Mechanical ventilation enhances HMGB1 expression in an LPS-induced lung injury model.
BACKGROUND
Mechanical ventilation (MV) can augment inflammatory response in lipopolysaccharide (LPS) challenged lungs. High mobility group box 1 protein (HMGB1) is a pro-inflammatory mediator in ventilator-induced lung injury, but its mechanisms are not well defined. This study investigated the role of HMGB1 in lung inflammation in response to the combination of MV and LPS treatment.


METHODS
Forty-eight male Sprague-Dawley rats were randomized to one of four groups: sham control; LPS treatment; mechanical ventilation; mechanical ventilation with LPS treatment. Mechanically ventilated animals received 10 ml/kg tidal volumes at a rate of 40 breaths/min for 4 h. In the HMGB1-blockade study, sixteen rats were randomly assigned to HMGB1 antibody group or control antibody group and animals were subjected to MV+LPS as described above. A549 cells were pre-incubated with different signal inhibitors before subjected to 4 h of cyclic stretch. Lung wet/dry weight (W/D) ratio, total protein and IgG concentration, number of neutrophils in bronchoalveolar lavage fluid (BALF), and lung histological changes were examined. The levels of interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-2 (MIP-2) and HMGB1 in BALF were measured using ELISA. Real-time quantitative PCR and Western blot were used to analyze mRNA and protein expression of HMGB1. Western blot were employed to analyze the activation of IκB-α, NF-κB, JNK, ERK, and p38.


RESULTS
MV significantly augmented LPS-induced lung injury and HMGB1 expression, which was correlated with the increase in IL-1β, IL-6 and MIP-2 levels in BALF. In vivo, intratracheally administration of HMGB1 antibody significantly attenuated pulmonary inflammatory injury. In vitro experiments showed cyclic stretch induced HMGB1 expression through signaling pathways including p38 and NF-κB.


CONCLUSIONS
The findings indicated that moderate tidal volume MV augmented LPS induced lung injury by up-regulating HMGB1. The mechanism of HMGB1-mediated lung injury is likely to be signaling through p38 and NF-κB pathways.
Department of Anesthesiology, Guangzhou First People's Hospital, Guangzhou Medical University, Guangzhou, China.
Ning
N
Ding
Fang
F
Wang
Hui
H
Xiao
Lixin
L
Xu
Shouzhang
S
She
D055371:Acute Lung Injury / Q000097:blood / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001784:Blood Gas Analysis; D016207:Cytokines / Q000097:blood; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D024243:HMGB1 Protein / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D011651:Pulmonary Artery / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D015398:Signal Transduction / Q000187:drug effects; D055397:Ventilator-Induced Lung Injury / Q000473:pathology / Q000517:prevention & control; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D019138:Antibodies, Blocking; D016207:Cytokines; D024243:HMGB1 Protein; D008070:Lipopolysaccharides; D016328:NF-kappa B; D048051:p38 Mitogen-Activated Protein Kinases