Inhibition of human monocyte functions by anthralin

Anthralin is a well-established and widely used compound for topical treatment of psoriasis. In recent years attention has been focused on the anti-inflammatory properties of anthralin, with particular reference to psoriasis. In this study the effect of anthralin on human monocyte chemotaxis, superoxide-anion generation, and enzyme degranulation, were investigated. For comparison, the effect of the clinically inactive anthralin derivative danthrone and the solvent (acetone) were also studied. The results show that anthralin potently inhibits stimulated human monocyte superoxide-anion generation and enzyme degranulation, with a half-maximal inhibitory concentration (IC50) of as low as 0.02 micrograms/ml. Chemotactic migration of monocytes, however, was only affected when very high doses of anthralin (10 micrograms/ml) were used for pretreatment of the cells. Danthrone, up to a concentration of 10 micrograms/ml, or acetone alone (0.1%, v/v), did not inhibit the monocyte functions tested. Our results indicate that anthralin at pharmacological concentrations is a potent and selective inhibitor of human monocyte pro-inflammatory activities, by inhibiting respiratory burst activity (e.g. superoxide-anion generation) and enzyme degranulation, without affecting chemotactic migration.