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CULTURE CONDITIONS AFFECT HUMAN AIRWAY EPITHELIAL CELL RESPONSE TO DIESEL PARTICLE EXPOSURE IN VITRO
Citation:
SILBAJORIS, R. A., L. A. DAILEY, AND J. M. SAMET. CULTURE CONDITIONS AFFECT HUMAN AIRWAY EPITHELIAL CELL RESPONSE TO DIESEL PARTICLE EXPOSURE IN VITRO. Presented at American Thoracic Society Meeting, San Francisco, CA, May 18 - 23, 2007.
Description:
Diesel exhaust particles (DEP) are a ubiquitous ambient air contaminant that may contribute to the health effects of particulate matter inhalation. In vitro studies have shown that DEP exposure induces pro-inflammatory proteins in human airway epithelial cells (HAEC) with varying potency. This study's aim was to characterize the effect of culture conditions on IL-8 expression in HAEC exposed to a standard reference material DEP derived from diesel forklift exhaust (National Institute of Sciences and Technology). HAEC obtained by brush biopsy of adult volunteers were plated at passage number 2-4 on collagen-coated culture plates or plates containing transwell inserts and grown in either bronchial epidermal growth medium (BEGM) or 1:1 Dulbecco's Modified Eagle Media High Glucose (DMEMH):BEGM containing full supplements. Supplements were withheld for 18 hrs prior to treatment. DEP was suspended in media at 200 µg/ml by sonication and added at 20µg/cm2 to 24-96 hr sub-confluent or confluent cultures. IL-8 mRNA levels were measured using real-time PCR following 4 hrs of DEP exposure. Compared to media controls, HAEC grown on transwells responded to DEP exposure with smaller increases in IL-8 mRNA than did HAEC grown on plastic. On both substrates, cells grown in DMEMH:BEGM media had lesser increases in IL-8 mRNA expression then in BEGM alone. IL-8 mRNA expression in DEP treated confluent HAEC transwell cultures decreased with time in culture. Sub-confluent cultures had higher baseline IL-8 mRNA expression than did fully confluent cultures, but fold increases over control induced by DEP exposure were unchanged. These findings show significant influence of culture conditions on the response of HAEC to DEP exposure and, therefore, experimental models should be optimized for these conditions. In the absence of optimization, in vitro findings of the effects of DEP should be interpreted with caution. THIS STUDY DOES NOT NECESSARILY REFLECT EPA POLICY.