Estudo do efeito de um novo agonista do receptor A2A de adenosina, ATL313, sobre a enterite induzida pela toxina a do clostridium difficile em alça ileal isolada de camundongos

Abstract

C. difficile toxin A (TxA) plays an important pathogenic role in antibiotic-induced diarrhea and pseudomembranous colitis, a condition characterized by intense mucosal inflammation and secretion. Agonist activity at A2A adenosine receptors (A2A ARs) attenuates inflammation and damage in many tissues. This study evaluated the effect of a new selective A2A AR agonist (4-{3-[6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl]prop-2-ynyl}piperidine-1-carboxylic acid methyl ester; ATL313) on TxA-induced enteritis in murine ileal loops. ATL313 (0.05-5 nM) and/or the A2A AR antagonist (ZM241385; 5 nM) or PBS were injected inside ileal loops immediately prior to challenge with TxA (1-10 mg/loop) or PBS. Intestinal fluid volume/length and weight/length ratios were calculated 3 h later. Ileal tissue samples were collected for measurement of myeloperoxidase (MPO) content, evaluation of ADA activity, for histopathology and apoptotic immunohistochemistry (ApopTagâ) and for assessment of TNF-α levels by ELISA. TxA (1-10 µg/loop) significantly (p<0.05) increased volume/length and weight/length, reaching maximum values at 5µg/loop dosage. ATL313 (5 nM) treatment significantly (p<0.05) reduced TxA-induced volume/length and weight/length, as well as prevented mucosal disruption and TxA-induced apoptosis. These protective effects were reversed by ZM241385 (5 nM), the A2A AR antagonist. ATL313 (5 nM) also reduced neutrophil infiltration, as measured by MPO content; reduced the toxin A-induced increase in ADA activity. Prior to the challenge with TxA, a systemic injection of fucoidin, but not PBS, also reduced tissue destruction and toxin A-induced increase in ADA activity. In conclusion, the A2A AR agonist ATL313 has a great antiinflammatory effect in TxA-induced mice enteritis, significantly reducing tissue destruction and ADA activity. In addition, our data suggested that TxA-induced increase in ADA activity and tissue damage in murine ileal loops are related to the neutrophil infiltration induced by this toxin.