Chemotherapy-induced peripheral neuropathy (CIPN) can be a chronic, severely debilitating consequence of cancer therapy for which there are no effective management strategies. Moreover, upwards of 80% of CIPN patients reported using prescription opioids for pain management despite the fact that there is only weak evidence that long-term continuation of opioids provides clinically significant pain relief in these patients. Mitochondrial dysfunction, oxidative stress, and inflammation have all been implicated in its etiology. We have shown that the non-psychoactive cannabinoid cannabidiol (CBD) prevents the development of CIPN in a mouse model of paclitaxel-induced cold and mechanical allodynia. In vitro, we observe that paclitaxel increases microglial expression of several putative mediators of neuropathic pain, and that this effect can be blocked by CBD in a mitochondrial Na+/Ca2+ exchanger (mNCX)- dependent manner. We have also recently shown that a more potent, hydrophilic analogue of CBD, KLS-13019, protects against paclitaxel-induced oxidative stress in cultured dorsal root ganglia neurons, and that the mechanism underlying this neuroprotection is also regulation of intracellular calcium via the mNCX. Preliminary results demonstrate that KLS-13019 can attenuate mechanical sensitivity associated with CIPN while also reducing microglial activation and T cell infiltration into the spinal cord. Our central hypothesis is that administration of CBD or KLS-13019 helps preserve Ca2+ homeostasis by promoting activity of the mNCX, which in turn protects from both mitochondrial dysfunction and microglial activation to prevent the neuronal and glial changes associated with the development and maintenance of paclitaxel-induced neuropathic pain. Results from experiments in AIM 1 will demonstrate that the neuroprotective properties of CBD and KLS-13019 can be reduced by pharmacological or gene knockdown of the mNCX in a statistically significant manner. Results from experiments in AIM 2 will further confirm the i.p. and p.o. efficacy of KLS-13019 vs CBD to prevent or reverse mechanical sensitivity and neuroinflammation in a mouse model of paclitaxel-induced neuropathic pain and that repeated administration of these compounds does not lead to analgesic tolerance. Remarkably, the non- psychoactive CBD has also been shown to inhibit cue-induced heroin-seeking and neurochemical correlates thereof in a rat model of relapse and decrease heroin craving in a small human study. Experiments in AIM 3 are designed to test the hypothesis that KLS-13019 and CBD will attenuate reinstatement of morphine seeking behavior in a rat model of opioid relapse. The overall impact of the results from the proposed research will be significant advancements into 1) identification of specific mechanisms that induce CIPN, 2) application of this knowledge to facilitate design of novel treatment strategies for neuropathic pain, and 3) novel treatment strategies to reduce or replace prescription opioid use and decrease prescription opioid abuse.
Chemotherapy-induced peripheral neuropathy (CIPN) can be a chronic, severely debilitating consequence of cancer therapy for which there are no effective management strategies. Moreover, upwards of 80% of CIPN patients reported using prescription opioids for pain management, despite the weak evidence of their efficacy and the risks of long term dependence. Mitochondrial dysfunction, calcium dysregulation, oxidative stress, and inflammation have all been implicated in its etiology. Cannabidiol (CBD) is a non-psychoactive component of Cannabis sativa is effective in both treating CIPN and relieving opiate dependence. However, CBD has severe limitations in terms of potency, safety, oral bioavailability, and regulatory restrictions. Kannalife has solved these problems in its patented series of derivatives that include KLS-13019. This grant will demonstrate the efficacy of KLS- 13019 in models of CIPN and opiate dependence, and will further elucidate its mechanism of action in regulation of calcium levels and inflammatory sequelae.