Abstract 319: Additional Lack of eNOS Promotes Cardiac Fibrosis in Endothelin-1 Transgenic Mice
ET-1 is antagonized by NO mainly derived from endothelial NO-synthase (eNOS). We recently established cross-bred animals of ET-1 transgenic mice (ET+/+) and eNOS knock out mice (eNOS−/−) characterized by endothelial dysfunction and elevated blood pressure. Using this model we aimed at elucidating the impact of lack of eNOS in ET+/+ mice on cardiac phenotype. Cardiac interstitial fibrosis was increased only in eNOS−/−ET+/+. Media-to-lumen ratio of cardiac arterioles was significantly decreased in ET+/+ and eNOS−/−ET+/+ group compared to WT. Lumen-area was significantly larger in ET+/+ and eNOS−/−ET+/+ group compared to WT and eNOS−/− groups. No differences in heart weight were detected. Quantitative analysis of in situ hybridization revealed no change in ETA expression in eNOS−/−ET+/+ whereas ETB was significantly downregulated in this group. Western Blot analysis showed a significantly decreased ETA expression in eNOS−/− only and a down regulation of ETB in eNOS−/−ET+/+ and eNOS−/−; iNOS was down regulated in ET+/+ and eNOS−/−. Immunohistological studies didn’t reveal any differences in MMP2, MMP9 and Collagen I protein expression in cardiac tissue. Collagen III was up regulated in eNOS−/−ET+/+ compared to WT. A 2-Dimensional Electrophoresis based proteomics study revealed that 33, 28 and 29 proteins are differentially expressed in the hearts of 3 months old male ET+/+, eNOS−/− and eNOS−/−ET+/+, respectively, in comparison to WT. We thus conclude that our eNOS−/−ET+/+ mice represent a novel model of myocardial fibrosis due to imbalance between the ET and NO systems in absence of hypertrophy. Imbalance of cardiac ETA and ETB signalling could be a possible mechanism promoting cardiac fibrosis. The idendification by mass spectrometry of the differentially expressed proteins will spot new molecular mechanisms leading to fibrosis in our model.