Endogenous Neuroprotection Research Articles

Chaperone-mediated autophagy (CMA) confers neuroprotection of HBO preconditioning against stroke

Previous attempts to identify neuroprotective targets for acute ischemic stroke by studying ischemic cascades and devising ways to suppress these pathways have failed in translational research. We hypothesized that studying the molecular determinants of endogenous neuroprotection, namely, the tolerance against ischemic stroke conferred by hyperbaric oxygen (HBO) preconditioning, via a well-established paradigm would reveal new neuroprotective targets. By a combination of proteomics, KEGG pathway analysis, lysosome fraction and western blot analysis, we found that chaperone-mediated autophagy (CMA) was activated by HBO preconditioning. In addition, LAMP2A is uniquely decreased in cortical neurons in the early stage of stroke. Suppression of CMA with recombinant adeno-associated viral vector (rAAV)-mediated delivery of short hairpin RNAs (shRNAs) targeting the LAMP2A transcript increased the neuronal susceptibility of apoptosis and abolished the neuroprotection induced by HBO preconditioning. Administration of the clinically utilized FDA-approved drug mycophenolate mofetil induced long-term neuroprotection post-stroke in a CMA-dependent manner. In summary, HBO preconditioning confers neuroprotection against ischemia by inducing CMA, which is a promising translational treatment target for stroke.

Indole-3-Carbinol and Its Derivatives as Neuroprotective Modulators.

Brain-derived neurotrophic factor (BDNF) and its downstream tropomyosin receptor kinase B (TrkB) signaling pathway play pivotal roles in the resilience and action of antidepressant drugs, making them prominent targets in psychiatric research. Oxidative stress (OS) contributes to various neurological disorders, including neurodegenerative diseases, stroke, and mental illnesses, and exacerbates the aging process. The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) serves as the primary cellular defense mechanism against OS-induced brain damage. Thus, Nrf2 activation may confer endogenous neuroprotection against OS-related cellular damage; notably, the TrkB/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, stimulated by BDNF-dependent TrkB signaling, activates Nrf2 and promotes its nuclear translocation. However, insufficient neurotrophin support often leads to the downregulation of the TrkB signaling pathway in brain diseases. Thus, targeting TrkB activation and the Nrf2-ARE system is a promising therapeutic strategy for treating neurodegenerative diseases. Phytochemicals, including indole-3-carbinol (I3C) and its metabolite, diindolylmethane (DIM), exhibit neuroprotective effects through BDNF's mimetic activity; Akt phosphorylation is induced, and the antioxidant defense mechanism is activated by blocking the Nrf2-kelch-like ECH-associated protein 1 (Keap1) complex. This review emphasizes the therapeutic potential of I3C and its derivatives for concurrently activating neuronal defense mechanisms in the treatment of neurodegenerative diseases.

Mobilizing endogenous neuroprotection: the mechanism of the protective effect of acupuncture on the brain after stroke.

Given its high morbidity, disability, and mortality rates, ischemic stroke (IS) is a severe disease posing a substantial public health threat. Although early thrombolytic therapy is effective in IS treatment, the limited time frame for its administration presents a formidable challenge. Upon occurrence, IS triggers an ischemic cascade response, inducing the brain to generate endogenous protective mechanisms against excitotoxicity and inflammation, among other pathological processes. Stroke patients often experience limited recovery stages. As a result, activating their innate self-protective capacity [endogenous brain protection (EBP)] is essential for neurological function recovery. Acupuncture has exhibited clinical efficacy in cerebral ischemic stroke (CIS) treatment by promoting the human body's self-preservation and "Zheng Qi" (a term in traditional Chinese medicine (TCM) describing positive capabilities such as self-immunity, self-recovery, and disease prevention). According to research, acupuncture can modulate astrocyte activity, decrease oxidative stress (OS), and protect neurons by inhibiting excitotoxicity, inflammation, and apoptosis via activating endogenous protective mechanisms within the brain. Furthermore, acupuncture was found to modulate microglia transformation, thereby reducing inflammation and autoimmune responses, as well as promoting blood flow restoration by regulating the vasculature or the blood-brain barrier (BBB). However, the precise mechanism underlying these processes remains unclear. Consequently, this review aims to shed light on the potential acupuncture-induced endogenous neuroprotective mechanisms by critically examining experimental evidence on the preventive and therapeutic effects exerted by acupuncture on CIS. This review offers a theoretical foundation for acupuncture-based stroke treatment.

Cholestane-3β,5α,6β-Triol Inhibits Acid-Sensing Ion Channels and Reduces Acidosis-Mediated Ischemic Brain Injury.

Activation of the acid-sensing ion channels (ASICs) by tissue acidosis, a common feature of brain ischemia, contributes to ischemic brain injury, while blockade of ASICs results in protection. Cholestane-3β,5α,6β-triol (Triol), a major cholesterol metabolite, has been demonstrated as an endogenous neuroprotectant; however, the mechanism underlying its neuroprotective activity remains elusive. In this study, we tested the hypothesis that inhibition of ASICs is a potential mechanism. The whole-cell patch-clamp technique was used to examine the effect of Triol on ASICs heterogeneously expressed in Chinese hamster ovary cells and ASICs endogenously expressed in primary cultured mouse cortical neurons. Acid-induced injury of cultured mouse cortical neurons and middle cerebral artery occlusion-induced ischemic brain injury in wild-type and ASIC1 and ASIC2 knockout mice were studied to examine the protective effect of Triol. Triol inhibits ASICs in a subunit-dependent manner. In Chinese hamster ovary cells, it inhibits homomeric ASIC1a and ASIC3 without affecting ASIC1β and ASIC2a. In cultured mouse cortical neurons, it inhibits homomeric ASIC1a and heteromeric ASIC1a-containing channels. The inhibition is use-dependent but voltage- and pH-independent. Structure-activity relationship analysis suggests that hydroxyls at the 5 and 6 positions of the A/B ring are critical functional groups. Triol alleviates acidosis-mediated injury of cultured mouse cortical neurons and protects against middle cerebral artery occlusion-induced brain injury in an ASIC1a-dependent manner. Our study identifies Triol as a novel ASIC inhibitor, which may serve as a new pharmacological tool for studying ASICs and may also be developed as a potential drug for treating stroke.

Functional reorganization of memory processing in the hippocampus is associated with neuroprotector GLP-1 levels in type 2 diabetes

Type 2 diabetes (T2D) often impairs memory functions, suggesting specific vulnerability of the hippocampus. In vivo neuroimaging studies relating encoding and retrieval of memory information with endogenous neuroprotection are lacking. The neuroprotector glucagon-like peptide (GLP-1) has a high receptor density in anterior/ventral hippocampus, as shown by animal models. Using an innovative event-related fMRI design in 34 participants we investigated patterns of hippocampal activity in T2D (n = 17) without mild cognitive impairment (MCI) versus healthy controls (n = 17) during an episodic memory task. We directly measured neurovascular coupling by estimating the hemodynamic response function using event-related analysis related to encoding and retrieval of episodic information in the hippocampus. We applied a mixed-effects general linear model analysis and a two-factor ANOVA to test for group differences. Significant between-group differences were found for memory encoding, showing evidence for functional reorganization: T2D patients showed an augmented activation in the posterior hippocampus while anterior activation was reduced. The latter was negatively correlated with both GLP-1 pre- and post-breakfast levels, in the absence of grey matter changes. These results suggest that patients with T2D without MCI have pre-symptomatic functional reorganization in brain regions underlying episodic memory, as a function of the concentration of the neuroprotective neuropeptide GLP-1.

Hypothermia promotes tunneling nanotube formation and the transfer of astrocytic mitochondria into oxygen-glucose deprivation/reoxygenation-injured neurons

Mitochondrial transfer occurs between cells, and it is important for damaged cells to receive healthy mitochondria to maintain their normal function and protect against cell death. Accumulating evidence suggests that the functional mitochondria of astrocytes are released and transferred to oxygen–glucose deprivation/reoxygenation (OGD/R)-injured neurons. Mild hypothermia (33 °C) is capable of promoting this process, which partially restores the function of damaged neurons. However, the pathways and mechanisms by which mild hypothermia facilitates mitochondrial transfer remain unclear. We are committed to studying the role of mild hypothermia in neuroprotection to provide reliable evidences and insights for the clinical application of mild hypothermia in brain protection. Tunneling nanotubes (TNTs) are considered to be one of the routes through which mitochondria are transferred between cells. In this study, an OGD/R-injured neuronal model was successfully established, and TNTs, mitochondria, neurons and astrocytes were double labeled using immunofluorescent probes. Our results showed that TNTs were present and involved in the transfer of mitochondria between cells in the mixed-culture system of neurons and astrocytes. When neurons were subjected to OGD/R exposure, TNT formation and mitochondrial transportation from astrocytes to injured neurons were facilitated. Further analysis revealed that mild hypothermia increased the quantity of astrocytic mitochondria transferred into damaged neurons through TNTs, raised the mitochondrial membrane potential (MMP), and decreased the neuronal damage and death during OGD/R. Altogether, our data indicate that TNTs play an important role in the endogenous neuroprotection of astrocytic mitochondrial transfer. Furthermore, mild hypothermia enhances astrocytic mitochondrial transfer into OGD/R-injured neurons via TNTs, thereby promoting neuroprotection and neuronal recovery.

Endogenous defense mechanism-based neuroprotection in large-vessel acute ischemic stroke: A hope for future.

Stroke is a leading cause of morbidity and mortality worldwide and a leading cause of disability. None of the neuroprotective agents have been approved internationally except edaravone in Japanese guidelines in acute ischemic stroke. We here discuss that there are two types of endogenous defense mechanisms (EDMs) after acute stroke for neuromodulation and neuroregeneration, and if both can be activated simultaneously, then we can have better recovery in stroke. We aimed to study the effect of combination of neuroprotection therapies acting on the two wings of EDM in acute large-vessel middle cerebral artery (LMCA) ischemic stroke. Sixty patients of LMCA stroke were enrolled and randomized within 72 h into two groups of 30 patients each. The control group received standard medical care without any neuroprotective agents while the intervention group received standard medical care combined with oral citicoline with vinpocetine for 3 months with initial 1 week intravenous and edaravone and cerebrolysin injection, started within 72 h of onset of stroke. Patients were assessed on the basis of the National Institutes of Health Stroke Scale, Fugl-Meyer Assessment Score, Glasgow Coma Scale, and Mini-Mental Status Examination at admission, discharge, and after 90 days. The intervention group showed significant and early improvements in motor as well as cognitive recovery. Combination therapy for neuroprotection which is acting on two pathways of EDM can be useful in functional recovery after acute ischemic stroke.

Differential Effects of Hypothermia and SZR72 on Cerebral Kynurenine and Kynurenic Acid in a Piglet Model of Hypoxic-Ischemic Encephalopathy.

Kynurenic acid (KYNA), an endogenous neuroprotectant with antiexcitotoxic, antioxidant, and anti-inflammatory effects, is synthesized through the tryptophan-kynurenine (KYN) pathway. We investigated whether brain KYN or KYNA levels were affected by asphyxia in a translational piglet model of hypoxic-ischemic encephalopathy (HIE). We also studied brain levels of the putative blood-brain barrier (BBB) permeable neuroprotective KYNA analogue SZR72, and whether SZR72 or therapeutic hypothermia (TH) modified KYN or KYNA levels. KYN, KYNA, and SZR72 levels were determined using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry in five brain regions 24 h after 20 min of asphyxia in vehicle-, SZR72- and TH-treated newborn piglets (n = 6-6-6) and naive controls (n = 4). Endogenous brain KYN levels (median range 311.2-965.6 pmol/g) exceeded KYNA concentrations (4.5-6.0 pmol/g) ~100-fold. Asphyxia significantly increased cerebral KYN and KYNA levels in all regions (1512.0-3273.9 and 16.9-21.2 pmol/g, respectively), increasing the KYN/Tryptophan-, but retaining the KYNA/KYN ratio. SZR72 treatment resulted in very high cerebral SZR72 levels (13.2-33.2 nmol/g); however, KYN and KYNA levels remained similar to those of the vehicle-treated animals. However, TH virtually ameliorated asphyxia-induced elevations in brain KYN and KYNA levels. The present study reports for the first time that the KYN pathway is altered during HIE development in the piglet. SZR72 readily crosses the BBB in piglets but fails to affect cerebral KYNA levels. Beneficial effects of TH may include restoration of the tryptophan metabolism to pre-asphyxia levels.

MTOR/α-ketoglutarate signaling: impact on brain cell homeostasis under ischemic conditions.

The multifunctional molecules mechanistic target of rapamycin (mTOR) and α-ketoglutarate (αKG) are crucial players in the regulatory mechanisms that maintain cell homeostasis in an ever-changing environment. Cerebral ischemia is associated primarily with oxygen-glucose deficiency (OGD) due to circulatory disorders. Upon exceeding a threshold of resistance to OGD, essential pathways of cellular metabolism can be disrupted, leading to damage of brain cells up to the loss of function and death. This mini-review focuses on the role of mTOR and αKG signaling in the metabolic homeostasis of brain cells under OGD conditions. Integral mechanisms concerning the relative cell resistance to OGD and the molecular basis of αKG-mediated neuroprotection are discussed. The study of molecular events associated with cerebral ischemia and endogenous neuroprotection is relevant for improving the effectiveness of therapeutic strategies.

Deficiency of the RNA-binding protein ELAVL1/HuR leads to the failure of endogenous and exogenous neuroprotection of retinal ganglion cells.

ELAVL1/HuR is a keystone regulator of gene expression at the posttranscriptional level, including stress response and homeostasis maintenance. The aim of this study was to evaluate the impact of hur silencing on the age-related degeneration of retinal ganglion cells (RGC), which potentially describes the efficiency of endogenous neuroprotection mechanisms, as well as to assess the exogenous neuroprotection capacity of hur-silenced RGC in the rat glaucoma model. The study consisted of in vitro and in vivo approaches. In vitro, we used rat B-35 cells to investigate, whether AAV-shRNA-HuR delivery affects survival and oxidative stress markers under temperature and excitotoxic insults. In vivo approach consisted of two different settings. In first one, 35 eight-week-old rats received intravitreal injection of AAV-shRNA-HuR or AAV-shRNA scramble control. Animals underwent electroretinography tests and were sacrificed 2, 4 or 6 months after injection. Retinas and optic nerves were collected and processed for immunostainings, electron microscopy and stereology. For the second approach, animals received similar gene constructs. To induce chronic glaucoma, 8 weeks after AAV injection, unilateral episcleral vein cauterization was performed. Animals from each group received intravitreal injection of metallothionein II. Animals underwent electroretinography tests and were sacrificed 8 weeks later. Retinas and optic nerves were collected and processed for immunostainings, electron microscopy and stereology. Silencing of hur induced apoptosis and increased oxidative stress markers in B-35 cells. Additionally, shRNA treatment impaired the cellular stress response to temperature and excitotoxic insults. In vivo, RGC count was decreased by 39% in shRNA-HuR group 6 months after injection, when compared to shRNA scramble control group. In neuroprotection study, the average loss of RGCs was 35% in animals with glaucoma treated with metallothionein and shRNA-HuR and 11.4% in animals with glaucoma treated with metallothionein and the scramble control shRNA. An alteration in HuR cellular content resulted in diminished photopic negative responses in the electroretinogram. Based on our findings, we conclude that HuR is essential for the survival and efficient neuroprotection of RGC and that the induced alteration in HuR content accelerates both the age-related and glaucoma-induced decline in RGC number and function, further confirming HuR's key role in maintaining cell homeostasis and its possible involvement in the pathogenesis of glaucoma.

Anti-Inflammatory Actions of G-Protein-Coupled Estrogen Receptor 1 (GPER) and Brain-Derived Estrogen Following Cerebral Ischemia in Ovariectomized Rats.

Global cerebral ischemia can elicit rapid innate neuroprotective mechanisms that protect against delayed neuronal death. Brain-derived 17β-estradiol (BDE2), an endogenous neuroprotectant, is synthesized from testosterone by the enzyme aromatase (Aro) and is upregulated by brain ischemia and inflammation. Our recent study revealed that G1, a specific G-protein-coupled estrogen receptor 1 (GPER) agonist, exerts anti-inflammatory and anti-apoptotic roles after global cerebral ischemia (GCI). Herein, we aimed to elucidate whether G1 modulates the early inflammatory process and the potential underlying mechanisms in the ovariectomized rat hippocampal CA1 region. G1 was found to markedly reduce pro-inflammatory (iNOS, MHCII, and CD68) and to enhance anti-inflammatory (CD206, Arginase 1, IL1RA, PPARγ, and BDNF) markers after 1 and 3 days of reperfusion after GCI. Intriguingly, the neuroprotection of G1 was blocked by the Aro inhibitor, letrozole. Conversely, the GPER antagonist, G36, inhibited Aro-BDE2 signaling and exacerbated neuronal damage. As a whole, this work demonstrates a novel anti-inflammatory role of GPER, involving a synergistic mediation with BDE2 during the early stage of GCI.

Neuroprotective effects of isatin and afobazole in rats with rotenone-induced Parkinsonism are accompanied by increased brain levels of Triton X-100 soluble alpha-synuclein.

Effects of the endogenous neuroprotector isatin and the pharmacological drug afobazole (exhibiting neuroprotective properties) on behavioral reactions and quantitative changes in the brain proteomic profile have been investigated in rats with experimental rotenone Parkinsonism. A single dose of isatin (100 mg/kg subcutaneously on the last day of a 7-day course of rotenone administration) improved the motor activity of rats with rotenone-induced Parkinsonism in the open field test (horizontal movements) and the rotating rod test. Afobazole (10 mg/kg intraperitoneally, daily during the 7-day course of rotenone administration) reduced the manifestations of rigidity and postural instability. Proteomic analysis, performed using brain samples obtained the day after the last administration of rotenone and neuroprotectors, revealed similar quantitative changes in the brain of rats with rotenone Parkinsonism. An increase in the relative content of 65 proteins and a decrease in the relative content of 21 proteins were detected. The most pronounced changes - an almost ninety-fold increase in the alpha-synuclein content - were found in the brains of rats treated with isatin. In animals of the experimental groups treated with "Rotenone + Isatin", as well as "Rotenone + Afobazole", the increase in the relative content of this protein in the brain was almost 60 and 50 times higher than the control values. Taking into consideration the known data on the physiological role of alpha-synuclein, an increase in the content of this protein in the brain upon administration of neuroprotectors to animals with rotenone Parkinsonism may represent a compensatory reaction, at least in the early stages of this disease and the beginning of its treatment.

Is Nrf2 Behind Endogenous Neuroprotection of the Hippocampal CA2-4,DG Region?

The transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) is the master regulator of genes known to be involved in antioxidant, and anti-inflammatory processes, metabolic regulation, and other cellular functions. Here, we also hypothesize a core role for it in endogenous neuroprotection, i.e., the natural adaptive mechanisms protecting the brain from ischemia–reperfusion (I/R) episode. An example of endogenous neuroprotection is ischemia-resistance of the hippocampal regions comprising the CA2, CA3, CA4 and dentate gyrus subfields (here abbreviated to CA2-4,DG) which can be contrasted with the ischemia-vulnerable CA1 region. In the work detailed here, we used a gerbil model of transient cerebral ischemia to examined Nrf2 activation in CA1 and CA2-4,DG, in a control group, and post I/R episode. Data obtained indicate enhanced Nrf2 activity in CA2-4,DG as compared with CA1 in the control, with this difference seen to persist even after I/R. While I/R does indeed cause further activation of Nrf2 in CA2-4,DG, it is associated with slight and transient activation in CA1. Sub-regional differences in Nrf2 activity correlate with immunoreactivity of Keap1 (an Nrf2 suppressor) and Nrf2 target proteins, including heme oxygenase 1, the catalytic and modulatory sub-units of glutamate-cysteine ligase, and glutathione peroxidase 1. Pharmacological Nrf2 activation by sulforaphane results in protection of CA1 after I/R episode. Our results therefore suggest that high Nrf2 activity in CA2-4,DG may guarantee resistance of this region to I/R, potentially explaining the differential sensitivities of the hippocampal regions.

ELAVL1/HuR regulates both endo‐ and exogenous neuroprotection in retinal ganglion cells

AbstractPurpose: To evaluate the impact of HuR gene silencing on the ratio of age‐related degeneration of Retinal Ganglion Cells (RGC), which potentially describes the efficiency of endogenous neuroprotection mechanisms, as well as to assess the exogenous neuroprotection capacity of HuR‐ silenced RGC in rat glaucoma model treated with Metallothionein.Methods: Thirty‐five eight‐week‐old male Long Evans rats were divided into two groups: experimental and control. Animals from experimental group received intravitreal injection of AAV‐shRNA‐HuR. Control group received injection of AAV‐shRNA scramble control. Animals from both groups were sacrificed in 3 different time points: 2, 4 and 6 months after injection. Both healthy and treated retinas from each animal were collected and processed as whole mounts for immunostainings and RGC count. For the second trial, animals were divided into groups and transfected with virus particles as described above. To induce chronic glaucoma model, 8 weeks after AAV injection, unilateral episcleral vein cauterization was performed. Half of animals from each group received intravitreal injection of Metallothionein (MT), the other group received PBS injection. During the experiment IOP was monitored. Both healthy and treated retinas from each animal were collected and processed as whole mounts for immunostainings and RGC count.Results: RGC count (per visual field under 20× magnification) was 310 ± 31, 296 ± 25, 189 ± 41 in experimental group and 399 ± 51, 395 ± 49, 390 ± 23 in control respectively for 2, 4 and 6 months after injection (Kaplan‐Mayer trend rank p < 0.0001). Loss of RGC in central retina was 33.7% in animals from shRNA‐MT‐treated glaucoma and 11.4% in shRNA control‐MT‐treated glaucoma (p < 0.05). In peripheral part of the retina the loss was 37.4% in animals from shRNA‐MT‐treated glaucoma and 11.5% in shRNA control‐MT‐treated glaucoma (p < 0.01).Conclusions: Silencing of hur gene enhanced age‐related loss of RGC which translates into impaired endogenous neuroprotection pathways, moreover the absence of HuR critically limits neuroprotective activity of exogenously delivered Metallothionein.

ECT: An essential therapy in psychiatry

At a time when innovations in psychiatry are booming, particularly in the field of medical devices, we thought it necessary, as members of French Society for Biological Psychiatry and Neuropsychopharmacology (AFPBN), to reconsider one of the oldest medical devices in psychiatry: the ECT apparatus. First, we recall the regulatory aspects of ECT. National guidelines define means of implementation and conditions of administration of ECT. Second, we remind of the indications and levels of evidence of ECT in the main psychiatric disorders, including catatonia. Then, we synthetize the place of ECT alongside other brain stimulation therapies, especially repetitive Trancranial Magnetic Stimulation (rTMS). Furthermore, we explain the general effects of ECT: increased neuronal plasticity and neurogenesis, enhancement of the stress axis, resistance to oxidative stress, improved vascular endothelial function, activation of microglia and astrocytes, decrease in inflammatory events by upregulation of neuroinflammatory cytokines, and production of mitochondrial ATP. These effects appear from the first sessions and continue during the course of ECT treatment, suggesting activation of endogenous neuroprotection. Finally, we remember that most patients perform as well or better on neuropsychological assessments after ECT, relative to pre-ECT results, and this improvement continues over the following months. Memory disorders reported post-ECT are not all attributable to ECT. They may be subjective in nature or linked to residual depressive (and possibly comorbid neurogenerative) symptoms later attributed to ECT, on the basis of preexisting negative representations. We urgently need to reemphasize the crucial role of ECT in psychiatric treatment strategies as well as the need to update ECT recommendations.

Opposing reduced VPAC1 and enhanced VPAC2 VIP receptors in the hippocampus of the Li2+-pilocarpine rat model of temporal lobe epilepsy

VIP binding sites are upregulated in mesial temporal lobe epilepsy (MTLE) patients, also suffering from severe cognitive deficits. Although altered VIP and VIP receptor levels were described in rodent models of epilepsy, the VIP receptor subtype(s) were never identified. We now investigated how VPAC1 and VPAC2 receptor levels change in the Li2+-pilocarpine rat model of MTLE. Cognitive decline and altered synaptic plasticity as estimated from phosphorylation of AMPA GluA1 subunit on Ser831 and Ser845 and AMPA GluA1/GluA2 ratio was also probed. Animals showing spontaneous recurrent seizures (SRSs) for at least 4 weeks showed impaired learning in the radial arm maze (RAM) and presented decreased VPAC1 and increased VPAC2 receptor levels. In addition, SRSs rats showed increased AMPA GluA1 phosphorylation in Ser831 and Ser845, marked decrease in GluA1 levels and a milder decrease in GluA2 levels. Consequently, the GluA1/GluA2 ratio was also decreased in SRSs rats.Altered VIP receptor levels may differentially prevent or contribute to MTLE pathology, since VPAC1 receptors promote the endogenous control of LTP, mediate endogenous VIP neuroprotection against altered synaptic plasticity following epileptiform activity, and mediate anti-inflammatory actions in microglia, while VPAC2 receptors mediate VIP endogenous neuroprotection against neonatal excitotoxicity and prevent reactive astrogliosis. This discovery imposes a different mindset for considering VIP receptors as therapeutic targets in MTLE, allowing a differential targeting of the cellular events contributing to epileptogenesis.

EBNEO commentary: Dexmedetomidine versus morphine for neonates with encephalopathy undergoing therapeutic hypothermia.

Cosnahan A, Angert R, Jano E, Wachtel E. Dexmedetomidine versus intermittent morphine for sedation of neonates with encephalopathy undergoing therapeutic hypothermia. Journal of Perinatology 2021; 41(9):2284-2291. PMID 33649447 The use of sedation during TH is important to provide compassionate care and prevent stress and shivering. While non-pharmacologic approaches should be utilised first-line, some neonates require sedation to limit stress and provide comfort. A neonatal piglet study of HIE suggested that TH is not neuroprotective in the absence of sedation.1 However, animal studies have demonstrated that sedatives, analgesics and/or anaesthetics may have long-term deleterious effects on the developing brain through inhibition of NMDA glutamate receptors or enhancement of GABA-mediated depolarisation triggering widespread apoptotic neurodegeneration.2, 3 Healthcare providers must balance managing stress and pain with the risks that accompany sedation in neonates. Morphine and fentanyl, both opioid agonists, have historically been used during TH to provide sedation. However, these agents have significant side effects including respiratory depression, delayed gastrointestinal motility and hypotension. Additionally, the global hypoxic–ischemic insult that occurs during HIE leads to a high incidence of acute kidney injury and acute liver injury,4 which may slow metabolism and clearance of medications such as morphine and fentanyl. These pharmacokinetic alterations, along with PK alterations related to TH itself, can lead to accumulation of the medication, further increasing the risk of adverse effects.4, 5 In a secondary analysis of 169 neonates enrolled in one study, neonates receiving morphine were more likely to be hypotensive (49% vs. 25%, p = 0.02) and had a longer hospital stay (12 days vs. 9 days, p = 0.009) compared with those who did not receive morphine.6 Dexmedetomidine is an α2-adrenergic agonist that provides analgesia, anxiolysis and sedation. The activation of central α2-receptors prevents shivering during TH, inhibits inflammatory cytokines and may result in endogenous neuroprotection.5 Dexmedetomidine does not appear to have significant impact on the respiratory drive or gastrointestinal motility. The most common use-limiting adverse effect is bradycardia. Pharmacokinetic alterations have been demonstrated in animals, but there are limited data in neonates, with a single study reporting comparable or lower clearance, larger volume of distribution and longer elimination half-life in patients with HIE undergoing TH compared with those without HIE.7 In a single-centre retrospective cohort study of 19 neonates with HIE undergoing TH, dexmedetomidine was administered at an average rate of 0.3 mcg/kg/h (range 0.2–0.5 mcg/kg/h). Two patients received dexmedetomidine monotherapy, and 17 received fentanyl initially. Thirteen of those 17 patients had fentanyl discontinued within 4 h of starting dexmedetomidine. The authors concluded that dexmedetomidine was effective for sedation in neonates with HIE undergoing TH.8 The study presented here adds to the growing body of literature that dexmedetomidine may be effective and safe for sedation and analgesia during TH. It is important to note the small sample size and lack of significant differences between groups for many of the respiratory and gastrointestinal outcomes assessed. Despite the limitations of this study, the potential benefits of dexmedetomidine should be considered when selecting a sedative in neonates undergoing TH. Future research should focus on gathering additional pharmacokinetic data for dexmedetomidine in HIE/TH and the evaluation of longer-term neurologic outcomes in neonates undergoing TH. https://ebneo.org/ebneo-commentary-dexmedetomidine-vs-morphine This review did not have a funding source. The authors have no conflicts of interest to report.

Redistribution of Histone Marks on Inflammatory Genes Associated With Intracerebral Hemorrhage-Induced Acute Brain Injury in Aging Rats.

The contribution of histone mark redistribution to the age-induced decline of endogenous neuroprotection remains unclear. In this study, we used an intracerebral hemorrhage (ICH)-induced acute brain injury rat model to study the transcriptional and chromatin responses in 13- and 22-month-old rats. Transcriptome analysis (RNA-seq) revealed that the expression of neuroinflammation-associated genes was systematically upregulated in ICH rat brains, irrespective of age. Further, we found that interferon-γ (IFN-γ) response genes were activated in both 13- and 22-month-old rats. Anti-IFN-γ treatment markedly reduced ICH-induced acute brain injury in 22-month-old rats. At the chromatin level, ICH induced the redistribution of histone modifications in the promoter regions, especially H3K4me3 and H3K27me3, in neuroinflammation-associated genes in 13- and 22-month-old rats, respectively. Moreover, ICH-induced histone mark redistribution and gene expression were found to be correlated. Collectively, these findings demonstrate that histone modifications related to gene expression are extensively regulated in 13- and 22-month-old rats and that anti-IFN-γ is effective for ICH treatment, highlighting the potential of developing therapies targeting histone modifications to cure age-related diseases, including brain injury and neuroinflammation.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

Pharmacological Modulation of Endogenous Neuroprotection after Experimental Prenatal Hypoxia

Pharmacological Modulation of Endogenous Neuroprotection after Experimental Prenatal Hypoxia