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Isoflurane preconditioning reduces mouse microglial activation and injury induced by lipopolysaccharide and
1Department of Anesthesiology, University of Virginia Health System, University of Virginia, 1 Hospital Drive, PO Box 800710, Charlottesville, VA 22908-0710, USA; Department of Anesthesiology, the First People's Hospital of Guangzhou, Guangzhou, China.
Abstract:
Activation and injury of microglial cells are involved in a broad range of brain diseases including stroke, brain infection and neurodegenerative diseases. However, there is very little information regarding how to reduce microglial reaction and preserve these cells to provide neuroprotection. Here, we showed that the incubation of C8-B4 mouse microglial cells with lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma) for 24 h decreased the viability of these cells. Pretreatment of these cells with 1%, 2% or 3% isoflurane, a commonly used volatile anesthetic, for 1 h at 30 min before the exposure to LPS plus IFNgamma attenuated the reduction of cell viability (preconditioning effect). LPS plus IFNgamma also activated these microglial cells to express inducible nitric oxide synthase (iNOS) and to induce accumulation of nitrite, a stable oxidation product of nitric oxide, in the incubation medium. Isoflurane preconditioning attenuated these LPS plus IFNgamma effects on the iNOS expression and nitrite accumulation. Aminoguanidine, an iNOS inhibitor, attenuated the LPS plus IFNgamma-induced glutamate release and decrease of microglial viability. Isoflurane preconditioning also reduced LPS plus IFNgamma-induced glutamate release. Exogenous glutamate decreased microglial viability. Finally, the isoflurane preconditioning-induced protection was abolished by chelerythrine, a protein kinase C inhibitor. These results suggest that LPS plus IFNgamma activates the iNOS-nitric oxide-glutamate pathway to induce microglial injury and that this activation is attenuated by isoflurane preconditioning. Protein kinase C may be involved in the isoflurane preconditioning effects.
Insights
Isoflurane anesthesia protects microglial cells from injury by inhibiting the iNOS-nitric oxide-glutamate pathway. This preconditioning effect preserves cell viability and reduces inflammation, offering potential neuroprotection in brain diseases.
Area of Science:
- Neuroscience
- Immunology
- Anesthesiology
Background:
- Microglial cell activation and injury are implicated in various brain diseases.
- Limited strategies exist to reduce microglial reactivity and promote neuroprotection.
- Lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma) induce microglial cell death and activation.
Purpose of the Study:
- To investigate the neuroprotective effects of isoflurane preconditioning on microglial cells.
- To elucidate the molecular mechanisms underlying isoflurane-mediated protection.
- To determine the role of the iNOS-nitric oxide-glutamate pathway in microglial injury.
Main Methods:
- Primary mouse microglial cell cultures (C8-B4) were treated with LPS plus IFNgamma.
- Cells were preconditioned with varying concentrations of isoflurane prior to LPS/IFNgamma exposure.
- Cell viability, inducible nitric oxide synthase (iNOS) expression, nitrite accumulation, and glutamate release were measured.
- Inhibitors of iNOS (aminoguanidine) and protein kinase C (chelerythrine) were used.
Main Results:
- LPS plus IFNgamma decreased microglial viability and increased iNOS expression and nitrite accumulation.
- Isoflurane preconditioning attenuated the reduction in cell viability and inhibited iNOS/nitrite production.
- Isoflurane preconditioning reduced LPS/IFNgamma-induced glutamate release.
- Aminoguanidine and isoflurane preconditioning protected against microglial injury.
- Chelerythrine abolished the protective effects of isoflurane preconditioning.
Conclusions:
- LPS plus IFNgamma activate a pathway involving iNOS, nitric oxide, and glutamate, leading to microglial injury.
- Isoflurane preconditioning attenuates this pathway, offering neuroprotection.
- Protein kinase C signaling is likely involved in the protective mechanisms of isoflurane preconditioning.
