Smoking Linked To Brain Damage, New Study

Featured Article
Main Category: Smoking / Quit Smoking
Also Included In: Neurology / Neuroscience;  Multiple Sclerosis
Article Date: 23 Jun 2009 - 9:00 PDT

email to a friend   printer friendly   view / write opinions   rate article

Research led by scientists in India suggests there is a direct link between smoking and brain damage whereby a compound in tobacco that turns into a cancer-causing chemical once it has been through the body's metabolism, triggers white blood cells in the brain's immune system to attack healthy brain cells.

The study is the work of lead investigators Debapriya Ghosh and Dr Anirban Basu from the Indian National Brain Research Center (NBRC) and was published online on 2 June in the Journal of Neurochemistry.

NNK is a procarcinogen commonly found in tobacco. A procarcinogen is a chemical that becomes cancer-causing (carcinogenic) once it has been metabolised in the body.

While alcohol and many drugs used by drug abusers damages brain cells directly, the researchers believe NNK damages brain cells indirectly, by first causing inflammation in brain cells, similar to that which leads to disorders like Multiple Sclerosis.

For the study, Ghosh, Basu and colleagues carried out two types of test: one in the test tube and the other in live mice ( in vitro and in vivo).

Using a technique called Western blot analysis they showed that treatment with NNK led to significant increases in signalling and effector proteins that promote inflammation, as well as other stress-related proteins. They also found increased levels of proinflammatory cytokines, compounds that help cells communicate with each other.

The researchers suggest the NNK caused the brain's immune cells or microglia, which normally only destroy damaged or unhealthy cells, to overreact and attack healthy cells.

"Immunohistochemical staining of the brain sections of NNK-treated mice reveals massive microglial and astrocyte activation along with distinct foci of neuronal damage," they wrote and concluded that:

"Both in vitro and in vivo results provide strong indication that NNK causes significant upheaval of the inflammatory condition of brain and inflicts subsequent neuronal damage."

Basu said these findings prove that:

"Tobacco compound NNK can activate microglia significantly which subsequently harms the nerve cells."

NNK passes into the body not just through smoking tobacco, it can also pass into the body from chewing tobacco.

Second hand smoking or so called "passive" smoking is another way that NNK can enter the body since it is present in tobacco smoke. A smoke-filled room may contain as much as 26 nanograms of NNK, which is on a par with the amount of NNK found in cigarettes which ranges from 20 to 310 nanograms, said the authors.

Ghosh said this research helps us understand one way that people who smoke or consume tobacco regularly might end up with damaged nerve or brain cells.

According to research cited by the National Cancer Institute (NCI) and the US Centers for Disease Control and Prevention (CDC), cigarette smoke contains about 4,000 chemical agents, including over 60 carcinogens, many of which are also poisonous in their own right (eg carbon monoxide, tar, arsenic, and lead).

"Tobacco carcinogen induces microglial activation and subsequent neuronal damage."
Debapriya Ghosh, Manoj Kumar Mishra, Sulagna Das, Deepak Kumar Kaushik, Anirban Basu.
Journal of Neurochemistry. Published Online: Jun 2, 2009.
DOI: 10.1111/j.1471-4159.2009.06203.x

Source: Wiley-Blackwell, NCI, CDC.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today