Tobacco smoke-induced alterations of cytokeratin expression in the rat nasal activity cavity following chronic inhalation of room-aged sidestream smoke

In a 12-month inhalation study on rats using room-aged sidestream smoke (RASS, 12 microg total particulate matter (TPM)/l) as an experimental surrogate for environmental tobacco smoke (ETS), we investigated differentiation changes, i.e. altered cytokeratin (CK) expression, in the epithelial lining at nasal cavity level 1 (NL1) (anterior portion of nasal cavity), and their correlation with histomorphological changes. In addition to conventional histopathological examination, routine paraffin sections were immunohistologically stained for various rat CK and evaluated. Changes in CK expression were observed in the nonciliated respiratory epithelium of maxilloturbinate, lateral wall, and nasoturbinate: in basal cells, increase of CK14 and CK18 and decrease of CK15; in nonciliated columnar cells, increase of CK15 and CK19. These CK changes had histomorphological correlates, i.e. reserve cell hyperplasia and squamous metaplasia. CK expression changes were also seen at sites without histomorphological changes, e.g. enhanced expression of CK14, CK18 in ciliated cells at the dorsal meatus, and CK15 at the septum. Most of the CK expression changes seen after 1 year of RASS exposure resembled the changes previously seen after 8 days of exposure.