Previous studies have shown that heat shock protein 72 (Hsp72) is found in the extracellular space (eHsp72) and that eHsp72 has potent immunomodulatory effects. However, whether eHsp72 is present in the distal air spaces and whether eHsp72 could modulate removal of alveolar edema is unknown. The first objective was to determine whether Hsp72 is released within air spaces and whether Hsp72 levels in pulmonary edema fluid would correlate with the capacity of the alveolar epithelium to remove alveolar edema fluid in patients with ALI/ARDS. Patients with hydrostatic edema served as controls. The second objective was to determine whether activation of the stress protein response (SPR) caused the release of Hsp72 into the extracellular space in vivo and in vitro and to determine whether SPR activation and/or eHsp72 itself would prevent the IL-1β-mediated inhibition of the vectorial fluid transport across alveolar type II cells. We found that eHsp72 was present in plasma and pulmonary edema fluid of ALI patients and that eHsp72 was significantly higher in pulmonary edema fluid from patients with preserved alveolar epithelial fluid clearance. Furthermore, SPR activation in vivo in mice and in vitro in lung endothelial, epithelial, and macrophage cells caused intracellular expression and extracellular release of Hsp72. Finally, SPR activation, but not eHsp72 itself, prevented the decrease in alveolar epithelial ion transport induced by exposure to IL-1β. Thus SPR may protect the alveolar epithelium against oxidative stress associated with experimental ALI, and eHsp72 may serve as a marker of SPR activation in the distal air spaces of patients with ALI.Keywords pulmonary edema; alveolar fluid clearance; heat shock response; respiratory distress syndrome; heat shock protein 70 ACUTE LUNG INJURY (ALI) is a common cause of acute respiratory failure in critically ill patients. The early phase of ALI is characterized by the accumulation and activation of inflammatory cells (neutrophils and macrophages) within the distal air spaces that release high levels of oxidant species (46). Alveolar epithelial and lung endothelial injury leads to increased permeability,
Copyright © 2006 the American Physiological SocietyAddress for reprint requests and other correspondence: M. T. Ganter, Dept. of Anesthesia and Perioperative Care, San Francisco General Hospital, 1001 Potrero Ave., Rm. San Francisco, CA 94110 (mt.ganter@gmail.com)..
NIH Public AccessAuthor Manuscript Am J Physiol Lung Cell Mol Physiol. Author manuscript; available in PMC 2009 October 21.
NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript pulmonary edema, and acute respiratory failure. An important mechanism to prevent alveolar flooding is the maintenance or upregulation of lung alveolar fluid clearance (AFC), requiring an intact alveolar epithelium (47). However, AFC has been shown to be impaired in the majority of ALI patients, and an impaired AFC was associated with worse clinical outcomes (47).Heat shock or stress proteins (Hsp) are a ...