Nuclear factor kappa B (NF-kappa B) is a ubiquitous transcription factor activated by various stimuli implicated in heart failure progression. However, its activation in heart failure has not been well defined yet. Therefore. we investigated activation of NF-kappa B after myocardial infarction. For the first time, we performed serial, non-invasive in vivo molecular imaging of transcription factor activation in the heart. We used mice expressing a luciferase reporter whose transcription is dependent upon NF-kappa B activation for up to 8 weeks after myocardial infarction. There was a significant increase of NF-kappa B activity with a maximum at day 3 after myocardial infarction when compared to sham controls. Thus, in vivo measurement of the activation of NF-kappa B is feasible. NF-kappa B activity might play an important role for the remodeling process. (c) 2006 Elsevier Inc. All rights reserved.