Neonatal brain injury influences structural connectivity and childhood functional outcomes

Neonatal brain injury may impact brain development and lead to lifelong functional impairments. Hypoxic-ischemic encephalopathy (HIE) and congenital heart disease (CHD) are two common causes of neonatal brain injury differing in timing and mechanism. Maturation of whole-brain neural networks can be quantified during development using diffusion magnetic resonance imaging (dMRI) in combination with graph theory metrics. DMRI of 35 subjects with CHD and 62 subjects with HIE were compared to understand differences in the effects of HIE and CHD on the development of network topological parameters and functional outcomes. CHD newborns had worse 12–18 month language (P<0.01) and 30 month cognitive (P<0.01), language (P = 0.05), motor outcomes (P = 0.01). Global efficiency, a metric of brain integration, was lower in CHD (P = 0.03) than in HIE, but transitivity, modularity and small-worldness were similar. After controlling for clinical factors known to affect neurodevelopmental outcomes, we observed that global efficiency was highly associated with 30 month motor outcomes (P = 0.02) in both groups. To explore neural correlates of adverse language outcomes in CHD, we used hypothesis-based and data-driven approaches to identify pathways with altered structural connectivity. We found that connectivity strength in the superior longitudinal fasciculus (SLF) tract 2 was inversely associated with expressive language. After false discovery rate correction, a whole connectome edge analysis identified 18 pathways that were hypoconnected in the CHD cohort as compared to HIE. In sum, our study shows that neonatal structural connectivity predicts early motor development after HIE or in subjects with CHD, and regional SLF connectivity is associated with language outcomes. Further research is needed to determine if and how brain networks change over time and whether those changes represent recovery or ongoing dysfunction. This knowledge will directly inform strategies to optimize neurologic functional outcomes after neonatal brain injury.

Free Radicals and Neonatal Brain Injury: From Underlying Pathophysiology to Antioxidant Treatment Perspectives

Free radicals play a role of paramount importance in the development of neonatal brain injury. Depending on the pathophysiological mechanisms underlying free radical overproduction and upon specific neonatal characteristics, such as the GA-dependent maturation of antioxidant defenses and of cerebrovascular autoregulation, different profiles of injury have been identified. The growing evidence on the detrimental effects of free radicals on the brain tissue has led to discover not only potential biomarkers for oxidative damage, but also possible neuroprotective therapeutic approaches targeting oxidative stress. While a more extensive validation of free radical biomarkers is required before considering their use in routine neonatal practice, two important treatments endowed with antioxidant properties, such as therapeutic hypothermia and magnesium sulfate, have become part of the standard of care to reduce the risk of neonatal brain injury, and other promising therapeutic strategies are being tested in clinical trials. The implementation of currently available evidence is crucial to optimize neonatal neuroprotection and to develop individualized diagnostic and therapeutic approaches addressing oxidative brain injury, with the final aim of improving the neurological outcome of this population.

N-Acetyl Cysteine Restores Sirtuin-6 and Decreases HMGB1 Release Following Lipopolysaccharide-Sensitized Hypoxic-Ischemic Brain Injury in Neonatal Mice

Inflammation and neonatal hypoxia-ischemia (HI) are important etiological factors of perinatal brain injury. However, underlying mechanisms remain unclear. Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)+-dependent histone deacetylases. Sirtuin-6 is thought to regulate inflammatory and oxidative pathways, such as the extracellular release of the alarmin high mobility group box-1 (HMGB1). The expression and role of sirtuin-6 in neonatal brain injury are unknown. In a well-established model of neonatal brain injury, which encompasses inflammation (lipopolysaccharide, LPS) and hypoxia-ischemia (LPS+HI), we investigated the protein expression of sirtuin-6 and HMGB1, as well as thiol oxidation. Furthermore, we assessed the effect of the antioxidant N-acetyl cysteine (NAC) on sirtuin-6 expression, nuclear to cytoplasmic translocation, and release of HMGB1 in the brain and blood thiol oxidation after LPS+HI. We demonstrate reduced expression of sirtuin-6 and increased release of HMGB1 in injured hippocampus after LPS+HI. NAC treatment restored sirtuin-6 protein levels, which was associated with reduced extracellular HMGB1 release and reduced thiol oxidation in the blood. The study suggests that early reduction in sirtuin-6 is associated with HMGB1 release, which may contribute to neonatal brain injury, and that antioxidant treatment is beneficial for the alleviation of these injurious mechanisms.

Computational Analysis of Cortical Neuronal Excitotoxicity in a Large Animal Model of Neonatal Brain Injury

Background: Neonatal hypoxic brain injury is a major cause of intellectual and developmental disability. Hypoxia causes neuronal dysfunction and death in the developing cerebral cortex due to excitotoxic Ca2+-influx. In the translational piglet model of hypoxic encephalopathy, we have previously shown that hypoxia overactivates Ca2+/Calmodulin (CaM) signaling via Sarcoma (Src) kinase in cortical neurons, resulting in overexpression of proapoptotic genes. However, identifying the exact relationship between alterations in neuronal Ca2+-influx, molecular determinants of cell death, and the degree of hypoxia in a dynamic system represents a significant challenge. Methods: We used experimental and computational methods to identify molecular events critical to the onset of excitotoxicity-induced apoptosis in the cerebral cortex of newborn piglets. We used 2-3 day-old piglets (normoxic [Nx], hypoxic [Hx], and hypoxic + Src-inhibitor-treatment [Hx+PP2]groups) for biochemical analysis of ATP production, Ca2+-influx, and Ca2+/CaM-dependent protein kinase kinase 2(CaMKK2) expression. We then used SimBiology to build a computational model of the Ca2+/CaM-Src-kinase signaling cascade, simulating Nx, Hx, and Hx+PP2 conditions. To evaluate our model, we used Sobol variance decomposition, multiparametric global sensitivity analysis, and parameter scanning.Results: Our model captures important molecular trends caused by hypoxia in the piglet brain. Incorporating the action of Src kinase inhibitor PP2 further validated our model and enabled predictive analysis of the effect of hypoxia on CaMKK2. We determined the impact of a feedback loop related to Src phosphorylation of NMDA receptors and activation kinetics of CaMKII. We also identified distinct modes of signaling wherein Ca2+ level alterations following Src kinase inhibition may not be a linear predictor of changes in Bax expression. Importantly, our model indicates that while pharmacological pre-treatment significantly reduces the onset of abnormal Ca2+-influx, there exists a window of intervention after hypoxia during which targeted modulation of Src-NMDAR interaction kinetics in combination with PP2 administration can reduce Ca2+-influx and Bax expression to similar levels as pre-treatment. Conclusions: Our model identifies new dynamics of critical components in the Ca2+/CaM-Src signaling pathway leading to neuronal injury and provides an essential framework for drug efficacy studies in translational models of neonatal brain injury for the prevention of intellectual and developmental disabilities.

Treatment Device for Neonatal Birth Asphyxia Related Hypoxic Ischemic Encephalopathy

Background: Birth asphyxia is a leading cause of neonatal brain injury, morbidity and mortality globally. Birth asphyxia leads to multi-organ dysfunction in the neonate and to neurological dysfunction called Hypoxic Ischemic Encephalopathy (HIE). Cooling therapy is being used as a means of treatment in developed countries. However, these devices are not affordable for low-resource settings, including Ethiopia. Moreover, many cooling devices do not have a rewarming functionality after cooling therapy. The objective of this project was therefore to design and develop a cost effective and efficient total body cooling and rewarming device.Methods: Our design includes two water reservoirs that operate by pumping cold and warm sterile water to a mattress. After decreasing the core body temperature of the infant to 33.5 0C, the system is designed to maintain this temperature value for 72 hours. Feedback for temperature regulation will is provided by rectal temperature sensor. Once the cooling therapy is completed, the system again rewarms the water inside the matters and gradually increases the neonate temperature to 36.5-37 0C. The device also allows continuous monitoring of infant’s body temperature, mattress temperature reservoir temperature and pulse rate. Results: The prototype was built and undergone through different tests and iterations. The proposed device was tested for accuracy, cost effectiveness and ease to use. 93.2 % accuracy has been achieved for temperature sensor measurement and the prototype was built only with a component cost of less than 200 USD.Conclusion: The proposed devices allow an accurate, regulated and continuous monitoring of temperature of reservoirs, mattress and rectal temperature. was provided using sensors. The device can play a significant role by reducing neonatal brain injury and death due to HIE, especially in low resource settings, where the expertise and the means are in scarce.

Serum glial fibrillary acidic protein as a biomarker of brain injury in premature neonates

Neonatal brain injury is a serious adverse outcome of prematurity. Early detection of high risk premature neonates to develop neonatal brain injury is not currently feasible. The predictive value of many biomarkers has been tested, but none is used currently in clinical practice. The purpose of this study was to determine the levels and predictive value of serum glial fibrillary acidic protein (GFAP) in a prospective longitudinal case-control study during the first three days of life in premature neonates (<34 weeks of gestation) that later developed either intraventricular hemorrhage or periventricular leukomalacia. Each case (n=29) was matched according to birth weight and gestational age to one neonate with normal head ultrasound scans. No significant difference on GFAP levels was observed between the groups. Nevertheless, neonates with brain injury presented more frequently GFAP levels above the lowest detection limit (0.056 ng/ml) and this trend was significantly different during all days. The effectiveness of GFAP as an early biomarker of neonatal brain injury in premature neonates seems to be limited.