Decreased erythrocyte nucleoside transport and hENT1 transporter expression in glucose 6-phosphate dehydrogenase deficiency

Abstract

BackgroundGlucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with erythrocyte sensitivity to oxidative damage and hemolytic crises. In β-thalassemia major, where hemoglobin instability imposes oxidative stress, erythrocytes show reduced hENT1 nucleoside transporter expression and decreased nucleoside uptake. This study investigated hENT1 expression and nucleoside transport in G6PD-deficient erythrocytes to determine if decreased hENT1 activity might be a contributory feature in the variable pathology of this enzymopathy.MethodsUptake of 3H-uridine was measured at room temperature using an inhibitor-oil stop protocol and 5-s incubations. Erythrocyte membranes were analyzed by SDS-PAGE and nucleoside (hENT1), glucose (GLUT-1), and anion exchange (Band 3) transporter polypeptides quantitated on immunoblots.ResultsIn G6PD-deficient cells, uridine uptake (mean 8.18, 95 % CI 5.6–10.7 vs controls mean 12.35, 95 % CI 9.2–15.5, pmol uridine/gHb/min; P = 0.031) and expression of hENT1 (mean 50.4 %, 95 % CI 38.1–62.7 %, arbitrary units n = 11 vs controls mean 95.23 %, 95 % CI 88.38–102.1 % arbitrary units, n = 8; P < 0.001) were significantly lower; expression of GLUT-1 (mean 106.9 %, vs control mean 99.75 %; P = 0.308) and Band 3 polypeptides (mean 100.1 %, vs control mean 102.84 %; P = 0.329) were unchanged.ConclusionsNucleoside transporter activity in human erythrocytes sustains intracellular purine nucleotide levels and assists in control of plasma adenosine levels; decreased hENT1 expression and activity in G6PD-deficiency could affect red metabolism and influence a wide spectrum of responses mediated by adenosine receptors.

Erythrocyte type 1 equilibrative nucleoside transporter expression in sickle cell disease and sickle cell trait

“…Given the consequences of adenosine A2B‐receptor signalling on HbS polymerisation and RBC sickling, 5 a possible role for erythrocyte ENT1 transporter regulation in SCD pathophysiology remains to be investigated. A limitation of our present study is that measurements of erythrocyte ENT1 were based on immunoblots and flow cytometry, not on nucleoside uptake, although several studies have reported a good concordance of ENT1 expression and nucleoside transport 14–16 …”

“…A limitation of our present study is that measurements of erythrocyte ENT1 were based on immunoblots and flow cytometry, not on nucleoside uptake, although several studies have reported a good concordance of ENT1 expression and nucleoside transport. [14][15][16] The moderate but significant correlation of ENT1 expression levels in CD71 + reticulocytes and CD71 − mature RBC indicates that the variable erythrocyte ENT1 expression in patients with SCD is likely to be determined at least in part by its expression level in precursor cells. 6 In the mouse, erythroid expression of the Slc29a1 gene has been shown to be part of a complex regulatory network linked to adenosine homeostasis that involves its opposite regulation by the GATA-binding protein 2 (GATA2) and GATA1 transcription factors.…”

“…In β-thalassaemia major and deficiency of glucose-6-phosphate dehydrogenase (G6PD), two other prevalent polymorphic erythrocyte disorders, causing mild to moderate anaemia, expression of erythrocyte ENT1 transporters has been also shown to be significantly reduced compared with normal controls. 14,15 Increased intrinsic erythrocyte oxidative stress is a characteristic shared by G6PD deficiency and haemoglobinopathies such as thalassaemia that confer partial protection against P. falciparum malaria. A combination of oxidative stress and limited purine availability could produce a synergistic effect on parasite growth and replication.…”

“…Whether reduced expression of erythrocyte ENT1 contributes to the mechanism of SCT resistance to P. falciparum parasite infection remains to be investigated. In β‐thalassaemia major and deficiency of glucose‐6‐phosphate dehydrogenase (G6PD), two other prevalent polymorphic erythrocyte disorders, causing mild to moderate anaemia, expression of erythrocyte ENT1 transporters has been also shown to be significantly reduced compared with normal controls 14,15 . Increased intrinsic erythrocyte oxidative stress is a characteristic shared by G6PD deficiency and haemoglobinopathies such as thalassaemia that confer partial protection against P. falciparum malaria.…”

Redox Status, Procoagulant Activity, and Metabolome of Fresh Frozen Plasma in Glucose 6-Phosphate Dehydrogenase Deficiency

“…Extracellular adenosine signaling serves regulatory functions in inflammation, in acute lung injury ( 48 ) and in the O 2 delivery ability of red cell targets through boosting the production of 2,3-BPG ( 46 ). Nucleoside transporters assist in the control of plasma adenosine levels, and notably, decreased nucleoside transporter hENT1 [that also mediates hypoxanthine transport ( 49 )] expression and activity was detected in G6PD − RBCs ( 50 ). In G6PD − FFP, adenosine was correlated with red-cell vesiculation, lipid peroxidation, hemolysis, DAG, oxidized glutathione, and uric acid/allantoate levels, suggesting more influential effects compared with the control FFP and a second level of intercellular signaling potential.…”