RESUMO
Multiple mucosal immune factors, such as TNF-alpha and IL-1beta, are thought to be key mediators involved in inflammatory bowel disease. We evaluated the role of the pro-inflammatory cytokine TNF-alpha on nitric oxide synthase (NOS) expression in indomethacin-induced jejunoileitis in rats. Jejunoileitis was induced in rats with subcutaneous injections of indomethacin (7.5 mg/kg) 24 h apart for two consecutive days, and animals were randomized into four groups. Group 1 received only indomethacin. Group 2 was treated with a daily dose of phosphodiesterase (PDE) inhibitor (theophylline or pentoxifylline) by oral gavage for 2 days before and 4 days after indomethacin. Group 3 received a single dose of anti-TNF-alpha monoclonal antibody (TNF-Ab, IP) 30 min before indomethacin. Group 4 was treated with 1 h hyperbaric oxygenation (HBO(2)) for 5 days after indomethacin. Rats were sacrificed at 12 h or 4 days after final indomethacin injection. PDE inhibitor, TNF-Ab, or HBO(2) treatment significantly decreased indomethacin-induced ulceration, myeloperoxidase activity, and disease activity index. Although indomethacin significantly increased serum TNF-alpha and nitrate/nitrite (NOx) concentrations above control values at 12 h, inducible NOS (iNOS) expression was detected only at day 4. Serum IL-1beta levels did not change at 12 h but increased 4-fold after 4 days. Indomethacin had no effect on constitutive NOS. Treatment with PDE inhibitor, TNF-Ab, or HBO(2) significantly reduced serum/tissue TNF-alpha, IL-1beta, NOx, and iNOS expression. Our data show TNF-alpha plays an early pro-inflammatory role in indomethacin-induced jejunoileitis. Additionally, down-regulation of NOx by PDE inhibitors, TNF-Ab, or HBO(2) suggests that TNF-alpha modulates iNOS expression.
Assuntos
Enterite/metabolismo , Ileíte/metabolismo , Indometacina/toxicidade , Doenças do Jejuno/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Fator de Necrose Tumoral alfa/fisiologia , Animais , Relação Dose-Resposta a Droga , Enterite/sangue , Enterite/induzido quimicamente , Oxigenoterapia Hiperbárica , Ileíte/sangue , Ileíte/induzido quimicamente , Íleo/enzimologia , Íleo/metabolismo , Interleucina-1beta/sangue , Interleucina-1beta/metabolismo , Mucosa Intestinal/enzimologia , Mucosa Intestinal/metabolismo , Doenças do Jejuno/sangue , Doenças do Jejuno/induzido quimicamente , Jejuno/enzimologia , Jejuno/metabolismo , Masculino , Nitratos/sangue , Nitritos/sangue , Peroxidase/metabolismo , Inibidores de Fosfodiesterase/farmacologia , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Índice de Gravidade de Doença , Organismos Livres de Patógenos Específicos , Fatores de Tempo , Fator de Necrose Tumoral alfa/antagonistas & inibidores , Fator de Necrose Tumoral alfa/sangueRESUMO
Nitric oxide has been implicated in the pathogenic mechanism of inflammatory bowel disease states. We evaluated indomethacin-induced enteropathy in rats, in relation to the expression of the inducible isoform of NO synthase (iNOS) using aminosalicylic acid (5-ASA), its isomer 4-ASA (10 or 50 mg/kg/day, po), and dexamethasone, an iNOS transcription inhibitor (3 mg/kg/day, sc). Enteropathy was induced by indomethacin (7.5 mg/kg/day, sc) for two days and the small intestine was examined for lesions over the next 14 days. Indomethacin-induced small-intestinal ulcer size, mucosal myeloperoxidase activity, iNOS expression and serum nitrite/nitrate levels were maximally increased by day 4 and gradually decreased by day 14. Treatment with 5-ASA, but not 4-ASA, decreased indomethacin-induced ulcer length, myeloperoxidase activity, serum nitrite/nitrate levels and iNOS expression at day 4. Dexamethasone had a greater effect than 5-ASA in reducing myeloperoxidase activity and ulcer length by 26 and 32%, respectively. Dexamethasone also reduced serum nitrate/nitrite and iNOS expression to their basal levels. In conclusion, inhibition of iNOS expression by 5-ASA appears to be associated with diminished intestinal ulceration in indomethacin-induced enteropathy.
