The Orally Active Glutamate Carboxypeptidase II Inhibitor E2072 Exhibits Sustained Nerve Exposure and Attenuates Peripheral Neuropathy
Peripheral neuropathy from nerve trauma is a significant problem in the human population and often constitutes a dose limiting toxicity in patients receiving chemotherapy. E2072 is a potent (Ki=10 nM), selective and orally available inhibitor of glutamate carboxypeptidase II (GCPII). Here, we report that E2072 attenuates hyperalgesia and nerve conduction velocity (NCV) deficits in preclinical rodent models of neuropathic pain and oxaliplatin-induced neuropathy. In the chronic constrictive injury (CCI) model, orally administered E2072 reversed pre-existing thermal hyperalgesia in rats in a dose-dependent fashion, with a minimally effective dose of 0.1 mg/kg/day. Interestingly, multiple days of dosing of E2072 were required before analgesia was realized even though GCPII inhibitory exposures were achieved on the first day of dosing. In addition, analgesia was found to persist for up to 7 days after cessation of dosing, consistent with E2072's pharmacokinetic profile and sustained exposure. Furthermore, in a chronic oxaliplatin-induced neuropathy model, (6 mg/kg oxaliplatin ip twice weekly for 4 weeks), female BALB/C mice receiving daily oral E2072 at 1.0 and 0.1 mg/kg displayed no deficits in either caudal or digital velocity compared to significant deficits observed in oxaliplatin alone-treated mice (12±3% and 9±2% respectively). Similar findings were seen with oxaliplatin-induced digital and caudal amplitude deficits. Importantly, E2072 showed no interference with the antineoplastic efficacy of oxaliplatin in mice bearing leukemia (L1210), even at doses 100 times its neuroprotective/analgesic dose, indicating a selective effect on neuropathy. These data support the therapeutic utility of GCPII inhibitors in neuropathy and neuropathic pain.
Available from: Rana Rais
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ABSTRACT: δ-Thiolactones derived from thiol-based glutamate carboxypeptidase II (GCPII) inhibitors were evaluated as prodrugs. In rat liver microsomes, 2-(3-mercaptopropyl)pentanedioic acid (2-MPPA, 1) was gradually produced from 3-(2-oxo-tetrahydro-thiopyran-3-yl)propionic acid (5), a thiolactone derived from 1. Compound 1 was detected in plasma at concentrations well above its IC50 value for GCPII following oral administration of 5 in rats. Consistent with the oral plasma pharmacokinetics, thiolactone 5 exhibited efficacy in a rat model of neuropathic pain following oral administration.
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ABSTRACT: The present study compared ketamine-induced neurotoxicity in the neuron-glia mixed cultures and neuronal cultures and further explored the neuroprotective effect of the NAAG peptidase inhibitor 2-(phosphonomethyl) pentanedioic acid (2-PMPA). Firstly, Rosenfeld's staining and immunofluorescence staining of microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) were used to address the difference of morphology in the mixed cultures and neuronal cultures. Our results showed that neurons and astrocytes grew in good conditions. The ratio of neurons and astrocytes in the mixed cultures was around 1:1, and the purity of neurons in the neuronal cultures is 91.3%. Furthermore, ketamine was used to test the hypothesis that the presence of a higher proportion of glia in the mixed cultures would be protective against ketamine-induced neurotoxicity in the mixed cultures compared with neuronal cultures. The results showed that ketamine-induced morphological changes, cell viability decrease and lactate dehydrogenase (LDH) levels increase were significantly mitigated in neuron-glia mixed cultures compared with neuronal cultures. Furthermore, 2-PMPA was included to further explore efficient protective drug for ketamine-induced neurotoxicity. Our results showed that 2-PMPA reduced ketamine-induced decrease of cell viability and increase of LDH levels in the mixed cultures but not in the neuronal cultures. Further morphological changes of neurons and astrocytes also indicated that 2-PMPA could improve ketamine damaged neurons in the mixed cultures instead of neuronal cultures. These results indicate that glia protect neurons from ketamine-induced neurotoxicity. These data further suggest that glia mediate the neuroprotective effect of 2-PMPA and 2-PMPA has the potential to treat ketamine-induced neurotoxicity in vivo. Delineating the mechanisms underlying the communication between neurons and glia and the neuroprotective effects of 2-PMPA in the mixed cultures to ketamine-induced neurotoxicity require further investigation.
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ABSTRACT: Glutamate carboxypeptidase II (GCPII) is a transmembrane zinc metallopeptidase found mainly in the nervous system, prostate and small intestine. In the nervous system, glia-bound GCPII mediates the hydrolysis of the neurotransmitter N-acetylaspartylglutamate (NAAG) into glutamate and N-acetylaspartate. Inhibition of GCPII has been shown to attenuate excitotoxicity associated with enhanced glutamate transmission under pathological conditions. However, different strains of mice lacking the GCPII gene are reported to exhibit striking phenotypic differences. In this study, a GCPII gene knockout (KO) strategy involved removing exons 3 to 5 of GCPII generated a new GCPII KO mice line with no overt differences in standard neurological behavior compared to their wild-type (WT) littermates. However, GCPII KO mice were significantly less susceptible to moderate traumatic brain injury (TBI). GCPII gene KO significantly lessened neuronal degeneration and astrocyte damage in the CA2 and CA3 regions of the hippocampus 24h after moderate TBI. In addition, GCPII gene KO reduced TBI-induced deficits in long-term spatial learning/memory tested in the Morris water maze and motor balance tested via beam walking. Knockout of the GCPII gene is not embryonic lethal and affords histopathological protection with improved long-term behavioral outcomes after TBI, a result that further validates GCPII as a target for drug development consistent with results from studies using GCPII peptidase inhibitors. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
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