Immature Blood-brain Barrier Research Articles

Maternal atopic conditions and autism spectrum disorder: a systematic review.

Autism spectrum disorder (ASD) is a disabling neurodevelopmental condition with complex etiology. Emerging evidence has pointed to maternal atopy as a possible risk factor. It is hypothesized that maternal atopic disease during pregnancy can lead to increased levels of inflammatory cytokines in fetal circulation via placental transfer or increased production. These cytokines can then pass through the immature blood-brain barrier, causing aberrant neurodevelopment via mechanisms including premature microglial activation. The objective of this study is to systematically review observational studies that investigate whether a maternal history of atopic disease (asthma, allergy, or eczema/atopic dermatitis) is associated with a diagnosis of ASD in offspring. A search was conducted in Ovid MEDLINE, PsycINFO, and Embase databases for relevant articles up to November 2021; this was later updated in January 2022. Observational studies published in peer-reviewed journals were included. Data were synthesized and qualitatively analyzed according to the specific atopic condition. Quality assessment was done using the Newcastle-Ottawa Scale. Nine articles were identified, with all including asthma as an exposure, alongside four each for allergy and eczema. Findings were inconsistent regarding the association between a maternal diagnosis of either asthma, allergy, or eczema, and ASD in offspring, with variations in methodology contributing to the inconclusiveness. More consistent associations were demonstrated regarding maternal asthma that was treated or diagnosed during pregnancy. Evidence suggests that symptomatic maternal asthma during pregnancy could be associated with ASD in offspring, underscoring the importance of effective management of atopic conditions during pregnancy. Further research is needed, particularly longitudinal studies that use gold-standard assessment tools and correlate clinical outcomes with laboratory and treatment data.PROSPERO Registration Number and Date: CRD42018116656, 26.11.2018.

Correlating Biochemical Impact of Environmental Toxicants on Human Neural Stem Cells to Biophysical Changes

Today one out of six children are diagnosed with developmental disorders and there is a critical need to screen compounds such as environmental toxicants and pharmaceutical drugs for their potential developmental toxicity. It is widely accepted that developing central nervous system is highly susceptible to damage by exposure to toxicants due to the still immature blood-brain barrier. With current in vitro tests focusing mainly on cytotoxicity, many important biochemical and biophysical characteristics are not being explored. Such biochemical and biophysical cues play an integral role in regulating cell morphogenesis, movement, and metabolism during fetal development. In this study, we investigated the biophysical and biochemical effects of rotenone (an active ingredient of insecticides) on human neural stem cells (NSCs). NSCs were exposed to a wide range of rotenone concentrations and using dose-response curves, toxic concentration (IC50 = 0.24 μM) was flagged. IC50 and lower concentrations were tested for biophysical assessment of rotenone-exposed NSCs. Using a MFP-3D-BIO AFM and customized culture platform, the biomechanical characteristics were quantified from force-deflection curves obtained at various locations on live NSCs cultured under exposure conditions (n > 50 cells/ dose/ time). Cytoskeleton marker (actin) expression was assessed to correlate to changes in biomechanics. Results showed a negative dose-dependent effect on cell viability (p < 0.001) and a significant dose-time dependent reorganization of cytoskeleton (p < 0.05). NSC stiffness varied from 450 Pa to 5 kPa in the presence and absence of rotenone, respectively. The changes in membrane tension suggests a strong correlation between dosage and duration of rotenone exposure (p < 0.01). Adhesive forces between AFM probe and NSCs were strongly dependent on exposure duration and dosage of rotenone (p < 0.01), demonstrating the alterations of cell membrane with rotenone exposure.

Age Dependency of Blood-Brain Barrier Penetration by cis- and trans-Permethrin in the Rat.

Permethrin (PER), a type I pyrethroid, is the most widely used insecticide in domestic settings in the United States. The overall objective of this study was to assess the efficiency of the blood-brain barrier (BBB) as an obstacle to the 14C-cis-permethrin (CIS) and 14C-trans-permethrin (TRANS) isomers of PER, and to determine whether its barrier function changes during maturation of the rat. Experiments were conducted to quantify brain uptake of CIS and TRANS in postnatal day 145, 21, and 90 Sprague-Dawley rats. The common carotid artery of anesthetized rats was perfused for 2 or 4 minutes with 1, 10, or 50 µM 14C-CIS or 14C-TRANS in 4% albumin. Brain deposition of each isomer was inversely related to age, with levels in the youngest animals >5 times those in adults. Brain uptake was linear over the 50-fold range of pyrethroid concentrations, indicative of passive, nonsaturable BBB permeation. The extent of uptake of toxicologically relevant concentrations of CIS and TRANS was quite similar. Thus, dissimilar BBB permeation does not contribute to the greater acute neurotoxic potency of CIS, but greater permeability of the immature BBB to CIS and TRANS may contribute to the increased susceptibility of preweanling rodents to the insecticides.

Arsenic-Induced Autophagy in the Developing Mouse Cerebellum: Involvement of the Blood-Brain Barrier's Tight-Junction Proteins and the PI3K-Akt-mTOR Signaling Pathway.

This study was designed to determine whether the tight-junction (TJ) proteins of the blood-brain barrier (BBB) and the PI3K-Akt-mTOR signaling pathway are involved during arsenic (As)-induced autophagy in developing mouse cerebella after exposure to different As concentrations (0, 0.15, 1.5, and 15 mg/L As(III)) during gestational and lactational periods. The dosage was continually given to the pups until postnatal day (PND) 42. Studies conducted at different developmental age points, like PND21, 28, 35, and 42, showed that exposure to As led to a significant decrease in the mRNA-expression levels of TJ proteins (occludin, claudin, ZO-1, and ZO-2), PI3K, Akt, mTOR, and p62, with concomitant increases in Beclin1, LC3I, LC3II, Atg5, and Atg12. Also, As significantly downregulated occludin and mTOR protein-expression levels with concomitant upregulation of Beclin1, LC3, and Atg12 at all the developmental age points. However, no significant alterations were observed in low- and medium-dose-exposed groups at PND42. Histopathological analysis revealed the irregular arrangement of the Purkinje cell layer in the As-exposed mice. Ultrastructural analysis by transmission electron microscopy (TEM) revealed the occurrence of autophagosomes and vacuolated axons in the cerebella of the mice exposed to high doses of As at PND21 and 42, respectively. Finally, we conclude that developmental As exposure significantly alters TJ proteins, resulting an increase in BBB permeability, facilitating the ability of As to cross the BBB and induce autophagy, which might be partly the result of inhibition of the PI3K-Akt-mTOR signaling pathway, in an age-dependent manner (i.e., PND21 mice were found to be more vulnerable to As-induced neurotoxicity), which could be due to the immature BBB allowing As to cross through it. However, the effect was not significant in PND42, which could be due to the developed BBB.

Pediatric movement disorders.

Pediatric movement disorders are commonly encountered clinical entities in the pediatric outpatient department. These disorders are a heterogenous group of disorders and may represent an underlying genetic disorder, a metabolic disorder or a hypoxic-ischemic insult during the perinatal period. Hyperkinetic movement disorders are more common as compared to hypokinetic disorders. This is unlike the situation in adult movement disorders where hypokinetic disorders are more often seen. A child's nervous system is more prone to hypoxic-ischemic insults due to its higher metabolic demands and the presence of an immature blood-brain barrier. The commonest movement disorders seen are tics, dystonia and chorea. Myoclonus is commonly associated with epilepsy syndromes. The aetiology of paediatric movement disorders depends on their course, their static or progressive nature, and whether an isolated symptom or an association with other neurological symptoms is present. The clue to the diagnosis is the proper recognition of the movement prevalent in the disorder.

363. Improvement of Sandhoff Phenotype Following Intravenous Injection of Adeno-Associated Viral Vector Expressing a Hexosaminidase Isoenzyme in Adult Sandhoff Mice: Preclinical Safety and Efficacy Study

GM2 gangliosidosis disorders stem from a Hexosaminidase A (HexA) isoenzyme deficiency. In humans, HexA is the sole enzyme able to catabolize GM2 ganglioside (GM2). The inability to effectively catabolize GM2 leads to neurodegeneration of the central nervous system. HexA is comprised of 2 subunits (α, β) and works with the GM2 activator protein (GM2AP). In the recent work by Tropak et al. (Mol Ther Met Clin Dev, in press), a hybrid subunit, named µ-subunit, was created (patent pending) by combining the stabilization and GM2AP binding sites of the β-subunit while conserving the catalytic properties of the α-subunit. The ‘µ’-subunit, coded by HEXM, can homodimerize and form a stable, functional enzyme, named HexM, which can interact with GM2AP to hydrolyse GM2. Previous work for successful correction of Sandhoff mice using AAV was only shown in neonatal mice (with immature blood-brain barrier (BBB)) and may not directly help in designing a human clinical trial. In the current study, we examined the efficacy/safety of IV injections of the scAAV9/HEXM vector at two doses in adult SD mice (with mature BBB). In addition, we also tested if an adjunct IV injection of mannitol provides any enhancement in efficacy. At 6 weeks old, the vector was injected via tail vein in cohorts of n=17 and n=15 SD mice at 2.5E+12 or 1.0E+13 vg/mouse, respectively. Another cohort of 16 mice received IV mannitol (3g/kg) prior to an IV injection of 2.5E+12 vg scAAV9/HEXM. Some mice from low dose group were euthanized at 16 weeks for direct analysis with untreated SD control mice, while the remainder were left until for terminal survival. Analysis of survival benefit, locomotor behaviour, biochemical and molecular parameters were performed. While untreated SD mice had a 16 week humane endpoint, 4 of 7 mice in higher dose group are now surviving past 56 weeks, 1 of 12 mice in the low dose cohort, and 4 of 9 mice in the mannitol cohort are surviving past 52 weeks. These increases in survival are all highly significant compared to the ~16 week humane endpoint of untreated SD mice. Behaviourally, there are no major significant differences in locomotion between the groups until after 15 weeks, when the adjunct mannitol group significantly outperforms the PBS group. Survival and behaviour monitoring, and the biochemical analyses for this study are ongoing. The preliminary results from this study show delayed onset of the SD phenotype with a single AAV9/HEXM injection and a significant benefit of a pre-injection of IV mannitol. This study is the first to show that an IV gene transfer using a scAAV/HEXM vector can provide survival and behavioural benefit in adult SD mice especially with adjunct use of mannitol. We propose that these results can advise the design of a human gene therapy trial for SD and the related Tay-Sachs disease.

Ontogeny of ABC and SLC transporters in the microvessels of developing rat brain.

The blood-brain barrier (BBB) is responsible for the control of solutes' concentration in the brain. Tight junctions and multiple ATP-binding cassette (ABC) and SoLute Carrier (SLC) efflux transporters protect brain cells from xenobiotics, therefore reducing brain exposure to intentionally administered drugs. In epilepsy, polymorphisms and overexpression of efflux transporters genes could be associated with pharmacoresistance. The ontogeny of these efflux transporters should also be addressed because their expression during development may be related to different brain exposure to antiepileptic drugs in the immature brain. We detected statistically significant higher expression of Abcb1b and Slc16a1 genes, and lower expression of Abcb1a and Abcg2 genes between the post-natal day 14 (P14) and the adult rat microvessels. P-gP efflux activity was also shown to be lower in P14 rats when compared with the adults. The P-gP proteins coded by rodent genes Abcb1a and Abcb1b are known to have different substrate affinities. The role of the Abcg2 gene is less clear in pharmacoresistance in epilepsy, nonetheless the coded protein Bcrp is frequently associated with drug resistance. Finally, we observed a higher expression of the Mct1 transporter gene in the P14 rat brain microvessels. Accordingly to our results, we suppose that age may be another factor influencing brain exposure to antiepileptics as a consequence of different expression patterns of efflux transporters between the adult and immature BBB.

Derivation of a human in vitro BBB model from hiPSCs

Event Abstract Back to Event Derivation of a human in vitro BBB model from hiPSCs Catarina Praça1, 2, 3, Susana C. Rosa4, Romeo Cecchelli3, Marie-Pierre Dehouck3 and Lino S. Ferreira2, 4 1 CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Doctoral Programme in Experimental Biology and Biomedicine (PDBEB), University of Coimbra, Portugal 2 Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Portugal 3 Faculté des Sciences Jean Perrin, Université d´Artois, France 4 CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Portugal Introduction: The barriers of the central nervous system are essential protectors of the brain from the rest of the body. The blood-brain barrier (BBB) is the most selective one, being the major responsible for keeping the neuronal microenvironment homeostasis. Using BBB models is possible to make reliable predictions of drug-BBB interactions and also to study biological and pathological aspects of the barrier. Recently we have generated a stable and reproducible human in vitro BBB model derived from cord blood hematopoietic stem cells[1]. The cells were initially differentiated into endothelial cells (ECs) followed by the induction of BBB properties by co-culture with bovine pericytes. The brain-like endothelial cells (BLECs) expressed tight junctions and transporters typically observed in brain endothelium and maintained the expression of most BBB properties for at least 20 days [1]. However, so far, the derivation of disease models of human BBB has not been reported. Induced pluripotent stem cells (iPSCs) represent a promising source of BLECs with specific disease phenotypes such as Alzheimer, Parkinson and other neurodegenerative diseases. This is not currently possible using the human BBB system developed by us from human cord blood hematopoietic stem cells. Here, we describe a procedure to derive BLECs from iPSCs using well-characterized progenitor cells. We further document the effect of extracellular matrix (ECM) and soluble factors in this inductive process, and we report their functional activity. Results and Discussion: Vascular progenitor cells isolated from iPSCs express high levels of CD31 (~ 91%) and GLUT-1 (~ 91%), moderate levels of claudin-5 (~ 26%), occludin (~ 11%) and ZO-1 (~ 24%), and low levels of P-gp (~ 1%). Immunocytochemistry results showed that the expression of occludin and claudin-5 is not entirely at cell junctions, disclosing an immature BBB phenotype. These cells were matured for 4 passages in specific cell media conditions (not disclosed) and specific native decellularized matrices. Along the maturation process, there is an increase in the co-localization of the CD31 marker with some of the BBB markers (Claudin-5, ZO-1 and PgP), suggesting a specification for the BBB phenotype. Functionally, these cells when cultured in the transwell systems, present relatively low permeability to Lucifer yellow (1.24±0.14 ×10-3 cm/min), TEER values of 55±0.58Ωcm2 and are able to generate a continuous monolayer presenting ZO-1 and claudin-5 in the cell membrane. Conclusion: In this work we report a methodology to differentiate hiPSCs into ECs with BBB properties (BLECs). Our results further highlight the importance of spcefic soluble factors and neurovascular unit ECM in the differentiation of vascular progenitor cells. FCT Fundação para a Ciência e Tecnologia (SFRH/BD/51678/2011); FCT Fundação para a Ciência e Tecnologia (PTDC/SAU-TOX/121); COMPETE funding (Project “Stem cell based platforms for Regenerative and Therapeutic Medicine”, Centro-07-ST24-FEDER-002008)

Central anticholinergic syndrome in a neonate operated for tracheoesophageal fistula.

Sir, Several drugs used in anaesthesia and intensive care may cause blockade of the central cholinergic neurotransmission. We report a suspected case of central anticholinergic syndrome (CAS) in a neonate following general anaesthesia (GA) involving intra-operative use of anticholinergic agents. A one-day-old term male baby with tracheoesophageal fistula, weighing 2.5 kg, was posted for emergency surgical correction. Pre-operative examination revealed bilateral crepitations, oxygen saturation (SpO2) of 90% (room air) and heart rate (HR) of 150/min. Standard monitoring was established. Glycopyrrolate 12.5 μg and fentanyl 5 μg were administered intravenously (IV). Anaesthesia was induced with halothane in oxygen. The trachea was intubated with a tracheal tube of 3 mm ID under deep inhalational anaesthesia. Atracurium 1.25 mg IV was given, and respiration was controlled. A few minutes after intubation, before the patient was positioned for surgery, the baby developed bronchospasm, HR decreased to 40/min, and SpO2 was 70%. Atropine 0.1 mg IV and salbutamol inhalation were administerd via T piece, and ventilation continued with 100% oxygen. HR and SpO2 improved and surgery commenced after positioning. After few minutes, a similar episode occurred, and atropine 0.1 mg was repeated. During lung retraction, the patient again developed bradycardia and oxygen desaturation. Atropine 0.1 mg IV was administered as bradycardia persisted despite release of lung retraction and 100% oxygen administration. Surgery lasted for 1.5 h. At the end of surgery, after confirming adequate respiratory efforts, residual neuromuscular blockade was reversed with neostigmine 0.125 mg and glycopyrrolate 0.025 mg IV. Even though respiratory effort was adequate, the neonate was deeply sedated with no response to painful stimulation. He was normothermic, normoglycaemic with normal arterial blood gas parameters. Pupils were dilated bilaterally with poor reaction to light. The baby was suspected to have CAS. Due to non-availability of physostigmine, it could not be administered. The baby was not extubated and was maintained on T-piece with intermittent assistance of respiration. After 1 h, the baby started opening his eyes, moving his limbs and responding to touch with adequate respiratory efforts and thereafter his trachea was extubated. Pupils were mid-dilated with improved but sluggish response to light. Pupils returned to normal size 18 h post-operatively. The baby had an uneventful recovery. Our patient had delayed emergence from anaesthesia with bilateral dilated pupils. Common reasons for delayed emergence in a neonate include residual drug effect, hypoglycaemia, acid-base disturbances, hypoxia, hypercarbia and hypothermia.[1] The baby had none of these problems. Child had three episodes of desaturation with bradycardia. Bradycardia in a neonate is most commonly due to hypoxemia. Improvement in oxygenation improved desaturation, but bradycardia persisted, necessitating administration of atropine (0.1 mg) on each of the three occasions. A total dose of 0.3 mg of atropine (for bradycardia) and 25 μg of glycopyrrolate (intra-operatively) was administered. We used 0.1 mg of atropine because that is the minimum dose recommended in standard references.[23] Post-operatively, the baby was sedated with decreased responsiveness and bilateral dilated pupils. This suggests the possibility of CAS. Glycopyrrolate, even though a quaternary ammonium compound, can cause central effects in a neonate due to immature blood-brain barrier (BBB). In CAS, excitation or depression symptoms can occur due to central nervous system effects of the acetylcholine (restlessness, agitation, hallucination, disorientation, convulsions, respiratory failure, coma).[4] Incidence of CAS is between 1% and 11.2% after GA.[5] CAS is well-defined in elderly adults, but it has been reported rarely in children and only a single case in neonate.[67] Kulka et al. reported that a 6-week-old infant had symptoms consistent with CAS following uneventful GA for hernia repair.[6] The child who had received 0.03 mg atropine responded to two doses of physostigmine, and he awoke spontaneously after 24 h.[6] Gillick reported a case in which partial reversal of central anticholinergic toxicity of atropine (0.09 mg/kg) by physostigmine resulted in an incipient muscarinic crisis in a neonate that was averted by glycopyrrolate.[7] Physostigmine, neostigmine or edrophonium may be administered as treatment. As neostigmine and edrophonium are quaternary amines, they cannot cross the BBB; they are used to treat peripheral effects of anticholinergic drug overdoses. Physostigmine, a tertiary amine, can cross the BBB and is used to treat the central effects of anticholinergic drug overdoses in dose of 0.03–0.04 mg/kg, repeated at 10–30 min intervals, if needed. Central anticholinergic syndrome can develop in a neonate because of over dosage with atropine or glycopyrrolate. The use of atropine in 10–20 μg/kg dose (and not the minimum dose) could have averted this iatrogenic complication. The possibility of CAS should be considered in a patient with post-operative flushing, mydriasis, dry skin and mucous membranes, altered mental status or fever. Physostigmine, a tertiary amine, should be available in the operating room for treatment of CAS.

Leptin and IL-8: Two novel cytokines screened out in childhood lead exposure

Lead is a toxic heavy metal with many recognized adverse health side effects. The central nervous system is the main target of lead toxicity. Although many studies on lead toxicity were conducted, the mechanism of lead toxicity remains uncertain. One possible attribution is the immature blood–brain barrier that causes lead exposure in children. Few studies have investigated the cytokine changes caused by this exposure. Novel cytokines were detected by RayBio® Human Cytokine Antibody Array and validated by enzyme-linked immunosorbent assay. Several children were admitted to West China Second University Hospital, after a serious lead pollution event in longchang, Sichuan, China. A total of 4 children with elevated blood lead levels (BLLs) and 4 children with low BLLs were randomly chosen in the discovery set, and 40 children with elevated BLLs and 40 children with low BLLs were included in the validation set. Leptin and interleukin-8 (IL-8) were identified to be significantly different between children with elevated and low BLLs via RayBio® Human Cytokine Antibody Array. In the validation set, IL-8 was higher in children with elevated BLLs [median(P25–P75), 117.69(52.31–233.63) pg/mL] than in children with low BLLs [median(P25–P75): 17.70(10.75–26.52) pg/mL] (p=0.000). Leptin was lower in children with elevated BLLs [median(P25–P75): 1658.23(1421.86–2606.55) pg/mL] than in children with low BLLs [median(P25–P75): 4168.68(3246.32–4744.94) pg/mL] (p=0.000). In children with low BLLs, leptin was higher in children with BLLs<3μg/dL (N=7) [median(P25–P75): 7220.86(4265.72–7555.15) pg/mL] than in children with BLL ≥ 3μg/dL (N=33) [median(P25–P75): 4103.86(3163.40–4678.34) pg/mL] (p=0.026); IL-8 was significantly different in children with BLL<4μg/dL (N=13) [median(P25–P75): 12.49(8.25–14.86) pg/mL] than in children with BLL≥4μg/dL (N=27) [median(P25–P75): 21.98(13.64–33.50) pg/mL] (p=0.013). The results defined specific changes in cytokine expressions to lead exposure, which can be used to explore the mechanism of lead toxicity and monitor lead exposure.

In Vitro Blood-Brain Barrier Models Using Brain Capillary Endothelial Cells Isolated from Neonatal and Adult Rats Retain Age-Related Barrier Properties

The blood–brain barrier (BBB) restricts the entry of circulating drugs and xenobiotics into the brain, and thus its permeability to substances is a critical factor that determines their central effects. The infant brain is vulnerable to neurotoxic substances partly due to the immature BBB. The employment of in vitro BBB models to evaluate permeability of compounds provides higher throughput than that of in vivo animal experiments. However, existing in vitro BBB models have not been able to simulate the intrinsic neonatal BBB. To establish a neonatal BBB model that mimics age-related BBB properties, the neonatal and adult in vitro BBB models were constructed with brain endothelial cells isolated from 2- and 8-week-old rats, respectively. To evaluate BBB functions, transendothelial electrical resistance, permeability of sodium fluorescein and Evans blue-albumin, and transport of rhodamine123 were measured. Radiolabelled drugs were used for BBB permeability studies in the neonatal and adult BBB models (in vitro) and in age-matched rats (in vivo). The neonatal BBB model showed lower barrier and p-glycoprotein (P-gp) functions than the adult BBB model; these were well associated with lower expressions of the barrier-related proteins and P-gp, and a different distribution pattern of immunostained barrier-related proteins. Verapamil (a P-gp inhibitor) significantly increased the influx of rhodamine 123, supporting functional P-gp expression in the neonatal BBB model. Valproic acid, but not nicotine, showed higher BBB permeability in the neonatal BBB model, which was well in accordance with the in vivo BBB property. We established a neonatal BBB model in vitro. This could allow us to assess the age-dependent BBB permeability of drugs.

Long term survival and limited migration of genetically modified monocytes/macrophages grafted into the mouse brain

In mammals, myeloid progenitors infiltrate the developing central nervous system (CNS), through the immature blood-brain barrier (BBB), the ventricular layer or the pial surface migrate and give rise to resident microglia. In the mature brain, however, the BBB hampers such recruitment from the blood-stream and long-term establishment of blood borne myeloid cells in the CNS thus appears at best limited. Hematopoietic stem cell-derived microglia, nevertheless, represents a promising tool for the correction of genetic deficits in the brain. We thus investigated the fate of primary human monocytes, and monocyte-derived macrophages, following transplantation into the adult mouse brain overpassing the BBB. Furthermore, we documented the ability of such cells to deliver a lysosomal enzyme into the brain following genetic modification with a recombinant adenoviral vector carrying the human β-glucuronidase cDNA. When implanted into the mouse striatum, the engineered primary cells survived and expressed the transgene for as much as 8 months. Moreover, the donor cells could migrate out of the grafting site and settle along blood vessels or myelin tracts although at limited distance. Migrating donor cells down-regulated the expression of CD14 andHLA DR, suggesting the adoption of a deactivated microglia-like phenotype. Our observations establish the ability of circulating mononuclear phagocytes to integrate into the brain after transplantation and express a transgene on the long term. These cells might thus be employed for autologous transplantation for the delivery of secreted therapeutic proteins in the context of a wide range of brain affections.

Comparison of speciated arsenic levels in the liver and brain of mice between arsenate and arsenite exposure at the early life

The aim of this study was to compare the risk from exposure to arsenate (iAs(V) ) or arsenite (iAs(III) ) at the early life. Mother mice were exposed to equimolar dose of iAs(V) and iAs(III) via drinking water during gestation and lactation. Their offspring continually drank the same water after weaning. Levels of speciated arsenic in both liver and brain were analyzed by hydride generation of volatile arsines and atomic absorption spectrophotometry (HG-AAS). In the liver, inorganic arsenic (iAs) levels significantly increased from postnatal day (PND) 15, and those on PND 35 were significantly higher than on PND 15 and 21 in iAs(III) exposed mice, but iAs levels did not significantly differ until PND 35 in iAs(V) exposed mice; Furthermore, all speciated arsenic levels on PND 35 and dimethylarsinic acid (DMA) levels on PND 1 were significantly higher in iAs(III) exposed mice than those in iAs(V) exposed mice. In the brain, iAs levels increased significantly on PND 21, but those declined sharply on PND 35 in either iAs(III) or iAs(V) exposed mice, however the mean difference between the two exposure groups was not significant; whereas DMA levels in iAs(III) exposed mice were significantly higher than those in iAs(V) exposed mice on both PND 1 and 35. In conclusion, findings from this study suggested that iAs(III) was preferentially accumulated into liver, and expected to result in more efficient methylation capacity than iAs(V) ; either iAs(V) or iAs(III) might be accumulated in the brain readily, when immature blood brain barrier can not limit it into brain. Hence, exposure to either iAs(V) or iAs(III) at the early life may increase the risk of iAs exposure in the brain.

Roles of Activated Microglia in Hypoxia Induced Neuroinflammation in the Developing Brain and the Retina

Amoeboid microglial cells (AMCs) in the developing brain display surface receptors and antigens shared by the monocyte-derived tissue macrophages. Activation of AMCs in the perinatal brain has been associated with periventricular white matter damage in hypoxic-ischemic conditions. The periventricular white matter, where the AMCs preponderate, is selectively vulnerable to hypoxia as manifested by death of premyelinating oligodendrocytes and degeneration of axons leading to neonatal mortality and long-term neurodevelopmental deficits. AMCs respond vigorously to hypoxia by producing excess amounts of inflammatory cytokines e.g. the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) along with glutamate, nitric oxide (NO) and reactive oxygen species which collectively cause oligodendrocyte death, axonal degeneration as well as disruption of the immature blood brain barrier. A similar phenomenon is observed in the hypoxic developing cerebellum in which activated AMCs induced Purkinje neuronal death through production of TNF-α and IL-1β via their respective receptors. Hypoxia is also implicated in retinopathy of prematurity in which activation of AMCs has been shown to cause retinal ganglion cell death through production of TNF-α and IL-1β and NO. Because AMCs play a pivotal role in hypoxic injuries in the developing brain affecting both neurons and oligodendrocytes, a fuller understanding of the underlying molecular mechanisms of microglial activation under such conditions would be desirable for designing of a novel therapeutic strategy for management of hypoxic damage.

Protecting Children From Toxicants

Protecting Children From Toxicants

Comparative Effects of Glucose- and Mannitol-Induced Osmolar Stress on Blood—Brain Barrier Function in Ovine Fetuses and Lambs

We examined the effects of hyperglycemic hyperosmolality on blood-brain barrier (BBB) permeability during development. We hypothesized that the barrier becomes more resistant to hyperglycemic hyperosmolality during development, and the immature BBB is more resistant to glucose than to mannitol hyperosmolality. We quantified the BBB response to hyperosmolality with the blood-to-brain transfer constant (K(i)) in immature fetuses, premature, and newborn lambs. K(i) increased as a function of increases in osmolality. A segmented regression model described the relationship between K(i) and osmolality. At lower osmolalities, changes in K(i) were minimal but after a threshold, increases were linear. We examined responses of K(i) to hyperglycemic hyperosmolality by comparing the thresholds and slopes of the second regression segments. Lower thresholds and steeper slopes indicate greater vulnerability to hyperosmolality. Thresholds increased (P<0.05) during development in pons and superior colliculus. Thresholds were higher (P<0.05) during glucose than mannitol hyperosmolality in thalamus, superior colliculus, inferior colliculus and medulla of premature lambs, and in cerebrum and cerebellum of newborns. We conclude that BBB permeability increased as a function of changes in glucose osmolality, the barrier becomes more resistant to glucose hyperosmolality in two brain regions during development, and the barrier is more resistant to glucose than to mannitol hyperosmolality in some brain regions of premature and newborn lambs.

Cerebrospinal fluid findings in infants with pertussis or parapertussis1)

Pertussis has been increasing in frequency and can cause protean manifestation in infants, often resulting in extensive laboratory evaluation. We examined the prevalence of cerebrospinal fluid (CSF) anomalies in infants with pertussis and parapertussis over a 5-year period. In total, 239 of 1489 children (16.1%) had a positive PCR for pertussis or parapertussis. Eighty-three percent were infants; the mean age of the 39 years who received a lumbar puncture (LP) was 43 days. Reasons for performing LP included apnea (62%), toxic appearance (38%), fever (26%), and altered mentation (10%); several had >1 indication for LP. Twenty-four (62%) children had elevated CSF protein. No child had hypoglycorrhachia, bacterial meningitis, bacteremia, or intracranial hemorrhage; one child had a urinary tract infection and five had pneumonia. Seven children had brain imaging performed; one had a subarachnoid hemorrhage and six had normal studies. Elevated age-normalized CSF protein was a common finding in infants with pertussis, potentially due to transfer across a damaged or immature blood-brain barrier. This finding was seen in the absence of concomitant bacterial infections or detectable intracranial anomalies. While the diagnostic evaluation and clinical management of a toxic-appearing infant should not be limited by a positive pertussis or parapertussis PCR, it is useful for physicians to be cognizant that elevated CSF protein can be seen in association with these infections.

Safety of oseltamivir compared with the adamantanes in children less than 12 months of age.

When oseltamivir is administered in extremely high doses (500-1000 mg/kg) to young juvenile rats, central nervous system toxicity and death occurred in some animals. Mortality was not observed in older juvenile rats, suggesting a possible relationship between neurotoxicity and an immature blood-brain barrier. To assess potential neurologic adverse effects of oseltamivir use in infants, a retrospective chart review was performed in infants less than 12 months of age who received oseltamivir, amantadine, or rimantadine. The primary objective was to describe the frequency of neurologic adverse events among children less than 12 months of age who received oseltamivir compared with those receiving adamantanes. Medical record databases, emergency department databases, and/or pharmacy records at 15 medical centers were searched to identify patients. Of the 180 infants identified as having received antiviral therapy, 115 (64%) received oseltamivir, 37 (20%) received amantadine, and 28 (16%) received rimantadine. The median dose of oseltamivir was 2.0 mg/kg/dose in 3- to 5-month-old and 2.2 mg/kg/dose in 9- to 12-month-old infants. The maximum dose administered was 7.0 mg/kg/dose. There were no statistically significant differences in the occurrence of adverse neurologic events during therapy among subjects treated with oseltamivir versus those treated with the adamantanes (P = 0.13). This is the largest report to date of oseltamivir use in children less than 12 months of age. Neurologic events were not more common with use of oseltamivir compared with that of the adamantanes. Dosing of oseltamivir was variable, illustrating the need for pharmacokinetic data in this younger population.

Dopamine therapy promotes cerebral flow-metabolism coupling in preterm infants

Dopamine is widely used to maintain blood pressure in very preterm infants, but it may affect neurovascular regulation as it crosses the immature blood-brain barrier. We contrasted the relationship between cerebral perfusion and oxygen metabolism in preterm infants treated with dopamine because of hypotension with normotensive controls. Prospective observational study in a neonatal intensive care unit. Cerebral metabolic rate of oxygen consumption (CMRO2) was determined via measurements of cerebral blood flow (CBF) and cerebral venous saturation (CSvO2) using near infrared spectroscopy. Twenty-six infants (median gestation 26 weeks) were studied at a median postnatal age of 17 h. Infants were categorised as control (n = 16) or dopamine-treated (DOPA, n = 10). No relationship was found between CBF and CMRO2 in the control group, while a strong positive correlation was found in the DOPA group (R (2) = 0.62, P = 0.01). Cerebral fractional oxygen extraction (CFOE) and CBF showed strong negative correlation in the control infants (R2 = 0.65, P < 0.001), but not in the DOPA group. CSvO2 was lower at decreased CBF (R2 = 0.56, P < 0.001) in the control infants, but not in the DOPA group. Cerebral blood flow-metabolism coupling in the very preterm brain differs strikingly from that in the mature brain, where CBF is coupled to CMRO2. In the very preterm brain, variations of cerebral oxygen extraction, not CBF, sustain CMRO2. In contrast, preterm infants receiving dopamine exhibit flow-metabolism coupling similar to the mature brain. These findings suggest a previously unrecognised role for dopamine in the preterm brain in promoting flow-metabolism coupling.

Effects of prolonged iron overload and low frequency electromagnetic exposure on spatial learning and memory in the young rat

Low-frequency electromagnetic fields (EMF) have been suggested to affect the brain via alterations of blood–brain barrier permeability to iron. Because of an immature blood–brain barrier, the young brain may be particularly vulnerable to EMF exposure. It is therefore possible that behavioral and neurotoxic effects resulting from EMF-induced iron excess in the brain would be greater in young adults. The objective of the present study was to investigate the interaction between low-frequency EMF and iron overload in young rats. In Experiment 1, we tested the effects of iron overload on spatial learning and memory. Iron treatment did not affect performance in a reference (Morris water maze) and a working memory task (8-arm radial maze). In contrast, detection of a spatial change in an object exploration task was impaired. These effects correlated with modifications of the serotoninergic metabolism. In Experiment 2, the combination of EMF exposure and iron overload was tested. As in Experiment 1, rats were not impaired in reference and working memory tasks but were mildly impaired in the detection of the spatial change. Overall, the results showed an effect of iron overload on spontaneous spatial memory processes. However, low-frequency EMF exposure did not potentiate the effects of iron overload in young rats.