Co-injection of Aβ1-40 and ApoE4 impaired spatial memory and hippocampal long-term potentiation in rats

TDP-43 Pathology in Alzheimer’s Disease

Transactive response DNA binding protein of 43 kDa (TDP-43) is an intranuclear protein encoded by the TARDBP gene that is involved in RNA splicing, trafficking, stabilization, and thus, the regulation of gene expression. Cytoplasmic inclusion bodies containing phosphorylated and truncated forms of TDP-43 are hallmarks of amyotrophic lateral sclerosis (ALS) and a subset of frontotemporal lobar degeneration (FTLD). Additionally, TDP-43 inclusions have been found in up to 57% of Alzheimer’s disease (AD) cases, most often in a limbic distribution, with or without hippocampal sclerosis. In some cases, TDP-43 deposits are also found in neurons with neurofibrillary tangles. AD patients with TDP-43 pathology have increased severity of cognitive impairment compared to those without TDP-43 pathology. Furthermore, the most common genetic risk factor for AD, apolipoprotein E4 (APOE4), is associated with increased frequency of TDP-43 pathology. These findings provide strong evidence that TDP-43 pathology is an integral part of multiple neurodegenerative conditions, including AD. Here, we review the biology and pathobiology of TDP-43 with a focus on its role in AD. We emphasize the need for studies on the mechanisms that lead to TDP-43 pathology, especially in the setting of age-related disorders such as AD.

Rosmarinic acid ameliorates hypoxia/ischemia induced cognitive deficits and promotes remyelination

Rosmarinic acid, a common ester extracted from Rosemary, Perilla frutescens, and Salvia miltiorrhiza Bunge, has been shown to have protective effects against various diseases. This is an investigation into whether rosmarinic acid can also affect the changes of white matter fibers and cognitive deficits caused by hypoxic injury. The right common carotid artery of 3-day-old rats was ligated for 2 hours. The rats were then prewarmed in a plastic container with holes in the lid, which was placed in 37°C water bath for 30 minutes. Afterwards, the rats were exposed to an atmosphere with 8% O₂ and 92% N₂ for 30 minutes to establish the perinatal hypoxia/ischemia injury models. The rat models were intraperitoneally injected with rosmarinic acid 20 mg/kg for 5 consecutive days. At 22 days after birth, rosmarinic acid was found to improve motor, anxiety, learning and spatial memory impairments induced by hypoxia/ischemia injury. Furthermore, rosmarinic acid promoted the proliferation of oligodendrocyte progenitor cells in the subventricular zone. After hypoxia/ischemia injury, rosmarinic acid reversed to some extent the downregulation of myelin basic protein and the loss of myelin sheath in the corpus callosum of white matter structure. Rosmarinic acid partially slowed down the expression of oligodendrocyte marker Olig2 and myelin basic protein and the increase of oligodendrocyte apoptosis marker inhibitors of DNA binding 2. These data indicate that rosmarinic acid ameliorated the cognitive dysfunction after perinatal hypoxia/ischemia injury by improving remyelination in corpus callosum. This study was approved by the Animal Experimental Ethics Committee of Xuzhou Medical University, China (approval No. 20161636721) on September 16, 2017.

Inhibition of HDAC6 expression decreases brain injury induced by APOE4 and Aβ co‑aggregation in rats

The present study aimed to explore the effects of histone deacetylase 6 (HDAC6) on brain injury in rats induced by apolipoprotein E4 (APOE4) and amyloid β protein alloform 1‑40 (Aβ1‑40) copolymerization. The rats were randomly divided into four groups: Control group, sham group, APOE4 + Aβ1‑40 co‑injection group (model group) and HDAC6 inhibitor group (HDAC6 group). The brain injury model was established by co‑injection of APOE4 + Aβ1‑40. Morris water maze experiment was used to observe the spatial memory and learning the ability of rats. Histological changes of the hippocampus were observed by hematoxylin and eosin staining. The mRNA expression levels of choline acetyltransferase (ChAT) and HDAC6 were detected by reverse transcription‑quantitative PCR. Immunohistochemistry was used to detect the protein expression of HDAC6. Western blotting was used to detect the protein expression levels of HDAC6, microtubule‑associated protein tau and glycogen synthase kinase 3β (GSK3β). APOE4 and Aβ1‑40 co‑aggregation decreased the short‑term spatial memory and learning ability of rats, whereas inhibition of HDAC6 activity attenuated the injury. Inhibition of HDAC6 activity resulted in an attenuation of the APOE4 and Aβ1‑40 co‑aggregation‑induced increase in the number of dysplastic hippocampal cells. Further experiments demonstrated that APOE4 and Aβ1‑40 co‑aggregation decreased the expression levels of ChAT mRNA, and the phosphorylation levels of tau GSK3β protein in the hippocampus, whereas inhibition of HDAC6 activity resulted in increased expression of ChAT mRNA, tau protein and GSK3β phosphorylation. The inhibition of HDAC6 activity was also demonstrated to reduce brain injury induced by APOE4 and Aβ1‑40 co‑aggregation in model rats.

Baicalin and ginsenoside Rb1 promote the proliferation and differentiation of neural stem cells in Alzheimer's disease model rats

BACKGROUND

This study aimed to explore the effects of ginsenoside Rb1 and baicalin on the proliferation and differentiation of neural stem cells (NSC) in Alzheimer's disease model rats.

METHOD

The healthy Sprague Dawley male rats were randomly divided into 4 groups: control group, model group, ginsenoside Rb1 group and baicalin group. Besides, the animal model of dementia was induced by the injection of Aβ1-40. 2 weeks later, the rats in the baicalin and ginsenoside Rb1 groups were injected with baicalin and ginsenoside Rb1, respectively. The contents, expression sites of Nestin, GFAP and NSE and the percentage of viable cells were detected by immunohistochemistry. In addition, the expression levels of Nestin, GFAP and NSE in hippocampus of rats were detected by western-blot and metrology analysis was performed using quantity.

RESULTS

Injection of Aβ1-40 significantly reduced the number of neuronal cells (p < .05). In addition, compared with the control group, the percentages of positive cells of NSCs, astrocytes and neuronal were increased. Besides, compared with the model group, the percentage of positive neural cells was improved by ginsenoside Rb1 (p < .05), and the percentages of astrocytes and neuronal were increased by ginsenoside Rb1 and baicalin (p < .05). Moreover, the expressions of Nestin and NSE were enhanced by ginsenoside Rb1 and baicalin (p < .05), while the GFAP level was only affected by ginsenoside Rb1 (p < .05) when compared with the model group.

CONCLUSION

Ginsenoside Rb1 and baicalin might promote the proliferation and differentiation of endogenous NSCs in AD rat model.

Targeting Apolipoprotein E/Amyloid β Binding by Peptoid CPO_Aβ17-21 P Ameliorates Alzheimer's Disease Related Pathology and Cognitive Decline

Inheritance of the apolipoprotein E4 (apoE4) genotype has been identified as the major genetic risk factor for late onset Alzheimer's disease (AD). Studies have shown that apoE, apoE4 in particular, binds to amyloid-β (Aβ) peptides at residues 12-28 of Aβ and this binding modulates Aβ accumulation and disease progression. We have previously shown in several AD transgenic mice lines that blocking the apoE/Aβ interaction with Aβ12-28 P reduced Aβ and tau-related pathology, leading to cognitive improvements in treated AD mice. Recently, we have designed a small peptoid library derived from the Aβ12-28 P sequence to screen for new apoE/Aβ binding inhibitors with higher efficacy and safety. Peptoids are better drug candidates than peptides due to their inherently more favorable pharmacokinetic properties. One of the lead peptoid compounds, CPO_Aβ17-21 P, diminished the apoE/Aβ interaction and attenuated the apoE4 pro-fibrillogenic effects on Aβ aggregation in vitro as well as apoE4 potentiation of Aβ cytotoxicity. CPO_Aβ17-21 P reduced Aβ-related pathology coupled with cognitive improvements in an AD APP/PS1 transgenic mouse model. Our study suggests the non-toxic, non-fibrillogenic peptoid CPO_Aβ17-21 P has significant promise as a new AD therapeutic agent which targets the Aβ related apoE pathway, with improved efficacy and pharmacokinetic properties.