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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Infants and adults on oxygen often are treated with glucocorticoids in an attempt to reduce lung inflammatory injury. However, glucocorticoids hasten the development of hyperoxic lung injury in some animal models. The purpose of this study was to test the hypothesis that dexamethasone alters the lung inflammatory responses to hyperoxia exposure. We studied male Sprague-Dawley rats, placing them in >95% oxygen immediately after administration of 0, 0.1, 1, or 10 mg/kg of dexamethasone. At 0, 24, or 48 hr of exposure to hyperoxia, extravascular lung water contents were measured, and lung inflammatory responses were assessed by lung myeloperoxidase activities, lung neutrophil counts, and lung expression of E-Selectin and intercellular adhesions molecule-1 (ICAM-1). Dexamethasone, independent of exposure to hyperoxia, led to marked increases in lung neutrophil counts, without increases in lung myeloperoxidase activities or increases in the expression of the adhesion molecules. Hyperoxia exposure also enhanced lung neutrophil accumulation, and extravascular lung water increased earlier in animals exposed to hyperoxia and dexamethasone than in those exposed to hyperoxia alone. In conclusion, the increase in lung neutrophils in dexamethasone-treated rats without enhanced expression of E-Selectin or intracellular adhesions molecule-1 suggests that dexamethasone leads to lung neutrophil accumulation by its effect on neutrophils. The more rapid development of hyperoxic lung injury associated with earlier lung neutrophil accumulation suggests that dexamethasone-induced lung neutrophil sequestration primes the lung for the development of hyperoxic lung injury and supports further the conclusion that lung inflammation contributes significantly to the development of hyperoxic lung injury.
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PMID:Dexamethasone enhancement of hyperoxic lung inflammation in rats independent of adhesion molecule expression. 969 81

Dexamethasone is widely used in the postnatal period. Its impact on retinopathy of prematurity (ROP) is extremely controversial; published studies have found a detrimental, protective, or no effect on ROP. The goal of this study was to test the hypothesis that use of dexamethasone during the injury phase (oxygen exposure) reduces the severity of oxygen-induced retinopathy (OIR) in a mouse model. C57BL6 mice pups were exposed to either room air or hyperoxia (75% FiO2) from postnatal d 7 through 12 (PN7-12) with or without dexamethasone (0.5 mg/kg/d s.c.) and killed on PN17-21. Retinopathy was assessed by a scoring system of retinal flat mount preparations and periodic acid-Schiff (PAS) staining of retinal sections. Pups exposed to dexamethasone and oxygen had a lower median retinopathy score of 5 (4, 6) [median (25th, 75th quartile)] compared with animals exposed to oxygen alone with median score of 9 (6, 10) with p < 0.001. PAS staining for extra retinal neovascularization in the dexamethasone and oxygen treated animals showed a significant reduction in number of nuclei extending beyond the inner limiting membrane when compared with oxygen exposed alone (p = 0.04). Animals treated with dexamethasone had decreased weight gain compared with control animals. Dexamethasone did not appear to affect the normal development of retinal vasculature as assessed by the scoring system when compared with control animals. Thus, dexamethasone decreases severity of OIR without having an adverse effect on normal retinal vascular development in the mouse model. We speculate that dexamethasone decreases the injury response that occurs during the hyperoxic phase, thus protecting the developing vasculature and improving the subsequent retinopathy.
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PMID:Dexamethasone reduces oxygen induced retinopathy in a mouse model. 1040 Jan 41

Impaired septal formation and decreased alveolarization are often caused by hyperoxic injury to the developing lung and are characteristic features of bronchopulmonary dysplasia. Dexamethasone, frequently administered to infants during oxygen exposure, also inhibits septal formation in the newborn lung. Vitamin A administration reduces the incidence of bronchopulmonary dysplasia in vitamin A-deficient premature infants, and retinoic acid improves alveolarization in newborn rats treated with dexamethasone, indicating that retinoic acid may be useful in preventing hyperoxia-induced impaired septation in bronchopulmonary dysplasia. To investigate whether treatment with retinoic acid during exposure to hyperoxia would improve septal formation, newborn rats exposed to > or =90% O(2) from d 3 of life to d 14 were treated with retinoic acid (d 3-13 of life) and/or dexamethasone (d 4-13 of life). In contrast with the effects of retinoic acid on dexamethasone-induced inhibition of alveolarization, we found that retinoic acid did not improve septal formation or decrease airspace size in animals exposed to hyperoxia alone or to hyperoxia plus dexamethasone. Retinoic acid did, however, increase collagen in airspace walls as demonstrated by staining and immunohistochemistry. There was no increase in procollagen mRNA by Northern hybridization analysis, indicating that retinoic acid-associated increases in lung collagen are likely due to posttranscriptional regulation. There was a trend toward increased survival in hyperoxia in animals treated with retinoic acid to the extent that combined therapy with retinoic acid and dexamethasone resulted in the greatest improvement in animal survival. These results suggest that although retinoic acid may be of benefit in hyperoxia-induced lung injury and may have important effects on lung matrix, it does not prevent impairment of septation or induce alveolar formation during exposure to hyperoxia.
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PMID:Effects of retinoic acid on airspace development and lung collagen in hyperoxia-exposed newborn rats. 1100 32

TNF-alpha has been found in the retina. Hyperoxia and hypoxia regulate TNF-alpha expression. TNF-alpha is an important factor in inflammation and angiogenesis. Dexamethasone inhibits TNF-alpha production. Changes in TNF-alpha expression in the retina may play an important role in the development of oxygen-induced retinopathy. Oxygen-induced retinopathy was produced in C57BL6 mice by exposure to 75% oxygen at Postnatal Day 7 (P7) for 5 days and the mice recovered in room air until Day 17 (P17). Dexamethasone was administered at 0.5 mg/kg/day once daily subcutaneously during the 5 days of oxygen exposure. TNF-alpha expression was evaluated at Day 7 prior to oxygen exposure, at Day 12 (P12) immediately upon removal from oxygen, and at Day 17, the time of maximal vasoproliferation by RT-PCR. TNF-alpha is developmentally regulated in the retinae of C57BL6 mice. From P7 to P12, there is a 3-fold increase in TNF-alpha expression and from P7 to P17 there is a 2.7-fold increase. There was 2.7-fold suppression in expression immediately following oxygen exposure at P12. The expression was dramatically increased at P17, the time of maximal vasoproliferation. Dexamethasone inhibited the expression of TNF-alpha at P17 by 6.4-fold. At this dose, it also suppressed the baseline TNF-alpha expression in the mouse model. In summary, TNF-alpha is altered in the development of oxygen-induced retinopathy in the mouse. It increased markedly during the vasoproliferative phase and was suppressed by dexamethasone. Modulation of TNF-alpha expression may provide a potential site of action for future therapeutic targets.
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PMID:Dexamethasone alters TNF-alpha expression in retinopathy. 1116 42

The response of the fetal rat Type II pneumocyte (FTIIP), the stem cell of the alveolar epithelium, to hyperoxia would be helpful to understand the effects of oxygen-induced injury to the immature lung. In such a scenario, the presence of nitric oxide (NO) may have a protective or detrimental effect. Our goals were to evaluate the release of cytokines and apoptotic cell death in freshly isolated FTIIP (19-day) in the presence of 95% O(2) and/or NO. The effects of dexamethasone and pentoxifylline on the FTIIP cytokine response were also studied. There was no significant difference in the levels of IL-1beta and IL-10 from FTIIP, in room air, hyperoxia and/or NO at 2, 6 and 24 h. However, IL-6 release was significantly higher, when measured over time, after 2, 6 and 24 h of exposure to hyperoxia and NO. Dexamethasone in the presence of hyperoxia and/or NO increased the release of IL-10 at 24 h. There was increased apoptosis in FTIIP exposed to hyperoxia alone and in combination with NO; this was significantly attenuated in the presence of dexamethasone and pentoxifylline. We speculate that the cytoprotective effects of dexamethasone in the immature lung may, in part, be mediated via IL-10.
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PMID:Release of cytokines and apoptosis in fetal rat Type II pneumocytes exposed to hyperoxia and nitric oxide: modulatory effects of dexamethasone and pentoxifylline. 1263 66


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