PDF(Pubmed)
Abstract：
The root cause of sickle cell disease (SCD) is the polymerization of sickle hemoglobin (HbS) leading to sickling of red blood cells (RBC). Earlier studies showed that in patients with SCD, high-dose nitrite inhibited sickling, an effect originally attributed to HbS oxidation to methemoglobin-S even though the anti-sickling effect did not correlate with methemoglobin-S levels. Here, we examined the effects of nitrite on HbS polymerization and on methemoglobin formation in a SCD mouse model. In vitro, at concentrations higher than physiologic (>1 μM), nitrite increased the delay time for polymerization of deoxygenated HbS independently of methemoglobin-S formation, which only occurred at much higher concentrations (>300 μM). In vitro, higher nitrite concentrations oxidized 100% of normal hemoglobin A (HbA), but only 70% of HbS. Dimethyl adipimidate, an anti-polymerization agent, increased the fraction of HbS oxidized by nitrite to 82%, suggesting that polymerized HbS partially contributed to the oxidation-resistant fraction of HbS. At low concentrations (10 μM-1 mM), nitrite did not increase the formation of reactive oxygen species but at high concentrations (10 mM) it decreased sickle RBC viability. In SCD mice, 4-week administration of nitrite yielded no significant changes in methemoglobin or nitrite levels in plasma and RBC, however, it further increased leukocytosis. Overall, these data suggest that nitrite at supra-physiologic concentrations has anti-polymerization properties in vitro and that leukocytosis is a potential nitrite toxicity in vivo. Therefore, to determine whether the anti-polymerization effect of nitrite observed in vitro underlies the decreases in sickling observed in patients with SCD, administration of higher nitrite doses is required.
摘要：
镰状细胞病（SCD）的根本原因是镰状血红蛋白（HbS）的聚合导致红细胞（RBC）的镰状化。早期的研究表明，在SCD患者中，高剂量亚硝酸盐抑制镰状生长，最初归因于HbS氧化为高铁血红蛋白-S的作用，即使抗镰状化作用与高铁血红蛋白-S水平无关。这里,我们在SCD小鼠模型中研究了亚硝酸盐对HbS聚合和高铁血红蛋白形成的影响。体外，浓度高于生理浓度（>1μM），亚硝酸盐增加了脱氧HbS聚合的延迟时间，与高铁血红蛋白-S的形成无关，其仅在高得多的浓度(>300μM)下发生。体外，较高的亚硝酸盐浓度氧化100％的正常血红蛋白A（HbA），但只有70%的HbS。己二酸二甲酯,一种防聚剂,将亚硝酸盐氧化的HbS分数提高到82%，表明聚合的HbS部分贡献了HbS的抗氧化部分。在低浓度（10μM-1mM），亚硝酸盐不会增加活性氧的形成，但在高浓度（10mM）下会降低镰状红细胞的活力。在SCD小鼠中,4周的亚硝酸盐给药在血浆和红细胞中的高铁血红蛋白或亚硝酸盐水平没有显著变化，然而,它进一步增加了白细胞增多。总的来说,这些数据表明,亚硝酸盐在超生理浓度下在体外具有抗聚合特性,白细胞增多在体内是一种潜在的亚硝酸盐毒性.因此,为了确定在体外观察到的亚硝酸盐的抗聚作用是否是在SCD患者中观察到的镰状化减少的基础，需要施用较高的亚硝酸盐剂量。
