Ciprofloxacin suppresses Cyp3a in mouse liver by reducing lithocholic acid-producing intestinal flora.

Ciprofloxacin (CPX), a new quinolone antibiotic, is reported to reduce CYP3A expression in the liver when administered to rats. The present study investigates whether the reduction in intestinal flora is involved in this reduction of CYP3A. While hepatic Cyp3a11 expression and triazolam metabolic activity were significantly reduced by CPX treatment of SPF mice, no significant changes were seen by CPX treatment of germ-free (GF) mice. Lithocholic acid (LCA)-producing bacteria in the feces as well as hepatic level of taurine conjugate of LCA were significantly reduced in CPX-treated SPF mice. Cyp3a11 expression in GF mice was significantly elevated when treated with LCA, known as an activator of fernesoid X receptor and pregnane X receptor. These results indicate that antibiotics such as CPX, having antimicrobial spectrums against LCA-producing bacteria, possibly cause decrease in LCA in the liver, resulting in lower CYP3A expression. The intestinal flora is reported to be altered also by stress, disease and age etc. The findings of the present study suggest that these changes in intestinal flora may modify CYP expression and contribute to individual differences in pharmacokinetics.

Antibiotics suppress Cyp3a in the mouse liver by reducing lithocholic acid-producing intestinal flora.

We previously demonstrated that ciprofloxacin (CPX), a new quinolone antibiotic, suppresses Cyp3a in the mouse liver by reducing the hepatic level of lithocholic acid (LCA) produced by intestinal flora. The present study investigated the possibility that other antibiotics with antibacterial activity against LCA-producing bacteria also cause a decrease in the LCA level in the liver, leading to reduced expression of Cyp3a11. While the mRNA expression of Cyp3a11 in the liver was significantly reduced when SPF mice were administered antibiotics such as ampicillin, CPX, levofloxacin, or a combination of vancomycin and imipenem, no significant changes were observed after antibiotic treatment of GF mice lacking intestinal flora. LCA-producing bacteria in the feces as well as the hepatic level of the taurine conjugate of LCA were significantly reduced in the antibiotic-treated SPF mice, suggesting that the decrease in Cyp3a11 expression can be attributed to the reduction in LCA-producing intestinal flora following antibiotic administration. These results suggest that the administration of antibiotics with activity against LCA-producing bacteria can also cause a decrease in the LCA level in humans, which may lower CYP3A4 expression. The intestinal flora are reported to be altered not only by drugs, such as antibiotics, but also by stress, disease, and age. The findings of the present study suggest that these changes in intestinal flora could modify CYP expression and contribute to the individual differences in pharmacokinetics.