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ALMEIDA, C. S. Evaluation of immunomodulation induced by crotoxin from Crotalus durissus terrificus snake venom in experimental model of inflammatory bowel disease. 2014. 119 p. Ph. D. thesis (Immunology) Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, 2014. The loss of the tolerance against enteric bacteria, immune cells activation and leukocyte infiltration are characteristic of the gastrointestinal inflammations such as Crohn's disease and ulcerative colitis. However, the factors involved in the development of these intestinal diseases are not yet clearly established. In the present work it was analyzed the modulatory effect of the crotoxin (CTX), the major toxin isolated from Crotalus durissus terrificus snake venom, in the experimental model of colitis induced by intra-rectal instillation of 2,4,6 trinitrobenzene sulfonic acid (TNBS) in mice. It was firstly established the experimental model and determined the therapeutic administration of the CTX (18 hours after the TNBS instillation). We observed that this toxin was able to inhibit the weight loss, clinical and histological score, as well as the myeloperoxidase (MPO) synthesis and pro-inflammatory cytokines (TNF-α, IL6, IL-1 and IL -17) in BALB/c mice with bowel inflammation. Furthermore, we observed decreased number of neutrophils and macrophage (M1 and M2) in lamina propria from mice that received TNBS and CTX compared with TNBS-group. In contrast, the CTX induced increased secretion of anti-inflammatory cytokines, TGF-β and IL-10, and synthesis of prostaglandin E2 (PGE2) and lipoxin A4 (LXA4). The in vivo neutralization of these cytokines using specific monoclonal antibodies or blockage of these eicosanoids synthesis with Indomethacin and Nordihydroguaiaretic acid-NDGA inhibitors indicates that TGF-β, IL-10, PGE2 and LXA4 exert significant role in the improvement of intestinal inflammation induced by CTX in mice that received TNBS. The analyzes of distinct cell populations obtained from intestinal lamina propria and mesenteric lymph nodes and Peyer’s pathes showed that there was no significant difference in Th1 lymphocytes (CD4Tbet) between TNBS-mice and the TNBS-mice that received the CTX. However, CTX induced an increase of T regulatory cells (CD4FoxP3) that are involved in immune tolerance and decreased Th17 population (CD4RORγt), which is directly related with the exacerbation of mucosal immune response, as observed in Crohn's disease. Together, these results indicate that CTX is able to modulate intestinal acute inflammatory response induced by TNBS resulting in the improvement of clinical status of the mice. In addition, TGF-β, IL-10, PGE2 and LXA4 and T regulatory cells are involved in modulatory effect exerted by CTX in vivo.

Estudo da imunomodulação induzida pela crotoxina do veneno de Crotalus durissus terrificus em modelo experimental de doença inflamatória no intestino.