The Cellular Hypoxic Response upon Giardia Duodenalis Infection

DeMichele, Emily

The Cellular Hypoxic Response upon Giardia Duodenalis Infection

dc.contributor.advisor	Buret, Andre G.
dc.contributor.author	DeMichele, Emily
dc.contributor.committeemember	Hirota, Simon A.
dc.contributor.committeemember	Finney, Constance
dc.contributor.committeemember	Beck, Paul
dc.date	2024-11
dc.date.accessioned	2024-08-08T20:12:51Z
dc.date.available	2024-08-08T20:12:51Z
dc.date.issued	2024-08-08
dc.description.abstract	Oxygen tension plays an integral role in gastrointestinal homeostasis. When oxygen concentrations become suboptimal (hypoxia), mammalian cells rely on the hypoxia-inducible factor (HIF) to combat cellular stress and augment glycolytic flux. In the gastrointestinal epithelium, this cellular response is paramount as the luminal facing epithelial cells exist in a state of physiologic hypoxia that can be further altered by pathogens. Although growing evidence suggests tissue and blood protozoan parasites can activate HIF in a mammalian host, much remains to be understood in the context of enteric protozoan infections. This study uncovered the role of HIF-1α and associated epithelial hypoxic signature upon Giardia duodenalis infection, a leading cause of diarrheal disease worldwide. Coculture experiments were carried out using Caco-2 colonic epithelial cells infected with a human isolate of G. duodenalis (GSM) in normoxic (21% O2) or hypoxic (1% O2) conditions. Under normoxic conditions, infected cells displayed a time-dependent increase in HIF-1α protein expression, the oxygen-dependent subunit of HIF. This observation was concomitant with increased expression of HIF-target genes, including those responsible for combatting cellular stress (i.e., VEGFA, GADD45A, ANKRD37), and augmenting glycolytic flux (i.e., HK2, LDHA). Intracellular metabolomic analysis of normoxic infected cells revealed simultaneous increases in glucose-6-phosphate and lactate, the metabolic outputs of HK2 and LDHA, respectively. Under hypoxic conditions, HIF-1α stabilization was not significantly different compared to uninfected hypoxic control cells. However, HIF-target genes were still upregulated, albeit to a lesser degree compared to normoxic infected cells. Importantly, the metabolome of infected epithelial cells differed greatly between normoxic and hypoxic conditions, highlighting the influential role of oxygen during G. duodenalis infection. After 24 hours, HIF-1α stabilization and alterations to HIF-target gene expression were no longer detected. These findings indicate G. duodenalis induces a hypoxic response driven by HIF-1α stabilization in normoxic intestinal epithelial cells, while simply exacerbating this cellular response in hypoxic conditions. The stabilization of HIF-1α in the absence of oxygenic stress highlights a novel metabolic cell rescue mechanism in response to enteropathogens.
dc.identifier.citation	DeMichele, E. (2024). The cellular hypoxic response upon Giardia duodenalis infection (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/119366
dc.language.iso	en
dc.publisher.faculty	Graduate Studies
dc.publisher.institution	University of Calgary
dc.rights	University 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.subject	Giardia
dc.subject	Hypoxia
dc.subject	Gastrointestinal
dc.subject	Oxygen
dc.subject	Glycolysis
dc.subject.classification	Parasitology
dc.subject.classification	Biology--Molecular
dc.title	The Cellular Hypoxic Response upon Giardia Duodenalis Infection
dc.type	master thesis
thesis.degree.discipline	Biological Sciences
thesis.degree.grantor	University of Calgary
thesis.degree.name	Master of Science (MSc)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.