Inhibition of mTORC1 improves STZ-induced AD-like impairments in mice

Electroacupuncture improves cognitive impairment in diabetic cognitive dysfunction rats by regulating the mitochondrial autophagy pathway

Background

Diabetes-associated cognitive dysfunction has become a major public health concern. However, the mechanisms driving this disease are elusive. Herein, we explored how electroacupuncture improves learning and memory function in diabetic rats.

Methods

The diabetic model was established by intraperitoneal injection of streptozotocin (STZ) in adult Sprague–Dawley rats. Rats were fed on high-fat and high-sugar diets. Learning and memory functions were assessed using behavioral tests. The hematoxylin and eosin (H&E) staining, Western blotting, real-time PCR, ELISA, immunohistochemistry, and transmission electronic microscopy (TEM) was performed to test related indicators.

Results

High-fat and high-sugar diets impaired learning and memory function in rats, while electroacupuncture treatment reversed these changes. The model group presented highly prolonged escape latency compared to the control group, indicating impaired learning and memory functions. The TEM examination showed that electroacupuncture enhanced Aβ clearance and mitochondrial autophagy in hippocampal neuronal cells by increasing DISC1 expression.

Conclusions

Electroacupuncture improves learning and memory function in diabetic rats by increasing DISC1 expression to promote mitophagy. This enhanced Aβ clearance, alleviating cytotoxicity in hippocampal neuronal cells.

Arginine Reduces Glycation in γ2 Subunit of AMPK and Pathologies in Alzheimer's Disease Model Mice

The metabolism disorders are a common convergence of Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). The characteristics of AD are senile plaques and neurofibrillary tangles (NFTs) composed by deposits of amyloid-β (Aβ) and phosphorylated tau, respectively. Advanced glycation end-products (AGEs) are a stable modification of proteins by non-enzymatic reactions, which could result in the protein dysfunction. AGEs are associated with some disease developments, such as diabetes mellitus and AD, but the effects of the glycated γ2 subunit of AMPK on its activity and the roles in AD onset are unknown.

METHODS

We studied the effect of glycated γ2 subunit of AMPK on its activity in N2a cells. In 3 × Tg mice, we administrated L-arginine once every two days for 45 days and evaluated the glycation level of γ2 subunit and function of AMPK and alternation of pathologies.

RESULTS

The glycation level of γ2 subunit was significantly elevated in 3 × Tg mice as compared with control mice, meanwhile, the level of pT172-AMPK was obviously lower in 3 × Tg mice than that in control mice. Moreover, we found that arginine protects the γ2 subunit of AMPK from glycation, preserves AMPK function, and improves pathologies and cognitive deficits in 3 × Tg mice.

CONCLUSIONS

Arginine treatment decreases glycated γ2 subunit of AMPK and increases p-AMPK levels in 3 × Tg mice, suggesting that reduced glycation of the γ2 subunit could ameliorate AMPK function and become a new target for AD therapy in the future.

Anshen Dingzhi prescription in the treatment of PTSD in mice: Investigation of the underlying mechanism from the perspective of hippocampal synaptic function

BACKGROUND

Anshen Dingzhi prescription (ADP) is an important prescription for the treatment of mental diseases in traditional Chinese medicine and is widely used to treat neuropsychiatric disorders.

PURPOSE

To explore the ameliorative effect of ADP on post-traumatic stress disorder (PTSD)-like behaviors in mice and determine the underlying mechanism.

METHODS

The constituents of ADP were analyzed by UPLC-Q-TOF/MS. The PTSD-like behaviors of mice subjected to single prolonged stress (SPS) were evaluated using behavioral tests. Potential pathological changes in the hippocampus were assessed by hematoxylin and eosin (H&E) staining. Western blotting and immunohistochemistry (IHC) were employed to detect the expression of proteins involved in relevant signaling pathways.

RESULTS

Five quality control markers (ginsenoside Rg1, ginsenoside Rb1, tenuifolin, poricoic acid B, and α-asarone) were detected in the ADP solution. The ginsenoside Rg1 content in ADP was found to be 0.114 mg/g. Mice subjected to SPS showed obvious fear generalization and anxiety-like behaviors. ADP treatment prevented the behavioral changes caused by exposure to SPS. Compared with control animals, the number of normal pyramidal cells in the hippocampal CA1 region of mice exposed to SPS was decreased and the number of degenerating pyramidal cells was increased; however, ADP administration could counteract these effects. Furthermore, the protein expression of BDNF, p-TrkB, μ-calpain, PSD95, GluN2A, GluA1, p-AKT, p-mTOR, and ARC was decreased, while that of PTEN and GluN2B was increased in the hippocampus of mice subjected to SPS compared with that in control animals; however, these changes in protein expression were reversed following ADP treatment. Importantly, the ameliorative effect of ADP on PTSD-like behaviors and synaptic protein expression were inhibited by rapamycin administration.

CONCLUSIONS

ADP administration improves PTSD-like behaviors in mice and this effect may be mediated through an mTOR-dependent improvement in synaptic function in the hippocampus.

Exosomes derived from bone-marrow mesenchymal stem cells alleviate cognitive decline in AD-like mice by improving BDNF-related neuropathology

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive decline in cognitive ability. Exosomes derived from bone-marrow mesenchymal stem cells (BMSC-exos) are extracellular vesicles that can execute the function of bone-marrow mesenchymal stem cells (BMSCs). Given the versatile therapeutic potential of BMSC and BMSC-exos, especially their neuroprotective effect, the aim of this study was to investigate the potential effect of BMSC-exos on AD-like behavioral dysfunction in mice and explore the possible molecular mechanism.

METHODS

BMSC-exos were extracted from the supernatant of cultured mouse BMSCs, which were isolated from the femur and tibia of adult C57BL/6 mice, purified and sorted via flow cytometry, and cultured in vitro. BMSC-exos were identified via transmission electron microscopy, and typical marker proteins of exosomes were also detected via Western blot. A sporadic AD mouse model was established by intracerebroventricular injection of streptozotocin (STZ). Six weeks later, BMSC-exos were administered via lateral ventricle injection or caudal vein injection lasting five consecutive days, and the control mice were intracerebroventricularly administered an equal volume of solvent. Behavioral performance was observed via the open field test (OFT), elevated plus maze test (EPM), novel object recognition test (NOR), Y maze test (Y-maze), and tail suspension test (TST). The mRNA and protein expression levels of IL-1β, IL-6, and TNF-α in the hippocampus were measured via quantitative polymerase chain reaction (qPCR) and Western blot, respectively. Moreover, the protein expression of Aβ1-42, BACE, IL-1β, IL-6, TNF-α, GFAP, p-Tau (Ser396), Tau5, synaptotagmin-1 (Syt-1), synapsin-1, and brain-derived neurotrophic factor (BDNF) in the hippocampus was detected using Western blot, and the expression of GFAP, IBA1, Aβ1-42 and DCX in the hippocampus was measured via immunofluorescence staining.

RESULTS

Lateral ventricle administration, but not caudal vein injection of BMSC-exos improved AD-like behaviors in the STZ-injected mouse model, as indicated by the increased number of rearing, increased frequency to the central area, and increased duration and distance traveled in the central area in the OFT, and improved preference index of the novel object in the NOR. Moreover, the hyperactivation of microglia and astrocytes in the hippocampus of the model mice was inhibited after treatment with BMSC-exos via lateral ventricle administration, accompanied by the reduced expression of IL-1β, IL-6, TNF-α, Aβ1-42, and p-Tau and upregulated protein expression of synapse-related proteins and BDNF. Furthermore, the results of the Pearson test showed that the preference index of the novel object in the NOR was positively correlated with the hippocampal expression of BDNF, but negatively correlated with the expression of GFAP, IBA1, and IL-1β. Apart from a positive correlation between the hippocampal expression of BDNF and Syt-1, BDNF abundance was found to be negatively correlated with markers of glial activation and the expression of the inflammatory cytokines, Aβ1-42, and p-Tau, which are characteristic neuropathological features of AD.

CONCLUSIONS

Lateral ventricle administration, but not caudal vein injection of BMSC-exos, can improve AD-like behavioral performance in STZ-injected mice, the mechanism of which might be involved in the regulation of glial activation and its associated neuroinflammation and BDNF-related neuropathological changes in the hippocampus.

TTC3-Mediated Protein Quality Control, A Potential Mechanism for Cognitive Impairment

The tetrapeptide repeat domain 3 (TTC3) gene falls within Down's syndrome (DS) critical region. Cognitive impairment is a common phenotype of DS and Alzheimer’s disease (AD), and overexpression of TTC3 can accelerate cognitive decline, but the specific mechanism is unknown. The TTC3-mediated protein quality control (PQC) mechanism, similar to the PQC system, is divided into three parts: it acts as a cochaperone to assist proteins in folding correctly; it acts as an E3 ubiquitin ligase (E3s) involved in protein degradation processes through the ubiquitin–proteasome system (UPS); and it may also eventually cause autophagy by affecting mitochondrial function. Thus, this article reviews the research progress on the structure, function, and metabolism of TTC3, including the recent research progress on TTC3 in DS and AD; the role of TTC3 in cognitive impairment through PQC in combination with the abovementioned attributes of TTC3; and the potential targets of TTC3 in the treatment of such diseases.