Macrophage phenotype does not affect protease anti-protease imbalance in COPD

Matrix metalloproteases (MMP) 9 and 2, and the inhibitor, TIMP1, are elevated in COPD but there remains an imbalance towards higher protease activity. This may be due to macrophage (mΦ) dysfunction. To study this, monocyte-derived macrophages (MDM) from non-smokers (NS n=3), smokers (S n=4) and COPD patients (COPD n=4) were differentiated with GM-CSF (GΦ) or M-CSF (MΦ) for 12 days. MMP and TIMP gene expression was examined by qPCR and MMP9 protein and activity using zymography. Although there was a trend towards increased MMP9 and MMP2 expression in COPD MDM, this did not reach significance (Table1). TIMP1 expression showed a trend towards increased expression in COPD, while TIMP2 appeared to decrease in COPD compared to NS MDM (Table 1). mΦ phenotype had no effect on expression. Total MMP9 protein and activity were significantly higher in MDM from S and COPD at baseline compared to NS (p<0.05) (GΦ total MMP9; NS 29±9, S 97±10, COPD 69±20 µg/ml) with no difference between GΦ and MΦ. Stimulation with LPS or IL4 (10ng/ml) for 24h significantly increased total and active MMP9 in NS (p<0.05), but not in S or COPD MDM (GΦ total MMP9; NS LPS 58± 4, IL4 61±13; S LPS 89±6, IL4 51±4; COPD LPS 61±11, IL4 71±12 µg/ml). MMP9 activity is increased in MDM from COPD and S but is not stimulated further by LPS or IL4 suggesting that MMP9 is constituently activated in these mΦ and is unrelated to phenotype.