Characterization of Platelet Activating Factor (PAF)Binding Sites in Rabbit Platelet Membranes

本文用放射配基受体结合实验方法研究了兔血小板膜上血小板活化因子（PAF）受体的性质。[^3H]-PAF与膜的特异结合率达70－80％，在25℃测得PAF与膜结合的平衡解离常数（Kd）为40.8nmol/L，最大结合位点为5.4pmol/mg蛋白。特异的PAF受体拮抗剂海风藤酮对结合有较强的抑制作用，IC50为30.0μmol/L。（－）－denudatin B，樟叶素(polysyphorin）和南藤素（wallichinine）是从中草药中分离的化合物，均能抑制这一结合，其IC50分别为0.6μmol/L、10μmol/L和2.5μmol/L。

Dibenzocyclooctadiene Lignans with Platelet-Activating Factor (PAF) Antagonist Activity from Kadsura heteroclita

Seven known dibenzocyclooctadiene lignans,tigloylgomisin P(1), angeloylgomisin P(2),gomisin A(3),Schizandrin(4),angeloylgomisin H(5),gomisin B(6) and R(+)-gomisin M_1(7)were isolated from Kadsura heteroclita.The conformation of tiglolylgomisin P(1)was established by 2D NMR techniques.Using[~3H]platelet activating factor(PAF)binding to human platelet membrane assay,(1),(2)and(7)showed PAF receptor antagonistic activities.

Platelet-activating factor in cirrhotic liver and hepatocellular carcinoma

AIM： Platelet-activating factor （PAF） is a pro-inflammatory and angiogenic lipid mediator. Here we aimed to investigate levels of PAF, lyso-PAF （the PAF precursor）, phospholipase A2 （PLA2, the enzymatic activity generating lyso-PAF）, acetylhydrolase activity （AHA, the PAF degrading enzyme） and PAF receptor （PAF-R） transcripts in cirrhotic liver and hepatocellular carcinoma （HCC）. METHODS： Twenty-nine patients with HCC were enrolled in this study. Cirrhosis was present in fourteen patients and seven had no liver disease. Tissue PAF levels were investigated by a platelet-aggregation assay. Lyso- PAF was assessed after its chemical acetylation into PAR AHA was determined by degradation of [^3H]-PAE PLA2 levels were assessed by EIA. PAF-R transcripts were investigated using RT-PCR. RESULTS： Elevated amounts of PAF and PAF-R transcripts 1 （leukocyte-type） were found in cirrhotic tissues as compared with non-cirrhotic ones. Higher amounts of PAF and PAF-R transcripts 1 and 2 （tissue-type） were found in HCC tissues as compared with non-tumor tissues. PLA2, lyso-PAF and AHA levels were not changed in cirrhotic tissues and HCC. CONCLUSION： While the role of PAF is currently unknown in liver physiology, this study suggests its potential involvement in the inflammatory network found in the cirrhotic liver and in the angiogenic response during HCC.

Effect of increased hepatic platelet activating factor and its receptor portal hypertension in CCl_4-induced liver cirrhosis

AIM： To evaluate the changes in hepatic platelet activating factor （PAF） and its receptors and their effect on portal pressure of cirrhotic rats induced by CCh. METHODS： A model of liver cirrhosis was replicated in rats by intra-peritoneal injection of CCh for 8 wk. We determined the effect of hepatic PAF and its receptor level on portal and arterial pressure by EIA, saturation binding and RT-PCR technique. RESULTS： Compared to control rats, cirrhotic rats had higher hepatic PAF levels and output as well as higher plasma PAF levels （P〈0.01, P〈0.01, P〈0.05, respectively）. Both hepatic PAF receptor mRNA levels and PAF binding were nearly 3-fold greater in cirrhotic rats （P〈0.01）. Portal injection of PAF （1 g/kg WT） increased the portal pressure by 22% and 33% in control and cirrhotic rats, respectively. In contrast, the arterial pressure was decreased in the both groups （54% in control rats and 42% in cirrhotic rats）. Injection of the PAF antagonist BN52021 （5 mg/kg WT） decreased the portal pressure by 16% in cirrhotic rats but had no effect in the control rats. CONCLUSION： The upregulation of the PAF system contributes to hepatic hemodynamic and metabolic abnormalities in drrhosis, and the increased release of PAF into the circulation has impacts on the systemic hemodynamics.

Opposite effects of WEB2086 on angiogenesis in atheromas and ischemic hindlimb of apoE gene deficient mice

Background Our previous research has suggested that platelet activating factor receptor was related to atherosclerosis. The present study investigated the effect of a platelet activating factor receptor antagonist- WEB2086 on angiogenesis in aortal plaque and ischemic hindlimb of apolipoprotein E-deficient mice. Methods Eight-week-old apolipoprotein E-deficient mice were fed with a 0.15% cholesterol diet to develop advanced lesions. At age 32 weeks unilateral hindlimb ischemia was surgically induced and the mice were divided into two groups： with or without WEB2086 mixed with their drinking water （4.3 mg in 100 ml）. At age 40 weeks blood was collected from the orbit for measurement of serum lipids and an enzyme linked immunosorbent assay was used to determine platelet activating factor and oxidized low density lipoprotein in the gastrocnemius and aorta. Whole-Mount CD31 stain and plaque-associated sprouting have been used to estimate angiogenesis in plaque from the aorta and laser Doppler perfusion imaging and immunohistochemical expression of von Willebrand factor have been used to estimate angiogenesis in ischemic hindlimb. Results The lipid composition of serum was not different between the groups. However, the amount of platelet activating factor and oxidized low density lipoprotein detected in the aorta was significantly higher than that in the gastrocnemius of ischemic hindlimb. The ratio of lesion to aorta levels was significantly reduced by administration of WEB2086, （31.52±6.18）% vs （55.58±8.34）%, P〈0.01. The mean density of intimal capillaries in atherosclerotic plaque, （31.13±9.20）% vs （57.74±11.28）%, P〈0.01, and the mean number of sprouts per aorta were significantly reduced, 183.92±34.17 vs 392.54±76.79, P〈0.01, in the WEB2086 group. Blood flow （0.85±0.12 vs 0.45±0.06, P〈0.01） and capillary density of ischemic hindlimb （1.18±0.17 vs 0.53±0.09, P〈0.01） were markedly increased in apolipoprotein E-deficient mice treated with WEB2086 versus controls. Conclusion The study provides evidence that WEB2086 can inhibit angiogenesis in atherosclerotic plaque but promote it in ischemic hindlimb.