C9orf72 dipeptides activate the NLRP3 inflammasome

Area of Science:

• Neuroscience
• Immunology
• Genetics

Background:

• Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) share clinical, genetic, and pathological similarities.
• The C9orf72 hexanucleotide repeat expansion is a common cause of FTD and ALS, producing toxic dipeptides.
• Neuroinflammation is a key feature of FTD and ALS, but its underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate the role of C9orf72-derived dipeptides in driving neuroinflammation.
• To determine if the NLRP3 inflammasome is activated by C9orf72 dipeptides.
• To explore the therapeutic potential of targeting the inflammasome in C9orf72-associated neurodegeneration.

Main Methods:

• In vitro studies using microglia and macrophages exposed to poly-glycine-arginine (a C9orf72 dipeptide).
• Organotypic hippocampal slice cultures treated with poly-glycine-arginine.
• Assessment of inflammasome activation (e.g., IL-1β secretion, inflammasome speck formation) via ELISA and immunofluorescence.
• Testing the efficacy of clinically available anti-inflammatory drugs.

Main Results:

• Poly-glycine-arginine activated the NLRP3 inflammasome in microglia and macrophages.
• Activated inflammasome led to the secretion of pro-inflammatory interleukin-1β.
• Poly-glycine-arginine induced inflammasome activation and speck formation in hippocampal slice cultures.
• Clinically available anti-inflammatory drugs effectively inhibited poly-glycine-arginine-induced inflammasome activation.

Conclusions:

• C9orf72-derived dipeptides directly contribute to neuroinflammation in FTD and ALS.
• The NLRP3 inflammasome is a key mediator of C9orf72-associated neuroinflammation.
• Targeting the inflammasome presents a promising therapeutic strategy for FTD and ALS.