title: Metabolism of HeLa cells revealed through autofluorescence lifetime upon infection with enterohemorrhagic Escherichia coli.
abstract: Fluorescence lifetime imaging microscopy (FLIM) is a sensitive technique in monitoring functional and conformational states of nicotinamide adenine dinucleotide reduced (NADH) and flavin adenine dinucleotide (FAD),main compounds participating in oxidative phosphorylation in cells. In this study, we have applied FLIM to characterize the metabolic changes in HeLa cells upon bacterial infection and made comparison with the results from the cells treated with staurosporine (STS), a well-known apoptosis inducer. The evolving of NADH's average autofluorescence lifetime during the 3 h after infection with enterohemorragic Escherichia coli (EHEC) or STS treatment has been observed. The ratio of the short and the long lifetime components' relative contributions of NADH increases with time, a fact indicating cellular metabolic activity, such as a decrease of oxidative phosphorylation over the course of infection, while opposite dynamics is observed in FAD. Being associated with mitochondria, FAD lifetimes and redox ratio could indicate heterogeneous mitochondrial function, microenvironment with bacterial infection, and further pathway to cell death. The redox ratios for both EHEC-infected and STS-treated HeLa cells have been observed and these observations also indicate possible apoptosis induced by bacterial infection.
authors.affiliation: Institute of Biophotonics, National Yang-Ming University, 155 Linong Street, Section 2, Taipei 11221, Taiwan.
authors.forename: Tatyana Yu
authors.initials: TY
authors.lastname: Buryakina
authors.forename: Pin-Tzu
authors.initials: PT
authors.lastname: Su
authors.forename: Wan
authors.initials: W
authors.lastname: Syu
authors.forename: C Allen
authors.initials: CA
authors.lastname: Chang
authors.forename: Hsiu-Fang
authors.initials: HF
authors.lastname: Fan
authors.forename: Fu-Jen
authors.initials: FJ
authors.lastname: Kao
mesh_terms: D017209:Apoptosis; D054324:Enterohemorrhagic Escherichia coli / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism; D005434:Flow Cytometry; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods*; D008954:Models, Biological; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D061848:Optical Imaging / Q000379:methods*
chemical_list: D009243:NAD; D005182:Flavin-Adenine Dinucleotide