Pseudomonas aeruginosa is one of the leading causes of nosocomial infections throughout the world. P. aeruginosa nosocomial pneumonias are associated with higher mortality than other organisms, and ventilator- associated pneumonia has a mortality rate as high as 30%. P. aeruginosa infection is also the leading cause of death in cystic fibrosis patients. The increasing resistance of P. aeruginosa to antibiotics and the limited number of new antibiotics available for its treatment underscores the importance of understanding how to enhance the host response to P. aeruginosa, which is our long-term goal. A key component of the host response to acute lung infection by this pathogen is a robust recruitment of neutrophils, and we have determined that the protease ADAM17 is an important gatekeeper of neutrophil infiltration from the blood into the lungs during P. aeruginosa infection. ADAM17 is a membrane-associated protease constitutively expressed by leukocytes. Its activity is highly inducible upon leukocyte activation, and the protease regulates the density of cell surface adhesion molecules and the release of soluble pro-inflammatory factors. In our preliminary studies, gene-targeting ADAM17 in leukocytes markedly attenuated acute P. aeruginosa lung infection and bacteremia in mice. The overall objective of our study is to determine the mechanism by which ADAM17 exerts itself on the host response during acute P. aeruginosa lung infection. We hypothesize that overactivation of ADAM17 during severe infection promotes neutrophil dysfunction and pseudomonal pneumonia.
In Aim 1 of this R21 (exploratory/developmental) grant application, we will determine the immunomodulatory role of ADAM17 during acute P. aeruginosa lung infection. To determine the underlying mechanism of enhanced bacterial clearance in conditional ADAM17 knockout mice, we will carefully evaluate neutrophil recruitment into the infected lung and airspace as well as local and systemic inflammation, as suggested by our preliminary findings.
In Aim 2, we will explore for the first time the effects of a highly selective, small-molecule ADAM17 inhibitor in mice during acute pseudomonal pneumonia. We will evaluate therapeutic and prophylactic use of the inhibitor, and its effects on the host response. The impact of these studies is that they will critically advance our understanding of the mechanisms of action of ADAM17 during lung infection, as well as indicate the therapeutic potential of this immune regulator.

Public Health Relevance

Pseudomonas aeruginosa is one of the most frequently isolated bacteria causing hospital acquired or healthcare associated pneumonia, including ventilator-associated pneumonia. P. aeruginosa is also a leading cause of death in cystic fibrosis patients. The increasing resistance of this pathogen to antibiotics currently used to trea pseudomonal pneumonia and the limited number of new antibiotics that are becoming available for its treatment underscores the importance of understanding how to enhance the immune response to P. aeruginosa. Our studies reveal that the protease ADAM17 in white blood cells has a detrimental role during severe bacterial infections, in part, by impairing neutrophil recruitment. The objective of this proposal is to evaluate the potential of ADAM17 as a drug target for pseudomonal pneumonia .

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Exploratory/Developmental Grants (R21)
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Lung Cellular, Molecular, and Immunobiology Study Section (LCMI)
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Taylor, Christopher E,
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University of Minnesota Twin Cities
Veterinary Sciences
Schools of Veterinary Medicine
United States
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Mishra, Hemant K; Johnson, Timothy J; Seelig, Davis M et al. (2016) Targeting ADAM17 in leukocytes increases neutrophil recruitment and reduces bacterial spread during polymicrobial sepsis. J Leukoc Biol 100:999-1004
Mishra, Hemant K; Long, Chunmei; Bahaie, Nooshin S et al. (2015) Regulation of CXCR2 expression and function by a disintegrin and metalloprotease-17 (ADAM17). J Leukoc Biol 97:447-54
Romee, Rizwan; Foley, Bree; Lenvik, Todd et al. (2013) NK cell CD16 surface expression and function is regulated by a disintegrin and metalloprotease-17 (ADAM17). Blood 121:3599-608