Abstract
Physical exercise has been described as an important tool in the prevention and treatment of numerous diseases as it promotes a range of responses and adaptations in several biological systems, including the immune system. Studies on the effect of exercise on the immune system could play a critical role in improving public health. Current literature suggests that moderate intensity exercise can modulate the Th1/Th2 dichotomy directing the immune system to a Th1 cellular immune response, which favors the resolution of infections caused by intracellular microorganisms. Leishmaniasis is a group of diseases presenting a wide spectrum of clinical manifestations that range from self-limiting lesions to visceral injuries whose severity can lead to death. The etiological agents responsible for this group of diseases are protozoa of the genus Leishmania. Infections by the parasite Leishmania major in mice (Balb/c) provide a prototype model for the polarization of CD4+ T cell responses of both Th1 (resistance) or Th2 (susceptibility), which determines the progression of infections. The aim of this study was to evaluate the effect of exercise on the development of L. major experimental infections by scanning the pattern of immune response caused by exercise. Groups of Balb/c mice infected with L. major were divided into groups that preformed a physical exercise of swimming three times a week or were sedentary along with treatment or not with the reference drug, meglumine antimoniate. Animals in groups submitted to physical exercise did not appear to develop lesions and presented a significantly lower parasite load independent of drug treatment. They also showed a positive delayed hypersensitivity response to a specific Leishmania antigen compared to control animals. The IFN-γ/IL-4 and IFN-γ/IL10 ratios in trained animals were clearly tilted to a Th1 response in lymph node cells. These data suggest that moderate intensity exercise is able to modulate the Th1 response that provides a protective effect against the development of leishmanial lesions.
Highlights
Regular physical exercise promotes a series of responses and physiological adaptations that are dependent on different aspects of the activity such as volume and intensity (American College of Sports Medicine Position Stand American Heart Association, 1998, 2007; Walsh et al, 2011b)
Exercise intensity was adjusted by an increase in the weight overload (% body mass (BM)) or time of the exercise to maintain a moderate level of physical exertion
By the 8th week of exercise, the IEP, EAPI groups did not adapt satisfactorily to the increase of the overload to 6% of BM
Summary
Regular physical exercise promotes a series of responses and physiological adaptations that are dependent on different aspects of the activity such as volume and intensity (American College of Sports Medicine Position Stand American Heart Association, 1998, 2007; Walsh et al, 2011b). Intense exercise favors the resolution of bacterial infections by promoting a predominance to a Th2 type response (Malm, 2004, reviewed by Terra et al, 2012). Prolonged and strenuous exercise decreases the expression of Toll-Like Receptors in macrophages and compromises the presentation of antigens to T lymphocytes, which diminishes the Th1 inflammatory response. This anti-inflammatory effect prevents tissue damage caused by inflammatory mediators and reduces the risk of chronic inflammatory diseases, but increases the susceptibility to infections by intracellular microorganisms (Gleeson, 2006). In contrast, induces the immune system to a predominately Th1 type response that favors the resolution of viral infections and control of infections caused by intracellular microorganisms (Gleeson, 2006, 2007), which can include the bacteria Mycobacterium tuberculosis and Listeria monocytogenis along with the protozoa Toxoplasma gondii, Trypanosoma cruzi, and Leishmania spp. (Bogdan, 2008)
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