Avaliação do potencial imunomodulatório de linhagens de Lactococcus lactis portadoras de vetores de expressão eucariótica codificando as interleucinas 4 e 10 de Mus musculus no modelo de diabetes tipo 1 induzido quimicamente por estreptozotocina

Abstract

Type 1 diabetes (T1D) is an organ-specific autoimmune disease, characterized by the progressive destruction of insulin-producing pancreatic islets β cells by autoreactive leukocytes and their mediators. In the progression of inflammation in the islets of Langerhans, the determinant role of autoreactive CD4+ and CD8+ T lymphocytes with specificity for pancreatic autoantigens, as well as the increase of pro-inflammatory cytokines, such as IL-1b, IFN-g e TNF-a, is observed. In order to mimic the experimental diabetes in mice, it was chosen the model of multiple doses of streptozotocin (STZ), an alkylating agent with cytotoxic action able to establish phenotype and cellular infiltrate in the pancreatic islets more similar with the human T1D. Simultaneously, previous studies have shown that immune responses due to stimuli from the gut can modulate the harmful inflammation, which culminates in the onset of the disease. Therefore, the objective of the present study was to evaluate the immunomodulatory potential of Lactococcus lactis MG1363 FnBPA+ carrying the eukaryotic expression vectors pValac::dts::IL-4 and pValac::IL-10, administered by the intragastric route to male C57BL/6 mice, in the T1D chemically induced model by multiple doses of STZ. By monitoring weight and glycemia and glycosuria levels, all animals that received multiple doses of STZ became diabetic soon after the chemical induction of experimental T1D. However, animals that received both the L. lactis MG1363 FnBPA+ (pValac::dts::IL-4) and the L. lactis MG1363 FnBPA+ (pValac::IL-10) strains showed the lowest degree of insulitis among the groups that also received the intraperitoneal injections of STZ and also presented statistically higher levels of IL-2, when compared to the animals that received only the injections of STZ (positive control group), indicating a stimulus to expansion and activation of Treg cells in the pancreas. Thus, this study constitutes a first step in the search for the understanding of the mechanisms intrinsic to T1D using L. lactis for delivery of vectors encoding interleukins 4 and 10, by the intragastric route, in the STZinduced diabetes model. Therefore, the results obtained raise new questions about the immunomodulatory effects verified, aiming at the understanding of the mechanisms associated with the progression of T1D and, possibly, helping in the search for alternative therapies.