Hypoxia regulates human lung fibroblast proliferation via p53-dependent and -independent pathways

Authors

Shiro Mizuno, University of Fukui
Herman J. Bogaard, Virginia Commonwealth University
Norbert F. Voelkel, Virginia Commonwealth UniversityFollow
Yukihiro Umeda, University of Fukui
Maiko Kadowaki, University of Fukui
Shingo Ameshima, University of Fukui
Isamu Miyamori, University of Fukui
Takeshi Ishizaki, University of Fukui

Document Type

Article

Original Publication Date

2009

Journal/Book/Conference Title

Respiratory Research

Volume

2009

DOI of Original Publication

10.1186/1465-9921-10-17

Comments

Originally published at http://dx.doi.org/10.1186/1465-9921-10-17

Date of Submission

September 2014

Abstract

Background Hypoxia induces the proliferation of lung fibroblasts in vivo and in vitro. However, the subcellular interactions between hypoxia and expression of tumor suppressor p53 and cyclin-dependent kinase inhibitors p21 and p27 remain unclear.

Methods Normal human lung fibroblasts (NHLF) were cultured in a hypoxic chamber or exposed to desferroxamine (DFX). DNA synthesis was measured using bromodeoxyuridine incorporation, and expression of p53, p21 and p27 was measured using real-time RT-PCR and Western blot analysis.

Results DNA synthesis was increased by moderate hypoxia (2% oxygen) but was decreased by severe hypoxia (0.1% oxygen) and DFX. Moderate hypoxia decreased p21 synthesis without affecting p53 synthesis, whereas severe hypoxia and DFX increased synthesis of both p21 and p53. p27 protein expression was decreased by severe hypoxia and DFX. Gene silencing of p21 and p27 promoted DNA synthesis at ambient oxygen concentrations. p21 and p53 gene silencing lessened the decrease in DNA synthesis due to severe hypoxia or DFX exposure. p21 gene silencing prevented increased DNA synthesis in moderate hypoxia. p27 protein expression was significantly increased by p53 gene silencing, and was decreased by wild-type p53 gene transfection.

Conclusion These results indicate that in NHLF, severe hypoxia leads to cell cycle arrest via the p53-p21 pathway, but that moderate hypoxia enhances cell proliferation via the p21 pathway in a p53-independent manner. In addition, our results suggest that p27 may be involved in compensating for p53 in cultured NHLF proliferation.

Rights

© 2009 Mizuno et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Is Part Of

VCU Internal Medicine Publications