Microglial phagocytosis attenuated by short-term exposure to exogenous ATP through P2X receptor action
Kuan-Min Fang1, Chung-Shi Yang, Synthia H Sun
1Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan.
Abstract:
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.
Insights
High ATP levels after CNS injury impair microglial phagocytosis via P2X7 receptor activation. Blocking this receptor restores microglial function, aiding tissue repair.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are crucial for CNS repair after injury.
- Adenosine triphosphate (ATP) is released post-injury and influences microglial activity via P2X and P2Y receptors.
Purpose of the Study:
- To investigate the short-term effects of ATP on microglial phagocytosis.
- To identify the specific purinergic receptors involved in ATP-mediated microglial dysfunction.
Main Methods:
- Exposing microglia to high ATP concentrations and assessing cytoskeletal changes and phagocytosis.
- Utilizing pharmacological agonists (BzATP) and antagonists (oxATP, brilliant blue G) of P2X7 receptors.
- Employing lentiviral-mediated shRNA to knockdown P2X7 receptor expression.
Main Results:
- Short-term ATP exposure rapidly altered microglial cytoskeleton and significantly reduced phagocytosis.
- P2X7 receptor activation, not P2Y receptors, mediated the ATP-induced inhibition of phagocytosis.
- P2X7 receptor activation led to a Ca(2+)-independent reduction in microglial phagocytotic activity.
- Knockdown or blockade of P2X7 receptors restored phagocytosis in ATP-treated microglia.
Conclusions:
- P2X7 receptor activation by ATP reduces microglial phagocytosis through a Ca(2+)-independent pathway.
- Short-term ATP exposure may impair debris clearance after CNS injury by activating P2X7 receptors.
- Blocking P2X7 receptors could preserve microglial phagocytosis and promote CNS tissue repair.
