U-19451A: a selective inducible nitric oxide synthase inhibitor

Drugs with high selectivity for iNOS inhibition may be useful for treatment of neurodegenerative disorders, chronic inflammatory diseases, and septic shock. Therefore, U-19451A (2-benzyl-2-thio-pseudourea hydrochloride), a potential NOS inhibitor, has been investigated for its selectivity for iNOS using tissues, primary cerebellar granule cell cultures and glial cell cultures. Lungs isolated from rats treated with intravenous injection of E coli lipopolysaccharide and glial cell cultures treated with the same bacterial toxin plus gamma-interferon were used for iNOS activity. Rat cerebellum and primary cerebellar granule cell cultures were utilized for neuronal NOS (nNOS) activity. S-methylthiourea (SMT) and L-nitroarginine methyl ester (L-NAME), selective iNOS and nNOS inhibitors, respectively, were chosen as standards. Both U-19451A and SMT were 4-times more selective for iNOS as compared to nNOS in tissues. U-19451A was more selective than SMT for iNOS inhibition using cultures. L-NAME was 16-31 times more selective for inhibiting nNOS activity. Based on the selectivity of U-19451A for iNOS inhibition, this drug would be expected to be effective in the treatment of diseases with inflammatory pathology without producing side effects associated with nNOS inhibition.