GPR34 Knockdown Relieves Cognitive Deficits and Suppresses Neuroinflammation in Alzheimer's Disease via the ERK/NF-κB Signal

Tiaogeng decoction improves mild cognitive impairment in menopausal APP/PS1 mice through the ERs/NF-κ b/AQP1 signaling pathway

People with mild cognitive impairment (MCI) carry a considerable risk of developing dementia. Studies have shown that female sex hormones have long-lasting neuroprotective and anti-aging properties, and the increased risk of MCI and AD is associated with the lack of estrogen during menopause. Previous studies have shown that Tiao Geng Decoction (TGD) may have antioxidant and anti apoptotic properties, which may prevent neurodegenerative diseases. However, whether TGD is effective in improving mild cognitive impairment due to postmenopausal estrogen deficiency and its potential pharmacological mechanisms remain unclear. The aim of this study was to investigate the possible pharmacological mechanisms of TGD in preventing postmenopausal MCI. We utilized RNA-seq technology to screen for differentially expressed genes (DEGs) and enrichment pathways in the hippocampal tissue of different groups of mice. Additionally, we adopted single-cell sequencing technology to study the cell types of Alzheimer's disease (AD) group and Normal Control (NC) group, the differential marker genes of each cell subgroup, and the GO enrichment analysis of each cell type. Both RNA sequencing and single-cell sequencing results showed a significant correlation between TGD and NF-κb pathway in improving mild cognitive impairment in postmenopausal women. The experimental verification results showed that the spatial learning and memory abilities of APP/PS1 model mice were weakened after ovariectomy, and the reproductive cycle on vaginal smears was in the interphase of diestrus. The levels of serum E2, and P-tau181 in mice were significantly down regulated, while the levels of brain tissue homogenate A β 42, IL-1 β, and IL-18 were significantly up-regulated, indicating successful modeling. Combining Western blotting, RT-qPCR, and transmission electron microscopy analyses, it was found that the low estrogen environment induced by oophorectomy can activate the NF-κb signaling pathway, activate the expression of NLRP3 inflammasome and A β secretase BACE1, and induce neuroinflammatory damage in hippocampal astrocytes. These results conform to the modeling characteristics of MCI. After TGD intervention, the spatial learning and memory abilities of MCI mice were significantly improved. The pharmacological validation results indicated that high concentration doses of TGD had a more significant effect on MCI. Subsequently, we used high concentration TGD (0.32 g/ml) as the traditional Chinese medicine group for further validation, protein blotting and RT-qPCR results indicated that TGD can effectively stimulate the secretion of ER α and ER β, inhibit the NF-κb pathway, downregulate BACE1, and inhibit the expression of NLRP3 inflammasome related proteins. In addition, the immunofluorescence results of hippocampal astrocytes showed that TGD can effectively facilitate the expression of AQP1 and significantly lower the sedimentation of A β compared with the model group. Our research suggests that there is a high correlation between a low estrogen environment and the occurrence and development of MCI. TGD may regulate the ERs/NF - κ b/AQP1 signaling pathway, promote estrogen secretion, activate AQP1, reduce A β deposition, reverse MCI neuroinflammatory injury, improve mild cognitive impairment, and prevent the occurrence of AD. This study revealed for the first time that TGD may be a potential new alternative drug for preventing and improving menopausal MCI.

Demyelination-derived lysophosphatidylserine promotes microglial dysfunction and neuropathology in a mouse model of Alzheimer's disease

Microglia dysfunction-associated neuroinflammation is an important driver of Alzheimer's disease (AD), but the mechanism is poorly understood. Here, we show that demyelination promotes neuroinflammation and cognitive impairment via the lysophosphatidylserine (LysoPS)-GPR34 axis in AD. Demyelination is observed at the early stage and is accompanied by an increase in LysoPS in myelin debris in a 5xFAD mouse model of AD. Reducing the content of LysoPS in myelin or inhibiting its receptor GPR34 via genetic or pharmacological approaches can reduce microglial dysfunction and neuroinflammation and improve microglial Aβ phagocytosis, subsequently resulting in less Aβ deposition and memory restoration in 5xFAD mice. Furthermore, increased LysoPS production and microglial GPR34 expression were also observed in the brains of AD patients. These results reveal the pathogenic role of demyelination-derived LysoPS in microglial dysfunction and AD pathology and suggest that blocking GPR34 as a therapeutic strategy beyond targeting Aβ.

Ganoderic acid a alleviates Aβ25-35-induced HT22 cell apoptosis through the ERK/MAPK pathway: a system pharmacology and in vitro experimental validation

Alzheimer's disease (AD) is a neurodegenerative disorder that occurs with aging. Ganoderma lucidum (Curtis.) P. Karst. (G. lucidum) is a traditional medicinal fungus believed to nourish the brain and anti-aging. Ganoderic acid A (GAA), a triterpenoid from G. lucidum, has demonstrated natural neuroprotective effects. This study aims to explore the therapeutic effect and molecular mechanism of GAA on AD. Systematic network pharmacology identified 95 targets, 8 biological functions, and multiple pathways. The results highlighted MAPK family members as core genes, with MAPK1 (ERK2) showing the highest binding affinity to GAA in molecular docking. In vitro experiments revealed that GAA dose-dependently increased the viability of Aβ25-35-injured HT22 cells and inhibited MAPK pathway-related protein expression. Similar to FR180204, 100 µM GAA significantly reversed ERK protein expression, oxidative stress markers, and mitochondrial damage in AD cell model. GAA also downregulated cleaved caspase-3 protein levels, apoptosis rates, Aβ and p-Tau expression by inhibiting the ERK signaling pathway. The therapeutic effect of GAA on AD was predicted and validated through network pharmacology and in vitro experiments. The ability of GAA to inhibit apoptosis via the ERK/MAPK signaling pathway positions it as a promising candidate for AD treatment.

Lysophosphatidylserine: A Signaling Lipid with Implications in Human Diseases

Lysophosphatidylserine (lyso-PS) has emerged as yet another important signaling lysophospholipid in mammals, and deregulation in its metabolism has been directly linked to an array of human autoimmune and neurological disorders. It has an indispensable role in several biological processes in humans, and therefore, cellular concentrations of lyso-PS are tightly regulated to ensure optimal signaling and functioning in physiological settings. Given its biological importance, the past two decades have seen an explosion in the available literature toward our understanding of diverse aspects of lyso-PS metabolism and signaling and its association with human diseases. In this Review, we aim to comprehensively summarize different aspects of lyso-PS, such as its structure, biodistribution, chemical synthesis, and SAR studies with some synthetic analogs. From a biochemical perspective, we provide an exhaustive coverage of the diverse biological activities modulated by lyso-PSs, such as its metabolism and the receptors that respond to them in humans. We also briefly discuss the human diseases associated with aberrant lyso-PS metabolism and signaling and posit some future directions that may advance our understanding of lyso-PS-mediated mammalian physiology.

Sex- and region-specific cortical and hippocampal whole genome transcriptome profiles from control and APP/PS1 Alzheimer's disease mice

A variety of Alzheimer's disease (AD) mouse models has been established and characterized within the last decades. To get an integrative view of the sophisticated etiopathogenesis of AD, whole genome transcriptome studies turned out to be indispensable. Here we carried out microarray data collection based on RNA extracted from the retrosplenial cortex and hippocampus of age-matched, eight months old male and female APP/PS1 AD mice and control animals to perform sex- and brain region specific analysis of transcriptome profiles. The results of our studies reveal novel, detailed insight into differentially expressed signature genes and related fold changes in the individual APP/PS1 subgroups. Gene ontology and Venn analysis unmasked that intersectional, upregulated genes were predominantly involved in, e.g., activation of microglial, astrocytic and neutrophilic cells, innate immune response/immune effector response, neuroinflammation, phagosome/proteasome activation, and synaptic transmission. The number of (intersectional) downregulated genes was substantially less in the different subgroups and related GO categories included, e.g., the synaptic vesicle docking/fusion machinery, synaptic transmission, rRNA processing, ubiquitination, proteasome degradation, histone modification and cellular senescence. Importantly, this is the first study to systematically unravel sex- and brain region-specific transcriptome fingerprints/signature genes in APP/PS1 mice. The latter will be of central relevance in future preclinical and clinical AD related studies, biomarker characterization and personalized medicinal approaches.