Cardiac-specific abrogation of NF-κB activation in mice by transdominant expression of a mutant IκBα

Nuclear factor-kappaB (NF-kappaB) is a pleiotropic oxidant-sensitive transcription factor that is present in the cytosol in an inactive form complexed to an inhibitory kappaB (I kappaB) monomer. Various stimuli, including ischemia, hypoxia, free radicals, cytokines, and lipopolysaccharide (LPS), activate 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 pathophysiologic processes, definitive assessment of its role has been hindered by the inability to achieve specific inhibition in vivo. Pharmacologic inhibitors of NF-kappaB are available, but their utility for in vivo studies is limited by their relative lack of specificity. Targeted ablation of genes encoding NF-kappaB subunits has not been productive in this regard because of fetal lethality in the case of p65 and functional redundancy in the Rel family of proteins. To overcome these limitations, we have created a viable transgenic mouse that expresses a phosphorylation-resistant mutant of I kappaB alpha (I kappaB alpha (S32A,S36A)) under the direction of a cardiac-specific promoter. Several transgenic lines were obtained with copy numbers ranging from one to seven. The mice exhibit normal cardiac morphology and histology. 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. Importantly, expression of I kappaB(S32A,S36A) results in complete abrogation of myocardial NF-kappaB activation in response to tumor necrosis factor-alpha (TNF-alpha) and LPS stimulation. Thus, novel transgenic mice have been created that make it possible to achieve cardiac-specific and selective inhibition of NF-kappaB in vivo. These transgenic mice should be useful in studies of various cardiac pathophysiological phenomena that involve NF-kappaB activation, including ischemic preconditioning, heart failure, septic shock, acute coronary syndromes, cardiac allograft rejection, and apoptosis. (C) 2000 Academic Press.