Anaphylatoxin C3a Receptors in Asthma

The complement system forms the central core of innate immunity but also mediates a variety of inflammatory responses. Anaphylatoxin C3a, which is generated as a byproduct of complement activation, has long been known to activate mast cells, basophils and eosinophils and to cause smooth muscle contraction. However, the role of C3a in the pathogenesis of allergic asthma remains unclear. In this review, we examine the role of C3a in promoting asthma. Following allergen challenge, C3a is generated in the lung of subjects with asthma but not healthy subjects. Furthermore, deficiency in C3a generation or in G protein coupled receptor for C3a abrogates allergen-induced responses in murine models of pulmonary inflammation and airway hyperresponsiveness. In addition, inhibition of complement activation or administration of small molecule inhibitors of C3a receptor after sensitization but before allergen challenge inhibits airway responses. At a cellular level, C3a stimulates robust mast cell degranulation that is greatly enhanced following cell-cell contact with airway smooth muscle (ASM) cells. Therefore, C3a likely plays an important role in asthma primarily by regulating mast cell-ASM cell interaction. © 2005 Ali and Panettieri; licensee BioMed Central Ltd

Chemoattractant Receptor-Induced Phosphorylation of L-Selectin

The selectin adhesion molecules and chemoattractant receptors synergistically regulate leukocyte migration into lymphoid tissues and sites of inflammation, but little is known about how these families of receptors modulate each other\u27s function. In this study, L-selectin was found to be phosphorylated in lymphoblastoid cell lines, and phosphorylation was enhanced by phorbol ester (phorbol 12-myristate 13-acetate (PMA)) treatment. Interactions between L-selectin and chemoattractant receptors were therefore examined using transfected rat basophilic leukemia cell lines (RBL-2H3) that expressed human L-selectin along with human leukocyte chemoattractant receptors. L-selectin was rapidly phosphorylated in cells treated with chemoattractants, thrombin, IgE receptor agonists, or PMA. Pertussis toxin or the protein kinase C inhibitor, staurosporine, completely blocked chemoattractant receptor-induced phosphorylation of L-selectin. PMA-induced phosphorylation was on serine residues within the cytoplasmic tail of L- selectin that have been well conserved during recent evolution. Although L- selectin phosphorylation was not essential for basal levels of adhesion through L-selectin in transformed cell lines, the rapid increase in ligand binding activity of L-selectin that occurs following leukocyte activation was blocked by staurosporine. These results demonstrate that L-selectin can be phosphorylated following engagement of chemoattractant receptors and suggest that this may be a physiologically relevant mechanism for the synergistic regulation of these receptors during leukocyte migration

A heterofunctional ligand approach for the preparation of high connectivity coordination polymers: combining a “bridge” and “pillar” in one ligand

Two of the most successful strategies for the preparation of three-dimensional coordination polymers and MOFs are reticular synthesis and pillaring. Here we present a new approach which combines aspects of both of these by employing a heterofunctional dicarboxylic and dipyridyl ligand, 2,5-di(pyridin-4-yl)terephthalic acid (H2L). The reaction of H2L with zinc(II) produces a non-interpenetrated 3D coordination polymer [ZnL(H2O)]n

Preparation of superposed thin film (CdTe)1-xSex / ZnS and Studying the Effect of Concentration on Some its Electrical Properties.

Preparation of superposed thin film (CdTe)1-xSex / ZnS) with concentration of (x= 0.1, 0.3, 0.5) at a temperature of substrate (Ts= 80 0C) by using Thermal Vacuum Evaporation System. The measurement of X-ray diffraction shows that the compounds CdTe, ZnS, (CdTe)1-xSex and (CdTe)1-xSex / ZnS have a polycrystalline structure, the C-V characteristic shows that the capacitance degrease by increasing the concentration (x) in reverse bias, while the I-V characteristic shows the current dark (Id) increase in forward and reverse bias by increasing (x) and the photocurrent (Iph) increase in reverse bias by increasing the concentration (x), the values of photocurrent are greater than from the values of the dark current for all concentrations

Sterics and metal-ion radius control the self-assembly of [M2L3] helicates

The interplay of many factors influences the outcomes of self-assembly reactions. Using an acetylene-appended quaterpyridine ligand we show that both the size of the metal ion and the presence of steric repulsion between the acetylene groups result in the exclusive formation of [M2L3] helicates rather than a helicate/tetrahedron equilibrium.</p

Controlling the Complexity and Interconversion Mechanisms in Self-Assembled [Fe2L3]4+ Helicates and [Fe4L6]8+ Cages

Self-assembled coordination cages and metal–organic frameworks have relied extensively on symmetric ligands in their formation. Here we have prepared a relatively simple system employing an unsymmetric ligand that results in two distinct self-assembled structures, a [Fe2L3]4+ helicate and a [Fe4L6]8+ cage composed of 10 interconverting diastereomers and their enantiomers. We show that the steric profile of the ligand controls the complexity, thermodynamics and kinetics of interconversion of the system.</p