REGULATION OF COMPONENTS OF THE INFLAMMATORY RESPONSE BY 5-IODO-6-AMINO-1,2-BENZOPYRONE, AN INHIBITOR OF POLY(ADP-RIBOSE) SYNTHETASE AND PLEIOTROPIC MODIFIER OF CELLULAR SIGNAL PATHWAYS

Chronic inflammation is known to facilitate carcinogenic transformatio n in various tissues. 5-iodo-6-amino-1,2-benzopyrone (INH2BP), a novel inhibitor of the nuclear enzyme poly(ADP-ribose) polymerase (pADPRT) has recently been shown to regulate a variety of cellular signal trans duction pathways and to abrogate in vivo tumorigenicity by a Ha-ms tra nsfected endothelial cell line. Here we have investigated the effect o f INH2BP on the activation by endotoxin (bacterial lipopolysaccharide, LPS) on the production of the inflammatory mediators tumor necrosis f actor alpha (TNF alpha), interleukin-10 (IL-10) and interleukin-6 (IL- 6), nitric oxide (NO) and prostaglandins in vitro and in vivo. In addi tion, we studied the effect of INH2BP on the activation of mitogen-act ivated protein kinase (MAP kinase) and nuclear factor kappa B (NF-kapp a B) in vitro. In cultured J774 and RAW 264.7 macrophages, LPS induced the production of prostaglandin metabolites, the release of TNF and t he expression of the inducible isoform of NO synthase (iNOS). The prod uction of prostaglandins and of NO were inhibited by INH2BP in a dose- dependent manner, while the short-term release of TNF alpha was unaffe cted. INH2BP markedly suppressed LPS-mediated luciferase activity in R AW cells transiently transfected with a full length (-1,592 bp) murine macrophage iNOS promoter-luciferase construct, but not in a deletiona l construct consisting of -367 bp. In vivo, INH2BP pretreatment inhibi ted the induction of iNOS by LPS in rats, did not affect the LPS-induc ed TNF and IL-6 response, but enhanced LPS-induced IL-10 production. I NH2BP pretreatment markedly improved the survival of mice in a lethal model of endotoxin shock. Our results demonstrate that INH2BP has pote nt anti-inflammatory actions in vitro and in vivo.