p38 MAPK inhibitor SB202190 suppresses ferroptosis in the glutamate-induced retinal excitotoxicity glaucoma model

Glutamate excitotoxicity has been shown to play an important role in glaucoma, and glutamate can induce ferroptosis. The p38 mitogenactivated protein kinase(MAPK) pathway inhibitor SB202190 has a potential ability to suppress ferroptosis, and its downstream targets, such as p53, have been shown to be associated with ferroptosis. However, whether ferroptosis also occurs in retinal ganglion cells in response to glutamate excitotoxicity and whether inhibition of ferroptosis reduces the loss of retinal ganglion cells induced by glutamate excitotoxicity remain unclear. This study investigated ferroptosis in a glutamate-induced glaucoma rat model and explored the effects and molecular mechanisms of SB202190 on retinal ganglion cells. A glutamate-induced excitotoxicity model in R28 cells and an N-methyl-D-aspartate-induced glaucoma model in rats were used. In vitro experiments showed that glutamate induced the accumulation of iron and lipid peroxide and morphological changes of mitochondria in R28 cells, and SB202190 inhibited these changes. Glutamate induced the levels of p-p38 MAPK/p38 MAPK and SAT1 and decreased the expression levels of ferritin light chain, SLC7A11, and GPX4. SB202190 inhibited the expression of iron death-related proteins induced by glutamate. In vivo experiments showed that SB202190 attenuated N-methyl-D-aspartate-induced damage to rat retinal ganglion cells and improved visual function. These results suggest that SB202190 can inhibit ferroptosis and protect retinal ganglion cells by regulating ferritin light chain, SAT1, and SLC7A11/Gpx4 pathways and may represent a potential retina protectant.

Adenosine A_(2A)receptor blockade attenuates excitotoxicity in rat striatal medium spiny neurons during an ischemic-like insult

During brain ischemia,excitotoxicity and peri-infarct depolarization injuries occur and cause cerebral tissue damage.Indeed,anoxic depolarization,consisting of massive neuronal depolarization due to the loss of membrane ion gradients,occurs in vivo or in vitro during an energy failure.The neuromodulator adenosine is released in huge amounts during cerebral ischemia and exerts its effects by activating specific metabotropic receptors,namely:A_(1),A_(2A),A_(2B),and A_(3).The A_(2A)receptor subtype is highly expressed in striatal medium spiny neurons,which are particularly susceptible to ischemic damage.Evidence indicates that the A2Areceptors are upregulated in the rat striatum after stroke and the selective antagonist SCH58261 protects from exaggerated glutamate release within the first 4 hours from the insult and alleviates neurological impairment and histological injury in the following 24 hours.We recently added new knowledge to the mechanisms by which the adenosine A2Areceptor subtype participates in ischemia-induced neuronal death by performing patch-clamp recordings from medium spiny neurons in rat striatal brain slices exposed to oxygen and glucose deprivation.We demonstrated that the selective block of A2Areceptors by SCH58261 significantly reduced ionic imbalance and delayed the anoxic depolarization in medium spiny neurons during oxygen and glucose deprivation and that the mechanism involves voltage-gated K+channel modulation and a presynaptic inhibition of glutamate release by the A2Areceptor antagonist.The present review summarizes the latest findings in the literature about the possibility of developing selective ligands of A2Areceptors as advantageous therapeutic tools that may contribute to counteracting neurodegeneration after brain ischemia.

Adipose mesenchymal stem cell-derived extracellular vesicles reduce glutamate-induced excitotoxicity in the retina

Adipose mesenchymal stem cells(ADSCs)have protective effects against glutamate-induced excitotoxicity,but ADSCs are limited in use for treatment of optic nerve injury.Studies have shown that the extracellular vesicles(EVs)secreted by ADSCs(ADSC-EVs)not only have the function of ADSCs,but also have unique advantages including non-immunogenicity,low probability of abnormal growth,and easy access to target cells.In the present study,we showed that intravitreal injection of ADSC-EVs substantially reduced glutamate-induced damage to retinal morphology and electroretinography.In addition,R28 cell pretreatment with ADSC-EVs before injury inhibited glutamate-induced overload of intracellular calcium,downregulation ofα-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor(AMPAR)subunit GluA2,and phosphorylation of GluA2 and protein kinase C alpha in vitro.A protein kinase C alpha agonist,12-O-tetradecanoylphorbol 13-acetate,inhibited the neuroprotective effects of ADSC-EVs on glutamate-induced R28 cells.These findings suggest that ADSCEVs ameliorate glutamate-induced excitotoxicity in the retina through inhibiting protein kinase C alpha activation.

Bis(7)-tacrine protects retinal ganglion cells against excitotoxicity via NMDA receptor inhibition

AIM: To investigate whether bis (7)-tacrine, a multifunctional drug, inhibits N-methyl-D-aspartate (NMDA) -activated current in retinal ganglion cells (RGC) and provides neuroprotection against retinal cell damage. METHODS: Purified RGC cultures were obtained from retinas of 1-3 days old Sprague-Dawley (SD) rats, following a two-step immunopanning procedure. After 7 days of cultivation, the inhibition of NMDA-activated current by bis(7) -tacrine was measured by using patch-clamp recording techniques. In animal experiments, RGCs were damaged after intravitreal injection of NMDA (5 mu L, 40nmol) in adult rats. Bis (7)-tacrine(0.05, 0.1, 0.2mg/kg) or memantine(20mg/kg) was intraperitoneal administered to the rats fifteen minutes before intravitreally injection of NMDA. RGC damage was analyzed by histologic techniques, TUNEL and retrograde labeling techniques. RESULTS: Whole-cell patch-clamp recordings demonstrated that NMDA (30 mu mol/L) resulted in approximately -50 pA inward currents that were blocked by bis (7)-tacrine (1 mu mol/L). Histological examination and retrograde labeling analysis revealed that bis (7)-tacrine induced a significant neuroprotective effect against NMDA-induced cell damage 7 days after NMDA injection. TUNEL staining showed that pretreatment with bis(7)-tacrine was effective in ameliorating NMDA-induced apoptotic cell loss in the retinal ganglion cell layer 18 hours after injection. CONCLUSION: Bis (7)-tacrine possesses remarkable neuroprotective activities against retinal excitotoxicity through inhibition of NMDA receptors.

Molecular mechanisms of NMDA receptor-mediated excitotoxicity:implications for neuroprotective therapeutics for stroke

Excitotoxicity is a process observed in many disease states by which an excessive synaptic excitation causes neuronal death, and is thought to be triggered by the extracellular accumulation of the excitatory neurotransmitter glutamate, which binds and activates ionotropic N-methyl-D-aspartate glutamatergic receptors （NMDARs） in the brain. Normally, NMDARs mediate calcium entry into the cell to regulate physiological processes such as synaptic plasticity and memory,

Involvement of mitogen-activated protein kinase pathways in N-methyl-D-aspartate-induced excitotoxicity

Previous studies have shown that mitogen-activated protein kinase （MAPK） signaling pathways are involved in N-methyI-D-aspartate （NMDA）-mediated excitotoxicity. However, a systematic observation or analysis of the role of these various MAPK pathways in excitotoxicity processes does not exist. The present study further evaluated the role and contribution of three MAPK pathways extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAPK in an NMDA-mediated excitotoxicity model using MAPK^specific inhibitor. Results demonstrated that c-Jun N-terminal kinase inhibitor SP600125 and/or p38 MAPK inhibitor SB203580 inhibited NMDA-induced reduction in cell viability, as well as reduced NMDA-induced lactate dehydrogenase leakage and reactive oxygen species production. However, PD98059, an inhibitor of extracellular signal-regulated kinase, did not influence this model. Results demonstrated an involvement of c-Jun N-terminal kinase and p38 MAPK, but not extracellular signal-regulated kinase, in NMDA-mediated excitotoxicity in cortical neurons.

Neurochemical plasticity of Müller cells after retinal injury: overexpression of GAT-3 may potentiate excitotoxicity

The retina is a multilayered tissue that develops following a central-to-peripheral gradient. Its structure derives from multipotent precursors, as shown through clonal analysis of retinal cell lineage. These progenitors generate diverse cell types, controlled by complex influences of intrinsic and extrinsic factors （Hatakevama and Kagevama, 2004）.

Glutamate and excitotoxicity in central nervous system disorders:ionotropic glutamate receptors as a target for neuroprotection

Recent advances in neuroscience have illuminated the central role of glutamate dysregulation in various neurological disorders.The glutamatergic system has emerged as a central player in the pathophysiology of various neurological disorders.The dysregulation of glutamate signaling,leading to excitotoxicity and neuronal cell death,has been a focal point in understanding the underlying mechanisms of these conditions.This has prompted a paradigm shift in neuroprotection research,with a growing emphasis on targeting ionotropic glutamate receptors(iGluRs)to restore glutamatergic homeostasis.This review provides a comprehensive overview of recent advancements in the field of iGluR-targeted neuroprotection.We further investigate the implications of glutamate dysregulation in the central nervous system(CNS)disorders,highlighting the complex interplay between excitotoxicity and neuroprotection.We elucidate the multifaceted factors that render neurons vulnerable to excitotoxic damage,emphasizing the need for innovative therapeutic approaches.This review provides an extensive survey of the burgeoning field of iGluR-targeted neuroprotection.It showcases the significant potential of a wide array of compounds,encompassing both natural and synthetic agents,to modulate iGluRs and ameliorate excitotoxicity and oxidative stress-induced neuronal damage.These compounds have demonstrated impressive neuroprotective effects in diverse experimental models,from glutamate-induced toxicity to traumatic brain injuries.We advocate for further research and clinical investigations to harness the full therapeutic potential of iGluR modulation,heralding a promising era in neuroprotection and CNs disorder management.

Ruxolitinib improves the inflammatory microenvironment,restores glutamate homeostasis,and promotes functional recovery after spinal cord injury

The inflammatory microenvironment and neurotoxicity can hinder neuronal regeneration and functional recovery after spinal cord injury.Ruxolitinib,a JAK-STAT inhibitor,exhibits effectiveness in autoimmune diseases,arthritis,and managing inflammatory cytokine storms.Although studies have shown the neuroprotective potential of ruxolitinib in neurological trauma,the exact mechanism by which it enhances functional recovery after spinal cord injury,particularly its effect on astrocytes,remains unclear.To address this gap,we established a mouse model of T10 spinal cord contusion and found that ruxolitinib effectively improved hindlimb motor function and reduced the area of spinal cord injury.Transcriptome sequencing analysis showed that ruxolitinib alleviated inflammation and immune response after spinal cord injury,restored EAAT2 expression,reduced glutamate levels,and alleviated excitatory toxicity.Furthermore,ruxolitinib inhibited the phosphorylation of JAK2 and STAT3 in the injured spinal cord and decreased the phosphorylation level of nuclear factor kappa-B and the expression of inflammatory factors interleukin-1β,interleukin-6,and tumor necrosis factor-α.Additionally,in glutamate-induced excitotoxicity astrocytes,ruxolitinib restored EAAT2 expression and increased glutamate uptake by inhibiting the activation of STAT3,thereby reducing glutamate-induced neurotoxicity,calcium influx,oxidative stress,and cell apoptosis,and increasing the complexity of dendritic branching.Collectively,these results indicate that ruxolitinib restores glutamate homeostasis by rescuing the expression of EAAT2 in astrocytes,reduces neurotoxicity,and effectively alleviates inflammatory and immune responses after spinal cord injury,thereby promoting functional recovery after spinal cord injury.

On implications of somatostatin in diabetic retinopathy

Somatostatin,a naturally produced neuroprotective peptide,depresses excitatory neurotransmission and exerts anti-proliferative and anti-inflammatory effects on the retina.In this review,we summarize the progress of somatostatin treatment of diabetic retinopathy through analysis of relevant studies published from February 2019 to February 2023 extracted from the PubMed and Google Scholar databases.Insufficient neuroprotection,which occurs as a consequence of declined expression or dysregulation of retinal somatostatin in the very early stages of diabetic retinopathy,triggers retinal neurovascular unit impairment and microvascular damage.Somatostatin replacement is a promising treatment for retinal neurodegeneration in diabetic retinopathy.Numerous pre-clinical and clinical trials of somatostatin analog treatment for early diabetic retinopathy have been initiated.In one such trial(EUROCONDOR),topical administration of somatostatin was found to exert neuroprotective effects in patients with pre-existing retinal neurodysfunction,but had no impact on the onset of diabetic retinopathy.Overall,we concluded that somatostatin restoration may be especially beneficial for the growing population of patients with early-stage retinopathy.In order to achieve early prevention of diabetic retinopathy initiation,and thereby salvage visual function before the appearance of moderate non-proliferative diabetic retinopathy,several issues need to be addressed.These include the needs to:a)update and standardize the retinal screening scheme to incorporate the detection of early neurodegeneration,b)identify patient subgroups who would benefit from somatostatin analog supplementation,c)elucidate the interactions of somatostatin,particularly exogenously-delivered somatostatin analogs,with other retinal peptides in the context of hyperglycemia,and d)design safe,feasible,low cost,and effective administration routes.

Excitotoxicity effects of glutamate on human neuroblastoma SH-SY5Y cells via oxidative damage

Objective To investigate the mechanisms of excitotoxic effects of glutamate on human neuroblastoma SH-SY5Y cells. Methods SH-SY5Y cell viability was measured by MTT assay. Other damaged profile was detected by lactate dehydrogenase （LDH） release and by 4＇, 6-diamidino-2-phenylindole （DAPI） staining. The cytosolic calcium concentration was tested by calcium influx assay. The glutamate-induced oxidative stress was analyzed by cytosolic glutathione assay, superoxide dismutase （SOD） assay and extracellular malondialdehyde （MDA） assay. Results Glutamate treatment caused damage in SH- SY5Y cells, including the decrease of cell viability, the increase of LDH release and the alterations of morphological structures. Furthermore, the concentration of cytoplasmic calcium in SH-SY5Y cells was not changed within 20 min following glutamate treatment, while cytosolic calcium concentration significantly increased within 24 h after glutamate treatment, which could not be inhibited by MK801, an antagonist of NMDA receptors, or by LY341495, an antagonist of metabotropic glutamate receptors. On the other hand, oxidative damage was observed in SH-SY5Y cells treated with glutamate, including decreases in glutathione content and SOD activity, and elevation of MDA level, all of which could be alleviated by an antioxidant Tanshinone IIA （Tan IIA, a major active ingredient from a Chinese plant Salvia Miltiorrhiza Bge）. Conclusion Glutamate exerts toxicity in human neuroblastoma SH-SY5Y cells possibly through oxidative damage, not through calcium homeostasis destruction mediated by NMDA receptors.

Excitotoxicity, calcium and mitochondria: a triad in synaptic neurodegeneration

Glutamate is the most commonly engaged neurotransmitter in the mammalian central nervous system,acting to mediate excitatory neurotransmission.However,high levels of glutamatergic input elicit excitotoxicity,contribut-ing to neuronal cell death following acute brain injuries such as stroke and trauma.While excitotoxic cell death has also been implicated in some neurodegenerative disease models,the role of acute apoptotic cell death remains controversial in the setting of chronic neurodegeneration.Nevertheless,it is clear that excitatory synaptic dysregula-tion contributes to neurodegeneration,as evidenced by protective effects of partial N-methyl-D-aspartate receptor antagonists.Here,we review evidence for sublethal excitatory injuries in relation to neurodegeneration associated with Parkinson’s disease,Alzheimer’s disease,amyotrophic lateral sclerosis and Huntington’s disease.In contrast to classic excitotoxicity,emerging evidence implicates dysregulation of mitochondrial calcium handling in excitatory post-synaptic neurodegeneration.We discuss mechanisms that regulate mitochondrial calcium uptake and release,the impact of LRRK2,PINK1,Parkin,beta-amyloid and glucocerebrosidase on mitochondrial calcium transporters,and the role of autophagic mitochondrial loss in axodendritic shrinkage.Finally,we discuss strategies for normalizing the flux of calcium into and out of the mitochondrial matrix,thereby preventing mitochondrial calcium toxicity and excitotoxic dendritic loss.While the mechanisms that underlie increased uptake or decreased release of mitochondrial calcium vary in different model systems,a common set of strategies to normalize mitochondrial calcium flux can prevent excitatory mitochondrial toxicity and may be neuroprotective in multiple disease contexts.

Neuroprotective strategies for NMDAR-mediated excitotoxicity in Huntington＇s Disease

BACKGROUND： Huntington＇s Disease （HD） is an autosomal dominant neurodegenerative disease causing severe neurodegeneration of the striatum as well as marked cognitive and motor disabilities. Excitotoxicity, caused by overstimulation of NMDA receptors （NMDARs） has been shown to have a key role in the neuropathogenesis of liD, suggesting that targeting NMDAR-dependent signaling may be an effective clinical approach for HD. However, broad NMDAR antagonists are generally poor therapeutics in clinical practice. It has been suggested that GluN2A-containing, synaptically located NMDARs activate cell survival signaling pathways, while GluN2B-containing, primarily extrasynaptic NMDARs trigger cell death signaling. A better approach to development of effective therapeutics for HD may be to target, specifically, the cell-death specific pathways associated with extrasynaptic GluN2B NMDAR activation, while maintaining or potentiating the cell- survival activity of GluN2A-NMDARs. OBJECTIVE： This review outlines the role of NMDAR-mediated excitotoxicity in HD and overviews current efforts to develop better therapeutics for HD where NMDAR excitotoxicity is the target. METHODS： A systematic review process was conducted using the PubMed search engine focusing on research conducted in the past 5-10 years. 235 articles were consulted for the review, with key search terms including ＂Huntington＇s Disease,＂ ＂excitotoxicity,＂ ＂NMDAR＂ and ＂therapeutics.＂ RESULTS： A wide range of NMDAR excitotoxicity-based targets for HD were identified and reviewed, including targeting NMDARs directly by blocking GluN2B, extrasynaptic NMDARs and/or potentiating GluN2A, synaptic NMDARs, targeting glutamate release or uptake, or targeting specific downstream cell-death signaling of NMDARs. CONCLUSION： The current review identifies NMDAR-mediated excitotoxicity as a key player in HD pathogenesis and points to various excitotoxicity-focused targets as potential future preventative therapeutics for HD.

Effects of antisense oligodeoxynucleotides to NR1 on suppression of seizures and protection of cortical neurons from excitotoxicity in vivo and in vitro

Objective To investigate the effects of NR1 subunit on the initiation and development of seizures and protection of cortical neurons from excitotoxicity by using antisense oligodeoxynucleotides (ODN) to NR1 in vivo and in vitro. Methods Intracerebroventricular injection, temporal cortex slices discharge, cerebral cortical neuronal culture, induction of neurotoxicity and MK 801 binding were used in this study. Results After an antisense ODN for NR1 was administered intracerebroventricularly (i.c.v. 100 μg in 10 μl) once daily, for three days in genetically epilepsy prone rats (GEPR, P77PMC), the animals did not develop any clonic and tonic convulsions and their seizure scores were significantly lower compared to the control groups. The frequency and amplitude of early seizure like events (SLEs) and late reccurrent discharges (LRD), induced by lowering Mg 2+ , were reduced in entorhinal cortex (EC) of the temporal cortex slice treated by antisense ODNs. Pretreatment with antisense ODN (2 μM) protected more than 52% of glutamate sensitive neurons and reduced the MK 801 binding to 50% in cultured cerebral cortical neurons. Conclusions N methy D aspartate receptors(NMDAR), specifically the NR1 subunit, may participate and play important roles in the initiation and propagation of epilepsy in the P77PMC rat.

Neurosteroids as stress modulators and neurotherapeutics: lessons from the retina

Neurosteroids are rapidly emerging as important new therapies in neuropsychiatry, with one such agent, brexanolone, already approved for treatment of postpartum depression, and others on the horizon. These steroids have unique properties, including neuroprotective effects that could benefit a wide range of brain illnesses including depression, anxiety, epilepsy, and neurodegeneration. Over the past 25 years, our group has developed ex vivo rodent models to examine factors contributing to several forms of neurodegeneration in the retina. In the course of this work, we have developed a model of acute closed angle glaucoma that involves incubation of ex vivo retinas under hyperbaric conditions and results in neuronal and axonal changes that mimic glaucoma. We have used this model to determine neuroprotective mechanisms that could have therapeutic implications. In particular, we have focused on the role of both endogenous and exogenous neurosteroids in modulating the effects of acute high pressure. Endogenous allopregnanolone, a major stress-activated neurosteroid in the brain and retina, helps to prevent severe pressure-induced retinal excitotoxicity but is unable to protect against degenerative changes in ganglion cells and their axons under hyperbaric conditions. However, exogenous allopregnanolone, at a pharmacological concentration, completely preserves retinal structure and does so by combined effects on gamma-aminobutyric acid type A receptors and stimulation of the cellular process of macroautophagy. Surprisingly, the enantiomer of allopregnanolone, which is inactive at gamma-aminobutyric acid type A receptors, is equally retinoprotective and acts primarily via autophagy. Both enantiomers are also equally effective in preserving retinal structure and function in an in vivo glaucoma model. These studies in the retina have important implications for the ongoing development of allopregnanolone and other neurosteroids as therapeutics for neuropsychiatric illnesses.

Achyranthes bidentata polypeptides prevent apoptosis by inhibiting the glutamate current in cultured hippocampal neurons

Glutamate-induced excitotoxicity plays a critical role in the neurological impairment caused by middle cerebral artery occlusion.Achyranthes bidentata polypeptides have been shown to protect against neurological functional damage caused by middle cerebral artery occlusion,but the underlying neuroprotective mechanisms and the relationship to glutamate-induced excitotoxicity remain unclear.Therefore,in the current study,we investigated the protective effects of Achyranthes bidentata polypeptides against glutamate-induced excitotoxicity in cultured hippocampal neurons.Hippocampal neurons were treated with Mg^2+-free extracellular solution containing glutamate(300μM)for 3 hours as a model of glutamate-mediated excitotoxicity(glutamate group).In the normal group,hippocampal neurons were incubated in Mg^2+-free extracellular solution.In the Achyranthes bidentata polypeptide group,hippocampal neurons were incubated in Mg^2+-free extracellular solution containing glutamate(300μM)and Achyranthes bidentata polypeptide at different concentrations.At 24 hours after exposure to the agents,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Hoechst 33258 staining were used to assess neuronal viability and nuclear m'orphology,respectively.Caspase-3 expression and activity were evaluated using western blot assay and colorimetric enzymatic assay,respectively.At various time points after glutamate treatment,reactive oxygen species in cells were detected by H2 DCF-DA,and mitochondrial membrane potential was detected by rhodamine 123 staining.To examine the effect of Achyranthes bidentata polypeptides on glutamate receptors,electrophysiological recording was used to measure the glutamate-induced inward current in cultured hippocampal neurons.Achyranthes bidentata polypeptide decreased the percentage of apoptotic cells and reduced the changes in caspase-3 expression and activity induced by glutamate.In addition,Achyranthes bidentata polypeptide attenuated the amplitude of the glutamate-induced current.Furthermore,the glutamate-induced increase in intracellular reactive oxygen species and reduction in mitochondrial membrane potential were attenuated by Achyranthes bidentata polypeptide treatment.These findings collectively suggest that Achyranthes bidentata polypeptides exert a neuroprotective effect in cultured hippocampal neurons by suppressing the overactivation of glutamate receptors and inhibiting the caspase-3-dependent mitochondrial apoptotic pathway.All animal studies were approved by the Animal Care and Use Committee,Nantong University,China(approval No.20120216-001)on February 16,2012.

Mechanisms of secondary degeneration after partial optic nerve transection

Secondary degeneration occurs commonly in the central nervous system after traumatic injuries and following acute and chronic diseases, including glaucoma. A constellation of mechanisms have been shown to be associated with secondary degeneration including apoptosis, necrosis, autophagy, oxidative stress, excitotoxicity, derangements in ionic homeostasis and calcium influx. Glial cells, such as microglia, astrocytes and oligodendrocytes, have also been demon- strated to take part in the process of secondary injury. Partial optic nerve transection is a useful model which was established about 13 years ago. The merit of this model compared with other optic nerve injury models used for glaucoma study, including complete optic nerve transection model and optic nerve crush model, is the possibility to separate primary degeneration from secondary degeneration in location. Therefore, it provides a good tool for the study of secondary degeneration. This review will focus on the research progress of the mechanisms of secondary degeneration using partial optic nerve transection model.

Neuroprotective potential of Quercetin in combination with piperine against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity

1-Methy-4-phenyl-1,2,3,6-tetrahydropyridine（MPTP）is a neurotoxin that selectively damages dopaminergic neurons in the substantia nigra pars compacta and induces Parkinson＇s like symptoms in rodents.Quercetin（QC）is a natural polyphenolic bioflavonoid with potent antioxidant and anti-inflammatory properties but lacks of clinical attraction due to low oral bioavailability.Piperine is a well established bioavailability enhancer used pre-clinically to improve the bioavailability of antioxidants（e.g.,Quercetin）.Therefore,the present study was designed to evaluate the neuroprotective potential of QC together with piperine against MPTP-induced neurotoxicity in rats.MPTP（100μg/μL/rat,bilaterally）was injected intranigrally on days 1,4 and 7 using a digital stereotaxic apparatus.QC（25 and 50 mg/kg,intragastrically）and QC（25 mg/kg,intragastrically）in combination with piperine（2.5 mg/kg,intragastrically）were administered daily for 14 days starting from day 8 after the 3^（rd） injection of MPTP.On day 22,animals were sacrificed and the striatum was isolated for oxidative stress parameter（thiobarbituric acid reactive substances,nitrite and glutathione）,neuroinflammatory cytokine（interleukin-1β,interleukin-6,and tumor necrosis factor-α）and neurotransmitter（dopamine,norepinephrine,serotonin,gamma-aminobutyric acid,glutamate,3,4-dihydroxyphenylacetic acid,homovanillic acid,and 5-hydroxyindoleacetic acid）evaluations.Bilateral infusion of MPTP into substantia nigra pars compacta led to significant motor deficits as evidenced by impairments in locomotor activity and rotarod performance in open field test and grip strength and narrow beam walk performance.Both QC（25 and 50 mg/kg）and QC（25 mg/kg）in combination with piperine（2.5 mg/kg）,in particular the combination therapy,significantly improved MPTP-induced behavioral abnormalities in rats,reversed the abnormal alterations of neurotransmitters in the striatum,and alleviated oxidative stress and inflammatory response in the striatum.These findings indicate that piperine can enhance the antioxidant and anti-inflammatory properties of QC,and QC in combination with piperine exhibits strong neuroprotective effects against MPTP-induced neurotoxicity.

Magnesium acetyltaurate prevents retinal damage and visual impairment in rats through suppression of NMDA-induced upregulation of NF-κB,p53 and AP-1(c-Jun/c-Fos)

Magnesium acetyltaurate(MgAT)has been shown to have a protective effect against N-methyl-D-aspartate(NMDA)-induced retinal cell apoptosis.The current study investigated the involvement of nuclear factor kappa-B(NF-κB),p53 and AP-1 family members(c-Jun/c-Fos)in neuroprotection by MgAT against NMDA-induced retinal damage.In this study,Sprague-Dawley rats were randomized to undergo intravitreal injection of vehicle,NMDA or MgAT as pre-treatment to NMDA.Seven days after injections,retinal ganglion cells survival was detected using retrograde labelling with fluorogold and BRN3A immunostaining.Functional outcome of retinal damage was assessed using electroretinography,and the mechanisms underlying antiapoptotic effect of MgAT were investigated through assessment of retinal gene expression of NF-κB,p53 and AP-1 family members(c-Jun/c-Fos)using reverse transcription-polymerase chain reaction.Retinal phospho-NF-κB,phospho-p53 and AP-1 levels were evaluated using western blot assay.Rat visual functions were evaluated using visual object recognition tests.Both retrograde labelling and BRN3A immunostaining revealed a significant increase in the number of retinal ganglion cells in rats receiving intravitreal injection of MgAT compared with the rats receiving intravitreal injection of NMDA.Electroretinography indicated that pre-treatment with MgAT partially preserved the functional activity of NMDA-exposed retinas.MgAT abolished NMDA-induced increase of retinal phospho-NF-κB,phospho-p53 and AP-1 expression and suppressed NMDA-induced transcriptional activity of NF-κB,p53 and AP-1 family members(c-Jun/c-Fos).Visual object recognition tests showed that MgAT reduced difficulties in recognizing the visual cues(i.e.objects with different shapes)after NMDA exposure,suggesting that visual functions of rats were relatively preserved by pre-treatment with MgAT.In conclusion,pre-treatment with MgAT prevents NMDA induced retinal injury by inhibiting NMDA-induced neuronal apoptosis via downregulation of transcriptional activity of NF-κB,p53 and AP-1-mediated c-Jun/c-Fos.The experiments were approved by the Animal Ethics Committee of Universiti Teknologi MARA(UiTM),Malaysia,UiTM CARE No 118/2015 on December 4,2015 and UiTM CARE No 220/7/2017 on December 8,2017 and Ethics Committee of Belgorod State National Research University,Russia,No 02/20 on January 10,2020.