Regulation of extracellular matrix expression and distribution in Trypanosoma cruzi-infected cardiomyocytes

Alterations in the extracellular matrix have been observed in the cardiomyopathy of Chagas disease caused by Trypanosoma cruzi infection. However, the mechanism of extracellular matrix regulation in T. cruzi-infected cultured cardiomyocytes (CMs) is unclear. Using confocal laser microscopy, we demonstrated that treatment of these cultures with transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha) leads to an enhancement of the fibronectin matrix only in uninfected CMs, while infected myocytes displayed low fibronectin expression. Digital image analysis also revealed low superposition of the fibronectin signal with parasite nests in cytokine treated and untreated cultures. Cytochalasin D treatment resulted in microfilament disarray that induced a disturbance in the fibronectin network of CMs, suggesting that cytoskeleton disruption caused by T. cruzi infection disorganizes the fibronectin matrix. Western blot analysis revealed a 2-fold increase in the fibronectin expression in CM cultures after cytokine treatment, whereas T. cruzi infection significantly reduced fibronectin levels in all conditions. In contrast, no change in the laminin expression was detected after cytokine treatment. Laminin distribution was altered in T. cruzi-infected CMs, with intense laminin labeling only at the cell periphery even after cytokine treatment. Our observations indicate that TGF-beta and TNF-alpha stimulates fibronectin expression only in uninfected cells of the T. cruzi-infected cultures, whereas the cells harboring the parasites display low or no fibronectin fibrils.