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.

Keratinocyte Growth Factor Administration Attenuates Murine Pulmonary Mycobacterium tuberculosis Infection through Granulocyte-Macrophage Colony-stimulating Factor (GM-CSF)-dependent Macrophage Activation and Phagolysosome Fusion

“…7) and phagosome-lysosome fusion (Fig. 8) are important mechanisms by which KGF enhances clearance of M. tuberculosis, with the caveat that substantial differences in nitric oxide production exist between human and murine macrophages (34) and between primary cells and cell lines (35). Phagolysosome fusion was enhanced in AMs isolated from KGF-treated but not PBS-treated mice and was inhibited in AMs infected with M. tuberculosis ex vivo by the addition of anti-GM-CSF antibody (Fig.…”

Superoxide Dismutase 3 Dysregulation in a Murine Model of Neonatal Lung Injury

“…Although primary AEII cells would be a more accurate model to study O2 in vitro, the yield is often low during the isolation process, thus making analyzing various readouts difficult. However, there have been a few studies that have isolated murine primary AE II cells (40,49,50) with varying O2 exposure times between 24 to 48 hours. Although most described the overall cell survival and proliferation in such settings, none commented on the antioxidant profile associated with their findings.…”

Influenza virus-induced lung injury: pathogenesis and implications for treatment

“…Monocyte-derived alveolar macrophages were found to secrete hepatocyte growth factor (HGF), a potent lung epithelial cell mitogen, which induced proliferation of type II alveolar epithelial cells in a mouse IAV infection model [154,155]. Tissue resident alveolar macrophages promote the regeneration of type II alveolar epithelial cells after endotoxin-induced lung injury via a pathway that requires TNF-α and GM-CSF, another proliferative and anti-apoptotic factor for the lung epithelium [156,157]. There is evidence this same pathway is active during the resolution of IAV infection [113].…”