Academic journal article Environmental Health Perspectives

Effects of Hexamethylene Diisocyanate Exposure on Human Airway Epithelial Cells: In Vitro Cellular and Molecular Studies. (Articles)

Academic journal article Environmental Health Perspectives

Effects of Hexamethylene Diisocyanate Exposure on Human Airway Epithelial Cells: In Vitro Cellular and Molecular Studies. (Articles)

Article excerpt

In this study we developed an in vitro exposure model to investigate the effects of hexamethylene diisocyanate (HDI) on human airway epithelial cells at the cellular and molecular level. We used immunofluorescence analysis (IFA) to visualize the binding and uptake of HDI by airway epithelial cell lines (A549 and NCI-NCI-H292) and microarray technology to identify HDI sensitive genes. By IFA, we observed that subcytotoxic concentrations of HDI form microscopic micelles that appear to be taken up by cells over a 3-hr period postexposure. Microarray analysis (4.6K genes) of parallel cultures identified four genes (thioredoxin reductase, dihydrodiol dehydrogenase, TG interacting factor, and stanniocalcin) whose mRNA levels were up-regulated after HDI exposure. Northern analysis was used to confirm that HDI increased message levels of these four genes and to further explore the dose dependence and kinetics of the response. The finding that HDI exposure increases thioredoxin reductase expression supports previous studies suggesting that HDI alters thiol-redox homeostasis, an important sensor of cellular stress. Another of the HDI-increased genes, a dihydrodiol dehydrogenase, encodes a protein previously shown to be specifically susceptible to HDI conjugation, and known to detoxify other hydrocarbons. Together, the data describe a novel approach for investigating the effects of HDI binding and uptake by human airway epithelial cells and begin to identify genes that may be involved in the acute response to exposure. Key words: exposure, hexamethylene diisocyanate, human airway epithelial cell, redox, thiol, thioredoxin reductase. Environ Health Perspect 110:901-907 (2002). [Online 25 July 2002] http://ehpnet1.niehs.nih.gov/docs/2002/110p901-907wisnewski/abstract.html

**********

Diisocyanates are commercially important, toxic, human-made chemicals used in the manufacture of polyurethane (1,2). Although strict standards have been mandated by the U.S. Occupational Safety and Health Administration to limit respiratory tract exposure to these chemicals, diisocyanates remain a leading cause of occupational asthma worldwide (1,2). Environmental exposures to diisocyanates have been documented in individuals living near production facilities and may also occur in proximity to end-use settings in residential neighborhoods (3). Hexamethylene diisocyanate (HDI), the focus of this study, is one of the most commonly used diisocyanates and is employed in autobody spray paints, the manufacture of spinnable fibers, and the preservation of animal hides (4).

The effects of HDI on airway epithelial cells remain poorly described despite the documented susceptibility of airway epithelial cell proteins to diisocyanate conjugation (5,6) and their anatomical location at the air-liquid interface in the lung, a primary site of exposure. Our laboratory has recently identified specific epithelial cell proteins that selectively become conjugated with HDI after exposure, including keratin 18, dihydrodiol dehydrogenase, actin, and the 78-kDa glucose-regulated stress response protein (6). In addition, Lange et al. (7) have shown that toluene diisocyanate (TDI) colocalizes with tubulin present in the cilia of differentiated human airway epithelial cells. Thus, airway epithelial cell proteins may serve as biologically relevant carriers that present HDI to the human immune system after inhalation, thereby mediating diisocyanate-induced airway inflammation (5,8).

The functional consequences of HDI exposure on airway epithelial cells, including protein conjugation and potential effects on cellular homeostasis, remain unclear. Limited studies to date have suggested that cellular thiols may be especially sensitive to diisocyanate exposure under physiologic conditions. Occupationally relevant doses of TDI have been shown to cause a rapid reduction of glutathione levels in normal human bronchial epithelial cells in vitro (9-11). …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.