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Isoform-specific effects of apolipoprotein E on secretion of inflammatory mediators in adult rat microglia
Shuang Chen1, Natale T Averett, Arlene Manelli
1Department of Anatomy, University of Mississippi Medical Center, 2500 N. State St., Jackson, MS 39216, USA.
Abstract:
Inflammation mediated by activated microglia cells has been shown to contribute to the pathogenesis of Alzheimer disease (AD) [1]. Microglia are the immune cells in the central nervous system, and when activated they secrete the lipid-derived mediator prostaglandin E2 (PGE2), the cytokine interleukin-1beta (IL-1beta), and other inflammatory mediators. Apolipoprotein E isoform 4 (apoE4), coded for by the gene APOE4 (epsilon4), has been shown to correlate with higher risk of onset of AD, as well as with increased severity of other diseases with a neuroinflammatory component. This study investigated isoform-specific effects of apoE on the regulation of PGE2, COX2, and IL-1beta expression. Two physiologically relevant preparations of apoE displayed an isoform-specific effect on inflammation in primary adult microglia cultured from adult rat brain cortex. Specifically, apoE4 alone, but not the more common isoform apoE3, stimulated secretion of PGE2 and IL-1beta. The increase in PGE2 release stimulated by apoE4 was not accompanied by the upregulation of the COX-2 enzyme in microglia.
Insights
Apolipoprotein E4 (apoE4) stimulates inflammatory responses in microglia, contributing to Alzheimer disease (AD) pathogenesis. This study found apoE4, not apoE3, increased prostaglandin E2 and interleukin-1beta secretion in brain immune cells.
Area of Science:
- Neuroscience
- Immunology
- Genetics
Background:
- Microglia-mediated inflammation is implicated in Alzheimer disease (AD) pathogenesis.
- Activated microglia release inflammatory mediators like prostaglandin E2 (PGE2) and interleukin-1beta (IL-1beta).
- Apolipoprotein E4 (apoE4) is linked to increased AD risk and neuroinflammatory disease severity.
Purpose of the Study:
- To investigate the specific effects of different apolipoprotein E (apoE) isoforms on regulating inflammatory gene expression.
- To examine how apoE isoforms influence PGE2, COX2, and IL-1beta production in microglia.
Main Methods:
- Primary adult microglia were cultured from rat brain cortex.
- Physiologically relevant preparations of apoE isoforms (apoE3 and apoE4) were applied to cultured microglia.
- Secretion of PGE2 and IL-1beta, and expression of COX-2, were measured.
Main Results:
- Apolipoprotein E4 (apoE4) significantly stimulated the secretion of PGE2 and IL-1beta from microglia.
- The common isoform, apolipoprotein E3 (apoE3), did not induce similar inflammatory responses.
- The apoE4-induced increase in PGE2 was not associated with increased COX-2 enzyme expression.
Conclusions:
- Apolipoprotein E4 exhibits isoform-specific pro-inflammatory effects on microglia.
- These findings suggest apoE4 may exacerbate neuroinflammation in Alzheimer disease through direct microglial activation.
- Targeting apoE4-mediated inflammatory pathways could offer therapeutic strategies for AD.
