Human Nasal Respiratory Secretions and Host Defense

Abstract

The largest human body surface is the lining of the respiratory tract, gastrointestinal tract, and reproductive system each of which is covered by mucous membranes, named for their capacity to secrete mucus. Recent studies of mucus have defined some of the physiologic and pharmacologic controls of secretions. However, the constituents that are found in mucus and their roles in human health and disease are still in the initial phases of exploration. Human nasal respiratory secretions provide one convenient source of mucous membrane secretions. Nasal secretions include a variety of proteins, which appear to serve important functions in host-defense. Most, if not all, of the antiphlogistic products are synthesized and secreted by serous cells in the submucous glands, and it appears that the serous cell is the resident antimicrobial cell in mucous membranes.

Oxidative stress and antioxidants at biosurfaces: plants, skin, and respiratory tract surfaces.

“…Exposure of plasma to 03 resulted in rapid depletion of its major water-soluble antioxidants, ascorbate and urate, at similar rates (120,121). As urate appears to be the most predominant low molecular mass antioxidant in proximal and nasal RTLFs (123,124) (see below), it has been hypothesized that urate may provide the most significant antioxidant defense against 03.…”

“…Interest in the role of RTLF antioxidants in protecting against environmental oxidant pollutants has been stimulated by several observations. For example, uric acid, an important extracellular antioxidant, is thought to be secreted by the same upper RTECs that secrete mucin (123,124), and lower RTECs secrete a-tocopherol together with surfactant (130), the latter being itself a target for oxidative injury (131)(132)(133)(134). Bronchoalveolar RTLFs contain glutathione (GSH) in considerable excess of plasma levels and may contain more ascorbic acid than plasma (at least in some species) (18,135).…”

Oxidants, antioxidants, and respiratory tract lining fluids.

“…Interest in the role of RTLF antioxidants has been stimulated by observations that uric acid is secreted by the same upper RTECs that secrete mucin (4,5), that atocopherol is secreted by lower RTECs together with surfactant (6), that bronchoalveolar RTLFs contain ascorbic acid and reduced glutathione (GSH) excess of plasma levels (7)(8)(9), and that mucin itself shows antioxidant properties in vitro (10)(11)(12). Interest has been further aroused by the observation that the GSH content of the lower RTLF appears to be subnormal in AIDS (13), in idiopathic pulmonary fibrosis (14), in cystic fibrosis (15), and in adult respiratory distress syndrome (ARDS) (16).…”

CAM 17.1 - A new diagnostic marker in pancreatic cancer

“…Mucus covers the surface of most epithelia and plays a fundamental role in the lubrication and protection of mucosal surfaces (Neutra and Forstner, 1987). Mucus is biochemically complex and heterogeneous, its major components being mucin glycoproteins (Neutra and Forstner, 1987;Kaliner, 1991). Mucin glycoproteins are characterised by a high carbohydrate content (greater than 80%) and core peptides that are rich in Thr, Ser, Pro, Ala and Gly (Kaliner, 1991;Kim et al, 1991;Neutra and Forstner, 1987;Wesley et al, 1985).…”

“…Mucus is biochemically complex and heterogeneous, its major components being mucin glycoproteins (Neutra and Forstner, 1987;Kaliner, 1991). Mucin glycoproteins are characterised by a high carbohydrate content (greater than 80%) and core peptides that are rich in Thr, Ser, Pro, Ala and Gly (Kaliner, 1991;Kim et al, 1991;Neutra and Forstner, 1987;Wesley et al, 1985). As more than 90% of pancreatic cancers are adenocarcinomas of ductal origin, these cancers frequently contain mucin-producing cells as detected by histochemical stains, whereas normal pancreatic tissue constitutes only a minor portion of cells in the secretory ducts (Roberts and Burns, 1972).…”