Human respiratory syncytial virus (RSV) constitute highly pathogenic virus that cause severe respiratory diseases in newborn, children, elderly and immuno-compromised individuals. Airway inflammation is a critical regulator of disease outcome in RSV infected hosts. Although “controlled” inflammation is required for virus clearance, aberrant and exaggerated inflammation during RSV infection results in development of inflammatory diseases like pneumonia and bronchiolitis. Interleukin-1β (IL-1β) plays an important role in inflammation by orchestrating the pro-inflammatory response. IL-1β is synthesized as an immature pro-IL-1β form. It is cleaved by activated caspase-1 to yield mature IL-1β that is secreted extracellularly. Activation of caspase-1 is mediated by a multi-protein complex known as the inflammasome. Although RSV infection results in IL-1β release, the mechanism is unknown. Here in, we have characterized the mechanism of IL-1β secretion following RSV infection. Our study revealed that NLRP3/ASC inflammasome activation is crucial for IL-1β production during RSV infection. Further studies illustrated that prior to inflammasome formation; the “first signal” constitutes activation of toll-like receptor-2 (TLR2)/MyD88/NF-κB pathway. TLR2/MyD88/NF-κB signaling is required for pro-IL-1β and NLRP3 gene expression during RSV infection. Following expression of these genes, two “second signals” are essential for triggering inflammasome activation. Intracellular reactive oxygen species (ROS) and potassium (K+) efflux due to stimulation of ATP-sensitive ion channel promote inflammasome activation following RSV infection. Thus, our studies have underscored the requirement of TLR2/MyD88/NF-κB pathway (first signal) and ROS/potassium efflux (second signal) for NLRP3/ASC inflammasome formation, leading to caspase-1 activation and subsequent IL-1β release during RSV infection.
References
[1]
Hall CB (2001) Respiratory syncytial virus and parainfluenza virus. N Engl J Med 344: 1917–1928.
[2]
Ruuskanen O, Lahti E, Jennings LC, Murdoch DR (2011) Viral pneumonia. Lancet 377(9773): 1264–1275.
Kawai T, Akira S (2006) Innate immune recognition of viral infection. Nat Immunol 7: 131–137.
[5]
Bose S, Banerjee AK (2003) Innate immune response against nonsegmented negative strand RNA viruses. J Interferon Cytokine Res 23: 401–412.
[6]
O'Neill LA, Bowie AG (2010) Sensing and signaling in antiviral innate immunity. Curr Biol 20(7): R328–333. Review.
[7]
Rathinam VA, Fitzgerald KA (2010) Inflammasomes and anti-viral immunity. J Clin Immunol 30(5): 632–637.
[8]
Schmitz N, Kurrer M, Bachmann MF, Kopf M (2005) Interleukin-1 is responsible for acute lung immunopathology but increases survival of respiratory influenza virus infection. J Virol 79: 6441–6448.
[9]
Blanco JC, Richardson JY, Darnell ME, Rowzee A, Pletneva L, et al. (2002) Cytokine and chemokine gene expression after primary and secondary respiratory syncytial virus infection in cotton rats. J Infect Dis 185: 1780–1785.
[10]
Guerrero-Plata A, Casola A, Garofalo RP (2005) Human metapneumovirus induces a profile of lung cytokines distinct from that of respiratory syncytial virus. J Virol 79: 14992–14997.
[11]
Lindgren C, Gr？gaard J (1996) Reflex apnoea response and inflammatory mediators in infants with respiratory tract infection. Acta Paediatr 85: 798–803.
[12]
Bermejo-Martin JF, Garcia-Arevalo MC, De Lejarazu RO, Ardura J, Eiros JM, et al. (2007) Predominance of Th2 cytokines, CXC chemokines and innate immunity mediators at the mucosal level during severe respiratory syncytial virus infection in children. Eur Cytokine Netw 18: 162–167.
[13]
Becker CE, Creagh EM, O'Neill LA (2009) Rab39a binds caspase-1 and is required for caspase-1-dependent interleukin-1β secretion. Biol Chem 284(50): 34531–34537.
[14]
Davis BK, Wen H, Ting JP (2011) The inflammasome NLRs in immunity, inflammation, and associated diseases. Annu Rev Immunol 29: 707–735.
[15]
Bryant C, Fitzgerald KA (2009) Molecular mechanisms involved in inflammasome activation. Trends Cell Biol 19(9): 455–464.
[16]
Franchi L, Eigenbrod T, Mu？oz-Planillo R, Nu？ez G (2009) The inflammasome: a caspase-1-activation platform that regulates immune responses and disease pathogenesis. Nat Immunol 10(3): 241–247.
[17]
Lamkanfi M, Dixit VM (2009) The inflammasomes. PLoS Pathog 5(12): e1000510.
[18]
Schroder K, Tschopp J (2010) The inflammasomes. Cell 140(6): 821–832.
[19]
Martinon F, Mayor A, Tschopp J (2009) The inflammasomes: guardians of the body. Annu Rev Immunol 27: 229–265.
Ye Z, Ting JP (2008) NLR, the nucleotide-binding domain leucine-rich repeat containing gene family. Curr Opin Immunol 20(1): 3–9.
[22]
Franchi L, Warner N, Viani K, Nu？ez G (2009) Function of Nod-like receptors in microbial recognition and host defense. Immunol Rev 227(1): 106–128.
[23]
Tannahill GM, O'Neill LA (2011) The emerging role of metabolic regulation in the functioning of Toll-like receptors and the NOD-like receptor Nlrp3. FEBS Lett 585(11): 1568–1572.
[24]
Masters SL, Latz E, O'Neill LA (2011) The inflammasome in atherosclerosis and type 2 diabetes. Sci Transl Med 3(81): 81ps17.
[25]
Masters SL, Dunne A, Subramanian SL, Hull RL, Tannahill GM, et al. (2010) Activation of the NLRP3 inflammasome by islet amyloid polypeptide provides a mechanism for enhanced IL-1β in type 2 diabetes. Nat Immunol 11(10): 897–904.
[26]
Franchi L, Mu？oz-Planillo R, Reimer T, Eigenbrod T, Nú？ez G (2010) Inflammasomes as microbial sensors. Eur J Immunol 40(3): 611–615.
[27]
Schroder K, Zhou R, Tschopp J (2010) The NLRP3 inflammasome: a sensor for metabolic danger? Science 327(5963): 296–300.
[28]
Vandanmagsar B, Youm YH, Ravussin A, Galgani JE, Stadler K, et al. (2011) The NLRP3 inflammasome instigates obesity-induced inflammation and insulin resistance. Nat Med 17(2): 179–188.
[29]
Jin C, Flavell RA (2010) Molecular mechanism of NLRP3 inflammasome activation. J Clin Immunol 30(5): 628–631.
[30]
Thomas PG, Dash P, Aldridge JR Jr, Ellebedy AH, Reynolds C, et al. (2009) The intracellular sensor NLRP3 mediates key innate and healing responses to influenza A virus via the regulation of caspase-1. Immunity 30(4): 566–575.
[31]
Allen IC, Scull MA, Moore CB, Holl EK, McElvania-TeKippe E, et al. (2009) The NLRP3 inflammasome mediates in vivo innate immunity to influenza A virus through recognition of viral RNA. Immunity 30(4): 556–565.
[32]
Ichinohe T, Lee HK, Ogura Y, Flavell R, Iwasaki A (2009) Inflammasome recognition of influenza virus is essential for adaptive immune responses. J Exp Med 206(1): 79–87.
[33]
Kanneganti TD, Body-Malapel M, Amer A, Park JH, Whitfield J, et al. (2006) Critical role for Cryopyrin/Nalp3 in activation of caspase-1 in response to viral infection and double-stranded RNA. J Biol Chem 281(48): 36560–36568.
[34]
Kanneganti TD (2010) Central roles of NLRs and inflammasomes in viral infection. Nat Rev Immunol 10(10): 688–698.
[35]
Rajam？ki K, Lappalainen J, O？rni K, V？lim？ki E, Matikainen S, et al. (2010) Cholesterol crystals activate the NLRP3 inflammasome in human macrophages: a novel link between cholesterol metabolism and inflammation. PLoS One 5(7): e11765.
[36]
Wen H, Gris D, Lei Y, Jha S, Zhang L, et al. (2011) Fatty acid-induced NLRP3-ASC inflammasome activation interferes with insulin signaling. Nat Immunol 12(5): 408–415.
[37]
Duewell P, Kono H, Rayner KJ, Sirois CM, Vladimer G, et al. (2010) NLRP3 inflammasomes are required for atherogenesis and activated by cholesterol crystals. Nature 464(7293): 1357–1361.
[38]
Netea MG, Nold-Petry CA, Nold MF, Joosten LA, Opitz B, et al. (2009) Differential requirement for the activation of the inflammasome for processing and release of IL-1β in monocytes and macrophages. Blood 113(10): 2324–2335.
[39]
O'Neill LA (2006) How Toll-like receptors signal: what we know and what we don't know. Curr Opin Immunol 18: 3–9.
[40]
Sabbah A, Chang TH, Harnack R, Frohlich V, Tominaga K, et al. (2009) Activation of innate immune antiviral responses by Nod2. Nat Immunol 10(10): 1073–1080.
[41]
Duncan JA, Gao X, Huang MT, O'Connor BP, Thomas CE, et al. (2009) Neisseria gonorrhoeae activates the proteinase cathepsin B to mediate the signaling activities of the NLRP3 and ASC-containing inflammasome. J Immunol 182(10): 6460–6469.
[42]
Bauernfeind FG, Horvath G, Stutz A, Alnemri ES, MacDonald K, et al. (2009) NF-κB activating pattern recognition and cytokine receptors license NLRP3 inflammasome activation by regulating NLRP3 expression. J Immunol 183(2): 787–791.
[43]
Franchi L, Eigenbrod T, Nunez G (2009) Cutting edge: TNF-α mediates sensitization to ATP and silica via the NLRP3 inflammasome in the absence of microbial stimulation. J Immunol 183: 792–796.
[44]
O'Connor W Jr, Harton JA, Zhu X, Linhoff MW, Ting JP (2003) Cutting edge: CIAS1/cryopyrin/PYPAF1/NALP3/CATERPILLER 1.1 is an inducible inflammatory mediator with NF-κB suppressive properties. J Immunol 171: 6329–6333.
[45]
Harder J, Franchi L, Mu？oz-Planillo R, Park JH, Reimer T, et al. (2009) Activation of the Nlrp3 inflammasome by Streptococcus pyogenes requires streptolysin O and NF-κB activation but proceeds independently of TLR signaling and P2X7 receptor. J Immunol 183(9): 5823–5829.
[46]
Bose S, Kar N, Maitra R, Didonato J, Banerjee AK (2003) Temporal activation of NF-κB regulates an interferon independent innate anti-viral response against cytoplasmic RNA viruses. Proc Natl Acad Sci U S A 100: 10890–10895.
[47]
Kota S, Sabbah A, Chang TH, Harnack R, Xiang Y, et al. (2008) Role of human beta-defensin-2 during tumor necrosis factor-alpha/NF-κB mediated innate anti-viral response against human respiratory syncytial virus. J Biol Chem 283: 22417–22429.
[48]
Echchgadda I, Kota S, DeLa Cruz I, Sabbah A, Chatterjee B, et al. (2009) Anti-cancer oncolytic activity of respiratory syncytial virus. Cancer Gene Ther 16: 923–935.
[49]
Tian B, Zhang Y, Luxon BA, Garofalo RP, Casola A, et al. (2002) Identification of NF-κB-dependent gene networks in respiratory syncytial virus-infected cells. J Virol 76(13): 6800–6814.
[50]
Mastronarde JG, He B, Monick MM, Mukaida N, Matsushima K, et al. (1996) Induction of interleukin (IL)-8 gene expression by respiratory syncytial virus involves activation of nuclear factor (NF)- κB and NF-IL-6. J Infect Dis 174(2): 262–7.
[51]
Toma C, Higa N, Koizumi Y, Nakasone N, Ogura Y, et al. (2010) Pathogenic Vibrio activate NLRP3 inflammasome via cytotoxins and TLR/nucleotide-binding oligomerization domain-mediated NF-κB signaling. J Immunol 184(9): 5287–5297.
[52]
Lamkanfi M, Malireddi RK, Kanneganti TD (2009) Fungal zymosan and mannan activate the cryopyrin inflammasome. J Biol Chem 284(31): 20574–20581.
[53]
Babelova A, Moreth K, Tsalastra-Greul W, Zeng-Brouwers J, Eickelberg O, et al. (2009) Biglycan, a danger signal that activates the NLRP3 inflammasome via toll-like (TLR2/4) and P2X receptors. J Biol Chem 284(36): 24035–24048.
[54]
Delaloye J, Roger T, Steiner-Tardivel QG, Le Roy D, Knaup Reymond M, et al. (2009) Innate immune sensing of modified vaccinia virus Ankara (MVA) is mediated by TLR2-TLR6, MDA-5 and the NALP3 inflammasome. PLoS Pathog 5(6): e1000480.
[55]
van de Veerdonk FL, Joosten LA, Devesa I, Mora-Montes HM, Kanneganti TD, et al. (2009) Bypassing pathogen-induced inflammasome activation for the regulation of interleukin-1β production by the fungal pathogen Candida albicans. J Infect Dis 199(7): 1087–1096.
[56]
Haynes LM, Moore DD, Kurt-Jones EA, Finberg RW, Anderson LJ, et al. (2001) Involvement of toll-like receptor 4 in innate immunity to respiratory syncytial virus. J Virol 75(22): 10730–10737.
[57]
Kurt-Jones EA, Popova L, Kwinn L, Haynes LM, Jones LP, et al. (2000) Pattern recognition receptors TLR4 and CD14 mediate response to respiratory syncytial virus. Nat Immunol 1(5): 398–401.
[58]
Murawski MR, Bowen GN, Cerny AM, Anderson LJ, Haynes LM, et al. (2009) Respiratory syncytial virus activates innate immunity through Toll-like receptor 2. J Virol 83(3): 1492–1500.
[59]
Dostert C, Guarda G, Romero JF, Menu P, Gross O, et al. (2009) Malarial hemozoin is a Nalp3 inflammasome activating danger signal. PLoS One 4: e6510.
[60]
Dostert C, Petrilli V, Van Bruggen R, Steele C, Mossman BT, et al. (2008) Innate immune activation through Nalp3 inflammasome sensing of asbestos and silica. Science 320: 674–677.
[61]
Cassel SL, Eisenbarth SC, Iyer SS, Sadler JJ, Colegio OR, et al. (2008) The Nalp3 inflammasome is essential for the development of silicosis. Proc Natl Acad Sci U S A 105: 9035–9040.
[62]
Meissner F, Molawi K, Zychlinsky A (2008) Superoxide dismutase 1 regulates caspase-1 and endotoxic shock. Nat Immunol 9: 866–872.
[63]
Zhou R, Tardivel A, Thorens B, Choi I, Tschopp J (2010) Thioredoxin-interacting protein links oxidative stress to inflammasome activation. Nat Immunol 11: 136–140.
[64]
Sa？d-Sadier N, Padilla E, Langsley G, Ojcius DM (2010) Aspergillus fumigatus stimulates the NLRP3 inflammasome through a pathway requiring ROS production and the Syk tyrosine kinase. PLoS One 5(4): e10008.
[65]
Barlan AU, Griffin TM, McGuire KA, Wiethoff CM (2011) Adenovirus membrane penetration activates the NLRP3 inflammasome. J Virol 85(1): 146–155.
[66]
Liu T, Castro S, Brasier AR, Jamaluddin M, Garofalo RP, et al. (2004) Reactive oxygen species mediate virus-induced STAT activation: role of tyrosine phosphatases. J Biol Chem 279(4): 2461–2469.
[67]
Castro SM, Guerrero-Plata A, Suarez-Real G, Adegboyega PA, Colasurdo GN, et al. (2006) Antioxidant treatment ameliorates respiratory syncytial virus-induced disease and lung inflammation. Am J Respir Crit Care Med 174(12): 1361–1369.
[68]
Bauernfeind F, Bartok E, Rieger A, Franchi L, Nú？ez G, et al. (2011) Reactive Oxygen Species Inhibitors Block Priming, but Not Activation, of the NLRP3 Inflammasome. J Immunol 187(2): 613–617.
[69]
Okada SF, Zhang L, Kreda SM, Abdullah LH, Davis CW, et al. (2011) Coupled Nucleotide and Mucin Hypersecretion from Goblet Cell Metaplastic Human Airway Epithelium. Am J Respir Cell Mol Biol 45(2): 253–260.
[70]
Davis IC, Lazarowski ER, Hickman-Davis JM, Fortenberry JA, Chen FP, et al. (2006) Leflunomide prevents alveolar fluid clearance inhibition by respiratory syncytial virus. Am J Respir Crit Care Med 173(6): 673–682.
[71]
Abdul-Sater AA, Koo E, H？cker G, Ojcius DM (2009) Inflammasome-dependent caspase-1 activation in cervical epithelial cells stimulates growth of the intracellular pathogen Chlamydia trachomatis. J Biol Chem 284(39): 26789–26796.
[72]
Qu Y, Franchi L, Nunez G, Dubyak GR (2007) Nonclassical IL-1β secretion stimulated by P2X7 receptors is dependent on inflammasome activation and correlated with exosome release in murine macrophages. J Immunol 179(3): 1913–1925.
[73]
Hornung V, Ablasser A, Charrel-Dennis M, Bauernfeind F, Horvath G, et al. (2009) AIM2 recognizes cytosolic dsDNA and forms a caspase-1-activating inflammasome with ASC. Nature 458(7237): 514–518.
[74]
Poeck H, Bscheider M, Gross O, Finger K, Roth S, et al. (2010) Recognition of RNA virus by RIG-I results in activation of CARD9 and inflammasome signaling for interleukin 1β production. Nat Immunol 11(1): 63–69.
[75]
Rathinam VA, Jiang Z, Waggoner SN, Sharma S, Cole LE, et al. (2010) The AIM2 inflammasome is essential for host defense against cytosolic bacteria and DNA viruses. Nat Immunol 11(5): 395–402.
[76]
Ichinohe T, Pang IK, Iwasaki A (2010) Influenza virus activates inflammasomes via its intracellular M2 ion channel. Nat Immunol 11(5): 404–410.
[77]
Maitra R, Clement CC, Scharf B, Crisi GM, Chitta S, et al. (2009) Endosomal damage and TLR2 mediated inflammasome activation by alkane particles in the generation of aseptic osteolysis. Mol Immunol 47(2–3): 175–184.
[78]
Pazdrak K, Olszewska-Pazdrak B, Liu T, Takizawa R, Brasier AR, et al. (2002) MAPK activation is involved in posttranscriptional regulation of RSV-induced RANTES gene expression. Am J Physiol Lung Cell Mol Physiol 283(2): L364–372.
[79]
Chen W, Monick MM, Carter AB, Hunninghake GW (2000) Activation of ERK2 by respiratory syncytial virus in A549 cells is linked to the production of interleukin 8. Exp Lung Res 26(1): 13–26.
[80]
Zhou R, Yazdi AS, Menu P, Tschopp J (2011) A role for mitochondria in NLRP3 inflammasome activation. Nature 469(7329): 221–225.
[81]
Naik E, Dixit VM (2011) Mitochondrial reactive oxygen species drive proinflammatory cytokine production. J Exp Med 208(3): 417–420.
[82]
Gurcel L, Abrami L, Girardin S, Tschopp J, van der Goot FG (2006) Caspase-1 activation of lipid metabolic pathways in response to bacterial pore-forming toxins promotes cell survival. Cell 126(6): 1135–1145.
[83]
Mariathasan S, Weiss DS, Newton K, McBride J, O'Rourke K, et al. (2006) Cryopyrin activates the inflammasome in response to toxins and ATP. Nature 440(7081): 228–232.
[84]
Chu J, Thomas LM, Watkins SC, Franchi L, Nú？ez G, et al. (2009) Cholesterol-dependent cytolysins induce rapid release of mature IL-1β from murine macrophages in a NLRP3 inflammasome and cathepsin B-dependent manner. J Leukoc Biol 86(5): 1227–1238.
[85]
Franchi L, Kanneganti TD, Dubyak GR, Nú？ez G (2007) Differential requirement of P2X7 receptor and intracellular K+ for caspase-1 activation induced by intracellular and extracellular bacteria. J Biol Chem 282(26): 18810–18818.
[86]
Wickliffe KE, Leppla SH, Moayeri M (2008) Anthrax lethal toxin-induced inflammasome formation and caspase-1 activation are late events dependent on ion fluxes and the proteasome. Cell Microbiol 2008 10(2): 332–343.
[87]
Fink SL, Bergsbaken T, Cookson BT (2008) Anthrax lethal toxin and Salmonella elicit the common cell death pathway of caspase-1-dependent pyroptosis via distinct mechanisms. Proc Natl Acad Sci U S A 105(11): 4312–4317.
[88]
Gross O, Poeck H, Bscheider M, Dostert C, Hannesschl？ger N, et al. (2009) Syk kinase signalling couples to the Nlrp3 inflammasome for anti-fungal host defence. Nature 459(7245): 433–436.
[89]
Kankkunen P, Teiril？ L, Rintahaka J, Alenius H, Wolff H, et al. (2010) (1,3)-beta-glucans activate both dectin-1 and NLRP3 inflammasome in human macrophages. J Immunol 184(11): 6335–6342.
[90]
Cassel SL, Eisenbarth SC, Iyer SS, Sadler JJ, Colegio OR, et al. (2008) The Nalp3 inflammasome is essential for the development of silicosis. Proc Natl Acad Sci U S A 105(26): 9035–9040.
[91]
Allam R, Darisipudi MN, Rupanagudi KV, Lichtnekert J, Tschopp J, et al. (2011) Cyclic polypeptide and aminoglycoside antibiotics trigger IL-1β secretion by activating the NLRP3 inflammasome. J Immunol 186(5): 2714–2718.
[92]
Ueba O (1978) Respiratory syncytial virus - concentration and purification of the infectious virus. Acta Med Okayama 32: 265–272.
[93]
Racoosin EL, Swanson JA (1989) Macrophage colony stimulating factor (rM-CSF) stimulates pinocytosis in bone marrow-derived macrophages. J Exp Med 170: 1635–1648.
