Intensity-dependent activation of extracellular signal-regulated protein kinase 5 in sensory neurons contributes to pain hypersensitivity

J Pharmacol Exp Ther. 2007 Apr;321(1):28-34. doi: 10.1124/jpet.106.116749. Epub 2007 Jan 19.

Abstract

Alterations in the intracellular signal transduction pathway in primary afferents may contribute to pain hypersensitivity. Recently, we have reported that the phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) occurs in primary afferent neurons in response to noxious stimulation of the peripheral tissue, i.e., activity-dependent activation of ERK1/2 and p38 MAPK in dorsal root ganglion (DRG) neurons. In the present study, we investigated the phosphorylation of ERK5, also known as big MAPK1, in the DRG by noxious stimulation using immunohistochemistry. Capsaicin injection induced phosphorylated ERK5 (p-ERK5) in small-to-medium diameter sensory neurons with a peak at 2 min after capsaicin injection. Furthermore, we examined the p-ERK5 labeling in the DRG after noxious heat and cold stimuli and found a stimulus intensity-dependent increase in the number of activated neurons. Most of these p-ERK5-immunoreactive neurons were small- and medium-sized neurons, which coexpressed transient receptor potential (TRP) ion channel TRPV1 and TRPA1 after noxious heat and cold stimuli, respectively. In contrast, there was no change in ERK5 phosphorylation in the spinal dorsal horn. The i.t. administration of ERK5 antisense oligodeoxynucleotide reversed heat hyperalgesia, but not mechanical allodynia, produced by capsaicin injection. Taken together, these findings suggest that the in vivo activation of the ERK5 signaling pathway in sensory neurons by noxious stimulation may be, at least in part, correlated with functional activity and, further, involved in the development of pain hypersensitivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Behavior, Animal / drug effects
  • Behavior, Animal / physiology
  • Blotting, Western
  • Capsaicin / pharmacology
  • Cold Temperature
  • Enzyme Activation / physiology
  • Hot Temperature
  • Hyperalgesia / chemically induced
  • Hyperalgesia / physiopathology*
  • Immunohistochemistry
  • In Situ Hybridization
  • Male
  • Mitogen-Activated Protein Kinase 6 / biosynthesis
  • Mitogen-Activated Protein Kinase 6 / metabolism*
  • Neurons, Afferent / physiology*
  • Phosphorylation
  • Posterior Horn Cells / drug effects
  • Posterior Horn Cells / physiology
  • RNA, Antisense / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • TRPV Cation Channels / drug effects
  • TRPV Cation Channels / physiology

Substances

  • RNA, Antisense
  • TRPV Cation Channels
  • Trpv1 protein, rat
  • Mitogen-Activated Protein Kinase 6
  • Capsaicin