Enhanced liver tumor promotion activity in rats subjected to combined administration of phenobarbital and orphenadrine

Effect of Dietary Doses of Quercetin on Hepatic Drug Metabolizing Enzymes in Spontaneously Hypertensive Rats

BACKGROUND

Administration of quercetin (QR) has shown several health benefits in clinical and pre-clinical studies.

OBJECTIVE

This study investigates the effect of dietary doses of QR on hepatic drug metabolizing enzymes in spontaneously hypertensive rats in order to investigate the potential for herb-drug interactions.

METHODS

The activity and/or protein expression of selected cytochrome P450 (CYP) enzymes and microsomal epoxide hydrolase were measured in hepatic microsomes using specific probe substrates and/or polyclonal antibodies. Cytosolic fraction was utilized to measure protein level and activity of major antioxidant systems.

RESULTS

The doses employed in our study did not cause any significant alterations in the activity and/or protein level of CYP1A1, CYP2A6, CYP2E, and glutathione (GSH). While the activity and apoprotein levels of CYP1A2 and CYP2B1/2 were significantly reduced by the medium and high doses of QR, the activity and/or protein level of microsomal CYP3A and cytosolic GSH-S-transferase, GSH reductase, and GSH peroxidase were significantly enhanced. Activity and protein level of CYP2C9 were significantly inhibited by all doses. Only the high-dose QR resulted in significant inhibition of both microsomal and soluble epoxide hydrolase as well as induction of the antioxidant enzymes, catalase and superoxide dismutase.

CONCLUSION

This study demonstrates that dietary doses of QR may offer chemoprevention through stimulation of the endogenous antioxidant systems and inhibition of CYP enzymes involved in bioactivation of procarcinogens. However, modulation of drug metabolizing enzymes by QR could have potential for herb-drug interactions with the possibility of serious complications.

Dietary Doses of Sulforaphane Affect Hepatic Drug Metabolizing Enzymes in Spontaneously Hypertensive Rats

We previously demonstrated that exposure of spontaneously hypertensive rats (SHR) to dietary doses of sulforaphane (SF) results in resisting the progressive rise in blood pressure that is normally seen in these rats. This study investigates the potential effect of SF on hepatic drug metabolizing enzymes (DME) in SHR. The activity and/or protein expression of selected cytochrome P450 (CYP) enzymes and microsomal epoxide hydrolase (mEH) were measured in hepatic microsomes using specific probe substrates and/or polyclonal antibodies. Cytosolic fraction was utilized to measure protein level and activity of major antioxidant systems. The high dose SF resulted in a significant reduction of activity and apoproteins level of CYP1A2 and CYP2C9 and activities of CYP2B1/2 and mEH. No effect of SF was observed on the rest of the studied CYP enzymes. Both doses of SF resulted in a significant induction of both hepatic glutathione level and activities of superoxide dismutase and catalase. Activities of hepatic glutathione-S-transferases, glutathione reductase, and glutathione peroxidase were significantly induced only with the high dose. This study demonstrates that dietary doses of SF modulate the activity or protein expression of DME. Additionally, induction of the impaired antioxidant system in SHR may explain the blood pressure lowering effect of SF in this rat model. Copyright © 2015 John Wiley & Sons, Ltd.

Possible drug-drug interaction in dogs and cats resulted from alteration in drug metabolism: A mini review

Pharmacokinetic drug-drug interactions (in particular at metabolism) may result in fatal adverse effects in some cases. This basic information, therefore, is needed for drug therapy even in veterinary medicine, as multidrug therapy is not rare in canines and felines. The aim of this review was focused on possible drug-drug interactions in dogs and cats. The interaction includes enzyme induction by phenobarbital, enzyme inhibition by ketoconazole and fluoroquinolones, and down-regulation of enzymes by dexamethasone. A final conclusion based upon the available literatures and author's experience is given at the end of the review.

Modifying effects of liver tumor promotion in rats subjected to co-administration of indole-3-carbinol and phenobarbital

Indole-3-carbinol (I3C) and phenobarbital (PB) are cytochrome P450 (CYP) 1A and CYP2B inducers, respectively, and have liver tumor-promoting effects in rats. In this study, we investigated the modifying effects on tumor promotion by I3C and PB co-administration. Six-week-old male F344 rats received a single intraperitoneal injection of N-diethylnitrosamine for initiation treatment. Two weeks after the initiation, rats were given no tumor-promoting agents (DEN alone), I3C (2,500 or 5,000 ppm in diet), PB (60 or 120 ppm in drinking water), or 2,500 ppm I3C + 60 ppm PB for 6 weeks. One week after the I3C/PB treatments, all animals underwent a two-thirds partial hepatectomy. The number and area of liver cell foci positive for glutathione S-transferase placental form (GST-P(+) foci) were not significantly fluctuated in the PB+I3C group in the isoadditive statistical model. On the contrary, the mRNA levels of Cyp2b1/2 and Nqo1 were suppressed and enhanced, respectively, in the PB+I3C group in the isoadditive model, but there was no enhancement in the microsomal reactive oxygen species (ROS) production, thiobarbituric acid-reactive substance levels, and Ki-67(+) cell ratio in this group. The results suggest that the co-administration of I3C and PB causes no modifying effects in liver tumor promotion in rats.

Suppressive effect of liver tumor-promoting activities in rats subjected to combined administration of phenobarbital and piperonyl butoxide

Phenobarbital (PB) is a cytochrome P450 (CYP) 2B inducer, and piperonyl butoxide (PBO) is a CYP1A/2B inducer. These inducers have liver tumor-promoting effects in rats. In this study, we performed a rat two-stage liver carcinogenesis bioassay to examine the tumor-promoting effect of PB and PBO co-administration. Male rats received an intraperitoneal injection of N-diethylnitrosamine (DEN) for initiation. Two weeks after DEN administration, rats were given PB (60 or 120 ppm in drinking water), PBO (1,250 or 2,500 ppm in diet) or 60 ppm PB+1,250 ppm PBO for 6 weeks. One week after the PB/PBO treatment, all rats were subjected to a two-thirds partial hepatectomy. To evaluate the effect of the combined administration, we used two statistical additive models. In the isoadditive model, the average values of the area of GST-P positive foci in the PB+PBO group were significantly lower than those in the High PB or High PBO groups. In the heteroadditive model, the net values of Cyp1a1 mRNA level and microsomal reactive oxygen species (ROS) production in the PB+PBO group were significantly lower than the sum of those in the Low PB or Low PBO groups. On the contrary, there was no interactive effect in the PCNA-positive hepatocyte ratio, mRNA levels of Cyp2b1/2, Gstm3, Gpx2 and Nqo1, and the level of thiobarbituric acid-reactive substances in the PB+PBO group. These results suggest that PB and PBO co-administration causes suppressive effects in liver tumor-promoting activity in rats resulting from inhibited microsomal ROS production because of suppression of CYP1A induction.