Smoke gets in your brain

Smoking can lead to cancer and cardiovascular disease. Little was known about the effect of smoking on the brain until a team led by Maltese researcher Charles Scerri established that heavy smokers are also destroying their brains. Here he speaks to Cynthia Busuttil about the destructive effect of smoking.

A ground breaking study led by Dr Scerri, a scientist at the university's Clinical Pharmacology and Therapeutics Department, has found that people who smoke two or more packets of cigarettes a day are destroying cells in their brain.

Together with another three researchers, a few years ago Dr Scerri started looking into the effect of nicotine on the brain.

"There have been several studies about cigarette smoke but these almost always dealt with its harmful effects on the body or on foetal development.

"Nicotine is the addictive component and it is what smokers crave. Cigarettes are made up of over 4,000 other substances, a good percentage of which are known to induce cancer. Knowing that nicotine is addictive tells us that this chemical is interacting with brain function. Nicotine influences systems in the brain that are thought to be implicated in a range of higher cognitive processes."

The researchers conducted their study at the University of Dundee, Scotland, which is renowned for its scientific research on the effects of drugs on the brain.

Groups of laboratory rats were chronically infused with various doses of nicotine for 10 days, during which they had to learn a memory task in a water maze. This consisted of finding a small platform, hidden just below the water surface, using visual cues located outside the maze. In normal circumstances, and following a number of trials, rats learn to locate the platform in a very short while. After 10 days, the rats' brains were examined.

Dr Scerri explained that in the brain, unlike the rest of the body, cells do not divide and regenerate.

"The adult human brain contains about 100 billion brain cells. We lose approximately 85,000 brain cells every single day and they are not replaced," he said.

However, there are two known exceptions as it was recently discovered that cells do reproduce in some parts of the brain. One of these is the hippocampus, which is very important in memory formation.

Nicotine, in a dose usually found in heavy smokers, not only slows down processes involved in memory formation and retention but also impairs brain cells' regeneration in the hippocampus. Moreover, nicotine seems to increase the rate at which these cells "commit suicide and die. Nicotine is affecting a very important process in the brain," Dr Scerri emphasises.

"The rats that got a small dose of nicotine did not show any brain damage. On the other hand, the effect of high doses of nicotine is quite remarkable," he explained.

The study was published recently in an international scientific journal - Psychopharmacology.

Infusing nicotine for three weeks revealed that the rate of brain cell death was alarmingly higher than in the first study, thus suggesting that the longer the use, the greater the damage.

"This belies the belief that if a person has been smoking for years he has already damaged his brain and there is no reason to stop. These results are another good reason for people to stop smoking today before tomorrow," he said.

Asked whether nicotine patches would have the same negative effect on a person's brain as smoking a cigarette, Dr Scerri said that although no studies have been carried out, the concentration of nicotine in the blood would be similar, therefore a risk associated with high-dose nicotine patches is possible.

Nicotine is not the only substance that stops division and survival of brain cells in the hippocampus. Alcohol and other drugs, particularly heroin, have the same deleterious effects.

The damage is much worse if one smokes and drinks. This is a very important observation considering the fact that 90 per cent of drinkers are also smokers. The next step forward, Dr Scerri said, is to find out what makes these brain cells stop replicating themselves, and eventually die.

"We need to find out why these cells are dying and what we can do to stop this process and, more than that, to reverse it. If we manage to find this, we would probably have made the discovery of all time.

"The implications are enormous. The various functions that one loses with age related to brain cell loss, including memory loss, lack of concentration, problems with visual and auditory acuity, slower reaction speed, problems with motoric dexterity and executive functions would disappear," he said.

Stopping cells from dying would mean maintaining a young and flexible brain even in old age, Dr Scerri explained enthusiastically, adding that, in a small way, this would be shedding light on the concept of "forever young".

"In a single average lifetime you lose billions of them. Imagine stopping that."

But Dr Scerri admits that science is still far off from finding an answer to the ever-young brain. Funding for research is not easy to come by and he is still trying to secure funds to continue with his studies.

"A major hurdle is that fundamental scientific research in Malta is not sufficiently recognised, let alone properly funded. Researchers lack motivation and the majority of them willingly accept invitations from foreign academic institutions to continue with their research programme abroad, contributing further to the brain drain. Malta cannot afford such a loss".

Stem cell research is paramount in trying to discover and develop new therapeutic ways of treating brain degenerative disorders, Dr Scerri said.

"In diseases such as Alzheimer's and Parkinson's, the rate at which brain cells die is higher than normal. If we find a way to augment, possibly replace the cells that die, either via cellular transplantation or inducing cell division in healthy cells, we would have discovered a possible cure for the treatment of such debilitating diseases," he said.

Dr Scerri said there are other ways of deriving stem cells.

"I understand there are obvious moral and ethical issues surrounding the use of embryonic stem cells for research purposes. But adult stem cells can also be derived from various parts in the body. The primary role of these cells is to maintain, and in some cases, repair the tissue in which they are found."

While embryonic stem cells can develop into all types of cells, adult tissue stem cells can only produce cells specific to the tissue they are derived from, therefore limiting their potential to specific cell types. Neural stem cells exist in the brain and it is these cells that are damaged by nicotine.

"If we find a way to get neural stem cells out of the brain, multiply them, put them back in where needed and make them functional that would be a major breakthrough.

"We know how some basic brain functions work but certain processes involved in higher cognitive functions such as thought, logical reasoning, language, memory processing and emotions, are still grey areas. There's still so much work to do. It's a challenge we must face," he said.