STAT4 and chronic obstructive pulmonary disease: In comparison with the expression exhibited in the control group, the expression of STAT4/STAT6 and MMP-9/TIMP-1 was decreased in the COPD groups; the expression of STAT4/STAT6 and MMP-9/TIMP-1 was decreased in medium-dose and high-dose groups compared with the expression in the low-dose group; the expression of STAT4/STAT6 and MMP-9/TIMP-1 was decreased in high-dose groups compared with the expression in the medium dose group (all p < 0.05).