Transgenic overexpression of granulocyte macrophage-colony stimulating factor in the lung prevents hyperoxic lung injury.
Granulocyte macrophage-colony stimulating factor (GM-CSF) plays an important role in pulmonary homeostasis, with effects on both alveolar macrophages and alveolar epithelial cells. We hypothesized that overexpression of GM-CSF in the lung would protect mice from hyperoxic lung injury by limiting alveolar epithelial cell injury. Wild-type C57BL/6 mice and mutant mice in which GM-CSF was overexpressed in the lung under control of the SP-C promoter (SP-C-GM mice) were placed in >95% oxygen. Within 6 days, 100% of the wild-type mice had died, while 70% of the SP-C-GM mice remained alive after 10 days in hyperoxia. Histological assessment of the lungs at day 4 revealed less disruption of the alveolar wall in SP-C-GM mice compared to wild-type mice. The concentration of albumin in bronchoalveolar lavage fluid after 4 days in hyperoxia was significantly lower in SP-C-GM mice than in wild-type mice, indicating preservation of alveolar epithelial barrier properties in the SP-C-GM mice. Alveolar fluid clearance was preserved in SP-C-GM mice in hyperoxia, but decreased significantly in hyperoxia-exposed wild-type mice. Staining of lung tissue for caspase 3 demonstrated increased apoptosis in alveolar wall cells in wild-type mice in hyperoxia compared to mice in room air. In contrast, SP-C-GM mice exposed to hyperoxia demonstrated only modest increase in alveolar wall apoptosis compared to room air. Systemic treatment with GM-CSF (9 micro g/kg/day) during 4 days of hyperoxic exposure resulted in decreased apoptosis in the lungs compared to placebo. In studies using isolated murine type II alveolar epithelial cells, treatment with GM-CSF greatly reduced apoptosis in response to suspension culture. In conclusion, overexpression of GM-CSF enhances survival of mice in hyperoxia; this effect may be explained by preservation of alveolar epithelial barrier function and fluid clearance, at least in part because of reduction in hyperoxia-induced apoptosis of cells in the alveolar wall.
Paine
Robert
R
Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, Michigan 48105, USA. rpaine@umich.edu
Wilcoxen
Steven E
SE
Morris
Susan B
SB
Sartori
Claudio
C
Baleeiro
Carlos E O
CE
Matthay
Michael A
MA
Christensen
Paul J
PJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism* / Q000494:pharmacology; D018496:Hyperoxia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008171:Lung Diseases / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D011994:Recombinant Proteins / Q000494:pharmacology; D012709:Serum Albumin / Q000378:metabolism; D016019:Survival Analysis; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D011994:Recombinant Proteins; D012709:Serum Albumin; D042461:Vascular Endothelial Growth Factor A; D016178:Granulocyte-Macrophage Colony-Stimulating Factor