ANTIRADICAL AND CHELATING EFFECTS IN FLAVONOID PROTECTION AGAINST SILICA-INDUCED CELL INJURY

Quercetin, dihydroquercetin, and rutin are capable of scavenging super oxide anion (rate constants of the reaction with superoxide at pH 10 w ere 1.7 x 10(5), 1.5 x 10(5), and 0.5 x 10(5) M-1 s(-1), respectively) . At the same time rutin and quercetin but not dihydroquercetin are ir on ion chelators, These substances were used to elucidate the role of radical scavenging and iron chelating in flavonoid protection against asbestos-induced oxidative cellular injury. Exposure of rat peritoneal macrophages to chrysotile asbestos fibers resulted in ''frustrated'' phagocytosis, cell injury, and a LDH release. Quercetin, dihydroquerce tin, and rutin were effective in protecting the phagocytic cells again st injury caused by asbestos. Moreover, these flavonoids exhibited cel lular protection in the same order of effectiveness as that observed f or the quenching of superoxide: quercetin > dihydroquercetin > rutin. Exposure of human red blood cells to asbestos fibers also caused progr essive cell injury and lysis. Quercetin and rutin protected the red ce lls (quercetin > rutin), whereas dihydroquercetin was ineffective in p reventing asbestos-induced hemolysis. The protective ability of querce tin and rutin may be related to their iron-chelating activity. Due to this these flavonoids can be located on asbestos surface in sites of i nitiation of free radical reactions and their antiradical moieties can scavenge reactive oxygen species immediately after the appearance. Th us, both antiradical and chelating effects appear to be involved in th e flavonoid protection against silica-induced cell injury. (C) 1998 Ac ademic Press.