Abstract
Enalaprilat is the active metabolite of enalapril, a widely used antihypertension drug. The human organic anion transporter 3 (OAT3), which is highly expressed in the kidney, plays a critical role in the renal clearance of many drugs. While urinary excretion is the primary elimination route of enalaprilat, direct involvement of OAT3 has not been reported so far. In the present study, OAT3-mediated uptake of enalaprilat was first characterized, and the inhibition of OAT3 transport activity was then examined for a number of flavonoid and drug molecules with diverse structures. A varying degree of inhibition potency was demonstrated for flavonoids, with IC50 values ranging from 0.03 to 22.6 µM against OAT3 transport activity. In addition, commonly used drugs such as urate transporter 1 (URAT1) inhibitors also displayed potent inhibition on OAT3-mediated enalaprilat uptake. Pharmacophore and three-dimensional quantitative structure-activity relationship (3D-QSAR) analyses revealed the presence of a polar center and a hydrophobic region involved in OAT3-inhibitor binding. For the polar center, hydroxyl groups present in flavonoids could act as either hydrogen bond donors or acceptors and the number and position of hydroxyl groups were critical drivers for inhibition potency, while carboxyl groups present in some drugs could form ionic bridges with OAT3. The predicted inhibition potencies by comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were correlated well with experimental IC50 values. Taken together, the present study identified OAT3-mediated uptake of enalaprilat as an important mechanism for its renal clearance, which may be liable for drug-drug and herb-drug interactions. The established computational models revealed unique structural features for OAT3 inhibitors and could be used for structure-activity relationship (SAR) analysis of OAT3 inhibition. The clinical relevance of the inhibition of OAT3-mediated enalaprilat uptake warrants further investigation, particularly in populations where herbal remedies and drugs are used concomitantly.
Highlights
Natural remedies containing flavonoids and functional components are widely consumed to maintain health status and vigor
The uptake of enalaprilat was evaluated first using Human embryonic kidney 293 (HEK293) cell lines stably transfected with human uptake transporters including OAT1, organic anion transporter 3 (OAT3), organic cation transporter 2 (OCT2), OAPT1B1, OATP2B1 and OATP1B3, at two concentrations (10 and 100 mM)
While passive diffusion and/or other transportermediated processes was noticed at a very low level, the uptake of enalaprilat mediated by OAT3 was evident at high concentration
Summary
Natural remedies containing flavonoids and functional components are widely consumed to maintain health status and vigor. Herb-drug interaction represents an underlying risk as some natural components may alter pharmacokinetics, efficacy, and safety of therapeutic agents (Agbabiaka et al, 2018; Briguglio et al, 2018; Parvez and Rishi, 2019). Enalapril is rapidly absorbed with about 40% of the dose (10 mg) converted to enalaprilat (Ulm et al, 1982). Both enalapril and enalaprilat are excreted into the urine, suggesting the importance of renal clearance in the disposition of the drug and its active metabolite (Ulm et al, 1982; MacFadyen et al, 1993)
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