Homeobox B3, FoxA1 and FoxA2 interactions in epithelial lung cell differentiation of the multipotent M3E3/C3 cell line

HOM/C homeobox (Hox) and forkhead box (Fox) factors are reported to be expressed in the foregut endoderm and are subsequently detected in a spatio-temporal pattern during lung development. Some of these factors were reported to influence the expression of lung marker proteins or to modulate lung development. To clarify the molecular mechanisms for generating functional lung cells from progenitor cell populations, we introduced the forkhead box factors, FoxA1 and FoxA2, and the homeobox factor, HoxB3, into the differentiation process in a multipotent hamster lung epithelial M3E3/C3 cell line. Ectopic expression of FoxA2 promoted differentiation to Clara-like cells with up-regulation of the expression of the lung marker proteins, Clara cell-specific 10-kDa protein and surfactant protein-B. In contrast, FoxA1 repressed the differentiation. HoxB3 transfection induced FoxA2 expression transiently at the pre-differentiation stage. The endogenous HoxB3 expression level decreased at later stages of Clara-like cell differentiation, and the attenuation was enhanced by FoxA2 transfection. HoxB3 is a putative upstream regulator that enhances FoxA2 expression at the pre-differentiation stage. In addition, we found that the expression of HoxA4, HoxA5, and HoxC9 increased differentially during Clara-like cell differentiation. These results suggest that HoxB3 may be a putative positive regulator of FoxA2 expression at the pre-differentiation stage, and those interactions of Fox factors and Hox factors could participate in Clara cell differentiation.     

Uptake and intracellular transport of cationic ferritin in the bronchiolar and alveolar epithelia of the rat

Summary Cationic ferritin was used as a marker to reveal the processes of endocytosis and intracellular transport in bronchiolar and alveolar epithelia. The marker was injected into the lung via the trachea, and ultrastructural observation of the distribution of ferritin particles in bronchiolar and alveolar epithelial cells was carried out at intervals of 5, 15, 30 and 60 min after the injection. The luminal surface of the airway and the alveolar epithelium showed diffuse labeling with cationic ferritin. In general, ferritin particles were observed in vesicles and vacuoles of the bronchiolar and alveolar epithelial cells within 5 min of injection; they appeared in multivesicular bodies within 15 min. Multivesicular bodies and secondary lysosomes containing ferritin particles, some of which showed a positive reaction for acid phosphatase, were seen in the basal cytoplasm within 30 min; ferritin particles appeared in the basal lamina below the Clara cells, ciliated cells and type 2 alveolar cells within 30 min. Ferritin particles were seen in ovoid granules of some Clara cells and in lamellar inclusion bodies of many type 2 alveolar cells. Brush cells and type 1 alveolar cells took up only a small quantity of ferritin particles.     

Serotoninergic innervation of the alimentary canal of the Colorado potato beetle,Leptinotarsa decemlineata: structural and functional aspects

Phenol (aryl) sulfotransferases (PSTs) provide a conjugative pathway that detoxifies hydroxylated aromatic xenobiotics by esterification with sulfate. Both human and bovine airways have been reported to use this pathway, and in this investigation the bovine system is examined. PST activity in tracheal through fourth generation bronchial mucosal cytosols was 0.1–0.35 nmol/mg protein/min. Activity was generally greater in more distal bronchi and in parenchymal extracts, which contained 0.6–3 nmol/mg/min PST activity. Comparison of the PST activities of bronchial and parenchymal cytosols indicated similar pH activity profiles, although steady state kinetic measurements revealed different K_m values for the acceptor substrate 2-naphthol (13.7 M for bronchial, 31.3 M for parenchymal). Anion exchange chromatography indicated two PST isoforms being expressed in different ratios. Immunoblot analysis with mouse antibovine PST revealed a closely spaced doublet at 32 kDa in both bronchial mucosal and parenchymal cytosolic extracts; however, this doublet was unequally stained in parenchymal extracts. Immunohistochemical analyses revealed faint positive staining of the tracheobronchial epithelium. Greatest immunostaining was observed in the nonciliated secretory epithelial cells of the bronchioles, whereas surrounding smooth muscle, endothelial cells, and alveoli were immunonegative. These results are consistent with the known locations of other detoxification enzymes within the airways.