Knockdown of interleukin-1α does not attenuate LPS-induced production of interleukin-1β in mouse macrophages.
IL-1α and IL-1β are synthesized as 31kDa cell-associated precursors following TLR-4 stimulation, but their processing to the mature form and secretion require a second intracellular stimulus. The unique localization of the precursor of IL-1α (pro-IL-1α) to the nucleus suggested a role in transcriptional regulation of inflammatory cytokines. We explored the hypothesis that pro-IL-1α is involved in regulation of IL-1β expression following TLR-4 stimulation. IL-1β mRNA and protein levels were specifically decreased in macrophages from IL-1α-deficient mice following TLR-1/2, TLR-4 or TLR-9 stimulation, supporting the hypothesis. However, activation of the main upstream regulators of IL-1β expression, IRF3, NFkB and p38/JNK, were not reduced in macrophages from IL-1α-deficient mice. In order to assess the specific role of IL-1α in macrophages, we generated mice with myeloid cell deficiency of IL-1α (LyzMCre-loxp). Despite over 90% knockdown of IL-1α, TLR-4 stimulated macrophages from LyzMCre-loxp mice did not produce lower levels of IL-1β compared to IL-1α-loxp-flanked mice. In order to overcome the possibility that effects are caused by the incomplete deficiency of IL-1α, we generated new whole-body IL-1α knockout mice (GeneralCre-IL-1α) and the findings were similar to myeloid cell-deficient IL-1α. Collectively, our findings do not support the previously suggested role of nuclear IL-1α in gene regulation of IL-1β. Rather, they suggest that IL-1α acts mainly as an alarmin that is sequestered in the nucleus following stimulation with TLR-4.
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel.
Tal
T
Almog
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel.
Michal
M
Kandel-Kfir
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel.
Aviv
A
Shaish
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel; Sackler Faculty of Medicine, Tel-Aviv University, Israel.
Moshe
M
Dissen
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel; Sackler Faculty of Medicine, Tel-Aviv University, Israel.
Gadi
G
Shlomai
The Shraga Segal Department of Microbiology and Immunology, Ben-Gurion University, Beer-Sheva, Israel.
Elena
E
Voronov
The Shraga Segal Department of Microbiology and Immunology, Ben-Gurion University, Beer-Sheva, Israel.
Ron N
RN
Apte
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel; Sackler Faculty of Medicine, Tel-Aviv University, Israel.
Dror
D
Harats
The Bert W. Strassburger Lipid Center, Sheba Medical Center, Tel Hashomer, Israel; Sackler Faculty of Medicine, Tel-Aviv University, Israel. Electronic address: yehuda.kamari@sheba.health.gov.il.
Yehuda
Y
Kamari
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism; D053582:Interleukin-1alpha / Q000378:metabolism*; D053583:Interleukin-1beta / Q000096:biosynthesis*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000187:drug effects / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D002352:Carrier Proteins; D050838:Interferon Regulatory Factor-3; D053582:Interleukin-1alpha; D053583:Interleukin-1beta; C494233:Irf3 protein, mouse; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases
IL-1α; IL-1β; LyzMCre; Macrophages; TLR-4