Ricin exhibits well characterized ribotoxic actions that lead to the inhibition of protein synthesis and the phosphorylation of stress activated protein kinases (SAPKs). Proinflammatory effects of ricin are thought to be caused by upregulation of genes encoding proinflammatory transcripts as a result of the activation of c-Jun N-terminal kinase (JNK) and p38 MAPK. We reported previously that macrophages and interleukin-1β (IL-1β) signaling are required for murine host immune responses to ricin delivered to the lungs. Here we report that ricin-mediated IL-1β release from bone-marrow derived macrophages is dependent on the NALP3 inflammasome, a scaffolding complex that mediates pro-IL-1β cleavage to active IL-1β by caspase-1. Release of IL-1β from macrophages was suppressed by the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC) and high extracellular K+, which are two agents known to inhibit NALP3/cryopyrin/CIAS1 inflammasome formation. By employing inhibitors of p38 MAPK and JNK, we demonstrated that ricin-mediated release of IL-1β was enhanced, rather than suppressed, by inhibition of SAPK phosphorylation. In contrast, proteasomal inhibitors bortezomib and MG-132 completely suppressed ricin-induced IL-1β release from macrophages. These data suggest that ricin-mediated translational inhibition itself, by fostering the disappearance of labile protein(s) that normally suppress inflammasome formation, may constitute the mechanism underlying IL-1-dependent inflammatory signaling by ricin.
References
[1]
Greenfield, R.A.; Brown, B.R.; Hutchins, J.B.; Iandolo, J.J.; Jackson, R.; Slater, L.N.; Bronze, M.S. Microbiological, biological, and chemical weapons of warfare and terrorism. Am. J. Med. Sci.？2002, 323, 326–340, doi:10.1097/00000441-200206000-00005. 12074487
[2]
Brown, R.F.; White, D.E. Ultrastructure of rat lung following inhalation of ricin aerosol. Int. J. Exp. Pathol.？1997, 78, 267–276. 9505938
[3]
Korcheva, V.; Wong, J.; Lindauer, M.; Jacoby, D.B.; Iordanov, M.S.; Magun, B. Role of apoptotic signaling pathways in regulation of inflammatory responses to ricin in primary murine macrophages. Mol. Immunol.？2007, 44, 2761–2771, doi:10.1016/j.molimm.2006.10.025. 17257680
[4]
Zenilman, M.E.; Fiani, M.; Stahl, P.; Brunt, E.; Flye, M.W. Use of ricin A-chain to selectively deplete Kupffer cells. J. Surg. Res.？1988, 45, 82–89, doi:10.1016/0022-4804(88)90025-X. 3392996
[5]
Wong, J.; Korcheva, V.; Jacoby, D.B.; Magun, B. Intrapulmonary delivery of ricin at high dosage triggers a systemic inflammatory response and glomerular damage. Am. J. Pathol.？2007, 170, 1497–1510, doi:10.2353/ajpath.2007.060703. 17456757
[6]
Lindauer, M.L.; Wong, J.; Iwakura, Y.; Magun, B.E. Pulmonary inflammation triggered by ricin toxin requires macrophages and IL-1 signaling. J. Immunol.？2009, 183, 1419–1426, doi:10.4049/jimmunol.0901119. 19561099
[7]
Perregaux, D.; Gabel, C.A. Interleukin-1 beta maturation and release in response to ATP and nigericin. Evidence that potassium depletion mediated by these agents is a necessary and common feature of their activity. J. Biol. Chem.？1994, 269, 15195–15203. 8195155
Martinon, F.; Burns, K.; Tschopp, J. The inflammasome: A molecular platform triggering activation of inflammatory caspases and processing of proIL-beta. Mol. Cell？2002, 10, 417–426, doi:10.1016/S1097-2765(02)00599-3. 12191486
[11]
Tschopp, J.; Martinon, F.; Burns, K. NALPs: A novel protein family involved in inflammation. Nat. Rev. Mol. Cell Biol.？2003, 4, 95–104, doi:10.1038/nrm1019. 12563287
[12]
Srinivasula, S.M.; Poyet, J.L.; Razmara, M.; Datta, P.; Zhang, Z.; Alnemri, E.S. The PYRIN-CARD protein ASC is an activating adaptor for caspase-1. J. Biol. Chem.？2002, 277, 21119–21122, doi:10.1074/jbc.C200179200. 11967258
[13]
Sutterwala, F.S.; Ogura, Y.; Szczepanik, M.; Lara-Tejero, M.; Lichtenberger, G.S.; Grant, E.P.; Bertin, J.; Coyle, A.J.; Galan, J.E.; Askenase, P.W.; Flavell, R.A. Critical role for NALP3/CIAS1/Cryopyrin in innate and adaptive immunity through its regulation of caspase-1. Immunity？2006, 24, 317–327, doi:10.1016/j.immuni.2006.02.004. 16546100
[14]
Martinon, F.; Tschopp, J. NLRs join TLRs as innate sensors of pathogens. Trends Immunol.？2005, 26, 447–454, doi:10.1016/j.it.2005.06.004. 15967716
[15]
Stutz, A.; Golenbock, D.T.; Latz, E. Inflammasomes: Too big to miss. J. Clin. Invest.？2009, 119, 3502–3511, doi:10.1172/JCI40599. 19955661
[16]
Kanneganti, T.D.; Ozoren, N.; Body-Malapel, M.; Amer, A.; Park, J.H.; Franchi, L.; Whitfield, J.; Barchet, W.; Colonna, M.; Vandenabeele, P.; Bertin, J.; Coyle, A.; Grant, E.P.; Akira, S.; Nunez, G. Bacterial RNA and small antiviral compounds activate caspase-1 through cryopyrin/Nalp3. Nature？2006, 440, 233–236, doi:10.1038/nature04517. 16407888
[17]
Hise, A.G.; Tomalka, J.; Ganesan, S.; Patel, K.; Hall, B.A.; Brown, G.D.; Fitzgerald, K.A. An essential role for the NLRP3 inflammasome in host defense against the human fungal pathogen Candida albicans. Cell Host. Microbe？2009, 5, 487–497, doi:10.1016/j.chom.2009.05.002. 19454352
[18]
Ichinohe, T.; Lee, H.K.; Ogura, Y.; Flavell, R.; Iwasaki, A. Inflammasome recognition of influenza virus is essential for adaptive immune responses. J. Exp. Med.？2009, 206, 79–87, doi:10.1084/jem.20081667. 19139171
[19]
Hornung, V.; Bauernfeind, F.; Halle, A.; Samstad, E.O.; Kono, H.; Rock, K.L.; Fitzgerald, K.A.; Latz, E. Silica crystals and aluminum salts activate the NALP3 inflammasome through phagosomal destabilization. Nat. Immunol.？2008, 9, 847–856, doi:10.1038/ni.1631. 18604214
[20]
Cassel, S.L.; Eisenbarth, S.C.; Iyer, S.S.; Sadler, J.J.; Colegio, O.R.; Tephly, L.A.; Carter, A.B.; Rothman, P.B.; Flavell, R.A.; Sutterwala, F.S. The Nalp3 inflammasome is essential for the development of silicosis. Proc. Natl. Acad. Sci. USA？2008, 105, 9035–9040, doi:10.1073/pnas.0803933105. 18577586
[21]
Dostert, C.; Petrilli, V.; Van Bruggen, R.; Steele, C.; Mossman, B.T.; Tschopp, J. Innate immune activation through Nalp3 inflammasome sensing of asbestos and silica. Science？2008, 320, 674–677, doi:10.1126/science.1156995. 18403674
[22]
Mariathasan, S.; Weiss, D.S.; Newton, K.; McBride, J.; O'Rourke, K.; Roose-Girma, M.; Lee, W.P.; Weinrauch, Y.; Monack, D.M.; Dixit, V.M. Cryopyrin activates the inflammasome in response to toxins and ATP. Nature？2006, 440, 228–232, doi:10.1038/nature04515. 16407890
Halle, A.; Hornung, V.; Petzold, G.C.; Stewart, C.R.; Monks, B.G.; Reinheckel, T.; Fitzgerald, K.A.; Latz, E.; Moore, K.J.; Golenbock, D.T. The NALP3 inflammasome is involved in the innate immune response to amyloid-beta. Nat. Immunol.？2008, 9, 857–865, doi:10.1038/ni.1636. 18604209
[25]
Tschopp, J.; Schroder, K. NLRP3 inflammasome activation: The convergence of multiple signalling pathways on ROS production? Nat. Rev. Immunol.？2010, 10, 210–215, doi:10.1038/nri2725. 20168318
[26]
Petrilli, V.; Papin, S.; Dostert, C.; Mayor, A.; Martinon, F.; Tschopp, J. Activation of the NALP3 inflammasome is triggered by low intracellular potassium concentration. Cell Death Differ.？2007, 14, 1583–1589, doi:10.1038/sj.cdd.4402195. 17599094
[27]
Zhou, R.; Tardivel, A.; Thorens, B.; Choi, I.; Tschopp, J. Thioredoxin-interacting protein links oxidative stress to inflammasome activation. Nat. Immunol.？2010, 11, 136–140, doi:10.1038/ni.1831. 20023662
[28]
Cruz, C.M.; Rinna, A.; Forman, H.J.; Ventura, A.L.; Persechini, P.M.; Ojcius, D.M. ATP activates a reactive oxygen species-dependent oxidative stress response and secretion of proinflammatory cytokines in macrophages. J. Biol. Chem.？2007, 282, 2871–2879. 17132626
[29]
van de Veerdonk, F.L.; Smeekens, S.P.; Joosten, L.A.; Kullberg, B.J.; Dinarello, C.A.; van der Meer, J.W.; Netea, M.G. Reactive oxygen species-independent activation of the IL-1beta inflammasome in cells from patients with chronic granulomatous disease. Proc. Natl. Acad. Sci. USA？2009, 107, 3030–3033.
[30]
Saleh, M.; Green, D.R. Caspase-1 inflammasomes: Choosing between death and taxis. Cell Death Differ.？2007, 14, 1559–1560, doi:10.1038/sj.cdd.4402203. 17703235
[31]
Walev, I.; Reske, K.; Palmer, M.; Valeva, A.; Bhakdi, S. Potassium-inhibited processing of IL-1 beta in human monocytes. EMBO J.？1995, 14, 1607–1614. 7737113
[32]
Fernandes-Alnemri, T.; Wu, J.; Yu, J.W.; Datta, P.; Miller, B.; Jankowski, W.; Rosenberg, S.; Zhang, J.; Alnemri, E.S. The pyroptosome: a supramolecular assembly of ASC dimers mediating inflammatory cell death via caspase-1 activation. Cell Death Differ.？2007, 14, 1590–1604, doi:10.1038/sj.cdd.4402194. 17599095
[33]
Jandhyala, D.M.; Ahluwalia, A.; Obrig, T.; Thorpe, C.M. ZAK: A MAP3Kinase that transduces Shiga toxin- and ricin-induced proinflammatory cytokine expression. Cell Microbiol.？2008, 10, 1468–1477, doi:10.1111/j.1462-5822.2008.01139.x. 18331592
[34]
Manley, P.W.; Drueckes, P.; Fendrich, G.; Furet, P.; Liebetanz, J.; Martiny-Baron, G.; Mestan, J.; Trappe, J.; Wartmann, M.; Fabbro, D. Extended kinase profile and properties of the protein kinase inhibitor nilotinib. Biochim. Biophys. Acta？2010, 1804, 445–453, doi:10.1016/j.bbapap.2009.11.008. 19922818
Gasse, P.; Riteau, N.; Charron, S.; Girre, S.; Fick, L.; Petrilli, V.; Tschopp, J.; Lagente, V.; Quesniaux, V.F.; Ryffel, B.; Couillin, I. Uric acid is a danger signal activating NALP3 inflammasome in lung injury inflammation and fibrosis. Am. J. Respir. Crit. Care Med.？2009, 179, 903–913, doi:10.1164/rccm.200808-1274OC. 19218193
[37]
Martinon, F.; Mayor, A.; Tschopp, J. The inflammasomes: guardians of the body. Annu. Rev. Immunol.？2009, 27, 229–265, doi:10.1146/annurev.immunol.021908.132715. 19302040
[38]
Iordanov, M.S.; Pribnow, D.; Magun, J.L.; Dinh, T.H.; Pearson, J.A.; Chen, S.L.; Magun, B.E. Ribotoxic stress response: activation of the stress-activated protein kinase JNK1 by inhibitors of the peptidyl transferase reaction and by sequence-specific RNA damage to the alpha-sarcin/ricin loop in the 28S rRNA. Mol. Cell Biol.？1997, 17, 3373–3381. 9154836
[39]
Korcheva, V.; Wong, J.; Corless, C.; Iordanov, M.; Magun, B. Administration of ricin induces a severe inflammatory response via nonredundant stimulation of ERK, JNK, and P38 MAPK and provides a mouse model of hemolytic uremic syndrome. Am. J. Pathol.？2005, 166, 323–339, doi:10.1016/S0002-9440(10)62256-0. 15632024
[40]
Mariathasan, S. ASC, Ipaf and Cryopyrin/Nalp3: bona fide intracellular adapters of the caspase-1 inflammasome. Microbes Infect.？2007, 9, 664–671, doi:10.1016/j.micinf.2007.01.017. 17382568
[41]
Hoffman, H.M.; Mueller, J.L.; Broide, D.H.; Wanderer, A.A.; Kolodner, R.D. Mutation of a new gene encoding a putative pyrin-like protein causes familial cold autoinflammatory syndrome and Muckle-Wells syndrome. Nat. Genet.？2001, 29, 301–305, doi:10.1038/ng756. 11687797
[42]
Agostini, L.; Martinon, F.; Burns, K.; McDermott, M.F.; Hawkins, P.N.; Tschopp, J. NALP3 forms an IL-1beta-processing inflammasome with increased activity in Muckle-Wells autoinflammatory disorder. Immunity？2004, 20, 319–325, doi:10.1016/S1074-7613(04)00046-9. 15030775
