Diesel exhaust particles induce matrix metalloprotease-1 in human lung epithelial cells via a NADP(H) oxidase/NOX4 redox-dependent mechanism

NADPH oxidase-mediated redox signaling: roles in cellular stress response, stress tolerance, and tissue repair

NADPH oxidase (Nox) has a dedicated function of generating reactive oxygen species (ROS). Accumulating evidence suggests that Nox has an important role in signal transduction in cellular stress responses. We have reviewed the current evidence showing that the Nox system can be activated by a collection of chemical, physical, and biological cellular stresses. In many circumstances, Nox activation fits to the cellular stress response paradigm, in that (1) the response can be initiated by various forms of cellular stresses; (2) Nox-derived ROS may activate mitogen-activated protein kinases (extracellular signal-regulated kinase, p38) and c-Jun NH(2)-terminal kinase, which are the core of the cell stress-response signaling network; and (3) Nox is involved in the development of stress cross-tolerance. Activation of the cell survival pathway by Nox may promote cell adaptation to stresses, whereas Nox may also convey signals toward apoptosis in irreversibly injured cells. At later stage after injury, Nox is involved in tissue repair by modulating cell proliferation, angiogenesis, and fibrosis. We suggest that Nox may have an integral role in cell stress responses and the subsequent tissue repair process. Understanding Nox-mediated redox signaling mechanisms may be of prominent significance at the crossroads of directing cellular responses to stress, aiming at either enhancing the stress resistance (in such situations as preventing ischemia-reperfusion injuries and accelerating wound healing) or sensitizing the stress-induced cytotoxicity for proliferative diseases such as cancer. Therefore, an optimal outcome of interventions on Nox will only be achieved when this is dealt with in a timely and disease-and stage-specific manner.

NOX4/NADPH oxidase expression is increased in pulmonary fibroblasts from patients with idiopathic pulmonary fibrosis and mediates TGFbeta1-induced fibroblast differentiation into myofibroblasts

BACKGROUND

Persistence of myofibroblasts is believed to contribute to the development of fibrosis in idiopathic pulmonary fibrosis (IPF). Transforming growth factor beta1 (TGFbeta1) irreversibly converts fibroblasts into pathological myofibroblasts, which express smooth muscle alpha-actin (alpha-SMA) and produce extracellular matrix proteins, such as procollagen I (alpha1). Reactive oxygen species produced by NADPH oxidases (NOXs) have been shown to regulate cell differentiation. It was hypothesised that NOX could be expressed in parenchymal pulmonary fibroblasts and could mediate TGFbeta1-stimulated conversion of fibroblasts into myofibroblasts.

METHODS

Fibroblasts were cultured from the lung of nine controls and eight patients with IPF. NOX4, alpha-SMA and procollagen I (alpha1) mRNA and protein expression, reactive oxygen species production and Smad2/3 phosphorylation were quantified, in the absence and in the presence of incubation with TGFbeta1. Migration of platelet-derived growth factor (PDGF)-induced fibroblasts was also assessed.

RESULTS

It was found that (1) NOX4 mRNA and protein expression was upregulated in pulmonary fibroblasts from patients with IPF and correlated with mRNA expression of alpha-SMA and procollagen I (alpha1) mRNA; (2) TGFbeta1 upregulated NOX4, alpha-SMA and procollagen I (alpha1) expression in control and IPF fibroblasts; (3) the change in alpha-SMA and procollagen I (alpha1) expression in response to TGFbeta1 was inhibited by antioxidants and by a NOX4 small interfering RNA (siRNA); (4) NOX4 modulated alpha-SMA and procollagen I (alpha1) expression by controlling activation of Smad2/3; and (5) NOX4 modulated PDGF-induced fibroblast migration.

CONCLUSION

NOX4 is critical for modulation of the pulmonary myofibroblast phenotype in IPF, probably by modulating the response to TGFbeta1 and PDGF.

Induction of heme oxygenase-1, biliverdin reductase and H-ferritin in lung macrophage in smokers with primary spontaneous pneumothorax: role of HIF-1alpha

Background

Few data concern the pathophysiology of primary spontaneous pneumothorax (PSP), which is associated with alveolar hypoxia/reoxygenation. This study tested the hypothesis that PSP is associated with oxidative stress in lung macrophages. We analysed expression of the oxidative stress marker 4-HNE; the antioxidant and anti-inflammatory proteins heme oxygenase-1 (HO-1), biliverdin reductase (BVR) and heavy chain of ferritin (H-ferritin); and the transcription factors controlling their expression Nrf2 and HIF-1α, in lung samples from smoker and nonsmoker patients with PSP (PSP-S and PSP-NS), cigarette smoke being a risk factor of recurrence of the disease.

Methodology/Principal Findings

mRNA was assessed by RT-PCR and proteins by western blot, immunohistochemistry and confocal laser analysis. 4-HNE, HO-1, BVR and H-ferritin were increased in macrophages from PSP-S as compared to PSP-NS and controls (C). HO-1 increase was associated with increased expression of HIF-1α mRNA and protein in alveolar macrophages in PSP-S patients, whereas Nrf2 was not modified. To understand the regulation of HO-1, BVR and H-ferritin, THP-1 macrophages were exposed to conditions mimicking conditions in C, PSP-S and PSP-NS patients: cigarette smoke condensate (CS) or air exposure followed or not by hypoxia/reoxygenation. Silencing RNA experiments confirmed that HIF-1α nuclear translocation was responsible for HO-1, BVR and H-ferritin induction mediated by CS and hypoxia/reoxygenation.

Conclusions/Significance

PSP in smokers is associated with lung macrophage oxidative stress. The response to this condition involves HIF-1α-mediated induction of HO-1, BVR and H-ferritin.

Oxidative stress targets in pulmonary emphysema: focus on the Nrf2 pathway

IMPORTANCE OF THE FIELD

Oxidative stress has been implicated in the pathogenesis of pulmonary emphysema. Nuclear factor erythroid-2-related factor 2 (Nrf2) a major antioxidant transcription factor could play a protective role in pulmonary emphysema.

AREAS COVERED IN THIS REVIEW

Nrf2 is ubiquitously expressed throughout the lung, but is predominantly found in epithelium and alveolar macrophages. Evidence suggests that Nrf2 and several Nrf2 downstream genes have an essential protective role in the lung against oxidative stress from environmental pollutants and toxicants such as cigarette smoke, a major causative factor for the development and progression of pulmonary emphysema. Application of Nrf2-deficient mice identified an extensive range of protective roles for Nrf2 against the pathogenesis of pulmonary emphysema. Therefore, Nrf2 promises to be an attractive therapeutic target for intervention and prevention strategies.

WHAT THE READER WILL GAIN

In this review, we discuss recent findings on the association of oxidative stress with pulmonary emphysema. We also address the mechanisms of Nrf2 lung protection against oxidative stress based on emerging evidence from experimental oxidative disease models and human studie.

TAKE HOME MESSAGE

The current literature suggests that among oxidative stress targets, Nrf2 is a valuable therapeutic target in pulmonary emphysema.

Role of oxidative damage in toxicity of particulates

Particulates are small particles of solid or liquid suspended in liquid or air. In vitro studies show that particles generate reactive oxygen species, deplete endogenous antioxidants, alter mitochondrial function and produce oxidative damage to lipids and DNA. Surface area, reactivity and chemical composition play important roles in the oxidative potential of particulates. Studies in animal models indicate that particles from combustion processes (generated by combustion of wood or diesel oil), silicate, titanium dioxide and nanoparticles (C60 fullerenes and carbon nanotubes) produce elevated levels of lipid peroxidation products and oxidatively damaged DNA. Biomonitoring studies in humans have shown associations between exposure to air pollution and wood smoke particulates and oxidative damage to DNA, deoxynucleotides and lipids measured in leukocytes, plasma, urine and/or exhaled breath. The results indicate that oxidative stress and elevated levels of oxidatively altered biomolecules are important intermediate endpoints that may be useful markers in hazard characterization of particulates.

Prolonged cigarette smoke exposure decreases heme oxygenase-1 and alters Nrf2 and Bach1 expression in human macrophages: roles of the MAP kinases ERK(1/2) and JNK

Tobacco may be involved in the decreased macrophage heme oxygenase-1 (HO-1) expression described in smoking-induced severe emphysema, via the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1)-BTB and CNC homology 1, basic leucine zipper transcription factor 1 (Bach1) pathway. We assessed in vitro effects of cigarette smoke condensate (CS) in the human monocyte/macrophage cell line (THP-1). CS exposure led to increased HO-1 and nuclear Nrf2 expression (6 h) followed by decreased HO-1 expression concomitantly with nuclear Nrf2/Bach1 ratio decrease (72h). CS-induced mitogen-activated protein kinase (MAPK) phosphorylation. Extracellular-signal-regulated kinase(1/2) (ERK(1/2)) and c-Jun NH2-terminal kinase (JNK) inhibition completely abrogated CS effects on HO-1 expression and nuclear Nrf2/Bach1 translocation. These results suggest that ERK(1/2) and JNK are involved in CS-induced biphasic HO-1 expression by a specific regulation of Nrf2/Keap1-Bach1.

Practical strategies for targeting NF-kappaB and NADPH oxidase may improve survival during lethal influenza epidemics

The most foolproof way to promote survival in epidemics of potentially lethal influenza is to target, not highly mutable viral proteins, but rather intracellular signaling pathways which promote viral propagation or lung inflammation. NF-kappaB, activated in influenza-infected lung epithelial cells and macrophages, is one likely target in this regard, as it plays a role both in viral replication and in the excessive lung inflammation often evoked by influenza infection. Indeed, salicylates, which suppress NF-kappaB activation, have been shown to reduce the lethality of H5N1 avian-type influenza in mice. Another potential target is NADPH oxidase, as this may be a major source of influenza-evoked oxidant stress in lung epithelial cells as well as in phagocytes attracted to lung parenchyma. A number of studies demonstrate that oxidant stress contributes to overexuberant lung inflammation and lethality in influenza-infected mice. The documented utility of N-acetylcysteine, a glutathione precursor, for promoting survival in influenza-infected mice, and diminishing the severity of influenza-like infections in elderly humans, presumably reflects a key role for oxidative stress in influenza. The lethality of influenza is also reduced in mice pretreated with adenovirus carrying the gene for heme oxygenase-1; this benefit may be mediated, at least in part, by the ability of bilirubin to inhibit NADPH oxidase. It may be feasible to replicate this benefit clinically by administering biliverdin or its homolog phycocyanobilin, richly supplied by spirulina. If this latter speculation can be confirmed in rodent studies, a practical and inexpensive regimen consisting of high-dose salicylates, spirulina, and N-acetylcysteine, initiated at the earliest feasible time, may prove to have life-saving efficacy when the next killer influenza pandemic strikes.

Postural changes in blood pressure associated with interactions between candidate genes for chronic respiratory diseases and exposure to particulate matter

BACKGROUND

Fine particulate matter [aerodynamic diameter </= 2.5 mum (PM(2.5))] has been associated with autonomic dysregulation.

OBJECTIVE

We hypothesized that PM(2.5) influences postural changes in systolic blood pressure (DeltaSBP) and in diastolic blood pressure (DeltaDBP) and that this effect is modified by genes thought to be related to chronic lung disease.

METHODS

We measured blood pressure in participants every 3-5 years. DeltaSBP and DeltaDBP were calculated as sitting minus standing SBP and DBP. We averaged PM(2.5) over 48 hr before study visits and analyzed 202 single nucleotide polymorphisms (SNPs) in 25 genes. To address multiple comparisons, data were stratified into a split sample. In the discovery cohort, the effects of SNP x PM(2.5) interactions on DeltaSBP and DeltaDBP were analyzed using mixed models with subject-specific random intercepts. We defined positive outcomes as p < 0.1 for the interaction; we analyzed only these SNPs in the replicate cohort and confirmed them if p < 0.025 with the same sign. Confirmed associations were analyzed within the full cohort in models adjusted for anthropometric and lifestyle factors.

RESULTS

Nine hundred forty-five participants were included in our analysis. One interaction with rs9568232 in PHD finger protein 11 (PHF11) was associated with greater DeltaDBP. Interactions with rs1144393 in matrix metalloprotease 1 (MMP1) and rs16930692, rs7955200, and rs10771283 in inositol 1,4,5-triphosphate receptor, type 2 (ITPR2) were associated with significantly greater DeltaSBP. Because SNPs associated with DeltaSBP in our analysis are in genes along the renin-angiotensin pathway, we then examined medications affecting that pathway and observed significant interactions for angiotensin receptor blockers but not angiotensin-converting enzyme inhibitors with PM(2.5).

CONCLUSIONS

PM(2.5) influences blood pressure and autonomic function. This effect is modified by genes and drugs that also act along this pathway.

Cigarette smoke extract induces cytosolic phospholipase A2 expression via NADPH oxidase, MAPKs, AP-1, and NF-kappaB in human tracheal smooth muscle cells

Up-regulation of cytosolic phospholipase A2 (cPLA2) by cigarette smoke extract (CSE) may play a critical role in airway inflammatory diseases. However, the mechanisms underlying CSE-induced cPLA2 expression in human tracheal smooth muscle cells (HTSMCs) remain unknown. CSE induced cPLA2 protein and mRNA expression, and ROS generation was attenuated by pretreatment with a reactive oxygen species (ROS) scavenger (N-acetylcysteine), or inhibitors of NADPH oxidase (diphenyleneiodonium chloride, apocynin) and transfection with p47phox siRNA, suggesting that CSE-induced cPLA2 expression was mediated through NADPH oxidase activation and ROS production in HTSMCs. Furthermore, CSE-induced cPLA2 expression was attenuated by pretreatment with the inhibitors of MEK1/2 (U0126), p38 MAPK (SB202190), and JNK (SP600125), which were further confirmed by transfection with siRNAs of JNK1, p42, and p38 to down-regulate the expression of respective proteins and reduce cPLA2 expression. Induction of cPLA2 by CSE was attenuated by selective inhibitors of NF-kappaB (helenalin) and AP-1 (curcumin). Moreover, promoter assays revealed that increases of cPLA2, NF-kappaB, and AP-1 luciferase activities stimulated by CSE were attenuated by these inhibitors. These results suggest that in HTSMCs, CSE induced NADPH oxidase activation leading to phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK. These reactions induced nuclear transcription NF-kappaB and AP-1 activities which were essential for CSE-induced cPLA2 gene expression.

Air pollution and cardiac remodeling: a role for RhoA/Rho-kinase

Exposure to ambient air pollution has been associated with increases in blood pressure. We have previously demonstrated activation of the Rho/Rho kinase pathway in experimental hypertension in rats. In this investigation, we evaluated the effects of particulate matter of < 2.5 microm (PM(2.5)) exposure on cardiovascular responses and remodeling and tested the effect of Rho kinase inhibition on these effects. C57BL/6 mice were exposed to concentrated ambient PM(2.5) or filtered air for 12 wk followed by a 14-day ANG II infusion in conjunction with fasudil, a Rho kinase antagonist, or placebo treatment. Blood pressure was monitored, followed by analysis of vascular function and ventricular remodeling indexes. PM(2.5) exposure potentiated ANG II-induced hypertension, and this effect was abolished by fasudil treatment. Cardiac and vascular RhoA activation was enhanced by PM(2.5) exposure along with increased expression of the guanine exchange factors (GEFs) PDZ-RhoGEF and p115 RhoGEF in PM(2.5)-exposed mice. Parallel with increased RhoA activation, PM(2.5) exposure increased ANG II-induced cardiac hypertrophy and collagen deposition, with these increases being normalized by fasudil treatment. In conclusion, PM(2.5) potentiates cardiac remodeling in response to ANG II through RhoA/Rho kinase-dependent mechanisms. These findings have implications for the chronic cardiovascular health effects of air pollution.

Adverse effects of industrial multiwalled carbon nanotubes on human pulmonary cells

The aim of this study was to evaluate adverse effects of multiwalled carbon nanotubes (MWCNT), produced for industrial purposes, on the human epithelial cell line A549. MWCNT were dispersed in dipalmitoyl lecithin (DPL), a component of pulmonary surfactant, and the effects of dispersion in DPL were compared to those in two other media: ethanol (EtOH) and phosphate-buffered saline (PBS). Effects of MWCNT were also compared to those of two asbestos fibers (chrysotile and crocidolite) and carbon black (CB) nanoparticles, not only in A549 cells but also in mesothelial cells (MeT5A human cell line), used as an asbestos-sensitive cell type. MWCNT formed agglomerates on top of both cell lines (surface area 15-35 microm(2)) that were significantly larger and more numerous in PBS than in EtOH and DPL. Whatever the dispersion media, incubation with 100 microg/ml MWCNT induced a similar decrease in metabolic activity without changing cell membrane permeability or apoptosis. Neither MWCNT cellular internalization nor oxidative stress was observed. In contrast, asbestos fibers penetrated into the cells, decreased metabolic activity but not cell membrane permeability, and increased apoptosis, without decreasing cell number. CB was internalized without any adverse effects. In conclusion, this study demonstrates that MWCNT produced for industrial purposes exert adverse effects without being internalized by human epithelial and mesothelial pulmonary cell lines.

NOX family NADPH oxidases in liver and in pancreatic islets: a role in the metabolic syndrome and diabetes?

The incidence of obesity and non-esterified ('free') fatty acid-associated metabolic disorders such as the metabolic syndrome and diabetes is increasing dramatically in most countries. Although the pathogenesis of these metabolic disorders is complex, there is emerging evidence that ROS (reactive oxygen species) are critically involved in the aberrant signalling and tissue damage observed in this context. Indeed, it is now widely accepted that ROS not only play an important role in physiology, but also contribute to cell and tissue dysfunction. Inappropriate ROS generation may contribute to tissue dysfunction in two ways: (i) dysregulation of redox-sensitive signalling pathways, and (ii) oxidative damage to biological structures (DNA, proteins, lipids, etc.). An important source of ROS is the NOX family of NADPH oxidases. Several NOX isoforms are expressed in the liver and pancreatic beta-cells. There is now evidence that inappropriate activation of NOX enzymes may damage the liver and pancreatic beta-cells. In the context of the metabolic syndrome, the emerging epidemic of non-alcoholic steatohepatitis is thought to be NOX/ROS-dependent and of particular medical relevance. NOX/ROS-dependent beta-cell damage is thought to be involved in glucolipotoxicity and thereby leads to progression from the metabolic syndrome to Type 2 diabetes. Thus understanding the role of NOX enzymes in liver and beta-cell damage should lead to an increased understanding of pathomechanisms in the metabolic syndrome and diabetes and may identify useful targets for novel therapeutic strategies.

Agents associated with lung inflammation induce similar responses in NCI-H292 lung epithelial cells

The aim of this study was to investigate an in vitro lung epithelial model for assessment of potential inhalation toxicity. The selected NCI-H292 lung carcinoma cell line is sensitive to cigarette smoke, responds in a similar manner to primary human lung epithelial cells and produces airway mucins. The following agents associated with inhalation toxicity were tested in the model: cigarette smoke total particulate matter, fly ash, bleomycin, lipopolysaccharide, vanadyl sulphate, diesel exhaust particles and carbon black. Polystyrene, poly-methylmethacrylate and dimethyl sulphoxide were used as negative controls. Response markers were chosen on the basis of reported injurious effects of lung toxicants in humans, and included pro-inflammatory cytokines, matrix metalloprotease-1, the airway mucin MUC5AC and heparin-binding epidermal growth factor-like growth factor. Markers were quantified at the mRNA and/or protein level in control and treated cells. Many of the selected markers were regulated in a similar manner by cigarette smoke and the other toxic substances in the H292 cell model. By comparison, the negative control agents were largely ineffective. We conclude that, with further validation, this assay may form part of a tiered strategy for toxicological assessment of inhaled agents prior to more complex primary cell models and animal inhalation studies.