Evaluation of Factors to Decrease Plasma Concentration of an HIV Protease Inhibitor, Saquinavir in Ethanol-Treated Rats

Study on the pharmacokinetics, tissue distribution and excretion of Penthorum chinense Pursh in normal and acute alcoholic liver injury rats using validated UPLC-MS/MS method

Penthorum chinense Pursh (PCP), as a traditional medicine of Miao nationality in China, is often used for the treatment of various liver diseases. At present, information regarding the in vivo process of PCP is lacking. Herein, a sensitive and robust ultra-performance liquid chromatography tandem with mass spectrometry (UPLC-MS/MS) was developed and validated for the quantification of several components to study their pharmacokinetics, tissues distribution and excretion in normal and acute alcoholic liver injury (ALI) rats. Prepared samples were separated on a Thermo C18 column (4.6 mm × 50 mm, 2.4 μm) using water containing 0.1 % formic acid (A) and acetonitrile (B) as the mobile phase for gradient elution. Negative electrospray ionization was performed using multiple reaction monitoring (MRM) mode for each component. The validated UPLC-MS/MS assay gave good linearity, accuracy, precision, recovery rate, matrix effect and stability. This method was successfully applied to the pharmacokinetics, tissue distribution and excretion in normal and acute ALI rats. There were differences in pharmacokinetic process, tissue distribution and excretion characteristics, indicating that ALI had a significant influence on the in vivo process of PCP in rats. The research provided an experimental basis for the study of PCP quality control and further application in the clinic.

In-vitro evaluation of chronic alcohol effects on expression of drug-metabolizing and drug-transporting proteins

Objectives

In alcoholics without alcoholic liver disease, boosted drug elimination has been reported. However, mechanistic explanations for this phenomenon remain uncertain. In particular, data on the potential role of drug transporters are sparse.

Methods

Using a well-established in-vitro model for induction of human drug-metabolizing and drug-transporting proteins, we evaluated the potency of ethanol and the major fermentation side-product isopentanol to alter expression and function of these proteins by quantitative real-time polymerase chain reaction, Western blotting and flow cytometry. P-glycoprotein (Pgp)-inhibiting properties of ethanol and isopentanol were investigated via calcein extrusion assay.

Key findings

Ethanol and isopentanol significantly changed expression levels of drug-metabolizing and drug-transporting proteins that normalized within 2 weeks upon withdrawal. Cytochrome P-450 2C19 and Pgp were most strongly induced. Ethanol-induced Pgp at the messenger RNA (mRNA) (twofold to eightfold) and protein level (twofold), but not at the functional level. Both compounds did not inhibit Pgp.

Conclusions

Ethanol is demonstrated to increase mRNA and protein expression of human drug transporters such as Pgp in vitro. Withdrawal of ethanol exposure causes return to non-induced conditions within weeks. Functional consequences of increased Pgp expression in alcoholics need to be evaluated by clinical trials applying selective Pgp substrates such as digoxin.

Alcohol consumption effect on antiretroviral therapy and HIV-1 pathogenesis: role of cytochrome P450 isozymes

INTRODUCTION

Alcohol consumption, which is highly prevalent in HIV-infected individuals, poses serious concerns in terms of rate of acquisition of HIV-1 infection, HIV-1 replication, response to highly active antiretroviral therapy (HAART) and AIDS/neuroAIDS progression. However, little is known about the mechanistic pathways by which alcohol exerts these effects, especially with respect to HIV-1 replication and the patient's response to HAART.

AREAS COVERED

In this review, the authors discuss the effects of alcohol consumption on HIV-1 pathogenesis and its effect on HAART. They also describe the role of cytochrome P450 2E1 (CYP2E1) in alcohol-mediated oxidative stress and toxicity, and the role of CYP3A4 in the metabolism of drugs used in HAART (i.e., protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI)). Based on the most recent findings the authors discuss the role of CYP2E1 in alcohol-mediated oxidative stress in monocytes/macrophages and astrocytes, as well as the role of CYP3A4 in alcohol-PI interactions leading to altered metabolism of PI in these cells.

EXPERT OPINION

The authors propose that alcohol and PI/NNRTI interact synergistically in monocytes/macrophages and astrocytes through the CYP pathway leading to an increase in oxidative stress and a decrease in response to HAART. Ultimately, this exacerbates HIV-1 pathogenesis and neuroAIDS.

MDR1 C3435T polymorphism and interaction with environmental factors in risk of Parkinson's disease: a case-control study in Japan

It has been suggested that P-glycoprotein (P-gp), the product of multidrug resistance 1 (MDR1) gene, regulates the brain entry of various xenobiotics. Impaired function of P-gp may be associated with an increased risk of Parkinson's disease (PD). The aim of this study was to investigate the impact of a MDR1 C3435T polymorphism on PD risk alone or in combination with environmental factors. A total of 238 patients with PD and 368 controls were genotyped for the MDR1 C3435T polymorphism. Subjects with the TT genotype of the C3435T polymorphism showed a nonsignificantly increased risk of PD [odds ratio (OR)=1.49, 95% confidence interval (CI)=0.85-2.25] compared with those with the CC genotype. A gene-environment interaction was suggested, with a combination of at least one T allele and ever drinking conferring significantly higher risk (OR=1.83, 95% CI=1.07-3.15, p=0.029), compared with the CC genotype and never drinking. No significant interaction of smoking or occupational pesticide use with the C3435T polymorphism was observed. Our results suggest that the C3435T polymorphism may not play an important role in PD susceptibility in Japanese. Evidence of an interaction between the C3435T polymorphism and alcohol consumption was suggested.

Differential effects of ethanol on spectral binding and inhibition of cytochrome P450 3A4 with eight protease inhibitors antiretroviral drugs

BACKGROUND

Cytochrome P450 3A4 (CYP3A4) is the most abundant CYP enzyme in the liver, which metabolizes approximately 50% of the marketed drugs including antiretroviral agents. CYP3A4 induction by ethanol and its impact on drug metabolism and toxicity is known. However, CYP3A4-ethanol physical interaction and its impact on drug binding, inhibition, or metabolism is not known, except that we have recently shown that ethanol facilitates the binding of a protease inhibitor (PI), nelfinavir, with CYP3A4. The current study was designed to examine the effect of ethanol on spectral binding and inhibition of CYP3A4 with all currently used PIs that differ in physicochemical properties.

METHODS

We performed type I and type II spectral binding with CYP3A4 at 0 and 20 mM ethanol and varying PIs' concentrations. We also performed CYP3A4 inhibition using 7-benzyloxy-4-trifluoromethylcoumarin substrate and NADPH at varying concentrations of PIs and ethanol.

RESULTS

Atazanavir, lopinavir, saquinavir, and tipranavir showed type I spectral binding, whereas indinavir and ritonavir showed type II. However, amprenavir and darunavir did not show spectral binding with CYP3A4. Ethanol at 20 mM decreased the maximum spectral change (δA(max)) with type I lopinavir and saquinavir, but it did not alter δA(max) with other PIs. Ethanol did not alter spectral binding affinity (K(D)) and inhibition constant (IC(50)) of type I PIs. However, ethanol significantly decreased the IC(50) of type II PIs, indinavir and ritonavir, and markedly increased the IC(50) of amprenavir and darunavir.

CONCLUSIONS

Overall, our results suggest that ethanol differentially alters the binding and inhibition of CYP3A4 with the PIs that have different physicochemical properties. This study has clinical relevance because alcohol has been shown to alter the response to antiretroviral drugs, including PIs, in HIV-1-infected individuals.

Effect of ethanol on spectral binding, inhibition, and activity of CYP3A4 with an antiretroviral drug nelfinavir

Cytochrome P450 3A4 (CYP3A4) is the most abundant CYP enzyme in the liver and metabolizes approximately 50% of the drugs, including antiretrovirals. Although CYP3A4 induction by ethanol and impact of CYP3A4 on drug metabolism and toxicity is known, CYP3A4-ethanol physical interaction and its impact on drug binding, inhibition, or metabolism is not known. Therefore, we studied the effect of ethanol on binding and inhibition of CYP3A4 with a representative protease inhibitor, nelfinavir, followed by the effect of alcohol on nelfinavir metabolism. Our initial results showed that methanol, ethanol, isopropanol, isobutanol, and isoamyl alcohol bind in the active site of CYP3A4 and exhibit type I spectra. Among these alcohol compounds, ethanol showed the lowest K(D) (5.9±0.34mM), suggesting its strong binding affinity with CYP3A4. Ethanol (20mM) decreased the K(D) of nelfinavir by >5-fold (0.041±0.007 vs. 0.227±0.038μM). Similarly, 20mM ethanol decreased the IC(50) of nelfinavir by >3-fold (2.6±0.5 vs. 8.3±3.1μM). These results suggest that ethanol facilitates binding of nelfinavir with CYP3A4. Furthermore, we performed nelfinavir metabolism using LCMS. Although ethanol did not alter k(cat), it decreased the K(m) of nelfinavir, suggesting a decrease in catalytic efficiency (k(cat)/K(m)). This is an important finding because alcoholism is prevalent in HIV-1-infected persons and alcohol is shown to decrease the response to antiretroviral therapy.

Effect of cyclosporine on drug transport and pharmacokinetics of nifedipine

Nifedipine (NFP) is an anti-hypersensitive drug and a well-known substrate of cytochrome P450 3A4 (CYP3A4), while cyclosporine (CSP) is a potent p-glycoprotein (P-gp) inhibitor. P-gp is a drug transporter, which determines the absorption and bioavailability of many drugs that are substrates for P-gp. Drugs that induce or inhibit P-gp may have a profound effect on the absorption and pharmacokinetics (PK) of drugs transported by P-gp within the body, possibly compromising their bioavailability. But the role of P-gp in the NFP efflux and its impact on PK profile is not known. Hence in our present study we attempted to investigate the effect of CSP on oral absorption and PK of NFP. Rhodamine 123 (Rho 123), a known P-gp substrate was used as a positive control. Male Wistar rats (350-400 g) were used for the study. Rats were divided into 4 groups (n=6 each); one group was treated with vehicle (cremophor) followed by NFP (0.2 mg/kg; i.v. bolus) and the other group with CSP (10 mg/kg; i.v.) followed by NFP. Group 3 and 4 were treated with vehicle (cremophor) followed by Rho 123 (0.2 mg/kg, i.v.) and CSP (10 mg/kg; i.v.) followed by Rho 123 (0.2 mg/kg, i.v.) respectively. The blood samples were collected at 0, 5, 10, 15, 30, 60, 90, 120, 180 and 240 min after NFP administration. NFP concentrations in plasma were analyzed by LC-MS-MS and Rho 123 was analyzed by fluorimetric detector. NFP efflux was significantly decreased in CSP treated rats (49.1% decrease, P<0.05), while NFP concentration in plasma were not changed. However the decrease in NFP efflux did not show any significant changes in NFP PK parameters (T(max); 2.0 vs. 2.5 min, C(max); 0.084 vs. 0.076 microg/ml, T(1/2); 84.0 vs. 91.4 min, AUC(0-t); 4.183 vs. 3.467 microg h/ml, AUC(infinity); 5.915 vs. 4.769 microg h/ml, AUMC(0-t); 224.073 vs. 173.063 microg h/ml, AUMC(infinity); 776.871 vs. 575.038 microg h/ml, MRT(0-t); 53.608 vs. 49.538 microg h/ml, MRT(infinity); 118.194 vs. 115.246 microg h/ml, CL(tot); 0.0375 vs. 0.0433 l/h, Vd(ss); 3.999 vs. 4.641 l in NFP alone vs. CSP+NFP groups respectively). Thus the results indicate that NFP would belong to a group of P-gp substrate. The decrease in efflux of NFP by CSP, through inhibition of P-gp, into the intestinal lumen did not show any impact on PK. This could be due to the activity of other transporters and/or CYP3A4 may have more limiting role than P-gp on NFP metabolism and disposition that is why inhibiting P-gp did not lead to increase the bioavailability and PK alterations.

Relationship between Excretion Clearance of Rhodamine 123 and P-Glycoprotein (Pgp) Expression Induced by Representative Pgp Inducers

P-Glycoprotein (Pgp) locates in several tissues in the living body and acts as an efflux pump for many drugs. In this study, the usefulness of intravenous rhodamine 123 (Rho123) administration as a marker for detecting the inducing effect of Pgp by drugs was identified, and the relationship between excretion clearances of Rho123 via Pgp and its expression during treatment with the representative Pgp inducers rifampicin (RFP), dexamethasone (DEX) and St. John's Wort (SJW) were examined in rat liver, intestine and kidney. After pretreatment with RFP (10 mg/kg/d) for 4 d, DEX (50 mg/kg/d) for 4 d or SJW (15 mg/kg/d) for 7 d orally, the biliary excretion of Rho123 after intravenous administration (0.2 mg/kg) increased significantly by 40%, 55% and 14%, respectively, and the intestinal excretion increased significantly by 24%, 50% and 27%, respectively, as compared with the controls. In contrast, there were no notable changes in the urinary excretion of Rho123 among rats that received these inducers. Western blot analysis with a monoclonal antibody for Pgp (C219) showed that Pgp levels in the small intestine and liver in the inducer-treated rats increased markedly as compared with the controls. In addition, there was a significant correlation between the induction levels of Pgp in the liver or small intestine and their clearance ratios (r2=0.7583, p<0.05), but not in the kidney. These observations suggest that the excretion clearances of Rho123 from blood circulation to the small intestine or to the bile after its intravenous administration are useful indicators to assess the Pgp function in the presence of Pgp inducers.

In Vivo Effects of Cyclosporin A and Ketoconazole on the Pharmacokinetics of Representative Substrates for P-Glycoprotein and Cytochrome P450 (CYP) 3A in Rats

In this study, the in vivo effects of cyclosporin A (CsA) and ketoconazole (KCZ), which are used as inhibitors of P-glycoprotein (Pgp) and cytochrome P450 (CYP) 3A, respectively, on the pharmacokinetics of rhodamine 123 (Rho123), nelfinavir (NFV) and erythromycin (EM) were evaluated in rats. The biliary excretion clearance (Clbile) of a known Pgp substrate, Rho123, after intravenous pretreatment with CsA or KCZ (0-20 mg/kg after i.v. administration) showed maximum reduction by 85.6 or 54.1%, respectively, suggesting that the inhibitory potency of KCZ is about half that of Pgp in the liver. Without pretreatment with CsA or KCZ, the clearance ratio of Clbile relative to the total body clearances of Rho123, NFV and EM was 10.5, 0.07 and 31.1%, respectively. After CsA pretreatment, these ratios decreased markedly in a manner dependent on the dose of CsA, while after CZ pretreatment the clearance ratios of NFV and EM increased significantly in a manner dependent on the dose of KCZ. However, in the liver, the contribution of Pgp to the changes in the pharmacokinetic parameters of Rho123, NFV and EM after intravenous administration was much less than that of CYP3A. The portal levels of Rho123 and EM but not NFV after intra-loop administration in the presence of 10 microM CsA in the jejunal loop increased significantly, while in the presence of 25 microM KCZ in the jejunal loop, the portal levels of those substrates showed no notable change as compared to the control levels. In conclusion, KCZ had dual potency to inhibit CYP3A and Pgp, and its inhibitory potency for Pgp was half that of CsA in the rat liver. In addition, metabolism via CYP3A contributed more significantly to the clearance of these substrates that did excretion via Pgp in the liver. In the small intestine, the contribution of Pgp is a more important factor in determining the oral bioavailability of EM than metabolism via CYP enzymes. The elimination of NFV is mainly dependent on liver metabolism via CYP3A, and the Pgp efflux mechanism in the liver and intestine did not contribute as importantly to the oral bioavailability of NFV under in vivo conditions, although NFV has been demonstrated to be a substrate of Pgp under in vitro conditions.