ASA inhibition of MMP-9 expressions in THP-1 derived macrophages. Macrophages were cultured in medium containing 10% FBS and different concentrations of ASA for 24 h. Total RNAs were isolated and mRNA levels for MMP-9 and Actin genes were examined by RT-PCR analysis. Amplified cDNA products were applied to 1.5% agarose gels, stained with ethidium bromide and visualized under a UV light (A). The signal intensities from gels were qualified by the Quantity One software and transformed to the bar graph (B). Results are expressed as mean ±S.D, of three experiments with duplicated samples. * P < 0.05,compared to control.