Innate immune responses induced by lipopolysaccharide and lipoteichoic acid in primary goat mammary epithelial cells.

Background: Innate immune responses induced by in vitro stimulation of primary mammary epithelial cells (MEC) using Gram-negative lipopolysaccharide (LPS) and Gram-positive lipoteichoic acid (LTA) bacterial cell wall components are well- characterized in bovine species. The objective of the current study was to characterize the downstream regulation of the inflammatory response induced by Toll-like receptors in primary goat MEC (pgMEC). We performed quantitative real-time RT-PCR (qPCR) to measure mRNA levels of 9 genes involved in transcriptional regulation or antibacterial activity: Toll-like receptor 2 (), Toll-like receptor 4 (), prostaglandin-endoperoxide synthase 2 (), interferon induced protein with tetratricopeptide repeats 3 (), interferon regulatory factor 3 (), myeloid differentiation primary response 88 (), nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (), Toll interacting protein (), and lactoferrin (). Furthermore, we analyzed 7 cytokines involved in Toll-like receptor signaling pathways: C-C motif chemokine ligand 2 (), C-C motif chemokine ligand 5 (), C-X-C motif chemokine ligand 6 (), interleukin 8 (), interleukin 1 beta (), interleukin 6 (), and tumor necrosis factor alpha ().

Results: Stimulation of pgMEC with LPS for 3 h led to an increase in expression of , , , , , , , , and ( < 0.05). Except for , and , the same genes had greater expression than controls at 6 h post-LPS ( < 0.05). Expression of , , , , , and was greater than controls after 3 h of incubation with LTA ( < 0.05). Compared to controls, stimulation with LTA for 6 h led to greater expression of , , , and ( < 0.05) whereas the expression of , , and was lower ( < 0.05). At 3 h incubation with both toxins compared to controls a greater expression ( < 0.05) of , , , , , , , , , and was detected. After 6 h of incubation with both toxins, the expression of , , , , , and was higher than the controls ( < 0.05).

Conclusions: Data indicate that in the goat MEC, LTA induces a weaker inflammatory response than LPS. This may be related to the observation that gram-positive bacteria cause chronic mastitis more often than gram-negative infections.