Signal transduction pathways of tumor necrosis factor--mediated lung injury induced by ozone in mice

Ozone-induced lung injury and inflammation: Pathways and therapeutic targets for pulmonary diseases caused by air pollutants

Exposure to ambient Ozone (O3) air pollution directly causes by its oxidative properties, respiratory epithelial cell injury, and cell death, which promote inflammation and hyperreactivity, posing a significant public health concern. Recent clinical and experimental studies have made strides in elucidating the mechanisms underlying O3-induced epithelial cell injury, inflammation, and airway hyperreactivity, which are discussed herein. The current data suggest that O3-induced oxidative stress is a central event-inducing oxeiptotic cell death pathway. O3-induced epithelial barrier damage and cell death, triggering the release of alarmins and damage-associated molecular patterns (DAMPs), with subsequent endogenous activation of Toll-like receptors (TLRs), DNA sensing pathways, and inflammasomes, activating interleukin-1-Myd88 inflammatory pathway with the production of a range of chemokines and cytokines. This cascade orchestrates lung tissue-resident cell activation in response to O3 in leukocyte and non-leukocyte populations, driving sterile innate immune response. Chronic inflammatory response to O3, by repeated exposures, supports a mixed phenotype combining asthma and emphysema, in which their exacerbation by other particulate pollutants potentially culminates in respiratory failure. We use data from lung single-cell transcriptomics to map genes of O3-damage sensing and signaling pathways to lung cells and thereby highlight potential hotspots of O3 responses. Deeper insights into these pathological pathways might be helpful for the identification of novel therapeutic targets and strategies.

Unraveling the ozone impact and oxidative stress on the nervous system

Ozone (O₃), a potent oxidant, can penetrate the body through breathing, generating reactive oxygen species (ROS) and triggering inflammatory processes. Oxidative stress, an imbalance between the production of ROS and the body's antioxidant capacity, plays a crucial role in the pathophysiology of various neurodegenerative diseases. This phenomenon can negatively impact the Central Nervous System (CNS), inducing structural and functional alterations that contribute to the development of neurological pathologies. This review examines how O₃-induced oxidative stress affects the nervous system by analyzing existing literature on the involved molecular mechanisms and potential antioxidant systems to mitigate its effects. Through a comprehensive review of experimental studies, our objective is to shed light on the interaction between O₃ and the nervous system, as well as its signaling pathways and altered genes, providing a foundation for future research in this field. Several studies have demonstrated that prolonged exposure to O₃ leads to increased expression of reactive oxygen species, causing alterations in the blood-brain barrier and damage to astrocytes and microglia. These effects can lead to an increase in the production of proinflammatory cytokines, neurotoxins, and genes, exacerbating neuronal damage and accelerating the progression of neurodegenerative diseases such as Alzheimer's, Parkinson's, and other neurological disorders. The results of this review suggest that exposure to O₃ may induce oxidative damage to the nervous system, which could have significant implications for public health.

Overexpression of endothelial S1pr2 promotes blood-brain barrier disruption via JNK/c-Jun/MMP-9 pathway after traumatic brain injury in both in vivo and in vitro models

Objectives

The disruption of blood-brain barrier (BBB) is associated with poor outcomes of TBI patients. Sphingosine-1-phosphate receptor 2 (S1pr2), a member of the G protein-coupled receptor family, is involved in endothelial activation and the regulation of vascular integrity. We hypothesized that the inhibition of S1pr2 may alleviate BBB disruption and explored potential underlying molecular mechanisms.

Methods

Lesion volumes were assessed utilizing Nissl staining; neurological outcomes were evaluated through a battery of neurobehavioral assessments; phenotype-associated proteins were scrutinized via Western blot analysis; levels of reactive oxygen species (ROS), neuronal apoptosis, and S1pr2 expression were determined using immunofluorescence staining. The impact of S1pr2 inhibition after TBI and its underlying mechanism were elucidated using the selective S1pr2 inhibitor JTE-013, the JNK phosphorylation inhibitor SP600125, and cellular models. Chip-qPCR was employed to further elucidate the binding sites of the transcription factor c-Jun.

Results

The expression of S1pr2 significantly increased following TBI in mice. Pharmacological inhibition of S1pr2 alleviated secondary injury with reduced lesion volume, ROS generation, cerebral oedema, neurological deficits, and neuronal apoptosis; BBB disruption was also mitigated, accompanied by reduced degradation of tight junction proteins and decreased induction of matrix metalloproteinases-9 (MMP-9) post-TBI. Mechanistically, TBI induces an increase in S1pr2 specifically in endothelial cells, leading to the promotion of MMP-9 transactivation by enhancing JNK/c-Jun signaling. This results in the degradation of tight junction proteins and increased BBB permeability. Through in vitro and in vivo Chip-qPCR experiments, we verified that AP-1a and AP-1b of MMP-9 promoter function as binding sites for phosphorylated c-Jun.

Conclusion

Our findings identify a previously undisclosed role of S1pr2 in the pathophysiology of TBI. The S1pr2 inhibition presents a novel approach to alleviate BBB disruption after TBI through regulating the JNK/c-Jun/MMP-9 pathway.

The critical roles of caveolin-1 in lung diseases

Caveolin-1 (Cav-1), a structural and functional component in the caveolae, plays a critical role in transcytosis, endocytosis, and signal transduction. Cav-1 has been implicated in the mediation of cellular processes by interacting with a variety of signaling molecules. Cav-1 is widely expressed in the endothelial cells, smooth muscle cells, and fibroblasts in the various organs, including the lungs. The Cav-1-mediated internalization and regulation of signaling molecules participate in the physiological and pathological processes. Particularly, the MAPK, NF-κB, TGFβ/Smad, and eNOS/NO signaling pathways have been involved in the regulatory effects of Cav-1 in lung diseases. The important effects of Cav-1 on the lungs indicate that Cav-1 can be a potential target for the treatment of lung diseases. A Cav-1 scaffolding domain peptide CSP7 targeting Cav-1 has been developed. In this article, we mainly discuss the structure of Cav-1 and its critical roles in lung diseases, such as pneumonia, acute lung injury (ALI), asthma, chronic obstructive pulmonary disease (COPD), pulmonary hypertension, pulmonary fibrosis, and lung cancer.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

Multi-Omics Analysis of Lung Tissue Demonstrates Changes to Lipid Metabolism during Allergic Sensitization in Mice

Allergy and asthma pathogenesis are associated with the dysregulation of metabolic pathways. To understand the effects of allergen sensitization on metabolic pathways, we conducted a multi-omics study using BALB/cJ mice sensitized to house dust mite (HDM) extract or saline. Lung tissue was used to perform untargeted metabolomics and transcriptomics while both lung tissue and plasma were used for targeted lipidomics. Following statistical comparisons, an integrated pathway analysis was conducted. Histopathological changes demonstrated an allergic response in HDM-sensitized mice. Untargeted metabolomics showed 391 lung tissue compounds were significantly different between HDM and control mice (adjusted p < 0.05); with most compounds mapping to glycerophospholipid and sphingolipid pathways. Several lung oxylipins, including 14-HDHA, 8-HETE, 15-HETE, 6-keto-PGF1α, and PGE2 were significantly elevated in HDM-sensitized mice (p < 0.05). Global gene expression analysis showed upregulated calcium channel, G protein–signaling, and mTORC1 signaling pathways. Genes related to oxylipin metabolism such as Cox, Cyp450s, and cPla2 trended upwards. Joint analysis of metabolomics and transcriptomics supported a role for glycerophospholipid and sphingolipid metabolism following HDM sensitization. Collectively, our multi-omics results linked decreased glycerophospholipid and sphingolipid compounds and increased oxylipins with allergic sensitization; concurrent upregulation of associated gene pathways supports a role for bioactive lipids in the pathogenesis of allergy and asthma.

The relationship among air pollution, meteorological factors and COVID-19 in the Brussels Capital Region

In great metropoles, there is a need for a better understanding of the spread of COVID-19 in an outdoor context with environmental parameters. Many studies on this topic have been carried out worldwide. However, there is conflicting evidence regarding the influence of environmental variables on the transmission, hospitalizations and deaths from COVID-19, even though there are plausible scientific explanations that support this, especially air quality and meteorological factors. Different urban contexts, methodological approaches and even the limitations of ecological studies are some possible explanations for this issue. That is why methodological experimentations in different regions of the world are important so that scientific knowledge can advance in this aspect. This research analyses the relationship between air pollution, meteorological factors and COVID-19 in the Brussels Capital Region. We use a data mining approach that is capable of extracting patterns in large databases with diverse taxonomies. Data on air pollution, meteorological, and epidemiological variables were processed in time series for the multivariate analysis and the classification based on association. The environmental variables associated with COVID-19-related deaths, cases and hospitalization were PM_2.5, O₃, NO₂, black carbon, radiation, air pressure, wind speed, dew point, temperature and precipitation. These environmental variables combined with epidemiological factors were able to predict intervals of hospitalization, cases and deaths from COVID-19. These findings confirm the influence of meteorological and air quality variables in the Brussels region on deaths and cases of COVID-19 and can guide public policies and provide useful insights for high-level governmental decision-making concerning COVID-19. However, it is necessary to consider intrinsic elements of this study that may have influenced our results, such as the use of air quality aggregated data, ecological fallacy, focus on acute effects in the time-series study, the underreporting of COVID-19, and the lack of behavioral factors.

Selenium-Containing Compound Ameliorates Lipopolysaccharide-Induced Acute Lung Injury via Regulating the MAPK/AP-1 Pathway

Abstract-Acute lung injury (ALI) is characterized by a series of inflammatory reactions and serves as the main cause of mortality in intensive care unit patients. Although great progress has been made in understanding the pathophysiology of ALI, there are no effective treatments in clinic. Recently, we have synthesized a selenium-containing compound, which possesses obvious anti-inflammatory activity. The aim of the present study is to evaluate the protective effects of the selenium-containing compound 34# in LPS-induced ALI in mice as well as its underlying mechanism. Compound 34# was found to inhibit LPS-induced macrophage inflammatory cytokine release. These effects were observed to be produced via suppression of the MAPK/AP-1 pathway. Compound 34# was also noted to attenuate the LPS-induced lung inflammation in mice with ALI. The corresponding results suggested that compound 34# possesses remarkable protective effects on LPS-induced ALI. Furthermore, the MAPK/AP-1 pathway may prove to be the underlying mechanism. Accordingly, compound 34# may serve as a potential candidate for the prevention of ALI.

Murine Neonatal Oxidant Lung Injury: NRF2-Dependent Predisposition to Adulthood Respiratory Viral Infection and Protection by Maternal Antioxidant

NRF2 protects against oxidant-associated airway disorders via cytoprotective gene induction. To examine if NRF2 is an important determinant of respiratory syncytial virus (RSV) susceptibility after neonate lung injury, Nrf2-deficient (Nrf2^−/−) and wild-type (Nrf2^+/+) mice neonatally exposed to hyperoxia were infected with RSV. To investigate the prenatal antioxidant effect on neonatal oxidative lung injury, time-pregnant Nrf2^−/− and Nrf2^+/+ mice were given an oral NRF2 agonist (sulforaphane) on embryonic days 11.5–17.5, and offspring were exposed to hyperoxia. Bronchoalveolar lavage and histopathologic analyses determined lung injury. cDNA microarray analyses were performed on placenta and neonatal lungs. RSV-induced pulmonary inflammation, injury, oxidation, and virus load were heightened in hyperoxia-exposed mice, and injury was more severe in hyperoxia-susceptible Nrf2^−/− mice than in Nrf2^+/+ mice. Maternal sulforaphane significantly alleviated hyperoxic lung injury in both neonate genotypes with more marked attenuation of severe neutrophilia, edema, oxidation, and alveolarization arrest in Nrf2^−/− mice. Prenatal sulforaphane altered different genes with similar defensive functions (e.g., inhibition of cell/perinatal death and inflammation, potentiation of angiogenesis/organ development) in both strains, indicating compensatory transcriptome changes in Nrf2^−/− mice. Conclusively, oxidative injury in underdeveloped lungs NRF2-dependently predisposed RSV susceptibility. In utero sulforaphane intervention suggested NRF2-dependent and -independent pulmonary protection mechanisms against early-life oxidant injury.

Associations between time-weighted personal air pollution exposure and amino acid metabolism in healthy adults

The molecular mechanisms underlying the associations between air pollution exposure and adverse cardiopulmonary effects remain to be better understood. Altered amino acid metabolism may plays an important role in the development of cardiopulmonary diseases and may be perturbed by air pollution exposure. To test this hypothesized molecular mechanism, we conducted an association analysis from an existing intervention study to examine the relations of air pollution exposures with amino acids in 43 Chinese healthy adults. Plasma levels of amino acids were measured using a UPLC-QqQ-MS system. Time-weighted personal exposure to O₃, PM_2.5, NO₂, and SO₂ over four time windows, i.e., 12 h, 24 h, 1 week, and 2 weeks, were calculated using the measured indoor and outdoor concentrations coupled with the time-activity data for each participant. Linear mixed-effects models were used to estimate the associations between air pollutants at each exposure window and amino acids by controlling for potential confounders. We observed significant associations between exposures and plasma concentrations of amino acids, with the direction of associations varying by amino acid and air pollutant. While there is little evidence of associations for NO₂ and SO₂, the associations with amino acids were fairly pronounced for exposure to PM_2.5 and O₃. In particular, independent O₃ (12- and 24-hour) associations were observed with changes in the amino acids that were related to the urea cycle, including aspartate, asparagine, glutamate, arginine, citrulline, and ornithine. Our findings indicated that air pollution may cause acute perturbation of amino acid metabolism, and that O₃ and PM_2.5 may affect the metabolism of amino acids in different pathways. Main finding: Acute air pollution exposure might affect the perturbation of amino acid metabolism, and in particular, was associated with amino acids in relation to the urea cycle.

Transcriptomics Underlying Pulmonary Ozone Pathogenesis Regulated by Inflammatory Mediators in Mice

Ozone (O₃) is the predominant oxidant air pollutant associated with airway inflammation, lung dysfunction, and the worsening of preexisting respiratory diseases. We previously demonstrated the injurious roles of pulmonary immune receptors, tumor necrosis factor receptor (TNFR), and toll-like receptor 4, as well as a transcription factor NF-κB, in response to O₃ in mice. In the current study, we profiled time-dependent and TNFR- and NF-κB-regulated lung transcriptome changes by subacute O₃ to illuminate the underlying molecular events and downstream targets. Mice lacking Tnfr1/Tnfr2 (Tnfr^-/-) or Nfkb1 (Nfkb1^-/-) were exposed to air or O₃. Lung RNAs were prepared for cDNA microarray analyses, and downstream and upstream mechanisms were predicted by pathway analyses of the enriched genes. O₃ significantly altered the genes involved in inflammation and redox (24 h), cholesterol biosynthesis and vaso-occlusion (48 h), and cell cycle and DNA repair (48–72 h). Transforming growth factor-β1 was a predicted upstream regulator. Lack of Tnfr suppressed the immune cell proliferation and lipid-related processes and heightened epithelial cell integrity, and Nfkb1 deficiency markedly suppressed lung cell cycle progress during O₃ exposure. Common differentially regulated genes by TNFR and NF-κB1 (e.g., Casp8, Il6, and Edn1) were predicted to protect the lungs from cell death, connective tissue injury, and inflammation. Il6-deficient mice were susceptible to O₃-induced protein hyperpermeability, indicating its defensive role, while Tnf-deficient mice were resistant to overall lung injury caused by O₃. The results elucidated transcriptome dynamics and provided new insights into the molecular mechanisms regulated by TNFR and NF-κB1 in pulmonary subacute O₃ pathogenesis.

Effect of water-soluble PM10 on the production of TNF-α by human monocytes and induction of apoptosis in A549 human lung epithelial cells

Long-term exposure to airborne particles of 10 µm and less in size (PM₁₀) in dust can lead to increased risk of diseases such as respiratory, cardiovascular, lung cancer and atherosclerosis. The aim of the study was to evaluate the effects of water-soluble PM₁₀ particles in the Middle East Dust (MED) storm in Ahvaz, Iran, on the production of TNF-α by human monocytes. In addition, we assessed the level of induction of apoptosis in isolated A549 human pulmonary epithelial cells. For this purpose, isolated human blood monocytes (250,000 to 300,000 cell/ ml) as well as isolated human pulmonary A549 epithelial cells (100,0000 cell/ ml) were exposed to various concentrations (62.5, 125, 250, 500 µg/ml) of water-soluble PM₁₀ particles for different incubation periods (12, 24, 48 h). The results showed that exposure to PM₁₀ particles increased the production of TNF-α in human monocytes and promoted apoptosis induction in A549 cells, in both concentration and incubation of period-dependent manner. In conclusion, airborne dust particles in Ahvaz city contain active compounds capable of increasing production of the pro-inflammatory cytokine, TNF-α, and inducing apoptosis of lung epithelial cells.

Role for Mucin-5AC in Upper and Lower Airway Pathogenesis in Mice

Mucin-5AC (MUC5AC) is a major secreted mucin in pathogenic airways. To determine its role in mucus-related airway disorders, Muc5ac-deficient (Muc5ac^-/-) and wild-type (Muc5ac^+/+) mice were compared in bleomycin-induced pulmonary fibrosis, respiratory syncytial virus (RSV) disease, and ozone toxicity. Significantly greater inflammation and fibrosis by bleomycin were developed in Muc5ac^-/- lungs compared to Muc5ac^+/+ lungs. More severe mucous cell metaplasia in fibrotic Muc5ac^-/- lungs coincided with bronchial Muc2, Muc4, and Muc5b overexpression. Airway RSV replication was higher in Muc5ac^-/- than in Muc5ac^+/+ during early infection. RSV-caused pulmonary epithelial death, bronchial smooth muscle thickening, and syncytia formation were more severe in Muc5ac^-/- compared to Muc5ac^+/+. Nasal septal damage and subepithelial mucoserous gland enrichment by RSV were greater in Muc5ac^-/- than in Muc5ac^+/+. Ozone exposure developed more severe nasal airway injury accompanying submucosal gland hyperplasia and pulmonary proliferation in Muc5ac^-/- than in Muc5ac^+/+. Ozone caused periodic acid-Schiff-positive secretion only in Muc5ac^-/- nasal airways. Lung E-cadherin level was relatively lower in Muc5ac^-/- than in Muc5ac^+/+ basally and after bleomycin, RSV, and ozone exposure. Results indicate that MUC5AC is an essential mucosal component in acute phase airway injury protection. Subepithelial gland hyperplasia and adaptive increase of other epithelial mucins may compensate airway defense in Muc5ac^-/- mice.

Isoprostanes as Biomarker for White Matter Injury in Extremely Preterm Infants

Background and Aim: Preterm white matter is vulnerable to lipid peroxidation-mediated injury. F2-isoprostanes (IPs), are a useful biomarker for lipid peroxidation. Aim was to assess the association between early peri-postnatal IPs, white matter injury (WMI) at term equivalent age (TEA), and neurodevelopmental outcome in preterm infants. Methods: Infants with a gestational age (GA) below 28 weeks who had an MRI at TEA were included. IPs were measured in cord blood (cb) at birth and on plasma (pl) between 24 and 48 h after birth. WMI was assessed using Woodward MRI scoring system. Multiple regression analyses were performed to assess the association between IPs with WMI and then with BSITD-III scores at 24 months corrected age (CA). Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive value of pl-IPs for the development of WMI. Results: Forty-four patients were included. cb-IPs were not correlated with WMI score at TEA, whereas higher pl-IPs and lower GA predicted higher WMI score (p = 0.037 and 0.006, respectively) after controlling for GA, FiO2 at sampling and severity of IVH. The area under the curve was 0.72 (CI 95% = 0.51-0.92). The pl-IPs levels plotted curve indicated that 31.8 pg/ml had the best predictive threshold with a sensitivity of 86% and a specificity of 60%, to discriminate newborns with any WMI from newborns without WMI. IPs were not associated with outcome at 24 months. Conclusion: Early measurement of pl-IPs may help discriminate patients showing abnormal WMI score at TEA, thus representing an early biomarker to identify newborns at risk for brain injury.

Understanding the Functional Impact of VOC-Ozone Mixtures on the Chemistry of RNA in Epithelial Lung Cells

Introduction

Ambient air pollution is associated with premature death caused by heart disease, stroke, chronic obstructive pulmonary disease (COPD), and lung cancer. Recent studies have suggested that ribonucleic acid (RNA) oxidation is a sensitive environment-related biomarker that is implicated in pathogenesis.

Aims and Methods

We used a novel approach that integrated RNA-Seq analysis with detection by immunoprecipitation techniques of the prominent RNA oxidative modification 8-oxo-7,8-dihydroguanine (8-oxoG). Our goal was to uncover specific messenger RNA (mRNA) oxidation induced by mixtures of volatile organic compounds (VOCs) and ozone in healthy human epithelial lung cells. To this end, we exposed the BEAS-2B human epithelial lung cell line to the gas- and particle-phase products formed from reactions of 790 ppb acrolein (ACR) and 670 ppb methacrolein (MACR) with 4 ppm ozone.

Results

Using this approach, we identified 222 potential direct targets of oxidation belonging to previously described pathways, as well as uncharacterized pathways, after air pollution exposures. We demonstrated the effect of our VOC-ozone mixtures on the morphology and actin cytoskeleton of lung cells, suggesting the influence of selective mRNA oxidation in members of pathways regulating physical components of the cells. In addition, we observed the influence of the VOC-ozone mixtures on metabolic cholesterol synthesis, likely implicated as a result of the incidence of mRNA oxidation and the deregulation of protein levels of squalene synthase (farnesyl-diphosphate farnesyltransferase 1 [FDFT1]), a key enzyme in endogenous cholesterol biosynthesis.

Conclusions

Overall, our findings indicate that air pollution influences the accumulation of 8-oxoG in transcripts of epithelial lung cells that largely belong to stress-induced signaling and metabolic and structural pathways. A strength of the study was that it combined traditional transcriptome analysis with transcriptome-wide 8-oxoG mapping to facilitate the discovery of underlying processes not characterized by earlier approaches. Investigation of the processes mediated by air pollution oxidation of RNA molecules in primary cells and animal models needs to be explored in future studies. Our research has thus opened new avenues to further inform the relationship between atmospheric agents on the one hand and cellular responses on the other that are implicated in diseases.

Can atmospheric pollution be considered a co-factor in extremely high level of SARS-CoV-2 lethality in Northern Italy?

This paper investigates the correlation between the high level of Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) lethality and the atmospheric pollution in Northern Italy. Indeed, Lombardy and Emilia Romagna are Italian regions with both the highest level of virus lethality in the world and one of Europe's most polluted area. Based on this correlation, this paper analyzes the possible link between pollution and the development of acute respiratory distress syndrome and eventually death. We provide evidence that people living in an area with high levels of pollutant are more prone to develop chronic respiratory conditions and suitable to any infective agent. Moreover, a prolonged exposure to air pollution leads to a chronic inflammatory stimulus, even in young and healthy subjects. We conclude that the high level of pollution in Northern Italy should be considered an additional co-factor of the high level of lethality recorded in that area.

Major Effect of Oxidative Stress on the Male, but Not Female, SP-A1 Type II Cell miRNome

Pulmonary surfactant protein A (SP-A) plays an important role in surfactant metabolism and lung innate immunity. In humans there are two proteins, SP-A1 and SP-A2, encoded by SFTPA1 and SFTPA2, respectively, which are produced by the alveolar type II cells (T2C). We sought to investigate the differential influence of SP-A1 and SP-A2 in T2C miRNome under oxidative stress (OxS). SP-A knock out (KO) and hTG male and female mice expressing SP-A1 or SP-A2 as well as gonadectomized (Gx) mice were exposed to O₃-induced oxidative stress (OxS) or filtered air (FA). Expression of miRNAs and mRNAs was measured in the T2C of experimental animals. (a) In SP-A1 males after normalizing to KO males, significant changes were observed in the miRNome in terms of sex-OxS effects, with 24 miRNAs being differentially expressed under OxS. (b) The mRNA targets of the dysregulated miRNAs included Ago2, Ddx20, Plcg2, Irs1, Elf2, Jak2, Map2k4, Bcl2, Ccnd1, and Vhl. We validated the expression levels of these transcripts, and observed that the mRNA levels of all of these targets were unaffected in SP-A1 T2C but six of these were significantly upregulated in the KO (except Bcl2 that was downregulated). (c) Gondadectomy had a major effect on the expression of miRNAs and in three of the mRNA targets (Irs1, Bcl2, and Vhl). Ccnd1 was upregulated in KO regardless of Gx. (d) The targets of the significantly changed miRNAs are involved in several pathways including MAPK signaling pathway, cell cycle, anti-apoptosis, and other. In conclusion, in response to OxS, SP-A1 and male hormones appear to have a major effect in the T2C miRNome.

Dysregulation of Gap Junction Function and Cytokine Production in Response to Non-Genotoxic Polycyclic Aromatic Hydrocarbons in an In Vitro Lung Cell Model

Polycyclic aromatic hydrocarbons (PAHs), prevalent contaminants in our environment, in many occupations, and in first and second-hand smoke, pose significant adverse health effects. Most research focused on the genotoxic high molecular weight PAHs (e.g., benzo[a]pyrene), however, the nongenotoxic low molecular weight (LMW) PAHs are emerging as potential co-carcinogens and tumor promoters known to dysregulate gap junctional intercellular communication (GJIC), activate mitogen activated protein kinase pathways, and induce the release of inflammatory mediators. We hypothesize that inflammatory mediators resulting from LMW PAH exposure in mouse lung epithelial cell lines are involved in the dysregulation of GJIC. We used mouse lung epithelial cell lines and an alveolar macrophage cell line in the presence of a binary PAH mixture (1:1 ratio of fluoranthene and 1-methylanthracene; PAH mixture). Parthenolide, a pan-inflammation inhibitor, reversed the PAH-induced inhibition of GJIC, the decreased CX43 expression, and the induction of KC and TNF. To further determine the direct role of a cytokine in regulating GJIC, recombinant TNF (rTNF) was used to inhibit GJIC and this response was further enhanced in the presence of the PAH mixture. Collectively, these findings support a role for inflammation in regulating GJIC and the potential to target these early stage cancer pathways for therapeutics.

Clinical utility of ozone therapy for musculoskeletal disorders

Oxygen-ozone (O₃) therapy serves as an alternative medical technique that increases the oxygen in the body along with the introduction of O₃. O₃ therapy has finally reached a level where the biological mechanisms of action have been understood, showing that they are in the domain of physiology, biochemistry, and pharmacology. Few clinical applications have been reviewed here as well as exemplifying that O₃ therapy is particularly useful in musculoskeletal disorders. In the therapeutic range, O₃ can be used as a more effective and safe substitute of standard medications. O₃ therapy has been used for many years for its ability to inactivate various viruses, cancer, and acquired immune deficiency syndrome but is now making strides in the treatment of musculoskeletal disorders such as rheumatoid arthritis, lumbar facet joint syndrome, subacromial bursitis, carpal tunnel syndrome, osteoarthritis, hip bursitis, shoulder adhesive capsulitis, herniated disc, and temporomandibular joint disorder.

Angiotensin‑(1‑7) prevents lipopolysaccharide‑induced hepatocellular inflammatory response by inhibiting the p38MAPK/AP‑1 signaling pathway

The pathological mechanism of lipopolysaccharide (LPS)‑induced liver injury involves a number of inflammatory mediators and cytokines. Angiotensin (Ang)‑(1‑7), a ligand for the proto‑oncogene Mas (Mas) receptor, antagonizes the actions of Ang II in the renin angiotensin system and exerts an anti‑inflammatory effect on LPS‑induced macrophages. The present study investigated the potential role of Ang‑(1‑7) in the regulation of inflammatory responses in LPS‑induced hepatocytes using the rat liver BRL cell line. The results of the present study demonstrated that the inflammatory mediator, tumor necrosis factor (TNF)‑α, its upstream transcriptional regulatory factor activator protein (AP)‑1 and p38 mitogen activated protein kinase (MAPK) which were detected by reverse transcription‑quantitative polymerase chain reaction and western blotting were upregulated in LPS‑induced hepatic cells in a time‑dependent manner, peaking 12 h following LPS stimulation. By contrast, treatment with Ang‑(1‑7) significantly attenuated the expression of TNF‑α, AP‑1 and p38MAPK in a concentration‑dependent manner. The anti‑inflammatory effect of Ang‑(1‑7) was reversed by the Mas receptor selective antagonist, A779, in BRL cells. Furthermore, the p38MAPK inhibitor, SB 203580, abolished the protective effects of Ang‑(1‑7), suggesting the involvement of the p38MAPK pathway in the anti‑inflammatory activity of Ang‑(1‑7). The results of the present study indicated that Ang‑(1‑7) may serve an anti‑inflammatory role in LPS‑induced hepatocyte injury via the regulation of the p38MAPK/AP‑1 signaling pathway.

SP-A2 contributes to miRNA-mediated sex differences in response to oxidative stress: pro-inflammatory, anti-apoptotic, and anti-oxidant pathways are involved

BACKGROUND

Human innate host defense molecules, surfactant protein A1 (SP-A1), and SP-A2 differentially affect the function and proteome of the alveolar macrophage (AM). We hypothesized that SP-A genes differentially regulate the AM miRNome.

METHODS

Humanized transgenic mice expressing SP-A1 and SP-A2 were subjected to O3-induced oxidative stress (OxS) or filtered air (FA), AMs were isolated, and miRNA levels were measured.

RESULTS

In SP-A2 males, we found significant changes in miRNome in terms of sex and sex-OxS effects, with 11 miRNAs differentially expressed under OxS. Their mRNA targets included BCL2, CAT, FOXO1, IL6, NF-kB, SOD2, and STAT3. We followed the expression of these transcripts as well as key cytokines, and we found that (a) the STAT3 mRNA significantly increased at 4 h post OxS and returned to baseline at 18 h post OxS. (b) The anti-oxidant protein SOD2 level significantly increased, but the CAT level did not change after 4 h post OxS compared to control. (c) The anti-apoptotic BCL2 mRNA increased significantly (18 h post OxS), but the levels of the other transcripts were decreased. The presence of the SP-A2 gene had a protective role in apoptosis of AMs under OxS compared to mice lacking SP-A (knockout, KO). (d) Pro-inflammatory cytokine IL-6 protein levels were significantly increased in SP-A2 mice compared to KO (4 and 18 h post OxS), which signifies the role of SP-A2 in pro-inflammatory protein expression. (e) SOD2 and CAT mRNAs changed significantly in OxS indicating a plausible role of SP-A2 in the homeostasis of reactive oxygen species. (f) Gonadectomy of transgenic mice showed that sex hormones contribute to significant changes of the miRNome expression.

CONCLUSIONS

We conclude that SP-A2 influences the miRNA-mediated sex-specific differences in response to OxS. In males, these differences pertain to inflammatory, anti-apoptotic, and anti-oxidant pathways.

The perpetuation of the misconception that rats receive a 3-5 times lower lung tissue dose than humans at the same ozone concentration

This paper highlights the pervasive misconception concerning 1994 findings from Hatch et al. about ozone (O₃) tissue dose in humans versus rats. That study exposed humans to 0.4 ppm and rats to 2 ppm ¹⁸O-labeled O₃ and found comparable incorporation of ¹⁸O into bronchoalveolar lavage constituents. However, during O₃ exposure humans were exercising, which increased their ventilation rate five-fold, while rats were at rest. This resulted in similar O₃ tissue doses between the two species, and predominantly explained the comparable ¹⁸O incorporation at five-fold different concentrations. The five-times higher exercising human inhalation rate offset the five-times lower concentration, producing the same human dose expected at rest at 2 ppm (i.e. 0.4 ppm × 4686 L/2 hour ≈ 2 ppm × 998 L/2 hour). In 2013, Hatch et al. showed that resting humans and resting rats experienced fairly comparable ¹⁸O incorporation at the same O₃ exposure concentration and activity state into BALF cells. Despite these findings, we show here that in the peer-reviewed literature a substantial proportion of researchers continue to perpetuate the misunderstanding that human lung tissue doses of O₃ are simply 3-5 times greater than rat doses at the same O₃ concentration, due to interspecies differences, and not considering activity state. It is important to correct this misconception to ensure an appropriate understanding of the implications of O₃ studies by the scientific community and policy experts making regulatory decisions (e.g. the US Environmental Protection Agency's National Ambient Air Quality Standards for O₃).

Anti-TNFα therapy in inflammatory lung diseases

Increased levels of tumor necrosis factor (TNF) α have been linked to a number of pulmonary inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), sarcoidosis, and interstitial pulmonary fibrosis (IPF). TNFα plays multiple roles in disease pathology by inducing an accumulation of inflammatory cells, stimulating the generation of inflammatory mediators, and causing oxidative and nitrosative stress, airway hyperresponsiveness and tissue remodeling. TNFα-targeting biologics, therefore, present a potentially highly efficacious treatment option. This review summarizes current knowledge on the role of TNFα in pulmonary disease pathologies, with a focus on the therapeutic potential of TNFα-targeting agents in treating inflammatory lung diseases.

Vitamin E antagonizes ozone-induced asthma exacerbation in Balb/c mice through the Nrf2 pathway

Millions of people are regularly exposed to ozone, a gas known to contribute significantly to worsening the symptoms of patients with asthma. However, the mechanisms underlying these ozone exacerbation effects are not fully understood. In this study, we examined the exacerbation effect of ozone in OVA-induced asthma mice and tried to demonstrate the protective mechanism of vitamin E (VE). An asthma mouse model was established, and used to identify the exacerbating effects of ozone by assessing cytokine and serum immunoglobulin concentrations, airway leukocyte infiltration, histopathological changes in lung tissues, and airway hyper-responsiveness. We then determined the amount of reactive oxygen species (ROS) accumulated, the extent to which VE induced ROS elimination, and examined the antagonistic effects of VE on the ozone-induced exacerbating effects. This study showed that 1-ppm ozone exposure could exacerbate OVA-induced asthma in mice. More importantly we found that ozone induced oxidative stress in asthmatic airways may lead to the inhibition of Nuclear factor-erythroid 2-related factor 2 (Nrf2), and may subsequently induce even more exaggerated oxidative stress associated with asthma exacerbation. Through VE induced Nrf2 activation and the subsequent increase in Nrf2 target protein expression, this study suggests a novel mechanism for alleviating ozone exacerbated asthma symptoms.

Protective Role of Eosinophils and TNFa after Ozone Inhalation

Introduction

Exposure to ozone induces deleterious responses in the airways that include shortness of breath, inflammation, and bronchoconstriction. People with asthma have increased airway sensitivity to ozone and other irritants. Dr. Allison Fryer and colleagues addressed how exposure to ozone affects the immune and physiological responses in guinea pigs. Guinea pigs are considered a useful animal model for studies of respiratory and physiological responses in humans; their response to airborne allergens is similar to that in humans and shares some features of allergic asthma. Fryer and colleagues had previously observed that within 24 hours of exposure, ozone not only induced bronchoconstriction but also stimulated the production of new cells in the bone marrow, where all white blood cells develop. As a result of ozone exposure, increased numbers of newly synthesized white blood cells, particularly eosinophils, moved into the blood and lungs. The central hypothesis of the current study was that newly synthesized eosinophils recruited to the lungs 3 days after ozone exposure were beneficial to the animals because they reduced ozoneinduced bronchoconstriction. The investigators also hypothesized that the beneficial effect seen in normal (nonsensitized) animals was lost in animals that had been injected with an allergen, ovalbumin (sensitized). They also planned to explore the effects of inhibitors of certain cytokines (cellsignaling molecules). Immune responses in sensitized animals are dominated by a Th2 pattern, which is characterized by the synthesis of cytokines (interleukin [IL]-4, IL-5, and IL-13) and the Th2 subset of CD4+ T lymphocytes and the cells they activate (predominantly eosinophils, and B lymphocytes that switch to making immunoglobulin E [IgE]). Thus, sensitized animals were used as a model of allergic humans, whose immune responses tend to be dominated by IgE.

Approach

Fryer and colleagues exposed normal and sensitized (allergic) guinea pigs to 2 ppm ozone or filtered air for 4 hours and measured changes in cell numbers and airway responses 1 or 3 days later. They counted the numbers of eosinophils and other white blood cells (macrophages, neutrophils, and lymphocytes) in bone marrow, blood, and bronchoalveolar lung lavage fluid. The investigators also measured important physiological responses, including bronchoconstriction. Some animals were pretreated with etanercept and monoclonal anti-IL-5, which block tumor necrosis factor-a (TNFa) and IL-5, respectively. TNFa and IL-5 blockers have been used to treat patients with asthma. A key feature of the study was a technique to distinguish which white blood cells were synthesized after exposure from those that already existed, by injecting animals with bromodeoxyuridine (BrdU). BrdU is a thymidine analogue that is incorporated into the DNA of dividing cells, serving as a marker of newly produced cells. Therefore, a snapshot can be obtained of the proportion of newly synthesized (BrdU-positive) versus pre-existing (BrdU-negative) cell types.

Key results

1. Allergic and normal animals differed in the time course of bronchoconstriction and changes in cell types after ozone exposure. In normal animals, bronchoconstriction increased substantially at day 1 but decreased by day 3 after ozone exposure. In contrast, in allergic animals bronchoconstriction remained high at day 3. Ozone also increased the percentage of newly formed, BrdU2 positive eosinophils in the bone marrow and lungs of normal but not allergic animals. 2. Pretreatment with the TNFa blocker etanercept had complex effects, which differed between normal and allergic animals. In normal animals, etanercept decreased ozone-induced new synthesis of eosinophils in the bone marrow and blocked eosinophil migration to the lung; it also increased bronchoconstriction at day 3 (relative to day 1 without etanercept). In allergic animals, etanercept had no effect on any cell type in the bone marrow or lung after exposure to ozone and did not change bronchoconstriction compared with allergic animals not treated with etanercept. Etanercept tended to increase the numbers of blood monocytes and lymphocytes in air- and ozone-exposed normal and allergic animals at day 3, but had no effect on eosinophils in blood at this time point. This was one of the few statistically significant findings in the blood of exposed animals in the study. 3. Anti-IL-5 reduced bronchoconstriction at day 3 after exposure of allergic animals to ozone. In contrast, bronchoconstriction was greatly increased in normal animals treated with anti-IL-5.

Conclusions

Fryer and colleagues explored the airway and cellular responses in guinea pigs exposed to ozone. The HEI Review Committee, which conducted an independent review of the study, agreed that the findings supported the authors’ hypothesis (1) that exposure to ozone stimulates production of eosinophils in bone marrow, (2) that these newly formed eosinophils migrate to the lungs, and (3) that those eosinophils play a delayed but potentially beneficial role in reducing ozone-induced inflammation in the airways of healthy normal animals, but not in allergen-sensitized animals. The Committee also agreed that guinea pigs were a good model for studying responses to an allergen, because a major subtype of asthma (the high Th2 or allergic type) is associated with high levels of eosinophils in the blood. A novel finding was that the TNFa blocker etanercept decreased ozone-induced formation of eosinophils in the bone marrow and blocked eosinophil migration to the lung in normal animals. However, because injecting etanercept had little effect on eosinophils and did not decrease bronchoconstriction in allergic guinea pigs, the potential for treating patients with allergic asthma with TNFa blockers is uncertain. This is consistent with the poor performance of TNFa blockers in clinical studies of asthma treatment. Blocking the cytokine IL-5 with an anti-IL-5 antibody substantially decreased bronchoconstriction in sensitized animals. This suggests that therapies targeting IL-5 and eosinophils would be promising in at least some types of asthma. The Committee expressed caution toward experiments with cytokine blockers, both in animal models and humans, because such blockers are often not specific to a particular cell type and may differ at different sites in the body. Without further detailed confirmation of the effects of the blockers, interpreting these experiments can be challenging. The Committee concluded that the study by Fryer and colleagues raises several intriguing directions for future research, including exploring ways in which newly formed eosinophils differ from pre-existing ones, and how such findings apply to humans with allergy or asthma.

Editor's Highlight: CCR2 Regulates Inflammatory Cell Accumulation in the Lung and Tissue Injury following Ozone Exposure

Ozone-induced lung injury is associated with an accumulation of activated macrophages in the lung. Chemokine receptor CCR2 mediates the migration of inflammatory monocytes/macrophages to sites of tissue injury. It is also required for monocyte egress from the bone marrow. In the present studies, we analyzed the role of CCR2 in inflammatory cell trafficking to the lung in response to ozone. Treatment of mice with ozone (0.8 ppm, 3 h) resulted in increases in proinflammatory CCR2⁺ macrophages in the lung at 24 h, as well as proinflammatory CD11b ⁺ Ly6C^Hi and iNOS⁺ macrophages at 24 and 48 h. Mannose receptor⁺ anti-inflammatory macrophages were also observed in the lung 24 and 48 h post-ozone. Loss of CCR2 was associated with reduced numbers of proinflammatory macrophages in the lung and decreased expression of the proinflammatory cytokines, IL-1β and TNFα. Decreases in anti-inflammatory CD11b ⁺ Ly6C^Lo macrophages were also observed in lungs of CCR2^-/- mice treated with ozone, whereas mannose receptor⁺macrophage accumulation was delayed; conversely, CX3CL1 and CX3CR1 were upregulated. Changes in lung macrophage subpopulations and inflammatory gene expression in CCR2^-/- mice were correlated with reduced ozone toxicity and oxidative stress, as measured by decreases in bronchoalveolar lavage protein content and reduced lung expression of heme-oxygenase-1, 4-hydroxynonenal and cytochrome b5. These data demonstrate that CCR2 plays a role in both pro- and anti-inflammatory macrophage accumulation in the lung following ozone exposure. The fact that ozone-induced lung injury and oxidative stress are reduced in CCR2^-/- mice suggests more prominent effects on proinflammatory macrophages.

Lung transcriptional profiling: insights into the mechanisms of ozone-induced pulmonary injury in Wistar Kyoto rats

Acute ozone-induced pulmonary injury and inflammation are well characterized in rats; however, mechanistic understanding of the pathways involved is limited. We hypothesized that acute exposure of healthy rats to ozone will cause transcriptional alterations, and comprehensive analysis of these changes will allow us to better understand the mechanism of pulmonary injury and inflammation. Male Wistar Kyoto rats (10-12 week) were exposed to air, or ozone (0.25, 0.5 or 1.0 ppm) for 4 h and pulmonary injury and inflammation were assessed at 0-h or 20-h (n = 8/group). Lung gene expression profiling was assessed at 0-h (air and 1.0 ppm ozone, n = 3-4/group). At 20-h bronchoalveolar lavage, fluid protein and neutrophils increased at 1 ppm ozone. Numerous genes involved in acute inflammatory response were up-regulated along with changes in genes involved in cell adhesion and migration, steroid metabolism, apoptosis, cell cycle control and cell growth. A number of NRF2 target genes were also induced after ozone exposure. Based on expression changes, Rela, SP1 and TP3-mediated signaling were identified to be mediating downstream changes. Remarkable changes in the processes of endocytosis provide the insight that ozone-induced lung injury and inflammation are likely initiated by changes in cell membrane components and receptors likely from oxidatively modified lung lining lipids and proteins. In conclusion, ozone-induced injury and inflammation are preceded by changes in gene targets for cell adhesion/migration, apoptosis, cell cycle control and growth regulated by Rela, SP1 and TP53, likely mediated by the process of endocytosis and altered steroid receptor signaling.

Determinants of host susceptibility to murine respiratory syncytial virus (RSV) disease identify a role for the innate immunity scavenger receptor MARCO gene in human infants

Background

Respiratory syncytial virus (RSV) is the global leading cause of lower respiratory tract infection in infants. Nearly 30% of all infected infants develop severe disease including bronchiolitis, but susceptibility mechanisms remain unclear.

Methods

We infected a panel of 30 inbred strains of mice with RSV and measured changes in lung disease parameters 1 and 5 days post-infection and they were used in genome-wide association (GWA) studies to identify quantitative trait loci (QTL) and susceptibility gene candidates.

Findings

GWA identified QTLs for RSV disease phenotypes, and the innate immunity scavenger receptor Marco was a candidate susceptibility gene; targeted deletion of Marco worsened murine RSV disease. We characterized a human MARCO promoter SNP that caused loss of gene expression, increased in vitro cellular response to RSV infection, and associated with increased risk of disease severity in two independent populations of children infected with RSV.

Interpretation

Translational integration of a genetic animal model and in vitro human studies identified a role for MARCO in human RSV disease severity. Because no RSV vaccines are approved for clinical use, genetic studies have implications for diagnosing individuals who are at risk for severe RSV disease, and disease prevention strategies (e.g. RSV antibodies).

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In a panel of inbred strains of mice, RSV disease phenotypes were characterized that resemble those in human disease.

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We identified Marco as a susceptibility gene, and a human MARCO mutation increased risk of disease severity in children.

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These studies have implications for diagnosing individuals who are at risk for severe RSV disease and prevent disease.

RSV disease is the primary global cause for hospitalization one year after birth but the causes of differential RSV disease severity are not understood. We show that RSV disease phenotypes vary significantly between inbred strains of mice, and resemble those in human disease. We used genetic approaches to identify and validate the innate immunity gene Marco as a host susceptibility determinant for murine RSV disease. We then characterized a loss of function polymorphism in human MARCO that increases risk of severe RSV disease risk in infants. Results have important implications for identifying genetic risk factors for severe RSV disease.

Effects of mannose-binding lectin on pulmonary gene expression and innate immune inflammatory response to ozone

Ozone is a common, potent oxidant pollutant in industrialized nations. Ozone exposure causes airway hyperreactivity, lung hyperpermeability, inflammation, and cell damage in humans and laboratory animals, and exposure to ozone has been associated with exacerbation of asthma, altered lung function, and mortality. The mechanisms of ozone-induced lung injury and differential susceptibility are not fully understood. Ozone-induced lung inflammation is mediated, in part, by the innate immune system. We hypothesized that mannose-binding lectin (MBL), an innate immunity serum protein, contributes to the proinflammatory events caused by ozone-mediated activation of the innate immune system. Wild-type (Mbl(+/+)) and MBL-deficient (Mbl(-/-)) mice were exposed to ozone (0.3 ppm) for up to 72 h, and bronchoalveolar lavage fluid was examined for inflammatory markers. Mean numbers of eosinophils and neutrophils and levels of the neutrophil attractants C-X-C motif chemokines 2 [Cxcl2 (major intrinsic protein 2)] and 5 [Cxcl5 (limb expression, LIX)] in the bronchoalveolar lavage fluid were significantly lower in Mbl(-/-) than Mbl(+/+) mice exposed to ozone. Using genome-wide mRNA microarray analyses, we identified significant differences in transcript response profiles and networks at baseline [e.g., nuclear factor erythroid-related factor 2 (NRF2)-mediated oxidative stress response] and after exposure (e.g., humoral immune response) between Mbl(+/+) and Mbl(-/-) mice. The microarray data were further analyzed to discover several informative differential response patterns and subsequent gene sets, including the antimicrobial response and the inflammatory response. We also used the lists of gene transcripts to search the LINCS L1000CDS(2) data sets to identify agents that are predicted to perturb ozone-induced changes in gene transcripts and inflammation. These novel findings demonstrate that targeted deletion of Mbl caused differential levels of inflammation-related gene sets at baseline and after exposure to ozone and significantly reduced pulmonary inflammation, thus indicating an important innate immunomodulatory role of the gene in this model.

Using Multi-objective Optimization to Identify Dynamical Network Biomarkers as Early-warning Signals of Complex Diseases

Biomarkers have gained immense scientific interest and clinical value in the practice of medicine. With unprecedented advances in high-throughput technologies, research interest in identifying novel and customized disease biomarkers for early detection, diagnosis, or drug responses is rapidly growing. Biomarkers can be identified in different levels of molecular biomarkers, networks biomarkers and dynamical network biomarkers (DNBs). The latter is a recently developed concept which relies on the idea that a cell is a complex system whose behavior is emerged from interplay of various molecules, and this network of molecules dynamically changes over time. A DNB can serve as an early-warning signal of disease progression, or as a leading network that drives the system into the disease state, and thus unravels mechanisms of disease initiation and progression. It is therefore of great importance to identify DNBs efficiently and reliably. In this work, the problem of DNB identification is defined as a multi-objective optimization problem, and a framework to identify DNBs out of time-course high-throughput data is proposed. Temporal gene expression data of a lung injury with carbonyl chloride inhalation exposure has been used as a case study, and the functional role of the discovered biomarker in the pathogenesis of lung injury has been thoroughly analyzed.

Novel Roles for Notch3 and Notch4 Receptors in Gene Expression and Susceptibility to Ozone-Induced Lung Inflammation in Mice

BACKGROUND

Ozone is a highly toxic air pollutant and global health concern. Mechanisms of genetic susceptibility to ozone-induced lung inflammation are not completely understood. We hypothesized that Notch3 and Notch4 are important determinants of susceptibility to ozone-induced lung inflammation.

METHODS

Wild-type (WT), Notch3 (Notch3-/-), and Notch4 (Notch4-/-) knockout mice were exposed to ozone (0.3 ppm) or filtered air for 6-72 hr.

RESULTS

Relative to air-exposed controls, ozone increased bronchoalveolar lavage fluid (BALF) protein, a marker of lung permeability, in all genotypes, but significantly greater concentrations were found in Notch4-/- compared with WT and Notch3-/- mice. Significantly greater mean numbers of BALF neutrophils were found in Notch3-/- and Notch4-/- mice compared with WT mice after ozone exposure. Expression of whole lung Tnf was significantly increased after ozone in Notch3-/- and Notch4-/- mice, and was significantly greater in Notch3-/- compared with WT mice. Statistical analyses of the transcriptome identified differentially expressed gene networks between WT and knockout mice basally and after ozone, and included Trim30, a member of the inflammasome pathway, and Traf6, an inflammatory signaling member.

CONCLUSIONS

These novel findings are consistent with Notch3 and Notch4 as susceptibility genes for ozone-induced lung injury, and suggest that Notch receptors protect against innate immune inflammation.

Association of Nrf2 polymorphism haplotypes with acute lung injury phenotypes in inbred strains of mice

AIMS

Nrf2 is a master transcription factor for antioxidant response element (ARE)-mediated cytoprotective gene induction. A protective role for pulmonary Nrf2 was determined in model oxidative disorders, including hyperoxia-induced acute lung injury (ALI). To obtain additional insights into the function and genetic regulation of Nrf2, we assessed functional single nucleotide polymorphisms (SNPs) of Nrf2 in inbred mouse strains and tested whether sequence variation is associated with hyperoxia susceptibility.

RESULTS

Nrf2 SNPs were compiled from publicly available databases and by re-sequencing DNA from inbred strains. Hierarchical clustering of Nrf2 SNPs categorized the strains into three major haplotypes. Hyperoxia susceptibility was greater in haplotypes 2 and 3 strains than in haplotype 1 strains. A promoter SNP -103 T/C adding an Sp1 binding site in haplotype 2 diminished promoter activation basally and under hyperoxia. Haplotype 3 mice bearing nonsynonymous coding SNPs located in (1862 A/T, His543Gln) and adjacent to (1417 T/C, Thr395Ile) the Neh1 domain showed suppressed nuclear transactivation of pulmonary Nrf2 relative to other strains, and overexpression of haplotype 3 Nrf2 showed lower ARE responsiveness than overexpression of haplotype 1 Nrf2 in airway cells. Importantly, we found a significant correlation of Nrf2 haplotypes and hyperoxic lung injury phenotypes.

INNOVATION AND CONCLUSION

The results indicate significant influence of Nrf2 polymorphisms and haplotypes on gene function and hyperoxia susceptibility. Our findings further support Nrf2 as a genetic determinant in ALI pathogenesis and provide useful tools for investigators who use mouse strains classified by Nrf2 haplotypes to elucidate the role for Nrf2 in oxidative disorders.

Evaluating potential response-modifying factors for associations between ozone and health outcomes: a weight-of-evidence approach

BACKGROUND

Epidemiologic and experimental studies have reported a variety of health effects in response to ozone (O3) exposure, and some have indicated that certain populations may be at increased or decreased risk of O3-related health effects.

OBJECTIVES

We sought to identify potential response-modifying factors to determine whether specific groups of the population or life stages are at increased or decreased risk of O3-related health effects using a weight-of-evidence approach.

METHODS

Epidemiologic, experimental, and exposure science studies of potential factors that may modify the relationship between O3 and health effects were identified in U.S. Environmental Protection Agency's 2013 Integrated Science Assessment for Ozone and Related Photochemical Oxidants. Scientific evidence from studies that examined factors that may influence risk were integrated across disciplines to evaluate consistency, coherence, and biological plausibility of effects. The factors identified were then classified using a weight-of-evidence approach to conclude whether a specific factor modified the response of a population or life stage, resulting in an increased or decreased risk of O3-related health effects.

DISCUSSION

We found "adequate" evidence that populations with certain genotypes, preexisting asthma, or reduced intake of certain nutrients, as well as different life stages or outdoor workers, are at increased risk of O3-related health effects. In addition, we identified other factors (i.e., sex, socioeconomic status, and obesity) for which there was "suggestive" evidence that they may increase the risk of O3-related health effects.

CONCLUSIONS

Using a weight-of-evidence approach, we identified a diverse group of factors that should be considered when characterizing the overall risk of health effects associated with exposures to ambient O3.

Summer appendicitis

Acute appendicitis has been reported to be present throughout the year, but some particular months are associated with higher incidences. The aim of this study was designed to review previous studies and analyze the current knowledge and controversies related to seasonal variability of acute appendicitis, to examine whether appendicitis has an annual seasonal pattern. A search of the MEDLINE databases for English language publications over the period from 1970 to 2012 was conducted. This list was extended by including also references from a recent review of appendicitis epidemiology. We selected the studies, which were published in an English-language peer-reviewed journal, did not have intervention, were conducted for at least one year and had the outcome of histologically-confirmed appendicitis and those which reported case data temporally. A total of 30 titles and abstracts were screened for eligibility. Of these, 11 studies from 8 countries conducted across from 1970 to 2012 met the selection criteria and contributed to the systematic review. A seasonal pattern of appendicitis with a mostly predominant peak is seen during the summer months in all the countries (except Nigeria and Turkey). Appendicitis is more common in summer months. The existence of a seasonal pattern in the onset of appendicitis may be due to exposure to air pollution, decreasing fiber diet and increase in the incidence of gastrointestinal infections in summer.

Dual p38/JNK mitogen activated protein kinase inhibitors prevent ozone-induced airway hyperreactivity in guinea pigs

Ozone exposure causes airway hyperreactivity and increases hospitalizations resulting from pulmonary complications. Ozone reacts with the epithelial lining fluid and airway epithelium to produce reactive oxygen species and lipid peroxidation products, which then activate cell signaling pathways, including the mitogen activated protein kinase (MAPK) pathway. Both p38 and c-Jun NH₂ terminal kinase (JNK) are MAPK family members that are activated by cellular stress and inflammation. To test the contribution of both p38 and JNK MAPK to ozone-induced airway hyperreactivity, guinea pigs were pretreated with dual p38 and JNK MAPK inhibitors (30 mg/kg, ip) 60 minutes before exposure to 2 ppm ozone or filtered air for 4 hours. One day later airway reactivity was measured in anesthetized animals. Ozone caused airway hyperreactivity one day post-exposure, and blocking p38 and JNK MAPK completely prevented ozone-induced airway hyperreactivity. Blocking p38 and JNK MAPK also suppressed parasympathetic nerve activity in air exposed animals, suggesting p38 and JNK MAPK contribute to acetylcholine release by airway parasympathetic nerves. Ozone inhibited neuronal M₂ muscarinic receptors and blocking both p38 and JNK prevented M₂ receptor dysfunction. Neutrophil influx into bronchoalveolar lavage was not affected by MAPK inhibitors. Thus p38 and JNK MAPK mediate ozone-induced airway hyperreactivity through multiple mechanisms including prevention of neuronal M₂ receptor dysfunction.

Endogenous osteopontin promotes ozone-induced neutrophil recruitment to the lungs and airway hyperresponsiveness to methacholine

Inhalation of ozone (O₃), a common environmental pollutant, causes pulmonary injury, pulmonary inflammation, and airway hyperresponsiveness (AHR) in healthy individuals and exacerbates many of these same sequelae in individuals with preexisting lung disease. However, the mechanisms underlying these phenomena are poorly understood. Consequently, we sought to determine the contribution of osteopontin (OPN), a hormone and a pleiotropic cytokine, to the development of O₃-induced pulmonary injury, pulmonary inflammation, and AHR. To that end, we examined indices of these aforementioned sequelae in mice genetically deficient in OPN and in wild-type, C57BL/6 mice 24 h following the cessation of an acute (3 h) exposure to filtered room air (air) or O₃ (2 parts/million). In wild-type mice, O₃ exposure increased bronchoalveolar lavage fluid (BALF) OPN, whereas immunohistochemical analysis demonstrated that there were no differences in the number of OPN-positive alveolar macrophages between air- and O₃-exposed wild-type mice. O₃ exposure also increased BALF epithelial cells, protein, and neutrophils in wild-type and OPN-deficient mice compared with genotype-matched, air-exposed controls. However, following O₃ exposure, BALF neutrophils were significantly reduced in OPN-deficient compared with wild-type mice. When airway responsiveness to inhaled acetyl-β-methylcholine chloride (methacholine) was assessed using the forced oscillation technique, O₃ exposure caused hyperresponsiveness to methacholine in the airways and lung parenchyma of wild-type mice, but not OPN-deficient mice. These results demonstrate that OPN is increased in the air spaces following acute exposure to O₃ and functionally contributes to the development of O₃-induced pulmonary inflammation and airway and lung parenchymal hyperresponsiveness to methacholine.

Genes of innate immunity and the biological response to inhaled ozone

Ambient ozone has a significant impact on human health. We have made considerable progress in understanding the fundamental mechanisms that regulate the biological response to ozone. It is increasingly clear that genes of innate immunity play a central role in both infectious and noninfectious lung disease. The biological response to ambient ozone provides a clinically relevant environmental exposure that allows us to better understand the role of innate immunity in noninfectious airways disease. In this brief review, we focus on (1) specific cell types in the lung modified by ozone, (2) ozone and oxidative stress, (3) the relationship between genes of innate immunity and ozone, (4) the role of extracellular matrix in reactive airways disease, and (5) the effect of ozone on the adaptive immune system. We summarize recent advances in understanding the mechanisms that ozone contributes to environmental airways disease.

Ozone-induced lung injury and sterile inflammation. Role of toll-like receptor 4

Inhalation of toxic doses of ozone is associated with a sterile inflammatory response characterized by an accumulation of macrophages in the lower lung which are activated to release cytotoxic/proinflammatory mediators that contribute to tissue injury. Toll-like receptor 4 (TLR4) is a pattern recognition receptor present on macrophages that has been implicated in sterile inflammatory responses. In the present studies we used TLR4 mutant C3H/HeJ mice to analyze the role of TLR4 in ozone-induced lung injury, oxidative stress and inflammation. Acute exposure of control C3H/HeOuJ mice to ozone (0.8ppm for 3h) resulted in increases in bronchoalveolar lavage (BAL) lipocalin 24p3 and 4-hydroxynonenal modified protein, markers of oxidative stress and lipid peroxidation. This was correlated with increases in BAL protein, as well as numbers of alveolar macrophages. Levels of surfactant protein-D, a pulmonary collectin known to regulate macrophage inflammatory responses, also increased in BAL following ozone inhalation. Ozone inhalation was associated with classical macrophage activation, as measured by increased NF-κB binding activity and expression of TNFα mRNA. The observation that these responses to ozone were not evident in TLR4 mutant C3H/HeJ mice demonstrates that functional TLR4 contributes to ozone-induced sterile inflammation and macrophage activation.

Impact of aging on pulmonary responses to acute ozone exposure in mice: role of TNFR1

CONTEXT

Chamber studies in adult humans indicate reduced responses to acute ozone with increasing age. Age-related changes in TNFα have been observed. TNFα induced inflammation is predominantly mediated through TNFR1.

OBJECTIVE

To examine the impact of aging on inflammatory responses to acute ozone exposure in mice and determine the role of TNFR1 in age-related differences.

MATERIALS AND METHODS

Wildtype and TNFR1 deficient (TNFR1(-/-)) mice aged 7 or 39 weeks were exposed to ozone (2 ppm for 3 h). Four hours after exposure, bronchoalveolar lavage (BAL) was performed and BAL cells, cytokines, chemokines, and protein were examined.

RESULTS

Ozone-induced increases in BAL neutrophils and in neutrophil chemotactic factors were lower in 39- versus 7-week-old wildtype, but not (TNFR1(-/-)) mice. There was no effect of TNFR1 genotype in 7-week-old mice, but in 39-week-old mice, BAL neutrophils and BAL concentrations of MCP-1, KC, MIP-2, IL-6 and IP-10 were significantly greater following ozone exposure in TNFR1(-/-) versus wildtype mice. BAL concentrations of the soluble form of the TNFR1 receptor (sTNFR1) were substantially increased in 39-week-old versus 7-week-old mice, regardless of exposure.

DISCUSSION AND CONCLUSION

The data suggest that increased levels of sTNFR1 in the lungs of the 39-week-old mice may neutralize TNFα and protect these older mice against ozone-induced inflammation.

Targeted deletion of Nrf2 reduces urethane-induced lung tumor development in mice

Nrf2 is a key transcription factor that regulates cellular redox and defense responses. However, permanent Nrf2 activation in human lung carcinomas promotes pulmonary malignancy and chemoresistance. We tested the hypothesis that Nrf2 has cell survival properties and lack of Nrf2 suppresses chemically-induced pulmonary neoplasia by treating Nrf2^+/+ and Nrf2^-/- mice with urethane. Airway inflammation and injury were assessed by bronchoalveolar lavage analyses and histopathology, and lung tumors were analyzed by gross and histologic analysis. We used transcriptomics to assess Nrf2-dependent changes in pulmonary gene transcripts at multiple stages of neoplasia. Lung hyperpermeability, cell death and apoptosis, and inflammatory cell infiltration were significantly higher in Nrf2^-/- mice compared to Nrf2^+/+ mice 9 and 11 wk after urethane. Significantly fewer lung adenomas were found in Nrf2^-/- mice than in Nrf2^+/+ mice at 12 and 22 wk. Nrf2 modulated expression of genes involved cell-cell signaling, glutathione metabolism and oxidative stress response, and immune responses during early stage neoplasia. In lung tumors, Nrf2-altered genes had roles in transcriptional regulation of cell cycle and proliferation, carcinogenesis, organismal injury and abnormalities, xenobiotic metabolism, and cell-cell signaling genes. Collectively, Nrf2 deficiency decreased susceptibility to urethane-induced lung tumorigenesis in mice. Cell survival properties of Nrf2 were supported, at least in part, by reduced early death of initiated cells and heightened advantage for tumor cell expansion in Nrf2^+/+ mice relative to Nrf2^-/- mice. Our results were consistent with the concept that Nrf2 over-activation is an adaptive response of cancer conferring resistance to anti-cancer drugs and promoting malignancy.

Ambient ozone and pulmonary innate immunity

Ambient ozone is a criteria air pollutant that impacts both human morbidity and mortality. The effect of ozone inhalation includes both toxicity to lung tissue and alteration of the host immunologic response. The innate immune system facilitates immediate recognition of both foreign pathogens and tissue damage. Emerging evidence supports that ozone can modify the host innate immune response and that this response to inhaled ozone is dependent on genes of innate immunity. Improved understanding of the complex interaction between environmental ozone and host innate immunity will provide fundamental insight into the pathogenesis of inflammatory airways disease. We review the current evidence supporting that environmental ozone inhalation: (1) modifies cell types required for intact innate immunity, (2) is partially dependent on genes of innate immunity, (3) primes pulmonary innate immune responses to LPS, and (4) contributes to innate-adaptive immune system cross-talk.

Identification of candidate genes downstream of TLR4 signaling after ozone exposure in mice: a role for heat-shock protein 70

BACKGROUND

Toll-like receptor 4 (TLR4) is involved in ozone (O3)-induced pulmonary hyperpermeability and inflammation, although the downstream signaling events are unknown.

OBJECTIVES

The aims of our study were to determine the mechanism through which TLR4 modulates O3-induced pulmonary responses and to use transcriptomics to determine potential TLR4 effector molecules.

METHODS

C3H/HeJ (HeJ; Tlr4 mutant) and C3H/HeOuJ (OuJ; Tlr4 normal) mice were exposed continuously to 0.3 ppm O3 or filtered air for 6, 24, 48, or 72 hr. We assessed inflammation using bronchoalveolar lavage and molecular analysis by mRNA microarray, quantitative RT-PCR (real-time polymerase chain reaction), immunoblots, immunostaining, and ELISAs (enzyme-linked immunosorbent assays). B6-Hspa1a/Hspa1btm1Dix/NIEHS (Hsp70-/-) and C57BL/6 (B6; Hsp70+/+ wild-type control) mice were used for candidate gene validation studies.

RESULTS

O3-induced TLR4 signaling occurred through myeloid differentiation protein 88 (MyD88)-dependent and -independent pathways in OuJ mice and involved multiple downstream pathways. Genomewide transcript analyses of lungs from air- and O3-exposed HeJ and OuJ mice identified a cluster of genes that were significantly up-regulated in O3-exposed OuJ mice compared with O3-exposed HeJ mice or air-exposed controls of both strains; this cluster included genes for heat-shock proteins (e.g., Hspa1b, Hsp70). Moreover, O3-induced inflammation, MyD88 up-regulation, extracellular-signal-related kinase-1/2 (ERK1/2) and activator protein-1 (AP-1) activation, and kerotinocyte-derived chemokine (KC) protein content were significantly reduced in Hspa1a/Hspa1btm1Dix (Hsp70-/-) compared with Hsp70+/+ mice (p < 0.05).

CONCLUSIONS

These studies suggest that HSP70 is an effector molecule downstream of TLR4 and is involved in the regulation of O3-induced lung inflammation by triggering similar pathways to TLR4. These novel findings may have therapeutic and preventive implications for inflammatory diseases resulting from environmental exposures.