神経科学：炭疽毒素がマウスの痛みを和らげる

Anthrax toxin — the toxin released by the lethal bacterium Bacillus anthracis — can reduce pain in mice, according to a study published in Nature Neuroscience. These findings suggest that the anthrax toxin could represent a potential new therapeutic option for the treatment of pain, although further research is needed to determine its exact mechanism of action and potential relevance in other organisms.

Nociceptors are specialized sensory neurons that warn us when we encounter harmful environmental changes — or stimuli — such as extreme temperature or pressure. Their signals are translated as pain sensations in the brain. Nociceptors can also sense certain types of pathogenic bacteria, either directly or via toxins that bacteria produce. Some bacteria, however, release substances that can block pain signals in order to evade detection.

Isaac Chiu and colleagues reveal that specialized sensory neurons next to the spinal cord, known as dorsal root ganglion neurons, express receptors which bind to anthrax toxin in both mice and humans. Furthermore, treating mice with edema toxin — a form of anthrax toxin — reduced their sensitivity to painful stimuli, such as heat or pinpricks. This effect was dependent on sensory neurons expressing the anthrax receptor. Although the exact mechanisms by which edema toxin reduces pain signalling have yet to be determined, it was found to block signalling between sensory neurons in both mouse and human stem-cell models.

The authors conclude that this knowledge of interactions between derivatives of anthrax toxin and pain receptors could prompt the development of new research tools and improved therapeutic agents for treating pain.