SNP rs3088308 is a risk factor for poor lung function in healthy smokers.

Objective: To see if single nucleotide polymorphisms of pulmonary innate immune molecule surfactant protein D were associated with poor lung function in smokers.

Methods: The study was conducted at Shaikh Zayed Hospital, Lahore, Pakistan, from April 2008 to August 2010, and comprised relatives and attendants of patients, as well as college and university students. Self-reported healthy smokers who demonstrated no airflow obstruction on spirometry were included. Deoxyribonucleic acid was extracted from their blood sample and genotyped for single nucleotide polymorphisms rs721917 and rs3088308 by polymerase chain reaction and restriction analysis. Serum was separated for measurement of surfactant protein D levels by a commercially available enzyme-linked immunosorbent assay based kit. Lung functions were compared between subjects possessing major and minor alleles using two-tailed Student's t-test. Multiple linear regression analysis was conducted to analyse the effect of age, smoking and the two single nucleotide polymorphisms on forced expiratory volume in 1 second.

Results: Of the 122 participants, all of whom were men, 98(80.33%) were smokers while 24(19.67%) had never smoked. Of the former, 90(91.84%) were current smokers and 8(8.16%) were ex-smokers. The overall mean age was 35.8±10.9 years. The mean surfactant protein D level was 121.4±61.6ng/ml. In case of rs3088308, all lung function variables were reduced in patients with a minor allele and the results for forced expiratory volume in 1 second (p=0.016), forced expiratory volume in 1 second (%) predicted (p=0.009), forced vital capacity (p=0.048) and forced vital capacity (%) predicted (p=0.048) were statistically significant. Age had the highest influence on lung function (p<0.001) followed by smoking status (p=0.04) and single nucleotide polymorphisms rs3088308 minor allele (p=0.04).

Conclusions: Single nucleotide polymorphisms rs3088308 was found to modulate serum surfactant protein D levels and may be a risk factor for development of chronic obstructive pulmonary disease among smokers.