Background and Goal of Study:Binding of lipopolysaccharide (LPS) to Toll-like receptor 4, mediated by cluster of differentiation 14 (CD14), elicits intracellular inflammatory cascades. CD14 exists as either a membrane bound protein on the cell surface or as a soluble protein in supernatants. Shedding of CD14 caused by proteolytic cleavage leads to reduced expression of membrane bound CD14 (mCD14), followed by hypo-responsiveness to LPS. Magnesium sulfate (MgSO4) has anti-inflammatory effects and reduces LPS-induced cytokine release. However, the role of MgSO4 in LPS recognition remains unstudied. We conducted this study to elucidate the effects of MgSO4 on LPS-macrophage binding and CD14 expression. 
Materials and Methods:THP-1 cells were treated with LPS (1μg/ml) or LPS plus MgSO4 (20mM) (denoted as the LPS and LPS+M groups, respectively) to facilitate investigation. To assay LPS binding to THP-1 cells, cells were incubated with FITC-LPS for 60 min. The levels of LPS-macrophage binding and mCD14 were measured by flow cytometry. The concentration of soluble CD14 (sCD14) in supernatants was measured by enzyme-linked immunosorbent assay. 
Results and Discussion:After LPS stimulation, the signal intensities of FITC-LPS binding to cells and mCD14 expression in the LPS+M group were lower than the LPS group (Fig.1 & 2A). Correspondingly, the concentration of sCD14 in the LPS+M group was higher than the LPS group (Fig.2B). The increase of sCD14 in supernatants facilitated by MgSO4 treatment is suggested derived from mCD14 shedding. Previous observation that dietary magnesium deficiency relates to high CD14 levels seems to support our results.
Conclusion(s):MgSO4 decreases binding of LPS to macrophages, resulting from reduced mCD14 expression. The effects of MgSO4 on CD14 may involve enhanced proteolytic cleavage. 



01 / Magnesium sulfate decreases binding of lipopolysaccharide to macrophages by reducing membrane bound CD14