title: Inhibition of type 4 cyclic nucleotide phosphodiesterase blocks intracellular TLR signaling in chronic lymphocytic leukemia and normal hematopoietic cells.
abstract: A subset of chronic lymphocytic leukemia (CLL) BCRs interacts with Ags expressed on apoptotic cells, suggesting that CLL BCRs have the potential to internalize apoptotic cell RNA- or DNA-containing fragments with resultant activation of TLR7 or TLR9, respectively. By blocking cAMP degradation, type 4 cAMP phosphodiesterase (PDE4) inhibitors activate cAMP-mediated signaling and induce apoptosis in CLL cells. In this study, we show that autologous irradiated leukemic cells induce proliferation in CLL cells and that such proliferation is blocked by a TLR7/8/9 inhibitor, by DNase, and by the PDE4 inhibitor rolipram. Rolipram also inhibited CLL cell proliferation induced by synthetic TLR7 and TLR9 agonists, as well as TLR agonist-induced costimulatory molecule expression and TNF-a (but not IL-6 or IL-10) production. Whereas treatment with a TLR9 agonist protected IgH V region unmutated, but not mutated, CLL cells from apoptosis, PDE4 inhibitors augmented apoptosis in both subtypes, suggesting that cAMP-mediated signaling may abrogate a TLR9-mediated survival signal in prognostically unfavorable IGHV unmutated CLL cells. Rolipram inhibited both TLR7/8- and TLR9-induced IFN regulatory factor 5 and NF-kB p65 nuclear translocation. PDE4 inhibitors also blocked TLR signaling in normal human immune cells. In PBMC and CD14-positive monocytes, PDE4 inhibitors blocked IFN-a or TNF-a (but not IL-6) production, respectively, following stimulation with synthetic TLR agonists or RNA-containing immune complexes. These results suggest that PDE4 inhibitors may be of clinical utility in CLL or autoimmune diseases that are driven by TLR-mediated signaling.
authors.affiliation: Section of Hematology/Oncology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: Ying
authors.initials: Y
authors.lastname: Tan
authors.affiliation: Section of Nephrology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: Amanda A
authors.initials: AA
authors.lastname: Watkins
authors.affiliation: Section of Hematology/Oncology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: Benjamin B
authors.initials: BB
authors.lastname: Freeman
authors.affiliation: Section of Hematology/Oncology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: John A
authors.initials: JA
authors.lastname: Meyers
authors.affiliation: Section of Nephrology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: Ian R
authors.initials: IR
authors.lastname: Rifkin
authors.affiliation: Section of Hematology/Oncology, Evans Department of Medicine, Boston University School of Medicine, Boston, MA 02118 and Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA 02118
authors.forename: Adam
authors.initials: A
authors.lastname: Lerner
mesh_terms: D021581:Active Transport, Cell Nucleus; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001483:Base Sequence; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000494:pharmacology; D005260:Female; D006801:Humans; D050835:Interferon Regulatory Factors / Q000378:metabolism; D016898:Interferon-alpha / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology; D058988:Phosphodiesterase 4 Inhibitors / Q000627:therapeutic use*; D020889:Rolipram / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D051199:Toll-Like Receptor 7 / Q000037:antagonists & inhibitors; D051200:Toll-Like Receptor 8 / Q000037:antagonists & inhibitors; D051217:Toll-Like Receptor 9 / Q000037:antagonists & inhibitors; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: C508609:IL10 protein, human; C508600:IL6 protein, human; D050835:Interferon Regulatory Factors; D016898:Interferon-alpha; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D058988:Phosphodiesterase 4 Inhibitors; C495348:TLR7 protein, human; C495349:TLR8 protein, human; C495371:TLR9 protein, human; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; D051217:Toll-Like Receptor 9; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D000242:Cyclic AMP; D003851:Deoxyribonucleases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D020889:Rolipram