Ozone enhances pulmonary innate immune response to a Toll-like receptor-2 agonist

Ozone-induced neurotoxicity: In vitro and in vivo evidence

Together with cities in higher-income nations, it is anticipated that the real global ozone is rising in densely populated areas of Asia and Africa. This review aims to discuss the possible neurotoxic pollutants and ozone-induced neurotoxicity: in vitro and in vivo, along with possible biomarkers to assess ozone-related oxidative stress. As a methodical and scientific strategy for hazard identification and risk characterization of human chemical exposures, toxicological risk assessment is increasingly being implemented. While traditional methods are followed by in vitro toxicology, cell culture techniques are being investigated in modern toxicology. In both human and rodent models, aging makes the olfactory circuitry vulnerable to spreading immunological responses from the periphery to the brain because it lacks the blood-brain barrier. The ozone toxicity is elusive as it shows ventral and dorsal root injury cases even in the milder dose. Its potential toxicity should be disclosed to understand further the clear mechanism insights of how it acts in cellular aspects. Human epidemiological research has confirmed the conclusions that prenatal and postnatal exposure to high levels of air pollution are linked to behavioral alterations in offspring. O3 also enhances blood circulation. It has antibacterial action, which may have an impact on the gut microbiota. It also activates immunological, anti-inflammatory, proteasome, and growth factor signaling Prolonged O3 exposure causes oxidative damage to plasma proteins and lipids and damages the structural and functional integrity of the mitochondria. Finally, various studies need to be conducted to identify the potential biomarkers associated with ozone and the brain.

Acute and Repeated Ozone Exposures Differentially Affect Circadian Clock Gene Expression in Mice

Circadian rhythms have an established role in regulating physiological processes, such as inflammation, immunity, and metabolism. Ozone, a common environmental pollutant with strong oxidative potential, is implicated in lung inflammation/injury in asthmatics. However, whether O3 exposure affects the expression of circadian clock genes in the lungs is not known. In this study, changes in the expression of core clock genes are analyzed in the lungs of adult female and male mice exposed to filtered air (FA) or O3 using qRT-PCR. The findings are confirmed using an existing RNA-sequencing dataset from repeated FA- and O3 -exposed mouse lungs and validated by qRT-PCR. Acute O3 exposure significantly alters the expression of clock genes in the lungs of females (Per1, Cry1, and Rora) and males (Per1). RNA-seq data revealing sex-based differences in clock gene expression in the airway of males (decreased Nr1d1/Rev-erbα) and females (increased Skp1), parenchyma of females and males (decreased Nr1d1 and Fbxl3 and increased Bhlhe40 and Skp1), and alveolar macrophages of males (decreased Arntl/Bmal1, Per1, Per2, Prkab1, and Prkab2) and females (increased Cry2, Per1, Per2, Csnk1d, Csnk1e, Prkab2, and Fbxl3). These findings suggest that lung inflammation caused by O3 exposure affects clock genes which may regulate key signaling pathways.

Physiological status of House Sparrows (Passer domesticus) along an ozone pollution gradient

Mexico City is one of the most polluted cities in the world, and one in which air contamination is considered a public health threat. Numerous studies have related high concentrations of particulate matter and ozone to several respiratory and cardiovascular diseases and a higher human mortality risk. However, almost all of those studies have focused on human health outcomes, and the effects of anthropogenic air pollution on wildlife species is still poorly understood. In this study, we investigated the impacts of air pollution in the Mexico City Metropolitan Area (MCMA) on house sparrows (Passer domesticus). We assessed two physiological responses commonly used as biomarkers: stress response (the corticosterone concentration in feathers), and constitutive innate immune response (the concentration of both natural antibodies and lytic complement proteins), which are non-invasive techniques. We found a negative relationship between the ozone concentration and the natural antibodies response (p = 0.003). However, no relationship was found between the ozone concentration and the stress response or the complement system activity (p > 0.05). These results suggest that ozone concentrations in air pollution within MCMA may constrain the natural antibody response in the immune system of house sparrows. Our study shows, for the first time, the potential impact of ozone pollution on a wild species in the MCMA presenting the Nabs activity and the house sparrow as suitable indicators to assess the effect of air contamination on the songbirds.

Ozone impairs endogenous compensatory responses in allergic asthma

Asthma is a chronic inflammatory airway disease characterized by acute exacerbations triggered by inhaled allergens, respiratory infections, or air pollution. Ozone (O3), a major component of air pollution, can damage the lung epithelium in healthy individuals. Despite this association, little is known about the effects of O3 and its impact on chronic lung disease. Epidemiological data have demonstrated that elevations in ambient O3 are associated with increased asthma exacerbations. To identify mechanisms by which O3 exposure leads to asthma exacerbations, we developed a two-hit mouse model where mice were sensitized and challenged with three common allergens (dust mite, ragweed and Aspergillus fumigates, DRA) to induce allergic inflammation prior to exposure to O3 (DRAO3). Changes in lung physiology, inflammatory cells, and inflammation were measured. Exposure to O3 following DRA significantly increased airway hyperreactivity (AHR), which was independent of TLR4. DRA exposure resulted in increased BAL eosinophilia while O3 exposure resulted in neutrophilia. Additionally, O3 exposure following DRA blunted anti-inflammatory and antioxidant responses. Finally, there were significantly less monocytes and innate lymphoid type 2 cells (ILC2s) in the dual challenged DRA-O3 group suggesting that the lack of these immune cells may influence O3-induced AHR in the setting of allergic inflammation. In summary, we developed a mouse model that mirrors some aspects of the clinical course of asthma exacerbations due to air pollution and identified that O3 exposure in the asthmatic lung leads to impaired endogenous anti-inflammatory and antioxidant responses and alterations inflammatory cell populations.

Ozone effect on the inflammatory and proteomic profile of human macrophages and airway epithelial cells

Ozone (O₃) is one of the most harmful urban pollutants, but its biological mechanisms have not been fully elucidated yet. Human bronchial epithelial cells (HBEpC) and human macrophage cells (differentiated human monocytic cell line) were exposed to O₃ at the concentration of 240 μg/m³ (120 ppb), corresponding to the European Union alert threshold. Cell viability, reactive oxygen species (ROS) production, and pro-inflammatory cytokines release (IL-8 and TNF-α) were evaluated. Results indicated that O₃ exposure increases ROS production in both cell types and enhances cytokines release in macrophages. O₃ stimulated IL-8 and TNF-α in HBEpC when the cells were pretreated with Lipopolysaccharide, used to mimic a pre-existing inflammatory condition. Proteomics analysis revealed that, in HBEpC, O₃ caused the up-regulation of aldo-keto reductase family 1 member B10, a recognized critical protein in lung carcinogenesis. In conclusion, our results show that 120 ppb O₃ can lead to potential damage to human health suggesting the need for a revision of the actual alert levels.

Role of Macrophages in Air Pollution Exposure Related Asthma

Asthma is a chronic inflammatory airway disease characterized by variable airflow obstruction, bronchial hyper-responsiveness, and airway inflammation. The chronic inflammation of the airway is mediated by many cell types, cytokines, chemokines, and inflammatory mediators. Research suggests that exposure to air pollution has a negative impact on asthma outcomes in adult and pediatric populations. Air pollution is one of the greatest environmental risks to health, and it impacts the lungs' innate and adaptive defense systems. A major pollutant in the air is particulate matter (PM), a complex component composed of elemental carbon and heavy metals. According to the WHO, 99% of people live in air pollution where air quality levels are lower than the WHO air quality guidelines. This suggests that the effect of air pollution exposure on asthma is a crucial health issue worldwide. Macrophages are essential in recognizing and processing any inhaled foreign material, such as PM. Alveolar macrophages are one of the predominant cell types that process and remove inhaled PM by secreting proinflammatory mediators from the lung. This review focuses on macrophages and their role in orchestrating the inflammatory responses induced by exposure to air pollutants in asthma.

Medical Gas Therapy for Tissue, Organ, and CNS Protection: A Systematic Review of Effects, Mechanisms, and Challenges

Gaseous molecules have been increasingly explored for therapeutic development. Here, following an analytical background introduction, a systematic review of medical gas research is presented, focusing on tissue protections, mechanisms, data tangibility, and translational challenges. The pharmacological efficacies of carbon monoxide (CO) and xenon (Xe) are further examined with emphasis on intracellular messengers associated with cytoprotection and functional improvement for the CNS, heart, retina, liver, kidneys, lungs, etc. Overall, the outcome supports the hypothesis that readily deliverable "biological gas" (CO, H₂ , H₂ S, NO, O₂ , O₃ , and N₂ O) or "noble gas" (He, Ar, and Xe) treatment may preserve cells against common pathologies by regulating oxidative, inflammatory, apoptotic, survival, and/or repair processes. Specifically, CO, in safe dosages, elicits neurorestoration via igniting sGC/cGMP/MAPK signaling and crosstalk between HO-CO, HIF-1α/VEGF, and NOS pathways. Xe rescues neurons through NMDA antagonism and PI3K/Akt/HIF-1α/ERK activation. Primary findings also reveal that the need to utilize cutting-edge molecular and genetic tactics to validate mechanistic targets and optimize outcome consistency remains urgent; the number of neurotherapeutic investigations is limited, without published results from large in vivo models. Lastly, the broad-spectrum, concurrent multimodal homeostatic actions of medical gases may represent a novel pharmaceutical approach to treating critical organ failure and neurotrauma.

Molecular mechanisms of oxidative stress in asthma

The lungs are exposed to reactive oxygen species oxygen (ROS) produced as a result of inhalation of oxygen, as well as smoke and other air pollutants. Cell metabolism and the NADPH oxidases (Nox) generate low levels of intracellular ROS that act as signal transduction mediators by inducing oxidative modifications of histones, enzymes and transcription factors. Redox signalling is also regulated by localised production and sensing of ROS in mitochondria, the endoplasmic reticulum (ER) and inside the nucleus. Intracellular ROS are maintained at low levels through the action of a battery of enzymatic and non-enzymatic antioxidants. Asthma is a heterogeneous airway inflammatory disease with different immune endotypes; these include atopic or non-atopic Th2 type immune response associated with eosinophilia, or a non-Th2 response associated with neutrophilia. Airway remodelling and hyperresponsiveness accompany the inflammatory response in asthma. Over-production of ROS resulting from infiltrating immune cells, particularly eosinophils and neutrophils, and a concomitant impairment of antioxidant responses lead to development of oxidative stress in asthma. Oxidative stress is augmented in severe asthma and during exacerbations, as well as by air pollution and obesity, and causes oxidative damage of tissues promoting airway inflammation and hyperresponsiveness. Furthermore, deregulated Nox activity, mitochondrial dysfunction, ER stress and/or oxidative DNA damage, resulting from exposure to irritants, inflammatory mediators or obesity, may lead to redox-dependent changes in cell signalling. ROS play a central role in airway epithelium-mediated sensing, development of innate and adaptive immune responses, and airway remodelling and hyperresponsiveness. Nonetheless, antioxidant compounds have proven clinically ineffective as therapeutic agents for asthma, partly due to issues with stability and in vivo metabolism of these compounds. The compartmentalised nature of ROS production and sensing, and the role of ROS in homeostatic responses and in the action of corticosteroids and β2-adrenergic receptor agonists, adds another layer of complexity to antioxidant therapy development. Nox inhibitors and mitochondrial-targeted antioxidants are in clinical development for a number of diseases but they have not yet been investigated in asthma. A better understanding of the complex role of ROS in the pathogenesis of asthma will highlight new opportunities for more targeted and effective redox therapies.

Particulate matter air pollutants and cardiovascular disease: Strategies for intervention

Air pollution is consistently linked with elevations in cardiovascular disease (CVD) and CVD-related mortality. Particulate matter (PM) is a critical factor in air pollution-associated CVD. PM forms in the air during the combustion of fuels as solid particles and liquid droplets and the sources of airborne PM range from dust and dirt to soot and smoke. The health impacts of PM inhalation are well documented. In the US, where CVD is already the leading cause of death, it is estimated that PM2.5 (PM < 2.5 μm in size) is responsible for nearly 200,000 premature deaths annually. Despite the public health data, definitive mechanisms underlying PM-associated CVD are elusive. However, evidence to-date implicates mechanisms involving oxidative stress, inflammation, metabolic dysfunction and dyslipidemia, contributing to vascular dysfunction and atherosclerosis, along with autonomic dysfunction and hypertension. For the benefit of susceptible individuals and individuals who live in areas where PM levels exceed the National Ambient Air Quality Standard, interventional strategies for mitigating PM-associated CVD are necessary. This review will highlight current state of knowledge with respect to mechanisms for PM-dependent CVD. Based upon these mechanisms, strategies for intervention will be outlined. Citing data from animal models and human subjects, these highlighted strategies include: 1) antioxidants, such as vitamins E and C, carnosine, sulforaphane and resveratrol, to reduce oxidative stress and systemic inflammation; 2) omega-3 fatty acids, to inhibit inflammation and autonomic dysfunction; 3) statins, to decrease cholesterol accumulation and inflammation; 4) melatonin, to regulate the immune-pineal axis and 5) metformin, to address PM-associated metabolic dysfunction. Each of these will be discussed with respect to its potential role in limiting PM-associated CVD.

Role of Innate Immune System in Environmental Lung Diseases

The lung mucosa functions as a principal barrier between the body and inhaled environmental irritants and pathogens. Precise and targeted surveillance mechanisms are required at this lung-environment interface to maintain homeostasis and preserve gas exchange. This is performed by the innate immune system, a germline-encoded system that regulates initial responses to foreign irritants and pathogens. Environmental pollutants, such as particulate matter (PM), ozone (O₃), and other products of combustion (NO₂, SO₃, etc.), both stimulate and disrupt the function of the innate immune system of the lung, leading to the potential for pathologic consequences. PURPOSE OF REVIEW: The purpose of this review is to explore recent discoveries and investigations into the role of the innate immune system in responding to environmental exposures. This focuses on mechanisms by which the normal function of the innate immune system is modified by environmental agents leading to disruptions in respiratory function. RECENT FINDINGS: This is a narrative review of mechanisms of pulmonary innate immunity and the impact of environmental exposures on these responses. Recent findings highlighted in this review are categorized by specific components of innate immunity including epithelial function, macrophages, pattern recognition receptors, and the microbiome. Overall, the review supports broad impacts of environmental exposures to alterations to normal innate immune functions and has important implications for incidence and exacerbations of lung disease. The innate immune system plays a critical role in maintaining pulmonary homeostasis in response to inhaled air pollutants. As many of these agents are unable to be mitigated, understanding their mechanistic impact is critical to develop future interventions to limit their pathologic consequences.

Lipoxin A4 protects against paraquat‑induced acute lung injury by inhibiting the TLR4/MyD88‑mediated activation of the NF‑κB and PI3K/AKT pathways

Paraquat (PQ) causes serious oxidative stress and inflammatory responses, particularly to the lungs. Since lipoxin A4 (LXA4) functions as an anti‑inflammatory mediator, the present study aimed to explore its effects on PQ‑induced acute lung injury (ALI) and to elucidate the possible underlying mechanisms. PQ was administered to male SD rats and RAW264.7 cells to establish a model of poisoning, and LXA4 was used as an intervention drug. LXA4 treatment attenuated PQ‑induced lung injury, and this was accompanied by decreased tumor necrosis factor (TNF)‑α and interleukin (IL)‑1β secretion levels, and reduced oxidative stress damage. Additionally, LXA4 treatment inhibited the activation of the inflammation‑related signaling molecules, Toll‑like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor (NF)‑κB p65, p‑phosphoinositide 3‑kinase (PI3K) and p‑AKT. Furthermore, the in vitro experiments further confirmed that the beneficial effects of LXA4 on PQ‑induced damage were TLR4‑dependent. Hence, the present study demonstrated that LXA4 attenuated PQ‑induced toxicity in lung tissue and RAW264.7 macrophages, and that this protective effect may be closely related to the mitigation of inflammatory responses, oxidative stress damage and the TLR4/MyD88‑mediated activation of the PI3K/AKT/NF‑κB pathway.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Bacterial products in donor airways prevent the induction of lung transplant tolerance

Although postoperative bacterial infections can trigger rejection of pulmonary allografts, the impact of bacterial colonization of donor grafts on alloimmune responses to transplanted lungs remains unknown. Here, we tested the hypothesis that bacterial products present within donor grafts at the time of implantation promote lung allograft rejection. Administration of the toll-like receptor 2 (TLR2) agonist Pam₃ Cys₄ to Balb/c wild-type grafts triggered acute cellular rejection after transplantation into B6 wild-type recipients that received perioperative costimulatory blockade. Pam₃ Cys₄ -triggered rejection was associated with an expansion of CD8⁺ T lymphocytes and CD11c⁺ CD11b^hi MHC (major histocompatibility complex) class II⁺ antigen-presenting cells within the transplanted lungs. Rejection was prevented when lungs were transplanted into TLR2-deficient recipients but not when MyD88-deficient donors were used. Adoptive transfer of B6 wild-type monocytes, but not T cells, following transplantation into B6 TLR2-deficient recipients restored the ability of Pam₃ Cys₄ to trigger acute cellular rejection. Thus, we have demonstrated that activation of TLR2 by a bacterial lipopeptide within the donor airways prevents the induction of lung allograft tolerance through a process mediated by recipient-derived monocytes. Our work suggests that donor lungs harboring bacteria may precipitate an inflammatory response that can facilitate allograft rejection.

Compartment-specific transcriptomics of ozone-exposed murine lungs reveals sex- and cell type-associated perturbations relevant to mucoinflammatory lung diseases

Ozone is known to cause lung injury, and resident cells of the respiratory tract (i.e., epithelial cells and macrophages) respond to inhaled ozone in a variety of ways that affect their survival, morphology, and functioning. However, a complete understanding of the sex-associated and the cell type-specific gene expression changes in response to ozone exposure is still limited. Through transcriptome profiling, we aimed to analyze gene expression alterations and associated enrichment of biological pathways in three distinct cell type-enriched compartments of ozone-exposed murine lungs. We subchronically exposed adult male and female mice to 0.8 ppm ozone or filtered air. RNA-Seq was performed on airway epithelium-enriched airways, parenchyma, and purified airspace macrophages. Differential gene expression and biological pathway analyses were performed and supported by cellular and immunohistochemical analyses. While a majority of differentially expressed genes (DEGs) in ozone-exposed versus air-exposed groups were common between both sexes, sex-specific DEGs were also identified in all of the three tissue compartments. As compared with ozone-exposed males, ozone-exposed females had significant alterations in gene expression in three compartments. Pathways relevant to cell division and DNA repair were enriched in the ozone-exposed airways, indicating ozone-induced airway injury and repair, which was further supported by immunohistochemical analyses. In addition to cell division and DNA repair pathways, inflammatory pathways were also enriched within the parenchyma, supporting contribution by both epithelial and immune cells. Further, immune response and cytokine-cytokine receptor interactions were enriched in macrophages, indicating ozone-induced macrophage activation. Finally, our analyses also revealed the overall upregulation of mucoinflammation- and mucous cell metaplasia-associated pathways following ozone exposure.

Lung macrophages: current understanding of their roles in Ozone-induced lung diseases

Through the National Ambient Air Quality Standards (NAAQS), the Clean Air Act of the United States outlines acceptable levels of six different air pollutants considered harmful to humans and the environment. Included in this list is ozone (O₃), a highly reactive oxidant gas, respiratory health hazard, and common environmental air pollutant at ground level. The respiratory health effects due to O₃ exposure are often associated with molecular and cellular perturbations in the respiratory tract. Periodic review of NAAQS requires comprehensive scientific evaluation of the public health effects of these pollutants, which is formulated through integrated science assessment (ISA) of the most policy-relevant scientific literature. This review focuses on the protective and pathogenic effects of macrophages in the O₃-exposed respiratory tract, with emphasis on mouse model-based toxicological studies. Critical findings from 39 studies containing the words O₃, macrophage, mice, and lung within the full text were assessed. While some of these studies highlight the presence of disease-relevant pathogenic macrophages in the airspaces, others emphasize a protective role for macrophages in O₃-induced lung diseases. Moreover, a comprehensive list of currently known macrophage-specific roles in O₃-induced lung diseases is included in this review and the significant knowledge gaps that still exist in the field are outlined. In conclusion, there is a vital need in this field for additional policy-relevant scientific information, including mechanistic studies to further define the role of macrophages in response to O₃.

Transcriptional Effects of Ozone and Impact on Airway Inflammation

Epidemiological and challenge studies in healthy subjects and in individuals with asthma highlight the health impact of environmental ozone even at levels considered safe. Acute ozone exposure in man results in sputum neutrophilia in 30% of subjects particularly young children, females, and those with ongoing cardiopulmonary disease. This may be associated with systemic inflammation although not in all cases. Chronic exposure amplifies these effects and can result in the formation of asthma-like symptoms and immunopathology. Asthmatic patients who respond to ozone (responders) induce a greater number of genes in bronchoalveolar (BAL) macrophages than healthy responders with up-regulation of inflammatory and immune pathways under the control of cytokines and chemokines and the enhanced expression of remodeling and repair programmes including those associated with protease imbalances and cell-cell adhesion. These pathways are under the control of several key transcription regulatory factors including nuclear factor (NF)-κB, anti-oxidant factors such as nuclear factor (erythroid-derived 2)-like 2 NRF2, the p38 mitogen activated protein kinase (MAPK), and priming of the immune system by up-regulating toll-like receptor (TLR) expression. Murine and cellular models of acute and chronic ozone exposure recapitulate the inflammatory effects seen in humans and enable the elucidation of key transcriptional pathways. These studies emphasize the importance of distinct transcriptional networks in driving the detrimental effects of ozone. Studies indicate the critical role of mediators including IL-1, IL-17, and IL-33 in driving ozone effects on airway inflammation, remodeling and hyperresponsiveness. Transcription analysis and proof of mechanisms studies will enable the development of drugs to ameliorate the effects of ozone exposure in susceptible individuals.

The effects of neutralizing anti-murine interleukin-17A monoclonal antibody on ozone-induced inflammation and glucocorticoids insensitivity in a murine model of asthma

BACKGROUND AND OBJECTIVE

Exposure to ozone contributed to the worsening of inflammation and glucocorticoids insensitivity in OVA-challenged asthma. Interleukin-17A participates centrally in stages of the inflammatory response and glucocorticoids insensitivity. In this study, the effect of neutralizing anti-murine interleukin-17A monoclonal antibody (IL-17A mAb) on inflammation and glucocorticoids insensitivity in ozone-exposed and ovalbumin (OVA)-challenged mice was investigated.

METHODS

Mice were sensitized and challenged with OVA and then exposed to ozone. Dexamethasone (Dex) and IL-17A mAb were administrated in corresponding periods.

RESULTS

Compared with OVA-challenged mice, combination administration of ozone exposure and OVA challenge increased the recruitment of inflammatory cells in bronchoalveolar lavage fluid, enhanced the inflammation scores and levels of inflammatory cytokines and IL-17A mRNA, and caused the activation of p38 MAPK together with down regulation of glucocorticoids recepters (GR) in lung tissue. Monotherapy of IL-17A mAb partially attenuated lung inflammation in OVA-challenged and ozone-exposed mice, while the combination treatment of Dex and IL-17A mAb effectively reduced lung inflammation, inactivated p38 MAPK and up regulated GR in lung tissue.

CONCLUSIONS

Ozone exposure worsened OVA-challenged airway inflammation, activation of p38 MAPK and down regulation of GR in OVA-sensitized and -challenged mice, which was effectively counteracted by IL-17A mAb, and combination treatment of IL-17A mAb and Dex shows profound efficacy in inhibiting airway inflammation and improving glucocorticoids insensitivity synergistically.

Mapping macrophage polarization over the myocardial infarction time continuum

In response to myocardial infarction (MI), cardiac macrophages regulate inflammation and scar formation. We hypothesized that macrophages undergo polarization state changes over the MI time course and assessed macrophage polarization transcriptomic signatures over the first week of MI. C57BL/6 J male mice (3–6 months old) were subjected to permanent coronary artery ligation to induce MI, and macrophages were isolated from the infarct region at days 1, 3, and 7 post-MI. Day 0, no MI resident cardiac macrophages served as the negative MI control. Whole transcriptome analysis was performed using RNA-sequencing on n = 4 pooled sets for each time. Day 1 macrophages displayed a unique pro-inflammatory, extracellular matrix (ECM)-degrading signature. By flow cytometry, day 0 macrophages were largely F4/80^highLy6C^low resident macrophages, whereas day 1 macrophages were largely F4/80^lowLy6C^high infiltrating monocytes. Day 3 macrophages exhibited increased proliferation and phagocytosis, and expression of genes related to mitochondrial function and oxidative phosphorylation, indicative of metabolic reprogramming. Day 7 macrophages displayed a pro-reparative signature enriched for genes involved in ECM remodeling and scar formation. By triple in situ hybridization, day 7 infarct macrophages in vivo expressed collagen I and periostin mRNA. Our results indicate macrophages show distinct gene expression profiles over the first week of MI, with metabolic reprogramming important for polarization. In addition to serving as indirect mediators of ECM remodeling, macrophages are a direct source of ECM components. Our study is the first to report the detailed changes in the macrophage transcriptome over the first week of MI.

Gene Expression Analysis to Assess the Relevance of Rodent Models to Human Lung Injury

The relevance of animal models to human diseases is an area of intense scientific debate. The degree to which mouse models of lung injury recapitulate human lung injury has never been assessed. Integrating data from both human and animal expression studies allows for increased statistical power and identification of conserved differential gene expression across organisms and conditions. We sought comprehensive integration of gene expression data in experimental acute lung injury (ALI) in rodents compared with humans. We performed two separate gene expression multicohort analyses to determine differential gene expression in experimental animal and human lung injury. We used correlational and pathway analyses combined with external in vitro gene expression data to identify both potential drivers of underlying inflammation and therapeutic drug candidates. We identified 21 animal lung tissue datasets and three human lung injury bronchoalveolar lavage datasets. We show that the metasignatures of animal and human experimental ALI are significantly correlated despite these widely varying experimental conditions. The gene expression changes among mice and rats across diverse injury models (ozone, ventilator-induced lung injury, LPS) are significantly correlated with human models of lung injury (Pearson r = 0.33-0.45, P < 1E^-16). Neutrophil signatures are enriched in both animal and human lung injury. Predicted therapeutic targets, peptide ligand signatures, and pathway analyses are also all highly overlapping. Gene expression changes are similar in animal and human experimental ALI, and provide several physiologic and therapeutic insights to the disease.

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).

Short-term Effects of Outdoor Air Pollution on Lung Function among Female Non-smokers in China

Short-term exposures to outdoor air pollutants have been associated with lower lung function, but the results are inconsistence. The effects of different pollutant levels on lung function changes are still unclear. We quantified the effects of outdoor air pollution exposure (NO₂, PM₁₀, O₃, and PM_2.5) on lung function among 1,694 female non-smokers from the Wuhan-Zhuhai Cohort in China by using linear mixed model. We further investigated the associations in the two cities with different air quality levels separately to quantify the effects of different pollutant level exposure on lung function. We found the moving averages of NO₂, PM₁₀, and PM_2.5 concentrations were significantly associated with reduced FVC. In city at high pollutant level, the moving average of NO₂, PM₁₀, O₃, and PM_2.5 exposures were significantly associated with both FVC and FEV₁ reductions. In the low-level air pollution city, PM₁₀ (Lag03-Lag05) and O₃ concentrations (Lag01-Lag03) were significantly associated with reduced FVC, while PM₁₀ (Lag03-Lag05), O₃ (Lag0-Lag03), and PM_2.5 (Lag04-Lag06) exposure were significantly associated with reduced FEV₁. Our results suggest that outdoor air pollution is associated with short-term adverse effects on lung function among female non-smokers. The adverse effects may persist for longer durations within 7 days at higher air pollutant levels.

Inflammatory Cytokines and White Blood Cell Counts Response to Environmental Levels of Diesel Exhaust and Ozone Inhalation Exposures

Epidemiological observations of urban inhalation exposures to diesel exhaust (DE) and ozone (O3) have shown pre-clinical cardiopulmonary responses in humans. Identifying the key biological mechanisms that initiate these health bioindicators is difficult due to variability in environmental exposure in time and from person to person. Previously, environmentally controlled human exposure chambers have been used to study DE and O3 dose-response patterns separately, but investigation of co-exposures has not been performed under controlled conditions. Because a mixture is a more realistic exposure scenario for the general public, in this study we investigate the relationships of urban levels of urban-level DE exposure (300 μg/m3), O3 (0.3 ppm), DE + O3 co-exposure, and innate immune system responses. Fifteen healthy human volunteers were studied for changes in ten inflammatory cytokines (interleukins 1β, 2, 4, 5, 8, 10, 12p70 and 13, IFN-γ, and TNF-α) and counts of three white blood cell types (lymphocytes, monocytes, and neutrophils) following controlled exposures to DE, O3, and DE+O3. The results show subtle cytokines responses to the diesel-only and ozone-only exposures, and that a more complex (possibly synergistic) relationship exists in the combination of these two exposures with suppression of IL-5, IL-12p70, IFN-γ, and TNF-α that persists up to 22-hours for IFN-γ and TNF-α. The white blood cell differential counts showed significant monocyte and lymphocyte decreases and neutrophil increases following the DE + O3 exposure; lymphocytes and neutrophils changes also persist for at least 22-hours. Because human studies must be conducted under strict safety protocols at environmental levels, these effects are subtle and are generally only seen with detailed statistical analysis. This study indicates that the observed associations between environmental exposures and cardiopulmonary effects are possibly mediated by inflammatory response mechanisms.

Smoke-free legislation reduces hospital admissions for childhood lower respiratory tract infection

BACKGROUND

Previous studies showed reduction of hospital admissions for asthma after implementation of comprehensive smoke-free legislation. We aimed to evaluate the impact of comprehensive smoke-free legislation implemented in Hong Kong in 2007 on hospital admissions for childhood lower respiratory tract infection (LRTI).

METHODS

We obtained data on 75 870 hospital admissions for LRTI among children ≤18 years of age between January 2004 and December 2012 from all Hospital Authority hospitals. Using a negative binomial regression model, we assessed the impact of smoke-free legislation on admission counts.

RESULTS

After legislation implementation, there was an immediate effect with a change in the admission count of -33.5% (95% CI -36.4% to -30.5%), and a change in time trend to -13.9% per year (95% CI -16.0% to -11.7%). Overall, the legislation was associated with a net 47.4% reduction in admission counts in the first year. We estimated that the legislation was associated with a reduction of 13 635 admissions in the first 6 years after implementation. The immediate reduction and change in time trend was more apparent among school-age than preschool children.

CONCLUSIONS

Implementation of comprehensive smoke-free legislation was associated with a significant reduction in hospital admissions for childhood LRTI.

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.

Ozone promotes regeneration by regulating the inflammatory response in zebrafish

Ozone is thought to advance wound healing by inhibiting inflammation, but the mechanism of this phenomenon has not been determined. Although the zebrafish is often used in regeneration experiments, there has been no report of zebrafish treated with ozonated water. We successfully established a zebrafish model of ozonated water treatment and demonstrate that ozonated water stimulates the regeneration of the zebrafish caudal fin, its mechanism, and time dependence. The growth rate of the caudal fin and the number of neutrophils migrating to the caudal fin wound after resection were higher in the experimental (ozonated) group than in the control group, preliminarily confirming that ozone-promoted regeneration is related to the stimulation of an early inflammatory response by ozone. Ozone modulated the expression of tumor necrosis factor-α (TNF-α) in two ways by regulating interleukin 10 (IL-10) expression. Therefore, ozone promotes tissue regeneration by regulating the inflammatory pathways. This effect of ozone in an experimental zebrafish model is demonstrated for the first time, confirming its promotion of wound healing and the mechanism of its effect in tissue regeneration. These results will open up new directions for ozone and regeneration research.

Short-term exposure to air pollution and lung function in the Framingham Heart Study

RATIONALE

Short-term exposure to ambient air pollution has been associated with lower lung function. Few studies have examined whether these associations are detectable at relatively low levels of pollution within current U.S. Environmental Protection Agency (EPA) standards.

OBJECTIVES

To examine exposure to ambient air pollutants within EPA standards and lung function in a large cohort study.

METHODS

We included 3,262 participants of the Framingham Offspring and Third Generation cohorts living within 40 km of the Harvard Supersite monitor in Boston, Massachusetts (5,358 examinations, 1995-2011) who were not current smokers, with previous-day pollutant levels in compliance with EPA standards. We compared lung function (FEV1 and FVC) after previous-day exposure to particulate matter less than 2.5 μm in diameter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) in the "moderate" range of the EPA Air Quality Index to exposure in the "good" range. We also examined linear relationships between moving averages of pollutant concentrations 1, 2, 3, 5, and 7 days before spirometry and lung function.

MEASUREMENTS AND MAIN RESULTS

Exposure to pollutant concentrations in the "moderate" range of the EPA Air Quality Index was associated with a 20.1-ml lower FEV1 for PM2.5 (95% confidence interval [CI], -33.4, -6.9), a 30.6-ml lower FEV1 for NO2 (95% CI, -60.9, -0.2), and a 55.7-ml lower FEV1 for O3 (95% CI, -100.7, -10.8) compared with the "good" range. The 1- and 2-day moving averages of PM2.5, NO2, and O3 before testing were negatively associated with FEV1 and FVC.

CONCLUSIONS

Short-term exposure to PM2.5, NO2, and O3 within current EPA standards was associated with lower lung function in this cohort of adults.

A stimulatory role of ozone exposure on human natural killer cells

Ozone is claimed to have beneficial effects. While studies revealed the safe therapeutic use of ozone, there are conflicting results for the link between immune system and ozone encounter. Natural killer (NK) cells are important sentinels of immunity with their cytotoxic activity and immune-regulatory potentials. This study aimed to investigate the effects of direct ozone encountering on human immune system, at cellular level. Survival, proliferative capacity and subset content of peripheral blood mononuclear cells (PBMC) were analysed. PBMC of healthy donors (n=5, mean age: 27±6 years) were exposed to 1, 5, 10 and 50 µg/mL doses of medical ozone, directly injected into culture wells, once, initially. 1 and 5 µg/mL doses didn't show toxic effects while 10 and 50 µg/mL doses were toxic. PBMC were cultured for 5 days following 1 and 5 µg/mL ozone encountering. 1 µg/mL dose increased numbers of CD3-CD16+/56+ NK cells among PBMC. Following stimulation with ozone, no difference was observed in basal and phytohemaglutinin-stimulated proliferative capacity. 1 and 5 µg/mL doses of ozone were found to increase NK cytotoxicity. These data indicates influential effects of transient ozone exposure on NK cells, which in turn may have a role in control of immune responses.

Role of the Toll Like receptor (TLR) radical cycle in chronic inflammation: possible treatments targeting the TLR4 pathway

Activation of the Toll-like receptor 4 (TLR4) complex, a receptor of the innate immune system, may underpin the pathophysiology of many human diseases, including asthma, cardiovascular disorder, diabetes, obesity, metabolic syndrome, autoimmune disorders, neuroinflammatory disorders, schizophrenia, bipolar disorder, autism, clinical depression, chronic fatigue syndrome, alcohol abuse, and toluene inhalation. TLRs are pattern recognition receptors that recognize damage-associated molecular patterns and pathogen-associated molecular patterns, including lipopolysaccharide (LPS) from gram-negative bacteria. Here we focus on the environmental factors, which are known to trigger TLR4, e.g., ozone, atmosphere particulate matter, long-lived reactive oxygen intermediate, pentachlorophenol, ionizing radiation, and toluene. Activation of the TLR4 pathways may cause chronic inflammation and increased production of reactive oxygen and nitrogen species (ROS/RNS) and oxidative and nitrosative stress and therefore TLR-related diseases. This implies that drugs or substances that modify these pathways may prevent or improve the abovementioned diseases. Here we review some of the most promising drugs and agents that have the potential to attenuate TLR-mediated inflammation, e.g., anti-LPS strategies that aim to neutralize LPS (synthetic anti-LPS peptides and recombinant factor C) and TLR4/MyD88 antagonists, including eritoran, CyP, EM-163, epigallocatechin-3-gallate, 6-shogaol, cinnamon extract, N-acetylcysteine, melatonin, and molecular hydrogen. The authors posit that activation of the TLR radical (ROS/RNS) cycle is a common pathway underpinning many "civilization" disorders and that targeting the TLR radical cycle may be an effective method to treat many inflammatory disorders.