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Wu C, Jin Y, Cui Y, Zhu Y, Yin S, Li C. Effects of bilirubin on the development and electrical activity of neural circuits. Front Cell Neurosci 2023; 17:1136250. [PMID: 37025700 PMCID: PMC10070809 DOI: 10.3389/fncel.2023.1136250] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 03/06/2023] [Indexed: 04/08/2023] Open
Abstract
In the past several decades, bilirubin has attracted great attention for central nervous system (CNS) toxicity in some pathological conditions with severely elevated bilirubin levels. CNS function relies on the structural and functional integrity of neural circuits, which are large and complex electrochemical networks. Neural circuits develop from the proliferation and differentiation of neural stem cells, followed by dendritic and axonal arborization, myelination, and synapse formation. The circuits are immature, but robustly developing, during the neonatal period. It is at the same time that physiological or pathological jaundice occurs. The present review comprehensively discusses the effects of bilirubin on the development and electrical activity of neural circuits to provide a systematic understanding of the underlying mechanisms of bilirubin-induced acute neurotoxicity and chronic neurodevelopmental disorders.
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Hansen TWR, Wong RJ, Stevenson DK. Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn. Physiol Rev 2020; 100:1291-1346. [PMID: 32401177 DOI: 10.1152/physrev.00004.2019] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.
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Affiliation(s)
- Thor W R Hansen
- Division of Paediatric and Adolescent Medicine, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; and Department of Pediatrics, Stanford University School of Medicine, Stanford, California
| | - Ronald J Wong
- Division of Paediatric and Adolescent Medicine, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; and Department of Pediatrics, Stanford University School of Medicine, Stanford, California
| | - David K Stevenson
- Division of Paediatric and Adolescent Medicine, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; and Department of Pediatrics, Stanford University School of Medicine, Stanford, California
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Oakes GH, Bend JR. Global changes in gene regulation demonstrate that unconjugated bilirubin is able to upregulate and activate select components of the endoplasmic reticulum stress response pathway. J Biochem Mol Toxicol 2010; 24:73-88. [PMID: 20196124 DOI: 10.1002/jbt.20313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Elevated concentrations of unconjugated bilirubin (UCB) are responsible for neonatal jaundice and can eventually lead to kernicterus or death. The molecular mechanism of UCB toxicity is incompletely elucidated. The purpose of this study was to analyze changes in gene regulation mediated by UCB to determine novel pathways that contribute to UCB-mediated toxicity. We employed microarray analysis to determine changes in gene regulation mediated by UCB at both pro- (50 microM) and antioxidant (70 nM) concentrations in Hepa 1c1c7 cells at 1 and 6 h. The changes observed in select genes were validated with qPCR. Using immunoblot analysis, we validated these changes at the protein level for select genes and documented the activation of two proteins involved in the endoplasmic reticulum (ER) stress pathway, eIF2 alpha and PERK. Following treatment with 50 microM UCB, microarray analysis revealed the upregulation of many genes involved in ER stress (ATF3, BiP, CHOP, Dnajb1, and Herp). We demonstrate that upregulation of the proapoptotic transcription factor CHOP results in increased intracellular protein content. It was determined that activation of proteins involved in ER stress was an early event in UCB toxicity as eIF2 alpha and PERK were both phosphorylated and activated by 1 h posttreatment. We also demonstrate that procaspase-12 content, a proposed initiator caspase in ER stress-mediated apoptosis, is decreased by 4 h posttreatment. In conclusion, this study demonstrates that elevated concentrations of UCB (50 microM) are able to activate select components of the ER stress pathway in Hepa 1c1c7 cells, which may contribute to UCB-mediated apoptosis.
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Affiliation(s)
- Garth H Oakes
- Department of Physiology & Pharmacology, Siebens-Drake Medical Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, 1400 Western Road, London, Ontario, Canada
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Brito MA, Vaz AR, Silva SL, Falcão AS, Fernandes A, Silva RFM, Brites D. N-methyl-aspartate receptor and neuronal nitric oxide synthase activation mediate bilirubin-induced neurotoxicity. Mol Med 2010; 16:372-80. [PMID: 20593111 PMCID: PMC2935951 DOI: 10.2119/molmed.2009.00152] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 06/28/2010] [Indexed: 01/02/2023] Open
Abstract
Hyperbilirubinemia may lead to neurotoxicity and neuronal death. Although the mechanisms of nerve cell damage by unconjugated bilirubin (UCB) appear to involve a disruption of the redox status and excitotoxicity, the contribution of nitric oxide (NO·) and of N-methyl-D-aspartate (NMDA) glutamate receptors is unclear. We investigated the role of NO· and NMDA glutamate receptors in the pathways of nerve cell demise by UCB. Neurons were incubated with 100 micromol/L UCB, in the presence of 100 micromol/L human serum albumin for 4 h at 37ºC, alone or in combination with N-ω-nitro-L-arginine methyl ester (L-NAME) (an inhibitor of neuronal nitric oxide synthase [nNOS]), hemoglobin (an NO· scavenger) or (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) (an NMDA-receptor antagonist). Exposure to UCB led to increased expression of nNOS and production of both NO· and cyclic guanosine 3',5'-monophosphate (cGMP), along with protein oxidation and depletion of glutathione. These events concurred for cell dysfunction and death and were counteracted by L-NAME. Moreover, the UCB-induced loss of neuronal viability was abolished by hemoglobin, whereas the activation of nNOS and production of both NO· and cGMP were counteracted by MK-801, resulting in significant protection from cell dysfunction and death. These results reinforce the involvement of oxidative stress by showing that nerve cell damage by UCB is mediated by NO· and therefore is counteracted by NO· inhibitors or scavengers. Our findings strongly suggest that the activation of nNOS and neurotoxicity occur through the engagement of NMDA receptors. These data reveal a role for overstimulation of glutamate receptors in mediating oxidative damage by UCB.
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Affiliation(s)
- Maria A Brito
- Research Institute for Medicines and Pharmaceutical Sciences, Faculdade de Farmácia, University of Lisbon, Lisbon, Portugal.
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Alexandra Brito M, Silva RFM, Brites D. Bilirubin toxicity to human erythrocytes: a review. Clin Chim Acta 2006; 374:46-56. [PMID: 16887110 DOI: 10.1016/j.cca.2006.06.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 06/05/2006] [Accepted: 06/12/2006] [Indexed: 11/17/2022]
Abstract
Neonatal jaundice, a physiologic condition reflecting the interplay between developmentally modulated changes in bilirubin production and metabolism, affects virtually all newborn infants. Usually, it is an entirely benign process that is resolved at the end of the first week of life without treatment or sequelae. However, in a small percentage of neonates, unconjugated hyperbilirubinemia can pose a neurotoxic risk especially in the presence of aggravating conditions such as a diminished albumin binding capacity and/or affinity, acidosis, displacing drugs and prematurity. Although neuronal cells are considered the main target for unconjugated bilirubin (UCB) toxicity, circulating cells are also affected during neonatal hyperbilirubinemia. Moreover, the UCB ability to cause hemolysis shall further aggravate neonatal jaundice through a vicious circle. In this review, we summarize the most relevant data obtained by our group regarding UCB toxicity and the role of some risk factors for kernicterus. In order to improve the risk assessment of neurotoxicity it is essential to understand the underlying mechanisms of UCB pathophysiology.
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Affiliation(s)
- Maria Alexandra Brito
- Centro de Patogénese Molecular- UBMBE, Faculdade de Farmácia, University of Lisbon, Av. das Forças Armadas, 1600-083 Lisbon, Portugal.
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Brito MA, Brites D, Butterfield DA. A link between hyperbilirubinemia, oxidative stress and injury to neocortical synaptosomes. Brain Res 2004; 1026:33-43. [PMID: 15476695 DOI: 10.1016/j.brainres.2004.07.063] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2004] [Indexed: 11/28/2022]
Abstract
Cytotoxicity by unconjugated bilirubin involves disturbances of membrane structure, excitotoxicity and cell death. These events were reported to trigger elevated free radicals production and impairment of calcium homeostasis, and to result in loss of cell membrane integrity. Therefore, this study was designed to investigate whether interaction of clinically relevant concentrations of free unconjugated bilirubin with synaptosomal membrane vesicles could be linked to oxidative stress, cytosolic calcium accumulation and perturbation of membrane function. Synaptosomal vesicles were prepared from gerbil cortical brain tissue and incubated with purified bilirubin (<or=1 microM), for 4 h at 37 degrees C. Intracellular concentrations of reactive oxygen species (ROS) and calcium were determined by dichlorofluorescin and BAPTA fluorescent probes, respectively. Membrane protein and lipid oxidation were evaluated by immunocytochemistry and phosphatidylserine exposure by annexin V binding. Levels of reduced and oxidized glutathione (GSH and GSSG, respectively), as well as activities of Mg(2+)-ATPase aminophospholipid translocase (flippase) and Na(+),K(+)-ATPase, were also measured. Our results showed that bilirubin induced oxidative stress, due to a rise in lipid (>or=10%, P<0.05) and protein oxidation (>or=20%, P<0.01), ROS content (approximately 17%, P<0.01), and a decrease in GSH/GSSG ratio (>30%, P<0.01). In addition, synaptosomes exposed to bilirubin exhibited increased externalization of phosphatidylserine (approximately 10%, P<0.05), together with decreased flippase and NA(+),K(+)-ATPase (>or=15%, P<0.05) activities, events that were accompanied by enhanced intracellular calcium levels ( approximately 20%, P<0.01). The data obtained point out that interaction of unconjugated bilirubin with synaptosomal membrane vesicles leads to oxidative injury, loss of membrane asymmetry and functionality, and calcium intrusion, thus potentially contributing to the pathogenesis of encephalopathy by hyperbilirubinemia.
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Affiliation(s)
- Maria Alexandra Brito
- Centro de Patogénese Molecular--UBMBE, Faculdade de Farmácia, University of Lisbon, Av. das Forças Armadas, 1600-083 Lisbon, Portugal.
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Schulpis KH, Gavrili S, Tjamouranis J, Karikas GA, Kapiki A, Costalos C. The effect of neonatal jaundice on biotinidase activity. Early Hum Dev 2003; 72:15-24. [PMID: 12706308 DOI: 10.1016/s0378-3782(02)00097-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Jaundice is one of the most common and one of the vexing problems that can occur in newborns. A newborn screening test for biotinidase deficiency has been added to many national screening programmes. AIM To clarify the problem of false-positive screening tests in neonates, especially in term babies, we evaluated the biotinidase activity in the serum of fullterm, premature and small-for-dates newborn infants with jaundice. METHODS 1296 fullterms (controls N=426), 246 prematures (controls N=86) and 156 small-for-dates babies (controls N=38) aged 2-3 days with jaundice were included in the study. In jaundiced neonates and controls, 3.0 ml of blood was drawn for the evaluation of total bilirubin (t.bil), liver enzymes and biotinidase activity in the serum using a fluorimetric method. In order to test whether or not t.bil causes an artifact in the previous method, biotinidase activity was also evaluated in a number of jaundiced newborns using an HPLC method. Additionally, a preliminary in vitro experiment was carried out to test whether t.bil is an inhibitor of the enzyme. RESULTS Biotinidase activities in the group of controls of prematures (3.30+/-1.2 mmol/min/l) and small-for-dates babies (3.34+/-0.8 mmol/min/l) were lower than those of term babies (4.99+/-1.1 mmol/min/l, p<0.001). T.bil and liver enzymes showed a statistically significant inverse correlation with biotinidase activity (p<0.001) in all the jaundiced infants of this study. Additionally, biotinidase activity, evaluated in a number of neonates with both fluorimetric and HPLC methods showed similar results. Preincubation of the serum enzyme with t.bil (>10 mg/dl) resulted in a 50% or more inhibition. CONCLUSIONS (a) Low biotinidase activity was found in term babies, prematures and small-for-dates with jaundice. (b) The low activity of the enzyme could be due to their impaired liver function. (c) The high t.bil levels in the studied groups may play the role of an "inhibitor" of the enzyme. (d) Gestational age as well as t.bil levels should always be written on Guthrie cards for a correct evaluation of biotinidase activity.
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Affiliation(s)
- Kleopatra H Schulpis
- Institute of Child Health, "Aghia Sophia" Children's Hospital, 11527, Athens, Greece.
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Park WS, Chang YS, Lee M. Effect of 7-nitroindazole on bilirubin-induced changes in brain cell membrane function and energy metabolism in newborn piglets. Neonatology 2003; 82:61-5. [PMID: 12119543 DOI: 10.1159/000064154] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We evaluated the effects of 7-nitroindazole, a selective neuronal nitric oxide synthetase (nNOS) inhibitor, on bilirubin-induced alterations in brain cell membrane function and energy metabolism in the newborn piglets. The decreased cerebral cortical cell membrane Na(+),K(+)-ATPase activity and increased lipid peroxidation products, indicative of bilirubin-induced brain damage, were significantly attenuated by 7-nitroindazole treatment. 7-Nitroindazole also significantly improved the bilirubin-induced reduction in both brain ATP and phosphocreatine levels, decreased blood-to-brain glucose ratio and increased brain lactate level. In summary, 7-nitroindazole significantly attenuated the bilirubin-induced alterations in brain cell membrane function and energy metabolism in the newborn piglet. These findings suggest that nitric oxide produced by nNOS is involved in mediating or facilitating bilirubin-induced cerebral dysfunction.
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Affiliation(s)
- Won Soon Park
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Park WS, Chang YS, Chung SH, Seo DW, Hong SH, Lee M. Effect of hypothermia on bilirubin-induced alterations in brain cell membrane function and energy metabolism in newborn piglets. Brain Res 2001; 922:276-81. [PMID: 11743960 DOI: 10.1016/s0006-8993(01)03186-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aim of this study was to evaluate the effects of hypothermia on bilirubin-induced alterations in brain cell membrane function and energy metabolism in the developing brain. Thirty-seven newborn piglets were divided randomly into four groups: normothermic control (NC, n=9); hypothermic control (HC, n=7); normothermic bilirubin infusion (NB, n=11); and hypothermic bilirubin infusion (HB, n=10) groups. In bilirubin infusion groups (NB and HB), a loading dose of bilirubin (35 mg/kg) was given over 5 min, followed by a continuous infusion (25 mg/kg/h) for 4 h. The control groups (NC, HC) received a bilirubin-free buffer solution. Sulfadimethoxine was administered to animals in all experimental groups. Rectal temperature was maintained between 38.0 and 39.0 degrees C in normothermic groups, and between 34.0 and 35.0 degrees C in hypothermic groups for 4 h after the start of bilirubin infusion. The final blood and brain bilirubin concentrations in the bilirubin infusion groups (NB and HB) were not significantly different. Decreased cerebral cortical cell membrane Na(+),K(+)-ATPase activity and increased lipid peroxidation products observed in the NB group, indicative of bilirubin-induced brain damage, were significantly attenuated in the HB group. Hypothermia also significantly improved the bilirubin-induced reduction in brain ATP and phosphocreatine levels and increase in blood and brain lactate levels. In summary, hypothermia significantly attenuated the bilirubin-induced alterations in brain cell membrane function and energy metabolism in the newborn piglet. These findings suggest the possibility that hypothermia could be a good neuroprotective therapeutic modality in neonatal bilirubin encephalopathy.
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Affiliation(s)
- W S Park
- Department of Pediatrics, Samsung Medical Center, 50 Ilwon-Dong, Kangnam-Gu, Sungkyunkwan University School of Medicine, Seoul, South Korea
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Hoffman DJ, Zanelli SA, Kubin J, Mishra OP, Delivoria-Papadopoulos M. The in vivo effect of bilirubin on the N-methyl-D-aspartate receptor/ion channel complex in the brains of newborn piglets. Pediatr Res 1996; 40:804-8. [PMID: 8947954 DOI: 10.1203/00006450-199612000-00005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Bilirubin neurotoxicity can be mediated by numerous mechanisms due to its increased permeability in neuronal membranes. The present study tests the hypothesis that a prolonged bilirubin infusion modifies the N-methyl-D-aspartate (NMDA) receptor/ ion channel complex in the cerebral cortex of newborn piglets. Studies were performed in seven control and six bilirubin-exposed piglets, 2-4 d of age. Piglets in the bilirubin group received a 35 mg/kg bolus of bilirubin followed by a 4-h infusion (25 mg/kg/h) of a buffer solution containing 0.1 N NaOH, 5% human albumin, and 0.055 Na2HPO4 with 3 mg/mL bilirubin. The final mean bilirubin concentration in the bilirubin group was 495.9 +/- 85.5 mumol/L (29.0 +/- 5.0 mg/dL). The control group received a bilirubin-free buffer solution. Sulfisoxazole was administered to animals in both groups. P2 membrane fractions were prepared from the cerebral cortex. [3H]MK-801 binding assays were performed to study NMDA receptor modification. The Bmax in the control and bilirubin groups were 1.20 +/- 0.10 (mean +/- SD) and 1.32 +/- 0.14 pmol/mg protein, respectively. The value for Kd in the control brains was 6.97 +/- 0.80 nM compared with 4.80 +/- 0.28 nM in the bilirubin-exposed brains (p < 0.001). [3H]Glutamate binding studies did not show a significant difference in the Bmax and Kd for the NMDA-specific glutamate site in the two groups. The results show that in vivo exposure to bilirubin increases the affinity of the receptor (decreased Kd) for [3H]MK-801, indicating that bilirubin modifies the function of the NMDA receptor/ion channel complex in the brain of the newborn piglet. We speculate that the affinity of bilirubin for neuronal membranes leads to bilirubin-mediated neurotoxicity, resulting in either short- or long-term disruption of neuronal function.
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Affiliation(s)
- D J Hoffman
- Department of Pediatrics, Medical College of Pennsylvania/Hahnemann University School of Medicine, Philadelphia 19129, USA
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