https://orcid.org/0000-0001-6033-2945
KEY POINTS:
The activity of the key glycolytic enzyme pyruvate kinase is relatively decreased in hereditary spherocytosis red blood cells
Ex vivo treatment with pyruvate kinase activators lead to increased ATP levels and an improved hydration state
ABSTRACT
Hereditary spherocytosis (HS) is a hereditary hemolytic anemia with limited treatment options. A relative decrease in activity of pyruvate kinase (PK), an essential glycolytic enzyme in red blood cells, has been described in patients with HS. Due to their dependence on glycolysis, PK activation therapy could therefore potentially improve red cell health in HS. The aim of this study was to evaluate PK activity in HS red blood cells, and to investigate the effect of two PK activators (mitapivat and tebapivat). Blood samples from eighteen non-transfusion-dependent HS patients (splenectomized and non-splenectomized) were analyzed. Our results confirmed impaired glycolysis in HS at baseline, indicated by a relatively decreased PK activity (PK to hexokinase ratio: 7.6 in HS vs. 11.4 in controls). PK activity (increase >50%) and ATP levels (increase >44%) improved upon ex vivo treatment with mitapivat and tebapivat. Metabolomics showed various metabolic alterations upon treatment. Furthermore, the hydration state of the cells improved (Ohyper increase >2.1%). No improvements were found in deformability, intracellular calcium and cellular adhesion to laminin. When comparing splenectomized patients to non-splenectomized patients, we found that PK thermostability in non-splenectomized patients was decreased more than in splenectomized patients. Following this, PK activator therapy improved PK thermostability to a greater extent in red blood cells from splenectomized patients, which appears to relate to the degree of reticulocytosis. Overall, we demonstrated that PK activation improves the metabolic and cellular properties of HS red blood cells ex vivo, supporting the rationale for further evaluation of PK activation in HS.
