by us (Owenier et al. Cardiovasc Res. 2020). Similar studies were also conducted in aCFs, isolated from mouse hearts 7 days after MI. Oxygen consumption and metabolic switches of the cells were analyzed by using the glycolytic rate assay with the Extracellular Flux Technology (Seahorse XFe96). Results: Using the A_2BR-selective agonist BAY 60-6583 we found that even under normoxic conditions, A_2BR activation significantly increased HIF1-α mRNA expression in EpiSCs and aCFs. In addition, this activation was associated with a significant decrease in mitochondrial oxygen consumption. In aCFs, normoxic A_2BR activation similarly induced a HIF1-α-associated metabolic switch towards glycolysis. Both, the upregulation of HIF1-α mRNA together with the glycolytic switch and decreased oxygen consumption, were also observed in cardiac fibroblasts obtained from healthy mouse hearts. Conclusion: Even under normoxic conditions, extracellular adenosine can induce HIF1-α in EpiSCs and aCFs, via A2BR activation. The resulting metabolic switch towards glycolysis may be cardioprotective and discloses a novel aspect in HIF1-α regulation.
https://dgk.org/kongress_programme/jt2022/aP1970.html