Abstract 1342: The NF-kappaB P50 Subunit Protects Against Remodeling and Cardiac Dysfunction Following Myocardial Infarction
Introduction Left ventricular (LV) remodeling leads to congestive heart failure and is a main determinant of morbidity and mortality following myocardial infarction (MI). To further improve the treatment of post infarct LV remodeling, a better understanding of the molecular mechanisms involved in this complicated process is required. The nuclear factor (NF)- κB family (p50, p52, p65) usually forms dimers that regulate DNA transcription in response to a variety of stimuli including pro-inflammatory cytokines, oxidative stress and also ischemia. Inhibition of NF- κB has been shown to reduce heart failure following MI in rats. The specific role of the different NF- κB subunits during LV remodeling, however, has not been clarified thus far. In this study, we elucidate the role of the NF- κB p50 subunit in post infarct LV remodeling.
Methods and Results MI was induced in wild type C57Bl6 mice and NF- κB p50 KO mice. Without affecting infarct size (45.4 ± 4.3 vs. 42.5 ± 4.6%; p=0.461), the absence of NF- κB p50 increased the extent of LV remodeling (EDV: 175 ± 13 vs. 107 ± 11 μl; p=0.005) and aggravated systolic dysfunction (LVEF: 16.1 ± 1.5 % vs. 24.7 ± 3.7%; p=0.045) 28 days following MI as assessed by magnetic resonance imaging (9.4 T). In the non-infarcted myocardium, interstitial fibrosis (1.53 ± 0.28 vs. 1.05 ± 0.15 grayvalue/μm2; p=0.042) and hypertrophy (426 ± 51 vs. 251 ± 12 μm2/cardiomyocyte; p=0.018) were increased in NF-κB p50 KO mice. In the infarct area, however, collagen density was decreased (15.11 ± 1.16 vs. 27.28 ± 4.93 grayvalue/μm2; p=0.028), which was accompanied by increased TNF-alpha mRNA expression (0.086 ± 0.04 vs. 0.026 ± 0.015; p=0.046) and increased MMP9 activity (0.31 ± 0.03 vs. 0.19 ± 0.03; p=0.049)
Conclusion These data provide evidence for a protective role of NF- κB p50 in post infarct maladaptive LV remodeling, most likely by reducing inflammatory cytokine production and matrix degradation.