Role of cytoplasmic DNA sensor, STING, on development and maintenance of neuropathic pain induced by cisplatin

Author(s)

Fabio Bonifacio de Andrade

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2023-07-03

Examining board members

Thiago Mattar Cunha; Joice Maria da Cunha; Christie Ramos Andrade Leite Panissi

• Advisor: Thiago Mattar Cunha

Abstract

Cisplatin-induced neuropathic pain (CINP) is a common and serious side effect experienced by cancer patients receiving cisplatin treatment. This condition can impact quality of life and can persist even though the therapy is over. Associated with the low efficacy of current therapies for neuropathic pain management, the search for new molecular targets for pharmacological intervention is essential. In this context, emerging evidence associates the involvement of mitochondrial dysfunction with the development of cisplatin-induced neuropathy; moreover, it was seem that cisplatin treatment can induce leakage of mitochondrial DNA (mtDNA) to the cytoplasm in kidney cells. Therefore, we hypothesized that cisplatin-induced mitochondrial damage in sensory neurons of the dorsal root ganglia (DRG) could promote the activation of interferon gene stimulator (STING) to induce CINP. STING is a cytoplasmic DNA sensor that recognizes cyclic dinocleotides abnormally present in the cell cytoplasm which can be produced in response to the activation of cyclic GMP-AMP synthase (cGAS). The activation of STING promotes the activation of transcription factors that induces the expression of genes associated with inflammatory cytokines, such as type I interferons, tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6). Thus, the aim of this study was to evaluate the role of STING in the development and maintenance of CINP. Firstly, we observed that cisplatin treatment was able to induce increased quantification of double-stranded DNA in the cytoplasm of mouse DRG cells, as an indicative of mitochondrial dysfunction. Furthermore, STING expression was observed in different neuronal populations of mouse DRG. Notably, it was seem that mice lacking STING (STING GT) submitted to CINP showed a reduction in mechanical nociceptive hypersensitivity over the days when compared to wild-type (WT) mice. In addition, WT mice submitted to the CINP model and injected with systemic administration of STING antagonist (C-176) were also protected. Additionally, cGAS-/- mice were similarly protected against the development of CINP. To determine the cell type in which STING expression is necessary for the observed phenotype, we generated animals in which STING was selectively deleted in nociceptors. Remarkably, these animals also showed a reduction in mechanical nociceptive hypersensitivity over the days when compared to control group. Analysis of the increased expression of cytokines revealed an increase in IL-6 in the DRG of WT mice submitted to cisplatin injections, but not in the DRG of STING GT mice. In this context, it was seen that IL-6-/- mice are also protected against the development of CINP. Primary culture of DRG sensory neurons stimulated with STING agonist, CAY10748, showed increased expression of IL-6 in these cells. Taken together, our data show that STING expressed in DRG nociceptors of mice is necessary for the development of CINP. Furthermore, we demonstrated that activation of STING in response to cisplatin treatment id due to mitochondrial injury with the cytoplasmic scape of mtDNA and STING acts through the induction of IL-6 in the nociceptors. In summary, our data demonstrate that STING expressed in nociceptors plays a pro-nociceptive role for CINP and represents a possible target to be explored for the treatment of neuropathic pain. (AU)

• FAPESP's process: 21/09854-9 - Role of cytoplasmic DNA sensor, STING, in cisplatin-induced peripheral neuropathic pain development
• Grantee: Fabio Bonifacio de Andrade
• Support Opportunities: Scholarships in Brazil - Doctorate