Apoptotic Mechanisms Of Neural Cells And Neuroprotective Effects Of N-Acetylcysteine On The Newborn Animals With Hypoxic-Ischemic Brain Injury

PARTâ… :Further activation of apoptosis during the recovery of the hypoxic ischemic brain injury of 3-day old rat pups and the outcome in adulthoodObjectives:Although the persistent apoptosis is one of the important factors of poor longterm outcome of newborn infants with hypoxic ischemic(HI) brain injury after perinatal events,little information is available regarding the mechanism of the activation of apoptosis. We aimed to compare the differences of the activation of apoptotic genes between the acute and recovery stages after HI brain injury in a 3-day-old-rat HI brain injury model,to observe the expression of apoptotic proteins on the neural cells,and to investigate myelination of the brain,changes in cranial MRI and cognitive function in young adulthood.Methods:A 3-day-old SD rat HI brain injury model was established by right carotid artery ligation followed by 2.5 hours of hypoxia(6%O₂)(HI group,n=52).Control pups were sham-operated(n=41).Right brain cortex was collected at 12 hours(acute stage) and 7 days (recovery stage) after HI and subjected to an apoptosis Oligo GEArray^?,and the differences between 12 hours and 7 days after HI were analyzed.The expression of TRAIL and its receptors,Caspase-3 in the cerebral cortex and periventricular white matter regions was examined at 24 and 72 hours after HI using immunochemistry staining.MRI scanning, Morris water maze test and myelination assessment were performed in both groups at 42,44 and 48 days of age,respectively.Results:Comparing to 12 hours after HI,the apoptotic genes were further activated at 7 days after HI in the brain of HI rat pups,including TNF,Caspase,Bcl 2,Caspase Recruitment Domains,Death Domain and Death Effector Domain families.Although there were no changes in the expression of TRAIL and its other receptors,HI was disclosed to enhance the expression of DR5 in the pyramidal neurons in the subplate of cortex at 24 and 72 hours after HI(24 hours after HI:130±62 vs.72±17 and 35±20 cells/mm² in right,left side of HI group and right cortex of control group,respectively;n=5,F=6.54,p＜0.05,1-way ANOVA,SNK, right vs.left of HI,p＜0.05;72 hours after HI:147±67 vs.85±30 and 58±15 cells/mm², F=4.71,p＜0.05,SNK,right of HI vs right of Control,p＜0.05).Meanwhile,the expression of Caspase-3 in the cortex and periventricular white matter was found to be elevated at 72 hours after HI compared to those in control group(286±61 vs.171±63 cells/mm²,n=4, t=2.613,p＜0.05),with no change at 24 hours.Furthermore,the MRI assessment demonstrated that the volume of right cortex of HI rats(n=8) was significantly smaller than that of left side and controls(n=6)(84±15.1 vs.130.9±17.3 and 133.0±10.9[mm³],F=25.3, p＜0.001,SNK,right cortex of HI vs.left and control,p＜0.05).During the four days of navigation trial in the Morris water maze test,the HI rats demonstrated longer escape latency than the rats of control group(fourth day:52.71±35.87 vs 17.80±8.85[s],p＜0.01).They crossed the platform less than those in the control group as well(0.3±0.5 vs 1.1±0.8 times, t=3.28,p＜0.05) in Space probe trial.The myelination with myelin basic protein staining was impaired in the right white matter of HIBI rats compared to the left corresponding region and the right side of control group at 48 days of age.Conelusions:The activation of apoptotic genes induced by HI persist upto 7 days,involving intrinsic and extrinsic apoptotic pathways.The apoptosis of neural cells leads to poor development of the cortex and myelination,and might compromise the memory and learning function in the young adulthood in rats with neonatal HI.PARTâ…¡:N-Acetylcysteine improves hemodynamics and reduces oxidative stress in the brain of newborn piglets with hypoxia-reoxygenation injuryObjectives:Satisfied therapy of hypoxic ischemic brain injury(HIBI) of newborns needs to be developed with promising strategy on the different mechanisms of the damage.N-acetylcysteine (NAC),a free radical scavenger with anti-inflammatory and anti-apoptotic features,was proven to minimize HIBI in various acute models,but the effects of NAC on the brain during recovery from HIBI needs to be further explored.Using a sub-acute swine model of neonatal hypoxia-reoxygenation(H-R),we evaluated the long-term beneficial effect of NAC against oxidative stress and apoptosis.Methods:Newborn piglets were mechanical ventilated by a pressure-controlled ventilator via tracheostomy.The animals were randomly assigned into a sham group(without H-R,n=6) and two H-R experimental groups(n=8 each) with 2 hours normocapnic alveolar hypoxia and 1 hour 100%O₂ of reoxygenation followed by 0.21 of FiO₂ for 47 hours.Five minutes after reoxygenation,hypoxic piglets received either normal saline(H-R controls) or NAC (150 mg/kg bolus and 20 mg/kg/h i.v.for 24 hours) in a blinded randomized fashion. Hemodynamic changes and blood gas variables were recorded throughout H-R.The activity of cortical caspase-3 and lipid hydroperoxide(LPO) of the fight hemisphere of the piglets was detected after 48 hours of observation.Results:After hypoxia,the arterial pH decreased significantly with metabolic acidosis developed(mean arterial pH～7.05;mean arterial HCO₃ 10-11 mM).Upon reoxygenation, both arterial pH and HCO₃ recovered similarly in both H-R groups.Treating the piglets with NAC significantly increased both carotid blood flow(CCAF) and oxygen delivery during the early phase.Even though there was no difference between these two H-R groups thereafter, both CCAF and carotid oxygen delivery of the H-R group remained lower than the sham groups throughout the experimental period.Compared with H-R controls,significantly higher amount of anesthetics and sedative was required to maintain the NAC-treated piglets in stable condition throughout the experimental period,indicating a stronger recovery.Post-resuscitation NAC treatment also significantly attenuated the increase in cortical caspase-3 and LPO levels.Conclusions:In newborn piglets with H-R insults,post-resuscitation administration of NAC reduces cerebral oxidative stress with improved cerebral oxygen delivery,probably through anti-apoptosis mechanism. Partâ…¢:Sequential Changes of Hemodynamics and Blood Gases in Newborn Piglets with Developing PneumothoraxObjectives:Pneumothorax,a common complications of newborns hospitalized in NICU,is a high risk of major neurological disabilities due to the attenuation of cerebral perfusion and oxygen delivery in severe situation.But little information is available regarding the temporal changes in hemodynamics and blood gases during the development of a moderate pneumothorax in a neonate.Thus,we investigated the temporal changes of hemodynamics and arterial blood gases in a neonatal swine model of unilateral pneumothorax in this prospective observational controlled animal research.Methods:Experimental pneumothorax(n=9) was created by intermittent progressive introduction of 10 ml/Kg of room-air every 5 min to a total 40 ml/Kg,via a 20G Insyte^? angiocatheter placed in the fourth intercostal space in line with the fight frontal limb. Changes in heart rate,mean arterial pressure,central venous pressure(CVP),common carotid arterial flow(CCAF) and arterial blood gases were measured and compared with the normoxic baseline and a control group(n=7)(ANOVA).Results:As the pneumothorax developed,CVP increased alter injecting 30 ml/Kg of roomair (p＜0.001 vs.baseline and control) with no significant changes in heart rate and mean arterial pressure.After 20 ml/Kg of air was introduced,arterial blood gases showed deteriorating oxygenation.CCAF increased and carotid oxygen delivery declined after 30 ml/Kg(p＜0.05 vs.baseline and control).Conclusions:Deterioration in oxygenation was noted early in the development of pneumothorax in newborn piglets followed by metabolic acidosis.CVP progressively increased despite the lack of significant changes in systemic hemodynamics when moderate pneumothorax developed.Although CCAF increased during a moderate pneumothorax, carotid oxygen delivery decreased.