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A CD36-initiated signaling cascade mediates inflammatory effects of beta-amyloid
Kathryn J Moore1, Joseph El Khoury, Lea A Medeiros
1Lipid Metabolism Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
Abstract:
beta-Amyloid accumulation is associated with pathologic changes in the brain in Alzheimer's disease and has recently been identified in plaques of another chronic inflammatory disorder, atherosclerosis. The class B scavenger receptor, CD36, mediates binding of fibrillar beta-amyloid to cells of the monocyte/macrophage lineage, including brain macrophages (microglia). In this study, we demonstrate that in microglia and other tissue macrophages, beta-amyloid initiates a CD36-dependent signaling cascade involving the Src kinase family members, Lyn and Fyn, and the mitogen-activated protein kinase, p44/42. Interruption of this signaling cascade, through targeted disruption of Src kinases downstream of CD36, inhibits macrophage inflammatory responses to beta-amyloid, including reactive oxygen and chemokine production, and results in decreased recruitment of microglia to sites of amyloid deposition in vivo. The finding that engagement of CD36 by beta-amyloid initiates a Src kinase-dependent production of inflammatory mediators in cells of the macrophage lineage reveals a novel receptor-mediated pro-inflammatory signaling pathway of potential therapeutic importance.
Insights
Beta-amyloid triggers inflammation in macrophages via the CD36 receptor and Src kinases. Blocking this pathway reduces inflammatory responses and microglia recruitment in vivo, offering a potential therapeutic target.
Area of Science:
- Neuroimmunology
- Molecular Biology
- Cardiovascular Research
Background:
- Beta-amyloid (Aβ) accumulation is central to Alzheimer's disease pathology.
- Aβ has also been found in atherosclerotic plaques, suggesting shared inflammatory mechanisms.
- The scavenger receptor CD36 mediates Aβ binding to macrophages, including microglia.
Purpose of the Study:
- To investigate the signaling pathway initiated by beta-amyloid binding to CD36 in macrophages.
- To determine the role of Src kinases in mediating macrophage inflammatory responses to Aβ.
- To explore the therapeutic potential of inhibiting this Aβ-CD36-Src signaling cascade.
Main Methods:
- Studied beta-amyloid interaction with CD36 in microglia and tissue macrophages.
- Investigated the involvement of Src kinases (Lyn, Fyn) and p44/42 MAPK in the signaling cascade.
- Utilized targeted disruption of Src kinases to inhibit downstream signaling.
- Assessed inflammatory mediator production (reactive oxygen, chemokines) and microglia recruitment in vivo.
Main Results:
- Beta-amyloid binding to CD36 initiates a signaling cascade involving Lyn, Fyn, and p44/42 MAPK.
- Disruption of Src kinases downstream of CD36 inhibited macrophage inflammatory responses to beta-amyloid.
- Key inflammatory responses, including reactive oxygen and chemokine production, were reduced.
- Inhibition of the pathway led to decreased in vivo recruitment of microglia to amyloid deposits.
Conclusions:
- Beta-amyloid engagement of CD36 activates a novel Src kinase-dependent pro-inflammatory signaling pathway in macrophages.
- This pathway contributes to neuroinflammation and microglia recruitment in conditions like Alzheimer's disease.
- Targeting the CD36-Src signaling axis represents a potential therapeutic strategy for inflammatory disorders involving beta-amyloid.