Matrix metalloproteinase-9 is elevated in serum of patients with amyotrophic lateral sclerosis

Matrix metalloproteinase-9 (MMP-9) and its specific inhibitor, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), were analysed by enzyme-linked immunosorbent assay (ELISA) and by zymography in serum and cerebrospinal fluid (CSF) of patients with amyotrophic lateral sclerosis (ALS). In contrast to patients with inflammatory diseases, MMP-9 levels were not elevated in CSF of ALS patients. In serum, however, compared to healthy donors, MMP-9 was significantly (p = 0.0003) increased up to levels as high as those of viral meningoencephalitis (VM) or bacterial meningitis (BM) patients. MMP-9 levels remained elevated during long-term observation of ALS patients. In the absence of an inflammatory response, the results indicate that the increase of MMP-9 in serum of ALS patients might be caused by upregulation of MMP-9 in denervated muscles or in degenerating peripheral nerves following motor neurone loss.