Time-dependent inhibition of oxygen radical induced lung injury

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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44504/1/10753_2004_Article_BF00914272.pd

Oxidant injury of cells. DNA strand-breaks activate polyadenosine diphosphate-ribose polymerase and lead to depletion of nicotinamide adenine dinucleotide.

To determine the biochemical basis of the oxidant-induced injury of cells, we have studied early changes after exposure of P388D1 murine macrophages to hydrogen peroxide. Total intracellular NAD+ levels in P388D1 cells decreased with H2O2 concentrations of 40 microM or higher. Doses of H2O2 between 0.1 and 2.5 mM led to an 80% depletion of NAD within 20 min. With doses of H2O2 of 250 microM or lower, the fall in NAD and, as shown previously, ATP, was reversible. Higher doses of H2O2 that cause ultimate lysis of the cells, induced an irreversible depletion of NAD and ATP. Poly-ADP-ribose polymerase, a nuclear enzyme associated with DNA damage and repair, which catalyzes conversion of NAD to nicotinamide and protein-bound poly-ADP-ribose, was activated by exposure of the cells to concentrations of 40 microM H2O2 or higher. Activation of poly-ADP-ribose polymerase was also observed in peripheral lymphocytes incubated in the presence of phorbol myristate acetate-stimulated polymorphonuclear neutrophils. Examination of the possibility that DNA alteration was involved was performed by measurement of thymidine incorporation and determination of DNA single-strand breaks (SSB) in cells exposed to H2O2. H2O2 at 40 microM or higher inhibited DNA synthesis, and induced SSB within less than 30 s. These results suggest that DNA damage induced within seconds after addition of oxidant may lead to stimulation of poly-ADP-ribose polymerase, and a consequent fall in NAD. Excessive stimulation of poly-ADP-ribose polymerase leads to a fall in NAD sufficient to interfere with ATP synthesis