A new study has found that an ordinary microorganism may directly cause the itching it parasitizes.
If you're itchy, it could be that a microorganism has made its home in you, producing a chemical that acts directly on your nerve cells and triggers your urge to tickle.
Here's a hint of some new research that suggests that a certain type of bacteria, Staphylococcus aureus, can release an enzyme that produces an itchy sensation.
What's more, according to a new report in the journal Cell, a drug that interferes with this effect could stop itching in lab mice.
"It's exciting because the drug has already been approved for another disease, but it could be useful for itchy conditions like eczema," said Isaac Chiu, a scientist at Harvard Medical School who studies microbes' interactions with nerve cells. ”
He points out that eczema or atopic dermatitis is actually quite common, affecting about 20% of children and 10% of adults.
In the past, research on pruritus has focused on the role of immune response and inflammation in producing itchy sensations, Chiu says. People with eczema often take medications that target immune system molecules.
But scientists have also known for a long time that people with eczema often have Staphylococcus aureus on their **, although it has never been clear what role the bacteria might play in this situation, Chiu said.
Chiu's previous lab work led him to realize that bacteria can act directly on nerve cells to cause pain.
"This begs the question: Are certain microbes, like Staphylococcus aureus, also involved in itching in some way," Chiu said"Do microbes play a role in talking to itchy neurons?”
He and his colleagues first discovered that placing the bacterium on the rat's ** caused the animals to scratch violently, causing the damaged ** to spread beyond the original exposed site.
The researchers then discovered that once the bacterium began to grow on **, it released a series of enzymes. They tested each one to see if it triggered itching.
It turns out that a bacterial enzyme called protease V8 seems to do the job.
Further research has shown how this bacterial enzyme activates a protein on nerve cells. This creates a nerve signal that the brain will take for itching.
Our study is indeed the first to show that this microorganism can directly activate itchy neurons and cause itching," said Teresa Teng, a researcher at Harvard Medical School.
Proteins that are activated by bacteria are also present in certain blood cells and are involved in blood clotting. It has been proven that protein activation on neurons can be blocked by anticoagulant drugs already on the market.
"We're lucky that this is already an FDA-approved compound," Deng said. He said they had just conducted an experiment on experimental animals. "We administered them orally with this drug**, and it completely stopped the itching and scratching that we usually observe when administering bacteria to mice. ”
Maybe it's possible to make the same drug in some kind of skin cream or topical medication, she said.
Brian Kim, a physician and researcher at the Icahn School of Medicine at Mount Sinai in New York, who studies the immune factors that cause itching, said the new findings were "surprising."
He noted that in the past, some doctors used diluted bleach or oral antibiotics for eczema, and their theory was that killing Staphylococcus aureus might have some beneficial effects.
"We're very hungry for anything," Kim said. She points out that itching can be very uncomfortable and even debilitating, as constant scratching can lead to impaired **, poor sleep and embarrassing feelings.
He said the new study opens up a whole new way of thinking about what causes the urge to tickle.
Maybe there are other bacteria living on your ** that also cause itching," Kim said. "They can cause itching by interacting directly with your nerves. ”
One of the best approaches in the future, Kim says, would target specific itch-producing molecules, which would enable a more targeted approach without harming the good bacteria inside and outside the body.
The researchers speculate that it is possible that certain bacteria have evolved to cause people to scratch because scratching helps these microbes spread to other people or other parts of the body. Alternatively, scratching may be damaging** and allow the bacteria to gain a better foothold.
"We're not actually sure why Staphylococcus aureus would want to cause an itching response and whether it's beneficial for the microbe," Deng said. "We're very interested in testing that. ”
Although itching is common, she said, "the exact mechanism behind it works remains a mystery to scientists." ”
We think we've found a new way to think about the cause of itching," Deng said, "and how we can potentially ** it." ”