title: Acute exercise activates myocardial nuclear factor kappa B.
abstract: The myocardial stress response to exercise is dependent on exercise intensity and thus understanding the molecular responses between various exercise intensity levels might aid in exercise prescription. Nuclear factor kappa B (NF-κB) is a ubiquitous transcription factor that mediates a variety of cellular processes including inflammation, immune responses, apoptosis and cell growth/development. NF-κB can be comprised of homo- and/or heterodimers formed from five distinct proteins: p50 (NF-κB1), p52 (NF-κB2), RelA (p65), c-Rel, and RelB. NF-κB is located in the cytoplasm and kept inactive by inhibitory proteins but following the exposure to a myriad of stimuli, an activated NF-κB dimer translocates to the nucleus and exerts transcriptional effects on upwards of 150 genes. To examine the activation of NF-κB in the myocardium following exercise, male Sprague-Dawley rats (n = 24) were exercised by treadmill running at 20 m/min for 30 min or 30 m/min for 20 min. At 0, 2, or 24 h following exercise, animals were anesthetized, hearts excised and immediately frozen in liquid nitrogen. Portions of hearts were homogenized, protein concentrations determined and extracts assayed for NF-κB activation (DNA binding activity) using electrophoretic mobility shift assays (EMSA). Visual examination of EMSA autoradiographs revealed an enhanced NF-κB activation in the hearts from exercised animals when compared with non-running controls. Subsequent supershift analyses using antibodies specific for NF-κB subunits showed the higher intensity exercise was associated with p65 (RelA) in the activated NF-κB complex while the NF-κB complex in hearts from animals exercised at the lower intensity was comprised primarily of p50. These data suggest exercise is capable of activating myocardial NF-κB and that a threshold for the activation of specific NF-κB subunits may exist.
authors.affiliation: Faculty of Physical Education and Health, University of Toronto, 55 Harbord Street, Toronto, ON, M5S 2W6, Canada.
authors.forename: Marko
authors.initials: M
authors.lastname: Balan
authors.forename: Marius
authors.initials: M
authors.lastname: Locke
mesh_terms: D000818:Animals; D019281:Dimerization; D024202:Electrophoretic Mobility Shift Assay; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D052003:NF-kappa B p52 Subunit / Q000378:metabolism; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism; D051841:Transcription Factor RelB / Q000378:metabolism
chemical_list: D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D052003:NF-kappa B p52 Subunit; D018808:Transcription Factor AP-1; D051996:Transcription Factor RelA; D051841:Transcription Factor RelB