Sarm1 activation produces cADPR to increase intra-axonal Ca++ and promote axon degeneration in PIPN

Li et al. identify cADPR as a therapeutic target for preventing paclitaxel-induced peripheral neuropathy (PIPN). The authors show that paclitaxel triggers Sarm1-dependent cADPR production, causing increased axonal calcium and degeneration. cADPR antagonists protect against PIPN in vitro and in vivo, without mitigating paclitaxel's anti-neoplastic efficacy. Cancer patients frequently develop chemotherapy-induced peripheral neuropathy (CIPN), a painful and long-lasting disorder with profound somatosensory deficits. There are no effective therapies to prevent or treat this disorder. Pathologically, CIPN is characterized by a "dying-back" axonopathy that begins at intra-epidermal nerve terminals of sensory neurons and progresses in a retrograde fashion. Calcium dysregulation constitutes a critical event in CIPN, but it is not known how chemotherapies such as paclitaxel alter intra-axonal calcium and cause degeneration. Here, we demonstrate that paclitaxel triggers Sarm1-dependent cADPR production in distal axons, promoting intra-axonal calcium flux from both intracellular and extracellular calcium stores. Genetic or pharmacologic antagonists of cADPR signaling prevent paclitaxel-induced axon degeneration and allodynia symptoms, without mitigating the anti-neoplastic efficacy of paclitaxel. Our data demonstrate that cADPR is a calcium-modulating factor that promotes paclitaxel-induced axon degeneration and suggest that targeting cADPR signaling provides a potential therapeutic approach for treating paclitaxel-induced peripheral neuropathy (PIPN).