Mdr1a, Bcrp and Mrp2 regulate the efficacy and toxicity of mesaconitine and hypaconitine by altering their tissue accumulation and in vivo residence.

Mesaconitine (MA) and hypaconitine (HA) are the main bioactive/toxic alkaloids of Aconitum carmichaelii Debx, and MDR1, BCRP and MRP2 are involved in their efflux in vitro. This study aimed to explore the effects of Mdr1a, Bcrp and Mrp2 on the efficacy/toxicity of MA and HA by using efflux transporter gene knockout mouse models. The analgesic and anti-inflammatory effects, neurotoxicity/cardiotoxicity, and pharmacokinetic profiles of MA and HA were studied. Compared to wild-type mice, the analgesic effects of MA or HA were significantly enhanced in Mdr1a--/-, Bcrp1-/- and Mrp2-/- mice, and the anti-inflammatory effects notably increased in Bcrp1-/- and Mrp2-/- mice. Compared to wild-type mice, Mdr1a-/-, Bcrp1-/- and Mrp2-/- mice suffered from severe karyopyknosis and edema in the brain after MA or HA treatment. Meanwhile, significant arrhythmia appeared, and the heart rate and RR-interval were greatly altered in Mdr1a-/-, Bcrp1-/- and Mrp2-/- mice. Additionally, obvious disorder of cardiomyocytes were observed, and the CK and cTnT (indicators of heart injury) levels were greatly enhanced in efflux transporter gene knockout mice. The brain levels of MA and HA were markedly increased in Mdr1a-/-, Bcrp1-/- and Mrp2-/- mice, and the heart levels of MA and HA enhanced greatly in Mdr1a-/- mice. The MRT0-t values of MA and HA were remarkably enhanced in most efflux transporter gene knockout mice. In conclusion, Mdr1a, Bcrp and Mrp2 were all involved in regulating the efficacy/toxicity of MA and HA by altering their tissue accumulation and in vivo residence. Among the three efflux transporters, Mdr1a had a superior regulatory effect.

Breast Cancer Resistance Protein and Multidrug Resistance Protein 2 Determine the Disposition of Esculetin-7-O-Glucuronide and 4-Methylesculetin-7-O-Glucuronide.

Esculetin (ET)-7-O-glucuronide (ET-G) and 4-methylesculetin (4-ME)-7-O-glucuronide (4-ME-G) are the main glucuronide of ET and 4-ME, respectively. The disposition mediated by efflux transporters for glucuronide has significant influence on the pharmacokinetic profile and efficacy of bioactive compounds. In the current study, transporter gene knockout mice and Caco-2 cells were used to explore the effects of breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 2 (MRP2) on the disposition of ET-G and 4-ME-G. After oral or i.v. administration of ET and 4-ME, the area under the plasma concentration-time curve from time 0 to the last data point or infinity values of ET, 4-ME, and their glucuronides (ET-G and 4-ME-G) were remarkably and significantly increased in most Bcrp1-/- and Mrp2-/- mice compared with those in wild-type FVB mice (P < 0.05). These results were accompanied with a significant increase of maximum plasma concentration values (P < 0.05). In Caco-2 monolayers, the efflux and clearance rates of ET-G and 4-ME-G were markedly reduced by the BCRP inhibitor Ko143 and MRP2 inhibitor MK571 on the apical side (P < 0.05). In an intestinal perfusion study, the excretion of ET-G was significantly decreased in perfusate and increased in plasma in Bcrp1-/- mice compared with those in wild-type FVB mice (P < 0.05). The 4-ME-G concentration was also decreased in the bile in transporter gene knockout mice. ET and 4-ME showed good permeability in both Caco-2 monolayers [apparent permeability (Papp ) ≥ 0.59 × 10-5 cm/s] and duodenum (Papp ≥ 1.81). In conclusion, BCRP and MRP2 are involved in excreting ET-G and 4-ME-G. ET and 4-ME are most likely absorbed via passive diffusion in the intestines.