Xenon / Protexeon
May 30
LONDON (Reuters Health) - Xenon, a gas that has been used for decades in anesthesia, is about to enter clinical trials to determine whether it can prevent brain injury following heart surgery. The trials were prompted by the finding, published this week, that the gas protects against nerve cell damage in a rat model of brain injury.
The UK-based researchers say that it may be possible to use the gas to treat injury after stroke, or following brain or spinal cord injury.
Professor Nicholas Franks from Imperial College and colleagues there and elsewhere in London note that xenon blocks the action of the NMDA glutamate receptor, a molecule on the surface of nerve cells that serves as a critical factor in a pathway that leads to nerve cell death.
The investigators found that when rats were treated with xenon before the onset of brain injury, damage was reduced by up to 45% compared with untreated animals. The concentrations of the gas used were below those used in anesthesia, the research team notes.
Xenon also prevented injury in cultured mouse nerve cells, according to the report published in the June edition of Anesthesiology. It completely protected against nerve cell damage induced by oxygen deprivation and reduced chemically induced damage by up to 80%.
"We may eventually be able to prevent brain damage following stroke, as well as nerve cell death after brain and spinal cord injuries," study co-author Professor Mervyn Maze said in an interview with Reuters Health.
"Our upcoming clinical trials will test whether xenon prevents brain damage after heart surgery," said Maze. The trials, in which xenon will be administered during heart surgery as part of the anesthetic regimen, will be conducted in the UK and the USA, he noted.
Already the results of further studies in rodents of the effects of xenon in heart bypass injury have been encouraging, he pointed out.
"At present, nerve cells cannot regenerate when they die, but by using xenon, we may be able to prevent injury occurring in the first place," Maze added.
"Xenon is naturally occurring, remarkably safe, simple to administer, and has observable effects 1 minute after treatment. It has been used as an anesthetic for more than 50 years," said Maze. "Ironically, other anesthetics that inhibit this type of glutamate receptor can actually damage nerve cells. Xenon is the only one that doesn't."
Maze said that his team is currently in discussion with the US Food and Drug Administration about planned clinical trials of xenon. "They have been very helpful and we are almost agreed that there will be 250 patients in each of two multicenter trials, one in the US and one in the UK," he said.
"The exciting thing about these results is there is a huge unmet clinical need. Xenon is also a renewable resource and it has already had years of clinical use, so it has a proven safety track record," Maze stated.
Imperial College has formed a spin-off company, Protexeon, in collaboration with Pennsylvania-based Air Products and Chemicals, Inc., to "develop clinical applications" of the xenon technology, the college said in a press release.
SOURCE: Anesthesiology 2002;96:1485-1491. |
