Department of Biology and Cell Biology Program, Hospital for Sick Children, Toronto, Ontario, Canada.
Tissue inhibitor of metalloproteinase-3 (TIMP-3) is a natural inhibitor of metalloproteinases involved in matrix degradation and ectodomain shedding of many cell-surface proteins, including death receptors and/or their ligands. In the present study, we examined the role of TIMP-3 in Fas-mediated neuronal cell death following cerebral ischemia, using both gene deletion and pharmacological approaches. In culture, exposure of primary cortical neurons to 2 h of oxygen-glucose deprivation (OGD) resulted in delayed neuronal cell death that was dependent on activation of the death receptor, Fas. Cortical cultures derived from timp-3(-/-) mice displayed partial resistance against OGD-induced neuronal cell death and also displayed increased shedding of Fas ligand (FasL) into the culture media, compared to wild-type control cultures. Both the increased neuroprotection and increased FasL shedding in timp-3(-/-) cultures were reversed by addition of exogenous metalloproteinase inhibitors, recombinant TIMP-3 or GM6001. In vivo, timp-3(-/-) mice showed marked resistance to a brief (30 min) middle cerebral artery occlusion (MCAO), but were not protected against more severe lesions induced by 90 min of MCAO. These studies demonstrate that TIMP-3 facilitates Fas-mediated neuronal cell death following OGD and plays a pro-apoptotic role in mild cerebral ischemia.