Chronic lung infection with Pa remains a major cause of morbidity and mortality in CF. Previous data tell us that: a) alveolar macrophages (AM) and the exuberance of neutrophils (PMN) in the CF lung cannot clear Pa; b) antibodies to Pa in the CF lung are poor opsonins possibly due to protease cleavage or altered isotype; c) there are C3 fragments on Pa form CF lungs, but little is known about the specific form (e.g. C3b, C3bi); d) the C3b receptor (CR1) on phagocytes is deficient on CF lung PMNs, probably due to cleavage by elastase, abundant in CF lungs; the C3bi receptor (CR3) is spared; and e) C3bi, but not C3b, is cleaved in a model system by low concentrations of leukocytes elastase. This project will test the hypothesis that elastase int he CF lung also cleaves C3bi form Pa, and that this, coupled with the loss of PMN CR1 and intrinsically low CR1 on AM, causes impaired phagocyte-bacterial interactions that could help perpetuate lung infection in CF. Experiments will 1) evaluate the effects of bacterial and leukocyte elastases on phagocyte bactericidal activities for pa; 2) quantitate C3 and its fragments, C3bi, and C3d on opsonized Pa and measure their cleavage by elastase; 3) measure the ability of elastase inhibitors to protect opsonins and receptors from proteases in CF lung fluid; and 4) compare Pa with other selected bacterial pathogens to determine if its opsonic characteristics amy contribute to Pa's unique role in CF. These studies should clarify the role of elastase as an activity that impairs lung host defenses in CF and suggest new ways to evaluate the therapeutic potential of elastase inhibitors in future clinical trials. This award will allow me gain the expertise in immunochemistry and biochemistry of complement and proteases needed for this project and will provide me with the tools to understand the relationships between infection and lung tissue damage at the molecular level and to develop as an independent investigator in lung host defenses.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Clinical Investigator Award (CIA) (K08)
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Case Western Reserve University
Schools of Medicine
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Thai, Tiffany L; Arendshorst, William J (2008) ADP-ribosyl cyclase and ryanodine receptors mediate endothelin ETA and ETB receptor-induced renal vasoconstriction in vivo. Am J Physiol Renal Physiol 295:F360-8
Tosi, M F; Zakem-Cloud, H; Demko, C A et al. (1995) Cross-sectional and longitudinal studies of naturally occurring antibodies to Pseudomonas aeruginosa in cystic fibrosis indicate absence of antibody-mediated protection and decline in opsonic quality after infection. J Infect Dis 172:453-61
Berger, M; Norvell, T M; Tosi, M F et al. (1994) Tissue-specific Fc gamma and complement receptor expression by alveolar macrophages determines relative importance of IgG and complement in promoting phagocytosis of Pseudomonas aeruginosa. Pediatr Res 35:68-77
Tosi, M F; Hamedani, A; Brosovich, J et al. (1994) ICAM-1-independent, CD18-dependent adhesion between neutrophils and human airway epithelial cells exposed in vitro to ozone. J Immunol 152:1935-42
Tosi, M F; Zakem, H (1992) Surface expression of Fc gamma receptor III (CD16) on chemoattractant-stimulated neutrophils is determined by both surface shedding and translocation from intracellular storage compartments. J Clin Invest 90:462-70
Tosi, M F; Stark, J M; Hamedani, A et al. (1992) Intercellular adhesion molecule-1 (ICAM-1)-dependent and ICAM-1-independent adhesive interactions between polymorphonuclear leukocytes and human airway epithelial cells infected with parainfluenza virus type 2. J Immunol 149:3345-9
Tosi, M F; Zakem, H; Berger, M (1990) Neutrophil elastase cleaves C3bi on opsonized pseudomonas as well as CR1 on neutrophils to create a functionally important opsonin receptor mismatch. J Clin Invest 86:300-8