INHIBITION OF SUPEROXIDE AND NITRIC-OXIDE RELEASE AND PROTECTION FROM REOXYGENATION INJURY BY EBSELEN IN RAT KUPFFER CELLS

Luminol chemiluminescence in phorbolester-activated cultured rat liver Kupffer cells was strongly inhibited by the selenoorganic compound ebselen (IC50 = 2-mu-mol/L). Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]one) also diminished reduction of ferricytochrome c (IC50 = 10-mu-mol/L), indicating a suppression of superoxide anion formation. Likewise, in lipopolysaccharide-pretreated Kupffer cells, ebselen proved to be a potent inhibitor of the conversion of oxyhemoglobin to methemoglobin (IC50 = 3-mu-mol/L) as a measure of nitric oxide formation. The sulfur-containing analog (2-phenyl-1,2-benzisothiazol-3[2H]one) and the ebselen derivative, methylselenobenzanilide, were inactive. These results indicate that ebselen is a potent inhibitor of NADPH oxidase in Kupffer cells, as has been reported for other macrophages and granulocytes. In addition, they suggest a novel characteristic of ebselen, namely very effective inhibition of nitric oxide synthase of macrophages. In line with its inhibitory effects on the release of reactive oxygen species by macrophages, complemented by its antioxidant properties, ebselen was potent in the prevention of reoxygenation injury of Kupffer cells (IC50 approximately 5-mu-mol/L).