Medical marvel: the uses of cannabis continue to grow

Spare a thought for Bert Trautmann, a goalkeeper who suffered two cracked vertebrae in his neck while playing for Manchester City in the 1956 FA Cup final. "He played on for the last 15 minutes and made saves that won them the game," says Prof David Finn. No subs were allowed back then. It was not just adrenalin that got him through, says the NUI Galway researcher; he probably also relied on the body's own marijuana, which Finn now studies in order to develop new painkillers.

Finn is one of a number of Irish scientists studying cannabis-like compounds to search out drugs for diseases such as chronic pain, anxiety, stroke, multiple sclerosis and Alzheimer's disease. "People have used cannabis for thousands of years for things like pain relief, but now we realise that the body has its own cannabis-like system and this could be an important target for new therapeutics."

THC (tetrahydrocannabinol) was pinpointed in the 1960s as the substance that delivers the high of a cannabis joint, but it was only in the 1990s that scientists discovered that inhaled THC attaches to a common receptor in our bodies. Many cells, especially in our brains, are studded with these "cannabinoid" receptors, to which cannabis-like compounds bind and can give us a high.

This is why THC in marijuana has varied psychoactive effects. “It activates a receptor called CB1 that tends to inhibit neurons in parts of the brain that control pain, memory, mood and appetite,” says Finn. For example, CB1 activation is why weed smokers get the munchies and why mice without these receptors do not gain weight.

More than 100 chemicals

Along with THC, there are more than 100 cannabinoid chemicals in cannabis and an unknown number in the body that tinker with the receptors in more subtle ways and offer researchers an Aladdin’s cave to explore for new drugs.

“The levels of cannabinoids increase during stress and play a role in dampening down pain,” says Finn. This powerful system is likely to be activated in wounded soldiers or injured athletes. On the flipside, low-level anxiety or worry and depression can make pain worse, something the cannabinoid system is probably involved in.

"If we understand how this works, then we might be able to tap in to that to develop drugs," says Finn. One in five Irish people suffers from chronic pain, and in a Europe-wide study 75 per cent of patients said pain medication was inadequate at times. "We need better painkillers, and the cannabinoid system represents a very exciting target," says Finn. His research and that of other Irish cannabinoid scientists is funded by Science Foundation Ireland.

In the US, the legalised marijuana movement is gaining ground. But it was a Limerick-born physician and scientist, William B O’Shaughnessy, who first reported the plant’s medicinal potential in the West, in 1842. He experimented on it for the treatment of pain, spasticity and rheumatism.

The much later discovery of cannabis receptors set modern scientists on a hunt to find what binds them, what they do and what they might treat. Success came in 2005, when a drug called Sativex from GW Pharmaceuticals was approved in Canada to treat muscle spasms in multiple sclerosis; the spray has since been approved in 12 other countries, including the UK. Ireland is expected to follow suit. The drug is also in development for cancer pain. It consists of THC and cannabidiol (CBD) from cannabis, but the combination does not cause psychoactive symptoms.

Dr Eric Downer, a researcher in UCC, is trying to figure out how drugs such as Sativex work. His research focuses on chemicals from the cannabis plant and what happens in the cells of MS patients exposed to Sativex. Some modern cannabis strains are loaded with THC, but have far less CBD and other potentially beneficial compounds.

“It is pretty clear that compounds like THC and cannabidiol have neuroprotective effects,” says Downer, who predicts the system will soon become a regular feature of medical textbooks.

Drugs could stem from our body’s own cannabinoids or from cannabis plant-derived chemicals. Prof Veronica Campbell at Trinity College Dublin is studying both. Our body’s cannabis-like compounds are constantly produced, but they break down rapidly, allowing them to fine-tune our cells. Campbell says we can now manipulate the body’s cannabinoid levels using experimental drugs, and this may have uses in therapies for diseases such as Parkinson’s, Alzheimer’s and multiple sclerosis.

Cannabis-like receptors are not just found in the brain; Campbell is also investigating their role in bone and cartilage regeneration. A project involving industry aims to develop transplants for patients. “Our basic research suggests that cannabinoids might help promote and accelerate bone and cartilage repair,” she says.

“[Our body’s own] cannabinoid system can cause glial cells in the brain to stop releasing toxic-type chemicals that promote inflammation and may damage neurons,” says Dr Michelle Roche, a cannabis scientist in NUI Galway. Glial cells are support cells for neurons and have a protective role in the brain, but sometimes they spin out of control, causing harm.

CANNABIDIOL RESEARCH: NEW HOPE FOR STROKE SUFFERERS

Medical marijuana use is expanding in the US, but it seems the herb just keeps giving. There is evidence that chemicals in marijuana could help treat stroke patients.

Trinity graduate Dr Saoirse O’Sullivan began studying how cannabis compounds affect isolated arteries when she took up a job as a researcher at the University of Nottingham in 2002.

“I just fell in love with cannabinoids. The whole area intrigued me. So little was known about this system in the body,” she says.

Her research points to a compound in marijuana having the potential to treat stroke patients. Cannabidiol (CBD) is a non-psychoactive constituent of cannabis that has been shown to reduce stress during public speaking and may have value as a treatment. “[CBD] relaxes blood vessels. It could benefit stroke patients by restoring blood flow to areas of the brain affected by stroke,” she says.

Following a stroke, the robust defence separating the brain from the rest of the body – the blood-brain barrier – can become leaky, causing fluid to accumulate in the brain. O’Sullivan has discovered that CBD prevents this leakiness and so might prevent such harmful build-ups. “We would be hoping to see less damage and a reduced chance of a second stroke happening.” Her next step is to test CBD in stroke patients.

She recently found another compound from marijuana was good at reducing blood glucose levels in diabetic patients and improved their ability to secrete insulin. For now, she’s keeping the identity of this chemical under wraps.