Apical Oxidative Hyaluronan Degradation Stimulates Airway Ciliary Beating via RHAMM and RON

Abstract

Hyaluronan (HA) is synthesized in high-molecular-weight form at the apical pole of airway epithelial cells, covering the luminal surface. When human airway epithelial cells grown and redifferentiated at the air-liquid interface (ALI) were exposed to xanthine/xanthine oxidase (X/XO), ciliary beat frequency (CBF) increased. This effect was blocked by superoxide dismutase (SOD) and catalase. Inhibition of hyaluronan synthesis inhibited the CBF response to X/XO, while addition of exogenous HA amplified it. A functionally blocking antibody to the receptor for hyaluronic acid-mediated motility (RHAMM) reduced the CBF response to X/XO. Since RHAMM has no transmembrane domain and thus cannot signal on its own, the association of RHAMM with recepteur d'origine nantais (RON), a member of the hepatocyte growth factor receptor family, was explored. Immunohistochemistry of human airway epithelium showed co-localization of RHAMM and RON at the apex of ciliated cells. Physical association of RHAMM and RON was confirmed with co-immunoprecipitations. Macrophage-stimulating protein (MSP), an agonist of RON, stimulated CBF. Genistein, a nonspecific tyrosine kinase inhibitor, and MSP beta chain (beta-MSP), a specific RON inhibitor, blocked the X/XO-induced CBF increase. HA present in the apical secretions of human airway epithelial cells was shown to degrade upon exposure to X/XO, a process inhibited by SOD. Low-molecular-weight HA fragments stimulated CBF, an effect blocked by anti-RHAMM antibody and genistein. These data suggest that high molecular form HA is broken down by reactive oxygen species to form low-molecular-weight fragments that signal via RHAMM and RON to stimulate CBF.

Hyaluronan in the Treatment of Chronic Rhinosinusitis with Nasal Polyposis

“…Many studies have confirmed the physiological role of HA in the upper airway. It is able to stimulate the mucociliary clearance through which removes the secretions on the epithelial surface [13], regulates the activity of enzymes needed for the homeostasis of the respiratory mucosa involved in allergic bronchoconstriction which prevents bacterial colonization of the upper airways. The ability of HA to reduce the infectious exacerbation of bacterial infections has been demonstrated in a randomized controlled trial study on patients with chronic bronchitis [22].…”

“…To ensure effective mucociliary clearance it is important that ciliary activity remains at an adequate level, in vivo, ciliary activity is regulated by HA and adenosine triphosphate [13]. An experiment has shown that following exposure to an enzyme system that breaks down high molecular HA to generate superoxides, the ciliary activity of human respiratory epithelial cells increase [13]. Reactive oxygen species strongly induce the depolarization of HA into fragments of small size and able stimulate ciliary to beat.…”

Reactive Oxygen Species and Hyaluronidase 2 Regulate Airway Epithelial Hyaluronan Fragmentation

“…For instance, GPI-anchored Hyal2 is likely involved in normal HA turnover, where Hyal2 depolymerize HA into ϳ20 kDa (ϳ50 disaccharides units) fragments, delivering them for further lysosomal degradation by Hyal1 (39,50). Soluble Hyal2 could be specifically released by GPI-PLD during inflammation, generating excess HA fragments that overwhelm HA catabolic rates, resulting in the triggering of RHAMM-and CD44-mediated intracellular signaling (22,23). It is reasonable to argue then, that GPI-Hyal2 serves constitutive physiological functions, (39,57,58), while the soluble form actively participates in host defense (22,23).…”

“…Tissue kallikrein (TK), a serine protease involved in airway inflammation and mucus hypersecretion (15,21) is bound to, and inhibited by HMWHA at the airway epithelial surface. Exposure to reactive oxygen species (ROS) depolymerizes HA resulting in the release of active TK (15,21) and HA fragments that stimulate ciliary beating (22) and induce MUC5B up-regulation (23). Thus, fragmentation of HA at the epithelial surface can profoundly affect cell responses.…”

Heterodimerization controls localization of Duox-DuoxA NADPH oxidases in airway cells

“…This finding, if confirmed in more detail, could shed some light on Duox function in the lung. A recent report showed that the high molecular mass polymer hyaluronan (HA) is synthesized at the apical pole of airway epithelial cells (Manzanares et al, 2007). ROS led to depolymerization of HA into low molecular mass fragments, which stimulated ciliary beat frequency (CBF).…”