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Coenzyme A (CoASH) is compartmentalized preferentially in the mitochondria, and CoASH and its mixed disulfide with glutathione (CoASSG) undergo thiol/disulfide exchange reactions with glutathione (GSH) and glutathione disulfide (GSSG) in vitro. We measured CoASH and CoASSG in freeze-clamped lung tissues from Fischer-344 and Sprague-Dawley rats maintained in room air or exposed to >95% O(2) for 48 h to test the hypothesis that oxidant stresses on lung thiol status would be observed in the CoASH/CoASSG redox couple, suggesting oxidant stress responses in the mitochondria. Lung tissue concentrations of CoASSG in the Fischer-344 rats declined from 0.89 +/- 0.15 to 0.51 +/- 0.13 nmol/g of lung after 48 h of hyperoxia. CoASH levels declined from 6.40 +/- 0.84 to 3.0 +/- 0.65 nmol/g of lung, and acetyl CoA levels also were lower in the lungs of animals exposed to hyperoxia. CoASH/CoASSG ratios were lower in animals exposed to hyperoxia, satisfying our previously defined criteria for an oxidant stress on this thiol/disulfide redox couple, but absolute CoASSG levels were not increased, as would be expected for oxidant stresses driven simply by increases in reactive oxygen species or other oxidants. Pulmonary edema was observed in the hyperoxic rats and accounted for some of the declines in CoASH concentrations, but CoASH contents per total lung also declined. Lung mitochondrial succinate dehydrogenase activities were not diminished in rats exposed to hyperoxia, indicating that the decreases in CoASH concentrations are not attributable to general destruction of lung mitochondria. Lung GSSG contents were greater in the hyperoxia animals, but GSH/GSSG ratios, which are dominated by extramitochondrial pools, did not decrease in these animals. The mechanisms responsible for, and the possible pathophysiologic consequences of, the decreases in lung CoASH concentrations are not evident from the data available at the present time, but the loss of more than half the tissue contents of CoASH is likely to generate additional metabolic effects that could have significant pathophysiologic consequences.

Objective and Design: To test the hypothesis that glucocorticoid administration would diminish the lung expression of P-selectin mRNA in hyperoxia-exposed rats., Animals: Adult male Sprague-Dawley rats were divided into 6 separate groups containing 10 to 13 animals per group., Treatment: Rats were dosed with 1 mg/kg of dexamethasone or vehicle only, ip. Immediately after dosing, animals were placed in > 95 % oxygen. Some animals were maintained in room air and are presented as 0 h of exposure to hyperoxia. Another group of animals was dosed with 10 mg/kg lipopolysaccharide (LPS) ip immediately after dosing with either dexamethasone or vehicle as above., Methods: At 24 or 48 h, lung samples were obtained, and lung weight to body weight ratios calculated. In the LPS studies, samples were obtained 4 h after LPS dosing. In a subset of animals, lung sections were hybridized for P-selectin mRNA. All data except for hybridizations were analyzed with three-way ANOVA, with subsequent post-hoc testing. P-selectin hybridizations were quantified by counting the number of positive vessels per high-powered field, and subsequently analyzed by unpaired Student's t-test. Immunohistochemical analyses for P-selectin expression were also performed to determine whether changes in P-selectin mRNA were associated with differences in protein expression. All data are expressed as means +/- SEM., Results: Rats dosed with dexamethasone had higher lung/body weight ratios after 24 and 48 h of exposure to hyperoxia than did similarly exposed rats dosed only with vehicle (at 48 h, 0.87 +/- 0.04 versus 0.65 +/- 0.06, respectively, P < 0.05). The higher ratios in hyperoxic animals dosed with dexamethasone were associated with much higher levels of lung expression for P-selectin mRNA than was observed in similarly exposed rats dosed with vehicle alone (at 48 h, 3.93 +/- 1.02, versus 0.20 +/- 0.06, respectively, P < 0.01). In contrast dexamethasone dosing lead to lower lung P-selectin mRNA expression in animals exposed to LPS (1.23 +/- 1.08 in dexamethasone dosed animals versus 6.80 +/- 0.92 in vehicle only dosed animals). Consistent with the mRNA data, P-selectin immunoreactivity increased as a function of hyperoxia-exposure time in animals dosed with dexamethasone, while immunoreactivity decreased as a function of hyperoxia-exposure time in animals dosed with vehicle only., Conclusions: Increased P-selectin mRNA combined with increased P-selectin protein expression in animals exposed to hyperoxia and dosed with dexamethasone suggests that enhanced expression of P-selectin may contribute to the greater lung injury and inflammation caused by hyperoxia in rats treated with dexamethasone.

The pulmonary damage caused by prolonged exposure to high oxygen concentrations is accompanied by lung inflammation, which may contribute to the expression of hyperoxic lung injury. In turn, adhesion molecules are crucial for initiating inflammatory responses. The goal of the present study was to investigate the association of contents of soluble adhesion molecules in plasma or alveolar fluids of hyperoxic rats with lung expression of adhesion molecules, lung inflammation and lung injury. We exposed adult Sprague-Dawley rats to > 95% oxygen for up to 60 h and measured the contents of intercellular adhesion molecule-I (ICAM-I) and E-Selectin in plasma and lung tissue expression of the same molecules, and we assessed lung myeloperoxidase (MPO) activties and lung water contents as indices of lung inflammation and injury, respectively. We also assessed ICAM-I content in lavage samples, because ICAM-I may be shed from the alveolar epithelium. Lung water was elevated at 60 h of hyperoxia-exposure, and this effect was preceded by increases in lung MPO activities. Lung ICAM-I expression was more than doubled at 48 h, although soluble ICAM-I contents were not elevated in plasma or lavage. Soluble E-Selectin was increased by more than 50% at 24 h of hyperoxia-exposure, while lung expressions of E-Selectin were not increased until 48 h. The sequence of the events observed in the present studies suggests that E-Selectin contributes to lung inflammation in hyperoxia and the acceleration of lung injury immediately following the inflammatory response suggests a pivotal role for inflammation in this injury.