The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in the pathophysiology of neurodegeneration: a literature study.

Matrix metalloproteinases (MMPs) and their natural tissue inhibitors (TIMPs) are involved in cell signaling processes and the release of extracellular matrix (ECM) and non-ECM molecules. Nonregulated MMP activity and an imbalance between metalloproteinases and their inhibitors might contribute to various disorders, including neurodegenerative diseases such as Alzheimer's disease (AD), which is the most common cause of dementia. There is a complex relationship between MMPs and TIMPs with AD. It has been shown that MMPs and TIMPs are localized in neuritic senile plaques and neurofibrillary tangles in the postmortem brains of patients with AD. Some MMPs have also been shown to induce tau aggregation and the formation of neurofibrillary tangles in vitro. Moreover, MMPs contribute to AD pathogenesis via the disruption of the blood-brain barrier and promotion of neurodegeneration. However, MMPs can degrade both soluble and fibrillar forms of amyloid-β (Aβ). It has also been shown that Aβ enhances the expression of MMPs in neuroglial cultures and induces the release of TIMP-1 by brain cells. Inhibition of Aβ-induced MMP activity resulted in an improvement of performance tests in mice. Moreover, simultaneous examination of MMP-9, MMP-2, and TIMP-1 in the CSF contributed to the ability to differentiate between AD and other types of dementia. Thus, the aim of this literature study was to describe the role of MMPs and TIMPs in neurodegeneration, as well as their potential usefulness as CSF or plasma biomarkers in the diagnosis of AD as well as other neurodegenerative disorders and vascular dementia.