ABSTRACT
Spontaneous intracerebral hemorrhage (ICH) is one of the most recognized complications of cerebral amyloid angiopathy (CAA), but little is known about the molecular pathogenesis of this life-threatening complication. In this review, we present preliminary evidence which suggests that the extracellular-matrix-degrading protease, matrix metalloproteinase-9 (MMP-9), may play a role in the development of spontaneous ICH resulting from CAA. The amyloid-beta peptide (Abeta) induced the synthesis, cellular release, and activation of MMP-9 in murine cerebral endothelial cells (CECs), resulting in increased extracellular matrix (ECM) degradation. Furthermore, in a mouse model of CAA (APPsw transgenic mice), MMP-9 immunoreactivity was observed in amyloid-laden cerebral vessels in aged APPsw mice but not in young APPsw or aged wild-type mice. More extensive MMP-9 immunostaining was present in amyloid-laden vessels with evidence of microhemorrhage. These results suggest that increased vascular MMP-9 expression, stimulated by Abeta, may play a role in the pathogenesis of spontaneous intracerebral hemorrhage (ICH) in patients with CAA.
Subject(s)
Cerebral Amyloid Angiopathy/pathology , Cerebral Hemorrhage/pathology , Matrix Metalloproteinase 9/physiology , Animals , Cerebral Amyloid Angiopathy/complications , Cerebral Hemorrhage/etiology , Endothelium, Vascular/pathology , Extracellular Matrix/pathology , Humans , Immunohistochemistry , Mice , Mice, TransgenicABSTRACT
We examined the potential role of the extra-cellular matrix-degrading enzyme, matrix metalloproteinase-9 (MMP-9), in the pathogenesis of cerebral amyloid angiopathy (CAA)-induced spontaneous hemorrhage. The amyloid-beta peptide (Abeta) induced the synthesis, release and activation of MMP-9 in murine cerebral endothelial cells, resulting in increased extracellular matrix degradation. Furthermore, extensive MMP-9 immunoreactivity was observed in CAA-vessels with evidence of microhemorrhage in aged APPsw transgenic mice, but not detected in aged wild type or young APPsw mice. These results suggest that increased vascular MMP-9 expression, stimulated by Abeta, may play a role in the pathogenesis of spontaneous intracerebral hemorrhage in patients with CAA.