Potential toxic effects in the lung of planetary dust

Abstract

As space exploration extends to the Moon and Mars, both astronauts and workers in earth-based test facilities will be exposed to extraterrestrial dust. In this study, the ESA Topical Team on the Toxicity of Celestial Dust (T3CD) exposed lung mucosa models to dust simulants, to investigate its potential pulmonary toxicity.

JSC-Mars1 simulant was wet milled in a zirconia ball-mill to obtain respirable dust (median:1.45µm). To examine the absence of oxygen and water, additional milling was conducted in inert or oxidizing atmospheres. Multicellular lung models using human primary bronchial epithelial cells were cultured at an air-liquid interface (ALI). 40µl of PBS as control (sham) or containing different doses of dust (55, 220, 890µg/cm2 as low, med, high doses respectively) was added to the apical side of the model. Cell viability, cellular apoptosis rate and cell membrane integrity (TEER) were assessed. Inflammatory biomarkers (CXCL8 and IL6) and a tissue injury related biomarker (MMP-9) were measured in the basal medium by ELISA. Reactive oxygen species (ROS) production was detected by FACS.

There was no difference between sham exposure and different doses of JSC-Mars1 dust exposure regarding cell viability and TEER. Exposure to the highest dose of JSC-Mars1 reduced both early and late cellular apoptosis (40%, 42%; P<0.001). The production of ROS was increased 2H after exposure to the two highest doses of JSC-Mars1, compared to sham exposure (27%, 69%; P<0.001). CXCL8 level was increased after exposure to the highest dose of JSC-Mars1 compared to sham exposure (40%; P<0.01).

JSC-Mars1 dust increased pulmonary inflammation and oxidative stress, but not cellular apoptosis, suggesting potential toxic effects of JSC-Mars1.