Cigarettes lower immunity

 
By Maureen Nandini Mitra
Published: Thursday 15 May 2008

-- (Credit: SURYA SEN)more bad news for smokers. The cancer stick undermines the body's immune system, leaving it more susceptible to bacterial infections, shows new research. It is already known that smokers are more prone to infections and inflammatory diseases due to the hundreds of toxic components in cigarettes. Now researchers have found that the nicotine in tobacco affects the functioning of neutrophils--a type of white blood cells that are the body's natural defence against infections. Nicotine reduces these cells' ability to seek and destroy microbes.

Like all other white blood cells, neutrophils are generated by our bone marrow. They are usually the first responders to any microbial infection. Although nicotine has been known to affect neutrophils, there has been no study until now of the mechanisms at work when nicotine is present during neutrophil differentiation. That is, when they are being formed from stem cells in the marrow through the process of cell division and differentiation.

David Scott of the Oral Health and Systemic Disease Research Group at the University of Louisville School of Dentistry, Kentucky, usa, along with a colleagues from the uk and Canada, decided to investigate how nicotine presence influenced the differentiation process. Their findings were published in the April 15 issue of bmc Cell Biology.

The team used serum samples from a group of 20 smokers (with reported consumption of about 10 cigarettes a day) and 20 non-smokers. They modelled the neutrophil differentiation process using promyelocytic cells--large mononuclear bone marrow cells that are still in an undifferentiated state--of the hl -60 cell line (a leukaemic human tissue culture commonly used to study cell differentiation). Batches of these cells were put in a medium (dimethylsufoxide or dmso) that keeps the cells active. In some batches, nicotine was added to the medium.

The researchers found that once these cells differentiated into neutrophils, the ones treated with nicotine were less able to seek and destroy bacteria than nicotine-free neutrophils. The nicotine suppressed the oxidative burst in hl -60 cells, a function that helps kill invading bacteria. The authors suggest the processes partially explain tobacco users' increased susceptibility to bacterial infection and inflammatory diseases.

A better understanding of this relationship could pave the way for specific therapeutic strategies to treat tobacco-associated inflammatory diseases and conditions, they say. "It must be acknowledged that our study model, dmso -differentiated hl -60 cells, are not entirely similar to normal neutrophils," says Scott. "This leukaemic human cell line permits the reproducible study of differentiation and retains many of the key functions of neutrophils."

Through their research "the authors have found another example of how nicotine concentrations acquired through tobacco smoking or smokeless products can be bad for our health; in this case a detrimental effect on granulocyte function and how we fight infection", John Minna, director of the Hammon Center for Therapeutic Oncology Research in Dallas, Texas, told Down To Earth. Minna has studied the effect of nicotine exposure in the pathogenesis of lung cancer.

India critical
These findings come at a time when researchers are predicting that 2010 onwards, around one million people will die every year of smoking-related causes in India.

A study by the University of Toronto's Centre for Global Health Research, published in the New England Journal of Medicine in February, says India is in the midst of a "catastrophic epidemic of smoking deaths". It also says that most tobacco deaths will occur in rural India and the risk of heart disease to passive smokers will increase by 60 per cent. The findings were based on the first nationally representative study of smoking in India.

Union health minister Anbumani Ramadoss has been spearheading a campaign against tobacco products. The centre is soon to come out with a national anti-tobacco campaign that will warn youth against using such products. "If an individual is caught smoking then he will have to pay a fine of Rs 1,000 and if it takes place in an institution then a fine of Rs 5,000 would be collected from the institution for each person caught," Ramdoss says.

Industry sources say such measures will affect livelihood of millions. "In all, 35 million people are dependent on tobacco cultivation, trading, processing and cigarette and bidi manufacturing.This amounts to 3.5 per cent of the country's population," says Bellam Kotaiah, president of the Indian Tobacco Association.

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