Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

Abstract

Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggests that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure.

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure

“…75 In addition, nano-WC-Co has been found to induce greater cellular toxicity and higher levels of oxidative stress than micro-WC-Co particles of the same composition under identical conditions (Figure 2). 86 These studies are consistent with the other reports where the Toxicity of nano-wC-Co was cell dependent, macrophages in the co-culture may play a protective role against nano-wCCo-mediated toxicity, and nano-wC-Co exposure stimulated the M1 phenotype of macrophages 87…”

“…Early data concerning the effects of inhaled WC-Co dusts first emerged in the 1960s and continued through the 1980s, providing researchers the foundation to further explore the toxic effects of hard metal exposure using in vitro [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] and in vivo 72,[89][90][91][92][93][94][95][96] models. Although cobalt itself was originally considered the causative agent of HMLD, several studies demonstrated that this is not the case and the disease mainly develops due to the simultaneous presence of WC with Co. 71,74,[76][77][78][79]90,91 It is currently understood that the combination of WC-Co is more toxic than Co, W, or WC particles alone, both in vitro and in vivo, 71,72,74,78,79,81,85,90,91,93,94,…”

In vitro inflammatory effects of hard metal (WC–Co) nanoparticle exposure

“…The presence of WC-Co particles did not interfere with the MTT assays in our studies as we described earlier. 49 Macrophage polarization assay THP-1 cells were seeded at a density of 5×10 5 cells/mL in RPMI-1640 containing 10 ng/mL PMA in a 12-well culture dish and incubated for 48 h to stimulate M0 cell differentiation. Media were then aspirated from each well and replaced with DMEM containing 100 ng/mL LPS (M1 stimulus/ positive control), 20 ng/mL IL-4 (M2 stimulus/positive control) and 0, 1, 10 or 100 μg/mL nano-WC-Co particles.…”

“…49 Briefly, nano-WC-Co particles averaged 98 nm in diameter in suspension determined by dynamic light scattering and transmission electron microscopy. Compositional analysis by energy-dispersive X-ray (EDX) determined that nano-WC-Co contained 72.13% tungsten, 13.42% cobalt, 7.63% carbon and 6.81% oxygen.…”

“…17,24 In particular, exposure to tungsten carbide-cobalt (WC-Co) NPs in occupational settings is known to cause hard metal lung disease (HMLD), characterized by progressive inflammation and fibrosis of the lung, [25][26][27][28][29] which is further associated with a twofold increased risk of lung cancer. [30][31][32] While the toxicity of WC-Co particles has been studied, [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] the relationship between WC-Co toxicity, inflammation and lung cancer remains poorly understood.…”