Characterization of NLRP3 in the Maintenance of Cardiac Tissue Homeostasis

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atmire.migration.oldid1946
dc.contributor.advisorDuff, Henry
dc.contributor.advisorBeck, Paul
dc.contributor.authorBracey, Nathan
dc.date.accessioned2014-02-13T18:50:55Z
dc.date.available2015-07-31T07:00:47Z
dc.date.issued2014-02-13
dc.date.submitted2014en
dc.description.abstractChronic cardiovascular diseases are characterized by tissue destruction and ongoing inflammation that impairs organ function. This non-microbial and chronic inflammation is mediated by pattern recognition receptors (PRRs). NLRP3 is one intracellular PRR that regulates pro-inflammatory cytokine secretion in response to endogenous signals from dying cells. While much in known regarding NLRP3 regulation of cytokine secretion, its broader function in diverse cell populations during cardiac injury has not been explored. Using murine models, we sought to characterize the role and expression of NLRP3 in chronic cardiovascular disease. We discovered that in addition to its established roles in regulating cytokine secretion, Nlrp3-/- mice were protected against Angiotensin II-induced hypertensive cardiac fibrosis despite negligible leukocytic infiltrate, apoptosis and cytokine processing. These results suggested the possibility of non-canonical signalling mechanisms in non-immune cells. We further explored the possibility of cytokine-independent roles for NLRP3 with the use of primary human and murine cell culture, microscopy and in vitro reporter systems. We began looking in cardiac fibroblasts, which displayed significant NLRP3 expression in left ventricular tissue samples from human patients with heart failure. NLRP3 was induced by pro-fibrotic signalling during cardiac fibroblast differentiation to myofibroblast phenotype by TGFβ. We found that NLRP3 augmented TGFβ-induced receptor associated Smad (R-Smad2/3) phosphorylation, nuclear accumulation and transcriptional activity in a Nucleotide Binding Domain-dependent mechanism. Interestingly, these phenotypes appeared independent from canonical NLRP3 signalling through caspase-1, IL-1β and IL-18. The ability of NLRP3 to regulate diverse cellular processes suggested a potentially broad function in cellular physiology. We went on to establish that endogenous NLRP3 localized to mitochondrial structures in primary human cardiac fibroblasts, macrophages and epithelial cell lines. Finally, using live-cell imaging and flow cytometry we found that NLRP3 potentiated the production of mitochondrial reactive oxygen species (ROS), which are required for TGFβ signalling and differentiation. Our results propose for the first time a general function for NLRP3 in structural and professional immune cells. A role for NLRP3 upstream of ROS offers a potentially unifying explanation for NLRP3 cytokine-dependent and independent pathways, and provides novel insight into the pathogenesis of chronic inflammation and fibrosis in cardiovascular disease.en_US
dc.description.embargotermsindefiniteen_US
dc.identifier.citationBracey, N. (2014). Characterization of NLRP3 in the Maintenance of Cardiac Tissue Homeostasis (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25279en_US
dc.identifier.doihttp://dx.doi.org/10.11575/PRISM/25279
dc.identifier.urihttp://hdl.handle.net/11023/1377
dc.language.isoeng
dc.publisher.facultyGraduate Studies
dc.publisher.institutionUniversity of Calgaryen
dc.publisher.placeCalgaryen
dc.rightsUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subjectBiology--Cell
dc.subjectBiology--Molecular
dc.subject.classificationInflammationen_US
dc.subject.classificationHeart Diseaseen_US
dc.subject.classificationFibrosisen_US
dc.titleCharacterization of NLRP3 in the Maintenance of Cardiac Tissue Homeostasis
dc.typedoctoral thesis
thesis.degree.disciplineMedical Science
thesis.degree.grantorUniversity of Calgary
thesis.degree.nameDoctor of Philosophy (PhD)
ucalgary.item.requestcopytrue
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