Research supports toxoplasmosis link to schizophrenia (FierceBiotech)
Posted March 12, 2009
Research supports toxoplasmosis link to schizophrenia
Scientists have discovered how the toxoplasmosis parasite may trigger the development of schizophrenia and other bipolar disorders.
The team from the University of Leeds’ Faculty of Biological Sciences has shown that the parasite may play a role in the development of these disorders by affecting the production of dopamine – the chemical that relays messages in the brain controlling aspects of movement, cognition and behaviour.
Toxoplasmosis, which is transmitted via cat faeces (found on unwashed vegetables) and raw or undercooked infected meat, is relatively common, with 10-20% of the UK population and 22% of the US population estimated to carry the parasite as cysts. Most people with the parasite are healthy, but for those who are immune-suppressed – and particularly for pregnant women – there are significant health risks that can occasionally be fatal.
Dr Glenn McConkey, lead researcher on the project, says: “Toxoplasmosis changes some of the chemical messages in the brain, and these changes can have an enormous effect on behaviour. Studies have shown there is a direct statistical link between incidences of schizophrenia and toxoplasmosis infection and our study is the first step in discovering why there is this link.”
The parasite infects the brain by forming a cyst within its cells and produces an enzyme called tyrosine hydroxylase, which is needed to make dopamine. Dopamine’s role in mood, sociability, attention, motivation and sleep patterns are well documented and schizophrenia has long been associated with dopamine, which is the target of all schizophrenia drugs on the market.
The team has recently received $250,000 (£160,000) to progress its research from the US-based Stanley Medical Research Institute, which focuses on mental health conditions and has a particular emphasis on bipolar illnesses.
Dr McConkey says: “It’s highly unlikely that we will find one definitive trigger for schizophrenia as there are many factors involved, but our studies will provide a clue to how toxoplasmosis infection – which is more common than you might think – can impact on the development of the condition in some individuals.
“In addition, the ability of the parasite to make dopamine implies a potential link with other neurological conditions such as Parkinson’s Disease, Tourette’s syndrome and attention deficit disorders, says Dr McConkey. “We’d like to extend our research to look at this possibility more closely.”
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Notes to editors:
1. The paper entitled A unique dual activity amino acid hydroxylase in toxoplasma gondii is published today (11 March 2009) in PLoS ONE (Public Library of Science) journal dx.plos.org/10.1371/journal.pone.0004801 . Copies of the paper are available on request.
2. Previous studies have shown that rodents infected by toxoplasmosis become attracted to – rather than fearful of – cat odour. This behavioural manipulation enhances the passage of the parasite to its cat host by making it easier for the cat to catch its prey.
3. The enzyme tyrosine hydroxylase is a crucial step in making L-DOPA (prescribed as levodopa for Parkinson’s Disease), a chemical that is readily converted to the neurotransmitter dopamine.
4. The Faculty of Biological Sciences at the University of Leeds is one of the largest in the UK, with over 150 academic staff and over 400 postdoctoral fellows and postgraduate students.
The Faculty is ranked 4th in the UK (Nature Journal, 457 (2009) doi:10.1038/457013a) based on results of the 2008 Research Assessment Exercise (RAE). The RAE feedback noted that “virtually all outputs were assessed as being recognized internationally, with many (60%) being internationally excellent or world-leading” in quality. The Faculty’s research grant portfolio totals some £60M and funders include charities, research councils, the European Union and industry.