Increased glycolysis facilitates reciprocal activation between myeloid cells and endothelial cells in pathological retinal angiogenesis.

Adenosine/adenosine receptor-mediated signaling has been implicated in the development of various ischemic diseases, including ischemic retinopathies. Here, we show that the adenosine A2a receptor (ADORA2A) promotes hypoxia-inducible transcription factor-1 (HIF-1)-dependent endothelial cell glycolysis, which is crucial for pathological angiogenesis in proliferative retinopathies. Adora2a expression is markedly increased in the retina of mice with oxygen-induced retinopathy (OIR). Endothelial cell-specific, but not macrophage-specific Adora2a deletion decreases key glycolytic enzymes and reduces pathological neovascularization in the OIR mice. In human primary retinal microvascular endothelial cells, hypoxia induces the expression of ADORA2A by activating HIF-2α. ADORA2A knockdown decreases hypoxia-induced glycolytic enzyme expression, glycolytic flux, and endothelial cell proliferation, sprouting and tubule formation. Mechanistically, ADORA2A activation promotes the transcriptional induction of glycolytic enzymes via ERK- and Akt-dependent translational activation of HIF-1α protein. Taken together, these findings advance translation of ADORA2A as a therapeutic target in the treatment of proliferative retinopathies and other diseases dependent on pathological angiogenesis.

Citri Reticulatae Pericarpium (CRP) has been utilized as a versatile medicinal herb with wide cardiovascular benefits in Asian nations for centuries. Accumulating evidence suggests that CRP and its components are effective in preventing cardiovascular diseases (CVDs) such as atherosclerosis, myocardial infarction, myocardial ischemia, arrhythmia, cardiac hypertrophy, heart failure, and hypertension. Studies show that the two most bioactive components of CRP are flavonoids and volatile oils. The cardiovascular protective effects of CRP have attracted considerable research interest due to its hypolipidemic, antiplatelet activity, antioxidant and anti-inflammatory effects. Hereby, we provide a rigorous and up-to-date overview of the cardiovascular protective properties and the potential molecular targets of CRP, and finally highlight the pharmacokinetics and the therapeutic potential of the main pharmacologically active components of CRP to treat CVDs.

Background and Purpose: Inactivation of the gene for adenosine A_2A receptors (ADORA2A for humans and Adora2a for rodents) protects against brain injury in experimental stroke. However, the cell‐specific pathogenic effects of A_2A receptors in thromboembolic stroke and the underlying mechanisms remain undefined. Here, we tested the hypothesis that inhibition of endothelial A_2A receptors after thromboembolic stroke improves post‐stroke outcomes via down‐regulation of inflammation.Experimental Approach: Thromboembolic stroke was induced by embolic middle cerebral artery occlusion in mice. Post‐stroke outcomes were determined with neurological deficit scoring, infarct volume, inflammatory marker expression, brain leukocyte infiltration, blood–brain barrier (BBB) leakage, and oedema assessment. Anti‐inflammatory effects of silencing the gene for A_2A receptors or pharmacological antagonism of these receptors were assessed in vitro.Key Results: Thromboembolic stroke induced Adora2a expression in the brain. Mice globally deficient in Adora2a (Adora2a^−/−) were resistant to stroke injury. Mice specifically deficient in endothelial Adora2a (Adora2a^ΔVEC) showed reduced leukocyte infiltration, BBB leakage, and oedema after stroke, along with attenuated downstream proinflammatory markers, both in vivo and in vitro. The A_2A receptor antagonist, KW 6002, also reduced brain injury and inflammation after stroke. Inactivation of ADORA2A inhibited endothelial inflammation via suppression of the NLRP3 inflammasome, down‐regulating cleaved caspase 1 and IL‐1β expression.Conclusions and Implications: Specific inactivation of endothelial A_2A receptors mitigated ischaemic brain injury and improved post‐stroke outcomes, at least partly, through anti‐inflammatory effects via blockade of NLRP3 inflammasome activity. Our findings may open new approaches to vascular protection after ischaemic stroke.