New insights on microglial lysosomal acidification: A therapeutic target of neurodegenerative diseases

Background: Microglia, the resident immune cells of the central nervous system (CNS), maintain brain homeostasis and respond to pathological insults. Microglial dysfunction has been implicated in the pathogenesis of several neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Impaired lysosomal function, particularly defective lysosomal acidification, leads to the accumulation of undegraded material, thereby promoting neuroinflammation and neuronal damage.

Purpose: This review examines the mechanisms governing lysosomal acidification in microglia and evaluates its potential as both a therapeutic target and a prognostic biomarker in neurodegenerative diseases.

Methods: The literature on microglial lysosomal acidification, lysosomal pH regulation, autophagy, and neurodegeneration was searched in PubMed, Scopus, and Web of Science. Relevant mechanistic, preclinical, and translational studies were critically appraised and synthesized.

Results: Lysosomal acidification is increasingly recognized as a key regulator of microglial function and homeostasis. Defective acidification, driven by dysregulation of the vacuolar H+-ATPase (V-ATPase) proton pump, TFEB/TFE3 signaling pathways, and lysosomal ion channels such as TRPML1 and TMEM175, impairs autophagic flux and substrate degradation, facilitating the accumulation of neurotoxic aggregates including amyloid-β and α-synuclein. Emerging evidence suggests that the degree of microglial lysosomal acidification may serve as a prognostic biomarker for disease progression and therapeutic response. Restoration or enhancement of lysosomal acidification through pharmacological modulation of lysosomal pH, activation of autophagy, or targeting of key regulatory pathways has been shown to re-establish microglial homeostasis, attenuate neuroinflammation, and confer neuroprotection in preclinical models.

Conclusion: Restoration of microglial lysosomal acidification represents a promising therapeutic strategy for neurodegenerative diseases. A deeper understanding of the molecular mechanisms regulating lysosomal acidification in microglia may facilitate the identification of novel biomarkers and therapeutic targets, ultimately contributing to the development of innovative interventions for neurodegenerative disorders.