Chronic administration of Tat-GluR23Y ameliorates cognitive dysfunction targeting CREB signaling in rats with amyloid beta neurotoxicity

AMPA receptor potentiation alleviates NLRP3 knockout-induced fear generalization in mice

Genetic knockout and pharmaceutical inhibition of the NLRP3 inflammasome enhances the extinction of contextual fear memory, which is attributed to its role in neuronal and synaptic dysregulation, concurrent with neurotransmitter function disturbances. This study aimed to determine whether NLRP3 plays a role in generalizing fear via the inflammatory axis. We established the NLRP3 KO mice model, followed by behavioral and biochemical analyses. The NLRP3 KO mice displayed impaired fear generalization, lower neuroinflammation levels, and dysregulated neurotransmitter function. Additionally, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, but not the inhibition of NMDA or 5-HT2C receptors, resulted in fear generalization in NLRP3 KO mice because TAT-GluA2 3Y, but not SB242084 and D-cycloserine, treated blocked NLRP3 deprivation effects on fear generalization. Thus, global knockout of NLRP3 is associated with aberrant fear generalization, possibly through AMPA receptor signaling.

Protective effect of miR-34c antagomir against STZ-induced memory impairment by targeting mTOR and PSD-95 in the hippocampus of rats

After long times of ongoing research, still there is no appropriate cure for Alzheimer's disease (AD). Recently, epigenetic alterations, particularly miRNA, have gotten attention in AD research. Among various miRNA, miR-34c has been addressed to be elevated in the brain of AD patients, however, its exact role and downstream mechanisms have not been elucidated yet. This study aimed to investigate the therapeutic potential of miR-34c antagomir on cognitive dysfunction induced by streptozocin (STZ), considering postsynaptic density protein 95 (PSD-95) and mammalian target of rapamycin expression (mTOR). Forty rats were cannulated intraventricularly under deep anesthesia using stereotaxic apparatus and divided into five groups: saline + saline, STZ + saline, STZ + miR-34c antagomir, STZ + lipofectamine, and STZ + scrambled, and received the related treatments for two weeks. At the end of the treatments, spatial memory and locomotor activity were assessed by Morris water maze (MWM), and open fields, respectively. Finally, PSD-95 and mTOR levels were measured by quantitative real-time PCR (qPCR) and western blotting on hippocampal samples. Results showed that miR-34c antagomir markedly ameliorated spatial learning and memory deficits induced by STZ, and significantly enhanced PSD-95 and mTOR levels in the hippocampus. In conclusion, miR-34c antagomir may be considered as a promising novel therapeutic target for AD patients.

TAT-MeCP2 protein variants rescue disease phenotypes in human and mouse models of Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder caused by pathogenic variants leading to functional impairment of the MeCP2 protein. Here, we used purified recombinant MeCP2e1 and MeCP2e2 protein variants fused to a TAT protein transduction domain (PTD) to evaluate their transduction ability into RTT patient-derived fibroblasts and the ability to carry out their cellular function. We then assessed their transduction ability and therapeutic effects in a RTT mouse model. In vitro, TAT-MeCP2e2-eGFP reversed the pathological hyperacetylation of histones H3K9 and H4K16, a hallmark of abolition of MeCP2 function. In vivo, intraperitoneal administration of TAT-MeCP2e1 and TAT-MeCP2e2 extended the lifespan of Mecp2^-/y mice by >50%. This was accompanied by rescue of hippocampal CA2 neuron size in animals treated with TAT-MeCP2e1. Taken together, these findings provide a strong indication that recombinant TAT-MeCP2 can reach mouse brains following peripheral injection and can ameliorate the phenotype of RTT mouse models. Thus, our study serves as a first step in the development of a potentially novel RTT therapy.

Nacre extract from pearl oyster attenuates amyloid beta-induced memory impairment

Shells are composed of two types of calcium carbonate polymorphs-the prismatic layer and the nacreous layer. Pearls, composed of the nacreous layer, have been used in Chinese medicine since ancient times. We have previously shown that extracts from the nacreous layer improves scopolamine-induced memory impairment. However, whether pearl ameliorates cognitive disorders induced by amyloid-β 1-40 (Aβ1-40) has not been elucidated. In this study, we investigated whether nacre extract improves memory impairment induced by intracerebroventricular injection of Aβ1-40. Administration of nacre extract led to recovery from Aβ1-40-induced impairments in object recognition, short-term memory, and spatial memory. Nacre extract reversed the increase in lipid peroxidation caused by Aβ1-40 in the cerebral cortex by increasing the expression of catalase and superoxide dismutase. In addition, nacre extract recovered the expression and phosphorylation of cyclic AMP response element-binding protein (CREB), which decreased with Aβ1-40 treatment, and increased the expression of brain-derived neurotrophic factor and neuropeptide Y, which are regulated by CREB. Nacre extract also suppressed acetylcholine esterase activity and Aβ1-40-induced tau phosphorylation. Histochemical analysis of the hippocampus region showed that the nacre extract protected against Aβ1-40-induced neuronal loss in the hippocampus. These results suggest that nacre extract protects against Aβ1-40-induced neuronal cell death by suppressing oxidative stress and increasing the expression and phosphorylation of CREB.