C70-31 Uranium-Bearing Mine Dust Exposure Stimulates Neutrophil Elastase Release

Rationale The Southwestern U.S is home to thousands of abandoned uranium mines, with a large percentage occurring in the Four Corners region. These mines are geographically close to residential areas, including rural Hispanic and Native American communities, where miners and non-miner residents are exposed to the uranium-bearing dust (UBD) through now closed legacy mines, currently lacking proper cleanup and remediation procedures. Windblown, fugitive dust blows into nearby communities, potentially causing chronic inflammatory health diseases, involving pulmonary, cardiovascular, renal and autoimmune systems. The health risks from UBD exposure from open-pit abandoned mines (Jackpile and St. Anthony in the Grants Mining District in New Mexico) are inadequately studied. We hypothesize neutrophil stimulation with cytokine-rich supernatant from UBD exposed macrophages, and direct exposure to UBD, will lead to an increase in neutrophil elastase release (NER) compared to controls. Dysregulated chronic activation of neutrophils and release of neutrophil extracellular traps causes a cycle of inflammation and severe tissue damage. Methods We utilized HL-60 promyelocyte-derived neutrophils and THP-1 monocyte-derived macrophages to investigate inflammatory effects following UBD exposure. Controls included: blank media (negative control); Colorado Red (non-UBD metal control). UBD tested included Jackpile and St. Anthony mines. THP-1 macrophages were exposed to 100 µg/mL of Jackpile or St. Anthony UBD and the environmental control of Colorado Red mine dust (MD) for 24 hours. Media was then changed and THP-1 macrophage supernatant was collected after 48 hours. Neutrophils were stimulated with either the collected macrophage supernatant or directly with respective MD samples at 100 µg/mL. Endpoint analyses include ELISA based detection of NER as well as cytokine secretion from macrophage supernatants. Results ELISA NETosis Assay showed NER increased following direct exposure to MD from Jackpile, St. Anthony and Colorado Red mines. Indirect exposure of UBD via macrophage supernatant led to lower NER than blank media. Conclusions Direct exposure o UBD stimulates NER but indirect exposure does not. HL-60 media used in indirect exposure may have elevated baseline NER, masking the effects of UBD-treated macrophage supernatants. Future research needs to implement a THP-1 control. The neutrophil activation by direct UBD exposure suggests its enhanced inflammatory potential.