Perinatal Hypoxic-Ischemic Encephalopathy and Neuroprotective Peptide Therapies: A Case for Cationic Arginine-Rich Peptides (CARPs)

Celastrol ameliorates hypoxic-ischemic brain injury in neonatal rats by reducing oxidative stress and inflammation

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is caused by perinatal hypoxia and subsequent reductions in cerebral blood flow and is one of the leading causes of severe disability or death in newborns. Despite its prevalence, we currently lack an effective drug therapy to combat HIE. Celastrol (Cel) is a pentacyclic triterpene extracted from Tripterygium Wilfordi that can protect against oxidative stress, inflammation, and cancer. However, whether Cel can alleviate neonatal hypoxic-ischemic (HI) brain damage remains unclear.

METHODS

Here, we established both in vitro and in vivo models of HI brain damage using CoCl2-treated PC12 cells and neonatal rats, respectively, and explored the neuroprotective effects of Cel in these models.

RESULTS

Analyses revealed that Cel administration reduced brain infarction size, microglia activation, levels of inflammation factors, and levels of oxidative stress markers by upregulating levels of p-AMPKα, Nrf2, HO-1, and by downregulating levels of TXNIP and NLRP3. Conversely, these beneficial effects of Cel on HI brain damage were largely inhibited by AMPKα inhibitor Compound C and its siRNA.

CONCLUSIONS

We present compelling evidence that Cel decreases inflammation and oxidative stress through the AMPKα/Nrf2/TXNIP signaling pathway, thereby alleviating neonatal HI brain injury. Cel therefore represents a promising therapeutic agent for treating HIE.

IMPACT

We firstly report that celastrol can ameliorate neonatal hypoxic-ischemic brain injury both in in vivo and in vitro, which represents a promising therapeutic agent for treating related brain injuries. Celastrol activates the AMPKα/Nrf2/TXNIP signaling pathway to relieve oxidative stress and inflammation and thereby alleviates neonatal hypoxic-ischemic brain injury.

Sub-dose anesthetics combined with chloride regulators protect the brain against chronic ischemia-hypoxia injury

BACKGROUND

Cerebral ischemia-hypoxia leads to excitotoxicity-mediated neuronal damage and cognitive dysfunction, especially in the elderly. Excessive intracellular [Cl- ]i accumulation weakens γ-aminobutyric acid (GABA) compensatory effects. Sub-anesthetic dose of propofol protected the brain against ischemia-hypoxia, which was abolished by blocking Cl- efflux transporter K+ /Cl- cotransporter 2 (KCC2). We aimed to determine whether low-dose anesthetic combined with [Cl- ]i regulators could restore the compensatory GABAergic system and improve cognitive function.

METHODS

Chronic cerebral hypoxia (CCH) model was established by bilateral carotid artery ligation in aged rats. Sub-dose of anesthetics (propofol and sevoflurane) with or without KCC2 agonist N-ethylmaleimide (NEM) or Na+ /K+ /Cl- cotransporter 1 (NKCC1) antagonist bumetanide (BTN) was administered systemically 30 days post-surgery. Primary rat hippocampal neuronal cultures were subjected to hypoxic injury with or without drug treatment. Memory function, hippocampal neuronal survival, GABAergic system functioning, and brain-derived neurotrophic factor (BDNF) expressions were evaluated.

RESULTS

Sub-anesthetic dose of combined propofol (1.2 μg mL-1 ) and sevoflurane [0.7 MAC (minimum alveolar concentration)] did not aggravate the hypoxic brain injury in rats or cell damage in neuronal cultures. Adding either BTN or NEM protected against hypoxic injury, associated with improved cognitive function in vivo, less intracellular accumulation of [Cl- ]i , reduced cell death, restored GABAergic compensation, and increased BDNF expression both in vivo and in vitro.

CONCLUSION

Sub-anesthetic dose of propofol and sevoflurane is a recommended anesthesia regimen in at-risk patients. Restoration of [Cl- ]i homeostasis and GABAergic could further reduce the brain damage caused by ischemia-hypoxia.

Effects of Prolactin on Brain Neurons under Hypoxia

The levels and potential role of prolactin (PRL) in the brain under conditions of acute systemic hypoxia were examined, focusing on the accumulation of PRL in cerebrospinal fluid (CSF) and its effects on neuronal activity and injury. The amount of PRL in the brain was investigated using brain tissues from forensic autopsy cases. We counted the number of neurites that formed in human primary neurons (HNs) after the addition of PRL. Furthermore, HNs supplemented with PRL or triiodothyronine (T3) were exposed to hypoxic conditions, and the dead cells were counted. The results showed correlations between brain PRL and CSF PRL levels. Additionally, PRL accumulation in the brain was observed in cases of asphyxia. In vitro experimental findings indicated increased neurite formation in the HNs treated with PRL. Moreover, both PRL and T3 demonstrated neuroprotective effects against hypoxia-induced neuronal cell death, with PRL showing stronger neuroprotective potential than T3. These results suggest that PRL accumulates in the brain during hypoxia, potentially influences neuronal activity, and exhibits neuroprotective properties against hypoxia-induced neuronal injury.

Neuroprotective effect of a novel brain-derived peptide, HIBDAP, against oxygen-glucose deprivation through inhibition of apoptosis in PC12 cells

BACKGROUND

The effect of a novel brain-derived peptide, hypoxic-ischemic brain damage associated peptide (HIBDAP), on apoptosis after oxygen-glucose deprivation (OGD) in PC12 cells was investigated.

METHODS

The HIBDAP sequence (HSQFIGYPITLFVEKER) was coupled with the carrier peptide of the transactivator of transcription (TAT) sequence (YGRKKRRQRRR). FITC-labelled TAT-HIBDAP was observed by fluorescence microscopy. After TAT-HIBDAP treatment and OGD treatment, the PC12 cell apoptosis rate was analysed using lactate dehydrogenase (LDH) leakage and Annexin V-fluorescein isothiocyanate (FITC) assays. Mitochondrial membrane potential (ΔΨm) was examined by fluorescence microscopy. Protein expression of apoptotic factors was examined by Western blotting.

RESULTS

FITC-labelled TAT-HIBDAP entered the PC12 cell nucleus. Compared with the OGD group, TAT-HIBDAP at low concentrations (1 µM, 5 µM, 10 µM) significantly reduced the apoptosis rate of PC12 cells (except at 20 µM); 5 µM TAT-HIBDAP had the most obvious effect. There were remarkable increases in ΔΨm at different concentrations (1 µM, 5 µM, 10 µM, 20 µM) of TAT-HIBDAP pretreatment, and 5 µM TAT-HIBDAP also had the most obvious effect. TAT-HIBDAP reversed the increased ratio of Bax/Bcl-2 and activation of Caspase-3 induced by OGD.

CONCLUSION

TAT-HIBDAP is resistant to OGD-induced PC12 cell apoptosis by regulating the Bax/Bcl-2/Caspase-3 pathway, which may provide a novel therapeutic strategy for neonatal HIBD.

Efficacy of polyarginine peptides in the treatment of stroke: A systematic review and meta-analysis

BACKGROUND

Disparities exist regarding an efficient treatment for stroke. Polyarginines have shown promising neuroprotective properties based on available published studies. Thus, the present study aims to systemically review and analyze existing evidence regarding polyarginine's administration efficacy in animal stroke models.

METHOD

Medline, Scopus, Embase, and Web of Science were systematically searched, in addition to manual search. Inclusion criteria were administrating polyarginine peptides in stroke animal models. Exclusion criteria were previous polyarginine administration, lacking a control group, review articles, and case reports. Data were collected and analyzed using STATA 17.0; a pooled standardized mean difference (SMD) with a 95% confidence interval (CI), meta-regression, and subgroup analyses were presented. Risk of bias, publication bias, and level of evidence were assessed using SYRCLE's tool, Egger's analysis, and Grading of Recommendations Assessment, Development and Evaluation framework, respectively.

RESULTS

From the 468 searched articles, 11 articles were included. Analyses showed that R18 significantly decreases infarct size (SMD = -0.65; 95% CI: -1.01, -0.29) and brain edema (SMD = -1.90; 95% CI: -3.28, -0.51) and improves neurological outcome (SMD = 0.67; 95% CI: 0.44, 0.91) and functional status (SMD = 0.55; 95% CI: 0.26, 0.85) in stroke animal models. Moreover, R18D significantly decreases infarct size (SMD = -0.75; 95% CI: -1.17, -0.33) and improves neurological outcome (SMD = 0.46; 95% CI: 0.06, 0.86) and functional status (SMD = 0.35; 95% CI: 0.16, 0.54) in stroke models.

CONCLUSION

Moderate level of evidence demonstrated that both R18 and R18D administration can significantly improve stroke outcomes in animal stroke models. However, considering the limitations, further pre-clinical and clinical studies are warranted to substantiate the neuroprotective efficacy of polyarginines for stroke.

Insight into the Neuroprotective Effect of Genistein-3'-Sodium Sulfonate Against Neonatal Hypoxic-Ischaemic Brain Injury in Rats by Bioinformatics

Therapeutic hypothermia (TH) is the only intervention approved for the treatment of neonatal hypoxic-ischaemic encephalopathy (HIE), but its treatment window is narrow (within 6 h after birth), and its efficacy is not ideal. Thus, alternative treatments are urgently needed. Our previous studies showed that genistein-3'-sodium sulfonate (GSS), a derivative of genistein (Gen), has a strong neuroprotective effect in rats with ischaemic stroke, but its role in HIE is unclear. A hypoxia-ischaemia (HI) brain injury model was established in neonatal male Sprague‒Dawley (SD) rats. Twenty-four hours after reperfusion, rats treated with GSS were assessed for cerebral infarction, neurological function, and neuronal damage. RNA-Seq and bioinformatics analysis were used to explore differentially expressed genes (DEGs) and regulated signalling pathways, which were subsequently validated by Western blotting and immunofluorescence. In this study, we found that GSS not only significantly reduced the size of brain infarcts and alleviated nerve damage in rats with HIE but also inhibited neuronal loss and degeneration in neonatal rats with HIE. A total of 2170 DEGs, of which 1102 were upregulated and 1068 were downregulated, were identified in the GSS group compared with the HI group. In an analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) categories, the downregulated DEGs were significantly enriched in the pathways "Phagosome", "NF-κB signalling", and "Complement and coagulation cascades", amongst others. Meanwhile, the upregulated DEGs were significantly enriched in the pathways "Neurodegeneration", "Glutamatergic synapse", and "Calcium signalling pathway", amongst others. These results indicate that GSS intervenes in the process of HIE-induced brain injury by participating in multiple pathways, which suggests potential candidate drugs for the treatment of HIE.

Diagnostic and Therapeutic Roles of the “Omics” in Hypoxic–Ischemic Encephalopathy in Neonates

Perinatal asphyxia and neonatal encephalopathy remain major causes of neonatal mortality, despite the improved availability of diagnostic and therapeutic tools, contributing to neurological and intellectual disabilities worldwide. An approach using a combination of clinical data, neuroimaging, and biochemical parameters is the current strategy towards the improved diagnosis and prognosis of the outcome in neonatal hypoxic–ischemic encephalopathy (HIE) using bioengineering methods. Traditional biomarkers are of little use in this multifactorial and variable phenotype-presenting clinical condition. Novel systems of biology-based “omics” approaches (genomics, transcriptome proteomics, and metabolomics) may help to identify biomarkers associated with brain and other tissue injuries, predicting the disease severity in HIE. Biomarker studies using omics technologies will likely be a key feature of future neuroprotective treatment methods and will help to assess the successful treatment and long-term efficacy of the intervention. This article reviews the roles of different omics as biomarkers of HIE and outlines the existing knowledge of our current understanding of the clinical use of different omics molecules as novel neonatal brain injury biomarkers, which may lead to improved interventions related to the diagnostic and therapeutic aspects of HIE.

The effect of sulforaphane on perinatal hypoxic-ischemic brain injury in rats

Perinatal hypoxic-ischemic insult (HII) is one of the main devastating causes of morbidity and mortality in newborns. HII induces brain injury which evolves to neurological sequelae later in life. Hypothermia is the only therapeutic approach available capable of diminishing brain impairment after HII. Finding a novel therapeutic method to reduce the severity of brain injury and its consequences is critical in neonatology. The present paper aimed to evaluate the effect of sulforaphane (SFN) pre-treatment on glucose metabolism, neurodegeneration, and functional outcome at the acute, sub-acute, and sub-chronic time intervals in the experimental model of perinatal hypoxic-ischemic insult in rats. To estimate the effect of SFN on brain glucose uptake we have performed 18F-deoxyglucose (FDG) microCT/PET. The activity of FDG was determined in the hippocampus and sensorimotor cortex. Neurodegeneration was assessed by histological analysis of Nissl-stained brain sections. To investigate functional outcomes a battery of behavioral tests was employed. We have shown that although SFN possesses a protective effect on glucose uptake in the ischemic hippocampus 24 h and 1 week after HII, no effect has been observed in the motor cortex. We have further shown that the ischemic hippocampal formation tends to be thinner in HIE and SFN treatment tends to reverse this pattern. We have observed subtle chronic movement deficit after HII detected by ladder rung walking test with no protective effect of SFN. SFN should be thus considered as a potent neuroprotective drug with the capability to interfere with pathophysiological processes triggered by perinatal hypoxic-ischemic insult.

The Effect of Sulphoraphane on Brain Glucose Uptake during Neonatal Hypoxic-Ischemic Encephalopathy in Newborn Rats

Neonatal hypoxic-ischemic insult (HII) is one of the leading causes of morbidity and mortality in newborns. It has long-term consequences and represents a socioeconomic burden. It is an urgent issue in current neonatology. The aim of the present pilot study was to evaluate the possible effect of sulforaphane on brain glucose uptake expressed as 18F-fluorodeoxyglucose (18F-FDG) activity at the acute, subacute, and subchronic time intervals after the experimental perinatal HII in rats. Significant protection has been observed in the hippocampus 5 weeks after the insult as represented by normalisations of interhemispheric ratio of measured 18F-FDG activity. In conclusion, positron emission tomography (PET) with 18F-FDG revealed a protective effect of SFN on glucose metabolism in the subchronic phase after HII. Further research within the field of neonatal HII in newborn rats will be necessary.

Panax notoginseng saponin attenuates the hypoxic-ischaemic injury in neonatal rats by regulating the expression of neurotrophin factors

Neonatal hypoxic-ischaemic (HI) injury is a serious complication of neonatal asphyxia and the leading cause of neonatal acute death and chronic neurological injury, and the effective therapeutic method is lacking to improve patients' outcomes. We reported in this study that panax notoginseng saponin (PNS) may provide a treatment option for HI. HI model was established using neonatal Sprague-Dawley rats and then intraperitoneally injected with different dosage of PNS, once a day for 7 days. Histological staining and behavioural evaluations were performed to elucidate the pathological changes and neurobehavioural variation after PNS treatment. We found PNS administration significantly reduced the infarct volume of brain tissues and improved the autonomous activities of neonatal rats, especially with higher dosage. PNS treatment at 40 mg/kg reduced neuronal damage, suppressed neuronal apoptosis and depressed astroglial reactive response. Moreover, the long-term cognitive and motor functions were also improved after PNS treatment at 40 mg/kg. Importantly, PNS treatment elevated the levels of BDNF and TrkB but decreased the expression of p75NTR both in the cortex and hippocampus of HI rats. The therapeutic efficacy of PNS might be correlated with PNS-activated BDNF/TrkB signalling and inactivation of p75NTR expression, providing a novel potential therapy for alleviating HI injury.

Drug delivery platforms for neonatal brain injury

Hypoxic-ischemic encephalopathy (HIE), initiated by the interruption of oxygenated blood supply to the brain, is a leading cause of death and lifelong disability in newborns. The pathogenesis of HIE involves a complex interplay of excitotoxicity, inflammation, and oxidative stress that results in acute to long term brain damage and functional impairments. Therapeutic hypothermia is the only approved treatment for HIE but has limited effectiveness for moderate to severe brain damage; thus, pharmacological intervention is explored as an adjunct therapy to hypothermia to further promote recovery. However, the limited bioavailability and the side-effects of systemic administration are factors that hinder the use of the candidate pharmacological agents. To overcome these barriers, therapeutic molecules may be packaged into nanoscale constructs to enable their delivery. Yet, the application of nanotechnology in infants is not well examined, and the neonatal brain presents unique challenges. Novel drug delivery platforms have the potential to magnify therapeutic effects in the damaged brain, mitigate side-effects associated with high systemic doses, and evade mechanisms that remove the drugs from circulation. Encouraging pre-clinical data demonstrates an attenuation of brain damage and increased structural and functional recovery. This review surveys the current progress in drug delivery for treating neonatal brain injury.

Advances in D-Amino Acids in Neurological Research

D-amino acids have been known to exist in the human brain for nearly 40 years, and they continue to be a field of active study to today. This review article aims to give a concise overview of the recent advances in D-amino acid research as they relate to the brain and neurological disorders. This work has largely been focused on modulation of the N-methyl-D-aspartate (NMDA) receptor and its relationship to Alzheimer’s disease and Schizophrenia, but there has been a wealth of novel research which has elucidated a novel role for several D-amino acids in altering brain chemistry in a neuroprotective manner. D-amino acids which have no currently known activity in the brain but which have active derivatives will also be reviewed.

Peptidome analysis of cerebrospinal fluid in neonates with hypoxic-ischemic brain damage

Hypoxic-ischemic brain injury (HIBD) causes neonatal death and serious neurological disability; however, there are currently no promising therapies for it excepting cooling. Therefore, in this study, we used peptidome analysis to identify differentially expressed peptides in cerebrospinal fluid (CSF) of neonates with HIBD or controls, which may give a foundation for finding new promising drugs of neonatal HIBD. CSF samples were collected from neonates with HIBD (n = 4) or controls (n = 4). ITRAQ LC-MS/MS was used to identify differentially expressed peptides between two groups. A total of 35 differentially expressed peptides from 25 precursor proteins were identified. The 2671.5 Da peptide (HSQFIGYPITLFVEKER), one of the down-regulated peptides in neonatal HIBD, is a fragment of heat shock protein 90-alpha (HSP90α/HSP90AA1). Results of bioinformatics analysis showed that HSP90α/HSP90AA1 was located in the protein-protein interaction (PPI) network hub and was involved in the NOD-LIKE receptor (NLR) signaling pathway. This peptide, we named it Hypoxic-Ischemic Brain Damage Associated Peptide (HIBDAP), is a hydrophilic peptide with high stability and has a long half-life of 3.5 h in mammalian reticulocytes. It was demonstrated that TAT-HIBDAP could successfully enter PC12 cells and further into the nucleus. After HIBDAP pretreatment and 6 h of OGD treatment, low concentrations of HIBDAP increased the survival rate of cells, except 40 μM had a toxic effect. Safe concentrations of HIBDAP reduced pyroptosis of PC12 cells under OGD, except 20 μM had no effect, by suppressing expressions of NLRP3, ASC and Caspase-1 except NLRP1. The results of our study identified the characterization and expression profiles of peptides in CSF of neonatal HIBD. Several meaningful peptides such as HIBDAP may play significant roles in neonatal HIBD and provide new therapeutic targets for neonatal HIBD.

Pathophysiology of hypoxic-ischemic encephalopathy: a review of the past and a view on the future

Hypoxic-ischemic encephalopathy, also referred as HIE, is a type of brain injury or damage that is caused by a lack of oxygen to the brain during neonatal period. The incidence is approximately 1.5 cases per 1000 live births in developed countries. In low and middle-income countries, the incidence is much higher (10‒20 per 1000 live births). The treatment for neonatal HIE is hypothermia that is only partially effective (not more than 50% of the neonates treated achieve an improved outcome). HIE pathophysiology involves oxidative stress, mitochondrial energy production failure, glutaminergic excitotoxicity, and apoptosis. So, in the last years, many studies have focused on peptides that act somewhere in the pathway activated by severe anoxic injury leading to HIE. This review describes the pathophysiology of perinatal HIE and the mechanisms that could be the target of innovative HIE treatments.

Assessment of recombinant tissue plasminogen activator (rtPA) toxicity in cultured neural cells and subsequent treatment with poly-arginine peptide R18D

Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) in ischaemic stroke has been associated with neurotoxicity, blood brain barrier (BBB) disruption and intra-cerebral hemorrhage. To examine rtPA cellular toxicity we investigated the effects of rtPA on cell viability in neuronal, astrocyte and brain endothelial cell (bEnd.3) cultures with and without prior exposure to oxygen-glucose deprivation (OGD). In addition, the neuroprotective peptide poly-arginine-18 (R18D; 18-mer of D-arginine) was examined for its ability to reduce rtPA toxicity. Studies demonstrated that a 4- or 24-h exposure of rtPA was toxic, affecting neuronal cell viability at ≥ 2 µM, and astrocyte and bEnd.3 cells viability at ≥ 5 μM. In addition, a 4-h exposure to rtPA after a period of OGD (OGD/rtPA) exacerbated toxicity, affecting neuronal, astrocyte and bEnd.3 cell viability at rtPA concentrations as low as 0.1 µM. Treatment of cells with low concentrations of R18D (0.5 and 1 µM) reduced the toxic effects of rtPA and OGD/rtPA, while on some occasions a higher 2 µM R18D concentrations exacerbated neuronal and bEnd.3 cell toxicity in OGD/rtPA exposed cultures. In exploratory studies we also demonstrated that OGD activates matrix metalloproteinase-9 (MMP-9) release into the supernatant of astrocyte and bEnd.3 cell cultures, but not neuronal cultures, and that OGD/rtPA increases MMP-9 activation. Furthermore, R18D decreased MMP-9 activation in OGD/rtPA treated astrocyte and bEnd.3 cell cultures. In summary, the findings show that rtPA can be toxic to neural cells and that OGD exacerbates toxicity, while R18D has the capacity to reduce rtPA neural cellular toxicity and reduce MMP-9 activation in astrocytes and bEnd.3. Poly-arginine-18 peptides, which are being developed as neuroprotective therapeutics for ischaemic stroke, therefore have the additional potential of reducing cytotoxic effects associated with rtPA thrombolysis in the treatment of ischaemic stroke.

Nose-to-brain delivery of hyaluronate - FG loop peptide conjugate for non-invasive hypoxic-ischemic encephalopathy therapy

The intranasal drug administration has attracted great interest as a non-invasive route allowing targeted delivery of drugs directly to the brain. However, one of the main issues in nasal drug administration is mucociliary clearance. Hyaluronate (HA) has been widely used as a mucoadhesive excipient for ocular, rectal, and vaginal delivery. Here, FG loop peptide (FGL) was conjugated to HA for improving enzymatic stability and delivery efficiency from the nose to the brain. The successful conjugation of FGL to aldehyde modified HA was confirmed by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (NMR). The outstanding enzymatic stability of HA-FGL conjugate was also corroborated by the GPC. The HA-FGL conjugate showed enhanced binding affinity onto nasal epithelial cells. In addition, in vivo nose-to-brain delivery of HA-FGL conjugate could be visualized by using an IVIS imaging system and fluorescence microscopy. Finally, in vivo therapeutic effect of HA-FGL conjugate was successfully confirmed by histological analysis, transferase-mediated uridine 5-triphosphate-biotin nick end-labeling (TUNEL) assay, immunofluorescent staining, transmission electron microscopy (TEM), and rotarod tests in hypoxic-ischemic encephalopathy model animals.