Cytokine response in cerebrospinal fluid after birth asphyxia

Systemic pro-inflammatory cytokine status following therapeutic hypothermia in a piglet hypoxia-ischemia model

Background

Inflammatory cytokines are implicated in the pathogenesis of perinatal hypoxia-ischemia (HI). The influence of hypothermia (HT) on cytokines after HI is unclear. Our aim was to assess in a piglet asphyxia model, under normothermic (NT) and HT conditions: (i) the evolution of serum cytokines over 48 h and (ii) cerebrospinal fluid (CSF) cytokine levels at 48 h; (iii) serum pro/anti-inflammatory cytokine profile over 48 h and (iv) relation between brain injury measured by magnetic resonance spectroscopy (MRS) and brain TUNEL positive cells with serum cytokines, serum pro/anti-inflammatory cytokines and CSF cytokines.

Methods

Newborn piglets were randomized to NT (n = 5) or HT (n = 6) lasting 2–26 h after HI. Serum samples were obtained 4–6 h before, during and at 6–12 h intervals after HI; CSF was obtained at 48 h. Concentrations of interleukin (IL)-1β, −4, −6, −8, −10 and TNF-α were measured and pro/anti-inflammatory status compared between groups. White matter and thalamic voxel lactate/N-acetyl aspartate (Lac/NAA) (a measure of both oxidative metabolism and neuronal loss) were acquired at baseline, after HI and at 24 and 36 h.

Results

Lac/NAA was reduced at 36 h with HT compared to NT (p = 0.013 basal ganglia and p = 0.033 white matter). HT showed lower serum TNF-α from baseline to 12 h (p < 0.05). Time-matched (acquired within 5 h of each other) serum cytokine and MRS showed correlations between Lac/NAA and serum IL-1β and IL-10 (all p < 0.01). The pro/anti-inflammatory ratios IL-1β/IL-10, IL-6/IL-10, IL-4/IL-10 and IL-8/IL-10 were similar in NT and HT groups until 36 h (24 h for IL-6/IL-10); after this, 36 h pro/anti-inflammatory cytokine ratios in the serum were higher in HT compared to NT (p < 0.05), indicating a pro-inflammatory cytokine surge after rewarming in the HT group. In the CSF at 48 h, IL-8 was lower in the HT group (p < 0.05). At 48 h, CSF TNF-α correlated with Lac/NAA (p = 0.02) and CSF IL-8 correlated with white matter TUNEL positive cell death (p = 0.04).

Conclusions

Following cerebral HI, there was a systemic pro-inflammatory surge after rewarming in the HT group, which is counterintuitive to the putative neuroprotective effects of HT. While serum cytokines were variable, elevations in CSF inflammatory cytokines at 48 h were associated with MRS Lac/NAA and white matter cell death.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0821-x) contains supplementary material, which is available to authorized users.

Inflammatory Biomarkers of Birth Asphyxia

Although therapies in addition to whole-body cooling are being developed to treat the neonate at risk for hypoxic-ischemic encephalopathy, we have no quickly measured serum inflammatory or neuronal biomarkers to acutely and accurately identify brain injury or to follow the efficacy of therapy. This review covers inflammatory serum biomarkers in the setting of birth asphyxia that can help assess the degree or severity of encephalopathy at birth and neurodevelopmental outcomes. These biomarkers still need to be independently validated in large cohorts before they are ready for clinical implementation in practice.

Increased CSF aquaporin-4, and interleukin-6 levels in dogs with idiopathic communicating internal hydrocephalus and a decrease after ventriculo-peritoneal shunting

Background

Studies in animal models, in which internal hydrocephalus has been induced by obstructing the cerebrospinal fluid pathways, have documented an up-regulation of the concentrations of aquaporin-4 (AQP4) in the brain. In this study, the concentrations of aquaporin-1 (AQP1), AQP1, AQP4 and interleukin-6 (IL-6) were determined in the CSF of dogs with idiopathic communicating hydrocephalus before and after the reduction of intraventricular volume following ventriculo-peritoneal shunt (VP-shunt) treatment.

Results

The concentrations of AQP4 and IL-6 were increased in the cerebrospinal fluid of dogs with hydrocephalus compared to controls. Both parameters significantly decreased after surgical treatment, accompanied by decrease of ventricular size and the clinical recovery of the dogs. AQP1 was not detectable in CSF.

Conclusions

Brain AQP4 up-regulation might be a compensatory response in dogs with hydrocephalus. Future determination of AQP4 at the mRNA and protein level in brain tissue is warranted to substantiate this hypothesis.

Inflammatory mediators as predictors of outcome in perinatal asphyxia

OBJECTIVES

To identify biomarkers for neuronal injury and outcome in perinatal asphyxia.

METHODS

This prospective cohort study was done in authors' level III NICU involving 80 neonates - 40 babies with perinatal asphyxia and 40 weight and gender matched normal neonates. Levels of cytokines IL-6, IL -1β, IL-2 and TNF -α in cord blood of these neonates were estimated and correlated with the severity of asphyxia and developmental outcome at 6 mo using Baroda Developmental Score.

RESULTS

The baseline parameters revealed that there was no statistically significant difference between the two groups in terms of maternal age, parity, gestational age, gender and birth weight. The levels of cytokines IL-6 (p < 0.001) and IL-1beta (p < 0.03) were significantly higher in babies with perinatal asphyxia and correlated with the severity of asphyxia. The levels of IL-6 and IL-1β had significant negative correlation with developmental score at 6 mo. A cut off level of 14.18 pg/ml for IL-6 had 92.3 % sensitivity and 57.7 % specificity [Area under the curve = 0.80 (0.62-0.84)] for adverse neuro-developmental outcome while it was 11.17 pg/ml for IL-1β with a sensitivity of 69.2 % and specificity of 71.2 % [Area under the curve = 0.67 (0.57-0.80)].

CONCLUSIONS

IL-6 and IL-1 β are good predictive markers of severity of asphyxia and adverse neurological outcome.

Fetal and early neonatal interleukin-6 response

In 1998, a systemic fetal cytokine response, defined as a plasma interleukin-6 (IL-6) value above 11 pg/mL, was reported to be a major independent risk factor for the subsequent development of neonatal morbid events even after adjustments for gestational age and other confounders. Since then, the body of literature investigating the use of blood concentrations of IL-6 as a hallmark of the fetal inflammatory response syndrome (FIRS), a diagnostic marker of early-onset neonatal sepsis (EONS) and a risk predictor of white matter injury (WMI), has grown rapidly. In this article, we critically review: IL-6 biological functions; current evidence on the association between IL-6, preterm birth, FIRS and EONS; IL-6 reference intervals and dynamics in the early neonatal period; IL-6 response during the immediate postnatal period and perinatal confounders; accuracy and completeness of IL-6 diagnostic studies for EONS (according to the Standards for Reporting of Diagnostic Accuracy statement); and recent breakthroughs in the association between fetal blood IL-6, EONS, and WMI.

Early predictors of outcome in infants treated with hypothermia for hypoxic-ischaemic encephalopathy

Hypoxic-ischaemic encephalopathy (HIE) is a leading cause of acquired neonatal brain injury. Assessment of the severity of cerebral injury and likely neurological outcome in infants with HIE is important for determining management and prognosis, for counselling parents, and for selection for neuroprotective trials. The condition of the infant at birth, the severity of HIE, neurophysiological tests, including amplitude-integrated electroencephalography (aEEG), biochemical markers, and neuroimaging have been used to assess prognosis and predict long-term outcome. The predictive accuracy of these indicators in the early postnatal period is modest. Neurophysiological assessment seems to be most helpful during the first 24 to 48 hours after birth whilst magnetic resonance imaging (MRI) seems most informative later. Several biochemical markers, including serum S100β and neuron-specific enolase (NSE), are also associated with HIE but their levels depend on the timing of sampling and their prognostic value is uncertain. Comprehensive neurophysiological assessment and neuroimaging may be limited to specialist centres. Therapeutic hypothermia is now standard care in infants with moderate to severe HIE so it is important to examine the influence of hypothermia on the assessment of prognosis in these infants.

The role of inflammation in perinatal brain injury

Inflammation is increasingly recognized as being a critical contributor to both normal development and injury outcome in the immature brain. The focus of this Review is to highlight important differences in innate and adaptive immunity in immature versus adult brain, which support the notion that the consequences of inflammation will be entirely different depending on context and stage of CNS development. Perinatal brain injury can result from neonatal encephalopathy and perinatal arterial ischaemic stroke, usually at term, but also in preterm infants. Inflammation occurs before, during and after brain injury at term, and modulates vulnerability to and development of brain injury. Preterm birth, on the other hand, is often a result of exposure to inflammation at a very early developmental phase, which affects the brain not only during fetal life, but also over a protracted period of postnatal life in a neonatal intensive care setting, influencing critical phases of myelination and cortical plasticity. Neuroinflammation during the perinatal period can increase the risk of neurological and neuropsychiatric disease throughout childhood and adulthood, and is, therefore, of concern to the broader group of physicians who care for these individuals.

Serum biomarkers to evaluate the integrity of the neurovascular unit

Biomarkers have the potential to enable the clinicians to screen infants for brain injury, monitor progression of disease, identify injured brain regions, assess efficacy of neuroprotective therapies, and offer hope to identify the timing of the injury, thus shedding light on the potential pathophysiology and the most effective therapy. Currently, clinicians do not routinely use biomarkers to care for neonates with Neonatal Encephalopathy (NE) and brain injury due to prenatal hypoxia-asphyxia. This review will cover potential biomarkers of the neurovascular unit in the setting of NE that (i) can help assess the degree or severity of encephalopathy at birth; (ii) can help monitor progression of disease process and efficacy of neuroprotective therapy; (iii) can help assess neurodevelopmental outcome. These biomarkers will be summarized in two categories: 1) Specific biomarkers targeting the neurovascular unit such as glial fibrillary acidic protein (GFAP), ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), S100B, and neuron specific enolase (NSE) and 2) general inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-1b (IL-1b), and pNF-H, among others.

Fingerprint changes in CSF composition associated with different aetiologies in human neonatal hydrocephalus: inflammatory cytokines

PURPOSE

Hydrocephalus (HC) has a multifactorial and complex picture of pathophysiology due to aetiology, age at and duration since onset. We have previously identified distinctions in markers of cell death associated with different aetiologies. Here, we examined cerebrospinal fluid (CSF) from human HC neonates for cytokines to identify further distinguishing features of different aetiologies.

METHODS

CSF was collected during routine lumbar puncture or ventricular tap from neonates with hydrocephalus, or with no neurological condition (normal controls). Total protein, Fas receptor, Fas ligand, stem cell factor (SCF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin growth factor-1 (IGF-1), tumour necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) were measured and compared between 8 unaffected and 28 HC neonatal CSF samples.

RESULTS

Total protein was significantly (P < 0.05) raised in late-onset hydrocephalus (LOH). Fas receptor was raised (P < 0.05) in post-haemorrhagic hydrocephalus (PHH) and spina bifida with hydrocephalus (SB/HC), but no difference in Fas ligand was found. SCF was raised (P < 0.05) in SB/HC. HGF was found in all HC and was increased (P < 0.01) in PHH. Increased VEGF was found in PHH (P < 0.01) and SB/HC (P < 0.05). Variable levels of IL-6, TNF-α and IGF-1 were found in all HC groups compared with none in normal.

CONCLUSIONS

LOH was unusual with significantly raised total protein indicating an inflammatory state. Increased Fas receptor, VEGF, IGF-1 and HGF suggest anti-apoptotic and repair mechanism activation. By contrast, elevated TNF-α and IL-6 indicate inflammatory processes in these neonatal brains. Taken with our previous study, these data indicate that different pathophysiology, inflammation and repair are occurring in HC of different aetiologies and that additional treatment strategies may benefit these infants in addition to fluid diversion.

Knockdown of IL-1β improves hypoxia-ischemia brain associated with IL-6 up-regulation in cell and animal models

A study was conducted to investigate the effect of interleukin-1β (IL-1β) on hypoxia ischemia (HI) of cultured astrocyte and neonatal rat models and to explore the underlying molecular regulation mechanism. Primary rat astrocyte was exposed to hypoxia (2 % O2, 98 % N2) and cultured in serum-free medium for 6, 12, and 18 h to establish cell model of HI. Morphologic changes of astrocyte were monitored and gene expression change of IL-1β evaluated by real-time polymerase chain reaction (PCR). To establish the HI animal model, 3 days old postnatal Sprague-Dawley (SD) rats were treated with the right carotid artery ligation and were exposed to 8 % oxygen for 8, 16 and 24 h, respectively. Longa score scale, hematoxylin and eosin (HE) staining and water content were examined to assess neurologic function and morphology changes. IL-1β siRNA lentivirus (IL-1β-RNAi-LV) was injected into cerebral cortex motor area 2 days before HI and the interference efficiency examined by real-time PCR and Western blotting, respectively. Immunofluorescence staining of GFAP and IL-1β was performed to identify the location and interference effect of IL-1β, respectively. To further explore the potential mechanisms, the expression of inflammatory factors, including IL-6, IL-10 and tumor necrosis factor-alpha (TNF-α), was examined following IL-1β down-regulation. The size of soma astrocyte was increased greatly after 12 and 18 h of HI with IL-1β up-regulation. IL-1β knockdown by siRNA in vitro or by lentivirus in vivo can reverse cell swelling, brain edema and neurologic function deficiencies induced by HI. Lastly, interference of IL-1β remarkably increased IL-6 expression but not IL-10 and TNF-α. Therefore, down-regulation of IL-1β improves the deficiencies of neurologic function and morphology induced by HI, maybe closely associating with IL-6 regulation.

Neuroinflammation and neuroimmune dysregulation after acute hypoxic-ischemic injury of developing brain

Hypoxic-ischemic (HI) injury to developing brain results from birth asphyxia in neonates and from cardiac arrest in infants and children. It is associated with varying degrees of neurologic sequelae, depending upon the severity and length of HI. Global HI triggers a series of cellular and biochemical pathways that lead to neuronal injury. One of the key cellular pathways of neuronal injury is inflammation. The inflammatory cascade comprises activation and migration of microglia - the so-called "brain macrophages," infiltration of peripheral macrophages into the brain, and release of cytotoxic and proinflammatory cytokines. In this article, we review the inflammatory and immune mechanisms of secondary neuronal injury after global HI injury to developing brain. Specifically, we highlight the current literature on microglial activation in relation to neuronal injury, proinflammatory and anti-inflammatory/restorative pathways, the role of peripheral immune cells, and the potential use of immunomodulators as neuroprotective compounds.

Dual role of astrocytes in perinatal asphyxia injury and neuroprotection

Perinatal asphyxia represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. However, at the moment, most of the therapeutic strategies were not well targeted toward the processes that induced the brain injury during perinatal asphyxia. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related with the damage mechanisms of perinatal asphyxia. In this work, we propose to review possible protective as well as deleterious roles of astrocytes in the asphyctic brain with the aim to stimulate further research in this area of perinatal asphyxia still not well studied.

Inflammatory response and oxidative stress in developing rat brain and its consequences on motor behavior following maternal administration of LPS and perinatal anoxia

Cerebral palsy (CP) is a disorder of locomotion, posture and movement that can be caused by prenatal, perinatal or postnatal insults during brain development. An increased incidence of CP has been correlated to perinatal asphyxia and maternal infections during gestation. The effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) associated or not with perinatal anoxia (PA) in oxidative and inflammatory parameters were examined in cerebral cortices of newborns pups. Concentrations of TNF-α, IL-1, IL-4, SOD, CAT and DCF were measured by the ELISA method. Other newborn rats were assessed for neonatal developmental milestones from day 1 to 21. Motor behavior was also tested at P29 using open-field and Rotarod. PA alone only increased IL-1 expression in cerebral cortex with no changes in oxidative measures. PA also induced a slight impact on development and motor performance. LPS alone was not able to delay motor development but resulted in changes in motor activity and coordination with increased levels of IL-1 and TNF-α expression associated with a high production of free radicals and elevated SOD activity. When LPS and PA were combined, changes on inflammatory and oxidative stress parameters were greater. In addition, greater motor development and coordination impairments were observed. Prenatal exposure of pups to LPS appeared to sensitize the developing brain to effects of a subsequent anoxia insult resulting in an increased expression of pro-inflammatory cytokines and increased free radical levels in the cerebral cortex. These outcomes suggest that oxidative and inflammatory parameters in the cerebral cortex are implicated in motor deficits following maternal infection and perinatal anoxia by acting in a synergistic manner during a critical period of development of the nervous system.

Toll-like receptor-3 activation increases the vulnerability of the neonatal brain to hypoxia-ischemia

Susceptibility and progression of brain injury in the newborn is closely associated with an exacerbated innate immune response, but the underlying mechanisms are often unclear. Toll-like receptors (TLRs) are important innate immune sensors that may influence the vulnerability of the developing brain. In the current study, we provide novel data to show that activation of the viral innate immune receptor TLR-3 sensitizes the neonatal brain to subsequent hypoxic-ischemic (HI) damage. Poly inosinic:poly cytidylic acid (Poly I:C), a synthetic ligand for TLR-3, was administered to neonatal mice 14 h before cerebral HI. Activation of TLR-3 before HI increased infarct volume from 3.0 ± 0.5 to 15.4 ± 2.1 mm³ and augmented loss of myelin basic protein from 13.4 ± 6.0 to 70.6 ± 5.3%. The sensitizing effect of Poly I:C was specific for the TLR-3 pathway because mice deficient in the TLR-3 adaptor protein Toll/IL-1R domain-containing adaptor molecule-1 (TRIF) did not develop larger brain damage. The increased vulnerability was associated with a TRIF-dependent heightened inflammatory response, including proinflammatory cytokines, chemokines, and the apoptosis-associated mediator Fas, whereas there was a decrease in reparative M2-like CD11b⁺ microglia and phosphorylation of Akt. Because TLR-3 is activated via double-stranded RNA during most viral infections, the present study provides evidence that viral infections during pregnancy or in the neonate could have great impact on subsequent HI brain injury.

Characterization of phenotype markers and neuronotoxic potential of polarised primary microglia in vitro

Microglia mediate multiple facets of neuroinflammation, including cytotoxicity, repair, regeneration, and immunosuppression due to their ability to acquire diverse activation states, or phenotypes. Modulation of microglial phenotype is an appealing neurotherapeutic strategy but a comprehensive study of classical and more novel microglial phenotypic markers in vitro is lacking. The aim of this study was to outline the temporal expression of a battery of phenotype markers from polarised microglia to generate an in vitro tool for screening the immunomodulatory potential of novel compounds. We characterised expression of thirty-one macrophage/microglial phenotype markers in primary microglia over time (4, 12, 36, and 72 h), using RT-qPCR or multiplex protein assay. Firstly, we selected Interleukin-4 (IL-4) and lipopolysaccharide (LPS) as the strongest M1-M2 polarising stimuli, from six stimuli tested. At each time point, markers useful to identify that microglia were M1 included iNOS, Cox-2 and IL-6 and a loss of M2a markers. Markers useful for quantifying M2b-immunomodulatory microglia included, increased IL-1RA and SOCS3 and for M2a-repair and regeneration, included increased arginase-1, and a loss of the M1 and M2b markers were discriminatory. Additional markers were regulated at fewer time points, but are still likely important to monitor when assessing the immunomodulatory potential of novel therapies. Further, to facilitate identification of how novel immunomodulatory treatments alter the functional affects of microglia, we characterised how the soluble products from polarised microglia affected the type and rate of neuronal death; M1/2b induced increasing and M2a-induced decreasing neuronal loss. We also assessed any effects of prior activation state, to provide a way to identify how a novel compound may alter phenotype depending on the stage of injury/insult progression. We identified generally that a prior M1/2b reduced the ability of microglia to switch to M2a. Altogether, we have characterised a profile of phenotype markers and a mechanism of assessing functional outcome that we can use as a reference guide for first-line screening of novel immunomodulatory therapies in vitro in the search for viable neuroprotectants.

Cord blood proteins and multichannel-electroencephalography in hypoxic-ischemic encephalopathy

OBJECTIVE

To explore the association between multiple umbilical cord blood proteins and severity of hypoxic-ischemic encephalopathy as defined by continuous multichannel electroencephalography.

DESIGN

A prospective case-control cohort study, which was divided into separate exploratory and validation cohorts.

SETTING

A single tertiary neonatal intensive care facility.

PATIENTS

The study recruited full-term infants with perinatal asphyxia and controls. Identical procedures were used to recruit a representative exploratory sample (n = 30) and a subsequent validation cohort (n = 100).

INTERVENTION

All had umbilical cord blood drawn and biobanked at delivery, continuous multichannel electroencephalography commenced in the first 24 hours, and a modified Sarnat score assigned. Analysis of 37 potential cord blood protein markers of hypoxic-ischemic encephalopathy was performed using Luminex multiplex assays.

MEASUREMENTS AND RESULTS

Cord blood from 130 infants was analyzed. Interleukin-16 and interleukin-6 significantly differentiated between a moderate-severely abnormal and normal-mildly abnormal electroencephalography background in both exploratory (p = 0.005 and p = 0.016, respectively) and validation cohorts (p = 0.039 and p = 0.024, respectively). To develop a predictive model for a moderate-severely abnormal electroencephalography, stepwise regression analysis was used to combine these analytes with current standard clinical markers of asphyxia (pH, base deficit, and 10-min Apgar). Only Apgar score and interleukin-16 remained in the model, which was highly predictive of an abnormal electroencephalography (area under the curve [AUC] = 0.956, p < 0.001, positive predictive value = 89%, and negative predictive value = 94%).

CONCLUSIONS

Cord blood interleukin-6 and interleukin-16 were associated with electrographic grade of hypoxic-ischemic encephalopathy. To predict an abnormal electroencephalography, interleukin-16 and 10-minute Apgar used in combination performed better than current markers.

Prenatal inflammation and neurodevelopment in schizophrenia: a review of human studies

A confluence of evidence supports an association between prenatal inflammation and risk of schizophrenia. Outside of studies of prenatal infections and risk of schizophrenia, other relevant human studies of prenatal inflammation and neurodevelopment in schizophrenia have not been reviewed. In this paper, we review human studies of 1) prenatal inflammation and risk of schizophrenia, 2) inflammation as a potential common mediator of several prenatal risk factors for schizophrenia other than prenatal infections, 3) prenatal inflammation and immune function, neurocognition, brain morphology, and gene expression in adult offspring with schizophrenia, and 4) gene by environment and gene by gene interactions relevant to these associations. We suggest future areas for human studies research based on existing findings.

Serum biomarkers of MRI brain injury in neonatal hypoxic ischemic encephalopathy treated with whole-body hypothermia: a pilot study

OBJECTIVES

To determine if candidate biomarkers, ubiquitin carboxyl-terminal esterase L1 and glial fibrillary acidic protein, are elevated in neonates with hypoxic ischemic encephalopathy who die or have severe MRI injury compared with surviving infants with minimal or no injury on brain MRI.

DESIGN

Prospective observational study.

SETTING

Level IIIC outborn neonatal ICU in a free-standing children's hospital.

PATIENTS

Term newborns with moderate-to-severe hypoxic ischemic encephalopathy referred for therapeutic hypothermia

INTERVENTIONS

Serum specimens were collected at 0, 12, 24, and 72 hours of cooling. MRI was performed in surviving infants at target 7-10 days of life and was scored by a pediatric neuroradiologist masked to biomarker and clinical data.

MEASUREMENTS AND MAIN RESULTS

Serial biomarker levels were determined in 20 hypoxic ischemic encephalopathy patients. Ubiquitin carboxyl-terminal esterase L1 was higher at initiation and 72 hours of cooling, while glial fibrillary acidic protein was higher at 24 and 72 hours in babies with adverse outcome compared with those with favorable outcome.

CONCLUSIONS

This preliminary data support further studies to evaluate ubiquitin carboxyl-terminal esterase L1 and glial fibrillary acidic protein as immediate biomarkers of cerebral injury severity in newborns with hypoxic ischemic encephalopathy.

Acid extrusion via blood-brain barrier causes brain alkalosis and seizures after neonatal asphyxia

Birth asphyxia is often associated with a high seizure burden that is predictive of poor neurodevelopmental outcome. The mechanisms underlying birth asphyxia seizures are unknown. Using an animal model of birth asphyxia based on 6-day-old rat pups, we have recently shown that the seizure burden is linked to an increase in brain extracellular pH that consists of the recovery from the asphyxia-induced acidosis, and of a subsequent plateau level well above normal extracellular pH. In the present study, two-photon imaging of intracellular pH in neocortical neurons in vivo showed that pH changes also underwent a biphasic acid–alkaline response, resulting in an alkaline plateau level. The mean alkaline overshoot was strongly suppressed by a graded restoration of normocapnia after asphyxia. The parallel post-asphyxia increase in extra- and intracellular pH levels indicated a net loss of acid equivalents from brain tissue that was not attributable to a disruption of the blood–brain barrier, as demonstrated by a lack of increased sodium fluorescein extravasation into the brain, and by the electrophysiological characteristics of the blood–brain barrier. Indeed, electrode recordings of pH in the brain and trunk demonstrated a net efflux of acid equivalents from the brain across the blood–brain barrier, which was abolished by the Na/H exchange inhibitor, N-methyl-isobutyl amiloride. Pharmacological inhibition of Na/H exchange also suppressed the seizure activity associated with the brain-specific alkalosis. Our findings show that the post-asphyxia seizures are attributable to an enhanced Na/H exchange-dependent net extrusion of acid equivalents across the blood–brain barrier and to consequent brain alkalosis. These results suggest targeting of blood–brain barrier-mediated pH regulation as a novel approach in the prevention and therapy of neonatal seizures.

Microglia/macrophage-derived inflammatory mediators galectin-3 and quinolinic acid are elevated in cerebrospinal fluid from newborn infants after birth asphyxia

Activation of microglia/macrophages is important in neonatal hypoxic–ischemic (HI) brain injury. Based on experimental studies, we identified macrophage/microglia-derived mediators with potential neurotoxic effects after neonatal HI and examined them in cerebrospinal fluid (CSF) from newborn infants after birth asphyxia. Galectin-3 is a novel inflammatory mediator produced by microglia/macrophages. Galectin-3 is chemotactic for inflammatory cells and activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase resulting in production and release of reactive oxygen species (ROS). Matrix metalloproteinase-9 (MMP-9) is a tissue-degrading protease expressed by activated microglia in the immature brain after HI. Both galectin-3 and MMP-9 contribute to brain injury in animal models for neonatal HI. Quinolinic acid (QUIN) is a neurotoxic N-methyl-d-aspartate (NMDA) receptor agonist also produced by activated microglia/macrophages. Galectin-3 and MMP-9 were measured by ELISA and QUIN by mass spectrometry. Asphyxiated infants (n = 20) had higher levels of galectin-3 (mean (SEM) 2.64 (0.43) ng/mL) and QUIN (335.42 (58.9) nM) than controls (n = 15) (1.36 (0.46) ng/mL and 116.56 (16.46) nM, respectively), p < 0.05 and p < 0.01. Infants with septic infections (n = 10) did not differ from controls. Asphyxiated infants with abnormal outcome had higher levels of galectin-3 (3.96 (0.67) ng/mL) than those with normal outcome (1.76 (0.32) ng/mL), p = 0.02, and the difference remained significant in the clinically relevant group of infants with moderate encephalopathy. MMP-9 was detected in few infants with no difference between groups. The potentially neurotoxic macrophage/microglia-derived mediators galectin-3 and QUIN are increased in CSF after birth asphyxia and could serve as markers and may contribute to injury.

Serum cytokines in a clinical trial of hypothermia for neonatal hypoxic-ischemic encephalopathy

Inflammatory cytokines may mediate hypoxic-ischemic (HI) injury and offer insights into the severity of injury and the timing of recovery. In our randomized, multicenter trial of hypothermia, we analyzed the temporal relationship of serum cytokine levels in neonates with hypoxic-ischemic encephalopathy (HIE) with neurodevelopmental outcome at 12 months. Serum cytokines were measured every 12 hours for 4 days in 28 hypothermic (H) and 22 normothermic (N) neonates with HIE. Monocyte chemotactic protein-1 (MCP-1) and interleukins (IL)-6, IL-8, and IL-10 were significantly higher in the H group. Elevated IL-6 and MCP-1 within 9 hours after birth and low macrophage inflammatory protein 1a (MIP-1a) at 60 to 70 hours of age were associated with death or severely abnormal neurodevelopment at 12 months of age. However, IL-6, IL-8, and MCP-1 showed a biphasic pattern in the H group, with early and delayed peaks. In H neonates with better outcomes, uniform down modulation of IL-6, IL-8, and IL-10 from their peak levels at 24 hours to their nadir at 36 hours was observed. Modulation of serum cytokines after HI injury may be another mechanism of improved outcomes in neonates treated with induced hypothermia.

Genetic factors that influence short-term neurodevelopmental outcome in term hypoxic-ischaemic encephalopathic neonates

It is difficult to predict outcome in neonates that experience perinatal hypoxic ischaemia. Morbidity and mortality may be affected by genetic factors that augment inflammatory and coagulative responses. This prospective study analysed the effects of proinflammatory cytokine gene polymorphisms (tumour necrosis factor-α [TNFA] 308G>A and interleukin-6 [IL6] 174G>C) and prothrombotic factor gene mutations (prothrombin G20210A, factor V Leiden G1691A and methylenetetra hydrofolate reductase [MTHFR] C677T) on the early neurological prognosis in 40 term hypoxic ischaemic encephalopathic neonates. There were significant relationships for Sarnat and Sarnat staging with electroencephalographic findings, transfontanelle ultrasound (US) results, early neonatal outcome and neurological morbidity. Genetic mutations in the prothrombotic proteins, the TNFA 308G>A polymorphism and the cerebrospinal fluid levels of TNF-α protein were not related to clinical stage, electroencephalography, transfontanelle US or neurological status at discharge or at postnatal months 6 and 12. The IL6 174GC genotype demonstrated a protective role, being significantly correlated with normal electroencephalography, transfontanelle US and normal neurological findings at discharge. In conclusion, the IL6 174GC gene polymorphism seems to play a role in determining the risk and/or severity of perinatal cerebral injury.

The role of cytokines and inflammatory cells in perinatal brain injury

Perinatal brain injury frequently complicates preterm birth and leads to significant long-term morbidity. Cytokines and inflammatory cells are mediators in the common pathways associated with perinatal brain injury induced by a variety of insults, such as hypoxic-ischemic injury, reperfusion injury, toxin-mediated injury, and infection. This paper examines our current knowledge regarding cytokine-related perinatal brain injury and specifically discusses strategies for attenuating cytokine-mediated brain damage.

Inflammation during fetal and neonatal life: implications for neurologic and neuropsychiatric disease in children and adults

Inflammation is increasingly recognized as being of both physiological and pathological importance in the immature brain. The rationale of this review is to present an update on this topic with focus on long-term consequences of inflammation during childhood and in adults. The immature brain can be exposed to inflammation in connection with viral or bacterial infection during pregnancy or as a result of sterile central nervous system (CNS) insults. Through efficient anti-inflammatory and reparative processes, inflammation may resolve without any harmful effects on the brain. Alternatively, inflammation contributes to injury or enhances CNS vulnerability. Acute inflammation can also be shifted to a chronic inflammatory state and/or adversely affect brain development. Hypothetically, microglia are the main immunocompetent cells in the immature CNS, and depending on the stimulus, molecular context, and timing, these cells will acquire various phenotypes, which will be critical regarding the CNS consequences of inflammation. Inflammation has long-term consequences and could speculatively modify the risk of a variety of neurological disorders, including cerebral palsy, autism spectrum disorders, schizophrenia, multiple sclerosis, cognitive impairment, and Parkinson disease. So far, the picture is incomplete, and data mostly experimental. Further studies are required to strengthen the associations in humans and to determine whether novel therapeutic interventions during the perinatal period can influence the occurrence of neurological disease later in life.

New insights into the pathogenesis of perinatal hypoxic-ischemic brain injury

BACKGROUND

Pathogenesis of perinatal hypoxic-ischemic brain injury (HIE) is complex. In this study, we examined the role of neuroinflammation, oxidative stress and growth factors in perinatal hypoxic-ischemic brain damage.

METHODS

Ninety neonates (>32 weeks' gestation) with perinatal HIE were enrolled prospectively. Perinatal HIE was categorized into three stages according to the Sarnat and Sarnat clinical scoring system and changes seen on amplitude integrated electroencephalography. Cerebrospinal fluid (CSF) for interleukin-6 (IL-6) and glutathione peroxidase analysis was taken in the first 48 h of life and subsequent CSF for neuron-specific enolase (NSE) and vascular endothelial growth factor (VEGF) analysis 72 h after birth. Neurodevelopmental outcome was assessed at 12 months of corrected gestational age using the Denver Developmental Screening Test.

RESULTS

Concentrations of NSE in CSF correlated with severity of HIE (P < 0.0001) and corresponded well with subsequent neurodevelopmental outcome. Concentrations of IL-6 in CSF were markedly increased in neonates with severe HIE (P < 0.0001) and those with subsequent neurological sequels, but were normal in the majority of neonates with mild and moderate HIE. Glutathione peroxidase activity in CSF was significant with the stage of HIE (P < 0.0001) and gestational age (P < 0.0001) and corresponded well with subsequent neurodevelopmental outcome. Advanced stage of HIE was associated with increased concentrations of VEGF in CSF (P < 0.0001). Neurological outcomes at 12 months of age correlated best with CSF level of NSE (P < 0.001) and IL-6 (P < 0.001).

CONCLUSION

Our results suggest that neuroinflammation plays a principal role in perinatal hypoxic-ischemic brain damage and we postulate that oxidative stress and upregulation of VEGF might be important contributing factors in the pathogenesis of hypoxic-ischemic brain injury, particularly in preterm neonates.

Opposite effect of inflammation on subventricular zone versus hippocampal precursors in brain injury

OBJECTIVE

Inflammation promotes epidermal wound healing but is considered detrimental to recovery from central nervous system injury. Sick infants have increased levels of cytokines in their cerebrospinal fluid that correlate with poor neurological outcome. In this study, we investigated the role of neuroinflammation and more specifically interleukin 6 (IL-6) in the amplification of subventricular zone (SVZ) and subgranular zone (SGZ) neural precursors after neonatal brain injury.

METHODS

Neonatal hypoxia/ischemia (H/I) was induced in P6 rat pups, and IL-6 was quantified with or without indomethacin administration. Neural precursor responses were evaluated by neurosphere assays as well as by stereological analyses. Studies were performed to determine how IL-6 and leukemia-inhibiting factor (LIF) affect SVZ cell expansion, proliferation, and self-renewal.

RESULTS

Consistent with earlier studies, medially situated SVZ cells expanded after H/I. Contrary to our expectations, indomethacin significantly decreased both the initial reactive increase in these precursors and their ability to self-renew. By contrast, indomethacin increased proliferation in the SGZ and lateral SVZ. Indomethacin diminished the accumulation of microglia/macrophages and IL-6 production after H/I. In vitro IL-6 enhanced neurosphere growth, self-renewal, and tripotentiality and was more effective than LIF in promoting self-renewal. Enhanced precursor self-renewal also was obtained using prostaglandin E2, which is downstream of cyclooxygenase 2 and a target of indomethacin.

INTERPRETATION

These data implicate neuroinflammation and in particular IL-6 as a positive effector of primitive neural precursor expansion after neonatal brain injury. These findings have important clinical implications, as indomethacin and other anti-inflammatory agents are administered to premature infants for a variety of reasons.

Regulation of toll-like receptor 1 and -2 in neonatal mice brains after hypoxia-ischemia

Background

Hypoxic-ischemic (HI) brain injury remains a major problem in newborns, resulting in increased risk of neurological disorders. Neonatal HI triggers a broad inflammatory reaction in the brain, including activation of the innate immune system. Toll-like receptors (TLRs), which are key components of the innate immune system, are believed to play a role in adult cerebral ischemic injury. The expression of TLRs in the neonatal brain and their regulation after HI is unknown.

Methods

Wild type C57BL/6, TLR 1 knockout (KO) and TLR 2 KO mice were subjected to HI at postnatal day 9 and sacrificed 30 min, 6 h, 24 h or 5 days after HI. TLR mRNA expression was determined by RT-qPCR and protein and cell type localisation by immunohistochemistry (IHC). To evaluate brain injury, infarct volume was measured in the injured hemisphere.

Results

mRNA expression was detected for all investigated TLRs (TLR1-9), both in normal and HI exposed brains. After HI, TLR-1 was down-regulated at 30 min and up-regulated at 6 h and 24 h. TLR-2 was up-regulated at 6 h and 24 h, and TLR-7 at 24 h. Both TLR-5 and TLR-8 were down-regulated at 24 h and 30 min respectively. IHC showed an increase of TLR-1 in neurons in the ipsilateral hemisphere after HI. TLR-2 was constitutively expressed in astrocytes and in a population of neurons in the paraventricular nucleus in the hypothalamus. No changes in expression were detected following HI. Following HI, TLR-2 KO mice, but not TLR-1 KO, showed a decreased infarct volume compared to wild type (p = 0.0051).

Conclusions

This study demonstrates that TLRs are regulated after HI in the neonatal brain. TLR-1 protein was up-regulated in injured areas of the brain but TLR-1 KO animals were not protected from HI. In contrast, TLR-2 was constitutively expressed in the brain and TLR-2 deficiency reduced HI injury. These data suggest that TLR-2, but not TLR-1, plays a role in neonatal HI brain injury.

The evolving landscape of neuroinflammation after neonatal hypoxia-ischemia

Hypoxic-ischemic brain injury remains a leading cause of mortality and morbidity in neonates. The inflammatory response, which is characterized in part by activation of local immune cells, has been implicated as a core component for the progression of damage to the immature brain following hypoxia-ischemia (HI). However, mounting evidence implicates circulating immune cells recruited to the site of damage as orchestrators of neuron-glial interactions and perpetuators of secondary brain injury. This suggests that re-directing our attention from the local inflammatory response toward the molecular mediators believed to link brain-immune cell interactions may be a more effective approach to mitigating the inflammatory sequelae of perinatal HI. In this review, we focus our attention on cyclooxygenase-2, a mediator by which peripheral immune cells may modulate signaling pathways in the brain that lead to a worsened outcome. Additionally, we present an overview of emerging therapeutic modalities that target mechanisms of neuroinflammation in the hypoxic-ischemic neonate.

High cerebrospinal fluid antioxidants and interleukin 8 are protective of hypoxic brain damage in newborns

The objective was to explain the discrepancy in the development of hypoxic ischemic brain injury (HIE) in some asphyxiated newborns rather than others. Forty newborns were classified according to their cerebrospinal neuron-specific-enolase (CSF-NSE) levels on their 5th-day of life; group 1 with low-NSE (n = 25). The remaining 15 newborns had high-NSE and were further divided into a group with no HIE (n = 10, group 2) and another with HIE (n = 5, group 3). CSF-NSE, total-hydroperoxide (TH), biological-antioxidant-potentials (BAPs), 12 cytokines and erythropoietin (EPO) were measured. The TH/BAP gave the oxidative-stress-index (OSI). The BAPs of serial dilutions of three types of EPO were tested. CSF-NSE and TH and mean OSIs were higher in group 3. IL-8 and mean BAPs were higher in group 2 than in group 1. EPO was less detected in group 3. Serial EPO dilutions correlated with their BAPs. Compensatory antioxidants and IL-8 elevation could be protective of perinatal asphyxic brain injury. Antioxidative effect of EPO could be neuroprotective.

Increased umbilical cord plasma interleukin-1 beta levels was correlated with adverse outcomes of neonatal hypoxic-ischemic encephalopathy

To explore whether or not the umbilical blood levels of cytokines can be used to indicate the adverse outcomes of hypoxic-ischemic encephalopathy (HIE) patients. Umbilical artery blood and peripheral venous blood samples were collected on the 1st, 3rd and 7th days after birth to detect the levels of IL-1 beta, IL-8 and TNF-alpha. Neurological examination and Denver developmental screening test (DDST-II) were performed at the 6 and 12 months evaluations to detect any neurodevelopmental abnormalities. The results showed: (i) the serum concentrations of IL-1 beta, IL-8 and TNF-alpha in umbilical and peripheral blood were significantly higher in HIE patients than control groups; (ii) the umbilical blood concentrations of IL-1 beta exhibited the best positive correlation with HIE grades, when compared with IL-8 and TNF-alpha; and (iii) abnormal neurological outcomes at 6 and 12 months of age were best predicted by umbilical levels of IL-1 beta. Thus, umbilical concentrations of IL-1 beta were associated with the grades and adverse outcomes of HIE.

Hypoxic-ischemic encephalopathy in the term infant

Hypoxia-ischemia in the perinatal period is an important cause of cerebral palsy and associated disabilities in children. There has been significant research progress in hypoxic-ischemic encephalopathy over the last 2 decades, and many new molecular mechanisms have been identified. Despite all these advances, therapeutic interventions are still limited. In this article the authors discuss several molecular pathways involved in hypoxia-ischemia, and potential therapeutic targets.

Diffusion MRI brain findings in neonates exposed to chorioamnionitis: a case series

OBJECTIVE

The primary objective of this study was to determine the feasibility of using diffusion-weighted magnetic resonance imaging (DWMRI) to assess white matter changes in high-risk neonates. Secondary objectives were to determine if exposure to chorioamnionitis (clinical or histopathologic) is associated with DWMRI findings in the neonatal brain, and to calculate the sample size required for a more definitive prospective cohort study.

METHODS

Seventeen women with PPROM (preterm premature rupture of the membranes) who delivered 18 infants not requiring ventilatory support were recruited to participate in this case series. When stable, infants underwent DWMRI scanning. All placentas were examined for evidence of histopathologic chorioamnionitis (HCA).

RESULTS

There was histopathologic evidence of chorioamnionitis in seven of the 18 placentas examined; three of these patients had clinical chorioamnionitis. Diffusion MRI revealed changes in both the diffusion-weighted imaging and the apparent diffusion coefficient in three of the seven infants confirmed to have HCA (43%), while only one of the 11 infants with normal placentas (9%) showed similar findings. Routine head ultrasound examination demonstrated abnormal cortical findings that would normally prompt further investigation in only one of these infants.

CONCLUSION

Exposure to HCA may be associated with abnormal DWMRI findings on imaging of the neonatal brain within 96 hours of delivery. Further study is required to delineate the association of chorioamnionitis and white matter changes with long-term neurodevelopmental sequelae.

Inflammatory response and neurodevelopmental outcome after open-heart surgery in children

Long-term neurodevelopmental sequelae are commonly detectable in children after open-heart surgery with cardiopulmonary bypass (CPB). The objective of the study was to determine the neurodevelopmental outcome in these children in relation to postoperative inflammatory reaction. This is a prospective, observational study on children with congenital heart defects (n = 32) undergoing elective open-heart surgery in a tertiary pediatric cardiac center. Neurodevelopmental outcome was assessed in the median 6 months after CPB. Neurological examination was done in all children before the operation and, additionally, complete neurodevelopmental status was assessed preoperatively in 14 children. Three hours after the end of CPB, plasma concentrations of interleukin (IL)-6 and IL-8 were strongly elevated (p < 0.001). Moreover, there was a rise of neutrophils and C-reactive protein at 24 h postoperatively (p < 0.001). Intellectual performance after surgery was correlated with preoperative performance, r ( S ) = 0.83, p < 0.001 (mean IQ scores after CPB = 90.4 +/- 18.4 and before CPB = 87.5 +/- 14.5, p = 0.20). Multiple regression analysis demonstrated that preoperative IQ scores accounted for 83.8% of the variance of postoperative IQ scores (p < 0.0001). Inflammatory variables were not significant predictors of postoperative IQ scores. The frequency of neuromotor abnormalities at 6 months after CPB was influenced by the presence of a cyanotic heart defect, duration of CPB and aortic clamp time, and plasma levels of IL-6 shortly after CPB (R (2) = 67.8%, p = 0.002). In conclusion, in the examined population, preexisting neurodevelopmental impairment is frequent and predicts postoperative outcome. The high frequency of postoperative neuromotor disabilities seems to be associated with the type of congenital heart defect but also with the procedure and possible complications of CPB.

Systematic review of biomarkers of brain injury in term neonatal encephalopathy

Although neonatal hypoxic-ischemic encephalopathy is a common cause of childhood developmental disability, its timing, duration, and outcomes are poorly defined. Biomarkers serve as surrogates for disease injury, evolution, and outcome, but no tissue biomarker in routine clinical use can help predict outcomes in term newborn encephalopathy. We reviewed biomarkers in human term neonatal encephalopathy, to determine if current biomarkers are strong enough for clinical use as predictors of outcomes. A comprehensive search of databases identified 110 publications that met our inclusion criteria, i.e., (1) newborns at >36 weeks; (2) neonatal encephalopathy as defined by the American College of Obstetrics and Gynecology; (3) the use of a serum, urine, or cerebrospinal fluid biomarker; and (4) reported outcomes beyond age 12 months. Of those 110 publications, 22 reported outcomes beyond age 12 months. In single reports, urine lactate (P < 0.001), first urine S100 (P < 0.0001), cord-blood interleukin-6 (P = 0.02), serum nonprotein-bound iron (P < 0.001), serum CD14 cell NFkappaB activation (P = 0.014), serum interleukin-8 (P = 0.03), and serum ionized calcium (P = 0.001) were potential predictors of death or abnormal outcomes. A meta-analysis identified serum interleukin-1b (P = 0.04, n = 3), serum interleukin-6 (P = 0.04, n = 2), cerebrospinal fluid neuron-specific enolase (P = 0.03, n = 3), and cerebrospinal fluid interleukin-1b (P = 0.003, n = 2) as putative predictors of abnormal outcomes in survivors, when measured before age 96 hours. Several serum, urine, and cerebrospinal fluid biomarkers of term neonatal encephalopathy may provide important information regarding long-term outcomes. None, however, were studied extensively enough to warrant routine clinical use. Validation of these markers, either alone or in combination, is required in the development of viable therapeutic interventions.

The sex differences of cerebrospinal fluid levels of interleukin 8 and antioxidants in asphyxiated newborns

Newborn males are more sensitive to brain injury than newborn females are. The aim of the present study was to find an explanation for this. We used the neuron-specific enolase (NSE) levels in the cerebrospinal fluid (CSF) for the classification of 32 newborns (19 males and 13 females) on their fifth postnatal day. The NSE levels were higher than normal (8.4 +/- 1.6 ng/mL) in 10 newborn males and 6 females and were, respectively, considered asphyxiated male and female groups. The remaining newborns, 9 males and 7 females, had normal CSF levels of NSE and were considered normal newborn male and female groups. The CSF samples were measured for 12 cytokines, using a cytokine array kit, and for total hydroperoxide and biological antioxidant potentials (BAPs), using the free radical analytic system. Among the 12 cytokines measured, only interleukin 8 (IL-8) was properly detected. The CSF levels of IL-8 were higher in the asphyxiated newborn females than in the other three groups. The mean CSF levels of BAPs in the asphyxiated newborn females were higher compared with the other three groups, but significance was detected only in comparison with the BAP levels in the CSF samples of the normal newborn males. There were no differences in total hydroperoxide levels among the groups. There are sex-related differences in the CSF levels of IL-8 and antioxidants in asphyxiated newborns, with higher levels in newborn females; this might contribute in the sexual dimorphism regarding the fact that females have better protection from brain injury than the males.

Chronic interleukin-6 alters the level of synaptic proteins in hippocampus in culture and in vivo

There is now considerable evidence that the level of expression of the proinflammatory cytokine, interleukin-6 (IL-6), is increased in the central nervous system (CNS) during neuroinflammatory conditions such as occurs in neurological disorders and in disease and injury. However, our understanding of the consequences of increased expression of IL-6 on the CNS is still limited, especially with respect to the developing nervous system, which is known to be particularly vulnerable to environmental factors. To address this issue, we investigated the properties of cultured hippocampal neurons exposed chronically to IL-6 during the main period of morphological and physiological development, which occurs during the first 2 weeks of culture. IL-6 was tested at 500 U/mL, considered to reflect a pathophysiologic concentration. The morphological features of neuronal development in the control and IL-6-treated cultures appeared similar. However, Western blot analysis showed a significant reduction in the level of Group-II metabotropic receptors (mGluR2/3) and L-type Ca(2+) channels in the IL-6-treated cultures. A similar reduction in mGluR2/3 and L-type Ca(2+) channel protein was observed in transgenic mice that over-express IL-6 in the CNS through astrocyte production starting early in development. Analysis of Ca(2+) signals produced by spontaneous synaptic network activity in the hippocampal cultures and effects of a mGluR2/3 agonist and antagonist showed that the reduced levels of mGluR2/3 impact on the functional properties of hippocampal synaptic network activity. These results have important implications relative to the mechanisms responsible for altered CNS function during conditions associated with increased levels of IL-6 in the CNS.

Interleukin-8 and monocyte chemotactic protein-1 mRNA expression in perinatally infected and asphyxiated preterm neonates

BACKGROUND

Inflammation due to perinatal infection (PI) and perinatal asphyxia (PA) may cause damage to various tissues and very often to the immature brain of the fetus and the newborn. Previously, we have shown that the neonatal immune system has the ability to produce increased chemokine protein levels in the serum during the inflammatory response caused by PI and PA.

AIM

The aim of our present study was to investigate mRNA levels of the proinflammatory chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) in peripheral blood leukocytes from infected and asphyxiated neonates.

METHODS

Forty-two premature neonates were studied; 11 with PI, 16 with PA and 15 without PA and PI, were used as controls. IL-8 and MCP-1 mRNA levels were investigated in whole blood and in phytohemagglutinin-activated lymphocytes using semi-quantitative polymerase chain reaction and real-time polymerase chain reaction, respectively.

RESULTS

IL-8 mRNA levels were significantly increased in whole blood both during PA and PI, while MCP-1 mRNA levels were not. In vitro activated lymphocytes expressed significantly increased IL-8 mRNA levels during PI, whereas no increase was observed during PA. MCP-1 mRNA levels were significantly increased in activated lymphocytes during PA, while no increase was observed during PI.

CONCLUSIONS

Our data show that chemokine mRNA levels expressed by activated lymphocytes during inflammation caused by PIs are different to those expressed during PAs. These findings might have important implications during the administration of specific chemokine antagonists in order to prevent or reduce tissue damage caused by inflammation.

Effect of acidosis on IL-8 and MCP-1 during hypoxia and reoxygenation in human NT2-N neurons

Inflammation probably plays a significant role in perinatal brain injury. To study the contribution of locally produced cytokines, the effect on cell death of addition of IL-8 and MCP-1 or antibodies to these, and the impact of acidosis, human postmitotic NT2-N neurons were exposed to 3 h of hypoxia and glucose deprivation and reoxygenated for 21 h. After 3 h of hypoxia with neutral medium, IL-8 was significantly increased compared to controls (150 (100-250)% vs. 100 (85-115)%, p=0.023). After 21 h of neutral reoxygenation, both IL-8 (380 (110-710)% vs. 150 (85-260)%, p=0.041) and monocyte chemoattractant protein-1 (MCP-1) (650 (440-2000)% vs. 310 (230-340)%, p=0.007) were significantly increased compared to controls. After 3 h of hypoxia, both IL-8 (p=0.002) and MCP-1 (p=0.008) were significantly lower in cells with acidotic compared with cells with neutral medium. Acidosis during reoxygenation, however, significantly increased IL-8 release, whereas MCP-1 release was diminished. Similar effects of acidosis were seen in normoxic controls. The cells also secreted RANTES and IP-10, but not 8 other cytokines tested. We found no effect on cell death, measured by MTT assay, of addition of IL-8, MCP-1 or antibodies to these. We conclude that human NT2-N neurons release IL-8 and MCP-1 during 21 h of reoxygenation after 3 h of hypoxia. Acidosis led to a differential effect on IL-8 and MCP-1, with increased IL-8 and decreased MCP-1, both during reoxygenation and in normoxic controls. IL-8 and MCP-1 had no effect on cell death.

Altered expression of pro-inflammatory and developmental genes in the fetal brain in a mouse model of maternal infection

Human studies of unexplained cerebral palsy (CP) suggest an association with maternal infection. We used an established model of maternal infection, lipopolysaccharide (LPS) administration, to investigate the molecular changes in the fetal brain that may link maternal infection and CP. We compared gene expression in brains from mouse pups exposed to LPS in utero to those from saline-treated controls. Dams were injected with 50 microg LPS or saline on E18 with surgical delivery from 0.5 to 6h later. Differential gene expression was analyzed in the whole mouse brain using RT-PCR. When compared to control mice, pups exposed to LPS showed increased expression of pro-inflammatory genes monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta), as well as VEGF, a regulator of vascular development and permeability, the anti-apoptotic protein Y-box-binding protein-1 (YB-1), and the neuronal differentiation factor necdin. LPS-exposed mice also showed downregulation of semaphorin 5b and groucho, involved in axon guidance and neurogenesis, respectively, providing evidence that LPS may disrupt normal developmental pathways. These data suggest possible mechanisms for adverse neurological outcomes following maternal infection involving elevated cytokine levels and altered expression of developmental genes in the fetal brain.

Elevation of Cytokine Concentrations in Asphyxiated Neonates

BACKGROUND

Various cytokines are reportedly associated with many neonatal diseases. Asphyxia is considered to result in ischemia-reperfusion injuries and induces abnormal inflammatory responses involving excessive cytokine production.

OBJECTIVES

To evaluate alteration in sera levels of various cytokines/chemokines in case of perinatal asphyxia at birth.

METHODS

In order to determine the concentrations of various cytokines/chemokines in sera, we used a highly sensitive fluorescence microsphere method. We measured the concentration of 8 types of cytokines/chemokines in sera obtained from 17 cases of asphyxia, 10 normal neonates, and 6 healthy adults.

RESULTS

The concentrations of IL-6, IL-8, and IL-10 in the sera of asphyxiated neonates were higher than those in the normal neonates. Irrespective of the presence or absence of asphyxia, sera concentrations of IL-2, IL-4, IFN-gamma, and TNF-alpha were higher in the neonates than those in the adults. The concentration of IFN-gamma in the asphyxiated neonates was lower than that in the normal neonates. Sera levels of IL-10 were higher in the asphyxiated cases than those in the normal neonates. The sera levels of IL-6, IL-8, and IL-10 in asphyxiated neonates with either a poor outcome or death were higher than those without poor outcomes.

CONCLUSIONS

The concentrations of various types of cytokines/chemokines were different in neonatal sera and some of them increased drastically during asphyxia. The concentration of an anti-inflammatory cytokine IL-10 was elevated in asphyxiated neonates immediately after birth, thereby suggesting that IL-10 might be associated with neuroprotective functions.

IL-1beta, IL-6 and TNF-alpha and outcomes of neonatal hypoxic ischemic encephalopathy

The role of cytokines in the pathogenesis of brain injury and their relation to neurological outcomes of asphyxiated neonates is not fully defined. We hypothesize that interleukin-1 beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in cerebrospinal fluid (CSF) correlate with the severity of brain injury and can predict neurological deficits in infants who suffered from hypoxic ischemic encephalopathy (HIE). A prospective study was conducted on 24 term infants diagnosed with HIE and 13 controls. HIE was clinically classified into mild, moderate and severe according to Sarnat and Sarnat grading. Blood and CSF samples were obtained from all infants in the first 24h of life as part of routine investigations for suspected meningitis and/or sepsis. Neurological examination and Denver Developmental Screening Test II (DDST II) were performed at 6 and 12 months of life. IL-1beta, IL-6 and TNF-alpha were all significantly increased in HIE infants when compared to control. IL-1beta in the CSF correlated with the severity of HIE (r=0.61, P=0.001) more than IL-6 (r=0.45, P=0.004) or TNF-alpha (r=0.47, P=0.003). IL-1beta exhibited the highest CSF/serum ratio among the three studied cytokines suggesting its local release in the brain after the initial hypoxic injury. Abnormal neurological findings and/or abnormal DDST II at 6 and 12 months were best predicted by IL-1beta in the CSF (sensitivity=88% and specificity=80%). This study confirms the role of IL-1beta in the ongoing neuronal injury that occurs in the latent phase following the original HIE insult.

Perinatal infections, prematurity and brain injury

PURPOSE OF REVIEW

The association between perinatal infection and brain injury is widely accepted but a cause-and-effect relationship has not yet been proven. This article summarizes available evidence and current primary publications for debate.

RECENT FINDINGS

Work completed during the review period has reinforced current understanding of perinatal infection, prematurity and brain injury. In animal experiments: lipopolysaccharides have been further implicated in brain injury, not only as a cause of brain injury but also as mediators of preconditioning and protection. Recent studies suggest that cerebral injury following low-dose lipopolysaccharide administration may become compensated in adulthood. Other studies have emphasized the complexity of the response by showing that plasma cytokine levels may not reflect those in the central nervous system or inflammatory events in the brain.

SUMMARY

Perinatal infection and maternofetal inflammation is strongly associated with preterm birth. Inflammation probably represents an important mechanism for cerebral damage, and both overt lesions and maldevelopment can result. Epidemiological data and multiple animal models to link infection, inflammation and brain damage exist, but proof of causation is elusive.

Inflammatory chemokine expression in the peripheral blood of neonates with perinatal asphyxia and perinatal or nosocomial infections

AIM

The inflammatory response induced by perinatal infections and asphyxia is considered to participate in neonatal brain damage. Inflammatory responses are characterized by the expression of chemokines. Although chemokine levels have been investigated in healthy newborns, their role during neonatal pathological conditions has not been studied. The aim of our study was to examine chemokine serum levels in asphyxiated and infected neonates.

METHODS

Peripheral blood samples were obtained from perinatally asphyxiated and infected neonates during the first days of life and from neonates who developed nosocomial infections. Serum levels of interleukin-8 (IL-8), interferon-gamma-inducible protein-10 (IP-10), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha), and regulated upon activation, normal T cells expressed and secreted (RANTES) were determined.

RESULTS

In perinatally asphyxiated neonates, IL-8 levels were significantly elevated on the 1st day of life. In perinatally infected neonates, IL-8 and IP-10 levels were significantly increased on the 1st day of life, while RANTES levels were significantly lower and remained so until the 4th day. In nosocomially infected neonates, IL-8, IP-10 and MIP-1alpha levels were significantly increased on diagnosis of infection.

CONCLUSION

The neonatal immune system is able to produce chemokines for the induction of an inflammatory response during perinatal asphyxia and perinatal or nosocomial infections. Blockade of inflammatory chemokines could possibly contribute to the prevention of brain damage.

Fetal and maternal Doppler velocimetry and cytokines in high-risk pregnancy

OBJECTIVE

Fetal hypoxia and preterm delivery are reported to be strongly associated with brain damage and neurodevelopmental delay. Doppler signs of fetal brain sparing have been described during chronic hypoxia, but whether they are related to brain damage is unknown. The aim of this study was to evaluate if markers of tissue injury, i.e., tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) are related to signs of increased perinatal vascular impedance and/or fetal brain sparing in high-risk pregnancies.

STUDY DESIGN

TNF-alpha and IL-6 levels were evaluated in maternal blood serum of 67 high-risk pregnancies. Serum samples were taken at the time of umbilical, middle cerebral artery and uterine artery Doppler velocimetry examination. The values for TNF-a and IL-6 were correlated with reference median values obtained with gestational age in the form of a Z-score.

RESULTS

TNF-alpha levels showed values within the normal range in only four cases. IL-6 values were found normal in 14 cases. The Z-score for mean middle cerebral artery pulsatility index (PI) showed a significant correlation to TNF-alpha and IL-6 levels, P < 0.0001 and P < 0.003, respectively. This might suggest a strong correlation between signs of fetal brain sparing and increased maternal serum TNF-alpha and IL-6 levels. Abnormal uterine artery PI and the presence of a "notch" were also highly significantly related to TNF-alpha and IL-6 levels, which were nearly two-fold higher compared to normal uterine artery blood flow and the absence of a "notch". Abnormal cerebro/placental ratios showed significant correlations to TNF-alpha and IL-6 levels.

CONCLUSION

The present results suggest a strong correlation between levels of TNF-alpha and IL-6 not only for signs of fetal brain sparing, but also for uteroplacental blood flow. This finding supports the role of tissue injury in cases of fetal brain sparing, but whether this is a reflection of brain damage or secondary to placental pathology needs further evaluation.

Interleukin 1beta and interleukin 6 relationship with paediatric head trauma severity and outcome

BACKGROUND

Based on the known inflammatory role of interleukins (IL), we evaluated IL-1beta and IL-6 expressions and their association with the severity of traumatic brain injury (TBI; Glasgow Coma Scale [GCS]) and the outcome (Glasgow Outcome Score [GOS]) recorded in a paediatric population.

DESIGN

The design was a perspective observational clinical study carried out in the paediatric intensive care unit of the University Hospital.

METHODS

We measured the IL-1beta and IL-6 levels in 14 children with severe TBI (patients) and in 12 children with obstructive hydrocephalus (control group). Cerebrospinal fluid (CSF) and plasma samples were collected 2 h (T1) and 24 h (T2) after TBI. Interleukins were assayed using the immunoenzymatic method.

RESULTS

The IL-1beta mean level was significantly lower than the IL-6 mean level both in the CSF and plasma of TBI children. In the CSF, the IL-1beta level increased from 55.71+/-72.79 pg/ml at T1 to 106.10+/-142.12 pg/ml at T2 and the IL-6 level increased from 405.43+/-280.28 pg/ml at T1 to 631.57+/-385.35 pg/ml at T2; a similar trend was observed in plasma. We found a statistically significant correlation between the increase in CSF and plasma interleukin levels between T1 and T2 and head injury severity (GCS<or=5) as well as poor outcome (GOS<or=3).

CONCLUSIONS

The increases in IL-1beta and IL-6 expression were correlated with head injury severity and were indicative of poor clinical outcome, reflecting an endogenous neuroinflammatory response after TBI.