Sickle cell disease (SCD) is characterized by reperfusion injury and chronic oxidative stress. Oxidative stress and hemolysis in SCD result in inactivation of nitric oxide (NO) and depleted arginine levels. We hypothesized that augmenting NO production by arginine supplementation will reduce oxidative stress in SCD. To this end, we measured the effect of arginine (5% in mouse chow) on NO metabolites (NOx), lipid peroxidation (LPO) and selected antioxidants in transgenic sickle mouse models. Untreated transgenic sickle (NY1DD) mice (expressing ~75% β S -globin of all β-globins; mild pathology) and knockout sickle (BERK) mice (expressing exclusively hemoglobin S; severe pathology) showed reduced NOx levels and significant increases in the liver LPO compared with C57BL mice, with BERK mice showing maximal LPO increase in accordance with the disease severity. This was accompanied by reduced activity of antioxidants (glutathione [GSH], total superoxide dismutase [SOD], catalase and glutathione peroxidase [GPx]). However, GSH levels in BERK were higher than in NY1DD mice indicating a protective response to greater oxidative stress. Importantly, dietary arginine significantly increased NOx levels, reduced LPO and increased antioxidants in both sickle mouse models. In contrast, L-NAME, a potent non-selective NOS inhibitor, worsened the oxidative stress in NY1DD mice. Thus, attenuating effect of arginine on oxidative stress in SCD mice suggests its potential application in the management of this disease.

In sickle cell disease, nitric oxide (NO) depletion by cell-free plasma hemoglobin and/or oxygen radicals is associated with arginine deficiency, impaired NO bioavailability, and chronic oxidative stress. In transgenic-knockout sickle (BERK) mice that express exclusively human alpha- and beta(S)-globins, reduced NO bioavailability is associated with induction of non-NO vasodilator enzyme, cyclooxygenase (COX)-2, and impaired NO-mediated vascular reactivity. We hypothesized that enhanced NO bioavailability in sickle mice will abate activity of non-NO vasodilators, improve vascular reactivity, decrease hemolysis, and reduce oxidative stress. Arginine treatment of BERK mice (5% arginine in mouse chow for 15 days) significantly reduced expression of non-NO vasodilators COX-2 and heme oxygenase-1. The decreased COX-2 expression resulted in reduced prostaglandin E(2) (PGE(2)) levels. The reduced expression of non-NO vasodilators was associated with significantly decreased arteriolar dilation and markedly improved NO-mediated vascular reactivity. Arginine markedly decreased hemolysis and oxidative stress and enhanced NO bioavailability. Importantly, arteriolar diameter response to a NO donor (sodium nitroprusside) was strongly correlated with hemolytic rate (and nitrotyrosine formation), suggesting that the improved microvascular function was a response to reduced hemolysis. These results provide a strong rationale for therapeutic use of arginine in sickle cell disease and other hemolytic diseases.

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Dasgupta T, Fabry ME, Kaul DK. Antisickling property of fetal hemoglobin enhances nitric oxide bioavailability and ameliorates organ oxidative stress in transgenic-knockout sickle mice. Am J Physiol Regul Integr Comp Physiol 298: R394 -R402, 2010. First published December 9, 2009 doi:10.1152/ajpregu.00611.2009.-In sickle cell disease (SCD), the events originating from hemoglobin S polymerization and intravascular sickling lead to reperfusion injury, hemolysis, decreased nitric oxide (NO) bioavailability, and oxidative stress. Oxidative stress is implicated as a contributing factor to multiple organ damage in SCD. We hypothesize that inhibition of sickling by genetic manipulation to enhance antisickling fetal hemoglobin (HbF) expression will have an ameliorating effect on oxidative stress by decreasing intravascular sickling and hemolysis and enhancing NO bioavailability. We tested this hypothesis in BERK (Berkeley) mice expressing exclusively human ␣-and ␤ S -globins and varying levels of HbF, i.e., BERK (Ͻ1% HbF), BERK␥M (20% HbF) and BERK␥H (40% HbF). Intravascular sickling showed a distinct decrease with increased expression of HbF, which was accompanied by decreased hemolysis and increased NO metabolites (NOx) levels. Consistent with decreased intravascular sickling and increased NO bioavailability, BERK␥M and BERK␥H mice showed markedly decreased lipid peroxidation accompanied by increased activity/levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and reduced glutathione (GSH)] in the muscle, kidney, and liver compared with BERK mice (P Ͻ 0.05-0.0001). NOx levels showed a strong inverse correlation with hemolytic rate and oxidative stress. Decreased oxidative stress in the presence of elevated HbF levels led to an anti-inflammatory effect as evidenced by decreased peripheral leukocyte counts. These results show that the protective effect of HbF is mediated primarily by decreasing intravascular sickling resulting in decreased oxidative stress and increased NO bioavailability.sickle cell disease; hemolysis; inflammation; reperfusion; multipleorgan damage CENTRAL TO THE VASO-OCCLUSIVE pathophysiology of sickle cell disease (SCD) is polymerization of hemoglobin S (HbS) and intravascular sickling under deoxygenated conditions, the consequences of which can lead to vaso-occlusion, reperfusion injury, hemolysis, decreased nitric oxide (NO) bioavailability, and oxidative stress (15,22,39,46,48). Oxidative stress in SCD results from hypoxia-reperfusion (vaso-occlusive events) and inactivation of anti-inflammatory nitric oxide (NO) by oxidants and plasma heme (hemolysis). Chronic oxidative stress is implicated as a critical factor in endothelial activation, inflammatory effects (e.g., higher peripheral leukocyte counts), and multiple organ damage in SCD (22).Because intravascular sickling is considered etiologic to the pathophysiology of SCD, attempts have been made to employ antisickling strategies to alleviate pathophysiology of this disease. In view of the antisickling p...

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