Cell alkalinization is not necessary and increased sodium influx is not sufficient for stimulated superoxide production

AbstractPreincubation of rabbit neutrophils for 5 min with the protein kinase C inhibitor H7 causes inhibition of the rise in intracellular pH but not the increase in Na+ influx or stimulated oxidative burst produced by the chemotactic factor formyl-methionyl-leucyl-phenylalanine. On the other hand, the stimulated superoxide production, but not the increase in Na+ influx produced by phorbol 12-myristate 13-acetate, is inhibited by H7. The effect is more pronounced on the rate than the extent of the stimulated superoxide release. Furthermore, cell acidification produced by the phorbol ester but not by the chemotactic factor is decreased in the presence of H7. These results suggest that (i) most of the stimulated Na+ influx is not coupled to H+ efflux, (ii) in the case of the chemoattractant, the rise in intracellular pH is not necessary for stimulated superoxide production, (iii) the increase in Na+influx, in the case of the phorbol ester, is not sufficient for the stimulation of the oxidative burst, and (iv) the sources of the H+ responsible for the stimulated pH drop are the various metabolic activities of the cell, including NADPH oxidation and activation of the hexose monophosphate shunt

Rat Parotid Gland Cell Differentiation in Three-Dimensional Culture

The use of polarized salivary gland cell monolayers has contributed to our understanding of salivary gland physiology. However, these cell models are not representative of glandular epithelium in vivo, and, therefore, are not ideal for investigating salivary epithelial functions. The current study has developed a three-dimensional (3D) cell culture model for rat Par-C10 parotid gland cells that forms differentiated acinar-like spheres on Matrigel. These 3D Par-C10 acinar-like spheres display characteristics similar to differentiated acini in salivary glands, including cell polarization, tight junction (TJ) formation required to maintain transepithelial potential difference, basolateral expression of aquaporin-3 and Na+/K+/2Cl− cotransporter-1, and responsiveness to the muscarinic receptor agonist carbachol that is decreased by the anion channel blocker diphenylamine-2-carboxylic acid or chloride replacement with gluconate. Incubation of the spheres in the hypertonic medium increased the expression level of the water channel aquaporin-5. Further, the proinflammatory cytokines tumor necrosis factor-α and interferon-γ induced alterations in TJ integrity in the acinar-like spheres without affecting individual cell viability, suggesting that cytokines may affect salivary gland function by altering TJ integrity. Thus, 3D Par-C10 acinar-like spheres represent a novel in vitro model to study physiological and pathophysiological functions of differentiated acini