Toxic effects of mechlorethamine on mammalian respiratory mucociliary epithelium in primary culture.

Mechlorethamine (HN2) is an alkylating agent usually used in cancer chemotherapy. Nevertheless, HN2 is extremely toxic and its use is accompanied by severe side-effects that may cause lung complications. Many studies report the morphological and biochemical modifications induced by sulfur mustard (SM) but no report has been published concerning the toxic effects of HN2 on the ultrastructural and functional activity of surface respiratory epithelial cells. This study was performed on rabbit tracheal epithelium (RTE) cells in primary culture. The functional activity of the culture was evaluated by measuring the ciliary beating frequency (CBF) of the ciliated cells using a videomicroscopic method, and the culture growth was determined by an image analysis system. The morphological aspects of the cells were analyzed by light, scanning electron, and transmission electron microscopy. An important inhibition of cell growth was observed associated with a detachment of the outgrowth cells. Morphological changes were expressed by vacuolization, increases in the intercellular spaces, and by disorganization of the cytoskeleton associated with a specific attack of the ciliated cells that show ciliary blebbing. The sudden CBF inhibition is more likely due to the detachment and the death of the ciliated cells than to a specific ciliotoxic effect of HN2. All these observations demonstrated the high sensitivity of respiratory epithelial cells to HN2 and showed that HN2-induced injuries were irreversible, and time- and dose-dependent.