Stéphane Loriot

Mutagenicity of diesel engine exhaust in the Ames / Salmonella assay using a direct exposure method

The aim of this study was to investigate the potential mutagenic activity of diesel engine exhaust in the Ames/Salmonella assay using a direct aerosol exposure system. So, TA 98 and TA 100 strains, with or without added S9 mix, were exposed to diesel emissions after varying degrees of filtration. Variants of these two strains, deficient in nitroreductase (TA 98NR and TA 100NR) or over-expressing O-Acetyl Transferase (YG 1024 and YG 1029), were also exposed to total (unfiltered) diesel exhaust to highlight the putative mutagenicity of any nitro-PAHs present in these emissions. Mutagenic activity of the diesel exhaust was demonstrated on Salmonella typhimurium, strains TA 100 and variants TA 100 NR and YG1029. The use of a particle filter did not modify the genotoxicity of the diesel emissions, indicating a major contribution of the gas phase to the mutagenicity of these diesel emissions. The prominent role of the particulate-associated nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) claimed by some authors working on diesel exhaust organic extracts was not confirmed by our results with native diesel exhaust exposure. Our results show that the gas phase is potentially more mutagenic than the particles alone.

QT interval correction for drug-induced changes in body temperature during integrated cardiovascular safety assessment in regulatory toxicology studies in dogs: A case study.

INTRODUCTION Cardiovascular safety assessment requires accurate evaluation of QT interval, which depends on the length of the cardiac cycle and also on core body temperature (BT). Increases in QT interval duration have been shown to be associated with decreases in BT in dogs. METHODS An example of altered QT interval duration associated with changes in body temperature observed during a 4-week regulatory toxicology study in dogs is presented. Four groups of Beagle dogs received the vehicle or test item once on Day 1, followed by a 4-week observation period. Electrocardiogram (ECG) parameters were continuously recorded on Days 1 and 26 by jacketed external telemetry (JET). Core body temperature (BT) was measured with a conventional rectal thermometer at appropriate time-points during the Day 1 recording period. RESULTS Decreased BT was observed approximately 2h after treatment on Day 1, along with increased QT interval duration corrected according to the Van de Water formula (QTcV), but the effect was no longer observed after correction for changes in BT [QTcVcT=QTcV-14(37.5-BT)] according to the Van der Linde formula. No significant changes in QTcV were reported at the end of the observation period, on Day 26. DISCUSSION The present study demonstrates that core body (rectal) temperature can easily be monitored at appropriate time-points during JET recording in regulatory toxicology studies in dogs, in order to correct QT interval duration values for treatment-related changes in BT. The successful application of the Van der Linde formula to correct QTc prolongation for changes in BT was demonstrated.

Proposed QT-interval correction method for the influence of changes in core body temperature based on circadian variations in conscious non-restrained cynomolgus monkeys

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In vitro screening method for the evaluation of histamine release from rat peritoneal cells

Rat peritoneal mast cells offer a convenient approach for the evaluation of histamine release by chemicals. Peritoneal mast cells obtained by centrifugation on density gradients are routinely used for the assessment of histamine release. Manipulation of the cells during this purification step may lead to cell membrane damage and spontaneous release of histamine. The purpose of the present study was to evaluate two procedures of peritoneal cell purification. Rat peritoneal cells were purified (i) by three centrifugations in PIPES only (PIPES purification) or (ii) by three centrifugations in PIPES followed by density gradient centrifugation in Percoll (PIPES/Percoll purification). The effect of a reference compound 48/80 was evaluated at two or three concentrations (0.1, 1 and 10 μg/ml) under several experimental conditions

Safety assessment of auditory function in rat: Ototoxicity and measurements of Auditory Brainstem Response

Evaluation of the auditory function is part of the functional assessment of the Central Nervous System in the follow-up studies mentioned in ICH S7A guideline for Safety Pharmacology Studies for Human Pharmaceuticals. The Auditory Brainstem Response globally tests functional integrity of the inner ear and auditory nerve, and their ability to properly transmit a sound signal along the whole pathway to the brainstem. The purpose of the present study was to validate the Auditory Brainstem Response (ABR) as a general evaluation of auditory loss in rats. Cisplatin was used to induce hearing function impairment as it is a well documented ototoxic compound which induces early outer hair cell death through free radical generations beginning at the basal turn of the cochlea.

Use of a functional observational battery in the assessment of safety pharmacology endpoints in general toxicology studies in conscious cynomolgus monkey

Assessment of a drug effect on the Central Nervous System (CNS) during the preclinical development of a new chemical entity is part of the ICH S7A guideline on Safety Pharmacology studies for human pharmaceuticals. This is commonly performed in dedicated safety pharmacology studies involving mainly rodents. However, for biotechnology derived products, integrated safety pharmacology assessment in regulatory toxicology studies are required (ICH S6, S9 and M3(R2)). These integrated safety pharmacology studies are generally focused on cardiovascular and respiratory functions, but also on the central nervous system in appropriate animal models. The non-human primate is one of the large animal models commonly used for the development of biologics. Therefore, the aim of this study was fi rst to validate a functional observational battery (FOB) as a neurobehavioral screening method that could be easily integrated in a 4-week toxicity study or greater. The second objective of the study was to defi ne and validate a tool to help in the interpretation of the results obtained from these tests. The validation of this model was performed using two reference compounds: D-amphetamine hemisulfate salt, a sympathomimetic molecule known to increase the CNS activity, and ketamine hydrochloride, an NMDA receptor antagonist known to induce a state referred to as “dissociative anaesthesia”.