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Cholesterol oxides induce programmed cell death in microglial cells
J Y Chang1, J A Chavis, L Z Liu
1Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
Abstract:
N9 microglial cells were used as a model to examine the effect of cholesterol oxides on central nervous system microglia. Results indicated that 25-OH-cholesterol was the most cytotoxic agent among the cholesterol oxides tested. During the process of cell death, this agent caused prominent nuclei condensation and significant DNA fragmentation, a phenomenon association with programmed cell death. Cholesterol oxides were able to potentiate the bacterial lipopolysaccharide (LPS)-induced nitric oxide production to various degrees. Consistent with this finding, Northern blot analysis indicated that 25-OH-cholesterol potentiated the LPS-induced nitric oxide synthase RNA levels. The cytotoxicity of 25-OH-cholesterol could be prevented by methyl-beta-cyclodextrin, a glucose polymer known to cause cholesterol oxide efflux from cells. While much attention has been focused on the cytotoxicity of cholesterol oxides on immune cells within the blood, including lymphocytes and macrophages, the results from this study indicated for the first time that these agents are toxic to microglial cells derived from the central nervous system.
Insights
Cholesterol oxides, particularly 25-OH-cholesterol, are toxic to central nervous system microglia, inducing programmed cell death. These findings highlight a novel toxicity pathway for cholesterol oxides in the brain.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Cholesterol oxides are implicated in various pathologies.
- Their effects on central nervous system (CNS) immune cells, microglia, are not well understood.
- Previous research focused on peripheral immune cells.
Purpose of the Study:
- To investigate the toxicity of cholesterol oxides on N9 microglial cells.
- To determine the specific cytotoxic effects of different cholesterol oxides.
- To explore the impact of cholesterol oxides on microglial inflammatory responses.
Main Methods:
- N9 microglial cells were exposed to various cholesterol oxides.
- Cytotoxicity was assessed by examining cell death markers like nuclear condensation and DNA fragmentation.
- Nitric oxide (NO) production and nitric oxide synthase (NOS) RNA levels were measured after lipopolysaccharide (LPS) stimulation.
- Methyl-beta-cyclodextrin was used to investigate protective mechanisms.
Main Results:
- 25-OH-cholesterol was identified as the most cytotoxic cholesterol oxide.
- 25-OH-cholesterol induced features of programmed cell death, including DNA fragmentation.
- Cholesterol oxides potentiated LPS-induced nitric oxide production and NOS RNA levels.
- Methyl-beta-cyclodextrin treatment protected cells from 25-OH-cholesterol toxicity.
Conclusions:
- Cholesterol oxides, especially 25-OH-cholesterol, are toxic to CNS microglia.
- These findings reveal a novel mechanism of neuroinflammation and cell damage.
- This study expands the understanding of cholesterol oxide toxicity beyond peripheral immune cells.