Cornel Iridoid Glycoside Ameliorated Alzheimer’s Disease-Like Pathologies and Necroptosis through RIPK1/MLKL Pathway in Young and Aged SAMP8 Mice

Background. Aging is an important risk factor for sporadic Alzheimer’s disease (AD) and other neurodegenerative diseases. Senescence-accelerated mouse-prone 8 (SAMP8) is used as an animal model for brain aging and sporadic AD research studies. The aim of the current study was to investigate the pharmacological effects of cornel iridoid glycoside (CIG), an active ingredient of Cornus officinalis, on AD-type pathological changes in young and aged SAMP8 mice. Methods. Locomotor activity test was used to detect the aging process of SAMP8 mice. Nissl staining and immunohistochemical staining were applied to detect neurons and myelin basic protein-labelled myelin sheath. Western blotting was used to detect the expression levels of related proteins of synapse, APP processing, and necroptosis. Results. The results showed that SAMP8 mice at the age of 6 and 14 months exhibited lower locomotor activity, age-related neuronal loss, demyelination, synaptic damage, and APP amyloidogenic processing. In addition, the increased levels of receptor-interacting protein kinase-1 (RIPK1), mixed lineage kinase domain-like protein (MLKL), and p-MLKL indicating necroptosis were found in the brain of SAMP8 mice. Intragastric administration of CIG for 2 months improved locomotor activity; alleviated neuronal loss and demyelination; increased the expression of synaptophysin, postsynaptic density protein 95, and AMPA receptor subunit 1; elevated the levels of soluble APPα fragment and disintegrin and metalloproteinase 10 (ADAM10); and decreased the levels of RIPK1, p-MLKL, and MLKL in the brain of young and aged SAMP8 mice. Conclusion. This study denoted that CIG might be a potential drug for aging-related neurodegenerative diseases such as AD.

Cornel Iridoid Glycoside Protects Against STAT1-Dependent Synapse and Memory Deficits by Increasing N-Methyl-D-aspartate Receptor Expression in a Tau Transgenic Mice

P301S transgenic mice are an animal model of tauopathy and Alzheimer’s disease (AD), exhibiting tau pathology and synaptic dysfunction. Cornel iridoid glycoside (CIG) is an active ingredient extracted from Cornus officinalis, a traditional Chinese herb. In the present study, the purpose was to investigate the effects and mechanisms of CIG on tau pathology and synaptic dysfunction using P301S transgenic mice. The results showed that intragastric administration of CIG for 3.5 months improved cognitive impairments and the survival rate of P301S mice. Electrophysiological recordings and transmission electron microscopy study showed that CIG improved synaptic plasticity and increased the ultrastructure and number of synapse. Moreover, CIG increased the expression levels of N-methyl-D-aspartate receptors (NMDAR) subunits GluN1, GluN2A, and GluN2B, and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) subunit GluA1. We inferred that the major mechanism of CIG involving in the regulation of synaptic dysfunctions was inhibiting the activation of Janus kinase-2 (JAK2)/signal transducer and activator of transcription 1 (STAT1) signaling pathway and alleviating STAT1-induced suppression of NMDAR expressions. Based on our findings, we thought CIG might be a promising candidate for the therapy of tauopathy such as AD.

Cornel iridoid glycoside ameliorated Alzheimer's disease-like pathologies and necroptosis through RIPK1/MLKL pathway in young and aged SAMP8 mice

Background Aging is an important risk factor for sporadic Alzheimer’s disease (AD) and other neurodegenerative diseases. Senescence-accelerated mouse-prone 8 (SAMP8) is used as an animal model for brain aging and sporadic AD researches. The aim of the current study was to investigate the pharmacological effects of cornel iridoid glycoside (CIG), an active ingredient of Cornus officinalis, on AD-type pathological changes in young and aged SAMP8 mice. Methods Nissl and immunohistochemical staining was applied to detect NeuN-labeled neurons and myelin basic protein-labeled myelin sheath,. Western blotting was used to detect the expression levels of related proteins of synapse, APP processing and necroptosis. Results The results showed that SAMP8 mice at the age of 6 and 14 months exhibited age-related neuronal loss, demyelination, synaptic damage, and APP amyloidogenic processing. In addition, the increased levels of receptor-interacting protein kinase-1 (RIPK1), mixed lineage kinase domain-like protein (MLKL) and p-MLKL indicating necroptosis were found in the brain of SAMP8 mice. Intragastric administration of CIG for 2 months alleviated neuronal loss and demyelination, increased the expression of synaptophysin, postsynaptic density protein 95 and AMPA receptor subunit 1, elevated the levels of soluble APPα fragment and a disintegrin and metalloproteinase 10 (ADAM10), and decreased the levels of RIPK1, p-MLKL and MLKL in the brain of young and aged SAMP8 mice. Conclusion This study denoted that CIG might be a potential drug for aging-associated neurodegenerative diseases such as AD.

Cornel Iridoid Glycoside Suppresses Tau Hyperphosphorylation and Aggregation in a Mouse Model of Tauopathy through Increasing Activity of PP2A

Background: rTg4510 mice are transgenic mice expressing P301L mutant tau and have been developed as an animal model of tauopathy including Alzheimer’s Disease (AD). Cornel Iridoid Glycoside (CIG) is an active ingredient extracted from Cornus officinalis, a traditional Chinese herb. The purpose of the present study was to investigate the effects of CIG on tau pathology and underlying mechanisms using rTg4510 mice. Methods: The cognitive functions were detected by Morris water maze and objective recognition tests. Western blotting and immunofluorescence were conducted to measure the levels of phosphorylated tau and related proteins. Serine/threonine phosphatase assay was applied to detect the activity of protein phosphatase 2A (PP2A). Results: Intragastric administration of CIG for 3 months improved learning and memory abilities, prevented neuronal and synapse loss, halted brain atrophy, elevated levels of synaptic proteins, protected cytoskeleton, reduced tau hyperphosphorylation and aggregation in the brain of rTg4510 mice. In the mechanism studies, CIG increased the activity of PP2A, elevated the methylation of PP2A catalytic C (PP2Ac) at leucine 309, decreased the phosphorylation of PP2Ac at tyrosine 307, and increased protein expression of leucine carboxyl methyltransferase 1 (LCMT-1), protein tyrosine phosphatase 1B (PTP1B), and protein phosphatase 2A phosphatase activator (PTPA) in the brain of rTg4510 mice. Conclusion: CIG might have the potential to treat tauopathy such as AD via activating PP2A.