Oxidants induce a corticosteroid-insensitive phosphorylation of histone 3 at serine 10 in monocytes

Oxidative stress enhances inflammation and reduces the effectiveness of corticosteroids, but the inflammatory signalling pathways induced by oxidants remain ill-defined. Phosphorylation of histone 3 at serine 10 (H3-Pser10) marks out a subset of inflammatory genes for transcription, several of which are induced in oxidant-associated inflammation. However, the influence of oxidants or of corticosteroids on this modification remains unknown. We assessed the regulation of H3-Pser10 by oxidants and lipopolysaccharide (LPS) in human blood monocytes and lung macrophages and the effectiveness of its abolition in controlling inflammatory gene expression in cells from asthmatic subjects compared to corticosteroids alone. Both oxidants and LPS promoted the induction of H3-Pser10 which was unaffected by corticosteroids. The induction of H3-Pser10 was mediated through p38α mitogen-activated protein kinase (MAPK) and IκB kinase 2 (IKK-2) signalling. Consequently, inhibitors of p38α MAPK or IKK-2 used in combination with dexamethasone were more effective at controlling inflammatory gene expression from monocytes and lung macrophages from asthmatic patients than the corticosteroid alone. Therefore, reduction of H3-Pser10 by inhibition of p38α MAPK or of IKK-2 may provide greater anti-inflammatory control than corticosteroids alone in oxidant-associated inflammation such as severe asthma

A Polymorphism Affecting MYB Binding within the Promoter of the PDCD4 Gene is Associated with Severe Asthma in Children

A previous genome-wide association study in asthma revealed putative associations that merit further investigation. In this study, the genome-wide significant associations of SNPs at the 5% false discovery rate were examined in independent groups of severe asthmatics. The panel consisted of 397 severe asthmatic adults, 116 severe asthmatic children, and a collection of 207 family-trios with an asthmatic proband. Three SNPs in the PDCD4 gene (rs6585018:G>A, rs1322997:C>A, and rs34104444:G>A) were significantly associated with severe childhood asthma (P values: 0.003, 0.002, 0.004) and total immunoglobulin E (IgE) levels (P values: 0.034, 0.041, 0.052). In an independent group of 234 asthmatic children and 652 controls, PDCD4 SNPs rs1407696:T>G and rs11195360:T>C were associated with total IgE levels (P values: 0.006, 0.014). In silico analysis of PDCD4 locus showed that rs6585018:G>A had the potential to affect MYB transcription factor binding, shown to act as a PDCD4-transcription inducer. Electromobility shift assays and reporter assays revealed that rs6585018:G>A alters MYB binding thereby influencing the expression of PDCD4. SNPs within MYB itself confer susceptibility to eosinophilia and asthma. Our association between a variant MYB binding site in PDCD4 and the severest form of childhood asthma therefore suggests that PDCD4 is a novel molecule of importance to asthmatic inflammatory responses

EMMPRIN (CD147) regulation of MMP-9 in bronchial epithelial cells in COPD.

International audienceBACKGROUND AND OBJECTIVE: Extracellular matrix metalloproteinase inducer (EMMPRIN or CD147) induces the production of matrix metalloproteinases (MMP) such as MMP-9, which plays an important role in COPD. We determined its cellular origin and role in MMP-9 production in COPD. METHODS: Bronchial biopsies, alveolar macrophages (AM) and blood monocytes (BM) from patients with COPD, healthy smokers and non-smokers, and bronchial epithelial cells (EC) from surgically resected airways from patients with COPD were stimulated with LPS or CRP in the presence and absence of an anti-EMMPRIN blocking antibody. EMMPRIN in BAL, plasma, conditioned media and cell lysates was quantified and immunohistochemical localization of EMMPRIN was determined in bronchial biopsies. MMP-9 activity and mRNA was also determined. RESULTS: EMMPRIN levels in BAL fluid were higher in patients with COPD compared with non-smokers and smokers. There was greater EMMPRIN expression in EC from patients with COPD compared with smokers and non-smokers. EC secreted and expressed more EMMPRIN protein than BM and AM. Blocking EMMPRIN decreased MMP-9 activity in supernatant of EC, but not in those from AM and BM, and decreased MMP-9 mRNA expression in EC. CONCLUSIONS: The increased EMMPRIN expression in COPD is reflected by an increased release from bronchial EC, which are one of the main source of EMMPRIN. EMMPRIN regulates MMP-9 expression in COPD

TGF-β regulates Nox4, MnSOD and catalase expression, and IL-6 release in airway smooth muscle cells

Reactive oxygen species (ROS) are generated as a result of normal cellular metabolism, mainly through the mitochondria and peroxisomes, but their release is enhanced by the activation of oxidant enzymes such as NADPH oxidases or downregulation of endogenous antioxidant enzymes such as manganese-superoxide dismutase (MnSOD) and catalase. Transforming growth factor-β (TGF-β), found to be overexpressed in airway smooth muscle (ASM) from asthmatic and chronic obstructive pulmonary disease patients, may be a pivotal regulator of abnormal ASM cell (ASMC) function in these diseases. An important effect of TGF-β on ASMC inflammatory responses is the induction of IL-6 release. TGF-β also triggers intracellular ROS release in ASMCs by upregulation of NADPH oxidase 4 (Nox4). However, the effect of TGF-β on the expression of key antioxidant enzymes and subsequently on oxidant/antioxidant balance is unknown. Moreover, the role of redox-dependent pathways in the mediation of the proinflammatory effects of TGF-β in ASMCs is unclear. In this study, we show that TGF-β induced the expression of Nox4 while at the same time inhibiting the expression of MnSOD and catalase. This change in oxidant/antioxidant enzymes was accompanied by elevated ROS levels and IL-6 release. Further studies revealed a role for Smad3 and phosphatidyl-inositol kinase-mediated pathways in the induction of oxidant/antioxidant imbalance and IL-6 release. The changes in oxidant/antioxidant enzymes and IL-6 release were reversed by the antioxidants N-acetyl-cysteine (NAC) and ebselen through inhibition of Smad3 phosphorylation, indicating redox-dependent activation of Smad3 by TGF-β. Moreover, these findings suggest a potential role for NAC in preventing TGF-β-mediated pro-oxidant and proinflammatory responses in ASMCs. Knockdown of Nox4 using small interfering RNA partially prevented the inhibition of MnSOD but had no effect on catalase and IL-6 expression. These findings provide novel insights into redox regulation of ASM function by TGF-β

Induction of H3-Pser10 by LPS and oxidants.

<p>Panels A-F show the induction of H3-Pser10 measured by western blot analysis in blood monocytes from a normal healthy subject, with the dose-dependent effect of LPS (A), time-course (B), the comparative effect of LPS and oxidants H₂O₂, GEA and pyocyanin (C), dose-dependency and time-course effect of H₂O₂ (D, E) and the interaction of H₂O₂ and LPS (F).</p

Inhibition of p38α MAPK or IKK-2 in combination with corticosteroids is more effective at reducing LPS induced inflammatory gene expression in asthmatic patients than corticosteroids alone.

<p>Panels A to B show the mean mRNA expression determined by real time qRT-PCR of IL-6, TNFα, CCL-2, and CXCL-8 in monocytes from non-severe and severe asthmatic subjects at baseline (A) or after exposure to LPS (B). Panels C to F show the mean mRNA expression of IL-6 (C), TNFα (D), CCL-2 (E), and CXCL-8 (F) in monocytes from non-severe and severe asthmatic subjects after exposure to LPS in the presence of dexamethasone (DEX), SB239063 or TPCA-1 or a combination of dexamethasone and either SB239063 or TPCA-1. Data is presented as mean ± SEM. Severe asthmatics n = 8, non-severe asthmatics n = 8. *p<0.05, **p<0.01, ***p<0.001 as compared to LPS-treated severe asthmatics; #p<0.05, ##p<0.01, ###p<0.001 as compared to LPS-treated non-severe asthmatics.</p