Delirium and sleep disturbances-A narrative review

BACKGROUND

Delirium is considered a severe complication. It increases morbidity and mortality and represents a major financial burden for healthcare systems. Thus, prevention becomes a focal point of research. Sleep disturbances have been linked to the occurrence of delirium. Consequently, several interventions that target a possible connection have been studied in recent years.

OBJECTIVE

This narrative literature review explores the published data for an association between delirium and different types of sleep disturbances, the pathophysiological interactions and prevention methods.

MATERIAL AND METHODS

A literature search was carried out utilizing PubMed, the Cochrane Library, Livivo and Google Scholar.

RESULTS

Although an association between several types of sleep disturbances and delirium has been shown, no causality has been proven so far. Nevertheless, several pharmacological and nonpharmacological interventions for delirium prevention have been attempted; however, the level of evidence is insufficient at this point.

CONCLUSION

Further research is required to prove causality between sleep disturbances and delirium. Nonpharmacological interventions should be used in construction and maintenance of intensive care units and hospitals. Pharmacological interventions could be effective for prevention but further research is needed. Screening patients at risk of delirium for sleep disturbances and antihistaminergic/anticholinergic medication seems beneficial.

Calcium-mediated actin reset (CaAR) mediates acute cell adaptations

Actin has well established functions in cellular morphogenesis. However, it is not well understood how the various actin assemblies in a cell are kept in a dynamic equilibrium, in particular when cells have to respond to acute signals. Here, we characterize a rapid and transient actin reset in response to increased intracellular calcium levels. Within seconds of calcium influx, the formin INF2 stimulates filament polymerization at the endoplasmic reticulum (ER), while cortical actin is disassembled. The reaction is then reversed within a few minutes. This Calcium-mediated actin reset (CaAR) occurs in a wide range of mammalian cell types and in response to many physiological cues. CaAR leads to transient immobilization of organelles, drives reorganization of actin during cell cortex repair, cell spreading and wound healing, and induces long-lasting changes in gene expression. Our findings suggest that CaAR acts as fundamental facilitator of cellular adaptations in response to acute signals and stress.

DOI:http://dx.doi.org/10.7554/eLife.19850.001

Our skeleton plays a vital role in giving shape and structure to our body, it also allows us to make coordinated movements. Similarly, each cell contains a microscopic network of structures and supports called the cytoskeleton that helps cells to adopt specific shapes and is crucial for them to move around. Unlike our skeleton, which is relatively unchanging, the cytoskeleton of each cell constantly changes and adapts to the specific needs of the cell.

One part of the cytoskeleton is a dense, flexible meshwork of fibers called the cortex that lies just beneath the surface of the cell. The cortex is constructed using a protein called actin, and many of these proteins join together to form each fiber. When cells need to adapt rapidly to an injury or other sudden changes in their environment they activate a so-called stress response. This response often begins with a rapid increase in the amount of calcium ions inside a cell, which can then trigger changes in actin organization. However, it is not clear how cells under stress are able to globally remodel their actin cytoskeleton without compromising stability and integrity of the cortex.

Wales, Schuberth, Aufschnaiter et al. used a range of mammalian cells to investigate how actin responds to stress signals. All cells responded to the resulting influx of calcium ions by deconstructing large parts of the actin cortex and simultaneously forming actin filaments near the center of the cell. Wales, Schuberth, Aufschnaiter et al. termed this response calcium-mediated actin reset (CaAR), as it lasted for only a few minutes before the actin cortex reformed. The experiments show that a protein called INF2 controls CaAR by rapidly removing actin from the cortex and forming new filaments near a cell compartment called the endoplasmic reticulum.

CaAR allows cells to rapidly and drastically alter the cortex in response to stress. The experiments also show that this sudden shift in actin can change the activity of certain genes, leading to longer-term effects on the cell. The findings of Wales, Schuberth, Aufschnaiter et al. suggest that calcium ions globally regulate the actin cytoskeleton and hence cell shape and movement under stress. This could be relevant for many important processes and conditions such as wound healing, inflammation and cancer. A future challenge will be to understand the role of CaAR in these processes.

DOI:http://dx.doi.org/10.7554/eLife.19850.002

Regorafenib in combination with FOLFOX or FOLFIRI as first- or second-line treatment of colorectal cancer: results of a multicenter, phase Ib study

Background

Metastatic colorectal cancer (mCRC) is commonly treated with 5-fluorouracil, folinic acid, and oxaliplatin or irinotecan. The multitargeted kinase inhibitor, regorafenib, was combined with chemotherapy as first- or second-line treatment of mCRC to assess safety and pharmacokinetics (primary objectives) and tumor response (secondary objective).

Patients and methods

Forty-five patients were treated every 2 weeks with 5-fluorouracil 400 mg/m² bolus then 2400 mg/m² over 46 h, folinic acid 400 mg/m², and either oxaliplatin 85 mg/m² or irinotecan 180 mg/m². On days 4–10, patients received regorafenib 160 mg orally once daily.

Results

The median duration of treatment was 108 (range 2–345 days). Treatment was stopped for adverse events or death (17 patients), disease progression (11 patients), and consent withdrawal or investigator decision (11 patients). Six patients remained on regorafenib at data cutoff (two without chemotherapy). Drug-related adverse events occurred in 44 patients [grade ≥3 in 32 patients: mostly neutropenia (17 patients) and leukopenia, hand–foot skin reaction, and hypophosphatemia (four patients each)]. Thirty-three patients achieved disease control (partial response or stable disease) for a median of 126 (range 42–281 days).

Conclusion

Regorafenib had acceptable tolerability in combination with chemotherapy, with increased exposure of irinotecan and SN-38 but no significant effect on 5-fluorouracil or oxaliplatin pharmacokinetics.

Impact of beta-amyloid-specific florbetaben PET imaging on confidence in early diagnosis of Alzheimer's disease

BACKGROUND

Early diagnosis of Alzheimer's disease (AD) may be corroborated by imaging of beta-amyloid plaques using positron emission tomography (PET). Here, we performed an add-on questionnaire study to evaluate the relevance of florbetaben imaging (BAY 949172) in diagnosis and consecutive management of probable AD patients.

METHODS

AD patients with a clinical diagnosis in accordance with the NINCDS-ADRDA criteria or controls were imaged using florbetaben. Referring physicians were asked on a voluntary basis about their confidence in initial diagnosis, significance of PET imaging results, and their anticipated consequences for future patient care.

RESULTS

121 questionnaires for probable AD patients and 80 questionnaires for controls were evaluated. In 18% of patients who had initially received the diagnosis of probable AD, PET scans were rated negative, whereas in controls 18% of scans were positive. An increase in confidence in the initial diagnosis was frequently reported (80%). Imaging results had a significant impact on the intended patient care, as judged by the referring physicians; this was most prominent in those patients with a contradicting scan and/or a low confidence in the initial diagnosis.

CONCLUSION

Florbetaben amyloid imaging increases the overall confidence in diagnosis of AD and may frequently influence clinical decisions and patient management.

Analytical approaches for MCPD esters and glycidyl esters in food and biological samples: a review and future perspectives

Esters of 2 - and 3-monochloropropane-1,2-diol (MCPD) and glycidol esters are important contaminants of processed edible oils used as foods or food ingredients. This review describes the occurrence and analysis of MCPD esters and glycidol esters in vegetable oils and some other foods. The focus is on the analytical methods based on both direct and indirect methods. Methods of analysis applied to oils and lipid extracts of foods have been based on transesterification to free MCPD and determination by gas chromatography-mass spectrometry (indirect methods) and by high-performance liquid chromatography-mass spectrometry (direct methods). The evolution and performance of the different methods is described and their advantages and disadvantages are discussed. The application of direct and indirect methods to the analysis of foods and to research studies is described. The metabolism and fate of MCPD esters and glycidol esters in biological systems and the methods used to study these in body tissues studies are described. A clear understanding of the chemistry of the methods is important when choosing those suitable for the desired application, and will contribute to the mitigation of these contaminants.

Population pharmacokinetics-pharmacodynamics of alemtuzumab (Campath) in patients with chronic lymphocytic leukaemia and its link to treatment response

AIMS

To characterize alemtuzumab pharmacokinetics and its exposure-response relationship with white blood cell (WBC) count in patients with B-cell chronic lymphocytic leukaemia (CLL).

METHODS

Nonlinear mixed effects models were used to characterize plasma concentration-time data and WBC count-time data from 67 patients. Logistic regression was used to relate summary measures of drug exposure to tumour response.

RESULTS

Alemtuzumab pharmacokinetics were best characterized by a two-compartment model with nonlinear elimination where V(max) (microg h(-1)) was [1020 x (WBC count/10 x 10(9) l(-1))(0.194)], K(m) was 338 microg l(-1), V(1) was 11.3 l, Q was 1.05 l h(-1) and V(2) was 41.5 l. Intersubject variability (ISV) in V(max), K(m), V(1) and V(2) was 32%, 145%, 84% and 179%, respectively. The reduction in WBC over time was modelled by a stimulatory loss indirect response model with values of 18.2 for E(max), 306 microg l(-1) for EC(50), 1.56 x 10(9) cells l(-1) h(-1) for K(in) and 0.029 per h for K(out). The probability of achieving a complete or partial response was >/=50% when the maximal trough concentration exceeded 13.2 microg ml(-1) or when AUC(0-tau) exceeded 484 microg h(-1) ml(-1).

CONCLUSIONS

Alemtuzumab displayed time- and concentration-dependent pharmacokinetics with large interpatient variability, both in pharmacokinetics and pharmacodynamics, which was probably reflective of differences in tumour burden among patients. A direct relationship between maximal trough concentrations and clinical outcomes was observed, with increasing alemtuzumab exposure resulting in a greater probability of positive tumour response.

The applications of biomarkers in early clinical drug development to improve decision-making processes

Selecting and evaluating biomarkers in drug discovery and early drug development can substantially shorten clinical development time or the time to reach a critical decision point in exploratory drug development. Critical decisions such as candidate selection, early proof of concept/principle, dose ranging, development risks, and patient stratification are based on the appropriate measurements of biomarkers that are biologically and/or clinically validated. The use of biomarkers helps to streamline clinical development by determining whether the drug is reaching and affecting the molecular target in humans, delivering findings that are comparable to preclinical data, and by providing a measurable endpoint that predicts desired or undesired clinical effects and will increase the success rate in the confirmatory stage of clinical development. Appropriateness of biomarkers depends on the stage of development, development strategy, and the nature of the medical indication. Even if a biomarker fails in the validation process there may be still a benefit of having used it. More knowledge about pathophysiology of the disease and the drug has been obtained. Different levels of validation exist at different development phases. Biomarkers are perhaps most useful in the early phase of clinical development when measurement of clinical endpoints may be too time-consuming or cumbersome to provide timely proof of concept or dose-ranging information. Examples of biomarkers are illustrated for the development of new drugs in variant cardiovascular, pulmonary, and CNS diseases.

Synthesis of palmitoylated Ras-peptides and -proteins

In this review, an overview is given and details are provided for the synthesis of lipidated Ras (rat-adeno-sarcoma)-peptides and -proteins. The progress made in the synthesis of the lipidated peptides from the Ras superfamily is discussed with special emphasis on the recently developed solid-phase synthesis methods, since these methods have turned out to be the preferred synthesis method for the majority of the required peptides. Solid-phase lipopeptide synthesis has given access to native and modified peptides on a scale that allows peptide-consuming studies like for ligation to proteins and concomitant X-ray crystal structure determination. The access to these peptides has also enabled biological questions concerning these peptides and proteins to be resolved. The review describes different solid-phase methods, which are individually suited for different types of lipopeptides, differing for example in lipidation pattern or amino acid side-chain functionality, and their ligation to proteins. Finally, an example is provided how these peptides can serve to resolve biological aspects of the Ras family GTPases.

Intein-mediated in vitro synthesis of lipidated Ras proteins

Fully functional lipid-modified Ras proteins suitable for the study of Ras-membrane interactions and embodying exclusively native amide bonds can be synthesized in preparative amounts by means of Expressed Protein Ligation.

Correlation between insulin resistance and intramyocellular lipid levels in rats

Increased intramyocellular lipid (IMCL) content has been proposed as biomarker for insulin resistance (IR). An inverse correlation between IMCL and insulin sensitivity (IS) was found in nonathletic humans, whereas in animal models only a few validation studies have been performed. The aim of this study was to investigate the interrelation between IS indices determined by the glucose clamp technique (glucose disposal (GD), exogenous glucose infusion rates (GIR)) and IMCL content in the tibialis (TIB) and the soleus (SOL) muscle obtained by magnetic resonance spectroscopy in different rat models of IR. Diet-induced insulin-resistant Wistar rats as well as genetic disease models (ZDF rats) were used. In both muscles, elevated IMCL correlated with an impaired IS in all models of IR. The correlation of IMCL with both parameters for IS was comparable in TIB and SOL. The best fit between IMCL and IS was obtained using TIB and GIR data (r = -0.69, P < 0.001). Diabetic male ZDF rats exhibited comparatively low IMCL levels due to their catabolic state: exclusion of this group improved r. In summary, IMCL, especially in TIB, is a valid biomarker for IS in various rat models of IR with the advantage of a fast repeatable noninvasive measurement in individual animals.

Doppelseitige Hodenschussverletzung

Gunshot injuries to the testicles are rare and usually result in testicular atrophy. In the case of severe bilateral testicular injuries, this could cause not only infertility but also the need for lifetime testosterone-substitution. We report an 18-year-old patient with bilateral testicular gunshot injury. During the surgical exploration an orchiectomy of the complete ruptured left testicle was necessary. Debridement of the damaged tissue and a partial orchiectomy was performed on the right side. After the operation, the patient developed an incretory hypogonadism and oligozoospermia. During follow-up, an improvement in the sperm count and of the hormonal status occurred. These finally reached normal levels. After genital traumata, immediate surgical exploration should be performed. Based on the above results, the patient benefits from conservative debridement and primary repair of the injured testicle, if possible. An improvement in hormonal status and sperm parameters after testicular injury and consecutive testicular malfunction can occur. Regeneration of the testicular tissue seems possible.

Adverse events in volunteers participating in phase I clinical trials: a single-center five-year survey in 1,559 subjects

OBJECTIVE

This report analyzes all adverse events (AEs) which occurred in healthy volunteers in a phase I center over a five-year period. It included 142 phase I studies with a total of 1,559 participants receiving 2,955 treatments with 32 different active drugs and placebo (ratio 6.5 : 1 in terms of follow-up days). The observation period covered a total of 29,664 follow-up days.

METHODS

All adverse events (AEs) as well as clinically relevant laboratory findings were counted. The incidence of AEs was defined as the ratio between the number of AEs and the number of follow-up days. Severity of AEs was classified as mild, moderate and severe; serious AEs were analyzed separately. A chi2-test was used to compare incidence rates of the AEs. Statistical tests based on the normal distribution were used for comparison of demographic data and relative frequencies; p < 0.05 was defined as the minimum level of significance.

RESULTS

There were 2,604 AEs and 291 different types of AEs with headache (2.23%), diarrhea (1.37%) and common cold (0.72%) being the most frequent. The overall incidence of AEs was 8.8% with no significant difference between those occurring with active drug and those on placebo when the studies were taken as a whole (8.5% vs. 9.1%), but the incidence of AEs in the active treatment groups was higher than under placebo (14.1% vs. 9.1%; p < 0.001) in placebo-controlled studies. The overall rate of AEs was 1.7 per subject and 0.9 per treatment. The vast majority of AEs were of mild or moderate intensity (99.2%). Only six AEs were serious as defined by GCP but two, a pseudoallergic reaction and a prolonged orthostatic dysregulation were rated as possibly or probably drug-related and these resolved completely. The incidence of AEs was three-fold (all AEs) and six-fold (AEs with probable relationship to study medication) higher (p < 0.001) in multiple-dose studies than in single-dose trials, and within multiple-dose trials the difference between AEs on active drug and on placebo was also significant (22.9% vs. 12.5%; p < 0.001). Irrespective of whether on active drug or placebo, AEs occurred with a significantly higher incidence on the first day of the study drug administration, in the first study period, with respect to the overall population in elderly subjects and in volunteers with a high body weight.

CONCLUSION

AEs in phase I studies are common, but usually of mild or moderate intensity. Placebo effects and study conditions contribute significantly to the rate of their occurrence. Multiple-dose placebo-controlled studies are of particular importance in determining the substance-specific AE profile.

Glucuronidation of acetaminophen is independent of UGT1A1 promotor genotype

The metabolism of acetaminophen (paracetamol) is thought to be altered in patients with Gilbert's syndrome (GS), a chronic unconjugated hyperbilirubinemia. The underlying cause of GS is a polymorphism in the promotor region of the uridine diphosphate glucuronosyltransferase isoform 1A1 gene (UGT1A1*28), its encoded enzyme being responsible for the glucuronidation of bilirubin and presumably acetaminophen. Decreased enzyme activity results in elevated bilirubin levels and may activate various metabolic pathways leading to higher amounts of potentially hepatotoxic acetaminophen metabolites. Patients with GS might be more susceptible to unexpected side effects while taking acetaminophen and other drugs which are substrates of UGT1A1. The possibility of a correlation between glucuronidation capacity with respect to acetaminophen, UGT1A1 promotor polymorphism and the bilirubin serum level were investigated in 23 healthy male volunteers selected for UGT1A1 genotype (6 wildtypes, 9 mutants and 8 heterozygotes). One gram acetaminophen was administered p.o. and urine was collected over 2 4-hour periods. Unchanged acetaminophen and its glucuronide metabolite were determined using HPLC. The metabolic ratios unchanged acetaminophen/acetaminophen glucuronide in UGT1A1-wildtypes, heterozygotes and mutants showed no statistically significant differences. An association between metabolic ratio and serum bilirubin level could not be detected in any of the urine collection periods. These data confirm that there is no correlation between the capacity to glucuronidate acetaminophen, the UGT1A1 genotype and the bilirubin serum level. Acetaminophen is likely to be substrate of a UGT isoform other than the UGT1A1.

Predicting the risk of sporadic elevated bilirubin levels and diagnosing Gilbert's syndrome by genotyping UGT1A1*28 promoter polymorphism

Elevated fluctuating levels of bilirubin are a common problem in clinical studies. Differentiation between a drug-related adverse event and the diagnostic symptom for Gilbert's syndrome (GS), an idiopathic unconjugated hyperbilirubinemia, is more or less impracticable since the diagnosis of GS is by exclusion. The aim of this investigation was to evaluate the correlation of unspecific elevated bilirubin levels and the occurrence of GS with a described polymorphism in the uridine diphosphat glucuronosyltransferase 1A1 (UGT1A1) in a predominately Caucasian population. 304 volunteers (152 male, 152 female) were genotyped for the UGT1A1 promoter polymorphism by PCR amplification and polyacrylamide gel electrophoresis. Serum bilirubin levels and liver enzymes were determined and GS was diagnosed using clinico-chemical criteria. 23/13 subjects displayed the homocygote variant, 73/66 the heterozygote variant and 56/72 wildtype (male/female, respectively). 23 male and 3 female volunteers fulfilled the clinical criteria for GS (15.1, respectively 2.0%). Men exhibited higher serum bilirubin levels than women with a mean (SD) of 14.37 (8.92) micromol/l compared to 10.17 (5.37) micromol/l, respectively (p < 0.001). The homocygote mutant promoter length correlated well with serum bilirubin levels and with the clinical diagnosis of GS (p < 0.001 each). Genotyping of the UGT1A1 promoter polymorphism is a cheap and unequivocal method for predicting elevated and fluctuating bilirubin levels. It is better suited to this purpose than the clinical diagnosis which is based on exclusion. The genotyping of UGT1A1 promoter polymorphism can help to improve safety and the reliable assessment of adverse events in clinical studies. Our data additionally support the demand to refine the bilirubin reference values.

Clinical-pharmacological strategies to assess drug interaction potential during drug development

Drug interactions in patients receiving multiple drug regimens are a constant concern for the clinician. With the increased availability of new drugs and their concomitant use with other drugs, there has been a rise in the potential for adverse drug interactions as demonstrated by the recent withdrawals of newly marketed drugs because of unacceptable interaction profiles. Therefore, the interaction potential of a new compound has to be assessed in detail, starting with preclinical in vitro and in vivo studies at candidate selection and continuously followed up through preclinical and clinical development. Since formal in vivo studies of all possible drug interactions are neither practicable nor suggestive, a careful selection of a limited number of drug combinations to be investigated in vivo during the development phase is indicated. Based on knowledge of pharmacokinetic and biopharmaceutical properties, a well balanced link between in vitro investigations and carefully selected in vivo interaction studies allows full assessment of the potential of a new drug to cause clinically relevant pharmacokinetic drug-drug interactions, prediction of a lack of interactions and derivation of the proper dose recommendations. Clinical pharmacology plays a number of key roles within the process of collecting information on drug interactions during preclinical and clinical development: addressing issues and/or favourable properties to be expected, thus contributing to the scientific assessment of development potential; setting up a rational in vivo drug-drug interaction programme; performing early mechanistic studies to link in vitro with in vivo information (employing 'cocktail' approaches if possible); reviewing co-medication sections for clinical trials; and conducting labelling-oriented interaction studies, after proof of concept. The fact that interactions can occur between various active substances should by itself be a conclusive argument against unnecessary polypharmacy. Prescribing fewer drugs on a rational basis can reduce the risk of adverse effects secondary to drug interactions and may help to improve the quality of drug treatment and to save costs.

Microplate enzyme-linked immunosorbent assay for the detection of primary DNA alterations based on the interaction with UvrA/UvrB

An enzyme-linked microplate immunoassay for the analysis of primary DNA lesions is described. The assay principle is based on the interaction of the bacterial DNA repair proteins UvrA and UvrB with DNA and on the immunodetection of UvrB forming a stable complex with covalently modified nucleotides. Using this technique we were able to detect damages in genomic DNA induced by uv light and by several different genotoxic agents. The detection sensitivity of the method reaches down to the nanomolar range of the mutagenic compound depending on the type of the DNA alteration. The method might be used in automated high-throughput studies.

Structural basis for guanine nucleotide exchange on Ran by the regulator of chromosome condensation (RCC1)

RCC1 (regulator of chromosome condensation), a beta propeller chromatin-bound protein, is the guanine nucleotide exchange factor (GEF) for the nuclear GTP binding protein Ran. We report here the 1.8 A crystal structure of a Ran*RCC1 complex in the absence of nucleotide, an intermediate in the multistep GEF reaction. In contrast to previous structures, the phosphate binding region of the nucleotide binding site is perturbed only marginally, possibly due to the presence of a polyvalent anion in the P loop. Biochemical experiments show that a sulfate ion stabilizes the Ran*RCC1 complex and inhibits dissociation by guanine nucleotides. Based on the available structural and biochemical evidence, we present a unified scenario for the GEF mechanism where interaction of the P loop lysine with an acidic residue is a crucial element for the overall reaction.

Synthesis of functional Ras lipoproteins and fluorescent derivatives

For the study of biological signal transduction, access to correctly lipidated proteins is of utmost importance. Furthermore, access to bioconjugates that embody the correct structure of the protein but that may additionally carry different lipid groups or labels (i.e., fluorescent tags) by which the protein can be traced in biological systems, could provide invaluable reagents. We report here of the development of techniques for the synthesis of a series of modified Ras proteins. These modified Ras proteins carry a number of different, natural and non-natural lipid residues, and the process was extended to also provide access to a number of fluorescently labeled derivatives. The maleimide group provided the key to link chemically synthesized lipopeptide molecules in a specific and efficient manner to a truncated form of the H-Ras protein. Furthermore, a preliminary study on the biological activity of the natural Ras protein derivative (containing the normal farnesyl and palmitoyl lipid residues) has shown full biological activity. This result highlights the usefulness of these compounds as invaluable tools for the study of Ras signal transduction processes and the plasma membrane localization of the Ras proteins.

Linking the fields--the interplay of organic synthesis, biophysical chemistry, and cell biology in the chemical biology of protein lipidation

Research in the biological sciences has undergone a fundamental and dramatic change during the last decades. Whereas biology was more phenomenologically oriented for a long time, today many biological processes are investigated and understood in molecular detail. It has become evident that all biological phenomena have a chemical basis: Biology is based on chemical principles. In the past, this insight had led to the development of biochemistry, molecular biology, and modern pharmacology. Today it increasingly determines the manner in which various biological phenomena are studied. The tools provided by classical biological techniques often are not sufficient to address the prevailing issues in precise molecular detail. Instead, the strengths of both chemical and biological methodology have to be used. Several recent research projects have proven that combining the power of organic synthesis with cell biology may open up entirely new and alternative opportunities for the study of biological problems. In this review we summarize the successful interplay between three disciplines-organic synthesis, biophysics, and cell biology-in the study of protein lipidation and its relevance to targeting of proteins to the plasma membrane of cells in precise molecular detail. This interplay is highlighted by using the Ras protein as a representative example. The development of methods for the synthesis of Ras-derived peptides and fully functional Ras proteins, the determination of their biophysical properties, in particular the ability to bind to model membranes, and finally the use of synthetic Ras peptides and Ras proteins in cell biological experiments are addressed. The successful combination of these three disciplines has led to a better understanding of the factors governing the selective targeting of Ras and related lipid-modified proteins to the plasma membrane.

Different structural and kinetic requirements for the interaction of Ran with the Ran-binding domains from RanBP2 and importin-beta

The cytoplasmic disassembly of Ran.GTP.importin and Ran.GTP.exportin. cargo complexes is an essential step in the corresponding nuclear import and export cycles. It has previously been shown that such disassembly can be mediated by RanBP1 in the presence of RanGAP. The nuclear pore complex protein RanBP2 (Nup358) contains four Ran-binding domains (RanBDi) that might function like RanBP1. We used biophysical assays based on fluorescence-labeled probes and on surface plasmon resonance to investigate the dynamic interplay of Ran in its GDP- and GTP-complexed states with RanBDis and with importin-beta. We show that RanBP1 and the four RanBDis from RanBP2 have comparable affinities for Ran.GTP (10(8)-10(9) M(-1)). Deletion of Ran's C-terminal (211)DEDDDL(216) sequence weakens the interaction of Ran.GTP with RanBPis approximately 2000-fold, but accelerates the association of Ran.GTP with importin-beta 10-fold. Importin-beta binds Ran.GTP with a moderate rate, but attains a high affinity for Ran (K(D) = 140 pM) via an extremely low dissociation rate of 10(-5) s(-)(1). Association with Ran is accelerated 3-fold in the presence of RanBP1, which presumably prevents steric hindrance caused by the Ran C-terminus. In addition, we show that the RanBDis of RanBP2 are full equivalents of RanBP1 in that they also costimulate RanGAP-catalyzed GTP hydrolysis in Ran and relieve the GTPase block in a Ran.GTP.transportin complex. Our data suggest that the C-terminus of Ran functions like a loose tether in Ran.GTP complexes of importins or exportins that exit the nucleus. This flag is then recognized by the multiple RanBDis at or near the nuclear pore complex, allowing efficient disassembly of these Ran.GTP complexes.

The Adenomatous Polyposis Coli-protein (APC) interacts with the protein tyrosine phosphatase PTP-BL via an alternatively spliced PDZ domain

Mutations of the tumor suppressor protein APC (Adenomatous Polyposis Coli) are linked to familiar and sporadic human colon cancer. Here we describe a novel interaction between the APC protein and the protein tyrosine phosphatase PTP-BL carrying five PDZ protein-protein interaction domains. Exclusively, the second PDZ domain (PDZ2) of PTP-BL is binding to the extreme C-terminus of the APC protein, as determined by yeast two-hybrid studies. Using surface plasmon resonance analysis we established a dissociation constant (K(D)) of 8.1 x 10(-9) M. We find that a naturally occurring splice insertion of five amino acids (PDZ2b) abolishes its binding affinity to the APC protein. The in vivo interaction between PTP-BL and the APC protein was shown by coprecipitation experiments in transfected COS cells. Furthermore, in cultured epithelial Madine Carnine Kidney cells the subcellular colocalization was demonstrated for the nucleus and also for the tips of cellular extensions. The interaction of the APC protein with a protein tyrosine phosphatase may indirectly modulate the steady state levels of tyrosine phosphorylations of associated proteins, such as beta-catenin playing a major role in the regulation of cell division, migration and cell adhesion.

[Responsibilities of clinical pharmacology in the early phase of drug development]

The path of a new drug from the idea to the product may be divided into 2 phases, namely drug discovery and drug development. Due to the scientific progress new and simple methods could be developed to determine the biological efficacy of a large number of compounds. During the first part of drug development necessary requirements for the first use in man are met by performing preclinical pharmacological, toxicological and pharmacokinetic investigations in the animal and in in-vitro testing. After a first clinical-pharmacological profile of the new substance has been established during phase I on the basis of which a decision for the continuation of the clinical trial is made, the aim of phases II and III is now to answer the important questions of the therapeutic efficacy and tolerability in a large number of patients with the target indication. Due to the continuously increasing time and costs of drug development, drug development should be streamlined combining preclinical and early clinical phases as an exploratory stage and later clinical development as a confirmatory stage. The development and appropriate use of surrogates and models may be helpful to determine drug actions in human and to assist in dose selection as the main requirement for a successful large clinical trial in the confirmatory stage. Identifying the genes responsible for the huge variations in how different patients respond to a drug, in terms of both the product's effectiveness and its side effects, and genotyping patients before including in large clinical trials may prevent selecting the wrong patient population and avoid expensive repetition of these studies. Taking responsibility as the link between research and development gives clinical pharmacology a major opportunity to assume a pivotal role in drug development. To reach this goal, clinical pharmacology must be fully integrated in the whole process of drug development from the candidate selection until the approval.

Dissecting the interactions between NTF2, RanGDP, and the nucleoporin XFXFG repeats

We have used a range of complementary biochemical and biophysical methods to investigate the interactions between nuclear transport factor 2 (NTF2), the Ras family GTPase Ran, and XFXFG nucleoporin repeats that are crucial for nuclear trafficking. Microcalorimetry, microtiter plate binding, and fluorescence quenching in solution are all consistent with the binding constant for the NTF2-RanGDP interaction being in the 100 nM range, whereas the interaction between NTF2 and XFXFG repeat-containing nucleoporins such as Nsp1p is in the 1 microM range. Although the accumulation of NTF2 at the nuclear envelope is enhanced by RanGDP, we show that Ran binding does not alter the affinity of NTF2 for nucleoporins nor does the binding of nucleoporins alter the affinity of NTF2 for RanGDP. These results indicate that, instead, Ran increases the binding of NTF2 to nucleoporins by another mechanism, most probably by Ran itself binding to nucleoporins and NTF2 binding to this nuclear pore-associated Ran.

Bioorganic synthesis of lipid-modified proteins for the study of signal transduction

Biological membranes define the boundaries of the cellular compartments in higher eukaryotes and are active in many processes such as signal transduction and vesicular transport. Although post-translational lipid modification of numerous proteins in signal transduction is crucial for biological function, analysis of protein-protein interactions has mainly focused on recombinant proteins in solution under defined in vitro conditions. Here we present a new strategy for the synthesis of such lipid-modified proteins. It involves the bacterial expression of a carboxy-terminally truncated non-lipidated protein, the chemical synthesis of differently lipidated peptides representing the C terminus of the proteins, and their covalent coupling. Our technique is demonstrated using Ras constructs, which exhibit properties very similar to fully processed Ras, but can be produced in high yields and are open for selective modifications. These constructs are operative in biophysical and cellular assay systems, showing specific recognition of effectors by Ras lipoproteins inserted into the membrane surface of biosensors and transforming activity of oncogenic variants after microinjection into cultured cells.

Guidances related to bioavailability and bioequivalence: European industry perspective

The investigations of bioavailability and bioequivalence can be classified according to three separate areas of information. Firstly, estimation of bioavailability judged on a drug substance's in vivo characteristics taking into account solubility, polymorphism, stability (especially under the conditions of the GI tract), gut wall permeability and first pass metabolism. Secondly, evaluation of formulation properties including dissolution profile in the GI tract and its contribution to exposure variability with respect to the desired absorption characteristics. Finally, maintaining quality during the market phase with respect to equivalence to the clinical trial formulations. While in the first two areas, the range of the estimated mean values and the intra- and inter-subject variabilities contain the desired information for proper medical decisions, in the third area the mean values and their confidence limits describe the quality with regard to the formulations of proven efficacy. Guidelines should clearly distinguish between the different areas in their recommendations regarding the intended information, e.g. mean values and/or ranges and confidence intervals. New approaches of granting limited waivers for BE studies (e.g. Biopharmaceutical Classification System (BCS)) should be expanded to consideration of pharmacokinetic properties of drugs (e.g. gastrointestinal metabolism, evidence for an absorption window, magnitude of first-pass effect, half-life) as already partly implemented in the German waiver concept, and further (scientifically) validated to achieve world-wide harmonisation (e.g. via ICH).

Alternative strategies in drug development: clinical pharmacological aspects

Due to the continuous increase in time and cost of drug development and the considerable amount of resources required by the traditional approach, companies can no longer afford to continue to late phase 3 with drugs which are unlikely to be therapeutically effective. The future challenge must be for the pharmaceutical industry to slash its research and development costs by achieving a significant cut in the attrition rate for drugs entering preclinical and clinical development, and to reduce the development time and to increase the probability of success in later clinical trials by streamlining the development processes. In the 100 years to 1995, the pharmaceutical industry worked on about 500 targets with a limited number of compounds, whereas now, using new technologies like genomics, high throughput screening and combinatorial chemistry, drug companies will see an explosion in the number of targets and leads it can explore. Therefore, a tough selection process for picking candidate compounds out of research and a quick kill process for the candidate, which does not measure up in advanced trials, is mandatory to avoid wasting time, energy and money. To improve the transition from research to development it is necessary to validate new targets, define success criteria for research, integrate bioinformation at every stage in drug discovery, define prerequisites for development, identify the "losers" and select the "winners" early and concentrate efforts on them, and to automate the research and development (R&D) process to optimize resource requirements versus time lines and to ensure effective flow of information from drug discovery to late phase of development. In drug development a deeper understanding of a drugs' action is necessary from animal models and phase I, IIa studies prior to taking the drug further in development. Instead of moving from discovery thorough development phases in sequential steps, drug development should be streamlined combining preclinical and early clinical development as an exploratory stage and phases IIb, III as a confirmatory stage. Preclinical and clinical-pharmacological studies in the exploratory stage of drug development should be designed for decision making in contrast to later clinical trials that require power for proof-of-safety and efficacy. Strategies to improve the quality of decisions in drug development are: the use and integration of new tools and technologies such as pharmacogenomics to improve our knowledge about the origin of the disease and to identify new therapeutic strategies; modelling and simulation of preclinical and clinical trials to bridge the gap between the early stages of the development of a new drug and its potential effects in humans; more sophisticated clinical pharmacokinetics to answer the question if the drug is present at the disease site for a sufficient time and to provide information on concentration-effect-relationships; selecting and evaluating surrogates/biomarkers for safety and efficacy; involvement of the target population as soon as possible; using information technologies to make better use of existing data. The more thorough and profound studies have been carried out during this exploratory stage of development, the earlier a decision can be made on the continuation or discontinuation of further development, thus saving development time and money and assessing and considerably reducing the risk for the patients and increasing the success-rate of the project in the later confirmatory effectiveness trial. Taking responsibility as the link between research and development gives clinical pharmacology a major opportunity to assume a pivotal role in research and development of new drugs. To reach this goal, clinical pharmacology must be fully integrated in the whole process from the candidate selection to its approval.

The influence of valerian treatment on "reaction time, alertness and concentration" in volunteers

A randomised, controlled, double-blind trial was performed on 102 male and female volunteers to determine whether reaction time, alertness and concentration might be impaired by treatment with a native valerian root extract (VRE). The effect was first examined the morning after a single evening dose of VRE (600 mg LI 156) vs. flunitrazepam (FNZ) (1 mg) and placebo (PL) (trial section A), and then after two weeks of evening administration of VRE (600 mg LI 156) vs. PL (trial section B). 99 volunteers were analysed in section A and 91 in section B. The primary criterion was the median of reaction time (MRT) measured with the Vienna Determination Test. Secondary criteria were cognitrones (alertness test), tracking test (two-handed co-ordination), sleep quality (VIS-A, Vis-M), further VDT parameters, and safety criteria. The single administration of LI 156 did not impair the reaction abilities, concentration and co-ordination. After 14 days of treatment, the equivalence of VRE and PL was proven by confirmative analysis concerning the improvement of MRT (p = 0.4481). Evaluation of the secondary criteria were consistent with the results of the primary criterion. It is concluded that neither single nor repeated evening administrations of 600 mg of VRE have a relevant negative impact on reaction time, alertness and concentration the morning after intake.

Conformational states of the nuclear GTP-binding protein Ran and its complexes with the exchange factor RCC1 and the effector protein RanBP1

It has been shown before by (31)P NMR that Ras bound to the nonhydrolyzable GTP analogue guanosine 5'-O-(beta, gamma-imidotriphosphate) (GppNHp) exists in two conformations which are rapidly interconverting with a rate constant of 3200 s-1 at 30 degrees C [Geyer, M., et al. (1996) Biochemistry 35, 10308-10320]. Here we show that Ran complexed with GTP also exists in two conformational states, 1 and 2, which can be directly inferred from the occurrence of two (31)P NMR resonance lines for the gamma-phosphate group of bound GTP. The exchange between the two states is slow on the NMR time scale with a value of <200 s-1 at 5 degrees C for the corresponding first-order rate constants. In wild-type Ran, the equilibrium constant K' between the two states is 0.7 at 278 K, is different for various mutants, and is strongly dependent on the temperature. The standard enthalpy DeltaH degrees and the standard entropy DeltaS degrees for the conformational transitions determined from the NMR spectra are as follows: DeltaH degrees = 37 kJ mol-1 and DeltaS degrees = 130 J mol-1 K-1 for wild-type Ran.GTP. In complex with the Ran-binding protein RanBP1, one of the Ran.GTP conformations (state 2) is stabilized. The interaction of Ran with the guanine nucleotide exchange factor protein RCC1 was also studied by (31)P NMR spectroscopy. In the presence of nucleotide, the ternary complex of Ran.nucleotide.RCC1, an intermediate in the guanine nucleotide exchange reaction, could be observed. A model for the conformational transition of Ran.GTP is proposed where the two states observed are caused by the structural flexibility of the effector loop of Ran; in solution, state 2 resembles the GTP-bound form found in the crystal structure of the Ran-RanBP complex.

[Responsibilities of clinical pharmacology in the early phase of drug development]

The path of a new drug from the idea to the product may be divided into 2 phases, namely drug discovery and drug development. Due to the scientific progress new and simple methods could be developed to determine the biological efficacy of a large number of compounds. During the first part of drug development necessary requirements for the first use in man are met by performing preclinical pharmacological, toxicological and pharmacokinetic investigations in the animal and in in-vitro testing. After a first clinical-pharmacological profile of the new substance has been established during phase I on the basis of which a decision for the continuation of the clinical trial is made, the aim of phases II and III is now to answer the important questions of the therapeutic efficacy and tolerability in a large number of patients with the target indication. Due to the continuously increasing time and costs of drug development, drug development should be streamlined combining preclinical and early clinical phases as an exploratory stage and later clinical development as a confirmatory stage. The development and appropriate use of surrogates and models may be helpful to determine drug actions in human and to assist in dose selection as the main requirement for a successful large clinical trial in the confirmatory stage. Identifying the genes responsible for the huge variations in how different patients respond to a drug, in terms of both the product's effectiveness and its side effects, and genotyping patients before including in large clinical trials may prevent selecting the wrong patient population and avoid expensive repetition of these studies. Taking responsibility as the link between research and development gives clinical pharmacology a major opportunity to assume a pivotal role in drug development. To reach this goal, clinical pharmacology must be fully integrated in the whole process of drug development from the candidate selection until the approval.

Structure of a Ran-binding domain complexed with Ran bound to a GTP analogue: implications for nuclear transport

The protein Ran is a small GTP-binding protein that binds to two types of effector inside the cell: Ran-binding proteins, which have a role in terminating export processes from the nucleus to the cytoplasm, and importin-beta-like molecules that bind cargo proteins during nuclear transport. The Ran-binding domain is a conserved sequence motif found in several proteins that participate in these transport processes. The Ran-binding protein RanBP2 contains four of these domains and constitutes a large part of the cytoplasmic fibrils that extend from the nuclear-pore complex. The structure of Ran bound to a non-hydrolysable GTP analogue (Ran x GppNHp) in complex with the first Ran-binding domain (RanBD1) of human RanBP2 reveals not only that RanBD1 has a pleckstrin-homology domain fold, but also that the switch-I region of Ran x GppNHp resembles the canonical Ras GppNHp structure and that the carboxy terminus of Ran is wrapped around RanBD1, contacting a basic patch on RanBD1 through its acidic end. This molecular 'embrace' enables RanBDs to sequester the Ran carboxy terminus, triggering the dissociation of Ran x GTP from importin-beta-related transport factors and facilitating GTP hydrolysis by the GTPase-activating protein ranGAP. Such a mechanism represents a new type of switch mechanism and regulatory protein-protein interaction for a Ras-related protein.

Increase in cerivastatin systemic exposure after single and multiple dosing in cyclosporine-treated kidney transplant recipients

OBJECTIVE

The mutual drug-drug interaction potential of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor cerivastatin and cyclosporine (INN, ciclosporin) in kidney transplant recipients receiving individual immunosuppressive treatment was evaluated with respect to pharmacokinetic behavior of either drug and tolerability of concomitant use.

METHODS

Plasma and urine concentrations of cerivastatin and its major metabolites were determined after administration of 0.2 mg single-dose cerivastatin to 12 kidney transplant recipients (9 men and 3 women) who were receiving stable individual cyclosporine treatment (mainly 200 mg twice a day). These results were compared with the single-dose pharmacokinetic results obtained from a healthy control group (n = 12, age-comparable men). Cerivastatin steady-state pharmacokinetics were evaluated in the same patients during continued immunosuppressive treatment 4 to 6 weeks later, after a 7-day treatment of 0.2 mg cerivastatin once a day. Cyclosporine steady-state concentration-time profiles were determined in blood with monoclonal (EMIT [enzyme multiplied immunoassay technique] assay, parent drug specific) and polyclonal antibodies (FPIA [fluorescence polarization immunoassay] assay, cyclosporine plus metabolites) during cerivastatin cotreatment and compared with predosing data.

RESULTS

Coadministration of 0.2 mg cerivastatin once a day to the kidney transplant recipients treated with individual doses of cyclosporine and other immunosuppressive agents resulted in a 3- to 5-fold increase in cerivastatin and metabolites plasma concentrations. Cerivastatin and metabolites elimination half-lives were unaffected, and no accumulation occurred during multiple-dosing conditions. Cerivastatin had no influence on steady-state blood concentrations of cyclosporine or cyclosporine metabolites in these patients. The concomitant use of both drugs was well tolerated.

CONCLUSIONS

Cerivastatin and metabolites plasma concentrations were significantly increased in kidney transplant recipients treated with cyclosporine and other immunosuppressive agents. Displacement from the main site for cerivastatin distribution-the liver-by cyclosporine-inhibited liver transport processes may explain the decrease in both metabolic clearance and volume of distribution for cerivastatin and metabolites.

Pharmacokinetics of cerivastatin in renal impairment are predicted by low serum albumin concentration rather than by low creatinine clearance

The influence of renal impairment on the clearance of the new HMG-CoA reductase inhibitor cerivastatin was evaluated. A single oral dose of 300 microg cerivastatin was given to 18 patients with different degrees of renal impairment and 6 healthy controls. Concentrations of total cerivastatin, its fraction unbound, and the total concentrations of the active metabolites M1 and M23 were measured in plasma. Serum concentrations of unbound cerivastatin were calculated for each individual from the concentration of total cerivastatin and cerivastatin's fraction unbound at t = 2.5 hours. In contradiction to what had been expected, renal impairment significantly influenced the pharmacokinetics of cerivastatin. The best correlation to the AUC and Cmax of unbound cerivastatin was found with serum albumin concentration. Also, serum albumin concentration was the only factor significantly correlated to t 1/2 of cerivastatin. Significant but slighter correlation with the AUC and Cmax of unbound cerivastatin was also observed for creatinine clearance and cerivastatin's fraction unbound, while no correlation was observed with total plasma protein. No significant correlation of creatinine clearance, serum albumin concentration, fu, or total plasma protein concentration with the AUC and Cmax of total cerivastatin or the AUC, Cmax or t 1/2 of M1 and M23 was observed. The authors conclude that low serum albumin concentration rather than low creatinine clearance predicts the pharmacokinetics of cerivastatin in renal impairment.