title: Certain S-substituted isothioureas not only inhibit NO synthase catalytic activity but also decrease translation and stability of inducible NO synthase protein.
abstract: In an attempt to identify potent inhibitors of inducible (type II) NO synthase (iNOS) for use in cell culture systems, we found that two S-substituted isothioureas were very potent in cell culture but one such compound also interfered with the induction of NO synthase. S-Ethylisothiourea (EITU) and S-aminoethylisothiourea (AEITU) were found to be much more potent than NG-methylarginine, NG-nitroarginine methy lester, or aminoguanidine as inhibitors of NO production by cultured RAW 264.7 cell macrophages activated by lipopolysaccharide (LPS). The approximate EC50 values as inhibitors of NO production, assessed by 24-h accumulation in cell culture media, were 10 microM (EITU), 30 microM (AEITU), 300 microM (NG-methylarginine), and 1000 microM (aminoguanidine). EITU was found to inhibit NO production by activated macrophages without interfering with the induction of iNOS. More specifically, EITU failed to influence transcription of iNOS mRNA (Northern blot analysis), translation of iNOS protein (pulse experiments), or degradation of translated iNOS protein (pulse-chase experiments). In contrast, however, AEITU interfered markedly with the induction of iNOS by mechanisms attributed to inhibition of translation of iNOS mRNA into functional protein as well as acceleration of degradation of already translated iNOS protein. These observations indicate that AEITU should not be used in cell culture experiments where the intent is solely to assess the consequences of inhibition of iNOS catalytic activity.
authors.affiliation: Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, California 90095-1735, USA.
authors.forename: L H
authors.initials: LH
authors.lastname: Wei
authors.forename: N
authors.initials: N
authors.lastname: Arabolos
authors.forename: L J
authors.initials: LJ
authors.lastname: Ignarro
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability / Q000187:drug effects; D007550:Isothiuronium / Q000031:analogs & derivatives* / Q000494:pharmacology; D008262:Macrophage Activation; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D014176:Protein Biosynthesis / Q000187:drug effects*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D000338:beta-Aminoethyl Isothiourea / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D000338:beta-Aminoethyl Isothiourea; D007550:Isothiuronium; C007687:etiron; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D013890:Thiourea