Crosstalk between Cdk5/p35 and ERK1/2 signalling mediates spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury. Issue 2 (9th September 2019)

• Record Type: Journal Article
• Authors: Zhong, Yu; Chen, Jialin; Chen, Jing; Chen, Yanhua; Li, Li; Xie, Yubo
• Is Part Of: Journal of neurochemistry. Volume 151:Issue 2(2019)
• Page Start: 166
• Page End: 184
• Publication Date: 2019-09-09
• Subjects: Cdk5/p35 -- PPARγ -- GFAP -- neuroinflammation -- neuropathic pain -- ERK1/2; Neurochemistry -- Periodicals; 616.8042
• DOI: 10.1111/jnc.14827
• Languages: English
• ISSNs: 0022-3042

Abstract

Abstract: The specific mechanisms underlying cyclin‐dependent kinase 5 (Cdk5)‐mediated neuropathic pain at the spinal cord level remain elusive. The aim of the present study was to explore the role of crosstalk between Cdk5/p35 and extracellular signal‐regulated kinase 1/2 (ERK1/2) signalling in mediating spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury (CCI). Here, we quantified pain behaviour after CCI; detected the localization of p35, Cdk5, phosphorylated ERK1/2 (pERK1/2), phosphorylated peroxisome proliferator‐activated receptor γ (pPPARγ), neuronal nuclei (a neuronal marker), glial fibrillary acidic protein (GFAP, an activated astrocyte marker) and ionized calcium binding adaptor molecule 1 (a microglial marker) in the dorsal horn using immunofluorescence; measured the protein levels of Cdk5, p35, pERK1/2, pPPARγ and GFAP using western blot analysis; and gauged the enzyme activity of Cdk5/p35 kinase using a Cdk5/p35 kinase activity assay kit. Tumour necrosis factor‐α, interleukin (IL)‐1β and IL‐6 levels were measured using enzyme‐linked immunosorbent assay (ELISA). Ligation of the right sciatic nerve induced mechanical allodynia; thermal hyperalgesia; and the time‐dependent upregulation of p35, pERK1/2 and GFAP and downregulation of pPPARγ. p35 colocalized with Cdk5, pERK1/2, pPPARγ, neurons and astrocytes but not microglia. Meanwhile, intrathecal injection of the Cdk5 inhibitor roscovitine, the mitogen‐activated ERK kinase (MEK) inhibitor U0126 and the PPARγ agonist pioglitazone prevented or reversed behavioural allodynia, increased pPPARγ expression, inhibited astrocyte activation and alleviated proinflammatory cytokine (tumour necrosis factor‐α, IL‐1β, and IL‐6) release from activated astrocytes. Furthermore, crosstalk between the Cdk5/p35 and ERK1/2 pathways was observed with CCI. Blockade of either Cdk5/p35 or ERK1/2 inhibited Cdk5 activity. These findings indicate that spinal crosstalk between the Cdk5/p35 and ERK1/2 pathways mediates astrocyte activity via the PPARγ pathway in CCI rats and that targeting this crosstalk could be an effective strategy to attenuate CCI and astrocyte‐derived neuroinflammation. Abstract : The specific mechanisms underlying cyclin‐dependent kinase 5 (Cdk5)‐mediated neuropathic pain at the spinal cord level remain elusive. In this study, we could show that after chronic constriction injury (CCI) surgery, signalling molecules like p35 and phosphorylated extracellular signal‐regulated kinase (pERK1/2) were upregulated while phosphorylated peroxisome proliferator‐activated receptor γ (pPPARγ) was downregulated. These molecules have been identified to signal the activation of astrocytes, leading to pain sensitization and neuroinflammation. Further, we show that inhibition of Cdk5/p35 and ERK1/2 or activation of PPARγ attenuates pain behaviour allodynia and astrocyte activation and reduces the production of astrocyte‐derived proinflammatory cytokines. Furthermore, crosstalk between the Cdk5/p35 and ERK1/2 pathways was observed with CCI. These findings could be a critical mechanism to attenuate neuropathic pain.