SODIUM-CALCIUM EXCHANGER PIVOTAL ROLE IN OXALIPLATIN-INDUCED ALTERATIONS LEADING TO PERIPHERAL NEUROTOXICITY, AXONAL DAMAGE AND NECROPTOSIS

Di Girolamo S¹, Invernizzi C¹, Kraus MF³, Ballarini E¹ and Alberti P^1,2 | ¹Experimental Neurology Unit and Milan Center for Neuroscience, University of Milano-Bicocca, Monza, Italy; ²Department of Neurology, Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy; ³S.C. Neuroscienze, Istituto Zooprofilattico Sperimentale del Piemonte Liguria e Valle D’Aosta, Torino, Italy

Oxaliplatin (OHP) is the cornerstone drug for Colorectal Cancer treatment, but is hampered by OHP-induced Peripheral Neurotoxicity (OIPN), which comprises an acute and chronic form. Acute OIPN consists of a precocious axonal hyperexcitability syndrome, caused by OHP-induced functional alterations of Voltage-gated Sodium Channels (NaV). Prolonged OHP treatment, instead, leads to a chronic OIPN, mainly characterized by a sensory neuropathy with a potentially persistent axonal damage (AxD). The Sodium-Calcium exchanger (NCX) might play a role in AxD development, consequent to a NaV physiological dysfunction. NCX is, in fact, highly co-expressed with NaV. Indeed, OHPinduced NaV prolonged opening may cause an unbalance in Na+ and Ca2+ neuronal levels: the excessive Na+ intake can lead to NCX switching to reverse-mode, which in turn causes Ca2+ abundant intake to rebalance Na+, thus leading to Ca2+-related AxD. We aimed to investigate OHP-induced morphological and physiological changes and to clarify the potential role of NCX in AxD development. For this purpose, we performed multiple toxicological studies on primary Dorsal Root Ganglia (DRG) neuronal culture of adult mice (male C57BL/6 mice; 8-10 weeks) using primarily the Nanolive CX-A 3D holotomographic microscope, a state-ofart live-imaging platform. OHP-exposed neurons (25 μM, 48h) showed an overall neurite fragmentation and a high-reduced viability, preceded by autophagic stress and necroptosis. Moreover, chronic exposure (48h) of DRG neurons to different OHP concentrations (7.5, 15, 25, 50 μM) highlighted alterations in both viability and neurites elongation in a dose and time-dependent manner, that can be efficiently counteracted by SEA0400 low-dose pretreatment (1 μM, 3h before OHP-incubation), a potent and selective NCX inhibitor, confirming the pivotal role of NCX in AxD development. In conclusion, we observed that OIPN is related to both morphological and functional changes in NaV and NCX, paving the way to potential new treatment strategies to prevent AxD. Furthermore, for the first time, we were able to follow AxD leading events longitudinally by exploiting such an advanced approach as holotomographic live-imaging.