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Lear CA, Westgate JA, Bennet L, Ugwumadu A, Stone PR, Tournier A, Gunn AJ. Fetal defenses against intrapartum head compression-implications for intrapartum decelerations and hypoxic-ischemic injury. Am J Obstet Gynecol 2023; 228:S1117-S1128. [PMID: 34801443 DOI: 10.1016/j.ajog.2021.11.1352] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 11/05/2021] [Accepted: 11/14/2021] [Indexed: 01/27/2023]
Abstract
Uterine contractions during labor and engagement of the fetus in the birth canal can compress the fetal head. Its impact on the fetus is unclear and still controversial. In this integrative physiological review, we highlight evidence that decelerations are uncommonly associated with fetal head compression. Next, the fetus has an impressive ability to adapt to increased intracranial pressure through activation of the intracranial baroreflex, such that fetal cerebral perfusion is well-maintained during labor, except in the setting of prolonged systemic hypoxemia leading to secondary cardiovascular compromise. Thus, when it occurs, fetal head compression is not necessarily benign but does not seem to be a common contributor to intrapartum decelerations. Finally, the intracranial baroreflex and the peripheral chemoreflex (the response to acute hypoxemia) have overlapping efferent effects. We propose the hypothesis that these reflexes may work synergistically to promote fetal adaptation to labor.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand; Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Austin Ugwumadu
- Department of Obstetrics and Gynaecology, St. George's University of London, London, United Kingdom
| | - Peter R Stone
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Alexane Tournier
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand; Department of Paediatrics, Starship Children's Hospital, Auckland, New Zealand.
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2
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Kelly SB, Stojanovska V, Zahra VA, Moxham A, Miller SL, Moss TJM, Hooper SB, Nold MF, Nold-Petry CA, Dean JM, Bennet L, Polglase GR, Gunn AJ, Galinsky R. Interleukin-1 blockade attenuates white matter inflammation and oligodendrocyte loss after progressive systemic lipopolysaccharide exposure in near-term fetal sheep. J Neuroinflammation 2021; 18:189. [PMID: 34465372 PMCID: PMC8408978 DOI: 10.1186/s12974-021-02238-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 08/11/2021] [Indexed: 12/14/2022] Open
Abstract
Background Increased systemic and tissue levels of interleukin (IL)-1β are associated with greater risk of impaired neurodevelopment after birth. In this study, we tested the hypothesis that systemic IL-1 receptor antagonist (Ra) administration would attenuate brain inflammation and injury in near-term fetal sheep exposed to lipopolysaccharide (LPS). Methods Chronically instrumented near-term fetal sheep at 0.85 of gestation were randomly assigned to saline infusion (control, n = 9), repeated LPS infusions (0 h = 300 ng, 24 h = 600 ng, 48 h = 1200 ng, n = 8) or repeated LPS plus IL-1Ra infusions (13 mg/kg infused over 4 h) started 1 h after each LPS infusion (n = 9). Sheep were euthanized 4 days after starting infusions for histology. Results LPS infusions increased circulating cytokines and were associated with electroencephalogram (EEG) suppression with transiently reduced mean arterial blood pressure, and increased carotid artery perfusion and fetal heart rate (P < 0.05 vs. control for all). In the periventricular and intragyral white matter, LPS-exposure increased IL-1β immunoreactivity, numbers of caspase 3+ cells and microglia, reduced astrocyte and olig-2+ oligodendrocyte survival but did not change numbers of mature CC1+ oligodendrocytes, myelin expression or numbers of neurons in the cortex and subcortical regions. IL-1Ra infusions reduced circulating cytokines and improved recovery of EEG activity and carotid artery perfusion. Histologically, IL-1Ra reduced microgliosis, IL-1β expression and caspase-3+ cells, and improved olig-2+ oligodendrocyte survival. Conclusion IL-1Ra improved EEG activity and markedly attenuated systemic inflammation, microgliosis and oligodendrocyte loss following LPS exposure in near-term fetal sheep. Further studies examining the long-term effects on brain maturation are now needed. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-021-02238-4.
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Affiliation(s)
- Sharmony B Kelly
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia
| | - Vanesa Stojanovska
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia
| | - Valerie A Zahra
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia
| | - Alison Moxham
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia
| | - Suzanne L Miller
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia
| | - Timothy J M Moss
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia
| | - Marcel F Nold
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Paediatrics, Monash University, Melbourne, Victoria, Australia.,Monash Newborn, Monash Children's Hospital, Melbourne, Australia
| | - Claudia A Nold-Petry
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Paediatrics, Monash University, Melbourne, Victoria, Australia
| | - Justin M Dean
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Graeme R Polglase
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia
| | - Alistair J Gunn
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- The Ritchie Centre, Hudson Institute of Medical Research, 27-31 Wright street, Melbourne, Victoria, 3168, Australia. .,Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria, Australia.
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3
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Recher M, Prevost ALD, Sharma D, De Jonckheere J, Garabedian C, Storme L. Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep. PLoS One 2021; 16:e0254155. [PMID: 34228770 PMCID: PMC8259953 DOI: 10.1371/journal.pone.0254155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 06/21/2021] [Indexed: 01/08/2023] Open
Abstract
Fetal heart rate (FHR) deceleration is the most common change seen during labor. The role of the autonomic nervous system in regulating the fetal cardiovascular response during multiple uterine contractions has been well-established. However, the mechanism underlying the hemodynamic response remains unclear and the specific reflex that mediates the cardiovascular modifications is still controversial. This study aimed to determine the role of the sympathetic and parasympathetic systems on fetal hemodynamics in complete cord occlusion. Chronically instrumented fetal sheep were randomized to receive an intravenous injection of atropine 2.5 mg (n = 8), propranolol 5 mg (n = 7), atropine and propranolol (n = 7), or a control protocol (n = 9), followed by three episodes of 1-minute umbilical cord occlusion repeated every 5 minutes. Cord compression induces a rapid decrease in the FHR and a rapid increase in MAP. The decrease in FHR is caused by an increase in parasympathetic activity, (atropine and atropine-propranolol abolish the FHR response to the occlusion). The change in FHR during occlusion was not modified by propranolol injection, showing no effect of sympathetic tone. The increase in MAP during occlusion was similar in the four protocols. After releasing occlusion, the FHR was still lower than that at baseline due to a sustained parasympathetic tone. Suppression of the parasympathetic output to the cardiovascular system unmasks an increase in the FHR above baseline values. The lower FHR with the propranolol protocol further supports an increase in myocardial β-adrenoceptor stimulation after cord release. The increase in MAP after cord release was similar in the four protocols, except after the early stage of interocclusion period in atropine protocol. Four minutes after cord release, the FHR returned to baseline irrespective of the drugs that were infused, thereby showing recovery of ANS control. Blood gases (pH, PaCO2, PaO2) and plasma lactate concentrations was similar between the four protocols at the end of three applications of UCO. Complete cord compression-induced deceleration is likely due to acute activation of parasympathetic output. β-adrenoceptor activity is involved in the increase in FHR after cord release. Understanding the reflexes involved in FHR deceleration may help us understand the mechanisms underlying fetal autonomic adaptation during cord occlusion.
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Affiliation(s)
- Morgan Recher
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- Department of Pediatric Intensive Care Unit, CHU Lille, Jeanne de Flandre Hospital, Lille, France
- * E-mail:
| | - Arthur Lauriot Dit Prevost
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- Department of Pediatric Surgery, CHU Lille, Jeanne de Flandre Hospital, Lille, France
| | - Dyuti Sharma
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- Department of Pediatric Surgery, CHU Lille, Jeanne de Flandre Hospital, Lille, France
| | - Julien De Jonckheere
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- CHU Lille, Centre d’Innovation Technologique, Lille, France
| | - Charles Garabedian
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- Department of Obstetrics, CHU Lille, Jeanne de Flandre Hospital, Lille, France
| | - Laurent Storme
- Univ. Lille, ULR 2694 – METRICS: Evaluation des technologies de santé et des pratiques médicales, Lille, France
- Department of Neonatology, CHU Lille, Jeanne de Flandre Hospital, Lille, France
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4
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Galinsky R, van de Looij Y, Mitchell N, Dean JM, Dhillon SK, Yamaguchi K, Lear CA, Wassink G, Davidson JO, Nott F, Zahra VA, Kelly SB, King VJ, Sizonenko SV, Bennet L, Gunn AJ. Magnetic Resonance Imaging Correlates of White Matter Gliosis and Injury in Preterm Fetal Sheep Exposed to Progressive Systemic Inflammation. Int J Mol Sci 2020; 21:ijms21238891. [PMID: 33255257 PMCID: PMC7727662 DOI: 10.3390/ijms21238891] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 12/17/2022] Open
Abstract
Progressive fetal infection/inflammation is strongly associated with neural injury after preterm birth. We aimed to test the hypotheses that progressively developing fetal inflammation leads to neuroinflammation and impaired white matter development and that the histopathological changes can be detected using high-field diffusion tensor magnetic resonance imaging (MRI). Chronically instrumented preterm fetal sheep at 0.7 of gestation were randomly assigned to receive intravenous saline (control; n = 6) or a progressive infusion of lipopolysaccharide (LPS, 200 ng intravenous over 24 h then doubled every 24 h for 5 days to induce fetal inflammation, n = 7). Sheep were killed 10 days after starting the infusions, for histology and high-field diffusion tensor MRI. Progressive LPS infusion was associated with increased circulating interleukin (IL)-6 concentrations and moderate increases in carotid artery perfusion and the frequency of electroencephalogram (EEG) activity (p < 0.05 vs. control). In the periventricular white matter, fractional anisotropy (FA) was increased, and orientation dispersion index (ODI) was reduced (p < 0.05 vs. control for both). Histologically, in the same brain region, LPS infusion increased microglial activation and astrocyte numbers and reduced the total number of oligodendrocytes with no change in myelination or numbers of immature/mature oligodendrocytes. Numbers of astrocytes in the periventricular white matter were correlated with increased FA and reduced ODI signal intensities. Astrocyte coherence was associated with increased FA. Moderate astrogliosis, but not loss of total oligodendrocytes, after progressive fetal inflammation can be detected with high-field diffusion tensor MRI.
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Affiliation(s)
- Robert Galinsky
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria 3168, Australia; (F.N.); (V.A.Z.); (S.B.K.)
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria 3800, Australia
| | - Yohan van de Looij
- Division of Child Development & Growth, Department of Pediatrics, Gynaecology & Obstetrics, School of Medicine, University of Geneva, 1015 Geneva, Switzerland; (Y.v.d.L.); (S.V.S.)
| | - Natasha Mitchell
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Justin M. Dean
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Simerdeep K. Dhillon
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Kyohei Yamaguchi
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Christopher A. Lear
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Guido Wassink
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Joanne O. Davidson
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Fraser Nott
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria 3168, Australia; (F.N.); (V.A.Z.); (S.B.K.)
| | - Valerie A. Zahra
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria 3168, Australia; (F.N.); (V.A.Z.); (S.B.K.)
| | - Sharmony B. Kelly
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria 3168, Australia; (F.N.); (V.A.Z.); (S.B.K.)
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, Victoria 3800, Australia
| | - Victoria J. King
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Stéphane V. Sizonenko
- Division of Child Development & Growth, Department of Pediatrics, Gynaecology & Obstetrics, School of Medicine, University of Geneva, 1015 Geneva, Switzerland; (Y.v.d.L.); (S.V.S.)
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
| | - Alistair J. Gunn
- Department of Physiology, University of Auckland, Auckland 1023, New Zealand; (R.G.); (N.M.); (J.M.D.); (S.K.D.); (K.Y.); (C.A.L.); (G.W.); (J.O.D.); (V.J.K.); (L.B.)
- Correspondence:
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5
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Lear CA, Kasai M, Booth LC, Drury PP, Davidson JO, Maeda Y, Magawa S, Miyagi E, Ikeda T, Westgate JA, Bennet L, Gunn AJ. Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep. J Physiol 2020; 598:4523-4536. [PMID: 32705685 DOI: 10.1113/jp279573] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 07/13/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The majority of intrapartum decelerations are widely believed to be mediated by the baroreflex secondary to brief umbilical cord occlusions (UCOs) but this remains unproven. We examined the responses to brief-UCOs in fetal sheep and compared these to a phenylephrine-stimulated baroreflex in a separate cohort. A further cohort was instrumented with near-infrared spectroscopy to measure cerebral oxygenation during UCO. The first 3-4 s of the brief-UCOs were consistent with a baroreflex, and associated with a minor fall in fetal heart rate (FHR). Thereafter, the remainder of the FHR decelerations were highly consistent with the peripheral chemoreflex. The baroreflex is not sufficient to produce deep, rapid decelerations characteristic of variable decelerations and it is therefore likely to be a minor contributor to intrapartum decelerations. ABSTRACT Fetal heart rate (FHR) monitoring is widely used to assess fetal wellbeing during labour, yet the physiology underlying FHR patterns remains incompletely understood. The baroreflex is widely believed to mediate brief intrapartum decelerations, but evidence supporting this theory is lacking. We therefore investigated the physiological changes in near-term fetal sheep during brief repeated umbilical cord occlusions (brief-UCOs, n = 15). We compared this to separate cohorts that underwent a phenylephrine challenge to stimulate the baroreflex (n = 9) or were instrumented with near-infrared spectroscopy and underwent prolonged 15-min complete UCO (prolonged-UCO, n = 9). The first 3-4 s of brief-UCOs were associated with hypertension (P = 0.000), a fall in FHR by 9.7-16.9 bpm (P = 0.002). The FHR/MAP relationship during this time was consistent with that observed during a phenylephrine-induced baroreflex. At 4-5 s, the FHR/MAP relationship began to deviate from the phenylephrine baroreflex curve as FHR fell independently of MAP until its nadir in association with intense peripheral vasoconstriction (P = 0.000). During prolonged-UCO, cerebral oxygenation remained steady until 4 s after the start of prolonged-UCO, and then began to fall (P = 0.000). FHR and cerebral oxygenation then fell in parallel until the FHR nadir. In conclusion, the baroreflex has a minor role in mediating the first 3-4 s of FHR decelerations during complete UCO, but thereafter the peripheral chemoreflex is the dominant mediator. Overall, the baroreflex is neither necessary nor sufficient to produce deep, rapid decelerations characteristic of variable decelerations; it is therefore likely to be a minor contributor to intrapartum decelerations.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Michi Kasai
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - Lindsea C Booth
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Paul P Drury
- 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
| | - Yoshiki Maeda
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Shoichi Magawa
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Etsuko Miyagi
- Department of Obstetrics and Gynecology, Yokohama City University, Yokohama, Japan
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Jenny A Westgate
- 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
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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6
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Rodríguez M, Valez V, Cimarra C, Blasina F, Radi R. Hypoxic-Ischemic Encephalopathy and Mitochondrial Dysfunction: Facts, Unknowns, and Challenges. Antioxid Redox Signal 2020; 33:247-262. [PMID: 32295425 DOI: 10.1089/ars.2020.8093] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Significance: Hypoxic-ischemic events due to intrapartum complications represent the second cause of neonatal mortality and initiate an acute brain disorder known as hypoxic-ischemic encephalopathy (HIE). In HIE, the brain undergoes primary and secondary energy failure phases separated by a latent phase in which partial neuronal recovery is observed. A hypoxic-ischemic event leads to oxygen restriction causing ATP depletion, neuronal oxidative stress, and cell death. Mitochondrial dysfunction and enhanced oxidant formation in brain cells are characteristic phenomena associated with energy failure. Recent Advances: Mitochondrial sources of oxidants in neurons include complex I of the mitochondrial respiratory chain, as a key contributor to O2•- production via succinate by a reverse electron transport mechanism. The reaction of O2•- with nitric oxide (•NO) yields peroxynitrite, a mitochondrial and cellular toxin. Quantitation of the redox state of cytochrome c oxidase, through broadband near-infrared spectroscopy, represents a promising monitoring approach to evaluate mitochondrial dysfunction in vivo in humans, in conjunction with the determination of cerebral oxygenation and their correlation with the severity of brain injury. Critical Issues: The energetic failure being a key phenomenon in HIE connected with the severity of the encephalopathy, measurement of mitochondrial dysfunction in vivo provides an approach to assess evolution, prognosis, and adequate therapies. Restoration of mitochondrial redox homeostasis constitutes a key therapeutic goal. Future Directions: While hypothermia is the only currently accepted therapy in clinical management to preserve mitochondrial function, other mitochondria-targeted and/or redox-based treatments are likely to synergize to ensure further efficacy.
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Affiliation(s)
- Marianela Rodríguez
- Departamento de Bioquímica and Centro de Investigaciones Biomédicas (CEINBIO) and Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay.,Departamento de Neonatología, Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay
| | - Valeria Valez
- Departamento de Bioquímica and Centro de Investigaciones Biomédicas (CEINBIO) and Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay
| | - Carolina Cimarra
- Departamento de Bioquímica and Centro de Investigaciones Biomédicas (CEINBIO) and Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay
| | - Fernanda Blasina
- Departamento de Neonatología, Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay
| | - Rafael Radi
- Departamento de Bioquímica and Centro de Investigaciones Biomédicas (CEINBIO) and Facultad de Medicina, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay
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7
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Broadband NIRS Cerebral Evaluation of the Hemodynamic and Oxidative State of Cytochrome-c-Oxidase Responses to +Gz Acceleration in Healthy Volunteers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1232:339-345. [PMID: 31893429 PMCID: PMC7612835 DOI: 10.1007/978-3-030-34461-0_43] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We used a miniature broadband NIRS system to monitor concentration changes in brain oxygenation (oxy- and deoxy- haemoglobin [HbO2], [HHb]) and oxidised cytochrome-c-oxidase ([oxCCO]) during a high +Gz acceleration, induced by a human centrifuge, on two healthy experienced volunteers (2 male, 34 and 37 years). We performed a sequence of several +Gz exposures that were terminated at the onset of visual symptoms (loss of peripheral vision). Systemic parameters were recorded (i.e. heart rate, blood pressure and arterial saturation), and brain tissue blood volume changes ([HbT] = [HbO2] + [HHb]) and oxygen delivery ([HbDiff] = [HbO2] - [HHb]) were calculated. Volunteer 1 demonstrated a decrease in [HbT] of −3.49 ± 0.02 μMol and [HbDiff] of −3.23 ± 0.44 μMol, and an increase of [oxCCO] of 0.42 ± 0.01μMol. Volunteer 2 demonstrated a decrease in [HbDiff] of −4.37 ± 0.23 μMol, and no significant change in [HbT] (0.53 ± 0.06 μMol) and [oxCCO] (0.09 ± 0.06 μMol). The variability of the brain metabolic response was related to the level of ischaemia, suggesting that suppression of metabolism was due to lack of glucose substrate delivery rather than oxygen availability.
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8
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Kasai M, Lear CA, Davidson JO, Beacom MJ, Drury PP, Maeda Y, Miyagi E, Ikeda T, Bennet L, Gunn AJ. Early sinusoidal heart rate patterns and heart rate variability to assess hypoxia-ischaemia in near-term fetal sheep. J Physiol 2019; 597:5535-5548. [PMID: 31529698 DOI: 10.1113/jp278523] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/26/2019] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS •Therapeutic hypothermia needs to be started as early as possible in the first 6 h after acute injury caused by hypoxia-ischaemia (HI), but the severity and timing of HI are often unclear. In this study we evaluated whether measures of heart rate variability (HRV) might provide early biomarkers of HI. •The duration but not magnitude of suppression of HRV power and conversely increased sample entropy of the heart rate were associated with severity of HI, such that changes in the first 3 h did not discriminate between groups. •Relative changes in HRV power bands showed different patterns between groups and therefore may have the potential to evaluate the severity of HI. •Aberrant fetal heart rate patterns and increased arginine vasopressin levels in the first hour after moderate and severe HI were correlated with loss of EEG power after 3 days' recovery, suggesting potential utility as early biomarkers of outcome. ABSTRACT Therapeutic hypothermia is partially neuroprotective after acute injury caused by hypoxia-ischaemia (HI), likely because the timing and severity of HI are often unclear, making timely recruitment for treatment challenging. We evaluated the utility of changes in heart rate variability (HRV) after HI as biomarkers of the timing and severity of acute HI. Chronically instrumented fetal sheep at 0.85 gestational age were exposed to different durations of umbilical cord occlusion to produce mild (n = 6), moderate (n = 8) or severe HI (n = 8) or to sham occlusion (n = 5). Heart rate (HR) and HRV indices were assessed until 72 h after HI. All HI groups showed suppressed very low frequency HRV power and elevated sample entropy for the first 3 h; more prolonged changes were associated with greater severity of HI. Analysis of relative changes in spectral power showed that the moderate and severe groups showed a shift towards higher HRV frequencies, which was most marked after severe HI. This shift was associated with abnormal rhythmic HR patterns including sinusoidal patterns in the first hour after HI, and with elevated plasma levels of arginine vasopressin, which were correlated with subsequent loss of EEG power by day 3. In conclusion, absolute changes in HRV power in the first 3 h after acute HI were not significantly related to the severity of HI. The intriguing relative shift in spectral power towards higher frequencies likely reflects greater autonomic dysfunction after severe HI. However, sinusoidal HR patterns and elevated vasopressin levels may have utility as biomarkers of severe HI.
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Affiliation(s)
- Michi Kasai
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand.,Department of Obstetrics and Gynecology, Yokohama City University School of Medicine, Yokohama, Japan
| | - Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
| | - Joanne O Davidson
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
| | - Michael J Beacom
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
| | - Paul P Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
| | - Yoshiki Maeda
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand.,Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Etsuko Miyagi
- Department of Obstetrics and Gynecology, Yokohama City University School of Medicine, Yokohama, Japan
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynecology, Mie University, Mie, Japan
| | - Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
| | - Alistair J Gunn
- Fetal Physiology and Neuroscience Group, Department of Physiology, University of Auckland, New Zealand
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9
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Zhou KQ, Green CR, Bennet L, Gunn AJ, Davidson JO. The Role of Connexin and Pannexin Channels in Perinatal Brain Injury and Inflammation. Front Physiol 2019; 10:141. [PMID: 30873043 PMCID: PMC6400979 DOI: 10.3389/fphys.2019.00141] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/07/2019] [Indexed: 12/21/2022] Open
Abstract
Perinatal brain injury remains a major cause of death and life-long disability. Perinatal brain injury is typically associated with hypoxia-ischemia and/or infection/inflammation. Both hypoxia-ischemia and infection trigger an inflammatory response in the brain. The inflammatory response can contribute to brain cell loss and chronic neuroinflammation leading to neurological impairments. It is now well-established that brain injury evolves over time, and shows a striking spread from injured to previously uninjured regions of the brain. There is increasing evidence that this spread is related to opening of connexin hemichannels and pannexin channels, both of which are large conductance membrane channels found in almost all cell types in the brain. Blocking connexin hemichannels within the first 3 h after hypoxia-ischemia has been shown to improve outcomes in term equivalent fetal sheep but it is important to also understand the downstream pathways linking membrane channel opening with the development of injury in order to identify new therapeutic targets. Open membrane channels release adenosine triphosphate (ATP), and other neuroactive molecules, into the extracellular space. ATP has an important physiological role, but has also been reported to act as a damage-associated molecular pattern (DAMP) signal mediated through specific purinergic receptors and so act as a primary signal 1 in the innate immune system inflammasome pathway. More crucially, extracellular ATP is a key inflammasome signal 2 activator, with purinergic receptor binding triggering the assembly of the multi-protein inflammasome complex. The inflammasome pathway and complex formation contribute to activation of inflammatory caspases, and the release of inflammatory cytokines, including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-18, and vascular endothelial growth factor (VEGF). We propose that the NOD-like receptor protein-3 (NLRP3) inflammasome, which has been linked to inflammatory responses in models of ischemic stroke and various inflammatory diseases, may be one mechanism by which connexin hemichannel opening especially mediates perinatal brain injury.
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Affiliation(s)
- Kelly Q Zhou
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Colin R Green
- Department of Ophthalmology, 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.,Department of Ophthalmology, The University of Auckland, Auckland, New Zealand
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10
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Lear CA, Westgate JA, Ugwumadu A, Nijhuis JG, Stone PR, Georgieva A, Ikeda T, Wassink G, Bennet L, Gunn AJ. Understanding Fetal Heart Rate Patterns That May Predict Antenatal and Intrapartum Neural Injury. Semin Pediatr Neurol 2018; 28:3-16. [PMID: 30522726 DOI: 10.1016/j.spen.2018.05.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Electronic fetal heart rate (FHR) monitoring is widely used to assess fetal well-being throughout pregnancy and labor. Both antenatal and intrapartum FHR monitoring are associated with a high negative predictive value and a very poor positive predictive value. This in part reflects the physiological resilience of the healthy fetus and the remarkable effectiveness of fetal adaptations to even severe challenges. In this way, the majority of "abnormal" FHR patterns in fact reflect a fetus' appropriate adaptive responses to adverse in utero conditions. Understanding the physiology of these adaptations, how they are reflected in the FHR trace and in what conditions they can fail is therefore critical to appreciating both the potential uses and limitations of electronic FHR monitoring.
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Affiliation(s)
- Christopher A Lear
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand; Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Austin Ugwumadu
- Department of Obstetrics and Gynaecology, St George's, University of London, London, United Kingdom
| | - Jan G Nijhuis
- Department of Obstetrics and Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, Netherlands
| | - Peter R Stone
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Antoniya Georgieva
- Nuffield Department of Obstetrics and Gynaecology, The John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynaecology, Mie University Graduate School of Medicine, Mie, Japan
| | - Guido Wassink
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- Department of Physiology, The Fetal Physiology and Neuroscience Group, The University of Auckland, Auckland, New Zealand; Department of Paediatrics, Starship Children's Hospital, Auckland, New Zealand.
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11
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Lear CA, Wassink G, Westgate JA, Nijhuis JG, Ugwumadu A, Galinsky R, Bennet L, Gunn AJ. The peripheral chemoreflex: indefatigable guardian of fetal physiological adaptation to labour. J Physiol 2018; 596:5611-5623. [PMID: 29604081 DOI: 10.1113/jp274937] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 03/29/2018] [Indexed: 01/10/2023] Open
Abstract
The fetus is consistently exposed to repeated periods of impaired oxygen (hypoxaemia) and nutrient supply in labour. This is balanced by the healthy fetus's remarkable anaerobic tolerance and impressive ability to mount protective adaptations to hypoxaemia. The most important mediator of fetal adaptations to brief repeated hypoxaemia is the peripheral chemoreflex, a rapid reflex response to acute falls in arterial oxygen tension. The overwhelming majority of fetuses are able to respond to repeated uterine contractions without developing hypotension or hypoxic-ischaemic injury. In contrast, fetuses who are either exposed to severe hypoxaemia, for example during uterine hyperstimulation, or enter labour with reduced anaerobic reserve (e.g. as shown by severe fetal growth restriction) are at increased risk of developing intermittent hypotension and cerebral hypoperfusion. It is remarkable to note that when fetuses develop hypotension during such repeated severe hypoxaemia, it is not mediated by impaired reflex adaptation, but by failure to maintain combined ventricular output, likely due to a combination of exhaustion of myocardial glycogen and evolving myocardial injury. The chemoreflex is suppressed by relatively long periods of severe hypoxaemia of 1.5-2 min, longer than the typical contraction. Even in this setting, the peripheral chemoreflex is consistently reactivated between contractions. These findings demonstrate that the peripheral chemoreflex is an indefatigable guardian of fetal adaptation to labour.
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Affiliation(s)
- Christopher A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Guido Wassink
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand.,Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Jan G Nijhuis
- Department of Obstetrics and Gynaecology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Austin Ugwumadu
- Department of Obstetrics and Gynaecology, St George's, University of London, London, UK
| | - Robert Galinsky
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
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12
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Galinsky R, Dhillon SK, Lear CA, Yamaguchi K, Wassink G, Gunn AJ, Bennet L. Magnesium sulfate and sex differences in cardiovascular and neural adaptations during normoxia and asphyxia in preterm fetal sheep. Am J Physiol Regul Integr Comp Physiol 2018; 315:R205-R217. [PMID: 29561649 DOI: 10.1152/ajpregu.00390.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Magnesium sulfate (MgSO4) is recommended for preterm neuroprotection, preeclampsia, and preterm labor prophylaxis. There is an important, unmet need to carefully test clinical interventions in both sexes. Therefore, we aimed to investigate cardiovascular and neurophysiological adaptations to MgSO4 during normoxia and asphyxia in preterm male and female fetal sheep. Fetuses were instrumented at 98 ± 1 days of gestation (term = 147 days). At 104 days, unanesthetized fetuses were randomly assigned to intravenous MgSO4 ( n = 12 female, 10 male) or saline ( n = 13 female, 10 male). At 105 days fetuses underwent umbilical cord occlusion for up to 25 min. Occlusions were stopped early if mean arterial blood pressure (MAP) fell below 8 mmHg or asystole occurred for >20 s. During normoxia, MgSO4 was associated with similar reductions in fetal heart rate (FHR), EEG power, and movement in both sexes ( P < 0.05 vs. saline controls) and suppression of α- and β-spectral band power in males ( P < 0.05 vs. saline controls). During occlusion, similar FHR and MAP responses occurred in MgSO4-treated males and females compared with saline controls. Recovery of FHR and MAP after release of occlusion was more prolonged in MgSO4-treated males ( P < 0.05 vs. saline controls). During and after occlusion, EEG power was lower in MgSO4-treated females ( P < 0.05 vs. saline controls). In conclusion, MgSO4 infusion was associated with subtle sex-specific effects on EEG spectral power and cardiac responses to asphyxia in utero, possibly reflecting sex-specific differences in interneuronal connectivity and regulation of cardiac output.
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Affiliation(s)
- Robert Galinsky
- Department of Physiology, University of Auckland , Auckland , New Zealand.,The Ritchie Centre, Hudson Institute of Medical Research , Clayton, VIC , Australia
| | | | - Christopher A Lear
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Kyohei Yamaguchi
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Guido Wassink
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Alistair J Gunn
- Department of Physiology, University of Auckland , Auckland , New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland , Auckland , New Zealand
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13
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Bennet L. Sex, drugs and rock and roll: tales from preterm fetal life. J Physiol 2017; 595:1865-1881. [PMID: 28094441 DOI: 10.1113/jp272999] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Accepted: 12/22/2016] [Indexed: 12/14/2022] Open
Abstract
Premature fetuses and babies are at greater risk of mortality and morbidity than their term counterparts. The underlying causes are multifactorial, but include exposure to hypoxia. Immaturity of organs and their functional control may impair the physiological defence responses to hypoxia and the preterm fetal responses, or lack thereof, to moderate hypoxia appear to support this concept. However, as this review demonstrates, despite immaturity, the preterm fetus responds to asphyxia in a qualitatively similar manner to that seen at term. This highlights the importance in understanding metabolism versus homeostatic threat when assessing fetal responses to adverse challenges such as hypoxia. Data are presented to show that the preterm fetal adaptation to asphyxia is triphasic in nature. Phase one represents the rapid institution of maximal defences, designed to maintain blood pressure and central perfusion at the expense of peripheral organs. Phase two is one of adaptive compensation. Controlled reperfusion partially offsets peripheral tissue oxygen debt, while maintaining sufficient vasoconstriction to limit the fall in perfusion. Phase three is about decompensation. Strikingly, the preterm fetus generally performs better during phases two and three, and can survive for longer without injury. Paradoxically, however, the ability to survive can lead to longer exposure to hypotension and hypoperfusion and thus potentially greater injury. The effects of fetal sex, inflammation and drugs on the triphasic adaptations are reviewed. Finally, the review highlights the need for more comprehensive studies to understand the complexity of perinatal physiology if we are to develop effective strategies to improve preterm outcomes.
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Affiliation(s)
- Laura Bennet
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton, Auckland, 1023, New Zealand
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14
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Lear CA, Koome ME, Davidson JO, Drury PP, Quaedackers JS, Galinsky R, Gunn AJ, Bennet L. The effects of dexamethasone on post-asphyxial cerebral oxygenation in the preterm fetal sheep. J Physiol 2014; 592:5493-505. [PMID: 25384775 DOI: 10.1113/jphysiol.2014.281253] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Exposure to clinical doses of the glucocorticoid dexamethasone increases brain activity and causes seizures in normoxic preterm fetal sheep without causing brain injury. In contrast, the same treatment after asphyxia increased brain injury. We hypothesised that increased injury was in part mediated by a mismatch between oxygen demand and oxygen supply. In preterm fetal sheep at 0.7 gestation we measured cerebral oxygenation using near-infrared spectroscopy, electroencephalographic (EEG) activity, and carotid blood flow (CaBF) from 24 h before until 72 h after asphyxia induced by 25 min of umbilical cord occlusion. Ewes received dexamethasone intramuscularly (12 mg 3 ml(-1)) or saline 15 min after the end of asphyxia. Fetuses were studied for 3 days after occlusion. During the first 6 h of recovery after asphyxia, dexamethasone treatment was associated with a significantly greater fall in CaBF (P < 0.05), increased carotid vascular resistance (P < 0.001) and a greater fall in cerebral oxygenation as measured by the difference between oxygenated and deoxygenated haemoglobin (delta haemoglobin; P < 0.05). EEG activity was similarly suppressed in both groups. From 6 to 10 h onward, dexamethasone treatment was associated with a return of CaBF to saline control levels, increased EEG power (P < 0.005), greater epileptiform transient activity (P < 0.001), increased oxidised cytochrome oxidase (P < 0.05) and an attenuated increase in [delta haemoglobin] (P < 0.05). In conclusion, dexamethasone treatment after asphyxia is associated with greater hypoperfusion in the critical latent phase, leading to impaired intracerebral oxygenation that may exacerbate neural injury after asphyxia.
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Affiliation(s)
- Christopher A Lear
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Miriam E Koome
- 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
| | - Paul P Drury
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Josine S Quaedackers
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - 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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15
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Bale G, Mitra S, Meek J, Robertson N, Tachtsidis I. A new broadband near-infrared spectroscopy system for in-vivo measurements of cerebral cytochrome-c-oxidase changes in neonatal brain injury. BIOMEDICAL OPTICS EXPRESS 2014; 5:3450-66. [PMID: 25360364 PMCID: PMC4206316 DOI: 10.1364/boe.5.003450] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 08/15/2014] [Accepted: 08/22/2014] [Indexed: 05/02/2023]
Abstract
We present a novel lens-based broadband near-infrared spectroscopy system to simultaneously measure cerebral changes in tissue oxygenation and haemodynamics via estimation of the changes in haemoglobin concentration; in addition to oxygen utilization via the measurement of the oxidation state of cytochrome-c-oxidase (CCO). We demonstrate the use of the system in a cohort of 6 newborn infants with neonatal encephalopathy in the Neonatal Intensive Care Unit for continuous measurement periods of up to 5 days. NIRS data was collected from above the frontal lobe on the left and right hemispheres simultaneously with systemic data to allow multimodal data analysis. This allowed us to study the NIRS variables in response to global pathophysiological events and we focused our analysis to spontaneous oxygen desaturations. We identified changes from the NIRS variables during 236 oxygen desaturations from over 212 hours of data with a change from the baseline to nadir of -12 ± 3%. There was a consistent negative change in the Δ[HbD] (= oxygenated - deoxygenated haemoglobin) and Δ[oxCCO] measurements, mean decreases were 3.0 ± 1.7μM and 0.22 ± 0.11μM, and a positive change in the Δ[HbT] (= oxygenated + deoxygenated haemoglobin) measurements across all subjects, mean increase was 0.85 ± 0.58μM. We have shown with a feasibility study that the relationship between haemoglobin oxygenation changes and CCO oxidation changes during these desaturation events was significantly associated with a magnetic resonance spectroscopy (MRS)-measured biomarker of injury severity (r = 0.91, p<0.01).
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Affiliation(s)
- Gemma Bale
- Department of Medical Physics and Bioengineering, Malet Place Engineering Building, University College London, UK
| | - Subhabrata Mitra
- Institute for Women’s Health, University College London and Neonatal Unit, University College London Hospitals Trust, London, UK
| | - Judith Meek
- Institute for Women’s Health, University College London and Neonatal Unit, University College London Hospitals Trust, London, UK
| | - Nicola Robertson
- Institute for Women’s Health, University College London and Neonatal Unit, University College London Hospitals Trust, London, UK
| | - Ilias Tachtsidis
- Department of Medical Physics and Bioengineering, Malet Place Engineering Building, University College London, UK
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16
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Status epilepticus after prolonged umbilical cord occlusion is associated with greater neural injury in [corrected] fetal sheep at term-equivalent. PLoS One 2014; 9:e96530. [PMID: 24797081 PMCID: PMC4010475 DOI: 10.1371/journal.pone.0096530] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 04/08/2014] [Indexed: 12/24/2022] Open
Abstract
The majority of pre-clinical studies of hypoxic-ischemic encephalopathy at term-equivalent have focused on either relatively mild insults, or on functional paradigms of cerebral ischemia or hypoxia-ischemia/hypotension. There is surprisingly little information on the responses to single, severe ‘physiological’ insults. In this study we examined the evolution and pattern of neural injury after prolonged umbilical cord occlusion (UCO). 36 chronically instrumented fetal sheep at 125–129 days gestational age (term = 147 days) were subjected to either UCO until mean arterial pressure was < = 8 mmHg (n = 29), or sham occlusion (n = 7). Surviving fetuses were killed after 72 hours for histopathologic assessment with acid-fuchsin thionine. After UCO, 11 fetuses died with intractable hypotension and 5 ewes entered labor and were euthanized. The remaining 13 fetuses showed marked EEG suppression followed by evolving seizures starting at 5.8 (6.8) hours (median (interquartile range)). 6 of 13 developed status epilepticus, which was associated with a transient secondary increase in cortical impedance (a measure of cytotoxic edema, p<0.05). All fetuses showed moderate to severe neuronal loss in the hippocampus and the basal ganglia but mild cortical cell loss (p<0.05 vs sham occlusion). Status epilepticus was associated with more severe terminal hypotension (p<0.05) and subsequently, greater neuronal loss (p<0.05). In conclusion, profound UCO in term-equivalent fetal sheep was associated with delayed seizures, secondary cytotoxic edema, and subcortical injury, consistent with the predominant pattern after peripartum sentinel events at term. It is unclear whether status epilepticus exacerbated cortical injury or was simply a reflection of a longer duration of asphyxia.
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17
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Czikk MJ, Totten S, Hammond R, Richardson BS. Microtubule-associated protein 2 and synaptophysin in the preterm and near-term ovine fetal brain and the effect of intermittent umbilical cord occlusion. Reprod Sci 2014; 22:367-76. [PMID: 24700051 DOI: 10.1177/1933719114529371] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We have determined the change in immunoreactivity (IR) for microtubule-associated protein 2 (MAP-2) and synaptophysin (SYN) as markers for dendritic and presynaptic nerve development, respectively, in the ovine fetal brain with advancing gestation and in response to intermittent umbilical cord occlusion (UCO), which might then contribute to adverse neurodevelopment. Fetal sheep (control and experimental groups preterm at 111-115 and near term at 132-138 days of gestation; term = 145 days) were studied over 4 days with UCOs performed by inflation of an occluder cuff for 90 seconds every 30 minutes for 3 to 5 hours each day. Animals were then euthanized and fetal brains assessed for IR of MAP-2 and SYN. In control animals, the IR of SYN increased in the gray matter with advancing gestation consistent with a developmental increase in presynaptic vesicles and/or nerve terminals as expected; however, the IR of MAP-2 decreased in all brain regions studied, suggesting concurrent refinement in dendritic branching and spine development. Intermittent UCO as studied with marked but limited hypoxemia resulted in a decrease in IR of SYN for the brain regions of the preterm animals when protein turnover is higher and indicates decreased presynaptic vesicle formation; whereas, MAP-2 IR was selectively increased in the hippocampus CA1 and thalamus of the near-term animals, consistent with reactive dendritic change and heightened vulnerability for neuronal injury. As such, intermittent cord compressions in the ovine fetus can impact protein markers for dendritic and presynaptic nerve development depending on their timing, which might then lead to alterations in synapse formation and neuronal circuitry.
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Affiliation(s)
- Marie J Czikk
- Department of Obstetrics & Gynaecology, University of Toronto, Toronto, Canada
| | - Stephanie Totten
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Robert Hammond
- Department of Pathology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Bryan S Richardson
- Departments of Obstetrics and Gynecology, Physiology and Pharmacology, and Pediatrics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
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18
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Drury PP, Davidson JO, van den Heuij LG, Tan S, Silverman RB, Ji H, Blood AB, Fraser M, Bennet L, Gunn AJ. Partial neuroprotection by nNOS inhibition during profound asphyxia in preterm fetal sheep. Exp Neurol 2013; 250:282-92. [PMID: 24120436 DOI: 10.1016/j.expneurol.2013.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 09/30/2013] [Accepted: 10/02/2013] [Indexed: 11/19/2022]
Abstract
Preterm brain injury is partly associated with hypoxia-ischemia starting before birth. Excessive nitric oxide production during HI may cause nitrosative stress, leading to cell membrane and mitochondrial damage. We therefore tested the hypothesis that therapy with a new, selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10 (0.022mg/kg bolus, n=8), given 30min before 25min of complete umbilical cord occlusion was protective in preterm fetal sheep at 101-104day gestation (term is 147days), compared to saline (n=8). JI-10 had no effect on fetal blood pressure, heart rate, carotid and femoral blood flow, total EEG power, nuchal activity, temperature or intracerebral oxygenation on near-infrared spectroscopy during or after occlusion. JI-10 was associated with later onset of post-asphyxial seizures compared with saline (p<0.05), and attenuation of the subsequent progressive loss of cytochrome oxidase (p<0.05). After 7days recovery, JI-10 was associated with improved neuronal survival in the caudate nucleus (p<0.05), but not the putamen or hippocampus, and more CNPase positive oligodendrocytes in the periventricular white matter (p<0.05). In conclusion, prophylactic nNOS inhibition before profound asphyxia was associated with delayed onset of seizures, slower decline of cytochrome oxidase and partial white and gray matter protection, consistent with protection of mitochondrial function.
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Affiliation(s)
- Paul P Drury
- Department of Physiology, University of Auckland, Auckland, New Zealand.
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Dean JM, McClendon E, Hansen K, Azimi-Zonooz A, Chen K, Riddle A, Gong X, Sharifnia E, Hagen M, Ahmad T, Leigland LA, Hohimer AR, Kroenke CD, Back SA. Prenatal cerebral ischemia disrupts MRI-defined cortical microstructure through disturbances in neuronal arborization. Sci Transl Med 2013; 5:168ra7. [PMID: 23325800 DOI: 10.1126/scitranslmed.3004669] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Children who survive preterm birth exhibit persistent unexplained disturbances in cerebral cortical growth with associated cognitive and learning disabilities. The mechanisms underlying these deficits remain elusive. We used ex vivo diffusion magnetic resonance imaging to demonstrate in a preterm large-animal model that cerebral ischemia impairs cortical growth and the normal maturational decline in cortical fractional anisotropy (FA). Analysis of pyramidal neurons revealed that cortical deficits were associated with impaired expansion of the dendritic arbor and reduced synaptic density. Together, these findings suggest a link between abnormal cortical FA and disturbances of neuronal morphological development. To experimentally investigate this possibility, we measured the orientation distribution of dendritic branches and observed that it corresponds with the theoretically predicted pattern of increased anisotropy within cases that exhibited elevated cortical FA after ischemia. We conclude that cortical growth impairments are associated with diffuse disturbances in the dendritic arbor and synapse formation of cortical neurons, which may underlie the cognitive and learning disabilities in survivors of preterm birth. Further, measurement of cortical FA may be useful for noninvasively detecting neurological disorders affecting cortical development.
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Affiliation(s)
- Justin M Dean
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Evelyn McClendon
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Kelly Hansen
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Aryan Azimi-Zonooz
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Kevin Chen
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Art Riddle
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Xi Gong
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Elica Sharifnia
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Matthew Hagen
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Tahir Ahmad
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA
| | - Lindsey A Leigland
- Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR 97239, USA.,Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA
| | - A Roger Hohimer
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, OR 97239, USA
| | - Christopher D Kroenke
- Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR 97239, USA.,Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA
| | - Stephen A Back
- Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA.,Department of Neurology, Oregon Health & Science University, Portland, OR 97239, USA
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Wassink G, Bennet L, Davidson JO, Westgate JA, Gunn AJ. Pre-existing hypoxia is associated with greater EEG suppression and early onset of evolving seizure activity during brief repeated asphyxia in near-term fetal sheep. PLoS One 2013; 8:e73895. [PMID: 23991209 PMCID: PMC3749175 DOI: 10.1371/journal.pone.0073895] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 07/23/2013] [Indexed: 11/19/2022] Open
Abstract
Spontaneous antenatal hypoxia is associated with high risk of adverse outcomes, however, there is little information on neural adaptation to labor-like insults. Chronically instrumented near-term sheep fetuses (125 ± 3 days, mean ± SEM) with baseline PaO2 < 17 mmHg (hypoxic group: n = 8) or > 17 mmHg (normoxic group: n = 8) received 1-minute umbilical cord occlusions repeated every 5 minutes for a total of 4 hours, or until mean arterial blood pressure (MAP) fell below 20 mmHg for two successive occlusions. 5/8 fetuses with pre-existing hypoxia were unable to complete the full series of occlusions (vs. 0/8 normoxic fetuses). Pre-existing hypoxia was associated with progressive metabolic acidosis (nadir: pH 7.08 ± 0.04 vs. 7.33 ± 0.02, p<0.01), hypotension during occlusions (nadir: 24.7 ± 1.8 vs. 51.4 ± 3.2 mmHg, p<0.01), lower carotid blood flow during occlusions (23.6 ± 6.1 vs. 63.0 ± 4.8 mL/min, p<0.01), greater suppression of EEG activity during, between, and after occlusions (p<0.01) and slower resolution of cortical impedance, an index of cytotoxic edema. No normoxic fetuses, but 4/8 hypoxic fetuses developed seizures 148 ± 45 minutes after the start of occlusions, with a seizure burden of 26 ± 6 sec during the inter-occlusion period, and 15.1 ± 3.4 min/h in the first 6 hours of recovery. In conclusion, in fetuses with pre-existing hypoxia, repeated brief asphyxia at a rate consistent with early labor is associated with hypotension, cephalic hypoperfusion, greater EEG suppression, inter-occlusion seizures, and more sustained cytotoxic edema, consistent with early onset of neural injury.
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Affiliation(s)
- Guido Wassink
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | | | | | - Alistair J. Gunn
- Department of Physiology, University of Auckland, Auckland, New Zealand
- * E-mail:
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