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A proposal advocating the use of toxicogenomics as a test method for rapid screening of chemicals

Summary of the submission (1) by Antidote Europe to the OECD and to ECVAM in September 2007

The EU has acknowledged the fact that thousands of new chemicals have been allowed onto the market over the past several decades without due consideration for their potential deleterious effects on human health and the environment. Senior EU officials have already conceded that the current legislative system for chemicals has been largely unable to identify the risks posed by many chemicals and is slow to act where risks have been established.

This "admission of guilt" has, in part, taken the form of the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) program, which entered into force on 1st June 2007. Although the principal aim of REACH is to tackle the problem of untested chemicals, the fact that it will not be completed for at least a decade, means that public health will continue to be compromised for the foreseeable future.

Whilst Antidote Europe and the REACH program share the same basic goal of wanting to protect human health, the path suggested by both differs significantly on the issue of animal testing. Antidote Europe maintains that the key to achieving faster and more reliable results for people exposed to pesticides, air fresheners, food additives, nail polish and any other chemical substance is by studying human cells and not rats, dogs and monkeys or any other animal species.

The proposal summarised here, advocating the use of such testing methods utilising human cells, was submitted by Antidote Europe to the EU regulatory authorities in September 2007. The regulatory bodies who deal with these issues are the Organisation for Economic Co-operation and Development (OECD) and the European Centre for the Validation of Alternative Methods (ECVAM). Both set similar standards for the submission of new or updated test methods (2,3).

The test method in question is based on modern developments in molecular biology, and in particular, the science of molecular toxicology. An important branch of this science is called toxicogenomics )- the study of how the genes inside living cells respond to environmental stressors or toxicants. By studying selected genes, whose behaviour is known to be associated with early warning signs of damage to cell function, it is possible to obtain an indication of how cells will respond to a given chemical. Indeed, toxic endpoints are intimately related to specific alterations in gene expression. These changes in gene activity can be observed in a matter of days, whereas the equivalent animal test may require up to two years in order to yield a result - a result of questionable relevance to human health.

The test method submitted to the OECD utilises a selection of the human cells most susceptible to the effects of toxic chemicals. These include cells from the liver, the kidneys, the nervous system, the digestive system, the immune system and the reproductive system. Using modern laboratory equipment, it becomes possible to test thousands of chemicals on these cells and to analyse the results within a matter of days - not the months or years associated with animal tests. Another major advantage of this system is the ability to test combinations of chemicals, in order to study the effect of chemical 'cocktails' on the cell defence mechanisms. Traditional animal tests can cope with only one chemical at a time.

Whilst toxicogenomics may not always predict the effect of chemical damage on a whole human being, it is nevertheless far more relevant as an early screening method than animal tests. And when used in combination with other technologies, such as microfluidics, lab-on-a-chip and virtual ADME/TOX studies, it should be possible to do away with animal tests altogether.

The test method submission by Antidote Europe therefore calls upon the OECD to:
1. Promote the concept of toxicogenomics as a universal screening tool, as part of an integrated testing strategy (i.e. high throughput screening) prior to any investigation in integrated living systems; and
2. Make compulsory the submission of the resulting data to a publicly available toxicogenomics database.

A "proof of principle" as to the efficacy of toxicogenomics as a screening method has been demonstrated in a study by Antidote Europe on several test chemicals, including ingredients found in pesticides and cosmetics. The results have been logged in ArrayExpress in compliance with the MIAME (Minimum Information About a Microarray Experiment) database.

(1) The entire submission can be obtained from Antidote Europe upon request to info@antidote-europe.org

(2) OECD Series on testing and assessment Number 34 ; Guidance document on the validation and international acceptance of new or updated test methods for hazard assessment ; Organisation for Economic Co-operation and Development 18 August 2005

(3) http://ecvam.jrc.it/index.htm