gsk525762a and Inflammation

Bromodomain-containing proteins are vital for controlling the expression of many pro-inflammatory genes. Consequently, compounds capable of inhibiting specific bromodomain-facilitated protein-protein interactions would be predicted to alleviate inflammation, making them valuable agents in the treatment of diseases caused by dysregulated inflammation, such as age-related macular degeneration. Here, we assessed the ability of known inhibitors JQ-1, PFI-1, and IBET-151 to protect from the inflammation and cell death caused by etoposide exposure in the human retinal pigment epithelial cell line, ARPE-19. The potential anti-inflammatory effects of the bromodomain inhibitors were assessed by ELISA (enzyme-linked immunosorbent assay) profiling. The involvement of NF-κB and SIRT1 in inflammatory signaling was monitored by ELISA and western blotting. Furthermore, SIRT1 was knocked down using a specific siRNA or inhibited by EX-527 to elucidate its role in the inflammatory reaction. The bromodomain inhibitors effectively decreased etoposide-induced release of IL-6 and IL-8. This anti-inflammatory effect was not related to SIRT1 activity, although all bromodomain inhibitors decreased the extent of acetylation of p53 at the SIRT1 deacetylation site. Overall, since bromodomain inhibitors display anti-inflammatory properties in human retinal pigment epithelial cells, these compounds may represent a new way of alleviating the inflammation underlying the onset of age-related macular degeneration.

Topics: Anti-Inflammatory Agents; Azabicyclo Compounds; Azepines; Benzodiazepines; Carbazoles; Cell Line; Cell Survival; Epithelial Cells; Etoposide; Gene Expression Regulation; Humans; Inflammation; Interleukin-6; Interleukin-8; Models, Biological; NF-kappa B; Protein Domains; Pyridines; Retinal Pigment Epithelium; RNA, Small Interfering; Signal Transduction; Sirtuin 1; Topoisomerase II Inhibitors; Transcription Factors; Triazoles; Tumor Suppressor Protein p53

Interaction of pathogens with cells of the immune system results in activation of inflammatory gene expression. This response, although vital for immune defence, is frequently deleterious to the host due to the exaggerated production of inflammatory proteins. The scope of inflammatory responses reflects the activation state of signalling proteins upstream of inflammatory genes as well as signal-induced assembly of nuclear chromatin complexes that support mRNA expression. Recognition of post-translationally modified histones by nuclear proteins that initiate mRNA transcription and support mRNA elongation is a critical step in the regulation of gene expression. Here we present a novel pharmacological approach that targets inflammatory gene expression by interfering with the recognition of acetylated histones by the bromodomain and extra terminal domain (BET) family of proteins. We describe a synthetic compound (I-BET) that by 'mimicking' acetylated histones disrupts chromatin complexes responsible for the expression of key inflammatory genes in activated macrophages, and confers protection against lipopolysaccharide-induced endotoxic shock and bacteria-induced sepsis. Our findings suggest that synthetic compounds specifically targeting proteins that recognize post-translationally modified histones can serve as a new generation of immunomodulatory drugs.

Topics: Acetylation; Animals; Anti-Inflammatory Agents; Benzodiazepines; Cells, Cultured; Epigenomics; Gene Expression Regulation; Genome-Wide Association Study; Heterocyclic Compounds, 4 or More Rings; Histone Deacetylase Inhibitors; Hydroxamic Acids; Inflammation; Kaplan-Meier Estimate; Lipopolysaccharides; Macrophages; Mice; Mice, Inbred C57BL; Models, Molecular; Protein Serine-Threonine Kinases; Protein Structure, Tertiary; Salmonella Infections; Salmonella typhimurium; Sepsis; Shock, Septic