Targeted Degradation of the NLRP3 Inflammasome via Microglial LC3-Associated Phagocytosis: A Novel Therapeutic Strategy for Alzheimer’s Disease Neuroinflammation

Introduction: Alzheimer’s disease (AD) is a neurodegenerative illness that causes cognitive decline and memory loss. In addition to the accumulation of tau tangles and amyloid plaques, chronic inflammation in the brain has been identified as a key contributor to the development of illness. A key contributor to this inflammation is the NLRP3 inflammasome, a complex of proteins found in microglia, the immune cells of the brain. When activated, this inflammasome causes the release of inflammatory molecules like interleukin (IL)-1β and IL-18, which damage neurons and worsen disease progression. Although efforts have been made to block NLRP3 activity with drugs, many current treatments affect the immune system more broadly than intended. This can interfere with normal defence mechanisms in the brain. To address this, we explored a different method: removing the overactive NLRP3 inflammasomes from microglial cells through a natural cellular process, without disrupting the cell’s normal functions. Methods: Our approach involves LC3-associated phagocytosis (LAP), a pathway in which microglia use autophagy-related proteins to digest harmful or unnecessary material. We created nanoparticles coated with phosphatidylserine (PS), a molecule known to signal cells for clearance. These particles were designed to bind to TIM4, a receptor found on microglia that detects PS. After the nanoparticles bind to TIM4, they attract LC3-II proteins, which causes LAP, and direct the undesirable inflammasomes to lysosomes for degradation. To test this system in the laboratory, we activated NLRP3 by administering ATP and lipopolysaccharide to primary microglial cells. After treatment with PS-coated nanoparticles, we used ELISA to measure IL-1β levels and western blotting and microscopy to examine protein expression and localisation. For animal testing, we used 5 × FAD mice, a model that develops amyloid plaques and memory loss. Mice were given the nanoparticles intranasally once per day for 2 weeks. After the treatment, we assessed brain inflammation, plaque levels and memory function using standard behavioural and histological methods. Results: In cell culture, the PS-nanoparticles led to a clear reduction in NLRP3 inflammasome structures and a sharp drop in IL-1β release – over 80% and 85%, respectively. These effects were dependent on the LAP pathway, as blocking Rubicon or lysosomal enzymes eliminated the benefits. The effective activation of LAP was validated by the presence of LC3 surrounding inflammasome regions. In mice given 5 × FAD, inflammation was considerably decreased, and Iba1 expression – a marker of microglial activation – dropped by 60%. The amount of amyloid plaques in brain tissue also fell by more than 50%. In behavioural testing, mice that received the treatment showed improved performance in memory tasks, particularly in the Morris water maze, where escape latency improved by 40% compared to controls. Importantly, the treatment was well tolerated, and no changes in weight or overall behaviour were observed. Conclusion: This study presents a novel and targeted approach to managing neuroinflammation in AD by using the microglia’s own clean-up system. Rather than shutting down the inflammasome entirely, our method helps the cells recognise and break down only the harmful, activated forms. This avoids the side effects seen with broad immune inhibitors. Our results suggest that PS-coated nanoparticles can safely and effectively reduce inflammation, lower amyloid levels and improve cognitive outcomes in a mouse model of AD. Because the mechanism relies on natural signalling and cell processes, it offers a promising direction for further development. This strategy might also be used for other illnesses like Parkinson’s or some autoimmune diseases where inflammasome activity is implicated. Before considering clinical trials, more work will be done to optimise distribution to the brain and guarantee long-term safety.