Suppression effect of soy isoflavones on nitric oxide production in RAW 264.7 macrophages.
Genistein, daidzein, and glycitein, as primary isoflavones in soybeans, are reported to have beneficial effects on atherosclerosis, chronic inflammatory diseases, and cancers that are conducted by nitric oxide (NO) injury. The objectives of this study were to investigate the effects and mechanisms of these soy isoflavones on the inducible nitric oxide synthase (iNOS) system in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Genistein, daidzein, and glycitein dose-dependently suppress NO production (IC(50) = 50 microM) in supernatants of LPS-activated macrophages as measured on the basis of nitrite accumulation. In addition, direct inhibition of iNOS activity, determined by means of the conversion of L-[(3)H]arginine to L-[(3)H]citrulline, and markedly reduced iNOS protein and mRNA levels, evaluated by means of Western blot and RT-PCR, respectively, were found in homogenates of LPS-activated cells treated with each isoflavone. Moreover, genistein was found to have a greater inhibitory effect on NO production but no significant effect on iNOS activity or protein and gene expression to daidzein and glycitein. These observations reveal that the suppression of NO production by genistein, daidzein, and glycitein might be due to the inhibition of both the activity and expression of iNOS in LPS-activated macrophages. The result suggests that soy isoflavones might attenuate excessive NO generation at inflammatory sites.
Sheu
F
F
Department of Food Science, National Chung Hsing University, 250 Kuokuang Road, Taichung 40227, Taiwan, Republic of China.
Lai
H H
HH
Yen
G C
GC
D015153:Blotting, Western; D002478:Cells, Cultured; D007529:Isoflavones / Q000494:pharmacology*; D008070:Lipopolysaccharides; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013025:Glycine max / Q000737:chemistry*
D007529:Isoflavones; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase