Date Approved

4-2023

Document Type

Dissertation

Degree Name

PhD in Molecular Cell Biology & Neuroscience

Department

Cell Biology and Neuroscience

College

Graduate School of Biomedical Sciences, Virtua Health College of Medicine & Life Sciences of Rowan University

First Advisor

Kingsley Yin, PhD

Committee Member 1

Nimish Acharya, PhD

Committee Member 2

Robert Nagele, PhD

Committee Member 3

Bernd Spur, PhD

Committee Member 4

Lark Perez, PhD

Subject(s)

Pseudomonas aeruginosa, Biofilms, Quorum Sensing, Bacterial Infections, Lipoxins, Immune System Phenomena

Disciplines

Bacterial Infections and Mycoses | Bacteriology | Biological Phenomena, Cell Phenomena, and Immunity | Cell Biology | Immunology of Infectious Disease | Laboratory and Basic Science Research | Medical Immunology | Medicine and Health Sciences | Molecular Biology | Pathogenic Microbiology | Therapeutics

Abstract

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen known as a major cause of hospital-acquired secondary infections, commonly causing chronic respiratory infections in immunocompromised individuals, especially those with cystic fibrosis, and often found in wound infections. P. aeruginosa uses the quorum sensing pathway to readily form protective biofilms, which reduce the efficacy of antibiotics and access by host immune cells to eradicate the pathogen. Specialized pro-resolving mediators (SPMs) are lipids endogenously produced by the host immune response to infection to aid in infection resolution. One SPM, Lipoxin A4 (LxA4), has been shown to be a robust quorum sensing inhibitor.

The studies presented here suggest SPM inhibition of biofilm formation has selectivity, and that LxA4 can reduce P. aeruginosa biofilm formation, possibly through reducing quorum sensing virulence gene expression. LxA4 also shows improvement to the efficacy of antibiotics against P. aeruginosa infection. In combination, LxA4 and ciprofloxacin increase killing of biofilm-associated bacteria in established biofilms, which may be an effect of LxA4 reducing quorum sensing gene expression, thereby reducing biofilm formation, and allowing better penetration of ciprofloxacin into the biofilm. When co-incubated with established biofilms, untreated THP-1 monocytes induced a rise in the proportion of live bacteria. Importantly, LxA4 pre-treatment of monocytes abolished this induced reaction from the bacterial population. Also of great significance, LxA4 pre-treatment increases the adhesion ability of the monocytes to the established biofilms, suggesting an increased duration of direct contact to be a possible method for increased host immune response against biofilms. TNF-α production of pre-treated monocytes showed an initial hyper-inflammatory response to co-incubation with established biofilms but resolved to circulating levels roughly half that seen in untreated monocytes, suggesting LxA4 pre-treatment enhances the initial activation of immune response mechanisms, which then necessitates a quicker approach to inflammation resolution.

In summary, these studies highlight the possibilities of LxA4 as an additive treatment against P. aeruginosa infections in two ways: by acting in conjunction with antibiotics directly on bacteria and biofilms; and by priming host immune cells to achieve infection resolution more effectively.

Download

Share

COinS