Crosstalk between Cdk5/p35 and ERK1/2 signalling mediates spinal astrocyte activity via the PPARγ pathway in a rat model of chronic constriction injury

J Neurochem. 2019 Oct;151(2):166-184. doi: 10.1111/jnc.14827. Epub 2019 Sep 9.

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.

Keywords: Cdk5/p35; ERK1/2; GFAP; PPARγ; neuroinflammation; neuropathic pain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Butadienes / pharmacology
  • Butadienes / therapeutic use
  • Constriction, Pathologic / drug therapy
  • Constriction, Pathologic / metabolism
  • Cyclin-Dependent Kinase 5 / antagonists & inhibitors
  • Cyclin-Dependent Kinase 5 / biosynthesis
  • Cyclin-Dependent Kinase 5 / genetics
  • Disease Models, Animal
  • Enzyme Inhibitors / pharmacology
  • Enzyme Inhibitors / therapeutic use
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / physiology*
  • Male
  • Nitriles / pharmacology
  • Nitriles / therapeutic use
  • PPAR gamma / biosynthesis*
  • PPAR gamma / genetics
  • Phosphotransferases / antagonists & inhibitors
  • Phosphotransferases / biosynthesis*
  • Phosphotransferases / genetics
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinase Inhibitors / therapeutic use
  • Rats
  • Rats, Sprague-Dawley
  • Roscovitine / pharmacology
  • Roscovitine / therapeutic use
  • Sciatic Neuropathy / drug therapy
  • Sciatic Neuropathy / metabolism*
  • Spinal Cord / drug effects
  • Spinal Cord / metabolism*

Substances

  • Butadienes
  • Cdk5r1 protein, rat
  • Enzyme Inhibitors
  • Nitriles
  • PPAR gamma
  • Protein Kinase Inhibitors
  • U 0126
  • Roscovitine
  • Phosphotransferases
  • Cyclin-Dependent Kinase 5
  • Cdk5 protein, rat