Elie Saliba

Systemic inflammation disrupts the developmental program of white matter

Perinatal inflammation is a major risk factor for neurological deficits in preterm infants. Several experimental studies have shown that systemic inflammation can alter the programming of the developing brain. However, these studies do not offer detailed pathophysiological mechanisms, and they rely on relatively severe infectious or inflammatory stimuli that most likely do not reflect the levels of systemic inflammation observed in many human preterm infants. The goal of the present study was to test the hypothesis that moderate systemic inflammation is sufficient to alter white matter development.

Inflammatory mediators and neonatal brain damage.

Inflammatory mediators are multifunctional cytokines that play important roles both in normal central nervous system (CNS) development and in the response of the brain to diverse forms of injury. Interleukin (IL)-1β, tumor necrosis factor-α and IL-6 are among the best-characterized early-response cytokines. Recent data suggest that they may be synthesized and secreted by several CNS cell types, including microglia, astrocytes and neurons. Biological effects of these cytokines that could influence the progression of injury in the brain include stimulating the synthesis of other cytokines and neuronal injury mediators such as nitric oxide synthase, inducing leukocyte infiltration and the expression of adhesion molecules, influencing glial gene expression and damaging oligodendrocytes. In the immature brain, proinflammatory cytokines might lead to white matter damage during prenatal intrauterine infection and contribute to progressive neuronal damage in acute brain injury evoked by cerebral hypoxia-ischemia. Interrupting the proinflammatory cascade might limit the extent of irreversible injury.

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 μg/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-1β, tumor necrosis factor-α, and IL-6 expression in the fetal brain were determined by reverse transcription quantitative polymerase chain reaction. Brain injury was examined in 16-μm coronal brain sections by GFAP, MBP, caspase-3 immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Expression of IL-1β 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.

Obstetrical and neonatal characteristics vary with birthweight in a cohort of 100 term newborns with symptomatic arterial ischemic stroke

OBJECTIVES Many questions remain regarding the mechanism of perinatal stroke. METHODS In a series of 100 prospectively enrolled term neonates with symptomatic arterial ischemic stroke, we explored family antecedents, pregnancy and delivery conditions and clinical presenting features and distinguished features of the 50 larger infants with the remainder. Cardiac and cervical arterial imaging were performed in 70 and 51 cases. RESULTS Previous fetal loss, first pregnancy, primiparity, twin-gestation, cesarean and traumatic delivery, neonatal distress, male sex and premature rupture of membranes were statistically more common than in the general population. Normal pregnancy proportion and mean birthweight were in the normal range, arguing against a vasculo-placental origin in the majority. Furthermore, there was an excess of large babies. The larger infants were more subject to suffer from acute perinatal events, with a trend for an excess of neonatal distress (p=0.065) and for more severe presenting features (p=0.027), while the lighter were more likely to have experienced longstanding obstetrical risk factors such as complicated pregnancy (p=0.047) and tobacco exposure (p=0.028). Cervical MR angiography showed an internal carotid occlusion in two babies, whereas echo-Doppler was always normal; in one case the two methods were discordant. Echocardiography was non-informative. INTERPRETATION The data from this prospective cohort of neonates with stroke confirm that many obstetrical and perinatal factors are risk determinants. They also suggest that birthweight and gender may be biomarkers of two populations of neonates with different pathological mechanisms. MR angiography appears more sensitive than echo-Doppler for the exploration of the neonatal cervical vasculature.

The effect of the odour of mother's milk on breastfeeding behaviour of premature neonates

Aim: To assess the effects of exposure to the odour of mothers milk on breastfeeding behaviour of premature neonates.

Antenatal bacterial endotoxin sensitizes the immature rat brain to postnatal excitotoxic injury

Intracerebral injection of ibotenate in newborn rodents produces brain damage that mimics that of infants with cerebral palsy. Because maternal infection may contribute to brain injury in preterm infants, we investigated brain damage after maternal inflammation and postnatal ibotenate treatment in a rat model of cerebral palsy. Pregnant rats were injected intraperitoneally with lipopolysaccharide at Days 19 and 20 of gestation. Neonates were given intracerebral injections of ibotenate at postnatal Day 4 and were then killed at Day 9. Lesion sizes were measured by cresyl violet staining, and microglial activation, astrogliosis, and myelination were evaluated by immunohistochemistry. The lipopolysaccharide groups had larger cortical and white matter lesions than the control group; they also had significantly greater microglial activation and astrogliosis and less white matter myelination in the lesioned hemispheres compared with the controls. Thus, maternal endotoxin exposure may affect prenatal development of the offspring and modulate the subsequent development of excitotoxic brain lesions. These results demonstrate the critical influence of prenatal immune events on neonatal central nervous system vulnerability and provide a model for studying the pathophysiology of cerebral damage in preterm infants and, specifically, the interplay between brain inflammation and excitotoxicity.

Melatonin modulates neonatal brain inflammation through endoplasmic reticulum stress, autophagy, and miR-34a/silent information regulator 1 pathway.

Maternal infection/inflammation represents one of the most important factors involved in the etiology of brain injury in newborns. We investigated the modulating effect of prenatal melatonin on the neonatal brain inflammation process resulting from maternal intraperitoneal (i.p.) lipopolysaccharide (LPS) injections. LPS (300 μg/kg) was administered to pregnant rats at gestational days 19 and 20. Melatonin (5 mg/kg) was administered i.p. at the same time as LPS. Melatonin counteracted the LPS sensitization to a second ibotenate‐induced excitotoxic insult performed on postnatal day (PND) 4. As melatonin succeeded in reducing microglial activation in neonatal brain at PND1, pathways previously implicated in brain inflammation regulation, such as endoplasmic reticulum (ER) stress, autophagy and silent information regulator 1 (SIRT1), a melatonin target, were assessed at the same time‐point in our experimental groups. Results showed that maternal LPS administrations resulted in an increase in CHOP and Hsp70 protein expression and eIF2α phosphorylation, indicative of activation of the unfolded protein response consequent to ER stress, and a slighter decrease in the autophagy process, determined by reduced lipidated LC3 and increased p62 expression. LPS‐induced inflammation also reduced brain SIRT1 expression and affected the expression of miR‐34a, miR146a, and miR‐126. All these effects were blocked by melatonin. Cleaved‐caspase‐3 apoptosis pathway did not seem to be implicated in the noxious effect of LPS on the PND1 brain. We conclude that melatonin is effective in reducing maternal LPS‐induced neonatal inflammation and related brain injury. Its role as a prophylactic/therapeutic drug deserves to be investigated by clinical studies.

Neuroprotection par hypothermie contrôlée dans l’encéphalopathie hypoxique-ischémique du nouveau-né à terme

Resume L’encephalopathie hypoxique-ischemique (EHI) est une cause importante de deces ou de sequelles neurologiques affectant deux a trois nouveau-nes pour 1000 naissances vivantes a terme. Malgre les avancees dans les soins intensifs neonatals, le devenir de ces enfants reste mauvais. Le traitement classique des nouveau-nes avec EHI reste decevant et repose essentiellement sur le maintien d’une homeostasie au niveau liquidien, electrolytique et respiratoire ainsi que le traitement des convulsions et de l’hypotension arterielle. Une hypoxie-ischemie (HI) n’entraine pas necessairement une mort neuronale immediate mais declenche le plus souvent une cascade biochimique qui entraine une mort neuronale retardee. Plusieurs phases sont decrites apres une HI : une phase latente qui suit la reperfusion cerebrale avec une recuperation du metabolisme energetique cerebral, suivie d’une phase secondaire debutant 6 a 15 h apres et caracterisee par une accumulation d’excitotoxines, la survenue d’oedeme cytotoxique, d’une defaillance energetique secondaire et de convulsions. Plusieurs etudes experimentales ont ete realisees autour de ce concept et ont demontre qu’une hypothermie moderee initiee le plus tot possible avant la phase secondaire et poursuivie pendant un temps suffisamment prolonge etait associee a une neuroprotection. Trois grandes etudes controlees randomisees ont demontre l’innocuite et l’efficacite a 18 mois d’âge de cette therapeutique. L’hypothermie est actuellement recommandee en pratique courante. Son implantation en pratique doit cependant etre soumise a des recommandations nationales precises tant sur le plan de l’organisation que celui de la prise en charge. Il est souhaitable qu’un suivi de ces enfants soit assure avec l’etablissement d’un registre national.

G protein-coupled receptor kinase 2 and group I metabotropic glutamate receptors mediate inflammation-induced sensitization to excitotoxic neurodegeneration

The concept of inflammation‐induced sensitization is emerging in the field of perinatal brain injury, stroke, Alzheimer disease, and multiple sclerosis. However, mechanisms underpinning this process remain unidentified.

Effect of caffeine on cerebral blood flow velocity in preterm infants.

A continuous-wave form Doppler monitor was used to examine the effect of caffeine on cerebral blood flow velocity (CBFV) in 7 clinically stable preterm neonates suffering from apnea. Caffeine, in the form of caffeine citrate, or saline were given intravenously at loading doses of 20 mg/kg. Every subject was his own control. Placebo (saline) was systematically injected prior to caffeine citrate. Simultaneous recording of heart rate, arterial blood pressure, respiratory rate, TcPO2, TcPCO2 were made before, then at the end of the injection, and 30, 60 and 120 min after the end of each administration of either placebo or caffeine. Compared with placebo, caffeine injection was not associated with significant changes in CBFV. An increase was found in both heart-rate and respiratory rate (p less than 0.05). Mean arterial blood pressure, TcPCO2 and TcPO2 did not change significantly. Our data suggest that a caffeine citrate loading dose of 20 mg/kg as currently used at the beginning of treatment of apnea in preterm neonates has no effect on CBFV.