Abstract 13345: Programmed Necrosis Mediates Adverse Remodeling after Myocardial Infarction
Objective: Programmed necrosis (necroptosis) represents a newly identified mechanism of cell death combining features of both apoptosis and necrosis. Like apoptosis, necroptosis is tightly regulated by distinct signaling pathways. Signaling associated with the kinase Receptor interacting Protein 3 (RIP3) seems to be a key mediator of programmed necrosis. However, the functional relevance of RIP3-dependent signaling and necroptosis in the heart is currently not known.
Methods and Results: As a sign of a potential functional role of RIP3 in the heart, immunoblots showed a strong expression of RIP3 in murine hearts. Confocal lase scan microscopy of cultured rat cardiomyocytes revealed co-localization of RIP3 and mitochondria, implicating a role of RIP3 as a metabolic regulator. Stimulation of neonatal rat cardiomyocytes (NRVCMs)with TNF-α and a caspase inhibitor (zVAD-FMK) induced formation of a “death complex” of RIP1 and RIP3. Moreover, adenoviral overexpression of RIP3 induced necroptosis of cardiomyocytes (+42% vs. WT±1.2%, p<0.05), as measured by propidium jodid staining and FACS analysis. Consistently, overexpression of RIP3 markedly decreased survival of NRVCMs (-57% ± 0.83%, p<0.05), as measured by an MTT-based cell survival assay. The rate of apoptotic cardiomyocytes was unchanged, as measured by annexin V-staining. In vivo, cardiac expression of RIP3 was upregulated upon myocardial infarction (+76%±12%,p<0.05). Mice deficient for RIP3 (RIP3-/-, kindly provided by Genentech) showed a significantly better ejection fraction (45% ± 3.6% vs. 32% ± 4.4%, p<0.05) and less hypertrophy (-17% vs. WT ±7%, p<0.05) in MRI studies 30 days after experimental infarction due to LAD ligation. On the histological level, this was accompanied by a diminished inflammatory response of infarcted hearts, while the rate of apoptotic cells in the ischemic border zone was unchanged.
Conclusions: Here we show a role of programmed necrosis and RIP3 in modulating adverse cardiac remodeling due to ischemia. This novel signaling pathway may be a target for novel therapies that aim to limit the unfavourable consequences of ischemic cell death.
- © 2012 by American Heart Association, Inc.