GASDERMIN D-mediated pyroptosis as a therapeutic target in TAU-dependent frontotemporal dementia mouse model.

Abstract

Background: Recent research has revealed a strong connection between neuroinflammation and TAU protein-related neurodegeneration. A key discovery shows that the NLRP3 inflammasome, when activated, can significantly impact TAU pathology and subsequent neuronal death. This process involves pyroptosis, a lytic form of programmed cell death driven by inflammasome activation, leading to GASDERMIN D (GSDMD) cleavage and the subsequent release of inflammatory molecules IL-1β and IL-18. In this study, we explore the role of pyroptosis and GSDMD in Alzheimer's disease (AD) and tauopathy models, focusing on the TAU-induced neuroinflammatory process and its correlation with synaptic plasticity loss.

Methods: Hippocampal tissue from AD patients at Braak stage II-III has been analyzed using qPCR to assess pyroptosis-related gene expression. To determine the role of TAU in pyroptosis and neuroinflammation, we used two different models: one based on intracerebral injection of an adeno-associated virus that specifically overexpresses TAU in the neurons of the hippocampus (AAV-TAU^P301L), and a transgenic mouse model Tg-TAU^P301S at 8 and 10 months of age. Gene expression, protein levels, and neuroinflammation markers were evaluated using qPCR and immunofluorescence. Additionally, both genetic (GSDMD-deficient mice) and pharmacological (dimethyl fumarate, DMF) interventions targeting pyroptosis have been explored to assess their impact on neuroinflammation and synaptic plasticity.

Results: AD patients exhibited increased expression of pyroptosis-related genes, supporting the involvement of pyroptosis in neurodegeneration. Furthermore, TAU overexpression induced pyroptosis in both mouse models, and GSDMD protein levels increased alongside reactive microglial morphology. Our data supports that TAU-induced neuroinflammation correlated with synaptic plasticity impairment. GSDMD deficiency significantly reduced pyroptosis-related markers associated to TAU, but unexpectedly worsened synaptic plasticity deficits, suggesting GSDMD may play a dual role in inflammation and synaptic function. Finally, we showed that DMF treatment suppressed pyroptosis gene expression, reduced GSDMD levels, and alleviated neuroinflammation, correlating with improved synaptic marker expression.

Conclusion: Our findings demonstrate that TAU-induced pyroptosis contributes to neuroinflammation and synaptic dysfunction. While GSDMD inhibition mitigates inflammation, its absence exacerbates synaptic impairment, highlighting its complex role in tauopathies. Our results indicate that DMF treatment could offer a promising therapeutic avenue to modulate pyroptosis and neuroinflammation, and restore synaptic integrity in tauopathies.