Oxidized phospholipids impair pulmonary antibacterial defenses: evidence in mice exposed to cigarette smoke

Scavenger receptor BI attenuates oxidized phospholipid-induced pulmonary inflammation

Damage associated molecular patterns (DAMPs) are molecules released from dead/dying cells following toxicant and/or environmental exposures that activate the immune response through binding of pattern recognition receptors (PRRs). Excessive production of DAMPs or failed clearance leads to chronic inflammation and delayed inflammation resolution. One category of DAMPs are oxidized phospholipids (oxPLs) produced upon exposure to high levels of oxidative stress, such as following ozone (O3) induced inflammation. OxPLs are bound by multiple classes of PRRs that include scavenger receptors (SRs) such as SR class B-1 (SR-BI) and toll-like receptors (TLRs). Interactions between oxPLs and PRRs appear to regulate inflammation; however, the role of SR-BI in oxPL-induced lung inflammation has not been defined. Therefore, we hypothesize that SR-BI is critical in protecting the lung from oxPL-induced pulmonary inflammation/injury. To test this hypothesis, C57BL/6J (WT) female mice were dosed with oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (oxPAPC) by oropharyngeal aspiration which increased pulmonary SR-BI expression. Following oxPAPC exposure, SR-BI deficient (SR-BI-/-) mice exhibited increased lung pathology and inflammatory cytokine/chemokine production. Lipidomic analysis revealed that SR-BI-/- mice had an altered pulmonary lipidome prior to and following oxPAPC exposure, which correlated with increased oxidized phosphatidylcholines (PCs). Finally, we characterized TLR4-mediated activation of NF-κB following oxPAPC exposure and discovered that SR-BI-/- mice had increased TLR4 mRNA expression in lung tissue and macrophages, increased nuclear p65, and decreased cytoplasmic IκBα. Overall, we conclude that SR-BI is required for limiting oxPAPC-induced lung pathology by maintaining lipid homeostasis, reducing oxidized PCs, and attenuating TLR4-NF-κB activation, thereby preventing excessive and persistent inflammation.

Compartmentalized regulation of lipid signaling in oxidative stress and inflammation: Plasmalogens, oxidized lipids and ferroptosis as new paradigms of bioactive lipid research

Perturbations in lipid homeostasis combined with conditions favoring oxidative stress constitute a hallmark of the inflammatory response. In this review we focus on the most recent results concerning lipid signaling in various oxidative stress-mediated responses and inflammation. These include phagocytosis and ferroptosis. The best characterized event, common to these responses, is the synthesis of oxygenated metabolites of arachidonic acid and other polyunsaturated fatty acids. Major developments in this area have highlighted the importance of compartmentalization of the enzymes and lipid substrates in shaping the appropriate response. In parallel, other relevant lipid metabolic pathways are also activated and, until recently, there has been a general lack of knowledge on the enzyme regulation and molecular mechanisms operating in these pathways. Specifically, data accumulated in recent years on the regulation and biological significance of plasmalogens and oxidized phospholipids have expanded our knowledge on the involvement of lipid metabolism in the progression of disease and the return to homeostasis. These recent major developments have helped to establish the concept of membrane phospholipids as cellular repositories for the compartmentalized production of bioactive lipids involved in cellular regulation. Importantly, an enzyme classically described as being involved in regulating the homeostatic turnover of phospholipids, namely the group VIA Ca²⁺-independent phospholipase A₂ (iPLA₂β), has taken center stage in oxidative stress and inflammation research owing to its key involvement in regulating metabolic and ferroptotic signals arising from membrane phospholipids. Understanding the role of iPLA₂β in ferroptosis and metabolism not only broadens our knowledge of disease but also opens possible new horizons for this enzyme as a target for therapeutic intervention.

Targeting the human β c receptor inhibits inflammatory myeloid cells and lung injury caused by acute cigarette smoke exposure

Background and objective

Chronic obstructive pulmonary disease (COPD) is a devastating disease commonly caused by cigarette smoke (CS) exposure that drives tissue injury by persistently recruiting myeloid cells into the lungs. A significant portion of COPD patients also present with overlapping asthma pathology including eosinophilic inflammation. The β_c cytokine family includes granulocyte monocyte‐colony‐stimulating factor, IL‐5 and IL‐3 that signal through their common receptor subunit β_c to promote the expansion and survival of multiple myeloid cells including monocytes/macrophages, neutrophils and eosinophils.

Methods

We have used our unique human β_c receptor transgenic (hβ_cTg) mouse strain that expresses human β_c instead of mouse β_c and β_IL3 in an acute CS exposure model. Lung tissue injury was assessed by histology and measurement of albumin and lactate dehydrogenase levels in the bronchoalveolar lavage (BAL) fluid. Transgenic mice were treated with an antibody (CSL311) that inhibits human β_c signalling.

Results

hβ_cTg mice responded to acute CS exposure by expanding blood myeloid cell numbers and recruiting monocyte‐derived macrophages (cluster of differentiation 11b⁺ [CD11b⁺] interstitial and exudative macrophages [IM and ExM]), neutrophils and eosinophils into the lungs. This inflammatory response was associated with lung tissue injury and oedema. Importantly, CSL311 treatment in CS‐exposed mice markedly reduced myeloid cell numbers in the blood and BAL compartment. Furthermore, CSL311 significantly reduced lung CD11b⁺ IM and ExM, neutrophils and eosinophils, and this decline was associated with a significant reduction in matrix metalloproteinase‐12 (MMP‐12) and IL‐17A expression, tissue injury and oedema.

Conclusion

This study identifies CSL311 as a therapeutic antibody that potently inhibits immunopathology and lung injury caused by acute CS exposure.

Myeloid cells, including macrophages, neutrophils and eosinophils, are important cellular drivers of inflammation and injury. In this study, we blocked granulocyte monocyte‐colony stimulating factor, IL‐5 and IL‐3 signalling with an anti‐β_c receptor antibody (CSL311), which greatly reduced lung inflammation and injury in a pre‐clinical model of acute cigarette smoke exposure.

Innate immune detection of lipid oxidation as a threat assessment strategy

Oxidized phospholipids that result from tissue injury operate as immunomodulatory signals that, depending on the context, lead to proinflammatory or anti-inflammatory responses. In this Perspective, we posit that cells of the innate immune system use the presence of oxidized lipids as a generic indicator of threat to the host. Similarly to how pathogen-associated molecular patterns represent general indicators of microbial encounters, oxidized lipids may be the most common molecular feature of an injured tissue. Therefore, microbial detection in the absence of oxidized lipids may indicate encounters with avirulent microorganisms. By contrast, microbial detection and detection of oxidized lipids would indicate encounters with replicating microorganisms, thereby inducing a heightened inflammatory and defensive response. Here we review recent studies supporting this idea. We focus on the biology of oxidized phosphocholines, which have emerged as context-dependent regulators of immunity. We highlight emerging functions of oxidized phosphocholines in dendritic cells and macrophages that drive unique inflammasome and migratory activities and hypermetabolic states. We describe how these lipids hyperactivate dendritic cells to stimulate antitumour CD8⁺ T cell immunity and discuss the potential implications of the newly described activities of oxidized phosphocholines in host defence.

Lipid peroxidation index of particulate matter: Novel metric for quantifying intrinsic oxidative potential and predicting toxic responses

Using particulate matter (PM) mass as exposure metric does not reveal the intrinsic PM chemical characteristics or toxic potential, which is crucial for monitoring the sources of emission causing adverse health effects and developing risk mitigating strategies. Oxidative stress and ensuing lipid peroxidation (LPO) in the lung are crucial underlying mechanisms of action by which PM drives cardiorespiratory disease. In the current study, we have postulated and demonstrated that the intrinsic potential of PM to elicit LPO, defined as "LPO index" as a novel approach for characterizing oxidative potential of PM (PMOP) and predicting biological toxicity. First, we exposed unsaturated phosphatidylcholine (PC), an abundant phospholipid in the cell membrane, pulmonary surfactant, and lipoproteins to PM and analyzed the total burden of LPO byproducts generated as a measure of LPO index using a LPO reporter dye, BODIPY-C11. PM exposure resulted in a concentration-dependent increase in LPO. Second, we developed a novel method to expose the captured serum apoB100 lipoprotein particles to PM or its constituents and assessed the levels of specific oxidized-phospholipid on apoB100 particles by immunoassay using E06 monoclonal antibody (mab) that recognizes only PC containing oxidized-phospholipids (Ox-PCs). The immunoassay was highly sensitive to evaluate the PM LPO index and was modifiable by metal quenchers and exogenous antioxidant and radical quenchers. Third, to prove the pathophysiological relevance of Ox-PCs, we found that PM exposure generates Ox-PCs in mice lungs, pulmonary surfactant and lung cells. Fourth, we observed that treatment of macrophages with BAL fluid from PM exposed mice or PM-exposed pulmonary surfactant stimulated IL-6 production, which was abrogated by neutralization of Ox-PCs by mab E06 suggesting that Ox-PCs in lungs are proinflammatory. Overall, our study suggests that Ox-PCs as a probe of PM LPO index is a biologically relevant pathogenic biomarker and has a high value for evaluating PMOP.

Characterization of the Structural Diversity and Structure-Specific Behavior of Oxidized Phospholipids by LC-MS/MS

Polyunsaturated fatty acids (PUFAs), esterified to phospholipids, are susceptible to oxidation. They form oxidized phospholipids (OxPLs) by oxygenases or reactive oxygen species (ROS), or both. These OxPLs are associated with various diseases, such as atherosclerosis, pulmonary injuries, neurodegenerative diseases, cancer, and diabetes. Since many types of OxPLs seem to be generated in vivo, precise determination of their structural diversity is required to understand their potential structure-specific functions. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful method to quantitatively measure the structural diversity of OxPLs present in biological samples. This review outlines recent advances in analytical methods for OxPLs and their physiological relevance in health and diseases.

Lecithinized superoxide dismutase in the past and in the present: Any role in the actual pandemia of COVID-19?

The Coronavirus disease 19 (Covid-19) pandemic is devastating the public health: it is urgent to find a viable therapy to reduce the multiorgan damage of the disease. A validated therapeutic protocol is still missing. The most severe forms of the disease are related to an exaggerated inflammatory response. The pivotal role of reactive oxygen species (ROS) in the amplification of inflammation makes the antioxidants a potential therapy, but clinical trials are needed. The lecitinized superoxide dismutase (PC-SOD) could represent a possibility because of bioaviability, safety, and its modulatory effect on the innate immune response in reducing the harmful consequences of oxidative stress. In this review we summarize the evidence on lecitinized superoxide dismutase in animal and human studies, to highlight the rationale for using the PC-SOD to treat COVID-19.

Allergen inhalation generates pro-inflammatory oxidised phosphatidylcholine associated with airway dysfunction

Oxidised phosphatidylcholines (OxPCs) are produced under conditions of elevated oxidative stress and can contribute to human disease pathobiology. However, their role in allergic asthma is unexplored. The aim of this study was to characterise the OxPC profile in the airways after allergen challenge of people with airway hyperresponsiveness (AHR) or mild asthma. The capacity of OxPCs to contribute to pathobiology associated with asthma was also to be determined.Using bronchoalveolar lavage fluid from two human cohorts, OxPC species were quantified using ultra-high performance liquid chromatography-tandem mass spectrometry. Murine thin-cut lung slices were used to measure airway narrowing caused by OxPCs. Human airway smooth muscle (HASM) cells were exposed to OxPCs to assess concentration-associated changes in inflammatory phenotype and activation of signalling networks.OxPC profiles in the airways were different between people with and without AHR and correlated with methacholine responsiveness. Exposing patients with mild asthma to allergens produced unique OxPC signatures that associated with the severity of the late asthma response. OxPCs dose-dependently induced 15% airway narrowing in murine thin-cut lung slices. In HASM cells, OxPCs dose-dependently increased the biosynthesis of cyclooxygenase-2, interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor and the production of oxylipins via protein kinase C-dependent pathways.Data from human cohorts and primary HASM cell culture show that OxPCs are present in the airways, increase after allergen challenge and correlate with metrics of airway dysfunction. Furthermore, OxPCs may contribute to asthma pathobiology by promoting airway narrowing and inducing a pro-inflammatory phenotype and contraction of airway smooth muscle. OxPCs represent a potential novel target for treating oxidative stress-associated pathobiology in asthma.

Lipid Mediators Regulate Pulmonary Fibrosis: Potential Mechanisms and Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease of unknown etiology characterized by distorted distal lung architecture, inflammation, and fibrosis. The molecular mechanisms involved in the pathophysiology of IPF are incompletely defined. Several lung cell types including alveolar epithelial cells, fibroblasts, monocyte-derived macrophages, and endothelial cells have been implicated in the development and progression of fibrosis. Regardless of the cell types involved, changes in gene expression, disrupted glycolysis, and mitochondrial oxidation, dysregulated protein folding, and altered phospholipid and sphingolipid metabolism result in activation of myofibroblast, deposition of extracellular matrix proteins, remodeling of lung architecture and fibrosis. Lipid mediators derived from phospholipids, sphingolipids, and polyunsaturated fatty acids play an important role in the pathogenesis of pulmonary fibrosis and have been described to exhibit pro- and anti-fibrotic effects in IPF and in preclinical animal models of lung fibrosis. This review describes the current understanding of the role and signaling pathways of prostanoids, lysophospholipids, and sphingolipids and their metabolizing enzymes in the development of lung fibrosis. Further, several of the lipid mediators and enzymes involved in their metabolism are therapeutic targets for drug development to treat IPF.

An Increase of Oxidized Phospholipids and the Role of Macrophages in Intraocular Inflammation

Purpose

The present study was conducted to examine the profile of oxidized phospholipids (OxPLs) in uveitis using rat model and clinical specimens, and to elucidate the role of macrophages in the metabolism of OxPLs.

Methods

Lewis rats were immunized with a bovine interphotoreceptor retinoid- binding protein (bIRBP) peptide with complete Freund's adjuvant (CFA) to induce experimental autoimmune uveitis (EAU). The aqueous humor (AH) was collected 2 weeks after immunization. Fifty-four human AH specimens, among which 21 eyes had a history of chronic uveitis, were collected during their cataract surgery. The profile of OxPLs in the AH specimens were analyzed by liquid-chromatography tandem mass spectrometry (LC-MS/MS). In addition, the involvement of macrophages in the viability of cells treated by OxPLs was investigated through a WST-1 assay using ARPE-19 cells and C57BL/6 mouse alveolar macrophages (AMs). The influence of macrophages in the trend of OxPLs was traced by thin layer chromatography (TLC) using AMs.

Results

Six species of OxPLs were detected in the AHs of rats and humans. The content of each OxPL was higher in the uveitis group. Four kinds of OxPLs found in AHs showed cytotoxicity to ARPE-19 cells in a dose-dependent manner. The cytotoxicity was reduced by pretreatment of OxPLs with AMs. When the OxPLs were applied on AMs, a marked reduction of OxPLs in the medium was observed.

Conclusions

The OxPLs formed by intraocular inflammation could induce cytotoxicity. The present findings suggest that the phagocytic macrophages emerging in the inflammation site eliminate OxPLs, and prevent intraocular tissue damage following uveitis.

Pain Control by Targeting Oxidized Phospholipids: Functions, Mechanisms, Perspectives

Within the lipidome oxidized phospholipids (OxPL) form a class of chemically highly reactive metabolites. OxPL are acutely produced in inflamed tissue and act as endogenous, proalgesic (pain-inducing) metabolites. They excite sensory, nociceptive neurons by activating transient receptor potential ion channels, specifically TRPA1 and TRPV1. Under inflammatory conditions, OxPL-mediated receptor potentials even potentiate the action potential firing rate of nociceptors. Targeting OxPL with D-4F, an apolipoprotein A-I mimetic peptide or antibodies like E06, specifically binding oxidized headgroups of phospholipids, can be used to control acute, inflammatory pain syndromes, at least in rodents. With a focus on proalgesic specificities of OxPL, this article discusses, how targeting defined substances of the epilipidome can contribute to mechanism-based therapies against primary and secondary chronic inflammatory or possibly also neuropathic pain.

Oxidative Stress Mechanisms in the Pathogenesis of Environmental Lung Diseases

Globally, respiratory diseases are major cause of disability and mortality, and more alarmingly, it disproportionately affects developing countries, which is largely attributed to poor quality of air. Tobacco smoke and emissions from combustion of fossil fuel and biomass fuel are the major airborne pollutants affecting human lung health. Oxidative stress is the dominant driving force by which the airborne pollutants exert their toxicity in lungs and cause respiratory diseases. Most airborne pollutants are associated with intrinsic oxidative potential and, additionally, stimulate endogenous production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Elevated ROS and RNS in lungs modulate redox signals and cause irreversible damage to critical biomolecules (lipids, proteins and DNA) and initiate various pathogenic cellular process. This chapter provides an insight into oxidative stress-linked pathogenic cellular process such as lipid peroxidation, inflammation, cell death, mitochondrial dysfunction, endoplasmic reticulum stress, epigenetic changes, profibrotic signals and mucus hypersecretion, which drive the development and progression of lung diseases. Lungs are associated with robust enzymatic and non-enzymatic (GSH, ascorbic acid, uric acid, vitamin E) antioxidant defences. However, sustained production of free radicals due to continuous exposures to airborne pollutants overwhelms lung antioxidant defences and causes oxidative injury. Preclinical studies have demonstrated the critical roles and therapeutic potential of upregulating lung antioxidants for intervention of respiratory diseases; however, so far clinical benefits in antioxidant supplementation trials have been minimal and conflicting. Antioxidants alone may not be effective in treatment of respiratory diseases; however it could be a promising adjunctive therapy.

Oxidative stress and macrophages: driving forces behind exacerbations of asthma and chronic obstructive pulmonary disease?

Oxidative stress is a common feature of obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD). Lung macrophages are key innate immune cells that can generate oxidants and are known to display aberrant polarization patterns and defective phagocytic responses in these diseases. Whether these characteristics are linked in one way or another and whether they contribute to the onset and severity of exacerbations in asthma and COPD remain poorly understood. Insight into oxidative stress, macrophages, and their interactions may be important in fully understanding acute worsening of lung disease. This review therefore highlights the current state of the art regarding the role of oxidative stress and macrophages in exacerbations of asthma and COPD. It shows that oxidative stress can attenuate macrophage function, which may result in impaired responses toward exacerbating triggers and may contribute to exaggerated inflammation in the airways.

Impact of immunization against OxLDL on the pulmonary response to cigarette smoke exposure in mice

Background

Cigarette smoke exposure can affect pulmonary lipid homeostasis and cause a progressive increase in pulmonary antibodies against oxidized low-density lipoproteins (OxLDL). Similarly, increased anti-OxLDL antibodies are observed in atherosclerosis, a pathology also tightly associated with smoking and lipid homeostasis disruption. Several immunization strategies against oxidized lipid species to help with their clearance have been shown to reduce the formation of atherosclerotic lesions. Since oxidized lipids are generated during cigarette smoke exposure, we investigated the impact of a prophylactic immunization protocol against OxLDL on the pulmonary effects of cigarette smoke exposure in mice.

Methods

Mice were immunized systemically with a mixture of human OxLDL (antigen source) and AddaVax (adjuvant) or PBS alone prior to the initiation of acute (2 week) or sub-chronic (8 weeks) cigarette smoke exposure protocols. Anti-OxLDL antibodies were measured in the bronchoalveolar lavage (BAL) fluid and serum by direct ELISA. Pulmonary impacts of cigarette smoke exposure and OxLDL immunization were assessed by measuring BAL inflammatory cells, lung functions, and changes in lung structure and gene levels of matrix/matrix-related genes.

Results

Immunization to OxLDL led to a marked increase in circulating and pulmonary antibodies against OxLDL that persisted during cigarette smoke exposure. OxLDL immunization did not exacerbate or reduce the inflammatory response following acute or sub-chronic exposure to cigarette smoke. OxLDL immunization alone had effects similar to cigarette smoke exposure on lung functions but OxLDL immunization and cigarette smoke exposure had no additive effects on these parameters. No obvious changes in lung histology, airspace or levels of matrix and matrix-related genes were caused by OxLDL immunization compared to vehicle treatment.

Conclusions

Overall, this study shows for the first time that a prophylactic immunization protocol against OxLDL can potentially have detrimental effects lung functions, without having additive effects over cigarette smoke exposure. This work sheds light on a complex dynamic between anti-OxLDL antibodies and the pulmonary response to cigarette smoke exposure.

Phagocytosis and Inflammation: Exploring the effects of the components of E-cigarette vapor on macrophages

E‐cigarettes are perceived as harmless; however, evidence of their safety is lacking. New data suggests E‐cigarettes discharge a range of compounds capable of physiological damage to users. We previously established that cigarette smoke caused defective alveolar macrophage phagocytosis. The present study compared the effect E‐cigarette of components; E‐liquid flavors, nicotine, vegetable glycerine, and propylene glycol on phagocytosis, proinflammatory cytokine secretion, and phagocytic recognition molecule expression using differentiated THP‐1 macrophages. Similar to CSE, phagocytosis of NTHi bacteria was significantly decreased by E‐liquid flavoring (11.65–15.75%) versus control (27.01%). Nicotine also decreased phagocytosis (15.26%). E‐liquid, nicotine, and E‐liquid+ nicotine reduced phagocytic recognition molecules; SR‐A1 and TLR‐2. IL‐8 secretion increased with flavor and nicotine, while TNFα, IL‐1β, IL‐6, MIP‐1α, MIP‐1β, and MCP‐1 decreased after exposure to most flavors and nicotine. PG, VG, or PG:VG mix also induced a decrease in MIP‐1α and MIP‐1β. We conclude that E‐cigarettes can cause macrophage phagocytic dysfunction, expression of phagocytic recognition receptors and cytokine secretion pathways. As such, E‐cigarettes should be treated with caution by users, especially those who are nonsmokers.

Dysregulated Functions of Lung Macrophage Populations in COPD

Chronic obstructive pulmonary disease (COPD) is a diverse respiratory disease characterised by bronchiolitis, small airway obstruction, and emphysema. Innate immune cells play a pivotal role in the disease's progression, and in particular, lung macrophages exploit their prevalence and strategic localisation to orchestrate immune responses. To date, alveolar and interstitial resident macrophages as well as blood monocytes have been described in the lungs of patients with COPD contributing to disease pathology by changes in their functional repertoire. In this review, we summarise recent evidence from human studies and work with animal models of COPD with regard to altered functions of each of these myeloid cell populations. We primarily focus on the dysregulated capacity of alveolar macrophages to secrete proinflammatory mediators and proteases, induce oxidative stress, engulf microbes and apoptotic cells, and express surface and intracellular markers in patients with COPD. In addition, we discuss the differences in the responses between alveolar macrophages and interstitial macrophages/monocytes in the disease and propose how the field should advance to better understand the implications of lung macrophage functions in COPD.

Lung Macrophage Phenotypes and Functional Responses: Role in the Pathogenesis of COPD

Lung macrophages (LMs) are essential immune effector cells that are pivotal in both innate and adaptive immune responses to inhaled foreign matter. They either reside within the airways and lung tissues (from early life) or are derived from blood monocytes. Similar to macrophages in other organs and tissues, LMs have natural plasticity and can change phenotype and function depending largely on the microenvironment they reside in. Phenotype changes in lung tissue macrophages have been implicated in chronic inflammatory responses and disease progression of various chronic lung diseases, including Chronic Obstructive Pulmonary Disease (COPD). LMs have a wide variety of functional properties that include phagocytosis (inorganic particulate matter and organic particles, such as viruses/bacteria/fungi), the processing of phagocytosed material, and the production of signaling mediators. Functioning as janitors of the airways, they also play a key role in removing dead and dying cells, as well as cell debris (efferocytic functions). We herein review changes in LM phenotypes during chronic lung disease, focusing on COPD, as well as changes in their functional properties as a result of such shifts. Targeting molecular pathways involved in LM phenotypic shifts could potentially allow for future targeted therapeutic interventions in several diseases, such as COPD.

Cigarette Smoke Exposure Inhibits Bacterial Killing via TFEB-Mediated Autophagy Impairment and Resulting Phagocytosis Defect

INTRODUCTION

Cigarette smoke (CS) exposure is the leading risk factor for COPD-emphysema pathogenesis. A common characteristic of COPD is impaired phagocytosis that causes frequent exacerbations in patients leading to increased morbidity. However, the underlying mechanism is unclear. Hence, we investigated if CS exposure causes autophagy impairment as a mechanism for diminished bacterial clearance via phagocytosis by utilizing murine macrophages (RAW264.7 cells) and Pseudomonas aeruginosa (PA01-GFP) as an experimental model.

METHODS

Briefly, RAW cells were treated with cigarette smoke extract (CSE), chloroquine (autophagy inhibitor), TFEB-shRNA, CFTR(inh)-172, and/or fisetin prior to bacterial infection for functional analysis.

RESULTS

Bacterial clearance of PA01-GFP was significantly impaired while its survival was promoted by CSE (p < 0.01), autophagy inhibition (p < 0.05; p < 0.01), TFEB knockdown (p < 0.01; p < 0.001), and inhibition of CFTR function (p < 0.001; p < 0.01) in comparison to the control group(s) that was significantly recovered by autophagy-inducing antioxidant drug, fisetin, treatment (p < 0.05; p < 0.01; and p < 0.001). Moreover, investigations into other pharmacological properties of fisetin show that it has significant mucolytic and bactericidal activities (p < 0.01; p < 0.001), which warrants further investigation.

CONCLUSIONS

Our data suggests that CS-mediated autophagy impairment as a critical mechanism involved in the resulting phagocytic defect, as well as the therapeutic potential of autophagy-inducing drugs in restoring is CS-impaired phagocytosis.

Oxidative Phospholipidomics in health and disease: Achievements, challenges and hopes

Phospholipid peroxidation products are recognized as important bioactive lipid mediators playing an active role as modulators in signalling events in inflammation, immunity and infection. The biochemical responses are determined by the oxidation structural features present in oxPL modulating biophysical and biological properties in model membranes and lipoproteins. In spite of the extensive work conducted with model systems over the last 20 years, the study of oxPL in biological systems has virtually stagnated. In fact, very little is known concerning the predominant oxPL in fluids and tissues, their basal levels, and any variations introduced with age, gender and ethnicity in health and disease. In consequence, knowledge on oxPL has not yet translated into clinical diagnostic, in the early and timely diagnosis of "silent" diseases such as atherosclerosis and cardiovascular diseases, or as prognosis tools in disease stratification and particularly useful in the context of multimorbidities. Their use as therapeutic solutions or the development of innovative functional biomaterials remains to be explored. This review summarizes the achievements made in the identification of oxPL revealing an enormous structural diversity. A brief overview of the challenges associated with the analysis of such diverse array of products is given and a critical evaluation on key aspects in the analysis pipeline that need to be addressed. Once these issues are addressed, Oxidative Phospholipidomics will hopefully lead to major breakthrough discoveries in biochemistry, pharmaceutical, and clinical areas for the upcoming 20 years. This article is part of Special Issue entitled 4-Hydroxynonenal and Related Lipid Oxidation Products.

Pleiotropic effects of oxidized phospholipids

Oxidized phospholipids (OxPLs) are increasingly recognized to play a role in a variety of normal and pathological states. OxPLs were implicated in regulation of inflammation, thrombosis, angiogenesis, endothelial barrier function, immune tolerance and other important processes. Rapidly accumulating evidence suggests that OxPLs are biomarkers of atherosclerosis and other pathologies. In addition, successful application of experimental drugs based on structural scaffold of OxPLs in animal models of inflammation was recently reported. This review briefly summarizes current knowledge on generation, methods of quantification and biological activities of OxPLs. Furthermore, receptor and cellular mechanisms of these effects are discussed. The goal of the review is to give a broad overview of this class of lipid mediators inducing pleiotropic biological effects.

Surfactant Lipids at the Host-Environment Interface. Metabolic Sensors, Suppressors, and Effectors of Inflammatory Lung Disease

The lipid composition of pulmonary surfactant is unlike that of any other body fluid. This extracellular lipid reservoir is also uniquely susceptible by virtue of its direct and continuous exposure to environmental oxidants, inflammatory agents, and pathogens. Historically, the greatest attention has been focused on those biophysical features of surfactant that serve to reduce surface tension at the air-liquid interface. More recently, surfactant lipids have also been recognized as bioactive molecules that maintain immune quiescence in the lung but can also be remodeled by the inhaled environment into neolipids that mediate key roles in inflammation, immunity, and fibrosis. This review focuses on the roles in inflammatory and infectious lung disease of two classes of native surfactant lipids, glycerophospholipids and sterols, and their corresponding oxidized species, oxidized glycerophospholipids and oxysterols. We highlight evidence that surfactant composition is sensitive to circulating lipoproteins and that the lipid milieu of the alveolus should thus be recognized as susceptible to diet and common systemic metabolic disorders. We also discuss intriguing evidence suggesting that oxidized surfactant lipids may represent an evolutionary link between immunity and tissue homeostasis that arose in the primordial lung. Taken together, the emerging picture is one in which the unique environmental susceptibility of the lung, together with its unique extracellular lipid requirements, may have made this organ both an evolutionary hub and an engine for lipid-immune cross-talk.

Oxidized Phospholipid OxPAPC Activates TRPA1 and Contributes to Chronic Inflammatory Pain in Mice

Oxidation products of the naturally occurring phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycerol-3-phosphatidylcholine (PAPC), which are known as OxPAPC, accumulate in atherosclerotic lesions and at other sites of inflammation in conditions such as septic inflammation and acute lung injury to exert pro- or anti-inflammatory effects. It is currently unknown whether OxPAPC also contributes to inflammatory pain and peripheral neuronal excitability in these conditions. Here, we observed that OxPAPC dose-dependently and selectively activated human TRPA1 nociceptive ion channels expressed in HEK293 cells in vitro, without any effect on other TRP channels, including TRPV1, TRPV4 and TRPM8. OxPAPC agonist activity was dependent on essential cysteine and lysine residues within the N-terminus of the TRPA1 channel protein. OxPAPC activated calcium influx into a subset of mouse sensory neurons which were also sensitive to the TRPA1 agonist mustard oil. Neuronal OxPAPC responses were largely abolished in neurons isolated from TRPA1-deficient mice. Intraplantar injection of OxPAPC into the mouse hind paw induced acute pain and persistent mechanical hyperalgesia and this effect was attenuated by the TRPA1 inhibitor, HC-030031. More importantly, we found levels of OxPAPC to be significantly increased in inflamed tissue in a mouse model of chronic inflammatory pain, identified by the binding of an OxPAPC-specific antibody. These findings suggest that TRPA1 is a molecular target for OxPAPC and OxPAPC may contribute to chronic inflammatory pain through TRPA1 activation. Targeting against OxPAPC and TRPA1 signaling pathway may be promising in inflammatory pain treatment.

Phospholipid Ozonation Products Activate the 5-Lipoxygenase Pathway in Macrophages

Ozone is a highly reactive environmental toxicant that can react with the double bonds of lipids in pulmonary surfactant. This study was undertaken to investigate the proinflammatory properties of the major lipid-ozone product in pulmonary surfactant, 1-palmitoyl-2-(9'-oxo-nonanoyl)-glycerophosphocholine (16:0/9al-PC), with respect to eicosanoid production. A dose-dependent increase in the formation of 5-lipoxygenase (5-LO) products was observed in murine resident peritoneal macrophages (RPM) and alveolar macrophages (AM) upon treatment with 16:0/9al-PC. In contrast, the production of cyclooxygenase (COX) derived eicosanoids did not change from basal levels in the presence of 16:0/9al-PC. When 16:0/9al-PC and the TLR2 ligand, zymosan, were added to RPM or AM, an enhancement of 5-LO product formation along with a concomitant decrease in COX product formation was observed. Neither intracellular calcium levels nor arachidonic acid release was influenced by the addition of 16:0/9al-PC to RPM. Results from mitogen-activated protein kinase (MAPK) inhibitor studies and direct measurement of phosphorylation of MAPKs revealed that 16:0/9al-PC activates the p38 MAPK pathway in RPM, which results in the activation of 5-LO. Our results indicate that 16:0/9al-PC has a profound effect on the eicosanoid pathway, which may have implications in inflammatory pulmonary disease states where eicosanoids have been shown to play a role.

The regulation of inflammation by oxidized phospholipids

During inflammation or under conditions of oxidative stress, the polyunsaturated fatty acid side chains of phospholipids in cellular membranes or lipoproteins can be oxidatively modified. This process generates a complex mixture of structurally diverse oxidized phospholipid (OxPL) species, each of which may exert distinct biological effects. The presence of OxPLs has been documented in acute and chronic microbial infections, metabolic disorders, and degenerative diseases. It is now well recognized that OxPLs actively influence biological processes and contribute to the induction and resolution of inflammation. While many pro- and anti-inflammatory effects have been documented for bulk OxPL preparations, we are only beginning to understand the exact molecular mechanisms and signaling events that mediate the individual proinflammatory or anti-inflammatory bioactivities of discrete isolated OxPL species. Here, we review the current knowledge on the regulation of inflammation by OxPLs and summarize recent studies that establish cyclopentenone-containing OxPLs as a category of potent anti-inflammatory lipid mediators.

Cyclopentenone-containing oxidized phospholipids and their isoprostanes as pro-resolving mediators of inflammation

Inflammation represents a powerful innate immune response that defends tissue homeostasis. However, the appropriate termination of inflammatory processes is essential to prevent the development of chronic inflammatory disorders. The resolution of inflammation is actively induced by specialized pro-resolving lipid mediators, which include eicosanoids, resolvins, protectins and maresins. The responsible pro-resolution pathways have emerged as promising targets for anti-inflammatory therapies since they mitigate excessive inflammation without compromising the anti-microbial defenses of the host. We have recently shown that the lipid peroxidation of membrane phospholipids, which is associated with inflammatory conditions, generates oxidized phospholipid (OxPL) species with potent pro-resolving activities. These pro-resolving OxPLs contain a cyclopentenone as their common determinant, and are structurally and functionally related to endogenous pro-resolving prostaglandins. Here, we review the regulation of inflammatory responses by OxPLs with particular focus on the bioactivities and structural characteristics of cyclopentenone-OxPLs, and discuss the impact of the responsible signaling pathways on inflammatory diseases. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.

Role for phospholipid acyl chains and cholesterol in pulmonary infections and inflammation

Review on how complex mixtures of bioactive lipids and cholesterol may influence the pulmonary immune response during infection.

Bacterial and viral respiratory tract infections result in millions of deaths worldwide and are currently the leading cause of death from infection. Acute inflammation is an essential element of host defense against infection, but can be damaging to the host when left unchecked. Effective host defense requires multiple lipid mediators, which collectively have proinflammatory and/or proresolving effects on the lung. During pulmonary infections, phospholipid acyl chains and cholesterol can be chemically and enzymatically oxidized, as well as truncated and modified, producing complex mixtures of bioactive lipids. We review recent evidence that phospholipids and cholesterol and their derivatives regulate pulmonary innate and adaptive immunity during infection. We first highlight data that oxidized phospholipids generated in the lung during infection stimulate pattern recognition receptors, such as TLRs and scavenger receptors, thereby amplifying the pulmonary inflammatory response. Next, we discuss evidence that oxidation of endogenous pools of cholesterol during pulmonary infections produces oxysterols that also modify the function of both innate and adaptive immune cells. Last, we conclude with data that n‐3 polyunsaturated fatty acids, both in the form of phospholipid acyl chains and through enzymatic processing into endogenous proresolving lipid mediators, aid in the resolution of lung inflammation through distinct mechanisms. Unraveling the complex mechanisms of induction and function of distinct classes of bioactive lipids, both native and modified, may hold promise for developing new therapeutic strategies for improving pulmonary outcomes in response to infection.

Murine models of cardiovascular comorbidity in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for cardiovascular disease (CVD). Currently, COPD patients with atherosclerosis (i.e., the most important underlying cause of CVD) receive COPD therapy complemented with standard CVD therapy. This may, however, not be the most optimal treatment. To investigate the link between COPD and atherosclerosis and to develop specific therapeutic strategies for COPD patients with atherosclerosis, a substantial number of preclinical studies using murine models have been performed. In this review, we summarize the currently used murine models of COPD and atherosclerosis, both individually and combined, and discuss the relevance of these models for studying the pathogenesis and development of new treatments for COPD patients with atherosclerosis. Murine and clinical studies have provided complementary information showing a prominent role for systemic inflammation and oxidative stress in the link between COPD and atherosclerosis. These and other studies showed that murine models for COPD and atherosclerosis are useful tools and can provide important insights relevant to understanding the link between COPD and CVD. More importantly, murine studies provide good platforms for studying the potential of promising (new) therapeutic strategies for COPD patients with CVD.

NOD1 agonist iE-DAP reverses effects of cigarette smoke extract on NOD1 signal pathway in human oral mucosal epithelial cells

Smoking is a well-known risk factor for many systemic diseases and oral disorders. Smoking has been recognized to cause diminished defense, persistent inflammation and result in disease development. Nucleotide binding oligomerization domain 1 (NOD1) signal pathway plays a key role in innate immune and tissue homeostasis. Our recent studies confirmed that cigarette smoke extract (CSE) could inhibit NOD1 expression and affect expression levels of crucial molecules of NOD1 signaling in oral mucosal epithelial cells. In the present study, immortalized human oral mucosal epithelial (Leuk-1) cells were treated with CSE, iE-DAP (NOD1 agonist), CSE + iE-DAP, respectively. Western blotting analysis demonstrated that iE-DAP triggered NOD1 expression of leuk-1 cells in a dose-dependent manner. iE-DAP also reversed the suppressive effect of CSE on NOD1 expression and prevented the overactivation of RIP2 and P-NF-κB following CSE exposure. Real-time PCR and ELISA results confirmed that iE-DAP reversed CSE-mediated effects on the mRNA levels and releases of IL-6, IL-8, TNF-α and IFN-γ by Leuk-1 cells. Taken together, our results indicated that NOD1 activation with iE-DAP could reverse CSE-mediated effects on NOD1 signaling in human oral mucosal epithelial cells.

Identification of Metabolites and Metabolic Pathways Related to Treatment with Bufei Yishen Formula in a Rat COPD Model Using HPLC Q-TOF/MS

As a traditional Chinese medicine, Bufei Yishen Formula (BYF) is widely used in China as an effective treatment for chronic obstructive pulmonary disease (COPD). Because of the component complexity and multiple activities of Chinese herbs, the mechanism whereby BYF affects COPD is not yet fully understood. Herein, pulmonary function experiments and histomorphological assessments were used to evaluate the curative effect of BYF, which showed that BYF had an effect on COPD. Additionally, a high performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC QTOF/MS) metabonomics method was used to analyze the mechanism of the actions of BYF on rats with COPD induced by a combination of bacteria and smoking. Partial least squares discriminate analysis (PLS-DA) was used to screen biomarkers related to BYF treatment. Candidate biomarkers were selected and pathways analysis of these metabolites showed that three types of metabolic pathways (unsaturated fatty acid metabolism-related pathways, phenylalanine metabolism-related pathways, and phospholipid metabolism-related pathways) were associated with BYF treatment. Importantly, arachidonic acid and related metabolic pathways might be useful targets for novel COPD therapies.

Antagonism of miR-328 increases the antimicrobial function of macrophages and neutrophils and rapid clearance of non-typeable Haemophilus influenzae (NTHi) from infected lung

Pathogenic bacterial infections of the lung are life threatening and underpin chronic lung diseases. Current treatments are often ineffective potentially due to increasing antibiotic resistance and impairment of innate immunity by disease processes and steroid therapy. Manipulation miRNA directly regulating anti-microbial machinery of the innate immune system may boost host defence responses. Here we demonstrate that miR-328 is a key element of the host response to pulmonary infection with non-typeable haemophilus influenzae and pharmacological inhibition in mouse and human macrophages augments phagocytosis, the production of reactive oxygen species, and microbicidal activity. Moreover, inhibition of miR-328 in respiratory models of infection, steroid-induced immunosuppression, and smoke-induced emphysema enhances bacterial clearance. Thus, miRNA pathways can be targeted in the lung to enhance host defence against a clinically relevant microbial infection and offer a potential new anti-microbial approach for the treatment of respiratory diseases.

MicroRNAs regulate pathogen recognition pathways by modulating translation. In the immune system, miRNAs have been identified as important regulators of gene expression programs, which regulate differentiation, growth and function of innate and adaptive immune cells. Using miRNA microarray, we demonstrated that lung miRNAs were differentially expressed following non-typeable Haemophilus Influenzae (NTHi) infection in mice. To study the role of a specific miRNA in macrophages, we used antagomir (chemically modified single-stranded RNA analogues, complementary to the target miRNA) to block miRNA function. Interestingly, inhibition of microRNA-328 in mouse and human macrophages increases microbicidal activity by amplifying phagocytosis and production of reactive oxygen species. Inhibition of mR-328 in the lung enhanced bacterial clearance in mouse models of immunosuppression and emphysema. Our study provides proof of principle that miRNA pathways can be targeted in the lung and offer a potential new anti-microbial approach for the treatment of respiratory infection.

Exposure to electronic cigarettes impairs pulmonary anti-bacterial and anti-viral defenses in a mouse model

Electronic cigarettes (E-cigs) have experienced sharp increases in popularity over the past five years due to many factors, including aggressive marketing, increased restrictions on conventional cigarettes, and a perception that E-cigs are healthy alternatives to cigarettes. Despite this perception, studies on health effects in humans are extremely limited and in vivo animal models have not been generated. Presently, we determined that E-cig vapor contains 7x10¹¹ free radicals per puff. To determine whether E-cig exposure impacts pulmonary responses in mice, we developed an inhalation chamber for E-cig exposure. Mice that were exposed to E-cig vapor contained serum cotinine concentrations that are comparable to human E-cig users. E-cig exposure for 2 weeks produced a significant increase in oxidative stress and moderate macrophage-mediated inflammation. Since, COPD patients are susceptible to bacterial and viral infections, we tested effects of E-cigs on immune response. Mice that were exposed to E-cig vapor showed significantly impaired pulmonary bacterial clearance, compared to air-exposed mice, following an intranasal infection with Streptococcus pneumonia. This defective bacterial clearance was partially due to reduced phagocytosis by alveolar macrophages from E-cig exposed mice. In response to Influenza A virus infection, E-cig exposed mice displayed increased lung viral titers and enhanced virus-induced illness and mortality. In summary, this study reports a murine model of E-cig exposure and demonstrates that E-cig exposure elicits impaired pulmonary anti-microbial defenses. Hence, E-cig exposure as an alternative to cigarette smoking must be rigorously tested in users for their effects on immune response and susceptibility to bacterial and viral infections.

Lipoprotein(A) with An Intact Lysine Binding Site Protects the Retina From an Age-Related Macular Degeneration Phenotype in Mice (An American Ophthalmological Society Thesis)

PURPOSE

To test the hypothesis that the accumulation of oxidized phospholipids (OxPL) in the macula is toxic to the retina unless neutralized by a variety of mechanisms, including binding by lipoprotein(a) [Lp(a)], which is composed of apolipoprotein(a) [apo(a)] and apolipoprotein B-100 (apoB).

METHODS

Human maculas and eyes from two Lp(a) transgenic murine models were subjected to morphologic, ultrastructural, and immunohistochemical analysis. "Wild-type Lp(a)" mice, which express human apoB-100 and apo(a) that contains oxidized phospholipid, and "mutant LBS(-) Lp(a)" mice with a defective apo(a) lysine binding site (LBS) for oxidized phospholipid binding, were fed a chow or high-fat diet for 2 to 12 months. Oxidized phospholipid-containing lipoproteins were detected by immunoreactivity to E06, a murine monoclonal antibody binding to the phosphocholine headgroup of oxidized, but not native, phospholipids.

RESULTS

Oxidized phospholipids, apo(a), and apoB accumulate in maculas, including drusen, of age-related macular degeneration (AMD) samples and age-matched controls. Lp(a) mice fed a high-fat diet developed age-related changes. However, mutant LBS(-) Lp(a) mice fed a high-fat diet developed retinal pigment epithelial cell degeneration and drusen. These changes were associated with increased OxPL, decreased antioxidant defenses, increased complement, and decreased complement regulators.

CONCLUSIONS

Human maculas accumulate Lp(a) and OxPL. Mutant LBS(-) Lp(a) mice, lacking the ability to bind E06-detectable oxidized phospholipid, develop AMD-like changes. The ability of Lp(a) to bind E06-detectable OxPL may play a protective role in AMD.

Accumulating evidence for a role of oxidized phospholipids in infectious diseases

Oxidized phospholipids (OxPL) were originally discovered as by-products and mediators of chronic inflammation such as in atherosclerosis. Over the last years, an increasing body of evidence led to the notion that OxPL not only contribute to the pathogenesis of chronic inflammatory processes but in addition play an integral role as modulators of inflammation during acute infections. Thereby, host defense mechanisms involve the generation of oxygen radicals that oxidize ubiquitously present phospholipids, which in turn act as danger-associated molecular patterns (DAMPs). These OxPL-derived DAMPs can exhibit both pro- and anti-inflammatory functions that ultimately alter the host response to pathogens. In this review, we summarize the currently available data on the role of OxPL in infectious diseases.

Impacts of peroxisome proliferator-activated receptor-γ activation on cigarette smoke-induced exacerbated response to bacteria

Chronic obstructive pulmonary disease (COPD) is characterised by a state of chronic pulmonary inflammation punctuated by microbial exacerbations. Despite advances in treatment options, COPD remains difficult to manage. In this study, we investigated the potential of peroxisome proliferator-activated receptor (PPAR)γ activation as a new therapy against cigarette smoke-induced inflammation and its associated bacterial exacerbation. C57BL/6 mice were exposed to room air or cigarette smoke for either 4 days or 4 weeks and treated either prophylactically or therapeutically with rosiglitazone. The impact of rosiglitazone on cigarette smoke-induced exacerbated response to the bacterial pathogen nontypeable Haemophilus influenzae (NTHi) was studied using the therapeutic treatment protocol. We found that rosiglitazone was able to reduce cigarette smoke-induced neutrophilia both when administered prophylactically or therapeutically. Therapeutic intervention with rosiglitazone was also effective in preventing cigarette smoke-induced neutrophilia exacerbation following NTHi infection. Moreover, the anti-inflammatory effects of rosiglitazone did not lead to an increase in the pulmonary bacterial burden, unlike dexamethasone. Altogether, our data suggest that pharmacological activation of PPARγ may be an effective therapeutic approach to improve COPD management, as it is able to reduce cigarette smoke-induced inflammation and decrease the magnitude of bacterial exacerbations, without compromising the ability of the immune system to control the infection.

Neutrophils and emerging targets for treatment in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by a decreased airflow due to airway narrowing that, once it occurs, is not fully reversible. The disease usually is progressive and associated with an enhanced inflammatory response in the lungs after exposure to noxious particles or gases. After removal of the noxious particles, the inflammation can continue in a self-sustaining manner. It has been established that improper activation of neutrophils lies at the core of the pathology. This paper provides an overview of the mechanisms by which neutrophils can induce the pulmonary damage of COPD. As the pathogenesis of COPD is slowly being unraveled, new points of intervention are discovered, some of which with promising results.

B cells and humoral immunity in atherosclerosis

Insights into the important contribution of inflammation and immune functions in the development and progression of atherosclerosis have greatly improved our understanding of this disease. Although the role of T cells has been extensively studied for decades, only recently has the role of B cells gained more attention. Recent studies have identified differential effects of different B-cell subsets and helped to clarify the still poorly understood mechanisms by which these act. B1 cells have been shown to prevent lesion formation, whereas B2 cells have been suggested to promote it. Natural IgM antibodies, mainly derived from B1 cells, have been shown to mediate atheroprotective effects, but the functional role of other immunoglobulin classes, particularly IgG, still remains elusive. In this review, we will focus on recent insights on the role of B cells and various immunoglobulin classes and how these may mediate their effects in atherosclerotic lesion formation. Moreover, we will highlight potential therapeutic approaches focusing on B-cell depletion that could be used to translate experimental evidence to human disease.

Systemic effects of acute cigarette smoke exposure in mice

CONTEXT

Cigarette smoke (CS) causes both pulmonary and extrapulmonary disorders.

OBJECTIVE

To determine the pulmonary and extrapulmonary effects of acute CS exposure in regard to inflammation, oxidative stress and DNA damage.

MATERIALS AND METHODS

Mice were exposed to CS for 10 days and then their lungs, heart, liver, pancreas, kidneys, gastrocnemius muscle and subcutaneous (inguinal and flank) and visceral (retroperitoneum and periuterus) adipose tissues were excised. Bronchoalveolar lavage fluid samples were obtained for differential cell analysis. Inflammatory cell infiltration of the tissues was assessed by immunohistochemistry for Mac-3(+) cells, F4/80(+) cells and CD45(+) cells. Oxidative stress was determined by immunohistochemistry for thymidine glycol (a marker of DNA peroxidation) and 4-hydroxy hexenal (a marker of lipid peroxidation), by enzyme-linked immunosorbent assay for protein carbonyls (a marker of protein peroxidation) and by measurements of enzyme activities of glutathione peroxidase, superoxide dismutase and catalase. DNA double-strand breaks were assessed by immunohistochemistry for γH2AX.

RESULTS

CS exposure-induced inflammatory cell infiltration, oxidative stress and DNA damage in the lung. Neither inflammatory cell infiltration nor DNA damage was observed in any extrapulmonary organs. However, oxidative stress was increased in the heart and inguinal adipose tissue.

DISCUSSIONS

Induction of inflammatory cell infiltration and DNA damage by acute CS exposure was confined to the lung. However, an increased oxidative burden occurred in the heart and some adipose tissue, as well as in the lung.

CONCLUSIONS

Although extrapulmonary effects of CS are relatively modest compared with the pulmonary effects, some extrapulmonary organs are vulnerable to CS-induced oxidative stress.

Impaired macrophage phagocytosis of bacteria in severe asthma

Background

Bacteria are frequently cultured from sputum samples of severe asthma patients suggesting a defect in bacterial clearance from the airway. We measured the capacity of macrophages from patients with asthma to phagocytose bacteria.

Methods

Phagocytosis of fluorescently-labelled polystyrene beads, Haemophilus influenzae or Staphylococcus aureus by broncholaveolar lavage alveolar macrophages (AM) and by monocyte-derived macrophages (MDM) from non-asthmatics, mild-moderate and severe asthmatic patients was assessed using fluorimetry.

Results

There were no differences in phagocytosis of polystyrene beads by AMs or MDMs from any of the subject groups. There was reduced phagocytosis of Haemophilus influenzae and Staphylococcus aureus in MDMs from patients with severe asthma compared to non-severe asthma (p < 0.05 and p < 0.01, respectively) and healthy subjects (p < 0.01and p < 0.001, respectively). Phagocytosis of Haemophilus influenzae and Staphylococcus aureus by AM was also reduced in severe asthma compared to normal subjects (p < 0.05). Dexamethasone and formoterol did not suppress phagocytosis of bacteria by MDMs from any of the groups.

Conclusions

Persistence of bacteria in the lower airways may result partly from a reduced phagocytic capacity of macrophages for bacteria. This may contribute to increased exacerbations, airway colonization and persistence of inflammation.

Impact of cigarette smoke on the human and mouse lungs: a gene-expression comparison study

Cigarette smoke is well known for its adverse effects on human health, especially on the lungs. Basic research is essential to identify the mechanisms involved in the development of cigarette smoke-related diseases, but translation of new findings from pre-clinical models to the clinic remains difficult. In the present study, we aimed at comparing the gene expression signature between the lungs of human smokers and mice exposed to cigarette smoke to identify the similarities and differences. Using human and mouse whole-genome gene expression arrays, changes in gene expression, signaling pathways and biological functions were assessed. We found that genes significantly modulated by cigarette smoke in humans were enriched for genes modulated by cigarette smoke in mice, suggesting a similar response of both species. Sixteen smoking-induced genes were in common between humans and mice including six newly reported to be modulated by cigarette smoke. In addition, we identified a new conserved pulmonary response to cigarette smoke in the induction of phospholipid metabolism/degradation pathways. Finally, the majority of biological functions modulated by cigarette smoke in humans were also affected in mice. Altogether, the present study provides information on similarities and differences in lung gene expression response to cigarette smoke that exist between human and mouse. Our results foster the idea that animal models should be used to study the involvement of pathways rather than single genes in human diseases.