Impact of low and high tidal volumes on the rat alveolar epithelial type II cell proteome.
BACKGROUND
Mechanical ventilation with high tidal volumes leads to increased permeability, generation of inflammatory mediators, and damage to alveolar epithelial cells (ATII).


OBJECTIVE
To identify changes in the ATII proteome after two different ventilation strategies in rats.


METHODS
Rats (n = 6) were ventilated for 5 hours with high- and low tidal volumes (VTs) (high VT: 20 ml/kg; low VT: 6 ml/kg). Pooled nonventilated rats served as control animals. ATII cells were isolated and lysed, and proteins were tryptically cleaved into peptides. Cellular protein content was evaluated by peptide labeling of the ventilated groups with (18)O. 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
High Vt resulted in a significant increase in airspace neutrophils without an increase in extravascular lung water. Compared with low-VT samples, high-VT samples showed a 32% decrease in the inositol 1,4,5-trisphosphate 3 receptor (p < 0.01), a 34% decrease in Na(+), K(+)-ATPase (p < 0.01), and a significantly decreased content in ATP synthase chains. Even low-VT samples displayed significant changes, including a 66% decrease in heat shock protein 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-VT ventilation, significant reductions in membrane receptors, ion channel proteins, enzymes of the mitochondrial energy system, and structural proteins in ATII cells were present. The data supports the two-hit concept that an unfavorable ventilatory strategy may make the lung more vulnerable to an additional insult.
Hirsch
Jan
J
Cardiovascular Research Institute, University of California, San Francisco, CA 94143-0130, USA. jhirsch@itsa.ucsf.edu
Hansen
Kirk C
KC
Sapru
Anil
A
Frank
James A
JA
Chalkley
Robert J
RJ
Fang
Xiaohui
X
Trinidad
Jonathan C
JC
Baker
Peter
P
Burlingame
Alma L
AL
Matthay
Michael A
MA
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000032:analysis / Q000378:metabolism; D020543:Proteome / Q000032:analysis / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D012123:Pulmonary Ventilation; D051381:Rats; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry; D013990:Tidal Volume
D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D020543:Proteome