Sanguinarine is a potent inhibitor of oxidative burst in DMSO-differentiated HL-60 cells by a non-redox mechanism

Sanguinarine (SA), a member of the benzo[c]phenanthridine isoquinoline alkaloids, has been shown to possess antimicrobial, anti-inflammatory, and antioxidant properties. We examined the effects of SA on oxidative burst in DMSO-differentiated HL-60 cells, an excellent model for studying oxidative burst. SA inhibited both N-formyl-Met-Leu-Phe (fMLP) and phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst with half-maximal concentration for inhibition (IC50) of 1.5 and 1.8 muM, respectively. Despite suggestions of SA antioxidant activity this inhibition cannot be ascribed to radical scavenging property of SA because the IC50 for superoxide dismutase-like activity in a non-cellular system was 60 muM. TROLOX, a water-soluble vitamin E analog, had IC50 of 3 muM in the same system. Moreover, cyclic voltammetry measurements show that SA is not an easily oxidisable species, with a peak anodic potential at 700 mV, as compared to TROLOX with peak anodic potential at 200 my On the other hand, TROLOX, when used in cell suspension, was much poorer inhibitor of oxidative burst than SA. When testing direct effect of SA on NADPH oxidase in the post-granular fraction of disrupted cells, the IC50 was found to be 8.3 muM. It is higher than that observed in whole cells, however, the shift may be ascribed to SDS effect on SA activity. We conclude the SA inhibition of oxidative burst is not caused by SA redox activity but most likely is a result of SA affecting the activity of NADPH oxidase directly and in part by preventing the formation of NADPH oxidase protein complex. (C) 2003 Elsevier Ireland Ltd. All rights reserved.