Giardia duodenalis stabilizes HIF-1α and induces glycolytic alterations in intestinal epithelial cells

The gastrointestinal epithelium relies on activation of the hypoxia-inducible factor (HIF) to promote cell survival and maintain bioenergetic homeostasis during hypoxia. While many pathogens can activate HIF, the effects of enteric protozoa on HIF activation in gastrointestinal epithelial cells remain unclear. Giardia duodenalis, a prevalent protozoan enteropathogen, causes intestinal barrier dysfunction characterized by epithelial malabsorption, mucus depletion, altered mucin glycosylation, and microbiota dysbiosis. Findings from the present study reveal an epithelial hypoxic signature upon Giardia infection. Human intestinal epithelial cells were exposed to vehicle or Giardia duodenalis isolate GS/M under normoxic (21% O₂) or hypoxic (1% O₂) conditions. In normoxia, infected cells displayed a time-dependent increase in HIF-1α protein expression, the oxygen-dependent subunit of HIF-1. In normoxia, Giardia infection upregulated HIF-1 target genes involved in cellular stress (i.e., VEGFA, ANKRD37, GADD45A) and glycolysis (i.e., HK2, LDHA). This was accompanied by changes in the abundance of glycolytic intermediates (i.e., glucose-6-phosphate, pyruvate, lactate). Although infection in hypoxia failed to augment the hypoxia-induced HIF-1α stabilization, HIF-1 target genes were still upregulated, albeit to a lesser degree. These findings indicate that Giardia induces a transient epithelial hypoxic response in normoxic conditions, revealing a hitherto unrecognized epithelial rescue response to this intestinal parasite.