In vivo comparison of epithelial responses for S-8 versus JP-8 jet fuels below permissible exposure limit

Abstract

This study was designed to characterize and compare the pulmonary effects in distal lung from a low-level exposure to jet propellant-8 fuel (JP-8) and a new synthetic-8 fuel (S-8). It is hypothesized that both fuels have different airway epithelial deposition and responses. Consequently, male C57BL/6 mice were nose-only exposed to S-8 and JP-8 at average concentrations of 53mg/m(3) for 1h/day for 7 days. A pulmonary function test performed 24h after the final exposure indicated that there was a significant increase in expiratory lung resistance in the S-8 mice, whereas JP-8 mice had significant increases in both inspiratory and expiratory lung resistance compared to control values. Neither significant S-8 nor JP-8 respiratory permeability changes were observed compared to controls, suggesting no loss of epithelial barrier integrity. Morphological examination and morphometric analysis of airway tissue demonstrated that both fuels showed different patterns of targeted epithelial cells: bronchioles in S-8 and alveoli/terminal bronchioles in JP-8. Collectively, our data suggest that both fuels may have partially different deposition patterns, which may possibly contribute to specific different adverse effects in lung ventilatory function.

Figure 1

Total hydrocarbon (THC) concentrations of S-8 and JP-8 at exposure chamber. THC levels were continuously monitored by Heated THC Analyzer (F.I.D. Model-20 Heated, VIG Industries, Anaheim, CA, USA) during 60-minute exposure (A) for 7 days (B).

Figure 2

Representative transmission electron micrographs of alveolar epithelial cells from mice following ambient air (A), S-8 (B), and JP-8 (C) exposure. Note the apparent alteration in surfactant-producing lamellar bodies (arrows) of alveolar type II epithelial cells with swollen mitochondria (arrow heads) in the JP-8 group (C). N: Nucleus. Uranyl acetate and lead citrate. Magnification: 8,000×.

Figure 3

Representative transmission electron micrographs of terminal bronchiole epithelial cells from mice following ambient air (A), S-8 (B), and JP-8 (C) exposure. Note Clara cells with apical membrane blebbing (arrows) and the vacuolated mitochondria (arrows head) in the JP-8 group (C). M: macrophages; N: Nucleus. Uranyl acetate and lead citrate. Magnification: 1,800×.

Figure 4

Representative transmission electron micrographs of small airway epithelial cells from mice following ambient air (A), S-8 (B), and JP-8 (C) exposure. Note vacuolated mitochondria (arrows head) with occasional occurrence of sloughing of mucosal lining (arrow) in the S-8 group (B). Uranyl acetate and lead citrate. N: Nucleus. Magnification: 1,800×.