New Cause Found of Brain Cell Death After Stroke

When brain cells are deprived of oxygen and nutrients following a stroke, a special channel on those cells is activated, triggering a lethal chain reaction that causes the cells to produce large quantities of free radicals, which break down the cell's DNA and other components and ultimately result in the death of the brain cells. The findings were reported in the December 26, 2003, issue of Cell.

The free radicals cause the channel, called TRPM7, to become even more active, causing massive overproduction of free radicals and the death of cells. Prior to this discovery, scientists thought the reason why brain cells died when deprived of oxygen and nutrients was due to their release of glutamate, which attaches to a channel called the NMDA receptor, located on the surface of neighboring brain cells. This causes the NMDA channel to open, allowing an influx of calcium ions into the brain cells, causing them to die. Many medications developed for treating stroke were aimed at blocking the effects of glutamate on NMDA receptors, but they failed to reduce brain damage in humans. The new findings lead researchers to believe that interfering with the activity of TRPM7 allows brain cells to survive for more than three hours without oxygen and vital nutrients.

"This is a quantum leap forward in understanding how stroke causes brain damage,” says Dr. Michael Tymianski, associate professor of surgery and physiology at the University of Toronto (Canada). "Now we can see the bigger picture of why brain cells die from stroke.”





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