Listeria monocytogenes-infected human peripheral blood mononuclear cells produce IL-1beta, depending on listeriolysin O and NLRP3.
Different NOD-like receptors, including NLRP1, NLRP3, and NLRC4, as well as the recently identified HIN-200 protein, AIM2, form multiprotein complexes called inflammasomes, which mediate caspase-1-dependent processing of pro-IL-1beta. Listeria monocytogenes is an intracellular pathogen that is actively phagocytosed by monocytes/macrophages and subsequently escapes from the phagosome into the host cell cytosol, depending on its pore-forming toxin listeriolysin O (LLO). In this study, we demonstrate that human PBMCs produced mature IL-1beta when infected with wild-type L. monocytogenes or when treated with purified LLO. L. monocytogenes mutants lacking LLO or expressing a noncytolytic LLO as well as the avirulent Listeria innocua induced strongly impaired IL-1beta production. RNA interference and inhibitor experiments in human PBMCs as well as experiments in Nlrp3 and Rip2 knockout bone marrow-derived macrophages demonstrated that the Listeria-induced IL-1beta release was dependent on ASC, caspase-1, and NLRP3, whereas NOD2, Rip2, NLRP1, NLRP6, NLRP12, NLRC4, and AIM2 appeared to be dispensable. We found that L. monocytogenes-induced IL-1beta production was largely dependent on phagosomal acidification and cathepsin B release, whereas purified LLO activated an IL-1beta production independently of these mechanisms. Our results indicate that L. monocytogenes-infected human PBMCs produced IL-1beta, largely depending on an LLO-mediated phagosomal rupture and cathepsin B release, which is sensed by Nlrp3. In addition, an LLO-dependent but cathepsin B-independent NLRP3 activation might contribute to some extent to the IL-1beta production in L. monocytogenes-infected cells.
Meixenberger
Karolin
K
Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité Universitätsmedizin Berlin, Berlin, Germany.
Pache
Florence
F
Eitel
Julia
J
Schmeck
Bernd
B
Hippenstiel
Stefan
S
Slevogt
Hortense
H
N'Guessan
Philippe
P
Witzenrath
Martin
M
Netea
Mihai G
MG
Chakraborty
Trinad
T
Suttorp
Norbert
N
Opitz
Bastian
B
D000818:Animals; D001427:Bacterial Toxins; D002352:Carrier Proteins / Q000502:physiology*; D002401:Cathepsin B / Q000378:metabolism; D002460:Cell Line; D006360:Heat-Shock Proteins / Q000502:physiology*; D006460:Hemolysin Proteins / Q000502:physiology*; D006801:Humans; D053583:Interleukin-1beta / Q000096:biosynthesis*; D007963:Leukocytes, Mononuclear / Q000378:metabolism / Q000382:microbiology*; D008089:Listeria monocytogenes / Q000276:immunology* / Q000472:pathogenicity; D008264:Macrophages; D051379:Mice; D008810:Mice, Inbred C57BL; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010588:Phagosomes
D001427:Bacterial Toxins; D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D002401:Cathepsin B; C038705:hlyA protein, Listeria monocytogenes