Concomitant exercise training attenuates the cardioprotective effects of pharmacological therapy in a murine model of acute infectious myocarditis.

When administered alone, preinfection exercise training and benznidazole-based chemotherapy induce cardioprotection in Chagas disease. However, the effect of concomitant exercise and benznidazole treatment is unknown. We investigated whether exercise and specific chemotherapy could interact to modulate parasitemia, inflammation, redox status and heart damage in a murine model of T. cruzi infection. Wistar rats were randomized into an uninfected control group (CNT) and four groups infected with T. cruzi: sedentary untreated (SUN) and treated (STR), and trained untreated (TUN) and treated (TTR). Running training was administered 5 days/week for 4 weeks. Treated animals concomitantly received 100 mg/kg/day benznidazole. Heart inflammation and reactive damage were not detected in CNT animals. Compared to SUN, TUN animals presented increased levels of parasitemia, myocarditis, nitric oxide, hydrogen peroxide, protein carbonyl, malondialdehyde, cytokines (IFN-γ, TNF-α, IL-4, IL-6, IL-10 and IL-17), catalase, superoxide dismutase and glutathione reductase activity, as well as reduced heart non-protein antioxidant levels (P < 0.05). TTR animals exhibited higher levels of parasitemia, myocarditis, hydrogen peroxide, malondialdehyde, IFN-γ, TNF-α and IL-6 than STR animals (P < 0.05), which showed the lowest levels of all analyzed parameters compared to the other groups (P < 0.05). Our findings indicate that exercise aggravates acute infection. When concomitantly administered with benznidazole, exercise training impaired parasitic control and chemotherapy-induced cardioprotection in T. cruzi-infected rats. Considering that exercise training and T. cruzi infection constitute independent metabolic challenges, the negative effects of concomitant treatment are potentially related to the overlapping oxidative and immunoinflammatory demands of exercise and the infection itself.