Related Experiment Videos
Protective effects of O2 radical scavengers and adenosine in PMA-induced lung injury
R C Allison1, E M Hernandez, V R Prasad
1Department of Medicine, College of Medicine, University of South Alabama, Mobile 36688.
Abstract:
We have previously shown that phorbol myristate acetate (PMA) produces acute lung injury in blood-perfused lungs but not in plasma-dextran-perfused lungs. This is compatible with the concept that its major mechanism of injury is the stimulation of O2 radicals by neutrophils, which in turn increase permeability by damaging the endothelial cells. In this study we measured vascular permeability and resistance before and 1 h after PMA in five groups of blood-perfused dog lungs: PMA alone in one group and pretreatment with catalase, superoxide dismutase, deferoxamine, and adenosine each in four other groups. By the use of two indexes of permeability, the filtration coefficient and the isogravimetric capillary pressure, we found that, compared with PMA alone, catalase, deferoxamine, and adenosine provided significant protection, whereas the results with superoxide dismutase were variable. These four drugs also significantly attenuated the marked increased resistance seen with PMA alone. Although the effects seen with the first three can be explained by their scavenging of O2 radicals, adenosine appears to provide protection through a separate mechanism.
Insights
Phorbol myristate acetate (PMA) causes lung injury via oxygen radicals from neutrophils. Catalase, deferoxamine, and adenosine protected lungs from PMA-induced injury and resistance, suggesting distinct protective mechanisms.
Area of Science:
- Pulmonary medicine
- Cellular biology
- Toxicology
Background:
- Phorbol myristate acetate (PMA) induces acute lung injury in blood-perfused lungs.
- This injury is linked to oxygen radical stimulation by neutrophils, damaging endothelial cells and increasing permeability.
- Previous studies suggest neutrophils play a key role in PMA-induced lung injury.
Purpose of the Study:
- To investigate the protective effects of antioxidants and adenosine against PMA-induced acute lung injury.
- To determine the role of oxygen radicals in PMA-induced increases in vascular permeability and resistance.
- To elucidate the mechanisms by which catalase, superoxide dismutase, deferoxamine, and adenosine modulate lung injury.
Main Methods:
- Blood-perfused dog lungs were used to model acute lung injury.
- Five experimental groups were established: PMA alone, and PMA with pretreatment of catalase, superoxide dismutase, deferoxamine, or adenosine.
- Vascular permeability (filtration coefficient, isogravimetric capillary pressure) and resistance were measured before and after PMA administration.
Main Results:
- Catalase, deferoxamine, and adenosine significantly protected against PMA-induced increases in vascular permeability.
- Superoxide dismutase showed variable protective effects.
- All four pretreatments (catalase, superoxide dismutase, deferoxamine, adenosine) attenuated the PMA-induced increase in vascular resistance.
- Adenosine demonstrated protection potentially through a mechanism independent of oxygen radical scavenging.
Conclusions:
- Neutrophil-derived oxygen radicals are major mediators of PMA-induced acute lung injury.
- Catalase, deferoxamine, and adenosine offer significant protection against PMA-induced lung injury and vascular dysfunction.
- Adenosine may exert its protective effects via a distinct pathway separate from direct oxygen radical scavenging.