Elevated plasma cathepsin B and cystatin C levels in chronic obstructive pulmonary disease

Background: The aim of this study was to investigate differential changes in plasma levels of cathepsin B and its naturally inhibitory protein cystatin C in chronic obstructive pulmonary disease (COPD) patients during and 2 weeks as well as 8 weeks after acute exacerbation (AE). Materials and methods: Forty six COPD patients, including 44 male and 2 female, were included in this study. Plasma were collected in three different times, i.e., during, and 2 weeks as well as 8 weeks after AE. Plasma cathepsin B and cystatin C levels were measured in 46 adult patients with COPD and 18 healthy controls using a commercial enzyme-linked immunosorbent assay (ELISA). Results: The plasma levels of cathepsin B were significantly higher in COPD patients at 2 weeks and 8 weeks after AE when compared with those of healthy subjects. The plasma level of cystatin C showed significantly higher than the plasma levels of healthy subjects at time of AE, also 2 weeks and 8 weeks after AE. However, there was no significant difference between the time of AE and 2 or 8 weeks after AE. Conclusions: The persistently significant higher plasma levels of cystatin C in COPD patients not only on AE but also at 2 and 8 weeks after AE than those in healthy subjects might represent a chronic inflammatory status in COPD. Moreover, plasma level of cathepsin B significantly increased at 2 weeks after AE and which returned to be non-significant at 8 weeks after AE in COPD patients. These findings might hint cathepsin B is one of the acute phase reactive protein in AE of COPD.