The impact of surfactant protein-A on ozone-induced changes in the mouse bronchoalveolar lavage proteome.
BACKGROUND
Ozone is a major component of air pollution. Exposure to this powerful oxidizing agent can cause or exacerbate many lung conditions, especially those involving innate immunity. Surfactant protein-A (SP-A) plays many roles in innate immunity by participating directly in host defense as it exerts opsonin function, or indirectly via its ability to regulate alveolar macrophages and other innate immune cells. The mechanism(s) responsible for ozone-induced pathophysiology, while likely related to oxidative stress, are not well understood.


METHODS
We employed 2-dimensional difference gel electrophoresis (2D-DIGE), a discovery proteomics approach, coupled with MALDI-ToF/ToF to compare the bronchoalveolar lavage (BAL) proteomes in wild type (WT) and SP-A knockout (KO) mice and to assess the impact of ozone or filtered air on the expression of BAL proteins. Using the PANTHER database and the published literature most identified proteins were placed into three functional groups.


RESULTS
We identified 66 proteins and focused our analysis on these proteins. Many of them fell into three categories: defense and immunity; redox regulation; and protein metabolism, modification and chaperones. In response to the oxidative stress of acute ozone exposure (2 ppm; 3 hours) there were many significant changes in levels of expression of proteins in these groups. Most of the proteins in the redox group were decreased, the proteins involved in protein metabolism increased, and roughly equal numbers of increases and decreases were seen in the defense and immunity group. Responses between WT and KO mice were similar in many respects. However, the percent change was consistently greater in the KO mice and there were more changes that achieved statistical significance in the KO mice, with levels of expression in filtered air-exposed KO mice being closer to ozone-exposed WT mice than to filtered air-exposed WT mice.


CONCLUSIONS
We postulate that SP-A plays a role in reactive oxidant scavenging in WT mice and that its absence in the KO mice in the presence or absence of ozone exposure results in more pronounced, and presumably chronic, oxidative stress.
Haque
Rizwanul
R
Penn State Center for Host defense, Inflammation, and Lung Disease (CHILD) Research and the Department of Pediatrics, Penn State College of Medicine, Hershey, PA, USA.
Umstead
Todd M
TM
Penn State Center for Host defense, Inflammation, and Lung Disease (CHILD) Research and the Department of Pediatrics, Penn State College of Medicine, Hershey, PA, USA.
Freeman
Willard M
WM
The Department of Pharmacology, Penn State College of Medicine, Hershey, PA, USA.
Floros
Joanna
J
Penn State Center for Host defense, Inflammation, and Lung Disease (CHILD) Research and the Department of Pediatrics, Penn State College of Medicine, Hershey, PA, USA.|The Department of Obstetrics and Gynecology, Penn State College of Medicine, Hershey, PA, USA.
Phelps
David S
DS
Penn State Center for Host defense, Inflammation, and Lung Disease (CHILD) Research and the Department of Pediatrics, Penn State College of Medicine, Hershey, PA, USA.