Data integration for identification of important transcription factors of STAT6-mediated cell fate decisions.

Data integration has become a useful strategy for uncovering new insights into complex biological networks. We studied whether this approach can help to delineate the signal transducer and activator of transcription 6 (STAT6)-mediated transcriptional network driving T helper (Th) 2 cell fate decisions. To this end, we performed an integrative analysis of publicly available RNA-seq data of Stat6-knockout mouse studies together with STAT6 ChIP-seq data and our own gene expression time series data during Th2 cell differentiation. We focused on transcription factors (TFs), cytokines, and cytokine receptors and delineated 59 positively and 41 negatively STAT6-regulated genes, which were used to construct a transcriptional network around STAT6. The network illustrates that important and well-known TFs for Th2 cell differentiation are positively regulated by STAT6 and act either as activators for Th2 cells (e.g., Gata3, Atf3, Satb1, Nfil3, Maf, and Pparg) or as suppressors for other Th cell subpopulations such as Th1 (e.g., Ar), Th17 (e.g., Etv6), or iTreg (e.g., Stat3 and Hif1a) cells. Moreover, our approach reveals 11 TFs (e.g., Atf5, Creb3l2, and Asb2) with unknown functions in Th cell differentiation. This fact together with the observed enrichment of asthma risk genes among those regulated by STAT6 underlines the potential value of the data integration strategy used here. Thus, our results clearly support the opinion that data integration is a useful tool to delineate complex physiological processes.

Paracetamol (acetaminophen) - a popular and widely used nonopioid analgesic.

For several decades paracetamol has proven its clinical efficacy and safety in the treatment of various acute and chronic pain states. Whereas its pharmacokinetic properties (high oral bioavailability, good penetration into the brain, relative rapid hepatic elimination) are well known, its exact central mode of action remains to be elucidated. According to many international guidelines/recommendations paracetamol is a drug of first choice for relieving mild to moderate pain. It has been successfully combined with opioids for severe pain. Due to its cardiovascular, renal and gastrointestinal safety paracetamol offers several advantages vs. NSAIDs. It should be realized that the maximum daily dose is restricted to 4 g to avoid unnecessary hepatic complications. Keeping this limitation in mind paracetamol still represents a valuable first-line agent in the pharmacological management of pain.

The pharmacological profile and clinical use of mesalazine (5-aminosalicylic acid).

For more than 30 years mesalazine (5-aminosalicylic acid; 5-ASA) has been used for the treatment of chronic inflammatory bowel disease (IBD) especially in ulcerative colitis (UC). During this time various rectal and oral formulations have been developed. The modified drug delivery systems were designed to release sufficient 5-ASA at the sites of inflammation. Such a drug targeting strategy is needed for its topical action and especially because local concentrations in the mucosa will determine the clinical outcome. The absorbed part (20-40% of the dose) of 5-ASA is rapidly and presystemically acetylated (t1/2: 1-2.5 h; CL: 300-690 mL/min). Consequently, the systemic exposure of 5-ASA is low and adverse effects are in the range of placebo treatment. The polypotent 5-ASA has a wide spectrum of pharmacological properties and its exact mode of action is not yet clear. Recent meta-analyses of randomized placebo-controlled clinical trials provide convincing data that 5-ASA is the preferred first-line therapy for the acute treatment of mild-to-moderate UC (NNT:6) and for remission management (NNT:4). There is also some clinical benefit for patients with active Crohn's disease (NNT:7) and in the prevention of postsurgical relapse (NNT:10). There is increasing evidence that 5-ASA also has some therapeutic potential for chemoprevention of colorectal cancer, diverticular disease and irritable bowel syndrome. In all clinical studies, the side effects of 5-ASA were very low (5-10%), mild and comparable to placebo. Thus, its use is very safe and 5-ASA will remain an interesting and valuable agent. It is anticipated that more selective drug targeting, including galenic innovations and an optimized dosaging schedule, could result in some improvement of the wide use of 5-ASA.

The influence of chitosan content in cationic chitosan/PLGA nanoparticles on the delivery efficiency of antisense 2'-O-methyl-RNA directed against telomerase in lung cancer cells.

Tailorable cationic chitosan/PLGA nanoparticles (CPNP) were used for the delivery of an antisense 2'-O-methyl-RNA (2OMR) directed against RNA template of human telomerase. Here, we describe the influence of the chitosan content on binding efficiency, complex stability, uptake in different human lung cell types and finally demonstrate the efficacy of this nanoplex system. CPNPs were prepared by the emulsion-solvent evaporation method using different amounts of chitosan and purified by preparative size exclusion chromatography. The characterization by photon correlation spectroscopy and zeta potential measurements showed a small increase in size and an increase of zeta potential with increasing amounts of chitosan. Binding efficiency and complex stability with 2OMR was high in water and correlated well with the chitosan content of particles but was weak in physiologically relevant media (PBS and RPMI cell culture medium). However, flow cytometry analysis showed that the uptake of 2OMR into A549 lung cancer cells was considerably higher in combination with nanoparticles and dependent on the amount of chitosan when compared to 2OMR alone. Confocal laser scanning microscopy revealed that the uptake into A549 cells is mediated via complexes of 2OMR and chitosan/PLGA nanoparticles despite the weak binding in cell culture medium. The nanoparticles were well tolerated and efficient in inhibiting telomerase activity.

Decomposition of the telomere-targeting agent BRACO19 in physiological media results in products with decreased inhibitory potential.

The stability of the acridine-based telomere-targeting agent BRACO19, a G-quadruplex stabilizing substance, was tested at different pH, temperature and in different dissolution media. Analysis was performed by HPLC. Decomposition products were examined by LC/MS and NMR. The TRAP assay was used to determine the inhibitory potential of the decomposition products on telomerase activity. The results show that the stability of BRACO19 strongly depends on pH and temperature. Decomposition was fastest at physiological pH and temperature while the type of dissolution medium had no major influence on stability. The most probable mechanism for this decomposition seems to be a hydrolysis of the amide bonds in position 3 and 6 of the acridine ring and/or a deamination of the phenyl ring. The decomposition products showed a reduced inhibitory potential compared to the parent compound BRACO19. The results demonstrate that the preparation of dosage forms and their storage conditions will have an important influence on the stability--and hence biological efficacy--of BRACO19 and related substances.

Hepatic expression of galectin-3 and receptor for advanced glycation end products in patients with liver disease.

BACKGROUND: Advanced glycation end products (AGEs) are a heterogeneous group of glycosylated proteins (of which carboxymethyl-lysine (CML) is the most common) which accumulate during ageing processes and play an important role in the pathogenesis of a variety of chronic diseases. Impaired hepatic function might result in elevated levels of AGEs, as the liver represents the major site of AGE metabolism. The actions of AGEs are mediated by various receptors, among which the AGE-receptor complex (including galectin-3 as an essential part) is thought to have a cytoprotective effect, and receptor for advanced glycation end product (RAGE) a cytotoxic effect. AIM: To assess the relationship between CML and expression of galectin-3 and RAGE in different histological structures in biopsy specimens from patients with varying degrees of liver impairment. METHOD: Immunohistochemical staining of 164 biopsies from patients with varying degrees of liver impairment was performed to determine the levels of CML, galectin-3 and RAGE in hepatocytes, Kupffer cells and bile ducts by a semiquantative score. RESULTS: Independent of diagnosis, CML and RAGEs were detected in hepatocytes, whereas galectin-3 was present only in hepatocytes of cirrhotics. By contrast, CML and galectin-3 were highly expressed in Kupffer cells (well correlating levels, highest scores in cholestasis) whereas expression of RAGEs was not significant. All three assessed biochemical markers showed their highest levels of expression/detection in bile ducts. CONCLUSION: These findings indicate an increased susceptibility of hepatocytes to the detrimental effects of AGEs and underline the protective function of Kupffer cells. Furthermore, the biliary system seems to play an important role in the disposition of AGEs.

Ziconotide--a novel neuron-specific calcium channel blocker for the intrathecal treatment of severe chronic pain--a short review.

Worldwide a large number of patients suffer from severe chronic pain even after treatment with opioids following the 3-step analgesic ladder developed by the WHO. Intraspinal agents, including morphine, have been tried as a fourth step. However, approximately 20% of cases remain refractory. Ziconotide, an intrathecal analgesic with orphan drug status, is a novel alternative for the management of chronic intractable pain. Ziconotide is a synthetic peptide based on the toxin of the fish-hunting marine snail, Conus magus. It is the first therapeutic agent in a new pharmacological class of "topically" active analgesics that selectively target neuron-specific (N-type), voltage-gated calcium channels. Ziconotide produces potent analgesia by interruption of Ca-dependent primary afferent transmission of pain signals in the spinal cord. Ziconotide was significantly more effective than placebo in the treatment of chronic malignant (p < 0.001) and non-malignant pain (p < 0.001). In several clinical studies morphine dosages could be substituted by ziconotide. The drug has a lag-time for the onset and offset of analgesia and adverse effects. Initial doses should therefore be low (2.4 microg/day) and titrated slowly (increasing up to a maximum of 21.6 microg/day in increases of 2.4 microg/day no more than twice weekly). The gradual increase in dose helps to reduce the incidence and severity of adverse events which affect primarily the central nervous system (e.g. dizziness, nausea, confusion). Ziconotide maintains its analgesic efficacy over months and does not cause tolerance, dependence or respiratory depression. Following intrathecal infusion ziconotide is distributed within the cerebral spinal fluid (CSF) where its clearance (0.38 ml/min) corresponds to the rate of turnover of the CSF. Negligible amounts of ziconotide are present in the systemic circulation where it is rapidly degraded by proteolysis. In conclusion, ziconotide is a new and valuable alternative analgesic for the acute and long-term treatment of severe pain, especially in patients refractory to opioids.

Clinical impact of CYP2C19 polymorphism on the action of proton pump inhibitors: a review of a special problem.

Proton pump inhibitors (e.g. omeprazole/esomeprazole, lansoprazole, pantoprazole, rabeprazole) have a prominent role in the short- and long-term management of acid-related intestinal disease. They are eliminated by the hepatic route and the polymorphic CYP2C19 is involved in their metabolism. Three phenotypes have been identified in various populations: extensive metabolizers (homEM), poor metabolizers (PM) and individuals carrying one wild type and one mutant allele (hetEM). Therefore, systemic drug exposure (AUC) varies widely between these three populations and the AUC for omeprazole, lansoprazole and rabeprazole are approximately 7.5-, 4.5- and 4-fold higher in PM than in homEM. Since the pharmacodynamic response to proton pump inhibitors (PPIs) is related to their AUC, intragastric pH is much more elevated in PM (median around 6) and hetEM (4 - 5) than in homEM (3 - 4). This genotype-dependent increase in AUC and intragastric pH has clinical consequences because the healing rate in peptic ulcer (PU, target pH > or = 3) and gastroesophageal reflux disease (GERD, target pH > or = 4) and the eradication of Helicobacter pylori (Hp) depend on a long-lasting (> or = 16 hours) and effective inhibition of acid secretion. Several clinical studies have shown that PM and hetEM benefit from an approximately 18% higher Hp eradication rate compared to homEM when standard dosages of PPIs are administered orally. In our own study with lansoprazole (+ amoxicillin, clarithromycin, metronidazole) the eradication rates were 100, 98 and 80% in PM, hetEM and homEM, respectively, and in patients with GERD treated with lansoprazole (30 mg/day) the healing rates after 8 weeks were much higher in PM (85 - 100%) and hetEM (68 - 95%) than in homEM (46 - 77%). In a further study with esomeprazole (40 mg/day) in 205 patients with GERD we were surprised to observe that the healing rate after 4 weeks was not dependent on the CYP2C19 genotype. In an accompanying pharmacokinetic trial in 10 patients with GERD, both esomeprazole and 5-OH-esomeprazole (formed by CYP2C19) plasma levels and those of omeprazole-sulfone (formed by CYP3A4) were determined. Based on the calculated metabolic ratios it could be shown that CYP3A4 plays a major role in kinetics of esomeprozale, particularly after multiple dosing when there is a metabolic shift in favor of the formation of the sulfone. In conclusion, for most PPIs the activity of CYP2C 19 determines the level of drug exposure (AUC), pharmacodynamic response (elevation of intragastric pH and serum levels of gastrin) and clinical outcome (Hp eradication, healing rates of PU and GERD). Thus, a genotype-adjusted dosage regimen will improve therapeutic efficacy of PPIs.

Biopharmaceutical characterization of the telomerase inhibitor BRACO19.

PURPOSE: To characterize the telomerase inhibitor and G-quadruplex stabilizing substance 9-[4-(N,N-dimethylamino)phenylamino]-3,6-bis (3-pyrrolodino-propionamido) acridine x 3HCl (BRACO19) in terms of biopharmaceutical properties such as solubility, protein binding, interaction with membrane lipids, cytotoxicity, and permeability across pulmonary epithelial cells. METHODS: Protein binding and interaction with membrane lipids were investigated by two high-performance liquid chromatography methods with immobilized human serum albumin and immobilized phosphatidylcholine, respectively. Cytotoxicity (methyl-thiazolyl-tetrazolium assay) and transport studies were performed with the bronchial cell lines 16HBE14o- and Calu-3, primary human alveolar epithelial cells, and the intestinal cell line Caco-2. Transport experiments were also done in the presence of cyclosporin A (10 microM) and tetraethylammonium chloride (5 mM) and at low temperature (4 degrees C). RESULTS: BRACO19 has good solubility of at least 2 mg/mL in water and in physiological buffers of pH 7.4 and below. Protein binding to human serum albumin was 38%. No interaction with membrane lipids could be found. Cytotoxicity in 16HBE14o-, Calu-3, and human alveolar epithelial cells was in the range of IC50 = 3.5 to 13.5 microM. Caco-2 cells were not affected at concentrations up to 50 microM. No transport of BRACO19 was detected across either cell monolayer in absorptive direction. In secretory direction, permeability was very low, with P (app) values in the range of 0.25 x 10(-7) to 0.98 x 10(-7) cm/s for all epithelial cell cultures tested. The transport was not influenced by cyclosporin A or tetraethylammonium chloride or at 4 degrees C, indicating that no efflux/influx systems or active transport are involved. CONCLUSIONS: From these results, we conclude that the very poor permeability of BRACO19 is its main biopharmaceutical limitation. Further applications will require a suitable formulation to warrant adequate delivery across cellular barriers.

Colonic targeting of aminosalicylates for the treatment of ulcerative colitis.

Aminosalicylates (5-aminosalicylic acid) represent drugs of first choice in the treatment of ulcerative colitis. Two different therapeutic approaches have been employed to target the active 5-aminosalicylic acid to its site of action. Either inactive azo-prodrugs (e.g. sulfasalazine, olsalazine, balsalazide) or special galenic formulations have been developed for topical delivery of 5-aminosalicylic acid to the colon. However, as intestinal physiology, the extent of ulcerative colitis as well as drug disposition demonstrate large interindividual differences, acute healing rates (40-80%) and the maintenance of remission are quite variable. Apparently, therapeutic effects depend on local concentrations of 5-aminosalicylic acid in the colonic mucosa whereas systemic drug exposure might be one determinant of side effects. In general, 5-aminosalicylic acid is well tolerated and withdrawal from therapy is rare. Following administration of azo-prodrugs (e.g. olsalazine), lower plasma concentrations and higher delivery into the colon of 5-aminosalicylic acid can be observed in comparison to special galenic formulations of 5-aminosalicylic acid. Whether such changes in drug disposition will affect therapeutic efficacy remains to be proved by clinical data. Consequently, selection of a particular agent should be based primarily on clinical efficacy, profile of adverse effects, patients' acceptance and economic considerations.

Effects of aminosalicylates on thiopurine S-methyltransferase activity: an ex vivo study in patients with inflammatory bowel disease.

BACKGROUND: Based on in vitro experiments using recombinant human thiopurine S-methyltransferase this enzyme is inhibited by sulfasalazine (sulphasalazine) and 5-aminosalicylate. Thus, during treatment with azathioprine or mercaptopurine, both metabolized by thiopurine S-methyltransferase, sulfasalazine or 5-aminosalicylate could modify the action of azathioprine/mercaptopurine. AIMS: To examine whether this interaction is effective under ex vivo conditions. METHODS: In 18 azathioprine-free patients and in 12 patients on azathioprine the inhibitory potential of sulfasalazine, 5-aminosalicylate and its metabolite (Ac-5-aminosalicylate) was assessed by ex vivo measurement of thiopurine S-methyltransferase in red blood cells. RESULTS: According to concentration response curves mean IC50 values (microm) for sulfasalazine, 5-aminosalicylate and Ac-5-aminosalicylate have been calculated in three groups of azathioprine-free patients and variable basal levels of thiopurine S-methyltransferase activity (very high, normal and intermediate). In all three groups sulfasalazine was the strongest inhibitor (IC50: 9-17 microm) if compared with 5-aminosalicylate (129-236) and Ac-5-aminosalicylate (58-74). In patients on azathioprine similar IC50 values have been calculated. CONCLUSIONS: Comparing human plasma concentrations of sulfasalazine (15-77 microm), 5-aminosalicylate (3-14 microm) and Ac-5-aminosalicylate (8-18 microm) with the IC50 values one can assume that only sulfasalazine would have the potential to inhibit thiopurine S-methyltransferase in vivo. However, the therapeutic impact should be proved by clinical studies.

Dyspeptic symptoms associated with Helicobacter pylori infection are influenced by strain and host specific factors.

BACKGROUND: Dyspepsia can be associated with H. pylori infection. AIM: To assess dyspeptic symptoms and potentially influencing factors before and up to 6 months following successful H. pylori eradication therapy. METHODS: Prospective cohort study involving H. pylori positive subjects from ambulatory or hospitalized care. Main outcome measures were symptoms during baseline and follow-up, the proportion of symptom-free patients, and symptom scores. RESULTS: After successful eradication, the summary score of all dyspeptic symptoms decreased and during follow-up, the proportion of symptom-free patients was higher in the group with peptic ulcers (69.4% vs. 40.9%, P < 0.0001) than with functional dyspepsia (FD). Regardless of diagnosis, virulent strains of H. pylori were associated with a higher prevalence of epigastric pain before treatment: absolute risk-difference (ARD) with Oip-A: 18.2%, Odds Ratio (OR) 2.35 [1.3-4.2, 95%-CI], P = 0.01; with Cag-A: 24.6%, OR 2.81 [1.6-5], P = 0.01. Low-dose aspirin in part was a major risk factor in FD for previous weight loss bdfore study entry. Post-treatment, non-ulcer patients were more likely to suffer from distention/bloating. Likewise, alcohol induced persistence of nausea and vomiting in this population. CONCLUSIONS: Dyspeptic symptoms in H. pylori infected patients are more common with virulent strains. Symptoms are more likely to persist despite successful eradication if patients initially harboured virulent strains or concomitant aspirin or alcohol intake are present. In one-third of peptic ulcer patients, symptoms will not be cured 3 months after therapy.

[Drug interactions. Mechanisms and clinical relevance]. / Arzneimittelinteraktionen. Mechanismen und klinische Bedeutung

During the last few years 3 important drugs (terfenadine, mibefradil, cisapride) had to been withdrawn from the market because of serious drug-drug interactions. Polypragmacy, not only in advanced age, is often applied. Consequently the possibility of pharmacokinetic and/or pharmacodynamic drug interactions has always to be taken into account which can cause adverse effects, therapeutic failures, hospital admissions and extra costs. Clinically relevant interactions can be observed especially on the level of drug metabolism and transport. Both pharmacokinetic processes can be induced or inhibited by numerous agents. Taking proton pump inhibitors as an example it could be shown that the various compounds can differ in their interaction potential.

Impact of furazolidone-based quadruple therapy for eradication of Helicobacter pylori after previous treatment failures.

BACKGROUND: One week of quadruple therapy including metronidazole is recommended for Helicobacter pylori treatment failures after first line therapy regardless of resistance status. This study investigated whether a quadruple regimen containing furazolidone could be effective as a third-line (salvage) therapy. METHODS: All patients with previous H. pylori treatment failure after a clarithromycin-metronidazole +/- amoxicillin combination plus acid suppression were given lansoprazole 30 mg twice a day (bid), tripotassiumdicitratobismuthate 240 mg bid, tetracycline 1 g bid, metronidazole 400 mg (PPI-B-T-M) three times a day (tid) for 1 week. In the case of treatment failure with this second-line therapy, the same regimen was applied for 1 week except for using furazolidone 200 mg bid (PPI-B-T-F) instead of metronidazole (sequential study design). RESULTS: Eighteen consecutive patients were treated with PPI-B-T-M. Eleven of those 18 remained H. pylori positive (38.9% cured). Pretherapeutic metronidazole resistance was associated with a lower probability of eradication success (10% vs. 75%, p=.04). Ten of these 11 patients agreed to be retreated by PPI-B-T-F. Final cure of H. pylori with PPI-B-T-F was achieved in 9/10 patients (90%) nonresponsive to PPI-B-T-M. CONCLUSIONS: In the presence of metronidazole resistance, PPI-B-T-M as a recommended second-line therapy by the Maastricht consensus conference achieved unacceptable low cure rates in our metronidazole pretreated population. In this population, metronidazole based second-line quadruple therapy may be best suited in case of a metronidazole-free first line-regimen (e.g. PPI-clarithromycin-amoxicillin) or a low prevalence of metronidazole resistance. Furazolidone in the PPI-B-T-F combination does not have a cross-resistance potential to metronidazole and is a promising salvage option after a failed PPI-B-T-M regimen.

Pharmacokinetic considerations in the treatment of inflammatory bowel disease.

This review describes the pharmacokinetics of the major drugs used for the treatment of inflammatory bowel disease. This information can be helpful for the selection of a particular agent and offers guidance for effective and well tolerated regimens. The corticosteroids have a short elimination half-life (t1/2beta) of 1.5 to 4 hours, but their biological half-lives are much longer (12 to 36 hours). Most are moderate or high clearance drugs that are hepatically eliminated, primarily by cytochrome P450 (CYP) 3A4-mediated metabolism. Prednisone and budesonide undergo presystemic elimination. Any disease state or comedication affecting CYP3A4 activity should be taken into account when prescribing corticosteroids. Depending on the preparation used, 10 to 50% of an oral or rectal dose of mesalazine is absorbed. Rapid acetylation in the intestinal wall and liver (t1/2beta 0.5 to 2 hours) and transport probably by P-glycoprotein affect mucosal concentrations of mesalazine, which apparently determine clinical response. Any clinical condition influencing the release and topical availability of mesalazine might modify its therapeutic potential. Metronidazole has high (approximately 90%) oral bioavailability, with hepatic elimination characterised by a t1/2beta of 6 to 10 hours and a total clearance of about 4 L/h/kg. Ciprofloxacin is largely excreted unchanged both renally (about 45% of dose) and extrarenally (25%), with a relatively short t1/2beta (3.5 to 7 hours). Thus, renal function affects the systemic availability of ciprofloxacin. Both mercaptopurine and its prodrug azathioprine are metabolised to active compounds (6-thioguanine nucleotides; 6-TGN) by hypoxanthine-guanine phosphoribosyltransferase and to inactive metabolites by the polymorphically expressed thiopurine S-methyltransferase (TPMT) and xanthine oxidase. Patients with low TPMT activity have a higher risk of developing haemopoietic toxicity. Both mercaptopurine and azathioprine have a short t1/2beta (1 to 2 hours), but the t1/2beta of 6-TGN ranges from 3 to 13 days. Therapeutic response seems to be related to 6-TGN concentration. Almost complete bioavailability has been observed after intramuscular and subcutaneous administration of methotrexate, which is predominantly (85%) excreted as unchanged drug with a t1/2beta of up to 50 hours. Thus, renal function is the major determinant for disposition of methotrexate. Cyclosporin is slowly and incompletely absorbed. It is extensively metabolised by CYP3A4/5 in the liver and intestine (median t1/2beta and clearance 7.9 hours and 0.46 L/h/kg, respectively), and inhibitors and inducers of CYP3A4 can modify response and toxicity. Infliximab is predominantly distributed to the vascular compartment and eliminated with a t1/2beta between 10 and 14 days. No accumulation was observed when it was administered at intervals of 4 or 8 weeks. Methotrexate may reduce the clearance of infliximab from serum.

P-glycoprotein-mediated transport of digitoxin, alpha-methyldigoxin and beta-acetyldigoxin.

Digoxin is a drug with a narrow therapeutic index, which is substrate of the ATP-dependent efflux pump P-glycoprotein. Increased or decreased digoxin plasma concentrations occur in humans due to inhibition or induction of this drug transporter in organs with excretory function such as small intestine, liver and kidneys. Whereas particle size, dissolution rate and lipophilic properties have been identified as determinants for absorption of digitalis glycosides, little is known about P-glycoprotein transport characteristics of digitalis glycosides such as digitoxin, alpha-methyldigoxin, beta-acetyldigoxin and ouabain. Using polarized P-glycoprotein-expressing cell lines we therefore studied whether these compounds are substrates of P-glycoprotein. Polarized transport of digitalis glycosides was assessed in P-glycoprotein-expressing Caco-2 and L-MDR1 cells (LLC-PK1 cells stably transfected with the human MDR1 P-glycoprotein). Inhibition of P-glycoprotein-mediated transport of these compounds in Caco-2 cells was determined using the cyclosporine analogue PSC-833 (valspodar) as inhibitor of P-glycoprotein. No polarized transport was observed for ouabain. However, basal-to-apical transport of digitoxin, alpha-methyldigoxin and beta-acetyldigoxin was greater than apical-to-basal transport in Caco-2 and L-MDR1 cells. In Caco-2 cells net transport rates of these compounds were similar to those of digoxin (digoxin: 16.0+/-4.4%, digitoxin: 15.0+/-3.3%, beta-acetyldigoxin: 16.2+/-1.6%, alpha-methyldigoxin: 13.5+/-4.8%). Furthermore, polarized transport of these compounds could be completely inhibited by 1 microM PSC-833. In summary, these data provide evidence that not only digoxin, but also digitoxin, alpha-methyldigoxin and beta-acetyldigoxin are substrates of P-glycoprotein.

[Drug interactions--their impact on safe drug therapy in the example of the new thiazolidinedione group (glitazone)]. / Arzneimittelinteraktionen--ihre Bedeutung für eine sichere Therapie am Beispiel der neuen Wirkstoffgruppe der Thiazolidindione (Glitazone).

Troglitazone (CAS 97322-87-7), rosiglitazone (CAS 155141-29-0) and pioglitazone (CAS 111025-46-8) represent novel agents for the treatment of diabetes mellitus. Very often such patients receive several drugs at the same time and consequently their interaction potential needs to be known, especially as troglitazone was recently withdrawn from the market partly because it inhibited and induced drug metabolism.

Telomeres in neonates: new insights in fetal hematopoiesis.

Progressive telomere shortening occurs in somatic cells, and with increasing donor age a significant decline in telomere length has been shown in various postnatal tissues. In contrast, little is known about changes in telomere length during human fetal development. Therefore, we measured telomere length in the leukocyte fraction of umbilical cord blood samples from 15 preterm (<37 wk of gestation) and 11 full-term (>37 wk of gestation) neonates using the telomere restriction fragment assay. Whereas no differences in mean (+/- SD) telomere restriction fragment between the groups of preterm neonates (8512 +/- 523 bp) and full-term newborns (8323 +/- 503 bp) could be found, significantly longer telomeres (p = 0.002) were found in very low birth weight preterm neonates when compared with low birth weight preterm neonates. In addition, a rapid and significant decline in mean telomere restriction fragment was observed between 27 and 32 wk of gestation (p = 0.02, r = 0.79) followed by a period of no significant loss of telomere repeats between 33 and 42 wk of gestation. These results are consistent with the known almost maximal proliferation rate of hematopoietic progenitor cells before 32 wk of gestation. The initial decrease in telomere restriction fragment could be caused by ontogeny-related functional alterations of hematopoietic cells or differences in stem cell turnover or the rate of telomere loss per cell division.

Interaction of omeprazole, lansoprazole and pantoprazole with P-glycoprotein.

Proton pump inhibitors are a class of drugs which are widely prescribed for acid-related diseases. They are primarily metabolized by CYP2C19 and CYP3A4. It is unknown so far whether proton pump inhibitors are also substrates of the ATP-dependent efflux transporter P-glycoprotein. Moreover, it is not established whether proton pump inhibitors are also inhibitors of P-glycoprotein function. The aim of our study was therefore to characterize omeprazole, lansoprazole and pantoprazole as P-glycoprotein substrates and inhibitors. Polarized transport of these compounds was assessed in P-glycoprotein-expressing Caco-2 and L-MDR1 cells. Inhibition of P-glycoprotein-mediated transport was determined using the cyclosporine analogue PSC-833 (valspodar) as P-glycoprotein inhibitor. Inhibition of efflux transport by omeprazole, lansoprazole and pantoprazole was assessed using digoxin as P-glycoprotein substrate. At concentrations of 5 microM, basal-to-apical transport of omeprazole, lansoprazole and pantoprazole was greater than apical-to-basal transport in Caco-2 and L-MDRI cells. Addition of PSC-833 (1 microM) showed a clear effect only for lansoprazole, suggesting that other transporters contribute to omeprazole and pantoprazole cellular translocation. Furthermore, all of the tested compounds inhibited digoxin transport with IC50 values of 17.7, 17.9 and 62.8 microM for omeprazole, pantoprazole and lansoprazole, respectively. In summary, our data provide evidence that proton pump inhibitors are substrates and inhibitors of P-glycoprotein. These findings might explain some of the drug interactions with proton pump inhibitors observed in vivo.