Shifting Microglial Phenotypes: Targeting Disease-Associated Microglia in Neurodegeneration

Neurodegenerative disorders are marked by the gradual degeneration of neurons and deterioration of cognitive function. One key underlying factor in these diseases is neuroinflammation. An essential component of this process is microglia, which are the innate immune cells that maintain homeostasis in the brain. A common outcome of microglial dysregulation in neurodegenerative diseases is chronic neuroinflammation, which exacerbates neuronal damage and impairs synaptic function. This review focuses on the dual roles that disease-associated microglia (DAMs) play in neural inflammation and neuroprotection as well as their distinct transcriptional profile in neurodegenerative diseases. DAMs engage in phagocytosis to remove debris, in addition to releasing cytokines that promote inflammation. To create an effective medicine, it is imperative to comprehend these dual functions. The roles of DAMs in Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) are discussed, along with the mechanisms (such as the TREM2-APOE pathway) causing their activation. This review attempts to highlight the important aspects that could direct future investigations and treatment development by clarifying the interactions between DAMs and neurodegenerative diseases.