Orthogonal arrays in normal and injured respiratory airway epithelium.

Abstract

Orthogonal arrays are found on plasma membranes of glial cells, in the central nervous system, on muscle plasma membranes at neuromuscular junctions, and on a variety of epithelial cells. These structures have been correlated with ion flux. With the aid of freeze fracture technique, orthogonal particle arrays were found on plasma membranes on airway epithelial cells of rats and hamsters. They have been found in abundance at the base of secretory cells throughout normal airway epithelium. These structures were found to increase in number during regeneration in response to injury and they were found in great numbers on plasma membranes of all airway cells in response to acute and chronic NO2 exposure. The lateral and basal plasma membranes of the respiratory epithelium are a new source for studying orthogonal arrays. The normal number and distribution of these arrays can be perturbed in response to mechanical and chemical injury.Orthogonal particle assemblies (rectangular arrays) are closely packed 6-nm intramembrane particles arranged in a square lattice. These assemblies have been found on the P-face of freeze-fractured plasma membranes of a variety of cells (1-11). Mammalian astrocytes, in particular, can be identified in freeze fractures by the abundance of these structures on their plasma membrane (12).The biochemical nature of these particles and their function in the membrane have not been determined. It has been speculated that these structures are associated with ion flux, at least in astrocytes (13).In this report we describe a rich source for these orthogonal structures in respiratory epithelium of rats and hamsters. We also describe conditions that increase their abundance, thereby perhaps providing a mechanism whereby these structures could be biochemically characterized and their function determined. MATERIALS AND METHODS20 male Syrian Golden hamsters weighing -60 g for the chronic study and 125 g for the acute study were divided into two groups. One group of eight animals was exposed to NO2:2 for 6 h, 2 for 24 h, 2 for 48 h, and the last 2 remained as controls breathing room air. The second group of 12 animals was exposed to NO2:2 for 1 mo, 2 for 5 mo, 2 for 9 mo, and the remaining six animals were used as unexposed age controls, two animals corresponding to each exposure period (1, 5, and 9 mo).Rationale for NOz Exposure: NO2 is a noxious gas that has been known to cause emphysematous lesions in rats (14) and hamsters (15). We have been using continuous NO2 exposure in hamsters as an animal model for the study of the development and progression of lesions caused by this agent in bronchioles and alveolar epithelium. During the studies in which we examined barrier function disruption of respiratory epithelium we made the observations reported in this manuscript. NO2 Exposure Techniques:The exposure groups were treated with NO2 at concentrations of 30 ppm for 22 h per day, 7 d per wk. 30 ppm was chosen because it was low enough not to cause death and yet high enough to cause a consistent lesi...

Orthogonal arrays of intramembrane particles in the supporting cells of the guinea‐pig vestibular sensory epithelium

“…Orthogonal arrays of intramembrane particles similar to those described in the present paper also have been reported in a wide variety of other cells and tissues, including skeletal muscle fibers Smith et al, 1975;Ishikawa et al, 1975;Saito et al, 19841, cardiac myocytes (McNutt, 19751, renal epithelia (Humbert et a]., 1975;Nakamura and Nagano, 1985;Orci et al, 1981;Hatae, 1983), tracheal epithelia (Inoue and Hogg, 1977;Gordon, 1985), stomach parietal cells (Bordi and Perrelet, 19781, uterus (Robenek and Greven, 1980), gill epithelia (Bartels, 1984;Lane et al, 19871, eye lens fibers (Zampighi et al, 1982;Lo and Harding, 1984), and olfactory epithelia (Kerjaschki and Horandner, 1976;Usukura and Yamada, 1978;Miragall, 1983). The square shape of intramembrane particles also has been observed in olfactory receptor cells (Usukura and Yamada, 1978), olfactory supporting cells (Kerjaschki and Horandner, 1976), and renal collecting tubules (Nakamura and Nagano, 1985).…”

“…These include membrane excitation (Rash and Ellisman, 19741, functional polarization of membranes (Hatton and Ellisman, 1981), representing ionophore (Usukura and Yamada, 19781, water transport (Humbert et al, 1975;Nakamura and Nagano, 19851, transport or permeability of other substances (Dermietzel, 1974;Landis, 1974;Nakai et al, 19801, ion-exchange responsible for maintaining the cells' micromilieu (Bartels, 1984;Gordon, 1985), signalling for axon regeneration (Neu- one-half of a supporting cell. Many microfilaments (MF) are seen in…”

Freeze-fracture and immunogold analysis of aquaporin-4 (AQP4) square arrays, with models of AQP4 lattice assembly

“…However, unambiguous correlation of AQP4 with square arrays was by no means certain because those same membranes also contained abundant potassium "leak channels" [including particularly Kir4.1 (Nagelhus et al, 1999;Higashi et al, 2001)], as well as numerous unidentified 8 nm "tubular" IMPs in the same membranes (Rash et al, 1997). Conversely, apparently identical square arrays (by whatever name) also have been found in several tissues that either lacked AQP4 or that had not been shown to contain AQP4, including "tetragonally arranged particles" in lens fibers (Zampighi et al, 1989), "orthogonal arrays" in tracheal pneumocytes (Gordon, 1985;Bartels and Miragall, 1986) and gastric parietal cells (Bordi et al, 1986), and continuous sheets of square lattices in the plasma membranes of cells that comprise the filter chambers of sap-sucking and blood-sucking insects (Hubert et al, 1989;Duchesne et al, 2003). Thus, it was essential to determine if AQP4 is localized to square lattices of IMPs in astrocyte plasma membranes, to the tubular IMPs, or to an unrecognized class of IMPs near the square arrays (Warth et al, 2004).…”

Section I: Freeze‐fracture

“…Fracturing through the basolateral portion of the type I cell or the ciliated respiratory epithelial cell (Figs. 6 and 7) reveals numerous particles in orthogonal or square packing (Gordon, 1985). Excluding cells and portions of cell membranes that do not have square arrays, the ciliated cells of the trachea have about 50 square arrays per pm2 membrane, and the type I cells have about 20 arrays per pm2.…”