RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

RENEB Inter-Laboratory Comparison 2021: The Cytokinesis-Block Micronucleus Assay

The goal of the RENEB inter-laboratory comparison 2021 exercise was to simulate a large-scale radiation accident involving a network of biodosimetry labs. Labs were required to perform their analyses using different biodosimetric assays in triage mode scoring and to rapidly report estimated radiation doses to the organizing institution. This article reports the results obtained with the cytokinesis-block micronucleus assay. Three test samples were exposed to blinded doses of 0, 1.2 and 3.5 Gy X-ray doses (240 kVp, 13 mA, ∼75 keV, 1 Gy/min). These doses belong to 3 triage categories of clinical relevance: a low dose category, for no exposure or exposures inferior to 1 Gy, requiring no direct treatment of subjects; a medium dose category, with doses ranging from 1 to 2 Gy, and a high dose category, after exposure to doses higher than 2 Gy, with the two latter requiring increasing medical attention. After irradiation the test samples (no. 1, no. 2 and no. 3) were sent by the organizing laboratory to 14 centers participating in the micronucleus assay exercise. Laboratories were asked to setup micronucleus cultures and to perform the micronucleus assay in triage mode, scoring 500 binucleated cells manually, or 1,000 binucleated cells in automated/semi-automated mode. One laboratory received no blood samples, but scored pictures from another lab. Based on their calibration curves, laboratories had to provide estimates of the administered doses. The accuracy of the reported dose estimates was further analyzed by the micronucleus assay lead. The micronucleus assay allowed classification of samples in the corresponding clinical triage categories (low, medium, high dose category) in 88% of cases (manual scoring, 88%; semi-automated scoring, 100%; automated scoring, 73%). Agreement between scoring laboratories, assessed by calculating the Fleiss' kappa, was excellent (100%) for semi-automated scoring, good (83%) for manual scoring and poor (53%) for fully automated scoring. Correct classification into triage scoring dose intervals (reference dose ±0.5 Gy for doses ≤2.5 Gy, or reference dose ±1 Gy for doses >2.5 Gy), recommended for triage biodosimetry, was obtained in 79% of cases (manual scoring, 73%; semi-automated scoring, 100%; automated scoring, 67%). The percentage of dose estimates whose 95% confidence intervals included the reference dose was 58% (manual scoring, 48%; semi-automated scoring, 72%; automated scoring, 60%). For the irradiated samples no. 2 and no. 3, a systematic shift towards higher dose estimations was observed. This was also noticed with the other cytogenetic assays in this intercomparison exercise. Accuracy of the rapid triage modality could be maintained when the number of manually scored cells was scaled down to 200 binucleated cells. In conclusion, the micronucleus assay, preferably performed in a semi-automated or manual scoring mode, is a reliable technique to perform rapid biodosimetry analysis in large-scale radiation emergencies.

RENEB Inter-Laboratory Comparison 2021: The Dicentric Chromosome Assay

After large-scale radiation accidents where many individuals are suspected to be exposed to ionizing radiation, biological and physical retrospective dosimetry assays are important tools to aid clinical decision making by categorizing individuals into unexposed/minimally, moderately or highly exposed groups. Quality-controlled inter-laboratory comparisons of simulated accident scenarios are regularly performed in the frame of the European legal association RENEB (Running the European Network of Biological and Physical retrospective Dosimetry) to optimize international networking and emergency readiness in case of large-scale radiation events. In total 33 laboratories from 22 countries around the world participated in the current RENEB inter-laboratory comparison 2021 for the dicentric chromosome assay. Blood was irradiated in vitro with X rays (240 kVp, 13 mA, ∼75 keV, 1 Gy/min) to simulate an acute, homogeneous whole-body exposure. Three blood samples (no. 1: 0 Gy, no. 2: 1.2 Gy, no. 3: 3.5 Gy) were sent to each participant and the task was to culture samples, to prepare slides and to assess radiation doses based on the observed dicentric yields from 50 manually or 150 semi-automatically scored metaphases (triage mode scoring). Approximately two-thirds of the participants applied calibration curves from irradiations with γ rays and about 1/3 from irradiations with X rays with varying energies. The categorization of the samples in clinically relevant groups corresponding to individuals that were unexposed/minimally (0-1 Gy), moderately (1-2 Gy) or highly exposed (>2 Gy) was successfully performed by all participants for sample no. 1 and no. 3 and by ≥74% for sample no. 2. However, while most participants estimated a dose of exactly 0 Gy for the sham-irradiated sample, the precise dose estimates of the samples irradiated with doses >0 Gy were systematically higher than the corresponding reference doses and showed a median deviation of 0.5 Gy (sample no. 2) and 0.95 Gy (sample no. 3) for manual scoring. By converting doses estimated based on γ-ray calibration curves to X-ray doses of a comparable mean photon energy as used in this exercise, the median deviation decreased to 0.27 Gy (sample no. 2) and 0.6 Gy (sample no. 3). The main aim of biological dosimetry in the case of a large-scale event is the categorization of individuals into clinically relevant groups, to aid clinical decision making. This task was successfully performed by all participants for the 0 Gy and 3.5 Gy samples and by 74% (manual scoring) and 80% (semi-automatic scoring) for the 1.2 Gy sample. Due to the accuracy of the dicentric chromosome assay and the high number of participating laboratories, a systematic shift of the dose estimates could be revealed. Differences in radiation quality (X ray vs. γ ray) between the test samples and the applied dose effect curves can partly explain the systematic shift. There might be several additional reasons for the observed bias (e.g., donor effects, transport, experimental conditions or the irradiation setup) and the analysis of these reasons provides great opportunities for future research. The participation of laboratories from countries around the world gave the opportunity to compare the results on an international level.

Effect of low-dose rivaroxaban with low-dose aspirin vs low-dose aspirin on platelet and oxidative biomarkers: a randomized study in diabetes patients with stable peripheral or coronary artery disease

Background

Rivaroxaban (Riva), a direct FXa inhibitor, at 2.5 mg twice-daily (bid) combined with low-dose aspirin (ASA, 100 mg once daily-od) reduced major vascular events vs. ASA alone in subjects with stable coronary artery (CAD) or symptomatic peripheral artery disease (PAD). Whether this benefit is due to the anticoagulant effect or additional FXa-mediated effects through the platelet and endothelial cell thrombin receptors is unknown. Type 2 diabetes mellitus (T2DM) is characterized by high platelet activation and oxidative stress that may contribute to increased cardiovascular risk.

Purpose

We investigated the effects of Riva (2.5 mg bid) + ASA (100 mg od) vs. ASA (100 mg od) alone on platelet and oxidative biomarkers in subjects with T2DM and stable vascular disease (stable CAD, symptomatic PAD and/or significant carotid stenosis).

Methods

In this randomized, open-label, cross-over trial, patients were randomized to continue ASA for 4 weeks and then add Riva for 4 weeks, or add Riva in the first 4 weeks and then continue with ASA alone for 4 weeks. Primary endpoints were: in vivo platelet activation and lipid peroxidation, assessed by the urinary excretion of 11-dehydro-TXB2 (TXM) and 8-iso-PGF2alpha (ISOP), respectively. Secondary endpoints included: routine coagulation tests, D-dimer, thrombin generation, serum TXB2, and Riva plasma concentrations.

Results

Seventy-6 subjects (10 females) were recruited: age 68±7 years (mean±SD); BMI 27.1±3.5 kg/m2; fasting glucose 129±31 mg/dL; HbA1c 6.8±0.9%; serum creatinine 1±0.25 mg/dL; LDL-cholesterol 77±31 mg/dL. Two patients dropped out: one for benign, self-limiting hematuria, one for unwillingness to continue, 8 subjects are completing the study leaving 66 who completed the 8-week randomized treatment and showed no sequence effect. Urinary TXM and ISOP were significantly reduced by Riva+ASA vs. ASA alone: TXM was 260 [195–398] vs. 335 [225–441] pg/mg creatinine and ISOP 722 [601–991] vs. 827 [648–1350] pg/mg creatinine (median [IQR]) on Riva+ASA vs. ASA alone, respectively (p&lt;0.001 for paired samples). Riva plasma concentrations were 48±1.9 ng/ml at peak and 21±1.4 ng/ml at trough. The velocity of thrombin formation significantly decreased with Riva+ASA vs. ASA alone (velocity index, 46±3% vs. 83±3%; peak-height, 66±2% vs. 83±1%, respectively). aPTT levels were slightly but significantly prolonged by Riva vs. ASA alone (44±1 vs. 39±1 sec). Serum TXB2, D-dimer, von Willebrand factor, PT, fibrinogen and endogenous thrombin potential values were similar between treatments.

Conclusions

In ASA-treated subjects with T2DM and stable vascular disease, the addition of very low-dose Riva restrained incompletely-suppressed lipid peroxidation and platelet activation and modified the kinetics of thrombin formation. These changes may contribute to the beneficial effects of the Riva+ASA combination.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Investigator-initiated study funded by Bayer AG

Thromboxane metabolite excretion is associated with serious vascular events in diabetes mellitus: a sub-study of the ASCEND trial

Background

Platelet activation plays a major role in the atherothrombotic complications of diabetes. Thromboxane (TX)A2 is a pro-thrombotic prostanoid, synthesized via cyclooxygenase-1 and released by activated platelets. The metabolism of TXA2 in vivo leads to a major stable end-product, 11-dehydro-TXB2 (TXM), measurable in urine and reflecting the whole-body rate of TXA2 biosynthesis. In two large trials of high-risk, aspirin-treated (mostly, without diabetes) patients, (CHARISMA and HOPE trials), the baseline rate of urinary TXM excretion was an independent predictor of future cardiovascular events.

Purpose

The aim of the ASCEND (A Study of Cardiovascular Events in Diabetes) TXM sub-study was to investigate the association between baseline urinary TXM and future serious vascular events or revascularization (SVE-R), major bleeds and incident cancer independent of other risk factors and treatment, in people with diabetes and no manifest cardiovascular disease at trial entry.

Methods

Urinary TXM was measured by a previously GC/MS-validated, immunoassay in 6,487 participants with eligible baseline samples. Analyses excluded 539 participants using NSAIDs. TXM appeared log-normally distributed, so analyses were by quintiles and per SD (=0.622) of continuous loge TXM. The association of loge TXM with outcome was adjusted by basic factors (age, sex, sample volume and randomized treatment allocation) and by the predictors of log TXM (smoking, type 2 diabetes treated with insulin or oral hypoglycaemics, HDL cholesterol, body mass index, urinary albumin/creatinine ratio, eGFR). The association of log TXM with non-vascular, non-cancer MedDRA outcomes was investigated to determine whether TXM had a general effect on outcome. During a mean of 6.6 years follow-up there were 618 SVE-Rs, 206 bleeds and 700 cancers among these patients.

Results

Log TXM correlated significantly with SVE-R, hazard ratio (HR) per 1 SD of log TXM: 1.13 (1.04–1.23), p=0.003 (Figure 1, panel a), non-significantly with major bleeds [HR 1.15 (1.00–1.32), p=0.055] (Figure 1, panel b), and marginally significantly with cancer [HR 1.09 (1.01–1.17), p=0.03] (Figure 1, panel c). There was no association of log TXM with non-vascular non-cancer MedDRA outcomes (HR per 1 SD, 0.99; 99% CI, 0.94–1.05).

Conclusion

The rate of urinary TXM excretion, a non-invasive biomarker of TXA2-mediated platelet activation in vivo, is log-linearly associated with serious vascular events independent of other risk factors in people with diabetes. Its potential association with cancer must be viewed as hypothesis-generating and needs confirmation.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): IMI1: Surrogate markers for micro- and macro-vascular hard endpoints for innovative diabetes tools (SUMMIT).

A NOVEL BIOLOGICAL DOSIMETRY ASSAY AS A POTENTIAL TOOL FOR TRIAGE DOSE ASSESSMENT IN CASE OF LARGE-SCALE RADIOLOGICAL EMERGENCY

In case of mass radiological emergencies, new strategies involving biological and clinical endpoints are requested for an efficient triage classification of casualties. For this purpose, we developed a novel protocol combining the two most established cytogenetic methods used in biological dosimetry (dicentric and micronucleus assays) into a single one, in order to have a time-saving, inexpensive and potentially automatable instrument to be used for triage purposes in case of large-scale radiological events. This method could be considered as a 'three in one' assay allowing the simultaneous scoring of chromosome aberrations and micronuclei on a single slide, and also enabling to discriminate between metaphases in first and second cell division without the Fluorescence plus Giemsa staining. This method needs further validation through inter-comparisons involving biological dosimetry laboratories, to verify its reproducibility. Moreover, the possibility to apply the already existing software for automation for dicentric and micronucleus assays could be also verified.

Equal Antiplatelet Effects of Aspirin 50 or 324 mg/Day in Patients After Acute Myocardial Infarction

This study explores the effects on some hematological parameters of a low-dose aspirin regimen (50 mg/day) versus a conventional aspirin treatment with reported antithrombotic efficacy (324 mg/day), in patients with acute myocardial infarction. Fifteen patients were randomized into 3 equal groups receiving 50 mg or 324 mg aspirin or placebo, daily for 21 days. Compared with placebo, bleeding time was significantly and similarly prolonged with both aspirin doses (+ 71 ± 22% and + 69 ± 20%, mean ± S.D.). Aspirin 50 mg/day suppressed arachidonate-induced platelet aggregation and secondary phase aggregation after ADP and adrenaline. Collagen aggregation was inhibited by 44 ± 15%. In no case were differences in the antiplatelet effects of the two doses observed. The effects of 50 mg/day persisted without attenuation during the observation period. Platelet thromboxane B2 generation during arachidonate-induced aggregation was inhibited by 95 ± 2 and 99 ± 1% compared to placebo group after 50 and 324 mg/day, respectively (P between doses <0.05). No change was observed with any treatment in coagulation time, prothrombin time or plasma thromboplastin time. Thus, in patients with acute myocardial infarction, the antiplatelet effects of aspirin 50 mg/day are stable over time and superimposable on those of 324 mg/day. The antithrombotic efficacy of aspirin 50 mg/day remains to be tested clinically.

In Silico Modeling of the Antiplatelet Pharmacodynamics of Low-dose Aspirin in Health and Disease

The influence of platelet turnover on cyclooxygenase (COX-1) inhibition by low-dose aspirin remains largely uncharacterized due to limited feasibility of studying aspirin pharmacodynamics in bone marrow precursors. We developed an in silico compartmental model describing the aspirin effects on COX-1 activity in a population of megakaryocytes (MK) and in peripheral platelets. Model parameters were inferred from the literature and calibrated using measurements of serum thromboxane B₂ (sTXB₂ ), as proxy of COX-1 activity in peripheral platelets, in 17 healthy subjects and 24 patients with essential thrombocythemia (ET). The model reproduced well the average time-course of sTXB₂ inhibition in healthy (accuracy = 10.4%), the reduced inhibition of sTXB₂ observed in ET, and the effect of different dosing regimens. In conclusion, the in silico model accurately describes COX-1 inactivation by low-dose aspirin in MK and platelets in different clinical settings, and might help personalize aspirin regimens in conditions of altered megakaryopoiesis.

NOS Evaluations in Human Dental Pulp-Capping with MTA and Calcium-Hydroxide

The aim of this study is to compare mineral trioxide aggregate (MTA) with calcium hydroxide when used as pulp-capping material in human teeth. 40 teeth were divided into groups based on clinical diagnosis: healthy and hyperaemic. The teeth were pulp capped with MTA and calcium hydroxide. We localized the eNOS and iNOS by immunohistochemistry, tested their mRNA expression by RT-PCR and protein levels by western blots. The evaluation of the samples was based on the cell inflammatory response and on the pulp tissue organization. In particular, evaluation of eNOS and iNOS differences between the various groups and the cellular evolution after the first 7 days from the treatment, and at a distance of 28 days. Our results suggest that there are differences in localization and expression between eNOS and iNOS in dental pulp. Our study has helped us to better understand the effects that calcium hydroxide and MTA have on pulp tissue.

Coxibs, Traditional NSAIDs, and Cardiovascular Safety Post-PRECISION: What We Thought We Knew Then and What We Think We Know Now

The aim of the present review is to analyze how thinking about the cardiovascular safety of nonsteroidal antiinflammatory drugs has evolved during the past two decades, and discuss to what extent the additional information from the Prospective Randomized Evaluation of Celecoxib Integrated Safety Versus Ibuprofen or Naproxen study may alter our current mechanistic understanding and/or clinical practice.

'BioQuaRT' project: design of a novel in situ protocol for the simultaneous visualisation of chromosomal aberrations and micronuclei after irradiation at microbeam facilities

The aim of the 'BioQuaRT' (Biologically weighted Quantities in RadioTherapy) project is to develop measurement techniques for characterising charged particle track structure on different length scales, and to correlate at the cellular level the track structure properties with the biological effects of radiation. This multi-scale approach will allow characterisation of the radiation qualities used in radiotherapy and the related biological effects. Charged-particle microbeam facilities were chosen as the platforms for all radiobiology experiments in the 'BioQuaRT' project, because they allow targeting single cells (or compartments of a cell) with a predefined number of ionising particles and correlating the cell-by-cell induced damage with type and energy of the radiation and with the number of ions per cell. Within this project, a novel in situ protocol was developed for the analysis of the misrepaired and/or unrepaired chromosome damage induced by charged-particle irradiations at the Physikalisch-Technische Bundesanstalt (PTB) ion microbeam facility. Among the cytogenetic biomarkers to detect and estimate radiation-induced DNA damage in radiobiology, chromosomal aberrations and micronuclei were chosen. The characteristics of the PTB irradiation system required the design of a special in situ assay: specific irradiation dishes with a base made from a biofoil 25-µm thick and only 3000-4000 cells seeded and irradiated per dish. This method was developed on Chinese hamster ovary (CHO) cells, one of the most commonly used cell lines in radiobiology in vitro experiments. The present protocol allows the simultaneous scoring of chromosome aberrations and micronuclei on the same irradiated dish. Thanks to its versatility, this method could also be extended to other radiobiological applications besides the single-ion microbeam irradiations.

Reappraisal of the clinical pharmacology of low-dose aspirin by comparing novel direct and traditional indirect biomarkers of drug action

BACKGROUND

Even though the acetylation of platelet cyclooxygenase (COX)-1 at serine-529 is the direct mechanism of action of low-dose aspirin, its antiplatelet effect has been characterized using indirect indexes of COX-1 activity.

OBJECTIVES

We performed a clinical study with enteric-coated low-dose aspirin (EC-aspirin), in healthy subjects, to evaluate the effects on the extent and duration of platelet COX-1 acetylation, using a novel proteomic strategy for absolute protein quantification (termed AQUA), as compared with traditional pharmacokinetic and pharmacodynamic parameters.

SUBJECTS AND METHODS

In a phase I, single-arm, open-label study of EC aspirin (100 mg day(-1) ) administered to 24 healthy subjects, we compared, over a 24 h-period on day 1 and 7, % platelet acetylated COX-1 (AceCOX-1) with traditional pharmacokinetic and pharmacodynamics [i.e. serum thromboxane (TX) B2 , platelet function by monitoring CEPI(collagen/epinephrine) closure time (CT) using whole-blood PFA-100 and urinary excretion of 11-dehydro-TXB2 ] parameters.

RESULTS

Acetylation of platelet COX-1 was measurable before detection of aspirin levels in the systemic circulation and increased in a cumulative fashion upon repeated dosing. After the last dose of EC-aspirin, %AceCOX-1, serum TXB2 and CEPI-CT values were maximally and persistently modified throughout 24 h; they averaged 76 ± 2%, 99.0 ± 0.4% and 271 ± 5 s, respectively. EC-aspirin caused 75% reduction in urinary 11-dehydro-TXB2 excretion. After chronic dosing with aspirin, the pharmacokinetics of acetylsalicylic acid was completely dissociated from pharmacodynamics.

CONCLUSIONS

The demonstrated feasibility of quantifying the extent and duration of platelet COX-1 acetylation will allow characterizing the genetic, pharmacokinetic and pharmacodynamic determinants of the inter-individual variability in the antiplatelet response to low-dose aspirin as well as identifying extra-platelet sites of drug action.

In vivo prostacyclin biosynthesis and effects of different aspirin regimens in patients with essential thrombocythaemia

Essential thrombocythaemia (ET) is characterised by enhanced platelet generation and thrombosis. Once daily (od) aspirin incompletely inhibits platelet thromboxane (TX)A2 production in ET. A twice daily (bid) dosing is necessary to fully inhibit TXA2. Whether this dosing regimen affects in vivo prostacyclin (PGI2) biosynthesis is unknown. PGI2 biosynthesis was characterised in 50 ET patients on enteric-coated (EC) aspirin 100 mg od, by measuring its urinary metabolite, 2,3-dinor-6-keto-PGF1α (PGI-M). Moreover, in a crossover study 22 patients poorly responsive to standard aspirin based on serum TXB2 levels (≥4 ng/ml) were randomised to different seven-day aspirin regimens: EC aspirin 100 mg od, 100 mg bid, 200 mg od, or plain aspirin 100 mg od. PGI-M measured 24 hours after the last aspirin intake (EC, 100 mg od) was similar in patients and healthy subjects both on (n=10) and off (n=30) aspirin. PGI-M was unrelated to in vivo TXA2 biosynthesis, and not affected by EC aspirin 100 mg bid or 200 mg od as compared to EC 100 mg od. PGI2 biosynthesis in aspirin-treated ET patients appears unrelated to TXA2 biosynthesis, and not affected by an improved aspirin regimen, demonstrating its vascular safety for future trials.

Vascular and upper gastrointestinal effects of non-steroidal anti-inflammatory drugs: meta-analyses of individual participant data from randomised trials

BACKGROUND

The vascular and gastrointestinal effects of non-steroidal anti-inflammatory drugs (NSAIDs), including selective COX-2 inhibitors (coxibs) and traditional non-steroidal anti-inflammatory drugs (tNSAIDs), are not well characterised, particularly in patients at increased risk of vascular disease. We aimed to provide such information through meta-analyses of randomised trials.

METHODS

We undertook meta-analyses of 280 trials of NSAIDs versus placebo (124,513 participants, 68,342 person-years) and 474 trials of one NSAID versus another NSAID (229,296 participants, 165,456 person-years). The main outcomes were major vascular events (non-fatal myocardial infarction, non-fatal stroke, or vascular death); major coronary events (non-fatal myocardial infarction or coronary death); stroke; mortality; heart failure; and upper gastrointestinal complications (perforation, obstruction, or bleed).

FINDINGS

Major vascular events were increased by about a third by a coxib (rate ratio [RR] 1·37, 95% CI 1·14-1·66; p=0·0009) or diclofenac (1·41, 1·12-1·78; p=0·0036), chiefly due to an increase in major coronary events (coxibs 1·76, 1·31-2·37; p=0·0001; diclofenac 1·70, 1·19-2·41; p=0·0032). Ibuprofen also significantly increased major coronary events (2·22, 1·10-4·48; p=0·0253), but not major vascular events (1·44, 0·89-2·33). Compared with placebo, of 1000 patients allocated to a coxib or diclofenac for a year, three more had major vascular events, one of which was fatal. Naproxen did not significantly increase major vascular events (0·93, 0·69-1·27). Vascular death was increased significantly by coxibs (1·58, 99% CI 1·00-2·49; p=0·0103) and diclofenac (1·65, 0·95-2·85, p=0·0187), non-significantly by ibuprofen (1·90, 0·56-6·41; p=0·17), but not by naproxen (1·08, 0·48-2·47, p=0·80). The proportional effects on major vascular events were independent of baseline characteristics, including vascular risk. Heart failure risk was roughly doubled by all NSAIDs. All NSAID regimens increased upper gastrointestinal complications (coxibs 1·81, 1·17-2·81, p=0·0070; diclofenac 1·89, 1·16-3·09, p=0·0106; ibuprofen 3·97, 2·22-7·10, p<0·0001; and naproxen 4·22, 2·71-6·56, p<0·0001).

INTERPRETATION

The vascular risks of high-dose diclofenac, and possibly ibuprofen, are comparable to coxibs, whereas high-dose naproxen is associated with less vascular risk than other NSAIDs. Although NSAIDs increase vascular and gastrointestinal risks, the size of these risks can be predicted, which could help guide clinical decision making.

FUNDING

UK Medical Research Council and British Heart Foundation.

Autosomal recessive hereditary spastic paraplegia with thin corpus callosum: a novel mutation in the SPG11 gene and further evidence for genetic heterogeneity

BACKGROUND AND PURPOSE

Autosomal Recessive Hereditary Spastic Paraplegia with Thin Corpus Callosum (AR-HSPTCC) is a clinically and genetically heterogeneous complicated form of spastic paraplegia. Two AR-HSPTCC loci have been assigned to chromosome 15q13-15 (SPG11) and chromosome 8p12-p11.21 respectively. Mutations in the SPG11 gene, encoding the spatacsin protein, have been found in the majority of SPG11 families. In this study, involvement of the SPG11 or 8p12-p11.21 loci was investigated in five Italian families, of which four consanguineous.

METHODS

Families were tested for linkage to the SPG11 or 8p12-p11.21 loci and the SPG11 gene was screened in all the affected individuals.

RESULTS

Linkage was excluded in the four consanguineous families. In the only SPG11-linked family the same homozygous haplotype 4.2 cM across the SPG11 locus was shared by all the three affected siblings. A novel c.2608A>G mutation predicted to affect the splicing was found in exon 14 of the SPG11 gene.

DISCUSSION

This collection of families contributes to highlight the intra and inter locus heterogeneity in AR-HSPTCC, already remarked in previous reports. In particular, it confirms heterogeneity amongst Italian families and reports a new mutation predicted to affect splicing in the spatacsin gene.

Thromboxane biosynthesis and metabolism in relation to cardiovascular risk factors

Enhanced platelet biosynthesis of thromboxane A(2) is associated with several cardiovascular risk factors, as a consequence of a direct effect on platelet biochemistry and/or some form of endothelial dysfunction. Moreover, episodic increases in thromboxane biosynthesis occur in acute coronary and cerebral ischemic syndromes. Thromboxane-dependent platelet activation represents an important mechanism that amplifies the consequences of acute vascular lesions as well as those of longstanding metabolic or hemodynamic disturbances, and results in increased risk of vascular occlusive events.

The recovery of platelet cyclooxygenase activity explains interindividual variability in responsiveness to low-dose aspirin in patients with and without diabetes

BACKGROUND

Interindividual variability in response to aspirin has been popularized as 'resistance'. We hypothesized that faster recovery of platelet cyclooxygenase-1 activity may explain incomplete thromboxane (TX) inhibition during the 24-h dosing interval.

OBJECTIVE

To characterize the kinetics and determinants of platelet cyclooxygenase-1 recovery in aspirin-treated diabetic and non-diabetic patients.

PATIENTS/METHODS

One hundred type 2 diabetic and 73 non-diabetic patients on chronic aspirin 100 mg daily were studied. Serum TXB(2) was measured every 3 h, between 12 and 24 h after a witnessed aspirin intake, to characterize the kinetics of platelet cyclooxygenase-1 recovery. Patients with the fastest TXB(2) recovery were randomized to aspirin 100 mg once daily, 200 mg once daily or 100 mg twice daily, for 28 days and TXB(2) recovery was reassessed.

RESULTS AND CONCLUSIONS

Platelet TXB(2) production was profoundly suppressed at 12 h in both groups. Serum TXB(2) recovered linearly, with a large interindividual variability in slope. Diabetic patients in the third tertile of recovery slopes (≥ 0.10 ng mL(-1) h(-1) ) showed significantly higher mean platelet volume and body mass index, and younger age. Higher body weight was the only independent predictor of a faster recovery in non-diabetics. Aspirin 100 mg twice daily completely reversed the abnormal TXB(2) recovery in both groups. Interindividual variability in the recovery of platelet cyclooxygenase activity during the dosing interval may limit the duration of the antiplatelet effect of low-dose aspirin in patients with and without diabetes. Inadequate thromboxane inhibition can be easily measured and corrected by a twice daily regimen.

Thromboxane and prostacyclin biosynthesis in heart failure of ischemic origin: effects of disease severity and aspirin treatment

SUMMARY BACKGROUND

Thromboembolism is a relatively common complication of chronic heart failure (HF) and the place of antiplatelet therapy is uncertain.

OBJECTIVES

We characterized the rate of thromboxane and prostacyclin biosynthesis in chronic HF of ischemic origin, with the aim of separating the influence of HF on platelet activation from that of the underlying ischemic heart disease (IHD).

PATIENTS AND METHODS

We compared urinary 11-dehydro-thromboxane (TX)B(2), 2,3 dinor 6-keto-PGF(1alpha,) 8-iso-prostaglandin (PG)F(2alpha), and plasma N-terminal pro-brain natriuretic peptide (NT-pro-BNP), asymmetric dimethylarginine (ADMA), and soluble CD40 ligand (sCD40L), in 84 patients with HF secondary to IHD, 61 patients with IHD without HF and 42 healthy subjects.

RESULTS

HF patients not on aspirin had significantly higher urinary 11-dehydro-TXB(2) as compared with healthy subjects (P < 0.0001) and IHD patients not on aspirin (P = 0.028). They also showed significantly higher 8-iso-PGF(2alpha) (P = 0.018), NT-pro-BNP (P = 0.021) and ADMA (P < 0.0001) than IHD patients not on aspirin. HF patients on low-dose aspirin had significantly lower 11-dehydro-TXB(2) (P < 0.0001), sCD40L (P = 0.007) and 2,3-dinor-6-keto-PGF(1alpha) (P = 0.005) than HF patients not treated with aspirin. HF patients in NYHA classes III and IV had significantly higher urinary 11-dehydro-TXB(2) than patients in classes I and II, independently of aspirin treatment (P < 0.05). On multiple linear regression analysis, higher NT-pro-BNP levels, lack of aspirin therapy and sCD40L, predicted 11-dehydro-TXB(2) excretion rate in HF patients (R(2) = 0.771).

CONCLUSIONS

Persistent platelet activation characterizes HF patients. This phenomenon is related to disease severity and is largely suppressable by low-dose aspirin. The homeostatic increase in prostacyclin biosynthesis is impaired, possibly contributing to enhanced thrombotic risk in this setting.

Postprandial hyperglycemia is a determinant of platelet activation in early type 2 diabetes mellitus

BACKGROUND

Chronic hyperglycemia is a major contributor to in vivo platelet activation in diabetes mellitus.

OBJECTIVES

To evaluate the effects of acarbose, an alpha-glucosidase inhibitor, on platelet activation and its determinants in newly diagnosed type 2 diabetic patients.

METHODS

Forty-eight subjects (26 males, aged 61 +/- 8 years) with early type 2 diabetes (baseline hemoglobin A(1c) < or = 7% and no previous hypoglycemic treatment) were randomly assigned to acarbose up to 100 mg three times a day or placebo, and evaluated every 4 weeks for 20 weeks. The main outcome measures were urinary 11-dehydro-thromboxane (TX)B(2) (marker of in vivo platelet activation) and 8-iso-prostaglandin (PG)F(2alpha) (marker of in vivo lipid peroxidation) excretion rate, 2-h postprandial plasma glucose (PPG) after a test meal, and assessment of glucose fluctuations by mean amplitude of glycemic excursions (MAGE).

RESULTS

Baseline measurements revealed biochemical evidence of enhanced lipid peroxidation and platelet activation. As compared with the placebo group, patients treated with acarbose had statistically significant reductions in urinary 11-dehydro-TXB(2) and 8-iso-PGF(2alpha) excretion rate as early as after 8 weeks and at each subsequent time point (between-group P < 0.0001 at 12, 16 and 20 weeks), following earlier decreases in PPG and MAGE. Multiple regression analyses in the acarbose group revealed that PPG was the only significant predictor of 11-dehydro-TXB(2) urinary excretion rate (beta = 0.39, P = 0.002) and MAGE the only predictor of 8-iso-PGF(2alpha) urinary excretion rate (beta = 0.42, P = 0.001).

CONCLUSIONS

Postprandial hyperglycemia is associated with enhanced lipid peroxidation and platelet activation in early type 2 diabetes. A moderate decrease in PPG achieved with acarbose causes time-dependent downregulation of these phenomena, suggesting a causal link between early metabolic abnormalities and platelet activation in this setting.

Aspirin, 110 years later

Although conceived at the end of the 19th century as a synthetic analgesic agent with improved gastric tolerability vs. naturally occurring salicylates, acetylsalicylic acid (marketed as aspirin in 1899) turned out to be an ideal antiplatelet agent about 90 years later, following the understanding of its mechanism of action, the development of a mechanism-based biomarker for dose-finding studies, and the initiation of a series of appropriately sized, randomized clinical trials to test its efficacy and safety at low doses given once daily. At the turn of its 110th anniversary, aspirin continues to attract heated debates on a number of issues including (i) the optimal dose to maximize efficacy and minimize toxicity; (ii) the possibility that some patients may be 'resistant' to its antiplatelet effects; and (iii) the balance of benefits and risks in primary vs. secondary prevention.

Silver syndrome variant of hereditary spastic paraplegia: A locus to 4p and allelism with SPG4

OBJECTIVE

To perform a clinical and genetic study of two large Italian families (RM-36 and RM-51) showing the cardinal clinical features of Silver syndrome (SS), a rare dominantly inherited form of hereditary spastic paraplegia (HSP) complicated by amyotrophy of the small hand muscles.

METHODS

Clinical assessment including neurophysiologic, neuropsychological, and neuroimaging evaluations. Genetic studies included linkage and sequence analyses.

RESULTS

Using a genome-wide survey in the RM-36 family, a novel locus (SPG38) has been identified and mapped within the 13.1-cM region on chromosome 4p16-p15 between markers D4S432 and D4S1599. The RM-51 family was linked to the SPG4 locus at 2p21-p24 and sequence analysis of SPG4 showed a novel frameshift mutation p.Asp321GlyfsX6. Clinical examination of the affected members carrying the mutation showed high frequency of additional clinical features including decreased vibration sense, pes cavus, temporal lobe epilepsy, and cognitive impairment.

CONCLUSIONS

This study demonstrates evidence of a novel locus SPG38 for Silver syndrome (SS) and suggests that genetic defects in SPG4 might lead to broad clinical features overlapped with those of SS.

Determinants of the interindividual variability in response to antiplatelet drugs

The aim of this review article is to discuss the main determinants of the interindividual variability in response to antiplatelet agents. The main sources of pharmacokinetic and pharmacodynamic variability are reviewed, with particular emphasis on aspirin and clopidogrel. The term 'resistance' is uninformative of the mechanism(s) underlying interindividual variability in response to these antiplatelet agents, and is potentially misleading. Increased awareness of the distinct factors potentially interfering with the desired antiplatelet effects of aspirin or clopidogrel, particularly avoidable drug interactions, may ultimately result in better patient management than requesting unnecessary costly tests of platelet function. Similarly, new studies addressing the interindividual variability in response to these antiplatelet agents should rely upon mechanism-based biochemical end-points rather than platelet aggregation measurements. As with any drug used to prevent atherothrombosis, treatment 'failure' can occur with aspirin or clopidogrel perhaps not surprisingly, given the multifactorial nature of atherothrombosis. There is no scientific basis for changing antiplatelet therapy in the face of a treatment 'failure', as we cannot be sure whether a second vascular event occurring in the same patient will reflect the same pathophysiological event that led to the first. Moreover, we have no controlled evidence that changing therapy is a more effective strategy than maintaining an evidence-based therapy.

Genetic heterogeneity of megalencephalic leukoencephalopathy and subcortical cysts

Reported are the clinical, neuroradiologic, and molecular findings in 18 patients with megalencephalic leukoencephalopathy and subcortical cysts (MLC) syndrome. Marked clinical intrafamilial and interfamilial variability in mutation-proven cases was found. A broad spectrum of pathogenetic mutations (missense, splice site, insertion, and deletions) were identified in the MLC1 gene, enlarging the spectrum of allelic variants without a straightforward genotype-phenotype correlation. Five patients did not harbor mutations in MLC1, supporting the existence of at least one other MLC locus.

Lipid and protein oxidation contribute to a prothrombotic state in patients with type 2 diabetes mellitus

Diabetes mellitus (DM) is associated with enhanced lipid oxidation and persistent platelet activation. We investigated whether oxidant stress (OS) also affects circulating proteins and is associated with an abnormal coagulative pattern. In 72 type 2 DM (T2DM) patients, urinary 8-iso-prostaglandin (PG) F2alpha and 11-dehydro-thromboxane B2 (TXM) were measured as markers of lipid peroxidation and platelet activation, respectively. The carbonyl content of plasma proteins (PCARB) was measured as global index of protein oxidation. 8-Iso-PGF2alpha and PCARB levels were higher in DM patients than in controls (P < 0.05). Likewise, both TXM and prothrombin F1+2 levels were higher in diabetics (P < 0.05). By contrast, anticoagulant markers, such as activated protein C, protein C activation peptide, and soluble thrombomodulin (TM) were depressed in T2DM (P < 0.05). In conclusion, OS in T2DM involves circulating proteins and is associated with an unbalanced promotion of procoagulant reactions. These effects in concert with platelet activation may contribute to atherothrombotic complications in T2DM.

SPG3A: An additional family carrying a new atlastin mutation

The authors report on a novel frameshift mutation (c.1688insA) in the SPG3A gene resulting in premature translation termination of the gene product atlastin. These data add a new variant to the second disease gene in autosomal dominant hereditary spastic paraplegia (ADHSP) and lend definitive support to its causative role. By combining direct testing of SPAST and SPG3A, at least 50% of ADHSP families can now receive appropriate genetic diagnosis.

Two novel mutations of the human Δ7-sterol reductase (DHCR7) gene in children with Smith–Lemli–Opitz syndrome

We analyzed seven unrelated children with the Smith-Lemli-Opitz syndrome (SLOS) for mutations in the delta7-sterol reductase gene by using SSCP and direct sequencing. We identified two novel mutations (V330M and R363C) in the DHCR7 gene. Reported mutations found in this study were T93M (3/14 alleles), E448K (2/14), and W151X, G244R, P329L, and R446Q (each found in one allele). The so-called common IVS8-1 G --> C was found in three alleles, confirming its relative rarity among Italian SLOS families. By using a scoring system, clinical severity did not seem to correlate with 7DHC levels and type of mutation. Expanding the spectrum of mutations in SLOS, our study does not support direct genotype-phenotype correlation.

Measurement of cyclooxygenase isozyme inhibition in humans: exploring the clinical relevance of biochemical selectivity

Treatment with highly selective cyclooxygenase-2 inhibitors is associated with significantly fewer serious adverse gastrointestinal events than is treatment with non-selective NSAIDs, provided that the drug employed inhibits COX-2 but not COX-1 at therapeutic plasma levels. Several factors might influence the gastrointestinal (GI) safety of a COX-2 inhibitor administered to an individual patient. These factors include pharmacokinetic and pharmacodynamic variables (e.g. COX-2 selectivity), the interaction of these features with preexisting risk factors for drug-dependent adverse effects, as well as the variability in the individual response. Biochemical selectivity is one of the determinants of the risk of experiencing a serious GI complication during long-term NSAID therapy. The wider the separation between the COX-2 and COX-1 dose-response curves of the inhibitor (an index of biochemical selectivity), the lower the probability of experiencing a clinically relevant inhibition of platelet COX-1 due to an unusually high drug level or intense pharmacodynamic response to a normal drug level. The clinical relevance of biochemical selectivity has to be studied in large GI outcome trials with adequate statistical power to detect realistic differences in these relatively rare events.

The human pharmacology of monocyte cyclooxygenase 2 inhibition by cortisol and synthetic glucocorticoids

BACKGROUND

We studied the concentration dependence of the inhibitory effects of cortisol, 6-methylprednisolone, and dexamethasone on cyclooxygenase-2 (COX-2) expression and activity in human monocytes in response to lipopolysaccharide (LPS) in vitro. Moreover, we characterized the time and dose dependence of the inhibitory effects of 6-methylprednisolone, administered to healthy subjects, on LPS-inducible prostaglandin E2 (PGE2) biosynthesis in whole blood ex vivo.

METHODS

Heparinized whole-blood samples obtained from healthy subjects and patients with rheumatoid arthritis were incubated with LPS (10 microg/ml) for 24 hours at 37 degrees C, and PGE2 was measured in plasma as an index of monocyte COX-2 activity. Comparative experiments were performed in LPS-stimulated isolated monocytes. The levels of COX-2-like immunoreactivity in monocyte lysates were measured by a specific Western blot technique. PGE2 was evaluated by radioimmunoassay.

RESULTS

Nanomolar concentrations of cortisol, 6-methylprednisolone, and dexamethasone suppressed LPS-induced PGE2 biosynthesis both in whole blood and in isolated monocytes in vitro with relative potencies similar to those reported for their anti-inflammatory effects in vivo. The administration of single oral doses (4, 8, or 16 mg) of 6-methylprednisolone caused a dose- and time-dependent inhibition of whole-blood COX-2 activity. Whole-blood samples obtained from patients with rheumatoid arthritis treated with comparable maintenance doses of glucocorticoids produced significantly lower levels of LPS-inducible PGE2 than were found in untreated patients.

CONCLUSIONS

Therapeutic plasma levels of synthetic glucocorticoids down-regulate inducible prostanoid biosynthesis in circulating monocytes. This effect may represent a readily measurable surrogate marker of their clinical efficacy for dose-finding studies.

Oxidative stress and platelet activation in homozygous homocystinuria

BACKGROUND

Severe hyperhomocysteinemia due to cystathionine beta-synthase deficiency (CbetaSD) is associated with early atherothrombotic vascular disease. Homocysteine may exert its effects by promoting oxidative damage. In the present study, we investigated whether in vivo formation of 8-iso-prostaglandin (PG) F(2alpha), a platelet-active product of arachidonic acid peroxidation, is enhanced in CbetaSD and whether it correlates with in vivo platelet activation, as reflected by thromboxane (TX) metabolite excretion.

METHODS AND RESULTS

Urine and blood samples were obtained from patients with homozygous CbetaSD (n=13) and age-matched healthy subjects. Urinary 8-iso-PGF(2alpha) excretion was significantly higher in CbetaSD patients than in control subjects (640+/-384 versus 213+/-43 pg/mg creatinine; P=0.0015) and correlated with plasma homocysteine (rho=0.398, P=0.0076). Similarly, urinary 11-dehydro-TXB(2) excretion was enhanced in CbetaSD (1166+/-415 versus 324+/-72 pg/mg creatinine; P=0.0015) and correlated with urinary 8-iso-PGF(2alpha) (rho=0.362, P=0.0153). Vitamin E supplementation (600 mg/d for 2 weeks) was associated with a statistically significant increase in its plasma levels (from 16.6+/-4.6 to 40.4+/-8.7 micromol/L, P=0.0002) and with reductions in 8-iso-PGF(2alpha) (from 790+/-159 to 559+/-111 pg/mg creatinine, P=0.018) and 11-dehydro-TXB(2) (from 1273+/-383 to 913+/-336 pg/mg creatinine, P=0.028). A statistically significant inverse correlation was found between urinary 8-iso-PGF(2alpha) and plasma vitamin E levels (rho=-0.745, P=0.0135).

CONCLUSIONS

The results of the present study suggest that enhanced peroxidation of arachidonic acid to form bioactive F(2)-isoprostanes may represent an important mechanism linking hyperhomocysteinemia and platelet activation in CbetaSD patients. Moreover, they provide a rationale for dose-finding studies of vitamin E supplementation in this setting.

Respiratory chain defects in hereditary spastic paraplegias

Hereditary Spastic Paraplegias (HSPs) are heterogeneous neurodegenerative disorders whose etiopathogenesis is still unclear. The identification of pathogenic mutations in a gene (SPG7) encoding a mitochondrial metalloprotease suggested that oxidative phosphorylation (OXPHOS) alterations might underlie HSP in a subgroup of patients. We performed clinical, morphological, biochemical, and molecular genetic studies in six HSP patients and in six sporadic patients to investigate OXPHOS in muscle biopsies. Complicated and pure forms were included in our study. Morphological alterations of the type seen in OXPHOS-related disorders were found in three patients. Five patients showed an isolated defect of complex I activity. No mutations in the SPG7 gene were detected. Our results suggest that OXPHOS defects in HSP patients are more common than previously believed.