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Diesel exhaust particulates down‐regulate transcriptionally respiratory neutral endopeptidase
Author(s) -
Sun Ni.,
Hersh Louis B.,
Witten Mark L.,
Wong Simon S.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a212-b
Subject(s) - diesel exhaust , particulates , chemistry , microbiology and biotechnology , biology , diesel fuel , ecology , organic chemistry
Neutral endopeptidase (NEP) is a 90‐110 kDa zinc‐dependent, type II integral membrane protein abundantly expressed on airway epithelial cells. To determine the molecular effects of diesel exhaust particulates (DEP) on NEP expression, we analyzed temporal/concentrational patterns following exposure to 5‐60 μg/ml standard DEP, SRM 2975 by using BEAS‐2B cells. Data show that the NEP mRNA levels decreased in a time‐dependent manner during 24 h DEP incubation. The significant change was detected as early as 8 h after DEP addition, persisting up to 24 h. To examine the sensitivity and specificity of NEP mRNA responses, we conducted a dose‐effect experiment at concentrations of 0 (air controls), 5, 10, 20, 40, 60 μg/ml DEP. After 24 h exposure, NEP mRNA exhibits a concentration‐dependent downregulation, with a maximum effect beginning at the exposure concentration of 40 μg/ml. Moreover, NEP protein and activity also decreased in a concentration‐dependent manner after 24‐h incubation. Todetermine whether the repression of NEP by DEP, occurs at the transcriptional or post‐transcriptionallevel, we assessed the effect of DEP on NEP mRNA transcriptstability. BEAS‐2B cells were treated with actinomycin D, exposed to DEP (40 μg/ml) or vehicle, and then assayed for NEP mRNA levels at various time points up to 24 h. Real‐time PCRindicated no difference in the rate of NEP mRNA degradationbetween DEP and vehicle‐treated samples, thusdemonstrating that DEP regulation of NEP gene expressionlikely occurs at the transcriptional level (Supported by HEI).