The prophylactic effects of U75412E pretreatment in a smoke-induced lung injury rabbit model

The effects of the lazaroid analogue U75412E (21-[4-(3-ethylamino-2-pyridinyl)-1-piperazinyl]-16 alpha-methylpregna-1,4,9]-(11)-triene-3,20-dione) were examined in an acute lung injury rabbit model. Standard doses of 0, 8 and 16 mM U75412E were aerosolized and ventilated into the lungs for 3 min. via an endotracheal tube. A 60 tidal volume dose of diesel fuel-polycarbonate plastic smoke was then instilled, followed by mechanical ventilation for one hour. Pretreatment with 16 mM U75412E significantly increased blood PaO2 and pH values, and decreased blood PaCO2 as compared to smoke only exposures. It also significantly decreased the total cell counts and granulocytes in bronchoalveolar lavage fluid, and the ability of pulmonary alveolar macrophages to produce tumour necrosis factor-alpha in vitro after cell isolation and culture. Histopathology indicated that 16 mM U75412E pretreatment attenuated increases in wet lung/body weight ratios, inflammatory focus, and interstitial oedema associated with smoke insult. In summary, U75412E pretreatment may possess the potential to improve acute smoke-induced lung injury, in part, through modulation of tumour necrosis factor-alpha production from pulmonary alveolar macrophages.

Changes in lung permeability correlate with lung histology in a chronic exposure model

In a simulated military flight-line exposure protocol, the effects of JP-8 jet fuel exposure on lung epithelial permeability were evaluated in male Fischer 344 rats (F344). Exposures were nose-only and for one hour daily. Groups were exposed for 7, 28, and 56 days. A protocol for administering a low dose (500mg/m3/hr) and a high dose (813-1094mg/m3/hr) of JP-8 jet fuel was used. Longitudinal sham-exposure groups (no jet fuel) for 7, 28, and 56 days were included in the protocol. Lung epithelial permeability was measured by clearance of technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, molecular weight = 492 daltons, physical half-life = 6.02 hours). The percent clearance of 99mTcDTPA per minute was calculated. Alveolar epithelial clearance for JP-8-exposed rats was dependent on both exposure concentration and duration. It was noted that at low-dose exposure concentrations alveolar epithelial clearance of 99mTcDTPA returned to low levels (LD56 = 1.09% per min; LC56 = 0.98% per min), suggesting recovery as evidenced by microscopic exam. The corresponding 56-day high-dose group (n = 10) had a significantly higher (p < 0.05) value of 2.25% per minute. The 28-day low-dose (n = 15) and high-dose (n = 20) groups had clearance values that were significantly increased from their longitudinal control group (n = 17). The alveolar epithelial permeability values were 2.51, 1.95, and 1.20, respectively. The seven-day longitudinal control, low-dose, and high-dose groups had alveolar permeability values of 1.57, 2.16, and 2.07, respectively. The lung histology correlated with the clearance values. Electron micrographs showed that all groups had interstitial edema resulting from endothelial damage. There was apparent thickening of the alveolar septa, and alveolar macrophages were activated in all groups. Lung permeability data, as determined by 99mTcDTPA alveolar clearance, indicated that lung injuries peaked at 28 days of jet fuel exposure, and this finding corresponded with the histology data. There was a discrepancy in the seven-day group between the number of cells and the 99mTcDTPA clearance values. The HD7 group had a total cell count significantly higher than all other groups, but the 99mTcDTPA clearance values in that group were not significantly different from that of any other group.