Establishment of inhalation injury mice model and study on the inhalation injury-induced changes of survival rate, levels of internal organ TNF-α and NF-κB expressions

Abstract

Objective To establish mice model of smoke inhalation injury, and observe the changes in the levels of lung tumor necrosis factor-alpha(TNF-α), the expressions of internal organ nuclear transcription factor-κB(NF-κB) and survival rate after smoke inhalation injury. Methods One hundred and niney BALB/c mice, randomly selected 10, set as the control group, the rest of the 180 mice were randomly divided into 6 groups, each group of 30. Adopting homemade injuries device, the mix of pine sawdust and kerosene was used as the fuming materials. The mice were subjected to smoke inhalation in a smoke chamber for different time intervals of 6, 8, 10, 12, 14, and 16 min, respectively, under anesthesia condition. The mice in the control group underwent the same treatment except for the inhalation of air only. Post-injury behavior changes and survivalrate at post-injury 72 h were documented, the tissue morphology changes and the NF-κB activation of multiple organs, presented by the integrated optical density (IOD), were evaluated. The expression of TNF-α in lung tissues was also determined. Data was compared using single factor analysis of variance and t test. Results (1) The mice in the control group and 6, 8 and 10 min inhalation injury groups survived while several or all in 12, 14 and 16 min inhalation injury groups died in the smoking chamber during the smoke inhalation period. Except for the control group, increased respiratory rate and decreased activity were observed immediately after smoke inhalation injury in the live mice of each group and these abnormal signs were subsided several hours later. The survival rates at 72 h post-inhalation injury for the above control, 6, 8, 10, 12, 14 and 16 min smoke-inhalation groups were 100%, 100%, 97%, 73%, 52%, 43%, and 0, respectively; (2)Smoke inhalation induced varied extents of inflammatory cell infiltration, hyperemia, and swelling in tissues of multiple organs were observed in smoke inhalation-induced dead mice. (3)For 14 min smoke-inhalation injury group, the mice that died at post-injury 24-72 h demonstrated significantly enhanced positive nuclear expression of NF-κB p65 in cells of lung, heart, liver, and kidney tissues with higher IOD of NF-κB p65 expression of 3 245.37±296.40, 2 022.92±356.52, 2 148.70±310.99 and 2 054.61±260.56, respectively, in comparison with the control group(P values were less than 0.05); (4) For 14 min smoke-inhalation injury group, the level of TNF-α expression (54.86±5.24) pg/mL in lung tissues of mice that died during post-injury 24-72 h was significantly increased relative to that of the control group (27.84±4.08) pg/mL, death in the injury (31.24±4.46) pg/mL and death within 0-24 h after injury(45.09±4.69)pg/mL (P values were less than 0.05). Conclusions The 8-14 min duration of smoke inhalation leads to the proportional decline of mice 72-hour survival rate, significant up-regulation of TNF-α expression in lung tissues, acute inflammation and robust activation of NF-κB pathway in multiple organs. No mice survives the smoke inhalation for more than 16 minutes. Key words: Burns, inhalation; Mice; Models, animal; Tumor necrosis factor-alpha; NF-kappa B