Cardiac-specific abrogation of NF-kappa B activation in mice by transdominant expression of a mutant I kappa B alpha

Nuclear factor-kappaB (NF-kappaB) is a pleiotropic oxidant-sensitive transc ription factor that is present in the cytosol in an inactive form complexed to an inhibitory kappaB (I kappaB) monomer. Various stimuli, including isc hemia, hypoxia, free radicals, cytokines, and lipopolysaccharide (LPS), act ivate NF-kappaB by inducing phosphorylation of I kappaB. Phosphorylation of serine residues at positions 32 and 36 is critical for ubiquitination and degradation of I kappaB alpha with consequent migration of NF-kappaB to the nucleus. Although NF-kappaB is thought to contribute to numerous pathophys iologic processes, definitive assessment of its role has been hindered by t he inability to achieve specific inhibition in vivo. Pharmacologic inhibito rs of NF-kappaB are available, but their utility for in vivo studies is lim ited by their relative lack of specificity. Targeted ablation of genes enco ding NF-kappaB subunits has not been productive in this regard because of f etal lethality in the case of p65 and functional redundancy in the Rel fami ly of proteins. To overcome these limitations, we have created a viable tra nsgenic mouse that expresses a phosphorylation-resistant mutant of I kappaB alpha (I kappaB alpha (S32A,S36A)) under the direction of a cardiac-specif ic promoter. Several transgenic lines were obtained with copy numbers rangi ng from one to seven. The mice exhibit normal cardiac morphology and histol ogy. Total myocardial I kappaB alpha protein level is elevated 3.5- to 6.5- fold with a concomitant 50-60% decrease in the level of I kappaB beta. Impo rtantly, expression of I kappaB(S32A,S36A) results in complete abrogation o f myocardial NF-kappaB activation in response to tumor necrosis factor-alph a (TNF-alpha) and LPS stimulation. Thus, novel transgenic mice have been cr eated that make it possible to achieve cardiac-specific and selective inhib ition of NF-kappaB in vivo. These transgenic mice should be useful in studi es of various cardiac pathophysiological phenomena that involve NF-kappaB a ctivation, including ischemic preconditioning, heart failure, septic shock, acute coronary syndromes, cardiac allograft rejection, and apoptosis. (C) 2000 Academic Press.