Effects Of Cyclic Mechanical Stretch On The Expression Of TLR4in Alveolar Macrophages Of Rats

Background and objective Mechanical ventilation is one of the important measures for the treatment of critically ill patients in the clinical, early mechanical ventilation can not only correct refractory hypoxemia, but also play an important role in the prevention and treatment of alveolar collapse against pulmonary edema. As one of the complications of mechanical ventilation, ventilation-induced lung injury is being more and more concernd by many scholars. Mechanical ventilation-induced lung injury as the There are many kinds of cells involved in VILI, neutrophils, alveolar epithelial cells, capillary endothelial cells attract more researches, the current research focus is the role of alveolar macrophages in the VILI. Studies have found that the type and quantity of AM secretion of cytokines in physiological circumstances are very limited, but in tidal volume mechanical stretch which leads to pathological lung injury (the noxious mechanical ventilation), activated AM may secrete a large number of inflammatory cytokines, chemokines, inflammatory mediators, and other biologically active substances causing lung damage. TLR4of the article mainly presents in the surface of the macrophage of mammalian lungs. TLR4is one of the members of the Toll-like receptor families which are important innate immune molecules. Because of the influence of neurohumoral factors in vivo experiments, the influence of purely mechanical stretch on the TLR4receptor in rat alveolar macrophages is unclear. Our Purpose of the experiment is to investigate the effects of mechanical stretch on the expression of TLR4in alveolar macrophages of rats.Methods Rats were carried out bronchoalveolar lavage with precooled sterile PBS-H (containing10U/ml heparin and10%fetal calf serum, PBS), then separated and purified, the final collection of adherent cells were alveolar macrophages. The experiment was divided into mechanical stretch of6hours and8hours groups (cyclic mechanical stretch at30%. the frequency was0.3HZ and square wave) and static control group. Alveolar macrophages of mechanical stretch groups were cyclic stretched in vitro by flexible substrate loading device FX4000T made in the Flexercell Company of the United States. TLR4mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR); the concentration of macrophage inflammatory protein2was detected by ELISA while TLR4protein was determined by immunocytochemistry, the final data was processed with statistical methods.Results TLR4RT-PCR results of AM are expressed with optical density value (OD value) of TLR4mRNA/ACTIN mRNA. Compared to the control group, the difference of increasing OD value in stretch groups was statistically significant (P0.01), the difference between stretch6h and8h was not significant; the difference of increasing concentration of MIP-2in stretch groups was statistically significant (P0.01), the difference between stretch6h and8h was not significant. The TLR4immunocytochemistry results of AM are expressed with TLR4absorbance value of the experimental groups-the absorbance value of the negative control group (Δ TLR4). Compared to the control group, the difference of increasing ΔTLR4in stretch groups was statistically significant (P<0.01), the difference between stretch6h and8h was not significant.Conclusion Cyclic mechanical stretch upregulates the expressions of TLR4and MIP-2in alveolar macrophages.