Role of Interleukin-33 in Ventilator-Induced Lung Injury

Autor: YANG, SHIH-HSING, 楊式興
Rok vydání: 2016
Druh dokumentu: 學位論文 ; thesis
Popis: 104
Positive-pressure type ventilator could assist artificial breath to the acute respiratory failure patient. It is also well known that ventilator led to lung a repetitive strain and a mechanical overdistension resulted in alveolar edema and inflammation, that is termed ventilator-induced lung injury (VILI), the clinical features of VILI are including lung inflammation and congestion phenomenon, cause to high mortality. Despite the lung protective strategy is implemented to the situation of used ventilator in clinical but reduce the mortality rate is still limited. Therefore, it is very important to understand the VILI-associated with the mechanism of inflammatory mechanism and lung injury. The IL-33 is a newly identified pro-inflammatory cytokine of the IL-1 family. There are two isoforms of the IL-33 receptor including the transmembrane ST2 (ST2L) and soluble ST2 (sST2) isoforms. The IL-33/ST2 pathway is a very important mechanism which regulates immunity effect and involved in pathophysiological mechanism of clinical diseases. It is closely associated with such as acute lung injury, severe asthma, colitis, arthritis, and cardiovascular diseases. The expression of IL-33 in lung tissue appears both constitutive and inducible. The constitutive expression of IL-33 is described in smooth muscle cells and bronchial epithelial cells in lung. The expression of IL-33 is clearly induced if murine was infected by influenza A virus in lungs. Damage to cardio fibroblasts can induce necrosis and release of IL-33 by mechanical strech, IL-33 newly synthesized that is initially existed the nucleus transit into the cytoplasmic space and reside in membrane-bound vesicles. However, it is unclear what does the IL-33/ST2 pathway act to VILI mechanism. The purpose of this study was to study whether the IL-33 and its ST2 receptor to involving in acute lung injury induced by a mechanical ventilator in rats. And, we also to explore IL-33/ST2 pathway participate in the lung protective strategies by hydrocortisone and hypercapnia administration in VILI. Male Wistar rats were intubated after tracheostomy and received ventilation at 10/20 cm H2O of inspiratory pressure PC10/PC20 by a G5 ventilator for 4 hours. And catheters were inserted in femoral artery and vein were collected hemodynamic change and serum sampling. The hemodynamic and respiratory parameters were collected and analyzed. Collecting lung tissue and bronchoalveolar lavage fluid (BALF) when animals were sacrificed after the experiment completed. The morphological changes of lung injury were also assessed by histological H&E stain. The dynamic changes of lung injury markers TNF-α, IL-1β and IL-33 level were measured by ELISA assay in serum, BALF, and lung tissue. Using the immunochemistry and western blotting assay to determine the IL-33 and its receptor ST2 changes in lung tissue. A VILI study model of rat were established, rats received a G5 ventilator and used a pressure control mode, the peak inspiration gas channel pressure maintains separately at 10 cmH2O (PC10) and 20 cmH2O (PC20). The results found that tidal volume was significantly higher in PC20 than PC10 group, but was no difference within group during VILI for 4 hours in PC10 or PC20 groups. The mean arterial blood pressure was decreased by higher pressure in PC20 group, but was no difference within group during VILI for 4 hours in PC10 or PC20 groups. The heart rate was not significant difference. Analyzed the severity of lung injury in VILI, the obvious alveolar space increase, alveolar wall thicker, inflammatory cell accumulation, hyaline membrane generation, pulmonary edema, and alveolar hemorrhage were found in the PC10 and PC20 groups. Moreover, the concentration of TNF-α and IL-1β was increased in BALF and serum in the VILI groups. There is no significant of serum IL-33 in both groups. But, the concentration of IL-33 in BALF were obvious reduced in both group. In addition, the IL-33 expression was increased in lung tissue with VILI. Interestingly, the data showed that ST2L membrane form was highly accumulated in the membrane fraction of lung tissue in the PC10 and the PC20 group compared to control group, but the ST2L was dramatically decreased in cytosol fraction. Conversely, the sST2 soluble form was slightly decreased in the membrane and cytosol fractions in the VILI group compared to the control group. These results indicated ST2L receptor translocated to membrane from cytosol in VILI rats. Then, whether the IL-33 cytokine and its receptor ST2 involved in the hydrocortisone and hypercapnia treated VILI were explored. Rats were administered by hydrocortisone after high-pressure ventilation 2 hours could reduce lung injury. Moreover, the VILI-induced the reduction of IL-33 in BALF were restored to more by hydrocortisone. Take together, examination of the IL-33 in BALF as a biomarker of VILI may provide a new concept of lung protection strategy. Furthermore, the VILI rats were received high volume ventilation and were giving hypercapnia, it is 5% CO2 inhalation for four hours. Those consequences of 5% CO2 inhalation could improve hemodynamic changes and gas exchange. And, the VILI-induced pulmonary inflammation symptom was significantly reduced. In addition, the VILI-induced the increase of TNF-α in BALF was reduced by using the 5% CO2 inhalation. In addition, the reduction of IL-33 cytokine release to BALF also was restored to rich. The VILI-induced the increase of IL-33 and its receptor ST2 were reduced by 5%CO2 inhalation, then ventilator-associated lung injury was improved. In conclusion, this present study used the clinical ventilators success established the experimental VILI animal model. The hemodynamic parameters and respiratory parameters from the ventilator were collected and analyzed. Using the lung tissue histology and detection of inflammatory cytokines from different sources to confirm VILI experimental model. Rats were through VILI, resulting in IL -33 cytokine expression increases in the amount of lung tissue, ST2L receptors significantly accumulated in the cell membrane. However, the clinical lung protective strategies of hydrocortisone or hypercapnia treatment could reduce IL-33 cytokine generation in lung and reduced the accumulation of ST2L receptors on the cell membrane, and BALF could be detected changes in IL-33 expression increased. Therefore, the IL-33/ST2 pathway can be an examined function as new biomarkers of VILI and probably a biological target in therapy. Moreover, IL-33/ST2 signaling activated by mechanically responsive lung injury may potentially serve as a new therapy target.
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