The importance of mineralogical composition for the cytotoxic and pro-inflammatory effects of mineral dust

Abstract

Background Respirable mineral particles represent a potential health hazard in occupational settings and ambient air. Previous studies show that mineral particles may induce cytotoxicity and inflammatory reactions in vitro and in vivo and that the potency varies between samples of different composition. However, the reason for these differences is largely unknown and the impact of mineralogical composition on the biological effects of mineral dust remains to be determined. Methods We have assessed the cytotoxic and pro-inflammatory effects of ten mineral particle samples of different composition in human bronchial epithelial cells (HBEC3-KT) and THP-1-derived macrophages, as well as their membranolytic properties in erythrocytes. Moreover, the results were compiled with the results of recently published experiments on the effects of stone particle exposure and analysed using linear regression models to elucidate which mineral components contribute most to the toxicity of mineral dust. Results While all mineral particle samples were more cytotoxic to HBEC3-KT cells than THP-1 macrophages, biotite and quartz were among the most cytotoxic in both cell models. In HBEC3-KT cells, biotite and quartz also appeared to be the most potent inducers of pro-inflammatory cytokines, while the quartz, Ca-feldspar, Na-feldspar and biotite samples were the most potent in THP-1 macrophages. All particle samples except quartz induced low levels of membranolysis. The regression analyses revealed associations between particle bioactivity and the content of quartz, muscovite, plagioclase, biotite, anorthite, albite, microcline, calcite, chlorite, orthopyroxene, actinolite and epidote, depending on the cell model and endpoint. However, muscovite was the only mineral consistently associated with increased cytotoxicity and cytokine release in both cell models. Conclusions The present study provides further evidence that mineral particles may induce cytotoxicity and inflammation in cells of the human airways and that particle samples of different mineralogical composition differ in potency. The results show that quartz, while being among the most potent samples, does not fully predict the toxicity of mineral dust, highlighting the importance of other particle constituents. Moreover, the results indicate that the phyllosilicates muscovite and biotite may be more potent than other minerals assessed in the study, suggesting that this group of sheet-like minerals may warrant further attention.

Spatial Distribution and Physicochemical Properties of Respirable Volcanic Ash From the 16–17 August 2006 Tungurahua Eruption (Ecuador), and Alveolar Epithelium Response In‐Vitro

“…However, the in‐vitro response to volcanic ash is generally lower than that observed for crystalline silica (Damby et al., 2018 ), and varies among samples (Damby et al., 2016 ). The cytotoxic and pro‐inflammatory effects of crushed pure phase silicate minerals have proved to be mineral and cell‐dependant, with feldspar crystals (a common mineral in volcanic ash) triggering a pro‐inflammatory response in macrophages (Damby et al., 2018 ; Grytting et al., 2022 ). The physicochemistry of volcanic ash has been studied in relation to the bioreactivity described above, and key properties relevant to toxicity have been identified, namely the particle size distribution, specifically the content in particles finer than 10, 4, 2.5, and 1 μm (Horwell, 2007 ), the particle morphology (Damby et al., 2013 ; Horwell et al., 2013 ), the mineralogical (e.g., crystalline silica content) and chemical composition (Damby et al., 2017 ; Horwell et al., 2013 ), and the oxidative potential of the particles (Horwell et al., 2003 ).…”

Nicotinamide Mononucleotide Ameliorates Silica-Induced Lung Injury through the Nrf2-Regulated Glutathione Metabolism Pathway in Mice

“…Silica dust deposited in bronchioles and alveolar spaces after inhalation is the predominant risk factor for silicosis. Due to the physical properties of its fine particles, including the surface effect, electrification, and sedimentation [ 6 , 7 ], silica dust is easily adsorbed on the cell surface and damages cells—for example, by inducing reactive oxygen species causing cell stress [ 8 , 9 ]. Under normal physiological conditions, stressed cells secrete signaling molecules, recruit inflammatory cells to activate immune responses, and mobilize macrophages and other phagocytes to remove silica [ 10 ].…”