TNF-ALPHA AND IL-1-BETA UP-REGULATE NITRIC OXIDE-DEPENDENT CILIARY MOTILITY IN BOVINE AIRWAY EPITHELIUM

Airway epithelial cells can be modulated by cytokines such as tumor ne crosis factor (TNF)-alpha and interleukin (IL)-1 beta that are release d 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 m icroscopy in cultured ciliated bovine bronchial epithelial cells (BBEC s) incubated for 24 h with bovine alveolar macrophage-conditioned medi um (AM-CM). Exposure to AM-CM resulted in a delayed (greater than or e qual to 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-alpha or anti-IL-1 beta antibodies. rTNF-alpha or rIL-1 beta similarly increased CBF, which co uld be blocked by preincubation with either anti-rTNF-alpha or anti-rI L-1 beta antibodies. Preincubation of BBECs with actinomycin D or dexa methasone also blocked rTNF-alpha- and rIL-1 beta-induced cilia stimul ation, suggesting that new protein synthesis is required for cytokine- induced upregulation of CBF. Since NO is known to upregulate ciliary m otility and cytokines can induce NO synthase (NOS), we hypothesized th at TNF-alpha and IL-1 beta increase CBF by inducing NOS in BBECs. The cilia stimulatory effects of TNF-alpha or IL-1 beta were inhibited by N-G-monomethyl-L-arginine, a competitive NOS inhibitor, and restored b y the addition of either L-arginine, an NOS substrate, or sodium nitro prusside, an NO donor. These studies show that TNF-alpha or IL-1 beta can upregulate ciliary motility presumably by releasing NO via inducti on of NOS and suggest a mechanism by which inflammation increases cili ary motility.