Related Experiment Videos
Polymorphonuclear leukocyte cytoplasts mediate acute lung injury
V B Antony1, C L Owen, D English
1Department of Medicine, Veterans Administration Medical Center, Indianapolis, Indiana.
Abstract:
Injection of phorbol 12-myristate 13-acetate (PMA) into polymorphonuclear leukocyte (PMN)-depleted, PMN cytoplast-repleted New Zealand White rabbits caused the development of acute lung injury in vivo. PMN cytoplasts are nucleus- and granule-free vesicles of cytoplasm capable of releasing toxic O2 radicals but incapable of releasing granule enzymes. PMN cytoplasts when activated by PMA reduced 66 +/- 12.7 nmol of cytochrome c compared with 2.6 +/- 0.7 nmol in their resting state and did not release a significant quantity of granule enzymes (P greater than 0.05). Injection of PMA into New Zealand White rabbits caused a significant decrease (P less than 0.05) in the number of circulating cytoplasts. Increases in lung weight-to-body weight ratios in PMA-treated rabbits (9.8 +/- 0.5 X 10(-3] compared with saline-treated rabbits (5.3 +/- 0.2 X 10(-3] were also noted. Levels of angiotensin-converting enzyme in lung lavage as well as the change in alveolar-arterial O2 ratio correlated with the numbers of cytoplasts in lung lavage (P = 0.001, r = 0.84 and P = 0.0166, r = 0.73, respectively). Albumin in lung lavage increased to 1,700 +/- 186 mg/ml in PMA-treated rabbits from 60 +/- 30 mg/ml in saline-treated rabbits. These changes were attenuated by pretreatment of rabbits with dimethylthiourea (DMTU). In vitro, cytoplasts were able to mediate increases in endothelial monolayer permeability. This was evidenced by increases in fractional transit of albumin across endothelial monolayers when treated with PMA-activated cytoplasts (0.08 +/- 0.01 to 0.28 +/- 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Activated polymorphonuclear leukocyte (PMN) cytoplasts, vesicles released by PMNs, induce acute lung injury by increasing vascular permeability. Dimethylthiourea (DMTU) pretreatment attenuated these effects, suggesting a role for reactive oxygen species.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Toxicology
Background:
- Polymorphonuclear leukocytes (PMNs) play a role in inflammatory lung injury.
- PMN cytoplasts are anucleated cytoplasmic fragments capable of releasing reactive oxygen species (ROS).
- The specific contribution of PMN cytoplasts to acute lung injury (ALI) is not fully understood.
Purpose of the Study:
- To investigate the role of PMN cytoplasts in the development of ALI.
- To determine if PMN cytoplasts can mediate increased endothelial permeability.
- To assess the potential protective effect of dimethylthiourea (DMTU) against PMN cytoplast-induced ALI.
Main Methods:
- Acute lung injury was induced in PMN-depleted rabbits by injecting phorbol 12-myristate 13-acetate (PMA) to activate PMN cytoplasts.
- Measurements included lung weight-to-body weight ratios, circulating cytoplast counts, and levels of angiotensin-converting enzyme and albumin in lung lavage.
- In vitro experiments assessed the effect of activated PMN cytoplasts on endothelial monolayer permeability.
Main Results:
- PMA injection into PMN cytoplast-repleted rabbits caused ALI, evidenced by increased lung weight and elevated albumin in lung lavage.
- Activated PMN cytoplasts significantly increased endothelial monolayer permeability in vitro.
- Pretreatment with DMTU attenuated the ALI and vascular permeability changes.
Conclusions:
- PMN cytoplasts, when activated, can induce acute lung injury.
- PMN cytoplasts mediate increased endothelial permeability, likely through the release of toxic O2 radicals.
- DMTU demonstrates a protective effect, suggesting that ROS contribute to PMN cytoplast-induced lung injury.