gpi-5693 and Peripheral-Nervous-System-Diseases

Pyridoxine is used as a supplement for treating conditions such as vitamin deficiency as well as neurological disorders such as depression, epilepsy and autism. A significant neurologic complication of pyridoxine therapy is peripheral neuropathy thought to be a result of long-term and high dose usage. Although pyridoxine-induced neuropathy is transient and can remit after its withdrawal, the process of complete recovery can be slow. Glutamate carboxypeptidase II (GCP II) inhibition has been shown to improve symptoms of both chemotherapy- and diabetic-induced neuropathy. This study evaluated if GCP II inhibition could behaviorally and physiologically improve pyridoxine-induced neuropathy. In the current study, high doses of pyridoxine (400 mg/kg, twice a day for seven days) were used to induce neuropathy in rats. An orally bioavailable GCP II inhibitor, 2-(3-mercaptopropyl) pentanedioic acid (2-MPPA), was administered daily at a dose of 30 mg/kg starting from the onset of pyridoxine injections. Body weight, motor coordination, heat sensitivity, electromyographical (EMG) parameters and nerve morphological features were monitored. The results show beneficial effects of GCP II inhibition including normalization of hot plate reaction time, foot fault improvements and increased open field distance travelled. H wave frequency, amplitude and latency as well as sensory nerve conduction velocity (SNCV) were also significantly improved by 2-MPPA. Lastly, GCP II inhibition resulted in morphological protection in the spinal cord and sensory fibers in the lumbar region dorsal root ganglia (DRG). In conclusion, inhibition of GCP II may be beneficial against the peripheral sensory neuropathy caused by pyridoxine.

Topics: Animals; Behavior, Animal; Female; Glutamate Carboxypeptidase II; Glutarates; Motor Activity; Neurodegenerative Diseases; Neuroprotective Agents; Peripheral Nervous System Diseases; Protease Inhibitors; Pyridoxine; Rats; Rats, Sprague-Dawley; Sensation; Sulfhydryl Compounds

A series of thiol-based inhibitors containing a benzyl moiety at the P1' position have been synthesized and tested for their abilities to inhibit glutamate carboxypeptidase II (GCP II). 3-(2-Carboxy-5-mercaptopentyl)benzoic acid 6c was found to be the most potent inhibitor with an IC(50) value of 15 nM, 6-fold more potent than 2-(3-mercaptopropyl)pentanedioic acid (2-MPPA), a previously discovered, orally active GCP II inhibitor. Subsequent SAR studies have revealed that the phenoxy and phenylsulfanyl analogues of 6c, 3-(1-carboxy-4-mercaptobutoxy)benzoic acid 26a and 3-[(1-carboxy-4-mercaptobutyl)thio]benzoic acid 26b, also possess potent inhibitory activities toward GCP II. In the rat chronic constriction injury (CCI) model of neuropathic pain, compounds 6c and 26a significantly reduced hyperalgesia following oral administration (1.0 mg/kg/day).

Topics: Analgesics; Animals; Antigens, Surface; Benzoates; Chronic Disease; Constriction, Pathologic; Glutamate Carboxypeptidase II; Glutarates; Humans; Pain; Peripheral Nervous System Diseases; Rats; Structure-Activity Relationship; Sulfhydryl Compounds

Two representative glutamate carboxypeptidase II (GCP II) inhibitors, 2-(hydroxypentafluorophenylmethyl-phosphinoylmethyl)pentanedioic acid 2 and 2-(3-mercaptopropyl)pentanedioic acid 3, were synthesized in high optical purities (>97%ee). The two enantiomers of 2 were prepared from previously reported chiral intermediates, (R)- and (S)-2-(hydroxyphosphinoylmethyl)pentanedioic acid benzyl esters 8. The synthesis of (R)- and (S)-3 involves the hydrolysis of (R)- and (S)-3-(2-oxo-tetrahydro-thiopyran-3-yl)propionic acids, (R)- and (S)-11, the corresponding optically pure thiolactones delivered by chiral chromatographic separation of the racemic 11. GCP II inhibitory assay revealed that (S)-2 is 40-fold more potent than (R)-2. In contrast, both enantiomers of 3 inhibited GCP II with nearly equal potency. The efficacy observed in subsequent animal studies with these enantiomers correlated well with the inhibitory potency in a GCP II assay.

Topics: Analgesics; Animals; Brain Ischemia; Cerebral Cortex; Constriction, Pathologic; Crystallography, X-Ray; Glutamate Carboxypeptidase II; Glutarates; Infarction, Middle Cerebral Artery; L-Lactate Dehydrogenase; Molecular Structure; Neuroprotective Agents; Pain; Peripheral Nervous System Diseases; Phosphinic Acids; Rats; Stereoisomerism; Structure-Activity Relationship; Sulfhydryl Compounds; Tissue Culture Techniques

A series of 2-(thioalkyl)pentanedioic acids were synthesized and evaluated as inhibitors of glutamate carboxypeptidase II (GCP II, EC 3.4.17.21). The inhibitory potency of these thiol-based compounds against GCP II was found to be dependent on the number of methylene units between the thiol group and pentanedioic acid. A comparison of the SAR of the thiol-based inhibitors to that of the phosphonate-based inhibitors provides insight into the role of each of the two zinc-binding groups in GCP II inhibition. The most potent thiol-based inhibitor, 2-(3-mercaptopropyl)pentanedioic acid (IC(50) = 90 nM), was found to be orally bioavailable in rats and exhibited efficacy in an animal model of neuropathic pain following oral administration.

Topics: Administration, Oral; Analgesics; Animals; Biological Availability; Carboxypeptidases; Constriction, Pathologic; Enzyme Inhibitors; Glutamate Carboxypeptidase II; Glutarates; Hot Temperature; Hyperalgesia; Male; Pain; Peripheral Nervous System Diseases; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Structure-Activity Relationship; Sulfhydryl Compounds