MK-801 attenuates lesion expansion following acute brain injury in rats: a meta-analysis

Targeting NMDA receptors with an antagonist is a promising therapeutic strategy for treating neurological disorders

Glutamate activates the NMDARs, significantly affecting multiple processes such as learning, memory, synaptic integration, and excitatory transmission in the central nervous system. Uncontrolled activation of NMDARs is a significant contributor to synaptic dysfunction. Having a properly functioning NMDAR and synapse is crucial for maintaining neuronal communication. In addition, the dysfunction of NMDAR and synapse function could contribute to the development of neurological disorders at the neuronal level; hence, targeting NMDARs with antagonists in the fight against neurological disorders is a promising route. Recently published results from the animal study on different kinds of brain diseases like stroke, epilepsy, tinnitus, ataxia, Alzheimer's disease, Parkinson's disease, and spinal cord injury have demonstrated promising therapeutic scopes. Several NMDA receptor antagonists, such as memantine, MK801, ketamine, ifenprodil, gacyclidine, amantadine, agmatine, etc., showed encouraging results against different brain disease mouse models. Given the unique expression of different subunits of the well-organized NMDA receptor system by neurons. It could potentially lead to the development of medications specifically targeting certain receptor subtypes. For a future researcher, conducting more targeted research and trials is crucial to fully understand and develop highly specific medications with good clinical effects and potential neuroprotective properties.

Efficacy of N-Methyl-D-Aspartate (NMDA) Receptor Antagonists in Treating Traumatic Brain Injury-Induced Brain Edema: A Systematic Review and Meta-analysis of Animal Studies

Traumatic brain injury leads to glutamate release, which overstimulates N-methyl-D-aspartate (NMDA) receptors, leading to neurotoxicity and cytotoxic edema. NMDA receptor antagonists may offer neuroprotection by blocking this pathway. The objective of this systematic review is to assess the efficacy of NMDA receptor antagonists for traumatic brain injury-induced brain edema in rodent models. This systematic review followed Cochrane Handbook guidelines and registered its protocol in PROSPERO (ID: CRD42023440934). Here, we included controlled rodent animal models comparing NMDA antagonist use with a placebo treatment. Outcome measures included the reduction of cerebral edema, Neurobehavioral Severity Scale, and adverse effects. The search strategy used Medical Subject Headings terms related to traumatic brain injury and NMDA receptor antagonists. The Collaborative Approach to Meta Analysis and Review of Animal Experimental Studies (CAMARADES) checklist and Systematic Review Centre for Laboratory Animal Experimentation's (SYRCLE's) tools were used to measure the quality and bias of included studies. The synthesis of results was presented in a meta-analysis of standard mean difference. Sixteen studies were included, with the predominant drugs being ifenprodil, MK-801, magnesium, and HU-211. The subjects consisted of Sprague-Dawley or Sabra rats. The analysis showed a significant reduction in brain edema with NMDA antagonist treatment (Standardized mean difference [SMD] - 1.17, 95% confidence interval [CI] - 1.59 to - 0.74, p < 0.01), despite high heterogeneity (I2 = 72%). Neurobehavioral Severity Scale also significantly improved (mean difference - 3.32, 95% CI - 4.36 to - 2.28, p < 0.01) in animals receiving NMDA antagonists. Administration within 1 h after injury showed a modest enhancement in reducing brain edema compared with the baseline (SMD - 1.23, 95% CI - 1.69 to - 0.77, p < 0.01). Studies met standards for animal welfare and model appropriateness. Although baseline comparability and selective reporting bias were generally addressed, key biases such as randomization, allocation concealment, and blinding were often unreported. Overall, NMDA antagonists exhibit promising efficacy in the treatment of traumatic brain injury. Notably, our systematic review consistently demonstrated a significant reduction in brain edema with compounds including HU-211 and NPS 150.

Neuroprotective effects of MK-801 against cerebral ischemia reperfusion

Introduction

& Objective: Cerebral ischemia/reperfusion (I/R) injury, the second cause of death globally, involves increased NMDA receptor activity leading to neuronal damage due to excessive sodium and calcium ion entry. Therefore, targeting NMDA receptor may potentially reduce cell death induced by brain injury. Our study aimed to investigate the role of NMDA receptors in hippocampal neuronal activity induced by I/R.

Methods

In this study, Wistar rats were divided into four groups: sham, I/R, I/R + MK801, and I/R + NMDA. Cerebral I/R injury was induced by temporarily occluding the common and vertebral carotid arteries, followed by reperfusion. MK801 or NMDA was administered to the rats after a specific reperfusion time. Neuronal density and cell morphology in the hippocampal CA1 region were assessed using Nissl and H&E staining. The expression of BDNF, p-CREB, and c-fos was evaluated through Western blot analysis. Additionally, neuronal activity in CA1 pyramidal neurons were examined using single unit recording technique.

Results

Our results showed that cerebral I/R injury caused significant damage to CA1 pyramidal neurons compared to the sham group. However, treatment with MK-801 improved hippocampal cell survival compared to the I/R group. Furthermore, MK-801 administration in I/R rats increased BDNF, c-fos, and p-CREB levels while decreasing cleaved caspase-3 activity compared to the I/R group. Additionally, electrophysiological data showed that MK-801 increased firing rates of CA1 pyramidal neurons during the reperfusion phase.

Conclusion

MK-801 shows promise as a therapeutic agent for cerebral I/R injury by enhancing cell survival, upregulating neuroplasticity factors, and increasing firing rates of CA1 pyramidal neurons. It exerts a specific protective effect against cerebral I/R injury.

Inhibiting Caveolin-1-Related Akt/mTOR Signaling Pathway Protects Against N-methyl-D-Aspartate Receptor Activation-Mediated Dysfunction of Blood-Brain Barrier in vitro

BACKGROUND

The aim of this study was to further explore the role of caveolin-1 (Cav-1) related Akt/mTOR signaling pathway in blood brain barrier (BBB) dysfunction caused by NMDAR activation.

METHODS

The cell localization of NMDAR GluN1 subunit and Cav-1 was observed on human brain microvascular HBEC-5i cells after immunofluorescence double staining. The transendothelial resistance (TEER) of BBB in vitro was measured by Millicell-ERS cell resistance meter. Sodium fluorescein (SF) was used to measure the permeability of BBB in vitro. A stable Cav-1-silenced HBEC-5i cell line was established by infecting the cells with a lentivirus encoding Cav-1 shRNA. The changes of the protein and mRNA of MMP9 and Occludin induced by NMDA were detected by Western blot (WB) and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), respectively. The phosphorylated proteins of Cav-1, Akt, and mTOR were detected by WB.

RESULTS

NMDAR GluN1 was expressed in the cytoplasm and part of the cell membrane of the HBEC-5i cell line. NMDAR activation decreased TEER and increased the SF of BBB in vitro. HBEC-5i cells incubated with NMDA enhanced the phosphorylation of Cav-1, Akt, and mTOR, also promoting the expression of MMP9 along with the degradation of Occludin. These effects could be reversed by pretreatment with NMDAR antagonist (MK801) or Cav-1 antagonist (Daidzein), or Akt antagonist (LY294002), respectively. Further silencing Cav-1 with LV-Cav-1-RNAi also played a similar protective effect.

CONCLUSION

Caveolin-1 (Cav-1) related Akt/mTOR signaling probably contributes to BBB dysfunction by activating NMDAR on human brain microvascular cells.

Glial Glutamate Transporter Modulation Prevents Development of Complete Freund's Adjuvant-Induced Hyperalgesia and Allodynia in Mice

Glial glutamate transporter (GLT-1) modulation in the hippocampus and anterior cingulate cortex (ACC) is critically involved in nociceptive pain. The objective of the study was to investigate the effects of 3-[[(2-methylphenyl) methyl] thio]-6-(2-pyridinyl)-pyridazine (LDN-212320), a GLT-1 activator, against microglial activation induced by complete Freund's adjuvant (CFA) in a mouse model of inflammatory pain. Furthermore, the effects of LDN-212320 on the protein expression of glial markers, such as ionized calcium-binding adaptor molecule 1 (Iba1), cluster of differentiation molecule 11b (CD11b), mitogen-activated protein kinases (p38), astroglial GLT-1, and connexin 43 (CX43), were measured in the hippocampus and ACC following CFA injection using the Western blot analysis and immunofluorescence assay. The effects of LDN-212320 on the pro-inflammatory cytokine interleukin-1β (IL-1β) in the hippocampus and ACC were also assessed using an enzyme-linked immunosorbent assay. Pretreatment with LDN-212320 (20 mg/kg) significantly reduced the CFA-induced tactile allodynia and thermal hyperalgesia. The anti-hyperalgesic and anti-allodynic effects of LDN-212320 were reversed by the GLT-1 antagonist DHK (10 mg/kg). Pretreatment with LDN-212320 significantly reduced CFA-induced microglial Iba1, CD11b, and p38 expression in the hippocampus and ACC. LDN-212320 markedly modulated astroglial GLT-1, CX43, and, IL-1β expression in the hippocampus and ACC. Overall, these results suggest that LDN-212320 prevents CFA-induced allodynia and hyperalgesia by upregulating astroglial GLT-1 and CX43 expression and decreasing microglial activation in the hippocampus and ACC. Therefore, LDN-212320 could be developed as a novel therapeutic drug candidate for chronic inflammatory pain.

Quest for Quality in Translational Stroke Research-A New Dawn for Neuroprotection?

Despite tremendous progress in modern-day stroke therapy, ischemic stroke remains a disease associated with a high socioeconomic burden in industrialized countries. In light of demographic change, these health care costs are expected to increase even further. The current causal therapeutic treatment paradigms focus on successful thrombolysis or thrombectomy, but only a fraction of patients qualify for these recanalization therapies because of therapeutic time window restrictions or contraindications. Hence, adjuvant therapeutic concepts such as neuroprotection are urgently needed. A bench-to-bedside transfer of neuroprotective approaches under stroke conditions, however, has not been established after more than twenty years of research, albeit a great many data have demonstrated several neuroprotective drugs to be effective in preclinical stroke settings. Prominent examples of substances supported by extensive preclinical evidence but which failed clinical trials are tirilazad and disodium 2,4-sulphophenyl-N-tert-butylnitrone (NXY-059). The NXY-059 trial, for instance, was retrospectively shown to have a seriously weak study design, a trial of insufficient quality and a poor statistical analysis, although it initially met the recommendations of the STAIR committee. In light of currently ongoing novel neuroprotective stroke trials, such as ESCAPE-NA, and to avoid the mistakes made in the past, an improvement in study quality in the field of stroke neuroprotection is urgently needed. In the present review, animal models closely reflecting the "typical" stroke patient, occlusion techniques and the appropriate choice of time windows are discussed. In this context, the STAIR recommendations could provide a useful orientation. Taking all of this into account, a new dawn for neuroprotection might be possible.

Revisiting Excitotoxicity in Traumatic Brain Injury: From Bench to Bedside

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality. Consequences vary from mild cognitive impairment to death and, no matter the severity of subsequent sequelae, it represents a high burden for affected patients and for the health care system. Brain trauma can cause neuronal death through mechanical forces that disrupt cell architecture, and other secondary consequences through mechanisms such as inflammation, oxidative stress, programmed cell death, and, most importantly, excitotoxicity. This review aims to provide a comprehensive understanding of the many classical and novel pathways implicated in tissue damage following TBI. We summarize the preclinical evidence of potential therapeutic interventions and describe the available clinical evaluation of novel drug targets such as vitamin B12 and ifenprodil, among others.

Investigation of the protective effect of resveratrol in an MK-801-induced mouse model of schizophrenia

Increasing evidence supports the view that oxidative stress and brain demyelination play an important role in the pathogenesis of schizophrenia. Resveratrol is a powerful antioxidant with neuroprotective effects. This study aimed to assess the effect of resveratrol on schizophrenia-like behaviors and possible brain demyelination induced by MK-801, an N-methyl-D-aspartate glutamate receptor antagonist, and the underlying neuroprotective mechanism. Resveratrol (40 mg/kg/day/, intraperitoneal) was administered to mice for 14 days. MK-801 (1 mg/kg/day, intraperitoneal) was injected into the mice 4 h after the resveratrol administration for 14 days. The open-field and elevated-plus maze tests were performed to detect behavior changes on the 15th day. Following the behavioral tests, the expression of the myelin basic protein (MBP) was measured with the real-time PCR (RT-PCR) method, while total oxidant capacity (TOS) and total antioxidant capacity (TAS), which are the biomarkers of oxidative damage, were measured with the ELISA method. Hematoxylin-eosin staining was also used to identify stereological and pathological changes in the brain. According to the results obtained, this study showed for the first time that resveratrol prevented glial cell infiltration induced in the brain by MK-801 and shrinkage of nerve cell nuclei in the hippocampus and corpus callosum. However, the resveratrol administrations did not correct behavioral disorders and demyelination of schizophrenia. Although resveratrol partially prevented oxidative damage in the brain in the mice that were injected with MK-801, it was determined that this effect was not statistically significant. These results showed that resveratrol administration partially protects tissues against MK-801-induced neurodegeneration, and resveratrol may be used in combination with different antioxidants or at different doses in future studies.

Long term neuroprotective effects of acute single dose MK-801treatment against traumatic brain injury in immature rats

Because brain development continues during adolescence, childhood trauma is a major health problem in pediatric ages. It is known traumatic brain injury (TBI) results in damage in hippocampal and cortical areas of the brain and impairs cognitive functions. The study aims to investigate the long-term effects of MK-801 (dizocilpine), an N-methyl d-aspartate (NMDA) receptor antagonist, on hippocampal damage, locomotor activity, and cognitive functions following TBI in immature rats. MK-801 (1 mg/kg) was injected intraperitoneally immediately after TBI. Thirty-seven litters were randomly allocated into three groups at 7 days (P7) of postnatal age: a control group, a trauma group, and an MK-801 treatment group. The control group received no treatment; the trauma group received saline as vehicle control for the MK-801 group and the MK-801 group received a single dose of 1 mg/kg MK-801 immediately after TBI. Hippocampal damage was examined by Hematoxylin-Eosin staining. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), NMDA-R, and glial fibrillar acidic protein (GFAP) immunohistochemistry and, BDNF, NGF, and NMDA-R ELISA protein levels were evaluated 125 days after trauma. Histopathological and immunohistochemical evaluations showed that treatment with MK-801 significantly ameliorated the trauma-induced hippocampal neuron loss and increased BDNF, NGF, NMDA-R, GFAP expressions in CA1, CA3, and DG hippocampal regions. Additionally, treatment with MK-801 decreased anxiety and increased hippocampus-dependent memory of animals subjected to brain injury after TBI. These results show that acute treatment of MK-801 has a neuroprotective role against trauma-induced hippocampal neuron loss and associated cognitive impairment in rats.

Preclinical animal studies in ischemic stroke: Challenges and some solutions

Despite the impressive efficacies demonstrated in preclinical research, hundreds of potentially neuroprotective drugs have failed to provide effective neuroprotection for ischemic stroke in human clinical trials. Lack of a powerful animal model for human ischemic stroke could be a major reason for the failure to develop successful neuroprotective drugs for ischemic stroke. This review recapitulates the available cerebral ischemia animal models, provides an anatomical comparison of the circle of Willis of each species, and describes the functional assessment tests used in these ischemic stroke models. The distinct differences between human ischemic stroke and experimental stroke in available animal models is explored. Innovative animal models more closely resembling human strokes, better techniques in functional outcome assessment and better experimental designs generating clearer and stronger evidence may help realise the development of truly neuroprotective drugs that will benefit human ischemic stroke patients. This may involve use of newer molecules or revisiting earlier studies with new experimental designs. Translation of any resultant successes may then be tested in human clinical trials with greater confidence and optimism.

Minocycline improves the recovery of nerve function and alleviates blood-brain barrier damage by inhibiting endoplasmic reticulum in traumatic brain injury mice model

Traumatic brain injury (TBI) is a clinical emergency with a very high incidence, disability, and fatality rate. Minocycline, a widely used semisynthetic second-generation tetracycline antibiotic, has anti-inflammatory and bactericidal effects. However, minocycline has not been explored as a therapeutic drug in TBI and if effective, the related molecular mechanism is also unclear. In this study, we examined the neuroprotective effect and possible mechanism of minocycline, in mice TBI model by studying the trauma-related functional and morphological changes. Also, in vitro cell studies were carried out to verify the animal model data. We found that minocycline significantly improved the neurobehavioral score, inhibited apoptosis, repaired the blood-brain barrier, and reduced the levels of inflammatory factors Interleukin-6 and tumor necrosis factor-α in TBI mice. In vitro, upon oxygen and glucose deprivation, minocycline reduced the levels of cellular inflammatory factors and increased the levels of tight junction and adherens junction proteins, thereby significantly improving the cell viability. Moreover, Mino treatment prevented the loss of tight junction and adherens junction proteins which were markedly reversed by an ER stress activator (tunicamycin) both in vivo and in vitro. Our findings set an effective basis for the clinical use of Mino to treat Traumatic brain injury-induced neurological deficits.

The role of spreading depolarizations and electrographic seizures in early injury progression of the rat photothrombosis stroke model

Spreading depolarization (SD) and seizures are pathophysiological events associated with cerebral ischemia. Here, we investigated their role for injury progression in the cerebral cortex. Cerebral ischemia was induced in anesthetized male Wistar rats using the photothrombosis (PT) stroke model. SD and spontaneous neuronal activity were recorded in the presence of either urethane or ketamine/xylazine anesthesia. Blood-brain barrier (BBB) permeability, cerebral perfusion, and cellular damage were assessed through a cranial window and repeated intravenous injection of fluorescein sodium salt and propidium iodide until 4 h after PT. Neuronal injury and early lesion volume were quantified by stereological cell counting and manual and automated assessment of ex vivo T2-weighted magnetic resonance imaging. Onset SDs originated at the thrombotic core and invaded neighboring cortex, whereas delayed SDs often showed opposite propagation patterns. Seizure induction by 4-aminopyridine caused no increase in lesion volume or neuronal injury in urethane-anesthetized animals. Ketamine/xylazine anesthesia was associated with a lower number of onset SDs, reduced lesion volume, and neuronal injury despite a longer duration of seizures. BBB permeability increase inversely correlated with the number of SDs at 3 and 4 h after PT. Our results provide further evidence that ketamine may counteract the early progression of ischemic injury.

Direct electrophysiological evidence that spreading depolarization-induced spreading depression is the pathophysiological correlate of the migraine aura and a review of the spreading depolarization continuum of acute neuronal mass injury

Spreading depolarization is observed as a large negative shift of the direct current potential, swelling of neuronal somas, and dendritic beading in the brain's gray matter and represents a state of a potentially reversible mass injury. Its hallmark is the abrupt, massive ion translocation between intraneuronal and extracellular compartment that causes water uptake (= cytotoxic edema) and massive glutamate release. Dependent on the tissue's energy status, spreading depolarization can co-occur with different depression or silencing patterns of spontaneous activity. In adequately supplied tissue, spreading depolarization induces spreading depression of activity. In severely ischemic tissue, nonspreading depression of activity precedes spreading depolarization. The depression pattern determines the neurological deficit which is either spreading such as in migraine aura or migraine stroke or nonspreading such as in transient ischemic attack or typical stroke. Although a clinical distinction between spreading and nonspreading focal neurological deficits is useful because they are associated with different probabilities of permanent damage, it is important to note that spreading depolarization, the neuronal injury potential, occurs in all of these conditions. Here, we first review the scientific basis of the continuum of spreading depolarizations. Second, we highlight the transition zone of the continuum from reversibility to irreversibility using clinical cases of aneurysmal subarachnoid hemorrhage and cerebral amyloid angiopathy. These illustrate how modern neuroimaging and neuromonitoring technologies increasingly bridge the gap between basic sciences and clinic. For example, we provide direct electrophysiological evidence for the first time that spreading depolarization-induced spreading depression is the pathophysiological correlate of the migraine aura.

Acer okamotoanumand isoquercitrin improve cognitive functionviaattenuation of oxidative stress in high fat diet- and amyloid beta-induced mice

High fat diet (HFD) and accumulation of amyloid beta (Aβ) are known as a risk factor of Alzheimer's disease.Acer okamotoanumand isoquercitrin improved cognition function against both HFD and Aβ accumulation by inhibiting oxidative stress.