Chromium(VI)-Induced Lung Injury Model

Female BALB/cJ mice were obtained from the National Cancer Institute (Frederick, MD) and were 6–8 weeks of age at first Cr(VI) treatment. All experiments were performed in accordance with and under the approval of the George Washington University Institutional Animal Care and Use Committee, and all animals were treated humanely and with regard for alleviation of suffering. We used fluorescent polystyrene particles (4 μm; Phosphorex, Inc., Fall River, MA) as a control to visualize deposition of particles (Figure 1F). Endotoxin-free basic zinc chromate [ZnCrO₄ 4Zn(OH)₂] was 4.7 μm in size and had a purity of 99–100% (Rockwood Pigments, Beltsville, MD) (Beaver et al. 2009 (link)). Cr(VI) was suspended in sterile 0.9% sodium chloride solution at a concentration of 0.6 mg/mL and prepared as previously described (Beaver et al. 2009 (link)). Animals under a light anesthesia (isoflurane) were intranasally exposed to a 50-μL dose of chromate or saline and sacrificed by exposure to carbon dioxide at indicated time points. To determine the duration of injury and inflammation after Cr(VI) exposure, we conducted a set of experiments up to 21 days after a single Cr(VI) treatment. Repetitive Cr(VI) studies were conducted after the described exposure regimen (Figure 2A) for up to 69 days after the initial Cr(VI) exposure. Lungs of animals from both the single and repetitive exposure experiments were further analyzed for inflammation and injury.