Desenvolvimento de um modelo experimental de esteatohepatite induzida pelo antineoplásico irinotecano

Abstract

The nonalcoholic steatohepatitis (NASH) is a relevant adverse effect of the chemotherapy with irinotecan, since it has been associated with increased surgical mortality after hepatic resections. So far there are no reports in the literature of a well established experimental irinotecan-induced NASH model. Aim: Develop an experimental model of irinotecan-induced NASH in mice that simulate the full histological alterations found in the clinical practice. Study the possible mechanisms and mediators involved into its pathophysiology including inflammatory cytokines, oxidative stress and the participation of intestinal bacterial translocation. Methods: Male swiss mice weighting between 35 and 30g were divided into experimental groups (n=8-10) and were injected with saline (5 mL/kg, i.p.) or irinotecan in the following dosages: 25, 50, 75 or 100 mg/kg, i.p, three times a week every other day. Mice were weighted and killed at the end of the weeks 1, 3, 5, 7 and 9. Measurements of ALT and AST, leukocytes, total proteins were performed in blood samples as well as cultures of portal vein and ocular plexus blood. In the hepatic tissue samples, total lipids, myeloperoxidase, malonaldehyde and nonproteic sulfidryl groups (NPSH) levels were analyzed, followed by histological evaluation, after slide preparation through HE and Masson methods. Duodenal samples were examined histologically for mucositis grading. Immunohistochemistry analysis for IL-1, IL-18, NOSi, TNFα e TLR-4 were performed in both hepatic and duodenal tissue samples. Statistical analysis was carried out through Student’s t test or Mann-Whitney test, as indicated. Results: The dose of 50mg/kg of irinotecan three times a week i.p. (IRI 50) associated to weight loss, low white cell count, hepatomegaly, decreased total plasma proteins and elevated hepatic enzymes (AST and ALT). IRI 50 altered oxidative stress parameters, elevating elevating malonaldehyde and decreasing NSPG levels at hepatic tissue starting at week 1. IRI 50 also was associated to the full histological changes found in NASH (steatosis, neutrophilic infiltration and hepatocyte balloning) when analyzed at the seventh week and compared to saline group. The duodenal samples showed severe mucositis changes starting at week three. It was also demonstrated elevated immunostaining for IL-1, iNOS and TLR-4 in both liver and duodenal samples at week seven. The cultures were positive for gram negative intestinal bacteria in portal and orbital blood since the first experimental week. Conclusion: The administration of the irinotecan 50mg/kg i.p. three times a week for seven consecutive weeks is an experimental model that reproduces all the histological changes found in the irinotecan-associated NASH found in clinical practice. Concomitant participation of inflammatory cytokines and oxidative stress were found to play a role in NASH pathogenesis in this model. Intestinal gram-negative bacterial translocation leading to portal bacteremia may represent the very first hepatic insult and the connection between the pathogenic factors.