Hypoxia is a potentially deadly lack of oxygen and is especially lethal for brain cells. When there is not enough oxygen in the brain, extra hydrogen sulfide is produced, a gas commonly found in sewers and geysers and known for the odor of rotten eggs. As hydrogen sulfide accumulates in the brain, it stops neurons from producing energy, thereby killing them.
To figure out how to treat hypoxia, a group of researchers wanted to understand how toxic levels of hydrogen sulfide are processed in the brain. First, they exposed a group of mice to the gas intermittently for several days in a row. After the initial exposure, the mice entered a hibernation-like state, in which they became immobile and their body temperatures dropped. However, their brains quickly adapted to the elevated levels of hydrogen sulfide and they were back to acting completely normal after breathing the gas on the fifth day. After that, the mice were able to tolerate severe hypoxia.
When studying the animals’ brains after this experiment, the researchers found elevated levels of a specific enzyme called sulfide: quinone oxidoreductase (SQOR) that metabolizes hydrogen sulfide. To verify that higher levels of this enzyme translated to better hypoxia tolerance, the scientists artificially increased SQOR levels in a separate group of mice and found that they were also much less affected by hypoxia than the untreated control group.
Unfortunately, human brains naturally have low levels of SQOR, making us particularly susceptible to hydrogen sulfide accumulation. However, this new research gives scientists a clear path towards protecting our brains from the effects of hypoxia by developing a drug that either increases levels of the SQOR enzyme or mimics its function. From strokes to cardiac arrests to severe brain injuries, such a drug could save many lives.