Multiscale modeling reveals inhibitory and stimulatory effects of caffeine on acetaminophen-induced toxicity in humans.

Acetaminophen (APAP) is a widely used analgesic drug that is frequently co-administered with caffeine (CAF) in the treatment of pain. It is well known that APAP may cause severe liver injury after an acute overdose. However, the understanding of whether and to what extent CAF inhibits or stimulates APAP-induced hepatotoxicity in humans is still lacking. Here, a multiscale analysis is presented that quantitatively models the pharmacodynamic (PD) response of APAP during co-medication with CAF. Therefore, drug-drug interaction (DDI) processes were integrated into physiologically based pharmacokinetic (PBPK) models at the organism level, whereas drug-specific PD response data were contextualized at the cellular level. The results provide new insights into the inhibitory and stimulatory effects of CAF on APAP-induced hepatotoxicity for crucially affected key cellular processes and individual genes at the patient level. This study might facilitate the risk assessment of drug combination therapies in humans and thus may improve patient safety in clinical practice.

Short-term study of the uptake of PrP(Sc) by the Peyer's patches in hamsters after oral exposure to scrapie.

The disease-associated prion protein (PrP(Sc)) has been detected in the ileal Peyer's patches of lambs as early as one week after oral exposure to scrapie. In hamsters, the earliest reported time of PrP(Sc) detection in the Peyer's patches after oral exposure to scrapie is 69 days post-infection. To evaluate the acute uptake of inoculum and to investigate whether the Peyer's patches constitute the primary site of entry for scrapie after oral exposure, hamsters were each exposed orally to 1 ml of a 10% brain homogenate from hamsters in the terminal stage of infection with the 263 K strain of the scrapie agent. PrP(Sc) was demonstrated in the Peyer's patches only a few days after exposure, i.e., much earlier than previously reported. This study supports the view that the Peyer's patches constitute at least one of the primary entry sites of PrP(Sc) after oral exposure to scrapie.

Mode of action and quantitative structure-activity correlations of tuberculostatic drugs of the isonicotinic acid hydrazide type.

Quantitative structure-activity studies have been performed for a series of 2-substituted isonicotinic acid hydrazides by correlating electronic, steric, and lipophilic properties of the substituents with the biological activity date (MIC) from serial dilution tests with Mycobacterium tuberculosis (strain H 37 Rv). The reaction rates for the quaternization of 2-substituted pyridines with methyl iodide were also determined. The rate constants show a similar dependence on the steric and electronic effects of the substituents as the antibacterial activities of the corresponding pyridine-4-carboxylic acid hydrazides. The obtained correlations give evidence that the reactivity of the pyridine nitrogen atom is essential for the biological activity of 2-substituted isonicotinic acid hydrazides and seem to support the hypothesis that isonicotinic acid derivatives are incorporated into an NAD analogue.

Quantitative structure-pharmacokinetic relationships derived on antibacterial sulfonamides in rats and its comparison to quantitative structure-activity relationships.

Quantitative structure-pharmacokinetic relationships have been derived for a series of substituted 2-sulfapyridines. Pharmacokinetic parameters, such as elimination rate constant (ke), clearance (Cl), and protein-binding constant (Kassoc), have been determined in rats. The observed variation is statistically significant, explained by changes in the lipophilic (deltaRm), electronic (pKa), and steric effects (I, ES) of the substituents. The obtained correlations are discussed with respect to the previously derived correlations for the antibacterial activity of these compounds. A scale up of the results opens up the possibility of a rational synthesis of highly active sulfonamides with special pharmacokinetic properties because lipophilicity influences strongly the pharmacokinetic properties, whereas no influence on the degree of antibacterial effect is observed. Steric substituent influence is opposite on specific binding to bacterial enzymes and unspecific binding to serum proteins.

Synthesis and quantitative structure-activity relationships of anticonvulsant 2,3,6-triaminopyridines.

The synthesis of 2,3,6-triaminopyridine derivatives, representing a unique chemical structure for anticonvulsants, is described. The synthetic program was performed (a) to identify more potent analogs, (b) to determine structural properties controlling potency as well as neurotoxicity, and (c) to reduce the requirements for animal testing. As a result, besides other structural properties, the overall molecular lipophilicity (log k', octanol-coated column) explained changes in anticonvulsant potency and neurotoxicity. Mimicking the interaction of the amphiphilic triaminopyridines with biological membranes, NMR experiments in the presence of lecithin vesicles were conducted in order to measure the phospholipid-binding parameter log delta (1/T2). Replacement of log k' with log delta (1/T2) in the correlation analysis afforded a more significant equation describing the anticonvulsant activity of 21 derivatives.

Structure-activity relationship studies on benzofuran analogs of propafenone-type modulators of tumor cell multidrug resistance.

A series of benzofurylethanolamine analogs of propafenone (1a) have been prepared and evaluated for multidrug resistance-reversing activity in two in vitro assay systems. As for propafenones, an excellent correlation of biological data with calculated lipophilicity values was found for benzofurans, whereby the latter generally had lower activity/lipophilicity ratios. Almost identical slopes of the regression lines were obtained for both propafenones and benzofurans. Multiple linear regression analysis of the complete data set yielded an equation with excellent predictive power (r2 cross-valid = 0.968). Interaction measurements with artificial membranes indicated that the differences in activity between these two series of compounds are not due to differences in the interaction pattern with biological membranes.

Membrane interactions of some catamphiphilic drugs and relation to their multidrug-resistance-reversing ability.

The multidrug-resistance (MDR)-reversing ability of the catamphiphilic drugs could be mediated through their interaction with the membrane phospholipids. This could lead directly (through changes in membrane permeability and fluidity) and/or indirectly (through inhibition of P-glycoprotein phosphorylation via inhibition of the phosphatidylserine-dependent protein kinase C or changes in the conformation and functioning of the membrane-integrated proteins via changes in the structure organization of the surrounding membrane bilayer) to the reversal of MDR. Using differential scanning calorimetry and NMR techniques and artificial membranes composed of phosphatidylcholine or phosphatidylserines we found a significant correlation between the MDR-reversing activity of the drugs in doxorubicin-resistant human breast carcinoma MCF-7/DOX and murine leukaemia P388/DOX tumour cells (data taken from the literature) and their ability to interact with phosphatidylserines. Trans- and cis-flupentixol were found to interact most strongly with both the phospholipids, followed by trifluoperazine, chlorpromazine, triflupromazine, flunarizine, imipramine, quinacrine and lidocaine. Differences in the interaction of trans- and cis-flupentixol with the phospholipids studied are suggested to be responsible for their different MDR-reversing ability. Verapamil showed moderate membrane activity, assuming that the membrane interactions are not the only reason for its high MDR-reversing ability. Amiodarone showed very strong interactions with phosphatidylserines and is recommended for further MDR-reversal studies.

Interaction of prostaglandin E1 with alpha-cyclodextrin in aqueous systems: stability of the inclusion complex.

Prostavasin, an inclusion complex of prostaglandin E1 (PGE1) with alpha-cyclodextrin (alpha-CD), is used in the therapy of thrombosis. Nuclear magnetic resonance measurements have been made to study the interaction of PGE1 with alpha-CD. The observed interaction (chemical shift) and the derived dissociation constant prove that only weak interaction forces are operative and that complete dissociation occurs upon dilution.

Partial resistance of E. coli mutants against 2, 4-diamino-5-benzylpyrimidines by interactions with bacterial membrane lipopolysaccharides. Derivation of quantitative structure-binding relationships.

A series of previously synthesized 2,4-diamino-5-benzylpyrimidines, inhibitors of bacterial dihydrofolate reductase (DHFR) showed decreased inhibition of E. coli cultures, despite increased inhibitory activity against DHFR. Preliminary studies using E. coli mutants with different degrees of outer membrane deficiencies suggested that the decrease in activity was partly due to inactivation because of binding to outer membrane constituents. In the present study antibacterial activities of the benzylpyrimidines have been systematically determined as a function of cell membrane defects in E. coli using bacterial growth kinetic techniques. It has been shown that the observed differences in activity were not due to different binding affinities to the target enzyme of the mutants. Lipopolysaccharides have been extracted from the mutants and used in binding studies by ultrafiltration, photometric and NMR techniques. The observed differences in binding affinity to the lipopolysaccharides have been related to the differences in the lipophilic properties and molecular weight of the substituents. Quantitative structure-activity relationships have been derived. The results of the study show the importance of drug-membrane interactions for the rational development of antibacterials.

[Pathophysiological-based diagnosis and therapy of iron-deficient anaemia in inflammatory bowel disease]. / Pathophysiologisch-orientierte Diagnostik und Therapie der Eisenmangelanämie bei chronisch entzündlichen Darmerkrankungen.

Anaemia is the most frequent extraenteric complication of inflammatory bowel disease (IBD, Crohn's disease and ulcerative colitis). A disabling complication of IBD, anaemia worsens the patient's general condition and quality of life, and increases hospitalization rates. The main types of anemia in IBD are iron deficiency anemia and anemia of chronic disease. The combination of the serum transferrin receptor with ferritin concentrations and inflammatory markers allows a reliable assessment of the iron status. Iron deficiency is usually treated with oral iron supplements. However, it is less effective in IBD and may lead to an increased inflammatory activity through the generation of reactive oxygen species. A systematic review of anemia in IBD, its pathogenetic features, epidemiology, diagnosis and therapy based on the evidence from recent studies will be the focus of this article.

[Bioclimatic consultation]. / Bioklimatische Beratung

The climatological environment may effect the human state of health, disadvantageously or favourably. This knowledge, confirmed by empiric as well as scientific research can be used by e.g. changing the place of residence towards a healthy and benefical climate. For a professional climatological planning of such a project the "Deutscher Wetterdienst" renders bioclimatic consultations within the Federal Republic of Germany. For this purpose individual reactions as well as state health of the person in question have to be considered. A method will be shown how to combine medical diagnostic facts and bioclimatic consultation.

Therapeutic plasma exchange in treatment of adrenoleukodystrophy.

Adrenoleukodystrophy (ALD) is an X-linked disorder of metabolism of very long-chain fatty acids (VLCFA) with a frequency of up to 1:20,000 in males. VLCFA C 24:0 and C 26:0 accumulate in the cholesterol ester and ganglioside fraction in plasma and red cells. Symptoms of ALD are ataxia, loss of visual and auditory functions, and cerebral convulsions. Presently, no sure therapeutic approaches are established. Efforts were reported by dietary regimens with VLCFA-restriction and glycerol trioleate and glycerol trierucate intake. In the present trial, we report on a 58-year-old white male suffering from progressive ALD with spastic paraparesis. He has a positive family history back to the 18th century. In this patient, although maximum dietary therapy was applied over a period of 60 months, no normalization of VLCFA C24:0 and C26:0 was reached, and neurological disorders were progressive. As a result, therapeutic plasma exchange (TPE) was applied from 1990 to 1994. Then, for more selective adsorption of VLCFA, dextran-sulfate adsorption (Liposorber, Kaneka, Osaka, Japan) until 1996, and after that, immunoadsorption (Therasorb, Baxter, Munchen, Germany) were used. During these periods (total, 101 months), VLCFA C 24:0 and C 26:0 levels were reduced by 55% and 50% (p < 0.001). The patient experienced a significant improvement in performance and general well-being. No further progression of neuronal disorders was documented. This anecdotal data suggest a very beneficial effect of TPE in treatment of progressive ALD.

[Early recognition of C-cell carcinoma by family screening (author's transl)]. / Früherkennung des C-Zell-Karzinoms durch Familien-Screening.

All available family members of five patients with C-cell carcinoma (medullary carcinoma of the thyroid) were tested for their basal serum-calcitonin level and after pentagastrin stimulation. In two females, aged 12 and 25 years, from two different families, serum-calcitonin was elevated, but only after repeated tests or after pentagastrin stimulation, to definitely abnormal levels. Neither had palpable thyroid nodules, lymph-adenopathy or diarrhoea. The thyroid scan was normal and there were no storage defects. But because of the family history and the elevated serum-calcitonin levels total thyroidectomy was performed in both. The specimens revealed multicentric, bilateral C-cell carcinomas. The serum-calcitonin concentration became completely normal postoperatively, so that one may justifiably speak of a curative effect of the thyroidectomy in these two instances of early diagnosis.

Drug membrane interaction and the importance for drug transport, distribution, accumulation, efficacy and resistance.

Some aspects of drug membrane interaction and its influence on drug transport, accumulation, efficacy and resistance have been discussed. The interactions manifest themselves macroscopically in changes in the physical and thermodynamic properties of "pure membranes" or bilayers. As various amounts of foreign molecules enter the membrane, in particular the main gel to liquid crystalline phase transition can be dramatically changed. This may change permeability, cell-fusion, cell resistance and may also lead to changes in conformation of the embedded receptor proteins. Furthermore, specific interactions with lipids may lead to drug accumulation in membranes and thus to much larger concentrations at the active site than present in the surrounding water phase. The lipid environment may also lead to changes in the preferred conformation of drug molecules. These events are directly related to drug efficacy. The determination of essential molecular criteria for the interaction could be used to design new and more selective therapeutics. This excursion in some aspects of drug membrane interaction underlines the importance of lipids and their interaction with drug molecules for our understanding of drug action, but this is not really a new thought but has been formulated in 1884 by THUDICUM: "Phospholipids are the centre, life and chemical soul of all bioplasm whatsoever, that of plants as well as of animals".

Plasmapheresis in treatment of adrenoleukodystrophy.

Adrenoleukodystrophy (ALD) is an X-linked disorder of metabolism of very long chain fatty acids (VLCFAs) with a frequency of up to 1:20,000 in males. VLCFAs C24:0 and C26:0 accumulate in the cholesterol ester and ganglioside fraction in plasma and red cells. Symptoms of ALD are ataxia, loss of visual and auditory functions, and cerebral convulsions. Up to the present, no sure therapeutic approaches have been established. Efforts were reported by dietary regimens with VLCFA restriction and glyceroltrioleate and glyceroltrierucate intake. In the present trial, we report a 55-year-old Caucasian male suffering from progressive ALD with spastic paraparesis. He has had a positive family history since the eighteenth century. In this patient treated with maximum dietary therapy over a period of 60 months, no normalization of C24:0 and C26:0 was reached, and neurological disorders were progressive. As a result, plasmapheresis was applied during the period 1990-1994 and since then for more selective adsorption of VLCFAs, dextran sulfate adsorption (Liposorber, Kaneka, Japan). During this period (64 months), C24:0 and C26:0 levels were reduced by 54.5% and 51.8%, respectively (p = 0.0001). The patient experienced a significant improvement in performance and general well-being. There has been no further progression of neuronal disorders to document.

Diameters of abdominal veins and arteries during nitrate therapy.

The effects of 1.6 mg NTG on the diameter of abdominal veins and arteries were investigated by means of ultrasound tomography in 26 and 28 healthy persons respectively. Fourteen patients served as controls in the venous studies and 28 in the arterial measurements. The diameter of the caval vein decreased in anterior-posterior direction within 5 minutes after nitroglycerin administration by about 22% from 14.2 +/- 4.0 mm to 11.1 +/- 3.3 mm (p less than 0.005). In contrast, the portal vein enlarged by about 27% from 10.3 +/- 1.8 mm to 13.1 +/- 2.3 mm, the superior mesenteric vein by about 12% from 8.2 +/- 1.6 to 9.2 +/- 1.4 mm, and the splenic vein by about 23% from 6.6 +/- 2.3 mm to 8.1 +/- 1.8 mm (p less than 0.001). The superior mesenteric artery and the proper hepatic artery dilated by about 12% from 7.8 +/- 0.9 mm to 8.7 +/- 0.9 mm and from 6.5 +/- 1.0 mm to 7.3 +/- 0.7 mm respectively (p less than 0.001). There was no significant change in the diameter of the abdominal aorta, however. The results show that NTG induces a relaxation of the abdominal veins and of the abdominal arteries of the muscular type. They suggest that the splanchnic veins participate essentially in the therapeutically important venous pooling effect of NTG. The reduced peripheral venous return is made sonographically visible by a collapse of the inferior vena cava. Furthermore, the influence on the windkessel function after administration of NTG seems to be mediated not by the aorta itself, but rather by its large muscular-type branches like the mesenteric and hepatic arteries.

Constrained glycopeptide ligands for MPRs. Limitations of unprotected phosphorylated building blocks.

A new methodology for the synthesis of cyclic and phosphorylated glycopeptide templates was developed. First, fully protected building blocks containing mannose and mannose disaccharides with bis-trichloroethyl phosphate on Fmoc-Thr-OPfp were synthesized. These were used in solid-phase assembly through side chain anchoring of glycosylated hexa- and octa-peptides protected at the C-terminal carboxylate as the allyl ester. Selective allyl ester cleavage and head-to-tail cyclization under pseudodilution conditions gave a high yield of pure cyclic peptide templates. Unprotected phosphate in the building block was evaluated as an alternative to the problematic trichloroethyl group. It was found that one unprotected phosphate is readily incorporated, whereas the second unprotected phosphorylated building block react very slowly due to electrostatic repulsion in the solid-phase synthesis. For comparison with previous binding studies modified glycopeptide templates containing only phosphorylated mannose monosaccharides or templates modified in the peptide part were synthesized. All the structures were tested for their binding to the mannose 6-phosphate receptor, and it was found that although mannose disaccharides are required for optimal interaction, the detailed structure of the peptide template has a strong influence on binding to the receptor. The restricted conformations of the cyclic peptides decreased the binding considerably.