Neuroprotective potential of the group III mGlu receptor agonist ACPT-I in animal models of ischemic stroke: In vitro and in vivo studies

- ACPT-I is neuroprotective against OGD-evoked neurotoxicity and in rats after MCAO.
- ACPT-I attenuated ischemic neuronal injury after delayed treatment.
- Antagonist of the group III mGluR, CPPG blocked neuroprotective effects of ACPT-I.
- ACPT-I inhibited the OGD-evoked calpain activation.
- ACPT-I improved functional outcome after MCAO-induced ischemia.

In the present study, we investigated the effect of ACPT-I [(1S, 3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid], a blood-brain-barrier permeable agonist of group III mGlu receptor, against oxygen-glucose deprivation (OGD)-evoked neuronal cell death in primary neuronal cell cultures and in the model of transient middle cerebral artery occlusion (MCAO) in rats. We found that ACPT-I (1-200 μM) in a concentration- and time-dependent way attenuated the OGD-induced neuronal cell damage, being also effective after a delayed application (30 min after OGD). The neuroprotective effects of ACPT-I were blocked by the group III mGlu receptor antagonist, (RS)-alpha-cyclopropyl-4-phosphonophenyl glycine (CPPG), and by the activator of cAMP-dependent PKA, 8-Bromo-cAMP, but not by an inhibitor of PI-3-K signaling pathway. Moreover, ACPT-I attenuated the OGD-induced calpain activity and glutamate release. In the in vitro study, we also demonstrated the neuroprotective potential of mGluR4 positive allosteric modulators (PAMs), PHCCC (30 μM) and VU0155041 (10 and 30 μM) and synergism in neuroprotective action of low concentrations of ACPT-I and mGluR4 PAMs suggesting an important role of mGluR4 activation in prevention of ischemic neuronal cell death. In the rat MCAO model, we demonstrated that ACPT-I (30 mg/kg) injected intraperitoneally either 30 min after starting MCAO or 30 min after beginning reperfusion not only diminished the infarction volume by about 30%, but also improved selected gait parameters (CatWalk analysis) and the mobility of animals in the open field test. In conclusion, our results indicate that ACPT-I may be not only neuroprotective against ischemic neuronal damage but may also diminish the postischemic functional deficits.