β-Glucan from Saccharomyces cerevisiae induces SBD-1 production in ovine ruminal epithelial cells via the Dectin-1-Syk-NF-κB signaling pathway.

The ruminal mucosal epithelium can secrete defensins, which play a key role in innate and adaptive immunity and are considered potential replacements for antibiotics. Of these, sheep β-defensin-1 (SBD-1) is one of the most potent molecules produced by ovine ruminal epithelial cells (ORECs). β-glucan, safe and effective immune activators, can stimulate innate and adaptive immune responses. Here we examined whether β-glucan from Saccharomyces cerevisiae can induce SBD-1 expression in ORECs, as well as the underlying mechanism. First, ORECs were cultured, and quantitative real-time PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to study the effects of different β-glucan concentrations. Then western blotting, immunohistochemistry, and immunocytofluorescence were performed to investigate the regulatory mechanism of β-glucan-induced SBD-1 upregulation. We show that β-glucan can induce the release of SBD-1 from ORECs; the highest SBD-1 mRNA and protein expression was achieved after treatment with 10 μg/mL at 2 and 4 h. Moreover, β-glucan-induced SBD-1 production was mediated by the activation of dendritic-cell-associated C-type lectin 1 (Dectin-1) receptors, Syk, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). These findings highlight the immunomodulatory effects of β-glucan on ORECs.