Gadd45A-mediated autophagy regulation and its impact on Alzheimer's disease pathogenesis: Deciphering the molecular...

The growth arrest and DNA damage-inducible 45 (Gadd45) gene has been implicated in various central nervous system (CNS) functions, both normal and pathological, including aging, memory, and neurodegenerative diseases. In this study, we examined whether Gadd45A deletion triggers pathways associated with neurodegenerative diseases including Alzheimer's disease (AD).

Utilizing transcriptome data from AD-associated hippocampus samples, we identified Gadd45A as a pivotal regulator of autophagy. Comprehensive analyses, including Gene Ontology enrichment and protein-protein interaction network assessments, highlighted Cdkn1A as a significant downstream target of Gadd45A. Experimental validation confirmed Gadd45A's role in modulating Cdkn1A expression and autophagy levels in hippocampal cells. We also examined the effects of autophagy on hippocampal functions and proinflammatory cytokine secretion. Additionally, a murine model was employed to validate the importance of Gadd45A in neuroinflammation and AD pathology.

Our study identified 20 autophagy regulatory factors associated with AD, with Gadd45A emerging as a critical regulator. Experimental findings demonstrated that Gadd45A influences hippocampal cell fate by reducing Cdkn1A expression and suppressing autophagic activity. Comparisons between wild-type (WT) and Gadd45A knockout (Gadd45A^-/-) mice revealed that Gadd45A^-/- mice exhibited significant cognitive impairments, including deficits in working and spatial memory, increased Tau hyperphosphorylation, and elevated levels of kinases involved in Tau phosphorylation in the hippocampus. Additionally, Gadd45A^-/- mice showed significant increases in pro-inflammatory cytokines and decreases autophagy markers in the brain. Neurotrophin levels and dendritic spine length were also reduced in Gadd45A^-/- mice, likely contributing to the observed cognitive deficits.

These findings support the direct involvement of the Gadd45A gene in AD pathogenesis, and enhancing the expression of Gadd45A may represent a promising therapeutic strategy for the treatment of AD.