A lipoteichoic acid fraction of Enterococcus hirae activates cultured human monocytic cells via a CD14-independent pathway to promote cytokine production, and the activity is inhibited by serum components

Abstract

To elucidate the cellular activation mechanisms of lipoteichoic acid (LTA) compared with those of lipopolysaccharide (LPS), a quantitatively major LTA fraction, QM-1M, was prepared from hot phenol-water extracts of Enterococcus hirae (ATCC 9790) by hydrophobic octyl-Sepharose chromatography and by ion-exchange membrane (QMA-Mem Sep 1010) chromatography as a 60% 1-propanol- and 1 M NaCl-eluted fraction. Unlike the reference Escherichia coli LPS, QM-1M did not demonstrate any ability to induce cytokines in a human whole blood culture system in this study, whereas QM-1M induced a few cytokines such as interleukin (IL)-8 and tumor necrosis factor-alpha in human monocytic THP-1 cell and human peripheral mononuclear cell (PBMC) cultures in the absence of serum. Fetal calf and human sera decreased the above cytokine induction by QM-1M in THP-1 and PBMC cultures, whereas sera increased activities of the reference LPS. IL-8 induction in the absence of serum in response to QM-1M was demonstrated to proceed through a CD14-independent pathway unlike the reference LPS.

Lipoteichoic Acids fromLactobacillus johnsoniiStrain La1 andLactobacillus acidophilusStrain La10 Antagonize the Responsiveness of Human Intestinal Epithelial HT29 Cells to Lipopolysaccharide and Gram-Negative Bacteria

“…Although components, such as peptidoglycan and LTA, induced the secretion of various proinflammatory cytokines, such as TNF-␣, IL-1␤, macrophage inflammatory protein 1␣, IL-6, and IL-12 from monocytes (2,6,11,13,28,36,40,41,45). However, only LTAs from specific species of bacteria were able to do so (6,28,30,41).…”

“…The potential stimulatory activity of LTAs from these two strains was confirmed by their capacity to induce the re- lease of IL-8 in human peripheral blood mononuclear cells which express TLR2. It has been shown that only certain LTAs were inducers of cytokine release (2,6,28,30,41). However, no structural motif explaining the divergent stimulatory potentials of these molecules has been identified.…”