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Release of prostaglandin E(2) and nitric oxide from spinal microglia is dependent on activation of p38

Tomohiro Matsui1, Camilla I Svensson, Yuka Hirata

  • 1Department of Laboratory Sciences, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.

Anesthesia and Analgesia
|July 9, 2010
PubMed
Abstract

Insights

Spinal microglia activation via Toll-like receptor 4 (TLR4) releases prostaglandin E2 (PGE2) and nitric oxide (NO). This release is regulated by p38 and NO synthase 2 (NOS2), highlighting p38's role in pain signaling.

Area of Science:

  • Neuroscience
  • Immunology
  • Pain Research

Background:

  • Spinal prostaglandins (PGs), nitric oxide (NO), and cytokines are involved in pain processing.
  • Microglia, the immune cells of the central nervous system, are potential sources of these pain-mediating substances.
  • Spinal microglia express Toll-like receptor 4 (TLR4) and neurokinin 1 (NK1) receptors, implicated in spinal sensitization following nerve injury or inflammation.

Purpose of the Study:

  • To investigate the signaling pathways in cultured rat spinal microglia activated by TLR4 and NK1 receptors.
  • To determine the production of prostaglandin E2 (PGE2) and nitric oxide (NO) in response to these activations.
  • To elucidate the roles of cyclooxygenase (COX), NO synthase 2 (NOS2), and p38 mitogen-activated protein kinase (p38) in these responses.

Main Methods:

  • Primary cultures of rat spinal microglia were treated with lipopolysaccharide (LPS, a TLR4 ligand) and/or substance P (SP, an NK1 agonist).
  • Inhibitors of COX (SC-560, SC-236), NOS2 (1400W), p38 (SB203580), and minocycline were used to block specific pathways.
  • PGE2 and nitrite (NO marker) concentrations in culture supernatants were measured via enzyme immunoassay and colorimetric assay.

Main Results:

  • LPS stimulation dose-dependently increased PGE2 and NO2- production, while SP had no effect alone or with LPS.
  • LPS-induced PGE2 release involved both COX-1 and COX-2.
  • LPS-induced NO release was inhibited by 1400W (NOS2 inhibitor).
  • Minocycline and the p38 inhibitor SB203580 attenuated both LPS-induced PGE2 and NO release.
  • Inhibition of NOS2 also blocked the increased PGE2 release, suggesting cross-talk between pathways.

Conclusions:

  • Activation of spinal microglia via TLR4, not NK1, triggers the release of PGE2 and NO.
  • Both COX-1 and COX-2 contribute to LPS-induced PGE2 production.
  • The COX-PGE2 pathway is modulated by p38 and NOS2.
  • p38 in spinal microglia is a critical regulator of pronociceptive molecule production (PGE2, NO), reinforcing its role in pain signaling.

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