Voltage gated calcium channels – molecular targets for trigeminal neuralgia
Date
2022-12-16
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Abstract
Trigeminal neuralgia (TN) is a rare debilitating disease which is characterised by excruciating facial pain and has a higher incidence in women. Recent studies demonstrated that some TN patients present mutations in genes that encode different voltage-gated calcium channels, a class of ion channel that are important players in pain pathways. Among them, mutations in the genes CACANA1A, CACNA1G, and CACNA1H, that encode CaV2.1, CaV3.1 and CaV3.2 channels, respectively, were investigated. First, we characterised the biophysical properties of these mutations using whole-cell patch-clamp recordings in tsA-201 cells. Second, we investigated the role of CaV3.2 channels in an animal model of trigeminal neuropathic pain. Finally, we explored the molecular mechanism of a selective T-type calcium channel blocker. Our data demonstrated a mix of loss- and gain-of-function in the CaV2.1 channel mutant P2455H, and a gain-of-function in a CaV3.1 channel variant (R706Q). For the CaV3.2 channel mutants, some presented a gain-of-function (G563R, P566T, P1605H), some a loss-of-function (E281K, H526Y, R1736C), and one exhibited no difference to wild type channels (D1779Y). These changes in channel function may affect pain pathways in the trigeminal system, thus potentially contributing to the pain phenotype. Considering that several studies demonstrated that CaV3.2 channels are dysregulated in models of chronic pain, we assessed the function of this channel in the constriction of the infraorbital nerve (CION) model. Both female and male CION mice developed facial thermal heat hyperalgesia. Treatment with the pan T-type blocker Z944 was able to produce an antihyperalgesic effect in CION mice, however its effect was absent in CaV3.2-/- mice. This suggests that Z944 targets CaV3.2 channels in the CION model. ELISA analysis revealed increased CaV3.2 channel expression in the spinal trigeminal subnucleus caudalis. Finally, the T-type channel blocker DX-416 was able to block CaV3.2 calcium channel current, however its effect is not altered by mutations in putative sites for A803467. Altogether, the present study demonstrates an important role of voltage-gated calcium channels in trigeminal pain.
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Gambeta de Andrade, E. (2022). Voltage gated calcium channels – molecular targets for trigeminal neuralgia (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.