Vincristine and bortezomib use distinct upstream mechanisms to activate a common SARM1-dependent axon degeneration program
Stefanie Geisler, … , Jeffrey Milbrandt, Aaron DiAntonio
Stefanie Geisler, … , Jeffrey Milbrandt, Aaron DiAntonio
Published September 5, 2019
Citation Information: JCI Insight. 2019;4(17):e129920. https://doi.org/10.1172/jci.insight.129920.
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Research Article Cell biology Neuroscience

Vincristine and bortezomib use distinct upstream mechanisms to activate a common SARM1-dependent axon degeneration program

Abstract

Chemotherapy-induced peripheral neuropathy is one of the most prevalent dose-limiting toxicities of anticancer therapy. Development of effective therapies to prevent chemotherapy-induced neuropathies could be enabled by a mechanistic understanding of axonal breakdown following exposure to neuropathy-causing agents. Here, we reveal the molecular mechanisms underlying axon degeneration induced by 2 widely used chemotherapeutic agents with distinct mechanisms of action: vincristine and bortezomib. We showed previously that genetic deletion of SARM1 blocks vincristine-induced neuropathy and demonstrate here that it also prevents axon destruction following administration of bortezomib in vitro and in vivo. Using cultured neurons, we found that vincristine and bortezomib converge on a core axon degeneration program consisting of nicotinamide mononucleotide NMNAT2, SARM1, and loss of NAD+ but engage different upstream mechanisms that closely resemble Wallerian degeneration after vincristine and apoptosis after bortezomib. We could inhibit the final common axon destruction pathway by preserving axonal NAD+ levels or expressing a candidate gene therapeutic that inhibits SARM1 in vitro. We suggest that these approaches may lead to therapies for vincristine- and bortezomib-induced neuropathies and possibly other forms of peripheral neuropathy.

Authors

Stefanie Geisler, Ryan A. Doan, Galen C. Cheng, Aysel Cetinkaya-Fisgin, Shay X. Huang, Ahmet Höke, Jeffrey Milbrandt, Aaron DiAntonio

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Figure 1

Vincristine and BTZ induce axon degeneration by distinct mechanisms.

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Vincristine and BTZ induce axon degeneration by distinct mechanisms. (A)...
(A) DRG neurons were treated with 40 nM vincristine or 100 nM BTZ, and axons imaged using high-throughput automated imaging at indicated time points. Axon degeneration was quantified using a degeneration index, which ranges from 0 (perfectly intact) to 1 (perfectly fragmented). Data were tested with a 2-way ANOVA showing significant main effects of group F (2, 185) = 484.8, P < 0.0001; time F (5, 185) = 213.4, P < 0.0001; and interaction F (10, 185) = 58.28; post hoc Šídák’s multiple-comparisons test, ***P = 0.0001 vincristine versus BTZ 12 hours (blue asterisks); ****P < 0.0001 vincristine versus BTZ (blue asterisks), vincristine versus vehicle, and BTZ versus vehicle (black asterisks); P = 0.3102 BTZ versus vehicle at 24 hours (n = 13). (B) Representative phase-contrast photomicrographs of axons treated with vincristine or BTZ taken at indicated time points showing axon degeneration 24 hours after vincristine but not BTZ administration. Instead, axons fragmented between 36 and 48 hours after BTZ. Original magnification 200×. (C) DRG neurons were grown in compartmentalized microfluidic chambers, and 40 nM vincristine was added to the compartment containing cell bodies (soma chamber, n = 3 experiments) or axons (axon chamber, n = 4 experiments) and degeneration in the axon compartment determined at indicated times. A 2-way ANOVA showed significant main effects of group F (1, 5) = 34.49, P = 0.002; time F (2, 10) = 18.96, P = 0.0004; and interaction F (2, 10) = 13.29, P = 0.0015. Šídák’s multiple-comparisons test, *P < 0.05, ****P < 0.0001. (D) DRG neurons were grown in compartmentalized chambers, and 100 nM BTZ was added to the soma (n = 5 experiments) or axon compartment (n = 3 experiments) and degeneration in the axon compartment determined over time. Two-way ANOVA showed significant main effects of group F (1, 6) = 8.389, P = 0.0275; time F (2, 12) = 16.39, P = 0.0004; and interaction F (2, 12) = 10.55, P = 0.0023. Šídák’s multiple-comparisons test, ***P < 0.001. (E) Representative bright-field photomicrographs of the axon compartment taken at indicated times after vincristine or BTZ was added to axon compartment or cell body chamber. Original magnification 200×.