Jannicke Hanne Andresen

Resuscitation of Hypoxic Newborn Piglets With Oxygen Induces a Dose-Dependent Increase in Markers of Oxidation

Newborn resuscitation with pure oxygen may be associated with long-term detrimental effects. Due to the change in attitude toward use of less oxygen upon resuscitation, there is a need to study effects of intermediate hyperoxia. The aim was to study dose-response correlation between inspiratory fraction of oxygen used for resuscitation and urinary markers of oxidative damage to DNA and amino acids. Hypoxemia was induced in newborn piglets following a standardized model; they were resuscitated for 15 min with either 21%, 40%, 60% or 100% oxygen and observed for 1 h. Urine samples were collected. Urinary elimination of 8-hydroxy-2′-deoxyguanosine (8-oxo-dG), 2′deoxyguanosine (2dG), ortho-tyrosine (o-Tyr) and phenylalanine (Phe) were determined by HPLC and tandem mass spectrometry (HPLC-MS/MS). Quotient of 8-oxo-dG/2dG and o-Tyr/Phe ratios were significantly and dose-dependant higher in piglets resuscitated with supplementary oxygen. 8-oxodG/dG: Mean (SD) 5.76 (1.81) versus 22.44 (12.55) p < 0.01 and o-Tyr/Phe: 19.07 (10.7) versus 148.7 (59.8)for 21% versus 100%, p < 0.001. Hypoxia and subsequent resuscitation for 15 min with graded inspiratory fraction of oxygen causes increased oxidative stress and a dose-dependant oxidation of DNA and Phenylalanine. The increase in the hydroxyl attack may lead to a pro-oxidative status and risk for genetic instability.

Resuscitation with 21 or 100% oxygen in hypoxic nicotine-pretreated newborn piglets: possible neuroprotective effects of nicotine.

Background: Perinatal asphyxia is a major concern in perinatal medicine. Resuscitation and ways to prevent and minimize adverse outcomes after perinatal asphyxia are subject to extensive research. Objectives: In this study we hypothesized that, prior to hypoxia, intravenously administered nicotine might have an effect on how newborn piglets tolerate hypoxia, with regard to the time and degree of damage inflicted, due to its suggested neuroprotective abilities, and further that resuscitation with 21 compared with 100% oxygen in nicotine-pretreated animals would cause less cerebral damage. Methods: Thirty anesthetized newborn piglets were randomized to either hypoxia or control groups, and pretreatment with either saline or nicotine. In addition, the nicotine/hypoxia group was randomized to resuscitation with either 21 or 100% oxygen for 15 min following hypoxia. Results: We found significantly more necrosis in the striatum and cortex combined (p = 0.036), and in the striatum alone (p = 0.026), in the animals pretreated with nicotine and resuscitated with 100% when compared to 21% oxygen. There was no significant difference in the cerebellum. We also found significantly increased tolerance to hypoxia as measured by the time interval that the animals endured hypoxia: 103.8 ± 28.2 min in the nicotine-pretreated animals vs. 66.5 ± 19.5 minin the saline-pretreated animals (p = 0.035). Conclusion: Nicotine enhances newborn piglets’ ability to endure hypoxia, and resuscitation with 21% oxygen inflicts less necrosis than 100% oxygen. The potential neuroprotective effects of nicotine in the newborn brain should be further investigated.

Resuscitation of newborn piglets. short-term influence of FiO2 on matrix metalloproteinases, caspase-3 and BDNF.

Background Perinatal hypoxia-ischemia is a major cause of mortality and cerebral morbidity, and using oxygen during newborn resuscitation may further harm the brain. The aim was to examine how supplementary oxygen used for newborn resuscitation would influence early brain tissue injury, cell death and repair processes and the regulation of genes related to apoptosis, neurodegeneration and neuroprotection. Methods and Findings Anesthetized newborn piglets were subjected to global hypoxia and then randomly assigned to resuscitation with 21%, 40% or 100% O2 for 30 min and followed for 9 h. An additional group received 100% O2 for 30 min without preceding hypoxia. The left hemisphere was used for histopathology and immunohistochemistry and the right hemisphere was used for in situ zymography in the corpus striatum; gene expression and the activity of various relevant biofactors were measured in the frontal cortex. There was an increase in the net matrix metalloproteinase gelatinolytic activity in the corpus striatum from piglets resuscitated with 100% oxygen vs. 21%. Hematoxylin-eosin (HE) staining revealed no significant changes. Nine hours after oxygen-assisted resuscitation, caspase-3 expression and activity was increased by 30–40% in the 100% O2 group (n = 9/10) vs. the 21% O2 group (n = 10; p<0.04), whereas brain-derived neurotrophic factor (BDNF) activity was decreased by 65% p<0.03. Conclusions The use of 100% oxygen for resuscitation resulted in increased potentially harmful proteolytic activities and attenuated BDNF activity when compared with 21%. Although there were no significant changes in short term cell loss, hyperoxia seems to cause an early imbalance between neuroprotective and neurotoxic mechanisms that might compromise the final pathological outcome.

Nicotine affects the expression of brain-derived neurotrophic factor mRNA and protein in the hippocampus of hypoxic newborn piglets

Abstract Brain-derived neurotrophic factor (BDNF) is highly expressed in the developing brain. It has anti-apoptotic abilities, and protects the neonatal brain. In experimental settings in adult animals, pre-treatment with nicotine has shown increased BDNF levels, indicating a possible contribution to nicotines anti-apoptotic effect. Apoptosis contributes to the development of brain damage in perinatal asphyxia. We examined the effects of nicotine on apoptosis-inducing factor (AIF), caspase-3 and BDNF in the hippocampus of a neonatal piglet model of global hypoxia. Forty-one anesthetized newborn piglets were randomized to one of four groups receiving different infusions after hypoxia (1) nicotine 130 μg/kg/h, 2) 260 μg/kg/h, 3) adrenaline, and 4) saline, all 2.6 mL/kg/h. Four hours after hypoxia they were euthanized. The left hemisphere/hippocampus was examined by histopathology and immunohistochemistry; the right hippocampus was analyzed using real time PCR. There was a significantly higher expression of BDNF mRNA and protein in the animals treated with nicotine 130 μg/kg/h vs. the saline treated group (mRNA P=0.038; protein P=0.009). There were no differences regarding AIF or caspase-3. We conclude that nicotine (130 μg/kg/h), infused over 1 h after global hypoxia in neonatal piglets, increases levels of both BDNF mRNA and protein in the hippocampus. This might imply neuroprotective effects of nicotine in asphyxiated neonates.

Newborn piglets exposed to hypoxia after nicotine or saline pretreatment: Long-term effects on brain and heart

Objective. We wished to assess the effect of global hypoxia and the effect of nicotine pretreatment on the brain and heart of newborn pigs. Hypothesising that nicotine might give a better outcome because of its anti-apoptotic and anti-inflammatory effects. Methods. Twenty-two anaesthetised piglets were randomised to pretreatment with saline or nicotine (130 μg/kg/h) before 45 min global hypoxia. They were observed for 27 h. The brain and heart were assessed with histopathological methods. Serum for Troponin t (TnT) analyses was collected at baseline and at the end of the experiment. Results. There were no significant differences between the groups. At the end of hypoxia, BE was −14.8 ± 4.9 mmol/l and MABP was 25 ± 9 mmHg. Seven animals had autolysis of the cerebrum/cerebellum, their BE after hypoxia was −19 ± 1.8 mmol/l and MABP 23 ± 3 mmHg. The remaining 15 animals had a BE of −13 ± 4.7mmol/l (p = 0.0004) and a MABP of 26 ± 11 mmHg (ns). Eleven animals presented myocardial damage. A significant increase in TnT occurred in both groups. TnT increase and myocardial damage correlated (p = 0.001; r = 0.67). Animals with severe increase in TnT presented severe brain damage. Conclusions. Severe increase in serum TnT levels was linked to severe cerebral damage. Nicotine pretreatment had no impact on cerebral or cardiac histopathology.

Resuscitation of Hypoxic Newborn Piglets With Supplementary Oxygen Induces Dose-Dependent Increase in Matrix Metalloproteinase-Activity and Down-Regulates Vital Genes

The optimal oxygen concentration for newborn resuscitation is still discussed. Oxygen administration during reoxygenation may induce short- and long-term pathologic changes via oxidative stress and has been associated to later childhood cancer. The aim was to study changes in oxidative stress-associated markers in liver and lung tissue of newborn pigs after acute hypoxia followed by reoxygenation for 30 min with 21, 40, or 100% oxygen compared with room air or to ventilation with 100% oxygen without preceding hypoxia. Nine hours after resuscitation, we found a dose-dependent increase in the matrix metalloproteinase gelatinase activity in liver tissue related to percentage oxygen supply by resuscitation (100% versus 21%; p = 0.002) pointing at more extensive tissue damage. Receiving 100% oxygen for 30 min without preceding hypoxia decreased the expression of VEGFR2 and TGFBR3 mRNA in liver tissue, but not in lung tissue. MMP-, VEGF-, and TGFβ-superfamily are vital for the development, growth, and functional integrity of most tissues and our data rise concern about both short- and long-term consequences of even a brief hyperoxic exposure.

Nicotine in a Small-to-Moderate Dose Does Not Cause a Significant Increase in Plasma Catecholamine Levels in Newborn Piglets

Background: Nicotine has a wide range of effects. Several studies are being undertaken investigating the positive effects on inflammation and apoptosis. Recently, nicotine has been investigated in a piglet model of perinatal asphyxia, where the question has been raised whether nicotine’s effect on the sympathetic nervous system can explain some of the positive effects. Objectives: We hypothesized that nicotine in small-to-moderate doses would not cause a significant increase in plasma catecholamine levels, whereas a higher dose would give a significant effect, confirming the believed dose-dependent matter in which nicotine exerts its effect on the sympathetic nervous system. Methods: Seventeen anesthetized newborn piglets were randomized to one of three doses of nicotine (130, 260 or 1,000 µg/kg/h) that was given intravenously for 1 h. Blood samples for catecholamine analyzes were drawn at baseline and at the end of the infusion. Catecholamines were determined using HPLC. Results: No significant increase in catecholamines was detected in the animals treated with the small or moderate nicotine doses, whereas the higher dose gave a significant increase in adrenaline (p = 0.019). Conclusion: Nicotine in small-to-moderate doses does not cause significant increase in plasma catecholamines, thus indicating that the positive effects of nicotine in studies using these doses most likely cannot be explained by the systemic release of catecholamines.

Effects of Nicotine Infusion on Striatal Glutamate and Cortical Non-Protein-Bound Iron in Hypoxic Newborn Piglets

Background: Perinatal asphyxia triggers a large cascade of mechanisms leading to brain damage. Release of glutamate and increased oxidative stress play substantial roles. Non-protein-bound iron (NPBI), which contributes to the production of free radical species through the Fenton reaction, increases in hypoxic-ischemic brain damage. Results from in vitro and adult animal studies show that nicotine can decrease extracellular levels of NPBI and glutamate. Nicotine’s effects have further been shown to be dose-dependent, with lower doses showing neuroprotective, and higher doses showing neurotoxic effects. Objectives: We wished to assess nicotine’s effect on levels of NPBI and glutamate in an animal model of neonatal hypoxic-ischemic brain damage. Methods: 47 anesthetized newborn piglets were randomized to one of four infusions after hypoxia (nicotine 130 µg/kg/h, 260 µg/kg/h, adrenaline 0.05 µg/kg/min, saline 2.6 ml/kg/h). Glutamate in striatum and NPBI in cortex were analyzed in microdialysate. Results: Striatal glutamate presented a significant rise for all the animals from baseline to the end of hypoxia (p < 0.001). There was a significant difference for nicotine 130 µg/kg/h versus saline (p = 0.002) 2 h after hypoxia. Cortical NPBI presented a significant rise from baseline to the end of hypoxia for all the animals (p < 0.001), and a significant difference between nicotine 130 µg/kg/h versus saline 2 h after hypoxia (p = 0.013). Conclusion: Our findings support the hypothesis that nicotine can decrease extracellular levels of glutamate and NPBI in a neonatal model of hypoxic-ischemic brain damage. This suggests possible neuroprotective effects of a low dose of nicotine in neonates, as it has already been shown in adult models.

Contents Vol. 94, 2008

S. Andersson, Helsinki E. Bancalari, Miami, Fla. G. Buonocore, Siena W.A. Carlo, Birmingham, Ala. V.P. Carnielli, Ancona W.J. Cashore, Providence, R.I. I.A. Choonara, Derby T. Curstedt, Stockholm O. Dammann, Boston, Mass. C. Dani, Florence B. Darlow, Christchurch P. Gluckman, Auckland M. Hallman, Oulu B. Jonsson, Stockholm S.E. Juul, Seattle, Wash. A. Llanos, Santiago R.J. Martin, Cleveland, Ohio C.J. Morley, Cambridge J. Neu, Gainesville, Fla. P.C. Ng, Hong Kong M. Obladen, Berlin A.G.S. Philip, Palo Alto, Calif. M. Post, Toronto E. Saliba, Tours O.D. Saugstad, Oslo B. Schmidt, Philadelphia, Pa. E. Shinwell, Rehovot J. Smith, Cape Town B. Sun, Shanghai H. Togari, Nagoya F. van Bel, Utrecht N. Vain, Buenos Aires M. Vento Torres, Valencia M. Weindling, Liverpool J.A. Widness, Iowa City, Iowa Fetal and Neonatal Research