TNF-α and IL-1β upregulate nitric oxide-dependent ciliary motility in bovine airway epithelium

Airway epithelial cells can be modulated by cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β that are released from inflammatory cells. Since ciliary motility is an important host defense function of airway epithelium, we hypothesized that cytokines, released from lung macrophages, upregulate ciliary motility. To test this hypothesis, ciliary beat frequency (CBF) was measured by video microscopy in cultured ciliated bovine bronchial epithelial cells (BBECs) incubated for 24 h with bovine alveolar macrophage-conditioned medium (AM-CM). Exposure to AM-CM resulted in a delayed (≥2 h) increase in CBF that was maximal after 24 h exposure (13.70 ± 0.43 for AM-CM vs. 9.44 ± 0.24 Hz for medium; P < 0.0001) and which was largely blocked by either anti-TNF-α or anti-IL-1β antibodies. rTNF-α or rIL-1β similarly increased CBF, which could be blocked by preincubation with either anti-rTNF-α or anti-rIL-1β antibodies. Preincubation of BBECs with actinomycin D or dexamethasone also blocked rTNF- α- and rIL-1β-induced cilia stimulation, suggesting that new protein synthesis is required for cytokine-induced upregulation of CBF. Since NO is known to upregulate ciliary motility and cytokines can induce NO synthase (NOS), we hypothesized that TNF-α and IL-1β increase CBF by inducing NOS in BBECs. The cilia stimulatory effects of TNF-α or IL-1β were inhibited by N(G)-monomethyl-L-arginine, a competitive NOS inhibitor, and restored by the addition of either L-arginine, an NOS substrate, or sodium nitroprusside, an NO donor. These studies show that TNF-α or IL-1β can upregulate ciliary motility presumably by releasing NO via induction of NOS and suggest a mechanism by which inflammation increases ciliary motility.