Molecular Characterization of Hypoxic Alveolar Epithelial Cells After Lung Contusion Indicates an Important Role for HIF-1α.
To understand the fate and regulation of hypoxic type II alveolar epithelial cells (AECs) after lung contusion (LC).



LC due to thoracic trauma is a major risk factor for the development of acute respiratory distress syndrome. AECs have recently been implicated as a primary driver of inflammation in LC. The main pathological consequence of LC is hypoxia, and a key mediator of adaptation to hypoxia is hypoxia-inducible factor (HIF)-1. We have recently published that HIF-1α is a major driver of acute inflammation after LC through type II AEC.



LC was induced in wild-type mice (C57BL/6), luciferase-based hypoxia reporter mice (ODD-Luc), and HIF-1α conditional knockout mice. The degree of hypoxia was assessed using hypoxyprobe and in vivo imaging system. The fate of hypoxic AEC was evaluated by luciferase dual staining with caspases-3 and Ki-67, terminal deoxynucleotidyl transferase dUTP nick end labeling, and flow cytometry with ApoStat. NLRP-3 expression was determined by western blot. Laser capture microdissection was used to isolate AECs in vivo, and collected RNA was analyzed by Q-PCR for HIF-related pathways.



Global hypoxia was present after LC, but hypoxic foci were not uniform. Hypoxic AECs preferentially undergo apoptosis. There were significant reductions in NLRP-3 in HIF-1α conditional knockout mice. The expression of proteins involved in HIF-related pathways and inflammasome activation were significantly increased in hypoxic AECs.



These are the first in vivo data to identify, isolate, and characterize hypoxic AECs. HIF-1α regulation through hypoxic AECs is critical to the initiation of acute inflammation after LC.
Department of Surgery, University of Michigan, Ann Arbor, MI.
Matthew A
MA
Sherman
Department of Surgery, University of Michigan, Ann Arbor, MI.
Madathilparambil V
MV
Suresh
Department of Surgery, University of Michigan, Ann Arbor, MI.
Vladislav A
VA
Dolgachev
Department of Surgery, University of Michigan, Ann Arbor, MI.
Lane K
LK
McCandless
Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI.
Xiang
X
Xue
Department of Surgery, University of Michigan, Ann Arbor, MI.
Li
L
Ziru
Department of Surgery, University of Michigan, Ann Arbor, MI.
David
D
Machado-Aranda
Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI.
Yatrik M
YM
Shah
Department of Surgery, University of Michigan, Ann Arbor, MI.
Krishnan
K
Raghavendran
D056809:Alveolar Epithelial Cells / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D003288:Contusions / Q000378:metabolism* / Q000503:physiopathology; D005434:Flow Cytometry; D000860:Hypoxia / Q000209:etiology* / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007249:Inflammation / Q000209:etiology / Q000378:metabolism; D055370:Lung Injury / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
D015415:Biomarkers; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit