Role of metal oxide nanoparticles in histopathological changes observed in the lung of welders

Abstract

Background

Although major concerns exist regarding the potential consequences of human exposure to nanoparticles (NP), no human toxicological data is currently available. To address this issue, we took welders, who present various adverse respiratory outcomes, as a model population of occupational exposure to NP.

The aim of this study was to evaluate if welding fume-issued NP could be responsible, at least partially, in the lung alterations observed in welders.

Methods

A combination of imaging and material science techniques including ((scanning) transmission electron microscopy ((S)TEM), energy dispersive X-ray (EDX), and X-ray microfluorescence (μXRF)), was used to characterize NP content in lung tissue from 21 welders and 21 matched control patients. Representative NP were synthesized, and their effects on macrophage inflammatory secretome and migration were evaluated, together with the effect of this macrophage inflammatory secretome on human lung primary fibroblasts differentiation.

Results

Welding-related NP (Fe, Mn, Cr oxides essentially) were identified in lung tissue sections from welders, in macrophages present in the alveolar lumen and in fibrous regions. In vitro macrophage exposure to representative NP (Fe ₂O ₃, Fe ₃O ₄, MnFe ₂O ₄ and CrOOH) induced the production of a pro-inflammatory secretome (increased production of CXCL-8, IL-1ß, TNF-α, CCL-2, −3, −4, and to a lesser extent IL-6, CCL-7 and −22), and all but Fe ₃O ₄ NP induce an increased migration of macrophages (Boyden chamber). There was no effect of NP-exposed macrophage secretome on human primary lung fibroblasts differentiation.

Conclusions

Altogether, the data reported here strongly suggest that welding-related NP could be responsible, at least in part, for the pulmonary inflammation observed in welders. These results provide therefore the first evidence of a link between human exposure to NP and long-term pulmonary effects.