Inhibitory kappa-B kinase-β inhibition prevents adaptive left ventricular hypertrophy.

BACKGROUND: Most cardiovascular studies have implicated the central transcription factor nuclear factor kappa-B (NF-κB) as contributing to the detrimental effects of cardiac injury. This ostensibly negative view of NF-κB competes with its important role in the normal host inflammatory and immune response. Pressure overload, left ventricular hypertrophy (LVH), and heart failure represent a spectrum of disease that has both adaptive and maladaptive components. In contrast to its known effects related to myocardial ischemia-reperfusion, we hypothesized that NF-κB is necessary for the compensatory phase of cardiac remodeling.
METHODS: C57BL6 mice underwent minimally invasive transverse aortic constriction with or without inhibition of the proximal NF-κB kinase, inhibitory kappa-B kinase-β. Isolated cardiomyocytes were cultured. Transthoracic echocardiography was performed on all mice.
RESULTS: Inhibitory kappa-B kinase-β inhibition successfully decreased cardiomyocyte expression of phosphorylated p65 NF-κB and decreased expression of hypertrophic markers with stimulation in vitro. Three weeks after transverse aortic constriction, the mice treated with inhibitory kappa-B kinase-β inhibition more aggressively developed LVH, as measured by heart weight/body weight ratio, left ventricular mass, and wall thickness. These mice also demonstrated a functional decline, as measured by decreased fractional shortening and ejection fraction. These findings were associated with decreased protein expression of p65 NF-κB.
CONCLUSIONS: Although short-term pressure-overload results in compensatory LVH with normal cardiac function, NF-κB inhibition resulted in increased LVH that was associated with functional deterioration. These observations suggest that NF-κB is an important part of the adaptive phase of LVH, and its inhibition detrimentally affects cardiac remodeling.