LSP5-2157 a new inhibitor of vesicular glutamate transporters

Abstract

Vesicular glutamate transporters (VGLUT1-3) mediate the uptake of glutamate into synaptic vesicles. VGLUTs are pivotal actors of excitatory transmission and therefore of all brain functions. Their implication in various pathologies such as Parkinson and Alzheimer disease, epilepsy, schizophrenia, anxiety, addiction or deafness has been clearly documented. Despite their functional importance, the pharmacology of VGLUTs is particularly underdeveloped and limited at non-specific dyes such as Trypan Blue, Rose Bengal or Brillant Yellow type. Here we report the design and the conception of new potent analogs based on Trypan Blue scaffold. Our best compound, named LSP5-2157, has an EC50 of 50nM on glutamate vesicular uptake. Using a 3D homology model, we determined putative binding subdomains of VGLUT1 that bind LSP5-2157. To better estimate the specificity and potency of LSP5-2157, we investigated its ability to block glutamatergic transmission in autaptic hippocampal cells. Neither ionotropic glutamate receptors nor GABAergic transmission or transmission machinery such as Ca 2+ channels were affected by application of LSP5-2157. Low doses of LSP5-2157 (2µM) reversibly reduce glutamatergic neurotransmission in hippocampal autpases. LSP5-2157 had a low and depressing effect on synaptic efficacy in hippocampal slice. Furthermore, LSP5-2157 (2µM) had no effect on NMDA-R-mediated fEPSP. This compound was able to reduce synaptic plasticity induced by 3 trains of 100Hz. However, LSP5-2157 had no effect on plasticity induced by theta burst, which suggests that the readily releasable pool of glutamate was not affected by the drug. Finally, we showed that LSP5-2157 had the capacity to inhibit VGLUT3-dependent auditory synaptic transmission in the guinea pig cochlea. In this model, LSP5-2157 abolished the compound action potential of auditory nerve at high concentration showing the limitation of LSP5-2157 permeation in an in-vivo model. Therefore, the new ligand LSP5-2157 has a high affinity for VGLUTs and shows some permeability in isolated neuron, tissue preparations or in vivo in the auditory system. These findings open the way to the use of VGLUTs inhibitors to assess glutamatergic functions in vitro and in vivo.

Disruption of Glutamate Release and Uptake-Related Protein Expression After Noise-Induced Synaptopathy in the Cochlea

“…Vglut3 dysfunction or deficiency disrupts nerve conduction in the peripheral auditory system. LSP5-2157, an inhibitor of Vglut3, inhibited the compound action potential of the peripheral auditory system in guinea pigs ( Poirel et al, 2020 ). Animals lose hearing after knockout of the Vglut3 allele; however, it can be restored using an adenoviral vector delivery system to re-establish Vglut3 expression ( Akil et al, 2015 ; Akil and Lustig, 2019 ; Kim et al, 2019 ).…”

Sucrose Consumption Alters Serotonin/Glutamate Co-localisation Within the Prefrontal Cortex and Hippocampus of Mice

“…Therefore, the decrease in DG 5-HT varicosities seen in sugar consuming mice may be a downstream effect of reduced VGLUT3 varicosities at the DG. As pharmacological agents that specifically target VGLUT3 are still being developed ( Poirel et al, 2020 ), it is difficult to directly manipulate VGLUT3 activity in vivo to test this hypothesis. Alterations of the serotonergic and glutamatergic co-localisation within PFC and DG are supported by immunohistochemistry data.…”

Targeting VGLUT Machinery: Implications on mGluR5 Signaling and Behavior

“…The mGluR5 drug library is diverse and various selective modulators hold promising therapeutic potential (Sengmany and Gregory, 2018), yet a more holistic understanding of the glutamatergic circuitry will be critical for higher-precision therapies. In addition, novel selective VGLUT ligands are currently being developed (Poirel et al, 2020). Thanks to the major advances in pharmacological research and optogenetics, genetically targetable toolkit can be developed to profile and dissect VGLUT3-mGluR5 signaling axis.…”