HDAC6 Inhibition Reverses Cisplatin-Induced Mechanical Hypersensitivity via Tonic Delta Opioid Receptor Signaling

Abstract

Peripheral neuropathic pain induced by the chemotherapeutic cisplatin can persist for months to years after treatment. Histone deacetylase 6 (HDAC6) inhibitors have therapeutic potential for cisplatin-induced neuropathic pain since they persistently reverse mechanical hypersensitivity and spontaneous pain in rodent models. Here, we investigated the mechanisms underlying reversal of mechanical hypersensitivity in male and female mice by a 2 week treatment with an HDAC6 inhibitor, administered 3 d after the last dose of cisplatin. Mechanical hypersensitivity in animals of both sexes treated with the HDAC6 inhibitor was temporarily reinstated by a single injection of the neutral opioid receptor antagonist 6β-naltrexol or the peripherally restricted opioid receptor antagonist naloxone methiodide. These results suggest that tonic peripheral opioid ligand-receptor signaling mediates reversal of cisplatin-induced mechanical hypersensitivity after treatment with an HDAC6 inhibitor. Pointing to a specific role for δ opioid receptors (DORs), Oprd1 expression was decreased in DRG neurons following cisplatin administration, but normalized after treatment with an HDAC6 inhibitor. Mechanical hypersensitivity was temporarily reinstated in both sexes by a single injection of the DOR antagonist naltrindole. Consistently, HDAC6 inhibition failed to reverse cisplatin-induced hypersensitivity when DORs were genetically deleted from advillin + neurons. Mechanical hypersensitivity was also temporarily reinstated in both sexes by a single injection of a neutralizing antibody against the DOR ligand met-enkephalin. In conclusion, we reveal that treatment with an HDAC6 inhibitor induces tonic enkephalin-DOR signaling in peripheral sensory neurons to suppress mechanical hypersensitivity. SIGNIFICANCE STATEMENT Over one-fourth of cancer survivors suffer from intractable painful chemotherapy-induced peripheral neuropathy (CIPN), which can last for months to years after treatment ends. HDAC6 inhibition is a novel strategy to reverse CIPN without negatively interfering with tumor growth, but the mechanisms responsible for persistent reversal are not well understood. We built on evidence that the endogenous opioid system contributes to the spontaneous, apparent resolution of pain caused by nerve damage or inflammation, referred to as latent sensitization. We show that blocking the δ opioid receptor or its ligand enkephalin unmasks CIPN in mice treated with an HDAC6 inhibitor (latent sensitization). Our work provides insight into the mechanisms by which treatment with an HDAC6 inhibitor apparently reverses CIPN.

A Novel Therapy for Cisplatin-Induced Allodynia and Dysfunctional and Emotional Impairments in Male and Female Mice

“…These results revealed that no differences in CIS-induced mechanical allodynia were observed between male and female mice. These findings are consistent with the non-sex differences reported by other authors in CIS- [4,14,57] and vincristine-provoked tactile allodynia [22]. However, in contrast, with the sex variations demonstrated by Woller et al (2015) [15], which showed that the tactile allodynia caused by CIS disappeared 20 days after its first injection in female but not in male mice.…”

“…Patients undergoing chemotherapy also develop other signs, such as anxiety, depression, muscle wasting and cognitive deficits that have a significant negative impact on the well-being and quality of life of patients and may even lead to the need for adjournment of the chemotherapy [1,2]. Furthermore, therapies to prevent or treat this type of pain such as anticonvulsant, antidepressant, and nonsteroidal anti-inflammatory drugs are not significantly effective and produce noteworthy side effects [3,4]. Therefore, our objective is to find an effective and safe treatment for alleviating the neuropathic pain related to chemotherapy, as well as the functional deficits and mood disorders that are associated with it.…”

“…Regarding the impact of sex in the chemotherapy-induced neuropathic pain provoked by CIS, contradictory results exist. Some studies revealed that the mechanical and/or cold allodynia caused by CIS are similarly displayed in male and female animals [4,14], whereas another showed sex discrepancies in the maintenance of mechanical allodynia [15]. Nevertheless, possible differences among sexes in the development of CIS-induced emotional disorders, muscle wasting and/or weight lose have been poorly investigated.…”

Combining RNAscope and immunohistochemistry to visualize inflammatory gene products in neurons and microglia

“…The experiments included here have shown that tissue which has been fixed by transcardial perfusion with a 4-h post-fixation in 4% paraformaldehyde before blocking can be used for highly sensitive and robust RNA plus IHC stains that capture differences in gene expression after nerve injury. As shown in many prior experiments using PCR to analyze RNA from saline perfused animals, much RNA remains in tissue without the use of DEPC treated water ( Frank et al, 2006 ; Green-Fulgham et al, 2022 ; Zhang et al, 2022 ). Cold formalin preserves nucleic acid integrity, so the solution of 4% paraformaldehyde was chilled and kept on ice throughout the perfusions ( Bussolati et al, 2011 ).…”

Kinin B2 Receptor Mediates Cisplatin-Induced Painful Peripheral Neuropathy by Intracellular Kinase Pathways and TRPA1 Channel Sensitisation

“…In the present study, mice treated with cisplatin developed mechanical allodynia and cold hypersensitivity, which were sustained for at least two weeks after the last cisplatin dose, consistent with a previous study [ 22 ]. Hypersensitivity in front of mechanical stimuli is a hallmark behavioural sign of CIPN observed in rodents [ 39 , 40 , 41 , 42 , 43 , 44 ], reflecting the allodynia phenotype in CIPN patients. This cisplatin dosage regimen also produced cold allodynia, another symptom associated with platinum-based anticancer drugs [ 5 , 16 , 24 ], and is in accordance with earlier reports of cold sensitivity in cisplatin-treated rodents [ 7 , 28 , 32 ].…”