Regional lung metabolic profile in a piglet model of cardiopulmonary bypass with circulatory arrest.

INTRODUCTION: Acute lung injury is common following cardiopulmonary bypass and deep hypothermic circulatory arrest for congenital heart surgery with the most severe injury in the dorsocaudal lung. Metabolomics offers promise in deducing mechanisms of disease states, providing risk stratification, and understanding therapeutic responses in regards to CPB/DHCA related organ injury. OBJECTIVES: Using an infant porcine model, we sought to determine the individual and additive effects of CPB/DHCA and lung region on the metabolic fingerprint, metabolic pathways, and individual metabolites in lung tissue. METHODS: Twenty-seven infant piglets were divided into two groups: mechanical ventilation + CPB/DHCA (n = 20) and mechanical ventilation only (n = 7). Lung tissue was obtained from dorsocaudal and ventral regions. Targeted analysis of 235 metabolites was performed using HPLC/MS-MS. Data was analyzed using Principal Component Analysis (PCA), Partial Least Square Discriminant Analysis (PLS-DA), ANOVA, and pathway analysis. RESULTS: Profound metabolic differences were found in dorsocaudal compared to ventral lung zones by PCA and PLS-DA (R2 = 0.7; Q2 = 0.59; p < 0.0005). While overshadowed by the regional differences, some differences by exposure to CPB/DHCA were seen as well. Seventy-four metabolites differed among groups and pathway analysis revealed 20 differential metabolic pathways. CONCLUSION: Our results demonstrate significant metabolic disturbances between dorsocaudal and ventral lung regions during supine mechanical ventilation with or without CPB/DHCA. CPB/DHCA also leads to metabolic differences and may have additive effects to the regional disturbances. Most pathways driving this pathology are involved in energy metabolism and the metabolism of amino acids, carbohydrates, and reduction-oxidation pathways.

Is Neurodevelopment Related to Exercise Capacity in Single Ventricle Patients Who Have Undergone Fontan Palliation?

Survivors of palliative surgery for single ventricle heart disease (SVHD) are at risk of poor neurodevelopmental outcomes and reduced exercise capacity. In healthy populations, reduced exercise capacity is related to decreased cognition suggesting a possible relationship between exercise capacity and neurodevelopment. Using cardiopulmonary exercise testing (CPET) and neuropsychological testing (NPT) as indicators of exercise capacity and neurodevelopment, respectively, we hypothesized that in SVHD, higher CPET measures are related to better NPT performance. Patients were retrospectively identified. CPET variables included VO2max, anaerobic threshold, peak heart rate, ventilatory efficiency, and respiratory exchange ratio. NPT instruments were divided into domains measuring attention, executive functioning, adaptive functioning, and emotional functioning. Linear regression was used to test for associations between CPET and NPT. 23 subjects with SVHD met inclusion criteria. On both CPET and NPT, the cohort scored worse than healthy, age-matched subjects. Higher VO2max and anaerobic threshold were associated with better parent-rated overall adaptive functioning (p = 0.01 and p = 0.02, respectively). Higher peak heart rate was related to better sustained visual attention (p = 0.01). In SVHD, CPET measures indicating better exercise capacity were positively associated with a subset of scores on NPT. Larger, multisite studies implementing cardiorespiratory fitness intervention and incorporating cognitive outcome measures will be needed to better characterize the relationship between neurodevelopment and functional capacity in this population. Results may assist in providing anticipatory guidance and optimizing post-Fontan developmental trajectories.

Outcome after Repetitive Mild Traumatic Brain Injury Is Temporally Related to Glucose Uptake Profile at Time of Second Injury.

Repeated mild traumatic brain injury (rmTBI) results in worsened outcomes, compared with a single injury, but the mechanism of this phenomenon is unclear. We have previously shown that mild TBI in a rat lateral fluid percussion model results in globally depressed glucose uptake, with a peak depression at 24 h that resolves by 16 days post-injury. The current study investigated the outcomes of a repeat injury conducted at various times during this period of depressed glucose uptake. Adult male rats were therefore subjected to rmTBI with a latency of 24 h, 5 days, or 15 days between injuries, followed by assessment of motor function, histopathology, and glucose uptake using positron emission tomography (PET). Rats that received a 24 h rmTBI showed significant deficits in motor function tasks, as well as significant increases in lesion volume and neuronal damage. The level of microglial and astrocytic activation also was associated with the timing of the second impact. Finally, rmTBI with latencies of 24 h and 5 days showed significant alterations in [(18)F]fluorodeoxyglucose uptake, compared with baseline scans. Therefore, we conclude that the state of the metabolic environment, as indicated by FDG-PET at the time of the repeat injury, significantly influences neurological outcomes.

Cellular and temporal expression of NADPH oxidase (NOX) isotypes after brain injury.

BACKGROUND: Brain injury results in an increase in the activity of the reactive oxygen species generating NADPH oxidase (NOX) enzymes. Preliminary studies have shown that NOX2, NOX3, and NOX4 are the most prominently expressed NOX isotypes in the brain. However, the cellular and temporal expression profile of these isotypes in the injured and non-injured brain is currently unclear. METHODS: Double immunofluorescence for NOX isotypes and brain cell types was performed at acute (24 hours), sub-acute (7 days), and chronic (28 days) time points after controlled cortical impact-induced brain injury or sham-injury in rats. RESULTS: NOX2, NOX3, and NOX4 isotypes were found to be expressed in neurons, astrocytes, and microglia, and this expression was dependent on both cellular source and post-injury time. NOX4 was found in all cell types assessed, while NOX3 was positively identified in neurons only, and NOX2 was identified in microglia and neurons. NOX2 was the most responsive to injury, increasing primarily in microglia in response to injury. Quantitation of this isotype showed a significant increase in NOX2 expression at 24 hours, with reduced expression at 7 days and 28 days post-injury, although expression remained above sham levels at later time points. Cellular confirmation using purified primary or cell line culture demonstrated similar patterns in microglia, astrocytes, and neurons. Further, inhibition of NOX, and more specifically NOX2, reduced pro-inflammatory activity in microglia, demonstrating that NOX is not only up-regulated after stimulation, but may also play a significant role in post-injury neuroinflammation. CONCLUSIONS: This study illustrates the expression profiles of NOX isotypes in the brain after injury, and demonstrates that NOX2, and to a lesser extent, NOX4, may be responsible for the majority of oxidative stress observed acutely after traumatic brain injury. These data may provide insight into the design of future therapeutic approaches.

808 nm wavelength light induces a dose-dependent alteration in microglial polarization and resultant microglial induced neurite growth.

BACKGROUND AND OBJECTIVE: Despite the success of using photobiomodulation (PBM), also known as low level light therapy, in promoting recovery after central nervous system (CNS) injury, the effect of PBM on microglia, the primary mediators of immune and inflammatory response in the CNS, remains unclear. Microglia exhibit a spectrum of responses to injury, with partial or full polarization into pro- and anti-inflammatory phenotypes. Pro-inflammatory (M1 or classically activated) microglia contribute to chronic inflammation and neuronal toxicity, while anti-inflammatory (M2 or alternatively activated) microglia play a role in wound healing and tissue repair; microglia can fall anywhere along this spectrum in response to stimulation. MATERIALS AND METHODS: The effect of PBM on microglial polarization therefore was investigated using colorimetric assays, immunocytochemistry, proteomic profiling and RT-PCR in vitro after exposure of primary microglia or BV2 microglial cell line to PBM of differing energy densities (0.2, 4, 10, and 30 J/cm(2) , 808 nm wavelength, 50 mW output power). RESULTS: PBM has a dose-dependent effect on the spectrum of microglial M1 and M2 polarization. Specifically, PBM with energy densities between 4 and 30 J/cm(2) induced expression of M1 markers in microglia. Markers of the M2 phenotype, including CD206 and TIMP1, were observed at lower energy densities of 0.2-10 J/cm(2) . In addition, co-culture of PBM or control-treated microglia with primary neuronal cultures demonstrated a dose-dependent effect of PBM on microglial-induced neuronal growth and neurite extension. CONCLUSION: These data suggest that the Arndt-Schulz law as applied to PBM for a specific bioassay does not hold true in cells with a spectrum of responses, and that PBM can alter microglial phenotype across this spectrum in a dose-dependent manner. These data are therefore of important relevance to not only therapies in the CNS but also to understanding of PBM effects and mechanisms.