The mechanism of action of MPTP-induced neuroinflammation and its modulation by melatonin in rat astrocytoma cells,C6

Abstract

The 1-methyl-4-phenyl 1,2,3,6 tetrahydropyridine (MPTP) induces reactive astrogliosis, the cellular manifestation of neuroinflammation, in various models of Parkinson's disease (PD), but its mechanism of action on astrocytes is not understood. The effect of melatonin on MPTP-induced neuroinflammation in astrocytes is also not known. The present study demonstrated that MPTP treatment of rat astrocytoma cells, C6 for 24 h significantly increased nitrative and oxidative stress and intracellular calcium (Ca²⁺⁺) level. MPTP also activated phosphorylated p38 mitogen activated protein kinase (P-p38 MAPK) and up-regulated expressions of inflammatory proteins. Moreover, MPTP modulated mRNA expressions of pro-inflammatory cytokine genes via activating nuclear factor kappa-B (NF-kB) translocation. Treatment of melatonin with MPTP reversed all these MPTP-induced changes. Study with deprenyl demonstrates that MPTP is inducing neuroinflammation in astrocytoma cells. The present findings elucidated the molecular mechanism of MPTP-induced neuroinflammation and its modulation by melatonin in astrocytoma cells (C6).     

Tau underlies synaptic and cognitive deficits for type 1, but not type 2 diabetes mouse models

Diabetes mellitus (DM) is one of the most devastating diseases that currently affects the aging population. Recent evidence indicates that DM is a risk factor for many brain disorders, due to its direct effects on cognition. New findings have shown that the microtubule‐associated protein tau is pathologically processed in DM; however, it remains unknown whether pathological tau modifications play a central role in the cognitive deficits associated with DM. To address this question, we used a gain‐of‐function and loss‐of‐function approach to modulate tau levels in type 1 diabetes (T1DM) and type 2 diabetes (T2DM) mouse models. Our study demonstrates that tau differentially contributes to cognitive and synaptic deficits induced by DM. On one hand, overexpressing wild‐type human tau further exacerbates cognitive and synaptic impairments induced by T1DM, as human tau mice treated under T1DM conditions show robust deficits in learning and memory processes. On the other hand, neither a reduction nor increase in tau levels affects cognition in T2DM mice. Together, these results shine new light onto the different molecular mechanisms that underlie the cognitive and synaptic impairments associated with T1DM and T2DM.     

Identification of 3-sulfonylindazole derivatives as potent and selective 5-HT(6) antagonists

As part of our efforts to develop agents for cognitive enhancement, we have been focused on the 5-HT₆ receptor in order to identify potent and selective ligands for this purpose. Herein we report the identification of a novel series of 3-sulfonylindazole derivatives with acyclic amino side chains as potent and selective 5-HT₆ antagonists. The synthesis and detailed SAR of this class of compounds are reported.     

Carotenoids and Alzheimer's disease: an insight into therapeutic role of retinoids in animal models

Carotenoids play a pivotal role in prevention of many degenerative diseases mediated by oxidative stress including neurodegenerative diseases like Alzheimer’s Disease (AD). The involvement of retinoids in physiology, AD pathology and their therapeutic role in vitro and in vivo has been extensively studied. This review focuses on the role of carotenoids like retinoic acid (RA), all trans retinoic acid (ATRA), lycopene and β-carotene in prevention of AD symptoms primarily through inhibition of amyloid beta (Aβ) formation, deposition and fibril formation either by reducing the levels of p35 or inhibiting corresponding enzymes. The role of antioxidant micronutrients in prevention or delaying of AD symptoms has been included. This study emphasizes the dietary supplementation of carotenoids to combat AD and warrants further studies on animal models to unravel their mechanism of neuroprotection.     

Rosuvastatin reduces microglia in the brain of wild type and ApoE knockout mice on a high cholesterol diet; Implications for prevention of stroke and AD

We have previously shown that a high cholesterol (HC) diet results in increases in microglia load and levels of the pro-inflammatory cytokine interleukin-6 (IL-6) in the brains of wild type (WT) and apolipoprotein E knockout (ApoE−/−) mice. In the present investigation, we analyzed whether treatment with rosuvastatin, an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, would prevent the increases in inflammatory microglia and IL-6 levels in the brain and plasma of WT and ApoE−/− mice. We report that a HC diet resulted in an increased microglia load in the brains of WT and ApoE−/− mice, in support of our previous study. Treatment with rosuvastatin significantly decreased the microglia load in the brains of WT and ApoE−/− mice on a HC diet. Rosuvastatin treatment resulted in lowered plasma IL-6 levels in WT mice on a HC diet. However, in the present study the number of IL-6 positive cells in the brain was not significantly affected by a HC diet. A recent clinical study has shown that rosuvastatin reduces risk of ischemic stroke in patients with high plasma levels of the inflammatory marker C-reactive protein by 50%. The results from our study show that rosuvastatin reduces inflammatory cells in the brain. This finding is essential for furthering the prevention and treatment of neurodegenerative diseases such as Alzheimer’s disease (AD) and stroke.     

ROCK, PAK, and Toll of synapses in Alzheimer's disease

Alzheimer’s disease is a neurodegenerative disorder where the cognitive deficit is the hallmark symptom reflecting the progression of the disease. Synaptic dysfunction is a sensitive parameter of the AD pathology. Rho GTPases and the Rho kinases, ROCK1/2, and PAK1-3, are important regulators of synaptic plasticity, especially in maintaining the actin cytoskeleton of dendritic spines. Recent studies have revealed that β-amyloid oligomers can inhibit PAK and stimulate ROCK-mediated signaling. Both of these effects enhance the disassembly of synaptic actin filaments and ultimately evoke synaptic loss. Brain tissue in AD recognizes the β-amyloid peptide oligomers as foreign protein particles and mounts an inflammatory defense via Toll-like receptor (TLR) signaling which causes synaptic impairment. We will review here the dysfunction of ROCK, PAK, and Toll signaling associated with AD pathology. The protection of synapses in AD may provide new therapeutic approaches to combatting the cognitive impairment in AD.     

Ibrutinib modulates Aβ/tau pathology,neuroinflammation, and cognitive function in mouse models of Alzheimer's disease

We previously demonstrated that ibrutinib modulates LPS‐induced neuroinflammation in vitro and in vivo, but its effects on the pathology of Alzheimer''s disease (AD) and cognitive function have not been investigated. Here, we investigated the effects of ibrutinib in two mouse models of AD. In 5xFAD mice, ibrutinib injection significantly reduced Aβ plaque levels by promoting the non‐amyloidogenic pathway of APP cleavage, decreased Aβ‐induced neuroinflammatory responses, and significantly downregulated phosphorylation of tau by reducing levels of phosphorylated cyclin‐dependent kinase‐5 (p‐CDK5). Importantly, tau‐mediated neuroinflammation and tau phosphorylation were also alleviated by ibrutinib injection in PS19 mice. In 5xFAD mice, ibrutinib improved long‐term memory and dendritic spine number, whereas in PS19 mice, ibrutinib did not alter short‐ and long‐term memory but promoted dendritic spinogenesis. Interestingly, the induction of dendritic spinogenesis by ibrutinib was dependent on the phosphorylation of phosphoinositide 3‐kinase (PI3K). Overall, our results suggest that ibrutinib modulates AD‐associated pathology and cognitive function and may be a potential therapy for AD.     

The APPswe/PS1A246E mutations in an astrocytic cell line leads to increased vulnerability to oxygen and glucose deprivation,Ca2+ dysregulation,and mitochondrial abnormalities

Growing evidence suggests a close relationship between Alzheimer′s Disease (AD ) and cerebral hypoxia. Astrocytes play a key role in brain homeostasis and disease states, while some of the earliest changes in AD occur in astrocytes. We have therefore investigated whether mutations associated with AD increase astrocyte vulnerability to ischemia. Two astroglioma cell lines derived from APP_SWE /PS 1A246E (APP , amyloid precursor protein; PS 1, presenilin 1) transgenic mice and controls from normal mice were subjected to oxygen and glucose deprivation (OGD ), an in vitro model of ischemia. Cell death was increased in the APP_SWE /PS 1A246E line compared to the control. Increasing extracellular calcium concentration ([Ca²⁺]) exacerbated cell death in the mutant but not in the control cells. In order to explore cellular Ca²⁺ homeostasis, the cells were challenged with ATP or thapsigargin and [Ca²⁺] was measured by fluorescence microscopy. Changes in cytosolic Ca²⁺ concentration ([Ca²⁺]_c) were potentiated in the APP_SWE /PS 1A246E transgenic line. Mitochondrial function was also altered in the APP_SWE /PS 1A246E astroglioma cells; mitochondrial membrane potential and production of reactive oxygen species were increased, while mitochondrial basal respiratory rate and ATP production were decreased compared to control astroglioma cells. These results suggest that AD mutations in astrocytes make them more sensitive to ischemia; Ca²⁺ dysregulation and mitochondrial dysfunction may contribute to this increased vulnerability. Our results also highlight the role of astrocyte dyshomeostasis in the pathophysiology of neurodegenerative brain disorders.

     

Neurochemistry,Neuropathology, and Heredity in SAMP8: A Mouse Model of Senescence

The SAMP8 strain spontaneously develops learning and memory deficits with characteristics of aging, and is a good model for studying the mechanism of cognitive dysfunction with age. Oxidative stress occurs systemically in SAMP8 from early on in life and increases with aging. Neuropathological changes such as the deposition of Aβ, hyperphosphorylation of tau, impaired development of dendritic spines, and sponge formation, and neurochemical changes were found in the SAMP8 brain. These changes may be partially mediated by oxidative stress. Oxidative damage is a major factor in neurodegenerative disorders and aging. A decline in the respiratory control ratio suggesting mitochondrial dysfunction was found in the brain of SAMP8. The rise in oxidative stress following mitochondrial dysfunction may trigger neuropathological and neurochemical changes, disrupting the development of neural networks in the brain in SAMP8. Special issue article in Honour of Dr. Akitane Mori.     

Discovery and optimization of a novel, selective and brain penetrant M1 positive allosteric modulator (PAM): the development of ML169, an MLPCN probe

This Letter describes a chemical lead optimization campaign directed at VU0108370, a weak M₁ PAM hit with a novel chemical scaffold from a functional HTS screen within the MLPCN. An iterative parallel synthesis approach rapidly established SAR for this series and afforded VU0405652 (ML169), a potent, selective and brain penetrant M₁ PAM with an in vitro profile comparable to the prototypical M₁ PAM, BQCA, but with an improved brain to plasma ratio.     

Collaboration of geldanamycin-activated P70S6K and Hsp70 against beta-amyloid-induced hippocampal apoptosis: an approach to long-term memory and learning

One of the neuropathological hallmarks of Alzheimer’s disease (AD) is the accumulation of beta-amyloid peptides (Aβ) in senile plaques. Aβ-induced oxidative stress is believed to be responsible for degeneration and apoptosis of neurons and consequent cognitive and memory deficits. Here, we investigated the possible neuroprotective effect of the heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) against amyloid pathogenesis in adult male Wistar rats. GA or vehicle was injected into the lateral cerebral ventricles of rats 24 h before injection of Aβ (1–42) in CA1 area of hippocampus. The learning and memory of the rats were assessed 7 days after injection of Aβ using passive avoidance (PA) task. As potential contributing factors in Aβ-induced memory decline, we evaluated apoptotic markers and also used terminal-transferase UTP nick end labeling (TUNEL) technique to detect apoptosis in the hippocampus of Aβ-injected rats. Our behavioral data suggest that GA pretreatment can significantly suppress memory deficits in Aβ-injected rats. There was also not only a marked increase in Hsp70 level but also upregulated 70 kDa ribosomal protein S6 kinase (p70S6K) in the hippocampus of GA-treated groups with a reduction in apoptotic factors including caspase-3, poly (ADP-ribose) polymerase, Bax/Bcl-2 ratio, and TUNEL-positive cells as well. Thus, we conclude that GA exerts its protective effects against Aβ (1–42) toxicity and memory deficits, at least in part, by upregulating of Hsp70 and P70S6K.     

Piceatannol attenuates cardiac hypertrophy in an animal model through regulation of the expression and binding of the transcription factor GATA binding factor 6

Piceatannol is found in grapes, passion fruit, and Japanese knotweed. Piceatannol pretreatment suppresses cardiac hypertrophy induced by isoproterenol as assessed by heart weight/body weight ratio, cross-sectional area, and expression of hypertrophic markers. The anti-hypertrophic effect of piceatannol in rat neonatal cardiomyocytes is the same as that in vivo. Piceatannol inhibits lentiviral-GATA6-induced cardiomyocyte hypertrophy. Furthermore, piceatannol reduces the interaction between GATA4 and GATA6 as well as the DNA-binding activity of endogenous GATA6 in the ANP promoter. Our results suggest that piceatannol may be a novel therapeutic agent for the prevention of cardiac hypertrophy.Structured summary of protein interactionsGATA6 physically interacts with GATA4 by anti V5 tag coimmunoprecipitation (View interaction)     

Melatonin attenuated mediators of neuroinflammation and alpha-7 nicotinic acetylcholine receptor mRNA expression in lipopolysaccharide (LPS) stimulated rat astrocytoma cells,C6

Abstract

Melatonin has been known to affect a variety of astrocytes functions in many neurological disorders but its mechanism of action on neuroinflammatory cascade and alpha-7 nicotinic acetylcholine receptor (α7-nAChR) expression are still not properly understood. Present study demonstrated that treatment of C6 cells with melatonin for 24 hours significantly decreased lipopolysaccharide (LPS) induced nitrative and oxidative stress, expressions of cyclooxigenase-2 (COX-2), inducible nitric-oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP). Melatonin also modulated LPS-induced mRNA expressions of α7-nAChR and inflammatory cytokine genes. Furthermore, melatonin reversed LPS-induced changes in C/EBP homologous protein 10 (CHOP), microsomal prostaglandin E synthase-1(mPGES-1) and phosphorylated p38 mitogen activated protein kinase (P-p38). Treatment with pyrrolidine dithiocarbamate (PDTC) inhibited α7-nAChR mRNA expression in LPS-induced C6 cells. Our findings explored anti-neuroinflammatory action of melatonin, which may suggests its beneficial roles in the neuroinflammation associated disorders.     

Neuroprotection by dipeptidyl-peptidase-4 inhibitors and glucagon-like peptide-1 analogs via the modulation of AKT-signaling pathway in Alzheimer’s disease

Alzheimer’s disease (AD) is the most common reason for progressive dementia in the elderly. It has been shown that disorders of the mammalian/mechanistic target of rapamycin (mTOR) signaling pathways are related to the AD. On the other hand, diabetes mellitus (DM) is a risk factor for the cognitive dysfunction. The pathogenesis of the neuronal impairment caused by diabetic hyperglycemia is intricate, which contains neuro-inflammation and/or neurodegeneration and dementia. Glucagon-like peptide-1 (GLP1) is interesting as a possible link between metabolism and brain impairment. Modulation of GLP1 activity can influence amyloid-beta peptide aggregation via the phosphoinositide-3 kinase/AKT/mTOR signaling pathway in AD. The GLP1 receptor agonists have been shown to have favorable actions on the brain such as the improvement of neurological deficit. They might also exert a beneficial effect with refining learning and memory on the cognitive impairment induced by diabetes. Recent experimental and clinical evidence indicates that dipeptidyl-peptidase-4 (DPP4) inhibitors, being currently used for DM therapy, may also be effective for AD treatment. The DPP-4 inhibitors have demonstrated neuroprotection and cognitive improvements in animal models. Although further studies for mTOR, GLP1, and DPP4 signaling pathways in humans would be intensively required, they seem to be a promising approach for innovative AD-treatments. We would like to review the characteristics of AD pathogenesis, the key roles of mTOR in AD and the preventive and/ or therapeutic suggestions of directing the mTOR signaling pathway.     

血清尿酸、白介素6、P-tau181与阿尔茨海默病患者认知功能、日常生活能力和预后的关系分析

摘要 目的：探讨血清尿酸（UA）、白细胞介素-6（IL-6）、磷酸化Tau181（P-tau181）与阿尔茨海默病（AD）患者认知功能、日常生活能力和预后的关系。方法：选择2018年5月至2021年1月上海交通大学医学院附属第九人民医院与上海交通大学医学院附属第九人民医院黄浦分院收治的98例AD患者（AD组）和71例门诊体检的健康志愿者（对照组）,检测血清UA、IL-6、P-tau181水平,使用简易智力状态检查量表（MMSE）、蒙特利尔认知评估量表（MoCA）评估患者认知功能,Barthel指数（BI）评估患者日常生活能力。所有患者出院后随访1年,统计随访期间不良预后发生情况。Pearson相关性分析UA、IL-6、P-tau181与MMSE、MoCA、BI的相关性,多因素Logistic回归分析AD患者预后不良的危险因素。结果：AD组血清UA水平和MMSE、MoCA评分、BI低于对照组（P＜0.05）,IL-6、P-tau181水平高于对照组（P＜0.05）。AD患者血清UA水平与MMSE、MoCA评分、BI呈正相关（P＜0.05）,IL-6、P-tau181水平与MMSE、MoCA评分、BI呈负相关（P＜0.05）。多因素Logistic回归分析结果显示：长期卧床、AD痴呆阶段、高水平IL-6、高水平P-tau181是AD患者预后不良的危险因素（P＜0.05）,高水平UA是保护因素（P＜0.05）。结论：AD患者血清UA水平降低,IL-6、P-tau181水平升高,且与认知功能障碍、日常生活能力降低以及预后不良有关,检测血清UA、IL-6、P-tau181可辅助评估AD病情和预后。     

Detection of oxidized methionine in selected proteins, cellular extracts and blood serums by novel anti-methionine sulfoxide antibodies

Methionine sulfoxide (MetO) is a common posttranslational modification to proteins occurring in vivo. These modifications are prevalent when reactive oxygen species levels are increased. To enable the detection of MetO in pure and extracted proteins from various sources, we have developed novel antibodies that can recognize MetO-proteins. These antibodies are polyclonal antibodies raised against an oxidized methionine-rich zein protein (MetO-DZS18) that are shown to recognize methionine oxidation in pure proteins and mouse and yeast extracts. Furthermore, mouse serum albumin and immunoglobulin (IgG) were shown to accumulate MetO as function of age especially in serums of methionine sulfoxide reductase A knockout mice. Interestingly, high levels of methionine-oxidized IgG in serums of subjects diagnosed with Alzheimer’s disease were detected by western blot analysis using these antibodies. It is suggested that anti-MetO-DZS18 antibodies can be applied in the identification of proteins that undergo methionine oxidation under oxidative stress, aging, or disease state conditions.     

Deletion of Irs2 reduces amyloid deposition and rescues behavioural deficits in APP transgenic mice

As impaired insulin signalling (IIS) is a risk factor for Alzheimer’s disease we crossed mice (Tg2576) over-expressing human amyloid precursor protein (APP), with insulin receptor substrate 2 null (Irs2^−/−) mice which develop insulin resistance. The resulting Tg2576/Irs2^−/− animals had increased tau phosphorylation but a paradoxical amelioration of Aβ pathology. An increase of the Aβ binding protein transthyretin suggests that increased clearance of Aβ underlies the reduction in plaques. Increased tau phosphorylation correlated with reduced tau-phosphatase PP2A, despite an inhibition of the tau-kinase glycogen synthase kinase-3. Our findings demonstrate that disruption of IIS in Tg2576 mice has divergent effects on pathological processes—a reduction in aggregated Aβ but an increase in tau phosphorylation. However, as these effects are accompanied by improvement in behavioural deficits, our findings suggest a novel protective effect of disrupting IRS2 signalling in AD which may be a useful therapeutic strategy for this condition.