Resumen de Mecanismes moleculars involucrats en la neuropatia perifèrica induïda per platins. Un estudi exploratori
Platinum-Induced Peripheral Neuropathy (PIPN) is a frequent serious dose-limiting adverse event of the platinum-based cytostatic agent cisplatin, oxaliplatin and carboplatin, which are given as a first line treatment against high prevalent cancers. Due to its severity, PIPN often causes cancer treatment reduction or even cessation, thus decreasing the survival probabilities of oncologic patients. It has been extensively reported that PIPN severity correlates with the amount of platinum drugs cumulated in sensory neurons of the dorsal root ganglia (DRG). Several pathophysiological mechanisms have been described for PIPN development, including DNA damage, mytotoxicity and channels dysfunction in DRG sensory neurons, among others. Despite the efforts of clinicians and researchers during the last decades, no successful translation from pre-clinical settings to the clinics has been achieved. The aim of this study was to determine the exact molecular mechanisms involved in the development of PIPN following a non-hypothesis driven methodology to find new therapeutical targets. By single-cell RNA sequencing (scRNA-seq), we studied the transcriptomic profile of DRG sensory neurons from 2 well characterized neurophysiological mice models of PIPN: one induced by cisplatin administration, and the second by oxaliplatin. We demonstrated that cisplatin treatment induced persistent DNA damage and the up-regulation of the Cdkn1a gene and its protein product p21 in the DRG neuronal population. While apoptosis activation pathways were not observed in DRG sensory neurons of cisplatin-treated mice, these neurons did express several senescence hallmarks, including senescence-associated beta-galactosidase (SA-bGAL), phosphor(p)-H2AX and nuclear Nfkb-p65 proteins. The senescent phenotype seen in sensory neurons persisted up to 6 weeks after cisplatin treatment discontinuation. Regarding oxaliplatin study, results of scRNA-seq showed an up-regulation of Lxn and Klk5 genes, and a down-regulation of the Kyat3 gene in oxaliplatin treated animals, among others. All three genes have been involved in the modulation of inflammatory responses, the immune system and pain behaviors. Although the protein products of Klk5 and Lxn did not appear up-regulated in the DRG of oxaliplatin-treated mice, we did see an increase in the pro-inflammatory cytokine profile in both the DRG and the sciatic nerves of oxaliplatin-treated mice, altogether with increased number of infiltrated cells. Based on these results, we checked for factors involved of the so-called Immunogenic Cell Death (ICD) response, which is activated in tumor cells after oxaliplatin treatment. However, we did not find any evidence of ICD activation in DRG of oxaliplatin-treated mice at any time point evaluated. On the other hand, and in contrast to cisplatin, the rapid repair of DNA damage after oxaliplatin treatment cessation could explain the lack of establishment of a senescence phenotype in the DRG. In vivo data showed that senescence pathways could play a key role in platinum neurotoxicity. Thus, we finally set up an in vitro model of cisplatin-induced neuronal senescence in which to start the screening of potential neuroprotective targets in a cost- and time-effective way.
