Differential Cytokine Response in Host Defence Mechanisms Triggered by Gram-Negative and Gram-Positive Bacteria, and the Roles of Gabexate Mesilate, a Synthetic Protease Inhibitor

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Abstract
Bacterial infection results in the production of inflammatory mediators and may be involved in the pathogenesis of sepsis and/or systemic inflammatory response syndrome. The effect of lipopolysaccharide (LPS), a major component of the outer surface of Gram-negative bacteria, and Staphylococcal enterotoxin B (SEB), a superantigen of Gram-positive bacteria, on cytokine production in peripheral blood mononuclear cells (PBMCs) was examined. LPS significantly increased the production of proinflammatory and anti-inflammatory cytokines, and SEB enhanced the production of helper T lymphocyte type cytokines. These results illustrated the different responses to Gram-negative and Gram-positive bacterial infections. The effect of gabexate mesilate, a synthetic protease inhibitor, on cytokine production and expression of the toll-like receptor (TLR) was also examined. The results suggest that gabexate mesilate-induced inhibition of tumour necrosis factor-α (TNF-α) and interleukin-18 (IL-18) production in LPS-stimulated PBMCs is due to the inhibition of the nuclear factor-κB activation pathway and/or inhibition of the processing pathway of pro-TNF-α and pro-IL-18, not to down-regulation of TLR-2 or TLR-4.