Inhibition of lipopolysaccharide-induced cyclooxygenase-2, tumor necrosis factor-alpha and [Ca2+]i responses in human microglia by the peripheral benzodiazepine receptor ligand PK11195

J Neurochem. 2002 Nov;83(3):546-55. doi: 10.1046/j.1471-4159.2002.01122.x.


The anti-inflammatory actions of the mitochondrial peripheral benzodiazepine receptor (PBR) agonist PK11195 [1-(2-chloro- phenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carboxamide] were investigated in human microglia. Application of the microglial inflammatory stimulus lipopolysaccharide (LPS, at 100 ng/mL for 3 h), induced enhancement of the expressions of the inducible enzyme, cyclooxygenase-2 (COX-2) and the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha). PK11195 (at 50 microm) significantly inhibited the LPS-induced up-regulation of both inflammatory factors; at a lower concentration of PK11195 (2 microm) expression of TNF-alpha, but not COX-2, was reduced. Production of both factors, using immunocytochemistry for COX-2 and ELISA for TNF-alpha, was markedly reduced with 50 microm of PK11195 added to LPS solution. Acute application of LPS induced a transient increase in intracellular Ca2+[Ca2+]i exhibiting both a slow development and recovery in kinetic behavior. This increase in [Ca2+]i consisted primarily of a Ca2+ influx component accompanied by a smaller mobilization from intracellular Ca2+ stores. In the presence of PK11195, the amplitude of the [Ca2+]i response induced by LPS was reduced by 54%. Another mitochondrial agent cyclosporin A (CsA), which also acts at the permeability transition pore (PTP) of mitochondrial membrane but at a site different from the PBR, was ineffective in reducing either the LPS-induced expression of COX-2 and TNF-alpha or the endotoxin increase in [Ca2+]i. These results indicate that the mitochondrial effector PK11195 is a specific and effective agent for inhibiting LPS-induced microglial expressions of COX-2 and TNF-alpha and that modulation of Ca2+-mediated signaling pathways could be involved in the anti-inflammatory actions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brain / cytology
  • Brain / embryology
  • Calcium / metabolism*
  • Cells, Cultured
  • Cyclooxygenase 2
  • Cyclosporine / pharmacology
  • Enzyme Induction / drug effects
  • Enzyme Inhibitors / pharmacology
  • Enzyme-Linked Immunosorbent Assay
  • GABA-A Receptor Agonists
  • Humans
  • Immunohistochemistry
  • Intracellular Fluid / metabolism
  • Isoenzymes / metabolism*
  • Isoquinolines / pharmacology*
  • Ligands
  • Lipopolysaccharides / pharmacology
  • Membrane Proteins
  • Microglia / cytology
  • Microglia / drug effects*
  • Microglia / metabolism
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Prostaglandin-Endoperoxide Synthases / metabolism*
  • Receptors, GABA-A / metabolism
  • Tumor Necrosis Factor-alpha / metabolism*
  • Up-Regulation / drug effects*


  • Enzyme Inhibitors
  • GABA-A Receptor Agonists
  • Isoenzymes
  • Isoquinolines
  • Ligands
  • Lipopolysaccharides
  • Membrane Proteins
  • Receptors, GABA-A
  • Tumor Necrosis Factor-alpha
  • Cyclosporine
  • Cyclooxygenase 2
  • PTGS2 protein, human
  • Prostaglandin-Endoperoxide Synthases
  • Calcium
  • PK 11195