The influence of OATP2B1 and atorvastatin on coproporphyrin isomers in rats

Kinzi, Jonny; Grube, Markus; Hussner, Janine; Seibert, Isabell; Hamburger, Matthias; Meyer zu Schwabedissen, Henriette E.

doi:10.1016/j.jphs.2023.09.003

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“…In rats, atorvastatin also undergoes hydroxylation (Black et al, 1999) most likely mediated by the rat orthologs of CYP3A4 of which especially rCYP3A1 and rCYP3A2 are considered to be expressed in the rat's liver (Takara et al, 2003). Accordingly, it was proposed that one explanation for the reduced hepatic content of atorvastatin in the livers of SLCO2B1 1/1 rats might be the observed higher rCYP3A1 protein abundance in the liver of the humanized animals (Kinzi et al, 2022(Kinzi et al, , 2024b. Unfortunately, this previous phenotyping study with atorvastatin in SLCO2B1 1/1 and rSlco2b1 À/À rats was not designed to monitor the metabolism of atorvastatin in the treated rats.…”

Section: Introductionmentioning

confidence: 99%

Humanization ofSLCO2B1in Rats Increases rCYP3A1 Protein Expression but Not the Metabolism of Erlotinib to OSI-420

Rysz,

Schäfer,

Paloumpis

et al. 2024

J Pharmacol Exp Ther

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The organic anion transporting polypeptide (OATP)2B1 [(gene: solute carrier organic anion transporter family member 2B1 (SLCO2B1)] is an uptake transporter that facilitates cellular accumulation of its substrates. Comparison of SLCO2B1 1/1 knockin and rSlco2b1 À/À knockout rats showed a higher expression of rCYP3A1 in the humanized animals. We hypothesize that humanization of OATP2B1 not only affects cellular uptake but also metabolic activity. To further investigate this hypothesis, we used SLCO2B1 1/1 and rSlco2b1 À/À rats and the OATP2B1 and rCYP3A1 substrate erlotinib, which is metabolized to OSI-420, for in vivo and ex vivo experiments. One hour after administration of a single dose of erlotinib, the knockin rats exhibited significantly lower erlotinib serum levels, but no change was observed in metabolite concentration or the OSI-420/erlotinib ratio. Similar results were obtained for liver tissue levels comparing SLCO2B1 1/1 and rSlco2b1 À/À rats. Liver microsomes isolated from the erlotinib-treated animals were characterized ex vivo for rCYP3A activity using testosterone, showing higher activity in the knockin rats. The contrary was observed when microsomes isolated from treatment-naïve animals were assessed for the metabolism of erlotinib to OSI-420.The latter is in contrast to the higher rCYP3A1 protein amount observed by western blot analysis in rat liver lysates and liver microsomes isolated from untreated rats. In summary, rats humanized for OATP2B1 showed higher expression of rCYP3A1 in liver and reduced serum levels of erlotinib but no change in the OSI-420/erlotinib ratio despite a lower OSI-420 formation in isolated liver microsomes. Studies with CYP3A-specific substrates are warranted to evaluate whether humanization affects not only rCYP3A1 expression but also metabolic activity in vivo. SIGNIFICANCE STATEMENTHumanization of rats for the organic anion transporting polypeptide (OATP)2B1 increases rCYP3A1 expression and activity in liver. Using the OATP2B1/CYP3A-substrate erlotinib to assess the resulting phenotype, we observed lower erlotinib serum and liver concentrations but no impact on the liver/serum ratio. Moreover, there was no difference in the OSI-420/erlotinib ratio comparing humanized and knockout rats, suggesting that OSI-420 is not applicable to monitor differences in rCYP3A1 expression as supported by data from ex vivo experiments with rat liver microsomes.

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Section: Introductionmentioning

confidence: 99%