adenosine-kinase and Reperfusion-Injury

Renal injury might originate from multiple factors like ischemia reperfusion (I/R), drug toxicity, cystic fibrosis, radio contrast agent etc. The four adenosine receptor subtypes have been identified and found to show diverse physiological and pathological roles in kidney diseases. The activation of A

Topics: Acute Kidney Injury; Adenosine; Adenosine Kinase; Animals; Humans; Kidney Diseases; Receptors, Purinergic P1; Reperfusion Injury

The endogenous metabolite adenosine has been recognized as a protective agent in the setting of ischemia-reperfusion. Because the formation of adenosine during ischemia is closely linked to ATP catabolism, and its actions antagonize the deleterious metabolic and cardiovascular consequences of ischemia, it has been named a "retaliatory" metabolite. During recent years, however, the insight into its diverse scope of anti-inflammatory actions has increased considerably. In this review, the beneficial metabolic and cardiovascular actions of adenosine in ischemia and reperfusion are briefly outlined, followed by an extensive discussion of the established and putative anti-inflammatory actions of adenosine in the inflammatory response to ischemia and reperfusion. It is demonstrated that adenosine interferes with activated neutrophil function, neutrophil-endothelial adhesive interactions, the production and release of various inflammatory mediators, the expression of adhesion molecules, and that it activates cellular antioxidant defense systems, thus providing protective effects at multiple levels in the pathogenesis of ischemia and reperfusion. Finally, several potential pharmacological strategies to enhance the "natural defense mechanism" provided by endogenous adenosine are presented.

Topics: Adenosine; Adenosine Deaminase Inhibitors; Adenosine Kinase; Adenosine Triphosphate; Aminoimidazole Carboxamide; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cardiovascular System; Enzyme Inhibitors; Humans; Ischemic Preconditioning; Nucleosides; Receptors, Purinergic P1; Reperfusion Injury; Ribonucleosides

Acute kidney injury (AKI) has a high morbidity and mortality, and there is no targeted treatment yet. One of the main causes of AKI is ischemia-reperfusion (IR). Increased release of adenosine under stress and hypoxia exerts anti-inflammatory and antioxidant effects. Adenosine kinase (ADK) is an important enzyme that eliminates adenosine in cells, and can maintain low adenosine concentration in cells. Our previous studies have shown that pretreatment of adenosine kinase inhibitor ABT-702 could markedly attenuate cisplatin-induced nephrotoxicity both in vivo and in vitro. This study is designed to investigate the effect of ADK inhibition on IR-induced AKI. The results showed that ADK expression was positively correlated with the degree of renal tubular injury, which suggested that the degree of ADK inhibition reflected the severity of acute tubular necrosis. In vivo, ADK inhibitor could reduce IR-induced renal injury, which might play a protective role by increasing tissue adenosine level, inhibiting oxidative stress, and reducing cell apoptosis. In HK2 cells, cobaltous dichloride (CoCl

Topics: Acute Kidney Injury; Adenosine Kinase; Adult; Animals; Apoptosis; Cell Line; Cobalt; Enzyme Inhibitors; Female; Humans; Inflammation; Inosine; Kidney Tubules; Male; Mice, Inbred C57BL; Morpholines; Necrosis; Oxidative Stress; Pyrimidines; Reperfusion Injury

The molecular mechanisms underlying vascular inflammation and associated inflammatory vascular diseases are not well defined. Here we show that endothelial intracellular adenosine and its key regulator adenosine kinase (ADK) play important roles in vascular inflammation. Pro-inflammatory stimuli lead to endothelial inflammation by increasing endothelial ADK expression, reducing the level of intracellular adenosine in endothelial cells, and activating the transmethylation pathway through increasing the association of ADK with S-adenosylhomocysteine (SAH) hydrolase (SAHH). Increasing intracellular adenosine by genetic ADK knockdown or exogenous adenosine reduces activation of the transmethylation pathway and attenuates the endothelial inflammatory response. In addition, loss of endothelial ADK in mice leads to reduced atherosclerosis and affords protection against ischemia/reperfusion injury of the cerebral cortex. Taken together, these results demonstrate that intracellular adenosine, which is controlled by the key molecular regulator ADK, influences endothelial inflammation and vascular inflammatory diseases.The molecular mechanisms underlying vascular inflammation are unclear. Here the authors show that pro-inflammatory stimuli lead to endothelial inflammation by increasing adenosine kinase expression, and that its knockdown in endothelial cells inhibits atherosclerosis and cerebral ischemic injury in mice.

Topics: Adenosine; Adenosine Kinase; Adenosylhomocysteinase; Animals; Atherosclerosis; Blood Vessels; Cerebral Cortex; Endothelial Cells; Epigenesis, Genetic; Gene Expression Regulation; Gene Knockdown Techniques; Inflammation; Mice; Mice, Knockout, ApoE; Reperfusion Injury

The rate of ischemic brain injury varies with the brain region, requiring only hours in striatum but days in hippocampus. Such maturation implies the existence of endogenous neuroprotective mechanisms. Adenosine is an endogenous neuroprotectant regulated by adenosine kinase (ADK). To investigate, whether adenosine might play a role in protecting the hippocampus after focal ischemia, we subjected transgenic mice, which overexpress ADK in hippocampal neurons (Adk-tg mice) to transient middle cerebral artery occlusion (MCAO). Although the hippocampus of wild-type (wt) mice was consistently spared from injury after 60 mins of MCAO, hippocampal injury became evident in Adk-tg mice after only 15 mins of MCAO. To determine, whether downregulation of hippocampal ADK might qualify as candidate mechanism mediating endogenous neuroprotection, we evaluated ADK expression in wt mice after several periods of reperfusion after 15 or 60 mins of MCAO. After 60 mins of MCAO, hippocampal ADK was significantly reduced in both hemispheres after 1, 3, and 24 h of reperfusion. Reduction of ADK-immunoreactivity corresponded to a 2.2-fold increase in hippocampal adenosine at 3 h of reperfusion. Remarkably, a significant reduction of ADK immunoreactivity was also found in the ipsilateral (stroked) hippocampus after 15 mins of MCAO and 3 h of reperfusion. Thus, transient downregulation of hippocampal ADK after stroke might be a protective mechanism during maturation hippocampal cell loss.

Topics: Adenosine; Adenosine Kinase; Animals; Corpus Striatum; Down-Regulation; Gene Expression Regulation, Enzymologic; Hippocampus; Infarction, Middle Cerebral Artery; Mice; Mice, Transgenic; Neurons; Neuroprotective Agents; Organ Specificity; Reperfusion Injury; Time Factors