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Innate Immune Sensing of a Bacterial Pore-forming Toxin: The Role of the NLRP3 Inflammasome

Chu, Jessica (2010) Innate Immune Sensing of a Bacterial Pore-forming Toxin: The Role of the NLRP3 Inflammasome. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Gram-positive bacterial infections have risen over recent years and current antibiotic treatments are not always sufficient to control these infections. Specifically, antibiotics target bacteria themselves, but not the bacterially secreted proteins that contribute to bacterial pathogenesis and host tissue damage (i.e. virulence factors). These virulence factors may linger after bacteria are eradicated, making their interaction with the host important to understand for the development of novel therapeutics to supplement antibiotics. One class of virulence factors studied in our laboratory is a large pore-forming toxin family known as the cholesterol-dependent cytolysins (CDC). These exotoxins are secreted by over twenty species of gram-positive bacteria and have been shown to contribute to the virulence of the bacteria that secrete them. We are interested in exploring the pathways initiated by CDC in host innate immune cells such as macrophages and dendritic cells. These cells would be expected to first encounter CDC after bacterial infection and therefore, pathways initiated in these cells by CDC could be targeted for the benefit of the host.We have characterized the mechanism of mature IL-1beta secretion induced by CDC tetanolysin O (TLO) from LPS-primed murine bone marrow-derived macrophages (BMDM). This process is dependent on TLO dose and relies on the caspase-1-containing NLRP3 inflammasome as well as associated signaling pathways, which include ion fluxes and iPLA2 and cathepsin B activities. Furthermore, TLO induces different cell death programs in BMDM that are dependent on TLO dose. High TLO doses induce conventional necrotic cell death while low TLO doses cause NLRP3 inflammasome-dependent and cathepsin B-dependent necrotic cell death that is characterized by lactate dehydrogenase (LDH) and high mobility group box 1 (HMGB1) release. Both IL-1beta and HMGB1 are pro-inflammatory cytokines that contribute to inflammation and may be useful therapeutic targets, in addition to the inflammasome. Finally, susceptibility to CDC-induced cell killing varies based on cell type. In order to determine pathways that might explain these differences, we created a variant murine dendritic cell line resistant to pore formation. Though this cell line has been characterized to some degree, future studies will be needed to pinpoint the pathways responsible for the phenotype observed.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chu, Jessicajec44@pitt.eduJEC44
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairSalter, Russell D.rds@pitt.eduRDS
Committee MemberLarregina, Adriana T.adrianal@pitt.eduADRIANAL
Committee MemberMcClane, Bruce A.bamcc@mgb.pitt.eduBAMCC
Committee MemberKane, Lawrence P.lkane@pitt.eduLKANE
Committee MemberMorel, Penelope A.morel@pitt.eduMOREL
Date: 4 March 2010
Date Type: Completion
Defense Date: 28 January 2010
Approval Date: 4 March 2010
Submission Date: 7 February 2010
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Immunology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: IL-1; Innate Immunity; Cholesterol-dependent cytolysin; Macrophage; HMGB1; NLRP3 Inflammasome
Other ID:, etd-02072010-153303
Date Deposited: 10 Nov 2011 19:31
Last Modified: 15 Nov 2016 13:36


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