Intermittent hypoxia degrades HIF-2α via calpains resulting in oxidative stress: Implications for recurrent apnea-induced morbidities

Jayasri Nanduri, Ning Wang, Guoxiang Yuan, Shakil A. Khan, Dangjai Souvannakitti, Ying Jie Peng, Ganesh K. Kumar, Joseph A. Garcia, Nanduri R. Prabhakar

Research output: Contribution to journalArticle

113 Scopus citations

Abstract

Intermittent hypoxia (IH) occurs in many pathological conditions including recurrent apneas. Hypoxia-inducible factors (HIFs) 1 and 2 mediate transcriptional responses to low O2. A previous study showed that HIF-1 mediates some of the IH-evoked physiological responses. Because HIF-2α is an orthologue of HIF-1α, we examined the effects of IH on HIF-2α, the O2-regulated subunit expression, in pheochromocytoma 12 cell cultures. In contrast to the up-regulation of HIF-1α, HIF-2α was down-regulated by IH. Similar down-regulation of HIF-2α was also seen in carotid bodies and adrenal medullae from IH-exposed rats. Inhibitors of calpain proteases (ALLM, ALLN) prevented IH-evoked degradation of HIF-2α whereas inhibitors of prolyl hydroxylases or proteosome were ineffective. IH activated calpain proteases and down-regulated the endogenous calpain inhibitor calpastatin. IH-evoked HIF-2α degradation led to inhibition of SOD2 transcription, resulting in oxidative stress. Over-expression of transcriptionally active HIF-2α prevented IH-evoked oxidative stress and restored SOD2 activity. Systemic treatment of IH-exposed rats with ALLM rescued HIF-2α degradation and restored SOD2 activity, thereby preventing oxidative stress and hypertension. These observations demonstrate that, unlike continuous hypoxia, IH leads to down-regulation of HIF-2α via a calpain-dependent signaling pathway and results in oxidative stress as well as autonomic morbidities.

Original languageEnglish (US)
Pages (from-to)1199-1204
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number4
DOIs
StatePublished - Jan 27 2009

Keywords

  • Calcium signaling
  • Hypoxia inducible factors

ASJC Scopus subject areas

  • General

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