L-NIL hydrochloride

Primary murine microglia are resistant to nitric oxide inhibition of indoleamine 2,3-dioxygenase.[Pubmed:20451602]

Brain Behav Immun. 2010 Nov;24(8):1249-53.

Indoleamine 2,3-dioxygenase (IDO) is an intracellular heme-containing enzyme that is activated by proinflammatory cytokines, including interferon-gamma (IFNgamma), and metabolizes tryptophan along the kynurenine pathway. Activation of murine macrophages induces not only IDO but also nitric oxide synthase (iNOS), and the ensuing production of nitric oxide (NO) inhibits IDO. To determine the sensitivity of primary cultures of murine microglia to NO, microglia were stimulated with recombinant murine IFNgamma (1 ng/ml) and lipopolysaccharide (LPS) (10 ng/ml). This combination of IFNgamma+LPS synergized to produce maximal amounts of nitrite as early as 16h. Steady-state mRNAs for both iNOS and IDO were significantly increased by IFNgamma+LPS at 4h post-treatment, followed by an increase in IDO enzymatic activity at 24h. Murine microglia (>95% CD11b(+)) were pretreated with the iNOS inhibitor, L-NIL hydrochloride, at a dose (30 muM) that completely abrogated production of nitrite. L-NIL had no effect on IDO mRNA at 4h or IDO enzymatic activity at 24h following stimulation with IFNgamma+LPS. These data establish that IDO regulation in murine microglia is not restrained by NO, thereby permitting the accumulation of kynurenine and its downstream metabolites in the central nervous system.

Suppression of adjuvant-induced arthritis by selective inhibition of inducible nitric oxide synthase.[Pubmed:7537678]

Eur J Pharmacol. 1995 Jan 24;273(1-2):15-24.

Adjuvant-induced arthritis is a model of chronic inflammation that exhibits several pathological changes similar to those occurring in rheumatoid arthritis, an autoimmune disease in humans characterized by chronic inflammation of the joints. We have examined the role of inducible nitric oxide synthase in producing the pathological changes associated with adjuvant-induced arthritis. Plasma nitrite concentrations were maximally elevated 14 days following adjuvant administration compared to untreated control animals. Arthritic changes in the paw were first observed between days 10-12 and were maximally elevated 21 days following adjuvant administration. Inducible nitric oxide synthase immunoreactivity was found localized in the synovial tissue from adjuvant-treated rats, while untreated controls exhibited no inducible nitric oxide synthase staining. Two selective inducible nitric oxide synthase inhibitors, aminoguanidine and N-iminoethyl-L-lysine, suppressed the increase in plasma nitrite levels and joint inflammation associated with adjuvant-induced arthritis in a dose-dependent manner. N-Iminoethyl-L-lysine attenuated the inducible nitric oxide synthase immunoreactivity in adjuvant-treated rats. Blood pressure was not affected by the highest dose of N-iminoethyl-L-lysine administered in the drinking water, indicating a lack of inhibition of constitutive nitric oxide synthase.

L-N6-(1-iminoethyl)lysine: a selective inhibitor of inducible nitric oxide synthase.[Pubmed:7525961]

J Med Chem. 1994 Nov 11;37(23):3886-8.

L-N6-(1-Iminoethyl)lysine (L-NIL) has been synthesized and is shown to be both a potent and selective inhibitor of mouse inducible nitric oxide synthase (miNOS). L-NIL has an IC50 of 3.3 microM for miNOS compared to an IC50 of 92 microM for rat brain constitutive NOS indicating that L-NIL is 28-fold more selective for inducible NOS. L-N5-(1-Iminoethyl)ornithine (L-NIO), which differs from L-NIL by having one less methylene group, has very similar potency for inducible NOS, but lacks selectivity. DL-N7-(1-Iminoethyl)homolysine was also synthesized and found to be substantially less potent than L-NIL or L-NIO, with intermediate selectivity for inducible NOS. These data suggest that L-NIL may be useful as a selective inhibitor of inducible NOS for determining the role of this enzyme in disease models.