Effects of liver fibrosis on verapamil pharmacokinetics in rats

A LC-ESI-MS method for the simultaneous determination of madecassoside and its metabolite madecassic acid in rat plasma: comparison pharmacokinetics in normal and collagen-induced arthritic rats

To develop a simple and highly sensitive high performance liquid chromatography with electrospray ionization mass spectrometric (LC-ESI-MS) method for the simultaneous determination of madecassoside and its major metabolite madecassic acid in rat plasma, and compare the pharmacokinetics of the two compounds in normal and collagen-induced arthritis (CIA) rats. Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was accomplished on an Inertsil ODS-3 column, using a gradient elution with the mobile phase composed of acetonitrile and water acidified with 0.1% (V/V) formic acid. Detection was achieved by ESI-MS under the negative selected ion monitoring (SIM) mode. In normal and CIA rats, madecassoside (30 mg·kg(-1)) was orally administered for 21 consecutive days from the day of arthritis onset. For madecassoside, the linear range was 10-1 000 ng·mL(-1) with the square regression coefficient (r) of 0.998 9, while for madecassic acid, the linear range was 10-500 ng·mL(-1) with the square regression coefficient (r) of 0.996 1. The lower limit of quantification was 10 ng·mL(-1) for both analytes. The intra- and inter-day precision ranged from 1.78% to 13.42% for madecassoside and 2.30% to 14.90% for madecassic acid, and the accuracy was between -0.95% and 6.30% for madecassoside and between -1.48% and 5.34% for madecassic acid. The average recoveries of madecassoside, madecassic acid and IS from spiked plasma samples were > 81%. The developed method was successfully applied to the pharmacokinetic study of madecassoside and madecassic acid in rats after an oral administration of madecassoside. During initial 7 days of dosing, the cmax and AUC of madecassoside were greatly decreased and Vd/F was markedly increased in CIA rats, and no significant difference was observed on the first day of dosing. In contrast, the T1/2, cmax and AUC of madecassic acid were significantly increased, and Ke of madecassic acid was greatly decreased in CIA rats compared with normal rats. Along with repeated administration of madecassoside, the differences of pharmacokinetic parameters of both madecassoside and madecassic acid between CIA and normal rats gradually subsided. The pharmacokinetic characteristics of both madecassoside and madecassic acid in rats were significantly altered by arthritis status, and the differences of pharmacokinetic parameters between arthritis and normal rats coincide with the severity of arthritis.

Pharmacokinetics of verapamil and its metabolite norverapamil in rats with hyperlipidaemia induced by poloxamer 407

In this study, the pharmacokinetics of verapamil and its active metabolite norverapamil were evaluated following intravenous and oral administration of 10 mg/kg verapamil to rats with hyperlipidaemia (HL) induced by poloxamer 407 (HL rats). The total area under the plasma concentration time curve (AUC) of verapamil in HL rats following intravenous administration was significantly greater (by 11.2%) than in control rats due to their slower (by 11%) non-renal clearance. The oral AUC of verapamil in HL rats was also significantly greater (by 116%) compared with controls, with a larger magnitude than the data observed following intravenous administration. This may have been a result of the decreased intestinal metabolism of verapamil in HL rats. The AUC of norverapamil and AUC(norverapamil)/AUC(verapamil) ratios following intravenous and oral administration of verapamil were unchanged in HL rats. Assuming that the HL rat model qualitatively reflects similar changes in patients with HL, the findings of this study have potential therapeutic implications. Further studies in humans are required to determine whether modification of the oral verapamil dosage regimen in HL states is necessary.

The role of nuclear receptors in the kidney in obesity and metabolic syndrome

Nuclear receptors are ligand-activated transcriptional regulators of several key aspects of renal physiology and pathophysiology. As such, nuclear receptors control a large variety of metabolic processes, including kidney lipid metabolism, drug clearance, inflammation, fibrosis, cell differentiation, and oxidative stress. Derangement of nuclear receptor regulation, that is, mainly due to obesity may induce metabolic syndrome, may contribute to the pathogenesis and progression of chronic renal disease and may result in end-stage renal disease. This places nuclear receptors at the forefront of novel therapeutic approaches for a broad range of kidney disorders and diseases, including glomerulosclerosis, tubulointerstitial disease, renal lipotoxicity, kidney fibrosis, and hypertension. This review focuses on the importance of the transcription factors peroxisome proliferator-activated receptor alpha, peroxisome proliferator-activated receptor beta, peroxisome proliferator-activated receptor gamma, liver X receptors, farnesoid X receptor, and the pregnane X receptor/steroid and xenobiotic receptor (PXR) on the physiology and pathophysiology of renal diseases associated with obesity and metabolic syndrome.

Role of high-fat diet in regulation of gene expression of drug metabolizing enzymes and transporters

AIM

Our aim is to investigate the molecular mechanism of regulation of gene expression of drug metabolizing enzymes (DMEs) and transporters in diet-induced obesity.

MAIN METHODS

Adult male CD1 mice were fed diets containing 60% kcal fat (HFD) or 10% kcal fat (LFD) for 14 weeks. RNA levels of hepatic DMEs, transporters and their regulatory nuclear receptors (NRs) were analyzed by real-time PCR. Activation of cell-signaling components (JNK and NF-κΒ) and pro-inflammatory cytokines (IL-1β, IL-6 and TNFα) were measured in the liver. Finally, the pharmacodynamics of drugs metabolized by DMEs was measured to determine the clinical relevance of our findings.

KEY FINDINGS

RNA levels of the hepatic phase I (Cyp3a11, Cyp2b10, Cyp2a4) and phase II (Ugt1a1, Sult1a1, Sultn) enzymes were reduced ~30-60% in HFD compared to LFD mice. RNA levels of Cyp2e1, Cyp1a2 and the drug transporters, multidrug resistance proteins, (Mrp)2, Mrp3 and multidrug resistant gene (Mdr)1b were unaltered in HFD mice. Gene expression of the NRs, PXR and CAR and nuclear protein levels of RXRα was reduced in HFD mice. Cytokines, JNK and NF-κΒ were induced in HFD mice. Thus reduction in hepatic gene expression in obesity may be modulated by cross-talk between NRs and inflammation-induced cell-signaling. Sleep time of Midazolam (Cyp3a substrate) was prolonged in HFD mice, while Zoxazolamine (Cyp1a2 and Cyp2e1 substrate)-induced sleep time was unaltered.

SIGNIFICANCE

This study demonstrates that gene-specific reductions in DMEs can affect specific drugs metabolized by these enzymes, thus providing a rationale to monitor the effectiveness of drug therapy in obese individuals.

Synergistic antifibrotic effect of verapamil and interferon-gamma in rats: partially based on enhanced verapamil oral bioavailability

OBJECTIVE

The objective of this study was to investigate the synergistic antifibrotic effect of verapamil and interferon-gamma (IFN-gamma) on rat liver fibrosis and its potential pharmacokinetic-based mechanism.

METHODS

Rat liver fibrosis model was successfully established, and both the therapeutic effects and pharmacokinetic parameters of verapamil were evaluated after the administration of verapamil with or without IFN-gamma. The activities of cytochrome P450 3A (CYP3A) and the expression of multidrug resistance (Mdr) mRNA were measured in liver and small intestine.

RESULTS

The results showed the synergistic antifibrotic effect of verapamil and IFN-gamma in rat liver fibrosis, in terms of decreased serum L-alanine aminotransferase activity and liver hydroxyproline content and improved liver histopathology, when compared with rats treated with verapamil or IFN-gamma alone. Meanwhile, the area under the curve of verapamil increased significantly after single administration of verapamil and IFN-gamma and the concentration of verapamil in plasma increased, but the metabolite : parent ratio of verapamil decreased after consecutive administrations of verapamil and IFN-gamma. Furthermore, the activities of CYP3A in both the liver and the small intestine and the expression of Mdr in small intestine decreased in rats treated with verapamil and IFN-gamma.

CONCLUSION

All these results indicated that the combination of verapamil and IFN-gamma exerts a synergistic antifibrotic effect on rat liver fibrosis. The mechanism was partially based on the enhanced oral bioavailability of verapamil by increasing the intestinal absorption as well as reducing the first-pass metabolism, through inhibition of CYP3A activity and P-glycoprotein expression by IFN-gamma