ag-490 and fludarabine

Type I interferon responses are considered the primary means by which viral infections are controlled in mammals. Despite this view, several pathogens activate antiviral responses in the absence of type I interferons. The mechanisms controlling type I interferon-independent responses are undefined. We found that RIG-I like receptors (RLRs) induce type III interferon expression in a variety of human cell types, and identified factors that differentially regulate expression of type I and type III interferons. We identified peroxisomes as a primary site of initiation of type III interferon expression, and revealed that the process of intestinal epithelial cell differentiation upregulates peroxisome biogenesis and promotes robust type III interferon responses in human cells. These findings highlight the importance of different intracellular organelles in specific innate immune responses.

Topics: Animals; Antineoplastic Agents; Benzimidazoles; Cell Differentiation; Cell Line; Cyclohexanes; DEAD Box Protein 58; DEAD-box RNA Helicases; Enzyme Inhibitors; Humans; Immunity, Innate; Interferons; Intestinal Mucosa; Janus Kinase 2; Mice; p38 Mitogen-Activated Protein Kinases; Peroxisomes; Pyridones; Receptors, Immunologic; Reoviridae; Reoviridae Infections; RNA Interference; RNA, Small Interfering; Signal Transduction; STAT1 Transcription Factor; Tyrphostins; Vidarabine

Signal transducers and activators of transcription (STAT) proteins comprise a family of transcription factors that have been implicated in tumoral transformation, especially in hematological malignancies. Because of this, the JAK/STAT pathway is attractive as a therapeutic target in these tumors. In the present study, we analyzed the ability of fludarabine and two JAK kinase inhibitors, AG490 and WHI-P131, to block STAT1 activation and induce apoptosis on B-cell chronic lymphocytic leukemia (B-CLL) cells. All drugs were able to induce a high percentage of apoptosis on B-CLL cells from all patients studied. However, only AG490 and WHI-P131 were able to strongly suppress the STAT1 activation of B-CLL cells. In conclusion, our data show that JAK kinase inhibitors, such as AG490 and WHI-P131 are able to inhibit the STAT1 pathway on B-CLL cells and are strong inductors of apoptosis on these cells.

Topics: Aged; Aged, 80 and over; Apoptosis; Cell Survival; DNA-Binding Proteins; Electrophoretic Mobility Shift Assay; Female; Flow Cytometry; Humans; Interferon-gamma; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Middle Aged; Protein-Tyrosine Kinases; Quinazolines; Signal Transduction; STAT1 Transcription Factor; Time Factors; Trans-Activators; Tumor Cells, Cultured; Tyrphostins; Vidarabine

STAT1 (signal transducer and activator of transcription 1) is potentially involved in cell survival, as well as cell death, in different types of cells. The present study was designed to examine the effects of STAT1 on hypoxia/re-oxygenation (H/R)-induced cell death and/or survival, and the underlying mechanisms of any such effects. H/R was shown to induce apoptotic cell death of rat hepatocytes. The addition of a STAT1-specific inhibitor, fludarabine, significantly increased the fraction of apoptotic cells after H/R. Following H/R, STAT1 was activated and sequential phosphorylation of Tyr701 and Ser727 was observed, which could be inhibited by the antioxidant N-acetyl-L-cysteine. Tyrosine and serine phosphorylation of STAT1 was mediated by Janus kinase 2 and phosphoinositide 3-kinase/Akt kinase respectively in a redox-dependent manner following H/R. STAT1-induced HSP70 (heat-shock protein 70) expression and the suppression of apoptosis occurred concomitantly. In conclusion, STAT1 activation, in a redox-dependent manner, following H/R may play crucial roles in cell survival, at least partly via HSP70 induction.

Topics: Acetylcysteine; Animals; Apoptosis; Cell Hypoxia; Cells, Cultured; DNA-Binding Proteins; Enzyme Inhibitors; Fibroblasts; Gene Expression Regulation; Hepatocytes; HSP70 Heat-Shock Proteins; Janus Kinase 2; Male; MAP Kinase Signaling System; Oxidation-Reduction; Oxidative Stress; Oxygen; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Rats; Rats, Inbred Lew; STAT1 Transcription Factor; Trans-Activators; Tyrphostins; Vidarabine