Increased PAI-1 expression has been implicated in accelerating atherogenesis. Increases under some conditions are modulated by growth factors. Genetic factors such as the 4G/5G poly-morphism in the promoter of the PAI-1 gene play a role under certain circumstances. The present study was designed to delineate for the first time interactions between growth factors and the 4G/5G polymorphism with respect to PAI-1 expression in human arterial smooth muscle cells (HASMC).
HASMC were genotyped and exposed to growth factors. PAI-1 gene and protein expression were induced consistently by TGF-β (up to 4.0-fold), PDGF (2.1-fold),TNF-α (1.7-fold), and thrombin (2.3-fold). Results were similar regardless of which genotype (4G/4G [n=9], 4G/5G [n=13], and 5G/5G [n=7]) was present.
The induction of increased PAI-1 expression in human arterial smooth muscle cells by growth factors implicated in accelerated atherogenesis is independent of the PAI-1 4G/5G polymorphism. Accordingly, modulation of PAI-1 expression is likely to be influenced predominantly by environmental factors acting on, rather than genetic factors intrinsic to the PAI-1 promoter.