title: Probing the dynamics of doxorubicin-DNA intercalation during the initial activation of apoptosis by fluorescence lifetime imaging microscopy (FLIM).
abstract: Doxorubicin is a potent anthracycline antibiotic, commonly used to treat a wide range of cancers. Although postulated to intercalate between DNA bases, many of the details of doxorubicin's mechanism of action remain unclear. In this work, we demonstrate the ability of fluorescence lifetime imaging microscopy (FLIM) to dynamically monitor doxorubicin-DNA intercalation during the earliest stages of apoptosis. The fluorescence lifetime of doxorubicin in nuclei is found to decrease rapidly during the first 2 hours following drug administration, suggesting significant changes in the doxorubicin-DNA binding site's microenvironment upon apoptosis initiation. Decreases in doxorubicin fluorescence lifetimes were found to be concurrent with increases in phosphorylation of H2AX (an immediate signal of DNA double-strand breakage), but preceded activation of caspase-3 (a late signature of apoptosis) by more than 150 minutes. Time-dependent doxorubicin FLIM analyses of the effects of pretreating cells with either Cyclopentylidene-[4-(4-chlorophenyl)thiazol-2-yl)-hydrazine (a histone acetyltransferase inhibitor) or Trichostatin A (a histone deacetylase inhibitor) revealed significant correlation of fluorescence lifetime with the stage of chromatin decondensation. Taken together, our findings suggest that monitoring the dynamics of doxorubicin fluorescence lifetimes can provide valuable information during the earliest phases of doxorubicin-induced apoptosis; and implicate that FLIM can serve as a sensitive, high-resolution tool for the elucidation of intercellular mechanisms and kinetics of anti-cancer drugs that bear fluorescent moieties.
authors.affiliation: Division of Medical Engineering Research, National Health Research Institutes, Zhunan, Taiwan.
authors.forename: Nai-Tzu
authors.initials: NT
authors.lastname: Chen
authors.forename: Chia-Yan
authors.initials: CY
authors.lastname: Wu
authors.forename: Chao-Yu
authors.initials: CY
authors.lastname: Chung
authors.forename: Yeukuang
authors.initials: Y
authors.lastname: Hwu
authors.forename: Shih-Hsun
authors.initials: SH
authors.lastname: Cheng
authors.forename: Chung-Yuan
authors.initials: CY
authors.lastname: Mou
authors.forename: Leu-Wei
authors.initials: LW
authors.lastname: Lo
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004317:Doxorubicin / Q000378:metabolism* / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007364:Intercalating Agents / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008856:Microscopy, Fluorescence; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D007364:Intercalating Agents; D004317:Doxorubicin; D004247:DNA; D053148:Caspase 3