Erythrocyte Glutathione Depletion Is Associated with Severity of Anemia and Pulmonary Hypertension in Patients with Sickle Cell Disease.
(2006)
Journal - ASH Annual Meeting Abstracts
Abstract :
Abstract
Background: Glutathione (GSH) is the most abundant intracellularnon-protein thiol and is an anti-oxidant present in high millimolarconcentration in erythrocytes. Additionally, GSH plays an importantrole in signal transduction, gene expression, apoptosis, proteinglutathionylation, nitric oxide metabolism, and is the principalthiol redox buffer in erythrocytes. We hypothesized that, insickle cell disease (SCD), GSH deficiency contributes to oxidativestress and pre-disposes the sickle erythrocyte to hemolysis.
Methods: A sensitive liquid chromatography coupled to tandemmass spectrometric technique was used to examine the availabilityof GSH and its precursors (glutamate, cysteine, glycine andglutamine) in plasma and within the erythrocytes of 25 patientswith SCD and 7 ethnically-matched normal volunteers. Given theassociation of hemolysis with pulmonary artery hypertension(PAH) in this population, tricuspid regurgitant jet velocity(TRV) by Doppler echocardiography was also determined in allpatients.
Results: Despite an increase in the amino acid precursors ofGSH in the plasma of SCD patients compared with controls, totalplasma GSH was significantly decreased (2.8 ± 1.5 vs.4.1 ± 2.1 mM, p<0.05, SCD vs. controls). Additionally,a striking 61% depletion of GSH was found within the erythrocytesof SCD patients compared with normal volunteers (308.1 ±112 vs. 790.8 ± 292 mM, p<0.0001). Erythrocyte glutamineconcentrations were also decreased in SCD patients comparedwith controls (404.6 ± 252 vs. 1061 ± 277 mM,p<0.0001), while cysteine, glycine and glutamate levels trendhigher. This indicates a potential loss of GSH synthesis capacityin SCD patients. The degree of erythrocyte GSH depletion correlatedstrongly with TRV (r = –0.64, p<0.0001), which is ofsignificant clinical interest given the increased mortalityrisk of PAH in patients with SCD. While erythrocyte glutamineconcentration also correlated inversely with TRV (r = –0.59,p < 0.001), erythrocyte glutamate and cysteine levels aswell as plasma GSH and its precursors were not associated withTRV. Erythrocyte GSH depletion strongly associated with hematocrit(r = 0.60, p<0.001), suggesting a link to chronic anemia.Plasma arginase concentration strongly correlated with plasma-freeHb (r=0.83, p<0.0001) and inversely correlated with erythrocyteGSH (r=–0.41, p=0.02), linking lower erythrocyte GSH levelsto increased red cell derived plasma arginase and thereforepotentially an increased risk of mortality in SCD & PAHas we have previously reported (Morris et al, JAMA 2005).
Conclusions: Lower levels of erythrocyte GSH may contributeto the development of PAH possibly by exacerbating oxidativestress and triggering hemolysis, resulting in release of erythrocytearginase and dysregulation of arginine and NO metabolism. Therole of GSH metabolism in the pathophysiology of SCD and itslink to PAH warrants further investigation.Footnotes* Corresponding authorDisclosure: No relevant conflicts of interest to declare.