Biochemical characterization of S-nitrosohemoglobin. Mechanisms underlying synthesis, no release, and biological activity.
S-Nitrosohemoglobin (SNO-Hb) has been suggested to act as an endogenous NO donor and physiological regulator of blood pressure. However, the mechanisms responsible for the formation of SNO-Hb and those underlying the release of NO and subsequent biological activity have yet to be elucidated. In the present study, a number of nitrosated oxyhemoglobin (HbO(2)) derivatives have been synthesized and characterized. HbO(2) can be nitrosated at up to three distinct residues, one in the alpha-globin chain and two in the beta-chain. A beta-chain mononitrosated species (designated "SNO-Hb"), generated by the reaction of HbO(2) and S-nitrosoglutathione, released NO via a thiol-dependent mechanism involving nucleophilic attack at the nitrosated thiol functionality of SNO-Hb; in the case of glutathione, this process was associated with the formation of a mixed disulfide. In contrast, multinitrosated hemoglobin species released NO and relaxed vascular smooth muscle by a thiol-independent mechanism. HbO(2) scavenged potently NO released from SNO-Hb and inhibited its vasorelaxant properties. These data show that the predominant vasoactive species released from SNO-Hb is NO, with HNO a putative intermediate; the presence of a low molecular weight thiol is a prerequisite for this process. Such observations have important implications for the generation, metabolic fate, and biological activity of S-nitrosothiols.
Wolzt
M
M
Centre for Clinical Pharmacology, University College London, 5 University Street, London WC1E 6JJ, United Kingdom.
MacAllister
R J
RJ
Davis
D
D
Feelisch
M
M
Moncada
S
S
Vallance
P
P
Hobbs
A J
AJ
D019794:2,3-Diphosphoglycerate / Q000494:pharmacology; D000818:Animals; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism; D016166:Free Radical Scavengers; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000494:pharmacology; D006454:Hemoglobins / Q000096:biosynthesis / Q000737:chemistry*; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D009603:Nitroso Compounds / Q000378:metabolism / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D010108:Oxyhemoglobins / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D026422:S-Nitrosoglutathione; D026403:S-Nitrosothiols; D013438:Sulfhydryl Compounds / Q000737:chemistry; D014664:Vasodilation / Q000187:drug effects
D016166:Free Radical Scavengers; D006454:Hemoglobins; D009603:Nitroso Compounds; D010108:Oxyhemoglobins; D026403:S-Nitrosothiols; C103574:S-nitrosohemoglobin; D013438:Sulfhydryl Compounds; D019794:2,3-Diphosphoglycerate; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; C021315:S-nitrosocysteine; D005978:Glutathione; D003545:Cysteine; D010100:Oxygen; D019803:Glutathione Disulfide