title: GM-CSF provides autocrine protection for murine alveolar epithelial cells from oxidant-induced mitochondrial injury.
abstract: Exposure of mice to hyperoxia induces alveolar epithelial cell (AEC) injury, acute lung injury and death. Overexpression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the lung protects against these effects, although the mechanisms are not yet clear. Hyperoxia induces cellular injury via effects on mitochondrial integrity, associated with induction of proapoptotic members of the Bcl-2 family. We hypothesized that GM-CSF protects AEC through effects on mitochondrial integrity. MLE-12 cells (a murine type II cell line) and primary murine type II AEC were subjected to oxidative stress by exposure to 80% oxygen and by exposure to H(2)O(2). Exposure to H(2)O(2) induced cytochrome c release and decreased mitochondrial reductase activity in MLE-12 cells. Incubation with GM-CSF significantly attenuated these effects. Protection induced by GM-CSF was associated with Akt activation. GM-CSF treatment also resulted in increased expression of the antiapoptotic Bcl-2 family member, Mcl-1. Primary murine AEC were significantly more tolerant of oxidative stress than MLE-12 cells. In contrast to MLE-12 cells, primary AEC expressed significant GM-CSF at baseline and demonstrated constitutive activation of Akt and increased baseline expression of Mcl-1. Treatment with exogenous GM-CSF further increased Akt activation and Mcl-1 expression in primary AEC. Conversely, suppression of AEC GM-CSF expression by use of GM-CSF-specific small interfering RNA resulted in decreased tolerance of oxidative stress, Furthermore, silencing of Mcl-1 prevented GM-CSF-induced protection. We conclude that GM-CSF protects alveolar epithelial cells against oxidative stress-induced mitochondrial injury via the Akt pathway and its downstream components, including Mcl-1. Epithelial cell-derived GM-CSF may contribute to intrinsic defense mechanisms limiting lung injury.
authors.affiliation: Division of Respiratory, Critical Care and Occupational Pulmonary Medicine, Univ. of Utah School of Medicine, Salt Lake City, UT 84132, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Sturrock
authors.forename: Elfateh
authors.initials: E
authors.lastname: Seedahmed
authors.forename: Mustafa
authors.initials: M
authors.lastname: Mir-Kasimov
authors.forename: Jonathan
authors.initials: J
authors.lastname: Boltax
authors.forename: Michael L
authors.initials: ML
authors.lastname: McManus
authors.forename: Robert
authors.initials: R
authors.lastname: Paine
mesh_terms: D000818:Animals; D019898:Autocrine Communication; D002478:Cells, Cultured; D019610:Cytoprotection; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D038341:Glycogen Synthase Kinases / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology*; D034622:RNA Interference
chemical_list: C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006861:Hydrogen Peroxide; D038341:Glycogen Synthase Kinases; D051057:Proto-Oncogene Proteins c-akt