TGFB1 promoter polymorphism C-509T and pathophysiology of asthma

Background: TGF-beta 1 can modulate airway inflammation and exaggerate airway remodeling. A polymorphism of a promoter region of TGFBI, C-509T, might be associated with the development of asthma, but its pathophysiologic relevance remains poorly understood. Objective: We investigated relations of the C-509T polymorphism to airflow obstruction, sputum eosinophilia, and airway wall thickening, as assessed by means of computed tomography, in 85 patients with stable asthma. Methods: The CC, CT, and TT genotypes were examined by means of PCR and restriction enzyme fragment length polymorphism. At a selected bronchus, 3 indices of airway wall thickness were measured with an automatic method. Results: The CC, CT, and TT genotypes were found in 22,46, and 17 patients, respectively. Serum TGF-beta 1 levels were significantly associated with the polymorphism and were increased in the CT/TT genotypes. FEV1 and sputum eosinophil percentages were also significantly associated with the polymorphism and were both decreased in the CT/TT genotypes. The polymorphism was unrelated to airway wall thickness. Conclusion: In addition to increased serum TGF-beta 1 levels, the T allele of the C-509T polymorphism is related to increased airflow obstruction but attenuated eosinophilic inflammation. The former relation is not attributed to thickening of the central airway walls. The latter relation might reflect the anti-inflammatory effect of TGF-beta 1. The C-509T polymorphism has a complex role in asthma pathophysiology, presumably because of the diverse functions of TGF-beta 1 and its various interactions with cells and humoral factors in vivo.