An intracellular adrenomedullin system reduces IL-6 release via a NF-kB-mediated, cAMP-independent transcriptional mechanism in rat thymic epithelial cells.

Thymic epithelial cells (TECs) play a key role in the regulation of central immune tolerance by expressing autoantigens and eliminating self-reactive T cells. In a previous paper we reported that adrenomedullin (ADM) and its co-receptor protein RAMP2 are located intracellularly in newborn human thymic epithelial cells (TECs). This work has two main aims: (1) to examine the cellular localization of ADM and its receptor in TECs of adult Wistar rats to validate this animal model for the study of the ADM system and its function(s) in thymus; (2) to investigate the potential modulating effect of ADM on the NF-kB pathway, which is involved through the production of cytokines such as IL-6, in the maturation of T-lymphocytes and immunological tolerance.

Pharmacokinetic drug interactions in liver disease: An update.

Inhibition and induction of drug-metabolizing enzymes are the most frequent and dangerous drug-drug interactions. They are an important cause of serious adverse events that have often resulted in early termination of drug development or withdrawal of drugs from the market. Management of such interactions by dose adjustment in clinical practice is extremely difficult because of the wide interindividual variability in their magnitude.

Differential effect of liver cirrhosis on the pregnane X receptor-mediated induction of CYP3A1 and 3A2 in the rat.

Conflicting results have been obtained by clinical studies investigating the effect of liver cirrhosis on enzyme induction. Because ethical concerns do not give consent for methodologically rigorous studies in humans, we addressed this question by examining the effect of the prototypical inducer dexamethasone (DEX) on the pregnane X receptor (PXR)-mediated induction of CYP3A1 and 3A2 in a validated animal model of liver cirrhosis obtained by exposure of rats to carbon tetrachloride. For this purpose, we assessed mRNA levels, protein expressions, and enzymatic activities of both CYP3A enzymes, as well as mRNA and protein expressions of PXR in rat populations rigorously stratified according to the severity of liver insufficiency.

Expression and distribution of the adrenomedullin system in newborn human thymus.

Adrenomedullin (AM) is a multifunctional peptide endowed with various biological actions mediated by the interaction with the calcitonin receptor-like receptor (CLR), which couples to the receptor activity-modifying proteins 2 or 3 (RAMP2 or RAMP3) to form the functional plasma membrane receptors AM1 and AM2, respectively. In this study, we investigated for the first time the expression and localization of AM, CLR, RAMP2 and RAMP3 in human thymic tissue from newborns and in primary cultures of thymic epithelial cells (TECs) and thymocytes. Immunohistochemical analysis of thymic tissue showed that both AM and RAMP2 are abundantly expressed in the epithelial cells of medulla and cortex, blood vessels and mastocytes.

Severe liver cirrhosis markedly reduces AhR-mediated induction of cytochrome P450 in rats by decreasing the transcription of target genes.

Although the induction of cytochrome P450 (CYP) has long been investigated in patients with cirrhosis, the question whether liver dysfunction impairs the response to CYP inducers still remains unresolved. Moreover, the mechanism underlying the possible effect of cirrhosis on induction has not been investigated. Since ethical constraints do not permit methodologically rigorous studies in humans, this question was addressed by investigating the effect of the prototypical inducer benzo[a]pyrene (BP) on CYP1A1 and CYP1A2 in cirrhotic rats stratified according to the severity of liver dysfunction.

Differential inducing effect of benzo[a]pyrene on gene expression and enzyme activity of cytochromes P450 1A1 and 1A2 in Sprague-Dawley and Wistar rats.

The objective of this study was to compare RT-PCR, Western blot and determination of enzyme activity in the assessment of the induction of cytochromes P450 (CYPs) 1A1 and 1A2 by benzo[a]pyrene (BaP) in Sprague-Dawley and Wistar rats. Inhibition studies and kinetic analyses confirmed literature data indicating that methoxyresorufin is a specific CYP1A2 substrate in both uninduced and BaP-treated rats, whereas ethoxyresorufin is a specific CYP1A1 substrate only in BaP-treated rats. BaP treatment increased mRNA and protein expressions of both CYP1A enzymes to a greater extent in Wistar than Sprague-Dawley rats.

Inhibition of cytochrome P450 2C8-mediated drug metabolism by the flavonoid diosmetin.

The aim of this study was to assess the effects of diosmetin and hesperetin, two flavonoids present in various medicinal products, on CYP2C8 activity of human liver microsomes using paclitaxel oxidation to 6α-hydroxy-paclitaxel as a probe reaction. Diosmetin and hesperetin inhibited 6α-hydroxy-paclitaxel production in a concentration-dependent manner, diosmetin being about 16-fold more potent than hesperetin (mean IC(50) values 4.25 ± 0.

Flavonoids diosmetin and hesperetin are potent inhibitors of cytochrome P450 2C9-mediated drug metabolism in vitro.

The aim of this study was to examine in vitro, by means of kinetic analysis and molecular docking simulations, the effects of the flavone diosmetin and its flavanone analog hesperetin on CYP (cytochrome P450) 2C9-mediated drug metabolism. To this purpose, the conversion of diclofenac to 4'-hydroxydiclofenac by human liver microsomes was used as a model assay for assessing the CYP2C9 inhibitory activity of these two flavonoids. Kinetic analyses showed that diosmetin and hesperetin were reversible, dead-end inhibitors of 4'-hydroxydiclofenac formation; their mean K(i) (inhibitor dissociation constant) values were 1.

The effect of liver disease on inhibitory and plasma protein-binding displacement interactions: an update.

Importance Of The Field: Inhibition of CYP-mediated metabolism is the most frequent and dangerous drug interaction, which causes serious problems in drug development, drug approval and clinical practice. The wide interindividual variability in the magnitude of such interactions constitutes the main hurdle to their management by dose adjustment.

Area Covered In This Review: This review focuses on a recently identified source of variability in the extent of inhibitory drug interactions, namely liver functional status.

Fluvoxamine pharmacokinetics in healthy elderly subjects and elderly patients with chronic heart failure.

Aims: To investigate the effects of age and chronic heart failure (CHF) on the oral disposition kinetics of fluvoxamine.

Methods: A single fluvoxamine dose (50 mg) was administered orally to 10 healthy young adults, 10 healthy elderly subjects and 10 elderly patients with CHF. Fluvoxamine concentration in plasma was measured for up to 96 h.

Enzyme inhibition and induction in liver disease.

This article reviews the influence of liver functional status on pharmacokinetic interactions due to inhibition and induction of drug-metabolizing enzymes. Recent human studies have shown that the magnitude of inhibitory interactions caused by the reversible CYP1A2 inhibitor fluvoxamine decreases as liver function worsens, and virtually vanishes in patients with more advanced hepatocellular insufficiency. This effect of liver dysfunction is independent of the pharmacokinetic characteristics of the CYP1A2 substrate, since it has been observed with both high- and low-clearance drugs.

In vitro hepatic conversion of the anticancer agent nemorubicin to its active metabolite PNU-159682 in mice, rats and dogs: a comparison with human liver microsomes.

We recently demonstrated that nemorubicin (MMDX), an investigational antitumor drug, is converted to an active metabolite, PNU-159682, by human liver cytochrome P450 (CYP) 3A4. The objectives of this study were: (1) to investigate MMDX metabolism by liver microsomes from laboratory animals (mice, rats, and dogs of both sexes) to ascertain whether PNU-159682 is also produced in these species, and to identify the CYP form(s) responsible for its formation; (2) to compare the animal metabolism of MMDX with that by human liver microsomes (HLMs), in order to determine which animal species is closest to human beings; (3) to explore whether differences in PNU-159682 formation are responsible for previously reported species- and sex-related differences in MMDX host toxicity. The animal metabolism of MMDX proved to be qualitatively similar to that observed with HLMs since, in all tested species, MMDX was mainly converted to PNU-159682 by a single CYP3A form.

Flavonoids diosmetin and luteolin inhibit midazolam metabolism by human liver microsomes and recombinant CYP 3A4 and CYP3A5 enzymes.

We evaluated the effects of increasing concentrations of the flavonoids salvigenin, diosmetin and luteolin on the in vitro metabolism of midazolam (MDZ), a probe substrate for cytochrome P450 (CYP) 3A enzymes, which is converted into 1'-hydroxy-midazolam (1'-OH-MDZ) and 4-hydroxy-midazolam (4-OH-MDZ) by human liver microsomes. Salvigenin had only a modest effect on MDZ metabolism, whereas diosmetin and luteolin inhibited in a concentration-dependent manner the formation of both 1'-OH-MDZ and 4-OH-MDZ, with apparent K(i) values in the 30-50mumol range. Both diosmetin and luteolin decreased 1'-OH-MDZ formation by human recombinant CYP3A4, but not CYP3A5, whereas they decreased 4-OH-MDZ formation by both recombinant enzymes.

Differential effect of chronic renal failure on the pharmacokinetics of lidocaine in patients receiving and not receiving hemodialysis.

Background And Objectives: The effect of chronic renal failure (CRF) on the pharmacokinetics of lidocaine, a drug cleared almost exclusively by hepatic metabolism, has thus far only been evaluated in patients undergoing regular hemodialysis. This study had 2 objectives: (1) to investigate the effect of CRF on the pharmacokinetics of lidocaine in both patients undergoing hemodialysis and patients not undergoing hemodialysis and (2) to test the effects of plasma from the patients examined and of lidocaine metabolites possibly accumulated in vivo on lidocaine biotransformation in vitro.

Methods: In a clinical investigation we studied the kinetics of lidocaine and its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), after intravenous injection of 1 mg/kg lidocaine in 15 healthy volunteers (creatinine clearance [CL(cr)] >80 mL/min x 1.

Co-administration of sirolimus alters tacrolimus pharmacokinetics in a dose-dependent manner in adult renal transplant recipients.

A combination of tacrolimus (TAC) and sirolimus (SIR) has recently proved to be a very effective immunosuppressive regimen in organ transplantation. In pediatric transplant recipients, co-administration of these two drugs has been shown to result in a significant decrease of exposure to TAC, whereas conflicting data have been obtained regarding this pharmacokinetic interaction in adults. The aim of this study was to investigate the effect of SIR on TAC pharmacokinetics in adult transplant recipients.

Liver dysfunction markedly decreases the inhibition of cytochrome P450 1A2-mediated theophylline metabolism by fluvoxamine.

Background And Objectives: In vivo inhibition of cytochrome P450 (CYP) 1A2 by fluvoxamine causes a reduction in the clearance of the high-extraction drug lidocaine, which decreases in proportion to the degree of liver dysfunction. The objectives of this study were (1) to evaluate the effect of liver cirrhosis on the inhibition by fluvoxamine of the metabolic disposition of theophylline, a CYP1A2 substrate with a low-extraction ratio, to assess whether decreased sensitivity to CYP1A2 inhibition in liver disease is a general characteristic of CYP1A2 substrates, regardless of their pharmacokinetic properties, and (2) to investigate the mechanism(s) underlying the effect of liver dysfunction on CYP1A2 inhibition.

Methods: The study was carried out in 10 healthy volunteers and 20 patients with cirrhosis, 10 with mild liver dysfunction (Child class A) and 10 with severe liver dysfunction (Child class C), according to a randomized, double-blind, 2-phase, crossover design.

Cytochrome P450 1A2 is a major determinant of lidocaine metabolism in vivo: effects of liver function.

Objectives: This study was designed (1) to evaluate the effect of a cytochrome P450 (CYP) 1A2 inhibitor, fluvoxamine, on the pharmacokinetics of intravenous lidocaine and its 2 pharmacologically active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), to confirm recent in vitro results indicating that CYP1A2 is the main isoform responsible for lidocaine biotransformation and (2) to assess whether liver function has any influence on the fluvoxamine-lidocaine interaction.

Methods: The study was carried out in 10 healthy volunteers and 20 patients with cirrhosis, 10 with mild (Child grade A) and 10 with severe (Child grade C) liver dysfunction, according to a randomized, double-blind, 2-phase, crossover design. In one phase all participants received placebo for 6 days; in the other phase they received 50 mg fluvoxamine for 2 days and 100 mg fluvoxamine for the next 4 days.

Pharmacokinetics of intraperitoneal cisplatin and doxorubicin.

Intraperitoneal chemotherapy, mainly when performed during HIIC after cytoreductive surgery, is considered potentially curative for the treatment of solid tumors with spread to the peritoneal surface. When selecting antiblastic agents to be administered intraperitoneally, it is important to bear in mind that a low lipophility and a high molecular weight are the ideal drug characteristics. Drugs with these features allow a favorable ratio to be achieved between peritoneal and plasma concentrations, due to the reduced tendency to diffuse through the plasma-peritoneal barrier, even after extensive removal of the peritoneum.

Needle and trocar injuries in diagnostic laparoscopy under local anesthesia: what is the true incidence of these complications?

Laparoscopy is a relatively safe invasive procedure, but complications can occur, mainly related to Veress needle and trocar insertion. The rate of these complications is generally reported to be low, but the true incidence may be higher because of underreporting. We retrospectively studied the records of 2650 consecutive diagnostic laparoscopies performed by the same operator with the aim of assessing the true incidence and nature of these complications.

Oral administration of trans-resveratrol to guinea pigs increases cardiac DT-diaphorase and catalase activities, and protects isolated atria from menadione toxicity.

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a natural phytoalexin found in grapes and wine. It has antioxidant and antiproliferative activities, and has been shown to induce NAD(P)H:quinone oxidoreductase, also known as DT-diaphorase, in cultured mouse hepatoma cells. DT-diaphorase is a detoxifying enzyme for quinone-containing substances, due to its ability to prevent their one-electron reduction and the consequent generation of reactive oxygen species (ROS).

Effect of the CYP3A4 inhibitor erythromycin on the pharmacokinetics of lignocaine and its pharmacologically active metabolites in subjects with normal and impaired liver function.

Aims: The objectives of this study were: (i) to evaluate the effect of a cytochrome P450 (CYP) 3A4 inhibitor, erythromycin, on the pharmacokinetics of intravenous lignocaine and its two pharmacologically active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX); (ii) to assess whether the effects of the erythromycin inhibitory action on lignocaine clearance and the results of the MEGX liver function test depend on liver functional status; and (iii) to determine the effects of both moderate and severe liver dysfunction on the disposition kinetics of lignocaine.

Methods: The study was carried out on 10 healthy volunteers, and 10 Child's class A and 10 class C cirrhotic patients, according to a double-blind, randomized, two-way crossover design. On day 1 of the investigation, all subjects received three oral doses of erythromycin (600 mg of the ethylsuccinate ester) or placebo, and two further doses on day 2.

Role of antioxidant defences in the species-specific response of isolated atria to menadione.

In previous works we demonstrated that 2-methyl-1,4-naphthoquinone (menadione) causes a marked increase in the force of contraction of guinea pig and rat isolated atria. This inotropic effect was significantly higher in the guinea pig than in the rat and was strictly related to the amount of superoxide anion (O(2)(*-)), generated as a consequence of cardiac menadione metabolism through mitochondrial NADH-ubiquinone oxidoreductase. The present study was designed to further elucidate the basis of these quantitatively different positive inotropic responses.

Diagnostic value of plasma cystatin C as a glomerular filtration marker in decompensated liver cirrhosis.

Background: Plasma creatinine concentration and calculated creatinine clearance are of limited value as glomerular filtration rate (GFR) markers in patients with decompensated liver cirrhosis. We assessed plasma cystatin C as an indicator of GFR in such patients.

Methods: We studied 36 patients with decompensated liver cirrhosis and 56 noncirrhotic controls, both groups including individuals with normal and impaired renal function.

Hyperthermic intraoperative intraperitoneal chemotherapy with cisplatin and doxorubicin in patients who undergo cytoreductive surgery for peritoneal carcinomatosis and sarcomatosis: phase I study.

Background: Hyperthermic intraperitoneal intraoperative chemotherapy (HIIC) combined with cytoreductive surgery (CS) has been proposed as a new multimodal treatment mainly for carcinomatosis of gastrointestinal origin. To evaluate whether this regimen could be used for other tumor types, the authors conducted a Phase I study on HIIC with doxorubicin and cisplatin in patients with peritoneal carcinomatosis or sarcomatosis.

Patients And Methods: Thirty-one patients with peritoneal carcinomatosis or sarcomatosis (PCS) were enrolled for the study.