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Targeting NLRP3 and Staphylococcal pore-forming toxin receptors in human-induced pluripotent stem cell-derived
Seong H Chow1, Pankaj Deo1, Amy T Y Yeung2
1Infection & Immunity Program, Biomedicine Discovery Institute and Department of Biochemistry & Molecular Biology, Monash University, Clayton, Victoria, Australia.
Abstract:
Staphylococcus aureus causes necrotizing pneumonia by secreting toxins such as leukocidins that target front-line immune cells. The mechanism by which leukocidins kill innate immune cells and trigger inflammation during S. aureus lung infection, however, remains unresolved. Here, we explored human-induced pluripotent stem cell-derived macrophages (hiPSC-dMs) to study the interaction of the leukocidins Panton-Valentine leukocidin (PVL) and LukAB with lung macrophages, which are the initial leukocidin targets during S. aureus lung invasion. hiPSC-dMs were susceptible to the leukocidins PVL and LukAB and both leukocidins triggered NLPR3 inflammasome activation resulting in IL-1β secretion. hiPSC-dM cell death after LukAB exposure, however, was only temporarily dependent of NLRP3, although NLRP3 triggered marked cell death after PVL treatment. CRISPR/Cas9-mediated deletion of the PVL receptor, C5aR1, protected hiPSC-dMs from PVL cytotoxicity, despite the expression of other leukocidin receptors, such as CD45. PVL-deficient S. aureus had reduced ability to induce lung IL-1β levels in human C5aR1 knock-in mice. Unexpectedly, inhibiting NLRP3 activity resulted in increased wild-type S. aureus lung burdens. Our findings suggest that NLRP3 induces macrophage death and IL-1β secretion after PVL exposure and controls S. aureus lung burdens.
Insights
Staphylococcus aureus necrotizing pneumonia involves leukocidins targeting immune cells. NLRP3 inflammasome activation by Panton-Valentine leukocidin (PVL) causes macrophage death and IL-1β secretion, controlling bacterial lung burdens.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Staphylococcus aureus secretes leukocidins, potent toxins targeting immune cells.
- The precise mechanisms of leukocidin-induced immune cell death and inflammation in S. aureus lung infections are not fully understood.
- Lung macrophages are initial targets for leukocidins during S. aureus invasion.
Purpose of the Study:
- To investigate the interaction of Panton-Valentine leukocidin (PVL) and LukAB with human-induced pluripotent stem cell-derived macrophages (hiPSC-dMs).
- To elucidate the role of NLRP3 inflammasome activation in leukocidin-mediated cytotoxicity and cytokine secretion.
- To determine the in vivo relevance of PVL and its receptor C5aR1 in S. aureus lung infection models.
Main Methods:
- Utilized human-induced pluripotent stem cell-derived macrophages (hiPSC-dMs) for in vitro studies.
- Assessed leukocidin susceptibility, NLRP3 inflammasome activation, IL-1β secretion, and cell death.
- Employed CRISPR/Cas9 gene editing to delete the PVL receptor (C5aR1) in hiPSC-dMs.
- Investigated PVL-deficient S. aureus in human C5aR1 knock-in mouse models.
Main Results:
- Both PVL and LukAB triggered NLRP3 inflammasome activation and IL-1β secretion in hiPSC-dMs.
- PVL-induced hiPSC-dM death was dependent on NLRP3 and its receptor C5aR1.
- LukAB-induced cell death was only transiently dependent on NLRP3.
- PVL-deficient S. aureus showed reduced IL-1β induction in vivo.
- NLRP3 inhibition led to increased S. aureus lung burdens in mice.
Conclusions:
- NLRP3 inflammasome activation and subsequent IL-1β secretion are critical responses to PVL in macrophages.
- PVL-induced macrophage death, mediated by C5aR1, plays a role in controlling S. aureus lung infection.
- NLRP3 activation by PVL contributes to the host defense against S. aureus pneumonia.
