Short-term perinatal oxygen exposure may impair lung development in adult mice

BACKGROUND: Hyperoxia at resuscitation increases oxidative stress, and even brief exposure to high oxygen concentrations during stabilization may trigger organ injury with adverse long-term outcomes in premature infants. We studied the long-term effects of short-term perinatal oxygen exposure on cell cycle gene expression and lung growth in adult mice. METHODS: We randomized mice litters at birth to 21,40, or 100%O2 for 30 min and recovered in room air for 4 or 12 weeks. Cell cycle gene expression, protein analysis, and lung morphometry were assessed at 4 and 12 weeks. RESULTS: The principal component analysis demonstrated a high degree of correlation for cell cycle gene expression among the three oxygen groups. Lung elastin was significantly lower in the 100%O2 groups at 4 weeks. On lung morphometry, radial alveolar count, alveolar number, and septal count were similar. However, the mean linear intercept (MLI) and septal length significantly correlated among the oxygen groups. The MLI was markedly higher in the 100%O2 groups at 4 and 12 weeks of age, and the septal length was significantly lower in the 100%O2 groups at 12 weeks. CONCLUSION: Short-term exposure to high oxygen concentrations lead to subtle changes in lung development that may affect alveolarization. The changes are related explicitly to secondary crest formation that may result in alteration in lung elastin. Resuscitation with high oxygen concentrations may have a significant impact on lung development and long-term outcomes such as BPD in premature infants.

Ultrastructural morphological alterations during hyperoxia exposure in relation to glutathione peroxidase activity and free radicals productions in the mitochondria of the cortical brain / Alteraciones morfológicas ultraestructurales durante la exposición a la hiperoxia en relación con la actividad de la glutatión peroxidasa y la producción de radicales libres en las mitocondrias de la corteza cerebral

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.

Long-Term (Postnatal Day 70) Outcome and Safety of Intratracheal Transplantation of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Neonatal Hyperoxic Lung Injury

PURPOSE: This study was performed to evaluate the long-term effects and safety of intratracheal (IT) transplantation of human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in neonatal hyperoxic lung injury at postnatal day (P)70 in a rat model. MATERIALS AND METHODS: Newborn Sprague Dawley rat pups were subjected to 14 days of hyperoxia (90% oxygen) within 10 hours after birth and allowed to recover at room air until sacrificed at P70. In the transplantation groups, hUCB-MSCs (5x10(5)) were administered intratracheally at P5. At P70, various organs including the heart, lung, liver, and spleen were histologically examined, and the harvested lungs were assessed for morphometric analyses of alveolarization. ED-1, von Willebrand factor, and human-specific nuclear mitotic apparatus protein (NuMA) staining in the lungs and the hematologic profile of blood were evaluated. RESULTS: Impaired alveolar and vascular growth, which evidenced by an increased mean linear intercept and decreased amount of von Willebrand factor, respectively, and the hyperoxia-induced inflammatory responses, as evidenced by inflammatory foci and ED-1 positive alveolar macrophages, were attenuated in the P70 rat lungs by IT transplantation of hUCB-MSCs. Although rare, donor cells with human specific NuMA staining were persistently present in the P70 rat lungs. There were no gross or microscopic abnormal findings in the heart, liver, or spleen, related to the MSCs transplantation. CONCLUSION: The protective and beneficial effects of IT transplantation of hUCB-MSCs in neonatal hyperoxic lung injuries were sustained for a prolonged recovery period without any long-term adverse effects up to P70.

Efeitos da hiperóxia sobre o pulmão de ratos Wistar / Effects of hyperoxia on Wistar rat lungs

OBJETIVO: Avaliar a repercussão da elevada concentração de oxigênio (hiperóxia) em um curto período de tempo no pulmão de ratos Wistar. MÉTODOS: Os animais foram divididos em grupos O10', O30', O90', ou seja, ratos expostos à hiperóxia por 10', 30' e 90', respectivamente, e no grupo controle (GC), exposto ao ar ambiente. Os animais foram sacrificados 24 h após a exposição. O lavado broncoalveolar foi realizado e os pulmões foram retirados para análise histológica e estereológica. RESULTADOS: Observamos um aumento do número de macrófagos (2169,9 ± 118,0, 1560,5 ± 107,0 e 1467,6 ± 39,0) e neutrófilos (396,3 ± 35,4, 338,4 ± 17,3 e 388,7 ± 11,7), concomitante a um aumento do dano oxidativo (143,0 ± 7,8 por cento, 180,4 ± 5,6 por cento e 235,0 ± 13,7 por cento) nos grupos O10', O30' e O90', respectivamente, quando comparados ao GC (781,3 ± 78,3 por cento, 61,6 ± 4,2 por cento e 100,6 ± 1,7 por cento). Na análise histológica e estereológica foram observados alvéolos e septos normais no GC (83,51 ± 1,20 por cento e 15 ± 1,21 por cento), no grupo O10' (81,32 ± 0,51 por cento e 16,64 ± 0,70 por cento) e no grupo O30' (78,75 ± 0,54 por cento e 17,73 ± 0,26 por cento). Entretanto, no grupo O90' foi notado um influxo de células inflamatórias nos alvéolos e nos septos alveolares. Hemácias extravasaram do capilar para o alvéolo (59,06 ± 1,22 por cento), com evidências de congestão, hemorragia e edema de septo (35,15 ± 0,69 por cento). CONCLUSÃO: Os resultados indicam que a hiperóxia induziu uma ação lesiva no grupo O90' sobre o parênquima pulmonar, com repercussões de dano oxidativo e infiltrado inflamatório.

OBJECTIVE: To study the effects of short-term exposure to high oxygen concentrations (hyperoxia) on Wistar rat lungs. METHODS: Animals were divided into three groups exposed to hyperoxia for 10', 30' and 90' (O10', O30', O90', respectively), together with a control group (exposed to room air). The animals were sacrificed 24 h after exposure. Bronchoalveolar lavage was performed, and the lungs were removed for histological and stereological analysis. RESULTS: In the O10', O30', and O90' groups, respectively and in comparison with the controls, we observed an increase in the numbers of macrophages (2169.9 ± 118.0, 1560.5 ± 107.0, and 1467.6 ± 39.0 vs. 781.3 ± 78.3) and neutrophils (396.3 ± 35.4, 338.4 ± 17.3, and 388.7 ± 11.7 vs. 61.6 ± 4.2), concomitant with an increase in oxidative damage (143.0 ± 7.8 percent, 180.4 ± 5.6 percent, and 235.0 ± 13.7 vs. 100.6 ± 1.7 percent). The histological and stereological analyses revealed normal alveoli and alveolar septa in the controls (83.51 ± 1.20 percent and 15 ± 1.21 percent), in the O10' group (81.32 ± 0.51 percent and 16.64 ± 0.70 percent), and in the O30' group (78.75 ± 0.54 percent and 17.73 ± 0.26 percent). However, in the O90' group, inflammatory cell infiltration was observed in the alveoli and alveolar septa. Red blood cells extravasated from capillaries to the alveoli (59.06 ± 1.22 percent), with evidence of congestion, hemorrhage, and septal edema (35.15 ± 0.69 percent). CONCLUSION: Hyperoxia for 90' caused injury of the lung parenchyma, resulting in oxidative damage and inflammatory cell infiltration.

Erythropoietin Attenuates Hyperoxia-Induced Lung Injury by Down-modulating Inflammation in Neonatal Rats

This study was done to determine whether recombinant human erythropoietin (rhEPO) treatment could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague Dawley rat pups were subjected to 14 days of hyperoxia (>95% oxygen) within 10 hr after birth. Treatment with rhEPO significantly attenuated the mortality and reduced body weight gain caused by hyperoxia. With rhEPO treatment, given 3 unit/gm intraperitoneally at 4th, 5th, and 6th postnatal day, hyperoxia- induced alterations in lung pathology such as decreased radial alveolar count, increased mean linear intercept, and fibrosis were significantly improved, and the inflammatory changes such as myeloperoxidase activity and tumor necrosis factor-alpha expression were also significantly attenuated. In summary, rhEPO treatment significantly attenuated hyperoxia-induced lung injury by down-modulating the inflammatory responses in neonatal rats.