The influx/efflux mechanisms of d-peptide ligand of nAChRs across the blood–brain barrier and its therapeutic value in treating glioma
Bing Han, Weiyi Xie, Yanxia Zhang, Shilin Zhou, Jiahong Yang, Ruifeng Wang, Yuqing Sun, Xiaoyi Wang, Jie Xu, Dawei Chen, Yinhang Wang, Jiasheng Lu, Fengling Ning, Fu‐Ming Shen, Min Liu, Hui Cai, Hong Xin, Weiyue Lu, Xuemei Zhang
Abstract
A d -peptide ligand of the nicotine acetylcholine receptors (nAChRs), termed D CDX, enables drug delivery to the brain when incorporated into liposomes and has shown promise as a nanocarrier for treating brain diseases. However, few reports have described the mechanisms whereby D CDX-modified liposomes traverse the blood–brain barrier (BBB). Here, we studied the molecular mechanisms enabling D CDX (and its associated liposomes) to cross an in vitro BBB using a simulated cerebral endothelium monolayer formed by brain capillary endothelial cells (bEnd.3 cells). We also examined the mechanisms whereby D CDX-modified liposomes cross the BBB in vivo using the brain efflux-index method. Transport of D CDX and its modified liposomes was dominantly mediated via the lipid raft/caveolae endocytic pathway. Both the endoplasmic reticulum (ER) and Golgi complex participated in delivering D CDX-modified liposomes to the plasma membrane (PM). D CDX-modified liposomes also participated in the endosome/lysosome pathway (with high-efficiency BBB crossing observed in vitro ), while competing for the ER/Golgi/PM pathway. In addition, nAChR α7 did not promote the transportation of D CDX-modified liposomes in vivo or in vitro , as assessed with α7-knockout mice and by performing α-bungarotoxin (α-Bgt) binding-competition experiments. P-glycoprotein (P-gp) was identified as the main efflux transporter across the BBB, in vivo and in vitro . Using a xenograft nude mouse model of human glioblastoma multiforme , blocking the efflux function of P-gp with verapamil enhanced the therapeutic efficiency of D CDX-modified liposomes that were formulated with doxorubicin against glioblastoma. The findings of this study reveal novel mechanisms underlying crossing of the BBB by D CDX-modified liposomes, suggesting that D CDX-modified liposomes can potentially serve as a powerful therapeutic tool for treating glioma.