zj43 and Brain-Injuries

Traumatic brain injury (TBI) leads to a rapid and excessive increase in glutamate concentration in the extracellular milieu, which is strongly associated with excitotoxicity and neuronal degeneration. N-acetylaspartylglutamate (NAAG), a prevalent peptide neurotransmitter in the vertebrate nervous system, is released along with glutamate and suppresses glutamate release by actions at pre-synaptic metabotropic glutamate autoreceptors. Extracellular NAAG is hydrolyzed to N-acetylaspartate and glutamate by peptidase activity. In the present study PGI-02776, a newly designed di-ester prodrug of the urea-based NAAG peptidase inhibitor ZJ-43, was tested for neuroprotective potential when administered intraperitoneally 30 min after lateral fluid percussion TBI in the rat. Stereological quantification of hippocampal CA2-3 degenerating neurons at 24 h post injury revealed that 10 mg/kg PGI-02776 significantly decreased the number of degenerating neurons (p<0.05). Both average latency analysis of Morris water maze performance and assessment of 24-hour memory retention revealed significant differences between sham-TBI and TBI-saline. In contrast, no significant difference was found between sham-TBI and PGI-02776 treated groups in either analysis indicating an improvement in cognitive performance with PGI-02776 treatment. Histological analysis on day 16 post-injury revealed significant cell death in injured animals regardless of treatment. In vitro NAAG peptidase inhibition studies demonstrated that the parent compound (ZJ-43) exhibited potent inhibitory activity while the mono-ester (PGI-02749) and di-ester (PGI-02776) prodrug compounds exhibited moderate and weak levels of inhibitory activity, respectively. Pharmacokinetic assays in uninjured animals found that the di-ester (PGI-02776) crossed the blood-brain barrier. PGI-02776 was also readily hydrolyzed to both the mono-ester (PGI-02749) and the parent compound (ZJ-43) in both blood and brain. Overall, these findings suggest that post-injury treatment with the ZJ-43 prodrug PGI-02776 reduces both acute neuronal pathology and longer term cognitive deficits associated with TBI.

Topics: Animals; Brain Injuries; Disease Models, Animal; Glutamate Carboxypeptidase II; Male; Mice; Mice, Inbred C57BL; Nerve Degeneration; Neuroprotective Agents; Neurotransmitter Agents; Protease Inhibitors; Rats; Rats, Sprague-Dawley; Urea

Traumatic brain injury (TBI) produces a rapid and excessive elevation in extracellular glutamate associated with excitotoxicity and secondary brain pathology. The peptide neurotransmitter Nacetylaspartylglutamate (NAAG) suppresses glutamate transmission through selective activation of presynaptic Group II metabotropic glutamate receptor subtype 3 (mGluR3). Thus, inhibition of NAAG peptidase activity and the prolong presence of synaptic NAAG were hypothesized to have significant potential for cellular protection following TBI. In the present study, a novel NAAG peptidase inhibitor, ZJ-43, was used in four different doses (0, 50, 100, or 150 mg/kg). Each dose was repeatedly administered i.p. (n=5/group) by multiple injections at three times (0 time, 8 h, 16 h) after moderate lateral fluid percussion TBI in the rat. An additional group was co-administered ZJ-43 (150 mg/kg) and the Group II mGluR antagonist, LY341495 (1 mg/kg), which was predicted to abolish any protective effects of ZJ-43. Rats were euthanized at 24 h after TBI, and brains were processed with a selective marker for degenerating neurons (Fluoro-Jade B) and a marker for astrocytes (GFAP). Ipsilateral neuronal degeneration and bilateral astrocyte loss in the CA2/3 regions of the hippocampus were quantified using stereological techniques. Compared with vehicle, ZJ-43 significantly reduced the number of the ipsilateral degenerating neurons (p<0.01) with the greatest neuroprotection at the 50 mg/kg dose. Moreover, LY341495 successfully abolished the protective effects of ZJ-43. 50 mg/kg of ZJ-43 also significantly reduced the ipsilateral astrocyte loss (p<0.05). We conclude that the NAAG peptidase inhibitor ZJ-43 is a potential novel strategy to reduce both neuronal and astrocyte damage associated with the glutamate excitotoxicity after TBI.

Topics: Animals; Astrocytes; Brain Injuries; Cell Death; Dose-Response Relationship, Drug; Glutamate Carboxypeptidase II; Male; Nerve Degeneration; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate; Urea