Knockdown siRNA Targeting the Mitochondrial Sodium-Calcium Exchanger-1 Inhibits the Protective Effects of Two Cannabinoids Against Acute Paclitaxel Toxicity.

Treatment with cannabidiol (CBD) or KLS-13019 (novel CBD analog), has previously been shown to prevent paclitaxel-induced mechanical allodynia in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN). The mechanism of action for CBD- and KLS-13019-mediated protection now has been explored with dissociated dorsal root ganglion (DRG) cultures using small interfering RNA (siRNA) to the mitochondrial Na⁺ Ca²⁺ exchanger-1 (mNCX-1). Treatment with this siRNA produced a 50-55% decrease in the immunoreactive (IR) area for mNCX-1 in neuronal cell bodies and a 72-80% decrease in neuritic IR area as determined with high-content image analysis. After treatment with 100 nM KLS-13019 and siRNA, DRG cultures exhibited a 75 ± 5% decrease in protection from paclitaxel-induced toxicity; whereas siRNA studies with 10 μM CBD produced a 74 ± 3% decrease in protection. Treatment with mNCX-1 siRNA alone did not produce toxicity. The protective action of cannabidiol and KLS-13019 against paclitaxel-induced toxicity during a 5-h test period was significantly attenuated after a 4-day knockdown of mNCX-1 that was not attributable to toxicity. These data indicate that decreases in neuritic mNCX-1 corresponded closely with decreased protection after siRNA treatment. Pharmacological blockade of mNCX-1 with CGP-37157 produced complete inhibition of cannabinoid-mediated protection from paclitaxel in DRG cultures, supporting the observed siRNA effects on mechanism.