Published ahead of print on March 15, 2007, doi:10.1164/rccm.200605-621OC Am. J. Respir. Crit. Care Med., Volume 175, Number 10, May 2007, 1006-1013 A more recent version of this article appeared on May 15, 2007
Submitted on May 6, 2006 Impact of Low and High Tidal Volumes on the Rat Alveolar Epithelial Type II Cell ProteomeJan Hirsch1*,1 Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA; Department of Anesthesia and Perioperative Pain, University of California, San Francisco, San Francisco, CA, USA, 2 Department of Pharmaceutical Chemistry, Mass Spectrometry Facility, University of California, San Francisco, San Francisco, CA, USA, 3 Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA * To whom correspondence should be addressed. E-mail: jhirsch{at}itsa.ucsf.edu.
Rationale: To identify changes in the proteome of alveolar type II cells (ATII) after two different ventilation strategies in rats. Methods: Rats (n=6) were ventilated for 5 hours with high and low tidal volumes(HTV: 20 ml/kg; LTV: 6 ml/kg). Pooled non-ventilated rats served as controls. ATII were isolated, lysed and proteins were tryptically cleaved into peptides. Cellular protein content was evaluated by peptide labeling of the ventilated groups with 18O. Samples were fractionated by cation exchange chromatography and identified using electrospray tandem mass spectrometry. Proteins identified by 15 or more peptides were statistically compared using t-tests corrected for the False Discovery Rate. Results: HTV resulted in a significant increase in air space neutrophils without an increase in extravascular lung water. Compared to LTV samples, HTV samples showed a 32% decrease in the IP3 receptor (p<0.01), a 34% decrease in Na+, K+-ATPase(p<0.01), and a significantly decreased content in ATP synthase chains. Even LTV samples displayed significant changes, including a 66% decrease in HSP 90-beta (p<0.01) and a 67% increase in mitochondrial pyruvate carboxylase (p<0.01). Significant differences were found in membrane, acute phase, structural and mitochondrial proteins. Conclusions: After short term exposure to high tidal volume ventilation significant reductions in membrane receptors, ion channel proteins, enzymes of the mitochondrial energy system, and structural proteins in alveolar type II cells were present. The data supports the 2-hit concept that an unfavorable ventilatory strategy may make the lung more vulnerable to an additional insult. Key words: proteomics, ventilator induced injury, isotope ratio mass spectrometry, alveolar epithelial type II cell, corticosterone
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