Bilirubin induces apoptosis and necrosis in human NT2-N neurons

Molecular events in brain bilirubin toxicity revisited

The mechanisms involved in bilirubin neurotoxicity are still far from being fully elucidated. Several different events concur to damage mainly the neurons among which inflammation and alteration of the redox state play a major role. An imbalance of cellular calcium homeostasis has been recently described to be associated with toxic concentrations of bilirubin, and this disequilibrium may in turn elicit an inflammatory reaction. The different and age-dependent sensitivity to bilirubin damage must also be considered in describing the dramatic clinical picture of bilirubin-induced neurological damage (BIND) formerly known as kernicterus spectrum disorder (KSD). This review aims to critically address what is known and what is not in the molecular events of bilirubin neurotoxicity to provide hints for a better diagnosis and more successful treatments. Part of these concepts have been presented at the 38th Annual Audrey K. Brown Kernicterus Symposium of Pediatric American Society, Washington DC, May 1, 2023.

Experiences with neonatal jaundice management in hospitals and the community: interviews with Australian health professionals

INTRODUCTION

Worldwide, neonatal jaundice accounts for considerable morbidity and mortality. Although severe adverse outcomes, such as hyperbilirubinaemia and kernicterus, are uncommon in high-income countries, these outcomes do occur, have enormous lifelong personal, health and social costs, and may be preventable. Evidence-based practice commonly relies on clinical guidelines; however, their implementation can be difficult. Implementation of neonatal jaundice care has been adversely affected by issues with professional boundaries, competing professional priorities and poor understanding of neonatal jaundice. This paper focuses on the perceptions and experiences of Australian health professionals involved in the management of neonatal jaundice.

METHODS

Using a qualitative descriptive approach, semistructured interviews were undertaken to gain understanding of the experiences of health professionals in Australia across the scope of care for jaundiced newborns through an interpretivist approach and to identify possible gaps in the delivery of evidence-based care. Health professionals from a range of disciplines and care settings were recruited by purposive maximum variation sampling. Interviews were conducted face-to-face or by telephone with detailed notes taken and a field journal maintained. Interview scripts were verified by participants and imported into NVivo software. Data were analysed for major themes according to type and contexts of practice.

RESULTS

Forty-one health professionals from six broad discipline areas were interviewed. Two major themes and explanatory subthemes were found. The first theme, falling through the gaps, highlighted gaps in evidence-based care, as described by four explanatory subthemes: professional boundaries, blindness to possibility of adverse outcomes, competing professional development priorities and unintended consequences.The second major theme, we know what should happen-but how?, described participant perceptions that it was known what was required to improve care but how to achieve such changes was unclear. The two subthemes are: improvements in education and training, and standardised policies and protocols.

CONCLUSIONS

Multiple barriers to the provision of evidence-based care related to neonatal jaundice management are experienced by health professionals in Australia. Clinical guidelines are not sufficient to support health professionals deliver evidence-based care in the complex contexts in which they work. Implementation strategies for evidence-based practice need to take account of the experiences of health professionals and the challenges they face. Such strategies need to focus on improving collaboration between different disciplines for the well-being of those needing care. In the case of neonatal jaundice management, consideration is also needed in how to raise awareness of the importance of avoiding severe adverse outcomes, even when they might be rare, and how this might be done. Addressing issues that lead to disjointed care or poor knowledge of neonatal jaundice among health professionals is essential.

A rare case of Crigler-Najjar syndrome type 2: A case report and literature review

Key Clinical Message

Crigler-Najjar syndrome type 2 should be suspected in any young patient presenting with isolated indirect hyperbilirubinemia where all other common etiologies have been excluded. It is a relatively benign condition that responds to phenobarbitone.

Abstract

Crigler-Najjar syndrome (CNS) type 2 is an inborn cause of isolated indirect hyperbilirubinemia characterized by a partial deficiency of the enzyme uridine 5'-diphosphate-glucuronosyltransferase (UGT) responsible for bilirubin conjugation. Typically, this condition is diagnosed based on clinical manifestations, supplemented by enzyme analysis if feasible, and exhibits a significant response to phenobarbitone, known for its enzyme-inducing properties. In this case, we present a young male patient who had experienced recurrent isolated indirect hyperbilirubinemia since early childhood, with negative results in the hemolytic workup. The patient exhibited a UGT1A1 gene defect and demonstrated a highly favorable response to phenobarbitone treatment. The purpose of this report is to raise awareness among physicians about this benign condition and underscore the importance of avoiding unnecessary investigations.

Non-enzymatic antioxidants, macro-minerals and monocyte/high-density lipoprotein cholesterol ratio among patients with bipolar disorder

OBJECTIVE

Recent studies show that oxidative stress is related to the pathogenesis of BD. Non-enzymatic antioxidants, macro-minerals and MHR (monocyte divided by high-density lipoprotein cholesterol) participated oxidative stress and can be obtained quickly in hematological examination. This study used large-scale clinical data to investigate them between BD and healthy controls (HCs), as well as between psychotic and non-psychotic BD to explore their roles in disease progression.

METHODS

A total of 3442 BD-manic (BD-M) and 1405 BD-depression (BD-D) in acute stage and 5000 HCs were enrolled, including 1592 BD-M with psychotic symptoms (P-BD-M), 1850 BD-M without psychotic symptoms (NP-BD-M), 655 P-BD-D, 750 NP-BD-D. The differences in these biological parameter levels among different groups were compared, and the contributing factors for the occurrence of BD-M or BD-D and psychotic symptoms of BD were analyzed.

RESULTS

We found higher levels of Na and MHR, and lower levels of K, Ca and ALB in BD-M or BD-D compared with the HCs respectively; levels of K, Na, Ca, ALB and MHR have differences among P-BD-M, NP-BD-M and HC; levels of K, Na, Ca and ALB have differences among P-BD-D, NP-BD-D and HC. In multiple logistic regression, higher levels of MHR and Na were associated with BD-M; MHR was shown to be independently associated with P-BD-M; K, Na, ALB were shown to be independently associated with P-BD-D.

CONCLUSIONS

Our study highlights the role of oxidative stress in the pathophysiology of BD. There is heterogeneity between BD-M and BD-D, and different oxidative stress mechanisms of psychotic symptoms exist in BD-M and BD-D.

Relation Between Unconjugated Bilirubin and Peripheral Biomarkers of Inflammation Derived From Complete Blood Counts in Patients With Acute Stage of Schizophrenia

BACKGROUND

Inflammation and oxidative stress are the major leading hypothetical causes of schizophrenia. Unconjugated bilirubin (UCB) is an efficient endogenous plasma antioxidant. Inflammation is closely linked to oxidative stress. The relationship between UCB and inflammatory markers should be paid close attention in schizophrenia acute stage. In this paper, combined UCB and inflammatory markers were evaluated for their capability in predicting schizophrenia in the acute stage to find an easy and effective indicator to identify acute schizophrenia.

METHODS

A total of 6,937 acute schizophrenia patients and 6,404 healthy controls (HCs) were enrolled. UCB and peripheral biomarkers of inflammation derived from complete blood counts (CBC) were investigated in the subjects with acute schizophrenia, and the results were compared with HCs. Simultaneously, Spearman test was employed to assess the correlation between the variables, while logistic regression was adopted to determine the combined equation and receiver operating characteristic curve was used to evaluate the combined value of UCB and peripheral biomarkers of inflammation derived from CBC to predict schizophrenia in the acute stage.

RESULTS

The study indicates that white blood cells, neutrophil, monocyte, mean platelet volume (MPV), red cell distribution width (RDW), neutrophil/lymphocyte ratio (NLR), and monocyte/lymphocyte ratio (MLR) have significantly increased in schizophrenia (p < 0.05 for all), while platelet, lymphocyte, and platelet/lymphocyte ratio (PLR) in schizophrenia have significantly decreased (p < 0.05 for all). UCB exhibits negative correlation with MPV significantly (r = 0.121, p < 0.001), and no correlation with neutrophil and monocyte. The correlations between UCB and other peripheral biomarkers of inflammation derived from CBC are very weak. MPV, RDW, NLR, MLR, PLR, and UCB were taken as independent variables for a logistic regression analysis. The model was as follows: Logit  ( P 1 ) = - 6 . 141 + 0 . 827  MPV + 5 . 613  MLR - 0 . 005  PLR - 0 . 346  UBC . The combination demonstrates better effectiveness in predicting schizophrenia in the acute stage (AUC 0.831, 95% CI 0.825 to 0.837).

CONCLUSION

UCB has a protective effect on acute stage of schizophrenia, which is weak and indirect by affecting the proinflammatory processes. Our findings suggest that a combination of MLR, MPV, PLR, and UBC could be used to predict acute stage of schizophrenia.

Predictive value of different bilirubin subtypes for clinical outcomes in patients with acute ischemic stroke receiving thrombolysis therapy

Aims

To explore the association of total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL) levels with, as well as the incremental predictive value of different bilirubin subtypes for, poor outcomes in acute ischemic stroke patients after thrombolysis.

Methods

We analyzed 588 individuals out of 718 AIS participants, and all patients were followed up at 3 months after thrombolysis. The primary outcome was 3‐month death and major disability (modified Rankin Scale (mRS) score of 3–6). The secondary outcomes were 3‐month mortality (mRS score of 6), moderate‐severe cerebral edema, and symptomatic intracranial hemorrhage (sICH), respectively.

Results

Elevated DBIL pre‐thrombolysis was associated with an increased risk of primary outcome (OR 3.228; 95% CI 1.595–6.535; p for trend = 0.014) after fully adjustment. Elevated TBIL pre‐thrombolysis showed the similar results (OR 2.185; 95% CI 1.111–4.298; p for trend = 0.047), while IBIL pre‐thrombolysis was not significantly associated with primary outcome (OR 1.895; 95% CI 0.974–3.687; p for trend = 0.090). Multivariable‐adjusted spline regression model showed a positive linear dose‐response relationship between DBIL pre‐thrombolysis and risk of primary outcome (p for linearity = 0.004). Adding DBIL pre‐thrombolysis into conventional model had greater incremental predictive value for primary outcome, with net reclassification improvement (NRI) 95% CI = 0.275 (0.084–0.466) and integrated discrimination improvement (IDI) 95% CI = 0.011 (0.001–0.024). Increased DBIL post‐thrombolysis had an association with primary outcome (OR 2.416; 95%CI 1.184–4.930; p for trend = 0.039), and it also elevated the incremental predictive value for primary outcome, with NRI (95% CI) = 0.259 (0.066–0.453) and IDI (95% CI) = 0.025 (0.008–0.043).

Conclusion

Increased DBIL pre‐thrombolysis had a stronger association with, as well as greater incremental predictive value for, poor outcomes than TBIL and IBIL did in AIS patients after thrombolysis, which should be understood in the context of retrospective design. The effect of DBIL on targeted populations should be investigated in further researches.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

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.

Unconjugated bilirubin and schizophrenia: a systematic review

Schizophrenia is a complex syndrome of unknown etiology and difficult to manage. Unconjugated bilirubin has been researched as a potential biological marker of this syndrome. The objective of this review article was to gather the studies published to date on the relationship between this molecule and schizophrenia. Broad inclusion criteria have been used (PRISMA) to include as many relevant studies as possible. Fourteen studies were selected: 3 analyzed the effects of unconjugated hyperbilirubinemia in animal models; 6 demonstrated an increased incidence of schizophrenia in patients with increased unconjugated bilirubin; 2 reported an increased incidence of the disease in patients with decreased unconjugated bilirubin; and 3 linked an increased incidence of schizophrenia with an increased excretion of the oxidative product of bilirubin, the so-called biopyrrins. Because of apparently contradictory reported results, the hypothesis that the relationship between schizophrenia and unconjugated bilirubin was not linear and that there was an inflammatory dysfunction explaining this was considered. The 2 most accepted models for the pathophysiology of schizophrenia are described, and the possible role of the molecule in each is clarified. The bilirubin buffer system and its role in antioxidant defense was explored. The average levels of unconjugated bilirubin in patients with schizophrenia, schizoaffective disorder, and bipolar disorder were also compared, having been hypothesized that these diseases could be different points of a same pathological spectrum. Finally, it was concluded that unconjugated bilirubin is a promising molecule that could be used as a possible biological marker for schizophrenia, and the necessity of subsequent efforts for its research was considered.

The Neuroprotective Effects of Hypothermia on Bilirubin-Induced Neurotoxicity in vitro

BACKGROUND

In high-risk newborns indirect hyperbilirubinemia can lead to acute bilirubin encephalopathy and kernicterus. Despite the current therapeutic modalities, preventing or reversing the neurotoxicity cannot be achieved in all infants.

OBJECTIVE

To investigate the neuroprotective effects of hypothermia on bilirubin-induced toxicity in primary mouse neuronal cell cultures.

METHODS

Hippocampal cell cultures, isolated from newborn mouse brains, were incubated with unconjugated bilirubin (UCB) at 3 days in vitro (DIV) and immediately exposed to varying degrees of hypothermia. Neuronal viability and mitochondrial health were compared between the normothermia (37°C), mild (34°C), moderate (32°C) and severe (29°C) hypothermia groups. Confocal microscopy and fluorescent dyes (propidium iodide and JC-1) were used for cell evaluation. To determine the late effects of hypothermia, the cultures were also examined at 7 DIV after returning to normothermic conditions.

RESULTS

Induction of any degree of hypothermia increased the neuronal survival after 24 h of UCB treatment. Neuronal death rate and mitochondrial membrane potential loss were lowest in the neurons exposed to moderate hypothermia. We also observed that mild to moderate hypothermia had late protective effects on neuronal cell viability, whereas deep hypothermia did not improve neuronal survival.

CONCLUSIONS

We conclude that hypothermia reduces the cell death induced by bilirubin toxicity in neuronal cells. Although moderate hypothermia has a better outcome than mild hypothermia, deep hypothermia as low as 29°C has adverse effects on neuronal cell viability.

Dual anti-ischemic effects of rosmarinic acid n-butyl ester via alleviation of DAPK-p53-mediated neuronal damage and microglial inflammation

The discovery of efficacious anti-ischemic drugs remains a challenge. Recently we have found that rosmarinic acid n-butyl ester (RABE), a derivative of rosmarinic acid, significantly protects SH-SY5Y cells against oxygen glucose deprivation (OGD)-induced cell death. In the present study we simultaneously investigated the effects of RABE on the two key players in the pathophysiology of cerebral ischemia, ischemic neuronal damage and microglial inflammation. Pretreatment with RABE (1, 10 μmol/L) dose-dependently attenuated OGD- or H2O2-induced reduction of the viability of SH-SY5Y neuroblastoma cells. RABE pretreatment concurrently reduced the apoptotic cell rate, down-regulated the expression of the pro-apoptotic proteins Bax and p53, and up-regulated the expression of the anti-apoptotic protein phosphorylated death-associated protein kinase (DAPK). Furthermore, pretreatment with RABE (3 μmol/L) markedly inhibited lipopolysaccharide (LPS)-induced increases in the release of TNF-α, IL-1β, NO and PGE2, and the expression levels of iNOS, and COX-2 in cultured rat microglial cells. In conclusion, these results reveal for the first time the potential anti-ischemic effects of RABE on neuronal and glial cells and elucidate the molecular mechanisms involved in its dual beneficial profiles in vitro. RABE may be a promising drug lead/candidate for the treatment of ischemic stroke.

Bilirubin and brain: A pharmacological approach

For many decades, the world scientific literature has accounted for a number of works on the biological effects of bilirubin-IXalpha (BR). The first studies focused on the neurotoxic effects of the excessive production of BR, in particular regarding both physiological neonatal jaundice and the more severe ones, typically as consequences of severe hemolysis or other underlying diseases. Only since 1987, has significant evidence, however, underlined the neuroprotective role of BR linked to the scavenging effect of free radicals as reactive oxygen species and nitric oxide and its congeners. Despite the presence in the literature of many excellent papers dealing with the multiple roles played by BR in health and disease, there were very few and somewhat dated reviews that summarize the key findings related to the neuroprotective and neurotoxic effects of the bile pigment and underlying mechanisms. In light of the previous statements, the aim of this review is to provide a summary of the main discoveries in the last years on the effects of BR on the central nervous system. An analytical description about the synthesis of BR, its distribution in the systemic circulation, liver metabolism and elimination through feces and urine will be provided, together with the main mechanisms claimed to describe the neurotoxicity and neuroprotection by the bile pigment. Finally, the possible translational aspects of pharmacological modulation in the production of BR in order to prevent or counteract toxic effects or enhance the protective actions, will be discussed.

Kernicterus in a Neonatal Foal

A 5-day-old Thoroughbred foal was submitted to the necropsy service at the University of Kentucky Livestock Disease Diagnostic Center. The foal had a clinical history of seizure activity and severe icterus. A complete blood count and serum chemistry analysis indicated that the foal was anemic (hematocrit, 16%), hyperbilirubinemic (45 mg/dl), and hypoglycemic. At necropsy, all tissues were discolored various shades of yellow. Microscopically, there was degeneration and necrosis of cerebral neurons and cerebellar Purkinje cells; severe hepatocellular degeneration and necrosis; and deposition of amorphous golden-yellow material in the cerebellar granular cell layer, pulmonary alveoli, renal tubular epithelium, splenic trabecula, and the lamina propria of the small and large intestine. The golden-yellow material in the brain, lung, spleen, and small intestine was identified as bilirubin by histochemistry. Based on the macroscopic and microscopic findings, a diagnosis of kernicterus (bilirubin encephalopathy) was made. This report describes a rare case of equine neonatal kernicterus.

Lineage-Specific Changes in Biomarkers in Great Apes and Humans

Although human biomedical and physiological information is readily available, such information for great apes is limited. We analyzed clinical chemical biomarkers in serum samples from 277 wild- and captive-born great apes and from 312 healthy human volunteers as well as from 20 rhesus macaques. For each individual, we determined a maximum of 33 markers of heart, liver, kidney, thyroid and pancreas function, hemoglobin and lipid metabolism and one marker of inflammation. We identified biomarkers that show differences between humans and the great apes in their average level or activity. Using the rhesus macaques as an outgroup, we identified human-specific differences in the levels of bilirubin, cholinesterase and lactate dehydrogenase, and bonobo-specific differences in the level of apolipoprotein A-I. For the remaining twenty-nine biomarkers there was no evidence for lineage-specific differences. In fact, we find that many biomarkers show differences between individuals of the same species in different environments. Of the four lineage-specific biomarkers, only bilirubin showed no differences between wild- and captive-born great apes. We show that the major factor explaining the human-specific difference in bilirubin levels may be genetic. There are human-specific changes in the sequence of the promoter and the protein-coding sequence of uridine diphosphoglucuronosyltransferase 1 (UGT1A1), the enzyme that transforms bilirubin and toxic plant compounds into water-soluble, excretable metabolites. Experimental evidence that UGT1A1 is down-regulated in the human liver suggests that changes in the promoter may be responsible for the human-specific increase in bilirubin. We speculate that since cooking reduces toxic plant compounds, consumption of cooked foods, which is specific to humans, may have resulted in relaxed constraint on UGT1A1 which has in turn led to higher serum levels of bilirubin in humans.

Riluzole is a promising pharmacological inhibitor of bilirubin-induced excitotoxicity in the ventral cochlear nucleus

BACKGROUND AND PURPOSE

Bilirubin encephalopathy as a result of hyperbilirubinemia is a devastating neurological disorder that occurs mostly in the neonatal period. To date, no effective drug treatment is available. Glutamate-mediated excitotoxicity is likely an important factor causing bilirubin encephalopathy. Thus, drugs suppressing the overrelease of glutamate may protect the brain against bilirubin excitotoxicity. Riluzole is a prescription drug known for its antiglutamatergic function. This study was conducted in the rat's ventral cochlear nucleus, a structure highly sensitive to bilirubin toxicity, to find whether riluzole can be used to inhibit bilirubin toxicity.

EXPERIMENTAL APPROACH

Electrophysiology changes were detected by perforated patch clamp technique. Calcium imaging using Rhod-2-AM as an indicator was used to study the intracellular calcium. Cell apoptosis and necrosis were measured by PI/Hoechst staining.

KEY RESULTS

In the absence of bilirubin, riluzole effectively decreased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) and suppressed neuronal firing but did not change the amplitude of sEPSC and glutamate-activated currents (I(Glu)). Moreover, riluzole inhibited bilirubin-induced increases in the frequency of sEPSC and neuronal firing. Riluzole could prevent the bilirubin-induced increase in intracellular calcium, mediated by AMPA and NMDA receptors. Furthermore, riluzole significantly reduced bilirubin-induced cell death.

CONCLUSIONS AND IMPLICATIONS

These data suggest that riluzole can protect neurons in the ventral cochlear nucleus from bilirubin-induced hyperexcitation and excitotoxicity through reducing presynaptic glutamate release.

A novel newborn rat kernicterus model created by injecting a bilirubin solution into the cisterna magna

BACKGROUND

Kernicterus still occurs around the world; however, the mechanism of bilirubin neurotoxicity remains unclear, and effective treatment strategies are lacking. To solve these problems, several kernicterus (or acute bilirubin encephalopathy) animal models have been established, but these models are difficult and expensive. Therefore, the present study was performed to establish a novel kernicterus model that is simple and affordable by injecting unconjugated bilirubin solution into the cisterna magna (CM) of ordinary newborn Sprague-Dawley (SD) rats.

METHODS

On postnatal day 5, SD rat pups were randomly divided into bilirubin and control groups. Then, either bilirubin solution or ddH2O (pH = 8.5) was injected into the CM at 10 µg/g (bodyweight). For model characterization, neurobehavioral outcomes were observed, mortality was calculated, and bodyweight was recorded after bilirubin injection and weaning. Apoptosis in the hippocampus was detected by H&E staining, TUNEL, flow cytometry and Western blotting. When the rats were 28 days old, learning and memory ability were evaluated using the Morris water maze test.

RESULTS

The bilirubin-treated rats showed apparently abnormal neurological manifestations, such as clenched fists, opisthotonos and torsion spasms. Bodyweight gain in the bilirubin-treated rats was significantly lower than that in the controls (P<0.001). The early and late mortality of the bilirubin-treated rats were both dramatically higher than those of the controls (P = 0.004 and 0.017, respectively). Apoptosis and necrosis in the hippocampal nerve cells in the bilirubin-treated rats were observed. The bilirubin-treated rats performed worse than the controls on the Morris water maze test.

CONCLUSION

By injecting bilirubin into the CM, we successfully created a new kernicterus model using ordinary SD rats; the model mimics both the acute clinical manifestations and the chronic sequelae. In particular, CM injection is easy to perform; thus, more stable models for follow-up study are available.

Evaluation of risk for late language emergence after in utero antiretroviral drug exposure in HIV-exposed uninfected infants

BACKGROUND

Combination antiretroviral (cARV) regimens are recommended for pregnant women with HIV to prevent perinatal HIV transmission. Safety is a concern for infants who were HIV-exposed but uninfected, particularly for neurodevelopmental problems, such as language delays.

METHODS

We studied late language emergence (LLE) in HIV-exposed but uninfected children enrolled in a US-based prospective cohort study. LLE was defined as a caregiver-reported score ≤10th percentile in any of 4 domains of the MacArthur-Bates Communicative Development Inventory for 1-year olds and as ≥1 standard deviation below age-specific norms for the Ages and Stages Questionnaire for 2-year olds. Logistic regression models were used to evaluate associations of in utero cARV exposure with LLE, adjusting for infant, maternal and environmental characteristics.

RESULTS

1129 language assessments were conducted among 792 1- and 2-year-old children (50% male, 62% black and 37% Hispanic). Overall, 86% had in utero exposure to cARV and 83% to protease inhibitors. LLE was identified in 26% of 1-year olds and 23% of 2-year olds, with higher rates among boys. In adjusted models, LLE was not associated with maternal cARV or ARV drug classes in either age group. Among cARV-exposed 1-year olds, increased odds of LLE was observed for those exposed to atazanavir (adjusted odds ratio = 1.83, 95% confidence interval: 1.10-3.04), particularly after the first trimester (adjusted odds ratio = 3.56, P = 0.001), compared with atazanavir-unexposed infants. No associations of individual ARV drugs with LLE were observed among 2-year olds.

CONCLUSIONS

In utero cARV exposure showed little association with LLE, except for a higher risk of language delay observed in 1-year-old infants with atazanavir exposure.

The evolving landscape of neurotoxicity by unconjugated bilirubin: role of glial cells and inflammation

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.

Dexamethasone reduces bilirubin-induced toxicity and IL-8 and MCP-1 release in human NT2-N neurons

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.

Evaluation of maternal knowledge level about neonatal jaundice

OBJECTIVE

To evaluate the knowledge of mothers on neonatal jaundice.

METHODS

This study was conducted on 161 mothers who had given birth to healthy newborns at Izmir Aegean Gynecology and Obstetrics Hospital between January 2010 and April 2010. A questionnaire was used to assess the mothers' knowledge on neonatal jaundice. Knowledge was evaluated as "sufficient" or "insufficient" based on responses. Sufficiently informed mothers were compared with insufficiently informed group for the knowledge level about neonatal jaundice.

RESULTS

The rate of insufficiently informed mothers was 53.6%. Logistic regression analysis showed that education level and having a previous offspring with jaundice were independent variables affecting the mothers' knowledge level. Low education level was found to increase the probability of the mothers' knowledge level to be insufficient by 2.1 folds (OR 2.1, 95% CI 1.3-3.4; p = 0.003). Being informed beforehand by a previous offspring with jaundice increased the probability of the mothers' knowledge to be sufficient by twofolds (OR 2, 95% CI 1.1-3.7; p = 0.03).

CONCLUSION

It is found that the mothers' knowledge about neonatal jaundice is insufficient. Maternal education level and having a previous offspring with jaundice are major factors affecting the knowledge of the mothers on hyperbilirubinemia.

Single dose of 50 mg/kg clofibrate in jaundice of healthy term neonates: randomised clinical trial of efficacy and safety

OBJECTIVE

To evaluate the effect of single oral dose of 50 mg/kg clofibrate in hyperbilirubinemia of term healthy neonates in Yazd, Iran.

METHODS

A parallel single- blinded randomized clinical trial, conducted on 60 healthy term neonates admitted between July and December 2007 to Shahid Sadoughi Hospital. Inclusion criteria were neonates with gestation age of 38-42 wk, birth weight of 2500-4000 g, product of normal vaginal delivery, breast-fed and total serum bilirubin (TSB) level of 17-29.9 mg/dL. Neonates with sepsis, anemia, severe asphyxia, hemolytic diseases, major congenital anomalies, indirect hyperbilirubinemia and underlying hepatic disorders were excluded. Selection of patients was based on random allocation via table of random numbers and the patients distributed into two groups. In group one, 30 neonates were treated with phototherapy alone and in 30 of other group treatment done with single dose of 50 mg/kg clofibrate and phototherapy. The primary endpoint with respect to efficacy in reducing of TSB was achieving TSB to less than 14 mg/dL as measured at the beginning, 12, 24 and 48 h after the start of phototherapy. Secondary outcomes were hospital stay days, duration of phototherapy and side effects of treatments during hospital stay and on the second day after discharge.

RESULTS

No significant differences were seen from the viewpoint of rout of delivery, gender, gestational age, birth weight, hemoglobin and bilirubin level at time of admission and weight in discharge time in the two groups. After 48 h of intervention, 27 (90%) neonates in clofibrate group and 15 (56.7%) in control group had TSB of less than 14 mg/dL (p 0.02). Mean TSB 12 h after treatment (mean ± SD: 14.82 ± 1.7 mg/dL vs. 16.67 ± 1.77 mg/dL, P 0.001), 24 h after treatment (mean ± SD: 11.97 ± 2.92 mg/dL vs. 14.61 ± 2.52 mg/dL, P 0.001) and 48 h after treatment (mean ± SD: 7.91 ± 2.45 mg/dL vs. 12.74 ± 2.21 mg/dL, P 0.0001), mean of hospital stay days (mean ± SD: 1.7 ± 0.7 days vs. 3.2 ± 1.2 days, P 0.03) and duration of phototherapy (mean ± SD: 30.2 ± 13.99 h vs. 46.2 ± 15.58 h, P 0.001] were significantly lower in clofibrate group. Only loose stool was seen in two patients of clofibrate group and no significant difference was seen from view of safety of the treatments.

CONCLUSIONS

A single dose of 50 mg/kg clofibrate in treatment of neonatal hyperbilirubinemia is effective, safe and cost effective in view of reducing hospital stay days.

Functional induction of the cystine-glutamate exchanger system Xc(-) activity in SH-SY5Y cells by unconjugated bilirubin

We have previously reported that exposure of SH-SY5Y neuroblastoma cells to unconjugated bilirubin (UCB) resulted in a marked up-regulation of the mRNA encoding for the Na⁺ -independent cystine∶glutamate exchanger System X_c⁻ (SLC7A11 and SLC3A2 genes). In this study we demonstrate that SH-SY5Y cells treated with UCB showed a higher cystine uptake due to a significant and specific increase in the activity of System X_c⁻, without the contribution of the others two cystine transporters (X_AG⁻ and GGT) reported in neurons. The total intracellular glutathione content was 2 folds higher in the cells exposed to bilirubin as compared to controls, suggesting that the internalized cystine is used for gluthathione synthesis. Interestingly, these cells were significantly less sensitive to an oxidative insult induced by hydrogen peroxide. If System X_c⁻ is silenced the protection is lost. In conclusion, these results suggest that bilirubin can modulate the gluthathione levels in neuroblastoma cells through the induction of the System X_c⁻, and this renders the cell less prone to oxidative damage.

Auditory impairment in infants at risk for bilirubin-induced neurologic dysfunction

Classical and subtypes of kernicterus associated with bilirubin toxicity can be differentiated in part with physiological auditory measures that include auditory-evoked potentials and measures of cochlear integrity. The combination of these auditory measures suggests that bilirubin exposure results in auditory system damage initially at the level of the brainstem, progressing to the level of the VIII cranial nerve and then to greater neural centers. There is no evidence of neural damage at the level of the cochlea. Auditory neural damage from bilirubin toxicity ranges from neural timing deficits, including neural firing delays and dyssynchrony, to neural response reduction and even elimination of auditory neural responses. This condition is comprehensively described as auditory neuropathy spectrum disorder. Independent measures of cochlear function and auditory neural function up to the level of the brainstem can effectively diagnose auditory neural damage resulting from bilirubin neurotoxicity. Intervention, including cochlear implants can be effective.

Displacement of bilirubin from albumin by ibuprofen in vitro

Ibuprofen binds to plasma albumin and could interfere with the binding of bilirubin in jaundiced newborn infants. Most clinical studies have not shown increased concentrations of unbound bilirubin (UB) in plasma from infants treated with ibuprofen for a patent ductus arteriosus. However, studies in vitro have not been equally conclusive. Plasma were obtained from routine samples from jaundiced newborn infants and pooled. Total and UB were measured with the peroxidase method after addition of ibuprofen or sulfisoxazole as a known bilirubin displacer. Final ibuprofen concentrations varied from 0.43 to 2.6 mM. Bilirubin concentrations were varied from 176 to 708 microM by adding bilirubin to plasma samples. Ibuprofen caused a linear increase in UB up to +54% at a concentration of 1.8 mM, compared with an increase of 87% by sulfisoxazole (1.32 mM). A double reciprocal plot of molar concentrations of bound versus UB at bilirubin concentrations ranging from 176 to 708 microM showed a competitive displacement of bilirubin by ibuprofen. The data indicate that ibuprofen is a competitive displacer of bilirubin in vitro. Ibuprofen should be used with caution in premature infants with a significant hyperbilirubinemia.

Ibuprofen augments bilirubin toxicity in rat cortical neuronal culture

Premature infants are at risk for bilirubin-associated brain damage. In cell cultures bilirubin causes neuronal apoptosis and necrosis. Ibuprofen is used to close the ductus arteriosus, and is often given when hyperbilirubinemia is at its maximum. Ibuprofen is known to interfere with bilirubin-albumin binding. We hypothesized that bilirubin toxicity to cultured rat embryonic cortical neurons is augmented by coincubation with ibuprofen. Incubation with ibuprofen above a concentration of 125 microg/mL reduced cell viability, measured by methylthiazole tetrazolium reduction, to 68% of controls (p < 0.05). Lactate dehydrogenase (LDH) release increased from 29 to 38% (p < 0.01). The vehicle solution did not affect cell viability. Coincubation with 10 microM unconjugated bilirubin (UCB)/human serum albumin in a molar ratio of 3:1 and 250 microg/mL ibuprofen caused additional loss of cell viability and increased LDH release (p < 0.01), DNA fragmentation, and activated caspase-3. Preincubation with the pan-caspase inhibitor z-val-ala-asp-fluoromethyl ketone abolished ibuprofen- and UCB-induced DNA fragmentation. The study demonstrates that bilirubin in low concentration of 10 microM reduces neuron viability and ibuprofen increases this effect. Apoptosis is the underlying cell death mechanism.

Calculated free bilirubin levels and neurotoxicity

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.

The cytotoxic effect of unconjugated bilirubin in human neuroblastoma SH-SY5Y cells is modulated by the expression level of MRP1 but not MDR1

In vitro and in vivo studies have demonstrated that UCB (unconjugated bilirubin) is neurotoxic. Although previous studies suggested that both MRP1 (multidrug resistance-associated protein 1) and MDR1 (multidrug resistance protein 1) may protect cells against accumulation of UCB, direct comparison of their role in UCB transport was never performed. To this end, we used an inducible siRNA (small interfering RNA) expression system to silence the expression of MRP1 and MDR1 in human neuroblastoma SH-SY5Y cells. The effects of in vitro exposure to clinically-relevant levels of unbound UCB were compared between unsilenced (control) cells and cells with similar reductions in the expression of MRP1 or MDR1, documented by RT–PCR (reverse transcription–PCR) (mRNA), immunoblotting (protein), and for MDR1, the enhanced net uptake of a specific fluorescent substrate. Cytotoxicity was assessed by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] test. MRP1-deficient cells accumulated significantly more UCB and suffered greater cytotoxicity than controls. By contrast, MDR1-deficient cells exhibited UCB uptake and cytotoxicity comparable with controls. At intermediate levels of silencing, the increased susceptibility to UCB toxicity closely correlated with the decrease in the expression of MRP1, but not of MDR1. These data support the concept that limitation of cellular UCB accumulation, due to UCB export mediated by MRP1, but not MDR1, plays an important role in preventing bilirubin encephalopathy in the newborn.

Serial brain MRI and ultrasound findings: relation to gestational age, bilirubin level, neonatal neurologic status and neurodevelopmental outcome in infants at risk of kernicterus

AIMS

To describe cranial ultrasound (cUS) and magnetic resonance imaging (MRI) findings in neonates at risk of kernicterus, in relation to gestational age (GA), total serum bilirubin (TSB), age at imaging and neurodevelopmental outcome.

PATIENTS AND METHODS

Neonates with peak TSB > 400 micromol/L and/or signs of bilirubin encephalopathy. Review of neonatal data, cUS, preterm, term and later MRI scans and neurodevelopmental outcome.

RESULTS

11 infants were studied, two < 31, four 34-36 and five 37-40 weeks GA. TSB levels: 235-583 micromol/L (preterms); 423-720 micromol/L (terms). Neonatal neurological examination was abnormal in 8/10. cUS showed increased basal ganglia (BG) in 4/9 infants and white matter (WM) echogenicity, lenticulostriate vasculopathy (LSV) and caudothalamic hyperechogencity/cysts (GLCs) in 5/9 infants. MRI showed abnormal signal intensity (SI) in the globus pallidum (GP) in 1/2 preterm, 8/9 term and 9/11 later scans. Abnormal WM SI occurred in 2 preterm, 7 term and 10/11 later scans. Seven infants developed athetoid/dystonic cerebral palsy (CP) and 6 hearing loss (HL). Adverse outcome was associated with abnormal BG on cUS (3/4 CP, 4/4 HL), with high SI in GP (7/9 CP, 6/9 HL) on late T2-weighted MRI (all GA) and on T1/T2-weighted term MRI, mainly in term-born infants. WM abnormalities, GLCs and LSV did not correlate with outcome.

CONCLUSIONS

Severe CP occurred with relatively low TSB levels in preterms but only at high levels in full-terms; HL was difficult to predict. Early scans did not reliably predict motor deficits whilst all children with CP had abnormal central grey matter on later scans. Abnormal WM was seen early suggesting primary involvement rather than change secondary to grey matter damage. Why characteristic central grey matter MRI features of kernicterus are not seen early remains unexplained.

Unconjugated bilirubin differentially affects the redox status of neuronal and astroglial cells

We investigated whether nerve cell damage by unconjugated bilirubin (UCB) is mediated by oxidative stress and ascertained the neuronal and astroglial susceptibility to injury. Several oxidative stress biomarkers and cell death were determined following incubation of neurons and astrocytes isolated from rat cortical cerebrum with UCB (0.01-1.0 microM). We show that UCB induces a dose-dependent increase in neuronal death in parallel with the oxidation of cell components and a decrease in the intracellular glutathione content. Comparison of the results obtained in both cell types demonstrates that neurons are more vulnerable than astrocytes to oxidative injury by UCB, for which accounts the lower glutathione stores in neuronal cells. Moreover, neuronal oxidative injury is prevented by supplementation with N-acetylcysteine, a glutathione precursor, whereas astroglial sensitivity to UCB is enhanced by inhibition of glutathione synthesis, using buthionine sulfoximine. Collectively, we demonstrate that oxidative stress is involved in UCB neurotoxicity and depict a new therapeutic approach for UCB-induced oxidative damage.

[Heme-iron in the human body]

Iron is essential for all living organism, although in excess amount it is dangerous via catalyzing the formation of reactive oxygen species. Absorption of iron is strictly controlled resulting in a fine balance of iron-loss and iron-uptake. In countries where the ingestion of heme-iron is significant by meal, great part of iron content in the body originates from heme. Heme derived from food is absorbed by a receptor-mediated manner by enterocytes of small intestine then it is degraded in a reaction catalyzed by heme oxygenase. Iron released from the porphyrin ring leaves enterocytes as transferrin associated iron. Prosthetic group of several proteins contains heme, therefore, it is synthesized by all cells. One of the most significant heme proteins is hemoglobin which transports oxygen in the erythrocytes. Hemoglobin released from erythrocyte during intravascular hemolysis binds to haptoglobin and is taken up by cells of the monocyte-macrophage lineage. Oxidation of hemoglobin (ferro) to methemoglobin (ferri) is inhibited by the structure of hemoglobin although it is not hindered. Superoxide anion is also formed in the reaction that initiates further free radical reactions. In contrast to ferrohemoglobin, methemoglobin readily releases heme, therefore, oxidation of hemoglobin drives the formation of free heme in plasma. Heme binds to a plasma protein, hemopexin, and is internalized by cells of monocyte-macrophage lineage in a receptor-mediated manner, then degraded in reaction catalysed by heme oxygenase. Heme is also taken up by plasma lipoproteins and endothelial cells leading to oxidation of LDL and subsequent endothelial cell damage. The purpose of this work was to summarize the processes related to heme.

Influence of hypoxia and ischemia preconditioning on bilirubin damage to astrocytes

Hypoxia-ischemia in the perinatal period is a common cause of neurologic disability in children and is often associated with neonatal morbidity and mortality. Another frequent condition of the newborn is hyperbilirubinemia and it is well known that deposition of unconjugated bilirubin (UCB) in the central nervous system can damage nerve cells and cause encephalopathy. Interestingly, some studies report the onset of cerebral hypoxia-ischemia as a risk factor for UCB encephalopathy, since that condition often precedes neonatal hyperbilirubinemia. However, the cellular mechanisms triggered by hypoxia-ischemia that may enforce UCB deleterious effects are not well elucidated. Therefore, we designed this study to investigate whether hypoxia (HP) or combined oxygen-glucose deprivation (OGD) followed by reoxygenation, modifies glial cell susceptibility to UCB injury. Thus, cultured astrocytes were exposed to HP or OGD for 4 h and returned to normoxic conditions for another 12 h prior to incubation with UCB for 4 h. HP and OGD effects in UCB toxicity were compared to normoxic conditions. Our results demonstrate that HP and OGD preconditioning increase the vulnerability of glial cells to UCB damage by enhancing some of the deleterious effects of UCB, namely cell death by both apoptosis and necrosis. This preconditioning also augments the UCB-induced stimulation of an inflammatory response by an effect that involves the activation of the nuclear factor kappaB activation. These findings provide a novel basis for the increased risk of brain damage in jaundiced newborns that were previously exposed to hypoxia or ischemia during the perinatal period, namely during delivery.

Apoptosis and impairment of neurite network by short exposure of immature rat cortical neurons to unconjugated bilirubin increase with cell differentiation and are additionally enhanced by an inflammatory stimulus

Nerve cell injury induced by unconjugated bilirubin (UCB) has been implicated in brain damage during severe neonatal hyperbilirubinemia, although the molecular mechanisms underlying UCB neurotoxicity are still not clarified. It has been suggested recently that there is an association between hyperbilirubinemia and long-term neurologic dysfunctions. We incubated immature neurons with UCB to evaluate the short- and long-term effects of UCB on apoptotic death and on neuritic outgrowth and ramification. We also evaluated whether mature neurons, exposed previously to UCB in an early stage of differentiation, are more sensitive to apoptosis or to neuritic breakdown when treated with inflammatory agents, such as lipopolysaccharide and tumor necrosis factor-alpha. Results show that exposure of immature neurons to UCB increased apoptosis and provoked a reduction of both neurite extension and number of nodes. These injurious effects observed in immature cells treated with UCB were increasingly perpetuated along cell differentiation, as compared to neurons incubated in the absence of UCB. In addition, neurons that were exposed to UCB when immature showed an increased susceptibility to death by apoptosis, as well as an additional decrease in neurite outgrowth when incubated with an inflammatory agent afterward. This work shows, for the first time, that UCB induces neurite changes consistent with neurodevelopment abnormalities. Furthermore, pre-exposure to UCB followed by an inflammatory stimulus leads to an enhanced susceptibility to long-term apoptosis, as well as a greater neuritic breakdown. These data support the association between neonatal hyperbilirubinemia and the later development of mental illness, such as schizophrenia.

NMDA channel antagonist MK-801 does not protect against bilirubin neurotoxicity

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.

Recovery after short-term bilirubin exposure in human NT2-N neurons

We used human NT2-N neurons to investigate delayed effects of short-term exposure to unconjugated bilirubin (UCB). Cell viability was evaluated with MTT reduction assays and nuclear morphology. A 6-h exposure to 1, 5, or 25 microM UCB and serum deprivation (SED) significantly diminished MTT reduction. 96 h after rescue of neurons with removal of UCB and re-incubation in the original serum-containing medium, delayed effects were evident as recovery (1 microM UCB), intermediate cell death (5 microM UCB), or near complete cell death (25 microM UCB). The impact of 6 h of SED alone appeared to be modest in rescued neurons. In this model, co-treatment with the specific caspase-3 inhibitor, zDEVD.FMK (100 microM), or the pancaspase inhibitor zVAD.FMK (100 microM) did not improve viability in rescued neurons exposed to 5 microM UCB, while treatment with the NMDA receptor antagonist MK-801 (1 microM) enhanced the number of undamaged nuclei (86 +/- 14% versus 50 +/- 12%, P = 0.001). MK-801 had, however, no impact on MTT reduction. In a different model with a 102-h continuous exposure to UCB and SED, we found a significant additional toxic impact of serum deprivation. Separate experiments suggested that this was a result of late caspase-mediated toxicity. We conclude that UCB-mediated effects may be reversible in this model. Blockade of excitotoxic mechanisms, but not caspase activity may prevent delayed cell death.

Bilirubin-induced immunostimulant effects and toxicity vary with neural cell type and maturation state

Hyperbilirubinemia remains one of the most frequent clinical diagnoses in the neonatal period. The increased vulnerability of premature infants to unconjugated bilirubin (UCB)-induced brain damage may be due to a proneness of immature nerve cells to UCB-toxic stimulus. Thus, in this study, we evaluated UCB-induced cell death, glutamate release and cytokine production, in astrocytes and neurons cultured for different days, in order to relate the differentiation state with cell vulnerability to UCB. The age-dependent activation of the nuclear factor-kappaB (NF-kappaB), an important transcription factor involved in inflammation, was also investigated. Furthermore, responsiveness of neurons and astrocytes to UCB were compared in order to identify the most susceptible to each induced effect, as an approach to what happens in vivo. The results clearly showed that immature nerve cells are more vulnerable than the most differentiated ones to UCB-induced cell death, glutamate release and tumour necrosis factor (TNF)-alpha secretion. Moreover, astrocytes seem to be more competent cells in releasing glutamate and in producing an inflammatory response when injured by UCB. Activation of NF-kappaB by UCB also presents a cell-age-dependent pattern, and values vary with neural cell type. Again, astrocytes have the highest activation levels, which are correlated with the greater amount of cytokine production observed in these cells. These results contribute to a better knowledge of the mechanisms leading to UCB encephalopathy by elucidation of age- and type-related differences in neural cell responses to UCB.

Hyperbilirubinemia and kernicterus

This article describes new findings concerning the basic science of bilirubin neurotoxicity, new considerations of the definition of clinical kernicterus, and new and useful tools to diagnose kernicterus in older children, and discusses treatments for kernicterus beyond the newborn period and why proper diagnosis is important.

Inflammatory signalling pathways involved in astroglial activation by unconjugated bilirubin

During neonatal hyperbilirubinaemia, astrocytes activated by unconjugated bilirubin (UCB) may contribute to brain toxicity through the production of cytokines. As a first step in addressing the signal transduction cascades involved in the UCB-induced astroglial immunological response, we tested whether tumour necrosis factor (TNF)-alpha receptor 1 (TNFR1), mitogen-activated protein kinase (MAPK) and nuclear factor kappaB (NF-kappaB) would be activated in astrocytes exposed to UCB, and examined the profile of cytokine production. Astrocyte cultures stimulated with UCB showed a rapid rise in TNFR1 protein levels, followed by activation of the MAPKs p38, Jun N-terminal kinase1/2 and extracellular signal-regulated kinase1/2, and NF-kappaB. Interestingly, the induction of these signal effectors preceded the early up-regulation of TNF-alpha and interleukin (IL)-1beta mRNAs, and later secretion of TNF-alpha, IL-1beta and IL-6. Treatment of astrocytes with UCB also induced cell death, with levels comparable to those obtained after exposure of astrocytes to recombinant TNF-alpha and IL-1beta. Moreover, loss of cell viability and cytokine secretion were reduced when the NF-kappaB signal transduction pathway was inhibited, suggesting a key role for NF-kappaB in the astroglial response to UCB. These results demonstrate the complexity of the molecular mechanisms involved in cell injury by UCB during hyperbilirubinaemia and provide a basis for the development of novel therapeutic strategies.

Toward understanding kernicterus: a challenge to improve the management of jaundiced newborns

PURPOSE

We sought to evaluate the sensitivity and specificity of total serum bilirubin concentration (TSB) and free (unbound) bilirubin concentration (Bf) as predictors of risk for bilirubin toxicity and kernicterus and to examine consistency between these findings and proposed mechanisms of bilirubin transport and brain uptake.

METHODS

A review of literature was undertaken to define basic principles of bilirubin transport and brain uptake leading to neurotoxicity. We then reviewed experimental and clinical evidence that relate TSB or Bf to risk for bilirubin toxicity and kernicterus.

RESULTS

There are insufficient published data to precisely define sensitivity and specificity of either TSB or Bf in determining risk for acute bilirubin neurotoxicity or chronic sequelae (kernicterus). However, available laboratory and clinical evidence indicate that Bf is better than TSB in discriminating risk for bilirubin toxicity in patients with severe hyperbilirubinemia. These findings are consistent with basic pharmacokinetic principles involved in bilirubin transport and tissue uptake.

CONCLUSIONS

Experimental and clinical data strongly suggest that measurement of Bf in newborns with hyperbilirubinemia will improve risk assessment for neurotoxicity, which emphasizes the need for additional clinical evaluation relating Bf and TSB to acute bilirubin toxicity and long-term outcome. We speculate that establishing risk thresholds for neurotoxicity by using newer methods for measuring Bf in minimally diluted serum samples will improve the sensitivity and specificity of serum indicators for treating hyperbilirubinemia, thus reducing unnecessary aggressive intervention and associated cost and morbidity.

Synergistic protection of a general caspase inhibitor and MK-801 in bilirubin-induced cell death in human NT2-N neurons

Unconjugated bilirubin (UCB) induces both apoptosis and necrosis in neurons. To investigate the role of caspases and excitotoxicity in UCB-induced cell death, we exposed NT2-N neurons to 5 microM UCB (a concentration known to induce apoptosis) or 2 microM staurosporine (positive apoptosis control) and investigated the effects of treatments with the specific caspase-3 inhibitor, zDEVD.FMK (20 and 100 microM), or the general caspase inhibitor, zVAD.FMK (20 and 100 microM), and/or the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (10 microM) during a 24- or 48-h exposure. UCB increased caspase-3 activity 2.3-fold after 6 h. Despite this, treatment with zDEVD.FMK did not prevent cell death. zVAD.FMK enhanced neuronal survival by reducing apoptotic nuclear fragmentation, while MK-801 enhanced survival by reducing apoptotic nuclear condensation; both without affecting the MTT assays. Combined treatment reduced both apoptotic morphologies (without affecting necrosis), and this effect was also reflected in the MTT assays [corrected] We conclude that NMDA receptor-mediated pathways and caspase-mediated pathways are involved in UCB-induced cell death in human NT2-N neurons. Concomitant inhibition of both pathways results in synergistic protection.