Poly(ADP-ribose)polymerase-1 modulates microglial responses to amyloid β

Area of Science:

• Neuroscience
• Neuroinflammation
• Alzheimer's Disease Research

Background:

• Amyloid beta (Aβ) accumulation and microglial activation are hallmarks of Alzheimer's disease (AD), contributing to neuroinflammation and disease progression.
• The nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) is known to regulate microglial activation via interactions with the transcription factor NF-κB.
• The precise role of PARP-1 in Aβ-induced microglial activation remains to be fully elucidated.

Purpose of the Study:

• To investigate the involvement of PARP-1 in Aβ-induced microglial activation.
• To determine if PARP-1 inhibition can modulate microglial responses to Aβ in the context of AD.

Main Methods:

• Crossed hAPP(J20) mice (Aβ accumulating) with PARP-1(-/-) mice to assess PARP-1 depletion effects on microglial activation, synaptic integrity, and cognition.
• Administered Aβ peptide directly into the brains of wild-type and PARP-1(-/-) mice to study direct effects.
• Utilized primary microglia and microglia-neuron co-cultures with PARP-1(-/-) cells and a PARP-1 inhibitor to evaluate cytokine production and neurotoxicity, assessing NF-κB activation.

Main Results:

• hAPP(J20) mice exhibited microglial activation, reduced hippocampal CA1 calbindin, and cognitive deficits, which were attenuated in hAPP(J20)/PARP-1(-/-) mice.
• Direct Aβ(1-42) injection induced microglial responses in wild-type mice, but this response was blocked in PARP-1 deficient mice.
• PARP-1 activity was essential for Aβ-induced NF-κB activation, microglial transformation, NO/TNFα release, and neurotoxicity; PARP-1 inhibition enhanced neurotrophic factor release (TGFβ, VEGF) without impairing phagocytosis.

Conclusions:

• PARP-1 is identified as a critical mediator of Aβ-induced microglial activation, partly through its interaction with NF-κB.
• PARP-1 inhibition effectively suppressed Aβ-induced microglial activation and neurotoxicity.
• Targeting PARP-1 presents a promising therapeutic avenue for Alzheimer's disease and other conditions involving microglial neurotoxicity.