A 1 adenosine receptor knockout mice exhibit increased mortality, renal dysfunction, and hepatic injury in murine septic peritonitis. Am J Physiol Renal Physiol 289: F369 -F376, 2005. First published March 22, 2005; doi:10.1152/ajprenal.00470.2004.-Sepsis is a leading cause of multiorgan dysfunction and death in hospitalized patients. Dysregulated inflammatory processes and apoptosis contribute to the pathogenesis of sepsis-induced organ dysfunction and death. A 1 adenosine receptor (A1AR) activation reduces inflammation and apoptosis after ischemia-reperfusion injury. Therefore, we questioned whether A 1AR-mediated reduction of inflammation and apoptosis could improve mortality and organ dysfunction in a murine model of sepsis. A 1AR knockout mice (A1 knockout) and their wild-type (A 1 wild-type) littermate controls were subjected to cecal ligation and double puncture (CLP) with a 20-gauge needle. A 1 knockout mice or A1 wild-type mice treated with 1,3-dipropyl-8-cyclopentylxanthine (a selective A 1AR antagonist) had a significantly higher mortality rate compared with A 1 wild-type mice following CLP. Mice lacking endogenous A 1ARs demonstrated significant elevations in plasma creatinine, alanine aminotransferase, aspartate aminotransferase, keratinocyte-derived chemokine, and tumor necrosis factor-␣ 24 h after induction of sepsis compared with wild-type mice. The renal corticomedullary junction from A 1 knockout mice also exhibited increased myeloperoxidase activity, intercellular adhesion molecule-1 protein, and mRNA encoding proinflammatory cytokines compared with renal samples from A 1 wild-type littermate controls. No difference in renal tubular apoptosis was detected between A 1 knockout and A 1 wild-type mice. We conclude that endogenous A1AR activation confers a protective effect in mice from septic peritonitis primarily by attenuating the hyperacute inflammatory response in sepsis.acute renal failure; multiorgan injury; survival SEPSIS REPRESENTS A MAJOR clinical problem in hospitalized patients. Despite advances in antibiotic, hemodynamic, and ventilatory support, the incidence of sepsis and the numbers of sepsis-related deaths are increasing. On an annual basis, sepsis affects ϳ750,000 patients in the United States and accounts for nearly 215,000 deaths (2). Development of sepsis-induced organ injury and subsequent progression to acute organ dysfunction are associated with increased morbidity and mortality.Although the pathogenesis of sepsis-induced acute organ injury and dysfunction is not completely understood, the initial hyperinflammatory process and subsequent hypoimmune phase contribute to mortality and morbidity in sepsis. The initial hyperinflammatory response seen in sepsis is associated with uncontrolled, hyperexuberant cytokine production that can be deleterious to various tissues and leads to organ injury and dysfunction. After this hyperinflammatory phase, a hypoimmune phase ensues with enhanced apoptotic cell death occurring in multiple organs including the spleen, kidney, liver, and he...