Role And Mechanism Of Platelet Activating Factor Receptor Antagonist (BN52021) In Early Stage Of Severe Acute Pancreatitis In Rats

AIMThis research is to investigate the role and mechanism of platelet activating factor receptor (PAF-R) antagonist (BN52021, Ginkgolide B) in early stage of severe acute pancreatitis (SAP) in rats.METHOD1.The method of immunity hisochemistry staining was employed to study the location and distribution of PAF-R in normal pancreas tissues of Wistar rats.2.The sodium aurocholatet was injected through pancreaticobiliary duct in retrograde direction to establish SAP model and the method of pharmacokinetics was used to explore the optimal dosage of BN52021 on rats with SAP.3.The methods of PT-PCR and Western blot were adopted respectively to investigate the changes of PAF-R and NF-κBp65 mRNA and proteins expression in pancreatic tissues of rats and the effect of BN52021.RESULTS1.In frozen section PAF-R located in pancreatic microvascular endothelial cells. In paraffin section PAF-R located in Pancreas islet cytoplasm and cell nucleus; there was little colouration in pancreatic microvascular endothelial cells.2.The results of the serum amylase, PLA2, ascites, pathologic score and PAF-RmRNA expression showed that, compared with 2.5 mg.kg-1 and 10.0 mg.kg-1, 5.0 mg.kg-1 of BN52021 by vein injection was the optimal dosage in treating rats with SAP(P<0.05). The results also showed that SAP model was successful.3.PAF-mRNA showed dynamic changes in SAP and BN groups. It increased gradually in early stage, reached a peak at 3h, and decreased gradually later. There were significant differences between PAF-mRNA in SAP and BN groups and that in SO groups at each time point except at 1h and 2h (P<0.05), whereas there was no significant difference between PAF-mRNA in BN groups and that in SAP groups at each time point except at 6h. The changes of PAF-R protein in SAP and BN groups shared the similar pattern with those of PAF-R mRNA. There were significant differences between PAF-R protein in SAP and BN groups and that in SO groups at each time point except at 1h(P<0.05), whereas there was no significant difference between PAF-R protein in BN groups and that in SAP groups.4.The expression of NF-κBp65 mRNA dynamically changed in both SAP and BN groups. The mRNA level was higher in SAP groups than that in SO groups at 2h, 3h, 12h, and 24h after operation (P<0.05). The mRNA level was higher in BN groups than that in SO groups at each time point (P<0.05), and also higher than that in SAP groups at 1 h (P<0.05). The NF-κBp65 protein level was higher in SAP groups than that in SO groups at 1h, 3h, and 6h (P<0.01), and 2h, 12h, and 24h (P<0.05). The NF-κBp65 protein level was higher in BN groups than that in SO groups at all time points (P<0.05), and lower in BN groups than that in SAP groups at 1h, 3h, and 6h (P<0.05).CONCLUSIONS1. It is found that PAF-R is distributed not only in pancreatic microvascular endothelial cells but also in pancreatic islet cells of Wistar rats.2. It is found that 5.0 mg.kg-1 of BN52021 by vein injection is the optimal dosage in treating rats with SAP.3. PAF-R is found to play an important role in occurrence and development of SAP. BN52021 exerts biological effects through the combination the increase of PAF expression achieved through competitive inhibition and the simultaneous increase of PAF-R expression rather than through regulating PAF-R expression in pancreatic tissues.4. The NF-κB is a key factor in the lower reaches of signal transduction pathways of PAF-R. The expression of NF-κBp65 in pancreatic tissues dynamically changed and the changing might have played a role in pathogenesis of SAP. BN52021 exerted therapeutic effect by reducing the expression level of NF-κBp65 protein in the early stage of SAP.