Progesterone and its metabolites 5-dihydroprogesterone and 5-3-tetrahydroprogesterone decrease LPS-induced NO release in the murine microglial cell line, BV-2
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Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates
Published on: January 30, 2014
Edith Müller1, Hubert H Kerschbaum
1Division of Animal Physiology, Department of Cellular Biology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria. Hubert.Kerschbaum@sbg.ac.at.
Objective:
Microglial cells, important immunosurveillance cells in the nervous system, respond to pathogens with an increase in inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) release. Because excessive release of NO may be neurotoxic, tight regulation of nitrosative stress is required.
Design And Setting:
We cultured the murine microglial cell-line, BV-2, with bacterial lipopolysaccharide (LPS) to induce NO synthesis and quantified the impact of progesterone and its metabolites, 5alpha-dihydroprogesterone (DHP) and 5alpha-3alpha-tetrahydroprogesterone (THP), on NO release.
Results:
Our in vitro experiments showed that in BV-2 cells LPS-induced NO release is suppressed by progesterone and THP. Both neurosteroids decreased NO release by about 40% when used at a concentration of 10 microM. NO release was less sensitive to DHP. This neurosteroid decreased NO release only by 20% when used at a concentration of 10 microM. NO release was sensitive to N(G)-methyl-L-arginine (L-NMMA), a completive inhibitor of NOS, indicating that LPS-induced NO release is mediated by NOS activity. Trypan blue exclusion experiments showed that the ratio of viable to dead cells did not vary using different concentrations of progesterone. Furthermore, progesterone did not increase apoptosis or necrosis when estimated by the distribution of DAPI-labelled condensed chromatin.
Conclusion:
These experiments indicate that the decline in NO release is mainly due to modulation of NOS activity or expression. Because progesterone, DHP, and THP are synthesized in astrocytes and oligodendrocytes, these neurosteroids may locally suppress an immune response.
Insights
Progesterone and its metabolite THP suppress nitric oxide (NO) release from microglial cells, potentially reducing neurotoxicity. These neurosteroids may locally regulate immune responses in the nervous system.
Area of Science:
- Neuroimmunology
- Neuroendocrinology
- Cellular Neuroscience
Background:
- Microglial cells are key in nervous system immunosurveillance.
- Pathogen exposure increases microglial inducible nitric oxide synthase (iNOS) and nitric oxide (NO) release.
- Excessive NO can be neurotoxic, necessitating regulation of nitrosative stress.
Purpose of the Study:
- To investigate the impact of progesterone and its metabolites on NO release in microglial cells.
- To determine if neurosteroids can modulate LPS-induced NO synthesis.
Main Methods:
- Murine microglial BV-2 cells were cultured with lipopolysaccharide (LPS) to induce NO synthesis.
- The effects of progesterone, 5alpha-dihydroprogesterone (DHP), and 5alpha-3alpha-tetrahydroprogesterone (THP) on NO release were quantified.
- Nitric oxide synthase (NOS) activity was assessed using N(G)-methyl-L-arginine (L-NMMA).
- Cell viability, apoptosis, and necrosis were evaluated using trypan blue exclusion and DAPI staining.
Main Results:
- Progesterone and THP significantly suppressed LPS-induced NO release by approximately 40% at 10 microM.
- DHP showed a weaker inhibitory effect, reducing NO release by 20% at 10 microM.
- LPS-induced NO release was confirmed to be NOS-dependent.
- Progesterone did not affect cell viability, apoptosis, or necrosis.
Conclusions:
- Progesterone and its metabolites, DHP and THP, can modulate NOS activity or expression, leading to reduced NO release.
- As these neurosteroids are synthesized in astrocytes and oligodendrocytes, they may play a role in locally suppressing neuroinflammatory responses.
