Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

NIOSHTIC-2 Publications Search

Search Results

HOCl exposure of a human airway epithelial cell line decreases its plasma membrane neutral endopeptidase.

Authors
Lang-Z; Murlas-CG
Source
Lung 1991 Nov-Dec; 169(6):311-323
NIOSHTIC No.
20024780
Abstract
It has recently been demonstrated that luminal exposure of airway segments in vitro to HOCl produces airway muscle hyperresponsiveness to substance P and a decrease in neutral endopeptidase (NEP) activity of tissue segment homogenates, suggesting that HOCl may decrease airway epithelial cell NEP activity. To confirm that this effect occurs in humans and to investigate possible subcellular mechanisms for it, we assessed HOCl exposure of the human airway epithelial cell line Calu-1. These cells, grown to confluency in Dulbecco's modified Eagle medium with 10% fetal bovine serum and penicillin-streptomycin, were exposed in situ for 5 min to 100 microM HOCl in a phosphate-buffered saline solution (PBS; pH 7.0 at 37 degrees C) or to PBS alone. Thereafter, cells were rinsed and assayed for NEP activity employing reverse-phase high-pressure liquid chromatography. This activity was characterized by the generation of phosphoramidon-inhibitable product (ANA) cleaved from the synthetic substrate succinyl-(ala)3-p-nitroaniline during a 30 min incubation at 37 degrees C. Cell viability was assessed by changes in LDH release, trypan blue exclusion, and cell volume. In some experiments, crude plasma membrane and soluble components of exposed cells were isolated and differential NEP activity was assayed. We found that a 5 min exposure to HOCl decreased whole cell NEP activity from 74.1 +/- 4.4 (mean +/- SE) to 54.3 +/- 6.0 pmoles of ANA/min/10(6) cells (p less than 0.05), while no parameter of cell viability was affected. NEP activity in the crude membrane fraction decreased 36.3 +/- 3.1% after exposure (p less than 0.01), whereas NEP activity in the soluble fraction increased 4.0 +/- 0.6%. Isolated membrane NEP exposed by itself was not affected. Subsequent experiments with reducing agents demonstrated that NEP activity of cell cultures pretreated with 100 mM of either beta-mercaptoethanol or dithiothrietol before HOCl exposure was not significantly different from control values. We conclude that whole cell HOCl exposure decreases Calu-1 plasma membrane NEP. This loss appears to occur by internalization of cell membrane NEP.
Keywords
Pulmonary-system-disorders; Enzyme-activity; Humans; Respiratory-irritants; Oxidizers; Lung-irritants; Mucous-membranes; In-vitro-study; Cellular-reactions
Contact
Internal Medicine Univ of Tennessee, Memphis 956 Court Avenue Memphis, TN 38163
CODEN
LUNGD9
CAS No.
7790-92-3; 7722-84-1
Publication Date
19911101
Document Type
Journal Article
Funding Amount
127961
Funding Type
Grant
Fiscal Year
1992
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-K01-OH-00060
Issue of Publication
6
ISSN
0341-2040
Priority Area
Pulmonary-system-disorders
Source Name
Lung
State
OH
Performing Organization
University of Cincinnati, Cincinnati, Ohio
TOP