P2X(7) receptor and macrophage function
Mark D Wewers1, Anasuya Sarkar
1Davis Heart and Lung Research Institute, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, The Ohio State University, Columbus, OH, USA, wewers.2@osu.edu.
Abstract:
Macrophages are unique innate immune cells that play an integral role in the defense of the host by virtue of their ability to recognize, engulf, and kill pathogens while sending out danger signals via cytokines to recruit and activate inflammatory cells. It is becoming increasingly clear that purinergic signaling events are essential components of the macrophage response to pathogen challenges and disorders such as sepsis may be, at least in part, regulated by these important sensors. The activation of the P2X(7) receptor is a powerful event in the regulation of the caspase-1 inflammasome. We provide evidence that the inflammasome activation requires "priming" of macrophages prior to ATP activation of the P2X(7)R. Inhibition of the inflammasome activation by the tyrosine kinase inhibitor, AG126, suggests regulation by phosphorylation. Finally, the P2X(7)R may also be activated by other elements of the host response such as the antimicrobial peptide LL-37, which adds a new, physiologically relevant agonist to the P2X(7)R pathway. Therapeutic approaches to inflammation and sepsis will certainly be enhanced by an increased understanding of how purinergic receptors modulate the inflammasomes.
Insights
Purinergic signaling via P2X7 receptors is crucial for macrophage inflammasome activation, requiring cell priming. This pathway, modulated by phosphorylation and LL-37, offers therapeutic targets for sepsis and inflammation.
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- Macrophages are key innate immune cells involved in host defense and inflammatory signaling.
- Purinergic signaling, particularly through P2X7 receptors (P2X7R), plays a critical role in macrophage responses to pathogens and in conditions like sepsis.
- Inflammasome activation is a central process in innate immunity and inflammation.
Purpose of the Study:
- To investigate the role of P2X7 receptor activation in inflammasome activation within macrophages.
- To elucidate the requirements for P2X7R-mediated inflammasome activation, including priming and potential regulatory mechanisms.
- To identify novel agonists for the P2X7R pathway relevant to host defense.
Main Methods:
- Macrophage cell cultures were utilized to study inflammasome activation.
- ATP was used to activate the P2X7 receptor, and its effect on inflammasome activation was assessed.
- The tyrosine kinase inhibitor AG126 was employed to investigate the role of phosphorylation.
- The antimicrobial peptide LL-37 was tested as a potential P2X7R agonist.
Main Results:
- Inflammasome activation via P2X7R requires a "priming" step in macrophages before ATP stimulation.
- Inhibition of inflammasome activation by AG126 suggests a role for phosphorylation in the regulation of this pathway.
- The antimicrobial peptide LL-37 was identified as a novel, physiologically relevant agonist for the P2X7R.
Conclusions:
- P2X7 receptor activation is a critical regulator of caspase-1 inflammasome assembly in macrophages.
- Macrophage priming is essential for subsequent P2X7R-mediated inflammasome activation.
- Understanding P2X7R modulation of inflammasomes provides insights for developing therapeutics for inflammatory diseases and sepsis.
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