Aim: To determine a relationship between matrix metalloproteinase-9 (MMP-9) activity and its tissue inhibitors TIMP-1 and 2, tumor necrosis factor-alpha (TNF-alpha), bone mineral density (BMD), and bone exchange in chronic obstructive pulmonary disease (COPD).
Subjects and methods: Seventy-six patients with COPD and 20 healthy volunteers were examined using dual-energy X-ray absorptiometry n the lumbar spine (L(II)-L(IV)) and femoral neck (FN). The serum levels of MMP-9, TIMP-1 and TIMP-2, TNF-alpha, and beta-Crosslaps (betaCL) were measured.
Results: There was a higher MMP-9 level in COPD than that in the controls ((383.8 +/- 54.2 and 137.6 +/- 31.4 pg/ml, respectively; p < 0.01). The levels of TIMP-1 and TIMP-2 were not different from those in the control group. An inverse correlation was found between forced expiratory volume in one second (FEV1) and MMP-9 concentration (r = -0.59; p = 0.002) and a positive correlation with smoking index (r = 0.47; p = 0.04). There was an inverse correlation between MMP-9 concentration and BMD in both L(II)-L(IV) and FN (r = -0.67; p < 0.001 and r = -0.61; p < 0.01, respectively) and a direct correlation with betaCL (r = 0.53; p = 0.04). An inverse correlation was established between TNF-alpha and T index in both L(II)-L(IV) (r = -0.54; p < 0.01) and FN (r = -0.48; p < 0.01). At the same time, the level of TNF-alpha directly correlated with the bone resorption marker betaCL (r = 0.53; p = 0.002) and MMP-9 (r = 0.57; p = 0.003).
Conclusion: Elevated MMP-9 levels may play an important role in type I collagen degradation, giving rise to enhanced bone resorption in COPD.