Fibrotic changes are initiated early in acute respiratory distress syndrome. This may involve overproliferation of alveolar type II cells. In an animal model of acute respiratory distress syndrome, we have shown that the administration of an adenoviral vector overexpressing the 70-kd heat shock protein (AdHSP) limited pathophysiological changes. We hypothesized that this improvement may be modulated, in part, by an early AdHSP-induced attenuation of alveolar type II cell proliferation.
Hadassah-Hebrew University and University of Pennsylvania animal laboratories.
Sprague-Dawley Rats (250 g).
Lung injury was induced in male Sprague-Dawley rats via cecal ligation and double puncture. At the time of cecal ligation and double puncture, we injected phosphate-buffered saline, AdHSP, or AdGFP (an adenoviral vector expressing the marker green fluorescent protein) into the trachea. Rats then received subcutaneous bromodeoxyuridine. In separate experiments, A549 cells were incubated with medium, AdHSP, or AdGFP. Some cells were also stimulated with tumor necrosis factor-α. After 48 hrs, cytosolic and nuclear proteins from rat lungs or cell cultures were isolated. These were subjected to immunoblotting, immunoprecipitation, electrophoretic mobility shift assay, fluorescent immunohistochemistry, and Northern blot analysis.
Alveolar type I cells were lost within 48 hrs of inducing acute respiratory distress syndrome. This was accompanied by alveolar type II cell proliferation. Treatment with AdHSP preserved alveolar type I cells and limited alveolar type II cell proliferation. Heat shock protein 70 prevented overexuberant cell division, in part, by inhibiting hyperphosphorylation of the regulatory retinoblastoma protein. This prevented retinoblastoma protein ubiquitination and degradation and, thus, stabilized the interaction of retinoblastoma protein with E2F1, a key cell division transcription factor.
Heat shock protein 70-induced attenuation of cell proliferation may be a useful strategy for limiting lung injury when treating acute respiratory distress syndrome if consistent in later time points.
From the Department of Anesthesiology and Critical Care Medicine, Goldyne Savad Institute of Gene Therapy, Hadassah-Hebrew University School of Medicine, Jerusalem, Israel (ZB, YGW); the Department of Anesthesiology and Critical Care, University of Pennsylvania School of Medicine, Philadelphia, PA (NR, CSD, YGW); and the Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland (PG).
Supported, in part, by grants from the Israel Science Foundation (586/03 to Dr. Weiss), the Israel Ministry of Health Chief Scientist (5304 to Dr. Weiss), the National Institutes of Health/National Institute of General Medical Sciences (GM059930 to Dr. Deutschman), and the Stavropoulos Sepsis Research Program (to Dr. Deutschman).
The authors have no known financial interest.
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