ABSTRACT
Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development.
Subject(s)
Anticonvulsants/pharmacology , Benzodiazepines/pharmacology , GABA-A Receptor Antagonists/pharmacology , Nootropic Agents/pharmacology , Receptors, GABA-A/drug effects , Animals , Anticonvulsants/chemical synthesis , Anticonvulsants/metabolism , Anticonvulsants/toxicity , Behavior, Animal/drug effects , Benzodiazepines/chemical synthesis , Benzodiazepines/metabolism , Benzodiazepines/toxicity , Blood-Brain Barrier/metabolism , Capillary Permeability , Disease Models, Animal , Dose-Response Relationship, Drug , GABA-A Receptor Antagonists/chemical synthesis , GABA-A Receptor Antagonists/metabolism , GABA-A Receptor Antagonists/toxicity , HEK293 Cells , Humans , Male , Mice , Molecular Structure , Motor Activity/drug effects , Nootropic Agents/chemical synthesis , Nootropic Agents/metabolism , Nootropic Agents/toxicity , Pentylenetetrazole , Rats, Sprague-Dawley , Receptors, GABA-A/genetics , Receptors, GABA-A/metabolism , Recognition, Psychology/drug effects , Seizures/chemically induced , Seizures/prevention & control , Structure-Activity Relationship , Xenopus laevisABSTRACT
Mutations in the CLN3 gene cause juvenile Batten disease, a fatal pediatric neurodegenerative disorder. The Cln3-knockout (Cln3(Δex1-6)) mouse model of the disease displays many pathological characteristics of the human disorder including a deficit in motor coordination. We have previously found that attenuation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptor activity in one-month-old Cln3(Δex1-6) mice resulted in an immediate improvement of their motor skills. Here we show that at a later stage of the disease, in 6-7-month-old Cln3(Δex1-6) mice, acute inhibition of AMPA receptors by a single intraperitoneal injection (1mg/kg) of the non-competitive AMPA antagonist, EGIS-8332, does not have an immediate effect. Instead, it induces a delayed but prolonged improvement of motor skills. Four days after the injection of the AMPA antagonist, Cln3(Δex1-6) mice reached the same motor skill level as their wild type (WT) counterparts, an improvement that persisted for an additional four days. EGIS-8332 was rapidly eliminated from the brain as measured by HPLC-MS/MS. Histological analysis performed 8 days after the drug administration revealed that EGIS-8332 did not have any impact upon glial activation or the survival of vulnerable neuron populations in 7-month-old Cln3(Δex1-6) mice. We propose that temporary inhibition of AMPA receptors can induce a prolonged correction of the pre-existing abnormal glutamatergic neurotransmission in vivo for juvenile Batten disease.
