Inhibition of myocardial NFκB activation reduces cardiac dysfunction following LPS challenge in transgenic mice

Introduction:We have previously shown that cardiac NFκB was activated following LPS challenge. Activation of NFκB may upregulate transcription of genes contributing to myocardial dysfunction. Thus, we hypothesized that inhibition of NFκB activation might prevent cardiac dysfunction after LPS stimulation. Methods: Transgenic mice having InBot selectively overexpressed in the heart were injected i.p. with 1mg/kg of LPS. Hearts were harvested and subjected to Langendorff preparations or homogenized for protein isolation. NFκB activation was determined by EMSA, TNFα levels by ELISA. Blood was obtained by cardiac puncture. Alternatively, untreated hearts were harvested and subjected to ex vivo LPS perfusion in a Langendorff apparatus or were digested for cardiomyocyte isolation. Primary cardiomyocytes were stimulated ex vivo with various LPS concentrations. Results: In IκBα overexpressing mice, NFκB activation was blocked after LPS challenge. Functional analysis of wild type hearts showed significant contractile depression 2h after LPS challenge, being depressed for up to 18h. In IκBα transgenics cardiac failure was prevented 2h following LPS challenge, but not after 18h. Serum, as well as cardiac TNFα levels did not differ between wild type and transgenic mice. In contrast, isolated transgenic mouse hearts perfused with 250 μg/ml of LPS showed no cardiac depression, whereas wild type hearts were impaired in their function. In addition, primary transgenic cardiomyocytes secreted significantly less TNFα than wild type cardiomyocytes upon LPS stimulation. Conclusion: These data indicate that inhibition of cardiac NFκB activation blocks cardiac TNFα production and also prevents cardiac failure following ex vivo LPS stimulation. After in vivo LPS stimulation, local NFκB inhibition was sufficient to retard, but not to prevent cardiac dysfunction. We speculate that systemically produced mediators impact the heart and contribute to its failure.