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Title: Time- and concentration-dependent genomic responses of the rat airway to inhaled nickel subsulfide

Objective: To provide insights into the mode of action for Ni{sub 3}S{sub 2} lung carcinogenicity by examining gene expression changes in target cells after inhalation exposure. Methods: Gene expression changes were determined in micro-dissected lung broncho-alveolar cells from Fischer 344 rats following inhalation of Ni{sub 3}S{sub 2} at 0.0, 0.04, 0.08, 0.15, and 0.60 mg/m{sup 3} (0.03, 0.06, 0.11, and 0.44 mg Ni/m{sup 3}) for one and four weeks (6 h/day, 5 days/week). Results: Broncho-alveolar lavage fluid evaluation and lung histopathology provided evidence of inflammation only at the two highest concentrations, which were similar to those tested in the 2-year bioassay. The number of statistically significant up- and down-regulated genes decreased markedly from one to four weeks of exposure, suggesting adaptation. Cell signal pathway enrichment at both time-points primarily reflected responses to toxicity, including inflammatory and proliferative signaling. While proliferative signaling was up-regulated at both time points, some inflammatory signaling reversed from down-regulation at 1 week to up-regulation at 4 weeks. Conclusions: These results support a mode of action for Ni{sub 3}S{sub 2} carcinogenicity driven by chronic toxicity, inflammation and proliferation, leading to mis-replication, rather than by direct genotoxicity. Benchmark dose (BMD) analysis identified the lowest pathway transcriptional BMD exposuremore » concentration as 0.026 mg Ni/m{sup 3}, for apoptosis/survival signaling. When conducted on the basis of lung Ni concentration the lowest pathway BMD was 0.64 μg Ni/g lung, for immune/inflammatory signaling. Implications: These highly conservative BMDs could be used to derive a point of departure in a nonlinear risk assessment for Ni{sub 3}S{sub 2} toxicity and carcinogenicity. - Highlights: • The mode of action for lung carcinogenicity of inhaled Ni{sub 3}S{sub 2} was investigated in rats. • Gene expression changes were determined in micro-dissected lung tissue at 1–4 weeks. • A non-genotoxic mode of action (toxicity, inflammation, proliferation) was supported. • Analyses of lung lavage fluid and histopathology provided complementary results. • Transcriptional benchmark doses could inform point of departure for risk assessment.« less
Authors:
 [1] ; ;  [1] ;  [2] ;  [1]
  1. The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709 (United States)
  2. NiPERA, Inc., 2525 Meridian Parkway, Suite 240, Durham, NC 27713 (United States)
Publication Date:
OSTI Identifier:
22439842
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 279; Journal Issue: 3; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; APOPTOSIS; BIOASSAY; CONCENTRATION RATIO; DOSES; ECOLOGICAL CONCENTRATION; FLUIDS; GENES; INFLAMMATION; INHALATION; LAVAGE; LUNGS; NICKEL; RATS; RISK ASSESSMENT; SIGNALS; TOXICITY