Some Gene damage: Permanent

Some gene damage from smoking is permanent: study

Aug. 30, 2007
Courtesy BioMed Central
and World Science staff

A new study may help ex­plain why form­er smok­ers are still more prone to lung can­cer than those who have nev­er smoked. It found that smok­ing causes some per­ma­nent ge­ne­tic da­mage.

Quit­ting still of­fers huge health ben­e­fits, re­search­ers stressed, as the risk to form­er smok­ers is much low­er than for cur­rent smok­ers.

A team led by Wan Lam and Ste­phen Lam from the BC Can­cer Agen­cy in Van­cou­ver, Can­a­da, took sam­ples from the lungs of 24 cur­rent and form­er smok­ers, as well as from peo­ple who have nev­er smoked.

They used the sam­ples to cre­ate li­brar­ies us­ing a tech­nique called se­ri­al anal­y­sis of gene ex­pres­sion, which helps to iden­ti­fy pat­terns of gene ac­ti­vity.

Only about a fifth of the genes in a cell are switched on at any giv­en time, but smok­ing leads to changes in gene ac­ti­vity. The re­search­ers found that some of these changes, though not all, per­sisted even years af­ter quit­ting smok­ing.

The re­vers­i­ble genes were par­tic­u­larly in­volved in “xeno­bi­otic” func­tion­s—ma­nag­ing chem­i­cals not pro­duced in the body—and me­tab­o­lism of ge­net­ic ma­te­ri­al and mu­cus se­cre­tion, sci­en­tists found. The irre­vers­i­ble dam­age was to some DNA re­pair genes, and to the ac­ti­vity of genes that help fight lung can­cer de­vel­op­ment.

“Those genes and func­tions which do not re­vert to nor­mal lev­els up­on smok­ing cessa­t­ion may pro­vide in­sight in­to why form­er smok­ers still main­tain a risk of de­vel­op­ing lung can­cer,” said Raj Cha­ri, first au­thor of the stu­dy. To­bac­co smok­ing ac­counts for 85 per­cent of lung can­cers, and form­er smok­ers ac­count for half of those newly di­ag­nosed with the dis­ease.

The gene find­ings are pub­lished in the Aug. 29 is­sue of the on­line re­search jour­nal BMC Ge­nomics.

Comprehensive smoking Bans Secondhand

De: Carlos Alberto Machado [mailto:carlos.a.machado@uol.com.br]
Enviada em: sábado, 21 de julho de 2007 09:56
Assunto: Comprehensive Smoking Bans May Decrease Secondhand Smoke Exposure

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Comprehensive Smoking Bans May Decrease Secondhand Smoke Exposure
Laurie Barclay, MD
Medscape Medical News 2007. © 2007 Medscape
July 20, 2007 — Comprehensive smoking bans may decrease secondhand smoke exposure, according to a report in the July 20 issue of the Morbidity and Mortality Weekly Report. Following the 2003 New York state ban on smoking in indoor workplaces and public places, reports of indoor smoking and saliva cotinine levels decreased in nonsmoking participants in the New York Adult Tobacco Survey (NYATS).
"Secondhand smoke (SHS) causes premature disease and death in nonsmokers, including heart disease and lung cancer," write U. Bauer, PhD, from the New York State Department of Health, and colleagues. "The Surgeon General has concluded that no risk-free level of SHS exposure exists; the only way to fully protect nonsmokers is to completely eliminate smoking in indoor spaces. Studies have determined that levels of airborne particulate matter in restaurants, bars, and other hospitality venues and levels of SHS exposure among nonsmoking hospitality employees decrease substantially and rapidly after implementation of laws that prohibit smoking in indoor workplaces and public places."
The New York State Department of Health analyzed data (from June 26, 2003 – June 30, 2004) on observations of indoor smoking by NYATS, as well as cotinine saliva levels in nonsmoking NYATS respondents. The study period began before and ended after implementation of the 2003 New York state ban on smoking in indoor workplaces, restaurants, bars, and other public places.
After the ban took effect, reports of indoor smoking declined significantly, from 19.8% (during June 26 – July 23, 2003) to 3.1% (during April 1 – June 30, 2004) for restaurant patrons, and from 52.4% to 13.4% for bar patrons during the same period. However, the proportion of respondents reporting exposure to SHS in workplaces did not change significantly from 13.6% before implementation of the no-smoking law.
Liquid chromatography with tandem mass spectrometry was used to measure concentration of cotinine in saliva samples that nonsmoking NYATS participants sent in by mail. Mean salivary cotinine decreased by 47.4%, from 0.078 ng/mL during June 26 to July 23, 2003, before the smoking ban was implemented, to 0.041 ng/mL during April 1 to June 30, 2004. During the same periods, the proportion of respondents with cotinine levels below the limit of detection (LOD) of 0.05 ng/mL increased from 32.5% to 52.4%.
"These findings suggest that comprehensive smoking bans can reduce SHS exposure among nonsmokers," the authors write.
An accompanying editorial note states the study limitations of low average quarterly response rates for both NYATS (22%) and the saliva cotinine study (33%, for a cumulative rate of 7%) and an error involved in estimating cotinine values below the LOD to calculate the geometric means.
"Additional research is needed to confirm the findings of this study," the editorial concludes. "However, the results suggest that comprehensive smoke-free air laws can substantially reduce SHS exposure to nonsmokers, even in jurisdictions with a high prevalence of existing smoking restrictions. Even greater reductions in SHS exposure might be expected in jurisdictions that had fewer smoking restrictions in place before implementing a statewide smoke-free air law."
MMWR Morb Mortal Wkly Rep. 2007;56(28):705–708.