Open Access Research article

Elevation of sputum matrix metalloproteinase-9 persists up to 6 months after smoking cessation: a research study

Noora Louhelainen1, Harri Stark2, Witold Mazur1, Paula Rytilä3, Ratko Djukanovic4 and Vuokko L Kinnula1*

Author Affiliations

1 Department of Medicine, Division of Pulmonary Medicine, University of Helsinki, Helsinki, Finland

2 Finnish Institute of Occupational Health, Helsinki, Finland

3 University of Helsinki, Helsinki, Finland

4 Department of Medicine, Division of Infection, Inflammation and Repair, Southampton General Hospital, Southampton, UK

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BMC Pulmonary Medicine 2010, 10:13  doi:10.1186/1471-2466-10-13

Published: 14 March 2010



Smoking cessation is the best possible way to prevent the progression of smoking related airway diseases. However, the effect and time scale of smoking cessation on airway inflammation/remodelling are largely unknown. This prospective study evaluated the effects of smoking cessation on induced sputum (IS) neutrophils, matrix metalloproteinases (MMP-7, -8, -9) and tissue inhibitor of metalloproteinase-1 (TIMP-1).


A total of 61 subjects participated in the study; 17 stopped smoking for 3 months and 9 for 6 months. The proportion of IS neutrophils and the levels of MMPs and TIMP-1 by ELISA were determined at baseline and at 3 and 6 months after cessation.


In the smokers, baseline IS neutrophils, MMPs and TIMP-1 were significantly higher compared to non-smokers. Levels of MMP-7, -8 and TIMP-1 decreased nearly to those of non-smokers but the levels of MMP-9 increased significantly from the baseline of the same subjects at 3 months after cessation (p = 0.009) with no significant decline at 6 months after cessation.


Sputum MMP-9 remained elevated after 6 months of smoking cessation, which may contribute to ongoing lung damage typical of COPD.