Suppression of inducible nitric oxide synthase expression in RAW 264. 7 macrophages by two beta-carboline alkaloids extracted from Melia azedarach.
We investigated the mechanism of suppression of inducible nitric oxide synthase (iNOS) by two beta-carboline alkaloids isolated from Melia azedarach, 4,8-dimethoxy-1-vinyl-beta-carboline (compound 1, C-1) and 4-methoxy-1-vinyl-beta-carboline (compound 2, C-2). iNOS activity in a cell-free extract of lipopolysaccharide/interferon-gamma-stimulated RAW 264.7 cells was found to be markedly increased, and this increase was prevented by C-1 and C-2, accompanied by the parallel reduction in nitrite accumulation in culture medium. However, C-1 and C-2 had no further effect on the iNOS activity prepared from fully lipopolysaccharide/interferon-gamma-stimulated RAW 264.7 cells. Treatment with C-1 or C-2 decreased the levels of iNOS protein and mRNA in a concentration-dependent manner. In addition, prostaglandin E(2) production, cyclooxygenase-2 protein and DNA binding of nuclear factor-kappaB (NF-kappaB) in lipopolysaccharide-stimulated RAW 264.7 cells were reduced by these compounds. These results indicate that C-1 and C-2 primarily inhibit iNOS and cyclooxygenase-2 activities via the suppression of de novo synthesis of these two enzymes, and that the inhibition of iNOS expression may be associated with the inhibition of NF-kappaB activation. Taken together, the results suggest that suppression of iNOS and cyclooxygenase-2 induction by lipopolysaccharide is responsible for the anti-inflammatory activity of these alkaloids through selective inhibition of the expression of genes, which play important roles in inflammatory signaling pathways.
Lee
B G
BG
College of Pharmacy, Sungkyunkwan University, 440-746, Suwon, South Korea.
Kim
S H
SH
Zee
O P
OP
Lee
K R
KR
Lee
H Y
HY
Han
J W
JW
Lee
H W
HW
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002243:Carbolines / Q000494:pharmacology*; D002460:Cell Line; D002956:Citrulline / Q000096:biosynthesis; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007527:Isoenzymes / Q000187:drug effects / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000235:genetics
C121891:4,8-dimethoxy-1-vinylcarboline; C121890:4-methoxy-1-vinylcarboline; D000470:Alkaloids; D002243:Carbolines; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009573:Nitrites; D002956:Citrulline; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone