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McDouall A, Zhou KQ, Davies A, Wassink G, Jones TLM, Bennet L, Gunn AJ, Davidson JO. Slow rewarming after hypothermia does not ameliorate white matter injury after hypoxia-ischemia in near-term fetal sheep. Pediatr Res 2024:10.1038/s41390-024-03332-y. [PMID: 39103629 DOI: 10.1038/s41390-024-03332-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 04/10/2024] [Accepted: 05/18/2024] [Indexed: 08/07/2024]
Abstract
BACKGROUND The optimal rate to rewarm infants after therapeutic hypothermia is unclear. In this study we examined whether slow rewarming after 72 h of hypothermia would attenuate white matter injury. METHODS Near-term fetal sheep received sham occlusion (n = 8) or cerebral ischemia for 30 min, followed by normothermia (n = 7) or hypothermia from 3-72 h, with either spontaneous fast rewarming (n = 8) within 1 h, or slow rewarming at ~0.5 °C/h (n = 8) over 10 h. Fetuses were euthanized 7 days later. RESULTS Ischemia was associated with loss of total and mature oligodendrocytes, reduced expression of myelin proteins and induction of microglia and astrocytes, compared with sham controls (P < 0.05). Both hypothermia protocols were associated with a significant increase in numbers of total and mature oligodendrocytes, area fraction of myelin proteins and reduced numbers of microglia and astrocytes, compared with ischemia-normothermia (P < 0.05). There was no difference in the number of oligodendrocytes, microglia or astrocytes or expression of myelin proteins between fast and slow rewarming after hypothermia. CONCLUSION The rate of rewarming after a clinically relevant duration of hypothermia had no apparent effect on white matter protection by hypothermia after cerebral ischemia in near-term fetal sheep. IMPACT Persistent white matter injury is a major contributor to long-term disability after neonatal encephalopathy despite treatment with therapeutic hypothermia. The optimal rate to rewarm infants after therapeutic hypothermia is unclear; current protocols were developed on a precautionary basis. We now show that slow rewarming at 0.5 °C/h did not improve histological white matter injury compared with rapid spontaneous rewarming after a clinically established duration of hypothermia in near-term fetal sheep.
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Affiliation(s)
- Alice McDouall
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Kelly Q Zhou
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Anthony Davies
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Timothy L M Jones
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, The University of Auckland, Auckland, New Zealand.
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Lv H, Wang Q, Liu F, Jin L, Ren P, Li L. A biochemical feedback signal for hypothermia treatment for neonatal hypoxic-ischemic encephalopathy: focusing on central nervous system proteins in biofluids. Front Pediatr 2024; 12:1288853. [PMID: 38766393 PMCID: PMC11100326 DOI: 10.3389/fped.2024.1288853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 04/15/2024] [Indexed: 05/22/2024] Open
Abstract
Hypothermia has been widely used to treat moderate to severe neonatal hypoxic-ischemic encephalopathy (HIE), yet evaluating the effects of hypothermia relies on clinical neurology, neuroimaging, amplitude-integrated electroencephalography, and follow-up data on patient outcomes. Biomarkers of brain injury have been considered for estimating the effects of hypothermia. Proteins specific to the central nervous system (CNS) are components of nervous tissue, and once the CNS is damaged, these proteins are released into biofluids (cerebrospinal fluid, blood, urine, tears, saliva), and they can be used as markers of brain damage. Clinical reports have shown that CNS-specific marker proteins (CNSPs) were early expressed in biofluids after brain damage and formed unique biochemical profiles. As a result, these markers may serve as an indicator for screening brain injury in infants, monitoring disease progression, identifying damage region of brain, and assessing the efficacy of neuroprotective measures. In clinical work, we have found that there are few reports on using CNSPs as biological signals in hypothermia for neonatal HIE. The aim of this article is to review the classification, origin, biochemical composition, and physiological function of CNSPs with changes in their expression levels after hypothermia for neonatal HIE. Hopefully, this review will improve the awareness of CNSPs among pediatricians, and encourage future studies exploring the mechanisms behind the effects of hypothermia on these CNSPs, in order to reduce the adverse outcome of neonatal HIE.
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Affiliation(s)
- Hongyan Lv
- Department of Neonatology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
- Department of Neonatal Pathology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
| | - Qiuli Wang
- Department of Neonatology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
| | - Fang Liu
- Department of Pediatrics, The 980 Hospital of the PLA Joint Logistics Support Force, Shijiazhuang, China
| | - Linhong Jin
- Department of Neonatology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
| | - Pengshun Ren
- Department of Neonatology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
| | - Lianxiang Li
- Department of Neonatal Pathology, Handan Maternal and Child Health Care Hospital, Handan, Hebei, China
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3
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Li R, Lee JK, Govindan RB, Graham EM, Everett AD, Perin J, Vezina G, Tekes A, Chen MW, Northington F, Parkinson C, O’Kane A, McGowan M, Krein C, Al-Shargabi T, Chang T, Massaro AN. Plasma Biomarkers of Evolving Encephalopathy and Brain Injury in Neonates with Hypoxic-Ischemic Encephalopathy. J Pediatr 2023; 252:146-153.e2. [PMID: 35944723 PMCID: PMC9828943 DOI: 10.1016/j.jpeds.2022.07.046] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 07/12/2022] [Accepted: 07/22/2022] [Indexed: 01/12/2023]
Abstract
OBJECTIVE The objective of the study was to evaluate the relationship between a panel of candidate plasma biomarkers and (1) death or severe brain injury on magnetic resonance imaging (MRI) and (2) dysfunctional cerebral pressure autoregulation as a measure of evolving encephalopathy. STUDY DESIGN Neonates with moderate-to-severe hypoxic-ischemic encephalopathy (HIE) at 2 level IV neonatal intensive care units were enrolled into this observational study. Patients were treated with therapeutic hypothermia (TH) and monitored with continuous blood pressure monitoring and near-infrared spectroscopy. Cerebral pressure autoregulation was measured by the hemoglobin volume phase (HVP) index; a higher HVP index indicates poorer autoregulation. Serial blood samples were collected during TH and assayed for Tau, glial fibrillary acidic protein, and neurogranin. MRIs were assessed using National Institutes of Child Health and Human Development scores. The relationships between the candidate biomarkers and (1) death or severe brain injury on MRI (defined as a National Institutes of Child Health and Human Development score of ≥ 2B) and (2) autoregulation were evaluated using bivariate and adjusted logistic regression models. RESULTS Sixty-two patients were included. Elevated Tau levels on days 2-3 of TH were associated with death or severe injury on MRI (aOR: 1.06, 95% CI: 1.03-1.09; aOR: 1.04, 95% CI: 1.01-1.06, respectively). Higher Tau was also associated with poorer autoregulation (higher HVP index) on the same day (P = .022). CONCLUSIONS Elevated plasma levels of Tau are associated with death or severe brain injury by MRI and dysfunctional cerebral autoregulation in neonates with HIE. Larger-scale validation of Tau as a biomarker of brain injury in neonates with HIE is warranted.
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Affiliation(s)
- Ruoying Li
- Department of Neurology, Children’s National Hospital, Washington, DC
| | - Jennifer K. Lee
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Rathinaswamy B. Govindan
- Department of Pediatrics, The George Washington University School of Medicine, Washington, DC;,Prenatal Pediatrics Institute, Children’s National Hospital, Washington, DC
| | - Ernest M. Graham
- Department of Gynecology and Obstetrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Allen D. Everett
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Jamie Perin
- Department of Pediatrics, Center for Child and Community Health Research, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Gilbert Vezina
- Department of Pediatrics, The George Washington University School of Medicine, Washington, DC;,Division of Diagnostic Imaging and Radiology, Children’s National Hospital, Washington, DC
| | - Aylin Tekes
- Department of Radiology, Division of Pediatric Radiology and Pediatric Neuroradiology, Johns Hopkins University School of Medicine, Baltimore, MD
| | - May W. Chen
- Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Frances Northington
- Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Charlamaine Parkinson
- Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Alexandra O’Kane
- Department of Neurology, Children’s National Hospital, Washington, DC
| | - Meaghan McGowan
- Department of Neurology, Children’s National Hospital, Washington, DC
| | - Colleen Krein
- Prenatal Pediatrics Institute, Children’s National Hospital, Washington, DC
| | - Tareq Al-Shargabi
- Prenatal Pediatrics Institute, Children’s National Hospital, Washington, DC
| | - Taeun Chang
- Department of Neurology, Children’s National Hospital, Washington, DC;,Department of Pediatrics, The George Washington University School of Medicine, Washington, DC
| | - An N. Massaro
- Department of Pediatrics, The George Washington University School of Medicine, Washington, DC;,Division of Neonatology, Children’s National Hospital, Washington, DC
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Targeting Persistent Neuroinflammation after Hypoxic-Ischemic Encephalopathy-Is Exendin-4 the Answer? Int J Mol Sci 2022; 23:ijms231710191. [PMID: 36077587 PMCID: PMC9456443 DOI: 10.3390/ijms231710191] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 08/26/2022] [Accepted: 08/30/2022] [Indexed: 11/17/2022] Open
Abstract
Hypoxic-ischemic encephalopathy is brain injury resulting from the loss of oxygen and blood supply around the time of birth. It is associated with a high risk of death or disability. The only approved treatment is therapeutic hypothermia. Therapeutic hypothermia has consistently been shown to significantly reduce the risk of death and disability in infants with hypoxic-ischemic encephalopathy. However, approximately 29% of infants treated with therapeutic hypothermia still develop disability. Recent preclinical and clinical studies have shown that there is still persistent neuroinflammation even after treating with therapeutic hypothermia, which may contribute to the deficits seen in infants despite treatment. This suggests that potentially targeting this persistent neuroinflammation would have an additive benefit in addition to therapeutic hypothermia. A potential additive treatment is Exendin-4, which is a glucagon-like peptide 1 receptor agonist. Preclinical data from various in vitro and in vivo disease models have shown that Exendin-4 has anti-inflammatory, mitochondrial protective, anti-apoptotic, anti-oxidative and neurotrophic effects. Although preclinical studies of the effect of Exendin-4 in perinatal hypoxic-ischemic brain injury are limited, a seminal study in neonatal mice showed that Exendin-4 had promising neuroprotective effects. Further studies on Exendin-4 neuroprotection for perinatal hypoxic-ischemic brain injury, including in large animal translational models are warranted to better understand its safety, window of opportunity and effectiveness as an adjunct with therapeutic hypothermia.
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Persistent cortical and white matter inflammation after therapeutic hypothermia for ischemia in near-term fetal sheep. J Neuroinflammation 2022; 19:139. [PMID: 35690757 PMCID: PMC9188214 DOI: 10.1186/s12974-022-02499-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 05/23/2022] [Indexed: 02/07/2023] Open
Abstract
Background Therapeutic hypothermia significantly improves outcomes after moderate–severe hypoxic-ischemic encephalopathy (HIE), but it is partially effective. Although hypothermia is consistently associated with reduced microgliosis, it is still unclear whether it normalizes microglial morphology and phenotype. Methods Near-term fetal sheep (n = 24) were randomized to sham control, ischemia-normothermia, or ischemia-hypothermia. Brain sections were immunohistochemically labeled to assess neurons, microglia and their interactions with neurons, astrocytes, myelination, and gitter cells (microglia with cytoplasmic lipid granules) 7 days after cerebral ischemia. Lesions were defined as areas with complete loss of cells. RNAscope® was used to assess microglial phenotype markers CD86 and CD206. Results Ischemia-normothermia was associated with severe loss of neurons and myelin (p < 0.05), with extensive lesions, astrogliosis and microgliosis with a high proportion of gitter cells (p < 0.05). Microglial wrapping of neurons was present in both the ischemia groups. Hypothermia improved neuronal survival, suppressed lesions, gitter cells and gliosis (p < 0.05), and attenuated the reduction of myelin area fraction. The “M1” marker CD86 and “M2” marker CD206 were upregulated after ischemia. Hypothermia partially suppressed CD86 in the cortex only (p < 0.05), but did not affect CD206. Conclusions Hypothermia prevented lesions after cerebral ischemia, but only partially suppressed microglial wrapping and M1 marker expression. These data support the hypothesis that persistent upregulation of injurious microglial activity may contribute to partial neuroprotection after hypothermia, and that immunomodulation after rewarming may be an important therapeutic target.
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Davidson JO, Gonzalez F, Gressens P, Gunn AJ. Update on mechanisms of the pathophysiology of neonatal encephalopathy. Semin Fetal Neonatal Med 2021; 26:101267. [PMID: 34274259 DOI: 10.1016/j.siny.2021.101267] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Therapeutic hypothermia is now well established to significantly improve survival without disability after neonatal encephalopathy (NE). To further improve outcomes, we need to better understand the mechanisms of brain injury. The central finding, which offers the potential for neuroprotective and neurorestorative interventions, is that brain damage after perinatal hypoxia-ischemia evolves slowly over time. Although brain cells may die during profound hypoxia-ischemia, even after surprisingly severe insults many cells show transient recovery of oxidative metabolism during a "latent" phase characterized by actively suppressed neural metabolism and activity. Critically, after moderate to severe hypoxia-ischemia, this transient recovery is followed after ~6 h by a phase of secondary deterioration, with delayed seizures, failure of mitochondrial function, cytotoxic edema, and cell death over ~72 h. This is followed by a tertiary phase of remodeling and recovery. This review discusses the mechanisms of injury that occur during the primary, latent, secondary and tertiary phases of injury and potential treatments that target one or more of these phases. By analogy with therapeutic hypothermia, treatment as early as possible in the latent phase is likely to have the greatest potential to prevent injury ("neuroprotection"). In the secondary phase of injury, anticonvulsants can attenuate seizures, but show limited neuroprotection. Encouragingly, there is now increasing preclinical evidence that late, neurorestorative interventions have potential to improve long-term outcomes.
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Affiliation(s)
- Joanne O Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.
| | - Fernando Gonzalez
- Department of Pediatrics, University of California, San Francisco, CA, USA.
| | | | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.
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7
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Wassink G, Davidson JO, Crisostomo A, Zhou KQ, Galinsky R, Dhillon SK, Lear CA, Bennet L, Gunn AJ. Recombinant erythropoietin does not augment hypothermic white matter protection after global cerebral ischaemia in near-term fetal sheep. Brain Commun 2021; 3:fcab172. [PMID: 34409290 PMCID: PMC8364665 DOI: 10.1093/braincomms/fcab172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/31/2021] [Indexed: 01/07/2023] Open
Abstract
Therapeutic hypothermia for hypoxic-ischaemic encephalopathy provides partial white matter protection. Recombinant erythropoietin reduces demyelination after hypoxia-ischaemia, but it is unclear whether adjunct erythropoietin treatment can further improve outcomes after therapeutic hypothermia. Term-equivalent fetal sheep received sham-ischaemia (n = 9) or cerebral ischaemia for 30 min (ischaemia-vehicle, n = 8), followed by intravenous infusion of recombinant erythropoietin (ischaemia-Epo, n = 8; 5000 IU/kg bolus dose, then 833.3 IU/kg/h), cerebral hypothermia (ischaemia-hypothermia, n = 8), or recombinant erythropoietin plus hypothermia (ischaemia-Epo-hypothermia, n = 8), from 3 to 72 h post-ischaemia. Foetal brains were harvested at 7 days after cerebral ischaemia. Ischaemia was associated with marked loss of total Olig2-positive oligodendrocytes with reduced density of myelin and linearity of the white matter tracts (P < 0.01), and microglial induction and increased caspase-3-positive apoptosis. Cerebral hypothermia improved the total number of oligodendrocytes and restored myelin basic protein (P < 0.01), whereas recombinant erythropoietin partially improved myelin basic protein density and tract linearity. Both interventions suppressed microgliosis and caspase-3 (P < 0.05). Co-treatment improved 2′,3′-cyclic-nucleotide 3′-phosphodiesterase-myelin density compared to hypothermia, but had no other additive effect. These findings suggest that although hypothermia and recombinant erythropoietin independently protect white matter after severe hypoxia-ischaemia, they have partially overlapping anti-inflammatory and anti-apoptotic effects, with little additive benefit of combination therapy.
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Affiliation(s)
- Guido Wassink
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alyssa Crisostomo
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Kelly Q Zhou
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- The Ritchie Centre, Hudson Institute of Medical Research, Victoria, Australia
| | | | - Christopher A Lear
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, The University of Auckland, Auckland, New Zealand
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8
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Lee JK, Santos PT, Chen MW, O'Brien CE, Kulikowicz E, Adams S, Hardart H, Koehler RC, Martin LJ. Combining Hypothermia and Oleuropein Subacutely Protects Subcortical White Matter in a Swine Model of Neonatal Hypoxic-Ischemic Encephalopathy. J Neuropathol Exp Neurol 2021; 80:182-198. [PMID: 33212486 DOI: 10.1093/jnen/nlaa132] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Neonatal hypoxia-ischemia (HI) causes white matter injury that is not fully prevented by therapeutic hypothermia. Adjuvant treatments are needed. We compared myelination in different piglet white matter regions. We then tested whether oleuropein (OLE) improves neuroprotection in 2- to 4-day-old piglets randomized to undergo HI or sham procedure and OLE or vehicle administration beginning at 15 minutes. All groups received overnight hypothermia and rewarming. Injury in the subcortical white matter, corpus callosum, internal capsule, putamen, and motor cortex gray matter was assessed 1 day later. At baseline, piglets had greater subcortical myelination than in corpus callosum. Hypothermic HI piglets had scant injury in putamen and cerebral cortex. However, hypothermia alone did not prevent the loss of subcortical myelinating oligodendrocytes or the reduction in subcortical myelin density after HI. Combining OLE with hypothermia improved post-HI subcortical white matter protection by preserving myelinating oligodendrocytes, myelin density, and oligodendrocyte markers. Corpus callosum and internal capsule showed little HI injury after hypothermia, and OLE accordingly had minimal effect. OLE did not affect putamen or motor cortex neuron counts. Thus, OLE combined with hypothermia protected subcortical white matter after HI. As an adjuvant to hypothermia, OLE may subacutely improve regional white matter protection after HI.
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Affiliation(s)
- Jennifer K Lee
- From the Department of Anesthesiology and Critical Care Medicine
| | - Polan T Santos
- From the Department of Anesthesiology and Critical Care Medicine
| | - May W Chen
- Division of Neonatology, Department of Pediatrics
| | | | - Ewa Kulikowicz
- From the Department of Anesthesiology and Critical Care Medicine
| | - Shawn Adams
- From the Department of Anesthesiology and Critical Care Medicine
| | - Henry Hardart
- From the Department of Anesthesiology and Critical Care Medicine
| | | | - Lee J Martin
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland
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Microglia: A Potential Drug Target for Traumatic Axonal Injury. Neural Plast 2021; 2021:5554824. [PMID: 34093701 PMCID: PMC8163545 DOI: 10.1155/2021/5554824] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/06/2021] [Accepted: 04/26/2021] [Indexed: 12/20/2022] Open
Abstract
Traumatic axonal injury (TAI) is a major cause of death and disability among patients with severe traumatic brain injury (TBI); however, no effective therapies have been developed to treat this disorder. Neuroinflammation accompanying microglial activation after TBI is likely to be an important factor in TAI. In this review, we summarize the current research in this field, and recent studies suggest that microglial activation plays an important role in TAI development. We discuss several drugs and therapies that may aid TAI recovery by modulating the microglial phenotype following TBI. Based on the findings of recent studies, we conclude that the promotion of active microglia to the M2 phenotype is a potential drug target for the treatment of TAI.
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Maeda Y, Lear CA, Beacom MJ, Davidson JO, Zhou KQ, Gunning M, Ikeda T, Gunn AJ, Bennet L. Transient effects of forebrain ischemia on fetal heart rate variability in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2021; 320:R916-R924. [PMID: 33881362 DOI: 10.1152/ajpregu.00032.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fetal heart rate variability (FHRV) is a key index of antenatal and intrapartum fetal well-being. FHRV is well established to be mediated by both arms of the autonomic nervous system, but it remains unknown whether higher centers in the forebrain contribute to FHRV. We tested the hypothesis that selective forebrain ischemia would impair the generation of FHRV. Sixteen chronically instrumented near-term fetal sheep were subjected to either forebrain ischemia induced by bilateral carotid occlusion or sham-ischemia for 30 min. Time, frequency, and nonlinear measures of FHRV were assessed during and for seven days after ischemia. Ischemia was associated with profound suppression of electroencephalographic (EEG) power, which remained suppressed throughout the recovery period (P < 0.001). During the first 5 min of ischemia, multiple time and frequency domain measures were increased (all P < 0.05) before returning back to sham levels. A delayed increase in sample entropy was observed during ischemia (P < 0.05). For the first 3 h after ischemia, there was moderate suppression of two measures of FHRV (very-low frequency power and the standard deviation of RR-intervals, both P < 0.05) and increased sample entropy (P < 0.05). Thereafter, all measures of FHRV returned to control levels. In conclusion, profound forebrain ischemia sufficient to lead to severe neural injury had only transient effect on multiple measures of FHRV. These findings suggest that the forebrain makes a limited contribution to FHRV. FHRV therefore primarily originates in the hindbrain and is unlikely to provide meaningful information on forebrain neurodevelopment or metabolism.
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Affiliation(s)
- Yoshiki Maeda
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,The Department of Obstetrics and Gynaecology, Mie University, Mie, Japan
| | - Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Michael J Beacom
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Kelly Q Zhou
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Mark Gunning
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Tomoaki Ikeda
- The Department of Obstetrics and Gynaecology, Mie University, Mie, Japan
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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11
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Magnesium sulfate: a last roll of the dice for anti-excitotoxicity? Pediatr Res 2019; 86:685-687. [PMID: 31412352 DOI: 10.1038/s41390-019-0539-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/02/2019] [Indexed: 11/08/2022]
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