Decision-making factors for the long-term topical treatment of mild-to-moderate plaque psoriasis: TEPPSO, a case-vignette study on clinical practice

OBJECTIVES

Topical maintenance therapy strategy with regard to patients with mild-to-moderate plaque psoriasis (PP) continues to be heterogeneous and insufficiently investigated in real-life clinical practice. The objective of this study was to describe the initiation of long-term maintenance treatment and to identify clinical parameters influencing the therapeutic decision.

METHODS

TEPPSO was a French and Belgian multicentre cross-sectional study based on completion of questionnaires and assessment of credible clinical scenarios of mild-to-moderate PP by physicians using the validated case-vignette method.

RESULTS

Maintenance therapy was recommended by dermatologists (Ds) and by general practitioners (GPs) in 79.1% and 76.8% of cases, respectively. GPs recommended the use of a fixed-dose combination of corticosteroid and vitamin D analogues in only 14.8% of cases, whereas this therapy was recommended by French and Belgian Ds in 54.8% and 39.8% of cases, respectively. In a multivariate analysis, significant determinants of the therapeutic decision were skin lesions impacting quality of life (OR 1.9 [95% CI: 1.1; 3.2] P=0.01) for Ds, and patient corticophobia (OR 1.7 [95% CI: 1.1; 2.7] P=0.03) or the presence of skin pruritus (OR 1.8 [95% CI: 1.2; 1.8] P=0.004) for GPs, respectively.

CONCLUSIONS

Maintenance treatment with topical agents in patients with mild-to-moderate PP was considered in more than two thirds of cases. Heterogeneity in the choice of topical agents was evidenced particularly between Ds and GPs. Our study is the first to identify significant clinical determinants affecting the therapeutic decision. Updated and validated clinical practice guidelines are needed to ensure uniform therapeutic choices.

POS1405 LESS THAN 50% FEMALES WITH CHRONIC RHEUMATIC INFLAMMATORY DISEASES CONTINUE A DMARD DURING PREGNANCY: A DESCRIPTIVE ANALYSIS OF THE NATIONAL FRENCH SOCIAL SECURITY DATABASE

Background

Treatment of patients with chronic rheumatic inflammatory diseases (CRID) during pregnancy has changed in the last decade, namely due to the availability of new DMARDs labelled to be used during pregnancy.

Objectives

To describe the anti-rheumatic drug use during pregnancy in women with CRID (i.e. rheumatoid arthritis (RA) or spondyloarthritis (SpA)) in France over the past decade.

Methods

This is a retrospective cohort study within the French Healthcare database (SNDS), which covers 98% of the French population. Adult women were included if they had RA or SpA according to CIM-10 codes, had started a singleton pregnancy between 2008 and 2017 (index date), and were continuously covered by this health insurance from 1-year before pregnancy onset to 1-year after end of the pregnancy or death (whichever comes first). The treatment exposures of interest were: NSAIDs, oral corticosteroids, csDMARD (methotrexate, leflunomide, sulfasalazine, azathioprine, hydroxychloroquine), biologics (anti-TNF, rituximab, abatacept, tocilizumab, ustekinumab, anakinra). Exposure during pregnancy was defined as at least one drug reimbursement from the 6 months before the last menstrual period (LMP) to the end of pregnancy period.

Results

Among the 35,737 adult women with a CIRD (40.7% with RA and 59.3% with SpA) who had a past history of DMARD reimbursement, 11,274 (41.7%) started a singleton pregnancy during the study period. In total, during preconception and pregnancy, 4,773 (42.3%) women were not delivered any DMARD nor corticosteroids, 769 (6.8%) were delivered corticosteroids alone, 3,639 (32.2%) a csDMARD alone and 2,862 (25.4%) a biologic (among whom 33.1% associated a csDMARD). Biologics delivered during pregnancy were mainly anti-TNFs (92.1%).

Exposure to NSAIDs was more frequent during the first trimester (30% patients) of pregnancy but occurred all along the pregnancy (6% and 2% in the second and third trimesters, respectively). Conversely, exposure to oral corticosteroids was stable during the pregnancy (33% to 27%); however, more than half of the prescriptions corresponded to doses higher than 10mg. Exposure to DMARDs including bDMARDs during pregnancy was more frequent during the first trimester, compared to the rest of the pregnancy (see graph).

Conclusion

Overall, less than 50% of women with a CRID who received a DMARD prior to the pregnancy continued to retrieve such treatment during pregnancy, and overall less than 20% were delivered biologics during pregnancy. Whether the withdrawal of DMARDs led to unfavorable maternal and pregnancy outcomes needs to be evaluated.

Acknowledgements

This study was conducted thanks to a grant from the French Ministry of Health - Programme Hospitalier de Recherche Clinique

Disclosure of Interests

Anna Moltó Consultant of: UCB, Abbvie, Lilly, Pfizer, BMS, MSD, Novartis, Biogen, Janssen, Grant/research support from: UCB, Aya Ajrouche: None declared, Diep Tran: None declared, Barbara Roux: None declared, Nathalie Costedoat-Chalumeau Grant/research support from: UCB, Elisabeth Elefant: None declared, Vassilis Tsatsaris: None declared, Jeanne Fresson: None declared, Brigitte Bader-Meunier: None declared, Bruno Fautrel: None declared, Florence Tubach: None declared

AB1391 19% PATIENTS WITH CHRONIC RHEUMATIC INFLAMMATORY DISEASES PRESENT AN UNFAVORABLE PREGNANCY OUTCOME: A DESCRIPTIVE ANALYSIS OF THE NATIONAL FRENCH SOCIAL SECURITY DATABASE

Background

patients with chronic rheumatic inflammatory diseases (CRID, i.e. rheumatoid arthritis (RA) or spondyloarthritis (SpA)) have been reported to have poorer pregnancy outcomes than the general population.

Objectives

to describe the pregnancy outcomes of singleton in patients with CRID in France in the past decade.

Methods

this is an analysis of the French Health Insurance claims database (SNDS), which represents 87% of the French population) from 2008 to 2016. To be included in the analysis patients had to be identified as RA or SpA according to existing diagnostic algorithms, to have at least one pregnancy declaration in the database, and to have continuous health insurance from 1-year before pregnancy onset to 1-year after end of the pregnancy or until death (if death occured before the 1-year-period after the end of pregnancy) to be included. Only the first singleton pregnancy occurring during the study period was included in this analysis. Both maternal and pregnancy outcomes were considered. Outcomes were identified either by ICM-10 codes or hospital discharge summaries discharge between 2008-2016.

Results

Among the 35 737 identified adult females with a CRID diagnosis (40.7% with RA and 59.3% with SpA), 27 722 (78%) had a pregnancy during the study period. 11 274 (42%) had received at least one DMARD prior to the pregnancy and were included in the analysis. Among them, only 4025 (36%) were exposed to DMARDs during pregnancy.

Mean (SD) age of females at the start of the pregnancy was 32 (5) years, and mean (SD) disease duration was 4 (4) years. Pregnancy ended before 13 WG in 21% and after 37 WG in 70% cases. Live-birth represented the most frequent pregnancy outcome (76.9%), and overall 34.7% patients presented at least one unfavorable outcome (see Table 1).

Table 1.Unfavourable outcomeN(%)Pregnancy outcomesMiscarriage (<22WG)579 (5.3%)Abortion91 (0.8%)Stillbirth48 (0.4%)Preterm delivery (>= 22WG and <37 WG)779 (7.1%)Low weight at birth (<3th percentile)287 (2.6%)Perinatal mortality (22WG to 6 days of life)2 (0%)Maternal outcomesSevere maternal infection*211 (1.9%)Newborn outcomesHospitalisation in neonatal intensive care > 48h in full-term newborns (after 37 WG)95 (0.8%)Neonatal mortality (27 first days of life)2 (0%)Severe infection * during first year603 (5.3%)

Conclusion

More than 75% pregnancies in patients with CRID resulted in a live-birth. Prevalence of miscarriage was surprisingly low, probably related to under-coding. Maternal and infant outcomes seemed comparable to general population. Whether medications had an impact on such outcomes is currently under evaluation.

Disclosure of Interests

None declared

Computational methods and theory for ion channel research

Ion channels are fundamental biological devices that act as gates in order to ensure selective ion transport across cellular membranes; their operation constitutes the molecular mechanism through which basic biological functions, such as nerve signal transmission and muscle contraction, are carried out. Here, we review recent results in the field of computational research on ion channels, covering theoretical advances, state-of-the-art simulation approaches, and frontline modeling techniques. We also report on few selected applications of continuum and atomistic methods to characterize the mechanisms of permeation, selectivity, and gating in biological and model channels.

Non-alcoholic fatty liver disease in a sample of individuals with bipolar disorders: results from the FACE-BD cohort

OBJECTIVE

Non-Alcoholic fatty liver disease (NAFLD) is becoming the most common liver disease in Western populations. While obesity and metabolic abnormalities are highly frequent in bipolar disorders (BD), no studies have been performed to estimate the prevalence of NALFD in individuals with BD. The aim of our study is to estimate the prevalence of NAFLD and to identify the potential associated risk factors in a large sample of BD individuals.

METHODS

Between 2009 and 2019, 1969 BD individuals from the FACE-BD cohort were included. Individuals with liver diseases, Hepatitis B or C, and current alcohol use disorders were excluded from the analyses. A blood sample was drawn from participants. Screening of NAFLD was determined using fatty liver index (FLI). Individuals with FLI> 60 were considered as having NAFLD.

RESULTS

The prevalence of NAFDL in this sample was estimated at 28.4%. NAFLD was observed in 40% of men and 21% of women. NAFLD was independently associated with older age, male gender, sleep disturbances, and current use of atypical antipsychotics or anxiolytics. As expected, the prevalence of NALFD was also higher in individuals with overweight and in those with metabolic syndrome.

CONCLUSIONS

This study reinforces the view that individuals with BD are highly vulnerable to metabolic and cardiovascular diseases. The prevalence of NAFLD in individuals with BD was two times higher than the prevalence reported in the general population. The regular screening of the MetS in individuals with BD should be therefore complemented by the additional screening of NAFLD among these vulnerable individuals.

FRI0091 A STUDY OF THERAPEUTIC PREFERENCES IN RHEUMATOID ARTHRITIS AFTER FAILURE OF A FIRST-LINE STRATEGY INCLUDING METHOTREXATE, USING THE DISCRETE CHOICE EXPERIMENTS METHODOLOGY

Background:

Therapeutic decisions in patients with rheumatoid arthritis (RA) who have an inadequate response to methotrexate (MTX-IR) are complex. European guidelines position at the same level all biological disease-modifying anti-rheumatic drugs (bDMARDs) and targeted synthetic DMARDs (tsDMARDs) for the treatment of RA(1,2). Furthermore, therapeutic decisions, or physician preferences, may be influenced by many factors related to patients and/or physicians.

Objectives:

To describe the therapeutic preferences of physicians involved in the management of RA after failure of a first-line strategy (including MTX) and the influence of predefined factors on these preferences.

Methods:

We planned to include 216 rheumatologists experienced in the management of RA in this cross-sectional multicenter study. A total of 64 hypothetical clinical cases (vignettes) were developed from a random combination of the following parameters: presence or absence of poor prognostic factors 1) RA-related autoantibodies, 2) structural damage progression on X-ray, 3) high or moderate disease activity, and presence or absence of a history of 4) infection, 5) pulmonary involvement, and 6) cardiovascular disease. Each participant was asked to complete 8 vignettes and were asked to choose the most and least appropriate therapeutic option (best-worst [BW] scaling method) from 3 of the following: replacing MTX by another conventional (c)sDMARD; adding one or more csDMARDs to MTX; adding a bDMARD (TNF inhibitor [TNFi], tocilizumab [TCZ], abatacept [ABA] or rituximab [RTX]). Each vignette was completed 10 times per participant. Physician preferences were assessed using discrete choice experiments methodology. Therapeutic option preference was expressed using a score – one point incremented when considered most appropriate; or removed when considered least appropriate. The therapeutic score was standardized for each vignette, ranging from -1 (more often chosen as the least appropriate) to +1 (more often chosen as the most appropriate). A normalized Best-to-Worst (BW) Score was then computed. The multiplication of vignettes and therapeutic options were used to elicit participants’ preferences without directly asking them to state their preferred options(3,4,5). Statistical analyses were carried out using SAS (version 9.4), or R (version 3.5.1).

Results:

A total of 211 French rheumatologists were recruited. Half of them had a hospital-only activity, 25% office-only activity and the rest had mixed activity. Each vignette was assessed by between 20 and 28 rheumatologists with a 94% completion rate. TNF inhibitors were the strategy of choice in 80% of the vignettes. ABA was the second preferred strategy in 75% of the vignettes; except in the 20% of patients with a history of infection and pulmonary comorbidity where it was the first choice. TCZ was chosen as a third strategy. All other strategies were associated with a negative BW score. Factors related to the prescribing physician appear to have no or only a limited impact on therapeutic decisions.

Conclusion:

This study provides information on the prescription habits of French rheumatologists in MTX-IR patients in RA, and reveals a conservative trend with TNFi the main therapeutic choice and ABA for patients with pulmonary involvement or high risk of infection. The study should be repeated in the future to include new therapeutic options.

References:

[1]Smolen J et al., EULAR 2019

[2]Daien C et al., Joint Bone Spine 2019

[3]Peabody JW et al., JAMA 2000

[4]Fautrel et al., Arthritis Rheum 2009

[5]Mühlbacher et al. Health Economics Review 2016

Disclosure of Interests:

Eric Senbel Consultant of: Nordic, Roche-Chugai, Lilly, Abbvie, Amgen, Pfizer, Sanofi, MSD, Biogen, UCB, frederick durand Shareholder of: Eli Lilly, Employee of: Lilly France, Baptiste Roux Grant/research support from: FAST4 company has received funding for research from Lilly, Pfizer, BMS, Vifor Pharma, Amgen, Novartis, Leo Pharma, Sanofi, Baxter, Abbvie, Astrazeneca, Novonordisk and Hac Pharma., Fatima Zohra Badaoui Employee of: Lilly France, Bruno Fautrel Grant/research support from: AbbVie, Lilly, MSD, Pfizer, Consultant of: AbbVie, Biogen, BMS, Boehringer Ingelheim, Celgene, Lilly, Janssen, Medac MSD France, Nordic Pharma, Novartis, Pfizer, Roche, Sanofi Aventis, SOBI and UCB

Management of oral bisphosphonates treatment by rheumatologists and determinants of therapeutic changes: a case-vignette-based study

Using case vignette methodology, this study shows that only 4% of patients are maintained on oral bisphosphonates over 5 years, and prescribers switch or stop the treatment in 20-30% of cases at each visit. There are few determinants of these changes. More information on appropriate follow-up could help in patients' management.

INTRODUCTION

Persistence to oral bisphosphonates, the most commonly prescribed anti-osteoporotic treatments, is low. The aim of this study was to evaluate the role of rheumatologists on the treatment patterns, and to assess the determinants of treatment changes.

METHODS

We used the methodology of case vignettes with the participation of 142 rheumatologists. Three baseline clinical vignettes were presented: (1) the physician was asked to indicate the most appropriate period to schedule the next visit over 5 years, (2) the physician was tested about parameters for follow-up (including traps), and (3) various results (both clinical, biological, densitometric, and radiological) were given by random and analyzed as determinants of treatment changes.

RESULTS

The study allowed assessment of 426 virtual clinical cases. Clinical examinations, patient's height, inquiries about falls, and adherence to treatment were deemed necessary in > 90% of cases. Bone mineral density was measured in 22, 40, and 71% of cases at 2, 3, and 5 years, respectively. Dental follow-up was recommended in less than 25% of cases. Only 4.2% of patients were maintained on the same treatment at 5 years, and a change of treatment (stop or switch) occurs in 20-30% of cases at each visit. Significant determinants were adherence to treatment, serum C-terminal crosslinking telopeptide of type 1 collagen (CTX) value, change in patient's height, and the occurrence of an incident vertebral fracture.

CONCLUSION

Our study shows that maintenance of oral bisphosphonate in postmenopausal women managed by rheumatologists is low; there are few determinants of these changes and more information on appropriate follow-up could help in patients' management.

Abstract 3641: Identification of naphthyridines as potent inhibitors of fibroblast growth factor receptor kinase family

The fibroblast growth factor receptor (FGFR) tyrosine kinase family members, FGFR1, 2, 3 and 4, have roles in a variety of key cellular processes, including proliferation, migration, survival, and differentiation1. Aberrant activation of FGFRs through mutation, amplification, chromosomal translocation, and ligand up-regulation being strongly implicated in oncogenic signalling in many tumour types, has triggered efforts to identify selective FGFR inhibitors. As a result, several potent FGFR kinase inhibitors are currently being evaluated in clinical studies across many tumor types, including non-small cell lung, breast and bladder cancers.

We have designed novel 1,5 and 1,7-naphthyridine derivatives that are potent kinase inhibitors of all FGFR family members in enzymatic and cellular systems. Initial hits were further optimized to increase potency and ADME properties leading to identification of a novel 1,5-naphthyridine-based chemical series with nanomolar affinity for FGFR1, 2, 3, and 4, activity in cells, and selectivity with respect to VEGFR-2. In vivo screening using an FGFR3-driven xenograft model revealed efficacious compounds that could be explored further as antitumoral agents.

This report represents the first disclosure of the structure-activity relationship and synthesis pathway of novel naphthyridine chemical series displaying nanomolar affinity for FGFRs1, 2, 3 and 4.

1 Dieci M. V., Ardenos M., Andre F., Soria J.C. Cancer Discovery. 2013, 3(3) 264-279.

Citation Format: Patrick R. Angibaud, Michel Obringer, Julien Marin, Matthieu Jeanty, Norbert Esser, Ron Gilissen, Peter King, Lieven Meerpoel, Olivier Querolle, David C. Rees, Bruno Roux, Gordon Saxty, Tinne Verhulst, Berthold Wroblowski, Christopher C. Murray, Jorge Vialard. Identification of naphthyridines as potent inhibitors of fibroblast growth factor receptor kinase family. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3641. doi:10.1158/1538-7445.AM2015-3641

All-atom empirical potential for molecular modeling and dynamics studies of proteins

New protein parameters are reported for the all-atom empirical energy function in the CHARMM program. The parameter evaluation was based on a self-consistent approach designed to achieve a balance between the internal (bonding) and interaction (nonbonding) terms of the force field and among the solvent-solvent, solvent-solute, and solute-solute interactions. Optimization of the internal parameters used experimental gas-phase geometries, vibrational spectra, and torsional energy surfaces supplemented with ab initio results. The peptide backbone bonding parameters were optimized with respect to data for N-methylacetamide and the alanine dipeptide. The interaction parameters, particularly the atomic charges, were determined by fitting ab initio interaction energies and geometries of complexes between water and model compounds that represented the backbone and the various side chains. In addition, dipole moments, experimental heats and free energies of vaporization, solvation and sublimation, molecular volumes, and crystal pressures and structures were used in the optimization. The resulting protein parameters were tested by applying them to noncyclic tripeptide crystals, cyclic peptide crystals, and the proteins crambin, bovine pancreatic trypsin inhibitor, and carbonmonoxy myoglobin in vacuo and in crystals. A detailed analysis of the relationship between the alanine dipeptide potential energy surface and calculated protein φ, χ angles was made and used in optimizing the peptide group torsional parameters. The results demonstrate that use of ab initio structural and energetic data by themselves are not sufficient to obtain an adequate backbone representation for peptides and proteins in solution and in crystals. Extensive comparisons between molecular dynamics simulations and experimental data for polypeptides and proteins were performed for both structural and dynamic properties. Energy minimization and dynamics simulations for crystals demonstrate that the latter are needed to obtain meaningful comparisons with experimental crystal structures. The presented parameters, in combination with the previously published CHARMM all-atom parameters for nucleic acids and lipids, provide a consistent set for condensed-phase simulations of a wide variety of molecules of biological interest.

[Successful use of recombinant factor VIIa in the control of a massive bleeding in two patients with biventricular assist device (Thoratec)]

Massive bleeding is a dreaded complication of biventricular mechanical assistance implantation. Its origin is multifactorial. Blood products transfusion associated with correction of coagulopathy are sometimes insufficient. We report two cases of massive bleeding after a Thoratec biventricular assistance implantation. After surgical haemostasis failure and despite the correction of coagulation disorders, a major bleeding persisted, so these patients received a single injection of 90 microg/kg of rFVIIa. This allowed in both cases a significant reduction of the bleeding and the restoration of normal haemodynamic conditions. This treatment was not complicated by any thrombotic accident.

CHARMM: the biomolecular simulation program

CHARMM (Chemistry at HARvard Molecular Mechanics) is a highly versatile and widely used molecular simulation program. It has been developed over the last three decades with a primary focus on molecules of biological interest, including proteins, peptides, lipids, nucleic acids, carbohydrates, and small molecule ligands, as they occur in solution, crystals, and membrane environments. For the study of such systems, the program provides a large suite of computational tools that include numerous conformational and path sampling methods, free energy estimators, molecular minimization, dynamics, and analysis techniques, and model-building capabilities. The CHARMM program is applicable to problems involving a much broader class of many-particle systems. Calculations with CHARMM can be performed using a number of different energy functions and models, from mixed quantum mechanical-molecular mechanical force fields, to all-atom classical potential energy functions with explicit solvent and various boundary conditions, to implicit solvent and membrane models. The program has been ported to numerous platforms in both serial and parallel architectures. This article provides an overview of the program as it exists today with an emphasis on developments since the publication of the original CHARMM article in 1983.

Can Commercial Digital Cameras Be Used as Multispectral Sensors? A Crop Monitoring Test

The use of consumer digital cameras or webcams to characterize and monitor different features has become prevalent in various domains, especially in environmental applications. Despite some promising results, such digital camera systems generally suffer from signal aberrations due to the on-board image processing systems and thus offer limited quantitative data acquisition capability. The objective of this study was to test a series of radiometric corrections having the potential to reduce radiometric distortions linked to camera optics and environmental conditions, and to quantify the effects of these corrections on our ability to monitor crop variables. In 2007, we conducted a five-month experiment on sugarcane trial plots using original RGB and modified RGB (Red-Edge and NIR) cameras fitted onto a light aircraft. The camera settings were kept unchanged throughout the acquisition period and the images were recorded in JPEG and RAW formats. These images were corrected to eliminate the vignetting effect, and normalized between acquisition dates. Our results suggest that 1) the use of unprocessed image data did not improve the results of image analyses; 2) vignetting had a significant effect, especially for the modified camera, and 3) normalized vegetation indices calculated with vignetting-corrected images were sufficient to correct for scene illumination conditions. These results are discussed in the light of the experimental protocol and recommendations are made for the use of these versatile systems for quantitative remote sensing of terrestrial surfaces.

Assessment of Unmanned Aerial Vehicles Imagery for Quantitative Monitoring of Wheat Crop in Small Plots

This paper outlines how light Unmanned Aerial Vehicles (UAV) can be used in remote sensing for precision farming. It focuses on the combination of simple digital photographic cameras with spectral filters, designed to provide multispectral images in the visible and near-infrared domains. In 2005, these instruments were fitted to powered glider and parachute, and flown at six dates staggered over the crop season. We monitored ten varieties of wheat, grown in trial micro-plots in the South-West of France. For each date, we acquired multiple views in four spectral bands corresponding to blue, green, red, and near-infrared. We then performed accurate corrections of image vignetting, geometric distortions, and radiometric bidirectional effects. Afterwards, we derived for each experimental micro-plot several vegetation indexes relevant for vegetation analyses. Finally, we sought relationships between these indexes and field-measured biophysical parameters, both generic and date-specific. Therefore, we established a robust and stable generic relationship between, in one hand, leaf area index and NDVI and, in the other hand, nitrogen uptake and GNDVI. Due to a high amount of noise in the data, it was not possible to obtain a more accurate model for each date independently. A validation protocol showed that we could expect a precision level of 15% in the biophysical parameters estimation while using these relationships.

Implicit solvent models

Implicit solvent models for biomolecular simulations are reviewed and their underlying statistical mechanical basis is discussed. The fundamental quantity that implicit models seek to approximate is the solute potential of mean force, which determines the statistical weight of solute conformations, and which is obtained by averaging over the solvent degrees of freedom. It is possible to express the total free energy as the reversible work performed in two successive steps. First, the solute is inserted in the solvent with zero atomic partial charges; second, the atomic partial charges of the solute are switched from zero to their full values. Consequently, the total solvation free energy corresponds to a sum of non-polar and electrostatic contributions. These two contributions are often approximated by simple geometrical models (such as solvent exposed area models) and by macroscopic continuum electrostatics, respectively. One powerful route is to approximate the average solvent density distribution around the solute, i.e. the solute-solvent density correlation functions, as in statistical mechanical integral equations. Recent progress with semi-analytical approximations makes continuum electrostatics treatments very efficient. Still more efficient are fully empirical, knowledge-based models, whose relation to explicit solvent treatments is not fully resolved, however. Continuum models that treat both solute and solvent as dielectric continua are also discussed, and the relation between the solute fluctuations and its macroscopic dielectric constant(s) clarified.

Optimized atomic radii for protein continuum electrostatics solvation forces

Recently, we presented a Green's function approach for the calculation of analytic continuum electrostatic solvation forces based on numerical solutions of the finite-difference Poisson-Botzmann (FDPB) equation [Im et al., Comp. Phys. Comm. 111 (1998) 59]. In this treatment the analytic forces were explicitly defined as the first derivative of the FDPB continuum electrostatic free energy with respect to the coordinates of the solute atoms. A smooth intermediate region for the solute-solvent dielectric boundary needed to be introduced to avoid abrupt discontinuous variations in the solvation free energy and forces as a function of the atomic positions. In the present paper we extend the set of optimized radii, which was previously parametrized from molecular dynamics free energy simulations of the 20 standard amino acids with explicit solvent molecules [Nina et al., J. Phys. Chem. 101 (1997) 5239], to yield accurate solvation free energy by taking the influence of the smoothed dielectric region into account.

Direct rosiglitazone-induced modifications in insulin secretion, action and clearance: a single-dose hyperglycaemic clamp study

AIMS/HYPOTHESIS

In addition to the improvement in insulin sensitivity, it has been shown that thiazolidinediones modulate beta cell function and insulin clearance in type 2 diabetic subjects. However, interactions between all these actions, and confounding factors due to co-morbidities and co-treatments in diabetic individuals, complicate the identification of specific effects. The aim of this pilot study was to investigate the potential acute effects of rosiglitazone on beta cell function and insulin sensitivity by the hyperglycaemic clamp technique in healthy volunteers.

SUBJECTS AND METHODS

Twelve healthy men were included in a randomised, double-blind crossover study. Rosiglitazone (8 mg) or placebo was given orally 45 min before the hyperglycaemic clamp (10 mmol/l for 2 h).

RESULTS

The second phase of the insulin response was significantly decreased by rosiglitazone: 13,066 +/- 1,531 vs 16,316 +/- 2,813 pmol l(-1) 110 min in controls (p < 0.05), without change in the first phase. Serum C-peptide was not modified. Rosiglitazone treatment significantly increased insulin clearance (molar ratio of the C-peptide to insulin AUCs: 12.80 +/- 1.34 vs 11.38 +/- .33, p < 0.05) and the insulin sensitivity index (12.0 +/- 1.5 vs 8.5 +/- 1.1 micromol m(-2) min(-1) pmol(-1)l, p < 0.01).

CONCLUSIONS/INTERPRETATION

The present results show that a single dose of rosiglitazone rapidly increases insulin clearance and insulin sensitivity index in healthy volunteers, with no direct effect on insulin secretion. The precise mechanisms mediating these actions remain to be determined.

Impact on farnesyltransferase inhibition of 4-chlorophenyl moiety replacement in the Zarnestra® series

Based on the structure of R115777 (tipifarnib, Zarnestra), a series of farnesyltransferase inhibitors have been synthesized by modification of the 2-quinolinone motif and transposition of the 4-chlorophenyl ring to the imidazole or its replacement by 5-membered rings. This has yielded a novel series of potent farnesyltransferase inhibitors.

Discovery of pyrimidyl-5-hydroxamic acids as new potent histone deacetylase inhibitors

A series of pyrimidyl-5-hydroxamic acids was prepared for evaluation as inhibitors of histone deacetylase (HDAC). Amino-2-pyrimidinyl can be used as a linker to provide HDAC inhibitors of good enzymatic potency.

Insertion of a Glycosylphosphatidylinositol-Anchored Enzyme into Liposomes

Incorporation of alkaline phosphatase (AP), a glycosylphosphatidylinositol (GPI)-anchored protein, into liposomes containing detergent, followed by detergent removal with hydrophobic resin was performed. Incorporation media were collected during different steps of detergent removal and were analyzed by flotation in sucrose gradient. The presence of protein was checked by measuring enzymatic activity, while the presence of (3)H-radio-labelled liposomes was followed by determination of the radioactivity. The incorporation yield of the protein into liposomes increased with incubation time in presence of hydrophobic resin. Protein was also incorporated at different protein/lipid ratios. At the highest protein lipid ratio, our data showed that 260 molecules of GPI-linked AP (AP-GPI) could be associated with one liposome, corresponding to 65% vesicle coverage. Finally, observations by electron cryomicroscopy indicated (i) that the protein seemed exclusively associated with the lipid bilayer via the GPI-anchor, as shown by the distance-about 2.5 nm-between the protein core and the liposome membrane; (ii) that the AP-GPI distribution was heterogeneous on the liposome surface, forming clusters of protein.

Substituted azoloquinolines and -quinazolines as new potent farnesyl protein transferase inhibitors

A series of (4-chlorophenyl)-alpha-(1-methyl-1H-imidazol-5-yl)azoloquinolines and -quinazolines was prepared. These compounds displayed potent Farnesyl Protein Transferase inhibitory activity and tetrazolo[1,5-a]quinazolines are promising agents for oral in vivo inhibition.

4-Methyl-1,2,4-triazol-3-yl heterocycle as an alternative to the 1-methylimidazol-5-yl moiety in the Farnesyltransferase inhibitor ZARNESTRA ™

Replacement of the 1-methylimidazol-5-yl moiety in the farnesyltransferase inhibitor ZARNESTRA series by a 4-methyl-1,2,4-triazol-3-yl group gave us compounds with similar structure-activity relationship profiles showing that this triazole is potentially a good surrogate to imidazole for farnesyltransferase inhibition.

Role of GPI-anchored enzyme in liposome detergent-resistance

In this work, we investigated the role of a glycosylphosphatidylinositol (GPI)-anchored protein, the alkaline phosphatase, on the solubilization of detergent-resistant liposomes. In vivo, GPI-anchored proteins are clustered into sphingolipid- and cholesterol-rich membrane domains and this peculiar composition provides cold-detergent-insolubility. To better understand the mechanisms involved in the clustering of these subdomain components, we built a model, namely sphingolipid- and cholesterol-rich liposomes. We show the cold-Triton X-100 resistance of liposomes before and after insertion of GPI-anchored enzyme. When the amount of incorporated enzyme varied, significant changes in membrane stability occurred. Low protein contents into liposomes increased detergent insolubility, whereas high amounts decreased it. Furthermore, significant differences in the detergent-resistance of each lipid were exhibited between liposomes and proteoliposomes. Thus, the enzyme insertion led to a dramatic decrease of cholesterol solubilization, in line with the existence of cholesterol/GPI interactions. Effect of temperature on detergent resistance was also investigated. Liposome solubilization increased with temperature up to a threshold value of 40/45 degrees C. This was also the temperature at which a phase transition of liposome membrane occurred, as evidenced by Laurdan fluorescence. Although the GPI-anchored enzyme insertion modified membrane stability, no change was observed on phase transition. Our work highlights the importance of GPI-anchored proteins in the structure of sphingolipid- and cholesterol-rich membrane domains, in the detergent-insolubility of these peculiar domains, as well as in interaction of GPI proteins with cholesterol.

Energetics of ion conduction through the K+ channel

K+ channels are transmembrane proteins that are essential for the transmission of nerve impulses. The ability of these proteins to conduct K+ ions at levels near the limit of diffusion is traditionally described in terms of concerted mechanisms in which ion-channel attraction and ion-ion repulsion have compensating effects, as several ions are moving simultaneously in single file through the narrow pore. The efficiency of such a mechanism, however, relies on a delicate energy balance-the strong ion-channel attraction must be perfectly counterbalanced by the electrostatic ion-ion repulsion. To elucidate the mechanism of ion conduction at the atomic level, we performed molecular dynamics free energy simulations on the basis of the X-ray structure of the KcsA K+ channel. Here we find that ion conduction involves transitions between two main states, with two and three K+ ions occupying the selectivity filter, respectively; this process is reminiscent of the 'knock-on' mechanism proposed by Hodgkin and Keynes in 1955. The largest free energy barrier is on the order of 2-3 kcal mol-1, implying that the process of ion conduction is limited by diffusion. Ion-ion repulsion, although essential for rapid conduction, is shown to act only at very short distances. The calculations show also that the rapidly conducting pore is selective.

Lipid-mediated interactions between intrinsic membrane proteins: dependence on protein size and lipid composition

The present study is an application of an approach recently developed by the authors for describing the structure of the hydrocarbon chains of lipid-bilayer membranes (LBMs) around embedded protein inclusions ( Biophys. J. 79:2867-2879). The approach is based on statistical mechanical integral equation theories developed for the study of dense liquids. First, the configurations extracted from molecular dynamics simulations of pure LBMs are used to extract the lateral density-density response function. Different pure LBMs composed of different lipid molecules were considered: dioleoyl phosphatidylcholine (DOPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dipalmitoyl phosphatidylcholine (DPPC), and dimyristoyl phosphatidylcholine (DMPC). The results for the lateral density-density response function was then used as input in the integral equation theory. Numerical calculations were performed for protein inclusions of three different sizes. For the sake of simplicity, protein inclusions are represented as hard smooth cylinders excluding the lipid hydrocarbon core from a small cylinder of 2.5 A radius, corresponding roughly to one aliphatic chain, a medium cylinder of 5 A radius, corresponding to one alpha-helix, and a larger cylinder of 9 A radius, representing a small protein such as the gramicidin channel. The lipid-mediated interaction between protein inclusions was calculated using a closed-form expression for the configuration-dependent free energy. This interaction was found to be repulsive at intermediate range and attractive at short range for two small cylinders in POPC, DPPC, and DMPC bilayers, whereas it oscillates between attractive and repulsive values in DOPC bilayers. For medium size cylinders, it is again repulsive at intermediate range and attractive at short range, but for every model LBM considered here. In the case of a large cylinder, the lipid-mediated interaction was shown to be repulsive for both short and long ranges for the DOPC, POPC, and DPPC bilayers, whereas it is again repulsive and attractive for DMPC bilayers. The results indicate that the packing of the hydrocarbon chains around protein inclusions in LBMs gives rise to a generic (i.e., nonspecific) lipid-mediated interaction which favors the association of two alpha-helices and depends on the lipid composition of the membrane.

Dynamic coupling between the SH2 and SH3 domains of c-Src and Hck underlies their inactivation by C-terminal tyrosine phosphorylation

The effect of C-terminal tyrosine phosphorylation on molecular motions in the Src kinases Hck and c-Src is investigated by molecular dynamics simulations. The SH2 and SH3 domains of the inactive kinases are seen to be tightly coupled by the connector between them, impeding activation. Dephosphorylation of the tail reduces the coupling between the SH2 and SH3 domains in the simulations, as does replacement of connector residues with glycine. A mutational analysis of c-Src expressed in Schizosaccharomyces pombe demonstrates that replacement of residues in the SH2-SH3 connector with glycine activates c-Src. The SH2-SH3 connector appears to be an inducible "snap lock" that clamps the SH2 and SH3 domains upon tail phosphorylation, but which allows flexibility when the tail is released.

Anchoring of a monotopic membrane protein: the binding of prostaglandin H2 synthase-1 to the surface of a phospholipid bilayer

Prostaglandin H2 synthases (PGHS-1 and -2) are monotopic peripheral membrane proteins that catalyse the synthesis of prostaglandins in the arachidonate cascade. Picot et al. (1994) proposed that the enzyme is anchored to one leaflet of the bilayer by a membrane anchoring domain consisting of a right-handed spiral of amphipathic helices (residues 73-116) forming a planar motif. Two different computational approaches are used to examine the association of the PGHS-1 membrane anchoring domain with a membrane via the proposed mechanism. The electrostatic contribution to the free energy of solvation is obtained by solving numerically the finite-difference Poisson equation for the protein attached to a membrane represented as a planar slab of low dielectric. The nonpolar cavity formation and van der Waals contributions to the solvation free energy are assumed to be proportional to the water accessible surface area. Based on the optimum position determined from the continuum solvent model, two atomic models of the PGHS-1 anchoring domain associated with an explicit dimyristoylphosphatidylcholine (DMPC) bilayer differing by the thickness of the membrane bilayer were constructed. A total of 2 ns molecular dynamics simulation were performed to study the details of lipid-protein interactions at the microscopic level. In the simulations the lipid hydrocarbon chains interacting with the anchoring domain assume various shapes, suggesting that the plasticity of the membrane is significant. The hydrophobic residues in the membrane side of the helices interact with the hydrophobic membrane core, while the positively charged residues interact with the lipid polar headgroups to stabilize the anchoring of the membrane domain to the upper half of the bilayer. The phosphate headgroup of one DMPC molecule disposed at the center of the spiral formed by helices A, B, C and D interacts strongly with Arg120, a residue on helix D that has previously been identified as being important in the activity of PGHS-1. In the full enzyme structure, this position corresponds to the entrance of a long hydrophobic channel leading to the cyclooxygenase active site. These observations provide insights into the association of the arachidonic acid substrate to the cyclooxygenase active site of PGHS-1.

Framework model for single proton conduction through gramicidin

This paper describes a framework model for proton conduction through gramicidin; a model designed to incorporate information from molecular dynamics and use this to predict conductance properties. The state diagram describes both motion of an excess proton within the pore as well as the reorientation of waters within the pore in the absence of an excess proton. The model is constructed as the diffusion limit of a random walk, allowing control over the boundary behavior of trajectories. Simple assumptions about the boundary behavior are made, which allow an analytical solution for the proton current and conductance. This is compared with corresponding expressions from statistical mechanics. The random walk construction allows diffusing trajectories underlying the model to be simulated in a simple way. Details of the numerical algorithm are described.

A combined molecular dynamics and diffusion model of single proton conduction through gramicidin

We develop a model for proton conduction through gramicidin based on the molecular dynamics simulations of Pomès and Roux (Biophys. J. 72:A246, 1997). The transport of a single proton through the gramicidin pore is described by a potential of mean force and diffusion coefficient obtained from the molecular dynamics. In addition, the model incorporates the dynamics of a defect in the hydrogen bonding structure of pore waters without an excess proton. Proton entrance and exit were not simulated by the molecular dynamics. The single proton conduction model includes a simple representation of these processes that involves three free parameters. A reasonable value can be chosen for one of these, and the other two can be optimized to yield a good fit to the proton conductance data of, Ann. N.Y. Acad. Sci. 339:8-20) for pH > or = 1.7. A sensitivity analysis shows the significance of this fit.

Lipid-mediated interactions between intrinsic membrane proteins: a theoretical study based on integral equations

This study of lipid-mediated interactions between proteins is based on a theory recently developed by the authors for describing the structure of the hydrocarbon chains in the neighborhood of a protein inclusion embedded in a lipid membrane [Lagüe et al., Farad. Discuss. 111:165-172, 1998]. The theory involves the hypernetted chain integral equation formalism for liquids. The exact lateral density-density response function of the hydrocarbon core, extracted from molecular dynamics simulations of a pure dipalmitoylphosphatidylcholine bilayer based on an atomic model, is used as input. For the sake of simplicity, protein inclusions are modeled as hard repulsive cylinders. Numerical calculations were performed with three cylinder sizes: a small cylinder of 2.5-A radius, corresponding roughly to an aliphatic chain; a medium cylinder of 5-A radius, corresponding to a alpha-helical polyalanine protein; and a large cylinder of 9-A radius, representing a small protein, such as the gramicidin channel. The calculations show that the average hydrocarbon density is perturbed over a distance of 20-25 A from the edge of the cylinder for every cylinder size. The lipid-mediated protein-protein effective interaction is calculated and is shown to be nonmonotonic. In the case of the small and the medium cylinders, the lipid-mediated effective interaction of two identical cylinders is repulsive at an intermediate range but attractive at short range. At contact, there is a free energy of -2k(B)T for the 2.5-A-radius cylinder and -9k(B)T for the 5-A-radius cylinder, indicating that the association of two alpha-helices of both sizes is favored by the lipid matrix. In contrast, the effective interaction is repulsive at all distances in the case of the large cylinder. Results were obtained with two integral equations theories: hypernetted chain and Percus-Yevick. For the two theories, all results are qualitatively identical.

A Grand Canonical Monte Carlo-Brownian dynamics algorithm for simulating ion channels

A computational algorithm based on Grand Canonical Monte Carlo (GCMC) and Brownian Dynamics (BD) is described to simulate the movement of ions in membrane channels. The proposed algorithm, GCMC/BD, allows the simulation of ion channels with a realistic implementation of boundary conditions of concentration and transmembrane potential. The method is consistent with a statistical mechanical formulation of the equilibrium properties of ion channels (; Biophys. J. 77:139-153). The GCMC/BD algorithm is illustrated with simulations of simple test systems and of the OmpF porin of Escherichia coli. The approach provides a framework for simulating ion permeation in the context of detailed microscopic models.

Protein inclusion in lipid membranes: a theory based on the hypernetted chain integral equation

A theory for describing the structure of the hydrocarbon chains around a protein inclusion embedded in a lipid bilayer is developed on the basis of the hypernetted chain integral equation formalism for liquids. The exact lateral density-density response function of the hydrocarbon core, which is extracted from a molecular dynamics simulation of a pure lipid bilayer, is used as input to the theory. Numerical calculations show that the average lipid order is perturbed over a distance of 25 to 30 A around a hard repulsive cylinder of 5 A radius representing an alpha-helical polyleucine protein inclusion. The lipid-mediated protein-protein interaction is calculated and is shown to be non-monotonic, being repulsive at an intermediate range but attractive at short range. It is found that the lipid matrix contributes a free energy well of 8 kBT to the association of two cylindrical inclusions.

Molecular dynamics of the KcsA K(+) channel in a bilayer membrane

Molecular dynamics (MD) simulations of an atomic model of the KcsA K(+) channel embedded in an explicit dipalmitoylphosphatidylcholine (DPPC) phospholipid bilayer solvated by a 150 mM KCl aqueous salt solution are performed and analyzed. The model includes the KcsA K(+) channel, based on the recent crystallographic structure of, Science. 280:69-77), 112 DPPC, K(+) and Cl(-) ions, as well as over 6500 water molecules for a total of more than 40,000 atoms. Three K(+) ions are explicitly included in the pore. Two are positioned in the selectivity filter on the extracellular side and one in the large water-filled cavity. Different starting configurations of the ions and water molecules in the selectivity filter are considered, and MD trajectories are generated for more than 4 ns. The conformation of KcsA is very stable in all of the trajectories, with a global backbone root mean square (RMS) deviation of less than 1.9 A with respect to the crystallographic structure. The RMS atomic fluctuations of the residues surrounding the selectivity filter on the extracellular side of the channel are significantly lower than those on the intracellular side. The motion of the residues with aromatic side chains surrounding the selectivity filter (Trp(67), Trp(68), Tyr(78), and Tyr(82)) is anisotropic with the smallest RMS fluctuations in the direction parallel to the membrane plane. A concerted dynamic transition of the three K(+) ions in the pore is observed, during which the K(+) ion located initially in the cavity moves into the narrow part of the selectivity filter, while the other two K(+) ions move toward the extracellular side. A single water molecule is stabilized between each pair of ions during the transition, suggesting that each K(+) cation translocating through the narrow pore is accompanied by exactly one water molecule, in accord with streaming potential measurements (, Biophys. J. 55:367-371). The displacement of the ions is coupled with the structural fluctuations of Val(76) and Gly(77), in the selectivity filter, as well as the side chains of Glu(71), Asp(80), and Arg(89), near the extracellular side. Thus the mechanical response of the channel structure at distances as large as 10-20 A from the ions in the selectivity filter appears to play an important role in the concerted transition.

Activity increase after extraction of alkaline phosphatase from human osteoblastic membranes by nonionic detergents: influence of age and sex

The solubilization of alkaline phosphatase (AP) from osteoblastic cell membranes obtained from human primary bone cell cultures was studied according to the age and sex of the donors (17 females, 11 males; age range: 2-77 years). Cell membranes were treated by non-ionic (n-octyl beta-D-glucopyranoside, OG), ionic or zwitterionic detergents, then centrifuged. When OG was used almost all the AP was solubilized. AP activity in supernatant of solubilization was compared to the activity of the suspension before centrifugation. The activity ratio (AR) increased in function of age for subjects between 65 and 74. Neither total nor specific AP activities were influenced by age or sex. Electrophoresis studies showed that the AP released was a GPI (glycosyl phosphatidylinositol)-anchored protein, amphipathic form, with 140 kDa as apparent molecular mass. The activity change of AP in the presence of OG may result from age-related modifications either in the AP structure or in the constituents of the plasma membranes (proteins or phospholipids).