[Show abstract][Hide abstract] ABSTRACT: Exposure of mice to hyperoxia produces pulmonary toxicity similar to acute lung injury/acute respiratory distress syndrome, but little is known about the interactions within the cardiopulmonary system. This study was designed to characterize the cardiopulmonary response to hyperoxia, and to identify candidate susceptibility genes in mice. Electrocardiogram and ventilatory data were recorded continuously from 4 inbred and 29 recombinant inbred strains during 96 hours of hyperoxia (100% oxygen). Genome-wide linkage analysis was performed in 27 recombinant inbred strains against response time indices (TIs) calculated from each cardiac phenotype. Reductions in minute ventilation, heart rate (HR), low-frequency (LF) HR variability (HRV), high-frequency HRV, and total power HRV were found in all mice during hyperoxia exposure, but the lag time before these changes began was strain dependent. Significant (chromosome 9) or suggestive (chromosomes 3 and 5) quantitative trait loci were identified for the HRTI and LFTI. Functional polymorphisms in several candidate susceptibility genes were identified within the quantitative trait loci and were associated with hyperoxia susceptibility. This is the first study to report highly significant interstrain variation in hyperoxia-induced changes in minute ventilation, HR, and HRV, and to identify polymorphisms in candidate susceptibility genes that associate with cardiac responses. Results indicate that changes in HR and LF HRV could be important predictors of subsequent adverse outcome during hyperoxia exposure, specifically the pathogenesis of acute lung injury. Understanding the genetic mechanisms of these responses may have significant diagnostic clinical value.
American Journal of Respiratory Cell and Molecular Biology 01/2012; 46(4):470-8. · 4.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To assess incidence, burden of illness, and risk factors for human rhinoviruses (HRVs) in a cohort of very low birth weight (VLBW) infants.
A 2-year prospective cohort study was conducted among VLBW premature infants in Buenos Aires, Argentina. Infants were enrolled in the NICU from June 1, 2003, to May 31, 2005, and managed monthly and with every acute respiratory illness (ARI) during the first year of life. Nasal wash samples were obtained during every respiratory episode and tested for HRV, respiratory syncytial virus (RSV), human parainfluenza viruses, influenza viruses, and human metapneumovirus using reverse transcriptase-polymerase chain reaction.
Of 119 patients, 66 (55%) had HRV-associated ARIs. The incidence of HRV-associated ARI was 123 events per 100 child-years of follow-up. Of those infants experiencing an episode of bronchiolitis, 40% had HRV versus 7% with RSV. The incidence of HRV-associated bronchiolitis was 75 per 100 infant-years of follow-up. HRV was associated with 12 of 36 hospitalizations (33%), and RSV was associated with 9 of 36 hospitalizations (25%). The incidence of HRV-associated hospitalization was 12 per 100 infant-years of follow-up. The risk of HRV-associated hospitalization was higher for infants with bronchopulmonary dysplasia and those who were not breastfed.
HRV is an important and frequent pathogen associated with severe respiratory infections in VLBW infants. Bronchopulmonary dysplasia and the absence of breastfeeding are risk factors for hospitalization. The results of our study reveal that HRV is the predominant pathogen of respiratory infections in premature infants.
[Show abstract][Hide abstract] ABSTRACT: Previous reports have proposed a cross-talk between the nuclear factor erythroid-2 p45-related factor-2 (Nrf2)/antioxidant response element (ARE) and the aryl hydrocarbon receptor (AhR)/xenobiotic response element (XRE) signaling pathways. Therefore, the aim of the current study was to examine the level of phase I, phase II drug metabolizing enzymes (DMEs), and phase III transporters and their related transcription factors in the Nrf2 knockout model. Our results showed that phase II DMEs that are under the control of Nrf2 typified by NAD(P)H: quinone oxidoreductase 1 (Nqo1), and glutathione S-transferase (Gst) were significantly lower at the mRNA, protein, and catalytic activity levels in the livers of Nrf2 knockout mice compared to wild type. Furthermore, phase I cytochrome P450s (CYPs), Cyp1, and Cyp2b10 at mRNA, protein, and catalytic activity levels were significantly lower in the livers of Nrf2 knockout mice. Interestingly, our results showed that the transcription factors AhR, constitutive androstane receptor (CAR), and pregnane X receptor (PXR) at mRNA, and protein expression levels were significantly lower in the livers of Nrf2 knockout mice compared to wild type. Importantly, phase III drug transporters mRNA levels of the multiple drug resistance associated proteins (Mrp2 and Mrp3), and solute carrier organic anion transporters (Slco1a6 and Slco2b1) were significantly lower in the liver of Nrf2 knockout mice. Co-activators, Ncoa1, Ncoa2, and Ncoa3 mRNA levels were not altered while co-repressors, Ncor1 and Ncor2 were significantly lower in the livers of Nrf2 knockout mice. In conclusion, knockout of Nrf2 causes disruption to the coordination of phase I, phase II drug DMEs, and phase III drug transporters through altering the transcription factors controlling them.
Toxicology in Vitro 06/2011; 25(4):785-95. · 3.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Toll-like receptor 4 (TLR4) is involved in ozone (O3)-induced pulmonary hyperpermeability and inflammation, although the downstream signaling events are unknown.
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.
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.
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).
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.
Environmental Health Perspectives 05/2011; 119(8):1091-7. · 7.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reactive oxygen species (ROS) generated by vascular endothelial and smooth muscle cells contribute to the development and progression of vascular diseases. We have recently shown that hyperoxia enhances NADPH oxidase 4 (Nox4) expression, which regulates lung endothelial cell migration and angiogenesis. Regulation of Nox4 in the vasculature is poorly understood. The objective of this study was to identify the transcriptional factor(s) involved in regulation of endothelial Nox4. We found that hyperoxia-induced Nox4 expression was markedly reduced in Nrf2(-/-) mice, compared to Nrf2(+/+) mice. Exposure of human lung microvascular endothelial cells (HLMVECs) to hyperoxia stimulated Nrf2 translocation from the cytoplasm to the nucleus and increased Nox4 expression. Knockdown of Nrf2 expression using an siRNA approach attenuated basal Nox4 expression; however, it enhanced superoxide/ROS generation under both normoxia and hyperoxia. In silico analysis revealed the presence of at least three consensus sequences for the antioxidant response element (ARE) in the promoter region of Nox4. In transient transfections, hyperoxia stimulated Nox4 promoter activity in HLMVECs, and deletion of the -438 to -458 and -619 to -636 sequences markedly reduced hyperoxia-stimulated Nox4 promoter activation. ChIP analysis revealed an enhanced recruitment of Nrf2 to the endogenous Nox4 promoter spanning these two AREs after hyperoxic insult. Collectively, these results demonstrate, for the first time, a novel role for Nrf2 in regulating hyperoxia-induced Nox4 transcription via AREs in lung endothelium.
Free Radical Biology and Medicine 03/2011; 50(12):1749-59. · 5.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To determine if the GSTM1 null genotype is a risk factor for increased inflammatory response to inhaled endotoxin.
35 volunteers who had undergone inhalation challenge with a 20 000 endotoxin unit dose of Clinical Center Reference Endotoxin (CCRE) were genotyped for the GSTM1 null polymorphism. Parameters of airway and systemic inflammation observed before and after challenge were compared in GSTM1 null (n=17) and GSTM1 (n=18) sufficient volunteers.
GSTM1 null volunteers had significantly increased circulating white blood cells (WBCs), polymorphonuclear neutrophils (PMNs), platelets and sputum PMNs (% sputum PMNs and PMNs/mg sputum) after CCRE challenge. GSTM1 sufficient volunteers had significant, but lower increases in circulating WBCs, PMNs and % sputum PMNs, and no increase in platelets or PMNs/mg sputum. Linear regression analysis adjusted for baseline values of the entire cohort revealed that the GSTM1 null genotype significantly increased circulating WBCs, platelets and % sputum PMNs after challenge.
These data support the hypothesis that the GSTM1 null genotype is a risk factor for increased acute respiratory and systemic inflammatory response to inhaled CCRE. These data are consistent with other observations that the GSTM1 null genotype is associated with increased respiratory, systemic and cardiovascular effects linked to ambient air particulate matter exposure and indicate that the GSTM1 null genotype should be considered a risk factor for adverse health effects associated with exposure to environmental endotoxin.
Occupational and environmental medicine 03/2011; 68(10):783-5. · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although the ABCB1 (P-glycoprotein) drug transporter is a constituent of several blood-tissue barriers (i.e., blood-brain and blood-nerve), its participation in a putative blood-heart barrier has been poorly explored. ABCB1 could decrease the intracardiac concentrations of drugs that cause QT prolongation and cardiotoxicity.
ABCB1-related romidepsin transport kinetics were explored in LLC-PK1 cells transfected with different ABCB1 genetic variants. ABCB1 plasma and intracardiac concentrations were determined in Abcb1a/1b (-/-) mice and wild-type FVB controls. These same mice were used to evaluate romidepsin-induced heart rate-corrected QT interval (QTc) prolongation over time. Finally, a cohort of 83 individuals with available QTcB and ABCB1 genotyping data were used to compare allelic variation in ABCB1 versus QTc-prolongation phenotype.
Here, we show that mice lacking the ABCB1-type P-glycoprotein have higher intracardiac concentrations of a model ABCB1 substrate, romidepsin, that correspond to changes in QT prolongation from baseline (ΔQTc) over time. Consistent with this observation, we also show that patients carrying genetic variants that could raise ABCB1 expression in the cardiac endothelium have lower ΔQTc following a single dose of romidepsin.
To our knowledge, this is the first evidence that Abcb1-type P-glycoprotein can limit intracardiac exposure to a drug that mediates QT prolongation and suggests that certain commonly inherited polymorphisms in ABCB1 may serve as markers for QT prolongation following the administration of ABCB1-substrate drugs.
Clinical Cancer Research 02/2011; 17(4):937-46. · 8.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
PLoS ONE 01/2011; 6(10):e26590. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The mechanisms underlying ozone (O₃)-induced pulmonary inflammation remain unclear. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that is known to inhibit inflammatory mediators.
We investigated the molecular mechanisms underlying interleuken-10 (IL-10)-mediated attenuation of O₃-induced pulmonary inflammation in mice.
Il10-deficient (Il10(-/-)) and wild-type (Il10(+/+)) mice were exposed to 0.3 ppm O₃ or filtered air for 24, 48, or 72 hr. Immediately after exposure, differential cell counts and total protein (a marker of lung permeability) were assessed from bronchoalveolar lavage fluid (BALF). mRNA and protein levels of cellular mediators were determined from lung homogenates. We also used global mRNA expression analyses of lung tissue with Ingenuity Pathway Analysis to identify patterns of gene expression through which IL-10 modifies O₃-induced inflammation.
Mean numbers of BALF polymorphonuclear leukocytes (PMNs) were significantly greater in Il10(-/-) mice than in Il10(+/+) mice after exposure to O₃ at all time points tested. O₃-enhanced nuclear NF-κB translocation was elevated in the lungs of Il10(-/-) compared with Il10(+/+) mice. Gene expression analyses revealed several IL-10-dependent and O₃-dependent mediators, including macrophage inflammatory protein 2, cathepsin E, and serum amyloid A3.
Results indicate that IL-10 protects against O₃-induced pulmonary neutrophilic inflammation and cell proliferation. Moreover, gene expression analyses identified three response pathways and several genetic targets through which IL-10 may modulate the innate and adaptive immune response. These novel mechanisms of protection against the pathogenesis of O₃-induced pulmonary inflammation may also provide potential therapeutic targets to protect susceptible individuals.
Environmental Health Perspectives 12/2010; 118(12):1721-7. · 7.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Asthma is a known risk factor for acute ozone-associated respiratory disease. Ozone causes an immediate decrease in lung function and increased airway inflammation. The role of atopy and asthma in modulation of ozone-induced inflammation has not been determined.
We sought to determine whether atopic status modulates ozone response phenotypes in human subjects.
Fifty volunteers (25 healthy volunteers, 14 atopic nonasthmatic subjects, and 11 atopic asthmatic subjects not requiring maintenance therapy) underwent a 0.4-ppm ozone exposure protocol. Ozone response was determined based on changes in lung function and induced sputum composition, including airway inflammatory cell concentration, cell-surface markers, and cytokine and hyaluronic acid concentrations.
All cohorts experienced similar decreases in lung function after ozone. Atopic and atopic asthmatic subjects had increased sputum neutrophil numbers and IL-8 levels after ozone exposure; values did not significantly change in healthy volunteers. After ozone exposure, atopic asthmatic subjects had significantly increased sputum IL-6 and IL-1beta levels and airway macrophage Toll-like receptor 4, Fc(epsilon)RI, and CD23 expression; values in healthy volunteers and atopic nonasthmatic subjects showed no significant change. Atopic asthmatic subjects had significantly decreased IL-10 levels at baseline compared with healthy volunteers; IL-10 levels did not significantly change in any group with ozone. All groups had similar levels of hyaluronic acid at baseline, with increased levels after ozone exposure in atopic and atopic asthmatic subjects.
Atopic asthmatic subjects have increased airway inflammatory responses to ozone. Increased Toll-like receptor 4 expression suggests a potential pathway through which ozone generates the inflammatory response in allergic asthmatic subjects but not in atopic subjects without asthma.
The Journal of allergy and clinical immunology 09/2010; 126(3):537-44.e1. · 12.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Prior microarray studies of smokers at high risk for lung cancer have demonstrated that heterogeneity in bronchial airway epithelial cell gene expression response to smoking can serve as an early diagnostic biomarker for lung cancer. As a first step in applying functional genomic analysis to population studies, we have examined the relationship between gene expression variation and genetic variation in a central molecular pathway (NRF2-mediated antioxidant response) associated with smoking exposure and lung cancer. We assessed global gene expression in histologically normal airway epithelial cells obtained at bronchoscopy from smokers who developed lung cancer (SC, n = 20), smokers without lung cancer (SNC, n = 24), and never smokers (NS, n = 8). Functional enrichment analysis showed that the NRF2-mediated, antioxidant response element (ARE)-regulated genes, were significantly lower in SC, when compared with expression levels in SNC. Importantly, we found that the expression of MAFG (a binding partner of NRF2) was correlated with the expression of ARE genes, suggesting MAFG levels may limit target gene induction. Bioinformatically we identified single nucleotide polymorphisms (SNPs) in putative ARE genes and to test the impact of genetic variation, we genotyped these putative regulatory SNPs and other tag SNPs in selected NRF2 pathway genes. Sequencing MAFG locus, we identified 30 novel SNPs and two were associated with either gene expression or lung cancer status among smokers. This work demonstrates an analysis approach that integrates bioinformatics pathway and transcription factor binding site analysis with genotype, gene expression and disease status to identify SNPs that may be associated with individual differences in gene expression and/or cancer status in smokers. These polymorphisms might ultimately contribute to lung cancer risk via their effect on the airway gene expression response to tobacco-smoke exposure.
PLoS ONE 08/2010; 5(8):e11934. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ozone (O(3)) remains a prevalent air pollutant and public health concern. Inf2 is a significant quantitative trait locus on murine chromosome 17 that contributes to susceptibility to O(3)-induced infiltration of polymorphonuclear leukocytes (PMNs) into the lung, but the mechanisms of susceptibility remain unclear. The study objectives were to confirm and restrict Inf2, and to identify and test novel candidate susceptibility gene(s). Congenic strains of mice that contained overlapping regions of Inf2 and their controls, and mice deficient in either major histocompatibility complex (MHC) class II genes or the Tnf cluster, were exposed to air or O(3). Lung inflammation and gene expression were assessed. Inf2 was restricted from 16.42 Mbp to 0.96 Mbp, and bioinformatic analysis identified MHC class II, the Tnf cluster and other genes in this region that contain potentially informative single nucleotide polymorphisms between the susceptible and resistant mice. Furthermore, O(3)-induced inflammation was significantly reduced in mice deficient in MHC class II genes or the Tnf cluster genes, compared with wild-type controls. Gene expression differences were also observed in MHC class II and Tnf cluster genes. This integrative genetic analysis of Inf2 led to identification of novel O(3) susceptibility genes that may provide important, new therapeutic targets in susceptible individuals.
European Respiratory Journal 08/2010; 36(2):428-37. · 7.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The rapid decline in the cost of dense genotyping is paving the way for new DNA sequence-based laboratory tests to move quickly into clinical practice, and to ultimately help realize the promise of 'personalized' therapies. These advances are based on the growing appreciation of genetics as an important dimension in science and the practice of investigative pharmacology and toxicology. On the clinical side, both the regulators and the pharmaceutical industry hope that the early identification of individuals prone to adverse drug effects will keep advantageous medicines on the market for the benefit of the vast majority of prospective patients. On the environmental health protection side, there is a clear need for better science to define the range and causes of susceptibility to adverse effects of chemicals in the population, so that the appropriate regulatory limits are established. In both cases, most of the research effort is focused on genome-wide association studies in humans where de novo genotyping of each subject is required. At the same time, the power of population-based preclinical safety testing in rodent models (e.g., mouse) remains to be fully exploited. Here, we highlight the approaches available to utilize the knowledge of DNA sequence and genetic diversity of the mouse as a species in mechanistic toxicology research. We posit that appropriate genetically defined mouse models may be combined with the limited data from human studies to not only discover the genetic determinants of susceptibility, but to also understand the molecular underpinnings of toxicity.
[Show abstract][Hide abstract] ABSTRACT: Environmental oxidants remain a major public health concern in industrialized cities throughout the world. Population and epidemiological studies have associated oxidant air pollutants with morbidity and mortality outcomes, and underscore the important detrimental effects of these pollutants on the lung. Interindividual variation in pulmonary responses to air pollutants suggests that some subpopulations are at increased risk to detrimental effects of pollutant exposure, and it has become clear that genetic background is an important susceptibility factor. A number of genetics and genomics tools have recently emerged to enable identification of genes that contribute to differential responsiveness to oxidants, including ozone (O(3)). Integrative omics approaches have been applied in inbred mice to identify genes that determine differential responsiveness to O(3)-induced injury and inflammation, including Tnf, Tlr4, and MHC Class II genes. Combined investigations across cell models, inbred mice, and humans have provided, and will continue to provide, important insight to understanding genetic factors that contribute to differential susceptibility to oxidants.
Annals of the New York Academy of Sciences 08/2010; 1203:113-9. · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ozone and lipopolysaccharide (LPS) are environmental pollutants with adverse health effects noted in both healthy and asthmatic individuals. The authors and others have shown that inhalation of ozone and LPS both induce airway neutrophilia. Based on these similarities, the authors tested the hypothesis that common biological factors determine response to these two different agents. Fifteen healthy, nonasthmatic volunteers underwent a 0.4 part per million ozone exposure for 2 h while performing intermittent moderate exercise. These same subjects underwent an inhaled LPS challenge with 20,000 LPS units of Clinical Center Reference LPS, with a minimum of 1 month separating these two challenge sessions. Induced sputum was obtained 24 h before and 4-6 h after each exposure session. Sputum was assessed for total and differential cell counts and expression of cell surface proteins as measured by flow cytometry. Sputum supernatants were assayed for cytokine concentration. Both ozone and LPS challenge augmented sputum neutrophils and subjects' responses were significantly correlated (R = .73) with each other. Ozone had greater overall influence on cell surface proteins by modifying both monocytes (CD14, human leukocyte antigen [HLA]-DR, CD11b) and macrophages (CD11b, HLA-DR) versus LPS where CD14 and HLA-DR were modified only on monocytes. However, LPS significantly increased interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha, with no significant increases seen after ozone challenge. Ozone and LPS exposure in healthy volunteers induce similar neutrophil responses in the airways; however, downstream activation of innate immune responses differ, suggesting that oxidant versus bacterial air pollutants may be mediated by different mechanisms.