Injection Of Homocysteine Research Articles

Preventing retinal homocysteine dysregulation protects against retinal ganglion cell death

Glaucoma, the most common cause of irreversible blindness, is characterized by progressive dysfunction and loss of retinal ganglion cells. There are no neuroprotective therapies. Metabolic dysfunction is an emerging pathophysiological mechanism in glaucoma with widespread changes to energy homeostasis, yet little is known about non‐energy metabolism. We recently identified elevated retinal homocysteine as a strong early metabolomic signature in a rat model of glaucoma. We tested whether local elevation of homocysteine to the retina compounded glaucoma in the rat model by artificially rising homocysteine through intravitreal injection. Short‐term elevation of homocysteine (from 1 to 15 μM, as has been detected in the vitreous of diabetic retinopathy patients) either alone or in addition to glaucoma does not worsen retinal ganglion cell death, suggesting that local elevation of homocysteine does not contribute to retinal ganglion cell degeneration, but may be an indicator of wider metabolic dysfunction. Homocysteine is central to one‐carbon metabolism, an anabolic pathway with an essential role in generation of methionine and methyl donors (necessary for the epigenetic regulation of gene expression), and glutathione (antioxidant). In a mouse model of glaucoma, we identified early‐ and sustained‐dysregulation of genes involved in one‐carbon metabolism in whole retina. In retinal ganglion cells, a number of these genes change prior to detectable neurodegeneration. These pathways require vitamin B6 and B12 as essential cofactors, and folic acid (B9) and choline are essential precursors, for the metabolism of homocysteine. Genes involved in the transport and utilization of these cofactors and precursors were also significantly dysregulated in the retina, further supporting dysfunctional homocysteine metabolism. Dietary deficiency in these leads to homocysteine accumulation and are well associated with optic neuropathies. We hypothesize that local retinal deficiency in these may contribute to dysfunction in one‐carbon metabolism and impact wider retinal ganglion cell homeostasis. To test this hypothesis, we first supplemented the drinking water of mice with B6 (4.5 mg/kg), folic acid (B9) (1.5 mg/kg), cobalamin (B12) (20 μg/kg), and choline (750 mg/kg) as a prophylactic treatment 7 days prior to intravitreal homocysteine injection. We used a supraphysiological dose of homocysteine (500 μM) that causes spontaneous death of ~10% of retinal ganglion cell death after 7 days in untreated animals. Pre‐treated animals were completely protected from retinal ganglion cell death. Next, we pre‐treated rats in the same way for 7 days prior to induction of our glaucoma model. In untreated rats there was a ~ 40% loss of retinal ganglion cells after 14 days, and this was significantly mitigated in pre‐treated rats (only ~25% loss), demonstrating that these cofactors can provide moderate neuroprotection in a complex, multifactorial neurodegenerative context.

Changes in Aβ42, Neprilysin, and γ-Secretase in the Hippocampus of Male Rats Alzheimer’s model: The Effects of Aerobic Training and Omega-3 Intake

Background: Alzheimer›s disease (AD) is characterized by excessive deposition of the amyloid-β peptide (Aβ) in the central nervous system and reducing its level is the goal of many medications. This study aimed to investigate the effect of aerobic training and omega-3 intake on Aβ42, neprilysin, and γ-secretase levels in the hippocampus of male rats Alzheimer›s model. Methods: Fifty male Wistar rats (age: 12 weeks-old and weight: 222.31±11.91 g), were divided into the five groups including control Alzheimer’s (AC), Alzheimer’s with omega-3 intake (AO), Alzheimer’s training (AT), Alzheimer’s with omega-3 intake and training (AOT) and Healthy Control (HC). AD was induced by the injection of homocysteine (60mM) into the rat brain ventricle. Training on the treadmill with a speed of 20 m/min (60 minutes and 5 days/week) was applied. The supplement group received omega-3 supplement 800 mg/kg of body weight, daily for eight weeks. Levels of Aβ42, γ-secretase, and neprilysin protein were measured using ELISA method. In data analysis, one-way ANOVA and Tukey test as post hoc were used (P<0.05). Results: The obtained results showed that the level of Aβ42 in the hippocampus of AC group was significantly higher than that of the HC group (P=0.001). Also, the level of Aβ42 in the hippocampus of AC group was significantly higher as compared to AO, AT, and AOT groups (P values 0.001, 0.007, and 0.003 respectively). The γ-Secretase level in the hippocampus of AC group was significantly higher than that in the HC group (P=0.001). Moreover, the γ-secretase levels in the hippocampus of the AC group were significantly higher compared to AO, AT, and AOT groups (P values: 0.002, 0.001, and 0.001 respectively). There was no significant difference in neprilysin levels of the hippocampus among the research groups (P=0.534). Conclusion: It appears that exercise training and omega-3 consumption, can affect amyloidogenic pathways through reducing the level of γ-secretase, and lead to reduced level of hippocampus Aβ in AD subjects. Therefore, aerobic exercise training and omega-3 intake can be studied as a complementary therapy in Alzheimer’s patients.

Neuronal circuits sustaining neocortical-injury-induced status epilepticus

ObjectivesAcute injuries or insults to the cortex, such as trauma, subarachnoid hemorrhage, lobar hemorrhage, can cause seizures or status epilepticus(SE). Neocortical SE is associated with coma, worse prognosis, delayed recovery, and the development of epilepsy. The anatomical structures progressively recruited during neocortical-onset status epilepticus (SE) is unknown. Therefore, we constructed large-scale maps of brain regions active during neocortical SE. MethodsWe used a neocortical injury-induced SE mouse model. We implanted cobalt (Co) in the right supplementary motor cortex (M2). We 16 h later administered a homocysteine injection (845 mg/kg, intraperitoneal) to C57Bl/6 J mice to induce SE and monitored it by video and EEG. We harvested animals for 1 h (early-stage) and 2 h (late-stage) following homocysteine injections. To construct activation maps, we immunolabeled whole-brain sections for cFos and NeuN, imaged them using a confocal microscope and quantified cFos immunoreactivity (IR). ResultsSE in the early phase consisted of discrete, focal intermittent seizures, which became continuous and bilateral in the late stage. In this early stage, cFos IR was primarily observed in the right hemisphere, ipsilateral to the Co lesion, specifically in the motor cortex, retrosplenial cortex, somatosensory cortex, anterior cingulate cortex, lateral and medial septal nuclei, and amygdala. We observed bilateral cFos IR in brain regions during the late stage, indicating the bilateral spread of focal seizures. We found increased cFOS IR in the bilateral somatosensory cortex and the motor cortex and subcortical regions, including the amygdala, thalamus, and hypothalamus. There was noticeably different, intense cFos IR in the bilateral hippocampus compared to the early stage. In addition, there was higher activity in the cortex ipsilateral to the seizure focus during the late stage compared with the early one. ConclusionWe present a large-scale, high-resolution map of seizure spread during neocortical injury-induced SE. Cortico-cortical and cortico subcortical re-entrant circuits sustain neocortical SE. Neuronal loss following neocortical SE, distant from the neocortical focus, may result from seizures.

Changes in Rat Weight due to Homocysteine Injection as an Animal Model of Alzheimer's Disease

Homocysteine in one of the compounds used to induced alzheimer’s disease in rats. Hyperhomocysteinemia triggers oxidative stress, nerve inflammation and the formation of amyloid-beta in the brain. This can affect a brain region involved in appetite regulation, which leads to weight loss. This study aimed to analyzed weight changes of rats injected with homocysteine for 7, 14 and 21 days. Nine of Sprague dawley rats, aged 8-12 weeks with weight ranging between 150-200 grams, were randomly divided into three groups. The first group was injected with homocysteine for 7 days. The second and third groups received injections with homocysteine for 14 and 21 days respectively. The rats were weighed before treatment and in 7, 14, and 21 days after homocysteine injection. The average weight of rats in each group increases of 3.33±1.15, 5.00±2.00, and 2.33±3.51 grams, respectively. There was a significant difference in weight between before and after homocysteine injection for 7 days in the first group (p=0.038) and 14 days in the second group (p=0.049), while the weight of rats in the third group did not have a significant change (p=0.369). There was no significant difference in weight among the group after homocysteine injection (p=0.182). The weight of alzheimer’s model rats increased slowly after being injected with homocysteine for 7, 14, and 21 days. The low weight gain is similar to the condition of alzheimer’s patients who generally experience weight loss. It is necessary to monitor the food intake of alzheimer’s patients to prevent further weight loss.

Ajwa Date (Phoenix dactylifera L.) Ethanolic Extract Ameliorates Oxidative Stress in Rats: Alzheimer’s Disease Model

Background: Alzheimer’s is a degenerative disease that results in decreased memory and cognitive function. The pathogenesis of Alzheimer’s disease is related to oxidative stress, which can promote damage to the brain. One of the natural ingredients that can be used as a treatment for Alzheimer’s disease is Ajwa dates. Ajwa dates contain lots of phytochemical compounds that act as antioxidants, providing a repair effect against disease.Objective: This study aimed to analyze the effect of dose and duration of Ajwa date extract administration on MDA (malondialdehyde) and SOD (superoxide dismutase) levels in Alzheimer’s model rats.Materials and Methods: Male Sprague Dawley rats, weighing 150-200 g, were orally given Ajwa date extract at dose of 200, 400 and 800 mg/kg body weight/day after the injection of homocysteine. MDA and SOD levels were measured before treatment, day seven and day 14. Data were then analyzed using the Oneway Anova test.Results: The group of Alzheimer’s rats that received Ajwa date extract for seven and 14 days experienced a decrease in MDA levels along with an increase in SOD levels compared to the control group. The group with highest doses had the same effect as the donepezil group on decreasing MDA levels and increasing SOD levels on day 14.Conclusion: Ajwa date fruit extract administration can reduce MDA levels and increase SOD levels in Alzheimer’s model rats. Ajwa dates have the potential for the treatment of Alzheimer’s disease.International Journal of Human and Health Sciences Vol. 05 No. 04 October’21 Page: 435-440

RESVERATROL PROTECT AGAINST HOMOCYSTEINE-INDUCED RENAL DAMAGE THROUGH ANTIOXIDANT ACTION IN SPONTANEOUS HYPERTENSIVE RATS

Objective: The aim of this study was to investigate the effect of resveratrol in renal damage and the underlying mechanism induced by Hhcy in SHRs. Design and method: Twenty-four SHRs were divided into control group, Hhcy group, Hhcy + resveratrol (Hhcy+Res) group. Hhcy groups were given intraperitoneal injection of homocysteine. In addition, the Hhcy + Res group was given resveratrol by gavage. The Systolic blood pressure (SBP), diastolic blood pressure (DBP), plasma Hcy, serum malondialdehyde (MDA), superoxide dismutase (SOD) and the urinary microalbumin (UACR) were measured. To quantify RNA and protein expression levels, the mRNA and the protein expression of nephrin and NADPH oxidase subunits NOX2 and NOX4 in the kidney were examined by quantitative Real-time PCR and western blot. Renal histological or pathological changes were observed under light and electron microscope. Results: There was no difference in blood pressure before and after Hcy or Res intervention among groups. The homocysteine levels in Hhcy and Res group were significantly higher than that in control group, which showed that the model was successfully built by intraperitoneal injection. The serum SOD level was significantly decreased in Hhcy group, while it was increased in Res group. On the contrary, the serum MDA and UACR levels of model group were significantly increased. after the intervention of resveratrol, the MDA and UACR levels were reduced. Furthermore, the expression levels of mRNA and the protein of NOX2 and NOX4 were elevated while those of the nephrin were reduced in Hhcy group. Resveratrol significantly reduced the expressions of NOX2 and NOX4, and increased the expression of nephrin in renal tissue of SHRs with Hhcy. Conclusions: These results suggested that resveratrol may improve renal damage in hypertensive rats with Hhcy by exerting oxidative stress beyond blood pressure.

Hyperhomocysteinemia alters cytokine gene expression, cytochrome c oxidase activity and oxidative stress in striatum and cerebellum of rodents

AimsHomocysteine has been linked to neurodegeneration and motor function impairments. In the present study, we evaluate the effect of chronic mild hyperhomocysteinemia on the motor behavior (motor coordination, functional performance, and muscular force) and biochemical parameters (oxidative stress, energy metabolism, gene expression and/or protein abundance of cytokine related to the inflammatory pathways and acetylcholinesterase) in the striatum and cerebellum of Wistar male rats. Main methodsRodents were submitted to one injection of homocysteine (0.03 μmol Hcy/g of body weight) between 30th and 60th postnatal days twice a day. After hyperhomocysteinemia induction, rats were submitted to horizontal ladder walking, beam balance, suspension, and vertical pole tests and/or euthanized to brain dissection for biochemical and molecular assays. Key findingsChronic mild hyperhomocysteinemia did not alter motor function, but induced oxidative stress and impaired mitochondrial complex IV activity in both structures. In the striatum, hyperhomocysteinemia decreased TNF-α gene expression and increased IL-1β gene expression and acetylcholinesterase activity. In the cerebellum, hyperhomocysteinemia increased gene expression of TNF-α, IL-1β, IL-10, and TGF-β, while the acetylcholinesterase activity was decreased. In both structures, hyperhomocysteinemia decreased acetylcholinesterase protein abundance without altering total p-NF-κB, NF-κB, Nrf-2, and cleaved caspase-3. SignificanceChronic mild hyperhomocysteinemia compromises several biochemical/molecular parameters, signaling pathways, oxidative stress, and chronic inflammation in the striatum and cerebellum of rats without impairing motor function. These alterations may be related to the mechanisms in which hyperhomocysteinemia has been linked to movement disorders later in life and neurodegeneration.

Chronic mild hyperhomocysteinemia induces anxiety-like symptoms, aversive memory deficits and hippocampus atrophy in adult rats: New insights into physiopathological mechanisms

In the last decade, increased homocysteine levels have been implicated as a risk factor for neurodegenerative and psychiatric disorders. We have developed an experimental model of chronic mild hyperhomocysteinemia (HHcy) in order to observe metabolic impairments in the brain of adult rodents. Besides its known effects on brain metabolism, the present study sought to investigate whether chronic mild HHcy could induce learning/memory impairments associated with biochemical and histological damage to the hippocampus. Adult male Wistar rats received daily subcutaneous injections of homocysteine (0.03 μmol/g of body weight) twice a day, from the 30th to the 60th day of life or saline solution (Controls). After injections, anxiety-like and memory tests were performed. Following behavioral analyses, brains were sliced and hippocampal volumes assessed and homogenized for redox state assessment, antioxidant activity, mitochondrial functioning (chain respiratory enzymes and ATP levels) and DNA damage analyses. Behavioral analyses showed that chronic mild HHcy may induce anxiety-like behavior and impair long-term aversive memory (24 h) that was evaluated by inhibitory avoidance task. Mild HHcy decreased locomotor and/or exploratory activities in elevated plus maze test and caused hippocampal atrophy. Decrease in cytochrome c oxidase, DNA damage and redox state changes were also observed in hippocampus of adult rats subjected to mild HHcy. Our findings show that chronic mild HHcy alters biochemical and histological parameters in the hippocampus, leading to behavioral impairments. These findings might be considered in future studies aiming to search for alternative strategies for treating the behavioral impairments in patients with mild elevations in homocysteine levels.

Chronic mild Hyperhomocysteinemia impairs energy metabolism, promotes DNA damage and induces a Nrf2 response to oxidative stress in rats brain.

Homocysteine (HCY) has been linked to oxidative stress and varied metabolic changes that are dependent on its concentration and affected tissues. In the present study we evaluate parameters of energy metabolism [succinate dehydrogenase (SDH), complex II and IV (cytochrome c oxidase), and ATP levels] and oxidative stress [DCFH oxidation, nitrite levels, antioxidant enzymes and lipid, protein and DNA damages, as well as nuclear factor erythroid 2-related (Nrf2) protein abundance] in amygdala and prefrontal cortex of HCY-treated rats. Wistar male rats were treated with a subcutaneous injection of HCY (0.03µmol/g of body weight) from the 30th to 60th post-natal day, twice a day, to induce mild hyperhomocysteinemia (HHCY). The rats were euthanatized without anesthesia at 12h after the last injection, and amygdala and prefrontal cortex were dissected for biochemical analyses. In the amygdala, mild HHCY increased activities of SDH and complex II and decreased complex IV and ATP level, as well as increased antioxidant enzymes activities (glutathione peroxidase and superoxide dismutase), nitrite levels, DNA damage, and Nrf 2 protein abundance. In the prefrontal cortex, mild HHCY did not alter energy metabolism, but increased glutathione peroxidase, catalase and DNA damage. Other analyzed parameters were not altered by HCY-treatment. Our findings suggested that chronic mild HHCY changes each brain structure, particularly and specifically. These changes may be associated with the mechanisms by which chronic mild HHCY has been linked to the risk factor of fear, mood disorders and depression, as well as in neurodegenerative diseases.

Liraglutide Ameliorates Hyperhomocysteinemia-Induced Alzheimer-Like Pathology and Memory Deficits in Rats via Multi-molecular Targeting.

Hyperhomocysteinemia (Hhcy) is an independent risk factor for Alzheimer's disease (AD), and insulin-resistance is commonly seen in patients with Hhcy. Liraglutide (Lir), a glucagon-like peptide that increases the secretion and sensitivity of insulin, has a neurotrophic or neuroprotective effect. However, it is not known whether Lir ameliorates the AD-like pathology and memory deficit induced by Hhcy. By vena caudalis injection of homocysteine to produce the Hhcy model in rats, we found here that simultaneous administration of Lir for 2weeks ameliorated the Hhcy-induced memory deficit, along with increased density of dendritic spines and up-regulation of synaptic proteins. Lir also attenuated the Hhcy-induced tau hyperphosphorylation and Aβ overproduction, and the molecular mechanisms involved the restoration of protein phosphatase-2A activity and inhibition of β- and γ-secretases. Phosphorylated insulin receptor substrate-1 also decreased after treatment with Lir. Our data reveal that Lir improves the Hhcy-induced AD-like spatial memory deficit and the mechanisms involve the modulation of insulin-resistance and the pathways generating abnormal tau and Aβ.

Emodin Rescued Hyperhomocysteinemia-Induced Dementia and Alzheimer’s Disease-Like Features in Rats

BackgroundHyperhomocysteinemia is an independent risk factor for dementia, including Alzheimer’s disease. Lowering homocysteine levels with folic acid treatment with or without vitamin B12 has shown few clinical benefits on cognition.MethodsTo verify the effect of emodin, a naturally active compound from Rheum officinale, on hyperhomocysteinemia-induced dementia, rats were treated with homocysteine injection (HCY, 400 μg/kg/d, 2 weeks) via vena caudalis. Afterwards, HCY rats with cognitive deficits were administered intragastric emodin at different concentrations for 2 weeks: 0 (HCY-E0), 20 (HCY-E20), 40 (HCY-E40), and 80 mg/kg/d (HCY-E80).Resultsβ-Amyloid overproduction, tau hyperphosphorylation, and losses of neuron and synaptic proteins were detected in the hippocampi of HCY-E0 rats with cognitive deficits. HCY-E40 and HCY-E80 rats had better behavioral performance. Although it did not reduce the plasma homocysteine level, emodin (especially 80 mg/kg/d) reduced the levels of β-amyloid and tau phosphorylation, decreased the levels of β-site amyloid precursor protein-cleaving enzyme 1, and improved the activity of protein phosphatase 2A. In the hippocampi of HCY-E40 and HCY-E80 rats, the neuron numbers, levels of synaptic proteins, and phosphorylation of the cAMP responsive element-binding protein at Ser133 were increased. In addition, depressed microglial activation and reduced levels of 5-lipoxygenase, interleukin-6, and tumor necrosis factor α were also observed. Lastly, hyperhomocysteinemia-induced microangiopathic alterations, oxidative stress, and elevated DNA methyltransferases 1 and 3β were rescued by emodin.ConclusionsEmodin represents a novel potential candidate agent for hyperhomocysteinemia-induced dementia and Alzheimer’s disease-like features.

Comparison of effects and electrophysiological mechanisms of action of valproic acid and levetyracetam in an experimental model of focal epilepsy

Introduction. Despite rapid development of the antiepileptic pharmaceuticals market, about 2/3 of patients suffering from epilepsy do not receive adequate treatment, which is partly due to the variety of mechanisms for the development of epileptic seizures Objective. А comparative study of the electrophysiological mechanisms of action and effects of valproic acid (Depakin Chrono) and levetiracetam (Levetinol) under experimental focal epilepsy and status epilepticus (SE) in rats. Materials and methods. Focal chronic epilepsy was caused by the application of cobalt to the sensorimotor cortex. On the 7th–8th day, SE was modeled by the injection of homocysteine, which provoked the development of secondary generalized tonic-clonic seizures. Results. Levetiracetam had a suppressing effect on the paroxysmal activity of the rat brain only under conditions of a stable SE on the 5th–6th day after the application of cobalt. Its most prominant effect was seen in the hippocampus and was characterized by a significant decrease in epileptic activity (EpiA) in this structure and in the maintenance of a regular rhythm. Valproic acid significantly suppressed EpiA in the ipsilateral cortex, hippocampus and hypothalamus at a stable stage of EpiS development, with the most pronounced effect on the primary cortical focus and hypothalamus. In the model of SE caused by the injection of homocysteine, levetiracetam was ineffective, whereas valproic acid decreased the severity of paroxysmal activity in all the studied structures, especially in the cortex (ipsi- and contralateral, 33 times) and hypothalamus (28 times), which was accompanied by suppression of generalized motor manifestations and reduced number of animal deaths. Conclusion. In the model of focal cobalt-induced epilepsy, the hippocampus is the leading structure and the target of the levetiracetam action, while the effect of valroic acid is executed through the inhibitory effect on the cortical foci of EpiA and the hypothalamus, which may be main feature in its ability to suppress the SE.

Folate/Vitamin B Alleviates Hyperhomocysteinemia-Induced Alzheimer-Like Pathologies in Rat Retina.

Hyperhomocysteinemia (Hhcy) is an independent risk factor for Alzheimer's disease (AD). Visual dysfunction is commonly found and is positively correlated with the severity of cognitive defects in AD patients. Our previous study demonstrated that Hhcy induces memory deficits with AD-like tau and amyloid-β (Aβ) pathologies in the hippocampus, and supplementation with folate and vitamin B12 (FB) prevents the Hhcy-induced AD-like pathologies in the hippocampus. Here, we investigated whether Hhcy also induces AD-like pathologies in the retina and the effects of FB. An Hhcy rat model was produced by vena caudalis injection of homocysteine for 14days, and the effects of FB were assessed by simultaneous supplementation with FB in drinking water. We found that Hhcy induced vessel damage with Aβ and tau pathologies in the retina, while simultaneous supplementation with FB remarkably attenuated the Hhcy-induced tau hyperphosphorylation at multiple AD-related sites and Aβ accumulation in the retina. The mechanisms involved downregulation of amyloid precursor protein (APP), presenilin-1, beta-site APP-cleaving enzyme 1, and protein phosphatase-2A. Our data suggest that the retina may serve as a window for evaluating the effects of FB on hyperhomocysteinemia-induced Alzheimer-like pathologies.

Accumulation of Cholesterol and Homocysteine in the Nigrostriatal Pathway of Brain Contributes to the Dopaminergic Neurodegeneration in Mice

Elevated levels of cholesterol (hypercholesterolemia) and homocysteine (hyperhomocysteinemia, HHcy) in blood have been linked with the pathology of Parkinson’s disease. However, the impact of their combined effect on brain is unknown. The present study aims to investigate the effect of HHcy on dopaminergic neurons in brain of mice with hypercholesterolemia. Mice were subjected to a high-cholesterol diet for 12 weeks to develop hypercholesterolemia, and were administered with homocysteine (250 mg/kg, b.w., i.p., 60 days) daily starting from 24th day of the high-cholesterol diet for induction of HHcy. The animals were subjected to Parkinsonian motor behavioral tests and sacrificed to estimate the levels of cholesterol, homocysteine and dopamine in brain, and to assess dopaminergic neuronal status. There occurred elevation in cholesterol and homocysteine levels in nigrostriatum of hypercholesterolemic animals with HHcy. Injection of homocysteine in hypercholesterolemic mice exacerbated the motor abnormalities as well as caused depletion of striatal dopamine level significantly, which was supported by a significant decrease in tyrosine hydroxylase (TH) immunoreactivity in striatum. While neither hypercholesterolemia nor HHcy caused significant changes in the number of TH-positive neurons, hypercholesterolemia in combination with HHcy resulted in a significant loss of nigral TH-positive neurons. The results highlighted the involvement of mitochondrial complex-I dysfunction with subsequent generation of hydroxyl radicals for the observed loss of midbrain dopamine neurons in animals receiving the combined treatment. Thus, the findings of the present study pointed out the combined effect of homocysteine and cholesterol toward dopamine neuronal dysfunctions, which has substantial relevance to Parkinson’s disease.

Epigallocatechin-3-Gallate Protects against Homocysteine-Induced Brain Damage in Rats.

High levels of homocysteine are implicated in many neurovascular and neurodegeneration diseases. Epigallocatechin 3-gallate (EGCG), one of green tea polyphenols, has potential anti-oxidative and anti-inflammatory activities. However, it has not been explored whether EGCG has an effect on homocysteine-induced neuro-inflammation and neurodegeneration. In this study, we investigated the effects of EGCG on memory deficit, oxidative stress, neuro-inflammation, and neurodegeneration in hyper-homocysteinemic rats after a 2 wk homocysteine injection by vena caudalis. We found that supplementation of EGCG could rescue deficit of spatial memory induced by homocysteine. Treatment of EGCG significantly reduced the expression of malondialdehyde, glial fibrillary acidic protein, tumor necrosis factor-α, and interleukin-1β and increased glutathione level in the homocysteine-treated group. In TdT-mediated dUTP nick end labeling (TUNEL) assay and Fluoro-Jade B staining, supplementation of EGCG could attenuate the apoptotic neurons and neurodegeneration. Interestingly, EGCG significantly ameliorated homocysteine-induced cerebrovascular injury. Our data suggest that EGCG could be a promising candidate for arresting homocysteine-induced neurodegeneration and neuro-inflammation in the brain.

HYPERHOMOCYSTEINEMIA IMPAIRS SYNAPTIC PLASTICITY BY MODULATION SYNAPSE-ASSOCIATED PROTEINS IN RAT

Hyperhomocysteinemia (HHcy)—abnormally elevated plasma levels of homocysteine (Hcy)—has been associated with the development of neurodegenerative dementia, such as Alzheimer's disease (AD). This association suggests that HHcy might facilitate memory loss in the elderly. In our lab, we had revealed that HHcy is harmful to the spatial memory and induces Alzheimer-like pathological changes in rats by vena caudalis injection of Hcy for 2 weeks. Learning and memory require orchestrated regulation of both structural and functional synaptic plasticity in the hippocampus. However, the effects of HHcy on synaptic plasticity remains unclear. Using Morris water-maze, we explored spatial memory in hyperhomocysteinemic rats after a 2-week induction by vena caudalis injection of homocysteine as previous reported in our lab. For measurement of synaptic plasticity, Golgi staining was used to analyse dendritic morphology and spine density in hippocampal dentate gyrus (DG) and CA1 neurons, and perforant path to DG (PP-DG) long-term potentiation (LTP) was recorded. Immunohistochemistry and western blot were used to detect explore the memory-related proteins. We found that hyperhomocysteinemia impaired spatial memory by Morris water-maze. HHcy impaired PP-DG LTP with reduction of CREB protein level. Calcium/calmodulin-dependent protein kinase II (CaMKII), highly expressed in brain, plays a pivotal role in synaptic plasticity. We found that the ratio of pT286CaMKII/tCaMKII (activation) was significantly increased in HHcy group, suggesting Hcy overactive CaMKII might involved memory deficits. Notably, HHcy decreased dendritic branches crossings and density of the dendritic spines, with down-regulation of synapsin I, synaptophysin, GluR1, GluR2, NR2B, and NR2A protein levels. These changes still existed in 1 week and then disappeared in 4 weeks after the end of Hcy injection. We conclude that hyperhomocysteinemia impairs the synaptic plasticity by modulation synapse-associated proteins, which may underlie hyperhomocysteinemia involved memory deficits.

Creatine prevents the imbalance of redox homeostasis caused by homocysteine in skeletal muscle of rats

Homocystinuria is a neurometabolic disease caused by severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction, being that the pathomechanism is not fully understood. In the present study we investigated the effect of chronic hyperhomocysteinemia on some parameters of oxidative stress, namely 2'7'dichlorofluorescein (DCFH) oxidation, levels of thiobarbituric acid-reactive substances (TBARS), antioxidant enzyme activities (SOD, CAT and GPx), reduced glutathione (GSH), total sulfhydryl and carbonyl content, as well as nitrite levels in soleus skeletal muscle of young rats subjected to model of severe hyperhomocysteinemia. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injection of homocysteine (0.3-0.6 μmol/g body weight), and/or creatine (50mg/kg body weight) from their 6th to the 28th days age. Controls and treated rats were decapitated at 12h after the last injection. Chronic homocysteine administration increased 2'7'dichlorofluorescein (DCFH) oxidation, an index of production of reactive species and TBARS levels, an index of lipoperoxidation. Antioxidant enzyme activities, such as SOD and CAT were also increased, but GPx activity was not altered. The content of GSH, sulfhydril and carbonyl were decreased, as well as levels of nitrite. Creatine concurrent administration prevented some homocysteine effects probably by its antioxidant properties. Our data suggest that the oxidative insult elicited by chronic hyperhomocystenemia may provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function. Creatine prevents some alterations caused by homocysteine.

Betaine attenuates Alzheimer‐like pathological changes and memory deficits induced by homocysteine

Hyperhomocysteinemia (Hhcy) may induce memory deficits with β-amyloid (Aβ) accumulation and tau hyperphosphorylation. Simultaneous supplement of folate and vitamin B12 partially restored the plasma homocysteine level and attenuated tau hyperphosphorylation, Aβ accumulation and memory impairments induced by Hhcy. However, folate and vitamin B12 treatment have no effects on Hhcy which has the methylenetetrahydrofolate reductase genotype mutation. In this study, we investigated the effects of simultaneous supplement of betaine on Alzheimer-like pathological changes and memory deficits in hyperhomocysteinemic rats after a 2-week induction by vena caudalis injection of homocysteine (Hcy). We found that supplementation of betaine could ameliorate the Hcy-induced memory deficits, enhance long-term potentiation (LTP) and increase dendritic branches numbers and the density of the dendritic spines, with up-regulation of NR1, NR2A, synaptotagmin, synaptophysin, and phosphorylated synapsin I protein levels. Supplementation of betaine also attenuated the Hcy-induced tau hyperphosphorylation at multiple AD-related sites through activation protein phosphatase-2A (PP2A) with decreased inhibitory demethylated PP2A(C) at Leu309 and phosphorylated PP2A(C) at Tyr307. In addition, supplementation of betaine also decreased Aβ production with decreased presenilin-1 protein levels. Our data suggest that betaine could be a promising candidate for arresting Hcy-induced AD-like pathological changes and memory deficits.

Homocysteine induces energy imbalance in rat skeletal muscle: Is creatine a protector?

Homocystinuria is a neurometabolic disease caused by a severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction. In this study, we investigated the effect of chronic hyperhomocysteinemia on the cell viability of the mitochondrion, as well as on some parameters of energy metabolism, such as glucose oxidation and activities of pyruvate kinase, citrate synthase, isocitrate dehydrogenase, malate dehydrogenase, respiratory chain complexes and creatine kinase in gastrocnemius rat skeletal muscle. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injections of homocysteine (0.3-0.6 µmol/g body weight) and/or creatine (50 mg/kg body weight) from the 6th to the 28th days of age. The animals were decapitated 12 h after the last injection. Homocysteine decreased the cell viability of the mitochondrion and the activities of pyruvate kinase and creatine kinase. Succinate dehydrogenase was increased other evaluated parameters were not changed by this amino acid. Creatine, when combined with homocysteine, prevented or caused a synergistic effect on some changes provoked by this amino acid. Creatine per se or creatine plus homocysteine altered glucose oxidation. These findings provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function, more studies are needed to elucidate them. Although creatine prevents some alterations caused by homocysteine, it should be used with caution, mainly in healthy individuals because it could change the homeostasis of normal physiological functions.

Evidence that AKT and GSK-3β pathway are involved in acute hyperhomocysteinemia

Homocysteine is a neurotoxic amino acid that accumulates in several disorders including homocystinuria, neurodegenerative and neuroinflammatory diseases. In the present study we evaluated the effect of acute and chronic hyperhomocysteinemia on Akt, NF-κB/p65, GSK-3β, as well as Tau protein in hippocampus of rats. For acute treatment, rats received a single injection of homocysteine (0.6μmol/g body weight) or saline (control). For chronic treatment, rats received daily subcutaneous injections of homocysteine (0.3–0.6μmol/g body weight) or saline (control) from the 6th to the 28th days-of-age. One or 12h after the last injection, rats were euthanized, the hippocampus was removed and samples were submitted to electrophoresis followed by Western blotting. Results showed that acute hyperhomocysteinemia increases Akt phosphorylation, cytosolic and nuclear immunocontent of NF-κB/p65 subunit and Tau protein phosphorylation, but reduces GSK-3β phosphorylation at 1h after homocysteine injection. However, 12h after acute hyperhomocysteinemia there is no effect on Akt and GSK-3β phosphorylation. Furthermore, chronic hyperhomocysteinemia did not alter Akt and GSK-3β phosphorylation at 1h and 12h after the last administration of this amino acid. Our data showed that Akt, NF-κB/p65, GSK-3β and Tau protein are activated in hippocampus of rats subjected to acute hyperhomocysteinemia, suggesting that these signaling pathways may be, at least in part, important contributors to the neuroinflammation and/or brain dysfunction observed in some hyperhomocystinuric patients.