Early identification of autism spectrum disorder in children with CHD attending a Cardiac Developmental Outcomes Program.

OBJECTIVE: To determine the prevalence and timing of autism spectrum disorder diagnosis in a cohort of congenital heart disease (CHD) patients receiving neurodevelopmental follow-up and identify associated risk factors. METHOD: Retrospective single-centre observational study of 361 children undergoing surgery for CHD during the first 6 months of life. Data abstracted included age at autism spectrum disorder diagnosis, child and maternal demographics, and medical history. RESULTS: Autism spectrum disorder was present in 9.1% of children with CHD, with a median age at diagnosis of 34 months and 87.9% male. Prematurity, history of post-operative extracorporeal membrane oxygenation, and seizures were higher among those with autism (p = 0.013, p = 0.023, p = 0.001, respectively). Infants with autism spectrum disorder were older at the time of surgery (54 days vs 13.5 days, p = 0.002), and infants with surgery at ≥ 30 days of age had an increased risk of autism spectrum disorder (OR 2.31; 95% CI =1.12, 4.77, p = 0.023). On multivariate logistic regression analysis, being male (OR 4.85, p = 0.005), surgery ≥ 30 days (OR 2.46, p = 0.025), extracorporeal membrane oxygenation (OR 4.91, p = 0.024), and seizures (OR 4.32, p = 0.003) remained associated with increased odds for autism spectrum disorder. Maternal age, race, ethnicity, and surgical complexity were not associated. CONCLUSIONS: Children with CHD in our cohort had more than three times the risk of autism spectrum disorder and were diagnosed at a much earlier age compared to the general population. Several factors (male, surgery at ≥ 30 days, post-operative extracorporeal membrane oxygenation, and seizures) were associated with increased odds of autism. These findings support the importance of offering neurodevelopmental follow-up after cardiac surgery in infancy.

Recurrent acute kidney injury is associated with delayed language development in infants with Congenital Heart Disease.

OBJECTIVE: Neurodevelopmental delay is common in children who undergo surgery for Congenital Heart Disease (CHD) in infancy. Cardiac surgery associated acute kidney injury (CS-AKI) occurs frequently in the paediatric cardiac Intensive care unit (ICU). Cardiac surgery associated acute kidney injury (CS-AKI) is associated with worse neurodevelopmental scores and delay in cognitive, language, and motor domains in children with CHD. No known data exist regarding the association of CS-AKI and motor and language subscales. In this study, we explored the relationship between CS-AKI and receptive and expressive language, as well as gross and fine motor delay. METHODS: This was a single centre retrospective observational cohort study. Children who underwent surgery for CHD and developed recurrent CS-AKI in the first year of life who had follow-up neurodevelopmental testing using the Bayley Scale of Infant Development Version III were included. Neurodevelopmental delay subscales assessed included: receptive and expressive language, fine and motor skills. RESULTS: The study cohort included 203 children. Recurrent CS-AKI was significantly associated with lower scores in receptive and expressive language, as well as fine and gross motor on unadjusted analyses. On adjusted analyses, recurrent CS-AKI was significantly associated with severe receptive language delay. CONCLUSION: The independent association of recurrent CS-AKI with severe language delay in children who undergo surgery for CHD in infancy is novel. Our findings may contribute to the understanding of language impairment in this population. Further studies are required to better understand this relationship and any potentially modifiable factors.

Development and validation of an open-source pipeline for automatic population of case report forms from electronic health records: a pediatric multi-center prospective study.

BACKGROUND: Clinical trials and registry studies are essential for advancing research and developing novel treatments. However, these studies rely on manual entry of thousands of variables for each patient. Repurposing real-world data can significantly simplify the data collection, reduce transcription errors, and make the data entry process more efficient, consistent, and cost-effective. METHODS: We developed an open-source computational pipeline to collect laboratory and medication information from the electronic health record (EHR) data and populate case report forms. The pipeline was developed and validated with data from two independent pediatric hospitals in the US as part of the Long-terM OUtcomes after Multisystem Inflammatory Syndrome In Children (MUSIC) study. Our pipeline allowed the completion of two of the most time-consuming forms. We compared automatically extracted results with manually entered values in one hospital and applied the pipeline to a second hospital, where the output served as the primary data source for case report forms. FINDINGS: We extracted and populated 51,845 laboratory and 4913 medication values for 159 patients in two hospitals participating in a prospective pediatric study. We evaluated pipeline performance against data for 104 patients manually entered by clinicians in one of the hospitals. The highest concordance was found during patient hospitalization, with 91.59% of the automatically extracted laboratory and medication values corresponding with the manually entered values. In addition to the successfully populated values, we identified an additional 13,396 laboratory and 567 medication values of interest for the study. INTERPRETATION: The automatic data entry of laboratory and medication values during admission is feasible and has a high concordance with the manually entered data. By implementing this proof of concept, we demonstrate the quality of automatic data extraction and highlight the potential of secondary use of EHR data to advance medical science by improving data entry efficiency and expediting clinical research. FUNDING: NIH Grant 1OT3HL147154-01, U24HL135691, UG1HL135685.

Examination of Adverse Reactions After COVID-19 Vaccination Among Patients With a History of Multisystem Inflammatory Syndrome in Children.

Importance: Data are limited regarding adverse reactions after COVID-19 vaccination in patients with a history of multisystem inflammatory syndrome in children (MIS-C). The lack of vaccine safety data in this unique population may cause hesitancy and concern for many families and health care professionals. Objective: To describe adverse reactions following COVID-19 vaccination in patients with a history of MIS-C. Design, Setting, and Participants: In this multicenter cross-sectional study including 22 North American centers participating in a National Heart, Lung, and Blood Institute, National Institutes of Health-sponsored study, Long-Term Outcomes After the Multisystem Inflammatory Syndrome in Children (MUSIC), patients with a prior diagnosis of MIS-C who were eligible for COVID-19 vaccination (age ≥5 years; ≥90 days after MIS-C diagnosis) were surveyed between December 13, 2021, and February 18, 2022, regarding COVID-19 vaccination status and adverse reactions. Exposures: COVID-19 vaccination after MIS-C diagnosis. Main Outcomes and Measures: The main outcome was adverse reactions following COVID-19 vaccination. Comparisons were made using the Wilcoxon rank sum test for continuous variables and the χ2 or Fisher exact test for categorical variables. Results: Of 385 vaccine-eligible patients who were surveyed, 185 (48.1%) received at least 1 vaccine dose; 136 of the vaccinated patients (73.5%) were male, and the median age was 12.2 years (IQR, 9.5-14.7 years). Among vaccinated patients, 1 (0.5%) identified as American Indian/Alaska Native, non-Hispanic; 9 (4.9%) as Asian, non-Hispanic; 45 (24.3%) as Black, non-Hispanic; 59 (31.9%) as Hispanic or Latino; 53 (28.6%) as White, non-Hispanic; 2 (1.1%) as multiracial, non-Hispanic; and 2 (1.1%) as other, non-Hispanic; 14 (7.6%) had unknown or undeclared race and ethnicity. The median time from MIS-C diagnosis to first vaccine dose was 9.0 months (IQR, 5.1-11.9 months); 31 patients (16.8%) received 1 dose, 142 (76.8%) received 2 doses, and 12 (6.5%) received 3 doses. Almost all patients received the BNT162b2 vaccine (347 of 351 vaccine doses [98.9%]). Minor adverse reactions were observed in 90 patients (48.6%) and were most often arm soreness (62 patients [33.5%]) and/or fatigue (32 [17.3%]). In 32 patients (17.3%), adverse reactions were treated with medications, most commonly acetaminophen (21 patients [11.4%]) or ibuprofen (11 [5.9%]). Four patients (2.2%) sought medical evaluation, but none required testing or hospitalization. There were no patients with any serious adverse events, including myocarditis or recurrence of MIS-C. Conclusions and Relevance: In this cross-sectional study of patients with a history of MIS-C, no serious adverse events were reported after COVID-19 vaccination. These findings suggest that the safety profile of COVID-19 vaccination administered at least 90 days following MIS-C diagnosis appears to be similar to that in the general population.

Neurodevelopmental Outcomes in Infants With Cardiac Surgery Associated Acute Kidney Injury.

BACKGROUND: Infants who undergo surgery for congenital heart disease are at risk of neurodevelopmental delay. Cardiac surgery-associated acute kidney injury (CS-AKI) is common but its association with neurodevelopment has not been explored. METHODS: This was a single-center retrospective observational study of infants who underwent cardiac surgery in the first year of life who had neurodevelopmental testing using the Bayley Scale for Infant Development, third edition. Single and recurrent episodes of stages 2 and 3 CS-AKI were determined. RESULTS: Of 203 children with median age at first surgery of 12 days, 31% had one or more episodes of severe CS-AKI; of those, 16% had recurrent CS-AKI. Median age at neurodevelopmental assessment was 20 months. The incidence of delay was similar for patients with and patients without CS-AKI but all children with recurrent CS-AKI had a delay in one or more domains and had significantly lower scores in all three domains, namely, cognitive, language, and motor. CONCLUSIONS: This study has assessed the association of CS-AKI with neurodevelopmental delay after surgery for congenital heart disease in infancy. Infants who have recurrent CS-AKI in the first year of life are more likely to be delayed and have lower neurodevelopmental scores.

In vitro and in vivo magnetic resonance imaging (MRI) detection of GFP through magnetization transfer contrast (MTC).

Green fluorescent protein (GFP) is a widely utilized molecular marker of gene expression. However, its use in in vivo imaging has been restricted to transparent tissue mainly due to the tissue penetrance limitation of optical imaging. Here, we report a novel approach to detect GFP with Magnetization transfer contrast (MTC) magnetic resonance imaging (MRI). MTC is an MRI methodology currently utilized to detect macromolecule changes such as decrease in myelin and increase in collagen content. We employed MTC MRI imaging to detect GFP both in vitro and in in vivo mouse models. We demonstrated that our approach produces values that are protein specific, and concentration dependent. This approach provides a flexible, non-invasive in vivo molecular MRI imaging strategy that is dependent upon the presence and concentration of the GFP reporter.

Impact of feeding mode on neurodevelopmental outcome in infants and children with congenital heart disease.

OBJECTIVE: To investigate the impact of feeding mode on neurodevelopmental outcomes in children with congenital heart defects. DESIGN: A retrospective cohort study of 208 children with congenital heart disease (CHD), who had surgery from 1 January 2013 until 31 December 2016 at Texas Children's Hospital, Houston, TX, US. SETTINGS: University Hospital, Developmental Outcome Clinic. OUTCOMES MEASURES: Standardized cognitive scores were assessed with Capute Scales and motor development with Revised Gesell Developmental Schedules. We analyzed anthropometrics, mode of feeding, surgical complexity, syndrome, and gender as predictors of developmental outcomes at four time points: hospital discharge, and 6, 12, and 24 months of age. RESULTS: Mode of feeding is associated with neurodevelopmental outcome in children with CHD. Children on enteral feeding tubes had significantly lower developmental quotient (DQ) scores in cognition, communication, and motor function at 12 and 24 months compared to orally fed children. There were greater proportions of developmental delays (DQ < 70) in enteral tube fed children at the 6, 12, and 24 months visits. Further, there was a strong association between presence of enteral feeding tube, syndrome, and developmental outcome. Greater surgical complexity, weight gain and ethnicity were not associated with the developmental outcomes. CONCLUSIONS: Our findings suggest that the presence of an enteral feeding tube following corrective congenital heart surgery are at increased risk of neurodevelopmental delays at 12 and 24 months.

Ancillary referral patterns in infants after initial assessment in a cardiac developmental outcomes clinic.

OBJECTIVE: Neurodevelopmental impairment is common after surgery for congenital heart disease (CHD) in infancy. While neurodevelopmental follow-up of high-risk patients has increased, the referral patterns for ancillary services following initial evaluation have not been reported. The aim of this study is to describe the rates and patterns of referral at the initial visit to our outcomes clinic of patients who underwent surgery for CHD during infancy. OUTCOMES MEASURES: The Cardiac Developmental Outcomes Program clinic at Texas Children's Hospital provides routine longitudinal follow-up with developmental pediatricians and child psychologists for children who required surgery for CHD within the first 3 months of life. Demographic, diagnostic, and clinical data, including prior receipt of intervention and referral patterns at initial presentation, were abstracted from our database. RESULTS: Between April 2013 and May 2017, 244 infants under 12 months of age presented for initial evaluation at a mean age of 7 ± 1.3 months. At presentation, 31% (76/244) were referred for either therapeutic intervention (early intervention or private therapies), ancillary medical services, or both. Referral rates for low-risk (STAT 1-3) and high-risk (STAT 4-5) infants were similar (28 vs. 33%, P = .48). Referrals were more common in: Hispanic white infants (P = .012), infants with non-cardiac congenital anomalies (P = .001), history of gastrostomy tube placement (P < .001), and infants with prior therapy (P = .043). Infants of non-English speaking parents were three times more likely to be referred (95% CI = 1.5, 6.4; P = .002). CONCLUSIONS: At the time of presentation, nearly 1 in 3 infants required referral. Referral patterns did not vary by traditional risk stratification. Sociodemographic factors and co-morbid medical conditions increased the likelihood of referral. This supports the need for routine follow-up for all post-surgical infants regardless of level of surgical complexity. Further research into the completion of referrals and long-term referral patterns is needed.

Aging-dependent alterations in synaptic plasticity and memory in mice that overexpress extracellular superoxide dismutase.

Oxidative damage caused by reactive oxygen species (ROS) has been proposed to be critically involved in several pathological manifestations of aging, including cognitive dysfunction. ROS, including superoxide, are generally considered as neurotoxic molecules whose effects can be alleviated by antioxidant enzymes. However, ROS also are known to be necessary components of the signal transduction cascades underlying normal synaptic plasticity. Therefore, we reasoned that the role that ROS and antioxidant enzymes play in modulating neuronal processes varies over the lifespan of an animal. We examined hippocampal long-term potentiation (LTP) and memory-related behavioral performance in transgenic mice overexpressing extracellular superoxide dismutase (EC-SOD) and their wild-type littermates at different ages. We found that aged EC-SOD transgenic mice exhibited enhanced hippocampal LTP, better cerebellum-dependent motor learning, and better hippocampus-dependent spatial learning compared with their wild-type littermates. We also found that EC-SOD overexpression impaired contextual learning, but the impairment was decreased in the aged transgenic mice. At the molecular level, aged EC-SOD transgenic mice had lower superoxide levels, a decrease in protein carbonyl levels, and a decrease in p38 and extracellular signal-regulated kinase 2 phosphorylation compared with aged wild-type mice. Our findings suggest that elevated levels of superoxide contribute to aging-related impairments in hippocampal LTP and memory, and that these impairments can be alleviated by overexpression of EC-SOD. We conclude that there is an age-dependent alteration in the role of superoxide in modulating synaptic plasticity and learning and memory.

Reactive oxygen species and synaptic plasticity in the aging hippocampus.

Aging is associated with a general decline in physiological functions including cognitive functions. Given that the hippocampus is known to be critical for certain forms of learning and memory, it is not surprising that a number of neuronal processes in this brain area appear to be particularly vulnerable to the aging process. Long-term potentiation (LTP), a form of synaptic plasticity that has been proposed as a biological substrate for learning and memory, has been used to examine age-related changes in hippocampal synaptic plasticity. A current hypothesis states that oxidative stress contributes to age-related impairment in learning and memory. This is supported by a correlation between age, memory impairment, and the accumulation of oxidative damage to cellular macromolecules. However, it also has been demonstrated that ROS are necessary components of signal transduction cascades during normal physiological processes. This review discusses the evidence supporting the dual role of reactive oxygen species (ROS) as cellular messenger molecules in normal LTP, as well their role as damaging toxic molecules in the age-related impairment of LTP. In addition, we will discuss parallel analyses of LTP and behavioral tests in mice that overexpress antioxidant enzymes and how the role of antioxidant enzymes and ROS in modulating these processes may vary over the lifespan of an animal.

NADPH oxidase immunoreactivity in the mouse brain.

Superoxide production via NADPH oxidase has been shown to play a role in neurotoxicity, ischemic stroke, and possibly Parkinson's and Alzheimer's diseases. In addition, NADPH oxidase-dependent production of superoxide may be necessary for normal brain functions, including neuronal differentiation and neuronal plasticity. To improve our understanding of NADPH oxidase in the brain, we studied the localization of the various protein components of NADPH oxidase in the central nervous system of the adult mouse using immunohistochemistry. We detected staining for the cytoplasmic NADPH proteins, p40(phox), p47(phox), and p67(phox), as well as the membrane-associated NADPH oxidase proteins, p22(phox) and gp91(phox) in neurons throughout the mouse brain. Staining of each of the NADPH oxidase proteins was observed in neurons in all regions of the neuraxis, with particularly prominent localizations in the hippocampus, cortex, amygdala, striatum, and thalamus. The expression of NADPH oxidase proteins in neurons suggests the possibility that enzymatic production of superoxide by a NADPH oxidase may play a role in both normal neuronal function as well as neurodegeneration in the brain.

Pseudorabies virus-induced expression of nitric oxide synthase isoforms.

In addition to its role as a neurotransmitter, studies have postulated both neuroprotective and neurotoxic roles for nitric oxide (NO) generated in response to infections with neurotropic viruses. This study examined the expression of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) isoforms of NOS induced by neuronal infection with virulent and attenuated strains of pseudorabies virus (PRV). Caudal brainstem neurons infected by peripheral inoculation of the viscera served as the model system. Neuronal infection induced the expression of nNOS and iNOS, but the timing and the apparent magnitude of NOS expression varied according to the virulence of the infecting strain of virus. Expression of nNOS was observed in infected neurons that did not express this enzyme in control animals, and the onset of expression was earlier in animals infected with virulent PRV. Expression of iNOS was largely restricted to monocytes and macrophages that invaded the brain in response to PRV infection. These iNOS-expressing cells were observed earlier in animals infected with the virulent virus, and were differentially concentrated in areas exhibiting virus-induced neuropathology. Collectively, these data suggest functionally diverse roles for NO in the brain response to PRV neuronal infection.

Hyperglycemia induces oxidative stress and impairs axonal transport rates in mice.

BACKGROUND: While hyperglycemia-induced oxidative stress damages peripheral neurons, technical limitations have, in part, prevented in vivo studies to determine the effect of hyperglycemia on the neurons in the central nervous system (CNS). While olfactory dysfunction is indicated in diabetes, the effect of hyperglycemia on olfactory receptor neurons (ORNs) remains unknown. In this study, we utilized manganese enhanced MRI (MEMRI) to assess the impact of hyperglycemia on axonal transport rates in ORNs. We hypothesize that (i) hyperglycemia induces oxidative stress and is associated with reduced axonal transport rates in the ORNs and (ii) hyperglycemia-induced oxidative stress activates the p38 MAPK pathway in association with phosphorylation of tau protein leading to the axonal transport deficits. RESEARCH DESIGN AND METHODS: T(1)-weighted MEMRI imaging was used to determine axonal transport rates post-streptozotocin injection in wildtype (WT) and superoxide dismutase 2 (SOD2) overexpressing C57Bl/6 mice. SOD2 overexpression reduces mitochondrial superoxide load. Dihydroethidium staining was used to quantify the reactive oxygen species (ROS), specifically, superoxide (SO). Protein and gene expression levels were determined using western blotting and Q-PCR analysis, respectively. RESULTS: STZ-treated WT mice exhibited significantly reduced axonal transport rates and significantly higher levels of ROS, phosphorylated p38 MAPK and tau protein as compared to the WT vehicle treated controls and STZ-treated SOD2 mice. The gene expression levels of p38 MAPK and tau remained unchanged. CONCLUSION: Increased oxidative stress in STZ-treated WT hyperglycemic mice activates the p38 MAPK pathway in association with phosphorylation of tau and attenuates axonal transport rates in the olfactory system. In STZ-treated SOD-overexpressing hyperglycemic mice in which superoxide levels are reduced, these deficits are reversed.

Brain preservation with selective cerebral perfusion for operations requiring circulatory arrest: protection at 25 degrees C is similar to 18 degrees C with shorter operating times.

BACKGROUND: Hypothermic circulatory arrest (HCA) is employed for aortic arch and other complex operations, often with selective cerebral perfusion (SCP). Our previous work has demonstrated real-time evidence of improved brain protection using SCP at 18 degrees C. The purpose of this study was to evaluate the utility of SCP at warmer temperatures (25 degrees C) and its impact on operating times. METHODS: Piglets undergoing cardiopulmonary bypass (CPB) and 60 min of HCA were assigned to three groups: 18 degrees C without SCP, 18 degrees C with SCP and 25 degrees C with SCP (n=8 animals per group). CPB flows were 100 ml kg(-1) min(-1) using pH-stat management. SCP flows were 10 ml kg(-1) min(-1) via the innominate artery. Cerebral oxygenation was monitored using NIRS (near-infrared spectroscopy). A microdialysis probe placed into the cerebral cortex had samples collected every 15 min. Animals were recovered for 4h after separation from CPB. All data are presented as mean+/-standard deviation (SD; p<0.05, significant). RESULTS: Cerebral oxygenation was preserved during deep and tepid HCA with SCP, in contrast to deep HCA without SCP (p<0.05). Deep HCA at 18 degrees C without SCP resulted in significantly elevated brain lactate (p<0.01) and glycerol (p<0.01), while the energy substrates glucose (p<0.001) and pyruvate (p<0.001) were significantly depleted. These derangements were prevented with SCP at 18 degrees C and 25 degrees C. The lactate/pyruvate ratio (L/P) was profoundly elevated following HCA alone (p<0.001) and remained persistently elevated throughout recovery (p<0.05). Piglets given SCP during HCA at 18 degrees C and 25 degrees C maintained baseline L/P ratios. Mean operating times were significantly shorter in the 25 degrees C group compared to both 18 degrees C groups (p<0.05) without evidence of significant acidemia. CONCLUSION: HCA results in cerebral hypoxia, energy depletion and ischaemic injury, which are attenuated with the use of SCP at both 18 degrees C and 25 degrees C. Procedures performed at 25 degrees C had significantly shorter operating times while preserving end organs.

NADPH oxidase mediates beta-amyloid peptide-induced activation of ERK in hippocampal organotypic cultures.

BACKGROUND: Previous studies have shown that beta amyloid (Abeta) peptide triggers the activation of several signal transduction cascades in the hippocampus, including the extracellular signal-regulated kinase (ERK) cascade. In this study we sought to characterize the cellular localization of phosphorylated, active ERK in organotypic hippocampal cultures after acute exposure to either Abeta (1-42) or nicotine. RESULTS: We observed that Abeta and nicotine increased the levels of active ERK in distinct cellular localizations. We also examined whether phospho-ERK was regulated by redox signaling mechanisms and found that increases in active ERK induced by Abeta and nicotine were blocked by inhibitors of NADPH oxidase. CONCLUSION: Our findings indicate that NADPH oxidase-dependent redox signaling is required for Abeta-induced activation of ERK, and suggest a similar mechanism may occur during early stages of Alzheimer's disease.

Selective cerebral perfusion: real-time evidence of brain oxygen and energy metabolism preservation.

BACKGROUND: Deep hypothermic circulatory arrest (DHCA) is commonly used for complex cardiac operations in children, often with selective cerebral perfusion (SCP). Little data exist concerning the real-time effects of DHCA with or without SCP on cerebral metabolism. Our objective was to better define these effects, focusing on brain oxygenation and energy metabolism. METHODS: Piglets undergoing cardiopulmonary bypass were assigned to either 60 minutes of DHCA at 18 degrees C (n = 9) or DHCA with SCP at 18 degrees C (n = 8), using pH-stat management. SCP was administered at 10 mL/kg/min. A cerebral microdialysis catheter was implanted into the cortex for monitoring of cellular ischemia and energy stores. Cerebral oxygen tension and intracranial pressure also were monitored. After DHCA with or without SCP, animals were recovered for 4 hours off cardiopulmonary bypass. RESULTS: With SCP, brain oxygen tension was preserved in contrast to DHCA alone (p < 0.01). Deep hypothermic circulatory arrest was associated with marked elevations of lactate (p < 0.01), glycerol (p < 0.01), and the lactate to pyruvate ratio (p < 0.001), as well as profound depletion of the energy substrates glucose (p < 0.001) and pyruvate (p < 0.001). These changes persisted well into recovery. With SCP, no significant cerebral microdialysis changes were observed. A strong correlation was demonstrated between cerebral oxygen levels and cerebral microdialysis markers (p < 0.001). CONCLUSIONS: Selective cerebral perfusion preserves cerebral oxygenation and attenuates derangements in cerebral metabolism associated with DHCA. Cerebral microdialysis provides real-time metabolic feedback that correlates with changes in brain tissue oxygenation. This model enables further study and refinement of strategies aiming to limit brain injury in children requiring complex cardiac operations.

Assessing transneuronal dysfunction utilizing manganese-enhanced MRI (MEMRI).

In this study we utilized manganese-enhanced MRI (MEMRI) to evaluate the in vivo transneuronal efficiency of manganese ion (Mn(2+)) movement as a means to assess overall changes in neuronal function. We designated this extension the manganese transfer index (MTI) value. To evaluate the MTI value as an index of transneuronal physiology we examined both pharmacological agents and different mouse models of neuronal dysfunction. We found that treatment with isoflurane, which attenuates synaptic vesicle release, or memantine, which attenuates postsynaptic uptake of Ca(2+) as well as Mn(2+), resulted in a decrease in the MTI value. Furthermore, we evaluated if changes in the MTI value can be detected in three knockout mice with altered brain function accompanied either with or without neurodegeneration. Our data demonstrate that the MTI values either decreased or increased in response to different functional as well as anatomical changes. These results demonstrate the potential utility of the MTI value as an in vivo index for the detection of changes in neuronal function in animal models of human disease.

NMDA receptor activation induces translocation and activation of Rac in mouse hippocampal area CA1.

Neuronal development requires several discrete morphological steps that are believed to involve the small GTPase Rac. For example, neural activity, through NMDA receptors and/or AMPA receptors, activates Rac leading to elaboration of dendritic arbors. In the current study, we have conducted studies which indicate that Rac might be an important molecule involved in morphological plasticity in the adult mouse. We demonstrate that Rac is expressed at synapses in the adult mouse hippocampus. We also demonstrate that treatment of hippocampal slices with NMDA induces membrane translocation and activation of Rac in area CA1. Interestingly, we also find that there is an increase in Rac that is associated with NMDA receptor complexes following NMDA receptor activation. Taken together, our data are consistent with the idea that Rac could be participating in NMDA receptor-dependent changes in morphology that occur during synaptic plasticity and memory formation in the adult mouse hippocampus.

NADPH oxidase mediates hypersomnolence and brain oxidative injury in a murine model of sleep apnea.

RATIONALE: Persons with obstructive sleep apnea may have significant residual hypersomnolence, despite therapy. Long-term hypoxia/reoxygenation events in adult mice, simulating oxygenation patterns of moderate-severe sleep apnea, result in lasting hypersomnolence, oxidative injury, and proinflammatory responses in wake-active brain regions. We hypothesized that long-term intermittent hypoxia activates brain NADPH oxidase and that this enzyme serves as a critical source of superoxide in the oxidation injury and in hypersomnolence. OBJECTIVES: We sought to determine whether long-term hypoxia/reoxygenation events in mice result in NADPH oxidase activation and whether NADPH oxidase is essential for the proinflammatory response and hypersomnolence. METHODS: NADPH oxidase gene and protein responses were measured in wake-active brain regions in wild-type mice exposed to long-term hypoxia/reoxygenation. Sleep and oxidative and proinflammatory responses were measured in adult mice either devoid of NADPH oxidase activity (gp91phox-null mice) or in which NADPH oxidase activity was systemically inhibited with apocynin osmotic pumps throughout hypoxia/reoxygenation. MAIN RESULTS: Long-term intermittent hypoxia increased NADPH oxidase gene and protein responses in wake-active brain regions. Both transgenic absence and pharmacologic inhibition of NADPH oxidase activity throughout long-term hypoxia/reoxygenation conferred resistance to not only long-term hypoxia/reoxygenation hypersomnolence but also to carbonylation, lipid peroxidation injury, and the proinflammatory response, including inducible nitric oxide synthase activity in wake-active brain regions. CONCLUSIONS: Collectively, these findings strongly support a critical role for NADPH oxidase in the lasting hypersomnolence and oxidative and proinflammatory responses after hypoxia/reoxygenation patterns simulating severe obstructive sleep apnea oxygenation, highlighting the potential of inhibiting NADPH oxidase to prevent oxidation-mediated morbidities in obstructive sleep apnea.

Synaptic localization of a functional NADPH oxidase in the mouse hippocampus.

Superoxide has been shown to be critical for hippocampal long-term potentiation (LTP) and hippocampus-dependent memory function. A possible source for the generation of superoxide during these processes is NADPH oxidase. The active oxidase consists of two membrane proteins, gp91phox and p22phox, and four cytosolic proteins, p40phox, p47phox, p67phox, and Rac. Upon stimulation, the cytosolic proteins translocate to the membrane to form a complex with the membrane components, which results in production of superoxide. Here, we determined the presence, localization, and functionality of a NADPH oxidase in mouse hippocampus by examining the NADPH oxidase proteins as well as the production of superoxide. All of the NADPH oxidase proteins were present in hippocampal homogenates and enriched in synaptoneurosome preparations. Immunocytochemical analysis of cultured hippocampal neurons indicated that all NADPH oxidase proteins were localized in neuronal cell bodies as well as dendrites. Furthermore, double labeling analysis using antibodies to p67phox and the presynaptic marker synaptophysin suggest a close association of the NADPH oxidase subunits with synaptic sites. Finally, stimulation of hippocampal slices with phorbol esters triggered translocation of the cytoplasmic NADPH oxidase proteins to the membrane and an increase in superoxide production that was blocked by inhibitors of NADPH oxidase. Taken together, our data suggest that NADPH oxidase is present in mouse hippocampus and might be the source of superoxide production required for LTP and memory function.