Novel Translational Research Methodology and the Prospect to a Better Understanding of Neurodegenerative Disease

KAT7/HMGN1 signaling epigenetically induces tyrosine phosphorylation-regulated kinase 1A expression to ameliorate insulin resistance in Alzheimer's disease

BACKGROUND

Epidemiological studies have revealed a correlation between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2D). Insulin resistance in the brain is a common feature in patients with T2D and AD. KAT7 is a histone acetyltransferase that participates in the modulation of various genes.

AIM

To determine the effects of KAT7 on insulin patients with AD.

METHODS

APPswe/PS1-dE9 double-transgenic and db/db mice were used to mimic AD and diabetes, respectively. An in vitro model of AD was established by Aβ stimulation. Insulin resistance was induced by chronic stimulation with high insulin levels. The expression of microtubule-associated protein 2 (MAP2) was assessed using immunofluorescence. The protein levels of MAP2, Aβ, dual-specificity tyrosine phosphorylation-regulated kinase-1A (DYRK1A), IRS-1, p-AKT, total AKT, p-GSK3β, total GSK3β, DYRK1A, and KAT7 were measured via western blotting. Accumulation of reactive oxygen species (ROS), malondialdehyde (MDA), and SOD activity was measured to determine cellular oxidative stress. Flow cytometry and CCK-8 assay were performed to evaluate neuronal cell death and proliferation, respectively. Relative RNA levels of KAT7 and DYRK1A were examined using quantitative PCR. A chromatin immunoprecipitation assay was conducted to detect H3K14ac in DYRK1A.

RESULTS

KAT7 expression was suppressed in the AD mice. Overexpression of KAT7 decreased Aβ accumulation and MAP2 expression in AD brains. KAT7 overexpression decreased ROS and MDA levels, elevated SOD activity in brain tissues and neurons, and simultaneously suppressed neuronal apoptosis. KAT7 upregulated levels of p-AKT and p-GSK3β to alleviate insulin resistance, along with elevated expression of DYRK1A. KAT7 depletion suppressed DYRK1A expression and impaired H3K14ac of DYRK1A. HMGN1 overexpression recovered DYRK1A levels and reversed insulin resistance caused by KAT7 depletion.

CONCLUSION

We determined that KAT7 overexpression recovered insulin sensitivity in AD by recruiting HMGN1 to enhance DYRK1A acetylation. Our findings suggest that KAT7 is a novel and promising therapeutic target for the resistance in AD.

SIRT5 Represses Neurotrophic Pathways and Aβ Production in Alzheimer's Disease by Targeting Autophagy

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in elderly individuals and characterized by impaired cognition and accumulation of β-amyloid (Aβ). Activating autophagy to clear Aβ is a plausible approach for AD treatment. The levels of Aβ and autophagy signaling factors in APP695/PS1-dE9 transgenic (APP/PS1) mice were detected by immuno histological analysis, real-time PCR, and the western blotting assay. The progression of AD was determined by Aβ levels, activated neurons (MAP2+), and microglia (Iba-1⁺). The learning ability was measured using a Morris water maze. Reactive oxygen species (ROS) production, malondialdehyde (MDA) levels, and mitochondrial superoxide dismutase (SOD) activity were checked to determine oxidative stress. AD mice exhibited impaired autophagy and a decreased level of SIRT5. SIRT5 overexpression promoted autophagy, manifested by elevated Becn1 and ratio of LC3b-II/I, as well as suppressed oxidative stress. The SIRT5-ameliorated neuron damage was correlated with suppressed activation of microglia and astrocytes. Elevated SIRT5 expression decreased the inflammation in AD brains and neurons. Inhibition of autophagy abolished the protective role of SIRT5 in neurons during AD. Our findings suggested that SIRT5 overexpression could ameliorate the progression of AD both in vitro and in vivo through activating autophagy. We presented ectopic expression of SIRT5 as a promising therapeutic approach for AD.

Effect of lncRNA WT1-AS regulating WT1 on oxidative stress injury and apoptosis of neurons in Alzheimer's disease via inhibition of the miR-375/SIX4 axis

Objective: To study the effect of lncRNA WT1-AS on oxidative stress injury (OSI) and apoptosis of neurons in Alzheimer's disease (AD) and its specific mechanisms related to the microRNA-375 (miR-375)/SIX4 axis and WT1 expression.

Results: After bioinformatic prediction, WT1-AS was found to be downregulated in Aβ_25-35treated SH-SY5Y cells, and WT1-AS overexpression inhibited WT1 expression. WT1 could target miR-375 to promote its expression. miR-375 bound to SIX4, and miR-375 overexpression inhibited SIX4 expression. WT1-AS inhibited OSI and apoptosis, while WT1 and miR-375 overexpression or SIX4 silencing reversed the WT1-AS effect on OSI and apoptosis. In vivo experiments revealed that WT1-AS improved learning/memory abilities and inhibited OSI and apoptosis in AD mice.

Conclusion: Overexpression of WT1-AS can inhibit the miR-375/SIX4 axis, OSI and neuronal apoptosis in AD by inhibiting WT1 expression.

Methods: Related lncRNAs were identified, and miR-375 downstream targets were predicted. WT1-AS, WT1, miR-375 and SIX4 expression was detected in a cell model induced by Aβ_25-35. The binding of WT1 with miR-375 and that of miR-375 with SIX4 were further confirmed. Adenosine triphosphate (ATP), reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and lactate dehydrogenase (LDH) activities, and apoptosis levels were tested after mitochondrial membrane potential observation. Learning/memory abilities and neuronal apoptosis were tested in a mouse model.