Neuroimmune Interactions in Neurodegeneration: The Role of Microglia in Alzheimer’s and Parkinson’s Disease Pathogenesis

Neuroimmune interactions play a critical role in the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), with microglia acting as key mediators of neuroinflammation. Microglia exhibit dual roles, contributing to both neuroprotection and neurotoxicity depending on their activation state. In AD, amyloid-beta (Aβ) aggregation leads to chronic microglial activation, resulting in excessive pro-inflammatory cytokine release (e.g., TNF-α, IL-1β, IL-6), oxidative stress, and synaptic dysfunction. In PD, α-synuclein aggregation triggers a similar neuroinflammatory cascade, exacerbating dopaminergic neuronal loss in the substantia nigra. Beyond inflammatory responses, microglia regulate synaptic plasticity, phagocytose pathological proteins, and interact with peripheral immune cells, influencing disease progression. Emerging evidence suggests that genetic variants in genes such as TREM2, CD33, and HLA modulate microglial function, thereby altering susceptibility to neurodegeneration. Dysregulated microglial responses, characterized by impaired clearance of protein aggregates and prolonged neuroinflammation, further amplify neuronal damage. Therapeutic strategies targeting microglial activation are under investigation, aiming to balance neuroinflammatory responses and enhance clearance mechanisms. Small-molecule inhibitors, monoclonal antibodies, and modulators of innate immune pathways are being explored to mitigate microglia-driven pathology. Understanding the complex interplay between microglia and neurodegeneration could pave the way for precision medicine approaches, optimizing treatments based on individual immune profiles. Further research is essential to delineate microglial heterogeneity across disease stages and uncover novel targets for therapeutic intervention.