Alan M. Goldberg

A roadmap for the development of alternative (non-animal) methods for systemic toxicity testing - t4 report

Systemic toxicity testing forms the cornerstone for the safety evaluation of substances. Pressures to move from traditional animal models to novel technologies arise from various concerns, including: the need to evaluate large numbers of previously untested chemicals and new products (such as nanoparticles or cell therapies), the limited predictivity of traditional tests for human health effects, duration and costs of current approaches, and animal welfare considerations. The latter holds especially true in the context of the scheduled 2013 marketing ban on cosmetic ingredients tested for systemic toxicity. Based on a major analysis of the status of alternative methods (Adler et al., 2011) and its independent review (Hartung et al., 2011), the present report proposes a roadmap for how to overcome the acknowledged scientific gaps for the full replacement of systemic toxicity testing using animals. Five whitepapers were commissioned addressing toxicokinetics, skin sensitization, repeated-dose toxicity, carcinogenicity, and reproductive toxicity testing. An expert workshop of 35 participants from Europe and the US discussed and refined these whitepapers, which were subsequently compiled to form the present report. By prioritizing the many options to move the field forward, the expert group hopes to advance regulatory science.

THE DETERMINATION OF PICOMOLE AMOUNTS OF ACETYLCHOLINE IN MAMMALIAN BRAIN

Abstract— In any assay for the determination of acetylcholine based on the conversion of choline to a product, the immediate problem is the removal of endogenous choline. Other published enzymatic assays have taken advantage of electrophoresis to accomplish this goal. In the assay to be described, this is accomplished by the enzymatic phosphorylation of endogenous choline by choline kinase. Once this reaction is complete, endogenous acetylcholine is simultaneously hydrolysed and then phosphorylated with [32P]ATP. The labelled product [32P]phosphorylcholine is separated from the labelled substrate by precipitation of the ATP and further separation is accomplished on microcolumns of ion exchange resin. Using this methodology, picomole amounts of acetylcholine, derived from tissue, can be measured.

Subtle Consequences of Methylmercury Exposure: Behavioral Deviations in Offspring of Treated Mothers

Overt neurological impairment is the endpoint currently used to document a case of methylmercury poisoning. No consideration is given to possible subtle consequences. Offspring from mice exposed to methylmercury on day 7 or 9 of pregnancy were apparently unaffected during postnatal development. However, subtle behavioral differences between treated and control offspring were found when the overtly normal animals were tested in an open field and evaluated in a swimming apparatus at 1 month of age. Brain weight, protein, choline acetyltransferase, and cholinesterase were not significantly altered.

Meeting Report: Hazard Assessment for Nanoparticles—Report from an Interdisciplinary Workshop

In this report we present the findings from a nanotoxicology workshop held 6–7 April 2006 at the Woodrow Wilson International Center for Scholars in Washington, DC. Over 2 days, 26 scientists from government, academia, industry, and nonprofit organizations addressed two specific questions: what information is needed to understand the human health impact of engineered nanoparticles and how is this information best obtained? To assess hazards of nanoparticles in the near-term, most participants noted the need to use existing in vivo toxicologic tests because of their greater familiarity and interpretability. For all types of toxicology tests, the best measures of nanoparticle dose need to be determined. Most participants agreed that a standard set of nanoparticles should be validated by laboratories worldwide and made available for benchmarking tests of other newly created nanoparticles. The group concluded that a battery of tests should be developed to uncover particularly hazardous properties. Given the large number of diverse materials, most participants favored a tiered approach. Over the long term, research aimed at developing a mechanistic understanding of the numerous characteristics that influence nanoparticle toxicity was deemed essential. Predicting the potential toxicity of emerging nanoparticles will require hypothesis-driven research that elucidates how physicochemical parameters influence toxic effects on biological systems. Research needs should be determined in the context of the current availability of testing methods for nanoscale particles. Finally, the group identified general policy and strategic opportunities to accelerate the development and implementation of testing protocols and ensure that the information generated is translated effectively for all stakeholders.

Pharmacological and neurochemical investigations of lead-induced hyperactivity

Abstract Mice chronically exposed to inorganic lead from birth, demonstrate levels of spontaneous motor activity approximately three times higher than coetaneous controls. In addition, their behavioural responses to (+)- and (−)-amphetamine, methylphenidate, and phenobarbital are altered. To further clarify the mechanism of action of lead involved in the induction of hyperactivity and altered pharmacological response, lead-treated mice were administered apomophrine, atropine, neostigmine, physostigmine, α-methylparatyrosine, benztropine, chlorpromazine, l -3,4-dihydroxyphenylalanine ( l -Dopa), fenfluramine and 2-dimethylaminoethanol. A comparison of the effects of these compounds on motor activity and reactivity showed significant differences between control and lead-treated hyperactive mice. Neurochemical investigations of lead-induced hyperactivity were undertaken in chronically treated hyperactive mice by measurement of steady state levels and of synaptosomal transport. The so-called high affinity transport systems were studied for the following putative neurotransmitters, precursors, and amino acids: choline, tyrosine, phenylalanine, norepinephrine, dopamine, leucine, glycine, 5-hydroxytryptamine and γ-aminobutyric acid. Significant changes in high affinity synaptosomal transport were found for choline, dopamine and tyrosine. The transport systems of other suspected neurotransmitters and the amino acid leucine were not different between lead-treated and coetaneous control mice. In addition, steady-state levels of acetylcholine, dopamine, and norepinephrine were measured in forebrains. Norepinephrine levels were increased, while dopamine and acetylcholine levels were not different in lead-treated animals.

Lead-induced behavioral dysfunction: An animal model of hyperactivity

Although clinically lead poisoning is thought to cause several serious behavioral problems, a causal relationship between lead ingestion and behavioral dysfunction has not been shown. An animal model of lead poisoning was developed in which suckling mice were exposed to lead acetate from birth indirectly through their mothers and then directly after weaning. For the first 60 days, no deaths of offspring occurred due to lead but their growth and development were significantly retarded. Epidemiological evidence exists for the coincidence of lead exposure and hyperactivity syndromes in children. Activity of offspring was measured between 40 and 60 days of age. Treated mice were more than three times as active as agematched controls. Treated and control animals were given drugs used in the treatment and diagnosis of minimal brain dysfunction hyperactivity in children: d- and l-amphetamine, methylphenidate, phenobarbital, and chloral hydrate. Lead-treated hyperactive mice responded paradoxically to all drugs except chloral hydrate: that is, d- and l-amphetamine and methylphenidate suppressed hyperactivity, while phenobarbital increased their levels of motor activity. Chloral hydrate was an effective sedative. Implications of these findings are discussed for the study of the central effects of lead poisoning and for the relationship between lead poisoning and minimal brain dysfunction hyperactivity.

A lead-induced behavioral disorder

Abstract Mice were exposed to lead from birth by substituting solutions of lead acetate (2, 5, and 10 mg/ml) for the drinking water of mice 12 hours after parturition. Controls received equal concentrations of sodium acetate. There were no deaths in mothers or offspring due to treatment, but growth and development were retarded in the lead-treated offspring. It has recently been suggested that lead exposure may account for some incidences of hyperactivity and retardation in children. Activity of offspring was measured between 40 and 60 days of age for four consecutive days. Treated mice were more than three times as active as age-matched controls. These studies show that chronic ingestion of lead can produce a significant behavior disorder in mice.

Workgroup Report: Incorporating In Vitro Alternative Methods for Developmental Neurotoxicity into International Hazard and Risk Assessment Strategies

This is the report of the first workshop on Incorporating In Vitro Alternative Methods for Developmental Neurotoxicity (DNT) Testing into International Hazard and Risk Assessment Strategies, held in Ispra, Italy, on 19–21 April 2005. The workshop was hosted by the European Centre for the Validation of Alternative Methods (ECVAM) and jointly organized by ECVAM, the European Chemical Industry Council, and the Johns Hopkins University Center for Alternatives to Animal Testing. The primary aim of the workshop was to identify and catalog potential methods that could be used to assess how data from in vitro alternative methods could help to predict and identify DNT hazards. Working groups focused on two different aspects: a) details on the science available in the field of DNT, including discussions on the models available to capture the critical DNT mechanisms and processes, and b) policy and strategy aspects to assess the integration of alternative methods in a regulatory framework. This report summarizes these discussions and details the recommendations and priorities for future work.

CONTROL OF ACETYLCHOLINE SYNTHESIS—THE INHIBITION OF CHOLINE ACETYLTRANSFERASE BY ACETYLCHOLINE

Abstract— The inhibition of choline acetyltransferase by acetylcholine in vitro occurs at a concentration of 10 mm and increases progressively to 45 per cent at a concentration of 100 mm. The inhibition is competitive for choline and noncompetitive for acetyl‐CoA. It is suggested that the synthesis of acetylcholine may be controlled by its accumulation in synaptic vesicles.

Meeting report: alternatives for developmental neurotoxicity testing.

Developmental neurotoxicity testing (DNT) is perceived by many stakeholders to be an area in critical need of alternatives to current animal testing protocols and guidelines. To address this need, the Johns Hopkins Center for Alternatives to Animal Testing (CAAT), the U.S. Environmental Protection Agency, and the National Toxicology Program are collaborating in a program called TestSmart DNT, the goals of which are to: (a) develop alternative methodologies for identifying and prioritizing chemicals and exposures that may cause developmental neurotoxicity in humans; (b) develop the policies for incorporating DNT alternatives into regulatory decision making; and (c) identify opportunities for reducing, refining, or replacing the use of animals in DNT. The first TestSmart DNT workshop was an open registration meeting held 13–15 March 2006 in Reston, Virginia. The primary objective was to bring together stakeholders (test developers, test users, regulators, and advocates for children’s health, animal welfare, and environmental health) and individuals representing diverse disciplines (developmental neurobiology, toxicology, policy, and regulatory science) from around the world to share information and concerns relating to the science and policy of DNT. Individual presentations are available at the CAAT TestSmart website. This report provides a synthesis of workgroup discussions and recommendations for future directions and priorities, which include initiating a systematic evaluation of alternative models and technologies, developing a framework for the creation of an open database to catalog DNT data, and devising a strategy for harmonizing the validation process across international jurisdictional borders.