The discovery offers hope of a new drug that may prevent agonising swelling and stiffness
The discovery offers hope of a new drug that may prevent the agonising swelling and stiffness suffered by patients in their knees, hips and hands.
Molecular physiologist Professor Christine Beeton, of Baylor College of Medicine, Houston, explained: “Rheumatoid arthritis is an autoimmune disease – one in which the immune system attacks its own body.
“In this case, it affects the joints. Cells called fibroblast-like synoviocytes (FLS) play a major role in the disease.
“As they grow and move from joint to joint, they secrete products that damage the joints and attract immune cells that cause inflammation and pain.
“As damage progresses, the joints become enlarged and are unable to move.”
In experiments on rats with a rodent form of the condition treating them with iberiotoxin – one of the hundreds of components of scorpion venom – stopped progression of the disease.
In some cases the established signs of rheumatoid arthritis were completely reversed, meaning the animals had better joint mobility and less inflammation.
Prof Beeton said: “We are scared of scorpions, we are scared of snakes, we are afraid of spiders – we don’t want them around us.
“But if we look at them from another side, if we look at them as mostly banks of compounds, then we have another view of them.
In some cases the established signs of rheumatoid arthritis were completely reversed
“Venoms are very, very complex solutions with a lot of different compounds.
“Some of them are going to be lethal. But we are using a single compound.
“So I would certainly not recommend using whole venom because that would be extremely dangerous!”
Rheumatoid arthritis is caused by the immune system accidentally attacking the cells that line joints.
Rheumatoid Arthritis is caused by the immune system accidentally attacking cells that line joints
This can damage the joint itself, as well as the cartilage and nearby bone.
Current treatments target the immune cells involved in the disease.
But none are specific for FLS which Prof Beeton and colleagues suspect may be its ‘Achilles’ heel’.
She said: “”In previous work, we identified a potassium channel on FLS of patients with rheumatoid arthritis and found the channel was very important for the development of the disease.
“We wanted to find a way to block the channel to stop the cells damaging the joints.”
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Potassium channels work by opening gates on the surface of cells that allow potassium ions – small charged atoms – to flow in and out of the cell.
The flow of ions through the channels is necessary for the cells to carry out many of their essential functions.
Animals such as scorpions have venoms that block potassium and other ion channels. They use the venoms to paralyse and kill prey.
Decades ago, scientists discovered this and realised that, if handled correctly, venoms also might have medicinal applications.
Scorpion venom has already shown promise as a therapy for a host of illnesses, including heart disease and cancer.
Scorpion venom has already shown promise as a therapy for a host of illnesses
Now it may lead to improved treatments for rheumatoid arthritis, according to the findings published in the Journal of Pharmacology and Experimental Therapeutics.
First author Dr Mark Tanner, who was a graduate student in Prof Beeton’s lab during the development phase of the project, said: “Scorpion venom has hundreds of different components.
“One of the components in the venom of the scorpion called Buthus tamulus specifically blocks the potassium channel of FLS and not the channels in other cells such as those of the nervous system.
“Here, we investigated whether this venom component, called iberiotoxin, would be able to specifically block the FLS potassium channel and reduce the severity of the rheumatoid arthritis in rat models of the disease.”
As well as dramatically improving the lab rodents’ condition iberiotoxin did not induce side effects, such as tremors and incontinence, that were caused by another channel blocker called paxilline.
Dr Tanner said: “It was very exciting to see that iberiotoxin is very specific for the potassium channel in FLS and that it did not seem to affect the channels in other types of cells, which might explain the lack of tremors and incontinence.”
Prof Beeton said venoms have evolved alongside humans, and their prey, which are mainly invertebrates, like us.
She said: “Our ion channels are not all that different from ion channels in insects.
“So what can be use by a scorpion to kill an insect we can use to our benefit to treat sickness.”
You are more likely to develop rheumatoid arthritis if you are a woman or a smoker
Added Prof Beeton: “Although these results are promising, much more research needs to be conducted before we can use scorpion venom components to treat rheumatoid arthritis.
“We think this venom component, iberiotoxin, can become the basis for developing a new treatment for rheumatoid arthritis in the future.”
You are more likely to develop rheumatoid arthritis if you are a woman, a smoker, or have a family history of it.
About 400,000 people have the condition in the UK. There is no cure.
It usually develops when a person is between 40 and 50 years old.
Symptoms also include fatigue, a fever, sweating, weight loss and a poor appetite.
Inflammation from rheumatoid arthritis may also cause dry eyes and chest pain.