Gelatinase: enzymatic activity as potential biomarker in multiple sclerosis

OBJECTIVE Gelatinases (MMP-9 and MMP-2) are enzymes which degrade components of the extracellular matrix. Their activity is the result of a balance between two processes: activation of proenzymes and inhibition by Tissue Inhibitors (TIMPs). Multiple Sclerosis (MS) appears associated to a unbalance MMP-2 and MMP-9. MMP-9 is present in three different forms: the inactive proenzyme (92 kDa), a "long" (82 kDa) active form lacking in the N-terminal propeptide, and a "short" (66 kDa) active form, lacking N- and C-terminal. TIMP-1 binds with high affinity to the C-terminal domain, the binding between "short" MMP-9 and TIMP-1 seems unlikely. The aim of this study is to verify the presence of the "short" active form of MMP-9 in vivo and its potential role as marker of disease in MS. MATERIALS AND METHODS MMP-9 and MMP-2 activity was measured using commercially Activity Assay Systems. The levels of gelatinases were, also, measured by zymography on gelatin-copolymerized gels. RESULTS We have observed that the different forms of MMP9 can be distinguished on the basis of the sensitivity to its inhibitor. When the mixture of 82kDa and 66 kDa MMP-9 was treated with TIMP1, only the 66 kDa form is detected by activity assay. Then we have assayed the levels of MMP-9 not regulated by TIMP-1 and active MMP-2 in serum of patients with active MS and patients with stable MS. The results show the in MS active patients the levels of 66 kDa MMP-9 are increased while the levels of active MMP-2 are decreased. CONCLUSIONS Our results show that the upregulation of the 66 kDa form of MMP-9, together with the downregulation of active MMP-2, could be a stronger biomarker of disease activity.