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Nitric oxide displays a biphasic effect on calcium dynamics in microglia
Matthew J E Maksoud1, Vasiliki Tellios1, Yun-Yan Xiang2
1Graduate Program of Neuroscience, The University of Western Ontario, Canada; Robarts Research Institute, The University of Western Ontario, Canada.
Nitric Oxide : Biology and Chemistry
|January 8, 2021
Summary
Nitric oxide (NO) modulates microglial calcium signaling by restricting store-operated calcium entry and enhancing TRPV2 channel activity, impacting neuroinflammation.
Area of Science:
- Neuroimmunology
- Cellular Physiology
- Molecular Biology
Background:
- Microglia, the immune cells of the central nervous system, utilize intracellular calcium (Ca2+) as a critical secondary messenger.
- Inflammation triggers microglia to increase inducible nitric oxide synthase (iNOS) expression, producing nitric oxide (NO).
- The precise role of NO in regulating microglial Ca2+ dynamics, particularly through transient receptor potential (TRP) channels, remains incompletely understood.
Purpose of the Study:
- To investigate whether NO regulates intracellular Ca2+ dynamics via TRP channels in primary microglia and the BV2 cell line.
- To elucidate the specific TRP channels involved in NO-mediated Ca2+ modulation.
- To determine the involvement of protein kinase G (PKG) in NO's effects on Ca2+ signaling.
Main Methods:
- Utilized calcium imaging and voltage-clamp recordings in primary wildtype (WT) and iNOS knockout (iNOS-/-) microglia, and the BV2 microglial cell line.
- Employed NO-donor SNAP, store-operated calcium channel (SOCC) inhibitor 2APB, TRPV2 inhibitor tranilast, and PKG inhibitor.
- Stimulated SOCCs using thapsigargin to assess NO's impact on nonselective cation conductance.
Main Results:
- NO-donor SNAP induced a biphasic Ca2+ response: Phase I showed reduced Ca2+ influx (SOCC-dependent, PKG-independent), while Phase II showed increased Ca2+ influx (TRPV2-dependent, PKG-dependent).
- SNAP application attenuated thapsigargin-induced Ca2+ influx through SOCCs.
- iNOS-/- microglia exhibited enhanced SOCC-mediated Ca2+ influx and reduced expression of key Ca2+ channel components (STIM1, Orai1, TRPC1/3) compared to WT microglia.
Conclusions:
- NO signaling restricts Ca2+ influx through SOCCs independently of PKG.
- NO signaling enhances Ca2+ influx through TRPV2 channels via a PKG-dependent mechanism.
- These findings reveal distinct roles for NO in microglial Ca2+ homeostasis, influencing neuroinflammatory responses.
Keywords:
CalciumInducible nitric oxide synthaseProtein kinase GStore operated calcium entryTransient receptor potentialMore Related Videos
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