Pulmonary clearance of inhaled 99mTc-DTPA: effects of surfactant depletion by lung lavage

The influence of surfactant depletion on clearance from the lungs of inhaled technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) was studied in rabbits. Surfactant was removed by repeated lung lavage with isotone saline. To minimize structural damage to the lungs, pressure generated insufflation with short expiration was utilized. Aerosolized 99mTc-DTPA was administered via a bag-in-bottle system. Radioactivity was measured with a gamma camera and time-activity curves were obtained over the base of the right lung. Six nonlavaged rabbits served as controls. In six lavaged rabbits clearance of 99mTc-DTPA was significantly faster than in controls. In three rabbits given natural surfactant into the trachea after lung lavage, 99mTc-DTPA was eliminated faster than in controls but slower than in surfactant-depleted animals. The results indicate a role of surfactant on clearance rate of 99mTc-DTPA from rabbit lungs. Measurements of 99mTc-DTPA clearance may be useful in studying the function of the surfactant system in different lung disorders.     

Comparison of basic peptides- and lipid-based strategies for the delivery of splice correcting oligonucleotides

Expression of alternatively spliced mRNA variants at specific stages of development or in specific cells and tissues contributes to the functional diversity of the human genome. Aberrations in alternative splicing were found as a cause or a contributing factor to the development, progression, or maintenance of numerous diseases. The use of antisense oligonucleotides (ON) to modify aberrant expression patterns of alternatively spliced mRNAs is a novel means of potentially controlling such diseases. Oligonucleotides can be designed to repair genetic mutations, to modify genomic sequences in order to compensate for gene deletions, or to modify RNA processing in order to improve the effects of the underlying gene mutation. Steric block ON approach have proven to be effective in experimental model for various diseases. Here, we describe our experience in investigating two strategies for ON delivery: ON conjugation with basic peptides and lipid-based particulate system (lipoplex). Basic peptides or Cell Penetrating Peptides (CPP) such as the TAT-derived peptide appear to circumvent many problems associated with ON and drug delivery. This strategy may represent the next paradigm in our ability to modulate cell function and offers a unique avenue for the treatment of disease. Lipoplexes result from the intimate interaction of ON with cationic lipids leading to ON carrying particles able to be taken up by cells and to release ON in the cytoplasm. We have used as an experimental model the correction of a splicing alteration of the mutated β-globin intron causing thalassemia. Data on cell penetration and efficacy of correction of specific steric block ON delivered either by basic peptides or lipoplex are described. A comparison of the properties of both delivery systems is made respective to the use of this new class of therapeutic molecules.     

CD40 ligand-activated human monocytes amplify glomerular inflammatory responses through soluble and cell-to-cell contact-dependent mechanisms.

Monocytes/macrophages play a critical role in the initiation and progression of a variety of glomerulonephritides. We sought to define the interactions between physiologically activated human monocytes and glomerular mesangial cells (MC) by employing a cell culture system that permits the accurate assessment of the contribution of soluble factors and cell-to-cell contact. Human peripheral blood monocytes, primed with IFN-gamma and GM-CSF, were activated with CD40 ligand (CD40L) or TNF-alpha and cocultured with MC. CD40L-activated monocytes induced higher levels of IL-6, monocyte chemoattractant protein-1 (MCP-1) and ICAM-1 synthesis by MC. Separation of CD40L-activated monocytes from MC by a porous membrane decreased the mesangial synthesis of IL-6 by 80% and ICAM-1 by 45%, but had no effect on MCP-1. Neutralizing Abs against the beta 2 integrins, LFA-1 and Mac-1, decreased IL-6 production by 40 and 50%, respectively. Ligation of mesangial surface ICAM-1 directly enhanced IL-6, but not MCP-1, production. Simultaneous neutralization of soluble TNF-alpha and IL-1 beta decreased MCP-1 production by 55% in membrane-separated cocultures of MC/CD40L-activated monocytes. Paraformaldehyde-fixed CD40L-activated monocytes (to preserve membrane integrity but prevent secretory activity), cocultured with MC at various ratios, induced IL-6, MCP-1, and ICAM-1 synthesis by MC. Plasma membrane preparations from activated monocytes also induced mesangial IL-6 and MCP-1 synthesis. The addition of plasma membrane enhanced TNF-alpha-induced mesangial IL-6 production by approximately 4-fold. Together, these data suggest that the CD40/CD40L is essential for optimal effector function of monocytes, that CD40L-activated monocytes stimulate MC through both soluble factors and cell-to-cell contact mediated pathways, and that both pathways are essential for maximum stimulation of MC.     

Influence of concentration and structure of quaternary ammonium salts on their antifouling efficiency tested against a community of marine bacteria

With the view of incorporating quaternary ammonium salts (QAs) in marine paints, nineteen of these were tested against a community of marine bacteria, at a temperature and salinity close to those of seawater. The concentration of QAs and the length of the main substituting chain are the main parameters affecting the growth and adhesion of bacteria, but the nature of (i) the other chains, (ii) the counter‐ion and (iii) the rings when inserted in the QA molecule also influenced the bacteria. Increasing the concentration of the QAs decreased the growth rate of the bacteria, the maximum cell density at the plateau and the rate of adhesion. The effect of increasing the length of the main chain depended on the range of carbon numbers. Below 7 carbon atoms, the growth rate was not significantly modified, but the numbers of cells at the plateau increased in contrast with the adhesion rate which decreased rapidly. Increasing the length of the chain to between 7 and 16 carbon atoms resulted in a decrease in the growth rate, a decrease and then a stabilisation in the numbers of cells at the plateau and no further change in the adhesion rate. Possibly an increase in growth rate, adhesion rate and in the numbers of cells at the plateau may occur above 16 carbon atoms. In contrast, the length of the other chains influenced positively the cell concentration at the plateau, and more generally the efficiency of QAs decreased substantially when these chains had the same numbers of carbon atoms. QAs with iodide as counter‐ion were more effective than those with chloride or bromide and phenyl was more effective than benzyl as rings inserted in QAs. The minimum inhibitory concentrations (MIC) were often very high if compared to standard methods with laboratory strains, and this can be tentatively explained by the dominance of Gram— bacteria in the community assayed, the development of resistant strains in the cultures used with time and the presence of organic matter in the culture medium.