S-nitrosohemoglobin (SNO-Hb) (SNO-Hb)

S-nitrosohemoglobin (SNO-Hb) is a post-translationally modified form of hemoglobin where nitric oxide (NO) is covalently attached to the highly conserved beta-93 cysteine residue (Science, 1997). It functions as a critical regulator of the microcirculation by coupling tissue oxygen demand with blood flow through a process known as hypoxic vasodilation (JCI, 2016). In the lungs, hemoglobin is S-nitrosylated as it binds oxygen; as it travels to hypoxic tissues and releases oxygen, the resulting allosteric transition triggers the release of NO bioactivity to dilate local resistance vessels (PNAS, 2023). Deficiencies in SNO-Hb levels or impaired NO release are implicated in the pathophysiology of various conditions, including sickle cell disease, heart failure, and peripheral artery disease (Circulation, 2017). Therapeutic interventions, such as the administration of ethyl nitrite, aim to replenish SNO-Hb levels to improve tissue oxygenation and organ function (ASCPT, 2017). Unlike traditional vasodilators, SNO-Hb-mediated therapy specifically targets hypoxic regions, potentially avoiding systemic side effects like hypotension (JCI, 2016).

Other names

S-nitrosylated hemoglobinSNOHbS-nitroso-hemoglobin

Pharmacological repletion of S-nitrosohemoglobin to restore hypoxic vasodilation and improve tissue perfusion (ASCPT, 2017; PMC, 2017).