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Sakamoto K, Hashimoto N, Kondoh Y, Imaizumi K, Aoyama D, Kohnoh T, Kusunose M, Kimura M, Kawabe T, Taniguchi H, Hasegawa Y. Differential modulation of surfactant protein D under acute and persistent hypoxia in acute lung injury. Am J Physiol Lung Cell Mol Physiol 2012; 303:L43-53. [DOI: 10.1152/ajplung.00061.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxia contributes to the development of fibrosis with epithelial-mesenchymal transition (EMT) via stimulation of hypoxia-inducible factor 1α (HIF-1α) and de novo twist expression. Although hypoxemia is associated with increasing levels of surfactant protein D (SP-D) in acute lung injury (ALI), the longitudinal effects of hypoxia on SP-D expression in lung tissue injury/fibrosis have not been fully evaluated. Here, the involvement of hypoxia and SP-D modulation was evaluated in a model of bleomycin-induced lung injury. We also investigated the molecular mechanisms by which hypoxia might modulate SP-D expression in alveolar cells, by using a doxycycline (Dox)-dependent HIF-1α expression system. Tissue hypoxia and altered SP-D levels were present in bleomycin-induced fibrotic lesions. Acute hypoxia induced SP-D expression, supported by the finding that Dox-induced expression of HIF-1α increased SP-D expression. In contrast, persistent hypoxia repressed SP-D expression coupled with an EMT phenotype and twist expression. Long-term expression of HIF-1α caused SP-D repression with twist expression. Ectopic twist expression repressed SP-D expression. The longitudinal observation of hypoxia and SP-D levels in ALI in vivo was supported by the finding that HIF-1α expression stabilized by acute hypoxia induced increasing SP-D expression in alveolar cells, whereas persistent hypoxia induced de novo twist expression in these cells, causing repression of SP-D and acquisition of an EMT phenotype. Thus this is the first study to demonstrate the molecular mechanisms, in which SP-D expression under acute and persistent hypoxia in acute lung injury might be differentially modulated by stabilized HIF-1α expression and de novo twist expression.
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Affiliation(s)
- Koji Sakamoto
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Naozumi Hashimoto
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yasuhiro Kondoh
- Division of Respiratory Medicine and Allergy, Tosei General Hospital, Seto, Japan
| | - Kazuyoshi Imaizumi
- Department of Respiratory Medicine and Allergy, Fujita Health University, Toyoake, Japan; and
| | - Daisuke Aoyama
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Takashi Kohnoh
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Masaaki Kusunose
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Motohiro Kimura
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tsutomu Kawabe
- Department of Medical Technology, Nagoya University Graduate School of Health Science, Nagoya, Japan
| | - Hiroyuki Taniguchi
- Division of Respiratory Medicine and Allergy, Tosei General Hospital, Seto, Japan
| | - Yoshinori Hasegawa
- Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
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