Pharmacological Co-Activation of TrkB and TrkC Receptor Signaling Ameliorates Striatal Neuropathology and Motor Deficits in Mouse Models of Huntington’s Disease
Affiliations: Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
Correspondence:
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Correspondence to: Danielle A. Simmons, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, 1201 Welch Dr., MSLS P252, Stanford, CA 94305, USA. Tel.: +1 650 736 0770; E-mail: simmons3@stanford.edu.
Abstract: Background:Loss of neurotrophic support in the striatum, particularly reduced brain-derived neurotrophic factor (BDNF) levels, contributes importantly to Huntington’s disease (HD) pathogenesis. Another neurotrophin (NT), NT-3, is reduced in the cortex of HD patients; however, its role in HD is unknown. BDNF and NT-3 bind with high affinity to the tropomyosin receptor-kinases (Trk) B and TrkC, respectively. Targeting TrkB/TrkC may be an effective HD therapeutic strategy, as multiple links exist between their signaling pathways and HD degenerative mechanisms. We developed a small molecule ligand, LM22B-10, that activates TrkB and TrkC to promote cell survival. Objective:This study aimed to determine if upregulating TrkB/TrkC signaling with LM22B-10 would alleviate the HD phenotype in R6/2 and Q140 mice. Methods:LM22B-10 was delivered by concomitant intranasal-intraperitoneal routes to R6/2 and Q140 mice and then motor performance and striatal pathology were evaluated. Results:NT-3 levels, TrkB/TrkC phosphorylation, and AKT signaling were reduced in the R6/2 striatum; LM22B-10 counteracted these deficits. LM22B-10 also reduced intranuclear huntingtin aggregates, dendritic spine loss, microglial activation, and degeneration of dopamine- and cyclic AMP-regulated phosphoprotein with a molecular weight of 32 kDa (DARPP-32) and parvalbumin-containing neurons in the R6/2 and/or Q140 striatum. Moreover, both HD mouse models showed improved motor performance after LM22B-10 treatment. Conclusions:These results reveal an NT-3/TrkC signaling deficiency in the striatum of R6/2 mice, support the idea that targeting TrkB/TrkC alleviates HD-related neurodegeneration and motor dysfunction, and suggest a novel, disease-modifying, multi-target strategy for treating HD.
