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Dexmedetomidine Alters the Inflammatory Profile of Rat Microglia In Vitro
Michael C Scott1, Candice M Haase2, Scott D Olson2
1Department of Pediatric Surgery, University of Texas Health Science Center at Houston, 1881 East Road, 3SCR6.3600, Houston, TX, USA. Michael.c.scott@uth.tmc.edu.
Background:
Microglia are a primary mediator of the neuroinflammatory response to neurologic injury, such as that in traumatic brain injury. Their response includes changes to their cytokine expression, metabolic profile, and immunophenotype. Dexmedetomidine (DEX) is an α2 adrenergic agonist used as a sedative in critically ill patients, such as those with traumatic brain injury. Given its pharmacologic properties, DEX may alter the phenotype of inflammatory microglia.
Methods:
Primary microglia were isolated from Sprague-Dawley rats and cultured. Microglia were activated using multiple mediators: lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (Poly I:C), and traumatic brain injury damage-associated molecular patterns (DAMP) from a rat that sustained a prior controlled cortical impact injury. After activation, cultures were treated with DEX. At the 24-h interval, the cell supernatant and cells were collected for the following studies: cytokine expression (tumor necrosis factor-α [TNFα], interleukin-10 [IL-10]) via enzyme-linked immunosorbent assay, 6-phosphofructokinase enzyme activity assay, and immunophenotype profiling with flow cytometry. Cytokine expression and metabolic enzyme activity data were analyzed using two-way analysis of variance. Cell surface marker expression was analyzed using FlowJo software.
Results:
In LPS-treated cultures, DEX treatment decreased the expression of TNFα from microglia (mean difference = 121.5 ± 15.96 pg/mL; p < 0.0001). Overall, DEX-treated cultures had a lower expression of IL-10 than nontreated cultures (mean difference = 39.33 ± 14.50 pg/mL, p < 0.0001). DEX decreased IL-10 expression in LPS-stimulated microglia (mean difference = 74.93 ± 12.50 pg/mL, p = 0.0039) and Poly I:C-stimulated microglia (mean difference = 23.27 ± 6.405 pg/mL, p = 0.0221). In DAMP-stimulated microglia, DEX decreased the activity of 6-phosphofructokinase (mean difference = 18.79 ± 6.508 units/mL; p = 0.0421). The microglial immunophenotype was altered to varying degrees with different inflammatory stimuli and DEX treatment.
Conclusions:
DEX may alter the neuroinflammatory response of microglia. By altering the microglial profile, DEX may affect the progression of neurologic injury.
Insights
Dexmedetomidine (DEX) alters microglial inflammatory responses by decreasing pro-inflammatory cytokines like TNFα and IL-10. This immunomodulatory effect suggests DEX may influence the progression of neurological injury.
Area of Science:
- Neuroscience
- Immunology
- Pharmacology
Background:
- Microglia are key players in neuroinflammation following brain injury.
- Their activation involves changes in cytokine release, metabolism, and surface markers.
- Dexmedetomidine (DEX), an α2 adrenergic agonist, is used for sedation in critically ill patients, including those with traumatic brain injury.
Purpose of the Study:
- To investigate the effects of DEX on activated microglia.
- To determine if DEX modulates microglial cytokine expression, metabolic activity, and immunophenotype.
Main Methods:
- Primary rat microglia were activated with lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (Poly I:C), or damage-associated molecular patterns (DAMPs).
- Activated microglia were treated with DEX.
- Cytokine levels (TNFα, IL-10), 6-phosphofructokinase activity, and cell surface markers were analyzed.
Main Results:
- DEX significantly reduced TNFα expression in LPS-activated microglia.
- DEX decreased IL-10 levels in both LPS- and Poly I:C-stimulated microglia.
- DEX reduced 6-phosphofructokinase activity in DAMP-stimulated microglia.
- Microglial immunophenotype was altered by DEX treatment, varying with inflammatory stimuli.
Conclusions:
- Dexmedetomidine (DEX) modulates the neuroinflammatory response of microglia.
- By altering microglial phenotype and cytokine production, DEX may impact the course of neurological injury.
