Dialyzable Leukocyte Extract differentially regulates the production of TNFα, IL-6, and IL-8 in bacterial component-activated leukocytes and endothelial cells
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Objective: To investigate i) whether the Dialyzable Leukocyte Extract (DLE) modulates the production of proinflammatory cytokines in leukocytes activated by the bacterial cell wall components lipopolysaccharide (LPS), lipoteichoic acid (LTA), and peptidoglycan (PGN); ii) the effect of DLE on LPS-stimulated endothelial cells; and iii) whether the regulatory effect of DLE on inflammatory mediators is related to the modulation of Toll-like receptors (TLRs), NF-κB and cAMP signaling pathways.
Methods: Leukocytes were stimulated with LPS, LTA, and PGN in the presence of DLE. Endothelial cells were stimulated with LPS and treated with DLE. The levels of Tumor Necrosis Factor-α(TNFα), Interleukin-6 (IL-6), and IL-8 in culture supernatants were evaluated by ELISA. The expression of Toll-like receptor 2 (TLR2) and 4 (TLR4), NF-κB activity and cAMP levels were evaluated by flow cytometry, EMSA, and EIA, respectively.
Results: The addition of DLE to leukocytes stimulated with cell wall constituents suppressed the production of TNFα. However, DLE induced IL-8 release in monocytes and enhanced IL-6 and IL-8 production by activated monocytes and endothelial cells. Also, DLE induced TLR2 and TLR4 expression, and increased cAMP levels, whereas NF-κB activity was inhibited.
Conclusions: The present data indicate the differential regulation by DLE of the production of TNFα, IL-6, and IL-8 cytokines, associated with effects on TLR2 and TLR4 expression and NF-κB and cAMP activities. We suggest a putative mechanism for the biological effects of DLE in activated leukocytes and endothelial cells.
Key words.LPS NF-kappaB cAMP inflammation TLR
cAMP-responsive element-binding protein
Dialyzable Leukocyte Extract
Electrophoretic mobility shift assay
Enzyme-linked immunoabsorbent assays
Human umbilical vein endothelial cells
Peripheral blood mononuclear cells
Tumor Necrosis Factor
3′,5′-cyclic adenosine monophosphate
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