Age-dependent modulation of NF-κB expression in rat adrenal gland

Abstract

The current studies were initiated to examine the expression and regulation of an oxidative stress-responsive transcription factor, NF-κB, in rat adrenals during aging. NF-κB DNA-binding activity and expression of constituent proteins (Rel family of proteins and IκBs) was measured in adrenal nuclear and cytoplasmic extracts from young mature (5 month) and old (24 month) Sprague–Dawley rats before and after treatment with LPS; the latter was used to further invoke oxidative stress. Administration of LPS to either young or old rats induced a dramatic activation of NF-κB DNA binding activity as assayed by EMSA. NF-κB hetero-dimers, RelA/NF-κB1 (p65/p50) accounted for the majority of proteins that bound to consensus NF-κB sequences in LPS-treated young and old animals. The intensity of DNA binding complexes was significantly reduced in old animals. The age-related decline in the activation of NF-κB could not be attributed to an alteration in the composition of constituent subunits or degradation of NF-κB inhibitory proteins (IκBα and IκBβ) but rather was due to selective down-regulation of RelA/p65 and NF-κB2/p52 proteins. No age-related or LPS-induced changes in the constitutively active transcription factors SP-1 and OCT-1 were detected. These data suggest that aberrancies in the activation of NF-κB DNA-binding activity may contribute to the excessive oxidative damage observed in adrenal tissue with aging and may adversely affect cellular processes crucial for intracellular cholesterol transport and steroid hormone production.