The Effects Of Mechanical Ventilation On The Expression Of Muc5ac In Airway Epithelial Cells And Its Signal Mechanism

Objective To study the effects of mechanical ventilation and stretching on the expression of MUC5AC in airway epithelial cells and investigation for its signal mechanism.Methods Rabbits were divide into control group and one, three, six, twelve, twenty-four hours mechanical ventilation groups, and 2, 5, 10cmH2O PEEP mechanical ventilation groups. Contents of TNF-α, IL-8, MUC5AC mRNA and protein in bronchoalveolar lavage fluid were determined by RT-PCR and ELISA methods,respectively. Neutrophil in bronchoalveolar lavage fluid were counted. Neutrophil elastase activity was measured by assays of substrate.Mini-type Multi-fuctional Bio-impact Machin was used to construct the model of mechanical stretching. The airway epithelial cells were divide into control group, stretch, stretch and gadolinium , stretch and low molecular weight heparin, stretch and nifedipine , stretch and the locked nucleic acids of MARCKS effective domain(ED),stretch and the control locked nucleic acids of MARCKS ED groups. Free calcium concentration was quantitative examined by flow cytometer, and observed through laser scanning confocal microscope. The expression of MUC5AC and SNAP23 protein in cells were determined by immunohistochemistry method, contents of MUC5AC and SNAP23 protein were measured by Image Pro Plus 5.0. MUC5AC protein in supernatant was determined by ELISA methods. SNAP23 mRNA was determined by RT-PCR methods.Mini-type Multi-fuctional Bio-impact Machin was used to construct the model of mechanical stretching. Three inhibitors of mitogen- activated protein kinase signal channel were respectively given. The expression of MUC5AC mRNA and protein were determined by RT-PCR and ELISA method.Results Mechanical ventilation could increase the expression of MUC5AC in bronchiorum endothelial cells(P<0.05). After mechanical ventilation for three hour, the expression of TNF-αreached the peak (P<0.05). The expression of IL-8 reached the peak after six hours(P<0.05). Neutrophil count and neutrophil elastase activity reached the peak after twelve hours(P<0.05). With the increase of PEEP, the mRNA and protein of TNF-α, IL-8 ,MUC5AC, the number of PMN and neutrophil elastase activity also would increase(P<0.05).Mechanical stretching could increase the concentration of the free Ca²⁺ in cell(P<0.05). Mechanical stretching could increase the expression of SNAP23 and MUC5AC in cells and MUC5AC in supernatant(P<0.05). Gadolinium , nifedipine and LNA of MARCKS ED could reduce the increase the expression of SNAP23 and MUC5AC in cells and MUC5AC in supernatant(all P<0.05). U0126 and SB203580 could decrease the expression of MUC5AC mRNA and protein (P<0.05 for all).Conclusion Mechanical ventilation and stretching could increase the expression of MUC5AC in bronchiorum endothelial cells. This maybe is concerned with inflammation, stretch sensitive positive ion channel, the internal flow of Ca²⁺,MARCKS,ERK1/2 and p38 MAPK signal mechanisms.