ABCG2 Modulates Chlorothiazide Permeability In Vitro–characterization of Its Interactions

Abstract

We are showing that chlorothiazide, a diuretic, is an ABCG2 substrate. It is a Biopharmaceutics Classification System/Biopharmaceutics Drug Distribution and Classification System (BCS/BDDCS) Class IV drug with low bioavailability. Therefore, we tested if chlorothiazide interacts with major apically located intestinal efflux transporters. Our data show that chlorothiazide is transported by ABCG2 with a Km value of 334.6 µM and does not interact with ABCB1 or ABCC2. The chlorothiazide-ABCG2 interaction results in a vectorial transport in MDCKII-BCRP and Caco-2 cells with efflux ratios of 36 and 8.1 respectively. Inhibition of ABCG2 in Caco-2 cells reduced the efflux ratio to 1.4, suggesting that ABCG2 plays a role in limiting chlorothiazide bioavailability in humans.

The role of drug transporters in the kidney: lessons from tenofovir

“…In the kidney, ABCB1 is expressed on the apical membrane and has broad substrate specificity, although substrates are usually hydrophobic and either neutral or cationic (DeGorter et al, 2012). ABCG2 plays a similar role to ABCB1 in drug disposition, is generally expressed in the same tissues, and contributes to renal excretion of some drugs (Kage et al, 2002; Jani et al, 2009; Beery et al, 2011). Unlike, ABCB1, the substrate preference for ABCG2 includes hydrophilic conjugated organic anions, particularly the sulfate forms.…”

Demonstrating suitability of the Caco-2 cell model for BCS-based biowaiver according to the recent FDA and ICH harmonised guidelines

“…Previous in‐vivo and in‐vitro studies suggest that nadolol is a P‐gp substrate, what is consistent with our results (ER = 3.6). Chlorothiazide interacts with well‐expressed efflux transporter ABCG2 (ER = 5.0). ER around 2 was calculated for acyclovir and famotidine, indicating that they are efflux pump substrates …”

Chlorothiazide is a Substrate for the Human Uptake Transporters OAT1 and OAT3

“…We have previously described the interaction between chlorothiazide and ABCG2 6. This efflux transporter is located on the apical membrane of renal proximal tubule epithelia,7 whereas the uptake transporters OAT1 and OAT3 have been localized to the basolateral membrane 8,9.…”

“…Renal secretion of compounds can be regarded as a two‐step process, involving first translocation across the basolateral membrane, and subsequently across the apical membrane. We have previously demonstrated the interaction between chlorothiazide and an ATP‐binding cassette transporter G2 (ABCG2),6 expressed on the apical membrane of renal proximal tubule epithelia 7. However, the uptake transporters responsible for chlorothizaide uptake at the basolateral membrane remain poorly characterized.…”