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Chloride extrusion enhancers as novel therapeutics for neurological diseases

Abstract

The K+-Cl cotransporter KCC2 is responsible for maintaining low Cl concentration in neurons of the central nervous system (CNS), which is essential for postsynaptic inhibition through GABAA and glycine receptors. Although no CNS disorders have been associated with KCC2 mutations, loss of activity of this transporter has emerged as a key mechanism underlying several neurological and psychiatric disorders, including epilepsy, motor spasticity, stress, anxiety, schizophrenia, morphine-induced hyperalgesia and chronic pain1,2,3,4,5,6,7,8,9. Recent reports indicate that enhancing KCC2 activity may be the favored therapeutic strategy to restore inhibition and normal function in pathological conditions involving impaired Cl transport10,11,12. We designed an assay for high-throughput screening that led to the identification of KCC2 activators that reduce intracellular chloride concentration ([Cl]i). Optimization of a first-in-class arylmethylidine family of compounds resulted in a KCC2-selective analog (CLP257) that lowers [Cl]i. CLP257 restored impaired Cl transport in neurons with diminished KCC2 activity. The compound rescued KCC2 plasma membrane expression, renormalized stimulus-evoked responses in spinal nociceptive pathways sensitized after nerve injury and alleviated hypersensitivity in a rat model of neuropathic pain. Oral efficacy for analgesia equivalent to that of pregabalin but without motor impairment was achievable with a CLP257 prodrug. These results validate KCC2 as a druggable target for CNS diseases.

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Figure 1: Screening for, and improvement of KCC2-dependent intracellular Cl lowering compounds.
Figure 2: CLP257 restores Cl transport in adult spinal cord slices with impaired KCC2 function.
Figure 3: CLP257 increases plasmalemmal KCC2 protein in BDNF-treated adult rat spinal cord slices.
Figure 4: In vivo assessment of the efficacy and pharmacokinetics of CLP257 and its prodrug CLP290.

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Acknowledgements

This work was supported by grants from the Canadian Institutes for Health Research and the Krembil Foundation to Y.D.K., a fellowship from the Savoy Foundation to M.J.B. and the Fonds de la recherche en santé du Québec Chercheur National Program to Y.D.K. We thank T. Kuner, University of Heidelberg, for the generous gift of the Clomeleon plasmid.

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M.G., J.A.M.C. and Y.D.K. conceived of and designed the project. M.G., J.A.M.C., P.I., I.K. and Y.D.K. supervised the experiments. M.G., M.J.B., G.L., A.C., R.P.B., J.P.-S., D.B., K.B. and M.J.-W. performed the experiments. G.A., S.T., B.W., L.D. and I.V. designed and synthesized analogs of CL-058. M.G., M.J.B., G.L., A.C., R.P.B., J.P.-S., D.B., M.J.-W., C.T. and I.K. analyzed the data. M.G., M.J.B., G.L., A.C., R.P.B. and Y.D.K. wrote the manuscript. All of the authors read and discussed the manuscript.

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Correspondence to Yves De Koninck.

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The authors declare no competing financial interests.

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Gagnon, M., Bergeron, M., Lavertu, G. et al. Chloride extrusion enhancers as novel therapeutics for neurological diseases. Nat Med 19, 1524–1528 (2013). https://doi.org/10.1038/nm.3356

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