Brian Sims

Histological Characteristics of the Fetal Inflammatory Response Associated with Neurodevelopmental Impairment and Death in Extremely Preterm Infants

OBJECTIVE To test the hypothesis that increasing severity of the fetal inflammatory response (FIR) would have a dose-dependent relationship with severe neurodevelopmental impairment or death in extremely preterm infants. STUDY DESIGN We report 347 infants of 23-28 weeks gestational age admitted to a tertiary neonatal intensive care unit between 2006 and 2008. The primary outcome was death or neurodevelopmental impairment at the 18- to 22-month follow-up. Exposure status was defined by increasing stage of funisitis (stage 1, phlebitis; stage 2, arteritis with or without phlebitis; stage 3, subacute necrotizing funisitis) and severity of chorionic plate vasculitis (inflammation with or without thrombosis). RESULTS A FIR was detected in 110 placentas (32%). The rate of severe neurodevelopmental impairment/death was higher in infants with subacute necrotizing funisitis compared with infants without placental/umbilical cord inflammation (60% vs 35%; P < .05). Among infants with stage 1 or 2 funisitis, the presence of any chorionic vasculitis was associated with a higher rate of severe neurodevelopmental impairment/death (47% vs 23%; P < .05). After adjustment for confounding factors, only subacute necrotizing funisitis (risk ratio, 1.87; 95% CI, 1.04-3.35; P = .04) and chorionic plate vasculitis with thrombosis (risk ratio, 2.21; 95% CI, 1.10-4.46; P = .03) were associated with severe neurodevelopmental impairment/death. CONCLUSION Severe FIR, characterized by subacute necrotizing funisitis and severe chorionic plate vasculitis with thrombosis, is associated with severe neurodevelopmental impairment/death in preterm infants.

B-type natriuretic peptide and mortality in extremely low birth weight infants with pulmonary hypertension: a retrospective cohort analysis

BackgroundB-type natriuretic peptide (BNP) is a strong predictor of mortality in adult patients with various forms of pulmonary hypertension (PH) and may be a strong prognostic marker in extremely low birth weight (ELBW) infants with bronchopulmonary dysplasia (BPD) associated PH as well. We sought to assess the relationship between BNP levels and all-cause mortality in a cohort of ELBW infants with BPD and PH.MethodsWe retrospectively identified ELBW infants with BPD and PH who had serum BNP levels measured as part of routine clinical care in the neonatal intensive care unit. Peak serum BNP levels were correlated with survival to discharge or death.ResultsThirty-six ELBW infants (mean gestational age 26.0 ± 1.9 weeks and mean birth weight 740 ± 290 grams) with BPD and PH had available survival data and had serum BNP levels measured. Peak BNP level was significantly lower among infants who survived than among those who died (128 pg/ml, [IQR 23 to 463] vs. 997 pg/ml, [IQR 278 to 1770], P < 0.004). On multivariate Cox proportional hazard analysis, BNP predicted survival independent of age, gender, and BPD severity. Area under receiver operator characteristic analysis identified a BNP value of 220 pg/ml to have 90% sensitivity and 65% specificity in predicting mortality.ConclusionBNP estimation may be useful as a prognostic marker of all-cause mortality in ELBW infants with BPD associated PH.

Erythropoietin-induced neuroprotection requires cystine glutamate exchanger activity.

Erythropoietin (Epo) has been used for many years in neonates for the treatment of anemia of prematurity. Epo has also been proposed for treatment of neonatal brain injury, as mounting evidence suggests neuroprotective properties for Epo. However, Epos neuroprotective mechanism of action is poorly understood. In this study we hypothesized that Epo may confer neuroprotection by enhancing cellular redox defense brought about by cellular glutathione (GSH). This was examined in cultures of differentiated cortical neural stem cells and using the B104 cell line as model systems. Our data shows that Epo causes a time- and dose-dependent increase in expression and activity of system Xc(-), the transporter responsible for uptake of cystine for the production of glutathione. Cystine uptake increases 3-5 fold in differentiated neural stem cells and B104 cells treated with Epo. Exposure of cells to 100 microM kainate suppressed cellular GSH and caused excitotoxicity, but GSH levels and cell viability were completely restored by Epo in the continued presence of kainate. This rescue effect of Epo vanished if system Xc(-) was inhibited pharmacologically using S4-CPG in the presence of Epo leading to marked cell death of B104 cells and cultured mouse cortical neural stem cells. This could also be achieved using xCT siRNA to decrease xCT expression. This data suggests that system Xc(-) activity and protein expression are positively regulated by Epo directly explaining its neuroprotective effect.

Elevated adenosine monophosphate deaminase activity in Alzheimer’s disease brain

Abnormal elevations in ammonia have been implicated in the pathogenesis of Alzheimers disease. However, the biochemical mechanism(s) leading to increased ammonia in Alzheimers disease have not yet been identified. A potential source of increased ammonia production is adenosine monophosphate (AMP) deaminase, an important enzyme in the regulation of the purine nucleotide cycle and adenylate energy charge. AMP deaminase activity is expressed in human brain and converts AMP to inosine monophosphate with the release of ammonia. We have investigated AMP deaminase activity in postmortem brain tissue from Alzheimers disease subjects and age-matched controls. Compared to control brain, Alzheimers disease brain AMP deaminase activity is 1.6- to 2.4-fold greater in the regions examined--the cerebellum, occipital cortex, and temporal cortex. Similar increases in AMP deaminase protein and mRNA levels are observed in Alzheimers disease brain. These results suggest that increased AMP deaminase activity may augment ammonia levels in the brain in Alzheimers disease.

Neural stem cell-derived exosomes mediate viral entry

Background Viruses enter host cells through interactions of viral ligands with cellular receptors. Viruses can also enter cells in a receptor-independent fashion. Mechanisms regarding the receptor-independent viral entry into cells have not been fully elucidated. Exosomal trafficking between cells may offer a mechanism by which viruses can enter cells. Methods To investigate the role of exosomes on cellular viral entry, we employed neural stem cell-derived exosomes and adenovirus type 5 (Ad5) for the proof-of-principle study. Results Exosomes significantly enhanced Ad5 entry in Coxsackie virus and adenovirus receptor (CAR)-deficient cells, in which Ad5 only had very limited entry. The exosomes were shown to contain T-cell immunoglobulin mucin protein 4 (TIM-4), which binds phosphatidylserine. Treatment with anti-TIM-4 antibody significantly blocked the exosome-mediated Ad5 entry. Conclusion Neural stem cell-derived exosomes mediated significant cellular entry of Ad5 in a receptor-independent fashion. This mediation may be hampered by an antibody specifically targeting TIM-4 on exosomes. This set of results will benefit further elucidation of virus/exosome pathways, which would contribute to reducing natural viral infection by developing therapeutic agents or vaccines.

Hypoxic preconditioning involves system Xc- regulation in mouse neural stem cells.

In animals, hypoxic preconditioning has been used as a form of neuroprotection. The exact mechanism involved in neuroprotective hypoxic preconditioning has not been described, yet could be valuable for possible neuroprotective strategies. The overexpression of the cystine-glutamate exchanger, system Xc-, has been demonstrated as being neuroprotective (Shih, Erb et al. 2006). Here, using immunohistochemistry, we demonstrate that C57BL/6 mice exposed to hypoxia showed an increase in system Xc- expression, with the highest level of intensity in the hippocampus. Western Blot analysis also showed an almost 2-fold increase in system Xc- protein in hypoxia-exposed versus control mice. The mRNA for the regulatory subunit of system Xc-, xCT, and the xCT/actin ratio were also increased under hypoxic conditions. Experiments using hypoxia-inducible factor (HIF-1α) siRNA showed a statistically significant decrease in HIF-1α and system Xc- expression. Under hypoxic conditions, system Xc- activity, as determined by cystine uptake, increased 2-fold. Importantly, hypoxic preconditioning was attenuated in neural stem cells by pharmacological inhibition of system Xc- activity with S4-carboxyphenylglycine. These data provide the first evidence of hypoxic regulation of the cystine glutamate exchanger system Xc-.

Cystine glutamate exchanger upregulation by retinoic acid induces neuroprotection in neural stem cells.

Oxidative stress and excitotoxic injury are commonly associated with several neurodegenerative diseases, such as Parkinsons disease, Alzheimers disease, and periventricular leukomalacia. As cystine is imported into the cell, it is used in the synthesis of intracellular glutathione, an important antioxidant necessary for the defense of brain cells from oxidative stress and glutamate-mediated excitotoxicity. Recent studies have shown that retinoic acid increases the activity of glutathione synthesis and exhibits neuroprotective properties in brain cells. Previously, we have shown that the regulation of the cystine glutamate exchanger (system Xc−) also leads to neuroprotection. Here, we examined the effects of retinoic acid on the regulation of system Xc−. Our results suggest that retinoic acid-induced neuroprotection is mediated through system Xc− by regulating glutathione biosynthesis.

B-type natriuretic peptide is a biomarker for pulmonary hypertension in preterm infants with bronchopulmonary dysplasia

Correspondence: Brian Sims Department of Pediatrics, Division of Neonatology, University of Alabama at Birmingham, 1700 6th Avenue South, Women and Infant’s Center, Birmingham, AL 35249, USA Tel +1 205 934 4680 Fax +1 205 934 3100 Email bsims@peds.uab.edu Background: B-type natriuretic peptide (BNP) is a cardiac biomarker useful in screening for pulmonary hypertension (PH) in adults. It is possible that BNP may also be useful in detecting PH among preterm infants with bronchopulmonary dysplasia (BPD). Objective: To determine the utility of BNP for identification of PH among preterm infants with BPD. Methods: We retrospectively identified preterm infants with BPD who underwent screening echocardiography for suspected PH and had serum BNP levels measured within 10 days before or after echocardiography. Eligible infants were classified based on echocardiographic diagnosis of either PH or no PH. Median and interquartile ranges (IQR) of BNP values were compared, and area under the curve (AUC) of receiver operator characteristic (ROC) analysis was used to determine the optimum threshold value for detection of PH. Results: Twenty-five preterm infants with BPD (mean gestational age 26.5 ± 1.7 weeks, mean birth weight 747 ± 248 g) were identified. The median difference in days between echocardiography and BNP measurement was 1 day (IQR 0–3, range 0–10 days). Based on echocardiography, 16 were diagnosed with PH and nine without PH. No significant difference in terms of gestational age, birth weight, sex, race, or respiratory support was found between the two groups. Median (IQR) BNP values of those with PH were higher than those without PH (413 [212–1178] pg/mL versus 55 [21–84] pg/mL, P , 0.001). AUC of ROC analysis showed that a BNP value of 117 pg/mL had 93.8% sensitivity and 100% specificity for detecting PH. Conclusion: BNP estimation may be useful for screening of PH in infants with BPD.

Differential binding of the HIV-1 envelope to phosphatidylserine receptors

Prior work has shown that the HIV-1 envelope of the human immunodeficiency virus (HIV) interacts directly with T-cell immunoglobulin mucin (TIM) family proteins. Herein, we demonstrate that HIV-1 envelope glycoproteins from varying HIV-1 clades bind differentially to TIM proteins and functionally similar proteins acting as phosphatidylserine (PtdSer) receptors. Using enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) technology, we show that lysate containing HIV-1 envelope and recombinant HIV-1 envelope glycoproteins bind TIM-4 and advanced glycosylation end product-specific receptor (AGER). The complex binding of HIV-1 UG21 gp140 to TIM-4 or AGER suggests a biphasic interaction with these proteins.

Melatonin Induces Neuroprotection via System Xc Regulation in Neural Stem Cells

Hypoxic-brain injury is a major cause of neonatal morbidity and mortality. However, melatonin (N-acetyl-5- methoxytryptamine) has been identified as an indirect anti-oxidant and direct free radical scavenger that could possibly reduce the injurious effects of hypoxic-ischemic brain injury in neonatal infants. Hypoxia-ischemia leads to multiple consequences such as an increase in extracellular glutamate. Yet the many mechanisms involved in melatonin-induced neuroprotection are still under investigation. We have hypothesized that melatonin could induce neuroprotection by increasing levels of cystine glutamate exchanger (xCT), an amino acid transporter as shown in previous work in our laboratory. Mouse neural stem cells were used for all in vitro studies for western blot analysis. In dose-response studies, melatonin increases xCT expression by 2.43 ± 0.81, 3.58 ± 0.6, 3.21 ± 1.13, 3.30 ± 0.96 and 3.48 ± 0.30 (p < 0.01) folds at 1 nM, 10 nM, 100 nM, 1 µM and 10 µM concentrations respectively in neural stem cells. In time-course studies, melatonin increases xCT by 2.60 ± 0.97, 2.65 ± 0.27, 3.29 ± 0.40, and 3.57 ± 0.60 fold at 4 hours, 8 hours, 12 hours, and 24 hours. Melatonin increases cystine uptake. System Xc inhibition decreased cell viability. These results suggest that melatonin may induce neuroprotection by increasing xCT expression and activity.