Measurement of hepatic and intestinal CYP3A4 and PGP activity by combined po + iv [14C]erythromycin breath and urine test

The aim of the present study was to develop a test for measuring hepatic and intestinal removal of cytochrome p-450 3A4 (CYP3A4)- and P-glycoprotein (PGP)-dependent xenobiotics that would be applicable for clinical use in humans. Orally and intravenously administered [N-methyl-14C]erythromycin was used for evaluation of 14C-labeled excretion dynamics in breath and urine. Simultaneous breath and urine test measurements were performed in 32 healthy volunteers and in 23 renal transplant recipients. Mathematical analysis of the excretion rate of labeled CO2 in breath and labeled carbon in urine resulted in 1). separation of both CYP3A4 and PGP activity in the liver and the intestinal mucosa and 2). numerical calculation of the dynamics of the different processes. The test was sufficiently sensitive to detect theoretically predicted process-specific pharmacological modulations by different drugs in healthy volunteers and after recent renal transplantation. It is concluded that the combined oral and intravenous erythromycin breath and urine test is a reliable and noninvasive test to measure phenotypic intestinal and hepatic CYP3A4 and PGP activity and may be a promising tool for prediction of drug interactions and dose adjustment of many pharmacotherapeutics in clinical practice, e.g., immunosuppressive agents after renal transplantation.     

Stability of apomorphine in plasma and its determination by high-performance liquid chromatography with electrochemical detection

Dilute solutions (50 ng/ml) of apomorphine in plasma are unstable at 37°C and pH 7.4. The chemical half-life is only 39 min. Mercaptoethanol (0.01%) is effective in stabilizing these samples while sodium metabisulphite (1%), which is generally used, is not effective. Biological samples are extracted with diethyl ether (recovery 96.5%) and analysed using HPLC with coulometric detection (oxidation potential 0.25 V). The stationary phase employed was C₁₈ material (4 μm) and the mobile phase was phosphate buffer (pH 3)—acetonitrile (70:30, v/v). The flow-rate was 1.8 ml/min. This bioanalytical method presents a reliable tool for pharmacokinetic studies in man.     

Metabolism and absorption enhancement of methionine enkephalin in human nasal epithelium

The objective of this study was to investigate absorption enhancing approaches for systemic delivery of methionine enkephalin via the nose. Absorption promotion of methionine enkephalin in the presence of protease inhibitors (bestatin, puromycin) and absorption enhancers (glycocholate, dimethyl-beta-cyclodextrin) were investigated in human nasal epithelium. Co-administration of the peptide with protease inhibitors and absorption enhancers resulted in a remarkable increase in Met-Enk permeation (4- to 94-fold). The increase was proportional to transepithelial resistance reduction and permeation of paracellular marker dye. Perturbation of the epithelial tight junctions seen in vitro may not occur in vivo due to mucus protection and mucociliary clearance.     

An organotypical in vitro model for vascular tissue remodelling and its application to study radiation effects

An organotypic in vitro model, to study vascular tissueremodeling, was evaluated as a function of culture period. Inorder to validate the model as a tool for studying vascularresponses to damage, a dose-response analysis to ionizingirradiation was included.Rat aortic rings were explanted in vitro after being irradiatedwith single doses of ⁶⁰Co -rays, namely 0, 5, 10, 15, 20or 25 Gy. Irradiated and sham-irradiated aortic rings werecultured for 3 weeks. Explant outgrowth on an adhesivesubstrate was evaluated by macroscopical scoring, and ringsderived from each irradiation group together with theoutgrowths were fixed and embedded in paraffin after 2, 7, 14and 21 days. Bromodeoxyuridine incorporation, smoothmuscle actin and collagen types I and III were scored onimmunohistochemically stained sections. For each studiedparameter, irradiated and sham-irradiated rings were compared.In cultures of sham-irradiated rings, alterations from acontractile towards a synthetic/migratory smooth muscle cellphenotype were confirmed. After 3 weeks, fullgrown cultures hadformed. Irradiation slowed down the phenotypical modifications.After 15 Gy, irradiation explant outgrowth was already retarded;after 25 Gy, the outgrowth was completely blocked. On the otherhand, a dose of 15 Gy or more induced an increased collagen Iproduction in the tunica media.In conclusion, the present organotypical in vitro model fits toanalyse dynamics in the original vascular tissues as well as inthe primary outgrowth. It enables to confirm features oftissular reorganization and effects of ionizing radiationdescribed in vivo.     

The Influence of Dietary Protein Intake on Mammalian Tryptophan and Phenolic Metabolites

Although there has been increasing interest in the use of high protein diets, little is known about dietary protein related changes in the mammalian metabolome. We investigated the influence of protein intake on selected tryptophan and phenolic compounds, derived from both endogenous and colonic microbial metabolism. Furthermore, potential inter-species metabolic differences were studied. For this purpose, 29 healthy subjects were allocated to a high (n = 14) or low protein diet (n = 15) for 2 weeks. In addition, 20 wild-type FVB mice were randomized to a high protein or control diet for 21 days. Plasma and urine samples were analyzed with liquid chromatography–mass spectrometry for measurement of tryptophan and phenolic metabolites. In human subjects, we observed significant changes in plasma level and urinary excretion of indoxyl sulfate (P 0.004 and P 0.001), and in urinary excretion of indoxyl glucuronide (P 0.01), kynurenic acid (P 0.006) and quinolinic acid (P 0.02). In mice, significant differences were noted in plasma tryptophan (P 0.03), indole-3-acetic acid (P 0.02), p-cresyl glucuronide (P 0.03), phenyl sulfate (P 0.004) and phenylacetic acid (P 0.01). Thus, dietary protein intake affects plasma levels and generation of various mammalian metabolites, suggesting an influence on both endogenous and colonic microbial metabolism. Metabolite changes are dissimilar between human subjects and mice, pointing to inter-species metabolic differences with respect to protein intake.     

The expression and role of CXC chemokines in colorectal cancer

Cancer is a life-threatening disease world-wide and colorectal cancer is the second common cause of cancer mortality. The interaction between tumor cells and stromal cells plays a crucial role in tumor initiation and progression and is partially mediated by chemokines. Chemokines predominantly participate in the chemoattraction of leukocytes to inflammatory sites. Nowadays, it is clear that CXC chemokines and their receptors (CXCR) may also modulate tumor behavior by several important mechanisms: regulation of angiogenesis, activation of a tumor-specific immune response by attracting leukocytes, stimulation of tumor cell proliferation and metastasis. Here, we review the expression and complex roles of CXC chemokines (CXCL1 to CXCL16) and their receptors (CXCR1 to CXCR6) in colorectal cancer. Overall, increased expression levels of CXC chemokines correlate with poor prognosis.