Cyclo(dehydrohistidyl-l-tryptophyl) inhibits nitric oxide production by preventing the dimerization of inducible nitric oxide synthase.
Dimerization of inducible NOS has been known to be a potential therapeutic target for iNOS-mediated pathologies. Cyclic dipeptides are among the simplest peptides commonly found as by-products of food processing or metabolites of microorganisms. In this study, we found that cyclo(dehydrohistidyl-l-tryptophyl) (CDHT), a cyclic dipeptide from an unidentified fungal strain Fb956, prevents iNOS dimerization in activated microglial BV-2 cells. CDHT inhibited NO production with an IC50 of 6.5 microM in LPS-treated BV-2 cells. Western blot analysis and iNOS activity measurement of fractions from size-exclusion chromatography of cell lysates indicated that CDHT inhibits dimerization of iNOS, while it has no effect on iNOS expression or enzyme activity. The CDHT inhibition of iNOS dimerization was confirmed by partially denaturing SDS-PAGE analysis. In contrast, CDHT did not affect cGMP production in endothelial HUVEC cells, which indicates no inhibition of endothelial NOS activity. These results reveal that CDHT, one of the simplest and cyclic dipeptides, selectively inhibits NO production by inhibiting iNOS dimerization, and could be a useful therapeutic agent for inflammation-mediated diseases.
Functional Metabolites Research Center, Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejeon 305-806, Republic of Korea.
Mi-Jin
MJ
Sohn
Gang-Min
GM
Hur
Hee-Sun
HS
Byun
Won-Gon
WG
Kim
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D008070:Lipopolysaccharides; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000737:chemistry; D010456:Peptides, Cyclic / Q000302:isolation & purification / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D010456:Peptides, Cyclic; C528114:cyclo(dehydrohistidyl-tryptophyl); D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D006152:Cyclic GMP