Cellular Uptake and Transport Mechanism of 6-Mercaptopurine Nanomedicines for Enhanced Oral Bioavailability

Abstract

Background Nanomedicines have significant advantages in enhancing the oral bioavailability of drugs, but a deeper understanding of the underlying mechanisms remains to be interpreted. Hence, the present study aims to explain the uptake and trafficking mechanism for 6-MP nanomedicines we previously constructed. Methods 6-MP loaded poly(lactide-co-glycolide) (PLGA) nanomedicines (6-MPNs) were prepared by the multiple emulsion method. The transcytosis mechanism of 6-MPNs was investigated in Caco-2 cells, Caco-2 monolayers, follicle associated epithelium (FAE) monolayers and rats, including transmembrane pathway, intracellular trafficking, paracellular transport and the involvement of transporter. Results Pharmacokinetics in rats showed that the area under the curve (AUC) of 6-MP in the 6-MPNs group (147.3 ± 42.89 μg/L·h) was significantly higher than that in the 6-MP suspensions (6-MPCs) group (70.31 ± 18.24 μg/L·h). The uptake of 6-MPNs in Caco-2 cells was time-, concentration- and energy-dependent. The endocytosis of intact 6-MPNs was mediated mainly through caveolae/lipid raft, caveolin and micropinocytosis. The intracellular trafficking of 6-MPNs was affected by endoplasmic reticulum (ER)-Golgi complexes, late endosome-lysosome and microtubules. The multidrug resistance associated protein 4 (MRP4) transporter-mediated transport of free 6-MP played a vital role on the transmembrane of 6-MPNs. The trafficking of 6-MPNs from the apical (AP) side to the basolateral (BL) side in Caco-2 monolayers was obviously improved. Besides, 6-MPNs affected the distribution and expression of zona occludens-1 (ZO-1). The transport of 6-MPNs in FAE monolayers was concentration- and energy-dependent, while reaching saturation over time. 6-MPNs improved the absorption of the intestinal Peyer’s patches (PPs) in rats. Conclusion 6-MPNs improve the oral bioavailability through multiple pathways, including active transport, paracellular transport, lymphatic delivery and MRP4 transporter. The findings of current study may shed light on the cellular uptake and transcellular trafficking mechanism of oral nanomedicines.

Mechanisms of Nanoparticle Transport across Intestinal Tissue: An Oral Delivery Perspective

“…Zhang et al recently unveiled the size-dependent transcytosis of gold nanoparticles via the ER-GB pathway in Caco-2 cells in vitro . The latest study by Zou et al used 6-mercaptopurine-loaded PLGA nanoparticles, which exhibited intracellular trafficking through ER-GB pathways . Nevertheless, several studies have been done to target other cell organelles, such as mitochondria and nuclei, for drug delivery in diseases, such as cancer and Alzheimer’s disease. − Drug delivery aimed at these compartments is generally associated with the effective release of particles into the cytosol to reach the target, which, from an oral delivery perspective, could be a barrier for transcytosis across intestinal epithelial cells for drugs intended to reach blood or lymphatic circulation.…”

2-Monoacylglycerol Mimetic Liposomes to Promote Intestinal Lymphatic Transport for Improving Oral Bioavailability of Dihydroartemisinin

“… 49 , 50 One possible transport route is that nanocarriers are delivered to lysosomes from early endosomes for degradation because lysosomes are digestive organelles containing various hydrolytic enzymes. Bafilomycin A1, a specific vacuolar-type H(+)-ATPase inhibitor that hinders the maturation process of early endosomes to lysosomes, 51 was applied to confirm the role of lysosomes in the exocytosis of SER-LPs. As shown in Figure 5B , the number of Dil-PEG-LPs and Dil-SER-LPs remaining in the Caco-2 cells exhibited a significant 0.70-fold and 0.44-fold increase compared with the control with the addition of bafilomycin A1, indicating that the maturation process of early endosomes to lysosomes had an obvious effect on the exocytosis process of Dil-SER-LPs and especially, Dil-PEG-LPs.…”

Combination of Chlorambucil and Mercaptopurine Show Effective Anti-Cancer Effects in Mice Model

“… 10 , 11 Moreover, for many years, 6MP has been the preferred medication for treating acute lymphoblastic leukemia. 12 , 13 It is believed that its biological activity is mediated through various modulations of cellular metabolism. The binding of 6MP metabolites to nucleic acids is the main pathway for its activity.…”