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Abstract

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 Haemophilus influenzae 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.

Item Type:	Article
Authors/Creators:	Williams, LJ and Tristram, SG and Zosky, GR
Keywords:	particulate matter, iron oxide, Haemophilus influenzae, bacterial invasion, macrophages
Journal or Publication Title:	International Journal of Environmental Research and Public Health
Publisher:	MDPI
ISSN:	1660-4601
DOI / ID Number:	10.3390/ijerph18010146
Copyright Information:	Copyright 2020 by the authors. Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Related URLs:	Google Scholar: Tristram, SG UTAS Profile: Tristram, SG Google Scholar: Zosky, GR UTAS Profile: Zosky, GR
Item Statistics:	View statistics for this item

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