Protective role of ETA endothelin receptors during the acute phase of Trypanosoma cruzi infection in rats.

Chagas' disease, caused by Trypanosoma cruzi, has an acute phase characterized by blood-circulating trypomastigotes and amastigote proliferation in several cell types, especially muscle cells. In the chronic phase, around 70% of infected people are asymptomatic (latent form). The remainder develop chagasic cardiomyopathy and/or digestive syndromes. There is evidence for aggravation of the chronic cardiac pathology by endothelin-mediated vasoconstriction. Holtzman rats have proven to be a good model for Chagas' disease acute phase and latent chronic phase. Now, we investigate the effects of prolonged treatment with an endothelin ET(A) receptor antagonist, BSF 461314, during the acute phase on parasitemia, coronary flow, tissue parasitism and the inflammatory process. Using isolated heart in Langendorff's preparation, endothelial dysfunction was observed only in non-treated infected animals. Histoquantitative analyses carried out in heart and diaphragm showed higher tissue parasitism and/or inflammatory process in BSF 461314-treated animals. Our data indicate that endothelin ET(A) receptors contribute to the initial mechanisms of parasite control. Impairment of the endothelium-dependent vasodilatation favors hazardous effects. However, blocking endothelin ET(A) receptors can prevent the latter.

Role of endothelin during experimental Trypanosoma cruzi infection in rats.

Chagas' disease is caused by the intracellular protozoan Trypanosoma cruzi. Here we have investigated the role of endothelin-1 in T. cruzi acute infection in rats, using the orally active ET(A) receptor antagonist BSF-461314. Treatment with BSF-461314 markedly increased parasitaemia, but animals managed to control the infection by day 15. Histopathological analysis of heart tissue at the end of the acute phase showed greater numbers of parasite nests in BSF-461314-treated animals. The perfusion of isolated rat hearts from infected animals with bradykinin failed to induce an increase, and actually reduced, coronary blood flow. Pretreatment with BSF-461314 prevented changes in coronary flow induced by T. cruzi infection. Together these results demonstrate that endothelin-1, through ET(A) receptor activation, contributes to the protective immune response against acute T. cruzi infection. Moreover, these data suggest that endothelin-1 is a mediator of impaired endothelium-dependent vasomotion in the coronary microcirculation associated with acute T. cruzi infection.