Proinflammatory treatment of astrocytes with lipopolysaccharide results in augmented Ca2+ signaling through increased expression of via phospholipase A2 (iPLA2)

Am J Physiol Cell Physiol. 2011 Mar;300(3):C542-9. doi: 10.1152/ajpcell.00428.2010. Epub 2010 Dec 22.

Abstract

Many Ca(2+)-regulated intracellular processes are involved in the development of neuroinflammation. However, the changes of Ca(2+) signaling in the brain under inflammatory conditions were hardly studied. ATP-induced Ca(2+) signaling is a central event of signal transmission in astrocytic networks. We investigated primary astrocytes after proinflammatory stimulation with lipopolysaccharide (LPS; 100 ng/ml) for 6-24 h. We reveal that Ca(2+) responses to purinergic ATP stimulation are significantly increased in amplitude and duration after stimulation with LPS. We detected that increased amplitudes of Ca(2+) responses to ATP in LPS-treated astrocytes can be explained by substantial increase of Ca(2+) load in stores in endoplasmic reticulum. The mechanism implies enhanced Ca(2+) store refilling due to the amplification of capacitative Ca(2+) entry. The reason for the increased duration of Ca(2+) responses in LPS-treated cells is also the amplified capacitative Ca(2+) entry. Next, we established that the molecular mechanism for the LPS-induced amplification of Ca(2+) responses in astrocytes is increased expression and activity of VIA phospholipase A(2) (VIA iPLA(2)). Indeed, both gene silencing with specific small interfering RNA and pharmacological inhibition of VIA iPLA(2) with S-bromoenol lactone reduced the load of the Ca(2+) stores and caused a decrease in the amplitudes of Ca(2+) responses in LPS-treated astrocytes to values, which were comparable with those in untreated cells. Our findings highlight a novel regulatory role of VIA iPLA(2) in development of inflammation in brain. We suggest that this enzyme might be a possible target for treatment of pathologies related to brain inflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / enzymology*
  • Calcium / physiology
  • Calcium Signaling / physiology*
  • Cells, Cultured
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum / pathology
  • Gene Expression Regulation, Enzymologic / physiology
  • Gene Silencing / physiology
  • Gliosis / enzymology*
  • Gliosis / pathology
  • Group VI Phospholipases A2 / antagonists & inhibitors
  • Group VI Phospholipases A2 / genetics
  • Group VI Phospholipases A2 / metabolism*
  • Inflammation Mediators / pharmacology*
  • Lipopolysaccharides / pharmacology*
  • Rats
  • Up-Regulation / genetics
  • Up-Regulation / physiology*

Substances

  • Inflammation Mediators
  • Lipopolysaccharides
  • Group VI Phospholipases A2
  • Pla2g6 protein, rat
  • Calcium