Magnesium sulfate inhibits binding of lipopolysaccharide to THP-1 cells by reducing expression of cluster of differentiation 14

We investigated effects of magnesium sulfate (MgSO4) on modulating lipopolysaccharide (LPS)-macrophage binding and cluster of differentiation 14 (CD14) expression. Flow cytometry data revealed that the mean levels of LPS-macrophage binding and membrane-bound CD14 expression (mCD14) in differentiated THP-1 cells (a human monocytic cell line) treated with LPS plus MgSO4 (the LPS+M group) decreased by 28.2% and 25.3% compared with those THP-1 cells treated with LPS only (the LPS group) (P<0.001 and P=0.037), indicating that MgSO4 significantly inhibits LPS-macrophage binding and mCD14 expression. Notably, these effects of MgSO4 were counteracted by L-type calcium channel activation. Moreover, the mean level of soluble CD14 (sCD14; proteolytic cleavage product of CD14) in the LPS+M group was 25.6% higher than in the LPS group (P<0.001), indicating that MgSO4 significantly enhances CD14 proteolytic cleavage. Of note, serine protease inhibition mitigated effects of MgSO4 on both decreasing mCD14 and increasing sCD14. In conclusion, MgSO4 inhibits LPS-macrophage binding through reducing CD14 expression. The mechanisms may involve antagonizing L-type calcium channels and activating serine proteases.