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Neurons are embedded in an extracellular matrix (ECM), which functions both as a scaffold and as a regulator of neuronal function. The ECM is in turn dynamically altered through the action of serine proteases, which break down its constituents. This pathway has been implicated in the regulation of synaptic plasticity and of neuronal intrinsic excitability. In this study, we determined the short-term effects of interfering with proteolytic processes in the ECM, with a newly developed serine protease inhibitor. We monitored the spontaneous electrophysiological activity of in vitro primary rat cortical cultures, using microelectrode arrays. While pharmacological inhibition at a low dosage had no significant effect, at elevated concentrations it altered significantly network synchronization and functional connectivity but left unaltered single-cell electrical properties. These results suggest that serine protease inhibition affects synaptic properties, likely through its actions on the ECM. [ABSTRACT FROM AUTHOR]

Objective Urokinase-type plasminogen activator ( uPA) and kallikrein-related peptidase 8 ( KLK8) are serine proteases that contribute to extracellular matrix ( ECM) remodeling after brain injury. They can be labelled with the novel radiotracer [111In] MICA-401. As the first step in exploring the applicability of [111In] MICA-401 in tracing the mechanisms of postinjury ECM reorganization in vivo, we performed in vitro and ex vivo studies, assessing [111In] MICA-401 distribution in the brain in two animal models: kainic acid-induced status epilepticus ( KASE) and controlled cortical impact ( CCI)-induced traumatic brain injury ( TBI). Methods In the KASE model, in vitro autoradiography with [111In] MICA-401 was performed at 7 days and 12 weeks post- SE. To assess seizure burden, rats were monitored using video-electroencephalography (EEG) for 1 month before the 12-week time point. In the CCI model, in vitro autoradiography was performed at 4 days and ex vivo autoradiography at 7 days post- TBI. Results At 7 days post- SE , in vitro autoradiography revealed significantly decreased [111In] MICA-401 binding in hippocampal CA3 subfield and extrahippocampal temporal lobe ( ETL). In the chronic phase, when animals had developed spontaneous seizures, specific binding was decreased in CA3 and CA1/ CA2 subfields of hippocampus, dentate gyrus, ETL, and parietal cortex. Of interest, KASE rats with the highest frequency of seizures had the lowest hippocampal [111In] MICA-401 binding ( r = −0.76, p ≤ 0.05). Similarly, at 4 days post- TBI, in vitro [111In] MICA-401 binding was significantly decreased in medial and lateral perilesional cortex and ipsilateral dentate gyrus. Ex vivo autoradiography at 7 days post- TBI, however, revealed increased tracer uptake in perilesional cortex and hippocampus, which was likely related to tracer leakage due to blood-brain barrier ( BBB) disruption. Significance Strong association of reduced [111In] MICA-401 binding with seizure burden in the KASE model suggests that analysis of reduced levels of active uPA/ KLK8 represents a novel biomarker candidate to be explored as a biomarker for epilepsy severity. However, limited BBB permeability of [111In] MICA-401 currently limits its application in vivo. [ABSTRACT FROM AUTHOR]

MMP-9 is a zinc-dependent endopeptidase that is involved in the proteolytic degradation of the extracellular matrix and plays an important role in cancer migration, invasion, and metastasis. The aim of this study was to evaluate the potential of MMP-tracers [18F]BR420 and [18F]BR351 for MMP-9 imaging in a colorectal cancer xenograft model. [18F]BR420 and [18F]BR351 were synthesized using an automated synthesis module. For [18F]BR420, a novel and improved radiosynthesis was developed. Plasma stability and MMP-9-targeting capacity of both radiotracers was compared in the Colo205 colorectal cancer model. MMP-9 and MMP-2 expression levels in the tumors were evaluated by immunohistochemistry and in situ zymography. μPET imaging as well as ex vivo biodistribution revealed a higher tumor uptake for [18F]BR420 (3.15% ± 0.03% ID/g vs 0.94% ± 0.18% ID/g for [18F]BR351 at 2 hours pi) but slower blood clearance compared with [18F]BR351. [18F]BR351 was quickly metabolized in plasma with 20.28% ± 5.41% of intact tracer remaining at 15 minutes postinjection (PI). By contrast, [18F]BR420 displayed a higher metabolic stability with >86% intact tracer remaining at 2 hours PI. Immunohistochemistry revealed the presence of MMP-9 and MMP-2 in the tumor tissue, which was confirmed by in situ zymography. However, an autoradiography analysis of tracer distribution in the tumors did not correlate with MMP-9 expression. [18F]BR420 displayed a higher tumor uptake and higher stability compared with [18F]BR351 but a low tumor-to-blood ratio and discrepancy between tracer distribution and MMP-9 immunohistochemistry. Therefore, both tracers will not be usefulness for MMP-9 imaging in colorectal cancer. [ABSTRACT FROM AUTHOR]

Objective: Urokinase-type plasminogen activator (uPA) and kallikrein-related peptidase 8 (KLK8) are serine proteases that contribute to extracellular matrix (ECM) remodeling after brain injury. They can be labelled with the novel radiotracer [ 111 In]MICA-401. As the first step in exploring the applicability of [ 111 In]MICA-401 in tracing the mechanisms of postinjury ECM reorganization in vivo, we performed in vitro and ex vivo studies, assessing [ 111 In]MICA-401 distribution in the brain in two animal models: kainic acid-induced status epilepticus (KASE) and controlled cortical impact (CCI)-induced traumatic brain injury (TBI)., Methods: In the KASE model, in vitro autoradiography with [ 111 In]MICA-401 was performed at 7 days and 12 weeks post-SE. To assess seizure burden, rats were monitored using video-electroencephalography (EEG) for 1 month before the 12-week time point. In the CCI model, in vitro autoradiography was performed at 4 days and ex vivo autoradiography at 7 days post-TBI., Results: At 7 days post-SE, in vitro autoradiography revealed significantly decreased [ 111 In]MICA-401 binding in hippocampal CA3 subfield and extrahippocampal temporal lobe (ETL). In the chronic phase, when animals had developed spontaneous seizures, specific binding was decreased in CA3 and CA1/CA2 subfields of hippocampus, dentate gyrus, ETL, and parietal cortex. Of interest, KASE rats with the highest frequency of seizures had the lowest hippocampal [ 111 In]MICA-401 binding (r = -0.76, p ≤ 0.05). Similarly, at 4 days post-TBI, in vitro [ 111 In]MICA-401 binding was significantly decreased in medial and lateral perilesional cortex and ipsilateral dentate gyrus. Ex vivo autoradiography at 7 days post-TBI, however, revealed increased tracer uptake in perilesional cortex and hippocampus, which was likely related to tracer leakage due to blood-brain barrier (BBB) disruption., Significance: Strong association of reduced [ 111 In]MICA-401 binding with seizure burden in the KASE model suggests that analysis of reduced levels of active uPA/KLK8 represents a novel biomarker candidate to be explored as a biomarker for epilepsy severity. However, limited BBB permeability of [ 111 In]MICA-401 currently limits its application in vivo., (Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.)

MMP-9 is a zinc-dependent endopeptidase that is involved in the proteolytic degradation of the extracellular matrix and plays an important role in cancer migration, invasion, and metastasis. The aim of this study was to evaluate the potential of MMP-tracers [ 18 F]BR420 and [ 18 F]BR351 for MMP-9 imaging in a colorectal cancer xenograft model. [ 18 F]BR420 and [ 18 F]BR351 were synthesized using an automated synthesis module. For [ 18 F]BR420, a novel and improved radiosynthesis was developed. Plasma stability and MMP-9-targeting capacity of both radiotracers was compared in the Colo205 colorectal cancer model. MMP-9 and MMP-2 expression levels in the tumors were evaluated by immunohistochemistry and in situ zymography. μPET imaging as well as ex vivo biodistribution revealed a higher tumor uptake for [ 18 F]BR420 (3.15% ± 0.03% ID/g vs 0.94% ± 0.18% ID/g for [ 18 F]BR351 at 2 hours pi) but slower blood clearance compared with [ 18 F]BR351. [ 18 F]BR351 was quickly metabolized in plasma with 20.28% ± 5.41% of intact tracer remaining at 15 minutes postinjection (PI). By contrast, [ 18 F]BR420 displayed a higher metabolic stability with >86% intact tracer remaining at 2 hours PI. Immunohistochemistry revealed the presence of MMP-9 and MMP-2 in the tumor tissue, which was confirmed by in situ zymography. However, an autoradiography analysis of tracer distribution in the tumors did not correlate with MMP-9 expression. [ 18 F]BR420 displayed a higher tumor uptake and higher stability compared with [ 18 F]BR351 but a low tumor-to-blood ratio and discrepancy between tracer distribution and MMP-9 immunohistochemistry. Therefore, both tracers will not be usefulness for MMP-9 imaging in colorectal cancer., (Copyright © 2016 John Wiley & Sons, Ltd.)