title: Erythropoietin inhibits HIF-1α expression via upregulation of PHD-2 transcription and translation in an in vitro model of hypoxia-ischemia.
abstract: Hypoxia inducible factor (HIF)-1α is the central transcriptional factor for the regulation of oxygen-associated genes in response to hypoxia. Erythropoietin (EPO), a hematopoietic growth factor, increases oxygen availability during hypoxia/ischemia and is associated with neuroprotection following hypoxia-ischemia in laboratory models of stroke. However, EPO has failed to translate in a clinical setting. Thus, it is critical to elucidate the key players in EPO-induced neuroprotection. Our preliminary studies have shown that EPO, as a downstream gene of HIF, inhibits HIF-1α in a dose-dependent manner in an in vitro model of hypoxia-ischemia. This study is designed to elucidate the primary mediator of EPO-induced HIF-1α inhibition and subsequent cell survival/neuroprotection. Oxygen and glucose deprivation (OGD) of nerve growth factor-differentiated rat pheochromocytoma (PC-12) cells were used to model hypoxia-ischemia in an in vitro environment. The profile of HIF-1α, HIF-2α and prolyl hydroxylase domain 2 (PHD-2) expression; HIF-1α and prolyl hydroxylase (PHD-2) mRNA levels; matrix metalloproteinase (MMP)-9; and cell death was evaluated in the presence and absence of either EPO or PHD-2 inhibitor during OGD. Our findings showed that EPO treatment resulted in an increase in PHD-2 transcription and translation, inhibition of HIF-1α expression, reactive oxygen species formation, and MMP-9 activity, resulting in increased cell survival after OGD. We also observed that EPO-induced cell survival/neuroprotection was reversed by siRNA silencing of PHD-2. This led to the conclusion that PHD-2 is a key mediator of EPO-induced HIF-1α inhibition and subsequent neuroprotection in an in vitro model of hypoxia-ischemia.
authors: Department of Microbiology and Molecular Genetics, Loma Linda University School of Medicine, Loma Linda, CA, 92350, USA.
authors: Rhonda
authors: R
authors: Souvenir
authors: Jerry J
authors: JJ
authors: Flores
authors: Robert P
authors: RP
authors: Ostrowski
authors: Anatol
authors: A
authors: Manaenko
authors: Kamil
authors: K
authors: Duris
authors: Jiping
authors: J
authors: Tang
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004921:Erythropoietin / Q000494:pharmacology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D016716:PC12 Cells; D011393:Procollagen-Proline Dioxygenase / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation
chemical_list: C554270:EPO protein, human; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; D004921:Erythropoietin; D011393:Procollagen-Proline Dioxygenase; C580731:Egln1 protein, rat; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases