Arginase activity in a murine macrophage cell line (RAW264.7) stimulated with lipopolysaccharide from Actinobacillus actinomycetemcomitans

Aims: The aim of the present study was to determine whether or not lipopolysaccharide from Actinobacillus actinomycetemcomitans could stimulate Arginase activity in a murine macrophage cell line (RAW264.7 cells).

Methods: RAW264.7 cells were treated with A. actinomycetemcomitans-lipopolysaccharide or lipopolysaccharide from Escherichia coli for 24 h. The effect of polymyxin B, l-norvaline, dl-norvaline, dexamethasone and cytokines (interferon-gamma and interleukin-4) on Arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells was also determined. The cells were pretreated with anti-CD14, anti -toll-like receptor 2, or anti-toll-like receptor 4 antibody prior to stimulation with A. actinomycetemcomitans-lipopolysaccharide. Arginase activity was determined by a colorimetric assay.

Results: A. actinomycetemcomitans-lipopolysaccharide stimulated Arginase activity in RAW264.7 cells in a dose-dependent manner, but was less potent than E. coli-lipopolysaccharide. Polymyxin B and l-norvaline, but not dl-norvaline, blocked the Arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells. Dexamethasone and interleukin-4 but not interferon-gamma augmented Arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells. Treatment of the cells with anti-CD14 and anti-toll-like receptor 4 but not anti-toll-like receptor 2 antibody decreased Arginase activity in A. actinomycetemcomitans-lipopolysaccharide-stimulated cells.

Conclusion: The results of the present study suggest that lipopolysaccharide from A. actinomycetemcomitans via CD14/Toll-like Receptor 4 complex molecules and the regulatory control of glucocorticoid and cytokines may stimulate Arginase activity in RAW264.7 cells.