The effect of passive smoking on the levels of matrix metalloproteinase 9 in nasal secretions of children

Matrix metalloproteinase (MMP) 9 is a gelatinase associated with tissue remodeling. It is thought to play a part in the pathogenesis of allergy. Increased levels of MMP-9 have been shown to increase in the acute allergic response in the nose, lungs, and skin. Exposure to passive tobacco smoke is associated with an increase in sneezing, nasal blockage, and a decreased sense of smell. The aim of this study was to study the effect of passive smoking on the levels of MMP-9 in nasal secretions of children. A prospective descriptive study was performed. Thirty-nine children aged between 7 and 16 years were enrolled in the study. They were selected based on attendance at the Otorhinolaryngology Outpatients Clinic with a primary complaint unrelated to the nose or paranasal sinuses. Children with allergic rhinitis, sinusitis, or a recent cold were excluded. The study was performed at a tertiary pediatric referral center. Exposure to passive smoking was determined by measuring the urinary cotinine to creatinine ratio. Nasal fluid was obtained by using a Rhino-Probe curette (Arlington Scientific, Inc., Springville, UT). The concentration of MMP-9 was determined by ELISA. MMP-9 activity was determined by gelatin zymography. Data were tabulated on Microsoft Excel (Microsoft Corp., Redmond, WA) and analyzed using SPSS (SPSS Inc., Chicago, IL). Using a cutoff urinary cotinine/creatinine ratio of 0.025 ng/mg, 15 children were found to be exposed to passive smoking. Both the MMP-9 concentration and the activity were significantly higher in nasal secretions of children exposed to passive smoking. There was a distinct difference between the two cohorts with regard to the level of enzyme activity per weight of protein. The lowest level of enzyme activity recorded in the "exposed" cohort was over twice that of the level in the "not exposed" cohort. MMP-9 activity and concentration is higher in nasal secretions of children exposed to passive smoking. This suggests that passive smoking might alter the inflammatory response within the nasal mucosa in a similar way to allergy.