β-Amyloid Clustering around ASC Fibrils Boosts Its Toxicity in Microglia

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Alzheimer's disease (AD) is a leading neurodegenerative disorder characterized by neuroinflammation.
• Microglia activation by beta-amyloid (Aβ) deposits is central to AD pathogenesis.
• Apoptosis-associated speck-like protein containing a CARD (ASC) has been implicated in binding and cross-seeding extracellular Aβ.

Purpose of the Study:

• To investigate the propagation of ASC between primary microglia.
• To determine the effects of ASC-Aβ composites on microglial inflammasomes and function.
• To elucidate the role of ASC in the transition from acute to chronic neuroinflammation in AD.

Main Methods:

• Primary microglia cultures were utilized.
• Exposure to ASC-Aβ composites was performed.
• Microglial inflammasome activation, pyroptosis, and Aβ clearance were assessed.

Main Results:

• ASC released from pyroptotic cells is incorporated into neighboring microglia's NOD-like receptor protein (NLRP3) inflammasome.
• ASC-Aβ composites significantly amplify the proinflammatory response compared to protein alone.
• ASC-Aβ composites induce pyroptotic cell death, releasing more ASC and creating a feedforward inflammatory loop.
• Microglial Aβ clearance is impaired by clustering around ASC fibrils.

Conclusions:

• ASC propagation and formation of ASC-Aβ composites represent a critical turning point in Alzheimer's disease.
• These interactions exacerbate neuroinflammation and hinder Aβ clearance, driving disease progression.
• Targeting ASC-Aβ interactions may offer a therapeutic strategy for Alzheimer's disease.