Biobran (MGN-3) concurrently reverses lipopolysaccharide-induced elevation of CD14 and impairment of macrophage-mediated bacterial clearance in a model of diabetic wound biofilms

Asif, Mohammed Subhan, El Mohtadi, Mohamed and Ashworth, Jason ORCID: https://orcid.org/0000-0001-7045-7899 (2023) Biobran (MGN-3) concurrently reverses lipopolysaccharide-induced elevation of CD14 and impairment of macrophage-mediated bacterial clearance in a model of diabetic wound biofilms. In: Phagocytes Gordon Research Conference 2023: Molecular and Cellular Diversity in Host Defense and Inflammation, 04 June 2023 - 09 June 2023, Waterville Valley, New Hampshire, United States. (Unpublished)

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Abstract

Hyperglycaemia found in type 2 diabetic patients can lead to several complications including a type of chronic wound called a diabetic foot ulcer (DFU). Diabetic foot ulcers are associated with elevated inflammatory markers but defective immune responses that can lead to microbial infection, often characterised by biofilm formation. Cereal-derived fibres called arabinoxylans have shown increased immune function in both the adaptive and innate immune responses in animal models. A cereal-derived fibre called Biobran (MGN-3) has been shown to stimulate immune cells including macrophages, T cell and dendritic cells suggesting it may be of therapeutic benefit to fight infections. This study investigated whether MGN-3 can stimulate the clearance of wound-associated bacterial biofilms under hyperglycaemic conditions and modulate levels of the pattern recognition receptor CD14 on the cell surface of M1 macrophages. Host-pathogen biofilm investigations (n=12) were performed to assess the effect of MGN-3 (0.5, 1.0 and 2.0 mg/ml for 24 hours) on the phagocytosis of both Gram-positive Methicillin resistant Staphylococcus aureus (MRSA) and Gram-negative Pseudomonas aeruginosa (PA01) biofilms by U937-derived M1 macrophages cultured in glucose-supplemented (11, 15, 20, 30mM) medium. CD14 on the cell surface of M1 macrophages was assessed by confocal microscopy and flow cytometry (n=4). Findings showed glucose-supplementation significantly (P<0.05) inhibits the M1 macrophage-mediated phagocytosis of both MRSA and PA01 biofilms in a dose-dependent manner. Moreover, hyperglycaemia significantly (P<0.05) enhanced lipopolysaccharide (LPS)-induced M1 macrophage CD14 surface levels. Treatment of M1 macrophages with MGN-3 (0.5, 1.0 and 2.0 mg/ml) for 24 hours significantly (P<0.05; n=12) promoted the clearance of both MRSA and PA01 biofilms in a dose-dependent manner. Moreover, this is the first study to demonstrate MGN-3 reverses the detrimental effects of hyperglycaemia in a dose-dependent manner, significantly (P<0.05) increasing M1-mediated clearance of bacterial biofilms and reducing LPS-induced CD14 levels (n=4). CD14 levels significantly (P < 0.05; n=4) decreased after dual treatment with LPS and MGN-3 compared to just LPS treatment alone, suggesting competition was taking place between MGN-3 and LPS at the CD14 receptor on M1 macrophages. The findings of this project suggest MGN-3 may be of potential therapeutic benefit for the treatment of DFU patients with wound biofilm infections.