HYALURONAN IS EXOCYTOSED FROM SEROUS, BUT NOT MUCOUS CELLS, OF HUMAN NASAL AND TRACHEOBRONCHIAL SUBMUCOSAL GLANDS

Background: Hyaluronan is a large, nonsulfated glycosaminoglycan that is a major component of many extracellular matrices, Secretion of hyal uronan has been associated with inflammation in the lungs and other ti ssues, The purpose of the present study was to determine the distribut ion of hyaluronan in human respiratory tissues and to determine if hya luronan was present in human nasal secretions. Method: Hyaluronan was localized in histological sections of human nasal and tracheobronchial mucosa using a biotin-labeled affinity-purified hyaluronan binding pr obe derived from cartilage proteoglycan (b-PG) (Green et al, Exp Cell Res 1988;178:224-32). Subjects had saline nasal provocation to collect baseline nasal secretions, then ate chili peppers to provoke parasymp athetic, cholinergic nasal glandular secretion (gustatory provocation) , Total protein and hyaluronan concentrations were measured in the lav age fluids. Results: Staining for hyaluronan was intense in basement m embranes of epithelium, glands and vessels, and perivascular adventiti a, Many epithelial cells contained hyaluronan, but the staining intens ity was less than that on the basolateral aspects of these cells, Subm ucosal gland serous cells contained variable amounts of hyaluronan, Hy aluronan was not present in goblet cells, submucosal gland mucous cell s, or sub-basement membrane collagen deposits, The gustatory, parasymp athetic stimulus induced a 4-fold increase in hyaluronan secretion (P < 0.01) and a 3.5-fold increase in total protein release (P < 0.0010), Hyaluronan accounted for 75% to 80% of the polymeric uronic acids in human nasal secretions. Conclusion: Hyaluronan was present human respi ratory epithelial cells and submucosal gland serous cells and was exoc ytosed in response to parasympathetic stimulation, This distribution s uggests roles in packaging cationic proteins in serous cells, cellular adhesion to basement membranes, and activation of macrophages in airw ay lumens.