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Effect of World Trade Center Dust Exposure and Chronic Intermittent Hypoxia on Macrophage Matrix Metalloproteinase-12 Expression in Mice

ABSTRACT: Rationale: The pathophysiologic mechanisms by which World Trade Center (WTC) dust exposure leads to pulmonary disease have not been established. Matrix metalloproteinase-12 (MMP-12) is involved in the development of pulmonary fibrosis and chronic obstructive pulmonary disease. We have previously shown that exposure of mice to WTC dust results in increased expression of matrix metalloproteinase 12 by alveolar macrophages. Matrix metalloproteinase 12 expression is regulated, in part, by oxidative stress, which is also increased after WTC dust exposure. A significant percentage of WTC dust–exposed individuals have concomitant obstructive sleep apnea, which is an added source of oxidative stress, through chronic intermittent hypoxia (CIH). Objectives: To determine if combined exposures of mice to WTC dust and CIH exacerbated matrix metalloproteinase 12 expression in alveolar macrophages. Methods: Male Balbc/J mice (12–24 wk) were treated intratracheally with phosphate-buffered saline (PBS) or WTC dust suspended in PBS, followed by CIH (cycles of 21 to 5% fraction of inspired oxygen, 2-min cycles) (CIH groups) or chronic intermittent air (CIA; cycles of 21 to 19% fraction of inspired oxygen, 2-min cycles) (CIA groups) 12 hours per day for 28 days. Histologic sections were then examined for macrophage expression of matrix metalloproteinase 12 by immunohistochemistry. Results: The mean number of positively stained alveolar macrophages from five fields per lobe was quantified. Mice exposed to WTC dust or CIH displayed increased macrophage expression of matrix metalloproteinase 12 compared with the control group. Exposure to WTC dust plus CIH was additive in effect (mean?±?SD, PBS/CIA: 20.8?±?5.2; PBS/CIH: 43.3?±?19.8; WTC/CIA: 43.3?±?12.5; WTC/CIH: 77.8?±?12.2). Conclusions: To our knowledge, this is the first study to suggest CIH increases macrophage matrix metalloproteinase 12 expression in mice. Combined exposures to WTC dust and CIH further increased macrophage matrix metalloproteinase 12 expression. Given the role of matrix metalloproteinase 12 in pulmonary fibrosis and chronic obstructive pulmonary disease pathogenesis, patients with obstructive sleep apnea who have been exposed to WTC dust may have added risk for pulmonary parenchymal disease.

SUBMITTER: Radbel J

PROVIDER: S-EPMC5955033 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Project description:The World Trade Center (WTC) collapse produced a massive exposure to respirable particulates in New York City Fire Department (FDNY) rescue workers. This group had spirometry examinations pre-September 11, 2001, and post-September 11, 2001, demonstrating declines in lung function with parallel declines in FEV(1) and FVC. To date, the underlying pathophysiologic cause for this has been open to question.Of 13,234 participants in the FDNY-WTC Monitoring Program, 1,720 (13%) were referred for pulmonary subspecialty evaluation at a single institution. Evaluation included 919 full pulmonary function tests, 1,219 methacholine challenge tests, and 982 high-resolution chest CT scans.At pulmonary evaluation (median 34 months post-September 11, 2001), median values were FEV(1) 93% predicted (interquartile range [IQR], 83%-101%), FVC 98% predicted (IQR, 89%-106%), and FEV(1)/FVC 0.78 (IQR, 0.72-0.82). The residual volume (RV) was 123% predicted (IQR, 106%-147%) with nearly all participants having normal total lung capacity, functional residual capacity, and diffusing capacity of carbon monoxide. Also, 1,051/1,720 (59%) had obstructive airways disease based on at least one of the following: FEV(1)/FVC, bronchodilator responsiveness, hyperreactivity, or elevated RV. After adjusting for age, gender, race, height and weight, and tobacco use, the decline in FEV(1) post-September 11, 2001, was significantly correlated with increased RV percent predicted (P < .0001), increased bronchodilator responsiveness (P < .0001), and increased hyperreactivity (P = .0056). CT scans demonstrated bronchial wall thickening that was significantly associated with the decline in FEV(1) post-September 11, 2001 (P = .024), increases in hyperreactivity (P < .0001), and increases in RV (P < .0001). Few had evidence for interstitial disease.Airways obstruction was the predominant physiologic finding underlying the reduction in lung function post-September 11, 2001, in FDNY WTC rescue workers presenting for pulmonary evaluation.

Project description:Over 400,000 people are estimated to have been exposed to World Trade Center particulate matter (WTCPM) since the attack on the Twin Towers in Lower Manhattan on September 11, 2001. Epidemiological studies have found that exposure to dust may cause respiratory ailments and cardiovascular diseases. However, limited studies have performed a systematic analysis of transcriptomic data to elucidate the biological responses to WTCPM exposure and the therapeutic options. Here, we developed an in vivo mouse exposure model of WTCPM and administered two drugs (i.e., rosoxacin and dexamethasone) to generate transcriptomic data from lung samples. WTCPM exposure increased the inflammation index, and this index was significantly reduced by both drugs. We analyzed the transcriptomics derived omics data using a hierarchical systems biology model (HiSBiM) with four levels, including system, subsystem, pathway, and gene analyses. Based on the selected differentially expressed genes (DEGs) from each group, WTCPM and the two drugs commonly affected the inflammatory responses, consistent with the inflammation index. Among these DEGs, the expression of 31 genes was affected by WTCPM exposure and consistently reversed by the two drugs, and these genes included Psme2, Cldn18, and Prkcd, which are involved in immune- and endocrine-related subsystems and pathways such as thyroid hormone synthesis, antigen processing and presentation, and leukocyte transendothelial migration. Furthermore, the two drugs reduced the inflammatory effects of WTCPM through distinct pathways, e.g., vascular-associated signaling by rosoxacin, whereas mTOR-dependent inflammatory signaling was found to be regulated by dexamethasone. To the best of our knowledge, this study constitutes the first investigation of transcriptomics data of WTCPM and an exploration of potential therapies. We believe that these findings provide strategies for the development of promising optional interventions and therapies for airborne particle exposure.

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Effect of World Trade Center Dust Exposure and Chronic Intermittent Hypoxia on Macrophage Matrix Metalloproteinase-12 Expression in Mice

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