INHIBITION OF LPS-INDUCED NFκB ACTIVATION BY A GLUCAN LIGAND INVOLVES DOWN-REGULATION OF IKKβ KINASE ACTIVITY AND ALTERED PHOSPHORYLATION AND DEGRADATION OF IκBα

Growing evidence supports the role of transcription factor activation in the pathophysiology of inflammatory disorders, sepsis, ARDS, SIRS, and shock. Kinase mediated phosphorylation of IkappaBalpha is a crucial step in the NFkappaB activation pathway. We investigated IKBalpha phosphorylation in murine liver and lung extracts after cecal ligation and puncture (CLP) in the presence and absence of a glucan ligand. ICR mice were subjected to CLP. Unoperated and sham-operated mice served as the controls. Glucan phosphate (50 mg/kg) was administered 1 h before or 15 min after CLP. CLP increased hepatic and pulmonary levels of phospho-IkappaBalpha by 48-192%. Pre- or post-treatment with glucan phosphate decreased (P < 0.05) tissue phospho-IkappaBalpha levels in CLP mice. Phospho-IkappaBalpha in the glucan-CLP group were not significantly different from the unoperated controls. To investigate mechanisms we examined IKKbeta kinase activity, IkappaBalpha phosphorylation and degradation, and NFkappaB activity in a murine macrophage cell line, J774a.1, treated with LPS (1 microg/mL) and/or glucan phosphate (1 microg/mL) for up to 120 min. The glucan ligand blunted LPS-induced IKKbeta kinase activity, phosphorylation and degradation of IkappaBalpha, and NFkappaB nuclear binding activity. The data indicate that one mechanism by which (1-->3)-beta-D-glucan may alter the response to endotoxin or polymicrobial sepsis involves modulation of IKK3 kinase activity with subsequent decreases in IkappaBalpha phosphorylation and NFkappaB activation.