Use of micro-CT to determine tracheobronchial airway geometries in three strains of mice used in inhalation toxicology as disease models.

Aerosol dosimetry estimates for mouse strains used as models for human disease are not available, primarily because of the lack of tracheobronchial airway morphometry data. By using micro-CT scans of in-situ prepared lung casts, tracheobronchial airway morphometry for four strains of mice were obtained: Balb/c, AJ, C57BL/6, and Apoe-/- . The automated tracheobronchial airway morphometry algorithms for airway length and diameter were successfully verified against previously published manual and automated tracheobronchial airway morphometry data derived from two identical in-situ Balb/c mouse lung casts. There was also excellent agreement in tracheobronchial airway length and diameter between the automated and manual airway data for the AJ, C57BL/6, and Apoe-/- mice. Differences in branch angle measurements were partially due to the differences in definition between the automated algorithms and manual morphometry techniques. Unlike the manual airway morphometry techniques, the automated algorithms were able to provide a value for inclination to gravity for each airway. Inclusion of an inclination to gravity angle for each airway along with airway length, diameter, and branch angle make the current automated tracheobronchial airway data suitable for use in dosimetry programs that can provide dosimetry estimates for inhaled material. The significant differences in upper tracheobronchial airways between Balb/c mice and between C57BL/6 and Apoe-/- mice highlight the need for mouse strain-specific aerosol dosimetry estimates.

Mechanism of an indirect effect of aqueous cigarette smoke extract on the adhesion of monocytic cells to endothelial cells in an in vitro assay revealed by transcriptomics analysis.

The adhesion of monocytic cells to the "dysfunctional" endothelium constitutes a critical step in the initiation of atherosclerosis. Cigarette smoke (CS) has been shown to contribute to this process, the complex mechanism of which still needs to be unraveled. We developed an in vitro adhesion assay to investigate the CS-induced adhesion of monocytic MM6 cells to human umbilical vein endothelial cells (HUVECs) following exposure to an aqueous CS extract (smoke-bubbled phosphate buffered saline: sbPBS), reasoning that in vivo monocytes and endothelial cells are exposed primarily to soluble constituents from inhaled CS absorbed through the lung alveolar wall. MM6 cell adhesion was increased exclusively by the conditioned medium from sbPBS-exposed MM6 cells, not by direct sbPBS exposure of the HUVECs within a range of sbPBS doses. Using a transcriptomics approach followed by confirmation experiments, we identified different exposure effects on both cell types and a key mechanism by which sbPBS promoted the adhesion of MM6 cells to HUVECs. While sbPBS provoked a strong oxidative stress response in both cell types, the expression of E-selectin, VCAM-1 and ICAM-1, responsible for the adhesion of MM6 cells to HUVECs, was induced in the latter through a proinflammatory paracrine effect. We confirmed that this effect was driven mainly by TNFα produced by MM6 cells exposed to sbPBS. In conclusion, we have elucidated an indirect mechanism by which sbPBS increases the adhesion of monocytic cells to endothelial cells in this in vitro assay that was designed for tobacco product risk assessment while mimicking the in vivo exposure conditions as closely as possible.