Cyclin-dependent kinase inhibitors enhance the resolution of inflammation by promoting inflammatory cell apoptosis.

Apoptosis is essential for clearance of potentially injurious inflammatory cells and subsequent efficient resolution of inflammation. Here we report that human neutrophils contain functionally active cyclin-dependent kinases (CDKs), and that structurally diverse CDK inhibitors induce caspase-dependent apoptosis and override powerful anti-apoptosis signals from survival factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF). We show that the CDK inhibitor R-roscovitine (Seliciclib or CYC202) markedly enhances resolution of established neutrophil-dependent inflammation in carrageenan-elicited acute pleurisy, bleomycin-induced lung injury, and passively induced arthritis in mice. In the pleurisy model, the caspase inhibitor zVAD-fmk prevents R-roscovitine-enhanced resolution of inflammation, indicating that this CDK inhibitor augments inflammatory cell apoptosis. We also provide evidence that R-roscovitine promotes apoptosis by reducing concentrations of the anti-apoptotic protein Mcl-1. Thus, CDK inhibitors enhance the resolution of established inflammation by promoting apoptosis of inflammatory cells, thereby demonstrating a hitherto unrecognized potential for the treatment of inflammatory disorders.

Regulation of neutrophil apoptosis and removal of apoptotic cells.

The accumulation of neutrophils during inflammation is essential for the destruction and removal of invading microorganisms. However, for resolution of inflammation to occur, neutrophils must also be removed from the inflammatory site since these cells are capable of releasing tissue toxic molecules. Neutrophil removal has been shown to occur via apoptosis and phagocyte clearance of apoptotic cells. Therefore, manipulation of these processes is likely to be a key therapeutic strategy in the management of inflammatory disease. In this review, we examine mediators of neutrophil survival and apoptosis and the signalling pathways that regulate the balance between life and death in these cells.

6th World Congress on Inflammation.

The 6th World Congress on Inflammation was held in the Vancouver Convention and Exhibition Center. This biennial meeting was organised by the Inflammation Research Association (USA) and Triangle 3 Ltd (UK), under the auspices of the International Association of Inflammation Societies. This meeting aimed to promote international cooperation amongst inflammation scientists and provide a communication network for various inflammation societies from around the world. The conference covered the most up-to-date concepts in inflammation, new drugs and treatments, and advances in cell biology. However, there were some topics which were either novel to many attendees or which provided links to a number of presentations, thus underlining their importance. The following is by no means an exhaustive review, but merely reflects the authors' interests.

Golgi fragmentation during Fas-mediated apoptosis is associated with the rapid loss of GM130.

During apoptosis, the Golgi complex becomes fragmented and key proteins (e.g., GRASP65 and p115) are targets for caspase cleavage. GM130, an integral membrane protein, contributes to the maintenance of Golgi structure and facilitates membrane fusion with secretory vesicles. We show that GM130 levels decrease during Fas-induced apoptosis but not during staurosporine-induced apoptosis while in both models p115 levels remain unaffected. We conclude that GM130 is rapidly diminished during Fas-mediated apoptosis associated with Golgi fragmentation in contrast to previous studies which have suggested that loss of GM130 during apoptosis is a late event.