Minimal amidine structure for inhibition of nitric oxide biosynthesis

• Published in: Biochemical pharmacology Vol. 61; no. 12; pp. 1581 - 1586
• Main Authors: BILLACK, Blase, HECK, Diane E, MARSHALL PORTERFIELD, D, PAUL MALCHOW, R, SMITH, Peter J. S, GARDNER, Carol R, LASKIN, Debra L, LASKIN, Jeffrey D
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Science 15.06.2001
• Subjects: Amidines - chemistry; Amidines - pharmacology; Animals; Biological and medical sciences; Cells, Cultured; General and cellular metabolism. Vitamins; Guanidines - chemistry; Guanidines - pharmacology; Humans; Medical sciences; Mice; Nitric Oxide - metabolism; Nitric Oxide Synthase - drug effects; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Pharmacology. Drug treatments; Rats; Structure-Activity Relationship; Human; Rat; Enzyme; Digestive system; Toxicity; Liver; Rodentia; Enzyme inhibitor; Biosynthesis; Guanidines; Citrulline; Gene expression; In vitro; Nitric-oxide synthase; Vertebrata; Amidine; Mammalia; Arginine; Hepatocyte; Mouse; Animal; Established cell line; Oxidoreductases
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/S0006-2952(01)00630-X

Pharmacological modulation of nitric oxide synthase activity has been achieved using structural analogs of arginine. In the present studies, we demonstrated that the minimal amidine structure required for enzymatic inhibition is formamidine. We found that the production of nitric oxide by primary cultures of rat hepatocytes and several mouse and human cell lines, including RAW 264.7 macrophages, PAM 212 keratinocytes, G8 myoblasts, S180 sarcoma, CX-1 human colon cells, and GH3 rat pituitary cells, was inhibited in a concentration- and time-dependent manner by formamidine. Formamidine was 2- to 6-fold more effective in inhibiting nitric oxide production in cells expressing inducible nitric oxide synthase (NOS2) than in a cell line expressing calcium-dependent neuronal nitric oxide synthase (NOS1). Whereas formamidine had no effect on gamma-interferon-induced expression of nitric oxide synthase protein, its enzymatic activity was blocked. Kinetic analysis revealed that formamidine acts as a simple competitive inhibitor with respect to arginine (K(i) formamidine approximately 800 microM). Using a polarographic microsensor to measure real-time flux of nitric oxide release from RAW 264.7 macrophages, formamidine was found to require 30-90 min to inhibit enzyme activity, suggesting that cellular uptake of the drug may limit its biological activity. Our data indicate that formamidine is an effective inhibitor of nitric oxide production. Furthermore, its low toxicity may make it useful as a potential therapeutic agent in diseases associated with the increased production of nitric oxide.