Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA.
Nitric Oxide. 2013 May 31;31:38-47. doi: 10.1016/j.niox.2013.03.006. Epub 2013 Mar 30.
Angeli's salt (Na₂N₂O₃) decomposes into nitroxyl (HNO) and nitrite (NO₂(-)), compounds of physiological and therapeutic interest for their impact on biological signaling both through nitric oxide and nitric oxide independent pathways. Both nitrite and HNO oxidize oxygenated hemoglobin to methemoglobin. Earlier work has shown that HNO catalyzes the reduction of nitrite by deoxygenated hemoglobin. In this work, we have shown that HNO accelerates the oxidation of oxygenated hemoglobin by NO₂(-). We have demonstrated this HNO mediated acceleration of the nitrite/oxygenated hemoglobin reaction with oxygenated hemoglobin being in excess to HNO and nitrite (as would be found under physiological conditions) by monitoring the formation of methemoglobin in the presence of Angeli's salt with and without added NO₂(-). In addition, this acceleration has been demonstrated using the HNO donor 4-nitrosotetrahydro-2H-pyran-4-yl pivalate, a water-soluble acyloxy nitroso compound that does not release NO₂(-) but generates HNO in the presence of esterase. This HNO donor was used both with and without NO₂(-) and acceleration of the NO₂(-) induced formation of methemoglobin was observed. We found that the acceleration was not substantially affected by catalase, superoxide dismutase, c-PTIO, or IHP, suggesting that it is not due to formation of extramolecular peroxide, NO₂ or H₂O₂, or to modulation of allosteric properties. In addition, we found that the acceleration is not likely to be related to HNO binding to free reduced hemoglobin, as we found HNO binding to reduced hemoglobin to be much weaker than has previously been proposed. We suggest that the mechanism of the acceleration involves local propagation of autocatalysis in the nitrite-oxygenated Hb reaction. This acceleration of the nitrite oxyhemoglobin reaction could affect studies aimed at understanding physiological roles of HNO and perhaps nitrite and use of these agents in therapeutics such as hemolytic anemias, heart failure, and ischemia reperfusion injury.
硝普钠（Na₂N₂O₃）分解为羟胺（HNO）和亚硝酸盐（NO₂(-)），这些化合物在生物信号传递方面具有生理和治疗意义，因为它们通过一氧化氮和一氧化氮非依赖性途径发挥作用。亚硝酸盐和 HNO 都将氧合血红蛋白氧化为高铁血红蛋白。早期的研究表明，HNO 可以催化脱氧血红蛋白还原亚硝酸盐。在这项工作中，我们已经证明 HNO 可以加速亚硝酸盐对氧合血红蛋白的氧化。我们通过监测硝普钠存在时高铁血红蛋白的形成，证明了 HNO 介导的亚硝酸盐/氧合血红蛋白反应的加速，其中氧合血红蛋白的量超过 HNO 和亚硝酸盐（在生理条件下会发现）。此外，我们还使用 HNO 供体 4-亚硝基四氢-2H-吡喃-4-基特戊酸（一种水溶性酰氧基亚硝化合物，不会释放 NO₂(-)，但在酯酶存在下会产生 HNO）证明了这种加速。该 HNO 供体在有无 NO₂(-)的情况下均被使用，并观察到了加速亚硝酸盐诱导高铁血红蛋白形成的现象。我们发现，该加速过程不会受到过氧化氢酶、超氧化物歧化酶、c-PTIO 或 IHP 的显著影响，这表明它不是由于形成了过氧物、NO₂ 或 H₂O₂，也不是由于对变构性质的调节。此外，我们发现这种加速可能与 HNO 与游离还原血红蛋白的结合无关，因为我们发现 HNO 与还原血红蛋白的结合比以前提出的要弱得多。我们认为，加速的机制涉及到亚硝酸盐-氧合血红蛋白反应中局部的自催化传播。这种对亚硝酸盐氧合血红蛋白反应的加速可能会影响到对 HNO 和亚硝酸盐生理作用的研究，并且可能会影响到这些药物在治疗溶血性贫血、心力衰竭和缺血再灌注损伤等疾病中的应用。
