Saccharomyces cerevisiae β-glucan-induced SBD-1 expression in ovine ruminal epithelial cells is mediated through the TLR-2-MyD88-NF-κB/MAPK pathway
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Ovine ruminal epithelial cells (ORECs) not only have a physical barrier function but also can secrete host defence peptides (HDPs), such as sheep β-defensin-1 (SBD-1). As a feed additive, Saccharomyces cerevisiae can enhance the host’s innate immunity. β-glucan, a cell wall component of Saccharomyces cerevisiae, can stimulate innate immune responses and trigger the up-regulation of SBD-1 in ORECs. The signaling mechanisms involved in β-glucan-induced SBD-1 expression are not completely understood. The aim of this study was to identify the receptors and intracellular pathways involved in the up-regulation of SBD-1 induced by β-glucan. ORECs were cultured, and the regulatory mechanisms of β-glucan-induced up-regulation of SBD-1 were detected using quantitative real-time PCR (qPCR), enzyme-linked immunosorbent assay (ELISA), and western blotting. TLR-2 and MyD88 knockdown or inhibition attenuated β-glucan-induced SBD-1 expression. We also showed that inhibition of MAPK and NF-κB pathways significantly reduced β-glucan-induced SBD-1 expression. These results demonstrate that β-glucan-induced SBD-1 expression is TLR-2-MyD88-dependent and may be regulated by both MAPK and NF-κB pathways. Since NF-κB inhibition had a greater effect on the down-regulation of β-glucan-induced SBD-1 expression, the NF-κB pathway may be the dominant signaling pathway involved in the regulation of defensin expression. Our studies demonstrate that β-glucan-induced SBD-1 expression is mediated through the TLR-2-MyD88-NF-κB/MAPK pathway. Our results would contribute to the understanding of immunological modulations in the gastrointestinal tract triggered by probiotic yeast cell wall components.
Keywordsβ-Glucan SBD-1 Defensins TLR-2 MyD88 Ovine rumen
analysis of variance
enzyme-linked immunosorbent assay
inducible nitric oxide synthase
mitogen-activated protein kinases
myeloid differentiation factor 88
nuclear factor kappa-light-chain-enhancer of activated B cells
ovine ruminal epithelial cells
polymerase chain reaction
pattern recognition receptors
quantitative real-time PCR
Toll-like receptor 2
tumor necrosis factor-α
We thank Editage for their assistance in editing our article and for language revision. We thank Prof. Gui-fang Cao for providing us with laboratory space for the experiments.
Availability of data and materials
The dataset supporting the conclusions of this article is included within the article and in Additional files.
XJ designed the experiments, cultured the cells, extracted RNA and prepared cDNA, performed western blotting, the statistical analysis, prepared the manuscript and figures; MZ performed qPCR and ELISA experiments, statistical analysis, and prepared the manuscript and figures; YY designed the experiments and revised the manuscript. All authors have read and approved the final manuscript.
This study was supported by the National Natural Science Foundation of China (Grant No. 31560682), and they provided suggestions about the study design.
Compliance with ethical standards
The authors declare that they have no competing interests.
Ethics approval and consent to participate
All animal treatments and procedures used in the present study were approved by the Institutional Animal Care and Use Committee of the IMAU with adherence to IMAU guidelines.
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