Glucocorticoids inhibit macrophage differentiation towards a pro-inflammatory phenotype upon wounding without affecting their migration.

Glucocorticoid drugs are widely used to treat immune-related diseases, but their use is limited by side effects and by resistance, which especially occurs in macrophage-dominated diseases. In order to improve glucocorticoid therapies, more research is required into the mechanisms of glucocorticoid action. In the present study, we have used a zebrafish model for inflammation to study glucocorticoid effects on the innate immune response.

Repetitive switching between DNA-binding modes enables target finding by the glucocorticoid receptor.

Transcription factor mobility is a determining factor in the regulation of gene expression. Here, we have studied the intranuclear dynamics of the glucocorticoid receptor (GR) by using fluorescence recovery after photobleaching and single-molecule microscopy. First, we have described the dynamic states in which the GR occurs.

Nuclear receptor research in zebrafish.

Nuclear receptors (NRs) form a superfamily of transcription factors that can be activated by ligands and are involved in a wide range of physiological processes. NRs are well conserved between vertebrate species. The zebrafish, an increasingly popular animal model system, contains a total of 73 NR genes, and orthologues of almost all human NRs are present.

Efferocytosis and extrusion of leukocytes determine the progression of early mycobacterial pathogenesis.

Macrophages and neutrophils are the first responders to invading pathogens and contribute strongly to the host defense against intracellular pathogens. The collective interplay and dynamic interactions between these leukocytes are to a large extent not understood. In the present study, we have investigated their role using a combination of confocal laser-scanning and electron microscopy in a zebrafish model for tuberculosis, a local Mycobacterium marinum infection in the tissue of the larval tail fin.

Single-molecule microscopy reveals membrane microdomain organization of cells in a living vertebrate.

It has been possible for several years to study the dynamics of fluorescently labeled proteins by single-molecule microscopy, but until now this technology has been applied only to individual cells in culture. In this study, it was extended to stem cells and living vertebrate organisms. As a molecule of interest we used yellow fluorescent protein fused to the human H-Ras membrane anchor, which has been shown to serve as a model for proteins anchored in the plasma membrane.

The zebrafish as a model system for glucocorticoid receptor research.

Glucocorticoids regulate a plethora of physiological processes, and are widely used clinically as anti-inflammatory drugs. Their effects are mediated by the glucocorticoid receptor (GR), a ligand-activated transcription factor. Currently, zebrafish embryos are being developed into a model system for GR research, since they are easy to manipulate genetically and their phenotype can easily be visualized because of their transparent bodies.

Discovery of a functional glucocorticoid receptor beta-isoform in zebrafish.

In humans, two glucocorticoid receptor (GR) splice variants exist: GRalpha and GRbeta, which are identical between amino acids 1-727 and then diverge. Whereas GRalpha (the canonical GR) acts as a ligand-activated transcription factor, GRbeta does not bind traditional glucocorticoid agonists, lacks GRalpha's transactivational activity, and acts as a dominant-negative inhibitor of GRalpha. It has been suggested that this receptor isoform is involved in the induction of glucocorticoid resistance in asthma patients.