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Updated: Jul 4, 2026
Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Zinc triggers microglial activation
Tiina M Kauppinen1, Youichirou Higashi, Sang Won Suh
1Department of Neurology, University of California, Veterans Affairs Medical Center, San Francisco, California 94121, USA.
Abstract:
Microglia are resident immune cells of the CNS. When stimulated by infection, tissue injury, or other signals, microglia assume an activated, "ameboid" morphology and release matrix metalloproteinases, reactive oxygen species, and other proinflammatory factors. This innate immune response augments host defenses, but it can also contribute to neuronal death. Zinc is released by neurons under several conditions in which microglial activation occurs, and zinc chelators can reduce neuronal death in animal models of cerebral ischemia and neurodegenerative disorders. Here, we show that zinc directly triggers microglial activation. Microglia transfected with a nuclear factor-kappaB (NF-kappaB) reporter gene showed a severalfold increase in NF-kappaB activity in response to 30 microm zinc. Cultured mouse microglia exposed to 15-30 microm zinc increased nitric oxide production, increased F4/80 expression, altered cytokine expression, and assumed the activated morphology. Zinc-induced microglial activation was blocked by inhibiting NADPH oxidase, poly(ADP-ribose) polymerase-1 (PARP-1), or NF-kappaB activation. Zinc injected directly into mouse brain induced microglial activation in wild-type mice, but not in mice genetically lacking PARP-1 or NADPH oxidase activity. Endogenous zinc release, induced by cerebral ischemia-reperfusion, likewise induced a robust microglial reaction, and this reaction was suppressed by the zinc chelator CaEDTA. Together, these results suggest that extracellular zinc triggers microglial activation through the sequential activation of NADPH oxidase, PARP-1, and NF-kappaB. These findings identify a novel trigger for microglial activation and a previously unrecognized mechanism by which zinc may contribute to neurological disorders.
Insights
Extracellular zinc directly activates microglia, the brain's immune cells, by triggering a signaling pathway involving NADPH oxidase, PARP-1, and NF-kappaB, contributing to neurological disorders.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are the primary immune cells in the central nervous system (CNS).
- Microglial activation, characterized by morphological changes and release of inflammatory factors, can contribute to neuronal damage.
- Zinc is released during conditions associated with microglial activation, and its chelation can mitigate neuronal death in neurological disease models.
Purpose of the Study:
- To investigate whether extracellular zinc directly triggers microglial activation.
- To elucidate the signaling pathway involved in zinc-induced microglial activation.
- To determine the role of zinc in microglial responses during neurological conditions like ischemia-reperfusion.
Main Methods:
- Utilized NF-kappaB reporter gene assays in transfected microglia.
- Assessed nitric oxide production, F4/80 expression, and cytokine profiles in zinc-exposed microglia.
- Employed genetic knockout models (PARP-1, NADPH oxidase deficient mice) and in vivo zinc injection.
- Investigated microglial activation following cerebral ischemia-reperfusion and the effect of zinc chelation.
Main Results:
- Zinc exposure significantly increased NF-kappaB activity, nitric oxide production, and F4/80 expression in microglia.
- Zinc-induced microglial activation was dependent on NADPH oxidase, PARP-1, and NF-kappaB activation.
- In vivo, zinc injection and ischemia-reperfusion-induced zinc release triggered microglial activation, which was attenuated in knockout mice or by zinc chelation.
Conclusions:
- Extracellular zinc acts as a direct trigger for microglial activation.
- The activation pathway involves sequential signaling through NADPH oxidase, PARP-1, and NF-kappaB.
- This mechanism highlights a novel role for zinc in neuroinflammation and its potential contribution to neurological disorders.
