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NAD+ supplementation normalizes neuroinflammation and senescence via the cGAS-STING pathway

ABSTRACT: Alzheimer's disease (AD) is a severe neurodegenerative disorder. Clinical trials to identify agents to treat AD have failed, and its underlying molecular pathology and etiology remain elusive. Neuroinflammation is thought to play a key role in the progression of AD. Emerging evidence has identified lower Nicotinamide adenine dinucleotide (NAD+) levels as a major factor in neurodegeneration, especially in AD. NAD+ is an important metabolite in all human cells, as it is at the convergence of many central processes in cellular and mitochondrial maintenance, including DNA repair and mitophagy (the degradation of damaged mitochondria). Our previous work found that treatment of 3xTgAD mice with an NAD+ precursor, nicotinamide riboside (NR), can improve key AD features including tau phosphorylation and learning deficits in mice. Here we used the APP/PS1 AD mouse model to interrogate the effect of NR on neuroinflammation. Microarray analysis revealed major changes in pathways and genes associated with inflammation and the APP/PS1 mice had lower NAD+ levels than WT mice. Thus, seven months old mice were treated with NR for five months and their NAD+/NADH ratio increased. Brain neuroinflammation decreased as determined by decreased activation of astrocytes and microglia, decreased pro-inflammatory cytokines and chemokines in the brains of the APP/PS1 mice. NR decreased neuroinflammation by lowering the NLRP3 inflammasome and NF-κB pathways. NR also attenuated DNA damage and apoptosis in the AD mouse brains. NR dramatically decreased senescence in the hippocampus and cortex of AD mice, relative to controls. Recent studies suggest that cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) activation are associated with DNA damage and senescence. cGAS-STING was activated in AD mice and decreases after NR treatment. Suggesting that NR can diminish neuroinflammation and senescence through the cGAS-STING pathway. NR treatment also greatly improved cognition and synaptic function in the APP/PS1 mice. We propose that the cGAS-STING pathway should be evaluated as a potential novel therapeutic target in AD.

ORGANISM(S): Mus musculus

PROVIDER: GSE135999 | GEO | 2021/08/25

REPOSITORIES: GEO

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Project description:Objective: The protective components ACE2/Ang(1-7)/MasR of the renin-angiotensin system has been verified to play a role in Alzheimer's disease (AD). Our previous study revealed that enhancement of brain ACE2 activity, an important effector of RAS, by diminazene aceturate (DIZE) ameliorated Alzheimer's disease-like neuropathology and attenuated neuroinflammation in the brain of SAMP8 mice. However, the potential molecular mechanisms by which DIZE modulates neuroinflammation in AD remain unclear. Materials and Methods: APP/PS1 mice were injected intraperitoneally with DIZE (once a day for 30 consecutive days). Cognitive functions, neuronal and synaptic integrity, and inflammation-related markers were assessed by Morris water maze, Nissl staining, Western blot and ELISA, respectively. Since astrocytes played a crucial role in AD-related neuroinflammation whilst miRNAs were reported to participate in modulating inflammatory responses, astrocytes of APP/PS1 mice were then isolated for high-throughput miRNAs sequencing to identify the most differentially expressed miRNA following DIZE treatment. Afterward, the downstream pathway of this miRNA in the anti-inflammatory action of DIZE was investigated using primary astrocytes. Results: The results showed that DIZE alleviated cognitive impairment and neuronal and synaptic damage in APP/PS1 mice. Simultaneously, DIZE suppressed the secretion of pro-inflammatory cytokines and the expression of NLRP3 inflammasome. Importantly, miR-224-5p was significantly up-regulated in the astrocytes of APP/PS1 mice treated by DIZE, and NLRP3 is one of the targets of miR-224-5p. Upregulation of miR-224-5p inhibited the expression of NLRP3 in Aβ1–42-stimulated cells, whereas miR-224-5p downregulation reversed this effect. Furthermore, the inhibition of miR-224-5p could reverse the inhibitory effect of DIZE on astrocytic NLRP3 inflammasome. Conclusion: These results firstly suggested that DIZE inhibits astrocyte-mediated neuroinflammation via miR-224-5p/NLRP3 pathway. Moreover, these results reveal the underlying mechanisms by which DIZE inhibits neuroinflammation under AD condition and uncovers the potential of DIZE in AD treatment.

Project description:Objective: Emerging evidence suggested that brain angiotensin-(1-7) (Ang-(1-7)) deficiency contributed to the pathogenesis of Alzheimer’s disease (AD). Meanwhile, our previous studies revealed that restoration of brain Ang-(1-7) levels provided neuroprotection by inhibition of inflammatory responses during AD progress. However, the potential molecular mechanisms by which Ang-(1-7) modulates neuroinflammation remain unclear. Materials and Methods: APP/PS1 mice were injected intraperitoneally with AVE0991 (a nonpeptide analogue of Ang-(1-7)) once a day for 30 consecutive days. Cognitive functions, neuronal and synaptic integrity, and inflammation-related markers were assessed. Since astrocytes played a crucial role in AD-related neuroinflammation whilst long noncoding RNAs (lncRNAs) were reported to participate in modulating inflammatory responses, astrocytes of APP/PS1 mice were then isolated for high-throughput lncRNA sequencing to identify the most differentially expressed lncRNA following AVE0991 treatment. Afterward, the downstream pathway of this lncRNA in the anti-inflammatory action of AVE0991 were investigated using primary astrocytes. Results: The protection of AVE0991 against cognitive impairment and neuronal and synaptic damage in APP/PS1 mice was confirmed. For the first time, we demonstrated that AVE0991 suppressed astrocytic NLRP3 inflammasome-mediated neuroinflammation via a lncRNA SNHG14-dependent manner. SNHG14 acted as a sponge of miR-223-3p while NLRP3 represented a direct target of miR-223-3p in astrocytes. In addition, miR-223-3p participated in the AVE0991-induced suppression of astrocytic NLRP3 inflammasome. Conclusion: These results suggest that AVE0991 inhibits astrocyte-mediated neuroinflammation via SNHG14/miR-223-3p/NLRP3 pathway. Moreover, these results reveal the underlying mechanisms by which Ang-(1-7) inhibits neuroinflammation under AD condition and uncovers the potential of its nonpeptide analogue AVE0991 in AD treatment.

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NAD+ supplementation normalizes neuroinflammation and senescence via the cGAS-STING pathway

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