BioEd Online

It seems that mice can be coaxed into a hibernation-like state by a whiff of hydrogen sulphide, the gas found in rotten eggs.

The discovery could improve the preservation of organs or tissues for transplants, and could lead to more effective treatments for illnesses as diverse as cancer and stroke.

Hydrogen sulphide can be deadly in high concentrations, causing burns and interfering with respiration. But it is also produced in small quantities by animals, in which it is thought to play a vital role in controlling body temperature and metabolism.

Mark Roth, a biochemist at the Fred Hutchinson Cancer Research Center, Seattle, and his colleagues tried exposing mice to air laced with relatively low concentrations of the gas: within minutes, the mice seemed to fall unconscious. Their core body temperature dropped by some 20ºC, and their breathing slowed from about 120 breaths a minute to fewer than 10, the team reports in Science¹.

When re-exposed to clean air after six hours, the mice bounced back without any evident side-effects, says Roth. "This indicates that it's possible to decrease metabolic rate on demand," says Roth.

Oxygen delivery

By shutting down metabolism, the body's need for oxygen diminishes, which could "revolutionize treatment for a host of human ills", says Roth.

In conditions such as stroke, cardiac arrest and other traumas, healing can be limited by the amount of oxygen that can be supplied to damaged tissues. This could be helped by reducing the body's overall need for oxygen, says Samuel Tisherman, professor of surgery and critical-care medicine at the University of Pittsburgh in Pennsylvania.

"Decreasing total oxygen demand during that period of time is of interest," Tisherman says. And inducing a state of suspended animation would buy doctors more time to address the trauma.

Roth says the gas may also help with cancer treatments. Radiotherapy works best when the target cells are well supplied with oxygen, but it can be detrimental to healthy cells. Inducing hibernation reduces oxygen demand in healthy cells and so should help to protect them.

"A lot of work needs to be done to determine how to use the treatment, when to use it, and what kind of benefits you get," cautions Tisherman.

To that end, Roth and colleagues are working to induce a state resembling suspended animation in larger animals.