In a new study from Massachusetts General Hospital, researchers found a mechanism that protects the brain from the effects of hypoxia, a potentially lethal deprivation of oxygen.
This finding could aid in the development of therapies for strokes, as well as a brain injury that can result from cardiac arrest, among other conditions.
The team previously focused on developing techniques for inducing suspended animation, that is, putting a human’s vital functions on temporary hold, with the ability to “reawaken” them later.
This state of being would be similar to what bears and other animals experience during hibernation.
The team believes that the ability to safely induce suspended animation could have valuable medical applications, such as pausing the life processes of a patient with an incurable disease until an effective therapy is found.
It could also allow humans to travel long distances in space (which has frequently been depicted in science fiction).
A 2005 study found that inhaling a gas called hydrogen sulfide caused mice to enter a state of suspended animation. Hydrogen sulfide, which has the odor of rotten eggs, is sometimes called ‘sewer gas.’
Oxygen deprivation in a mammal’s brain leads to increased production of hydrogen sulfide. As this gas accumulates in the tissue, hydrogen sulfide can halt energy metabolism in neurons and cause them to die.
Oxygen deprivation is a hallmark of ischemic stroke, the most common type of stroke, and other injuries to the brain.
In the study, the team initially set out to learn what happens when mice are exposed to hydrogen sulfide repeatedly, over an extended period.
At first, the mice entered a suspended-animation-like state—their body temperatures dropped and they were immobile.
But then the mice very quickly became tolerant to the effects of inhaling hydrogen sulfide. By the fifth day, they acted normally and were no longer affected by hydrogen sulfide.
Interestingly, the mice that became tolerant to hydrogen sulfide were also able to tolerate severe hypoxia.
The team found that levels of one enzyme, called SQOR, rose in the brains of mice when they breathed hydrogen sulfide several days in a row. They hypothesized that SQOR plays a part in resistance to hypoxia.
When the team ‘turned off’ the expression of SQOR in the brain, the protection against the effects of hypoxia vanished.
Human brains have very low levels of SQOR, meaning that even a modest accumulation of hydrogen sulfide can be harmful.
The researchers hope that in the future scientists will have drugs that could work like SQOR in the body.
Such medications could be used to treat ischemic strokes, as well as patients who have suffered cardiac arrest, which can lead to hypoxia.
If you care about stroke, please read studies about reversing prediabetes linked to fewer heart attacks, strokes and findings of these food linked to serious heart disease and stroke risk.
For more information about stroke prevention and treatment, please see recent studies about this blood thinner drug plus aspirin could strongly reduce stroke risk and results showing that adding these drugs to statins may lower stroke risk.
The study is published in Nature Communications. One author of the study is Fumito Ichinose, MD, Ph.D.
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