Modulation of Ciliary Activity by Tumor Necrosis Factor-alpha in Cultured Sinus Epithelial Cells. Possible Roles of Nitric Oxide.

The primary function of well-differentiated ciliated epithelium in the paranasal sinus is to eliminate harmful agents through the beating action of cilia. Respiratory epithelium also contributes to local inflammatory processes through the release of various proinflammatory cytokines. Recently, considerable attention has been focused on the intimate relationship between the cytokine-dependent regulation of the ciliary beat frequency (CBF) and intra-cellular production of nitric oxide (NO) in ciliated epithelial cells. The aims of this study are to examine the effect of tumor necrosis factor-alpha (TNF-α), one of the major proinflammatory cytokines, on the ciliary activity of human sinus epithelial cells and to assess the hypothesis that NO is involved in this regulatory mechanism. Human maxillary or ethmoidal sinus mucosa (n=23) were cultured by the explant-outgrowth method. CBF of the outgrowth ciliated cells was measured by the photoelectrical method before and after being treated with TNF-α (0.1, 1 and 10 ng/ml) or dexamethasone (10⁻⁶M and 10⁻⁷M). We also investigated the expression of nitric oxide synthase (NOS) isoforms, enzymes responsible for NO synthesis, by fluorescent immunohistochemistry. TNF-αincreased CBF at relatively low concentrations (0.1 and 1 ng/ml) and decreased CBF at a high concentration (10 ng/ml). Dexamethasone decreased CBF at a concentration of 10⁻⁶M. Fluorescent immunohistochemistry demonstrated that the expression of inducible NOS was augmented by TNF-αand attenuated by dexamethasone, whereas that of endothelial NOS remained unchanged. We conclude that human sinus epithelial cells potentially contribute to the inflammatory process by regulating their ciliary motility through an NO-dependent pathway. Proinflammatory cytokines and steroids are able to modulate this mechanism by the induction or inhibition of expression of different NOS isoforms.