IDENTIFICATION OF A SERUM GELATINASE ASSOCIATED WITH THE OCCURRENCE OF CEREBRAL ANEURYSMS AS PRO-MATRIX METALLOPROTEINASE-2

Background and Purpose-Subarachnoid hemorrhage from intracranial aneur ysm rupture produces a severe form of stroke. Extracellular matrix rem odeling is associated with cerebral aneurysms and may play a role in t he formation or rupture of these lesions. We previously reported a 3-f old increase in a 72-kDa serum gelatinase in a subgroup of aneurysm pa tients. The purpose of the present study was to further characterize a nd identify this gelatinase. Methods-Serum samples were collected from surgical patients with intracranial aneurysms. The following series o f experiments was designed to further characterize and identify the pr edominant serum gelatinase found in the subgroup of patients with incr eased gelatinase activity. Gelatin zymography was performed on native serum samples and compared with serum that had been pretreated with a known metalloproteinase activator (4-aminophenylmercuric acetate [APMA ]). Gelatin zymography was repeated in the presence of a matrix metall oproteinase (MMP) inhibitor (EDTA) and a serine proteinase inhibitor ( phenylmethylsulfonyl fluoride [PMSF]). Final identification was made b y Western blotting with the use of monoclonal antibodies to MMP-2 and MMP-9. Results-A consistent gelatinolytic band (72 kDa) was identified in all serum samples (n=60). Pretreatment of the serum by APMA (n=60) lowered the molecular weight of the band to 66 kDa. The band was inhi bited by EDTA (n=10) but not PMSF (n=10), thus characterizing the circ ulating 72-kDa gelatinase as an inactive pro-MMP. Western blotting (n= 20) identified the 72-kDa band as MMP-2. Conclusions-These findings co nfirm that the increased gelatinolytic activity observed in vitro in a subset of cerebral aneurysm patients is due to pro-MMP-2.