Carbon black nanoparticles (CBNP) are the most widely produced nanomaterial and are thus a concern for occupational exposures. CBNPs are known to cause inflammation upon inhalation; however, detailed time course data to evaluate the changing nature of inflammatory responses have not been evaluated. In this study, we investigate the short- and longer-term effects of CBNP following a single intratracheal exposure. Female C57BL/6BomTac mice were exposed to CBNPs (printex 90) via a single intratracheal instillation of 162 µg/mouse alongside vehicle controls. Mice were examined 3 hours (hrs), and 1, 2, 3, 4, 5, 14, and 42 days (d) post-exposure. Global gene expression was assessed using DNA microarrays in parallel with analysis of pulmonary inflammation assessed as bronchoalveolar lavage (BAL) cell counts and DNA strand breaks assessed by the comet assay. Pulmonary inflammation in terms of increased neutrophil influx was obverved at all time points. Increased levels of DNA strand breaks were observed in BAL cells 3 hrs post exposure and in lung tissue 2-5 d post exposure. Approximately 2600 significant differentially expressed genes (±1.5 fold; p ≤0.05) across all of the time-points in the lungs of exposed mice were identified upon comparison to time-matched controls. Transcriptional alterations were enriched for genes involved in common respiratory infectious diseases. The perturbed biological processes and pathways were primarily related to immune-inflammatory responses and acute phase responses, consistent with the BAL inflammatory profiles. Gene and pathway analysis revealed a biphasic inflammatory response, with changes occurring as early as 3 hrs post-exposure and declining to base-levels by 3 d post-exposure, but with inflammatory pathways increasing in response again at 14 d and persisting to 42 d post-exposure. Other perturbed pathways included DNA repair and apoptosis, cell cycle regulation, and muscle contraction. Single CBNP exposure induced a biphasic inflammatory response that lasted until 42 d post-exposure. Such persistent inflammatory response raises concerns over the chronic effects of CBNP exposure since the administered dose corresponds to pulmonary deposition in mice during nine 8-hour working days at the current occupational exposure limit for carbon black.
Overall design: This experiment consists of one dose of CBNP (162 ug) and one control. There are 8 time points (3 hours, and 1, 2, 3, 4, 5, 14, and 42 days) for each treatment and control group. Each dose or time point has 5-6 biological replicates. There are total 76 samples (arrays).
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