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Motor neurone clue in blue-green algae

Toxic link A toxin in blue-green algae could be taken up by the body's proteins and trigger motor neurone disease, new research suggests.

Recent studies have identified a link between the consumption of food or water contaminated by blue-green algae and motor neurone disease.

Blue-green algae (cyanobacteria) produce a neurotoxic amino acid called β-methylamino-L-alanine, or BMAA, but how this chemical could damage the central nervous system has remained unclear.

In a paper published today in PLOS ONE, researchers from the University of Technology, Sydney (UTS) and the Institute of EthnoMedicine in the US, show BMAA has a similar structure to an amino acid, serine, that is used to build proteins.

First author Dr Rachael Dunlop, of UTS, says the similarities between serine and BMAA mean when the toxin is present in the system it can be mistaken for serine and incorporated into human proteins.

This damages the proteins and inhibits their function - over time causing cell death.

"Common amongst all neurodegenerative diseases is the problem of clumps of proteins overloading cells and forcing them to 'commit suicide'. This research reveals that BMAA can also trigger this process," says Dunlop.

Motor neurone disease cases

Co-author Dr Paul Cox, of the Institute of EthnoMedicine, originally identified BMAA as the cause of motor neurone disease in the indigenous people of Guam, the Chamorros, after they were found to suffer the disease up to 100 times more often than other people.

The Chamorros used seeds from cycad palms to make flour, and regularly ate fruit bats, which also ate the seeds. Both these foodstuffs contained BMAA.

Since then, research has revealed increased incidences of motor neurone disease in people who live near lakes subject to frequent cyanobacterial blooms, among consumers of contaminated shellfish.

Increased incidences have also been found in soldiers deployed to the Gulf War between 1990-1991.

Dunlop says soldiers who fought in the first Gulf War have a two to three times higher incidence of motor neurone disease than those who went to the Gulf War but did not fight.

Research by colleagues in Qatar has revealed the desert sands have a crust of cyanobacteria.

"If you water the desert, and wait, after five minutes the sand turns green," says Dunlop.

"The theory is the soldiers were breathing in cyanobacteria particles because they were marching across the desert behind trucks that were churning up the desert crust."

Progressive paralysis

Motor neurone disease, also known as Lou Gehrig's disease and amyotrophic lateral sclerosis, is a neurodegenerative disease resulting in progressive paralysis and, eventually, death. Over 90 per cent of motor neurone diseases have no known cause or cure.

In Australia about one in 5000 people aged over 50 will be affected, with more deaths annually from motor neurone disease than HIV/AIDS.

Dunlop says the breakthrough in understanding how BMAA interacts with human proteins is the result of interdisciplinary work between plant and medical scientists.

"It's been known by plant scientists that these compounds can create illness, but ethnobotanists and medical scientists don't talk to each other that much," she says.

The US-based members of the team are currently using serine in clinical trials involving patients with motor neurone disease.

Dunlop says the hope is by adding lots of serine into the nervous system they can stop the damage caused by BMAA.

She says the take-home message of the research is for people to avoid contact with algal blooms.

"Blue-green algae is ubiquitous in Australia but not everyone has motor neuronee disease, so there are likely several other factors involved in triggering the disease," she says.

"But when people are warned to stay away from blue-green algae they should heed the warning."