肝硬化大鼠Kupffer细胞血小板活化因子合成水平及其受体表达

Synthesis of platelet activating factor(PAF) and expression of PAF receptor in Kupffer cells in portal hypertension in rat

目的研究肝硬化时Kupffer细胞血小板活化因子(PAF)生成水平及其受体表达的变化及意义。方法建立CCl4诱导的肝硬化模型,分离、培养Kupffer细胞,快速3H-PAF液闪检测Kupffer细胞及其培养上清液内PAF水平,免疫组织化学染色检测PAF在Kupffer细胞内的分布情况,受体饱和结合实验和RT-PCR分析Kupffer细胞PAF结合能力及PAF受体mRNA表达水平。结果肝硬化大鼠Kupffer细胞合成与释放PAF明显增加,分别为对照组的1·48倍(P<0·01)和2倍(P<0·01)。免疫组化显示Kupffer细胞胞浆内PAF呈阳性表达。肝硬化大鼠的Kupffer细胞PAF结合能力Bmax明显升高(P<0·01),而受体亲和力Kd与对照组比较无明显变化。RT-PCR显示PAF受体mRNA表达明显增加(P<0·05)。结论Kupffer细胞是肝硬化时PAF生成的一个重要来源,通过增加PAF合成和释放并上调PAF受体表达,Kupffer细胞参与肝硬化门脉高压的形成。

Objective To study the changes in PAF and its receptor in Kupffer cells in experimental cirrhosis and to evaluate the role of activated Kupffer cells in portal hypertension. Methods Kupffer cells, isolated from the livers of control and CCl4-induced cirrhotic rats, were cultured in serum-free medium overnight. PAF synthesis and release by Kupffer cells were determined 24 h later by rapid ^3H-PAF scintillation proximity assay, and the expression of PAF receptor in Kupffer cells by saturation binding technique and semi-quantitative reverse transcriptase polymerase chain reaction （RT-PCR）. By immunohistochemisty, the distribution of PAF in Kupffer cells was surveyed. Results Cell-associated PAF synthesis and release was increased about 1.48 fold and 2 fold, respectively, by Kupffer cells in cirrhotic liver as compared with the control （P〈0. 01）. Immunohistochemical analysis demonstrated that PAF positive-staining was present in Kupffer cell cytoplasm of cirrhotic liver and staining was weak in control. Scatchard analysis of the saturation binding rate indicated that the maximum PAF binding capacity in Kupffer cells of cirrhotic liver was promoted significantly compared with the control （P〈0. 01）, where as receptor affinity showed no significant difference between cirrhotic group and the control group （P〉0. 05）. Consistent with the receptor binding capacity, the mRNA expression of PAF receptor increased significantly in the Kupffer cells of cirrhotic liver （P〈0. 05）. Conclusion Kupffer cells are a main source of PAF in the cirrhotic rats due to elevation of PAF synthesis and release as well as upregulation of its receptor levels. Since PAF is a causative factor of portal hypertension, Kupffer cells may play a role in the pathogenesis of portal hypertension associated with liver cirrhosis.