Drug Transporters of Intestinal Absorption

Mechanisms Underlying the Differences in the Pharmacokinetics of Six Active Constituents of Huangqi Liuyi Decoction between Normal and Diabetic Nephropathy Mouse Models

The aim of this study was to explore the mechanisms underlying the differences in the pharmacokinetics of Huangqi Liuyi decoction extract (HQD) under physiological and pathological conditions. The roles of liver cytochrome P450 metabolic enzymes (Cyp450) and small intestinal transporters were also investigated. The cocktail probe drug method was used to investigate the effects of diabetic nephropathy (DN) and HQD on metabolic enzyme activity. The expression levels of liver Cyp450 metabolic enzymes (Cyp1A2, Cyp2C37, Cyp3A11, Cyp2E1, and Cyp2C11) and small intestinal transporters (breast cancer resistance protein (BCRP), P-glycoprotein (P-gp), organic cation transporters (OCTs), and multidrug resistance-associated protein (MRPs) were determined using western blot. Compared to normal mice, the expression of OCT1, OCT2, MRP1, and MRP2 was increased in DN mice, while that of P-gp and BCRP (P < 0.05 and P < 0.001) was inhibited. HQD inhibited expression of Cyp1A2 and Cyp3A11 and increased the expression of P-gp and BCRP in normal mice. In DN mice, HQD induced expression of BCRP and inhibited expression of Cyp2C37, Cyp3A11, OCT2, MRP1, and MRP2. The activity of each Cyp450 enzyme was consistent with changes in expression. The changes in pharmacokinetic parameters of HQD in DN might, in part, be secondary to decreased expression of P-gp and BCRP. HQD varied in regulating transporter activities between health and disease. These findings support careful application of HQD-based treatment in DN, especially in combination with other drugs.

A multiaspect study on transcytosis mechanism of sorafenib nanogranules engineered by high-gravity antisolvent precipitation

Nanotechniques show significant merits in terms of improving the oral bioavailability of poorly water-soluble drugs. However, the mechanisms behind are not clear yet. For instance, what is the contribution of free drug released during nanogranule transcytosis, as well as the impact of drug transporter and chylomicron? To address these issues, sorafenib nanogranules (SFN-NGs) were prepared as model by the high-gravity antisolvent precipitation method which approaches to practical mass production. Then, a multiaspect study on the transcytosis mechanism of SFN-NGs was conducted in Caco-2 cells and rats, including paracellular transport, endocytosis, intracellular trafficking, transmembrane pathway, as well as the involvement of transporter and chylomicron. Pharmacokinetics in rats demonstrated an obvious superiority of SFN-NGs in oral absorption and lymphatic transfer over SFN crude drugs. Different from free SFN, SFN-NGs could be internalized in cells in early stage by caveolin/lipid raft or clathrin induced endocytosis, and transported intactly through the polarized cell monolayers. While in late stage, transporter-mediated transport of free SFN began to play a vital role on the transmembrane of SFN-NGs. No paracellular transport of SFN-NGs was found, and the trafficking of SFN-NGs was affected by the pathway of ER-Golgi complexes. Surprisedly, the intracellular free SFN was the main source of transmembrane for SFN-NGs, which was entrapped into chylomicrons and then secreted into the extracellular space. Generally, the findings in current study may shed light on the absorption mechanism of oral nanoformulations.