Targeting PARP1-dependent parthanatos in Alzheimer's disease: Mechanisms and therapeutic opportunities

Alzheimer's disease (AD) is the predominant cause of dementia globally. This review clarifies the dual function of poly(ADP-ribose) polymerase 1 (PARP1) in AD pathogenesis, emphasizing its role in mediating parthanatos, a unique caspase-independent cell death mechanism. We analyze contemporary literature regarding PARP1 expression, parthanatos signaling, and pharmaceutical treatments in AD models. In addition, PARP1 exhibits context-dependent duality: its physiological nuclear expression in hippocampus neurons is essential for memory consolidation and decreases early in cognitive impairment, suggesting a correlative association with synaptic malfunction. In contrast, overactivity of PARP1 resulting from Aβ-induced oxidative stress and DNA damage induces neurodegeneration via multiple pathways, including NAD+/ATP exhaustion leading to metabolism collapse, creation of the AIF-MIF complex promoting parthanatos, NF-κB-induced neuroinflammation, dysregulation of mitophagy, and disruption of the neuroprotective SIRT1 signaling pathway. The overactivity contributes to a positive feedback loop, where PARP1 intensifies Aβ and tau protein accumulation while simultaneously disrupting the BBB. In preclinical models of AD, genetic knockout, pharmacologic agents such as PJ34 and MC2050, or precursors of NAD⁺ such as nicotinamide and NMN attenuate Aβ deposition, normalize metabolism, and ameliorate cognitive decline. The PARP1/parthanatos pathway is at the center of the confluence of oxidative stress, DNA damage, metabolism disorder, and neuroinflammation in AD. Metformin and other PARP1 inhibitors offer intriguing treatment options. PARP1's cell-type- and intracellular location-dependent activity necessitates careful consideration of context, dose, and disease stage while developing therapies. The present understanding in this review could inform future research on PARP1 regulation in AD clinical practice.