Effects of acid and lactone forms of statins on S-warfarin 7-hydroxylation catalyzed by human liver microsomes and recombinant CYP2C9 variants (CYP2C9.1 and CYP2C9.3).

The inhibition of CYP2C9-mediated warfarin metabolism by acid or lactone forms of statin converted in the body and effects of CYP2C9 genetic variants on their inhibition are not fully understood. Here, the effects of acid and lactone forms of statins on S-warfarin 7-hydroxylation were investigated in vitro. S-Warfarin 7-hydroxylase activities of human liver microsomes (HLMs), recombinant CYP2C9.1 (rCYP2C9.1), and rCYP2C9.3 (Ile359Leu variant) in the presence of statins were determined by high-performance liquid chromatography. Lactone forms of atorvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin inhibited the activity of HLMs more potently than the corresponding acid forms, whereas fluvastatin acid showed stronger inhibition than fluvastatin lactone. When the effects of statins on rCYP2C9 variants were examined, inhibition profiles of acid versus lactone forms of statins except for fluvastatin were similar between rCYP2C9.1 and rCYP2C9.3. However, the degrees of inhibition by atorvastatin lactone, fluvastatin acid, fluvastatin lactone, lovastatin lactone, and pitavastatin lactone (Ki values) were significantly different between these variants. These results indicated that lactone forms of statins other than fluvastatin showed more potent inhibition of CYP2C9-catalyzed S-warfarin 7-hydroxylation than the corresponding acid forms. Furthermore, our results indicated that Ile359Leu substitution in CYP2C9 affected the inhibitory potencies of statins.

In vitro inhibition of CYP2C9-mediated warfarin 7-hydroxylation by iguratimod: possible mechanism of iguratimod-warfarin interaction.

Iguratimod is a novel disease-modifying antirheumatic drug. A blue letter (safety advisory) for drug interaction between iguratimod and warfarin was issued by the Ministry of Health, Labour and Welfare of Japan in May 2013. Iguratimod may affect warfarin metabolism catalyzed by CYP. However, it is not clear whether iguratimod inhibits warfarin oxidation. This study was performed to investigate the effects of iguratimod on warfarin 7-hydroxylation with human liver microsomes (HLMs) and recombinant CYP enzymes. Iguratimod concentration-dependently inhibited R,S-warfarin 7-hydroxylase activity of HLMs with an IC50 value of 15.2 µM. The inhibitory effect was examined with S-warfarin and R-warfarin to determine which enantiomer was more potently inhibited by iguratimod. Iguratimod potently inhibited the S-warfarin 7-hydroxylase activity of HLMs with an IC50 value of 14.1 µM, but showed only slight inhibition of R-warfarin 7-hydroxylation. Furthermore, iguratimod inhibited the S-warfarin 7-hydroxylase activity of recombinant CYP2C9.1 (rCYP2C9.1) and rCYP2C9.3 in a concentration-dependent manner with IC50 values of 10.8 and 20.1 µM, respectively. Kinetic analysis of the inhibition of S-warfarin 7-hydroxylation by iguratimod indicated competitive-type inhibition for HLMs and rCYP2C9.1 but mixed-type inhibition for rCYP2C9.3. The Ki values for HLMs, rCYP2C9.1, and rCYP2C9.3 were 6.74, 4.23, and 14.2 µM, respectively. Iguratimod did not exert metabolism-dependent inhibition of S-warfarin 7-hydroxylation. These results indicated that iguratimod is a potent direct inhibitor of CYP2C9-mediated warfarin 7-hydroxylation and that its inhibitory effect on CYP2C9.1 was more sensitive than that on CYP2C9.3.

Differential mRNA expression and the uptake of methotrexate in primary MAEC and MLF cells: involvement of the Abc and Slco/Oatp transporters in alveolar epithelial cell toxicity.

Drug transporters play a pivotal role in the disposition and elimination of a wide variety of organic compounds across the biological membrane of the body. Recent studies have revealed that some drug transporters are involved in drug-induced toxicity. We have previously reported that methotrexate (MTX)-induced cytotoxicity and apoptosis in primary mouse alveolar epithelial cells (MAEC) are more sensitive than primary mouse lung fibroblasts (MLF). In the present study, we investigated the mRNA expression of ABCs, Slco/Slc/Oatp transporters by RT-PCR and quantitative real-time PCR (qRT-PCR) techniques in mouse lung tissues and primary lung cells. The ABC transporters (Mdr1, Mrp1, 3, 4, 5, and Bcrp) and the Slco/Oatp transporters (Rfc, Oatp1a1, 1a4, 1a5, 1b2, 2a1, 2b1, 3a1, 4c1, and 5a1) were detected in mouse lung tissues, whereas some ABCs, Slcs/Oats, and Slco/Oatps transporters were not expressed in the mouse lung. Additionally, we found that some Abc transporters are expressed predominantly in MLF whereas Mrp3 and Oatp4c1 are expressed predominantly in MAEC. The transport activity of [(3)H]MTX mediated via MAEC was significantly higher than the MLF-mediated transport. When MLF was treated with MK571, accumulated [(3)H]MTX significantly increased when compared with MAEC. Thus, our results indicate that depending on the type of cells, several types of drug transporters are expressed in mouse lung tissues. Our results also suggest that MTX-induced fibrosis with cell dysfunction may be caused by the accumulation within the alveolar epithelial cells of MTX in the lung.