Chinese medicine offers new Parkinson's treatments
A hooked herb, root extract and a dash of bark
it may sound like a witches' brew, but these compounds could provide treatments for diseases that have so far foiled western doctors, such as Parkinson's and irritable bowel syndrome.
For over 2000 years Chinese doctors have treated "the shakes" – now known as Parkinson's disease – with gou teng, a herb with hook-like branches.Early this year, 115 people with Parkinson's were given a combination of traditional Chinese medical herbs, including gou teng, or a placebo for 13 weeks. At the end of the study, volunteers who had taken the herbs slept better and had more fluent speech than those taking the placebo.Gou teng appears to stabilise symptoms, says Li Min, a traditional Chinese doctor at Hong Kong Baptist University.
Now, Li and her colleagues have figured out how it might work.Preserving dopamineParkinson's symptoms, such as muscle tremors, slowness of movement and rigidity, are caused by the progressive destruction of brain cells that produce dopamine. Previous work has suggested that an abundance of a protein called alpha-synuclein may be to blame.
Current treatments aim to boost levels of dopamine, which only partly alleviates symptoms and does not affect the protein clusters.It is thought that clumps of alpha-synuclein accumulate because brain cells cannot remove them through autophagy – a type of programmed cell death. Mice without the genes needed for autophagy quickly develop Parkinson's-like symptoms.According to Li, autophagy is the only known process that gets rid of abnormal proteins within cells.
"Enhancing this pathway may be key to treating Parkinson's," she says.Li's team screened gou teng for its active compounds and tested which of these compounds increase the rate of autophagy and remove alpha-synuclein. To do this, the team added the compounds to human nerve cells and fruit flies that had been genetically modified to develop alpha-synuclein clusters.Rapamycin connectionOne of the compounds, an alkaloid called isorhy, induced autophagy for alpha-synuclein at a similar rate to a drug called rapamycin. Rapamycin is normally used to suppress the immune system in transplant patients, but has recently been touted as a promising candidate for Parkinson's treatment because it prevents nerve cell death in flies with a Parkinson's-like disease.
However, because rapamycin depresses the immune system, it would have serious side effects for people with Parkinson's. Gou teng, meanwhile, has been taken for centuries with no apparent side effects.Further testing found that isorhy activates autophagy through a different pathway to rapamycin, which may explain why it does not affect the immune system in the same way. Li, who recently presented her results at the Keystone Symposia on Molecular and Cellular Biology in Whistler, British Columbia, Canada, will begin trials of Isorhy in rodents later this year.