Abstract 12514: Elevated Intracellular Adenosine Epigenetically Regulates Endothelial Inflammation (Best of Basic Science Abstract)

Abstract

Background and Objectives: Adenosine is a potent modulator of endothelial inflammation. However, the molecular mechanisms by which adenosine regulates endothelial inflammation has not been fully understood. This study aims to determine the effect of elevated intracellular adenosine on endothelial inflammation and investigate the involvement of epigenetic mechanism in this effect. Methods and Results: Adenosine but not adenosine receptor agonists alleviated the TNF-α-induced expression of endothelial adhesion molecules (E-selectin, ICAM-1 and VCAM-1). This effect was abrogated by nucleoside transporter inhibitor NBMPR but not by adenosine receptor antagonists. Knockdown of adenosine metabolic enzyme adenosine kinase (ADK) by shRNA or inhibition of ADK by inhibitors augmented intracellular adenosine and also attenuated TNF-α-induced expression of adhesion molecules. This effect was also not affected by adenosine receptor antagonists. Mechanistically, adenosine treatment or ADK knockdown deactivated the SAH hydrolase (SAHH) and histone H3K4 methyltransferase (HMT) and lowered H3K4 di- and tri- methylation levels. Erasing these histone marks by inhibition of SAHH and depletion of WDR5, a core subunit of HMT complex blocked the anti-inflammatory effects of adenosine and ADK knockdown. Co-IP assay showed that ADK can bind with SAHH and WDR5 to methylate H3K4 in a spatially effective manner. With the intravital microscopy we observed the compromised rolling and adhesion of leukocytes in postcapillary venues of endothelial specific ADK deficient mice. Furthermore, atheroprotection in Apoe-/- mice on a Western diet and neuroprotection in acute cerebral ischemic mice were conferred in endothelial specific ADK deficient mice. Conclusion: Our study provides evidence that intracellular adenosine attenuates endothelial inflammation through epigenetic pathways and ADK is a promising therapeutic target to treat inflammatory vascular diseases.