Inactivation of factor XIa in human plasma assessed by measuring factor XIa-protease inhibitor complexes: major role for C1-inhibitor

From experiments with purified proteins, it has been concluded that factor XIa (FXIa) is inhibited in plasma mainly by alpha 1-antitrypsin (a1AT), followed by antithrombin III (ATIII), C1-inhibitor (C1Inh), and alpha 2-antiplasmin (a2AP). However, the validity of this concept has never been studied in plasma. We established the relative contribution of different inhibitors to the inactivation of FXIa in human plasma, using enzyme-linked immunosorbent assays (ELISAs) for the quantification of complexes of FXIa with a1AT, C1Inh, a2AP, and ATIII. We found that 47% of FXIa added to plasma formed complexes with C1Inh, 24.5% with a2AP, 23.5% with a1AT, and 5% with ATIII. The distribution of FXIa between these inhibitors in plasma was independent of whether FXIa was added to plasma, or was activated endogenously by kaolin, celite, or glass. However, in the presence of heparin (1 or 50 U/mL), C1Inh appeared to be the major inhibitor of FXIa, followed by ATIII. Furthermore, at lower temperatures, less FXIa-C1Inh and FXIa-a1AT complexes but more FXIa-a2AP complexes were formed. These data demonstrate that the contribution of the different inhibitors to inactivation of FXIa in plasma may vary, but C1Inh is the principal inhibitor under most conditions.     

机械负荷调节猪腰椎间盘细胞表达α5β1整合素的体外研究

目的研究α5β1整合素在体外培养的猪腰椎间盘细胞中的表达和机械负荷对其的影响。方法取10只年龄5-6周、体重25-30kg的猪，处死后12h内，无菌条件下切取完整的腰椎，剔除腰椎周围的韧带和软组织，尤其是椎间盘周围的韧带。从腹侧一次性切开椎间盘取出髓核（nucleus pulpous，NP），仔细分离纤维环（anulus fibrous，AF），将两者立即置于Hanks平衡盐溶液中，制成细胞悬液。分别对腰椎间盘的AF和NP细胞施加1MPa、1Hz，3h／d，共3d的周期性液压，通过对细胞的形态学观察、Western免疫印迹和免疫组织化学染色，检测α5β1整合素在正常腰椎间盘AF细胞和NP细胞中的表达及周期性压力对其的影响。结果经周期性液压后，NP细胞的存活率大于90％，AF细胞的存活率大于85％，加压后的AF细胞和NP细胞均可见体积缩小。α5β1整合素在正常腰椎间盘AF细胞和NP细胞中的表达呈强阳性。Western免疫印迹结果显示：加压后α5β1整合素在AF细胞中的表达均明显减少，P值分别为0．000、0．003，与对照组比较差异有统计学意义；α5β1整合素在NP细胞中的表达也明显减少，P值分别为0．001、0．015，与对照组比较差异有统计学意义。结论机械负荷可引起腰椎间盘细胞中α5β1整合素的变化，提示α5β1整合素在腰椎间盘细胞中可能发挥力学传感器的作用。