M1 muscarinic allosteric modulators slow prion neurodegeneration and restore memory loss
Sophie J. Bradley, … , Christian C. Felder, Andrew B. Tobin
Sophie J. Bradley, … , Christian C. Felder, Andrew B. Tobin
Published December 19, 2016
Citation Information: J Clin Invest. 2017;127(2):487-499. https://doi.org/10.1172/JCI87526.
View: Text | PDF
Research Article Neuroscience

M1 muscarinic allosteric modulators slow prion neurodegeneration and restore memory loss

Abstract

The current frontline symptomatic treatment for Alzheimer’s disease (AD) is whole-body upregulation of cholinergic transmission via inhibition of acetylcholinesterase. This approach leads to profound dose-related adverse effects. An alternative strategy is to selectively target muscarinic acetylcholine receptors, particularly the M1 muscarinic acetylcholine receptor (M1 mAChR), which was previously shown to have procognitive activity. However, developing M1 mAChR–selective orthosteric ligands has proven challenging. Here, we have shown that mouse prion disease shows many of the hallmarks of human AD, including progressive terminal neurodegeneration and memory deficits due to a disruption of hippocampal cholinergic innervation. The fact that we also show that muscarinic signaling is maintained in both AD and mouse prion disease points to the latter as an excellent model for testing the efficacy of muscarinic pharmacological entities. The memory deficits we observed in mouse prion disease were completely restored by treatment with benzyl quinolone carboxylic acid (BQCA) and benzoquinazoline-12 (BQZ-12), two highly selective positive allosteric modulators (PAMs) of M1 mAChRs. Furthermore, prolonged exposure to BQCA markedly extended the lifespan of diseased mice. Thus, enhancing hippocampal muscarinic signaling using M1 mAChR PAMs restored memory loss and slowed the progression of mouse prion disease, indicating that this ligand type may have clinical benefit in diseases showing defective cholinergic transmission, such as AD.

Authors

Sophie J. Bradley, Julie-Myrtille Bourgognon, Helen E. Sanger, Nicholas Verity, Adrian J. Mogg, David J. White, Adrian J. Butcher, Julie A. Moreno, Colin Molloy, Timothy Macedo-Hatch, Jennifer M. Edwards, Jurgen Wess, Robert Pawlak, David J. Read, Patrick M. Sexton, Lisa M. Broad, Joern R. Steinert, Giovanna R. Mallucci, Arthur Christopoulos, Christian C. Felder, Andrew B. Tobin

×

Figure 1

M1 mAChRs play an important role in hippocampal-dependent learning and memory.

Options: View larger image (or click on image) Download as PowerPoint
M1 mAChRs play an important role in hippocampal-dependent learning and m...
(A) Fear-conditioning response of WT and M1-KO mice. Statistical analysis by 2-way ANOVA with Sidak’s multiple comparison test. ***P < 0.001. (B) Pain thresholds for WT and M1-KO mice. Statistical analysis by Student’s t test. (C) Locomotion of WT and M1-KO mice was determined by total distance traveled during an open field test. Data were analyzed using 2-way ANOVA with Sidak’s multiple comparisons. All WT and M1-KO behavioral data are shown as mean ± SEM of n = 8 mice. (D) An antibody-based biosensor for M1 mAChR activation (phosphorylation of the M1 mAChR on S228 in the third intracellular loop) was used to assess M1 mAChR activity in the hippocampus. Following fear-conditioning training, phosphorylation at S228 of the M1 mAChR was increased in the CA1 and CA3 regions and dentate gyrus of the hippocampus relative to control mice that received a 2-second unpaired foot shock. Magnification of the CA1 region (indicated by the rectangle) is shown in lower panels. (E) Fear-conditioning training increased neuronal activity, as assessed by an increase in ARC immunostaining, in the same regions of the hippocampus as those observed for activated M1 mAChR. D and E are composited images. Magnification of the CA1 region (indicated by the rectangle) is shown in lower panels (see D and E). Scale bars: 200 μm (upper panels); 100 μm (lower panels).