Immunomodulation From Moderate Exercise Promotes Control of Experimental Cutaneous Leishmaniasis

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.

Keywords: Balb/c; control of infection; exercise; immune response; leishmaniasis.

Figure 1

Control of exercise intensity [blood lactate concentrations (A) and TBARs (B)]: (A) Blood lactate concentrations were measured at rest as well as after a session of study protocol and intense exercise. (B) MDA concentrations (lipid peroxidation) were measured at rest as well as after a session of study protocol and intense exercise. The animals used in these dosages, lactate (n = 15) and lipid peroxidation (n = 15), did not participate of the experimental groups. (*P < 0.01 compared to rest, **P < 0.001 compared to rest and study protocol). Values are expressed as mean and ± SD. Data were analyzed by one-way ANOVA followed by Tukey's multiple comparison test.

Figure 2

Effect of exercise on the development of lesions on the paws of BALB/c mice that were infected with L. major (2 x 106 promastigotes): (A–C) The size of paws was measured weekly for 12 weeks with a pachymeter (Mitutoyo). Results are expressed as the difference between the contralateral paw and infected paw (mm). The arrow indicates the start of training and/or treatment. Values represent the average of two experiments with 8 animals per group in each experiment. (D) A representative image of the infected footpad from 1 animal of each different group at the end of the assay (13th week). Values were expressed as mean ± SD. I—Infected. IT—Animals infected and treated with therapeutic dose (8 mg) of Glucantime® after the onset of injury. ITE - Animals infected, trained and treated with therapeutic dose (8 mg) of Glucantime® after the onset of injury. IE—infected animals trained from the first week of infection. IEP—infected animals trained after the onset of injury (6th week). EAPI—Animals trained for 6 weeks, infected and trained for 12 weeks. * The week displaying significant difference (P < 0.001) from the control group (I).

Figure 3

Delayed type hypersensitivity (DTH) to total Leishmania major antigen in BALB / c mice trained and/or treated with Glucantime®. DTH was carried out in the 13th week, at the end of the experiment. The DTH was evaluated using 20 μg of total L. major antigen in 20 μL of saline inoculated into the contralateral non-infected paw. Results obtained after 48 h of antigen inoculum of L. major. Values are expressed as mean ± SD. Data were analyzed by one-way ANOVA followed by Tukey's multiple comparison test. *P < 0.05 compared to (I).

Figure 4

Parasitic burden of infected mice. Parasites were isolated from the paws after 13 weeks of infection and quantified by serial dilution in Schneider's medium plus 20% FBS. After isolation, they were kept at 26°C until the presence of parasites was observed in group I (7th day). Then, the parasites were quantified in Neubauer Chamber, and the number of parasites obtained was divided by the total weight (gram) of infected paws tissue. Values are expressed as the mean of two experiments with the samples of eight animals per group grouped as a pool. The bars represent the standard error of the mean. I—Infected. IT—Animals infected and treated with a therapeutic dose (8 mg) of Glucantime®, after the onset of the lesion. ITE—Animals infected, trained and treated with therapeutic dose (8 mg) of Glucantime® after the onset of injury. IE—Animals infected and trained from the first week of infection. IEP—Animals infected and trained after the appearance of the lesion (6th week). EAPI—Animals trained for 6 weeks, infected and trained for another 12 weeks. *P < 0.05 with respect to I.

Figure 5

Effect of physical exercise on cytokine production by lymph node cells of BALB/c mice. The concentration of cytokines was determined by ELISA according to Material and Methods. Values represent the mean of two experiments with samples of the eight animals per group grouped as a pool. (A) IL-4; (B) IL-10; (C) TGF-β; (D) IFN-γ; (E) IL-12; (F) TNF-α; (G) IFN-γ/IL-4 ratio; (H) IFN-γ/IL-10 ratio. The bars represent the standard error. C—Sedentary and uninfected. E—Trained not infected. I—Infected. IT—Animals infected and treated with a therapeutic dose (8 mg) of Glucantime®, after the onset of the lesion. ITE—Animals infected, trained and treated with therapeutic dose (8 mg) of Glucantime® after the onset of injury. IE—Animals infected and trained from the first week of infection. IEP—Animals infected and trained after the appearance of the lesion (6th week). #P < 0.05 in relation to C and in *P < 0.05 in relation to I.

Figure 6

Effect of physical exercise on cytokine production by cells in the paws of infected BALB/c mice. The cytokines IL-4 (A), IL-10 (B), TGF-β (C), IL-12 (D), IFN-γ (E) and TNF (F) were determined by ELISA (see Material and Methods). Values represent the mean of two experiments with samples of the eight animals per group grouped as a pool. The bars represent the standard error. C—Non-infected sedentary. E—Trained not infected. I—Infected. IT—Animals infected and treated with a therapeutic dose (8 mg) of Glucantime®, after the onset of the lesion. ITE—Animals infected, trained and treated with therapeutic dose (8 mg) of Glucantime® after the onset of injury. IE—Animals infected and trained from the first week of infection. IEP—Animals infected and trained after the appearance of the lesion (6 th week). EAPI—Animals trained for 6 weeks, infected and trained for another 12 weeks. *P < 0.05 with respect to I.