In search of safer anti-Alzheimer drugs, 14 NO-donor-tacrine hybrids (1- 14) were synthesized and evaluated for their ability to inhibit cholinesterases and for vasorelaxation effects. Compounds 1- 13 showed good cholinesterases inhibitory activities in vitro, while 14, particularly, was highly selective, preferring butyrylcholinesterase rather than acetylcholinesterase. Four selected compounds (1, 9, 11, and 14) moderately relaxed the porcine pulmonary arteries in organ bath. In the hepatotoxicity study, significant hepatotoxicity was caused by tacrine but not by 9.

Background and purpose:The chronic use of organic nitrates is limited by serious side effects including oxidative stress, nitrate tolerance and/or endothelial dysfunction. The side effects and potency of nitroglycerine depend on mitochondrial aldehyde dehydrogenase (ALDH-2). We sought to determine whether this concept can be extended to a new class of organic nitrates with amino moieties (aminoalkyl nitrates). Experimental approach: Vasodilator potency of the organic nitrates, in vitro tolerance and in vivo tolerance (after continuous infusion for 3 days) were assessed in wild-type and ALDH-2 knockout mice by isometric tension studies. Mitochondrial oxidative stress was analysed by L-012-dependent chemiluminescence and protein tyrosine nitration. Key results: Aminoethyl nitrate (AEN) showed an almost similar potency to glyceryl trinitrate (GTN), even though it is only a mononitrate. AEN-dependent vasodilatation was mediated by cGMP and nitric oxide. In contrast to triethanolamine trinitrate (TEAN) and GTN, AEN bioactivation did not depend on ALDH-2 and caused no in vitro tolerance. In vivo treatment with TEAN and GTN, but not with AEN, induced cross-tolerance to acetylcholine (ACh)-dependent and GTN-dependent relaxation. Although all nitrates tested induced tolerance to themselves, only TEAN and GTN significantly increased mitochondrial oxidative stress in vitro and in vivo. Conclusions and implications:The present results demonstrate that not all high potency nitrates are bioactivated by ALDH-2 and that high potency of a given nitrate is not necessarily associated with induction of oxidative stress or nitrate tolerance. Obviously, there are distinct pathways for bioactivation of organic nitrates, which for AEN may involve xanthine oxidoreductase rather than P450 enzymes. (2009) 8-amino-5-chloro-7-phenylpyrido[3,4-d]pyridazine-1,4-(2H,3H)dione sodium salt; L-NAME, N w -nitro-L-arginine methyl ester hydrochloride; NO, nitric oxide; NS2028, 4H-8-bromo-1,2,4-oxadiazolo[3,4-d]benz [b][1,4]oxazin-1-one; PBS, phosphate buffered saline; PETN, pentaerithrityl tetranitrate; PETriN, pentaerithrityl trinitrate; PTIO, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide; ROS, reactive oxygen species; TEAN, triethanolamine trinitrate British Journal of Pharmacology