Murine pulmonary inflammation model: a comparative study of anesthesia and instillation methods

Various techniques have been utilized historically to generate acute pulmonary inflammation in the murine system. Crystalline silica exposure results in acute inflammation followed by pulmonary fibrosis. Methods of exposure are varied in their techniques, as well as types of anesthesia. Therefore, the current study sought to compare the effects of two major anesthesia (isoflurane and ketamine) and three routes of instillation, intranasal (IN), intratracheal (IT), and trans-oral (TO), on markers of inflammation. Mice were anesthetized with isoflurane or ketamine and instilled IN with silica or phosphate-buffered saline (PBS). Mice were sacrificed and lavaged after 3 days. To assess inflammation, alveolar cells were assessed by cytospin and lavage fluid was analyzed for inflammatory cytokines and total protein. While all parameters were increased in silica-exposed groups, regardless of anesthesia type, there were significant increases in neutrophils and total protein in mice anesthetized with ketamine, compared to isoflurane. In comparing instillation techniques, mice were anesthetized with isoflurane and instilled IN, IT, or TO with silica. Increases were observed in all parameters, except tumor necrosis factor-alpha, following IT silica instillation as compared to the IN and TO instillation groups. In addition, fluorescent microsphere uptake by alveolar macrophages supported the notion that all methods of instillation were uniform, but IT had significantly greater dispersion. Taken together, these data show that each method of exposure tested generated significant inflammation among the silica groups, and any differences in parameters or techniques should be taken into consideration when developing an animal model to study pulmonary diseases.