Possible involvement of PPAR gamma in the regulation of basal channel opening of P2X7 receptor in cultured mouse astrocytes.
OBJECTIVE
Recently, we demonstrated that cultured mouse astrocytes exhibited basal channel opening of P2X7 receptor (P2X7R) in the absence of any exogenous ligand, but the regulatory mechanism involved was not elucidated. Since our preliminary experiments suggested possible involvement of peroxisome proliferator-activated receptor (PPAR) gamma in the regulation, we examined whether PPAR gamma regulated P2X7R basal channel opening in mouse astrocytes.


METHODS
P2X7R channel opening was assessed as to the uptake of a marker dye, YO-PRO-1 (YP), in the presence or absence of agonists and antagonists for PPAR gamma under a fluorescence microscope. Expression of PPAR gamma was evaluated by Western blotting and immunocytochemistry.


RESULTS
NSAIDs such as flufenamic acid (FFA) and indomethacin, which are a cyclooxygenase inhibitor and a PPAR gamma agonist, showed enhancing and inhibiting effects on YP uptake at low and high concentrations, respectively, and the enhanced uptake was abolished by periodate-oxidized ATP (oxATP), a selective P2X7R antagonist. The PPAR gamma agonists 15-deoxy-Delta(12,14)-prostaglandin J(2) and ciglitazone decreased the basal and FFA-enhanced YP uptake, while the antagonist GW9662 increased YP uptake, this effect being blocked by the agonists and also by oxATP. PPAR gamma was distributed in the nucleus and cytosolic/membrane fraction of cultured mouse astrocytes.


CONCLUSIONS
These findings indicate that basal channel opening of P2X7R in mouse astrocytes is at least in part regulated by PPAR gamma.
Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. nagasawa@mb.kyoto-phu.ac.jp
Kazuki
K
Nagasawa
Jun
J
Miyaki
Yuka
Y
Kido
Youichirou
Y
Higashi
Kentaro
K
Nishida
Sadaki
S
Fujimoto
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D007473:Ion Channels / Q000378:metabolism; D051379:Mice; D047495:PPAR gamma / Q000819:agonists / Q000502:physiology*; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007473:Ion Channels; C546469:P2rx7 protein, mouse; D047495:PPAR gamma; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7