Phosphoinositide 3-kinase gamma required for lipopolysaccharide-induced transepithelial neutrophil trafficking in the lung.

Phosphoinositide 3-kinase gamma(PI3Kgamma) is a critical mediator of directional cell movement. Here, we sought to characterise the role of PI3Kgamma in mediating the different steps of polymorphonuclear leukocyte (PMN) trafficking in the lung. In a murine model of lipopolysaccharide (LPS)-induced lung injury, PMN migration into the different lung compartments was determined in PI3Kgamma gene-deficient (PI3Kgamma(-/-)) and wild-type mice. Bone marrow chimeras were created to characterise the role of PI3Kgamma on haematopoietic versus nonhaematopoietic cells. A small-molecule PI3Kgamma inhibitor was tested in vitro and in vivo. PMN adhesion to the pulmonary endothelium and transendothelial migration into the lung interstitium was enhanced in PI3Kgamma(-/-) mice. However, transepithelial migration into the alveolar space was reduced in these mice. When irradiated PI3Kgamma(-/-) mice were reconstituted with bone marrow from wild-type mice, migratory activity into the alveolar space was restored partially. A small-molecule PI3Kgamma inhibitor reduced chemokine-induced PMN migration in vitro when PMNs or epithelial cells, but not when endothelial cells, were treated. The inhibitor also reduced LPS-induced PMN migration in vivo. We conclude that PI3Kgamma is required for transepithelial but not for transendothelial migration in LPS-induced lung injury. Inhibition of PI3Kgamma activity may be effective at curbing excessive PMN infiltration in lung injury.

Chemokine inhibition--why, when, where, which and how?

Chemokines are small chemoattractant cytokines that control a wide variety of biological and pathological processes, ranging from immunosurveillance to inflammation, and from viral infection to cancer. Genetic and pharmacological studies have shown that chemokines are responsible for the excessive recruitment of leucocytes to inflammatory sites and damaged tissue. In the present paper, we discuss the rationale behind interfering with the chemokine system and introduce various points for therapeutic intervention using either protein-based or small-molecule inhibitors. Unlike other cytokines, chemokines signal via seven-transmembrane GPCRs (G-protein-coupled receptors), which are favoured targets by the pharmaceutical industry, and, as such, they are the first cytokines for which small-molecule-receptor antagonists have been developed. In addition to the high-affinity receptor interaction, chemokines have an in vivo requirement to bind to GAGs (glycosaminoglycans) in order to mediate directional cell migration. Prevention of the GAG interaction has been shown to be a viable therapeutic strategy. Targeting chemokine intracellular signalling pathways offers an alternative small-molecule approach. One of the key signalling targets downstream of a variety of chemokine receptors identified to date is PI3Kgamma (phosphoinositide 3-kinase gamma), a member of the class I PI3K family. Thus the chemokine system offers many potential entry points for innovative anti-inflammatory therapies for autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis and allergic contact dermatitis.

Crystal structure of a synthetic cyclodecapeptide for template-assembled synthetic protein design.

The structural prototype of a new generation of regioselectively addressable functionalized templates (RAFTs) for use in protein de novo design has been synthesized and crystallized. The structure of the aromatically substituted cyclodecapeptide was determined by X-ray diffraction; it consists of an antiparallel beta sheet spanned by heterochirally induced type IIprime prime or minute beta turns, similar to that observed in gramicidin S. The three-dimensional structure of the artificial template was also examined by an NMR spectroscopic analysis in solution and shown to be compatible with a beta-sheet plane suitable for accommodating secondary functional peptide fragments for the synthesis of template-assembled synthetic proteins (TASPs).