The effect of xanthine oxidase and hypoxanthine on the permeability of red cells from patients with sickle cell anemia.
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Al Balushi, H., Rees, D. C., Brewin, J. N., Hannemann, A., & Gibson, J. (2018). The effect of xanthine oxidase and hypoxanthine on the permeability of red cells from patients with sickle cell anemia.. Physiological reports, 6 (5)https://doi.org/10.14814/phy2.13626
Red cells from patients with sickle cell anaemia (SCA) are under greater oxidative challenge than those from normal individuals. We postulated that oxidants generated by xanthine oxidase (XO) and hypoxanthine (HO) contribute to the pathogenesis of SCA through altering solute permeability. Sickling, activities of the main red cell dehydration pathways (Psickle, Gardos channel and KCl cotransporter) and cell volume were measured at 100, 30 and 0 mmHg O2, together with deoxygenation-induced non-electrolyte haemolysis. Unexpectedly, XO / HO mixtures had mainly inhibitory effects on sickling, Psickle and Gardos channel activities, whilst KCC activity and non-electrolyte haemolysis were increased. Gardos channel activity was significantly elevated in red cells pharmacologically loaded with Ca2+ using the ionophore A23187, consistent with an effect on the transport system per se as well as via Ca2+ entry likely via the Psickle pathway. KCC activity is controlled by several pairs of conjugate protein kinases and phosphatases. Its activity, however, was also stimulated by XO / HO mixtures in red cells pretreated with N-ethylmaleimide (NEM), which is thought to prevent regulation via changes in protein phosphorylation, suggesting that the oxidants formed could also have direct effects on this transporter. In the presence of XO / HO, red cell volume was better maintained in deoxygenated red cells. Overall, the most notable effect of XO / HO mixtures was an increase in red cell fragility. These findings increase our understanding of the effects of oxidative challenge in SCA patients and are relevant to the behaviour of red cells in vivo.
Erythrocytes, Cell Membrane, Humans, Anemia, Sickle Cell, Oxygen, Calcium, Reactive Oxygen Species, Ethylmaleimide, Hypoxanthine, Xanthine Oxidase, Symporters, Cell Size, Permeability
British Heart Foundation (PG/15/118/31966)
External DOI: https://doi.org/10.14814/phy2.13626
This record's URL: https://www.repository.cam.ac.uk/handle/1810/274766