Abstract
Epileptogenesis is the gradual process responsible for converting a healthy brain into an epileptic brain. This process can be triggered by a wide range of factors, including brain injury or tumors, infections, and status epilepticus. Epileptogenesis results in aberrant synaptic plasticity, neuroinflammation and seizure-induced cell death. As Matrix Metalloproteinases (MMPs) play a crucial role in cellular plasticity by remodeling the extracellular matrix (ECM), gelatinases (MMP-2 and MMP-9) were recently highlighted as key players in epileptogenesis. In this work, we engineered a biosensor to report in situ gelatinase activity in a model of epileptogenesis. This biosensor encompasses a gelatinase-sensitive activatable cell penetrating peptide (ACPP) coupled to a TAMRA fluorophore, allowing fluorescence uptake in cells displaying endogenous gelatinase activities. In a preclinical mouse model of temporal lobe epilepsy (TLE), the intrahippocampal kainate injection, ACPPs revealed a localized distribution of gelatinase activities, refining temporal cellular changes during epileptogenesis. The activity was found particularly but not only in the ipsilateral hippocampus, starting from the CA1 area and spreading to dentate gyrus from the early stages throughout chronic epilepsy, notably in neurons and microglial cells. Thus, our work shows that ACPPs are suitable molecular imaging probes for detecting the spatiotemporal pattern of gelatinase activity during epileptogenesis, suggesting their possible use as vectors to target cellular reactive changes with treatment for epileptogenesis.
Highlights
The biology of excitatory synapses relies on its tetrapartite organization, which includes pre- and post-synaptic neurons, glial cells and the extracellular matrix (ECM) stabilizing synaptic contacts
To characterize the uptake of activatable cell penetrating peptide (ACPP) in neuronal cells, we first searched for suitable gelatinase activation conditions in vitro in primary cultures of hippocampal neurons. β-dystroglycan (β-DG) was identified previously as a native substrate of Matrix Metalloproteinases (MMPs)-9 that is cleaved in response to enhanced neuronal activity (Michaluk et al, 2007)
The present work reports the in situ gelatinase activation during epileptogenesis using ACPPs
Summary
The biology of excitatory synapses relies on its tetrapartite organization, which includes pre- and post-synaptic neurons, glial cells and the extracellular matrix (ECM) stabilizing synaptic contacts. MMP-2 and MMP-9 constitute the class of gelatinases and are amongst the most abundant MMPs in the brain. They have emerged as regulators of diverse biological processes under normal and pathological conditions. These secreted endopeptidases have a significant role in extracellular proteolytic processes at the excitatory synapses. MMP-9 contributes to the regulation of structural and functional synaptic plasticity (Nagy et al, 2006; Szepesi et al, 2013).
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