Venom from spiders and other creatures help scientists by revealing nerve pathways in humans.
Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder.
If a person has a functional disorder, they experience symptoms, but diagnostic tests do not reveal any structural or biochemical abnormalities.
According to the International Foundation for Functional Gastrointestinal Disorders (IFFGD), around 10-15 percent of people experience IBS worldwide.
- Relief with defecation
- A change in frequency of stool
- A change in consistency of stools.
About 40 percent of cases are mild, 35 percent are moderate, and 25 percent are severe.
Not everyone who has IBS consults a doctor, but it is one of the most common disorders seen by physicians. In the United States, between 2.4-3.5 million visits per year are thought to be due to IBS. It accounts for up to 12 percent of all primary care consultations.
Between 60-65 percent of cases involve women, and it is thought that some women with IBS undergo unnecessary abdominal surgery in an attempt to end the problem.
Spider venom highlights key nerve pathways
In the current study, an international team of researchers, from the U.S. and Australia, used spider venom to pinpoint a protein that is involved in transmitting the type of pain felt by people with IBS.
The study was led jointly by Associate Prof. Stuart Brierley, of the University of Adelaide, and Prof. Glenn King, from the University of Queensland - both in Australia - as well as Prof. David Julius, from the University of California-San Francisco, and Dr. Frank Bosmans, from Johns Hopkins University in Baltimore, MD.
The team investigated 109 spider, scorpion, and centipede venoms. The strongest result was from the venom of a type of tarantula found in West Africa, known as Heteroscodra maculate.
The venom was found to activate an ion channel, or a protein in nerves and muscles, known as NaV1.1, which also plays a role in epilepsy.
The first finding (resource no longer available at www.nature.com) of the current study was that NaV1.1 could be important in sensing and transmitting pain.
The team then found that NaV1.1 was present in pain-sensing nerves in the intestines, suggesting that the pathological levels of abdominal pain experienced by people with IBS could stem from NaV1.1.
The authors believe that identifying NaV1.1's role in signaling chronic pain is the first step toward creating new treatments.
How can spider toxins help?
Prof. King notes that spider venom is useful for investigating the processes of pain signaling in humans.
"Spiders make toxins to kill prey and defend themselves against predators, and the most effective way to defend against a predator is to make them feel excruciating pain," he says.
Because of this, he explains, we can expect spider venom to be full of molecules that stimulate the pain-sensing nerves in the body.
Scientists can use this information to find new pain pathways, by observing which nerves are activated when they come into contact with the venoms.
"Irritable bowel syndrome places a large burden on individuals and on the health system, but there are currently no effective treatments. Instead, sufferers are advised to avoid triggers that will cause their symptoms to flare up."
Associate Prof. Stuart Brierley
The team is now developing molecules that will block NaV1.1 and alleviate irritable bowel syndrome pain.