Int. J. lmmunopharmac., Vol. 8, No. 6, pp. 605 620, 1986. 0192-0561/86 $3.00+ .00 Printed in Great Britain. International Society for Immunopharmacology. CLOFAZIMINE-MEDIATED REGULATION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTE MIGRATION BY PRO-OXIDATIVE INACTIVATION OF BOTH LEUKOATTRACTANTS AND CELLULAR MIGRATORY RESPONSIVENESS RONALD ANDERSON, PAULINE LUKEY, CONSTANCE VAN RENSBURG and URSULA DIPPENAAR Division of Immunology, Department of Medical Microbiology, Institute for Pathology, University of Pretoria, Republic of South Africa (Received 9 September 1985 and in final form 28 January 1986) Abstract - - The effects of clofazimine (0.15 - 20/ag/ml) on the spontaneous and N-formyl-L-methionyl-L- leucyl-L-phenylalanine (FMLP)-stimulated migration, membrane-associated oxidative metabolism, degranulation and production of prostaglandin (PG) E2 by human polymorphonuclear leukocytes (PMNL) in vitro have been investigated. Clofazimine at concentrations of 0.3 /ag/ml and greater significantly increased both the spontaneous and FMLP-stimulated chemiluminescence (CL), hexose monophosphate shunt (HMS) activity, myeloperoxidase-mediated protein iodination, auto-iodination, degranulation and PGE2 production by PMNL. At the same concentrations clofazimine inhibited both random and leukoattractant-induced migration of PMNL. Inhibitionof PMNL migration by clofazimine was due to both a cell-directed auto-oxidative mechanism and by functional inactivation of FMLP. Clofazimine mediated inhibition of PMNL migration was prevented by the anti-oxidants cysteineand dapsone but not by the potent inhibitors of PG synthetase indomethacin and piroxicam. Anti-oxidants also protected FMLP from functional inactivation by clofazimine-exposed PMNL. Clofazimine increased both the spontaneous and FMLP-stimulated production of PGE2 by PMNL from four children with chronic granulomatous disease (CGD). Clofazimine is not an oxidising agent nor did it stimulate membrane-associated oxidative metabolism in CGD or NaF-pulsed normal PMNL. These data show that clofazimine-mediated inhibition of PMNL migration is dependent on intact cellular membrane-associated oxidative metabolism. Clofazimine is therefore a pro-oxidative anti-inflammatory agent. Clofazimine 3-(4-chloroanilino)- 10-(4-chlorophenyl)-2, 10-dihydro-2-phenazin-2-ylidine isopropylamine is an anti-leprosy agent (Barry, Belton, Conalty, Denneny, Edward, O'Sullivan, Twomey & Winder, 1957). Apart from its direct anti-mycobacterial properties clofazimine stimulates the phagocytic and antimicrobial activities (Brandt & Svensson, 1973) of human and murine neutrophils and macrophages by potentiating the activity of lysozomal enzymes (Sarracent & Finlay, 1982) and by increasing the phagocytosis-associated respiratory burst (Cline, 1970). Interestingly clofazimine also possesses anti- inflammatory and immunosuppressive properties (Vischer, 1969) which make the drug useful in the treatment of patients with lepromatous leprosy who experience erythema nodosum leprosum (ENL) reactions (Waters, 1983). The anti-inflammatory properties of clofazimine have been documented in the treatment of various non-mycobacterial chronic inflammatory diseases such as discoid lupus erythematosus (McKey & Barnes, 1974) pyoderma gangrenosum (Micha~lsson, Molin, Ohman, Gip, Londstr6m, Skogh & Trolin, 1976) and pustular psoriasis (Chuaprapaisilp & Piamphongsant, 1978). The drug has been reported to inhibit the migration of human polymorphonuclear leukocytes (PMNL) and mitogen-induced lymphocyte transformation at supra-therapeutic concentrations in vitro (Van Rensburg, Gatner, Imkamp & Anderson, 1982). Administration of therapeutic oral doses of clofazimine to healthy adults and patients with lepromatous leprosy was associated with reduced PMNL migration and lymphocyte proliferation in the same studies. The anti-inflammatory, immuno- suppressive properties of clofazimine are probably related to the inhibitory effects of the drug on 605