Cytochromes and cytokines: changes in drug disposition in animals during an acute phase response: a mini-review

The influence of growth and E. coli endotoxaemia on amoxicillin pharmacokinetics in turkeys

1. This experiment aimed to determine if the pharmacokinetics of amoxicillin (AMO) was affected by rapid growth or intravenous (i.v.) injection of Escherichia coli lipopolysaccharide (LPS). 2. Turkeys of 2.0, 5.5 and 12.0 kg were administered i.v. or orally with AMO sodium at the dose of 15 mg/kg. Another group (5.7 kg) was treated with LPS prior to i.v. AMO administration. Plasma drug concentrations were determined using high-performance liquid chromatography and pharmacokinetic parameters were calculated using a non-compartmental model. To assess the haemodynamic effects of endotoxaemia, turkeys were subjected to echocardiography. 3. During growth from 2.0 to 5.5 kg, the area under the drug concentration-time curve after i.v. AMO administration increased from 9.37 ± 2.43 to 21.29 ± 5.49 mg×h/ml. Total body clearance decreased from 1.72 ± 0.55 to 0.75 ± 0.12 l/h/kg. Growth to 12.0 kg did not further affect these parameters. Mean residence time and elimination half-life gradually increased. Pharmacokinetics of orally administered drug followed a similar pattern. LPS injection affected stroke volume, heart rate and resistance index. However, it did not affect the pharmacokinetic profile of AMO in survivors. 4. It is concluded that rapid growth in turkeys affects AMO pharmacokinetics. Endotoxaemia, on the other hand, does not affect AMO elimination if compensatory mechanisms develop.

Effects of dextran sulfate sodium induced experimental colitis on cytochrome P450 activities in rat liver, kidney and intestine

Dextran sulfate sodium (DSS) induced experimental colitis presents a histologic resemblance to human ulcerative colitis (UC). Altered cytochrome P450s (CYPs) have been reported in this model and patients with UC. In this study, six CYPs activities were quantitatively determined in microsomes of liver (RLMs), kidney (RRMs) and intestine (RIMs) from rats with colitis at acute (5% DSS for 7 days, UCA) and remission (7-day DSS treatment followed by 7-day cessation, UCR) phases and compared with normal rats. Generally, CYPs activities varied with isoform, organ, and disease status. Hepatic CYP1A2, 2B1, 2C6/11, 2E1 and 3A1/2 activities were reduced by acute colitis and completely or partially restored after DSS was halted. Although DSS treatment decreased the V_max of renal CYP2C6/11 and increased that of CYP2D2, their CL_{int, in vitro} were comparable among normal, acute and remission stages. DSS treatment changed the kinetics of CYP3A1/2-mediated nifedipine metabolism in RRMs from biphasic to classical kinetics. Notably, CYP2D2 activity was elevated in liver and kidney in acute UC, while enhanced in liver and decreased in kidney in remission. In intestine, CYP3A1/2 activity was increased in UCA and further enhanced after DSS withdrawal. These findings highlight the necessity of quantifying enzyme activity for precision drug therapy.

Plasma and tissue disposition of florfenicol in Escherichia coli lipopolysaccharide-induced endotoxaemic sheep

1. The purpose of this study was to understand the effects of the acute inflammatory response (AIR) induced by Escherichia coli lipopolysaccharide (LPS) on florfenicol (FFC) and FFC-amine (FFC-a) plasma and tissue concentrations. 2. Ten Suffolk Down sheep, 60.5 ± 4.7 kg, were distributed into two experimental groups: group 1 (LPS) treated with three intravenous doses of 1 μg/kg bw of LPS at 24, 16, and 0.75 h (45 min) before FFC treatment; group 2 (Control) was treated with saline solution (SS) in parallel to group 1. An IM dose of 20 mg FFC/kg was administered at 0.75 h after the last injection of LPS or SS. Blood and tissue samples were taken after FFC administration. 3. The plasma AUC_0-4 h values of FFC were higher (p = 0.0313) in sheep treated with LPS (21.8 ± 2.0 μg·min/mL) compared with the control group (12.8 ± 2.3 μg·min/mL). Lipopolysaccharide injections increased FFC concentrations in kidneys, spleen, and brain. Low levels of plasma FFC-a were observed in control sheep (C_max = 0.14 ± 0.01 μg/mL) with a metabolite ratio (MR) of 4.0 ± 0.87%. While in the LPS group, C_max increased slightly (0.25 ± 0.01 μg/mL), and MR decreased to 2.8 ± 0.17%. 4. The changes observed in the plasma and tissue concentrations of FFC were attributed to the pathophysiological effects of LPS on renal hemodynamics that modified tissue distribution and reduced elimination of the drug.

Epoxy composite dusts with and without carbon nanotubes cause similar pulmonary responses, but differences in liver histology in mice following pulmonary deposition

Background

The toxicity of dusts from mechanical abrasion of multi-walled carbon nanotube (CNT) epoxy nanocomposites is unknown. We compared the toxic effects of dusts generated by sanding of epoxy composites with and without CNT. The used CNT type was included for comparison.

Methods

Mice received a single intratracheal instillation of 18, 54 and 162 μg of CNT or 54, 162 and 486 μg of the sanding dust from epoxy composite with and without CNT. DNA damage in lung and liver, lung inflammation and liver histology were evaluated 1, 3 and 28 days after intratracheal instillation. Furthermore, the mRNA expression of interleukin 6 and heme oxygenase 1 was measured in the lungs and serum amyloid A1 in the liver. Printex 90 carbon black was included as a reference particle.

Results

Pulmonary exposure to CNT and all dusts obtained by sanding epoxy composite boards resulted in recruitment of inflammatory cells into lung lumen: On day 1 after instillation these cells were primarily neutrophils but on day 3, eosinophils contributed significantly to the cell population. There were still increased numbers of neutrophils 28 days after intratracheal instillation of the highest dose of the epoxy dusts. Both CNT and epoxy dusts induced DNA damage in lung tissue up to 3 days after intratracheal instillation but not in liver tissue. There was no additive effect of adding CNT to epoxy resins for any of the pulmonary endpoints. In livers of mice instilled with CNT and epoxy dust with CNTs inflammatory and necrotic histological changes were observed, however, not in mice instilled with epoxy dust without CNT.

Conclusions

Pulmonary deposition of epoxy dusts with and without CNT induced inflammation and DNA damage in lung tissue. There was no additive effect of adding CNT to epoxies for any of the pulmonary endpoints. However, hepatic inflammatory and necrotic histopathological changes were seen in mice instilled with sanding dust from CNT-containing epoxy but not in mice instilled with reference epoxy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0148-2) contains supplementary material, which is available to authorized users.

Semiphysiologically Based Pharmacokinetic Model of Leflunomide Disposition in Rheumatoid Arthritis Patients

A semiphysiologically based pharmacokinetic (semi-PBPK) population model was used to evaluate the influence of enterohepatic recycling and protein binding, as well as the effect of genetic variability in CYP1A2, CYP2C19, and ABCG2, on the large interindividual variability of teriflunomide (active metabolite) concentrations following leflunomide administration in rheumatoid arthritis (RA) patients. The model was developed with total and free teriflunomide concentrations determined in RA patients taking leflunomide, as well as mean teriflunomide concentrations following the administration of leflunomide or teriflunomide extracted from the literature. Once developed, the 15-compartment model was able to predict total and free teriflunomide concentrations and was used to screen demographic and genotypic covariates, of which only fat-free mass and liver function (ALT) improved prediction. This approach effectively evaluated the effects of multiple covariates on both total and free teriflunomide concentrations, which have only been explored previously through simplistic one-compartment models for total teriflunomide.

Obesity, Inflammation and Neurological Alterations

Inflammation, neurodegeneration, imbalance of neurotransmitter systems, oxidative stress and depression are all risk factors for obesity. There is evidence regarding the cross-talk between adipose tissue and the immune system and obese patients may show an alteration of immune functions with major depression, including immune suppression with reduced T-cell and macrophage activity. Obesity is mediated by inflammatory cells such as lymphocytes, macrophages and mast cells which release pro-inflammatory cytokines and chemokines. Obesity-induced leukocyte infiltrations in adipose tissue cause cytokine/chemokine release and inflammation. Here, we report the relationship between obesity, neurological alterations and inflammation.

Turpentine oil induced inflammation decreases absorption and increases distribution of phenacetin without altering its elimination process in rats

Plasma concentrations and pharmacokinetics of phenacetin, a CYP1A2 substrate were determined in normal and experimentally induced inflamed rats by turpentine oil to know the role of inflammation on the pharmacokinetics of phenacetin and formation of its active metabolite (paracetamol) by CYP1A2 in wistar albino rats, weighing about 200-250 g that were randomly divided into two groups consisting six in each group. Rats in group I (control) received phenacetin (150 mg kg(-1), PO) where as group II received phenacetin 12 h after induction of inflammation by turpentine oil (0.4 mL, i.m). Blood samples were collected from retro orbital plexus at pre-determined time intervals prior to and at 0.166, 0.33, 0.67, 1.5, 2, 4, 8 and 12 h post-administration of phenacetin. Plasma was separated and analyzed for phenacetin and its metabolite paracetamol by HPLC assay. Based on plasma concentrations of phenacetin and its metabolite paracetamol, the pharmacokinetic parameters were determined by compartmental methods. C(max) of phenacetin was significantly (p < 0.01) decreased to 19.50 ± 2.74 μg mL(-1) in inflamed conditions compared to 38.13 ± 2.20 μg mL(-1) obtained in normal rats. Except, for significant (p < 0.001) increase in volume of distribution at steady state (V(dss)) from 2.87 ± 0.37 to 8.03 ± 1.26 L kg(-1) and increased the rate of absorption with shorter absorption half-life (t(1/2ka)) for phenacetin in inflammation. None of the pharmacokinetic parameters of either phenacetin or its metabolite paracetamol were affected. It can be concluded that turpentine oil induced inflammation has no role on the activity of CYP1A2 in rats, as the plasma concentrations and pharmacokinetic parameters of paracetamol were found unaltered.

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.

Use of population pharmacokinetic modeling and Monte Carlo simulation to capture individual animal variability in the prediction of flunixin withdrawal times in cattle

The objective of this study was to develop a population pharmacokinetic (PK) model and predict tissue residues and the withdrawal interval (WDI) of flunixin in cattle. Data were pooled from published PK studies in which flunixin was administered through various dosage regimens to diverse populations of cattle. A set of liver data used to establish the regulatory label withdrawal time (WDT) also were used in this study. Compartmental models with first-order absorption and elimination were fitted to plasma and liver concentrations by a population PK modeling approach. Monte Carlo simulations were performed with the population mean and variabilities of PK parameters to predict liver concentrations of flunixin. The PK of flunixin was described best by a 3-compartment model with an extra liver compartment. The WDI estimated in this study with liver data only was the same as the label WDT. However, a longer WDI was estimated when both plasma and liver data were included in the population PK model. This study questions the use of small groups of healthy animals to determine WDTs for drugs intended for administration to large diverse populations. This may warrant a reevaluation of the current procedure for establishing WDT to prevent violative residues of flunixin.

Pharmacokinetics of enrofloxacin and flunixin meglumine and interactions between both drugs after intravenous co-administration in healthy and endotoxaemic rabbits

The purpose of this study was to determine the pharmacokinetics and possible interactions of enrofloxacin (ENR) and flunixin meglumine (FM) in healthy rabbits and in rabbits where endotoxaemia had been induced by administering Escherichia coli lipopolysaccharide (LPS). Six male adult New Zealand White rabbits were used for the study. In Phase I, FM (2.2 mg/kg) and ENR (5 mg/kg) were given simultaneously as a bolus intravenous (IV) injection to each healthy rabbit. After a washout period, Phase II consisted of purified LPS administered as an IV bolus injection, then FM and ENR. LPS produced statistically significant increases in some serum biochemical concentrations. After the drugs were co-administered, the kinetic parameters of FM were not significantly different in healthy compared to endotoxaemic rabbits. It is concluded that ENR and FM could be co-administered to rabbits to treat endotoxaemia as no negative interaction was observed between the pharmacokinetics of both drugs.

Influence of Escherichia coli Endotoxin-Induced Endotoxaemia on the Pharmacokinetics of Enrofloxacin after Intravenous Administration in Rabbits

The main goal of present study was to determine the effects of an Escherichia coli endotoxin-induced endotoxaemic status on disposition of enrofloxacin after a single intravenous dose (5 mg/kg) in rabbits. Septic shock was induced by the i.v. bolus administration at a single dose of E. coli lipopolysaccharide. Six adult New Zealand White rabbits were used. Concentrations of drug in plasma were determined by HPLC. The plasma pharmacokinetic values for enrofloxacin were best represented using a two-compartment open model. Total plasma clearance (Cl(T)) decreased from 2.11 (l/h/kg) in healthy animals to 1.50 (l/h/kg) in rabbits with septic shock, which is related to an increase in the AUC(0-->infinity). In endotoxaemic rabbits, volume of distribution at steady state (V(dss) = 3.61 l/kg) was significantly lower (P < 0.05) than in healthy animals (V(dss) = 4.97 l/kg). However, the elimination half-life of enrofloxacin was not affected by lipopolysaccharide administration.

Impact of transgene expression on drug metabolism following systemic adenoviral vector administration

BACKGROUND

Systemic administration of a first-generation adenovirus expressing E. coli beta-galactosidase (AdlacZ) alters expression and function of two hepatic drug-metabolizing enzymes, cytochrome P450 (CYP) 3A2 and 2C11, for 14 days. The objective of these studies was to determine how the transgene cassette influences CYP expression and function.

METHODS

Sprague-Dawley rats were given 5.7 x 10(12) viral particles (vp)/kg of either: AdlacZ, Ad expressing murine erythropoietin (Epo), Ad without a transgene (Null), or phosphate-buffered saline (Vehicle). Hepatic CYP protein expression, activity, mRNA and alanine aminotransferase (ALT) levels were analyzed 0.25, 1, 4, and 14 days following a single intravenous injection.

RESULTS

Administration of Epo did not alter CYP3A2 activity, but induced RNA levels by a factor of 2 at 4 and 14 days (P< or =0.01). This vector suppressed CYP2C11 activity levels by 45% at 1 day (P< or =0.05) and RNA levels throughout the study period (P< or =0.05). The Null vector suppressed CYP3A2 activity by 36, 63, 34, and 45% at 0.25, 1, 4 and 14 days, respectively (P< or =0.05). CYP2C11 activity was suppressed 1 day after administration (41%) and RNA levels were suppressed at 6 h (53%) and 1 day (36%, P< or =0.05). In contrast, AdlacZ suppressed both CYP3A2 and 2C11 at all time points.

CONCLUSIONS

The immunogenic and biological nature of the transgene cassette can influence changes in CYP3A2, but not the 2C11 isoform. The shift in transcription and translation of protein for maintenance of physiologic homeostasis to production of viral proteins and transgene product and their associated toxicity during viral infection may explain our observations.

Pharmacokinetics of Flunixin after Intravenous Administration in Healthy and Endotoxaemic Rabbits

The pharmacokinetics of flunixin were determined after intravenous bolus injection at a single dose (2.2 mg/kg) in healthy rabbits and diseased rabbits with Escherichia coli lipopolysaccharide-induced septic shock. Six adult New Zealand White rabbits were used. Concentrations of drug in plasma were determined by HPLC. Pharmacokinetics were best described by a two-compartment open model. In healthy rabbits, there was a high plasma clearance (0.62 L/(h kg)), and a relatively short elimination half-life (1.19 h). In endotoxaemic rabbits, total plasma clearance (0.43 L/(h kg)) was significantly lower (p<0.05), and elimination half-life (1.90 h) and AUC(0-infinity) (5.29 (microg h)/ml) were significantly higher (p<0.05) than in healthy animals. The changes of pharmacokinetics of flunixin in rabbits with septic shock could be of clinical significance, and may require monitoring of plasma flunixin levels in endotoxaemic status.

Population pharmacokinetics of marbofloxacin in horses: preliminary analysis

Population pharmacokinetic of marbofloxacin was investigated on 21 healthy and 16 diseased horses to assess interindividual variability of drug exposure. Demographic, physiologic and disease covariables were tested using mixed effects models. As a preliminary analysis, this study has demonstrated that none of the tested covariables were significant in regression models for compartmental volumes or clearance of distribution, but the clinical status of the horse (healthy/diseased) was a significant covariable (P < 0.01) for systemic clearance. Clearance had a lower mean and a higher variance for diseased horses than healthy horses, with respectively a mean of 0.209 and 0.284 L/h/kg and a coefficient of variation of 52 and 15%. Consequently, variability of AUC was greater in diseased horses. Considering an AUC/MIC ratio below 60 h as a prediction of poor efficacy, a dosage regimen of 2 mg/kg intravenous was deemed to be inadequate for 19% of diseased horses if the MIC of the bacteria was 0.1 microg/mL. However 93% of diseased horses could achieve a ratio above 125 h, predicting a very good efficacy, for the MIC(90) of Enterobacteriacae (0.027 microg/mL).

Induction of nitric oxide production mediated by tumor necrosis factor alpha on staphylococcal enterotoxin C-stimulated bovine mammary gland cells

Mammary gland (MG) secretions (MGS) derived from secretory cows infected with coagulase-negative staphylococci (CoNS) showed somatic cell counts and lactoferrin similar to levels found in the MGS of secretory cows infected with Staphylococcus aureus. However, nitrite and nitrate (NOx) and staphylococcal enterotoxin C (SEC) were found in MGS infected with S. aureus at much higher levels than in cows infected with CoNS. These results suggested that NOx could be intimately correlated with the production of SEC in secretory cows infected with S. aureus. Therefore, we examined the production of NOx and the expression of proinflammatory cytokines and microsomal cytochrome P450 (CYP450) after injection of SEC into the MGS of secretory cows. We were able to detect NOx and the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) on MG cells of SEC-injected MGS. It was also found that CYP450 in the MG cells from SEC-injected MGS was down-regulated by approximately one-third in comparison with the cells from phosphate-buffered saline-injected MGS. This in vitro system also showed that NOx could be induced in the culture of bovine macrophage-lined cells (FBM-17) with the supernatants of SEC-stimulated bovine peripheral blood lymphocytes (BoPBLs) but not in the culture of peripheral mononuclear cells with SEC-stimulated BoPBLs. The expression of the mRNA for both inducible nitric oxide synthase and TNF-alpha in FBM-17 was enhanced by culturing with the supernatant of SEC-stimulated BoPBLs, although CYP450 was down-regulated. These results indicate that the down-regulation of CYP450 was caused by the production of TNF-alpha in SEC-stimulating MG cells containing macrophages and via NOx production. Therefore, we suggest that NOx released from activated MG cells via the superantigenic activity of SEC caused oxidative damage to the MG in S. aureus-induced mastitis.

Postnatal development of hepatic oxidative, hydrolytic and conjugative drug-metabolizing enzymes in female horses

Little is known about the effects of aging on the hepatic drug metabolizing capacity of horses despite the relatively long lifespan characterizing this species. A wide array of cytochrome P450 (CYP)-dependent monooxygenases, carboxylesterases and transferases were assayed in liver microsomes from 50 female horses in an age range between less than 1 year to over 12 years. Rather unexpectedly, both the CYP content and the activity of NADPH cytochrome c reductase rose as a function of age. Accordingly, a general increasing trend was recorded in the rate of the in vitro metabolism of the substrates reported to be related to CYP2B-, CYP2E- or CYP3A, although, as detected by Western immunoblotting, only the levels of proteins recognized by anti-rat CYP3A- and CYP2B antibodies appeared to increase consistently. Also the carboxylesterases and uridindiphosphoglucuronyl-transferase (UGT) activity toward 1-naphthol displayed a similar trend, glutathione S-transferase accepting 3,4-dichloronitrobenzene as a substrate being the only enzyme activity showing an age-related decline. A positive correlation was also found between liver cadmium content and CYP amount as well as the activities of most monooxygenases (except for those related to CYP1A), carboxylesterases, and UGT. While confirming that a number of enzyme activities are less expressed in foals, our results contradict the general view that the drug metabolizing capacity drops in elder individuals. Although several other factors can influence the kinetics of foreign compounds in aged animals, data from this study may provide insight in understanding possible age-related differences in drug efficacy and the response to toxic substances in horses.

Interleukin-1beta, interleukin-6, tumour necrosis factor-alpha and interferon-gamma released by a viral infection and an aseptic inflammation reduce CYP1A1, 1A2 and 3A6 expression in rabbit hepatocytes

Inflammation reduces activity and expression of hepatic cytochrome P450 (P450) and therefore diminishes drug biotransformation. This study aimed to identify the serum mediators triggered by a viral infection and an aseptic inflammation that downregulate P450 isoforms. Incubation of hepatocytes with serum from rabbits with a turpentine-induced inflammation or humans with a viral infection decreased the amount of cytochrome 1A1 (CYP1A1), 1A2 and 3A6 mRNA and apoproteins. By serum fractionation and immuno-neutralization, we showed that in the aseptic inflammation, interleukin-6 and, to a lesser degree, interleukin-1beta are involved in the downregulation of all three isoforms. In serum from humans with a viral infection, interleukin-1beta, interleukin-6, interferon-gamma and tumour necrosis factor-alpha contribute to the downregulation of P450 isoforms. CYP1A1 and 1A2 are regulated by serum mediators at the transcriptional level, while the expression of CYP3A6 appears to be under the control of pre- and posttranscriptional mechanisms.

The effect of endotoxin and dexamethasone on enrofloxacin pharmacokinetic parameters in swine

The impact of Escherichia coli-derived lipopolysaccharide (LPS) on the pharmacokinetic parameters of enrofloxacin in swine was assessed to determine whether this model would substitute for a pleuropneumonia infection model for pharmacokinetic evaluation of drugs. All animals received a single i.v. dose of enrofloxacin (5 mg/kg). Half the animals also received dexamethasone (0.5 mg/kg) to determine the impact of inflammation on any changes in enrofloxacin pharmacokinetics, as most of the effects of LPS are due to elaboration of inflammatory mediators. Administration of LPS alone (2.0 microg/kg) was associated with a decrease in clearance of enrofloxacin. Volume of distribution at steady state was increased in the dexamethasone-treated animals. The terminal elimination half-life of enrofloxacin was significantly increased in the LPS group. Dexamethasone administration, either alone or in combination with LPS challenge, increased the volume of distribution both at steady state and during the elimination phase. Lipopolysaccharide challenge did not affect the volume of distribution. Lipopolysaccharide challenge did not affect urinary excretion of enrofloxacin but did increase the urinary excretion of its principal metabolite, ciprofloxacin. However, the increased excretion did not begin until 24 h after administration of enrofloxacin. Because these pharamcokinetic results are different from those obtained with the pleuropneumonia model using the bacteria Actinobacillus pleuropneumoniae, the results of this study demonstrate that LPS is not a generic substitute for infection for the pharmacokinetic evaluation of drugs.

Present concepts on the inflammatory modulators with special reference to cytokines

The pro- and anti-inflammatory cytokines create a network of interactions between cells that lead to both stimulatory and inhibitory responses that maintain an effective homeostatic regulation. The anti-inflammatory cytokines are a family of peptides that modulate the pro-inflammatory cytokine response. Cytokines act in concert with non-cytokine mediators, such as prostaglandin E2, glucocorticosteroids, lipocortins, and catecholamines. This review highlights new developments in our understanding of the pathophysiology of inflammation and gives an example of a more recent approach to the modulation of acute systemic inflammatory disorders; activation of beta2-adrenergic receptors on macrophages. In this respect the potent beta2-adrenergic agonist clenbuterol seems of therapeutic interest.

UDP glucuronosyltransferase mRNA levels in human liver disease

The UDP glucuronosyltransferases (UGT) are a family of enzymes in which substrates include drugs, xenobiotics, and products of endogenous catabolism. The main source of most UGT enzymes is the liver, a major organ in the detoxification and inactivation of compounds. Previous studies have indicated that glucuronidation, as measured by pharmacokinetic studies, is relatively spared in liver disease. Because UGT activity toward most substrates is the result of metabolism by different isoforms with overlapping specificities, these studies may not indicate the effect of disease on the levels of individual isoforms. We sought to extend these studies to the measurement of mRNA for individual isoforms in the liver of patients with various forms of liver disease. RNA was extracted from liver tissue samples of patients undergoing clinically necessary percutaneous liver biopsies. UGT mRNA levels for isoforms 1A1, 1A3, 1A4, 1A6, 1A9, 2B4, 2B7, 2B10, 2B11, 2B15, and 2B17 were determined by real-time reverse transcription-polymerase chain reaction. Biopsies were graded using the Metavir system. Results from patients with low fibrosis or inflammatory scores were compared with those with high scores. We found large interindividual variation in the levels of the various isoforms. This was greatest for UGT2B17. A consistent downward trend, reaching statistical significance for UGT1A4, UGT2B4, and UGT2B7, was observed in samples from patients with high inflammation scores. There was no such correlation with the degree of fibrosis. Our results indicate that hepatic UGT mRNA levels are reduced while the tissue is inflamed, but they are not affected in the noninflamed, chronically diseased liver.

The pharmacokinetics of a long-acting oxytetracycline formulation in healthy dogs and in dogs infected with Ehrlichia canis

The pharmacokinetic properties of oxytetracycline were studied following a single injection of a long-acting formulation (20 mg/kg body weight) into the semimembranosus muscle of healthy dogs and of dogs that had been experimentally infected with Ehrlichia canis. The disposition curves of the long-acting oxytetracycline formulation before and after infection were best described by a bi-exponential decline after a first-order absorption. The mean maximum serum concentration (Cmax) following infection was significantly lower and the time taken to attain this concentration (tmax) was significantly shorter than that in the healthy dogs. The mean apparent elimination half-life (t(1/2) beta) was significantly increased following infection. The corresponding rate constant (beta) was significantly decreased. The absorption half-life (t(1/2) ab) was significantly decreased after infection. The volume of distribution at steady state (Vdss) increased significantly following infection. It was concluded that the pharmacokinetic behaviour of a long-acting oxytetracycline in dogs after intramuscular administration is characterized by a two-compartment model with a slow elimination phase. This could be due to flip-flop kinetics. The febrile reaction in experimental E. canis infection affected some pharmacokinetic parameters of oxytetracycline.

Enantiospecific pharmacokinetics of ketoprofen in plasma and synovial fluid of horses with acute synovitis

Pharmacokinetic parameters were established for enantiomers of the nonsteroidal anti-inflammatory drug (NSAID) ketoprofen (KTP) administered as the racemic mixture at a dose of 2.2 mg/kg and as separate enantiomers, each at a dose of 1.1 mg/kg to a group of six horses (five mares and one gelding). A four-period cross-over study in a LPS-induced model of acute synovitis was used. After administration of the racemic mixture S(+)KTP was the predominant enantiomer in plasma as well as in synovial fluid. Unidirectional inversion of R(-) to S(+)KTP was demonstrated but the inversion was less marked than previously reported. It is suggested that this reduction could be because of the influence of the inflammatory reaction on hepatic metabolism. The disposition of KTP enantiomers after administration of the racemic mixture was similar to those observed after administration of S(+) and R(-)KTP. The S(+) and R(-)KTP concentrations in synovial fluid were low and short lasting. After administration of R(-)KTP significant concentrations of the optical antipode were detected in synovial fluid.

Effects of endotoxin-induced fever and probenecid on disposition of enrofloxacin and its metabolite ciprofloxacin after intravascular administration of enrofloxacin in goats

Pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin were investigated in normal, febrile and probenecid-treated adult goats after single intravenous (i.v.) administration of enrofloxacin (5 mg/kg). Pharmacokinetic evaluation of the plasma concentration-time data of enrofloxacin and ciprofloxacin was performed using two- and one-compartment open models, respectively. Plasma enrofloxacin concentrations were significantly higher in febrile (0.75-7 h) and probenecid-treated (5-7 h) goats than in normal goats. The sum of enrofloxacin and ciprofloxacin concentrations in plasma > or =0.1 microg /mL was maintained up to 7 and 8 h in normal and febrile or probenecid-treated goats, respectively. The t1/2beta, AUC, MRT and ClB of enrofloxacin in normal animals were determined to be 1.14 h, 6.71 microg .h/mL, 1.5 h and 807 mL/h/kg, respectively. The fraction of enrofloxacin metabolized to ciprofloxacin was 28.8%. The Cmax., t1/2beta, AUC and MRT of ciprofloxacin in normal goats were 0.45 microg /mL, 1.79 h, 1.84 microg .h/mL and 3.34 h, respectively. As compared with normal goats, the values of t1/2beta (1.83 h), AUC (11.68 microg ? h/mL) and MRT (2.13 h) of enrofloxacin were significantly higher, whereas its ClB (430 mL/h/kg) and metabolite conversion to ciprofloxacin (8.5%) were lower in febrile goats. The Cmax. (0.18 microg /mL) and AUC (0.99 microg .h/mL) of ciprofloxacin were significantly decreased, whereas its t1/2beta (2.75 h) and MRT (4.58 h) were prolonged in febrile than in normal goats. Concomitant administration of probenecid (40 mg/kg, i.v.) with enrofloxacin did not significantly alter any of the pharmacokinetic variables of either enrofloxacin or ciprofloxacin in goats.

Prevention of pleuropneumonia in pigs by in-feed medication with sulphadimethoxine and sulphamethoxazole in combination with trimethoprim

The prophylactic effect of in-feed medication of conventional pigs with sulphadimethoxine (SDM), sulphamethoxazole (SMX), and trimethoprim (TMP) was tested by using an Actinobacillus pleuropneumoniae infection model. In each of five experiments, six pigs were given medicated feed twice daily and three pigs received antibiotic-free feed and served as positive (unmedicated, infected) controls. The following drugs or drug combinations were tested (in mg per kg feed): 500 SDM + 100 TMP, 500 SMX + 100 TMP, 125 SMX + 25 TMP, 125 SMX (alone) and 25 TMP (alone). After six days of feed medication, all animals were endobronchially inoculated with A. pleuropneumoniae in a dose of 1-3.10(4) colony-forming units (CFU). The response to the challenge in all control pigs was characterized by fever, lethargy, anorexia, reduced water consumption, and laboured breathing. At autopsy all controls manifested a fibrinous haemorrhagic pleuropneumonia. In-feed medication with 500 SDM + 100 TMP, 500 SMX + 100 TMP as well as 125 SMX + 25 TMP resulted in an effective protection against the challenge in all treated animals. After consumption of feed medicated with 125 mg per kg SMX or 25 mg per kg TMP, pleuropneumonia was evident in all challenged pigs. The results of this study indicate an in vivo potentiation of SMX and TMP in pigs against this respiratory tract pathogen.