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 7

Loss of SARM1 prevents BTZ-stimulated axon degeneration but not cell death.

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Loss of SARM1 prevents BTZ-stimulated axon degeneration but not cell dea...
(A) WT and SARM1-KO DRG neurons were treated with BTZ and incubated with Hoechst and ethidium homodimer (ETHD positive) at indicated time points to stain, respectively, live and dead cells. After BTZ administration, the number of dead (ETHD) WT and SARM1-KO DRG neurons increased over time to the same extent. A 2-way ANOVA showed a significant effect of time F (5, 20) = 72.27, P < 0.0001, but not group F (1, 4) = 0.2639, P = 0.6345, or interaction F (5, 20) = 0.3648, P = 0.8666; n = 3. (B) Representative photomicrographs of WT and SARM1-KO DRG neurons expressing Bcl-XL or vector and treated with BTZ for 48 or 96 hours that were incubated with ETHD (red) and Hoechst (blue) to label dead (ETHD) and living (Hoechst) cells. Expression of Bcl-XL prevented neuronal death in both WT and SARM1-KO neurons. Phase-contrast photomicrographs of axons corresponding to the cells above, showing that expression of Bcl-XL did not prevent axon degeneration in WT DRG neurons as potently as SARM1 KO. (C) WT and SARM1-KO DRG neurons expressing control vector or Bcl-XL were stained with ETHD and Hoechst 96 hours after BTZ was added. One-way ANOVA F (3, 10) = 128.6, P < 0.0001; ****P < 0.0001. n = 4 WT; n = 3 SARM1-KO. (D) Axon degeneration of experiments shown in C. WT and SARM1-KO DRG expressing indicated constructs were treated with BTZ or vehicle, and axon degeneration was determined at indicated time points. Two-way ANOVA showed significant effects of group F (5, 69) = 165.5, P < 0.0001; time F (4, 69) = 67, P < 0.0001; and interaction F (20, 69) = 14.99, P < 0.0001; Tukey’s multiple-comparisons test ***P < 0.001 WT BTZ Bcl-XL vs. SARM1-KO Bcl-XL; ****P < 0.0001; n = 4 WT; n = 3 SARM1-KO.