IL-8 Inhibits Isoproterenol-Stimulated Ciliary Beat Frequency in Bovine Bronchial Epithelial Cells

Abstract

Mucociliary clearance is a critical host defense that protects the lung. The mechanisms by which mucociliary function is altered by inflammation are poorly defined. Chronic exposure to cigarette smoke decreases ciliary beating and interferes with proper airway clearance. Bronchoalveolar lavage (BAL) fluid from smokers and ex-smokers has increased amounts of IL-8, which has played a critical role in airway inflammation. We hypothesized that IL-8 might interfere with stimulated ciliary beating in airway epithelium. To test this hypothesis, we stimulated bovine ciliated bronchial epithelial cells (BBECs) with a known activator of ciliary beat frequency (CBF), isoproterenol (ISO; 100 microM), in the presence or absence of IL-8 (100 pg/mL). We measured CBF digitally using the Sisson-Ammons Video Analysis (SAVA) system. CBF increased in untreated cells exposed to ISO (approximately 3 Hz) over baseline. In contrast, cells pre-incubated with IL-8 failed to respond to ISO. Pretreatment with IL-8 also blocked ISO-stimulated cAMP-dependent kinase (PKA) activation, which is known to control ISO-stimulated CBF. In addition, IL-8 pretreated cells revealed a marked decrease in PKA activity when cells were stimulated with forskolin (FSK; 10 microM). Cells were assayed specifically for cAMP-phosphodiesterase (PDE) activity. ISO-stimulated cells demonstrated an increase in PDE activity as compared to control. Pretreatment with IL-8 had no effect on ISO-stimulated PDE activity. Collectively, these data suggest that IL-8 appears to mediate its effect at the level of adenylyl cyclase. It is also possible that IL-8 may not only act as a chemotactic agent, but also as a potential autocrine/paracrine inhibitor of PKA-mediated stimulation of ciliary motility. In conclusion, IL-8 inhibits beta-agonist dependent ciliostimulation and such inhibition of stimulated ciliary activity may contribute to the impaired mucociliary clearance seen in airway diseases. Furthermore, since IL-8 levels are increased in the airway of cigarette smokers, it is likely they may be more resistant to the cilio and muco-ciliostimulating effects of beta-agonists.

Desensitization of PKA‐Stimulated Ciliary Beat Frequency in an Ethanol‐Fed Rat Model of Cigarette Smoke Exposure

“…This observation supports our in vitro cellular studies of intact ciliated epithelial CBF desensitization to isoproterenol after chronic ethanol exposure (Wyatt and Sisson, 2001). Results from similar in vitro studies have shown that the ethanol desensitization response is not exclusively regulated at the level of the β-adrenergic receptors (Wyatt and Sisson, 2001), phosphodiesterase activation (Forgèt et al, 2003), or proinflammatory cytokine production (Allen-Gipson et al, 2004). Instead, ethanol appears to acutely stimulate CBF via nitric oxide (Sisson, 1995) and cAMP-dependent (Sisson et al, 1999) pathways.…”

Tubal transport of gametes and embryos: a review of physiology and pathophysiology

“…Employing a culture system of ciliated epithelial cells of rabbit trachea, it was shown that beta adrenergic stimulation increases ciliary beat frequency and this effect can be reversed by using a beta adrenergic receptor blocker, propranolol [30]. This adrenergic stimulatory effect is probably subject to modulation by other factors as exemplified by the ability of IL-8 to block the stimulatory effects of isoproterenol in a bovine model [31]. Based on a murine knockout model in which muscarinic receptors are deficient, it appears that cholinergic system does not have any effect on CBF in the oviduct [32].…”

Adenosine activation of A2Breceptor(s) is essential for stimulated epithelial ciliary motility and clearance

“…Some rings were pretreated with an adenosine deaminase inhibitor, EHNA (10 M) or with a selective A 2B adenosine receptor antagonist, PSB1115 (100 nM), or with a selective and potent cAMP-dependent PKA inhibitor, KT-5720. Rings were incubated for 30 min at 37°C in 5% CO 2 and then allowed to equilibrate at 25°C for 10 min, and a final CBF reading was taken.…”

“…The cAMP-dependent PKA is established as an important regulator of the cilia stimulation pathway (2,42,51,62). To determine the mechanism of NECA-stimulation of CBF, we measured PKA activity in our primary ciliated BBEC model.…”

“…Regulation of airway ciliary motility is critical because mucociliary transport is considered the first line of defense between the lung and the environment. Stressful conditions such as exercise or inflammation cause cilia in the airway to beat faster, increase clearance, and move an increased number of inhaled particles (2). As a consequence, mucociliary transport is a regulable host defense that can be activated under numerous conditions.…”