Study summary · research use only
NAD(+) supplementation reduces neuroinflammation and cell senescence in a transgenic mouse model of Alzheimer's disease via cGAS-STING
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
In this mouse study using APP/PS1 transgenic mice modeling Alzheimer's disease (AD) beta-amyloid pathology, researchers examined NAD+ levels and inflammation markers in the brain. Treatment with the NAD+ precursor nicotinamide riboside (NR) for 5 mo increased brain NAD+ levels and was associated with reduced expression of proinflammatory cytokines and decreased activation of microglia and astrocytes, along with reduced NLRP3 inflammasome expression, DNA damage, apoptosis, and cellular senescence. cGAS-STING elevation seen in the AD mice was normalized by NR treatment; cell culture experiments in microglia suggested this effect involves a cGAS-STING-dependent pathway in part. Cytoplasmic DNA levels, increased in APP/PS1 mice and human AD fibroblasts, were reduced by NR. NR treatment was also associated with increased mitophagy and improved cognitive and synaptic function in APP/PS1 mice.
Abstract
Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disorder. Impaired neuronal bioenergetics and neuroinflammation are thought to play key roles in the progression of AD, but their interplay is not clear. Nicotinamide adenine dinucleotide (NAD+) is an important metabolite in all human cells in which it is pivotal for multiple processes including DNA repair and mitophagy, both of which are impaired in AD neurons. Here, we report that levels of NAD+ are reduced and markers of inflammation increased in the brains of APP/PS1 mutant transgenic mice with beta-amyloid pathology. Treatment of APP/PS1 mutant mice with the NAD+ precursor nicotinamide riboside (NR) for 5 mo increased brain NAD+ levels, reduced expression of proinflammatory cytokines, and decreased activation of microglia and astrocytes. NR treatment also reduced NLRP3 inflammasome expression, DNA damage, apoptosis, and cellular senescence in the AD mouse brains. Activation of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) are associated with DNA damage and senescence. cGAS-STING elevation was observed in the AD mice and normalized by NR treatment. Cell culture experiments using microglia suggested that the beneficial effects of NR are, in part, through a cGAS-STING-dependent pathway. Levels of ectopic (cytoplasmic) DNA were increased in APP/PS1 mutant mice and human AD fibroblasts and down-regulated by NR. NR treatment induced mitophagy and improved cognitive and synaptic functions in APP/PS1 mutant mice. Our findings suggest a role for NAD+ depletion-mediated activation of cGAS-STING in neuroinflammation and cellular senescence in AD.
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