Despite decades of research, Alzheimer’s disease (AD) remains without a curative therapy. While amyloid- and tau-centered approaches have dominated the field, failures of monotherapeutic strategies underscore the need for a broader system-level understanding. Here, this review critically revisits the principal hypotheses of AD pathogenesis, including the amyloid cascade, tauopathy, neuroinflammation, cholinergic dysfunction, oxidative and mitochondrial stress, metal dyshomeostasis, autophagy–lysosomal failure, genetic susceptibility, and infectious triggers. This review synthesizes molecular and cellular evidence from human genetics, neuropathology, and experimental models, correcting common misconceptions and emphasizing interactions between pathways. Neuroinflammation is increasingly recognized as a central hub linking amyloid, tau, and vascular factors, while mitochondrial and lysosomal dysfunctions emerge as amplifiers of proteotoxic stress. Genetic studies highlight apolipoprotein-E ε4 (APOE ε4) as the strongest common risk allele, but also implicate genes involved in endosomal trafficking, lipid metabolism, and immune regulation. Taken together, AD is best understood as a multi-hit disorder in which converging processes, rather than a single driver, dictate disease initiation and progression. This narrative review proposes a systems neurobiology framework that integrates these mechanisms and identifies key points of convergence amenable to therapeutic targeting and biomarker development. Finally, this reappraisal aims to inform future research directions and guide the rational design of multi-target interventions.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder marked by neuronal loss, cognitive decline, and pathological hallmarks such as amyloid-beta (Aβ) plaques and tau neurofibrillary tangles. Recent evidence highlights autophagy as a pivotal mechanism in cellular homeostasis, mediating the clearance of misfolded proteins and damaged organelles. However, impaired autophagy contributes significantly to AD pathogenesis by disrupting proteostasis, exacerbating neuroinflammation, and promoting synaptic dysfunction. This review aims to scrutinize the intricate relationship between autophagy dysfunction and AD progression, explaining key pathways including macroautophagy, chaperone-mediated autophagy (CMA), and selective autophagy processes such as mitophagy and aggrephagy. This further extends the discussion beyond the central nervous system, evaluating the role of hepatic autophagy in Aβ clearance and systemic metabolic regulation. An understanding of autophagy’s involvement in AD pathology via various mechanisms could give rise to a novel therapeutic strategy targeting autophagic modulation to mitigate disease progression in the future.

Neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease, multiple sclerosis, and amyotrophic lateral sclerosis share converging mechanisms of neuronal dysfunction, including protein aggregation, oxidative stress, and chronic neuroinflammation. Glial cells, once considered passive supporters, are now recognized as central drivers of these processes, offering both pathogenic triggers and therapeutic opportunities. Yet, despite compelling preclinical evidence, the translation of glial-targeted therapies into clinical success has been limited. This review provides a critical synthesis of current knowledge by examining therapeutic strategies through the lens of their translational challenges and failures. This narrative review highlights how interspecies variability of glial phenotypes, shifting neuroprotective versus neurotoxic states, limited biomarker stratification, and delivery barriers have constrained trials, such as anti-triggering receptor expressed on myeloid cells 2 (anti-TREM2) antibodies in AD and glial cell line-derived neurotrophic factor (GDNF) in PD. By analyzing these obstacles across major neurodegenerative disorders, this review argue that the next stage of glial medicine requires precision approaches that integrate stage-specific phenotyping, biomarker-guided patient selection, and innovative delivery platforms. Understanding not only what has been tried but why translation has stalled is essential to chart a roadmap for effective, disease-modifying glial therapies in the aging brain.