It is possible that nicotine is not all bad: The latest research discovered that nicotine encouraged new blood vessel growth in mice by actively signaling their bone marrow to release vessel-forming adult stem cells.
According to specialists, these findings may someday be translated into the use of nicotine as a way of helping wound healing and other health problems where new blood vessel growth is crucial. Moreover, it provides insight into unwanted vessel growth, such as that which takes place in the course of tumor formation.
Nevertheless, these study results do not mean that healthcare professionals will ever suggest smoking cigarettes.
One of four thousand compounds
"I don’t want people to think that smoking is beneficial," warned the co-author Dr John P. Cooke, a professor of medicine at Stanford University’s School of Medicine in California. "Tobacco smoke contains 4 000 compounds, and nicotine constitutes just one of them. And what we have found is that nicotine alone is able to stimulate blood vessel growth."
"The growth of blood vessel is like fire," Cooke explained. "It is neither good nor bad. Therefore, certainly nicotine-related blood vessel formation can lead to problems, in the context of stimulating tumor growth, resulting in macular degeneration and blindness, or promoting coronary plaque. However, on the other hand, being aware of the existence of this phenomenon, we are potentially able to manipulate it in a way that may appear to be therapeutic - such as to encourage insufficient wound healing where part of the problem is connected with poor blood vessel growth."
The findings are based on animal and test-tube study. They are published in the December 19 issue of the Journal of the American College of Cardiology.
The previous study of Cooke’s team had already shown the ability of nicotine to support blood vessel growth, known as the "angiogenic effect." In this latest research, they set out to reveal the mechanism driving this process.
Mice sewn together
The investigators first took a few pairs of 10-week old male and female mice and sewed them together by the surgery- male to female - at their flanks. The suturing provoked the development of a shared circulatory system.
Nearly four weeks after the surgery was carried out, the scientists surgically instigated a blood vessel blockage in the hind limb of the female mouse.
The objective was to check the idea that a dose of nicotine might encourage new blood vessels to grow around the blockage by triggering the mice’s bone marrow to release adult stem cells. These cells, known as EPCs, are released from marrow into the bloodstream, where they travel to the site of injury.
According to the explanation of the scientists, the only possibility to tell the blood-forming cells were coming from bone marrow and not appearing at the site of injury (on the female’s flank) was to track markers specific to the male mouse’s cells.
But would nicotine be able to accelerate this angiogenic process? To find out, the investigators exposed several mouse pairs to a daily oral dose of nicotine mixed with saccharine and water, shortly after surgery. The other pairs of mice were given a localized injection of nicotine directly into the limb with the blockage.
During a two-week nicotine diet, Cooke and his colleagues tracked the progress of bone marrow cell production and circulation in the paired mice.
Nicotine tied to stem cells
The scientists reported that nicotine treatment was connected with an increase in the number of EPC stem cells in both the bone marrow and spleen of the conjoined mice. This was confirmed by further laboratory analyses.
Additionally, some of the new blood vessels that structured around the hind limb blockage in the course of nicotine treatment were made up of those EPC cells originating in the marrow, the researchers explained.
Cooke and his team also discovered that the oral dose of nicotine had a more powerful effect on blood vessel growth than the local injection. The oral dose provoked a 76 per cent increase in capillary density at the site of the blockage vs. a 45 per cent increase from targeted injections.
Cooke’s team emphasized that not all the blood vessel growth was attributable to EPC cells mobilized into action by nicotine, and the precise mechanism driving nicotine’s angiogenic effect is still not clear.
Nonetheless, the results of the research indicate that nicotine-based agents may play an essential role in stimulating blood vessel formation in patients who require it.
Nothing in common with smoking
Nevertheless, all of this is separate from nicotine’s hazardously addictive properties in tobacco products.
"We are sure that nicotine is bad," agreed Dr Byron K. Lee, an assistant professor of cardiology at the University of California, San Francisco. "The way the majority of people consume it can lead to heart attacks and cancer and results in other vascular diseases such as stroke, for example."
"However, there could be a situation where you could release nicotine to have some positive effects," he noted, "for instance, in a small part of the body where there’s blockage of the arteries that feed the heart. Due to the fact that we know that, over time, the body develops new blood vessels relieving the pain. Nevertheless, that process takes months or even years to form. Therefore, if we could somehow use nicotine in order to get those areas to spring new blood vessels faster, we could help people."
"We’re not there yet," Lee added. "There was no research that has fully panned out yet. But we ought to try to find out whether or not nicotine works, and if it does work, then it could be potentially wonderful."
