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Wenjie Luo
Cornell University Joan and Sanford I Weill Medical College
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3752-8266
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Background : Genome-wide association studies of Alzheimer’s disease (AD) have implicated pathways related to lipid homeostasis and innate immunity in AD pathophysiology. However, the exact cellular and chemical mediators of neuroinflammation in AD remain poorly understood. The oxysterol 25-hydroxycholesterol (25-HC) is an important immunomodulator produced by peripheral macrophages with wide-ranging effects on cell signaling and innate immunity. Genetic variants of the enzyme responsible for 25-HC production, cholesterol 25‑hydroxylase (CH25H), have been found to be associated with AD.
Methods: We used real time-PCR and immunoblotting to examine CH25H expression in human AD brain tissue and in transgenic mouse brain tissue bearing amyloid-β plaques or tau pathology. The innate immune response of primary mouse microglia under different treatment condition or bearing different genetic backgrounds was analyzed using ELISA, western blotting or immunocytochemistry.
Results : We found that CH25H expression is upregulated in human AD brain tissue and in transgenic mouse brain tissue bearing amyloid-β plaques or tau pathology. Treatment with the toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) markedly upregulates CH25H expression in the mouse brain and stimulates CH25H expression and 25-HC secretion in mouse primary microglia. We found that LPS-induced microglial production of the pro-inflammatory cytokine IL-1β is markedly potentiated by 25-HC and attenuated by deletion of CH25H. Microglia expressing apolipoprotein E4 (apoE4), a genetic risk factor for AD, produce greater amounts of 25-HC than apoE3-expressing microglia following treatment with LPS. Remarkably, 25-HC treatment results in a greater level of IL-1β secretion in LPS-activated apoE4-expressing microglia than in apoE2- or apoE3-expressing microglia. Blocking potassium efflux or inhibiting caspase-1 prevents 25-HC-potentiated IL-1β release in apoE4-expressing microglia, indicating the involvement of caspase-1/NLRP3 inflammasome activity.
Conclusion : 25-HC may function as a microglial secreted inflammatory mediator in brain, promoting IL-1β-mediated neuroinflammation in an apoE isoform-dependent manner (E4>>E2/E3) and thus may be an important mediator of neuroinflammation in AD.
Keywords
Alzheimer’s disease, microglia, inflammation, lipid metabolism, apolipoprotein E, interleukin-1β, cholesterol 25 hydroxylase, oxysterol, 25-hydroxycholesterol, lipopolysaccharide, inflammasome
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View the published article at Journal of Neuroinflammation.
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A new preprint design is coming!
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See the published version of this preprint at Journal of Neuroinflammation.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research
Wenjie Luo
Cornell University Joan and Sanford I Weill Medical College
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3752-8266
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
View the published article at Journal of Neuroinflammation.
Version 1
Posted 03 Mar, 2020
No community comments so far
Editorial decision: Major Revision
On 04 Apr, 2020
Review #2 received
Received 29 Mar, 2020
Review #1 received
Received 29 Mar, 2020
Reviewer #2 agreed
On 08 Mar, 2020
Reviewer #1 agreed
On 08 Mar, 2020
Reviewers invited
Invitations sent on 07 Mar, 2020
Editor assigned
On 27 Feb, 2020
First submitted
On 26 Feb, 2020
Submission checks complete
On 26 Feb, 2020
Editor invited
On 26 Feb, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Neurobiology of Disease
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published article at Journal of Neuroinflammation.
Background : Genome-wide association studies of Alzheimer’s disease (AD) have implicated pathways related to lipid homeostasis and innate immunity in AD pathophysiology. However, the exact cellular and chemical mediators of neuroinflammation in AD remain poorly understood. The oxysterol 25-hydroxycholesterol (25-HC) is an important immunomodulator produced by peripheral macrophages with wide-ranging effects on cell signaling and innate immunity. Genetic variants of the enzyme responsible for 25-HC production, cholesterol 25‑hydroxylase (CH25H), have been found to be associated with AD.
Methods: We used real time-PCR and immunoblotting to examine CH25H expression in human AD brain tissue and in transgenic mouse brain tissue bearing amyloid-β plaques or tau pathology. The innate immune response of primary mouse microglia under different treatment condition or bearing different genetic backgrounds was analyzed using ELISA, western blotting or immunocytochemistry.
Results : We found that CH25H expression is upregulated in human AD brain tissue and in transgenic mouse brain tissue bearing amyloid-β plaques or tau pathology. Treatment with the toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) markedly upregulates CH25H expression in the mouse brain and stimulates CH25H expression and 25-HC secretion in mouse primary microglia. We found that LPS-induced microglial production of the pro-inflammatory cytokine IL-1β is markedly potentiated by 25-HC and attenuated by deletion of CH25H. Microglia expressing apolipoprotein E4 (apoE4), a genetic risk factor for AD, produce greater amounts of 25-HC than apoE3-expressing microglia following treatment with LPS. Remarkably, 25-HC treatment results in a greater level of IL-1β secretion in LPS-activated apoE4-expressing microglia than in apoE2- or apoE3-expressing microglia. Blocking potassium efflux or inhibiting caspase-1 prevents 25-HC-potentiated IL-1β release in apoE4-expressing microglia, indicating the involvement of caspase-1/NLRP3 inflammasome activity.
Conclusion : 25-HC may function as a microglial secreted inflammatory mediator in brain, promoting IL-1β-mediated neuroinflammation in an apoE isoform-dependent manner (E4>>E2/E3) and thus may be an important mediator of neuroinflammation in AD.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
This is a list of supplementary files associated with this preprint. Click to download.
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