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Cannabis May Soothe Inflamed Bowels
Gaia Vince | New Scientist | 08/01/2005

Cannabis-based drugs could offer treatment hope to sufferers of inflammatory bowel disease, UK researchers report.

Cannabis smokers with inflammatory bowel disease (IBD) have often claimed that smoking a joint seems to lessen their symptoms. So a group of researchers from Bath University and Bristol University, both in the UK, decided to explore the clinical basis for the claims.

“There is quite a lot of anecdotal evidence that using cannabis seems to reduce the pain and frequency of Crohn’s disease and ulcerative colitis, so we decided to see if we could find out what was going on there,” says Karen Wright, a pharmacologist at Bath University. “Historically, it was smoked in India and China centuries ago for its gastrointestinal properties.”

The chronic conditions, known collectively as IBD, are caused by an over-active immune system which produces severe inflammation in areas of the gastrointestinal tract. Up to 180,000 people in the UK are thought to have colitis or Crohn’s disease and suffer symptoms of pain, urgent diarrhoea, severe tiredness and loss of weight. Repeated attacks can lead to scarring of the colon and fibrosis to the extent that the bowel narrows to form a stricture, for which a colonectomy – the surgical removal of the bowel – is the only cure.

Repair trigger

Reports that cannabis eased IBD symptoms indicated the possible existence of cannabinoid receptors in the intestinal lining, which respond to molecules in the plant-derived chemicals. Wright and colleagues grew sections of human colon and examined them in vitro.

To their surprise, the team discovered CB1 cannabinoid receptors – which are known to be present in the brain – in the endothelial cells which line the gut. “I think they must be involved in repairing the lining of the gut when it is damaged,” Wright says.

She deliberately damaged the cells to cause inflammation of the gut lining and then added synthetically produced cannabinoids. “The gut started to heal: the broken cells were repaired and brought back closer together to mend the tears,” she told New Scientist.

Wright believes that in a healthy gut, natural endogenous cannabinoids are released from endothelial cells when they are injured, which then bind to the CB1 receptors. The process appears to set off a wound-healing reaction. “When people use cannabis, the cannabinoids bind to these receptors in the same way,” she said.

Excess cells

Previous studies have shown that CB1 receptors located on the nerve cells in the gut respond to cannabinoids by slowing gut motility, therefore reducing the painful muscle contractions associated with diarrhoea.

But Wright and her team also discovered another cannabinoid receptor, CB2, in the guts of IBD sufferers, which was not present in healthy guts. These receptors, which also respond to chemicals in cannabis, appear to be associated with apoptosis – programmed cell death – and may have a role in suppressing the overactive immune system and reducing inflammation by moping up excess cells, she suggests.

“Ideally we would want to be able to stimulate the body’s own endogenous cannabinoid system, which might become dysregulated during long-term inflammation. Knowing more about how this system actually works will help us to look for therapeutic targets,” Wright says. “We are not advocating cannabis use, particularly as smoking tobacco exacerbates Crohn's disease and many smokers of cannabis use tobacco as well.”

“Anything that offers hope is good news for sufferers of IBD,” says a spokesperson from the National Association for Colitis and Crohn’s Disease, commenting on the research.

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