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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.

BACKGROUND: Obesity is a global health problem that is associated with wide range of diseases, including atherosclerosis and Nonalcoholic fatty liver (NAFL) disease. Hepatic inflammation can cause cirrhosis, hepatic decompensation (liver failure) and cancer. Recent research now looks at the chronic systemic effects and inter-organ communication between atherosclerosis potentially promoting the development of NAFL. The resolution of inflammation is regulated naturally in the body by specialized pro-resolving mediators (SPMs). Immunoresolvents like ⍹6-derived Lipoxin A4 are suggested as a therapeutic strategy to overcome chronic inflammation and disease. In this study we investigated the therapeutic potential of Lipoxin A4 (LXA4) in cholesterol fed rabbit model of hypercholesterolemia, with atherosclerotic plaques and confined vascular endothelial injury and its effect on the progression of NAFL. OBJECTIVE: This is a continuation of studies pioneered in the Hamilton lab and an extension of the recent study by Taylor et. al in 201811 linking aortic plaque and liver disease. We will now investigate the therapeutic potential of Lipoxin A4 on lipid-rich atherosclerotic plaques in cholesterol fed rabbits and its effect on the progression of NAFL to NASH. METHODS: In vivo magnetic resonance imaging (MRI) measured aortic atherosclerotic inflammation (with plaque Gd-enhancement), plaque size (vessel wall area), and composition, within rabbits fed normal chow or a 1% cholesterol-enriched diet. Biomarkers in the blood were monitored in the rabbits, with follow-up by histology, which included Masson’s trichrome staining. Light Microscopy was used for liver imaging. Ex vivo MRI, T1W imaging was used to quantify VWA (vessel wall area), with Image J programming. RESULTS: Cholesterol-fed rabbits with and without aortic injury developed hypercholesterolemia, NAFL, and atherosclerotic plaques in the aorta. Elevated plasma gamma-glutamyl transferase (GGT; p =0.014) and the ratio of liver enzymes aspartate and alanine aminotransferases (AST/ALT; p = 0.033) confirmed the progression of steatosis to non-alcoholic steatohepatitis (NASH). Histological images showed less fibrosis in those rabbits fed 1% CHOL diet with injury treated with LipoxinA4, when compared to 1% CHOL diet and injury alone. The plasma biomarkers showed a decrease in cholesterol (79%) and triglycerides (49.9%) in those rabbits given LXA4 therapy. The LXA4 treated 1% CHOL diet with injury group showed a marked decrease in the aorta vessel wall area when compared to the 1% CHOL diet with injury, without treatment; as seen in ex vivo, MRI T1W imaging. CONCLUSION: Lipoxin implementation in cholesterol fed rabbits that have localized regions of highly inflamed aortic atherosclerotic plaques, may contribute to the attenuation on the progression of NAFL to NASH as seen in histology and plasma biomarkers including; cholesterol and triglycerides. Lipoxin as a therapeutic has an effect on treating atherosclerotic plaques and attenuating atherosclerosis progression.