Intracellular adenosine regulates epigenetic programming in endothelial cells to promote angiogenesis

Abstract

The nucleoside adenosine is a potent regulator of vascular homeostasis, but it remains unclear how expression or function of the adenosine‐metabolizing enzyme adenosine kinase (ADK) and the intracellular adenosine levels influence angiogenesis. We show here that hypoxia lowered the expression of ADK and increased the levels of intracellular adenosine in human endothelial cells. Knockdown (KD) of ADK elevated intracellular adenosine, promoted proliferation, migration, and angiogenic sprouting in human endothelial cells. Additionally, mice deficient in endothelial ADK displayed increased angiogenesis as evidenced by the rapid development of the retinal and hindbrain vasculature, increased healing of skin wounds, and prompt recovery of arterial blood flow in the ischemic hindlimb. Mechanistically, hypomethylation of the promoters of a series of pro‐angiogenic genes, especially for VEGFR2 in ADK KD cells, was demonstrated by the Infinium methylation assay. Methylation‐specific PCR, bisulfite sequencing, and methylated DNA immunoprecipitation further confirmed hypomethylation in the promoter region of VEGFR2 in ADK‐deficient endothelial cells. Accordingly, loss or inactivation of ADK increased VEGFR2 expression and signaling in endothelial cells. Based on these findings, we propose that ADK downregulation‐induced elevation of intracellular adenosine levels in endothelial cells in the setting of hypoxia is one of the crucial intrinsic mechanisms that promote angiogenesis.

Regulation of endothelial intracellular adenosine via adenosine kinase epigenetically modulates vascular inflammation

“…Additionally, inhibition of ADK in islet β-cells and cardiomyocytes promotes islet β-cell proliferation and cardiomyocyte growth 36 , 37 . In line with these reports, we have observed that the accumulation of intracellular adenosine due to ADK KD did not cause apoptosis, but induced the proliferation of endothelial cells 10 . Thus, the anti-inflammatory effect of elevated intracellular adenosine is not a consequence of endothelial injury.…”

“…Since intracellular and extracellular pools of adenosine are exchanged dynamically through the equilibrative nucleoside transporters (ENTs) 9 , we next tested whether adenosine receptors are responsible for the suppression of adhesion molecule expression upon ADK KD. Among the four adenosine receptors, A 2A Rs and A 2B Rs are prominently expressed in endothelial cells, and their expression levels were significantly upregulated by ADK KD 10 . We treated ADK-KD and -Ctrl HUVECs with vehicle or a combination of A 2A R (ZM241385) and A 2B R (MRS1754) antagonists, followed by incubation with TNF-α for 4 h. The combination of these two antagonists at concentrations that effectively lowered intracellular cAMP levels 10 did not affect TNF-α-induced expression of E-selectin, ICAM-1, or VCAM-1 in ADK-KD or -Ctrl HUVECs (Supplementary Fig.…”

PRKAA1/AMPKα1-driven glycolysis in endothelial cells exposed to disturbed flow protects against atherosclerosis

“…As described in a previous publication 57 , the collagen surface in a 24-well plate was prepared by mixing rat tail collagen type one (Cat. No.…”

Novel Players in the Aging Synapse: Impact on Cognition

“…253 Furthermore, an in vitro study showed that A 2A R (ZM 241385) and A 2B R (MRS1754) antagonism does not change adenosine-induced hypomethylation in human umbilical vein endothelial cells. 254 Interestingly, although epigenetic effect of adenosine is receptor-independent, adenosine receptor gene(s) could also be epigenetically modified through global methylation. A previous study has identified three CpG islands in the 5¢UTR region of human ADORA2A, which regulates its gene and protein expression.…”