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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: 40] [Impact Index Per Article: 10.0] [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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Dani C, Pratesi S, Ilari A, Lana D, Giovannini MG, Nosi D, Buonvicino D, Landucci E, Bani D, Mannaioni G, Gerace E. Neurotoxicity of Unconjugated Bilirubin in Mature and Immature Rat Organotypic Hippocampal Slice Cultures. Neonatology 2019; 115:217-225. [PMID: 30645995 DOI: 10.1159/000494101] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 09/27/2018] [Indexed: 11/19/2022]
Abstract
BACKGROUND The physiopathology of bilirubin-induced neurological disorders is not completely understood. OBJECTIVES The aim of our study was to assess the effect on bilirubin neurotoxicity of the maturity or immaturity of exposed cells, the influence of different unconjugated bilirubin (UCB) and human serum albumin (HSA) concentrations, and time of UCB exposure. METHODS Organotypic hippocampal slices were exposed for 48 h to different UCB and HSA concentrations after 14 (mature) or 7 (immature) days of in vitro culture. Immature slices were also exposed to UCB and HSA for 72 h. The different effects of exposure time to UCB on neurons and astrocytes were evaluated. RESULTS We found that 48 h of UCB exposure was neurotoxic for mature rat organotypic hippocampal slices while 72 h of exposure was neurotoxic for immature slices. Forty-eight-hour UCB exposure was toxic for astrocytes but not for neurons, while 72-h exposure was toxic for both astrocytes and neurons. HSA prevented UCB toxicity when the UCB:HSA molar ratio was ≤1 in both mature and immature slices. CONCLUSIONS We confirmed UCB neurotoxicity in mature and immature rat hippocampal slices, although immature ones were more resistant. HSA was effective in preventing UCB neurotoxicity in both mature and immature rat hippocampal slices.
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Affiliation(s)
- Carlo Dani
- Division of Neonatology, Careggi University Hospital of Florence, Florence, Italy, .,Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy,
| | - Simone Pratesi
- Division of Neonatology, Careggi University Hospital of Florence, Florence, Italy
| | - Alice Ilari
- Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy
| | - Daniele Lana
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Maria Grazia Giovannini
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Daniele Nosi
- Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Daniele Buonvicino
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Elisa Landucci
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Florence, Italy
| | - Daniele Bani
- Department of Clinical and Experimental Medicine, Research Unit of Histology and Embryology, University of Florence, Florence, Italy
| | - Guido Mannaioni
- Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy
| | - Elisabetta Gerace
- Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy
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Abdollahi FZ, Ahmadi T, Manchaiah V, Lotfi Y. Auditory Brainstem Response Improvements in Hyperbillirubinemic Infants. J Audiol Otol 2016; 20:13-6. [PMID: 27144228 PMCID: PMC4853896 DOI: 10.7874/jao.2016.20.1.13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Revised: 11/02/2015] [Accepted: 11/29/2015] [Indexed: 12/04/2022] Open
Abstract
Background and Objectives Hyperbillirubinemia in infants have been associated with neuronal damage including in the auditory system. Some researchers have suggested that the bilirubin-induced auditory neuronal damages may be temporary and reversible. This study was aimed at investigating the auditory neuropathy and reversibility of auditory abnormalities in hyperbillirubinemic infants. Subjects and Methods The study participants included 41 full term hyperbilirubinemic infants (mean age 39.24 days) with normal birth weight (3,200-3,700 grams) that admitted in hospital for hyperbillirubinemia and 39 normal infants (mean age 35.54 days) without any hyperbillirubinemia or other hearing loss risk factors for ruling out maturational changes. All infants in hyperbilirubinemic group had serum bilirubin level more than 20 milligram per deciliter and undergone one blood exchange transfusion. Hearing evaluation for each infant was conducted twice: the first one after hyperbilirubinemia treatment and before leaving hospital and the second one three months after the first hearing evaluation. Hearing evaluations included transient evoked otoacoustic emission (TEOAE) screening and auditory brainstem response (ABR) threshold tracing. Results The TEOAE and ABR results of control group and TEOAE results of the hyperbilirubinemic group did not change significantly from the first to the second evaluation. However, the ABR results of the hyperbilirubinemic group improved significantly from the first to the second assessment (p=0.025). Conclusions The results suggest that the bilirubin induced auditory neuronal damage can be reversible over time so we suggest that infants with hyperbilirubinemia who fail the first hearing tests should be reevaluated after 3 months of treatment.
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Affiliation(s)
| | - Tayebeh Ahmadi
- Department of Audiology, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Vinaya Manchaiah
- Department of Speech and Hearing Sciences, Lamar University, Beaumont, TX, USA.; Linnaeus Centre HEAD, The Swedish Institute for Disability Research, Department of Behavioral Sciences and Learning, Linköping University, Linköping, Sweden.; Audiology India, Mysore, Karnataka, India
| | - Yones Lotfi
- Department of Audiology, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
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Hu W, Cheng X, Ye X, Zhao L, Huang Y, Zhu H, Yan Z, Wang X, Wang X, Bai G, Gao H. Ex vivo (1)H nuclear magnetic resonance spectroscopy reveals systematic alterations in cerebral metabolites as the key pathogenetic mechanism of bilirubin encephalopathy. Mol Brain 2014; 7:87. [PMID: 25424547 PMCID: PMC4252999 DOI: 10.1186/s13041-014-0087-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 11/13/2014] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Bilirubin encephalopathy (BE) is a severe neurologic sequelae induced by hyperbilirubinemia in newborns. However, the pathogenetic mechanisms underlying the clinical syndromes of BE remain ambiguous. Ex vivo (1)H nuclear magnetic resonance (NMR) spectroscopy was used to measure changes in the concentrations of cerebral metabolites in various brain areas of newborn 9-day-old rats subjected to bilirubin to explore the related mechanisms of BE. RESULTS When measured 0.5 hr after injection of bilirubin, levels of the amino acid neurotransmitters glutamate (Glu), glutamine (Gln), and γ-aminobutyric acid (GABA) in hippocampus and occipital cortex significantly decreased, by contrast, levels of aspartate (Asp) considerably increased. In the cerebellum, Glu and Gln levels significantly decreased, while GABA, and Asp levels showed no significant differences. In BE 24 hr rats, all of the metabolic changes observed returned to normal in the hippocampus and occipital cortex; however, levels of Glu, Gln, GABA, and glycine significantly increased in the cerebellum. CONCLUSIONS These metabolic changes for the neurotransmitters are mostly likely the result of a shift in the steady-state equilibrium of the Gln-Glu-GABA metabolic cycle between astrocytes and neurons, in a region-specific manner. Changes in energy metabolism and the tricarboxylic acid cycle may also be involved in the pathogenesis of BE.
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Affiliation(s)
- Wenyi Hu
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
- Institute of Metabonomics & Medical NMR, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
| | - Xiaojie Cheng
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Xinjian Ye
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Liangcai Zhao
- Institute of Metabonomics & Medical NMR, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
| | - Yanan Huang
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Huanle Zhu
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Zhihan Yan
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Xuebao Wang
- Institute of Metabonomics & Medical NMR, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
| | - Xiaojie Wang
- Institute of Metabonomics & Medical NMR, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
| | - Guanghui Bai
- Radiology Department of the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, 325027, Zhejiang, China.
| | - Hongchang Gao
- Institute of Metabonomics & Medical NMR, School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
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Barateiro A, Domingues HS, Fernandes A, Relvas JB, Brites D. Rat Cerebellar Slice Cultures Exposed to Bilirubin Evidence Reactive Gliosis, Excitotoxicity and Impaired Myelinogenesis that Is Prevented by AMPA and TNF-α Inhibitors. Mol Neurobiol 2013; 49:424-39. [DOI: 10.1007/s12035-013-8530-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 08/05/2013] [Indexed: 12/11/2022]
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Brites D. The evolving landscape of neurotoxicity by unconjugated bilirubin: role of glial cells and inflammation. Front Pharmacol 2012; 3:88. [PMID: 22661946 PMCID: PMC3361682 DOI: 10.3389/fphar.2012.00088] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 04/23/2012] [Indexed: 12/13/2022] Open
Abstract
Unconjugated hyperbilirubinemia is a common condition in the first week of postnatal life. Although generally harmless, some neonates may develop very high levels of unconjugated bilirubin (UCB), which may surpass the protective mechanisms of the brain in preventing UCB accumulation. In this case, both short-term and long-term neurodevelopmental disabilities, such as acute and chronic UCB encephalopathy, known as kernicterus, or more subtle alterations defined as bilirubin-induced neurological dysfunction (BIND) may be produced. There is a tremendous variability in babies' vulnerability toward UCB for reasons not yet explained, but preterm birth, sepsis, hypoxia, and hemolytic disease are comprised as risk factors. Therefore, UCB levels and neurological abnormalities are not strictly correlated. Even nowadays, the mechanisms of UCB neurotoxicity are still unclear, as are specific biomarkers, and little is known about lasting sequelae attributable to hyperbilirubinemia. On autopsy, UCB was shown to be within neurons, neuronal processes, and microglia, and to produce loss of neurons, demyelination, and gliosis. In isolated cell cultures, UCB was shown to impair neuronal arborization and to induce the release of pro-inflammatory cytokines from microglia and astrocytes. However, cell dependent sensitivity to UCB toxicity and the role of each nerve cell type remains not fully understood. This review provides a comprehensive insight into cell susceptibilities and molecular targets of UCB in neurons, astrocytes, and oligodendrocytes, and on phenotypic and functional responses of microglia to UCB. Interplay among glia elements and cross-talk with neurons, with a special emphasis in the UCB-induced immunostimulation, and the role of sepsis in BIND pathogenesis are highlighted. New and interesting data on the anti-inflammatory and antioxidant activities of different pharmacological agents are also presented, as novel and promising additional therapeutic approaches to BIND.
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Affiliation(s)
- Dora Brites
- Neuron Glia Biology in Health and Disease Unit, Research Institute for Medicines and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon Lisbon, Portugal
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Almaas R, Hankø E, Mollnes TE, Rootwelt T. Dexamethasone reduces bilirubin-induced toxicity and IL-8 and MCP-1 release in human NT2-N neurons. Brain Res 2012; 1458:12-7. [PMID: 22546346 DOI: 10.1016/j.brainres.2012.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 04/02/2012] [Accepted: 04/05/2012] [Indexed: 12/11/2022]
Abstract
The mechanisms of neurotoxicity induced by unconjugated bilirubin (UCB) in newborns are incompletely understood. UCB may cause both necrotic and apoptotic neuronal death. We explored UCB toxicity and release of cytokines in human NT2-N neurons and the effect of dexamethasone on these processes. Cultured NT2-N neurons were exposed to UCB, and neuronal damage was evaluated by LDH release and MTT cleavage. After 96 hours, 2 μM UCB significantly increased release of IL-8 and MCP-1, but not IL-13, IP-10, PDGF, or VEGF. Dexamethasone significantly lowered the UCB-induced increase in MCP-1 release, and attenuated UCB-induced neuronal damage assessed with MTT cleavage and LDH release. For comparison, the effects of hydrogen peroxide on cytokine formation and neuronal damage were tested. Hydrogen peroxide increased MCP-1, IP-10, and VEGF, but not IL-8, IL-13, or PDGF. Dexamethasone inhibited the hydrogen peroxide-induced increase in MCP-1 and IP-10. We conclude that UCB causes release of IL-8 and MCP-1 in cultured human NT2-N neurons. Dexamethasone reduces UCB-induced cytokine release and protects against UCB-induced toxicity.
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Affiliation(s)
- Runar Almaas
- Department of Pediatric Research, Oslo University Hospital Rikshospitalet, N-0027 Oslo, Norway.
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Silva SL, Vaz AR, Diógenes MJ, van Rooijen N, Sebastião AM, Fernandes A, Silva RFM, Brites D. Neuritic growth impairment and cell death by unconjugated bilirubin is mediated by NO and glutamate, modulated by microglia, and prevented by glycoursodeoxycholic acid and interleukin-10. Neuropharmacology 2012; 62:2398-408. [PMID: 22361233 DOI: 10.1016/j.neuropharm.2012.02.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 02/01/2012] [Accepted: 02/07/2012] [Indexed: 12/28/2022]
Abstract
Neuronal oxidative damage and cell death by unconjugated bilirubin (UCB) showed to be mediated by overstimulation of glutamate receptors and nitric oxide (NO) production, which was abrogated by the bile acid glycoursodeoxycholic acid (GUDCA). Microglia, a crucial mediator of CNS inflammation, evidenced to react to UCB by releasing glutamate and NO before becoming senescent. Our studies demonstrated that neurite outgrowth deficits are produced in neurons exposed to UCB and that conditioned media from these UCB-treated neurons further stimulate NO production by microglia. Nevertheless, microglia protective and/or harmful effects in neonatal jaundice are poorly understood, or unrecognized. Here, we investigated the role of microglia, glutamate and NO in the impairment of neurite sprouting by UCB. Therapeutic potential of the anti-inflammatory cytokine interleukin (IL)-10 and GUDCA was also evaluated. By using MK-801 (a NMDA glutamate-subtype receptor antagonist) and L-NAME (a non-specific NO synthase inhibitor) we found that glutamate and NO are determinants in the early and enduring deficits in neurite extension and ramification induced by UCB. Both GUDCA and IL-10 prevented these effects and decreased the production of glutamate and NO. Only GUDCA was able to counteract neuronal death and synaptic changes. Data from organotypic-cultured hippocampal slices, depleted or non-depleted in microglia, supported that microglia participate in glutamate homeostasis and contribute to NO production and cell demise, which were again abrogated by GUDCA. Collectively our data suggest that microglia is a key player in UCB-induced neurotoxicity and that GUDCA might be a valuable preventive therapy in neonates at risk of UCB encephalopathy.
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Affiliation(s)
- Sandra L Silva
- Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Professor Gama Pinto, 1649-003 Lisbon, Portugal.
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Gao X, Yang X, Zhang B. Neuroprotection of taurine against bilirubin-induced elevation of apoptosis and intracellular free calcium ion in vivo. Toxicol Mech Methods 2011; 21:383-7. [PMID: 21250777 DOI: 10.3109/15376516.2010.546815] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Previous work has shown that taurine protected neurons against unconjugated bilirubin (UCB)-induced neurotoxicity by preventing cell apoptosis and maintaining intracellular Ca²⁺ homeostasis in primary neuron culture. This study investigates the neurotoxicity of hyperbilirubinemia and neuroprotection of taurine in a clinically relevant murine model in vivo. A hyperbilirubinemia baby mice model was established by intraperitoneal injection with UCB. After 24 h, the neural apoptotic level, transcriptional activity of caspase-3, and iCa²⁺ concentration were detected. It was found that UCB injection significantly increased both intracellular free Ca²⁺ concentrations and the activities of proapoptosis protease caspase-3, which is related to the elevation of neural apoptosis level. When baby mice were pretreated with 7.5 or 15 mg/kg body weight (bw) taurine for 4 h and then exposed to UCB, apoptotic death was significantly attenuated through down-regulation of activity of caspase-3 and i[Ca²⁺] in the brain. From these observations, it was concluded that taurine limits bilirubin-induced neural damage by inhibiting iCa²⁺ overload as well as decreasing activation of proapoptotic proteases caspase-3. This study might contribute to the development of taurine as a broad-spectrum agent for preventing and/or treating neural damage in neonatal jaundice.
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Affiliation(s)
- Xiaoling Gao
- Molecular Immunology, Center of Clinical laboratory, People's Hospital of Gansu Province, Gansu, P.R. China
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Taurine protects against bilirubin-induced neurotoxicity in vitro. Brain Res 2010; 1320:159-67. [DOI: 10.1016/j.brainres.2010.01.036] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/13/2010] [Accepted: 01/13/2010] [Indexed: 02/03/2023]
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Hansen TWR, Nietsch L, Norman E, Bjerre JV, Hascoet JM, Mreihil K, Ebbesen F. Reversibility of acute intermediate phase bilirubin encephalopathy. Acta Paediatr 2009; 98:1689-94. [PMID: 19583707 DOI: 10.1111/j.1651-2227.2009.01409.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIM To show the potential for reversing acute intermediate to advanced phase bilirubin encephalopathy. METHODS Case studies. RESULTS Six extremely jaundiced infants had symptoms of intermediate to advanced phase acute bilirubin encephalopathy. The infants were treated aggressively. Two patients had brain magnetic resonance imaging showing increased signals in the globus pallidus. On follow-up, all infants are neurologically normal. CONCLUSIONS Intermediate-to-advanced stage acute bilirubin encephalopathy may occasionally be reversible. These cases provide a strong argument in favour of rapid and aggressive intervention in infants presenting with extreme jaundice and neurological symptoms.
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Affiliation(s)
- Thor Willy Ruud Hansen
- Neonatal Intensive Care Unit, Division of Paediatrics, Oslo University Hospital, Oslo, Norway.
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12
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Abstract
Although most bilirubin in the circulation is bound to albumin, a relatively small fraction remains unbound. The concentration of this 'free' bilirubin (B(F)) is believed to dictate the biologic effects of bilirubin in jaundiced newborns, including its neurotoxicity. The threshold at which B(F) produces changes in cellular function culminating in permanent cell injury and cell death has been the subject of considerable debate. The objective of this study was to compare calculated central nervous system (CNS) B(F) levels in Gunn rat pups during (i) peak postnatal hyperbilirubinemia and (ii) sulfadimethoxine-induced acute bilirubin encephalopathy (ABE) previously reported from our laboratory with those predicted in human neonates with peak total serum bilirubin (TSB) levels of 35 mg per 100 ml (599 micromol l(-1)), a clinical cohort that often evidence moderate-to-severe adverse post-icteric neurodevelopmental sequelae. Homozygous j/j Gunn rat pups with neonatal hyperbilirubinemia due to a deficiency of the bilirubin conjugating enzyme uridine-diphosphate-glucuronosyl transferase 1A1 were studied along with non-jaundiced littermate heterozygous J/j controls. Sulfadimethoxine was used to displace bilirubin from albumin in hyperbilirubinemic j/j Gunn rat pups to increase their brain bilirubin content and induce ABE. Calculated Gunn rat CNS B(F) levels were determined as a function of genotype, sulfadimethoxine exposure and albumin-bilirubin binding constant. These data were compared with the human CNS B(F) predicted from the calculated serum B(F) in human neonates with a TSB of 35 mg per 100 ml as a function of albumin-bilirubin binding constant, albumin concentration and the assumption that at this hazardous bilirubin level there may be rapid equilibration of B(F) between serum and brain. There was a large gap between the upper limit of the calculated CNS B(F) 95% confidence interval (CI) range in non-jaundiced J/j pups (for example, 112 nM at k=9.2 l micromol(-1)) and the lower limit seen in the saline-treated hyperbilirubinemic j/j pups (556 nM at k=9.2 l micromol(-1)) as well as between the upper limit in saline-treated hyperbilirubinemic j/j pups (1110 nM at k=9.2 l micromol(-1)) and the lower limit seen in sulfadimethoxine-treated jaundiced j/j littermates (3461 nM at k=9.2 l micromol(-1)). There was considerable overlap and remarkable similarity between the predicted human CNS B(F) values at a TSB of 35 mg per 100 ml for a range of reported human serum bilirubin-albumin binding constants and albumin concentrations, and those calculated for saline-treated hyperbilirubinemic j/j Gunn rat pups. This exercise yielded strikingly similar apparent calculated neurotoxic B(F) levels for Gunn rat pups and human neonates rather than orders of magnitude differences that might have been predicted at the outset and add to a growing literature aimed at defining clinically germane neurotoxic B(F) thresholds.Journal of Perinatology (2009) 29, S14-S19; doi:10.1038/jp.2008.218.
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Shapiro SM, Sombati S, Geiger A, Rice AC. NMDA channel antagonist MK-801 does not protect against bilirubin neurotoxicity. Neonatology 2007; 92:248-57. [PMID: 17556843 DOI: 10.1159/000103743] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Accepted: 02/05/2007] [Indexed: 11/19/2022]
Abstract
BACKGROUND Bilirubin encephalopathy or kernicterus is a potentially serious complication of neonatal hyperbilirubinemia. The mechanism of bilirubin-induced neurotoxicity is not known. Many neurological insults are mediated through NMDA receptor activation. OBJECTIVE We assessed the effect of the NMDA channel antagonist, MK-801 on bilirubin neurotoxicity in vivo and in vitro. METHODS Bilirubin toxicity in vitro was assessed using trypan blue staining. Sulfadimethoxine injected (i.p.) jaundiced Gunn rat pups exhibit many neurological sequelae observed in human hyperbilirubinemia. Brainstem auditory-evoked potentials (BAEPs), a noninvasive sensitive tool to assess auditory dysfunction due to bilirubin neurotoxicity, were used to assess neuroprotection with MK-801 (i.p.) in vivo. RESULTS In primary cultures of hippocampal neurons, 20 min exposure to 64:32 microM bilirubin:human serum albumin reduced the cell viability by approximately 50% ten hours later. MK-801 treatment did not protect the cells. MK-801 pretreatment doses ranging from 0.1-4.0 mg/kg did not protect against BAEP abnormalities in Gunn rat pups 6 h after sulfadimethoxine injection. CONCLUSION Our findings suggest that bilirubin neurotoxicity is not mediated through NMDA receptor activation.
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MESH Headings
- Animals
- Animals, Newborn
- Anti-Infective Agents
- Bilirubin/adverse effects
- Cell Survival/drug effects
- Cell Survival/physiology
- Disease Models, Animal
- Dizocilpine Maleate/pharmacology
- Dose-Response Relationship, Drug
- Evoked Potentials, Auditory, Brain Stem/drug effects
- Evoked Potentials, Auditory, Brain Stem/physiology
- Hyperbilirubinemia/chemically induced
- Hyperbilirubinemia/complications
- Hyperbilirubinemia/physiopathology
- Jaundice/chemically induced
- Jaundice/complications
- Jaundice/physiopathology
- Kernicterus/etiology
- Kernicterus/physiopathology
- Kernicterus/prevention & control
- Neurons/drug effects
- Neurons/physiology
- Neuroprotective Agents/pharmacology
- Rats
- Rats, Gunn
- Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors
- Receptors, N-Methyl-D-Aspartate/physiology
- Sulfadimethoxine
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Affiliation(s)
- Steven M Shapiro
- Department of Neurology, Virginia Commonwealth University, Richmond, VA 23298-0599, USA
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