Quercetin treatment decreases levels of MMP9 and MMP12 and increases expression of SIRT1 in elastase/LPS-exposed mice. mRNA expression of Mmp9, Mmp12, and Sirt1 was measured by qPCR. MMP activity was determined by gelatin zymography. Sirt1 protein level was measured in the lung homogenates by Western blot analysis. A and B. Quercetin treated elastase/LPS exposed mice show significantly reduced Mmp9 and Mmp12 mRNA levels compared to mice treated with vehicle. C Quercetin treatment completely reduces MMP9 and MMP12 activities in elastase/LPS exposed mice. D and E. Quercetin increases Sirt1 mRNA and protein levels in elastase/LPS exposed mice. F. Ratio of Sirt1 protein/β-actin normalized to control mice calculated from 6 mice per group. Data represent mean and SEM (n = 10, *different from PBS/vehicle group, p≤0.05; † different from vehicle-treated, elastase/LPS-exposed mice, p≤0.05 one-way ANOVA). Images in C and E are representative of 4 to 6 animals per group.