Hypoxia Pathway Proteins are Master Regulators of Erythropoiesis

The adrenal gland and its hormones regulate numerous fundamental biological processes; however, the impact of hypoxia signalling on its function remains scarcely understood. Here, we reveal that deficiency of HIF (Hypoxia Inducible Factors) prolyl hydroxylase domain protein-2 (PHD2) in the adrenal medulla of mice results in HIF2α-mediated reduction in phenylethanolamine N-methyltransferase (PNMT) expression, and consequent reduction in epinephrine synthesis. Concomitant loss of PHD2 in renal erythropoietin (EPO) producing cells stimulated HIF2α-driven EPO overproduction, excessive RBC formation (erythrocytosis) and systemic hypoglycaemia. Using mouse lines displaying only EPO-induced erythrocytosis or anaemia, we show that hypo- or hyperglycaemia is necessary and sufficient to respectively enhance or reduce exocytosis of epinephrine from the adrenal gland. Based on these results, we propose that the PHD2-HIF2α axis in the adrenal medulla and beyond regulates both synthesis and release of catecholamines, especially epinephrine. Our findings are also of great significance in view of the small molecule PHD inhibitors being tested in phase III global clinical development trials for use in renal anaemia patients.

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Hypoxia pathway proteins regulate the synthesis and release of epinephrine in the mouse adrenal gland

Watts¹,

Bechmann

Meneses

et al. 2020

Preprint

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Murine trypanosomiasis recapitulates transcriptomic features of acute kidney injury

Ogunsola,

Cooper,

Quintana

et al. 2024

Preprint

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The African trypanosome, Trypanosoma brucei, disseminates systemically in tissues of the infected host resulting in complex immunopathology. The kidneys which are important in the response to the anaemia characteristic of African trypanosomiasis, are prone to acute kidney injury (AKI) from multiple noxious stimuli. Little is known about the transcriptional responses of the kidney to trypanosome infection. To assess the tissue-specific response to infection with Trypanosoma brucei, we profiled the clinicopathologic and transcriptional responses of the kidney in BALB/C (susceptible) and C57BL/6 (tolerant) murine models, at early (7 dpi) and late (21 dpi) time points of infection. Trypanosomes in the renal interstitium, tubular necrosis and inflammation characterised early infection in both mouse strains. By late infection, we observed extensive tubular necrosis in the susceptible BALB/C but reparative tubular regeneration in the tolerant C57BL/6 mice. T.b. brucei infection resulted in significant increases in serum creatinine in both strains. Consistent with the clinicopathologic findings, RNA-seq detected both mouse strain- and time-dependent transcriptional responses in the kidney. These included perturbations in genes associated with solute/ion transport, upregulation of markers of tubular injury, hypoxia, glycolysis, and a profound inflammatory and immune response, mirroring the responses observed in other models of AKI. Differential tissue pathology at late time point is preceded by expansion of CD8+ T cells, profound expression of transcription factors and upregulation of anti-inflammatory pathways in C57BL/6 mice. Our findings demonstrate that experimental T. brucei infection-induced kidney injury (TIKI) is a model of AKI and may have clinical implications for Human African Trypanosomiasis cases, who currently are not routinely screened for markers of kidney function.

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Exploring the Leukemogenic Potential of GATA-1S, the Shorter Isoform of GATA-1: Novel Insights into Mechanisms Hampering Respiratory Chain Complex II Activity and Limiting Oxidative Phosphorylation Efficiency

et al. 2021

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GATA-1 is a key regulator of hematopoiesis. A balanced ratio of its two isoforms, GATA-1FL and GATA-1S, contributes to normal hematopoiesis, whereas aberrant expression of GATA-1S alters the differentiation/proliferation potential of hematopoietic precursors and represents a poor prognostic factor in myeloid leukemia. We previously reported that GATA-1S over-expression correlates with high levels of the succinate dehydrogenase subunit C (SDHC). Alternative splicing variants of the SDHC transcript are over-expressed in several tumors and act as potent dominant negative inhibitors of SDH activity. With this in mind, we investigated the levels of SDHC variants and the oxidative mitochondrial metabolism in myeloid leukemia K562 cells over-expressing GATA-1 isoforms. Over-expression of SDHC variants accompanied by decreased SDH complex II activity and oxidative phosphorylation (OXPHOS) efficiency was found associated only with GATA-1S. Given the tumor suppressor role of SDH and the effects of OXPHOS limitations in leukemogenesis, identification of a link between GATA-1S and impaired complex II activity unveils novel pro-leukemic mechanisms triggered by GATA-1S. Abnormal levels of GATA-1S and SDHC variants were also found in an acute myeloid leukemia patient, thus supporting in vitro results. A better understanding of these mechanisms can contribute to identify novel promising therapeutic targets in myeloid leukemia.

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Hypoxia Pathway Proteins are Master Regulators of Erythropoiesis

Cited by 15 publications

References 159 publications

Hypoxia pathway proteins regulate the synthesis and release of epinephrine in the mouse adrenal gland

Hypoxia pathway proteins regulate the synthesis and release of epinephrine in the mouse adrenal gland

Murine trypanosomiasis recapitulates transcriptomic features of acute kidney injury

Exploring the Leukemogenic Potential of GATA-1S, the Shorter Isoform of GATA-1: Novel Insights into Mechanisms Hampering Respiratory Chain Complex II Activity and Limiting Oxidative Phosphorylation Efficiency

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