Differences in MEF2 and NFAT Transcriptional Pathways According to Human Heart Failure Aetiology

Background: Ca2+ handling machinery modulates the activation of cardiac transcription pathways involved in heart failure (HF). The present study investigated the effect of HF aetiology on Ca+2 handling proteins and NFAT1, MEF2C and GATA4 (transcription factors) in the same cardiac tissue. Methodology and Principal Findings: A total of 83 hearts from ischemic (ICM, n = 43) and dilated (DCM, n = 31) patients undergoing heart transplantation and controls (CNT, n = 9) were analyzed by western blotting. Subcellular distribution was analyzed by fluorescence and electron microscopy. When we compared Ca+2 handling proteins according to HF aetiology, ICM showed higher levels of calmodulin (24%, p<0.01), calcineurin (26%, p<0.01) and Ca2+/Calmodulin-dependent kinase II (CaMKII delta(b) nuclear isoform 62%, p<0.001) than the CNT group. However, these proteins in DCM did not significantly increase. Furthermore, ICM showed a significant elevation in MEF2C (33%, p<0.01), and GATA4 (49%, p<0.05); also NFAT1 (66%, p<0.001) was increased, producing the resultant translocation of this transcriptional factor into the nuclei. These results were supported by fluorescence and electron microscopy analysis. Whereas, DCM only had a significant increase in GATA4 (52%, p<0.05). Correlations between NFAT1 and MEF2C in both groups (ICM r = 0.38 and DCM r = 0.59, p<0.05 and p<0.01, respectively) were found; only ICM showed a correlation between GATA4 and NFAT1 (r = 0.37, p<0.05). Conclusions/Significance: This study shows an increase of Ca2+ handling machinery synthesis and their cardiac transcription pathways in HF, being more markedly increased in ICM. Furthermore, there is a significant association between MEF2, NFAT1 and GATA4. These proteins could be therapeutic targets to improve myocardial function.