Iron Oxide Particles Alter Bacterial Uptake and the LPS-Induced Inflammatory Response in Macrophages

• Published in: International journal of environmental research and public health Vol. 18; no. 1; p. 146
• Main Authors: Williams, Lewis J, Tristram, Stephen G, Zosky, Graeme R
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 28-12-2020; MDPI
• Subjects: Australia; Bacteria; Bacterial diseases; Cytokines; Cytokines - metabolism; Cytotoxicity; Enzyme-linked immunosorbent assay; Experiments; Exposure; Ferric Compounds - pharmacology; Flow cytometry; Haemophilus influenzae; Hematite; Humans; IL-1β; Infections; Inflammation; Inflammatory response; Interleukin 6; Interleukin 8; Iron oxides; Leukocytes, Mononuclear - drug effects; Lipopolysaccharides; Lipopolysaccharides - toxicity; Macrophages; Macrophages - drug effects; Magnetite; Outdoor air quality; Particulate emissions; Particulate matter; Peripheral blood; Phagocytosis; Silica; Silicon Dioxide - pharmacology; THP-1 Cells; Tumor necrosis factor-TNF; Tumor necrosis factor-α; Australia; St Louis Missouri; United States > US; particulate matter; macrophages; geogenic; NTHi; inflammatory cytokines
• ISSN: 1660-4601; 1661-7827; 1660-4601
• DOI: 10.3390/ijerph18010146

Exposure to geogenic (earth-derived) particulate matter (PM) is linked to severe bacterial infections in Australian Aboriginal communities. Experimental studies have shown that the concentration of iron in geogenic PM is associated with the magnitude of respiratory health effects, however, the mechanism is unclear. We investigated the effect of silica and iron oxide on the inflammatory response and bacterial phagocytosis in macrophages. THP-1 and peripheral blood mononuclear cell-derived macrophages were exposed to iron oxide (haematite or magnetite) or silica PM with or without exposure to lipopolysaccharide. Cytotoxicity and inflammation were assessed by LDH assay and ELISA respectively. The uptake of non-typeable
by macrophages was quantified by flow cytometry. Iron oxide increased IL-8 production while silica also induced significant production of IL-1β. Both iron oxide and silica enhanced LPS-induced production of TNF-α, IL-1β, IL-6 and IL-8 in THP-1 cells with most of these responses replicated in PBMCs. While silica had no effect on NTHi phagocytosis, iron oxide significantly impaired this response. These data suggest that geogenic particles, particularly iron oxide PM, cause inflammatory cytokine production in macrophages and impair bacterial phagocytosis. These responses do not appear to be linked. This provides a possible mechanism for the link between exposure to these particles and severe bacterial infection.