The Mechanism Of Alveolar Macrophages Toll-like Receptor2,4,9-Myeloid Differentiation Factor88Signaling In Ventilator-induced Lung Injury

Objective To investigate the role of Alveolar macrophages Toll-likeReceptor2,4,9-Myeloid Differentiation Factor88Signaling in ventilator-inducedlung injury in rat model.Methods Thirty adult male pathogen-free Sprague Dawley rats wereassigned to three groups with10rats in each group by randomized digitalnumber method. Group A as the control group, performed tracheotomy andbreathed spontaneously. Whereas, after tracheotomy, the Group B and Group Cventilated4h at normal tidal volume8ml/kg and large tidal volume40ml/kgrespectively. After the4h ventilation all rats were euthanized, the lungs wereremoved for microscopic examinationtransmission, and the electron microscopywas performed as well to observe the ultrastructure changes of alveolarepithelial cell typeⅡ（AECⅡ） of rats lung. Wet/dry ratios (W/D), total proteinconcentration and the content of IL-6and IL-1β in bronchoalveolar lavage fluidwere all detected. The protein expressions of TLR2, TLR4, TLR9, MyD88andNF-κ�' in alveolar macrophages were detected by Western Blot while the mRNAlevel of TLR2, TLR4, TLR9, MyD88and NF-κ�' were detected by real-time revere transcription polymerase chain reaction (RT-PCR).Results Lungs from animals ventilated with high VTin the group C hadacute inflammatory infiltrates and perivascular edema whereas there were nomajor histological differences between animals ventilated with low VTin thegroup B compared to spontaneously breathing animals in the group A. Theultrastructure of alveolar epithelial cell type Ⅱ (AEC Ⅱ) in the group A andgroup B were nearly to the normal level, whereas the chromatin of the nucleus,the lamellar corpuscle in the cytoplasm, the cell membrane and the microvilli ofthe AECⅡ in the group C had varying degrees of injurious changes. Comparewith the group A and the group B, the wet/dry ratios(W/D)(5.54±0.17vs4.58±0.17and4.69±0.16), total protein concentration, IL-6and IL-1β of theBALF (total protein concentration:6.33±0.61vs0.45±0.05and0.47±0.04, IL-6:1989.38±103.12vs1032.61±61.15and1009.89±69.04, IL-1β:2.79±0.25vs1.05±0.15and1.23±0.22), the protein expressions of TLR2, TLR4, TLR9,MyD88and NF-κ�'(TLR2:0.59±0.050vs0.35±0.036and0.36±0.031, TLR4:0.84±0.040vs0.40±0.026and0.40±0.020, TLR9:0.77±0.042vs0.30±0.027and0.31±0.037, MyD88:0.95±0.091vs0.56±0.082and0.58±0.084, NF-κ�':1.02±0.076vs0.74±0.052and0.70±0.076) in the group C in alveolarmacrophages were all increased significantly with statistically significantdifference (P＜0.05or P＜0.01). The mRNA level of TLR2, TLR4, TLR9,MyD88and NF-κ�' in alveolar macrophages in the group B were1.08±0.21、1.05±0.20、1.06±0.18、1.03±0.18、1.04±0.26folds than that of the group A withno statistically significant difference respectively(all P＞0.05), while the mRNAlevel of TLR9, MyD88and NF-κ�' in alveolar macrophages in the group C were4.98±0.85、5.16±0.78、9.31±0.82、4.42±0.44、5.63±0.72folds than that of thegroup A with statistically significant difference respectively(all P<0.01); Meanwhile the mRNA level of TLR2, TLR4, TLR9, MyD88and NF-κ�'inalveolar macrophages in the group C were4.72±1.10、5.05±1.07、8.96±1.05、4.34±0.56、5.8±0.98folds than that of the group B with statistically significantdifference respectively(all P<0.01).Conclusion Toll-like Receptor2,4,9-Myeloid Differentiation Factor88Signaling in alveolar macrophages Contributes to Ventilator-induced LungInjury.