Microglial phagocytosis attenuated by short-term exposure to exogenous ATP through P2X receptor action.
Microglia, the CNS resident macrophages responsible for the clearance of degenerating cellular fragments, are essential to tissue remodeling and repair after CNS injury. ATP can be released in large amounts after CNS injury and may mediate microglial activity through the ionotropic P2X and the metabotropic P2Y receptors. This study indicates that exposure to a high concentration of ATP for 30 min rapidly induces changes of the microglial cytoskeleton, and significantly attenuates microglial phagocytosis. A pharmacological approach showed that ATP-induced inhibition of microglial phagocytotic activity was due to P2X(7)R activation, rather than that of P2YR. Activation of P2X(7)R by its agonist, 2'-3'-O-(4-benzoyl)benzoyl-ATP (BzATP), produced a Ca(2+)-independent reduction in microglial phagocytotic activity. In addition, the knockdown of P2X(7)R expression by lentiviral-mediated shRNA interference or the blockade of P2X(7)R activation by the specific antagonists, oxidized ATP (oxATP) and brilliant blue G, has efficiently restored the phagocytotic activity of ATP and BzATP-treated microglia. Our results reveal that P2X(7)R activation may induce the formation of a Ca(2+)-independent signaling complex, which results in the reduction of microglial phagocytosis. This suggests that exposure to ATP for a short-term period may cause insufficient clearance of tissue debris by microglia through P2X(7)R activation after CNS injury, and that blockade of this receptor may preserve the phagocytosis of microglia and facilitate CNS tissue repair.
Fang
Kuan-Min
KM
Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan.
Yang
Chung-Shi
CS
Sun
Synthia H
SH
Tzeng
Shun-Fen
SF
D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001583:Benzoxazoles / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D021984:Cyclophilin A / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry / Q000379:methods; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects*; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D011806:Quinolinium Compounds / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058476:Receptors, Purinergic P2X2; D013997:Time Factors; D014161:Transduction, Genetic / Q000379:methods
D000199:Actins; D001583:Benzoxazoles; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011806:Quinolinium Compounds; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; C089813:YO-PRO 1; C022571:adenosine 5'-O-(3-thiotriphosphate); C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D011732:Pyridoxal Phosphate; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D021984:Cyclophilin A; D002118:Calcium