EFFECT OF EARLY PHASE ADJUVANT ARTHRITIS ON HEPATIC P450 ENZYMES AND PHARMACOKINETICS OF VERAPAMIL: AN ALTERNATIVE APPROACH TO THE USE OF AN ANIMAL MODEL OF INFLAMMATION FOR PHARMACOKINETIC STUDIES

Nimodipine systemic exposure and outcomes following aneurysmal subarachnoid hemorrhage: a pilot prospective observational study (ASH-1 study)

Background

Nimodipine improves outcomes following aneurysmal subarachnoid hemorrhage (aSAH). Guidelines recommend that all patients should receive a fixed-dose nimodipine for 21 days. However, studies reported variability of nimodipine concentrations in aSAH. It is not clear if reduced systemic exposure contributes to worsening outcomes. The aim of this study was to compare nimodipine systemic exposure in those who experienced poor outcomes to those who experienced favorable outcomes.

Methods

This was a pilot prospective observational study in 30 adult patients admitted to the University of Alberta Hospital with aSAH. Data were collected from the electronic health records following enrollment. Blood samples were collected around one nimodipine 60 mg dose at a steady state, and nimodipine [total, (+)-R and (-)-S enantiomers] plasma concentrations were determined. The poor outcome was defined as a modified Rankin Scale (mRS) score at 90 days of 3-6, while the favorable outcome was an mRS score of 0-2. The correlation between nimodipine concentrations and percent changes in mean arterial pressure (MAP) before and after nimodipine administration was also determined. Furthermore, covariates potentially associated with nimodipine exposure were explored.

Results

In total, 20 (69%) participants had favorable outcomes and 9 (31%) had poor outcomes. Following the exclusion of those with delayed presentation (>96 h from aSAH onset), among those presented with the World Federation of Neurological Surgeons (WFNS) grade 3-5, nimodipine median (interquartile range) area under the concentration time curve (AUC0-3h) in those with favorable outcomes were 4-fold higher than in those with poor outcomes [136 (52-192) vs. 33 (23-39) ng.h/mL, respectively, value of p = 0.2]. On the other hand, among those presented with WFNS grade 1-2, nimodipine AUC0-3h in those with favorable outcomes were significantly lower than in those with poor outcomes [30 (28-36) vs. 172 (117-308) ng.h/mL, respectively, value of p = 0.03)]. (+)-R-nimodipine AUC0-3h in those who did not develop vasospasm were 4-fold significantly higher than those who had vasospasm (value of p = 0.047). (-)-S-nimodipine was significantly correlated with percentage MAP reduction. Similar results were obtained when the whole cohort was analyzed.

Conclusion

The study was the first to investigate the potential association between nimodipine exposure following oral dosing and outcomes. In addition, it suggests differential effects of nimodipine enantiomers, shedding light on the potential utility of nimodipine enantiomers. Larger studies are needed.

Drug-disease interaction: Clinical consequences of inflammation on drugs action and disposition

Inflammation is a culprit in many conditions affecting millions of people worldwide. A plethora of studies has revealed that inflammation and inflammatory mediators such as cytokines and chemokines are associated with altered expression and activity of various proteins such as those involved in drug metabolism, specifically cytochrome P450 enzymes (CYPs). Emphasis of most available reports is on the inflammation-induced downregulation of CYPs, subsequently an increase in their substrate concentrations, and the link between the condition and the inflammatory mediators such as interleukin-6 and tumor necrosis factor alpha. However, reports also suggest that inflammation influences expression and/or activity of other proteins such as those involved in the drug-receptor interaction. These multifaced involvements render the clinical consequence of the inflammation unexpected. Such changes are shown in many inflammatory conditions including rheumatoid arthritis, Crohn's disease, acute respiratory illnesses as well as natural processes such as aging, among others. For example, some commonly used cardiovascular drugs lose their efficacy when patients get afflicted with inflammatory conditions such as rheumatoid arthritis and Crohn's disease. Interestingly, this is despite increased concentration subsequent to reduced clearance. The observation is attributed to a simultaneous reduction in the expression of target receptor proteins such as the calcium and potassium channel and β-adrenergic receptor as well as the metabolic enzymes. This narrative review summarizes the current understanding and clinical implications of the inflammatory effects on both CYPs and drug-receptor target proteins.

Resveratrol biotransformation and actions on the liver metabolism of healthy and arthritic rats

AIMS

To investigate the effects of resveratrol on glycogen catabolism and gluconeogenesis in perfused livers of healthy and arthritic rats. The actions of resveratrol-3-O-glucuronide (R3G) and the biotransformation of resveratrol into R3G was further evaluated in the livers.

MAIN METHODS

arthritis was induced with Freund's adjuvant. Resveratrol at concentrations of 10, 25, 50, 100 and 200 μM and 200 μM R3G were introduced in perfused livers. Resveratrol and metabolites were measured in the outflowing perfusate. Respiration of isolated mitochondria and activity of gluconeogenic enzymes were also evaluated in the livers.

KEY FINDINGS

resveratrol inhibited glycogen catabolism when infused at concentrations above 50 μM and gluconeogenesis even at 10 μM in both healthy and arthritic rat livers, but more sensitive in these latter. Resveratrol above 100 μM inhibited ADP-stimulated respiration and the activities of NADH- and succinate-oxidases in mitochondria, which were partially responsible for gluconeogenesis inhibition. Pyruvate carboxylase activity was inhibited by 25 μM resveratrol and should inhibit gluconeogenesis already at low concentrations. Resveratrol was significantly metabolized to R3G in healthy rat livers, however, R3G formation was lower in arthritic rat livers. The latter must be in part a consequence of a lower glucose disposal for glucuronidation. When compared to resveratrol, R3G inhibited gluconeogenesis in a lower extension and glycogen catabolism in a higher extension.

SIGNIFICANCE

the effects of resveratrol and R3G tended to be transitory and existed only when the resveratrol is present in the organ, however, they should be considered because significant serum concentrations of both are found after oral ingestion of resveratrol.

Anti-Inflammatory Effects of Ang-(1-7) Bone-Targeting Conjugate in an Adjuvant-Induced Arthritis Rat Model

Rheumatoid arthritis (RA) is a chronic inflammatory condition of synovial joints that causes disability and systemic complications. Ang-(1-7), one of the main peptides in the renin-angiotensin (Ang) system (RAS), imposes its protective effects through Mas receptor (MasR) signaling. It has a short half-life, limiting its feasibility as a therapeutic agent. In this study, we evaluated the anti-inflammatory effects of Ang-(1-7)’s novel and stable conjugate (Ang. Conj.) by utilizing its affinity for bone through bisphosphonate (BP) moiety in an adjuvant-induced arthritis (AIA) rat model. The rats received subcutaneous injections of vehicle, plain Ang-(1-7), or an equivalent dose of Ang. Conj. The rats’ body weights, paws, and joints’ diameters were measured thrice weekly. After 14 days, the rats were euthanized, and the blood and tissue samples were harvested for further analysis of nitric oxide (NO) and RAS components’ gene and protein expression. The administration of Ang. Conj. reduced body weight loss, joint edema, and serum NO. Moreover, the Ang. Conj. treatment significantly reduced the classical arm components at peptide, enzyme, and receptor levels while augmenting them for the protective arm. The results of this study introduce a novel class of bone-targeting natural peptides for RA caused by an inflammation-induced imbalance in the activated RAS. Our results indicate that extending the half-life of Ang-(1-7) augments the RAS protective arm and exerts enhanced therapeutic effects in the AIA model in rats.

Mitochondrial DNA Release Contributes to Intestinal Ischemia/Reperfusion Injury

Mitochondria release many damage-associated molecular patterns (DAMPs) when cells are damaged or stressed, with mitochondrial DNA (mtDNA) being. MtDNA activates innate immune responses and induces inflammation through the TLR-9, NLRP3 inflammasome, and cGAS-STING signaling pathways. Released inflammatory factors cause damage to intestinal barrier function. Many bacteria and endotoxins migrate to the circulatory system and lymphatic system, leading to systemic inflammatory response syndrome (SIRS) and even damaging the function of multiple organs throughout the body. This process may ultimately lead to multiple organ dysfunction syndrome (MODS). Recent studies have shown that various factors, such as the release of mtDNA and the massive infiltration of inflammatory factors, can cause intestinal ischemia/reperfusion (I/R) injury. This destroys intestinal barrier function, induces an inflammatory storm, leads to SIRS, increases the vulnerability of organs, and develops into MODS. Mitophagy eliminates dysfunctional mitochondria to maintain cellular homeostasis. This review discusses mtDNA release during the pathogenesis of intestinal I/R and summarizes methods for the prevention or treatment of intestinal I/R. We also discuss the effects of inflammation and increased intestinal barrier permeability on drugs.

Pharmacokinetics of metformin in collagen-induced arthritis rats

Due to the elevated presence of cytokines, the expressions of metabolic enzymes and drug transporters are altered in rheumatoid arthritis (RA). Given the high incidence of diabetes in patients with RA, the aim of the present study was to investigate the metformin pharmacokinetics of a single oral dose in rats with collagen-induced arthritis (CIA). Blood and urine samples were collected at different timepoints, and analyzed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Tissue samples were also collected to investigate the expression of metabolic enzymes and drug transporters by quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and western blot. The results indicated that the bioavailability of metformin was markedly decreased in the CIA rats. Moreover, metformin was not metabolized by enzymes of rat liver microsomes, suggesting that the decreased bioavailability of metformin was independent of the liver metabolism. In addition, the mRNA, protein expression level and activity of the renal organic cation transporter 2 (OCT2) was markedly increased, suggesting that the enhanced renal clearance of metformin in CIA rats may be due to the up-regulated activity of OCT2. In conclusion, our study suggested that the reduced bioavailability of metformin in CIA rats is possibly related to the up-regulated function of the renal protein OCT2.

Inflammation is a major regulator of drug metabolizing enzymes and transporters: Consequences for the personalization of drug treatment

Inflammation is an evolutionary process that allows survival against acute infection or injury. Inflammation is also a pathophysiological condition shared by numerous chronic diseases. In addition, inflammation modulates important drug-metabolizing enzymes and transporters (DMETs), thus contributing to intra- and interindividual variability of drug exposure. A better knowledge of the impact of inflammation on drug metabolism and its related clinical consequences would help to personalize drug treatment. Here, we summarize the kinetics of inflammatory mediators and the underlying transcriptional and post-transcriptional mechanisms by which they contribute to the inhibition of important DMETs. We also present an updated overview of the effect of inflammation on the pharmacokinetic parameters of most of the drugs that are DMET substrates, for which therapeutic drug monitoring is recommended. Furthermore, we provide opinions on how to integrate the inflammatory status into pharmacogenetics, therapeutic drug monitoring, and population pharmacokinetic strategies to improve the personalization of drug treatment for each patient.

Xenobiotic Metabolising Enzymes: Impact on Pathologic Conditions, Drug Interactions and Drug Design

Background:

The biotransformation of xenobiotics is a homeostatic defensive response of the body against bioactive invaders. Xenobiotic metabolizing enzymes, important for the metabolism, elimination and detoxification of exogenous agents, are found in most tissues and organs and are distinguished into phase I and phase II enzymes, as well as phase III transporters. The cytochrome P450 superfamily of enzymes plays a major role in the biotransformation of most xenobiotics as well as in the metabolism of important endogenous substrates such as steroids and fatty acids. The activity and the potential toxicity of numerous drugs are strongly influenced by their biotransformation, mainly accomplished by the cytochrome P450 enzymes, one of the most versatile enzyme systems.

Objective:

In this review, considering the importance of drug metabolising enzymes in health and disease, some of our previous research results are presented, which, combined with newer findings, may assist in the elucidation of xenobiotic metabolism and in the development of more efficient drugs.

Conclusion:

Study of drug metabolism is of major importance for the development of drugs and provides insight into the control of human health. This review is an effort towards this direction and may find useful applications in related medical interventions or help in the development of more efficient drugs.

The regulation of drug-metabolizing enzymes and membrane transporters by inflammation: Evidences in inflammatory diseases and age-related disorders

Drug-metabolizing enzymes (DMEs) and membrane transporters play important roles in the absorption, distribution, metabolism, and excretion processes that determine the pharmacokinetics of drugs. Inflammation has been shown to regulate the expression and function of these drug-processing proteins. Given that inflammation is a common feature of many diseases, in this review, the general mechanisms for inflammation-mediated regulation of DMEs and transporters are described. Also, evidences regarding the aberrant expression of these drug-processing proteins in several inflammatory diseases and age-related disorders are provided.

Differential changes in the pharmacokinetics of statins in collagen-induced arthritis rats

The elevated systemic levels of cytokines in rheumatoid arthritis (RA) can change the expression of metabolic enzymes and transporters. Given that statins are lipid-lowering agents frequently used in RA patients with concurrent cardiovascular diseases, the objective of the present study was to investigate the impacts of RA on the pharmacokinetics of statins of different disposition properties in rats with collagen-induced arthritis (CIA). The expression of metabolic enzymes and transporters in tissues of CIA rats were analyzed by RT-qPCR. Statins were given to CIA rats and controls through different routes, respectively. Blood samples were collected and analyzed by UPLC/MS/MS. Isolated microsomes and hepatocytes were used to determine the metabolic and uptake clearance of statins. The results showed that, compared with controls, the mRNA levels of intestinal Cyp3a1 and hepatic Cyp2c6, Cyp2c7, Cyp3a1, Oatp1a1, Oatp1b2, Oatp1a4, and Mrp2 were markedly decreased in the CIA rats. The maximal metabolic activities of Cyp2c and Cyp3a were reduced in liver microsomes of CIA rats. When given orally or injected through hepatic portal vein, the systemic levels of fluvastatin, simvastatin, and atorvastatin, but not of rosuvastatin and pravastatin, were increased in CIA rats. The metabolic clearance of simvastatin and hepatic uptake clearance of fluvastatin and atorvastatin were decreased in CIA rats. These findings suggest that the changes in the expression of enzymes and/or transporters in CIA rats differentially affect the pharmacokinetics of statins.

A semi-automated method for the integrated evaluation of half-life and metabolic soft spots of discovery compounds

Background: An integrated method that provides rates of both parent disappearance and metabolite formation was developed. Results: Buspirone, mirtazapine and verapamil were used as model compounds in developing the method. Incubations were carried out on a robotic platform. Qualitative analysis of metabolites in 30 µM samples was conducted by data-dependent HPLC–MS/MS on a high-resolution instrument. Quantitative analysis of the parent compound and metabolites in 0.5 µM samples was conducted by full-scan MS2 with product ion extraction using an ion trap mass spectrometer. Data generated for the compounds included half-life and intrinsic clearance of the parent molecule, characterization of metabolites and relative rates of metabolite formation. A correction factor was used to convert MS responses of metabolites in 0.5 µM samples to UV areas in order to compare relative metabolite concentrations. Conclusion: The approach allows for the investigation of a set of six compounds simultaneously, with a turnaround time of 1 week or less.

Absorption and bioavailability of glucosamine in the rat

The objective of this study was to determine reasons behind the low oral (p.o.) bioavailability of glucosamine. By using male Sprague-Dawley rats, the movement of glucosamine through everted gut, the effect of dose and glucose, and inhibition of a glucose transporter (GLUT2) by quercetin were studied. Glucosamine pharmacokinetics and the effect of dosing, route of administration, food and antibiotic to eradicate gut microflora was also studied. Both in vitro and in vivo studies demonstrated linear absorption kinetics for glucosamine. Absorption from duodenum was the greatest. Glucose had no effect on the transport, whereas quercetin significantly reduced the extent of glucosamine transport. Intraperitoneal doses were completely absorbed, whereas p.o. doses demonstrated low bioavailability, indicating the gut as the site of presystemic loss. Food had no significant effect on glucosamine pharmacokinetics. Antibiotic treatment resulted in strong trends towards increased bioavailability with significant increase in fecal recovery. Incubation of glucosamine with faeces resulted in a significant loss. Glucosamine's low bioavailability is, at least in part, due to its dependence on a transport-facilitated absorption and presystemic loss brought about by the gut microflora.

Drug-disease interaction: Crohn's disease elevates verapamil plasma concentrations but reduces response to the drug proportional to disease activity

AIM

Inflammation is involved in the pathogenesis of cardiovascular diseases that includes reduced response to pharmacotherapy due to altered pharmacokinetics and pharmacodynamics. It is not known if these effects exist in general in all inflammatory conditions. It also remains unknown whether in a given population the effect is a function of disease severity. We investigated whether pharmacokinetics and pharmacodynamics of a typical calcium channel inhibitor are influenced by Crohn's disease (CD), a disease for which the disease severity can be readily ranked.

METHODS

We administered 80 mg verapamil orally to (i) healthy control subjects (n= 9), (ii) patients with clinically quiescent CD (n= 22) and (iii) patients with clinically active CD (n= 14). Serial analysis of verapamil enantiomers (total and plasma unbound), blood pressure and electrocardiograms were recorded over 8 h post dose. The severity of CD was measured using the Harvey-Bradshaw Index.

RESULTS

CD substantially and significantly increased plasma verapamil concentration and in a stereoselective fashion (S, 9-fold; R, 2-fold). The elevated verapamil concentration, however, failed to result in an increased verapamil pharmacodynamic effect so that the patients with elevated verapamil concentration demonstrated no significant increase in response measured as PR interval and blood pressure. Instead, the greater the disease severity, the lower was the drug potency to prolong PR interval (r= 0.86, P < 0.0006),

CONCLUSIONS

CD patients with severe disease may not respond to cardiovascular therapy with calcium channel blockers. Reducing the severity increases response despite reduced drug concentration. This observation may have therapeutic implication beyond the disease and the drug studies herein.

Modulation of arthritis in rats by Toxicodendron pubescens and its homeopathic dilutions

BACKGROUND

Toxicodendron pubescens P. Mill (Anacardiaceae) known in homeopathy as Rhus toxicodendron (Rhus tox) is used as an anti-inflammatory medicine in homeopathic practice. In this study, Rhus tox in its crude form and homeopathic dilutions (3cH, 6cH, 30cH, 200cH) was evaluated for effects on Complete Freund's Adjuvant (CFA) induced arthritis in rats.

METHOD

We assessed the severity of arthritis through observations including inflammatory lesions, body and organ weight and hematological parameters including C-reactive protein (CRP). Blinded radiological analysis of the affected joints and pain intensity determination was also carried out.

RESULTS

Rhus tox protected rats from CFA-induced inflammatory lesions, body weight changes and hematological alterations. Rhus tox protected against radiological joint alterations due to arthritis. Arthritic pain scores were also favorably affected by Rhus tox. All the dilutions of Rhus tox including crude form showed anti-arthritic activity. The maximum protective effect was evident in the crude form at 10mg/kg/day, by mouth.

CONCLUSION

This study supports claims in the homeopathic literature on the role of Rhus tox and its ultra dilutions in the treatment of arthritis and associated pain. Further study is needed to explain this anti-arthritic effect of Rhus tox.

The effect of infliximab on hepatic cytochrome P450 and pharmacokinetics of verapamil in rats with pre-adjuvant arthritis: a drug-disease and drug-drug interaction

Inflammatory conditions result in increased concentration but reduced potency of some cardiovascular drugs. This is associated with increased levels of pro-inflammatory mediators. Infliximab reduces pro-inflammatory mediators and reverses the diminishing effect of inflammation on response in the rat. We suggested that infliximab treatment would also reverse the effects of inflammation on drug metabolism and clearance. We examined hepatic cytochrome P450 content and the pharmacokinetics of verapamil in pre-adjuvant arthritic rats treated with infliximab. Pre-adjuvant arthritis was induced in male Sprague-Dawley rats with a tail base injection of Mycobacterium butyricum. Animals were monitored for symptoms of arthritis, serum nitrite and C-reactive protein. On day 6, rats were administered with single s.c. doses of infliximab (10 mg/kg). On day 14, a single i.v. dose of racemic verapamil (2 mg/kg) was administered, and S- and R-verapamil concentrations were determined by high performance liquid chromatography. Hepatic cytochrome P450 content and verapamil protein binding were also measured. Serum nitrite levels were significantly elevated in pre-adjuvant arthritis. Infliximab did not affect mean nitrite concentrations but there was a significant correlation between nitrite and S-verapamil concentrations as well as cytochrome P450, CYP3A, and CYP1A contents. Infliximab increased cytochrome P450 enzymes content that had been diminished by pre-adjuvant arthritis but had no significant effect on verapamil protein binding. Infliximab partially restores hepatic cytochrome P450 enzyme contents. The effect of infliximab on the mean verapamil clearance was not significantly affected due, likely, to the lack of effect on plasma protein binding.

Influence of controlled rheumatoid arthritis on the action and disposition of verapamil: focus on infliximab

Active rheumatoid arthritis (RA), obesity, and old age are associated with reduced responsiveness to the calcium channel antagonist verapamil despite increased drug concentrations. The diminishing effect appears to be associated with the severity of inflammation. We examined pharmacodynamics and pharmacokinetics of verapamil in patients with controlled RA. Volunteers included RA patients in remission: 12 on infliximab, 8 on other antirheumatic therapy, and 12 healthy subjects. Verapamil plasma concentrations and selected inflammatory mediators as well as blood pressure and electrocardiographic parameters were recorded after a single 80-mg dose of verapamil. Inflammatory mediators were all below what is reported for active RA, confirming that RA was controlled. The tumor necrosis factor-alpha concentration, however, was significantly higher in the infliximab group compared with other groups and the literature value for active RA. No significant difference was observed between groups in terms of percentage prolongation of PR interval despite a trend toward a lower response in the RA groups, the mean plasma concentrations, and the total and unbound area under the curve of verapamil. However, the slope of the S-verapamil concentration-effect curve was steeper for controls compared with the RA patients. Remission from active disease appears to restore plasma protein levels and hepatic drug metabolism activity in patients with RA, resulting in relatively normal verapamil pharmacokinetics.

Pharmacokinetics of dexamethasone in a rat model of rheumatoid arthritis

Dexamethasone (DEX) is often given for the treatment of rheumatoid arthritis and clinical dosing regimens of DEX have often been based empirically. This study tests whether the inflammation processes in a rat model of rheumatoid arthritis alters the clearance and volume of distribution of DEX when compared with healthy controls. Groups of healthy and arthritic male Lewis rats received either a low (0.225 mg/kg) or high (2.25 mg/kg) intramuscular dose of DEX. Arthritis was induced by intradermal injection of type II porcine collagen in incomplete Freund's adjuvant emulsion at the base of the tail. DEX was dosed in the arthritic animals 22 days post arthritis induction. Plasma DEX concentrations were determined by HPLC. Plasma concentration versus time data were analysed by non-compartmental analysis and pharmacokinetic model fitting using the population pharmacokinetic software NONMEM V. A linear bi-exponential pharmacokinetic model with extravascular input described the data for both healthy and arthritic animals. Clearance was the only parameter determined statistically different between both groups (healthy=1.05 l/h/kg, arthritic=1.19 l/h/kg). The steady-state volume of distribution for both groups was 4.85 l/kg. The slight difference in clearance was visibly undetectable and unlikely to produce meaningful changes in DEX disposition in arthritic rats.

Effects of angiotensin II blockade on inflammation-induced alterations of pharmacokinetics and pharmacodynamics of calcium channel blockers

BACKGROUND AND PURPOSE

Inflammation elevates plasma verapamil concentrations but diminishes pharmacological response. Angiotensin II is a pro-inflammatory mediator. We examined the effect of angiotensin II receptor blockade on the pharmacokinetics and pharmacodynamics of verapamil, as well as the binding properties and amounts of its target protein in calcium channels, in a rat model of inflammation.

EXPERIMENTAL APPROACH

We used 4 groups of male Sprague-Dawley rats (220-280 g): inflamed-placebo, inflamed-treated, control-placebo and control-treated. Inflammation as pre-adjuvant arthritis was induced by injecting Mycobacterium butyricum on day 0. From day 6 to 12, 30 mg kg(-1) oral valsartan or placebo was administered twice daily. On day 12, a single oral dose of 25 mg kg(-1) verapamil was administered and prolongation of the PR interval measured and plasma samples collected for verapamil and nor-verapamil analysis. The amounts of the target protein Ca(v)1.2 subunit of L-type calcium channels in heart was measured by Western blotting and ligand binding with (3)H-nitrendipine.

KEY RESULTS

Inflammation reduced effects of verapamil, although plasma drug concentrations were increased. This was associated with a reduction in ligand binding capacity and amount of the calcium channel target protein in heart extracts. Valsartan significantly reversed the down-regulating effect of inflammation on verapamil's effects on the PR interval, and the lower level of protein binding and the decreased target protein.

CONCLUSIONS AND IMPLICATIONS

Reduced responses to calcium channel blockers in inflammatory conditions appeared to be due to a reduced amount of target protein that was reversed by the angiotensin II antagonist, valsartan.

Pravastatin reverses the down-regulating effect of inflammation on β-Adrenergic receptors: A disease–drug interaction between inflammation, pravastatin, and propranolol

Inflammatory conditions reduce the potency to prolong the PR interval of certain cardiovascular drugs including propranolol, sotalol, and verapamil in rats and humans despite elevated plasma drug concentrations. We tested whether pravastatin restores altered action and disposition of propranolol as well as inflammatory mediators concentrations in the Pre-Adjuvant Arthritis (Pre-AA) Sprague-Dawley rat model. Rats [Healthy/Placebo, Arthritis/Placebo, Healthy/Statin, and Arthritis/Statin groups (n=14-16/group)] received Mycobacterium butyricum on day 0 followed by 6 mg/kg pravastatin or placebo twice daily during days 4-8. PR-interval response to 25 mg/kg oral propranolol was measured on days 0, 4 and 8. On day 8, blood samples were collected for interferon-gamma, interleukin-10, C-reactive protein, and nitrite measurements. Propranolol enantiomer pharmacokinetics were delineated using another 4 groups (healthy n=5, Pre-AA n=9) on day 8. Pre-AA significantly reduced propranolol response despite a 10-fold increase in concentrations. Pravastatin restored the response but not the drug concentrations. Area under the % effect-time curve (% min) was 714+/-214 in Healthy/Placebo, 256+/-249 in Arthritis/Placebo, 1534+/-367 in Healthy/Statin, and 1713+/-393 in Arthritis/Statin. While pravastatin reduced elevated serum interferon-gamma concentration in the Pre-AA model, it did not influence other biomarkers. Pravastatin restores response to propranolol in inflamed rat but has no effect on the elevated propranolol concentrations. This was associated with lower serum interferon-gamma concentrations.

Selective effects of nitric oxide on the disposition of chlorzoxazone and dextromethorphan in isolated perfused rat livers

The rapid and direct effects of nitric oxide (NO) donors sodium nitroprusside (SNP) and isosorbide dinitrate (ISDN) on the hepatic and biliary disposition of chlorzoxazone (CZX), a marker of CYP2E1, and dextromethorphan (DEM), a marker of CYP2D1, were studied in a single-pass isolated perfused rat liver model. Livers (n = 30) were perfused with constant concentrations of NO donors (0-120 min) in addition to infusion of CZX or DEM (60-120 min), and periodical outlet and bile samples were collected. Both ISDN and SNP significantly reduced (30 and 60%, respectively) the hepatic extraction ratio of CZX and decreased (50 and 70%, respectively) the recovery of the CYP2E1-mediated metabolite, 6-hydroxychlorzoxazone, in the outlet perfusate and bile. As for DEM, both NO donors increased (up to 3.5-fold) the recovery of the CYP2D1-mediated metabolite dextrorphan (DOR) in the outlet perfusate. However, this was associated with a simultaneous decrease (50-75%) in the excretion of the metabolite into the bile, thus resulting in no change in the overall recovery of DOR as a result of NO donor treatment. The decrease in the biliary excretion of DOR was caused by NO-induced simultaneous reductions in both the conjugation of DOR and biliary clearance of DOR conjugate. Additionally, both SNP and ISDN significantly reduced the metabolism of DEM to 3-hydroxymorphinan, which is mostly regulated by CYP3A2. These studies in an intact liver model confirm the selectivity of the inhibitory effects of NO donors on cytochrome P450 enzymes, which was recently reported in microsomal studies, and expand these inhibitory effects to conjugation pathways.