title: FLIM and emission spectral analysis of caspase-3 activation inside single living cell during anticancer drug-induced cell death.
abstract: Two-photon excitation (TPE) fluorescence lifetime imaging microscopy (FLIM) and emission spectral imaging (ESI) are powerful tools for fluorescence resonance energy transfer (FRET) measurement. In this study, we use these two techniques to analyze caspase-3 activation inside single living cells during anticancer drug-induced human lung adenocarcinoma (ASTC-a-1) cell death. TPE-ESI of SCAT3, a caspase-3 indicator based on FRET, was performed inside single living cell stably expressing SCAT3. The TPE-ESI measurement was performed using 780 nm excitation which was considered to selectively excite the donor ECFP of SCAT3 by measuring the emission ratio of 526 to 476 nm. The emission peak at 526 nm disappeared and that of 476 nm increased after STS or bufalin treatment, but taxol treatment did not induce a significant change for the SCAT3 emission spectra, indicating that caspase-3 was activated during STS- or bufalin-induced cell apoptosis, but was not involved in taxol-induced PCD. Fluorescence lifetime of ECFP inside living cells was acquired using FLIM. The lifetime of ECFP was the same as that of the control group after taxol treatment, but increased from 1.83 +/- 0.02 to 2.05 +/- 0.03 and 1.90 +/- 0.03 ns, respectively after STS and bufalin treatment, which agree with the results obtained using TPE-ESI. Taken together, TPE-FLIM and ESI analysis were proved to be valuable approaches for monitoring caspase-3 activation inside single living cells.
authors.affiliation: MOE Key Libratory of Laser Life Science and Institute of Laser Life Science, South China Normal University, 510631, Guangzhou, China.
authors.forename: Wenliang
authors.initials: W
authors.lastname: Pan
authors.forename: Junle
authors.initials: J
authors.lastname: Qu
authors.forename: Tongsheng
authors.initials: T
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Sun
authors.forename: Jing
authors.initials: J
authors.lastname: Qi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002018:Bufanolides / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival; D004789:Enzyme Activation; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D049452:Green Fluorescent Proteins; D006801:Humans; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D036641:Microscopy, Fluorescence, Multiphoton; D017239:Paclitaxel / Q000494:pharmacology*; D038761:Photobleaching; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D002018:Bufanolides; C527701:enhanced cyan fluorescent protein; D049452:Green Fluorescent Proteins; D053148:Caspase 3; D019311:Staurosporine; D017239:Paclitaxel; C022777:bufalin