A synthetic double-stranded RNA, poly I:C, induces a rapid apoptosis of human CD34+ cells

• Published in: Experimental hematology 2012-04, Vol.40 (4), p.330-341
• Main Authors: Liu, Jiajia, Guo, Yong-Mei, Hirokawa, Makoto, Iwamoto, Keiko, Ubukawa, Kumi, Michishita, Yoshihiro, Fujishima, Naohito, Tagawa, Hiroyuki, Takahashi, Naoto, Xiao, Weiguo, Yamashita, Junsuke, Ohteki, Toshiaki, Sawada, Kenichi
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; Apoptosis - drug effects; Caspases - physiology; Cell Lineage; Cells, Cultured - cytology; Cells, Cultured - drug effects; Cysteine Proteinase Inhibitors - pharmacology; DEAD Box Protein 58; DEAD-box RNA Helicases - physiology; Dose-Response Relationship, Drug; Hematology, Oncology and Palliative Medicine; Hematopoiesis - drug effects; Hematopoietic Stem Cells - cytology; Hematopoietic Stem Cells - drug effects; Humans; Interferon-alpha - pharmacology; Interferon-beta - pharmacology; Interferon-Induced Helicase, IFIH1; Molecular Weight; Oligodeoxyribonucleotides - pharmacology; Oligopeptides - pharmacology; Poly A-U - pharmacology; Poly I-C - administration & dosage; Poly I-C - pharmacology; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; Proto-Oncogene Proteins c-bcl-2 - genetics; Receptors, Immunologic; Receptors, Interferon - antagonists & inhibitors; RNA, Messenger - biosynthesis; Toll-Like Receptor 3 - physiology; Up-Regulation
• ISSN: 0301-472X; 1873-2399
• DOI: 10.1016/j.exphem.2011.12.002

Toll-like receptor 3 (TLR3), retinoic acid-inducible gene I, and melanoma differentiation-associated antigen 5 (RIG-I/MDA-5) helicases are known to sense double-stranded RNA (dsRNA) virus and initiate antiviral responses, such as production of type-I interferons (IFNs). Recognition of dsRNA by TLR3 or RIG-I/MDA-5 is cell-type–dependent and recent studies have shown a direct link between TLRs and hematopoiesis. We hypothesized that viral dsRNA recognized by either TLR3 or RIG-I/MDA-5, affects the growth of human hematopoietic stem/progenitor cells. Here we show that polyinosinic polycytidylic acid (poly I:C)–mediated very rapid apoptosis occurs within 1 hour in CD34+ cells in a dose-dependent manner. Polyadenylic-polyuridylic acid, another synthetic dsRNA that signals only through TLR3, had no effect. Poly I:C-LMW/LyoVec, a complex between low molecular-weight poly I:C and the transfection reagent LyoVec, which signals only through RIG-I/MDA-5, induces apoptosis of CD34+ cells. A strong and sustained upregulation of messenger RNA and protein levels of Noxa, a proapoptotic BH3-only protein that can be induced by RIG-I/MDA-5 pathway, is found in CD34+ cells treated by poly I:C. Although poly I:C upregulates type-I IFNs in CD34+ cells, neither exogenous IFN-α nor IFN-β induces rapid apoptosis in CD34+ cells and neutralization or blocking of type-I IFN receptor does not rescue CD34+ cells, whereas Z-VAD, a pan-caspase inhibitor, rescues the cells from apoptosis. These results suggest that RIG-I/MDA-5, but not TRL3, signaling triggers poly I:C–induced rapid apoptosis of human CD34+  cells, which will provide an insight into the mechanisms of dsRNA virus-mediated hematopoietic disorders.