Interplay between Cellular Uptake, Intracellular Localization and the Cell Death Mechanism in Triphenylamine-Mediated Photoinduced Cell Death

Abstract

Béatrice Rambaud 1 , patrick tauc 1 , céline frochot 3 , Marie-paule teulade-fichou 2 ✉ , florence Mahuteau-Betzer 2 ✉ & eric Deprez 1 ✉ triphenylamines (tpAs) were previously shown to trigger cell death under prolonged one-or twophoton illumination. their initial subcellular localization, before prolonged illumination, is exclusively cytoplasmic and they translocate to the nucleus upon photoactivation. However, depending on their structure, they display significant differences in terms of precise initial localization and subsequent photoinduced cell death mechanism. Here, we investigated the structural features of tpAs that influence cell death by studying a series of molecules differing by the number and chemical nature of vinyl branches. All compounds triggered cell death upon one-photon excitation, however to different extents, the nature of the electron acceptor group being determinant for the overall cell death efficiency. Photobleaching susceptibility was also an important parameter for discriminating efficient/inefficient compounds in two-photon experiments. Furthermore, the number of branches, but not their chemical nature, was crucial for determining the cellular uptake mechanism of tpAs and their intracellular fate. the uptake of all tpAs is an active endocytic process but two-and three-branch compounds are taken up via distinct endocytosis pathways, clathrin-dependent or-independent (predominantly caveolae-dependent), respectively. two-branch tpAs preferentially target mitochondria and photoinduce both apoptosis and a proper necrotic process, whereas three-branch tpAs preferentially target late endosomes and photoinduce apoptosis only.

Physical Mechanism of Photoinduced Charge Transfer in One- and Two-Photon Absorption in D-D-π-A Systems

“…Vinyl triphenylamine compounds have a high TPA cross-section [ 30 , 31 ], which promotes the application of triphenylamine in two-photon applications. Recently, two compounds, TP2Py and TP2(3)Bzim, have been found to trigger cell death in response to one or two-photon excitation, which can yield promising results in two-photon photodynamic therapy [ 32 ]. Furthermore, the applications of triphenylamine in quantum dot light-emitting diodes [ 33 ] and dye-sensitized solar cells [ 34 ] should not be underestimated.…”

Modulation of Cellular Fate of Vinyl Triarylamines through Structural Fine Tuning: To Stay or Not To Stay in the Mitochondria?

“…Finally other parameters can play a role both in dye trapping and intramitochondrial localization in line with our recent observation that molecular shape /volume of TPA dyes affect dramatically the passage through the plasma membrane and their subcellular localization. [19] Finally, the relocalization of TPA-TNA dyes upon ΔΨ m dissipation induced by exogenous stimuli (CCCP, H 2 O 2 ) indicates the strong dependence on the membrane polarization status. However, in contrast to mitochondria trapping and internal localization, the spatial redistribution is directly correlated to their cellular localization in fixed cells as translocation to nuclear compartment was observed only for the two nuclear stains in fixed cells (TP 1 + -2Bzim, TP-2Bzim) whereas leakage to the cytosol was seen for TN-2Bzim.…”

“…We previously reported that translocation of TP-2Bzim from mitochondria to nucleus can be triggered by visible or NIR light upon prolonged irradiation. [17][18][19] In these conditions apoptosis was induced concomitantly due to ROS production initiated by the dye excited state which further causes strong mitochondria damages and membrane permeabilization. Differently from the present study, this photoinduced translocation phenomenon is irreversible and relevant of a photosensitization effect.…”

“…Therefore, on one hand TPA rank amongst the brightest DNA markers developed so far in fixed cells [16b] and on the other hand, act as photoactivatable mitochondria-targeted proapoptotic agents in live cells. [17][18][19] However, the structural determinants influencing the mitochondrial sequestration as well as the capacity to translocate out of the mitochondria in absence of light activation and in particular the dependence with regard to the mitochondrial membrane potential have not been examined in detail. In addition, the question of whether TPA mitochondrial localisation is in part driven by mtDNA binding remained unanswered.…”

“…This phenomenon is concomitant with ROS production and apoptosis. Therefore, on one hand TPA rank amongst the brightest DNA markers developed so far in fixed cells [16b] and on the other hand, act as photoactivatable mitochondria–targeted proapoptotic agents in live cells [17–19] …”