2. Academic Validation
  3. Attenuation of mechanical pain hypersensitivity by treatment with Peptide5, a connexin-43 mimetic peptide, involves inhibition of NLRP3 inflammasome in nerve-injured mice

Attenuation of mechanical pain hypersensitivity by treatment with Peptide5, a connexin-43 mimetic peptide, involves inhibition of NLRP3 inflammasome in nerve-injured mice

  • Exp Neurol. 2018 Feb;300:1-12. doi: 10.1016/j.expneurol.2017.10.016.
Ryan S Tonkin 1,  Callum Bowles 1,  Chamini J Perera 1,  Brooke A Keating 1,  Preet G S Makker 1,  Samuel S Duffy 1,  Justin G Lees 1,  Collin Tran 2,  Anthony S Don 3,  Thomas Fath 1,  Lu Liu 1,  Simon J O'Carroll 4,  Louise F B Nicholson 4,  Colin R Green 5,  Catherine Gorrie 6,  Gila Moalem-Taylor 7
Affiliations

Affiliations

  • 1 School of Medical Sciences, Faculty of Medicine, University of New South Wales, UNSW Sydney, NSW 2052, Australia.
  • 2 Centenary Institute, University of Sydney Medical School, Sydney, NSW 2006, Australia.
  • 3 Centenary Institute, University of Sydney Medical School, Sydney, NSW 2006, Australia; NHMRC Clinical Trials Centre, Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
  • 4 Department of Anatomy and Medical Imaging and the Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
  • 5 Department of Ophthalmology and New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
  • 6 School of Life Sciences, Faculty of Science, University of Technology, Sydney, NSW 2007, Australia.
  • 7 School of Medical Sciences, Faculty of Medicine, University of New South Wales, UNSW Sydney, NSW 2052, Australia. Electronic address: [email protected].
PMID: 29055716 DOI: 10.1016/j.expneurol.2017.10.016
Abstract

Connexin43 (Cx43) hemichannels in spinal cord astrocytes are implicated in the maintenance of neuropathic pain following peripheral nerve injury. Peptide5 is a Cx43 mimetic peptide that blocks hemichannels. In this study, we investigated the effects of spinal delivery of Peptide5 on mechanical pain hypersensitivity in two mouse models of neuropathic pain, peripheral nerve injury and chemotherapy-induced peripheral neuropathy (CIPN). We demonstrated that 10days following a chronic constriction injury (CCI) of the sciatic nerve, Cx43 expression, co-localised predominantly with astrocytes, was increased in the ipsilateral L3-L5 lumbar spinal cord. An intrathecal injection of Peptide5 into nerve-injured mice, on day 10 when pain was well-established, caused significant improvement in mechanical pain hypersensitivity 8h after injection. Peptide5 treatment resulted in significantly reduced Cx43, and microglial and astrocyte activity in the dorsal horn of the spinal cord, as compared to control saline-treated CCI mice. Further in vitro investigations on primary astrocyte cultures showed that 1h pre-treatment with Peptide5 significantly reduced adenosine triphosphate (ATP) release in response to extracellular calcium depletion. Since ATP is a known activator of the NOD-like receptor protein 3 (NLRP3) inflammasome complex, a key mediator of neuroinflammation, we examined the effects of Peptide5 treatment on NLRP3 inflammasome expression. We found that NLRP3, its adaptor apoptosis-associated spec-like protein (ASC) and Caspase-1 protein were increased in the ipsilateral spinal cord of CCI mice and reduced to naïve levels following Peptide5 treatment. In the models of oxaliplatin- and paclitaxel-induced peripheral neuropathy, treatment with Peptide5 had no effect on mechanical pain hypersensitivity. Interestingly, in these CIPN models, although spinal Cx43 expression was significantly increased at day 13 following chemotherapy, NLRP3 expression was not altered. These results suggest that the analgesic effect of Peptide5 is specifically achieved by reducing NLRP3 expression. Together, our findings demonstrate that blocking Cx43 hemichannels with Peptide5 after nerve injury attenuates mechanical pain hypersensitivity by specifically targeting the NLRP3 inflammasome in the spinal cord.

Keywords

ATP; Connexins; Gap junctions; Hemichannels; Inflammasome; Nerve injury; Neuropathic pain.

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