Maternal intrauterine infection, cytokines, and brain damage in the preterm newborn

Interleukin-6 in the maternal circulation reaches the rat fetus in mid-gestation

Maternal systemic infection during pregnancy may expose the fetus to infectious agents and high levels of mediators of the resulting inflammatory response, such as IL-6 (IL-6). Increased fetal and maternal levels of IL-6 have been associated with adverse neonatal outcome but might also stress the fetus and contribute to cardiovascular and neuroendocrine dysfunction in adulthood. It is unclear whether interleukins cross the placental barrier, although this matter has been little studied. The aim of this study was therefore to investigate if IL-6 administered to pregnant rats in vivo is transferred to the fetus. We injected 125I IL-6 i.v. to pregnant dams at gestation day 11-13 (mid-gestation) or 17-19 (late gestation). We found 125I-IL-6 in the exposed fetuses as well as in amniotic fluids. Fetal 125I-IL-6 levels were markedly higher in animals injected in mid-gestation compared with late pregnancy (p < 0.01). This difference was mirrored in a 15-fold higher unidirectional materno-fetal clearance for 125I-IL-6 in mid-gestation (p < 0.01). We conclude that the permeability of the rat placental barrier to IL-6 is much higher in mid-gestation than in late pregnancy. Maternally derived IL-6 may directly induce fetal injury but also stimulate the release of fetal stress hormones resulting in stimuli or insults in neuroendocrine structures and hormonal axes which might lead to disease at adult age.

Diminished response to interleukin-10 and reduced antibody-dependent cellular cytotoxicity of cord blood monocyte-derived macrophages

Monocyte-derived macrophage (MPhi) subsets are generated by antagonistic induction pathways. A helper MPhi-type (Mh-MPhi) is induced by interferon gamma (IFN-gamma), whereas a cytotoxic MPhi-type (Mc-MPhi), induced by interleukin-10 (IL-10), is a potent mediator of antibody-dependent cellular cytotoxicity (ADCC). Compared with MPhi from healthy adults [peripheral blood monocyte-derived macrophages (PBMPhi)], cord blood MPhi (CBMPhi) were found less capable of generating Mh-MPhi. Here we tested the hypothesis that their generation of Mc-MPhi via IL-10 is also impaired. MPhi surface markers were phenotyped. IL-10 protein and mRNA production were detected after stimulation [alphaCD3 monoclonal antibody (mAb)]. CBMPhi or PBMPhi were co-cultured with MPhi-depleted mononuclear cells of adults and CD4-targeting antibodies as models for ADCC were added. In cord blood, we found diminished alphaCD3-induced IL-10 protein and mRNA production (p < 0.05 versus adults). Basal CD16 and HLA-DR expressions on CBMPhi of preterm and full-term neonates were lower (p < 0.05 versus PBMPhi). IL-10 had reduced effects on CD16 up- and HLA-DR down-modulation on CBMPhi (p < 0.05 versus PBMPhi). CD4-directed receptor modulation and deletion were reduced in the presence of CBMPhi (p < 0.05 versus PBMPhi). IL-10 failed to enhance their ADCC capacity, which was in contrast to PBMPhi (p < 0.05). These data suggest that CBMPhi have an impaired cytotoxic capacity via lower sensitivity toward IL-10.

Reduction in cerebellar volumes in preterm infants: relationship to white matter injury and neurodevelopment at two years of age

A substantial number of prematurely born infants will experience later neurodevelopmental challenges. Abnormal development of the cerebellum may be related to some of the impairments exhibited by preterm children. To test the hypothesis that cerebellar development is structurally impaired in preterm infants and associated with adverse outcomes, we studied 83 preterm infants and 13 term controls using volumetric magnetic resonance imaging techniques to obtain cerebellar volumes (CV) at term corrected and subsequent neurodevelopmental assessment at 2 y of age. The preterm group had smaller mean CV at term compared with the term control infants [mean (SD) CV, 22.0 (5.0) versus 23.5 (5.0) cc; mean difference (95% confidence interval), 1.5 (-1.5, 4.4)] although this did not reach statistical significance. Within the preterm group, there was evidence of a reduction in CV related to the presence of white matter injury (WMI) after adjusting for intracranial volume (ICV) [WMI grade 1 versus grade 2: mean (SD) CV, 23.6 (5.0) versus 21.6 (4.5); p = 0.01; WMI grade 1 versus grade 3 and 4: 23.6 (5.0) versus 20.8 (5.6); p = 0.07]. Within the preterm infants, there was no apparent relationship between CV at term and gestational age at birth after adjusting for ICV. At 2 y of age, CV showed a weak correlation with cognitive and motor development, although this was principally mediated by WMI. In conclusion, we found no evidence for a primary impairment in cerebellar development in relation to prematurity, although there was evidence for a secondary effect of cerebral WMI on cerebellar development independent of immaturity.

Neonatal infection and long-term neurodevelopmental outcome in the preterm infant

PURPOSE OF REVIEW

The relationship between infection, the inflammatory response and adverse neurodevelopmental outcome in preterm infants is slowly being elucidated. The developing brain, particularly the periventricular white matter, is vulnerable to cytotoxic and hypoxic/ischemic injury, which places these infants at increased risk for abnormal cognitive and motor functioning. This review summarizes current data evaluating associations between infection and neurodevelopmental outcome in the preterm infant.

RECENT FINDINGS

Preterm infants are at risk for intrauterine and postnatal infections. Recent studies have linked infection/inflammation associated with chorioamnionitis, sepsis and necrotizing enterocolitis with adverse neurodevelopmental outcome and impaired growth in preterm infants. Investigators have also shown associations between infection and brain injury, including severe intraventricular hemorrhage and periventricular leukomalacia. Very-low-birth-weight preterm infants are at substantial risk for neonatal infection, with associated morbidity and mortality. It is postulated that exposure of the preterm brain to inflammatory mediators during infectious episodes contributes to brain injury and poor developmental outcome.

SUMMARY

Enhanced understanding of the interaction of infection, inflammation and brain injury will be critical to developing strategies to improve neurodevelopmental outcome in preterm infants.

Respiratory distress syndrome-associated inflammation is related to early but not late peri/intraventricular hemorrhage in preterm infants

OBJECTIVE

To investigate whether or not peri/intraventricular hemorrhages (PIVHs) occurring in the first 12 hours of life (early PIVHs) are related to respiratory distress syndrome (RDS)-associated inflammatory factors in contrast to PIVHs developing after 12 hours of life (late PIVHs).

STUDY DESIGN

Blood samples obtained at 0 to 12 hours, 48 to 72 hours, and 168 hours of life were evaluated for determination of the proinflammatory cytokines interleukin (IL)-8 and IL-6, tumor necrosis factor (TNF)-alpha, and malondialdehyde (MDA) as measures of lipid peroxidation. Simultaneously, cranial ultrasonography was performed in 114 neonates under 32 weeks gestational age.

RESULTS

Out of the total study group of 114 neonates, 67 (59%) had RDS. Early PIVH occurred in 16 neonates, 14 of whom (88%) had RDS. Late PIVHs occurred in 12 neonates. Neonates with RDS had higher IL-8 and IL-6 levels at 0 to 12 hours (P < .0001; < .0001) and at 48 to 72 hours (P < .001; < .01) than those without RDS. Neonates with early PIVH had higher IL-8 (P < .02), IL-6 (P < .02), and MDA (P < .01) levels at 0 to 12 hours than those with late PIVH or no PIVH. Those with early PIVH had higher IL-8 levels at 48 to 72 hours than those without PIVH (P < .02). Multiple linear regression revealed an association between RDS/early PIVH and IL-8, IL-6, and MDA levels.

CONCLUSIONS

An RDS-associated increase in proinflammatory cytokine and MDA levels was associated with early PIVHs, but not with late PIVHs, suggesting a different etiopathogenesis in early versus late PIVHs.

Perinatal infections and cerebral palsy

Infections of the mother, the intrauterine environment, the fetus, and the neonate can cause cerebral palsy through a variety of mechanisms. Each of these processes is reviewed. The recently proposed theory of cytokine-induced white matter brain injury and the systemic inflammatory response syndrome with multiple organ dysfunction syndrome is critically evaluated.

The time of prenatal immune challenge determines the specificity of inflammation-mediated brain and behavioral pathology

Disturbance to early brain development is implicated in several neuropsychiatric disorders including autism, schizophrenia, and mental retardation. Epidemiological studies have indicated that the risk of developing these disorders is enhanced by prenatal maternal infection, presumably as a result of neurodevelopmental defects triggered by cytokine-related inflammatory events. Here, we demonstrate that the effects of maternal immune challenge between middle and late gestation periods in mice are dissociable in terms of fetal brain cytokine responses to maternal inflammation and the pathological consequences in brain and behavior. Specifically, the relative expression of pro- and anti-inflammatory cytokines in the fetal brains in response to maternal immune challenge may be an important determinant among other developmental factors for the precise pathological profile emerging in later life. Thus, the middle and late gestation periods correspond to two windows with differing vulnerability to adult behavioral dysfunction, brain neuropathology in early adolescence, and of the acute cytokine responses in the fetal brain.

Animal models of germinal matrix hemorrhage

Germinal matrix hemorrhage refers to bleeding that arises from the subependymal (or periventricular) germinal region of the immature brain. Clinical studies have shown that infants who experience germinal matrix hemorrhage can develop hydrocephalus or suffer from long-term neurologic dysfunction, including cerebral palsy, seizures, and learning disabilities. Understanding the causative factors and the pathogenesis of subsequent brain damage is important if germinal matrix hemorrhage is to be prevented or treated. Appropriate animal models are necessary to achieve this understanding. A number of animal species, including mice, rats, rabbits, sheep, pigs, dogs, cats, and primates, have been used to model germinal matrix hemorrhage. This literature review critically evaluates the animal models of germinal matrix hemorrhage. Each model has its own advantages and disadvantages; no single model is suitable for the study of all aspects of brain damage.

Absence of pestivirus antigen in brains with white matter damage

We previously suggested that antenatal pestivirus infection might play a role in the pathogenesis of perinatal brain white matter damage (WMD) in preterm infants. We have now examined 22 brains from stillborns and deceased newborns (both preterm and term) for the presence of bovine virus diarrhoea virus (BVDV) antigen. The brains of five females and five males with WMD (median gestational age 36.5wks), and nine female and three male controls (median gestational age 36.5wks) were used in the study. No BVDV antigen was detected in any of the 22 brains. We conclude that brain infection with BVDV is unlikely to play a role in WMD pathogenesis among preterm or term newborns. Further research is needed to test the hypothesis that intrauterine exposure to pestivirus antigen elicits a fetal inflammatory response which then contributes to WMD.

Human placenta and fetal membranes express nerve growth factor mRNA and protein

The present study investigated whether trophoblast, decidua and fetal membranes express nerve growth factor (NGF) mRNA and peptide. Tissue specimens were collected in the first and third trimester of pregnancy from women undergoing voluntary pregnancy interruption (no.= 6; from 8 to 12 gestational weeks) and from women having an elective caesarean section at term (no.= 6; week 39-40 of pregnancy). Using reverse transcriptase-polymerase chain reaction (RT-PCR), trophoblast, amnion/chorion and maternal decidua showed the expression of NGF mRNA both in early gestation and at term. By immunohistochemistry, the immunoreactive NGF was found in the cyto and syncytial trophoblast cells, chorionic mesodermic cells and in decidua. Vessel endothelial cells were stained in maternal compartments, while fetal vessels were unstained. These results, showing the expression and localization of NGF, support the current concept that human placenta is a potent neuroendocrine organ throughout gestation.

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.

Possible interactions of genetic and immuno-neuro-endocrine regulatory mechanisms in pathogenesis of congenital anomalies

The process of organogenesis depends on genetic and environmental factors. Besides genetic background, congenital anomalies can also be influenced by micro environmental changes, which are related to maternal-foetal interactions followed by the production of cytokines, hormones, neurotransmitters, growth factors and biochemical mediators, and stress proteins. Pre-natal maternal stress, including infections, psychological stress and other teratogens, can influence a disregulation of maternal immune, endocrine and nervous systems, during pregnancy. This is a crucial condition for the abnormal growth and development of the foetus. Activated maternal immune system can alter the cytokine network and make it inadequate for normal embryogenesis and organogenesis. Heat-shock proteins play an important role in stress physiology repairing DNA errors or activating pro-inflammatory response. Regarded from this aspect, the altered cytokine network suggests aetiopathogenetic basis of congenital anomalies in neonates. It is our wish to point out our potentially harmful conditions in the development of congenital anomalies, as well as their control by using pre-natal and pre-conceptional diagnostics and treatment.

The association between inherited cytokine polymorphisms and cerebral palsy

OBJECTIVE

The purpose of this study was to investigate associations between inherited cytokine polymorphisms and cerebral palsy.

STUDY DESIGN

This was a case-control study that used DNA from the newborn infant screening cards of 443 white infants with cerebral palsy and 883 white control infants to test for the following cytokine polymorphisms: tumor necrosis factor-alpha-308, mannose-binding lectin-221, and 3 polymorphisms in exon-1 of the mannose-binding lectin gene at codon-52, -54, and -57.

RESULTS

At all gestational ages mannose-binding lectin codon-54 increased the risk of the development of diplegia (homozygous or heterozygous odds ratio, 1.55; 95% CI, 1.03-2.32). For babies who were born at term, the risk of the development of quadriplegia was associated with heterozygous tumor necrosis factor-alpha (odds ratio, 1.82; 95% CI, 1.04-3.15), and mannose-binding lectin codon-54 was associated with diplegia (homozygous or heterozygous odds ratio, 2.12; 95% CI, 1.10-4.05). The presence of any polymorphism in mannose-binding lectin exon-1 at term approximately doubled the risk of the development of diplegia (odds ratio, 1.94; 95% CI, 1.05-3.62). Homozygous or heterozygous tumor necrosis factor-alpha was associated with hemiplegia for babies who were born at <32 weeks of gestation (odds ratio, 2.38; 95% CI, 1.02-5.58). Overall, the presence of any cytokine polymorphism was associated with cerebral palsy (odds ratio, 1.37; 95% CI, 1.02-1.84).

CONCLUSION

Carriage of polymorphisms in the tumor necrosis factor-alpha and mannose-binding lectin genes are associated with an increased risk of cerebral palsy.

Maternal exposure to LPS induces hypomyelination in the internal capsule and programmed cell death in the deep gray matter in newborn rats

Epidemiologic and experimental findings implicate maternal infection in the etiology of injury to brain white matter, which may lead to cerebral palsy in preterm newborns. In the present study, inflammation and brain damage in 1- and 7-d-old rats were investigated after maternal inflammation. Intraperitoneal injection of 300 microg/kg of Escherichia coli lipopolysaccharide was administered to pregnant Wistar rats at d 19 and 20 of gestation (LPS group). Control females received a saline injection. Proinflammatory cytokines IL-1beta, tumor necrosis factor-alpha, and IL-6 expression in the fetal brain were determined by reverse transcription quantitative polymerase chain reaction. Brain injury was examined in 16-mum coronal brain sections by GFAP, MBP, caspase-3 immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Expression of IL-1beta was significantly increased 3 d after maternal administration (P1). A significant increase in cell death occurred at P1 and P7 in specific brain areas, i.e. in the subventricular striatal zone at P1, and in 1) the periventricular striatum, 2) the periventricular white matter, and 3) the germinative ventricular zone at P7. We also observed typical astrogliosis and strong hypomyelination in the external and internal capsule in the LPS group at P7. These results demonstrate that maternal LPS treatment induces persistent fetal inflammatory reactions associated with significant white matter injury in progeny at P1 and P7. This model should be relevant for the study of the pathophysiological mechanisms involved in cerebral white matter damage in preterm human newborns and in the development of therapeutic strategies.

Prognosis in cervical insufficiency at less than 32 weeks of gestation

OBJECTIVE

To identify prenatal events associated with adverse outcome in babies at less than 32 weeks of gestation in cases of cervical insufficiency and preterm labor (PTL)/premature rupture of the membranes (PROM).

STUDY DESIGN

A case-control study was performed using a logistic regression model at 17 tertiary hospitals in Japan. Adverse outcome was defined as neonatal death or abnormal cerebral ultrasound scans (intraventricular hemorrhage [IVH] and periventricular leukomalacia [PVL]) prior to discharge from hospital.

RESULTS

Data were analyzed for 307 cases (74 for cervical insufficiency and 233 for PTL/PROM). Neonatal death and IVH/PVL were noted in 25 and 29 cases, respectively. A significant association of cervical insufficiency (odds ratio (OR) 1.32, 95% confidence interval (CI) 1.02-1.68), gestational age at delivery (<26 weeks) (OR 4.64, 95% CI 1.73-12.44), and Apgar score <7 at 5 min (OR 3.3, 95% CI 1.42-7.64) with combined neonatal death or IVH and PVL was found in a logistic regression model that controlled for in utero transportation, gestational age on admission, clinical chorioamnionitis, and histopathologic chorioamnionitis.

CONCLUSION

Cervical insufficiency is a significant factor related to the occurrence of adverse outcome.

Population cohort associating chorioamnionitis, cord inflammatory cytokines and neurologic outcome in very preterm, extremely low birth weight infants

Intrauterine inflammation may relate to neurologic disability among preterm children. We investigated the relationship between chorioamnionitis, cord serum cytokines, and neurologic outcome. Sixty-one consecutively born very preterm extremely low birth weight (ELBW) infants were prospectively enrolled. Histologic inflammation in placenta and umbilical cord and vascular pathology were evaluated. Cord sera were analyzed for five proinflammatory cytokines. Serial brain ultrasound and magnetic resonance imaging were performed for evaluation of intraventricular hemorrhage (IVH grade I-III) and white matter damage (WMD: cystic periventricular leukomalacia or IVH grade IV). Neurologic and neurocognitive outcomes were assessed at the corrected age of 2 y. The incidences of HCA, WMD, and abnormal neurologic outcome were 48%, 13% and 19%, respectively. HCA or high IL-6 in cord serum predicted spontaneous preterm labor with high accuracy. HCA increased the risk of IVH grade II-III. In HCA, without either clinical chorioamnionitis or histologic placental perfusion defect, the children had a low risk of WMD (0%) and a low risk of abnormal neurologic outcome (6%). In HCA, the concentration of IL-6 in cord serum was lower in children with abnormal neurologic outcome than in children with normal neurologic outcome. In HCA and placental perfusion defect (compound defect) the risk of abnormal neurologic outcome was high. Compound placental defect and WMD additively predicted abnormal neurologic outcome. We propose that HCA together with other insults (placental perfusion defect or maternal systemic infection) increases the risk of poor neurologic outcome in very preterm ELBW infants.

Dietary zinc supplementation ameliorates LPS-induced teratogenicity in mice

Maternal infection during the first trimester of pregnancy has been associated with preterm birth, spontaneous abortion, growth retardation, and congenital anomalies. Previously, our group has shown that subcutaneous injection of zinc prevents endotoxin [lipopolysaccharide (LPS)]-induced teratogenicity. The purpose of this study was to investigate whether increasing or decreasing dietary zinc alters the teratogenic effects of LPS. Female C57BL6 mice were mated and fed diets containing 5, 35, or 100 mg/kg zinc. On gestational day (GD) 8, pregnant dams were injected with either LPS (0.5 mg/kg s.c.) or saline and killed on GD18. LPS-treated fetuses from dams fed 5 and 35 mg/kg zinc diet had a significantly higher number of abnormalities per litter (2- and 1- fold saline controls, respectively) compared with those from LPS + zinc supplemented dams, which were not significantly different from the saline control groups. The beneficial effect and importance of zinc was also reflected in the larger size of fetuses (weight and crown-rump length) from the LPS + zinc-supplemented treatment group. We have demonstrated that low dietary zinc during exposure to infection (i.e. LPS) in pregnancy augments the negative impact of LPS alone, and that dietary zinc supplementation throughout pregnancy ameliorates LPS-induced teratogenicity.

Cerebral oxygenation and cerebral oxygen extraction in the preterm infant: the impact of respiratory distress syndrome

Haemodynamic factors play an important role in the etiology of cerebral lesions in preterm infants. Respiratory distress syndrome (RDS), a common problem in preterms, is strongly related with low and fluctuating arterial blood pressure. This study investigated the relation between mean arterial blood pressure (MABP), fractional cerebral oxygen saturation (ScO2) and fractional (cerebral) tissue oxygen extraction (FTOE), a measure of oxygen utilisation of the brain, during the first 72 h of life. Thirty-eight infants (gestational age < 32 week) were included, 18 with and 20 without RDS. Arterial oxygen saturation (SaO2), MABP and near infrared spectroscopy-determined ScO2 were continuously measured. FTOE was calculated as a ratio: (SaO2-ScO2)/SaO2. Gestational age and birth weight did not differ between groups, but assisted ventilation and use of inotropic drugs were more common in RDS infants (P<0.01). MABP was lower in RDS patients (P<0.05 from 12 up to 36 h after birth), but increased in both groups over time. ScO2 and FTOE were not different between groups over time, but in RDS infants ScO2 and FTOE had substantial larger variance (P<0.05 at all time points except at 36-48 h for ScO2 and P<0.05 at 12-18, 18-24, 36-48 and 48-60 h for FTOE). During the first 72 h of life, RDS infants showed more periods of positive correlation between MABP and ScO2 (P<0.05 at 18-24, 24-36 36-48 48-60 h) and negative correlation between MABP and FTOE (P<0.05 at 18-24, 36-48 h). Although we found that the patterns of cerebral oxygenation and extraction in RDS infants were not different as compared to infants without RDS, we suggest that the frequent periods with possible lack of cerebral autoregulation in RDS infants may make these infants more vulnerable to cerebral damage.

Long-term changes in blood-brain barrier permeability and white matter following prolonged systemic inflammation in early development in the rat

Epidemiological evidence in human fetuses links inflammation during development with white matter damage. Breakdown of the blood-brain barrier has been proposed as a possible mechanism. This was investigated in the present study by inducing a prolonged inflammatory response in newborn rats, with intraperitoneal injections of lipopolysaccharide (LPS; 0.2 mg/kg) given at postnatal (P) day 0, P2, P4, P6 and P8. An acute phase response was present over the whole period of injections. Changes in blood-brain barrier permeability were determined for small (sucrose and inulin) and large (protein) molecules. During and immediately after the inflammatory response, plasma proteins were detected in the brain only within white matter tracts, indicating an increased permeability of the blood-brain barrier to protein during this period. The alteration in permeability to protein was transient. In contrast, the permeability of the blood-brain barrier to 14C-sucrose and 14C-inulin was significantly higher in adult animals that had received serial LPS injections during development. Adult animals receiving a single 1 mg/kg LPS injection at P0 showed no alteration in blood-brain barrier permeability to either small or larger molecules. A significant decrease in the volume of CNPase immunoreactive presumptive white matter tracts occurred in the external capsule and corpus callosum at P9. These results demonstrate that a prolonged systemic inflammatory response in the early postnatal period in rats causes size selective increases in blood-brain barrier permeability at different stages of brain development and results in changes in white matter volume.

Onset of mechanical ventilation is associated with rapid activation of circulating phagocytes in preterm infants

OBJECTIVE

In preterm infants with respiratory distress syndrome (RDS), circulating neutrophils are activated. Kinetics and effects of surfactant therapy on this activation are unknown. Therefore, we studied activation of circulating neutrophils and monocytes in newborn preterm infants with and without RDS.

PATIENTS AND METHODS

Preterm infants with RDS who were mechanically ventilated and received surfactant ("ventilated infants": n = 38; mean gestational age +/- SD: 28.3 +/- 2.2 weeks; mean birth weight +/- SD: 1086 +/- 353 g) and preterm infants who received nasal continuous positive airway pressure (n = 8) or no ventilatory support (n = 17) ("control infants": mean gestational age +/- SD: 32.1 +/- 1.2 weeks; mean birth weight +/- SD: 1787 +/- 457 g) were recruited. Blood samples were taken from ventilated infants at birth, before surfactant treatment, at 1 and 2 hours after surfactant, and at 12 to 24 hours of age. Blood samples were taken from control infants at birth, at 2 to 6 hours, and at 12 to 24 hours of age. Phagocyte CD11b expression was analyzed by flow cytometry.

RESULTS

In ventilated infants, phagocyte CD11b expression increased from birth to the first postnatal samples. It increased further by 12 to 24 hours of age. Control infants with or without nasal continuous positive airway pressure showed no significant increase after birth. At 12 to 24 hours of age, phagocyte CD11b expression was higher in ventilated infants than in control infants. In ventilated infants, neutrophil CD11b expression at 1 and 2 hours after surfactant correlated positively with gestational age.

CONCLUSIONS

In preterm infants with RDS, significant activation of circulating phagocytes occurs within 1 to 3 hours of the onset of mechanical ventilation, independent of surfactant administration, which indicates that mechanical ventilation may be the inducer of this systemic inflammatory response.

Lipopolysaccharide-binding protein in noninfected neonates and those with suspected early-onset bacterial infection

OBJECTIVES

To investigate postnatal lipopolysaccharide-binding protein (LBP) kinetics in term neonates and to test its diagnostic accuracy for early-onset bacterial infection (EOBI).

STUDY DESIGN

A total of 99 neonates with clinical and serological signs of EOBI comprised the study group; 198 neonates with risk factors, but without EOBI, served as controls. LBP, C-reactive protein (CRP) and interleukin-8 (IL-8) were determined.

RESULTS

LBP in the noninfected group increased until 24 h after birth (P < 0.05 vs 6 h). LBP and CRP correlated strongly in neonates with suspected EOBI (r = 0.63). Although LBP reached a higher sensitivity than CRP 6 and 12 h after clinical suspicion (45 (24-68) and 79% (54-94) vs 9 (0-24) and 39% (17-64); P < 0.05)), EOBI was most reliably detected by IL-8.

CONCLUSION

LBP kinetics were age-dependent. LBP was not sufficiently sensitive in the prediction of EOBI.

Variability in cerebral oxygen delivery is reduced in premature neonates exposed to chorioamnionitis

Premature infants exposed to chorioamnionitis are at increased risk for periventricular leukomalacia (PVL) and intraventricular hemorrhage (IVH), lesions that may result from inflammation and/or fluctuations in cerebral blood flow. The effect of chorioamnionitis on near-infrared spectroscopy (NIRS) measures of cerebral oxygen delivery has not been evaluated previously. Forty-nine infants born at 25-31 6/7 wk gestation underwent NIRS examination on d 1, 2, 3, and 7 of life. Variability in NIRS tracings was analyzed by partitioning each tracing into three components: long-term, intermediate, and short-term variability; the latter two components were analyzed. Chorioamnionitis-exposed infants manifest reduced intermediate variability in cerebral oxygenated and deoxygenated Hb but not total Hb. Infants with severe IVH/PVL had the lowest intermediate variability on d 1. Short-term variability was similar between chorioamnionitis-exposed and unexposed infants, and between infants with versus without severe IVH or PVL. We conclude that intermediate-term variability in NIRS cerebral oxygen delivery is reduced in chorioamnionitis-exposed infants. We speculate that intermediate variability represents the important time frame for evaluating the pathogenesis of perinatal brain injury. Further studies are needed to determine how these findings relate to cerebral blood flow autoregulation and oxygen utilization in premature infants.

Expression and Subcellular Localization of TLR-4 in Term and First Trimester Human Placenta

Toll-like receptor 4 (TLR-4) mediates Gram-negative bacterial-induced inflammatory responses, including production of pro-inflammatory cytokines. Maternal infection and inflammation play an important role in preterm birth and neonatal brain damage. The localization of placental TLR-4 as well as changes during normal gestation are critical issues in understanding the role of toll-like receptors in defending the placento-fetal unit from maternal infection. We therefore investigated, by immunohistochemistry (IHC) and Western blot, the subcellular localization of TLR-4 in first trimester and term human placenta. In both term placenta (n=4) and first trimester placenta villous samples (n=5), immunoreactivity for TLR-4 was found in the cytoplasm of the syncytiotrophoblast, with darker staining in some areas of the maternal facing plasma membrane (MVM). In addition, TLR-4 was found to be expressed in the first trimester cytotrophoblast cells. Using Western blot analysis, TLR-4 was identified in both placental homogenates and isolated MVM and the fetal facing basal membrane (BM). TLR-4 expression in MVM was significantly higher in term (n=9) as compared to first trimester (n=2) samples. We have shown for the first time that the subcellular localization of TLR-4 in term placenta is preferentially in the MVM compared to BM. The MVM is continuously bathed in maternal blood, suggesting that from this vantage point TLR-4 can initiate a rapid response to maternal bacterial infection.

The adaptive immune response in neonatal cerebral white matter damage

Hypotheses that inflammation contributes to neonatal cerebral white matter damage have evolved over the last three decades. The latest, expanded here, suggests that the adaptive immune system contributes to the intensity and duration of the processes that result in damage to cerebral white matter in the fetus and newborn. We propose several mechanisms by which fetal T lymphocytes could be activated during fetal exposure to infection. These include specific recognition of bacterial antigens, specific recognition of autoantigens, polyclonal activation by Toll-like receptors, and bystander activation by cytokines.

Neurotropic viruses and cerebral palsy: population based case-control study

OBJECTIVE

To investigate the association between cerebral palsy and direct evidence for perinatal exposure to neurotropic viruses.

DESIGN

Population based case-control study.

SETTING

Adelaide Women's and Children's Hospital Research Laboratory.

PARTICIPANTS AND MAIN OUTCOME MEASURES

Newborn screening cards of 443 white case patients with cerebral palsy and 883 white controls were tested for viral nucleic acids from enteroviruses and herpes viruses by using polymerase chain reaction. Herpes group A viruses included herpes simplex viruses 1 and 2 (HSV-1 and HSV-2), Epstein-Barr virus (EBV), cytomegalovirus (CMV), and human herpes virus 8 (HHV-8), and herpes group B viruses included varicella zoster virus (VZV) and human herpes viruses 6 and 7 (HHV-6 and HHV-7).

RESULTS

The prevalence of viral nucleic acids in the control population was high: 39.8% of controls tested positive, and the prevalence was highest in preterm babies. The detection of herpes group B viral nucleic acids increased the risk of developing cerebral palsy (odds ratio 1.68, 95% confidence interval 1.09 to 2.59).

CONCLUSIONS

Perinatal exposure to neurotropic viruses is associated with preterm delivery and cerebral palsy.

Activation of NF-κB transcription factor in the preterm ovine brain and placenta after acute LPS exposure

Intrauterine infection may be causally related to inflammation and injury of the fetal brain, however the mechanisms by which this occurs are unclear. We have investigated whether nuclear factor (NF)-kappaB, a transcription factor for proinflammatory cytokines, is activated in the fetal brain after acute LPS-exposure. At 95 days of gestation (term = approximately 147 days), 5 fetuses received a single intravenous bolus dose of LPS (1 microg/kg); 6 fetuses served as controls. Fetal blood samples were taken hourly for 6 hr post LPS-exposure to assess physiological status. Ewes and fetuses were then euthanased, placental and brain tissue examined histologically, and NF-kappaB activation assessed in several regions of the fetal brain using an electromobility shift assay (EMSA). Oxidative stress was measured using lipid peroxidation and 8-isoprostane biochemical assays and brain cytokine concentrations analysed by enzyme linked immunosorbent assay (ELISA). LPS-exposed fetuses (relative to controls) were hypoxemic and the haematocrit and lactate levels had increased. In the brains of LPS-exposed fetuses compared to controls, NF-kappaB binding activity was elevated in the hippocampus and the thalamus/basal ganglia; 8-isoprostane levels were elevated overall (P < 0.05) in the parietal/occipital/temporal lobes and thalamus/basal ganglia. TNF-alpha and IL-6 concentrations were not elevated, however, there was a tendency for an elevation of IFN-gamma concentrations in the thalamus/basal ganglia. IFN-gamma concentration was elevated (P < 0.05) in the plasma 4 hr after LPS-exposure. In the placenta, NF-kappaB binding activity was increased (P < 0.05). We conclude that acute systemic administration of LPS leads to increased binding activity of NF-kappaB subunits in specific regions of the fetal brain and in the placenta, but that there is no clear-cut relationship between this elevation and vulnerability to endotoxic damage.

Elucidating the early signal transduction pathways leading to fetal brain injury in preterm birth

Adverse neurologic outcome, including cerebral palsy, is a significant contributor to long-term morbidity in preterm neonates. However, the mechanisms leading to brain injury in the setting of a preterm birth are poorly understood. In the last decade, there has been a growing body of evidence correlating infection or inflammation with preterm birth. The presence of intrauterine inflammation significantly increases the risk for adverse neurologic outcome in the neonate. These studies were performed to elucidate the early signal transduction pathways activated in the fetal brain that may result in long-term neurologic injury. Using our mouse model of localized intrauterine inflammation, the activation of TH1/TH2 pathways in the placenta, fetus corpus, fetal liver, and fetal brain was investigated. Additional studies determined whether activation of TH1/TH2 pathways could promote cell death and alter glial development. Real-time PCR studies demonstrated that a robust TH1/TH2 response occurs rapidly in the fetal brain after exposure to intrauterine inflammation. The cytokine response in the fetus and placenta was not significantly correlated with the response in the fetal brain. Along with an immune response, cell death pathways were activated early in the fetal brain in response to intrauterine LPS. Implicating TH1/TH2 and cell death pathways in permanent brain injury are our findings of an increase in GFAP mRNA and protein as well as a loss of pro-oligodendrocytes. With increased understanding of the mechanisms by which inflammation promotes brain injury in the preterm neonate, identification of potential targets to limit adverse neonatal outcomes becomes possible.

Neonatal morbidity and placental pathology

OBJECTIVE

To investigate the association between gestational age, placental pathology and outcome among preterm births.

METHODS

Medical records and placental pathology results of 165 preterm infants (gestational age pound 34 weeks) were used to analyze the development of intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), patent ductus arteriosus (PDA) and sepsis, in association with placental findings in the gestational age categories of 22-27 (n=71) and 28-33 (n=93) weeks.

RESULTS

Significant differences were found in placental findings based on gestational age and neonatal morbidity. Lower gestational age was associated with increased infection-related lesions such as chorionic vasculitis (47.9%, P< 0.001) and acute chorioamnionitis (67.6%, P< 0.001). Placental lesions reflecting disturbances of fetal-placental blood flow (infarction, chorionic plate thrombi and basal perivillous fibrin) were predominantly seen in the 28-33 week gestational age category (P< 0.05-0.01). Despite the high prevalence of chorioamnionitis (38.8%), no significant association was found between this lesion and the tested preterm morbidity after controlling for gestational age. Only, villous edema and chorionic vasculitis were identified as independent predictors for the development of IVH (49.2%, ORA 2.57, 95% CI 1.01, 6.58 and 39.3%, ORA1.95, 95% CI 1.01, 4.21, respectively).

CONCLUSION

Villous edema and chorionic vasculitis are significant risk factors for the development of the IVH among neonates born at gestational age pound 34 weeks.

Endotoxin-induced hypoxic-ischemic tolerance is mediated by up-regulation of corticosterone in neonatal rat

Previous studies suggest that the endotoxin lipopolysaccharide (LPS) may have dual effects on brain damage induced by hypoxia-ischemia (HI) in 7-d-old rats, depending on the exposure paradigm. Although a 4-h interval between LPS administration and HI results in sensitization to HI brain injury, tolerance is observed when LPS is administered 24 h before HI. Our hypothesis is that endogenous corticosteroids are important in acquiring tolerance to HI. Neonatal rats received a single injection of LPS (1.0 mg/kg) either 4 h or 24 h before HI, or two LPS injections (4 h and 24 h) before HI. Increased brain injury was seen in animals subjected to a single LPS injection made 4 h before HI. In contrast, both the single 24-h exposure and the double injections of LPS resulted in tolerance to HI brain damage. To study the effects of corticosteroids on HI tolerance, RU486, a glucocorticoid receptor blocker, was subcutaneously injected at the same time as LPS (1.0 mg/kg), 24 h before HI stress. RU486-LPS treatment counteracted the LPS-induced tolerance effect, and aggravated the HI-induced brain injury compared with the vehicle-LPS-treated group. RU486 did not aggravate the HI-induced brain injury produced 24 h later in saline-injected animals. LPS (1.0 mg/kg) injected into 6-d-old rats transiently up-regulated serum corticosterone levels (119.6, 57.9, 56.8, and 28.3 ng/mL at 6, 12, 24, and 48 h after the LPS injection, respectively). We conclude that endotoxin-induced up-regulation of endogenous corticosterone appears to be critical for acquiring endotoxin-induced HI tolerance.

White matter damage and chemokine induction in developing rat brain after intrauterine infection

In order to investigate the neuropathological effects on the developing rat brain after intrauterine infection, identification of glail fibrillary acidic protein (GFAP), 2', 3'-cyclic nucleotide phosphodiesterase (CNPase), and neurofilament (NF) was observed. Escherichia coli (E. coli) was inoculated into uterine horn of pregnant rats when gestation was 70% complete (15 days) and the control group was inoculated with normal saline. Immunohistochemistry was used for evaluation of GFAP, CNPase, and NF expression in pup brains at postnatal day 7 (P7) and reverse transcriptase-PCR (RT-PCR) to analyze macrophage inflammatory protein-1 alpha mRNA (MIP-1 alpha mRNA), macrophage inflammatory protein-1 beta mRNA (MIP-1beta mRNA), the regulated upon activation normal T expressed and secreted chemokine mRNA (RANTES mRNA) and Eotaxin mRNA expression in pup brains at P1, P3 and P7. The numbers of GFAP-positive cells of the E. coli-treated group pups were marked increased in periventricular white matter and hippocampus at P7 compared with the control group but no significant different levels of GFAP expression in corpus callosum were found between two groups. The integrate density (ID) of CNPase-positive staining of the Escherichia coli-treated group pups were marked decreased in periventricular white matter and corpus callosum at P7 compared with the control group. The ID of NF-positive staining of the Escherichia coli-treated group pups were marked decreased in periventricular white matter at P7 compared with the control group and no significant different levels of NF expression in corpus callosum were found between two groups. The expression of MIP-1 alpha mRNA and MIP-1 beta mRNA in brain of the E. coli-treated pup rat were higher than the control at P1, but the expression of MIP-1 alpha mRNA and MIP-1 beta mRNA in brain of the pup rat at P3 and P7 had no significant difference between two groups. The alteration of expression of GFAP, CNPase, and NF in the brain of neonatal rats after intrauterine infection suggested that intrauterine infection could cause neonatal white matter damage. Moreover, the transient increase in expression of chemokine such as MIP-1 alpha, MIP-1 beta in neonatal brain after intrauterine infection indicated that MIP-1 alpha, MIP-1 beta may be a mechanism mediating between the neonatal white matter damage and the intrauterine infection.

Prenatal ischemia and white matter damage in rats

Ischemia/reperfusion injury to the developing brain is a major cause of neurologic abnormalities in preterm infants. To investigate the underlying mechanisms, we modified a previously described rat model of unilateral uterine-artery ligation on the 17th embryonic day (E17). Growth retardation was taken as an index of in utero ischemia, and pups born with a birth weight more than 2 standard deviations below that of controls were compared with the same-litter, normal-growth control pups born from the nonligated horn. Prenatal ischemia probably associated with hypoxia and followed by reperfusion at birth induced white matter damage at a developmental stage corresponding to extreme prematurity in humans. On P0 (day of birth), growth-retarded pups exhibited lesions in the cingular white matter and internal capsule with increased counts of activated microglial cells for 2 weeks compared with controls. Astrogliosis was detected in the injured white matter. On P3, increased apoptotic cell death was seen in O4-positive preoligodendrocytes, which were abnormally scarce on P7. Defective myelination, as assessed by myelin-binding-protein labeling, was detected until adulthood. The diffuse white matter damage in growth-retarded rats replicated the main features of white matter damage in human preterm infants.

Maturational effects of lipopolysaccharide on white-matter injury in fetal sheep

White-matter damage has been associated with the development of cerebral palsy in children born both prematurely and at term, and it has been suggested that intrauterine infection can contribute to the brain injury. However, the relative importance of age on white-matter injury following infectious exposure in utero remains unclear. In this study, fetal sheep were exposed to systemic endotoxemia by administration of Escherichia coli lipopolysaccharide (88.7 +/- 7.7 ng/kg) at 65% or 85% of gestation. These gestational ages approximately correspond to human brain development in preterm and near-term infants respectively. White-matter injury was evaluated 3 days after lipopolysaccharide exposure with regard to microglia activation and loss of neurofilament and myelin basic protein. The expression of oligodendrocytes at different maturational stages was demonstrated in preterm and near-term fetuses with the oligodendroglial markers O4 and 2 ,3 -cyclic nucleotide 3 -phospodiesterase. Forty percent of the fetuses in the preterm group and 22% in the near-term group died within 8 hours of the endotoxin exposure. Three of six preterm and two of seven near-term surviving fetuses demonstrated pathologic changes in the brain with regard to increased microglia activation and loss of neurofilament staining. The number of activated microglia was enhanced in the subcortical white matter in both the preterm lipopolysaccharide-exposed fetuses (lipopolysaccharide: 235 +/- 64 cells/mm2; control: 72 +/- 28 cells/mm2; P = .0374) and the near-term fetuses (lipopolysaccharide: 180 +/- 40 cells/mm2; control 23 +/- 16 cells/mm2; P = .0152). There was a loss of neurofilament staining in both preterm fetuses (lipopolysaccharide: 2.20 +/- 0.77 pixel units; control: 0.20 +/- 0.10 pixel units; P = .0306) and near-term fetuses (lipopolysaccharide: 1.15 +/- 0.48 pixel units; control: 0.06 +/- 0.06 pixel units; P = .0285). O4-positive cells were detected at both gestational ages, whereas 2,3-cyclic nucleotide 3-phospodiesterase-positive cells and myelin basic protein staining were mainly detected in the near-term fetuses. In summary, we found white-matter injury in a proportion of both preterm and near-term fetuses after administration of lipopolysaccharide. These results are in agreement with clinical evidence suggesting that both preterm and term infants are at risk of periventricular leukomalacia in association with intrauterine infection.

Histological chorioamnionitis and the risk of early intraventricular hemorrhage in infants born < or =28 weeks gestation

OBJECTIVE

To test the hypothesis that histological chorioamnionitis (CA) is not associated with increased risk of early onset intraventricular hemorrhage (IVH).

STUDY DESIGN

Clinical data were prospectively collected for 62 consecutive neonates born before 28 weeks of gestation. Placental histology for CA was performed by a pathologist unaware of the head ultrasound scan (HUS) results. The first HUS was obtained by 30 minutes of life. Follow-up HUS were performed before 24 hours and again at 48 to 72 postnatal hours of life. An IVH (grade I to IV) at less than 72 hours of life was deemed an early hemorrhage.

RESULTS

Nine of the 62 (14.5%) infants had early onset IVH. In all, 29 infants were born to women with histological evidence of CA; 33 infants did not have CA. Infants did not differ in birth weight, gestational age, sex, cord blood pH, 5-minute Apgar score of <7, cesarean delivery, prenatal use of steroids, administration of tocolytics, need for resuscitation, presence of pneumothorax, platelet count at birth, or use of surfactant. Early IVH rates (3/29 in CA vs 6/33 in non-CA) were similar (p=0.48). Two infants in each group with early IVH died before 2 weeks of age. Five additional infants from the CA group developed IVH at more than 72 postnatal hours of life (late onset IVH), and two of those infants progressed to develop periventricular leukomalacia (PVL). In contrast, only three non-CA infants had late IVH and none developed PVL. Logistic regression confirmed that no perinatal variables including CA were associated with early onset IVH.

CONCLUSION

Chorioamnionitis is not associated with increased risk of early IVH.

Circulating interferon-gamma and white matter brain damage in preterm infants

The fetal inflammatory response has been suggested as causal in neonatal morbidity. Serial levels of circulating cytokines were evaluated in 74 infants with a mean gestational age (GA) of 27.1 wk. Pro-inflammatory [tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-1 beta, IL-2, IL-6, IL-8, IL-12] [corrected] and modulatory (IL-4, IL-10) cytokines were analyzed from cord blood, and at 6, 24 [corrected] and 72 h postnatal age. Measure of cytokine burden over time was assessed by calculating the area under curve (AUC) for analyzed levels (0-72 h). Premature rupture of membranes (PROM) was associated with higher levels of IL-2 at birth and at 6 h, of IFN-gamma at 6 and 24 h postnatal age and of TNF-alpha at 6 and 24 h. Levels of IFN-gamma at 6, 24, and 72 h were increased in infants developing white matter brain damage (WMD) compared with those without WMD. Infants with arterial hypotension requiring dopamine treatment had an increase in IL-6 with a peak at 6 h of age. Severe intraventricular hemorrhage (IVH) was associated with increase in AUC [(IL-6) and (IL-8), odds ratio (OR) 2.8 and 13.2 respectively], whereas white matter brain damage (WMD) [corrected] was associated with increase in AUC (IFN-gamma; OR, 26.0) [corrected] A fetal immune response with increased postnatal levels of IFN-gamma was associated with development of WMD. PROM was associated with a T-helper 1 cytokine response with increased levels of IFN-gamma. Type of inflammatory response appears of importance for subsequent morbidity.

Apoptosis in perinatal hypoxic-ischemic brain injury: how important is it and should it be inhibited?

The discovery of safe and effective therapies for perinatal hypoxia-ischemia (HI) and stroke remains an unmet goal of perinatal medicine. Hypothermia and antioxidants such as allopurinol are currently under investigation as treatments for neonatal HI. Drugs targeting apoptotic mechanisms are currently being studied in adult diseases such as cancer, stroke, and trauma and have been proposed as potential therapies for perinatal HI and stroke. Before developing antiapoptosis therapies for perinatal brain injury, we must determine whether this form of cell death plays an important role in these injuries and if the inhibition of these pathways promotes more benefit than harm. This review summarizes current evidence for apoptotic mechanisms in perinatal brain injury and addresses issues pertinent to the development of antiapoptosis therapies for perinatal HI and stroke.

Simultaneous Measurement of 25 Inflammatory Markers and Neurotrophins in Neonatal Dried Blood Spots by Immunoassay with xMAP Technology

Background: Inflammatory reactions and other events in early life may be part of the etiology of late-onset diseases, including cerebral palsy, autism, and type 1 diabetes. Most neonatal screening programs for congenital disorders are based on analysis of dried blood spot samples (DBSS), and stored residual DBSS constitute a valuable resource for research into the etiology of these diseases. The small amount of blood available, however, limits the number of analytes that can be determined by traditional immunoassay methodologies.

Methods: We used new multiplexed sandwich immunoassays based on flowmetric Luminex® xMAP technology to measure inflammatory markers and neutrophins in DBSS.

Results: The high-capacity 25-plex multianalyte method measured 23 inflammatory and trophic cytokines, triggering receptor expressed on myeloid cells-1 (TREM-1), and C-reactive protein in two 3.2-mm punches from DBSS. It also measured 26 cytokines and TREM-1 in serum. Standards Recovery in the 25-plex method were 90%–161% (mean, 105%). The low end of the working range for all 25 analytes covered concentrations found in DBSS from healthy newborns. Mean recovery of exogenous analytes added at physiologic concentrations in DBSS models was 174%, mean intra- and interassay CVs were 6.2% and 16%, respectively, and the mean correlation between added and measured analytes was r2 = 0.91. In DBSS routinely collected on days 5–7 from 8 newborns with documented inflammatory reactions at birth, the method detected significantly changed concentrations of inflammatory cytokines. Measurements on DBSS stored at −24 °C for &gt;20 years showed that most cytokines are detectable in equal concentrations over time.

Conclusions: The method can reliably measure 25 inflammatory markers and growth factors in DBSS. It has a large potential for high-capacity analysis of DBSS in epidemiologic case–control studies and, with further refinements, in neonatal screening.

Immune pre-activation exacerbates hemorrhagic brain injury in immature mouse brain

Premature infants with placental infection and adult stroke patients with fever have worse outcomes following intracerebral hemorrhage (ICH). We hypothesized that immune pre-activation would aggravate brain injury in mouse brain following ICH. The immune system of 2-day, 10-day and 7-week young adult CD1 mice was stimulated by intraperitoneal injection of concanavalin A (ConA), lipopolysaccharide (LPS) or polyinosinic-polycytidilic acid (PolyI:C) 12 h prior to intracerebral injection of blood. Two days later, brain damage and inflammation were worse in 2-day mice that had received LPS. The other agents had less consistent effects in 2-day mice. Brain damage in young adults was aggravated less after immune stimulation. These data suggest that immune pre-activation modifies hemorrhagic brain injury in immature mouse brain.

Maternal infection and adverse fetal and neonatal outcomes

Adverse pregnancy outcomes can follow direct placental, fetal, or neonatal infection, or preterm birth associated with vaginal, cervical, intrauterine, or even nonpelvic infections. These latter infections appear to be associated with the majority of very early preterm births, and may explain some of the long-term neurologic damage associated with preterm birth. Bacterial vaginosis and its associated intrauterine infections likely contribute far more to the overall burden of adverse pregnancy outcomes than the more classical perinatal infections such as rubella and syphilis.

Fetal and neonatal origins of altered brain development

Abnormal development of the brain during fetal life is now thought to contribute to the aetiology of many neurological disorders that manifest throughout life. Many factors are likely to underlie such abnormal development including genetic makeup and an adverse intrauterine environment. This review will focus on prenatal hypoxic/ischaemic injury, inflammatory/infective insults and preterm birth. A range of experimental models have been used to characterize lesions formed in response to these insults and to determine mechanisms of damage resulting from such events. Relatively brief periods of fetal hypoxia result in neuronal death (cerebellum, hippocampus, and cerebral cortex), white matter damage and reduced growth of neural processes. These effects are more profound at mid than late gestation. Chronic mild placental insufficiency can result in fetal growth restriction and deficits in neural connectivity and myelination. Exposure of the preterm fetus to inflammatory agents causes brain damage particularly in the white matter and this is exacerbated by hypoxia. Premature birth without potentiating factors can result in subtle neuropathologies including cerebral white matter gliosis, hippocampal sclerosis and subarachnoid haemorrhage; the extent of the damage appears to be related to the regimen of ventilatory support. These studies show that the timing, severity and nature of specific insults are critical in determining the pattern of injury and thus the extent to which neurological function will be affected postnatally. Defining the causes, patterns and mechanisms of brain injury is crucial if we are to develop rational neuroprotective strategies to reduce the burden of altered brain growth and poor functional and behavioural outcomes.

Investigation of cerebral development and injury in the prematurely born primate by magnetic resonance imaging and histopathology

We summarize the preliminary results of brain histopathology and magnetic resonance imaging applied to a premature baboon model developed for evaluation of the pathogenesis and treatment of bronchopulmonary dysplasia. Cerebral development was assessed in 10 gestational control animals at time points of 125, 140 and 160 days of gestation (dg). On the basis of histopathology, conventional MRI and diffusion MRI, 125 dg is equivalent to 26-28 weeks of human gestation, 140 dg is equivalent to 30-32 weeks, and 160 dg is equivalent to term. Preliminary data are also presented for 33 experimental cases delivered at 125 dg, nursed for 2 weeks in an intensive care facility, and sacrificed at 139-140 dg. The commonest neuropathology in this cohort is white matter damage, manifest by reactive astrogliosis or activated microglia, and enlarged ventricular size. Subarachnoid, germinal matrix and intraventricular hemorrhages are also common. These preliminary results support the similarity of this model to the human preterm infant for both cerebral development and the pattern of cerebral injury. The prematurely born baboon appears an important model for the study of preterm human birth.

Cytotoxicant-induced trophoblast dysfunction and abnormal pregnancy outcomes: role of zinc and metallothionein

Normal trophoblast function, including implantation, hormone production, and formation of the selectively permeable maternofetal barrier, is essential for the establishment and maintenance of the fetoplacental unit and proper fetal development. Maternal cytotoxicant exposure causes the destruction of these cells, especially the terminally differentiated syncytiotrophoblasts, and results in a myriad of poor pregnancy outcomes. These outcomes range from intrauterine growth retardation and malformation to spontaneous abortion or stillbirth. There is recent evidence that the metal-binding protein, metallothionein, is involved in the protection of human trophoblastic cells from heavy metal-induced and severe oxidative stress-induced apoptosis. Metallothionein, with its unique biochemical structure, can both bind essential metal ions, such as the transcription modulator zinc, and yet allow their ready displacement by toxic nonessential metal ions or damaging free radicals. These properties suggest that metallothionein may be responsible not only for sequestering the cytotoxic agents, but also for altering signal transduction in the affected cells. Here, we review several identified causes of adverse pregnancy outcomes (specifically, prenatal exposure to cigarette smoke and alcohol, gestational infection, and exposure to environmental contaminants), discuss the role of zinc in modulating the cellular response to these toxic insults, and then propose how metallothionein may function to mediate this protective response.

Effect of tumor necrosis factor-alpha on developing optic nerve oligodendrocytes in culture

There is increasing evidence that proinflammatory cytokines are involved in the development of periventricular leukomalacia (PVL), a condition in which developing oliodendrocytes (OLs) are preferentially injured. In the present study, we utilized an in vitro assay to demonstrate that the A2B5+ OL progenitors as well as the O4+ prooligodendrocytes (pro-OLs) were more susceptible to tumor necrosis factor-alpha (TNF-alpha) cytotoxicity than the O4+/O1+ immature OLs. OL progenitors were isolated from optic nerves of 7-day-old rat pups and cultured in chemically defined medium supplemented with platelet-derived growth factor and basic fibroblast growth factor. OL progenitors were allowed to differentiate into pro-OLs and immature OLs under special cultural conditions. Cells at three different developmental stages were subjected to TNF-alpha treatment. Cell death, presumably by apoptosis as evidenced by TUNEL staining and caspase-3 activation, was observed following TNF-alpha treatment. Corresponding to TNF-alpha-induced apoptosis, cell survival rate decreased in a time- and dose-dependent manner. The sensitivity of different OL developmental stages to TNF-alpha decreased with the progression of cell maturation. However, this differential response was not related to differentially expressed TNF-alpha receptors. Consistent with reports that progenitor cells are preferentially injured in PVL, our results may further support the role of TNF-alpha as a potential mediator of PVL.

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.

Neonatal antecedents for cerebral palsy in extremely preterm babies and interaction with maternal factors

BACKGROUND

Preterm delivery is associated with an increased risk of cerebral palsy (CP). The greatest risk is for infants born <28 weeks' gestation.

AIMS

To identify significant neonatal risk factors for CP and explore the interactions between antenatal and neonatal risk factors, among extremely preterm infants of 27 weeks' gestation or less.

STUDY DESIGN

Nested case control design.

METHODS

Infants born between 1989 and 1996, at 24-27 weeks' gestation, were evaluated: 30 with CP at 2 years corrected age and 120 control infants matched for gestation age. Neonatal variables were compared using matched analyses with the interaction between antenatal and neonatal factors being examined using logistic regression analyses.

RESULTS

Risk factors for CP on matched analyses included patent ductus arteriosus requiring surgical ligation, peri-intraventricular haemorrhage, moderate to severe ventricular dilatation, periventricular leukomalacia (PVL) and need for home oxygen. Independent neonatal predictors were ventricular dilatation (OR 7.3; 95% CI 1.6, 32.3), PVL (OR 29.8; 95% CI 5.6, 159.1) and home oxygen use (OR 3.4; 95% CI 1.2, 9.4). No interaction terms in the logistic models were significant between the previously identified pregnancy risk factors of absence of antenatal steroids and intrauterine growth restriction and the neonatal risk factors.

CONCLUSIONS

PVL is the most powerful independent predictor of CP in extremely preterm infants of 27 weeks' gestation or less and appears to be uninfluenced by antenatal factors.

Preterm premature rupture of membranes: diagnosis, evaluation and management strategies

Preterm premature rupture of the membranes (PPROM) is responsible for one-third of all preterm births and affects 120,000 pregnancies in the United States each year. Effective treatment relies on accurate diagnosis and is gestational age dependent. The diagnosis of PPROM is made by a combination of clinical suspicion, patient history and some simple tests. PPROM is associated with significant maternal and neonatal morbidity and mortality from infection, umbilical cord compression, placental abruption and preterm birth. Subclinical intrauterine infection has been implicated as a major aetiological factor in the pathogenesis and subsequent maternal and neonatal morbidity associated with PPROM. The frequency of positive cultures obtained by transabdominal amniocentesis at the time of presentation with PPROM in the absence of labour is 25-40%. The majority of amniotic fluid infection in the setting of PPROM does not produce the signs and symptoms traditionally used as diagnostic criteria for clinical chorioamnionitis. Any evidence of infection by amniocentesis should be considered carefully as an indication for delivery. Documentation of amniotic fluid infection in women who present with PPROM enables us to triage our therapeutic decision making rationally. In PPROM, the optimal interval for delivery occurs when the risks of immaturity are outweighed by the risks of pregnancy prolongation (infection, abruption and cord accident). Lung maturity assessment may be a useful guide when planning delivery in the 32- to 34-week interval. A gestational age approach to therapy is important and should be adjusted for each hospital's neonatal intensive care unit. Antenatal antibiotics and corticosteroid therapies have clear benefits and should be offered to all women without contraindications. During conservative management, women should be monitored closely for placental abruption, infection, labour and a non-reassuring fetal status. Women with PPROM after 32 weeks of gestation should be considered for delivery, and after 34 weeks the benefits of delivery clearly outweigh the risks.

Breakdown of the blood-brain barrier to proteins in white matter of the developing brain following systemic inflammation

Compromised blood-brain barrier permeability resulting from systemic inflammation has been implicated as a possible cause of brain damage in fetuses and newborns and may underlie white matter damage later in life. Rats at postnatal day (P) 0, P8 and P20 and opossums (Monodelphis domestica) at P15, P20, P35, P50 and P60 and adults of both species were injected intraperitoneally with 0.2-10 mg/kg body weight of 055:B5 lipopolysaccharide. An acute-phase response occurred in all animals. A change in the permeability of the blood-brain barrier to plasma proteins during a restricted period of postnatal development in both species was determined immunocytochemically by the presence of proteins surrounding cerebral blood vessels and in brain parenchyma. Blood vessels in white matter, but not grey matter, became transiently permeable to proteins between 10 and 24 h after lipopolysaccharide injection in P0 and P8 rats and P35-P60 opossums. Brains of Monodelphis younger than P35, rats older than P20 and adults of both species were not affected. Permeability of the blood-cerebrospinal fluid (CSF) barrier to proteins was not affected by systemic inflammation for at least 48 h after intraperitoneal injection of lipopolysaccharide. These results show that there is a restricted period in brain development when the blood-brain barrier, but not the blood-CSF barrier, to proteins is susceptible to systemic inflammation; this does not appear to be attributable to barrier "immaturity" but to its stage of development and only occurs in white matter.

Chorioamnionitis increases neonatal morbidity in pregnancies complicated by preterm premature rupture of membranes

OBJECTIVE

To compare morbidities of neonates born to women who developed chorioamnionitis after premature preterm rupture of membranes versus those who did not.

STUDY DESIGN

We reviewed outcomes in singleton pregnancies with confirmed premature preterm rupture of membranes at 24 weeks or beyond that resulted in delivery less than 37 weeks. Management of premature preterm rupture of membranes included the use of antibiotics, betamethasone if less than 32 weeks, and expectant management with induction at 34 weeks or greater. Composite neonatal major and minor morbidity rates were compared between pregnancies complicated by chorioamnionitis and those that were not.

RESULTS

From August 1998 to August 2000, 430 cases of premature preterm rupture of membranes were identified among 6003 deliveries (7.2%). Thirteen percent of women (56/430) with premature preterm rupture of membranes developed chorioamnionitis. The incidence of chorioamnionitis increased significantly with decreasing gestational age. The composite neonatal major morbidity rate was significantly higher in neonates whose mothers developed chorioamnionitis (55%) versus those who did not (18%, P < .0001). In a multiple logistic regression model, chorioamnionitis ( P < .0001), infant gender ( P = .007), latency ( P = .03), and gestational age at delivery ( P < .0001) were significantly associated with composite neonatal morbidity.

CONCLUSION

Neonatal morbidities are significantly higher among pregnancies with premature preterm rupture of membranes complicated by chorioamnionitis when compared with pregnancies that were not.

Developmental changes induced by graded prenatal systemic hypoxic–ischemic insults in rats

In infants, a common consequence of systemic perinatal insults is disruption of neonatal brain development. Such insults can cause cerebral palsy, cognitive delay, epilepsy and other chronic neurologic deficits in children. The mechanisms underlying disruption of brain development after perinatal insults are poorly defined. To mimic human systemic insults, a transient prenatal hypoxic-ischemic insult model was developed in rodents. Ischemic animals showed reproducible histological lesions including oligodendrocyte loss, gliosis, and axonal disruption. Ischemic animals displayed persistent postnatal loss of oligodendrocyte lineage cells and cortical neurons, decreased cell proliferation, increased cell death, elevated pro-inflammatory cytokine levels, and impaired motor skills as young adults. Progressive ischemic intervals produced a graded pattern of injury. This systemic rodent prenatal hypoxic-ischemic insult accurately models human perinatal brain injury in several important criteria, including functional association of altered brain development with motor delay, and consequently provides novel insights into the pathogenesis of human perinatal brain insults.

Prevalence of cranial scan abnormalities in preterm twins in relation to chorionicity and discordant birth weight

OBJECTIVE

The purpose of this study was to determine the incidence of ultrasonographically detected cerebral white matter lesions (WMLs) in preterm twins at birth in relation to chorionicity, discordant weight and twin-twin transfusion syndrome (TTTS).

METHODS

In this retrospective study, perinatal, neonatal, and cranial scan data of 85 monochorionic (MC) and 94 dichorionic (DC) twin pregnancies (341 infants) delivered between 24 and 34 weeks of gestation were collected. Data were analysed according to chorionicity, discordant birth weight (>20%), single intrauterine death and TTTS.

RESULTS

The cerebral WML was seen in 14% of preterm twins. Monochorionic infants had higher risks of WML than DC twin (odds ratio 7.1; 95% CI 3.28-15.8). In MC group, discordant weight (37%), TTTS (38%), single intrauterine death (67%) had higher incidence of cerebral WML than concordant weight infants (7%). Similarly, incidence of WML was higher in DC discordant compared with concordant weight infants (13% versus 2%; P < 0.05).

CONCLUSION

Monochorionic infants had a seven-fold higher incidence of cerebral WML than DC infants. Discordant birth weight, TTTS and survivor of co-twin demise are an independent risk of cerebral white matter lesion.