Microglial inhibition of neuroprotection by antagonists of the EP1 prostaglandin E2 receptor.
BACKGROUND
The EP1 receptor for the prostanoid PGE2 is a G-protein coupled receptor that has been shown to contribute to excitotoxic neuronal death. In this study we examined the influence of non-neuronal cells on neuroprotective properties of EP1 receptor antagonists (Ono 8711 and SC 51089).


METHODS
Primary neuronal cultures systems with or without non-neuronal cells were used to examine how the neuroprotective properties of EP1 antagonists were influenced by non-neuronal cells. The influence of astrocytes or microglia were individually tested in excitotoxicity assays using a co-culture system with these cells grown on permeable transwell inserts above the neuronal-enriched cultures. The influence of microglia on PGE2 synthesis and EP1 receptor expression was examined.


RESULTS
EP1 antagonists were neuroprotective in neuronal-enriched cultures (> 90% neurons) but not in mixed cultures (30% neurons plus other non-neuronal cells). Co-cultures of microglia on permeable transwell inserts above neuronal-enriched cultures blocked neuroprotection by EP1 antagonists. Incubation of microglia with neuronal-enriched cultures for 48 hours prior to NMDA challenge was sufficient to block neuroprotection by EP1 antagonists. The loss of neuroprotection by EP1 antagonists was accompanied by a decrease of neuronal EP1 expression in the nucleus in cultures with microglia present.


CONCLUSIONS
These findings demonstrate microglial modulation of neuronal excitotoxicity through interaction with the EP1 receptor and may have important implications in vivo where microglia are associated with neuronal injury.
Carlson
Noel G
NG
Geriatric Research Education and Clinical Center (GRECC), VASLCHCS, Salt Lake City, UT 84148, USA. noel.carlson@med.va.gov
Rojas
Monica A
MA
Black
John-David
JD
Redd
Jonathan W
JW
Hille
John
J
Hill
Kenneth E
KE
Rose
John W
JW
D000818:Animals; D001253:Astrocytes / Q000502:physiology; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D002208:Caproates / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D006834:Hydrazines / Q000494:pharmacology; D051379:Mice; D017628:Microglia / Q000502:physiology*; D018613:Microscopy, Confocal; D016202:N-Methylaspartate / Q000633:toxicity; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010077:Oxazepines / Q000494:pharmacology; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors* / Q000378:metabolism; D058306:Receptors, Prostaglandin E, EP1 Subtype
D001643:Bridged Bicyclo Compounds; D002208:Caproates; D052246:Cyclooxygenase 2 Inhibitors; D018690:Excitatory Amino Acid Agonists; D006834:Hydrazines; D018696:Neuroprotective Agents; C122148:ONO 8711; D010077:Oxazepines; C545636:Ptger1 protein, mouse; D018078:Receptors, Prostaglandin E; D058306:Receptors, Prostaglandin E, EP1 Subtype; C086836:SC 51089; D016202:N-Methylaspartate; D015232:Dinoprostone