Efeitos do exercicio físico na infecção experimental por toxocara canis

Abstract

Human toxocarose is an important zoonotic disease caused by the larvae of Toxocara canis. The infection occurs by accidental ingestion of embryonated eggs released in dog feces. Physical exercise is associated with numerous health benefits, improving physical fitness and stimulating immune factors, which may help the immune response to combat the parasite. Thus, the aim of this study was to standardize an experimental model of T. canis infection and to evaluate the effect of physical exercise with moderate intensity in the immune response in experimental infection. Adult females BALB/c mice (8 weeks) were divided into the following groups: Sedentary without infection (CONTROL), Sedentary with infection (INF), Exercise without infection (EX and EX-EX), Exercise with infection (INF-EX), Infected with previous exercise (EX-INF) and Infected with previous exercise and trained (EX-INF-EX). The infection consisted in 100L of solution containing 1000 embryonated eggs by the intragastric way (gavage). The swimming training was conducted at moderate-intensity exercise, being classified by the training duration (1 session/day with 90 minutes with no extra load). The mice were euthanized at 7 and 14 days post-infection (p.i.) for characterization of the larval migration. The blood was collected for the hematological analysis and to determine the profile of systemic cytokines. The brain, liver and lungs were removed for histopathological analysis, to determine the cytokine profile and to recover and count the larvae. The results showed migrating larvae in the liver with 1 day p.i., in the lungs with 3 days p.i. and in the brain from 5 days p.i. The liver tissue showed inflammatory infiltrate, the lung tissue showed thickening of the septum and the brain tissue demonstrated hemorrhagic areas. The leukocytosis, neutrophilia and eosinophilia appeared from 7 dpi. The increase in the eosinophils peroxidases and neutrophils was present in the analyzed tissues. The innate inflammatory response/TH17/TH2, with the prevalence of the latter, was evidenced by increased IL-4, IL- 5, IL-13 and IL-33, despite the increase in IL-6 and IL- 17 levels. The conclusion was that the T. canis infection produced a systemic pro-inflammatory response by activating effector cells of the innate immune response and TH2-dominant immune response in histopathological changes. In addition, the exercise potentiated the immune system to a standard mixed response TH1/TH2 improving the body's ability to tolerate more adequately the damage caused by inflammatory events of T. canis infection.