TARGETING PROKINETICIN SYSTEM TO COUNTERACT EXPERIMENTAL CHEMOTHERAPY-INDUCED PERIPHERAL NEUROPATHY.

Chemotherapy induced peripheral neuropathy (CIPN) is a dose-limiting side effect of several antineoplastic agents commonly used in clinics. Up to now its management with common analgesic drugs is often unsatisfactory, therefore novel therapeutic approaches are needed. The molecular mechanisms underlying CIPN are still largely unknown, even if involvement of mitochondrial toxicity and oxidative stress, ion channels alterations and neuroinflammatory processes have been suggested (Boyette-Davis et al., 2015; Montague and Malcangio 2017). In particular, some cytokines and chemokines are involved in the initiation and persistence of pain (Sacerdote et al., 2013). Among chemokines, the Prokineticin family has an important role in immunomodulation, inflammation, nociception, inflammatory pain and in different experimental neuropathic conditions such as nerve lesion (Lattanzi et al., 2015; Guida et al., 2015) and diabetic neuropathy (Castelli et al., 2016). Both in humans and rodents, Prokineticin-1 (PK1) and Prokineticin-2 (PK2) (Negri et al., 2007) are ligands of two metabotropic receptors known as PK-R1 and PK-R2 (Masuda et al., 2002). Prokineticins and their receptors are expressed in the brain, spinal cord, dorsal root ganglia, granulocytes, macrophages and lymphocytes. It has been demonstrated that PK2 acts on macrophages and induces a pro-inflammatory profile (Martucci et al., 2006), which can lead to reduced nociceptive thresholds to thermal and mechanical stimuli (Negri et al., 2006; Giannini et al., 2009). Furthermore, in some nervous regions associated to pain, a co-localization of PK-Rs and TRPV receptors has been shown, and many neurons that respond to PK2 express and release typical pain mediators such as CGRP and substance P (Vellani et al., 2006). On the basis of these considerations, our study investigates the role of prokineticin system in a murine model of CIPN induced by the administration of two different chemotherapeutic agents commonly used in oncology and related to CIPN development: Vincristine (VCR), the most neurotoxic drug among Vinca Alkaloids, and bortezomib (BTZ), the first approved 26s proteasome inhibitor. These drugs, despite having different mechanisms of action on tumor cells, induce neurotoxicity and consequent neuropathy with similar mechanisms (Flatters et al., 2019; Boyette-Davis et al., 2015). C57BL/6J, 9 weeks old, male mice were used in all the experiments. Based on the most common protocols used in literature, CIPN was induced in mice through the intraperitoneal (i.p.) administration of bortezomib 0.4mg/kg, 3 times a week for 4 consecutive weeks (Boehmerle et al., 2014). Vincristine was administered at the dose of 0.1mg/kg, i.p. injected daily for 14 consecutive days (Kiguchi et al., 2008). Control mice were injected with the vehicle. Allodynia is one of the most frequent symptoms of CIPN, therefore, mechanical and thermal allodynia were monitored using Von Frey and Acetone Drop Test, respectively. Furthermore, thermal hyperalgesia was evaluated by Plantar test. Both bortezomib and vincristine induced in mice a painful neuropathy characterized by the presence of mechanical and thermal allodynia as well as thermal hyperalgesia. To assess the potential therapeutic effect of PC1, a non-peptidic antagonist of PK-Rs, BTZ- and VCR- mice in a clear hypersensitivity condition were subjected to chronic treatment with PC1 (150μg/kg, s.c. injected, daily administered for 14 or 7 consecutive days in the BTZ and VCR protocol respectively). Independently from the chemotherapeutic agent used to induce CIPN, PC1 was effective in ameliorating the painful symptoms. To assess the role of PK system in our model, for each experimental protocol (BTZ and VCR) we performed biochemical analysis at two different time po