Lim Ching-Jou, Shen Wei-Chiang
Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA.
J Control Release. 2005 Sep 2;106(3):273-86. doi: 10.1016/j.jconrel.2005.05.001.
Oligomeric transferrin (Tf) was used to investigate the effect that cross-linking of transferrin receptors (TfR) has on intracellular trafficking of the Tf-TfR complex and to determine whether or not the Tf-oligomer would be a better carrier than monomeric Tf for the oral delivery of protein drugs. The intracellular retention and transcytosis of the Tf-oligomer was determined by performing pulse chase studies on enterocyte-like Caco-2 cells. The intracellular retention of the Tf-oligomer was 2-fold higher than that of monomeric Tf while there was no significant difference in transcytosis. However, in vivo studies in CF-1 mice showed that the plasma concentrations of Tf from the orally administered Tf-oligomer were approximately 2-, 3- and 60-fold higher than that of orally administered monomeric Tf at 24, 48 and 72 h post-administration, respectively. In addition, the retention of the Tf-oligomer in the intestine was higher than that of monomeric Tf, which was consistent with in vitro studies. Insulin (In), when conjugated to the Tf-oligomer (Agg-Tf-S-S-In), was more effective than monomeric Tf-In conjugate (Mono-Tf-S-S-In) in reducing blood glucose levels when orally administered to streptozotocin (STZ)-induced diabetic rats. Post-oral administration of Agg-Tf-In, a delayed onset and prolonged hypoglycemic effect was observed. These results demonstrate that the cross-linking of TfR induced by the binding of the oligomeric Tf alters the intracellular trafficking and increases the intracellular retention of Tf-TfR complexes in polarized Caco-2 cells. The alteration of TfR trafficking could conceivably have caused the increase of insulin transport across the intestinal barrier when Agg-Tf-S-S-In was administered orally to STZ-induced diabetic rats. The delayed onset and prolonged effect of Agg-Tf-S-S-In in hypoglycemia strongly suggests that the Tf-oligomer can act as a sustained release carrier in the oral delivery of protein and peptide drugs.
寡聚转铁蛋白（Tf）被用于研究转铁蛋白受体（TfR）交联对Tf-TfR复合物细胞内运输的影响，并确定Tf-寡聚物作为蛋白质药物口服递送载体是否优于单体Tf。通过对肠上皮样Caco-2细胞进行脉冲追踪研究，确定了Tf-寡聚物的细胞内滞留和转胞吞作用。Tf-寡聚物的细胞内滞留量比单体Tf高2倍，而转胞吞作用无显著差异。然而，CF-1小鼠的体内研究表明，口服Tf-寡聚物后，在给药后24、48和72小时，血浆中Tf的浓度分别比口服单体Tf高约2倍、3倍和60倍。此外，Tf-寡聚物在肠道中的滞留量高于单体Tf，这与体外研究结果一致。当将胰岛素（In）与Tf-寡聚物（Agg-Tf-S-S-In）偶联后，口服给予链脲佐菌素（STZ）诱导的糖尿病大鼠时，其降低血糖水平的效果比单体Tf-In偶联物（Mono-Tf-S-S-In）更有效。口服Agg-Tf-In后，观察到血糖降低起效延迟且作用时间延长。这些结果表明，寡聚Tf结合诱导的TfR交联改变了细胞内运输，并增加了极化Caco-2细胞中Tf-TfR复合物的细胞内滞留。当口服Agg-Tf-S-S-In给STZ诱导的糖尿病大鼠时，TfR运输的改变可能导致胰岛素跨肠屏障转运增加。Agg-Tf-S-S-In在低血糖中的起效延迟和作用时间延长强烈表明，Tf-寡聚物可作为蛋白质和肽类药物口服递送的缓释载体。
