Unmethylated CpG-containing oligodeoxynucleotides inhibit apoptosis in WEHI 231 B lymphocytes induced by several agents: evidence for blockade of apoptosis at a distal signalling step.
Certain oligodeoxynucleotides (ODN) containing cytosine followed by guanosine (CpG) protect B cells from apoptosis, and induce B-cell proliferation and cytokine production. We investigated the effect of phosphorothioate CpG-containing ODNs (5'-ATAATCGACGTTCAAGCAAG-3' or 5'-TCCATGACGTTCCTGACGTT-3') and control ODNs (which did not contain CpG) on apoptosis and cell growth in WEHI 231 murine B lymphoma cells. Anti-surface (alpha-s)IgM antibody induces 40-60% DNA degradation and growth arrest of WEHI 231 cells in 24 h. Both of these effects were substantially reversed by 30 ng/ml CpG-ODN added up to 8 hr after alpha-sIgM. Control ODNs not containing the CpG motif were without effect. We explored various hypotheses to account for these effects. The phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate, inhibits apoptosis induced by alpha-sIgM, but the anti-apoptotic effect of CpG-ODN was not affected by inhibitors of protein kinase C, indicating that CpG-ODN does not act via protein kinase C. CpG-ODN inhibited apoptosis and growth arrest induced by C2- and C8-ceramide, sphingomyelinase and an intracellular Ca2+ pump inhibitor thapsigargin, indicating that inhibition is not mediated via suppression of the ceramide cycle or suppression of Ca2+ mobilization. CpG-ODN partially inhibited apoptosis induced by okadaic acid, a protein phosphatase inhibitor, and by menadione, a free radical generator. CpG-ODN also inhibited apoptosis and growth arrest induced by ultraviolet-irradiation, glucocorticoid, vinca alkaloids, and doxorubicin. CpG-ODN significantly protected cells from DNA fragmentation induced by alpha-sIgM in the presence of cycloheximide, but cycloheximide itself induces apoptosis which was unaffected by CpG-ODN. These results suggest that CpG-ODNs powerfully modulate the process by which immune cells are committed to death or proliferation by a mechanism acting on distal cell signalling events. CpG-ODNs may be able to decrease immunosuppression in patients undergoing cancer chemotherapy.
Macfarlane
D E
DE
Department of Medicine, Veterans Administration Hospital, USA.
Manzel
L
L
Krieg
A M
AM
D000818:Animals; D000970:Antineoplastic Agents / Q000037:antagonists & inhibitors; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D018899:CpG Islands / Q000276:immunology*; D053938:DNA Fragmentation / Q000187:drug effects; D051379:Mice; D019319:Okadaic Acid / Q000037:antagonists & inhibitors; D009841:Oligonucleotides / Q000737:chemistry / Q000494:pharmacology*; D011493:Protein Kinase C / Q000276:immunology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013109:Sphingomyelins / Q000276:immunology; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014812:Vitamin K / Q000494:pharmacology
D000970:Antineoplastic Agents; D009841:Oligonucleotides; D011500:Protein Synthesis Inhibitors; D013109:Sphingomyelins; D014812:Vitamin K; D019319:Okadaic Acid; D019284:Thapsigargin; D011493:Protein Kinase C