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.