ABSTRACT
Exposure to normobaric hyperoxia (NH) is known to increase the production of reactive oxygen species (ROS) by mitochondria. The present study was designed to examine mitochondrial ultrastructure morphological changes in the cortical brainin relation to glutathione peroxidase (GPX) activity and free radicals (FR) productions in brain tissue during hyperoxia exposure. The experimental groups were exposed to NH for 24 and 48 h continuously. Following the exposure periods, animals were sacrificed and cortical tissues were divided randomly into two parts; the first part was processed for the ultrastructural examination and the second was homogenized for GPX and FR determinations. Analysis of variance (ANOVA) showed that the main effects of O2 exposure periods were significant (p<0.05) for GPX and FR. Pair-wise means comparisons showed that NH elevated the average (+SE) GPX activity significantly (p<0.05) from the baseline control value of 5670.99+556.34 to13748.42+283.04 and 15134.19+1529.26 U/L with increasing length of NH exposure period from 24 to 48 h, respectively. Similarly, FR production was increased significantly (p<0.05) to 169.73+10.31 and 185.33+21.87, above baseline control of 105.27+5.25 Unit. Ultrastructure examination showed that O2 breathing for 48 h resulted in giant and swelled mitochondria associated with diluted inner membrane and damaged cristae. These mitochondria pathological alterations were associated with damages of myelin, axonal and cellular organelles. Normobaric-hyperoxia inducts mitochondria oxidative stress (MOS) and the subsequent rise of ROS causes variety of ultrastructure morphological pathological alterations in the organelles of cortical brain cells.
Se sabe que la exposición a la hiperoxia normobárica (HN) aumenta la producción de especies reactivas de oxígeno (ERO) por parte de las mitocondrias. El estudio se diseñó para examinar los cambios morfológicos de la ultraestructura mitocondrial en la corteza cerebral con la actividad de la glutatión peroxidasa (GPX) y la producción de radicales libres (RL) en el tejido cerebral durante la exposición a la hiperoxia. Los grupos experimentales fueron expuestos a HN durante 24 y 48 h continuamente. Tras los períodos de exposición, los animales se sacrificaron y los tejidos corticales se dividieron aleatoriamente en dos partes; la primera parte se procesó para el examen ultraestructural y la segunda se homogeneizó para las determinaciones de GPX y RL. El análisis de varianza (ANOVA) mostró que los efectos principales de los períodos de exposición al O2 fueron significativos (p <0,05) para GPX y RL. Las comparaciones de medias por pares mostraron que la HN elevó la actividad promedio de GPX (+ SE) significativamente (p <0,05) desde el valor de control de línea base de 5670,99 + 556,34 a 13748,42 + 283,04 y 15134,19 + 1529,26 U / L con una mayor duración del período de exposición a HN de 24 a 48 h, respectivamente. De manera similar, la producción de RL se incrementó significativamente (p <0,05) a 169,73 + 10,31 y 185,33 + 21,87, por encima del control de referencia de 105,27 + 5,25 unidades. El examen de la ultraestructura mostró que la respiración de O2 durante 48 h dio lugar a mitocondrias gigantes e hinchadas asociadas con la membrana interna diluida y las crestas dañadas. Estas alteraciones patológicas de las mitocondrias se asociaron con daños de mielina, axones y organelos celulares. La hiperoxia normobárica induce el estrés oxidativo mitocondrial (MOS) y el posterior aumento de las ERO provoca una variedad de alteraciones patológicas y morfológicas en los organelos de las células cerebrales corticales.
Subject(s)
Animals , Rats , Cerebral Cortex/ultrastructure , Hyperoxia/pathology , Mitochondria/pathology , Cerebral Cortex/enzymology , Cerebral Cortex/pathology , Analysis of Variance , Reactive Oxygen Species , Rats, Wistar , Reactive Nitrogen Species , Glutathione Peroxidase/metabolism , Mitochondria/ultrastructureABSTRACT
Objective To investigate the effects of lipopolysaccharide (LPS) and / or normobaric hyperoxia on brain development of neonatal rat and the possible mechanisms.Methods One hundred and twenty postnatal day 2 (P2) SD rats were randomly assigned into 4 groups:air group,LPS group,hyperoxia group,LPS + hyperoxia group.General condition and body weight of the rats in each group were observed and recorded every day.The expression of active Caspase-3 and nuclear factor-κappaB P65 (NF-κB P65) in the brain were detected by immunohistochemistry staining on P7,and the level of IL-6 and 8-iso-PGF2α in the brain homogenate were measured by enzyme-linked immunosorbent assay(ELISA).The expression of myelin basic protein (MBP) in the brain was detected by immunohistochemistry staining on P12.Results The expressions of Caspase-3 and NF-κB P65 had the same trends:the number of positive cells from high to low was in LPS + hyperoxia group,LPS group/hyperoxia group,air group.There were significant differences between the first three groups and air group(all P ＜ 0.05).There were also significant differences between LPS + hyperoxia group and LPS group or hyperoxia group(all P ＜0.01).MBP in the brain had the completely reverse expression:from high to low order was in air group,hyperoxia group,LPS group,LPS + hyperoxia group.There were significant differences between the last three groups and air group (all P ＜ 0.05).There were also significant differences between LPS + hyperoxia group and LPS group or hyperoxia group(all P ＜0.01).The level of IL-6 in the brain from high to low order respectively was in LPS + hyperoxia group,LPS group,hyperoxia group,air group;and 8-iso-PGF2α was also in LPS + hyperoxia group,hyperoxia group,LPS group,air group,Significant differences were found among the four groups (all P ＜ 0.05).Conclusions Both postnatal infection and normobaric hyperoxia may induce premature rat brain injury,and increase the number of apoptosis cell and reduce the expression of MBP.The combination of infection and normobaric hyperoxia may aggravate the degree of brain damage of neonatal rat.NF-κB pathway mediated by Toll-like receptor may be involved in inflammation and oxidative stress,and may mediate Caspase-3 related apoptosis of nerve cell and white matter injury.
ABSTRACT
Objective To investigate the effects of normobaric hyperoxia intervention on learning and memory abilities of valproic acid(VPA) autism model rats and the morphology of pyramidal cells in hippocampus CA1 area.Methods Animal model groups of autism were obtained in male offspring of the Wistar rats that received intraperitoneal injection of 600 mg/kg VPA at the 12.5 day after pregnancy.According to the eye opening time,behavior,weaning weight and the learning and memory abilities which were evaluated by the Y electricity maze test at the 28th day after birth,40 male VPA autism model rats were randomly selected 20 only and divided into normobaric hyperoxia model group (group A,n =10),atmospheric air model group (group B,n =10).Normal control groups were obtained in male offspring of Wistar rats that received intraperitoneal injection of equivalent physiological saline at the same period pregnancy.(group C,n =10).Rats in group A were treated with oxygen for 1 h per day and lasted 1 week;group B and C were treated with normal air.The learning and memory abilities of three groups were assessed at the 35th day after birth.The immunohistochemistry methods and image analysis were used to observe the pyramidal cells of autism model rats in hippocampal CA1 region.The effect of normobaric hyperoxia therapy on pyramidal cell of autism model rats in hippocampal CA1 region were evaluated by HE staining technique.Results The trying times of group A after treatment were less than those before treatment (31.15 ± 0.99 vs 31.54 ± 0.97,t =2.739,P =0.018).The memory times were more than those before treatment (3.00± 0.58 vs 2.69 ± 0.48,t =-2.309,P =0.040).The trying times of group A after treatment were less than those in group B after treatment (P =0.016).The memory times of group A were not different from that in group B after treatment(P=0.810).The morphology of pyramidal cells in hippocampal CA1 region showed that the pyramidal cells of the autism model rats had apoptosised.The number of apoptotic cells reduced and the number of normal form cells increased after the normobaric hyperoxia intervention compared with the autism model rats.Conclusion Normobaric hyperoxia intervention can improve the learning and memory abilities of the autism model rats.The apoptosis of the pyramidal neurons in hippocampal CA1 might be reduced after the normobaric hyperoxia intervention.