Alveolar epithelial type II cells

Fehrenbach H (2001) Alveolar epithelial type II cell defender of the alveolus revisited. Respir Res 2(1 ) 33—46... 

Mixtures of NiCl2 and C0CI2 induced a synergistic (that is, greater than additive) toxic response in cultures of immortahsed f tal rat alveolar epithelial type II cells (Cross et al. 2001). 

Me- C]Choline incorporation into phosphatidylcholines was decreased in isolated rat alveolar epithelial type II cells exposed to paraquat (5-10 ) and hyperoxia (90 % O2) (Haagsman et al. 1987). The incorporation of [1- C]acetate into phosphatidylcholines, phosphatidylglycerols and neutral lipids appeared to be very sensitive to inactivation by paraquat. The rate of [l- C]palmitate incorpora-... 

The human alveolar epithelium consists of two cell types type I (alveolar epithelial type I [ATI], pneumocyte I) and type n (alveolar epithelial type II... 

Collectins Alveolar type II cells and non-ciliated bronchiolar epithelial cells Bacterial and fungal cell walls and viruses Enhance phagocytosis of macrophages and neutrophils activating cells Cigarette smoke decreases the production of collectin [48] ozone decreases function [49]... 

Chen Z, Jin N, Narasaraju T, Chen J, McFarland LR, Scott M, Liu L (2004) Identification of two novel markers for alveolar epithelial type I and II cells. Biochem Biophys Res Commun 319(3) 774—780... 

Chen J, Chen Z, Narasaraju T, Jin N, Liu L (2004) Isolation of highly pure alveolar epithelial type I and type II cells from rat lungs. Lab Invest 84(6) 727-735 Erratum in Lab Invest 85(9) 1181 (2005)... 

Despite the fact that most of the alveolar surface is composited of alveolar epithelium, three primary types of cells are present in the alveoli type I alveolar cells, type II alveolar cells, and alveolar macrophages. Type I alveolar cells are also referred to as squamous pulmonary epithelial cells and are the continuous lining of the alveolar sac. Type II alveolar cells are also referred to as septal cells. Type II alveolar cells secrete the alveolar fluid that is necessary to keep the surface moist and to maintain surface tension of the alveolar fluid surface tension is necessary to keep the alveoli from collapsing. Alveolar fluid is a suitable environment for proteins when compared to the low pH and high protease levels associated with the intestine... 

The lung possesses a variety of epithelial cells, with different types found in different regions. Alveolar type II cells represent a potentially important target for the delivery of intracellular enzymes, such as superoxide dismutase (SOD) and catalase, which do not reach their full complement until the final 10-15% of gestation. Until the enzymes do reach their full complement, the premature baby... 

At the distal respiratory site, the alveolar epithelial cell layer is much flatter (0.1 -0.5 pm) and composed of two major cell types, squamous type I and agranular type II pneumocytes. Type I pneumocytes are non-phagocytic and highly flattened cells with broad and thin extensions. They occupy -95 % of the alveolar luminal surface, although they are less numerous than type II cells. The remaining surface is occupied by type II pneumocytes, which have blunt microvilli and contain multivesicular bodies [3, 11]. 

The lung comprises about 40 different cell types, amongst which type I and type II alveolar epithelial cells are the major types targeted by pulmonary drug delivery systems. Type I cells play an important role in the absorption process of proteins, while type II cells produce surfactant, regulate the immune response, and serve... 

The rate of liposome accumulation in alveolar type-II cells is dependent on lipid composition. It is therefore possible to select liposome compositions displaying minimal interaction with these cells and thereby function as controlled-release systems for entrapped solutes. For example, liposomes composed of dipalmitoylphosphatidylcholine and cholesterol and containing entrapped sodium cromoglycate will provide sustained delivery of the drag for over 24 hours. Conversely other liposome compositions could be utilized for enhanced epithelial interaction and transport of the drug (e g. cationic lipids for the cellular delivery of the CFTR gene). 

Huang X, Wu J, Zhu W, Pytela R, Sheppard D. Expression of the human integrin beta6 subunit in alveolar type II cells and bronchiolar epithelial cells reverses lung inflammation in beta6 knockout mice. Am J Respir Cell Mol Biol 1998 19(4) 636 12. 

Potential sources of NO in the lungs include activated alveolar macrophages, neutrophils alveolar type II cells endothelial cells and airway cells. nNOS is localized to nonadrenergic/noncholinergic nerve terminals and is present in human airway epithelial cells. eNOS is localized to human pulmonary epithelium and bronchial epithelium. Studies have suggested that iNOS is constitutively expressed in human upper airway epithelium... 

The respiratory alveolar epithelial response to toxic injury can be rapid, resulting in necrosis and subsequently sloughing of the sensitive type I cells. This type of response is seen with exposure to such toxicants as ozone, nitrogen dioxide, and butylated hydroxy toluene. This injury stimulates the proliferation of the more resistant type II cells. This proliferative response typically peaks at 48h after onset of the initial injury to the type I cells. The increase in number of type II cells can be expected to alter the diffusion capacity of the pulmonary region through populating this membrane with these thicker cells. 

Many cell types within the lung, such as the bronchial epithelial cells, Clara cells, type II pneumocy tes, and alveolar macrophages, are capable of metabolizing xenobiotics. In rodents and rabbits, however, Clara cells and type II cells are the... 

The respiratory part of the airways is also shielded by a ciliated epithelium. Along this region the ciliated cells are interspersed by Clara cells which are discussed as progenitor cells of the respiratory epithelium [8,9]. This epithelium has to be separated from the alveolar epithelium, which is a non-ciliated epithelium and formed by alveolar epithelial cells type I and type II. The major surface area of the alveoli is covered by type I cells. Nevertheless, the cuboidal alveolar type II cells represent about 90 % of the alveolar epithelial cells. 

---