Induction of NO Synthesis by Lipoteichoic Acid fromStaphylococcus aureusin J774 Macrophages: Involvement of a CD14-Dependent Pathway

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Lipoteichoic acid (LTA), a wall fragment of gram-positive bacteria, induces an isoform of NO synthase (iNOS) in vascular smooth muscle cells and macrophages which produces large quantities of NO and profound vasodilation in rats; this process may be involved in the cause of gram-positive septic shock. This study investigates the effect of LTA from Staphylococcus aureus on NO synthesis and iNOS mRNA induction in a mouse macrophage cell line (J774). LTA caused a time- and dose-dependent increase in NO production and a marked induction of iNOS mRNA. The induction of NO synthesis and iNOS gene expression in response to LTA was significantly inhibited by an anti-mouse CD14 monoclonal antibody. Studies utilizing a mutant cell line (J7.DEF3), which is defective in the expression of a CD14 antigen, showed that the increase in NO and iNOS mRNA caused by LTA is profoundly depressed in J7.DEF3 cells compared to that in parent J774 cells. In contrast, interferon-gamma produced a similar concentration-dependent increase in NO formation in both cell types. Thus, CD14 is involved in the signal transduction events leading to the enhanced expression of iNOS mRNA and activity elicited by LTA in murine macrophages. We propose that agents which block CD14-dependent events may be useful therapeutics in gram-positive shock.

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