The relationship of CSF and plasma cytokine levels to cerebral white matter injury in the premature newborn

Anti-IL-6 neutralizing antibody modulates blood-brain barrier function in the ovine fetus

Impaired blood-brain barrier function represents an important component of hypoxic-ischemic brain injury in the perinatal period. Proinflammatory cytokines could contribute to ischemia-related blood-brain barrier dysfunction. IL-6 increases vascular endothelial cell monolayer permeability in vitro. However, contributions of IL-6 to blood-brain barrier abnormalities have not been examined in the immature brain in vivo. We generated pharmacologic quantities of ovine-specific neutralizing anti-IL-6 mAbs and systemically infused mAbs into fetal sheep at 126 days of gestation after exposure to brain ischemia. Anti-IL-6 mAbs were measured by ELISA in fetal plasma, cerebral cortex, and cerebrospinal fluid, blood-brain barrier permeability was quantified using the blood-to-brain transfer constant in brain regions, and IL-6, tight junction proteins, and plasmalemma vesicle protein (PLVAP) were detected by Western immunoblot. Anti-IL-6 mAb infusions resulted in increases in mAb (P < 0.05) in plasma, brain parenchyma, and cerebrospinal fluid and decreases in brain IL-6 protein. Twenty-four hours after ischemia, anti-IL-6 mAb infusions attenuated ischemia-related increases in blood-brain barrier permeability and modulated tight junction and PLVAP protein expression in fetal brain. We conclude that inhibiting the effects of IL-6 protein with systemic infusions of neutralizing antibodies attenuates ischemia-related increases in blood-brain barrier permeability by inhibiting IL-6 and modulates tight junction proteins after ischemia.

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.

The immune response after hypoxia-ischemia in a mouse model of preterm brain injury

Background

Preterm brain injury consists primarily of periventricular leukomalacia accompanied by elements of gray-matter injury, and these injuries are associated with cerebral palsy and cognitive impairments. Inflammation is believed to be an important contributing factor to these injuries. The aim of this study was to examine the immune response in a postnatal day (PND) 5 mouse model of preterm brain injury induced by hypoxia-ischemia (HI) that is characterized by focal white and gray-matter injury.

Methods

C57Bl/6 mice at PND 5 were subjected to unilateral HI induced by left carotid artery ligation and subsequent exposure to 10% O₂ for 50 minutes, 70 minutes, or 80 minutes. At seven days post-HI, the white/gray-matter injury was examined. The immune responses in the brain after HI were examined at different time points after HI using RT-PCR and immunohistochemical staining.

Results

HI for 70 minutes in PND 5 mice induced local white-matter injury with focal cortical injury and hippocampal atrophy, features that are similar to those seen in preterm brain injury in human infants. HI for 50 minutes resulted in a small percentage of animals being injured, and HI for 80 minutes produced extensive infarction in multiple brain areas. Various immune responses, including changes in transcription factors and cytokines that are associated with a T-helper (Th)1/Th17-type response, an increased number of CD4+ T-cells, and elevated levels of triggering receptor expressed on myeloid cells 2 (TREM-2) and its adaptor protein DNAX activation protein of 12 kDa (DAP12) were observed using the HI 70 minute preterm brain injury model.

Conclusions

We have established a reproducible model of HI in PND 5 mice that produces consistent local white/gray-matter brain damage that is relevant to preterm brain injury in human infants. This model provides a useful tool for studying preterm brain injury. Both innate and adaptive immune responses are observed after HI, and these show a strong pro-inflammatory Th1/Th17-type bias. Such findings provide a critical foundation for future studies on the mechanism of preterm brain injury and suggest that blocking the Th1/Th17-type immune response might provide neuroprotection after preterm brain injury.

Neurodevelopmental impairment in preterm infants with late-onset infection: not only in extremely preterm infants

Late-onset infection is known to increase the risk of neurodevelopmental impairment in infants born extremely preterm. However, little data is available regarding infants born moderately preterm. The aim of this study was to determine whether late-onset infection in moderately preterm infants (<35 weeks of gestation) was associated with a non-optimal neurodevelopmental outcome at 2 years of age. We analyzed a regional, population-based cohort of infants (LIFT cohort) between January 2003 and December 2009, and we used a propensity score method to reduce bias. Among the 4,618 preterm infants assessed at 2 years, 618 had acquired late-onset infection (13.4 %), and 764 had a non-optimal outcome (16.5 %). The rate of non-optimal outcomes was significantly higher in preterm infants with late-onset infection, irrespective of subgroups of gestational age and birth weight Z-score. After adjusting for the propensity score, the relationship between late-onset infection and non-optimal neurodevelopmental outcome at 2 years among infants born before 35 weeks of gestation remained significant (aOR = 1.3; 95 % CI 1.01-1.7; p = .04).

CONCLUSION

Late-onset infection is associated with poor neurological outcome at 2 years of age among infants born moderately preterm before and after adjustment for the propensity score.

Infection-induced inflammation and cerebral injury in preterm infants

Preterm birth and infectious diseases are the most common causes of neonatal and early childhood deaths worldwide. The rates of preterm birth have increased over recent decades and account for 11% of all births worldwide. Preterm infants are at significant risk of severe infection in early life and throughout childhood. Bacteraemia, inflammation, or both during the neonatal period in preterm infants is associated with adverse outcomes, including death, chronic lung disease, and neurodevelopmental impairment. Recent studies suggest that bacteraemia could trigger cerebral injury even without penetration of viable bacteria into the CNS. Here we review available evidence that supports the concept of a strong association between bacteraemia, inflammation, and cerebral injury in preterm infants, with an emphasis on the underlying biological mechanisms, clinical correlates, and translational opportunities.

Perinatal biomarkers in prematurity: early identification of neurologic injury

Over the past few decades, biomarkers have become increasingly utilized as non-invasive tools in the early diagnosis and management of various clinical conditions. In perinatal medicine, the improved survival of extremely premature infants who are at high risk for adverse neurologic outcomes has increased the demand for the discovery of biomarkers in detecting and predicting the prognosis of infants with neonatal brain injury. By enabling the clinician to recognize potential brain damage early, biomarkers could allow clinicians to intervene at the early stages of disease, and to monitor the efficacy of those interventions. This review will first examine the potential perinatal biomarkers for neurologic complications of prematurity, specifically, intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL) and posthemorrhagic hydrocephalus (PHH). It will also evaluate knowledge gained from animal models regarding the pathogenesis of perinatal brain injury in prematurity.

Pathophysiology of glia in perinatal white matter injury

Injury to the preterm brain has a particular predilection for cerebral white matter. White matter injury (WMI) is the most common cause of brain injury in preterm infants and a major cause of chronic neurological morbidity including cerebral palsy. Factors that predispose to WMI include cerebral oxygenation disturbances and maternal-fetal infection. During the acute phase of WMI, pronounced oxidative damage occurs that targets late oligodendrocyte progenitors (pre-OLs). The developmental predilection for WMI to occur during prematurity appears to be related to both the timing of appearance and regional distribution of susceptible pre-OLs that are vulnerable to a variety of chemical mediators including reactive oxygen species, glutamate, cytokines, and adenosine. During the chronic phase of WMI, the white matter displays abberant regeneration and repair responses. Early OL progenitors respond to WMI with a rapid robust proliferative response that results in a several fold regeneration of pre-OLs that fail to terminally differentiate along their normal developmental time course. Pre-OL maturation arrest appears to be related in part to inhibitory factors that derive from reactive astrocytes in chronic lesions. Recent high field magnetic resonance imaging (MRI) data support that three distinct forms of chronic WMI exist, each of which displays unique MRI and histopathological features. These findings suggest the possibility that therapies directed at myelin regeneration and repair could be initiated early after WMI and monitored over time. These new mechanisms of acute and chronic WMI provide access to a variety of new strategies to prevent or promote repair of WMI in premature infants.

Cerebral vascular regulation and brain injury in preterm infants

Cerebrovascular lesions, mainly germinal matrix hemorrhage and ischemic injury to the periventricular white matter, are major causes of adverse neurodevelopmental outcome in preterm infants. Cerebrovascular lesions and neuromorbidity increase with decreasing gestational age, with the white matter predominantly affected. Developmental immaturity in the cerebral circulation, including ongoing angiogenesis and vasoregulatory immaturity, plays a major role in the severity and pattern of preterm brain injury. Prevention of this injury requires insight into pathogenesis. Cerebral blood flow (CBF) is low in the preterm white matter, which also has blunted vasoreactivity compared with other brain regions. Vasoreactivity in the preterm brain to cerebral perfusion pressure, oxygen, carbon dioxide, and neuronal metabolism is also immature. This could be related to immaturity of both the vasculature and vasoactive signaling. Other pathologies arising from preterm birth and the neonatal intensive care environment itself may contribute to impaired vasoreactivity and ineffective CBF regulation, resulting in the marked variations in cerebral hemodynamics reported both within and between infants depending on their clinical condition. Many gaps exist in our understanding of how neonatal treatment procedures and medications have an impact on cerebral hemodynamics and preterm brain injury. Future research directions for neuroprotective strategies include establishing cotside, real-time clinical reference values for cerebral hemodynamics and vasoregulatory capacity and to demonstrate that these thresholds improve long-term outcomes for the preterm infant. In addition, stimulation of vascular development and repair with growth factor and cell-based therapies also hold promise.

Strategies for repair of white matter: influence of osmolarity and microglia on proliferation and apoptosis of oligodendrocyte precursor cells in different basal culture media

The aim of the present study has been to obtain high yields of oligodendrocyte precursor cells (OPCs) in culture. This is a first step in facilitation of myelin repair. We show that, in addition to factors, known to promote proliferation, such as basic fibroblast growth factor (FGF-2) and platelet derived growth factor (PDGF) the choice of the basal medium exerts a significant influence on the yield of OPCs in cultures from newborn rats. During a culture period of up to 9 days we observed larger numbers of surviving cells in Dulbecco's Modified Eagle Medium (DMEM), and Roswell Park Memorial Institute Medium (RPMI) compared with Neurobasal Medium (NB). A larger number of A2B5-positive OPCs was found after 6 days in RPMI based media compared with NB. The percentage of bromodeoxyuridine (BrdU)-positive cells was largest in cultures maintained in DMEM and RPMI. The percentage of caspase-3 positive cells was largest in NB, suggesting that this medium inhibits OPC proliferation and favors apoptosis. A difference between NB and DMEM as well as RPMI is the reduced Na⁺-content. The addition of equiosmolar supplements of mannitol or NaCl to NB medium rescued the BrdU-incorporation rate. This suggested that the osmolarity influences the proliferation of OPCs. Plating density as well as residual microglia influence OPC survival, BrdU incorporation, and caspase-3 expression. We found, that high density cultures secrete factors that inhibit BrdU incorporation whereas the presence of additional microglia induces an increase in caspase-3 positive cells, indicative of enhanced apoptosis. An enhanced number of microglia could thus also explain the stronger inhibition of OPC differentiation observed in high density cultures in response to treatment with the cytokines TNF-α and IFN-γ. We conclude that a maximal yield of OPCs is obtained in a medium of an osmolarity higher than 280 mOsm plated at a relatively low density in the presence of as little microglia as technically achievable.

Neonatal infection and 5-year neurodevelopmental outcome of very preterm infants

OBJECTIVE

To determine whether neonatal infections are associated with a higher risk of adverse neurodevelopment at 5 years of age in a population-based cohort of very preterm children.

METHODS

We included all live births between 22 and 32 weeks of gestation, from 9 regions in France, in 1997 (EPIPAGE study). Of the 2665 live births, 2277 were eligible for a follow-up evaluation at 5 years of age: 1769 had a medical examination and 1495 underwent cognitive assessment. Cerebral palsy and cognitive impairment were studied as a function of early-onset sepsis (EOS) and late-onset sepsis (LOS), after adjustment for potential confounding factors, in multivariate logistic regression models.

RESULTS

A total of 139 (5%) of the 2665 live births included in the study presented with EOS alone (without associated LOS), 752 (28%) had LOS alone (without associated EOS), and 64 (2%) displayed both EOS and LOS. At 5 years of age, the frequency of cerebral palsy was 9% (157 of 1769) and that of cognitive impairment was 12% (177 of 1495). The frequency of cerebral palsy was higher in infants with isolated EOS (odds ratio [OR]: 1.70 [95% confidence interval (CI): 0.84-3.45]) or isolated LOS (OR: 1.71 [95% CI: 1.14-2.56]) than in uninfected infants, and this risk was even higher in cases of combined EOS and LOS (OR: 2.33 [95% CI: 1.02-5.33]). There was no association between neonatal infection and cognitive impairment.

CONCLUSIONS

Neonatal infections in these very preterm infants were associated with a higher risk of cerebral palsy at the age of 5 years, particularly in infants presenting with both EOS and LOS.

Intrauterine inflammation alters fetal cardiopulmonary and cerebral haemodynamics in sheep

Intrauterine inflammation impairs fetal pulmonary vascular development and increases cerebral metabolic rate in fetal sheep. We hypothesized that these structural and metabolic effects of intrauterine inflammation would be accompanied by reduced fetal pulmonary blood flow and increased cerebral perfusion. Fetal sheep were instrumented at 112 days of gestation (term is 147 days) for measurement of cardiopulmonary and cerebral haemodynamics. At 118 days ewes were randomly assigned to receive intra-amniotic lipopolysaccharide (LPS, 20 mg from Escherichia coli; n = 7) or saline (control, 4 ml; n = 6). Fetal haemodynamic data were recorded continually from 1 h before intra-amniotic LPS or saline, until 144 h after. Fetal arterial blood was sampled before, and periodically after, intra-amniotic LPS or saline. End-diastolic and mean pulmonary blood flows were significantly lower than control from 48 and 96 h after LPS exposure, respectively, until the end of the experiment. Carotid blood flow was transiently increased at 96 and 120 h after LPS exposure. Carotid arterial oxygen content was lower than control from 48 h after intra-amniotic LPS. Fetal arterial lactate concentration was higher than control between 4 and 12 h after intra-amniotic LPS. Experimental intrauterine inflammation reduces pulmonary blood flow in fetal sheep, over a time course consistent with impaired pulmonary vascular development. Increased carotid blood flow after LPS administration may reflect an inflammation-induced increase in cerebral metabolic demand.

Detection of cerebral spinal fluid-associated chemokines in birth traumatized premature babies by chip-based immunoaffinity CE

A major concern in treating premature infants with birth-associated head trauma is the rapid determination of reliable biomarkers of neuroinflammation. To this end a chip-based immunoaffinity CE device has been applied to determine the concentrations of inflammation-associated chemokines in samples of cerebral spinal fluid collected from such subjects. The chip utilizes replaceable immunoaffinity disks, to which reactive antibody fragments (FAb) of six antichemokine-specific antibodies were immobilized. Following injection of a sample into the device, the analytes were captured by the immobilized FAbs, labeled in situ with a red laser dye, chemically released and separated by CE. Each resolved peak was measured on-line by LIF detection and the results compared to standard curves produced by running known chemokine standards through the immunoaffinity system. The complete processing of a sample took 10 min with separation of all six analytes being achieved in less than 2 min. The system compared well to commercial ELISA, analysis of the results by linear regression demonstrating r(2) values in the range of 0.903-0.978, and intra and interassay CV of the migration times and the measured peak areas being less than 2.3 and 5%, respectively. Application of the system to analysis of cerebrospinal fluid from head traumatized babies clearly indicated the group with mild trauma versus those with severe injury. Additionally, CE analysis demonstrated that the severe trauma group could be divided into individuals with good and poor prognosis, which correlated with the clinical finding for each patient.

Long-term impact of infection on the preterm neonate

Prematurely born infants are at increased risk for infection throughout their hospitalization. Various developmentally regulated processes involving the central nervous and respiratory systems may be disrupted by the proinflammatory state associated with infection, resulting in an increased risk for death, chronic lung disease, and adverse neurodevelopmental outcome. This review summarizes the current understanding of the long-term impact of infection and/or inflammation in preterm infants, including the risks associated with perinatal infection, early-onset sepsis, late-onset sepsis, and necrotizing enterocolitis.

Cytokines and posthemorrhagic ventricular dilation in premature infants

OBJECTIVE

To determine in extremely low-birth-weight infants if elevated blood interferon-γ (IFN-γ), interleukin (IL)-1β, IL-18, tumor necrosis factor-α (TNF-α), and transforming growth factor-β are associated with need for shunt following severe intraventricular hemorrhage (IVH) or with ventricular dilation following milder grades/no IVH.

STUDY DESIGN

Whole blood cytokines were measured on postnatal days 1, 3, 7, 14, and 21. Maximum IVH grade in the first 28 days, and shunt surgery or ventricular dilation on subsequent ultrasound (28 days' to 36 weeks' postmenstrual age) were determined.

RESULTS

Of 902 infants in the National Institute of Child Health and Human Development Neonatal Research Network Cytokine study who survived to 36 weeks or discharge, 3.1% had shunts. Of the 12% of infants with severe (grade III to IV) IVH, 26% had a shunt associated with elevated TNF-α. None of the infants without IVH (69%) or with grade I (12%) or II (7%) IVH received shunts, but 8.4% developed ventricular dilation, associated with lower IFN-γ and higher IL-18.

CONCLUSION

Statistically significant but clinically nondiscriminatory alterations in blood cytokines were noted in infants with severe IVH who received shunts and in those without severe IVH who developed ventricular dilation. Blood cytokines are likely associated with brain injury but may not be clinically useful as biomarkers for white matter damage.

Decreased IFN-γ and IL-12 levels in panic disorder

OBJECTIVE

The aim of this study is to assess the measures of proinflammatory cytokines in patients with panic disorder in comparison with the healthy subjects.

METHODS

Twenty three patients with panic disorder with or without agoraphobia and twenty three controls were recruited for the study. Plasma samples of all subjects were analyzed for TNF-α, IFN-γ, IL-1β, IL-2, IL-6, and IL-12 concentrations and NK-cell activity is measured in the peripheral blood samples of the subjects.

RESULTS

We found significant differences on the mean values of IL-12 (p=0.01) and IFN-γ (p=0.02) between the panic disorder and control groups. In a logistic regression analysis, IFN-γ values were significant statistical predictors of the presence of panic disorder (B=-0.07, SE=0.03, p=0.04).

CONCLUSION

The most important implication of our results is to suggest a relation between panic disorder and low levels of IFN-γ, compatible with the results of the animal studies showing that IFN-γ plays a role by acting to regulate the development of anxiety-like behaviors.

Primary mixed glial cultures from fetal ovine forebrain are a valid model of inflammation-mediated white matter injury

Astrocytes, microglial cells and oligodendrocytes (OLs) have been employed separately in vitro to assess cellular pathways following a variety of stimuli. Mixed glial cell cultures, however, have not been utilized to the same extent, despite the observed discrepancy in outcomes resulting from cell-to-cell contact of different glia in culture. Our objective was to standardize and morphologically characterize a primary culture of preterm ovine glial cells in order to attain a relevant in vitro model to assess the intracellular effects of infection and inflammation. This would provide a high-throughput model necessary for in-depth studies on the various pathophysiological mechanisms of white matter injury (WMI), which may occur in the preterm infant as a consequence of maternal infection or the fetal inflammatory response. Glial cells from the forebrains of 0.65-gestation ovine fetuses (comparable to 24- to 26-week human fetal brain development) were mechanically and enzymatically isolated and plated at a final density of 250,000 cells per well. When reaching confluence at 5 days after plating, the cultures contained astrocytes, microglial cells, as well as progenitor, precursor and immature OLs. Glial cell morphology and phenotypic immunoreactivity were characteristic of and consistent with previous observations of separately cultured cell types. To determine the effects of infection or inflammation in our in vitro model, we then treated mixed glial cultures with tumour necrosis factor-α (TNF-α; 50 or 100 ng/ml) or lipopolysaccharide (LPS; 1 µg/ml) for a period of 48 h. Cytokine levels were measured by ELISA and cell numbers for specific glial cell types were determined along with OL proliferation and apoptosis by Ki67 and caspase-3 immunocytochemistry, respectively. Our results showed that exposure to TNF-α or LPS resulted in a characteristic inflammatory response entailed by up-regulation of pro-inflammatory cytokines, a lack of astrogliosis and a marked reduction in OLs attributable to increased apoptosis. In LPS-treated cultures, there was a marked increase in the pro-inflammatory cytokine TNF-α at both 24 and 48 h. In conclusion, this is the first report of the immunocytochemical description and characterization of fetal ovine-derived mixed glial cell primary cultures. This in vitro model provides a novel and efficient system to explore the mechanisms of infection/inflammation-mediated WMI at the cellular level and for screening candidate therapeutic strategies.

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.

Association between high cytokine levels with white matter injury in preterm infants with sepsis

OBJECTIVE

To examine the association among interleukin-6, interleukin-8, tumor necrosis factor-α, interleukin-10, and interleukin-1β and white matter injury in very-low-birth-weight infants with clinical sepsis and to help predict infants at risk for development of white matter injury.

DESIGN

A prospective cohort study was carried out.

SETTING

Neonatal intensive care unit.

PATIENTS

Very low birth weight infants with clinical early-onset sepsis. Exclusion criteria were death before 14 days, major malformations, and congenital infections.

INTERVENTION

Ultrasound brain scans were carried out on the third day and weekly until the sixth week of life or discharge and confirmed by a magnetic resonance image performed in the first year. Plasma was assayed for interleukin-6, interleukin-8, tumor necrosis factor-α, interleukin-10, and interleukin-1β in the same sample collected for sepsis work-up. Mann-Whitney, chi-square, t tests, multiple regression, and receiver operating characteristic analysis were applied.

MEASUREMENTS AND MAIN RESULTS

From July 2005 to October 2007 we studied 84 very-low-birth-weight infants, 27 (32%) with white matter injury, and 57 (68%) control subjects (with no white matter injury). Proven early-onset sepsis and necrotizing enterocolitis were high risk for white matter injury after adjustment for gestational age and birth weight (relative risk, 3.04; 1.93-4.80 and relative risk, 2.2; 1.31-3.74, respectively). Interleukin-6, interleukin-8, and tumor necrosis factor-α levels were higher in infants with white matter injury than in control subjects (p < .0001). Interleukin-1β and interleukin-10 were similar. The areas under the curve for interleukin-6, interleukin-8, and tumor necrosis factor-α were 0.96 (0.92-0.99), 0.97 (0.94-1.0), and 0.93 (0.86-0.99), respectively. Interleukin-8 ≥100 pg/mL was the best predictor of white matter injury; the sensitivity and specificity were 96% and 83%, respectively, and negative predictive value was 98%.

CONCLUSIONS

Very-low-birth-weight infants with proven early-onset sepsis, necrotizing enterocolitis, and high plasma levels of interleukin-6, interleukin-8, and tumor necrosis factor-α are at high risk for white matter injury.

Postnatal infection is associated with widespread abnormalities of brain development in premature newborns

INTRODUCTION

Infection is a risk factor for adverse neurodevelopmental outcome in preterm newborns. Our objective was to characterize the association of postnatal infection with adverse microstructural and metabolic brain development in premature newborns.

RESULTS

In 34/117 newborns studied, clinical signs were accompanied by positive cultures whereas 17 had clinical signs of sepsis alone. White matter injury (WMI) was identified in 34 newborns. In multivariate regression models, infected newborns had brain imaging measures indicative of delayed brain development: lower N-acetylaspartate/choline, elevated average diffusivity (D(AV)), and decreased white matter fractional anisotropy. These widespread brain abnormalities were found in both newborns with positive-culture infection and in those with clinical infection.

DISCUSSION

These findings suggest that postnatal infection, even without a positive culture, is an important risk factor for widespread abnormalities in brain development. These abnormalities extend beyond brain injuries apparent with conventional magnetic resonance injury (MRI).

METHODS

117 preterm newborns (24-32 wk gestation) were studied prospectively at a median of 32.0 and 40.3 wk ostmenstrual age with MRI (WMI, hemorrhage), magnetic resonance (MR) spectroscopy (metabolism), and diffusion tensor imaging (microstructure). Newborns were categorized as having "no infection," "clinical infection," or "positive-culture infection." We compared brain injuries as well as metabolic and microstructural development across these infection groups.

Genetic variations in fetal and maternal tumor necrosis factor-α and interleukin 10: is there an association with preterm birth or periventricular leucomalacia?

OBJECTIVE

The aim of the study was to identify whether tumor necrosis factor-α (TNF-α) (-308) and interleukin (IL)-10 (-1082; -819) genotypes were associated with preterm delivery and cystic periventricular leucomalacia (PVL).

STUDY DESIGN

Venous blood, buccal swabs or cord blood were collected from mother/child pairs with infants born at term (200) or preterm (106) in the presence and absence of neonatal PVL and of premature infants with PVL (7). Extracted genomic DNA served as template for determination of IL-10 (-1082), IL-10 (-819) and TNF-α (-308) genotypes by allele-specific PCR.

RESULT

No significant difference was observed in the frequencies of IL-10 (-1082), IL-10 (-819) and TNF-α (-308) genotypes in mothers or in children of term versus preterm deliveries with or without PVL.

CONCLUSION

Maternal and infant IL-10 (-1082, -819) and TNF-α (-308) genotypes are not indicative for an increased risk of preterm birth or the development of PVL in premature newborns.

The cerebral critical oxygen threshold of ventilated preterm lambs and the influence of antenatal inflammation

Perinatal inflammation is associated with adverse neurodevelopmental outcomes, which may be partly due to changes in the cerebral oxygen delivery/consumption relationship. We aimed to determine the critical oxygen delivery threshold of the brain of preterm, ventilated lambs and to determine whether the critical threshold is affected by exposure to inflammation in utero. Pregnant ewes received intra-amniotic injection of lipopolysaccharide or saline at 125 or 127 days of gestation. Pulmonary and systemic flow probes and catheters were surgically positioned in the fetus immediately before delivery at 129 days of gestation. After delivery, lambs were ventilated for 90 min using a positive end-expiratory pressure recruitment strategy. Cardio-respiratory variables and blood gases were measured regularly. Systemic and cerebral oxygen delivery, consumption (Fick), and extraction were calculated, and the relationship between cerebral delivery and consumption analyzed. Linear regression was used to define the transition or "critical" oxygen threshold as the point at which the slope of the oxygen delivery/consumption curve changed to be > 10°. Four subgroups were defined according to the calculated critical threshold. A total of 150 measurements were recorded in 18 lambs. Fetal cerebral oxygen consumption was increased by antenatal lipopolysaccharide (P < 0.05). The postnatal critical oxygen threshold was 3.6 ml·kg⁻¹·min⁻¹, corresponding to cerebral oxygen consumption of 0.73 ml·kg⁻¹·min⁻¹. High oxygen delivery and consumption were associated with increased pulmonary and carotid blood flow and systemic extraction compared with low oxygen delivery and consumption. No postnatal effect of antenatal inflammation was observed. Inflammation in utero increases fetal, but not postnatal, cerebral oxygen consumption. Adverse alterations to pulmonary blood flow can result in reduced cerebral blood flow, oxygen delivery, and consumption. Regardless of exposure to inflammation, there is a consistent postnatal relationship between cerebral oxygen delivery and consumption.

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.

The relationship between early concentrations of 25 blood proteins and cerebral white matter injury in preterm newborns: the ELGAN study

OBJECTIVE

To evaluate whether concentrations of inflammation-related proteins are elevated in the blood of preterm newborns who develop cerebral white matter damage.

STUDY DESIGN

We measured 25 proteins in blood collected on days 1, 7, and 14 from 939 infants born before the 28th week of gestation. Brain ultrasound scans were read by at least two sonologists, who agreed on the presence or absence of lesions. A protein concentration was considered elevated if it was in the highest quartile for gestational age and the day on which the specimen was collected.

RESULTS

In time-oriented models, elevated concentrations of vascular endothelial growth factor receptor 1, serum amyloid A, and macrophage inflammatory protein 1β on day 1 and interleukin-8 on day 7 were associated with increased risk of ventriculomegaly. Elevated concentrations of macrophage inflammatory protein 1β on day 1 and intercellular adhesion molecule 1 on day 7 were associated with increased risk of an echolucent lesion. Infants with elevated concentrations of inflammation-related proteins on two separate days were at significantly increased risk for ventriculomegaly, but at only modestly increased risk for an echolucent lesion.

CONCLUSIONS

Concentrations of inflammation-related proteins in the circulation in the first days after preterm birth provide information about the risk of sonographic white matter damage. The inflammatory process might begin in utero.

Preliminary study of the plasma and cerebrospinal fluid concentrations of IL-6 and IL-10 in patients with chronic pain receiving intrathecal opioid infusions by chronically implanted pump for pain management

OBJECTIVE

This preliminary study assessed possible relationships between plasma and/or cerebrospinal fluid (CSF) concentrations of the pleiotropic cytokine, interleukin (IL)-6, the anti-inflammatory cytokine, IL-10, and levels of pain reported by patients receiving intrathecal (i.t.) opioids.

DESIGN

A prospective study quantifying IL-6 and IL-10 concentrations using enzyme-linked immunoassays in samples of plasma and CSF as well as assessment of pain scores in patients receiving intrathecal opioids for management of chronic noncancer pain.

SETTING

Outpatient pain clinics.

PATIENTS

Patients with chronic pain receiving intrathecal morphine or hydromorphone alone or in combination with local anesthetics.

INTERVENTIONS

Two groups of patients were studied. The first group (n = 50) had been receiving long-term i.t. opioids by chronically implanted pump for approximately 5 years; paired samples of plasma and CSF were collected at the time of i.t. pump refill. For the second patient group (n = 10), possible temporal changes in the plasma and/or CSF concentrations of IL-6 and IL-10 were investigated for 3 months after initiation of i.t. opioid infusions.

RESULTS

For patients receiving long-term i.t. opioid infusions, there were significant inverse correlations (P < or = 0.05) between pain intensity and the plasma (but not CSF) IL-10 and IL-6 concentrations. Despite the considerable inter-patient variability in the CSF concentrations of IL-6 in the long-term cohort, the mean CSF IL-6 concentration was approximately fivefold higher in patients receiving long-term i.t. opioids relative to those receiving i.t. opioids for only 3 months.

CONCLUSIONS

The significant inverse correlations observed between pain intensity and the plasma IL-6 and IL-10 concentrations in patients receiving longterm i.t. opioids for chronic pain management, suggests that these cytokines are worthy of further investigation as possible biomarkers of persistent pain.

Integrated review of cytokines in maternal, cord, and newborn blood: part II-- associations with early infection and increased risk of neurologic damage in preterm infants

A growing body of literature supports the relationship of maternal inflammation with preterm birth and adverse neonatal outcomes, including infection and central nervous system (CNS) dysfunction. Mediators of inflammation, most notably proinflammatory cytokines, have been implicated as having an association with and perhaps playing a causal role in the pathogenesis, leading to adverse neonatal outcomes. Even though the association of cytokines with early adverse neonatal outcomes has been actively pursued as a line of research, there has been little integration of diverse findings across studies. Therefore, the purpose of this systematic review was to appraise and classify empirical evidence from human studies for the association of cytokine levels in blood (serum, plasma, or cells; maternal, cord, or neonatal) with two adverse early outcomes in preterm infants: early infection and increased risk of neurologic damage. The review revealed that the proinflammatory cytokines most frequently linked with sepsis are in the interleukin (IL) 1 family as well as tumor necrosis factor alpha (TNF-alpha) and IL-6. The proinflammatory cytokines most frequently linked to neurologic insult in the reviewed studies were IL-1beta, IL-6, and IL-8. In all cases where IL-1beta was studied, the levels were increased when there was neurologic insult. A better understanding of the relationship of these inflammatory substances with these adverse conditions is needed for the future development of maternal and neonatal biobehavioral nursing research.

Effect of chorioamnionitis on brain development and injury in premature newborns

OBJECTIVE

The association of chorioamnionitis and noncystic white matter injury, a common brain injury in premature newborns, remains controversial. Our objectives were to determine the association of chorioamnionitis and postnatal risk factors with white matter injury, and the effects of chorioamnionitis on early brain development, using advanced magnetic resonance imaging.

METHODS

Ninety-two preterm newborns (24-32 weeks gestation) were studied at a median age of 31.9 weeks and again at 40.3 weeks gestation. Histopathological chorioamnionitis and white matter injury were scored using validated systems. Measures of brain metabolism (N-acetylaspartate/choline and lactate/choline) on magnetic resonance spectroscopy, and microstructure (average diffusivity and fractional anisotropy) on diffusion tensor imaging were calculated from predefined brain regions.

RESULTS

Thirty-one (34%) newborns were exposed to histopathological chorioamnionitis, and 26 (28%) had white matter injury. Histopathological chorioamnionitis was not associated with an increased risk of white matter injury (relative risk: 1.2; p = 0.6). Newborns with postnatal infections and hypotension requiring therapy were at higher risk of white matter injury (p < 0.03). Adjusting for gestational age at scan and regions of interest, histopathological chorioamnionitis did not significantly affect brain metabolic and microstructural development (p > 0.1). In contrast, white matter injury was associated with lower N-acetylaspartate/choline (-8.9%; p = 0.009) and lower white matter fractional anisotropy (-11.9%; p = 0.01).

INTERPRETATION

Histopathological chorioamnionitis does not appear to be associated with an increased risk of white matter injury on magnetic resonance imaging or with abnormalities of brain development. In contrast, postnatal infections and hypotension are associated with an increased risk of white matter injury in the premature newborn.

CSF cytokine levels in preterm infants may reflect systemic inflammation and are independent of gestation

BACKGROUND

Among preterm infants, high concentrations of inflammatory mediators in cerebrospinal fluid (CSF) are associated with poor outcome. Previous studies have not indicated whether CSF concentrations of inflammatory mediators are associated with important confounders such as gestational age.

AIMS

To examine associations between CSF concentrations of inflammatory mediators and gestational age, maternal features suggestive of inflammation, characteristics of the CSF sample or the presence of a systemic inflammatory response.

STUDY DESIGN AND SUBJECTS

Aliquots of CSF obtained during routine investigation of potential sepsis among infants born before 35 weeks gestation were assayed for 17 mediators of inflammation using a fluorescent multi-bead analyser. Other information was collected from routine clinical records.

RESULTS

39 infants were assessed. CSF levels of mediators of inflammation were not correlated with gestational age. CSF red blood cell counts were correlated with CSF concentrations of IL-6, GM-CSF and IL-17 (each p<0.003). CSF lactate was correlated with CSF concentrations of IL-1beta, IL-6, GM-CSF, G-CSF, IFN-gamma and MIP-1beta. CSF concentrations of IL-1beta, IL-6, G-CSF, TNF-alpha and IFN-gamma were higher in infants with a raised CRP within 24 h of delivery (each p<0.003).

CONCLUSIONS

CSF concentrations of inflammatory mediators most probably reflect inflammatory pathologies and are not influenced by gestational age. They may also, however, reflect contamination with blood or systemic inflammation. CSF concentrations of inflammatory mediators may not provide a specific indicator of CNS inflammation.

Interleukin-6 -174 and -572 genotypes and the volume of deep gray matter in preterm infants

Preterm infants have smaller cerebral and cerebellar volumes at term compared with term born infants. Perinatal factors leading to the reduction in volumes are not well known. IL-6 -174 and -572 genotypes partly regulate individual immunologic responses and have also been connected with deviant neurologic development in preterm infants. Our hypothesis was that IL-6 -174 and -572 genetic polymorphisms are associated with brain lesions and regional brain volumes in very low birth weight or in very preterm infants. DNA was genotyped for IL-6 -174 and -572 polymorphisms (GG/GC/CC). Study infants (n = 175) were categorized into three groups according to the most pathologic brain finding in ultrasound examinations until term. The brain MRI performed at term was analyzed for regional brain volumes. Analyzed IL-6 genotypes did not show statistically significant association with structural brain lesions. However, IL-6 -174 CC and -572 GG genotypes associated with reduced volume of one brain region, the combined volume of basal ganglia and thalami, both in univariate and in multivariate analyses (p = 0.009, 0.009, respectively). The association of IL-6 -174 and -572 genetic polymorphisms with smaller volumes in deep gray matter provides us new ways to understand the processes leading to neurologic impairments in preterm infants.

Cytokines and perinatal brain damage

Perinatal brain damage has been implicated in the pathogenesis of neurodevelopmental impairments and psychiatric illnesses. This article reviews evidence that infection outside of the brain can damage the brain, and discusses specific cytokines and pathomechanisms that probably mediate the putative effect of remote infection on the developing brain. Events associated with increased circulating inflammatory cytokines, chemokines, and immune cells are described. Finally, studies of genetic variation in susceptibility to cytokine-related brain damage are reviewed.

Proteomics- and metabolomics-based neonatal diagnostics in assessing and managing the critically ill neonate

The use of proteomic-based neonatal screening has been relatively limited until the present era and has focused primarily on the evaluation of newborns for inborn errors of metabolism. The future of proteomic-based screening seems to be much more encompassing, however. Tandem mass spectrometry and other related technologies are highly likely to be used in the evaluation of acute disease processes. Proteomics has the advantage over genomics of permitting a more direct look at an evolving disease process, because genomics primarily relates only the potential for a disease or abnormality to express itself. This article reviews the current uses of proteomics-based newborn evaluation and evaluates how this rapidly evolving area of medicine may be used to assess the fetus and the neonate in the near future.

Candidate genes and cerebral palsy: a population-based study

OBJECTIVE

The objective of this study was to examine whether selected genetic polymorphisms in the infant are associated with later-diagnosed cerebral palsy.

METHODS

A population-based case-control study was conducted of 28 single-nucleotide polymorphisms measured in newborn screening blood spots. A total of 413 children with later-diagnosed cerebral palsy were born to white women in South Australia in 1986-1999, and there were 856 control children. Distributions of genotypic frequencies were examined in total cerebral palsy, in gestational age groups, and by types of cerebral palsy and gender. Genotyping was performed by using a TaqMan assay.

RESULTS

For inducible nitric-oxide synthase, possession of the T allele was more common in all children with cerebral palsy and for heterozygotes who were born at term. For lymphotoxin alpha, homozygous variant status was associated with risk for cerebral palsy and with spastic hemiplegic or quadriplegic cerebral palsy. Among term infants, heterozygosity for the endothelial protein C receptor single-nucleotide polymorphism was more frequent in children with cerebral palsy. In preterm infants, the variant A allele of interleukin 8 and heterozygosity for the beta-2 adrenergic receptor were associated with cerebral palsy risk. Interleukin 8 heterozygote status was associated with spastic diplegia. Variants of several genes were associated with cerebral palsy in girls but not in boys.

CONCLUSIONS

Two of the 28 single-nucleotide polymorphisms examined were associated with all types of spastic cerebral palsy in both gestational age groups and others with cerebral palsy in gestational age or cerebral palsy subgroups. Some of these associations support previous findings. There may be a genetic contribution to cerebral palsy risk, and additional investigation is warranted of genes and gene-environment interactions in cerebral palsy.

Systemic inflammation following hind-limb ischemia-reperfusion affects brain in neonatal mice

Antenatal and postnatal infection and inflammation are associated with neurological injury in neonates. However, no direct role for systemic inflammation in mediating neurodamage has been shown. The study was aimed to determine whether systemic inflammation following ischemia-reperfusion (IR) of an organ remotely located from the brain results in cerebral injury. Neonatal mice were subjected to 2 h of hind-limb IR. At 48 h of reperfusion, brains were examined for activation of microglia and caspase-3. Lungs were assessed for pulmonary edema and granulocyte infiltration. The levels of circulating inflammatory mediators were measured at 24 h of reperfusion. In a separate cohort of mice, changes in the cerebral and hind-limb blood flow were measured. All data were compared to that in sham mice. Compared to shams the degree of pulmonary edema in IR mice was 33% (p = 0.04) greater. This was associated with significantly (p = 0.0006) greater granulocytic infiltration and a markedly increased level of circulating cytokines. The brains of these same mice exhibited significantly (p = 0.02) greater numbers of caspase-3-immunopositive cells and activation of microglia compared to sham mice. These data indicate that systemic inflammation following IR in the organ remote from the brain can induce neuroinflammation and cerebral proapoptotic changes.

Corticosteroids reverse cytokine-induced block of survival and differentiation of oligodendrocyte progenitor cells from rats

Background

Periventricular leukomalacia (PVL) is a frequent complication of preterm delivery. Proinflammatory cytokines, such as interferon-γ (IFN-γ) and tumor necrosis factor α (TNF-α) released from astrocytes and microglia activated by infection or ischemia have previously been shown to impair survival and maturation of oligodendrocyte progenitors and could thus be considered as potential factors contributing to the generation of this disease. The first goal of the present study was to investigate whether exposure of oligodendrocyte precursors to these cytokines arrests the maturation of ion currents in parallel to its effects on myelin proteins and morphological maturation. Secondly, in the search for agents, that can protect differentiating oligodendrocyte precursor cells from cytokine-induced damage we investigated effects of coapplications of corticosteroids with proinflammatory cytokines on the subsequent survival and differentiation of oligodendrocyte progenitor cells.

Methods

To exclude influences from factors released from other cell types purified cultures of oligodendrocyte precursors were exposed to cytokines and/or steroids and allowed to differentiate for further 6 days in culture. Changes in membrane surface were investigated with capacitance recordings and Scanning Ion Conductance Microscopy. Na⁺- and K⁺- currents were investigated using whole cell patch clamp recordings. The expression of myelin specific proteins was investigated using western blots and the precursor cells were identified using immunostaining with A2B5 antibodies.

Results

Surviving IFN-γ and TNF-α treated cells continued to maintain voltage-activated Na⁺- and K⁺ currents characteristic for the immature cells after 6 days in differentiation medium. Corticosterone, dihydrocorticosterone and, most prominently dexamethasone, counteracted the deleterious effects of IFN-γ and TNF-α on cell survival, A2B5-immunostaining and expression of myelin basic protein. The most potent corticosteroid tested, dexamethasone, was shown to counteract cytokine effects on membrane surface extension and capacitance. Furthermore, coapplication of dexamethasone blocked the cytokine-induced downregulation of the inwardly rectifying potassium current in 80% of the precursor cells and restored the cytokine-blocked down-regulation of the voltage activated Na⁺- and K⁺ currents during subsequent differentiation.

Conclusion

Our results show that treatment of oligodendrocyte precursors with the inflammatory cytokines TNF-α and IFN-γ block the differentiation of oligodendrocyte precursors at the level of the differentiation of the voltage-gated ion currents. Co-treatment with corticosteroids at the time of cytokine application restores to a considerable extent survival and differentiation of oligodendrocytes at the level of morphological, myelin protein as well as ion current maturation suggesting the option for a functional restoration of cytokine-damaged immature oligodendrocytes.

Adverse neurodevelopment in preterm infants with postnatal sepsis or necrotizing enterocolitis is mediated by white matter abnormalities on magnetic resonance imaging at term

OBJECTIVES

To test the hypothesis that the impact of postnatal sepsis/necrotizing enterocolitis (NEC) on neurodevelopment may be mediated by white matter abnormality (WMA), which can be demonstrated with magnetic resonance imaging (MRI).

STUDY DESIGN

A prospective cohort of 192 unselected preterm infants (gestational age <30 weeks), who were evaluated for sepsis and NEC, underwent imaging at term-equivalent age and neurodevelopmental outcome at 2 years corrected age with the Bayley Scales of Infant Development.

RESULTS

Sixty-eight preterm (35%) infants had 100 episodes of confirmed sepsis, and 9 (5%) infants had confirmed NEC. Coagulase-negative staphylococci accounted for 73% (73/100) of the episodes of confirmed sepsis. Infants with sepsis/NEC had significantly more WMA on MRI at term compared with infants in the no-sepsis/NEC group. They also had poorer psychomotor development that persisted after adjusting for potential confounders but which became nonsignificant after adjusting for WMA.

CONCLUSIONS

Preterm infants with sepsis/NEC are at greater risk of motor impairment at 2 years, which appears to be mediated by WMA. These findings may assist in defining a neuroprotective target in preterm infants with sepsis/NEC.

Recurrent postnatal infections are associated with progressive white matter injury in premature infants

OBJECTIVE

Our objective was to identify clinical predictors of progressive white matter injury.

METHODS

We evaluated 133 infants of <34 weeks of gestation at birth from 2 university hospitals. Infants underwent MRI twice, initially when in stable condition for transport and again at term-equivalent age or before transfer or discharge. Two neuroradiologists who were blinded to the clinical course graded MRI white matter injury severity by using a validated scale. Potential risk factors were extracted from medical charts.

RESULTS

Twelve neonates (9.0%) had progressive white matter injury. In the unadjusted analysis of 10 newborns without Candida meningoencephalitis, recurrent culture-positive postnatal infection and chronic lung disease were associated with progressive white matter injury. Exposure to multiple episodes of culture-positive infection significantly increased the risk of progressive white matter injury. Of the 11 neonates with >1 infection, 36.4% (4 infants) had progressive injury, compared with 5.0% (6 infants) of those with <or=1 infection. Of the 35 infants with chronic lung disease, 17.1% (6 infants) had progressive injury, compared with 4.3% (4 infants) of those without chronic lung disease. After adjustment for gestational age at birth, the association between infection and white matter injury persisted, whereas chronic lung disease was no longer a statistically significant risk factor.

CONCLUSIONS

Recurrent postnatal infection is an important risk factor for progressive white matter injury in premature infants. This is consistent with emerging evidence that white matter injury is attributable to oligodendrocyte precursor susceptibility to inflammation, hypoxia, and ischemia.

Cytokines and Brain Injury: Invited Review

The brain reacts to injury or disease by cascades of cellular and molecular responses. Evidence suggests that immune-inflammatory processes are key elements in the physiopathological processes associated with brain injury or damage. Cytokines are among major mediators implicated in these processes. Cytokine responses in the initial phase of brain injury might have a role in aggravating brain damage. However, in later stages, these molecular mediators might contribute to recovery or repair. Hemodynamic stabilization and optimalization of oxygen delivery to the brain remain cornerstones in the management of acute brain injury. New approaches might use anticytokine therapy to limit progression and halt or attenuate secondary brain damage. Progress toward such novel neuroprotection strategies, however, awaits better understanding of the optimal timing and dosing of those neuromodulatory therapies and better knowledge of the numerous interactions of those mediators. This also requires understanding of how and when precisely immune mechanisms shift from noxious to protective or restorative actions.

Maturation-dependent sensitivity of oligodendrocyte lineage cells to apoptosis: implications for normal development and disease

Apoptosis plays a crucial role in brain development by ensuring that only appropriately growing, migrating, and synapse-forming neurons and their associated glial cells survive. This process involves an intimate relationship between cell-cell interactions and developmental cues and is further impacted by environmental stress during neurogenesis and disease. Oligodendrocytes (OLs), the major myelin-forming cells in the central nervous system, largely form after this wave of neurogenesis but also show a selective vulnerability to cell death stimuli depending on their stage of development. This can affect not only embryonic and early postnatal brain formation but also the response to demyelinating pathologies. In the present review, we discuss the stage-specific sensitivity of OL lineage cells to damage-induced death and how this might impact myelin survival and regeneration during injury or disease.

Neurodevelopmental outcome of extremely low birth weight infants with posthemorrhagic hydrocephalus requiring shunt insertion

OBJECTIVE

We aimed to evaluate neurodevelopmental and growth outcomes among extremely low birth weight infants who had severe intraventricular hemorrhage that required shunt insertion compared with infants without shunt insertion.

METHODS

Infants who were born in 1993-2002 with birth weights of 401 to 1000 g were enrolled in a very low birth weight registry at medical centers that participate in the National Institute of Child Health and Human Development Neonatal Research Network, and returned for follow-up at 18 to 22 months' corrected age were studied. Eighty-two percent of survivors completed follow-up, and 6161 children were classified into 5 groups: group 1, no intraventricular hemorrhage/no shunt (n = 5163); group 2, intraventricular hemorrhage grade 3/no shunt (n = 459); group 3, intraventricular hemorrhage grade 3/shunt (n = 103); group 4, intraventricular hemorrhage grade 4/no shunt (n = 311); and group 5, intraventricular hemorrhage grade 4/shunt (n = 125). Group comparisons were evaluated with chi(2) and Wilcoxon tests, and regression models were used to compare outcomes after adjustment for covariates.

RESULTS

Children with severe intraventricular hemorrhage and shunts had significantly lower scores on the Bayley Scales of Infant Development IIR compared with children with no intraventricular hemorrhage and with children with intraventricular hemorrhage of the same grade and no shunt. Infants with shunts were at increased risk for cerebral palsy and head circumference at the <10th percentile at 18 months' adjusted age. Greatest differences were observed between children with shunts and those with no intraventricular hemorrhage on these outcomes.

CONCLUSIONS

This large cohort study suggests that extremely low birth weight children with severe intraventricular hemorrhage that requires shunt insertion are at greatest risk for adverse neurodevelopmental and growth outcomes at 18 to 22 months compared with children with and without severe intraventricular hemorrhage and with no shunt. Long-term follow-up is needed to determine whether adverse outcomes persist or improve over time.

Circulatory disturbances during the first postnatal 24 hours in extremely premature infants 25 weeks or less of gestation with histological fetal inflammation

AIM

To investigate the effect of pre-existing fetal inflammation on hemodynamics during the first postnatal 24 h in extremely premature infants <or= 25 weeks of gestation.

METHODS

We defined fetal inflammation as the infiltration of neutrophils into the chorionic plate vessels or umbilical cord vessels on histological examination. In 41 infants born between 22 and 25 weeks of gestation, 23 displayed fetal inflammation and 18 displayed no fetal inflammation. Circulatory indices including blood pressure, heart rate, average urine flow, catecholamine index, ejection fraction of the left ventricle, and volume load for 24 h were compared between the two groups, as well as the incidence of intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), and death. The comparisons were made with repeated measure anova and with Fisher's exact test, or unpaired t-test. Probability values <0.05 were considered significant.

RESULTS

Infants with and without fetal inflammation had similar birthweights and gestational age. There was no significant difference in incidence of PVL and death. However, infants with fetal inflammation had a significantly higher incidence of IVH >or= 3 than infants with no fetal inflammation (49% vs 17%) (P=0.04). Infants with fetal inflammation had significantly higher heart rate (P=0.005), catecholamine index (P=0.019) and volume load (P=0.021).

CONCLUSION

Histological evidence of fetal inflammation in extremely premature infants is associated with circulatory disturbances over the first 24 h of life and increases in the incidence of IVH >or= 3.

Proinflammatory cytokine production by cultured neonatal rat microglia after exposure to blood products

Periventricular germinal matrix hemorrhage is a devastating complication of preterm birth. Inflammation appears to play a role in brain damage after premature birth and hypoxia. The effects of rat blood plasma and serum on cytokine expression by cultured rat microglial cells were investigated. We analyzed mRNA expression levels of tumor necrosis factor (TNF)-alpha, interleukin-6 and protease activated receptor-1 and -4 by quantitative RT-PCR. Protein expression for TNFalpha was done using immunocytochemistry and ELISPOT assays. Plasma and serum had dose dependent toxic effects on microglia as measured by lactate dehydrogenase release assay and activated caspase-3 immunocytochemistry. High concentrations of plasma enhanced TNFalpha mRNA expression and protein production, while high concentrations of serum enhanced IL-6 mRNA expression. This study suggests that soluble components of blood might be differentially responsible for up regulating production of the cytokines TNFalpha and IL-6 by microglia from immature rodent brain.

Pathogenesis of cerebral white matter injury of prematurity

Cerebral white matter injury, characterised by loss of premyelinating oligodendrocytes (pre-OLs), is the most common form of injury to the preterm brain and is associated with a high risk of neurodevelopmental impairment. The unique cerebrovascular anatomy and physiology of the premature baby underlies the exquisite sensitivity of white matter to the abnormal milieu of preterm extrauterine life, in particular ischaemia and inflammation. These two upstream mechanisms can coexist and amplify their effects, leading to activation of two principal downstream mechanisms: excitotoxicity and free radical attack. Upstream mechanisms trigger generation of reactive oxygen and nitrogen species. The pre-OL is intrinsically vulnerable to free radical attack due to immaturity of antioxidant enzyme systems and iron accumulation. Ischaemia and inflammation trigger glutamate receptor-mediated injury leading to maturation-dependent cell death and loss of cellular processes. This review looks at recent evidence for pathogenetic mechanisms in white matter injury with emphasis on targets for prevention and treatment of injury.

Diffuse white matter injury and neurologic outcomes of infants born very preterm in the 1990s

Neurocognitive outcomes of infants born very preterm (less than 32 weeks gestation) remain a major concern in perinatal practice. Very preterm birth rates have increased, with enhanced survival since 1990. As focal brain lesions become less common, diffuse injury to both gray and white matter is now the primary focus for improving neurologic outcomes in survivors. Recent evidence supports preoligodendrocytes as the principal cellular target of diffuse white matter injury due to their susceptibility to hypoxic-ischemic and inflammatory insults. An understanding of their development and vulnerability can inform acute nursing care of very preterm infants.

Interleukin-1beta, interleukin-18, and interferon-gamma expression in the cerebrospinal fluid of premature infants with posthemorrhagic hydrocephalus--markers of white matter damage?

Posthemorrhagic hydrocephalus (PHHC) represents a major complication of preterm birth. The aim of this study was to determine whether cerebrospinal fluid (CSF) levels of the pro-inflammatory cytokines IL-1beta, IL-18, and interferon (IFN)-gamma are altered in the CSF of preterm infants with PHHC and may serve as a marker of white matter damage (WMD). Twenty-seven preterm infants with PHHC were included in the study; 13 of them had signs of cystic WMD (cWMD) on ultrasound examinations. CSF sample 1 was obtained at first ventriculostomy, sample 2 at shunt implantation. Results were compared with a control group of 20 age-matched patients without neurologic diseases. IL-1beta concentrations were elevated in CSF sample 1 of PHHC patients without WMD and in sample 1 of patients with cWMD. Concentrations of IL-18 were increased in both samples of patients without WMD and in sample 2 of patients with cWMD. CSF levels of IFN-gamma were elevated in sample 1 of PHHC patients with cWMD. The pro-inflammatory cytokine IL-1beta and IL-18 levels in the CSF are elevated in patients with PHHC. Higher IFN-gamma levels are detected in a subgroup of patients developing cWMD, indicating its involvement in the pathogenesis of cWMD in the context of PHHC.

Neurodevelopmental outcomes of neonates with medically and surgically treated necrotizing enterocolitis

OBJECTIVES

(1) To characterise neurodevelopmental outcome of neonates with necrotizing enterocolitis (NEC); (2) to define whether NEC increases risk of neurodevelopmental impairment in very low birth weight neonates; (3) to investigate whether stage of disease or need for surgery increase risk of poor outcome.

DESIGN

A systematic review was performed. Searches identified 182 relevant papers. Ten studies compared extremely low birthweight neonates with NEC to infants of similar age and gestation who did not develop NEC. Data are reported as OR (95% CIs, p values for test for overall effect) and compared by chi2.

RESULTS

7843 children (821 with NEC) were included in the meta-analysis. Median follow-up was 20 months (range 12 to 156). Overall, 45% of children who had neonatal NEC were neurodevelopmentally impaired. Infants with NEC were significantly more likely than infants of similar age and gestation who did not develop NEC to be neurodevelopmentally impaired (1.6 (1.3 to 2.0), p = 0.0001) including a higher risk of cerebral palsy (1.5 (1.2 to 2.0), p = 0.001), visual (2.3 (1.0 to 5.1), p = 0.04), cognitive (1.7 (1.4 to 2.2), p<0.0001) and psychomotor impairment (1.7 (1.3 to 2.2), p<0.0001). The odds ratio of neurodevelopmental impairment was also 2.3 times higher in neonates with Bell's stage III disease or requiring surgery ((1.5 to 3.6), p = 0.0001).

CONCLUSIONS

NEC is associated with significantly worse neurodevelopmental outcome than prematurity alone. Presence of advanced NEC and need for surgery increase the risk of neurological impairment.

High Thrombopoietin Concentrations in The Cerebrospinal Fluid of Neonates with Sepsis And Intraventricular Hemorrhage May Contribute to Brain Damage

Thrombopoietin (TPO) and its receptor (TPOR) are expressed in the central nervous system (CNS). Although TPO shares significant homology with various neurotrophins, recent data indicate a proapoptotic function of TPO in the CNS. In this study, TPO concentrations were analyzed in the cerebrospinal fluid (CSF) of neonates. Human neuroblastoma-derived SH-SY5Y cells were established to elucidate the effects of inflammation and hypoxia on neuronal Tpo expression. TPO was detectable in the CSF of 6 of 15 neonates with bacterial infection/sepsis (median 140, range 2-613 pg/mL), 5 of 9 neonates with posthemorrhagic hydrocephalus (median 31, range 1.4-469 pg/mL), 3 of 4 neonates with posthemorrhagic hydrocephalus plus bacterial infection/sepsis or meningitis (median 97, range 6-397 pg/mL), but not in controls ( n = 3). Neither the presence of detectable TPO nor its level in the CSF significantly correlated with any clinical or laboratory parameter. In SH-SY5Y cells, TPO and TPOR expression was detected by RT-PCR and Western blot analysis. In vitro, interleukin-6 (IL-6) did not significantly change Tpo gene expression. In contrast, Tpo mRNA expression significantly decreased under hypoxia, whereas erythropoietin (EPO) mRNA expression increased. In conclusion, our data provide evidence that in neuronal cells, TPO production is regulated by different mechanisms than in hepatocytes.