Abstract: Objective:To investigate expressions and significance of aquaporin 1 (AQP-1) and nuclear factorkappa B (NF-κB) in lung tissues of rats with severe acute pancreatitis (SAP) associated lung injury.
Methods:The experimental study was adopted. Fortyeight Wistar rats were divided into the SAP group and control group with 24 rats in each group by random number table. Acute pancreatitis model was induced by retrograde infusion of 5% sodium taurocholate (3 mL/kg) into the biliopancreatic duct and rats were compensated with right amount normal of saline in the SAP group. Rats in the control group were administered with normal of saline using the same method. All the rats were sacrificed at 6, 12, 24 and 48 hours after the operation (n=6 per group). (1) The expressions of AQP-1 and NF-κB in lung tissues were measured using immunohistochemistry. (2) The expression of AQP-1 mRNA was measured using realtime polymerase chain reaction (RTPCR). (3) The apoptosis of cells in lung tissues was detected by terminaldeoxynucleoitidyl transferase mediated nick end labeling (TUNEL) method. (4) The degree of lung tissue damage was observed using HE staining. Measurement data with normal distribution were expressed by ±s, and comparison between groups was done using ANOVA.
Results:(1) Visual observation: lung tissues of rats in the SAP group showed obvious pulmonary edema with scattered bleeding points and lung injury aggravated gradually at 6, 12, 24, 48 hours. Lung tissues of rats in the control group showed no obvious pathological changes. (2) The results of immunohistochemistry showed positive expressions of AQP-1 and NF-κB at bronchial epithelial cells, alveolar epithelial cells, infiltrated neutrophils and mononuclear macrophages in the SAP group, and positive expression of NF-κB at very small amount of alveolar fibroblasts and epithelial cells in the control group. The rate of AQP-1 positive cells in lung tissues of rats at 6, 12, 24, 48 hours were 5.4%±1.7%, 6.4%±2.6%, 6.3%±1.4%, 6.3%±1.6% in the SAP group and 28.1%±5.0%, 31.2%±5.1%, 30.1%±6.2%, 29.7%±4.9% in the control group, with significant differences (F=27.52, 23.89, 22.85, 22.43, P<0.05). The rate of NF-κB positive cells in lung tissues of rats at 6, 12, 24, 48 hours were 58.6%±5.0%, 77.8%±5.2%, 89.3%±4.8%, 92.3%±6.8% in the SAP group and 5.4%±1.7%, 6.4%±2.6%, 6.3%±1.4%, 6.3%±1.6% in the control group, with significant differences (F=117.76, 147.70, 200.92, 214.64, P<0.05). (3) The results of RTPCR showed that relative expressions of AQP-1 mRNA of rats in the SAP group at 6, 12, 24, 48 hours were 14.17±0.18, 3.56±0.22, 2.87±0.21, 1.51±0.12, showing significant differences between 6 and 12 hours, 6 and 24 hours, 6 and 48 hours respectively (F=15.81, 24.44, 7.57, P<0.05).There were significant differences between 12 hours and 24 hours, 12 hours and 48 hours, 24 and 48 hours, respectively (F=12.36, 9.11, 6.58, P<0.05). (4) The cell apoptosis and the severity of lung injury: results of TUNEL showed that cell apoptosis was mainly distributed in mononuclear macrophages, bronchial epithelial cells, alveolar epithelial cells and a small number of vascular endothelial cells in the SAP group, and few of apoptosis could be seen in alveolar interstitial stromal cells and alveolar epithelial cells in the control group. The cell apoptosis rate in lung tissues of rats at 6, 12, 24, 48 hours, were 18.4%±5.0%, 26.9%±5.1%, 27.1%±4.2%, 28.7%±3.8% in the SAP group and 1.5%±0.7%, 1.6%±0.6%, 1.5%±0.4%, 1.5%±0.6% in the control group, respectively, showing significant differences (F=150.47, 272.14, 335.78, 350.64, P<0.05). The apoptosis rate at 12, 24, 48 hours was significantly higher than that at 6 hours (F=10.25, 10.42, 11.63, P<0.05). There were significant differences in the apoptosis rate between 12 and 24, 12 hours and 48 hours, 24 and 48 hours, respectively (F=7.22, 8.89, 7.75, P<0.05). The results of HE staining showed gradual aggravation of alveolar tissue injury, alveolar structure disorder, reduction of type II alveolar epithelial cell microvilli, intra alveolar hemorrhage, edema of endothelial cells and intercellular edema with the time changes in the SAP group, and normal basic structure of alveolar epithelial cells and vascular endothelial cells in the control group.
Conclusion:Increased expression of NF-κB, decreased expression of AQP-1 and time dependence of the cell apoptosis are detected in the SAP associated lung injury, revealing that imbalance apoptosis and the abnormal expressions of NF-κB and AQP-1 play important roles in SAP associated lung injury.