Macrophage Solubilization and Cytotoxicity of Indium-Containing Particles as in vitro Correlates to Pulmonary Toxicity in vivo

Abstract

Macrophage-solubilized indium-containing particles (ICPs) were previously shown in vitro to be cytotoxic. In this study, we compared macrophage solubilization and cytotoxicity of indium phosphide (InP) and indium-tin oxide (ITO) with similar particle diameters (∼ 1.5 µm) and then determined if relative differences in these in vitro parameters correlated with pulmonary toxicity in vivo. RAW 264.7 macrophages were treated with InP or ITO particles and cytotoxicity was assayed at 24 h. Ionic indium was measured in 24 h culture supernatants. Macrophage cytotoxicity and particle solubilization in vitro were much greater for InP compared with ITO. To correlate changes in vivo, B6C3F1 mice were treated with InP or ITO by oropharyngeal aspiration. On Days 14 and 28, bronchoalveolar lavage (BAL) and pleural lavage (PL) fluids were collected and assayed for total leukocytes. Cell differentials, lactate dehydrogenase activity, and protein levels were also measured in BAL. All lavage parameters were greatly increased in mice treated with InP compared with ITO. These data suggest that macrophage solubilization and cytotoxicity of some ICPs in vitro are capable of predicting pulmonary toxicity in vivo. In addition, these differences in toxicity were observed despite the two particulate compounds containing similar amounts of indium suggesting that solubilization, not total indium content, better reflects the toxic potential of some ICPs. Soluble InCl3 was shown to be more cytotoxic than InP to macrophages and lung epithelial cells in vitro further suggesting that ionic indium is the primary cytotoxic component of InP.

Indium oxide nanoparticles induce lung intercellular toxicity between bronchial epithelial cells and macrophages

“…In addition, the amount of In 3+ released by HBE cells was significantly higher than that released by RAW cells, which indicated that intracellular IO‐NPs were acidified in epithelial cells and In 3+ were released into the microenvironment. Several studies supported that In 3+ should be the important cytotoxic component of indium particles (Gwinn et al, 2015; Gwinn et al, 2013), which is consistent with our study. Our study further clarified that, despite the high percentage of IO‐NPs solubilized by the HBE cells after 24 hours, as measured by ICP‐MS, the solubilized form of indium was much more toxic to RAW cells than HBE cells suggests that RAW cells are more susceptible to In 3+ .…”

Nitrative DNA damage in cultured macrophages exposed to indium oxide

“…8-NitroG also forms a pair with adenine and causes a similar type of base substitution 32) . Although recent in vitro studies have demonstrated that indium compounds induce cytotoxicity 33) , inflammatory responses 34) and DNA damage 28) , this is the first study showing that indium compounds cause NO-dependent DNA damage in cultured cells.…”

Application of the ICRP respiratory tract model to estimate pulmonary retention of industrially sampled indium-containing dusts

“…In the study of commercially available unsintered ITO particles, Gwinn et al measured ionic indium in culture media following particle uptake and reported that dissolution in macrophage phagolysosomes was a key driver for cytotoxicity (Gwinn et al, 2013). In a follow-on study by the same group, macrophage-mediated dissolution of sintered ITO particles and indium phosphide particles was reported to predict pulmonary toxicity in vivo (Gwinn et al, 2015). In a study of In 2 O 3 nanoparticles, it was reported that the slow in vitro indium dissolution rate observed in artificial phagolysosomal fluid (pH 5.5) was consistent with the in vivo persistence of these particles in rats and the time course of development of PAP (Jeong et al, 2016).…”