RelB Is Differentially Regulated by IκB Kinase-α in B Cells and Mouse Lung by Cigarette Smoke

Abstract

The activation of transcription factor NF-kappaB is controlled by two main pathways: the classical canonical (RelA/p65-p50)- and the alternative noncanonical (RelB/p52)-NF-kappaB pathways. RelB has been shown to play a protective role in RelA/p65-mediated proinflammatory cytokine release in immune-inflammatory lymphoid cells. Increased infiltration of macrophages and lymphoid cells occurs in lungs of patients with chronic obstructive pulmonary disease, leading to abnormal inflammation. We hypothesized that RelB, and its signaling pathway, is differentially regulated in macrophages and B cells and in lung cells, leading to differential regulation of proinflammatory cytokines in response to cigarette smoke (CS). CS exposure increased the levels of RelB and NF-kappaB-inducing kinase associated with recruitment of RelB on promoters of the IL-6 and macrophage inflammatory protein-2 genes in mouse lung. Treatment of macrophage cell line, MonoMac6, with CS extract showed activation of RelB. In contrast, RelB was degraded by a proteasome-dependent mechanism in B lymphocytes (human Ramos, mouse WEHI-231, and primary mouse spleen B cells), suggesting that RelB is differentially regulated in lung inflammatory and lymphoid cells in response to CS exposure. Transient transfection of dominant negative IkappaB-kinase-alpha and double mutants of NF-kappaB-inducing kinase partially attenuated the CS extract-mediated loss of RelB in B cells and normalized the increased RelB level in macrophages. Taken together, these data suggest that RelB is differentially regulated in response to CS exposure in macrophages, B cells, and in lung cells by IkappaB-kinase-alpha-dependent mechanism. Rapid degradation of RelB signals for RelA/p65 activation and loss of its protective ability to suppress the proinflammatory cytokine release in lymphoid B cells.

Oxidative Stress and Chromatin Remodeling in Chronic Obstructive Pulmonary Disease and Smoking-Related Diseases

“…Based on the redox status of the cells, members of the MAPK family are activated, leading to a multifaceted transactivation of redox-sensitive transcription factors (ATF-2, CBP) (6,147). Furthermore, activation of upstream kinases, such as nuclear factor-jB (NF-jB)-inducing kinase, mitogenand stress-activated kinase 1, and IjB kinase-a, results in downstream chromatin remodeling events that alter the function of various gene promoters (27,28,138,179,181). This epigenetic mechanism modulates a series of specific proinflammatory gene transcription events that modulate apoptosis, autophagy, senescence, proliferation, transformation, and differentiation (53).…”

“…The lung is a direct target for oxidative injury from reactive oxygen species (ROS) and free radicals. Oxidative stress results in increased cellular signaling associated with posttranslational modifications of histones and nonhistone proteins, and redox modifications of proteins implicated in chromatin remodeling (48,152,179,181) (Fig. 1).…”

What shall we do with the damaged proteins in lung disease? Ask the proteasome!

“…As the proteasome takes centre stage in the degradation of oxidatively modified and misfolded proteins, it is reasonable to assume that cigarette smoke challenges the proteolytic capacity of this system. Accordingly, a number of studies have demonstrated the importance of proteasomal degradation of modified and misfolded proteins in response to cigarette smoke exposure: oxidative modification of histone modifying enzymes, such as histone deacetylase 2 and sirtuin 1 as well as of signalling mediators, such as interferon-c and vascular endothelial growth factor-receptor, Akt kinase, glutaredoxin-1 and the NF-kB family member relB, impairs the function of these molecules and makes them prone to proteasomal degradation [88][89][90][91][92][93][94][95][96]. The consequences of the nontimely degradation of central signalling mediators and the accompanying impairment of epigenetic, oxidative, inflammatory and growth factor signalling for the pathogenesis of COPD are evident and have been excellently reviewed elsewhere [97][98][99].…”

Protein Kinase Cζ Mediates Cigarette Smoke/Aldehyde- and Lipopolysaccharide-induced Lung Inflammation and Histone Modifications

“…It is well known that the transcription of pro-inflammatory genes is up-regulated by activation of NF-B signaling pathway and modifications of histones, such as acetylation on lysine residues of histones, leading to increased accessibility for transcription factor NF-B binding to coactivator complex (7,8). Recently we have shown that the recruitment of the RelA/p65 subunit of NF-B and the increased acetylation of histone proteins H3 and H4 on the promoters of pro-inflammatory genes in rodent lungs in response to CS exposure (1,9,10). This is corroborated by the findings that increased acetylation of histones occurs in lungs of smokers and patients with COPD (7,11,12).…”

“…Acid Extraction of Histone Proteins from Lung Tissues-Acid extraction of histone protein was performed as described previously (1,10). In brief, pellets from the aforementioned nuclear fraction were resuspended in 150 l of deionized water containing 0.2 N HCl and 0.36 N H 2 SO 4 .…”