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Infect Immun, May 1998, p. 2200-2206, Vol. 66, No. 5
Departments of Life
Science,1
Histopathology,2 and
Microbiology3 and
Division of
Gastroenterology,4 University of Nottingham,
Nottingham, United Kingdom
Received 10 November 1997/Returned for modification 23 December
1997/Accepted 18 February 1998
Epithelial cells are the first point of host contact for invasive
intestinal pathogens and may initiate mucosal inflammatory responses
via production of proinflammatory cytokines and mediators. The aim of
the present study was to investigate in vitro the initial invasion of a
parasitic nematode (Trichinella spiralis), to measure the
early production of specific epithelial cytokines and inflammatory mediators after invasion, and to compare these responses with those to
invasive bacteria. Monolayers of human colonic epithelial cell lines
(HT29, T84, and Caco-2) were infected by T. spiralis or
Listeria monocytogenes. Bile-activated infective larvae of T. spiralis invaded and migrated into the epithelial cell
monolayers, leaving trails of dead cells. Transmission electron
microscopy studies of damaged cells along the trail showed a
progressive increase in size, disruption of cell membranes, loss or
dilution of cytoplasmic proteins, and swelling of mitochondria and
nuclei. However, no nuclear fragmentation was observed. With reverse
transcription-PCR and an enzyme-linked oligonucleotide chemiluminescent
assay, mRNA transcripts of interleukin-1
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Production of Proinflammatory Cytokines and
Inflammatory Mediators in Human Intestinal Epithelial Cells
after Invasion by Trichinella spiralis
(IL-1
), IL-8, and
epithelial neutrophil-activating peptide 78 were shown to increase in
epithelial cells invaded by T. spiralis or L. monocytogenes, but only L. monocytogenes elicited
increased inducible nitric oxide synthase (iNOS) mRNA. No increase in
tumor necrosis factor alpha or transforming growth factor
mRNA was
seen after T. spiralis invasion. Increased levels of IL-8
were also released from the basolateral surfaces of infected monolayers
as detected by sandwich enzyme-linked immunosorbent assay. Induction
and secretion of proinflammatory cytokines in epithelial cells after
nematode or bacterial invasion may initiate the acute inflammatory
response of the small intestine. The upregulation of iNOS in bacterial
infections may contribute to mucosal defense and may also be associated
with subsequent cell death, whereas different mechanisms appear to
operate after nematode invasion.
*
Corresponding author. Mailing address: Department of
Life Science, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom. Phone: 44-(115)-9513232. Fax: 44-(115)-9513252. E-mail: D.Wakelin{at}nottingham.ac.uk.
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