Surfactant protein gene A, B, and D marker alleles in chronic obstructive pulmonary disease of a Mexican population

Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation. It is most likely the result of complex interactions of environmental and genetic factors. Because pulmonary surfactant components play important roles in normal lung function, innate host defence, and inflammation in the lung, this study investigated the hypothesis that the surfactant protein genes are involved in certain cases of COPD. Genotype analysis of surfactant protein (SP)-A, SP-B, SP-B-linked microsatellite, and SP-D marker alleles was performed in patients with COPD (n=97) and smoker (n=82) or nonsmoker (n=99) controls. Univariate and multiple logistic regression analyses were performed. The regression analysis results between COPD and smokers revealed several COPD susceptibility alleles (AA62 B1580 D2S388, based on an odds ratio (OR >2.5). The predictive ability of this model for developing COPD is good (c=0.926). Allele-allele (B1580and D2S388 and allele-environment (i.e. smoking) interactions were detected. When smoker controls were compared to nonsmoker controls, marker D2S388 appeared to be smoking-independent (p=0.874), whereas marker alleles AA62(p=0.045) and B1580(p=0.007) were smoking-dependent. Males were at higher risk (OR=6.05, p=0.001), and smoking (>50 packs·yr^-1) increased risk (OR=5.38, p=0.007). Males and alleles of loci flanking SP-B were associated with more severe cases (forced expiratory volume in one second/forced vital capacity ≤40%). The present results indicate that the surfactant protein alleles may be useful in chronic obstructive pulmonary disease by either predicting the disease in a subgroup and/or by identifying disease subgroups that may be used for therapeutic intervention. These observations should now be confirmed in a larger study, designed according to strict epidemiological criteria.