The findings were published recently in Science and will be the subject of an editorial in next month's issue of Nature Reviews Neuroscience.
"We've known for 40 years about chemicals flowing out of cells after stroke, but nobody knew the exact process ?so we went looking for the death channel. And we found it," says Roger Thompson, a UBC Psychiatry post-doctoral Fellow who made the discovery, along with graduate student Ning Zhou and Psychiatry Prof. Brian MacVicar, all members of the Brain Research Centre at UBC Hospital and of Vancouver Coastal Health Research Institute.
The researchers found, in animal models, that brain cell membranes were disrupted at the site of gap junction hemichannels. Gap junctions are connections that allow molecules and ions to flow between cells. Junctions are composed of two hemichannels that bridge the intercellular space.
Until now, scientists believed the disruption to occur at the site of glutamate channels. Glutamate is one of the brain's most abundant chemical messengers. However, therapeutic strategies targeted at glutamate channels failed to prevent brain cell death.
"Our discovery was unexpected ?we're now going to change channels and pursue a completely different research direction," says MacVicar, Canada Research Chair in Neuroscience. "This finding offers new possibilities for stroke therapies and reinforces the value of investing in basic science research."
When stroke occurs, hemichannels can form outside the junction and leak chemicals. The process drastically disrupts levels of critical brain cell ingredients such as calcium and potassium, and is a ssociated with rapid cell death.
Every year, 50,000 Canadians suffer a stroke. Another 300,000 people are living with the consequences of stroke, which is the leading cause of adult disability in Canada.
The next step in the investigation will be to determine the cause of the hemichannel malfunction. Scientists can then develop a compound to block brain cell hemichannels from opening, says MacVicar. Therapies for stroke patients may be available within five to 10 years, he adds.