Translational repression of HIF2α expression in mice with Chuvash polycythemia reverses polycythemia
Manik C. Ghosh, … , Michael A. Eckhaus, Tracey A. Rouault
Manik C. Ghosh, … , Michael A. Eckhaus, Tracey A. Rouault
Published April 2, 2018; First published February 26, 2018
Citation Information: J Clin Invest. 2018;128(4):1317-1325. https://doi.org/10.1172/JCI97684.
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Categories: Research Article Hematology

Translational repression of HIF2α expression in mice with Chuvash polycythemia reverses polycythemia

Abstract

Chuvash polycythemia is an inherited disease caused by a homozygous germline VHLR200W mutation, which leads to impaired degradation of HIF2α, elevated levels of serum erythropoietin, and erythrocytosis/polycythemia. This phenotype is recapitulated by a mouse model bearing a homozygous VhlR200W mutation. We previously showed that iron-regulatory protein 1–knockout (Irp1-knockout) mice developed erythrocytosis/polycythemia through translational derepression of Hif2α, suggesting that IRP1 could be a therapeutic target to treat Chuvash polycythemia. Here, we fed VhlR200W mice supplemented with Tempol, a small, stable nitroxide molecule and observed that Tempol decreased erythropoietin production, corrected splenomegaly, normalized hematocrit levels, and increased the lifespans of these mice. We attribute the reversal of erythrocytosis/polycythemia to translational repression of Hif2α expression by Tempol-mediated increases in the IRE-binding activity of Irp1, as reversal of polycythemia was abrogated in VhlR200W mice in which Irp1 was genetically ablated. Thus, a new approach to the treatment of patients with Chuvash polycythemia may include dietary supplementation of Tempol, which decreased Hif2α expression and markedly reduced life-threatening erythrocytosis/polycythemia in the VhlR200W mice.

Authors

Manik C. Ghosh, De-Liang Zhang, Hayden Ollivierre, Michael A. Eckhaus, Tracey A. Rouault

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Figure 3

Decreased erythropoiesis in Tempol-treated VhlR200W mice was the result of EPO downregulation caused by translational repression of HIF2α, which was a consequence of the increased HIF2α IRE–binding activity of Irp1.

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Decreased erythropoiesis in Tempol-treated VhlR200W mice was the result ...
(A) Serum EPO levels measured by ELISA were significantly increased in control diet–fed VhlR200W mice, and Tempol treatment reduced EPO levels in these mutant mice. (B) Immunoblot analyses of nuclear fractions from kidney lysates showed increased HIF2α protein levels in VhlR200W mice fed a control diet, and the HIF2α protein levels decreased when these mutant mice were fed a Tempol-supplemented diet. (C) Quantification of these HIF2α protein levels. (D) RNA mobility shift assays for ferritin IRE and HIF2α IRE binding of renal lysates in the absence or presence of β mercaptoethanol (ME) (which converts Irp1 from cytosolic aconitase to the IRE-binding form) showed that most of the IRE-binding activity was contributed by Irp1, and Tempol treatment significantly increased the IRE binding of Irp1 in VhlR200W mice. Quantifications of the Irp1-binding activities of (E) ferritin IRE and (F) HIF2α IRE. (G) Western blot analyses of kidney lysates revealed that Irp1 protein levels remained unchanged in Tempol diet–fed VhlR200W mice. Data in A, C, E, and F represent the mean ± SD. *P ≤ 0.05, **P ≤ 0.01, and ***P < 0.001, by unpaired, 2-tailed t test.