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Updated: May 29, 2026
Activation and Measurement of NLRP3 Inflammasome Activity Using IL-1β in Human Monocyte-derived Dendritic Cells
Published on: May 22, 2014
Francisella tularensis reveals a disparity between human and mouse NLRP3 inflammasome activation
Maninjay K Atianand1, Ellen B Duffy, Aaloki Shah
1Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York 12208, USA.
Abstract:
Pathogen-triggered activation of the inflammasome complex leading to caspase-1 activation and IL-1β production involves similar sensor proteins between mouse and human. However, the specific sensors used may differ between infectious agents and host species. In mice, Francisella infection leads to seemingly exclusive activation of the Aim2 inflammasome with no apparent role for Nlrp3. Here we examine the IL-1β response of human cells to Francisella infection. Francisella strains exhibit differences in IL-1β production by influencing induction of IL-1β and ASC transcripts. Unexpectedly, our results demonstrate that Francisella activates the NLRP3 inflammasome in human cells. Francisella infection of THP-1 cells elicits IL-1β production, which is reduced by siRNA targeting of NLRP3. Moreover, in reconstituted 293T cells, Francisella triggers assembly of the NLRP3 inflammasome complex. In addition, inhibitors of reactive oxygen species, cathepsin B, and K(+) efflux pathways, known to specifically influence NLRP3, substantially but not completely impair the Francisella-elicited IL-1β response, suggesting the involvement of another inflammasome pathway. Finally, shRNA targeting of NLRP3 and AIM2 reveals that both pathways contribute to the inflammasome response. Together these results establish NLRP3 as a cytosolic sensor for Francisella in human cells, a role not observed in mouse.
Insights
Francisella bacteria activate the NLRP3 inflammasome in human cells, unlike in mice. This finding reveals a new cytosolic sensor for Francisella, impacting IL-1β production.
Area of Science:
- Immunology
- Microbiology
- Cellular Biology
Background:
- Inflammasome activation is crucial for host defense against pathogens.
- While inflammasome sensors can be conserved, species-specific differences exist.
- In mice, Francisella infection primarily activates the Aim2 inflammasome, not Nlrp3.
Purpose of the Study:
- To investigate the inflammasome response of human cells to Francisella infection.
- To determine the specific inflammasome sensors involved in Francisella-induced IL-1β production in humans.
Main Methods:
- Utilized human cell lines (THP-1, 293T) infected with Francisella.
- Employed siRNA and shRNA to target NLRP3 and AIM2 inflammasome components.
- Assessed IL-1β production and inflammasome complex assembly.
- Used specific inhibitors for reactive oxygen species, cathepsin B, and K(+) efflux.
Main Results:
- Francisella infection induced IL-1β production in human THP-1 cells, reduced by NLRP3 knockdown.
- Francisella triggered NLRP3 inflammasome complex assembly in reconstituted 293T cells.
- Inhibitors targeting NLRP3-associated pathways partially impaired IL-1β production.
- Both NLRP3 and AIM2 pathways were found to contribute to the inflammasome response.
Conclusions:
- NLRP3 acts as a cytosolic sensor for Francisella in human cells, a role distinct from its function in mice.
- The Francisella-elicited IL-1β response in humans involves both NLRP3 and AIM2 inflammasomes.
- These findings highlight species-specific differences in inflammasome activation by Francisella.
