Oral Arginine Increases Erythrocyte Glutathione Levels in Sickle Cell Disease: Implications for Pulmonary Hypertension.

Abstract

Background: Pulmonary hypertension (PHT) is a strong predictor of mortality in sickle cell disease (SCD), and is associated with dysregulation of the arginine-nitric oxide (NO) pathway. This is in part the consequence of hemolysis, as erythrocyte release of plasma hemoglobin consumes NO, while simultaneous release of arginase consumes arginine, the substrate for NO production. The arginase-induced shift towards ornithine metabolism may then contribute to the proliferative changes in the lungs and vasculature associated with PHT through excess production of proline and polyamines. Glutathione (GSH) depletion may contribute to oxidative stress and pre-dispose sickle erythrocytes to hemolysis. We have found that erythrocyte GSH depletion is associated with severity of anemia and PHT measured by Doppler echocardiography (Morris C, Klings E, unpublished data). Kaul et al recently demonstrated that arginine supplementation in BERK mice markedly reduced hemolysis (> 60% reduction in plasma hemoglobin), increased NO generation, and decreased COX-2 expression and PGE2 levels. Since short-term arginine therapy improves PHT in SCD, we hypothesize that oral arginine therapy may impact GSH, a key erythrocyte anti-oxidant.Methods: Total erythrocyte GSH was analyzed using a sensitive liquid chromatography coupled to tandem mass spectrometric technique before and after arginine therapy at 0.1 mg/kg three times daily for 1 month, followed by 0.2 mg/kg three times daily for two more months, in 8 SCD patients already on stable hydroxyurea therapy.Results: Erythrocyte GSH levels increased significantly in SCD patients after arginine therapy (Mean±SEM: 1222±150 vs. 1593± 144mM, p=0.03; Figure 1).Conclusion: Arginine therapy increases erythrocyte GSH levels, which may decrease oxidative stress and hemolysis. Therapies that attenuate hemolysis and oxidative stress will likely benefit PHT in SCD. [Display omitted]