Submitted on November 19, 2003
Accepted on January 2, 2004
Interfacial Phospholipids Inhibit Ozone Reactive Absorption-Mediated Cytotoxicity in Vitro
Lydia M. Connor1, Carol A. Ballinger2, Thomas B. Albrecht3, and Edward M. Postlethwait2*
1 Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX, USA
2 Department of Environmental Health Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
3 Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA
* To whom correspondence should be addressed. E-mail: epostlethwait{at}ms.soph.uab.edu.
The intrapulmonary distribution of inhaled ozone (O3) and induction of site specific cell injury are related to complex interactions among airflow patterns, local gas phase concentrations, and the rates of O3 flux into and reaction/diffusion within the epithelial lining fluid (ELF). Recent studies demonstrated that interfacial phospholipid films appreciably inhibited NO2 absorption. Because surface active phospholipids are present on alveolar and airway interfaces, we investigated the effects of interfacial films on O3 reactive absorption and acute cell injury. Compressed films of dipalmitoyl-glycero-3-phosphocholine (DPPC) and rat lung lavage lipids significantly reduced O3 reactive absorption by ascorbic acid (AH2), reduced glutathione, and uric acid. Conversely, unsaturated PC films did not inhibit O3 absorption. We evaluated O3-ediated cell injury using a human lung fibroblast cell culture system, an intermittent tilting exposure regimen to produce a thin covering layer, and nuclear fluorochrome permeability. Exposure produced negligible injury in
cells covered with MEM. However, addition of AH2 produced appreciable (> 50%) cell injury. Film spreading of DPPC monolayers necessitated the use of untilted regimens. Induction of acute cell injury in untilted cultures required both AH2 plus very high O3 concentrations. Addition of DPPC films significantly reduced cell injury. We conclude that acute cell injury likely results from O3 reaction with ELF substrates. Furthermore, interfacial films of surface active, saturated phospholipids reduce the local dose of O3-derived reaction products. Finally, since O3 local dose and tissue damage likely correlate, we propose interfacial phospholipids may modulate
intrapulmonary distribution of inhaled O3 and the extent of site-specific cell injury.
