Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, PC44

Poster Communications

Using benzodiazepine site modulators to promote remyelination

L. E. New1, J. Deuchars1, S. A. Deuchars1

1. University of Leeds, Leeds, United Kingdom.

Current multiple sclerosis (MS) treatments include symptom management and disease modifying therapies to reduce the impact and frequency of symptom relapses by targeting the immune component of MS. No current treatments delay or repair the chronic progressive demyelination and neuroaxonal damage seen in MS. Whilst spontaneous remyelination and repair can occur, this process is rarely complete, and therefore its promotion could benefit patients. We have previously shown that modulation of the neurotransmitter acetylcholine increases proliferation within the spinal cord. A large proportion of newly proliferated cells express PanQKi, indicating an increase in the number of new oligodendrocyte lineage cells (Corns et al., 2015). Promoting endogenous proliferating populations, and inducing their differentiation to remyelinating oligodendrocyte lineage cells, may aid myelin repair in MS. Recent work has focused on manipulating GABAergic neurotransmission within the spinal cord to modulate proliferation and differentiation. Initial experiments examining the ependymal cell (EC) layer, a potential stem cell niche, indicated that ECs express the endogenous GABAAR positive allosteric modulator diazepam binding inhibitor (DBI). The presence of DBI within ECs suggests that the stem cell niche of the spinal cord, and the balance of proliferation vs. differentiation of ECs, is, at least in part, governed by GABA signalling. To investigate this further, adult C57BL/6 (6-8 weeks) mice were split into 3 experimental groups (n=3 animals per group). Each group received nightly I.P injections of EdU (10mM) to label dividing cells and either 1. The BZ site antagonist flumazenil (5mg/kg), 2. The BZ inverse agonist Ro15-4513 (3mg/kg), or 3. vehicle. Animals treated with flumazenil and Ro15-4513 exhibited greater total levels of proliferation compared to vehicle treated animals (132.1 ± 4.3 EdU+ cells vs. 112 ± 2.1 EdU+ cells (p < 0.0005) and 104.2 ± 3.7 vs. 85.3 ± 2.8 EdU+ cells (p < 0.0005) , respectively (students t-test)). Furthermore, animals treated with BZ inverse agonists showed greater colocalisation with PanQKi (30% colocalisation for PanQKi/EdU), compared to other differentiation markers such as NeuN and S100β (>1% for NeuN/EdU and S100β/EdU). To determine if BZ inverse agonist-induced proliferation aids remyelination, pilot studies are underway using focal intraspinal injections of the demyelinating agent lysolethicin in adult C57BL/6 mice, alongside I.P flumazenil (5mg/kg) to boost proliferation during oligodendrocyte progenitor proliferation, migration, and differentiation. Current results indicate that manipulation of GABAergic signalling via the BZ site of GABAAR is sufficient to increase levels of proliferation in the spinal cord and maintain the proportion of newly proliferated oligodendrocyte lineage cells. These new oligodendrocytes may provide greater scope for remyelination in MS lesions.

Where applicable, experiments conform with Society ethical requirements