Impact of Low and High Tidal Volumes on the Rat Alveolar Epithelial Type II Cell Proteome

Abstract

Rationale: Mechanical ventilation with high tidal volumes leads to increased permeability, generation of inflammatory mediators, and damage to alveolar epithelial cells (ATII). Objectives: To identify changes in the ATII proteome after two different ventilation strategies in rats. Methods: Rats (n ϭ 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. Measurements and Main 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 Ͻ 0.01), a 34% decrease in Na ϩ , K ϩ -ATPase (p Ͻ 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-␤ (p Ͻ 0.01) and a 67% increase in mitochondrial pyruvate carboxylase (p Ͻ 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.Keywords: acute lung injury; alveolar epithelium; corticosterone Acute lung injury is a major cause of morbidity (1) and mortality, and mechanical ventilation is critical to survival of most patients with acute lung injury. However, mechanical ventilation with high tidal volumes (Vts) is known to have deleterious side effects. The importance of ventilator-induced lung injury caused by mechanical ventilation has been established by several experimental and clinical studies (2, 3). Avoidance of excessive Vts Mechanical ventilation with high tidal volumes leads to increased permeability, generation of inflammatory mediators, and damage to alveolar epithelial cells that may contribute to ventilator-induced lung injury. What This Study Adds to the FieldUsing a proteomic approach, significant reductions of key proteins in alveolar type II cells from rats were identified after short-term positive-pressure ventilation.during mechanical ventilation reduces the risk of ventilatorinduced injury, and application of a lower Vt strategy to ventilate patients with acute respiratory distress syndrome has been shown to lead to a greater than 2...

Detection of Fibroproliferation by Chest High-Resolution CT Scan in Resolving ARDS

“…1 Ventilator parameters, including V t (mL), PEEP (cm H 2 O), and PPlat (cm H 2 O) were recorded been linked to increased inflammation, altered extracellular matrix composition, enhanced production of profi brotic molecules, and promotion of frank fibrosis within the lung. [10][11][12] Analogous observations have been reported in mechanically ventilated patients with ARDS. [13][14][15] Although large clinical trials have reassured clinicians that a low V t strategy 1 and judicious use of positive end-expiratory pressure (PEEP) 16,17 promote improved short-term outcomes in ARDS, including survival, their effects on early development of fibroproliferation remain unclear.…”

Chirurgische Intensivmedizin

“…Lungenprotektion bei septischen Pati enten ist keine Option, sondern Pflicht: Experimentelle Studien haben gezeigt, dass hohe Tidalvolumina und Beat mungsdrücke zu hoher Scherkraftbelas tung des Lungenparenchyms führen, was eine Verstärkung der inflammatorischen Reaktion mit konsekutivem Lungenscha den ("acute lung injury", ALI) herbeiführt und ein akutes Lungenversagen ("adult respiratory distress syndrome", ARDS) herbeiführen kann [41,42,43] Es wird empfohlen, wenn möglich auf eine neuromuskuläre Blockade bei sep tischen Patienten zu verzichten, da es zu einem verlängerten Blockadeeffekt nach Absetzen des Relaxans kommen kann (1B). Es konnte durch eine randomisierte, placebokontrollierte Studie gezeigt wer den, dass der Sauerstoffverbrauch und transport nicht durch Relaxation verbes sert wird [51].…”

Alterations in the proteome of pulmonary alveolar type II cells in the rat after hepatic ischemia-reperfusion

“…One goal of proteome research is to evaluate the responses to different stimuli (19,20) and to discover alterations in pathways that can then be further evaluated (21,22). We have recently reported that a modern quantitative proteomic approach is capable of quantifying changes in protein profiles, namely of the reactive oxidant and prostaglandin producing systems, in hepatic Kupffer cells after liver injury (8) and ATII after mechanical ventilation (23).…”

“…Therefore, the primary objective of this study was to use a proteomics approach to develop testable hypotheses that may identify mechanisms of injury to the pulmonary epithelium following hepatic I/R (8,21,23 Lean Zucker rats (n ϭ 4 in the I/R and sham-operated groups, n ϭ 8 normal control animals, all animals between 250 -300 g) were randomized to either 75 mins of warm I/R or sham operation. The rats had access to standard laboratory diet and were maintained on a light-dark cycle.…”

“…Bronchoalveolar lavage was done in all animals with 7 mL of normal saline. ATII were isolated as previously described (11,23). The cells in the supernatant were then collected by centrifugation, transferred to cell preservation medium (10% fetal calf serum, 10% dimethyl sulfoxide, in minimum essential medium, UCSF Cell Culture Facility), and stored at Ϫ80°C until further processing.…”