The expression of epidermal growth factor-like domain 7 regulated by oxygen tension via hypoxia inducible factor (HIF)-1α activity

Abstract

Objective. Hypoxia inducible factor-1α (HIF-1α) regulates many genes involved in angiogenesis during embryonic development. Epidermal growth factor-like domain 7 (Egfl7) is a specific marker for human arterial endothelial cells that are in an activated state of proliferation, migration, and remodeling. This study evaluates the intricate relationship between HIF-1α and Egfl7 under both hyperoxia and hypoxia states. Methods. The neonatal mice were exposed to either hyperoxia or hypoxia in order to detect the pulmonary and cardiac Egfl7 messenger RNA (mRNA) or protein expression regulated by oxygen tension in vivo by reverse transcriptase polymerase chain reaction or immunohistochemistry staining. Egfl7 expression in HIF-1α null pulmonary endothelial cells in hypoxia conditions and effects of overexpression or knockdown of HIF-1α on Egfl7 expression in human umbilical vein endothelial cells would be clarified in vitro by reverse transcriptase polymerase chain reaction and Western blot, respectively. Results. Hyperoxia exposure significantly reduced Egfl7 expression in neonatal mice lungs by 36% compared with age-matched normoxia control mice (P < 0.05, n = 6). The pulmonary Egfl7 transcription levels were increased by 1.7- and 1.9-fold in 24 hours and by day 8 in hypoxia groups compared with the normoxia control values (P < 0.05, n = 6). The cardiac Egfl7 mRNA expression was significantly increased by 4.5-fold in the day 8 group compared with the normoxia control values (P < 0.05, n = 6). The expression of Egfl7 decreased significantly in the HIF-1α^–/– endothelial cells (ECs), which was only 26% of wild-type HIF-1α^+/+ ECs (P < 0.05, n = 3). Hypoxia caused a mild but significant increase of Egfl7 expression in HIF-1α^+/+ ECs (P < 0.05). In vitro, overexpression of HIF-1α enhanced Egfl7 expression, whereas knockdown of HIF-1α reduced Egfl7 expression. Conclusions. Overexpression of HIF-1α enhanced Egfl7 expression, whereas knockdown of HIF-1α reduced Egfl7 expression. Egfl7 could be a HIF-1α responsive gene regulated by oxygen tension.

Keywords :

• Hyperoxia
• hypoxia
• HIF-1α
• Egfl7

Acknowledgments

This work was supported by the Seed Fund (grant S2013010008) and the Youth Fund (grant Y2013010030) of the Second Hospital of Shandong University, the Natural Scientific Fund (Y2006C59), excellent young-middled scientist research award fund of Shandong Province (2007BSBS 03046) and the Traditional Chinese Medicine of Shandong Province in China (2011-209). This work was also supported by The scientific and technologic development programme of Shandong province (NO. 2013G0021813), and the Ji’nan City College Institute Independent Innovation (NO. 201401218).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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