Genistein protects hippocampal neurons against injury by regulating calcium/calmodulin dependent protein kinase IV protein levels in Alzheimer's disease model rats

Genistein has a neuroprotective effect in Alzheimer's disease, but its mechanism of action needs further clarification. Accumulating evidence suggests that excessive phosphorylation of tau protein causes production of neurofibrillary tangles, which is one of the main pathological characteristics of Alzheimer's disease, and tau protein can be phosphorylated by calcium/calmodulin dependent protein kinase IV (CAMK4). After 7 days of pre-administration of genistein (90 mg/kg), an Alzheimer's disease rat model was established using an intraperitoneal injection of D-galactose combined with an intracerebral injection of amyloid-β peptide (25–35). The rat was then continu-ously administered genistein (90 mg/kg) for 42 days. The Morris water maze test, western blotting and hematoxylin-eosin staining results showed that genistein significantly decreased the escape latency and increased the number of times crossing the platform, reduced p-tau, CALM, CAMKK1 and p-CAMK4 protein levels in the hippocampus, and alleviated hippocampal neuron damage. These findings indicate that genistein may play a neuroprotective role in Alzheimer's disease through regulating CAMK4 to modulate tau hyperphosphorylation.     

Genistein suppresses the mitochondrial apoptotic pathway in hippocampal neurons in rats with Alzheimer’s disease

Genistein is effective against amyloid-β toxicity,but the underlying mechanisms are unclear.We hypothesized that genistein may protect neurons by inhibiting the mitochondrial apoptotic pathway,and thereby play a role in the prevention of Alzheimer's disease.A rat model of Alzheimer's disease was established by intraperitoneal injection of D-galactose and intracerebral injection of amyloid-β peptide(25–35).In the genistein treatment groups,a 7-day pretreatment with genistein(10,30,90 mg/kg) was given prior to establishing Alzheimer's disease model,for 49 consecutive days.Terminal deoxyribonucleotidyl transferase-mediated d UTP nick end labeling assay demonstrated a reduction in apoptosis in the hippocampus of rats treated with genistein.Western blot analysis showed that expression levels of capase-3,Bax and cytochrome c were decreased compared with the model group.Furthermore,immunohistochemical staining revealed reductions in cytochrome c and Bax immunoreactivity in these rats.Morris water maze revealed a substantial shortening of escape latency by genistein in Alzheimer's disease rats.These findings suggest that genistein decreases neuronal loss in the hippocampus,and improves learning and memory ability.The neuroprotective effects of genistein are associated with the inhibition of the mitochondrial apoptotic pathway,as shown by its ability to reduce levels of caspase-3,Bax and cytochrome c.     

Ketamine induces tau hyperphosphorylation at serine 404 in the hippocampus of neonatal rats

Male Wistar 7-day-old rats were injected with 40 mg/kg ketamine intraperitoneally, followed by three additional injections of 20 mg/kg ketamine each upon restoration of the righting reflex. Neonatal rats injected with equivalent volumes of saline served as controls. Hippocampal samples were collected at 1, 7 or 14 days following administration. Electron microscopy showed that neuronal structure changed noticeably following ketamine treatment. Specifically, microtubular structure became irregular and disorganized. Quantitative real time-PCR revealed that phosphorylated tau mRNA was upregulated after ketamine. Western blot analysis demonstrated that phosphorylated tau levels at serine 396 initially decreased at 1 day after ketamine injection, and then gradually returned to control values. At 14 days after injection, levels of phosphorylated tau were higher in the ketamine group than in the control group. Tau protein phosphorylated at serine 404 significantly increased after ketamine injection, and then gradually decreased with time. However, the levels of tau protein at serine 404 were significantly greater in the ketamine group than in the control group until 14 days. The present results indicate that ketamine induces an increase of phosphorylated tau mRNA and excessive phosphorylation of tau protein at serine 404, causing disruption of microtubules in the neonatal rat hippocampus and potentially resulting in damage to hippocampal neurons.     

Trillium tschonoskii maxim extract attenuates abnormal Tau phosphorylation

Large-scale epidemiological studies have found that hyperhomocysteinemia is a powerful, independent risk factor for Alzheimer's disease. Trillium tschonoskii maxim is a traditional Chinese medicine that is used to promote memory. However, scientific understanding of its mechanism of action is limited. This report studied the potential neuroprotective effects of Trillium tschonoskii maxim extract against homocysteine-induced cognitive deficits. Rats were intravenously injected with homocysteine(400 μg/kg) for 14 days to induce a model of Alzheimer's disease. These rats were then intragastrically treated with Trillium tschonoskii maxim extract(0.125 or 0.25 g/kg) for 7 consecutive days. Open field test and Morris water maze test were conducted to measure spontaneous activity and learning and memory abilities. Western blot assay was used to detect the levels of Tau protein and other factors involved in Tau phosphorylation in the hippocampus. Immunohistochemical staining was used to examine Tau protein in the hippocampus. Golgi staining was applied to measure hippocampal dendritic spines. Our results demonstrated that homocysteine produced learning and memory deficits and increased levels of Tau phosphorylation, and diminished the activity of catalytic protein phosphatase 2A. The total number of hippocampal dendritic spines was also decreased. Trillium tschonoskii maxim extract treatment reversed the homocysteine-induced changes. The above results suggest that Trillium tschonoskii maxim extract can lessen homocysteine-induced abnormal Tau phosphorylation and improve cognitive deterioration such as that present in Alzheimer's disease.     

Exogenous brain-derived neurotrophic factor attenuates cognitive impairment induced by okadaic acid in a rat model of Alzheimer's disease

Decreased expression of brain-derived neurotrophic factor(BDNF) plays an important role in the pathogenesis of Alzheimer's disease, and a typical pathological change in Alzheimer's disease is neurofibrillary tangles caused by hyperphosphorylation of tau. An in vivo model of Alzheimer's disease was developed by injecting okadaic acid(2 μL) and exogenous BDNF(2 μL) into the hippocampi of adult male Wister rats. Spatial learning and memory abilities were assessed using the Morris water maze. The expression levels of protein phosphatase 2 A(PP2 A), PP2 Ac-Yp307, p-tau(Thr231), and p-tau(Ser396/404) were detected by western blot assay. The expression levels of BDNF, TrkB, and synaptophysin mRNA were measured by quantitative real-time polymerase chain reaction. Our results indicated that BDNF expression was suppressed in the hippocampus of OA-treated rats, which resulted in learning and memory deficits. Intra-hippocampal injection of BDNF attenuated this OA-induced cognitive impairment. Finally, our findings indicated an involvement of the PI3 K/GSK-3β/AKT pathway in the mechanism of BDNF in regulating cognitive function. These results indicate that BDNF has beneficial effect on Alzheimer's disease, and highlight the potential of BDNF as a drug target for treatment of Alzheimer's disease.     

Alpha-7 nicotinic acetylcholine receptor agonist treatment in a rat model of Huntington's disease and involvement of heme oxygenase-1

Neuroinflammation is a common element involved in the pathophysiology of neurodegenerative diseases.We recently reported that repeated alpha-7 nicotinic acetylcholine receptor(α7 n ACh R) activations by a potent agonist such as PHA 543613 in quinolinic acid-injured rats exhibited protective effects on neurons.To further investigate the underlying mechanism,we established rat models of early-stage Huntington's disease by injection of quinolinic acid into the right striatum and then intraperitoneally injected 12 mg/kg PHA 543613 or sterile water,twice a day during 4 days.Western blot assay results showed that the expression of heme oxygenase-1(HO-1),the key component of the cholinergic anti-inflammatory pathway,in the right striatum of rat models of Huntington's disease subjected to intraperitoneal injection of PHA 543613 for 4 days was significantly increased compared to the control rats receiving intraperitoneal injection of sterile water,and that the increase in HO-1 expression was independent of change in α7 n ACh R expression.These findings suggest that HO-1 expression is unrelated to α7 n ACh R density and the increase in HO-1 expression likely contributes to α7 n ACh R activation-related neuroprotective effect in early-stage Huntington's disease.     

Loss of canonical Wnt signaling is involved in the pathogenesis of Alzheimer's disease

Alzheimer's disease(AD) is the most common form of dementia in the older population, however, the precise cause of the disease is unknown. The neuropathology is characterized by the presence of aggregates formed by amyloid-β(Aβ) peptide and phosphorylated tau; which is accompanied by progressive impairment of memory. Diverse signaling pathways are linked to AD, and among these the Wnt signaling pathway is becoming increasingly relevant, since it plays essential roles in the adult brain. Initially, Wnt signaling activation was proposed as a neuroprotective mechanism against Aβ toxicity. Later, it was reported that it participates in tau phosphorylation and processes of learning and memory. Interestingly, in the last years we demonstrated that Wnt signaling is fundamental in amyloid precursor protein(APP) processing and that Wnt dysfunction results in Aβ production and aggregation in vitro. Recent in vivo studies reported that loss of canonical Wnt signaling exacerbates amyloid deposition in a transgenic(Tg) mouse model of AD. Finally, we showed that inhibition of Wnt signaling in a Tg mouse previously at the appearance of AD signs, resulted in memory loss, tau phosphorylation and Aβ formation and aggregation; indicating that Wnt dysfunction accelerated the onset of AD. More importantly, Wnt signaling loss promoted cognitive impairment, tau phosphorylation and Aβ1–42 production in the hippocampus of wild-type(WT) mice, contributing to the development of an Alzheimer's-like neurophatology. Therefore, in this review we highlight the importance of Wnt/β-catenin signaling dysfunction in the onset of AD and propose that the loss of canonical Wnt signaling is a triggering factor of AD.     

Rosiglitazone ameliorates diffuse axonal injury by reducing loss of tau and up-regulating caveolin-1 expression

Rosiglitazone up-regulates caveolin-1 levels and has neuroprotective effects in both chronic and acute brain injury. Therefore, we postu-lated that rosiglitazone may ameliorate diffuse axonal injuryvia its ability to up-regulate caveolin-1, inhibit expression of amyloid-beta precursor protein, and reduce the loss and abnormal phosphorylation of tau. In the present study, intraperitoneal injection of rosiglitazone signiifcantly reduced the levels ofamyloid-beta precursor protein and hyperphosphorylated tau (phosphorylated at Ser404 (p-tau (S404)), and it increased the expression of total tau and caveolin-1 in the rat cortex. Our results show that rosiglitazone inhibits the expression of amyloid-beta precursor protein and lowers p-tau (S404) levels, and it reduces the loss of total tau, possibly by up-regulating caveolin-1. These actions of rosiglitazone may underlie its neuroprotective effects in the treatment of diffuse axonal injury.     

TLR2 and TLR4-mediated inflammation in Alzheimer's disease: self-defense or sabotage?

正Alzheimer's disease(AD) is an irreversible disease that leads to neurodegeneration.The underpinning mechanisms of neuronal cell death are a matter of ongoing debate regarding the impact of accumulation of the amyloid beta(Aβ)peptide and post-translation modifications of the tau protein.However,a growing area of research and one that may provide a more rigorous account of the early changes seen in Alzheimer's brains is inflammation.     

Phosphorylation of tau protein over time in rats subjected to transient brain ischemia

Transient brain ischemia has been shown to induce hyperphosphorylation of the micro- tubule-associated protein tau. To further determine the mechanisms underlying these processes, we investigated the interaction between tau, glycogen synthase kinase （GSK）-313 and protein phos- phatase 2A. The results confirmed that tau protein was dephosphorylated during brain ischemia; in addition, the activity of GSK-3β was increased and the activity of protein phosphatase 2A was de- creased. After reperfusion, tau protein was hyperphosphorylated, the activity of GSK-3β was de- creased and the activity of protein phosphatase 2A remained low. Importantly, the interaction of tau with GSK-3β and protein phosphatase 2A was altered during ischemia and reperfusion. Lithium chloride could affect tau phosphorylation by regulating the interaction of tau with GSK-3β and pro- tein phosphatase 2A, and improve learning and memory ability of rats after transient brain ischemia. The present study demonstrated that it was the interaction of tau with GSK-3β and protein phos- phatase 2A, rather than their individual activities, that dominates the phosphorylation of tau in tran- sient brain ischemia. Hyperphosphorylated tau protein may play an important role in the evolution of brain injury in ischemic stroke. The neuroprotective effects of lithium chloride partly depend on the inhibition of tau phosphorylation during transient brain ischemia.     

Heat shock protein 72 confers protection in retinal ganglion cells and lateral geniculate nucleus neurons via blockade of the SAPK/JNK pathway in a chronic ocular-hypertensive rat model

Optic nerve transection increased the expression of heat shock protein 72 （HSP72） in the lateral geniculate body, indicating that this protein is involved in the prevention of neuronal injury. Zinc sulfate and quercetin induced and inhibited the expression of HSP72, respectively. Intraperitoneal injections of zinc sulfate, SP600125 （c-Jun N-terminal kinase inhibitor）, or quercetin were performed on retinal ganglion cells in a Wistar rat model of chronic ocular hypertension. Our results showed that compared with the control group, the expression of HSP72 in retinal ganglion cells and the lateral geniculate body was increased after the injection of zinc sulfate, but was decreased after the injection of quercetin. The expression of phosphorylated c-Jun N-terminal kinases and phosphorylated c-Jun were visible 3 days after injection in the control group, and reached apeak at 7 days. Zinc sulfate and SP600125 significantly decreased the expression of p-c-Jun, whereas quercetin significantly enhanced the expression of this protein. These results suggest that HSP72 protects retinal ganglion cells and lateral geniculate body in a rat model of chronic ocular hypertension from injury by blocking the activation of the stress-activated kinase/c-Jun N-terminal kinase apoptotic pathway.     

The mechanism behind activation of the Nod-like receptor family protein 3 inflammasome in Parkinson's disease

Previous studies have shown that the ATP-P2 X4 receptor signaling pathway mediates the activation of the Nod-like receptor family protein 3(NLRP3)inflammasome.The NLRP3 inflammasome may promote renal interstitial inflammation in diabetic nephropathy.As inflammation also plays an important role in the pathogenesis of Parkinson's disease,we hypothesized that the ATP-P2 X4 receptor signaling pathway may activate the NLRP3 inflammasome in Parkinson's disease.A male rat model of Parkinson's disease was induced by stereotactic injection of 6-hydroxydopamine into the pars compacta of the substantia nigra.The P2 X4 receptor and the NLRP3 inflammasome(interleukin-1βand interleukin-18)were activated.Intracerebroventricular injection of the selective P2 X4 receptor antagonist 5-(3-bromophenyl)-1,3-dihydro-2 H-benzofuro[3,2-e]-1,4-diazepin-2-one(5-BDBD)or knockdown of P2 X4 receptor expression by si RNA inhibited the activation of the NLRP3 inflammasome and alleviated dopaminergic neurodegeneration and neuroinflammation.Our results suggest that the ATP-P2 X4 receptor signaling pathway mediates NLRP3 inflammasome activation,dopaminergic neurodegeneration,and dopamine levels.These findings reveal a novel role of the ATP-P2 X4 axis in the molecular mechanisms underlying Parkinson's disease,thus providing a new target for treatment.This study was approved by the Animal Ethics Committee of Qingdao University,China,on March 5,2015(approval No.QYFYWZLL 26119).     

Oxymatrine reduces neuroinflammation in rat brain A signaling pathway

Cerebral neuroinflammation models were established by injecting 10 μg lipopolysaccharide into the hippocampus of male Sprague-Dawley rats. The rats were treated with an intraperitoneal injection of 120, 90, or 60 mg/kg oxymatrine daily for three days prior to the lipopolysaccharide injection. Twenty-four hours after model induction, the hippocampus was analyzed by real-time quantitative PCR, and the cerebral cortex was analyzed by enzyme-linked immunosorbent assay and western blot assay. The results of the enzyme-linked immunosorbent assay and the real-time quantitative PCR showed that the secretion and mRNA expression of the pro-inflammatory cytokines interleukin-1β and tumor necrosis factor-α were significantly decreased in the hippocampus and cerebral cortex of model rats treated with oxymatrine. Western blot assay and real-time quantitative PCR analysis indicated that toll-like receptor 4 mRNA and protein expression were significantly decreased in the groups receiving different doses of oxymatrine. Additionally, 120 and 90 mg/kg oxymatrine were shown to reduce protein levels of nuclear factor-κB p65 in the nucleus and of phosphorylated IκBα in the cytoplasm of brain cells, as detected by western blot assay. Experimental findings indicate that oxymatrine may inhibit neuroinflammation in rat brain via downregulating the expression of molecules in the toll-like receptor 4/nuclear factor-κB signaling pathway.     

Hydrogen-rich water ameliorates neuropathological impairments in a mouse model of Alzheimer's disease through reducing neuroinflammation and modulating intestinal microbiota

Hydrogen exhibits the potential to treat Alzheimer's disease. Stereotactic injection has been previously used as an invasive method of administering active hydrogen, but this method has limitations in clinical practice. In this study, triple transgenic(3×Tg) Alzheimer's disease mice were treated with hydrogen-rich water for 7 months. The results showed that hydrogen-rich water prevented synaptic loss and neuronal death, inhibited senile plaques, and reduced hyperphosphorylated tau and neurofibrillary tangles in 3×Tg Alzheimer's disease mice. In addition, hydrogen-rich water improved brain energy metabolism disorders and intestinal flora imbalances and reduced inflammatory reactions. These findings suggest that hydrogen-rich water is an effective hydrogen donor that can treat Alzheimer's disease. This study was approved by the Animal Ethics and Welfare Committee of Shenzhen University, China(approval No. AEWC-20140615-002) on June 15, 2014.     

Arbutin effectively ameliorates the symptoms of Parkinson’s disease:the role of adenosine receptors and cyclic adenosine monophosphate

An antagonistic communication exists between adenosinergic and dopaminergic signaling in the basal ganglia,which suggests that the suppression of adenosine A2A receptors-cyclic adenosine monophosphate pathway may be able to restore the disrupted dopamine transmission that results in motor symptoms in Parkinson’s disease(PD).Arbutin is a natural glycoside that possesses antioxidant,antiinflammatory,and neuroprotective properties.The purpose of this study was to investigate whether arbutin could ameliorate the symptoms of PD and to examine the underlying mechanism.In this study,Swiss albino mouse models of PD were established by the intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine for 4 successive days,with the concurrent intraperitoneal administration of arbutin(50 and 100 mg/kg)for 7 days.The results showed that arbutin significantly reduced lipid peroxidation,total nitrite levels,and inflammation in the substantia nigra and striatum of PD mouse models.In addition,arbutin decreased the activity of endogenous antioxidants,reduced the levels of dopamine,3,4-dihydroxyphenylacetic acid,homovanillic acid,andγ-aminobutyric acid,and minimized neurodegeneration in the striatum.Arbutin also reduced the abnormal performance of PD mouse models in the open field test,bar test,pole test,and rotarod test.The therapeutic efficacy of arbutin was similar to that of madopar.The intraperitoneal injection of the A2AR agonist CGS21680(0.5 mg/kg)attenuated the therapeutic effects of arbutin,whereas the intraperitoneal injection of forskolin(3 mg/kg)enhanced arbutin-mediated improvements.These findings suggest that arbutin can improve the performance of PD mouse models by inhibiting the function of the A2AR and enhancing the effects of cyclic adenosine monophosphate.This study was approved by the Institutional Animal Ethics Committee(1616/PO/Re/S/12/CPCSEA)on November 17,2019(approval No.IAEC/2019/010).     

Preventive electroacupuncture reduces cognitive deficits in a rat model of D-galactose-induced aging

Acupuncture can reduce cognitive deficits in Alzheimer's disease. However, whether electroacupuncture can prevent or alleviate the cognitive deficits in animal models of aging remains poorly understood. Studies have shown that disordered epigenetic modifications play a critical role in age-related cognitive decline. Therefore, we hypothesized that preventive electroacupuncture might improve cognitive functions during aging by regulating epigenetic modifications. A rat model of aging was produced by intraperitoneal injection of 120 mg/kg D-galactose for 8 weeks. Baihui and Shenshu acupoints were stimulated by electroacupuncture for 8 weeks from the first day of D-galactose administration. Preventive electroacupuncture alleviated memory impairment, decreased tau hyperphosphorylation, and reduced glycogen synthase kinase-3β protein and m RNA expression levels in the brainstem dorsal raphe nucleus, where intracellular neurofibrillary tangle lesions first occur. In addition, the DNA methylation level in the promoter region of the glycogen synthase kinase-3β gene was increased. The effects of preventive electroacupuncture were stronger than those of preventive acupuncture. Intraperitoneal injection of 0.4 mg/kg 5-aza-2′-deoxycytidine, an inhibitor of DNA methyltransferase that blocks epigenetic modifications, antagonized the effects of preventive electroacupuncture. Our results suggest that preventive electroacupuncture treatment alleviates cognitive impairment in aging rats probably by affecting the epigenetic modification of the glycogen synthase kinase-3β gene in the dorsal raphe nucleus. This study was approved by the Animal Ethics Committee of Hubei University of Chinese Medicine, China(approval No. HUCMS201712001) on November 28, 2017.     

Isatin decreases Bax protein expression in the substantia nigra of a mouse model of Parkinson’s disease

The present study observed the action of 1H-indole-2, 3-dione (isatin) on Bax protein expression in the substantia nigra of a Parkinson’s disease animal model. Parkinson’s disease-like behaviors were induced in C57BL/6J mice treated with 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). Bax protein expression was significantly reduced in isatin (100, 200 mg/kg)-pretreated mice. Results demonstrate that isatin plays a neuroprotective role in mice treated with MPTP by down-regulating Bax protein express...     

Brain ischemia as a bridge to Alzheimer's disease

An update of the etiology of Alzheimer's disease(AD):The current theory of the etiology of AD and the guidelines for most of the wide-ranging treatments activities are built around amyloid and tau protein as causative agents of the disease(Atlante et al.,2020).At present,based on a comprehensive evaluation of existing and contemporary studies,important questions arise regarding the causal role of amyloid and tau protein in the pathogenesis of AD(Morris et al.,2018).Analyzes of the available evidence does not allow obvious conclusion that amyloid,and especially tau protein,plays a key role in the etiology of AD(Morris et al.,2018).     

Neuroprotective mechanisms of rutin for spinal cord injury through anti-oxidation and anti-inflammation and inhibition of p38 mitogen activated protein kinase pathway

Rutin has anti-inflammatory, antioxidant, anti-viral, anti-tumor and immune regulatory effects. However, the neuroprotective effects of rutin in spinal cord injury are unknown. The p38 mitogen activated protein kinase(p38 MAPK) pathway is the most important member of the MAPK family that controls inflammation. We assumed that the mechanism of rutin in the repair of spinal cord injury is associated with the inhibition of p38 MAPK pathway. Allen's method was used to establish a rat model of spinal cord injury. The rat model was intraperitoneally injected with rutin(30 mg/kg) for 3 days. After treatment with rutin, Basso, Beattie and Bresnahan locomotor function scores increased. Water content, tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6 levels, p38 MAPK protein expression and caspase-3 and-9 activities in T8–9 spinal cord decreased. Oxidative stress related markers superoxide dismutase and glutathione peroxidase levels increased in peripheral blood. Rutin exerts neuroprotective effect through anti-oxidation, anti-inflammation, anti-apoptosis and inhibition of p38 MAPK pathway.