ADENOSINE A2A RECEPTOR INACTIVATION INCREASES SURVIVAL IN POLYMICROBIAL SEPSIS

Abstract

Objective: The mechanisms that govern the impairment of bacterial clearance and immune function in sepsis are not known. High extracellular levels of the endogenous signaling nucleoside adenosine are generated during tissue hypoxia and damage associated with sepsis. Adenosine has strong immunosuppressive effects, many of which are mediated by A2A receptors expressed on immune cells. We examined whether A2A receptors are involved in the regulation of immune function in sepsis using the cecal ligation and puncture (CLP) model by genetically or pharmacologically inactivating A2A receptors. Methods: Survival after CLP was recorded for 5 days. The immunological status of animals was assessed by measuring cytokine levels, and bacterial and lymphocyte counts from blood and peritoneal lavage fluid. Apoptosis in thymus and spleen was determined using caspase-3 Western blotting, flow cytometry and TUNEL-staining. Gene expression levels were evaluated using cDNA microarray analysis. Results: A2A receptor knockout (KO) mice were protected from the lethal effect of CLP and had improved bacterial clearance when compared to wild-type (WT) animals. Levels of the cytokines IL-10 and IL-6 were markedly lower in A2A receptor KO mice. Expression of apoptotic markers was attenuated in immune organs of A2A KO mice. cDNA microarray analysis revealed strikingly distinct gene expression profiles between septic A2A receptor KO and WT mice. Similar to observations with A2A receptor KO mice, pharmacological blockade of A2A receptors provided a survival advantage and decreased IL-10 and IL-6 production. Conclusion: These studies demonstrate that A2A receptor blockade may be therapeutically useful for the treatment of sepsis.