Nitroksyl (HNO/NO-) - cząsteczka o potencjalnym znaczeniu farmakologicznym

Nitrogen compounds, as an essential component of many reactions occurring in living organisms, become the object of an extensive research. These compounds became the focus of interest after the properties of nitric oxide, currently the best known nitrogen oxide, had thoroughly been studied [1–3]. Recently, particular attention has been paid to nitroxyl (HNO/NO–), which is the product of one-electron reduction of NO• [4]. Formation of nitroxyl in vivo is still controversial. It seems that this compound could be formed by the reaction of S-nitrosothiols with other thiol proteins (e.g. GSH), directly through the nitric oxide synthetase (NOS), through the oxidation of hydroxylamine by the peroxidase activity of heme proteins or as a result of reduction of nitric oxide NO• [ 5, 6]. Nitroxyl is a liable compound due to dimerization, so it is necessary to use its donors in experiments. Angeli’s salt which forms HNO at physiological pH is the most commonly used donor [7]. Moreover, Piloty’s acid, cyanamide, diazonium diolates or a group of acyloxy nitroso compounds are also used. There are some difficulties with detection of nitroxyl in biological systems. So far, nitroxyl was indirectly identified by detection of N2O, a product of HNO dimerization. Presently, nitroxyl is an object of intensive studies aiming at finding techniques of its direct detection. Recently two such techniques have been designed: one using the reaction of HNO with triarylphosphines, and the other with BOT1 (staining agent) complexed with copper ions, which gives fluorescent signals revealing HNO in living cells [8, 9]. Nitroxyl turned out to have great pharmacological potential [10, 11]. It was demonstrated that this compound affected the activity of many proteins reacting with their thiol groups [12, 13]. Moreover, HNO/NO– influences the contractility of blood vessels and therefore has inotropic and lusitropic effects on myocardium [14]. Nitroxyl seems to be very promising in treating cancerous diseases as it inhibits the activity of an enzyme involved in the process which is the most important for cancer cells – glycolysis [15].