Biological effects of inhaled crude oil vapor. III. Pulmonary inflammation, cytotoxicity, and gene expression profile

Abstract

Objective: Workers may be exposed to vapors emitted from crude oil in upstream operations in the oil and gas industry. Although the toxicity of crude oil constituents has been studied, there are very few in vivo investigations designed to mimic crude oil vapor (COV) exposures that occur in these operations. The goal of the current investigation was to examine lung injury, inflammation, oxidant generation, and effects on the lung global gene expression profile following a whole-body acute or sub-chronic inhalation exposure to COV.

Materials and methods: To conduct this investigation, rats were subjected to either a whole-body acute (6 hr) or a sub-chronic (28 d) inhalation exposure (6 hr/d × 4 d/wk × 4 wk) to COV (300 ppm; Macondo well surrogate oil). Control rats were exposed to filtered air. One and 28 d after acute exposure, and 1, 28, and 90 d following sub-chronic exposure, bronchoalveolar lavage was performed on the left lung to collect cells and fluid for analyses, the apical right lobe was preserved for histopathology, and the right cardiac and diaphragmatic lobes were processed for gene expression analyses.

Results: No exposure-related changes were identified in histopathology, cytotoxicity, or lavage cell profiles. Changes in lavage fluid cytokines indicative of inflammation, immune function, and endothelial function after sub-chronic exposure were limited and varied over time. Minimal gene expression changes were detected only at the 28 d post-exposure time interval in both the exposure groups.

Conclusion: Taken together, the results from this exposure paradigm, including concentration, duration, and exposure chamber parameters, did not indicate significant and toxicologically relevant changes in markers of injury, oxidant generation, inflammation, and gene expression profile in the lung.

Keywords: Crude oil vapor; gene expression; inflammation; lung; pulmonary toxicity; rats.

Figure 1.

Lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF) recovered from rats at 1- and 28 d post-exposure to air or 300 ppm COV 6 hr/d for 1 day (A, acute COV) or at 1, 28, and 90 d after the last day of exposure to 300 ppm in the sub-chronic exposure of 6 hr/d for 4 d/wk for 4 wk (B, sub-chronic COV). No significant differences were observed between groups in either exposure. n = 8 per group per timepoint.

Figure 2.

Bronchoalveolar lavage (BAL) cells were recovered from rats and enumerated at 1 and 28 d post-exposure to air or 300 ppm COV 6 hr/d for 1 day (acute COV) or at 1, 28, and 90 days after the last day of exposure to 300 ppm for 6 hr/d for 4 d/wk for 4 wk (sub-chronic COV): total BAL cells recovered following acute (A) and sub-chronic (B) exposures, total alveolar macrophages (AM) following acute (C) and sub-chronic (D) exposure, and total neutrophils following acute (E) and sub-chronic (F) exposure. Lymphocyte and eosinophils not shown. AM accounted for >99% of all cells for all groups at all time points. No significant differences were observed. n = 8 per group per timepoint.

Figure 3.

Oxidant production by bronchoalveolar (BAL) alveolar macrophages (AM) recovered from rats at 1 and 28 d post-exposure to air or 300 ppm COV 6 hr/d for 1 day (A, acute COV) or at 1, 28, and 90 d after the last day of exposure to 300 ppm for 6 hr/d for 4 d/wk for 4 wk (B, sub-chronic COV) was measured by evaluating chemiluminescence in the presence of zymosan. *Significantly different from air, p ≤ 0.05. n = 8 per group per timepoint.