Why do smokers get sick more often
Smokers are more susceptible to bacterial infections and inflammatory diseases than non-smokers. This is due to the ingestion of hundreds of toxic compounds that are part of tobacco. Scientists at the University of Louisville (Kentucky), working under the guidance of Dr. David Scott, have established how nicotine reduces the ability of cells of the immune system – neutrophils – to search for and destroy bacteria.
Neutrophils are formed in the bone marrow, which they leave completely differentiated. The fact that nicotine has an effect on neutrophils was known before, but the mechanisms of nicotine's influence in the process of differentiation of these cells were not known until now.
The authors modeled the process of neutrophil differentiation using promyelocytes of the HL-60 line, which differentiated into neutrophils when exposed to dimethyl sulfoxide (DMSO) in the presence of nicotine and without it. Compared with exposure to DMSO alone, nicotine increased the relative number of cells entering the late stages of differentiation (metamyelocytes, rod-shaped and segmented neutrophils), but did not affect other analyzed markers of neutrophil differentiation.
At the same time, neutrophils differentiated in the presence of nicotine were characterized by a reduced ability to search for and destroy bacteria in comparison with the cells of the control experiment. Nicotine suppressed the function of "oxygen explosion" – the formation of a large amount of oxygen free radicals necessary for the destruction of bacterial cells. It also enhanced the release of matrix metalloprotease-9 (matrix metalloproteinase-9, MMP-9), a factor involved in tissue degradation.
The authors suggest that the deterioration of the functional state of neutrophils observed by them explains the increased susceptibility of smokers to bacterial infections and inflammatory diseases. A more detailed study of the mechanisms involved will help in the development of specific therapeutic strategies for the treatment of various smoking-related diseases.
The authors note that their chosen model – HL-60 cells differentiating under the action of DMSO – are not identical to normal neutrophils. However, this line of human leukemia cells has many key effector functions of neutrophil progenitor cells and allows reproducible experiments on their differentiation.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
21.04.2008