Differential immune-stimulatory effects of LTAs from different lactic acid bacteria via MAPK signaling pathway in RAW 264.7 cells

Objective: Lipoteichoic acid (LTA) is an immune-stimulatory component found in the cell wall of lactic acid bacteria, which are a major group of Gram-positive bacteria known to have beneficial health effects in humans. In this study, we evaluated the stimulatory effects of LTAs isolated from different lactobacilli species with mouse macrophage RAW 264.7 cells. Methods: RAW 264.7 cells were stimulated with pLTA (isolated from Lactobacillus plantarum K8), rLTA (isolated from Lactobacillus rhamnosus), dLTA (isolated from Lactobacillus delbreukii), and sLTA (isolated from Lactobacillus sakei 1(101). Tumor necrosis factor (TNE)-alpha and interleukin (IL)-10 production were examined by ELISA, and nitric oxide (NO) production was assayed using Griess reaction. The mRNA and protein expression levels of inducible nitric oxide synthase (iNOS) was examined by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. Signaling molecules were also examined by Western blotting. Results: pLTA and rLTA moderately induced TNF-alpha, IL-10, and NO production compared with stimulation of RAW 264.7 cells with dLTA and sLTA. Similar results were obtained for the mRNA and protein expression levels of iNOS. Western blot analysis showed that treatment of cells with pLTA or rLTA resulted in minimal phosphorylation of ERK, JNK and p38 MAPK while, dLTA and sLTA were strong activators of MAPK signaling. In addition, the glycolipid structure of LTAs was found to be composed of different fatty acid chain groups and lengths. Taken together, these results suggest that the differential immunostimulatory effects of LTAs isolated from different lactobacillus species may be related to their different ability to activate the MAPK signaling pathway, which are modulated by a unique glycolipid structure of LTA. (C) 2014 Elsevier GmbH. All rights reserved.