Related Experiment Videos
Platelet-activating factor induced Ca(2+) signaling in human microglia
1Department of Pharmacology and Therapeutics, Department of Medicine, The University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, Canada.
Brain Research
|October 20, 1999
Summary
Platelet-activating factor (PAF) rapidly increases intracellular calcium in human microglia, primarily through extracellular calcium influx, not internal stores. This influx is crucial for microglial cell signaling.
Area of Science:
- Neuroimmunology
- Cellular Physiology
- Calcium Signaling
Background:
- Microglia play critical roles in neuroinflammation and immune responses within the central nervous system.
- Intracellular calcium (Ca2+) concentration ([Ca2+]i) is a key second messenger regulating various cellular functions, including microglial activation.
- Platelet-activating factor (PAF) is a potent lipid mediator implicated in inflammatory processes.
Purpose of the Study:
- To investigate the source of intracellular calcium increases in human microglial cells stimulated by PAF.
- To differentiate the contributions of extracellular Ca2+ influx versus intracellular Ca2+ release to the PAF-induced Ca2+ signal.
- To elucidate the role of store-operated calcium entry in PAF-mediated microglial responses.
Main Methods:
- Utilized Ca2+-sensitive fluorescence microscopy to monitor intracellular Ca2+ dynamics in human microglial cells.
- Applied PAF in normal physiological solution (PSS) and zero-Ca2+ solution to assess Ca2+ influx.
- Employed cyclopiazonic acid (CPA), a SERCA blocker, to modulate intracellular Ca2+ stores and investigate store-operated Ca2+ entry.
- Measured divalent cation influx using Mn2+ quenching of fluorescence to directly assess Ca2+ entry.
Main Results:
- PAF induced transient increases in [Ca2+]i in PSS, returning to baseline within 200 s.
- In zero-Ca2+ solution, PAF-induced [Ca2+]i peaks were reduced to ~20% of PSS levels, indicating significant Ca2+ influx.
- CPA application in zero-Ca2+ solution also showed reduced Ca2+ signaling, supporting the role of store-operated Ca2+ entry.
- Both PAF and CPA stimulated Mn2+ influx, with PAF acting rapidly and CPA with a delay (~200 s).
- The primary source of PAF-induced [Ca2+]i elevation was extracellular Ca2+ influx, with intracellular Ca2+ release contributing minimally.
Conclusions:
- PAF-induced increases in intracellular calcium in human microglia are predominantly mediated by extracellular Ca2+ influx.
- Intracellular Ca2+ release plays a minor role in the total Ca2+ signal but is important for controlling Ca2+ entry.
- Store-operated Ca2+ channels are likely involved in mediating Ca2+ entry triggered by PAF or intracellular store depletion.