ABSTRACT
Six lactoperoxidase tolerant Escherichia coli transposon mutants isolated and characterized in an earlier study, and some newly constructed double mutants, were subjected to peroxide, superoxide and hypochlorite stress, and their inactivation was compared to that of the wild type strain MG1655. Knock out mutants of waaQ and waaO, which owed their lactoperoxidase tolerance to an impaired outer membrane permeability due to a reduced porin content, also exhibited higher resistance to hypochlorite, as did a knock-out strain of lrp, encoding a regulatory protein affecting a wide range of cellular functions. Unlike the outer membrane mutants however, the lrp strain was also more resistant to t-butyl hydroperoxide, but more susceptible to the superoxide generating compound plumbagin. Finally, a lactoperoxidase tolerant knock-out strain of ulaA, involved in ascorbic acid uptake, did not show resistance to any of the other oxidants. The possible modes of action of these different oxidants are discussed.
Subject(s)
Escherichia coli/drug effects , Escherichia coli/physiology , Lactoperoxidase/toxicity , Oxidants/toxicity , Oxidative Stress , Colony Count, Microbial , DNA Transposable Elements , Drug Resistance, Bacterial/genetics , Escherichia coli/genetics , Escherichia coli Proteins/genetics , Gene Deletion , Glycosyltransferases/genetics , Hypochlorous Acid/toxicity , Leucine-Responsive Regulatory Protein/genetics , Mutagenesis, Insertional , Mutation , Peroxides/toxicity , Sodium Hypochlorite , Superoxides/toxicity , tert-Butylhydroperoxide/toxicityABSTRACT
Experimental acute lung injury mediated by reactive metabolites of oxygen can be inhibited by the antioxidant enzymes catalase and superoxide dismutase (SOD). However, the specific time interval during which these enzymes must be present in order to cause protection is not well defined. Using two experimental models of oxidant-dependent acute lung injury, one involving the intratracheal injection of glucose, glucose oxidase, and lactoperoxidase and the other involving the intravenous injection of cobra venom factor (CVF), we investigated the effects of delaying antioxidant administration on the outcome of the inflammatory response. In both cases, the protective effects of catalase and SOD were rapidly attenuated when their administration was delayed for a short period of time. For example, intratracheal catalase resulted in 98% protection when given simultaneously with the glucose oxidase and lactoperoxidase, but only 13% protection when the catalase was delayed 4 min. Likewise, in the CVF-induced lung injury model, intravenous catalase resulted in 40% protection when given simultaneously with the CVF, but only 2% protection when the catalase was delayed 20 min, even though the peak of the injury occurred hours after the initiation of the injury. A similar time dependence was seen with SOD. These results indicate that antioxidant therapy is required early in the course of oxygen radical-mediated acute lung injury for effective protection.
Subject(s)
Catalase/pharmacology , Lung Diseases/chemically induced , Oxygen/toxicity , Superoxide Dismutase/pharmacology , Animals , Bronchoalveolar Lavage Fluid/enzymology , Catalase/administration & dosage , Elapid Venoms/administration & dosage , Elapid Venoms/toxicity , Endopeptidases/analysis , Free Radicals , Glucose/administration & dosage , Glucose/toxicity , Glucose Oxidase/administration & dosage , Glucose Oxidase/toxicity , Hemorrhage/chemically induced , Injections , Lactoperoxidase/administration & dosage , Lactoperoxidase/toxicity , Lung Diseases/pathology , Lung Diseases/prevention & control , Male , Rats , Superoxide Dismutase/administration & dosage , Time Factors , TracheaABSTRACT
The intrapulmonary instillation into rat lung of enzymes that generate oxygen metabolites results in acute lung injury. The injection of xanthine oxidase and xanthine produces acute lung injury that, in the presence of superoxide dismutase, but not in the presence of catalase, can be significantly diminished, suggesting that O2- has the capacity to injure the lung. Instillation of a generator of H2O2, namely glucose oxidase, will, in sufficient quantities, produce acute injury that is not neutrophil-dependent. When either a low dose of glucose oxidase alone or lactoperoxidase alone is employed, little lung injury occurs. However, instilling the combination of the two enzymes produces severe, acute injury that can be blocked in a dose-dependent manner by catalase, but not by superoxide dismutase. Purified human leukocytic myeloperoxidase, but not horseradish peroxidase, will substitute for lactoperoxidase in the model of lung injury. The lung damaging effects of these enzymes cannot be attributed to the presence of contaminating proteases. Acute lung injury produced by the instillation of glucose oxidase and lactoperioxidase progresses to interstitial fibrosis. These studies represent a direct application of generators of oxygen metabolites to the in vivo induction of lung injury. The data suggest that rat lung is susceptible to injury by a variety of oxygen metabolites, including O2-, H2O2 and its lactoperoxidase or myeloperoxidase-produced derivatives. The studies also indicate that lung injury produced by oxygen metabolites can result in interstitial pulmonary fibrosis.
