Utilizing single- and double-transfected cell models expressing human organic anion transporter 1 and human cytochrome P450 1A2 to investigate the interactions with ingredients of herbal medicines

Effects of rhein and Rheum palmatum L. extract on the pharmacokinetics and tissue distribution of aristolochic acid I and its demethylated metabolite in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acid nephropathy (AAN) is a kidney disease caused by the administration of plants containing aristolochic acids (AAs). Aristolochic acid I (AAI) is the main toxic component in AAs. Organic anion transporters (OATs) 1 and 3 mediate the renal uptake of AAI, which is related to AAN. In our previous study, we found that anthraquinones derived from the herbal medicine Rheum palmatum L. (RP) inhibited both OAT1 and OAT3, with rhein exhibiting the greatest potency among the components.

AIM OF THE STUDY

This study aimed to investigate the effects of rhein and RP extract on the pharmacokinetics and tissue distribution of AAI and its demethylated metabolite (8-hydroxy-aristolochic acid I [AAIa]) in rats.

MATERIALS AND METHODS

Rhein and RP extract were used as OAT inhibitors, and AAI was used as the toxic substrate. The pharmacokinetics and tissue distribution of AAI and AAIa in rats following the intravenous injection of AAI (10 mg/kg) in the presence and absence of rhein (100 mg/kg) or RP extract (5 g crude drug/kg) were investigated.

RESULTS

Co-administration with rhein increased AUC0-∞ of AAI and AAIa by 39 and 44%, respectively. However, the renal level of AAI was decreased to 50, 42, and 58% of those in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively, and the renal level of AAIa was decreased to 58, 57, and 61% of the level in rats treated with AAI alone, respectively, at these time points. In the RP extract co-administration group, AAI and AAIa plasma exposure was not significantly increased, but renal accumulation of AAI was decreased to 63, 58, and 68% of that in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively. In addition, renal accumulation of AAIa was decreased to 74, 70, and 70% of that in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively.

CONCLUSIONS

This study indicated that co-administration with rhein significantly increased the plasma exposure of AAI and AAIa while decreased their renal accumulation in rats. RP extract reduced the renal accumulation of AAI and AAIa, but have no significant effect on their plasma exposure levels in rats.

Development and Validation of Liquid Chromatography-mass Spectrometry Method for the Determination of Intracellular Concentration of Ginkgolide A, B, C, and Bilobalide in Transporter-Expressing Cells

Background:

Terpene lactones are major components of ginkgo biloba extract which are used in cardiovascular and degenerative diseases. To study the involvement of transporters in the transport/disposition of ginkgolides A, B, C, and bilobalide, a bioanalytical assay was developed by LCMS/ MS system for the quantitation of intracellular levels of terpene lactones in cells expressing organic cation transporter 2 (OCT2).

Methods:

The assay involved an optimized simple sample handling with methyl tert-butyl ether for liquid-liquid extraction and reconstitution in modified dissolution solution. Pretreatment of samples with 50 μM ascorbic acid and the addition of ascorbic acid and formic acid in dissolution solution significantly reduced matrix effect and stabilized the postpreparative samples. Separations were performed by Zobrax RRHD column (extend-C18 1.8μm, 3.0 x 100mm) and acetonitrile gradient elution. The analysis was carried out in the negative ion scan mode using multiple reaction monitoring.

Results:

The method was validated for linearity (concentration range of 20-5000nM), accuracy (±13.1%), precision (<11.0%), recovery (94.31–105.9%), matrix effect (93.8-111.0%) and stability. Finally, the method was applied in the determination of intracellular concentrations of ginkgolides A, B, C, and bilobalide in Madin-Darby canine kidney (MDCK-mock) and MDCK-OCT2 cells in uptake study.

Conclusion:

The developed method was successfully validated. Results suggest that OCT2 is involved in the renal disposition of ginkgolide A, B, and bilobalide. This method would foster the study of transport mediated activity via the interaction of ginkgolides and bilobalide with cellular systems.

Organic anion transporter 1 and 3 contribute to traditional Chinese medicine-induced nephrotoxicity

With the internationally growing popularity of traditional Chinese medicine (TCM), TCM-induced nephropathy has attracted public attention. Minimizing this toxicity is an important issue for future research. Typical nephrotoxic TCM drugs such as Aristolochic acid, Tripterygium wilfordii Hook. f, Rheum officinale Baill, and cinnabar mainly damage renal proximal tubules or cause interstitial nephritis. Transporters in renal proximal tubule are believed to be critical in the disposition of xenobiotics. In this review, we provide information on the alteration of renal transporters by nephrotoxic TCMs, which may be helpful for understanding the nephrotoxic mechanism of TCMs and reducing adverse effects. Studies have proven that when administering nephrotoxic TCMs, the expression or function of renal transporters is altered, especially organic anion transporter 1 and 3. The alteration of these transporters may enhance the accumulation of toxic drugs or the dysfunction of endogenous toxins and subsequently sensitize the kidney to injury. Transporters-related drug combination and clinical biomarkers supervision to avoid the risk of future toxicity are proposed.

Influence of organic anion transporter 1/3 on the pharmacokinetics and renal excretion of ginkgolides and bilobalide

ETHNOPHARMACOLOGICAL RELEVANCE

The major terpene lactones of ginkgo biloba extract (GBE) include ginkgolide A, B, C and bilobalide are used for the protection of cardiovascular, cerebrovascular and neurodegenerative diseases. Terpene lactones are orally bioavailable and predominantly eliminated via the renal pathway. However, information on the transporters involved in the pharmacokinetics (PK) and renal excretion of terpene lactones is limited.

AIM OF THE STUDY

The objective of this study is to assess the role of OAT1/3 which are important transporters in the human kidney in the PK and renal excretion ginkgolide A, B, C and bilobalide.

MATERIALS AND METHODS

Uptake of ginkgolide A, B, C and bilobalide in Madin-Darby Canine Kidney (MDCK) and human embryonic kidney 293 (HEK293) cells overexpressing OAT1 or OAT3, respectively were studied. To verify the result from in vitro cell models, the studies on PK, kidney accumulation and urinary excretion of ginkgolide A, B, C and bilobalide were carried out in rats.

RESULTS

The result showed that ginkgolide A, B, C and bilobalide are low-affinity substrates of OAT1/3. Following co-administration with probenecid, a typical inhibitor of OAT1/3, the rat plasma concentrations of ginkgolide A, B, C and bilobalide increased significantly. AUC showed a significant increase in the probenecid-treated rats compared to control rats (893.48 vs. 1123.85, 314.91 vs. 505.74, and 2724.97 vs. 3096.40 μg/L*h for ginkgolide A, B and bilobalide, respectively), while the clearance of these compounds significantly decreased. The accumulation of ginkgolide A, B and bilobalide in the kidney of the probenecid-treated rats was reduced by 1.8, 2.4, and 1.5-fold, respectively; further reducing the cumulative urinary recovery of these compounds.

CONCLUSION

The findings indicated that ginkgolide A, B and bilobalide are excreted via OAT1/3-mediated transport in the kidney and OAT1/3 inhibitor significantly influence the PK ginkgolides and bilobalide.