Surface Iron Inhibits Quartz-Induced Cytotoxic and Inflammatory Responses in Alveolar Macrophages

Abstract

The mechanism of enhancement/inhibition of quartz toxicity induced by iron is still unclear. Here the amount of iron on a fibrogenic quartz (Qz) was increased by wet impregnation (Fe(NO(3))(3) 0.67 and 6.7 wt %). X-ray diffraction (XRD), XRF diffuse reflectance, UV-vis, and infrared (IR) spectroscopies revealed dispersed ferric ions, and hematite aggregates at the higher loading. Surface features relevant to pathogenicity and cell responses were compared not only to the original quartz but also to reference quartz DQ12. Surface charge (ζ-potential) was more negative on the original and low-loaded specimen than on the high-loaded one. DQ12 had a less negative ζ-potential than Qz, ascribed to the absence of aluminium present in Qz (1.7 wt %). All quartz specimens were able to generate HO(•) radicals, iron-loaded samples being more reactive than original quartz. Iron deposition inhibited the rupture of a C-H bond. All quartzes were phagocytized by alveolar macrophages (AMΦ cell line NR8383) to the same extent, irrespective of their surface state. Conversely, iron loading increased AMΦ viability (evaluated by cytotoxicity and induction of apoptosis). Qz was found to be much less cytotoxic than DQ12. The induction of oxidative stress and inflammatory responses (evaluated by HO-1 mRNA expression and TNF-α mRNA and protein expression) revealed a reduction in inflammogenicity upon iron loading and a more inflammogenic potency of DQ12 ascribed to undissociated SiOH interacting via H-bonding with cell membrane components. The results suggest that besides aluminium also iron at the quartz surface may have an inhibitory effect on adverse health responses.

The role of iron in Libby amphibole-induced acute lung injury and inflammation

“…The ability to chelate Fe from endogenous sources has been shown to contribute to the inflammatory response to bacteria in the lung as they utilize host Fe resources (Weinberg, 2009). Recent research assessing the role of Fe in quartz-induced toxicity suggests that the movement of Fe is a key component in the inflammatory response (Ghiazza et al, 2011). In our study using LA, a mixture of relatively short asbestos fibers, with different physiochemistry yielded similar results.…”

Carbon in Intimate Contact with Quartz Reduces the Biological Activity of Crystalline Silica Dusts

“…[5][6][7][8] A loss of biological activity was also found when quartz was ground with coal dust 5,9 which suggests that the low toxicity of quartz-containing coal dust might be due to impurities, such as carbon or other mineral phases at the quartz surface. 9 In spite of occasional suggestions of a possible protecting role of carbon when in intimate contact with quartz as in coal mine dusts, 16 firm evidence about this has not been provided, nor are available data on the amount of carbon dust required for such effect. This is the aim of the present study.…”

Inhibition of the ROS-mediated cytotoxicity and genotoxicity of nano-TiO2 toward human keratinocyte cells by iron doping

“…Iron is generally associated to an increase of the surface reactivity, and hence toxicity of particulates (Kagan et al 2006;Pulskamp et al 2007;Ghiazza et al 2011). Having a standard redox potential in water E° = 0.77 V, iron ions may catalyze the formation of ROS, e.g., by generating hydroxyl radicals through reaction with hydrogen peroxide (Fenton reaction), which may in turn induce oxidative stress.…”

“…20 mg of dust was incubated in 20 mL of a 3 mM solution of ferrozine in the presence of 3 mM ascorbic acid for 5 days. The amount of iron extracted was determined on the supernatant spectrophotometrically (Uvkon 930) by measuring the absorption of the iron-ferrozine complex at 562 nm, following a technique previously described (Lund and Aust 1990;Ghiazza et al 2011).…”

“…Mobilized ions, being redox-active, may induce oxidative stress e.g., by generating free radicals through Fenton reaction . To investigate the possible occurrence of such a process the powders were incubated with a solution of a chelator having high affinity for Fe 2+ ions (Ferrozine) alone or in combination with a reducing agent (ascorbic acid) according to a method previously described (Lund and Aust 1990;Ghiazza et al 2011). The amount of iron ions extracted in this condition was lower than 15 % of the total amount for all the Fe-doped titania suggesting that iron ions were strongly coordinated at the surface or migrate in the sublayer of the particles.…”