Kennedy C J, Rakoczy P E, Robertson T A, Papadimitriou J M, Constable I J
Department of Surgery, University of Western Australia, Nedlands.
Exp Cell Res. 1994 Feb;210(2):209-14. doi: 10.1006/excr.1994.1031.
Using novel methodology, this study describes the kinetics of rod outer segment (ROS) phagocytosis and digestion by human retinal pigment epithelial (RPE) cells in vitro and examines the effect of certain lysosomal enzyme inhibitors on ROS digestion in these cells. Human RPE cells displayed saturation of phagocytosis with respect to both ROS concentration and time. While surface-binding and ingestion phases of ROS phagocytosis saturated after 24-36 h, the rate of ROS digestion reached a maximal level within 24 h. Increasing the concentration of zinc in the culture medium from 1.9 to 100 microM had no significant effect on ROS digestion. The effects of swainsonine (an alpha-mannosidase inhibitor), pepstatin (an aspartic protease inhibitor), and leupeptin (a cysteine protease inhibitor) were also examined. At 6 h, ROS digestion was reduced 27.3 +/- 15.3% by swainsonine, 69.4 +/- 20.9% by pepstatin, and 77.0 +/- 14.4% by leupeptin. The effect of these inhibitors declined with increasing time. This study is the first to demonstrate the functional importance of cysteine and aspartic proteases in the digestion of ROS by RPE cells in vitro.
本研究采用新方法描述了体外人视网膜色素上皮（RPE）细胞对视杆细胞外节（ROS）的吞噬和消化动力学，并研究了某些溶酶体酶抑制剂对这些细胞中ROS消化的影响。人RPE细胞在ROS浓度和时间方面均表现出吞噬作用的饱和。虽然ROS吞噬的表面结合和摄取阶段在24 - 36小时后饱和，但ROS消化速率在24小时内达到最高水平。将培养基中锌的浓度从1.9 microM提高到100 microM对ROS消化没有显著影响。还研究了苦马豆素（一种α - 甘露糖苷酶抑制剂）、胃蛋白酶抑制剂（一种天冬氨酸蛋白酶抑制剂）和亮抑蛋白酶肽（一种半胱氨酸蛋白酶抑制剂）的作用。在6小时时，苦马豆素使ROS消化减少27.3 +/- 15.3%，胃蛋白酶抑制剂使其减少69.4 +/- 20.9%，亮抑蛋白酶肽使其减少77.0 +/- 14.4%。这些抑制剂的作用随时间增加而减弱。本研究首次证明了半胱氨酸和天冬氨酸蛋白酶在体外RPE细胞消化ROS中的功能重要性。
