Functional characterization of the matrix metalloproteinase-1 cigarette smoke-responsive region and association with the lung health study

Abstract

Background: Prior studies have demonstrated that the distal 1.5 kb of the MMP-1 promoter is fundamental in directing the induction of the MMP-1 gene by cigarette smoke.

Methods: To characterize the genetic variants in the MMP-1 cigarette smoke-responsive element, deep re-sequencing of this element was performed on DNA samples from participants in the Lung Health Study. Furthermore, evidence of Sp1 binding to the MMP-1 promoter was assessed using chromatin immunoprecipitation assays and the influence of cigarette smoke exposure on this interaction was evaluated in cultured human small airway epithelial cells.

Results: Ten polymorphisms (four novel) were detected in the cigarette smoke-responsive element. Chromatin immunoprecipitation assays to assess the protein-DNA interactions at Sp1 sites in the MMP-1 promoter showed increased binding to the Sp1 sites in the cigarette smoke-responsive element in small airway epithelial cells treated with cigarette smoke extract. In contrast, a Sp1 site outside of the element exhibited the opposite effect. None of the polymorphisms were more prevalent in the fast decliners versus the slow decliners (fast decliners = mean -4.14% decline in FEV1% predicted per year vs. decline in FEV1% predicted per year).

Conclusions: Sequencing analyses identified four novel polymorphisms within the cigarette smoke-responsive element of the MMP-1 promoter. This study identifies functional activity within the cigarette smoke-responsive element that is influenced by cigarette smoke and examines this region of the promoter within a small patient population.

Figure 1

Sp1 action on the MMP-1 promoter is shown by the fold change in specific DNA sequences detected by qPCR. MMP-1 ChIP assays were done in cell cultures from human small airway epithelial cells with and without cigarette smoke extract (CSE) treatment using an antibody to Sp1 or nonimmune serum. We amplified DNA using primers spanning two Sp1 binding sites within the cigarette smoke-responsive element (a,b) and one sequence outside of this element (c). Samples from each experiment were run in triplicate. Data are mean ± SEM. *P < 0.05.

Figure 2

The detectable relative risk given the number of subjects is shown for a variety of marker allele frequencies using different genetic models.