Cavalcante I C, Castro M V, Barreto A R F, Sullivan G W, Vale M, Almeida P R C, Linden J, Rieger J M, Cunha F Q, Guerrant R L, Ribeiro R A, Brito G A C
Faculdade de Medicina, Universidade Federal do Ceará, Rua Delmiro de Farias, sn CEP 60.416-030, Fortaleza, CE, Brazil.
Infect Immun. 2006 May;74(5):2606-12. doi: 10.1128/IAI.74.5.2606-2612.2006.
Clostridium difficile is a spore-forming, anaerobic, gram-positive bacillus that releases two main virulence factors: toxins A and B. Toxin A 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 attenuates inflammation and damage in many tissues. This study evaluated the effects of a new selective A2A adenosine receptor agonist (ATL 313) on toxin A-induced injury in murine ileal loops. ATL 313 (0.5 to 5 nM) and/or the A2A adenosine receptor antagonist (ZM241385; 5 nM) or phosphate-buffered saline (PBS) were injected into ileal loops immediately prior to challenge with toxin A (1 to 10 microg/loop) or PBS. Intestinal fluid volume/length and weight/length ratios were calculated 3 h later. Ileal tissues were collected for the measurement of myeloperoxidase, adenosine deaminase activity, tumor necrosis factor alpha (TNF-alpha) production, histopathology, and detection of cell death by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) method. Toxin A significantly increased volume/length and weight/length ratios in a dose-dependent fashion. ATL 313 treatment significantly (P < 0.05) reduced toxin A-induced secretion and edema, prevented mucosal disruption, and neutrophil infiltration as measured by myeloperoxidase activity. ATL 313 also reduced the toxin A-induced TNF-alpha production and adenosine deaminase activity and prevented toxin A-induced cell death. These protective effects of ATL 313 were reversed by ZM241385. In conclusion, the A2A adenosine receptor agonist, ATL 313, reduces tissue injury and inflammation in mice with toxin A-induced enteritis. The finding of increased ileal adenosine deaminase activity following the administration of toxin A is new and might contribute to the pathogenesis of the toxin A-induced enteritis by deaminating endogenous adenosine.
艰难梭菌是一种形成孢子的厌氧革兰氏阳性杆菌，可释放两种主要毒力因子：毒素A和毒素B。毒素A在抗生素相关性腹泻和假膜性结肠炎中起重要致病作用，假膜性结肠炎以强烈的黏膜炎症和分泌为特征。A2A腺苷受体的激动剂活性可减轻许多组织中的炎症和损伤。本研究评估了一种新型选择性A2A腺苷受体激动剂（ATL 313）对毒素A诱导的小鼠回肠袢损伤的影响。在用毒素A（1至10微克/袢）或磷酸盐缓冲盐水（PBS）攻击之前，立即将ATL 313（0.5至5纳摩尔）和/或A2A腺苷受体拮抗剂（ZM241385；5纳摩尔）或磷酸盐缓冲盐水（PBS）注入回肠袢。3小时后计算肠液体积/长度和重量/长度比值。收集回肠组织以测量髓过氧化物酶、腺苷脱氨酶活性、肿瘤坏死因子α（TNF-α）产生、组织病理学，并通过TUNEL（末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记）方法检测细胞死亡。毒素A以剂量依赖性方式显著增加体积/长度和重量/长度比值。ATL 313治疗显著（P < 0.05）减少毒素A诱导的分泌和水肿，防止黏膜破坏以及通过髓过氧化物酶活性测量的中性粒细胞浸润。ATL 313还降低了毒素A诱导的TNF-α产生和腺苷脱氨酶活性，并防止毒素A诱导的细胞死亡。ZM241385逆转了ATL 313的这些保护作用。总之，A2A腺苷受体激动剂ATL-313可减轻毒素A诱导的小鼠肠炎中的组织损伤和炎症。毒素A给药后回肠腺苷脱氨酶活性增加这一发现是新的，可能通过使内源性腺苷脱氨而导致毒素A诱导的肠炎发病机制。
