title: Proinflammatory treatment of astrocytes with lipopolysaccharide results in augmented Ca2+ signaling through increased expression of via phospholipase A2 (iPLA2).
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.
authors.affiliation: Institut für Neurobiochemie, Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Leipziger Straße 44, 39120 Magdeburg, Germany.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Strokin
authors.forename: Marina
authors.initials: M
authors.lastname: Sergeeva
authors.forename: Georg
authors.initials: G
authors.lastname: Reiser
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000201:enzymology*; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D005911:Gliosis / Q000201:enzymology* / Q000473:pathology; D054522:Group VI Phospholipases A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018836:Inflammation Mediators / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051381:Rats; D015854:Up-Regulation / Q000235:genetics / Q000502:physiology*
chemical_list: D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D054522:Group VI Phospholipases A2; C535117:Pla2g6 protein, rat; D002118:Calcium