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Alteration of peripheral blood monocyte gene expression in humans following diesel exhaust inhalation.

ABSTRACT: Epidemiologic associations between acutely increased cardiorespiratory morbidity and mortality and particulate air pollution are well established, but the effects of acute pollution exposure on human gene expression changes are not well understood.In order to identify potential mechanisms underlying epidemiologic associations between air pollution and morbidity, we explored changes in gene expression in humans following inhalation of fresh diesel exhaust (DE), a model for particulate air pollution.Fourteen ethnically homogeneous (white males), young, healthy subjects underwent 60-min inhalation exposures on 2 separate days with clean filtered air (CA) or freshly generated and diluted DE at a concentration of 300 ?g/m(3) PM(2.5). Prior to and 24?h following each session, whole blood was sampled and fractionated for peripheral blood mononuclear cell (PBMC) isolation, RNA extraction, and generation of cDNA, followed by hybridization with Agilent Whole Human Genome (4X44K) arrays.Oxidative stress and the ubiquitin proteasome pathway, as well as the coagulation system, were among hypothesized pathways identified by analysis of differentially expressed genes. Nine genes from these pathways were validated using real-time polymerase chain reaction (PCR) to compare fold change in expression between DE exposed and CA days. Quantitative gene fold changes generated by real-time PCR were directionally consistent with the fold changes from the microarray analysis.Changes in gene expression connected with key oxidative stress, protein degradation, and coagulation pathways are likely to underlie observed physiologic and clinical outcomes and suggest specific avenues and sensitive time points for further physiologic exploration.

SUBMITTER: Pettit AP

PROVIDER: S-EPMC3755508 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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Alteration of peripheral blood monocyte gene expression in humans following diesel exhaust inhalation.

Pettit Ashley P AP Brooks Andrew A Laumbach Robert R Fiedler Nancy N Wang Qi Q Strickland Pamela Ohman PO Madura Kiran K Zhang Junfeng J Kipen Howard M HM

Inhalation toxicology 20120201 3

<h4>Context</h4>Epidemiologic associations between acutely increased cardiorespiratory morbidity and mortality and particulate air pollution are well established, but the effects of acute pollution exposure on human gene expression changes are not well understood.<h4>Objective</h4>In order to identify potential mechanisms underlying epidemiologic associations between air pollution and morbidity, we explored changes in gene expression in humans following inhalation of fresh diesel exhaust (DE), a ...[more]

PMID: 22369193

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Project description:Background: Epidemiologic associations between acutely increased cardiorespiratory morbidity and mortality and particulate air pollution are well-established, but the effects of acute pollution exposure on human gene expression changes are not well understood. Objectives: In order to identify potential mechanisms underlying epidemiologic associations between air pollution and morbidity, we explored changes in gene expression in humans following inhalation of fresh diesel exhaust (DE), a model for particulate air pollution. Methods: 14 ethnically homogeneous (white males), young, healthy subjects underwent sixty minute inhalation exposures on 2 separate days with clean air (CA) or freshly generated and diluted DE at a concentration of 300 Î¼g/m3 PM2.5. Prior to and 24 hours following each session, whole blood was sampled and fractionated for PBMC isolation, RNA extraction, and generation of cDNA, followed by hybridizationÂ withÂ Agilent Whole Human Genome (4X44K) arrays. Results: Oxidative stress and the ubiquitin proteasome pathway, as well as the coagulation system, were among hypothesized pathways identified by analysis of differentially expressed genes. Nine genes from these pathways were validated using real-time PCR comparing fold change in expression between DE exposed and clean (CA) days. Quantitative gene fold changes generated by real-time PCR were consistent with the directional fold changes from the microarray analysis. Conclusions: Changes in gene expression connected with key oxidative stress, protein degradation, and coagulation pathways are likely to underlie observed physiologic and clinical outcomes and suggest specific avenues and sensitive time points for further physiologic exploration. Diesel exhaust inhalation exposure-induced human gene expression changes were measured in peripheral blood mononuclear cells. 14 white males subjects were seated in a controlled environment facility for 2 separate 60 minute inhalation exposures which occurred at least 1 week apart to either clean air and freshly generate or diluted diesel exhaust (300ug/m3 PM2.5) .Blood collection occurred immediately prior to and 24 hours following exposures. Two microarrays per subject were completed using Agilent Whole Human Genome (4X44K) arrays. Genes that were of interest to our research group were verified using Real Time PCR analysis.

Project description:BackgroundExposure to traffic-related air pollution (TRAP) is considered a trigger for acute cardiovascular events. Diesel Exhaust (DE) is a major contributor to TRAP in the world. We evaluated the effect of DE inhalation on circulating blood cell populations, hematological indices, and systemic inflammatory cytokines in humans using a specialized facility.MethodsIn a randomized double-blind crossover study balanced to order, 17 metabolic syndrome (MetS) and 15 healthy subjects inhaled filtered air (FA) or DE exposure in two-hour sessions on different days with a minimum 2-week washout period. We collected blood pre-exposure, 7, and 22 hours after exposure initiation and measured the complete blood count and differential. We performed multiplex cytokine assay to measure the changes in the systemic inflammatory cytokines, and endothelial adhesion molecules (n=15). A paired analysis compared the effect of DE and FA exposures for the change from pre-exposure to the subsequent time points.ResultsA significant increase in the hematocrit was noted 7 hrs after DE [1.4% (95% CI: 0.9 to 1.9%)] compared to FA exposure [0.5% (95% CI: -0.09 to 1.0%); p=0.008. The hemoglobin levels increased non-significantly at 7 hrs post DE [0.3 gm/dL (95% CI: 0.2 to 0.5 gm/dL)] versus FA exposure [0.2 gm/dL (95% CI: 0 to 0.3 gm/dL)]; p=0.06. Furthermore, the platelet count increased 22 hrs after DE exposure in healthy, but not in MetS subjects [DE: 16.6 (95% CI: 10.2 to 23) thousand platelets/mL versus [FA: 3.4 (95% CI: -9.5 to 16.3) thousand platelets/mL)]; p=0.04. No DE effect was observed for WBC, neutrophils, lymphocytes or erythrocytes. Using the multiplex assay, small borderline significant increases in matrix metalloproteinase-9, interleukins (IL)-1 beta, 6 and 10 occurred 7 hrs post exposure initiation, whereas E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule -1, and myeloperoxidase 22 hrs post exposure.ConclusionsOur results suggest that short-term DE exposure results in hemoconcentration and thrombocytosis, which are important determinants of acute cardiovascular events. Multiplex assay showed a non-significant increase in IL-1? and IL-6 immediately post exposure followed by myeloperoxidase and endothelial activation molecules. Further specific assays in a larger population will improve our understanding of the systemic inflammatory mechanisms following acute exposure to TRAP.

Project description:Background: Diesel exhaust (DE) is the primary source of urban fine particulate matter, which has been associated with cardiovascular disease in epidemiological studies. These effects may be related to oxidative stress and systemic inflammation with resulting perturbation of vascular homeostasis. Peripheral leukocytes are involved in both inflammation and control of vascular homeostasis. Objectives: We conducted an exploratory study using microarray techniques to analyze whether global gene expression in peripheral blood mononuclear cells (PBMCs) can inform on potential mechanisms of effect of DE inhalation. Methods: In a double-blind, crossover, controlled exposure study, healthy adult volunteers were exposed in randomized order to filtered air (FA) and diluted DE in two-hour sessions. We isolated RNA (Trizol/Qiagen method) form PBMCs before, and two times after each exposure. RNA samples were arrayed using the AffymetrixÂ® platform (GeneChipÂ® Human Genome U133 Plus 2.0 Array). Results: Microarray analyses were conducted on five subjects with available RNA sample form exposures to FA and to the highest DE inhalation (200 Âµg/mÂ³ of fine particulate matter). Following data normalization and statistical analysis, a total of 1290 out of 54,675 probe sets with significant evidence for differential expression (more than 1.5-fold up or down regulated with p < 0.05) were identified. These include genes involved in inflammatory response (e.g., IL8RA, TNFAIP6, FOS), oxidative stress (e.g., HMOX1, BAX, PRDX1,), and in biochemical pathways like mitogen-activated protein kinases (MAPK) and tight junction pathways. Conclusions: These data suggest that DE may exert time-dependent changes in gene expression in PBMCs in healthy individuals. Genes that may be affected by DE inhalation are involved in inflammatory and oxidative stress processes. Experiment Overall Design: We conducted a crossover, double-blind experiment, randomized to order of DE and filtered-air (FA) exposure with each participant exposed on four different days to each of four conditions: FA and DE calibrated to 50Âµg/m3 (DE50), 100Âµg/m3 (DE100), and 200Âµg/m3 (DE200) of fine particulate matter (PM2.5- particles with aerodynamic diameter 2.5Âµm or less). Exposure sessions were conducted at least 2 weeks apart.

Project description: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.

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Alteration of peripheral blood monocyte gene expression in humans following diesel exhaust inhalation.

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Alteration of peripheral blood monocyte gene expression in humans following diesel exhaust inhalation.

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