Issue |
Vet. Res.
Volume 39, Number 2, March-April 2008
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Number of page(s) | 12 | |
DOI | https://doi.org/10.1051/vetres:2007047 | |
Published online | 21 December 2007 | |
How to cite this article | Vet. Res. (2008) 39:11 |
DOI: 10.1051/vetres:2007047
Bacterial lipopolysaccharide induces increased expression of toll-like receptor (TLR) 4 and downstream TLR signaling molecules in bovine mammary epithelial cells
Eveline M. Ibeagha-Awemu1, Jai-Wei Lee2, Aloysius E. Ibeagha1, Douglas D. Bannerman3, Max J.Paape3 and Xin Zhao11 Department of Animal Science, McGill University, 21111 Lakeshore Road, Ste-Anne-De-Bellevue, Quebec, H9X 3V9 Canada
2 Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, Neipu, Pingtung, 912 Taiwan
3 Bovine Functional Genomics Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705 USA
(Received 20 April 2007; accepted 11 October 2007; published online 21 December 2007)
Abstract - Bovine mammary epithelial cells contribute to the innate immune response to
intramammary infections by recognizing pathogens through specialized pattern
recognition receptors. Toll-like receptor 4 (TLR4) is one such receptor that
binds and is activated by lipopolysaccharide (LPS), a component of the outer
envelope of Gram-negative bacteria. In this study, MAC-T cells (a bovine
mammary epithelial cell line) were incubated in the presence or absence of
increasing concentrations of LPS for 24 h. Expression of TLR2 and TLR4 were
analyzed at both mRNA and protein levels by quantitative real-time PCR
(qPCR) and flow cytometry, respectively. The mRNA of both receptors were
up-regulated by all concentrations of LPS used (P<0.01). Similarly, flow
cytometry with specific antibodies against TLR2 and TLR4 detected increased
surface expression of these proteins. Furthermore, expression of downstream
TLR4 signaling molecules was examined by qPCR following varying exposure
times to 1 g/mL of LPS. Results demonstrate that the required adaptor
molecules and transcription factors were up-regulated in a time-dependent
manner. Both the MyD88 dependent and independent pathways in TLR4 signaling
were activated in MAC-T cells. Expression of TOLLIP increased in response to
LPS as did the pro-apoptotic protease, CASP8. These results suggest that the
bovine mammary epithelium possesses the necessary immune repertoires
required to achieve a robust defense against E. coli. The current findings, coupled
with previous findings that S. aureus ligands induce up-regulation of TLR4, may
indicate a positive adaptation by mammary epithelial cells to effectively
respond to different types of mastitis pathogens.
Key words: lipopolysaccharide / TLR4 and TLR2 / signal transduction / bovine mammary epithelial cells / mastitis
Corresponding author: xin.zhao@mcgill.ca
© INRA, EDP Sciences 2008