Background:Trypanosoma cruzi the causative agent of Chagas heart disease (CHD) remains incurable. The major pathology induced by the parasite is cardiac fibrosis leading to heart failure followed by death. The mechanisms of T. cruzi induced cardio-pathology remains largely unknown.
We hypothesize that T. cruzi infection regulates the expression of profibrotic genes in human cardiac myocytes (HCM), tilting the heart towards a profibrotic phenotype seen in CHD patients.
Methods and Results: To elucidate the molecular mechanisms of T. cruzi induced cardiac fibrosis, we challenged primary HCM with T. cruzi for two hours and purified total RNA for microarray. We investigated changes at the whole transcriptome level on an affymetrix platform. The arrays were done in triplicates at different time points; changes in gene expression greater than 2-fold and having a Benjamini and Hochburg false discovery rate corrected p-value <0.05 were considered significant. The microarray data was validated using real-time PCR followed by PCR array and immunoblotting, to evaluate changes in the protein expression levels of fibrotic transcription factors. Protein expression levels were evaluated in triplicate and analyzed by ANOVA. The fibrotic interactome induced by T. cruzi in HCM was elucidated using Cytoscape.
Our results indicate that exposure of HCM to T. cruzi upregulates the transcript levels of two transcription factors associated with fibrosis, SNAI1 (more than 2 fold up-regulated) and Early Growth Response protein 1, EGR1, (about four fold up-regulated). SNAI1 and EGR1 were increased at the protein level. Furthermore, we identified the first interactome regulating fibrosis in primary HCM induced by T. cruzi.
Conclusions: This is the first report showing that T. cruzi upregulates the expression of profibrotic transcription factors in HCM early during the process of cellular infection and the operational fibrotic interactome. Thus, abnormal sustained expression of SNAI1 and EGR1 upregulate the expression of genes essential for conversion of HCM towards a profibrotic phenotype in CHD. Elucidation of the molecular mechanisms by which T. cruzi induces cardiac fibrosis will lead to the identification of new therapeutic targets for CHD.