Development Of New Photochemical Tools For Applications In Cancer Research And Enzymatic Signaling

Photochemical tools empower researchers to act with precision and control over the cellular environment through production of reactive oxygen species (ROS), targeted drug delivery, and modulation of enzymatic activity. These molecular tools use light as a readily available, biorthogonal reagent for initiating advantageous light-activated reactions. Using light in this way allows researchers to affect the cellular environment in specific ways with high spatio-temporal control. This dissertation focuses on expanding the applications of, mostly Ru(II)-based, photoactivated chemicals. Complexes of this type are able to act as photosensitizers in photodynamic therapy (PDT), as photocages (PCT), or as dual-action compounds capable of both PDT and PCT. Five projects were carried out in this work, and while the specifics differ from project to project, we can derive lessons from the collective work and apply it to the field as a whole. In this work, due to physical limitations in ligand construction, the capacity of the applied Ru(II) polypyridyl complexes to act as efficient photosensitizers. The Ru(II) complexes applied here have, however, displayed excellent capacity to act as photocages, both singularly and as a component in dualaction complexes. Optimization of Ru(II) complexes for photocaging consequential ligands is a research area ripe for innovation

Stratégies et politiques nationalistes de René Lévesque (Québec) et de Lee Teng-hui (Taiwan) : essai de politique comparée

En Occident comme en Orient, la question nationale est un enjeu pour plusieurs États dont le statut politique est soit mal défini soit insatisfaisant aux yeux d'une part de la population. Dans l'espoir de rectifier la situation, des hommes politiques réclament davantage de pouvoirs locaux et une plus grande représentation internationale. Tant au Québec qu'à Taiwan, ce type de politicien exerce une influence considérable sur l'orientation du nationalisme d'État, contribuant ainsi à transformer les rapports entretenus avec les gouvernements canadiens et chinois. Bien qu'étant éloignées physiquement et culturellement, ces deux sociétés sont tiraillées entre leur appartenance locale et régionale, ce qui a permis à des leaders indépendantistes d'accéder au pouvoir et d'appliquer leurs politiques nationalistes. En cherchant à accroître la souveraineté de leur Etat, René Lévesque et Lee Teng-hui appartiennent à cette catégorie de politiciens pour qui le statu quo ne peut être maintenu indéfiniment. À la fois idéologues, pragmatiques et réformateurs, ils ont orienté la politique locale dans une voie nouvelle. En fait, leurs stratégies d'accession à l'indépendance empruntent trois canaux différents qui se complètent pour permettre à leurs politiques nationalistes de s'appliquer à l'échelle locale autant que régionale et internationale. Ces trois volets sont l'identité, la démocratie et la quête de pouvoirs souverains. À travers l'analyse de leurs actions et de leurs écrits, un parallèle peut être dressé entre René Lévesque et Lee Teng-hui qui indique que non seulement ces deux dirigeants oeuvrèrent à l'atteinte d'une plus grande souveraineté pour le Québec et pour Taiwan, mais qu'ils employèrent sensiblement les mêmes moyens pour y parvenir

BODIPY-Caged Photoactivated Inhibitors of Cathepsin B Flip the Light Switch on Cancer Cell Apoptosis

Acquired resistance to apoptotic agents is a long-standing challenge in cancer treatment. Cathepsin B (CTSB) is an enzyme which, among many essential functions, promotes apoptosis during cellular stress through regulation of intracelllular proteolytic networks on the minute timescale. Recent data indicate that CTSB inhibition may be a promising method to steer cells away from apoptotic death towards necrosis, a mechanism of cell death that can overcome resistance to apoptotic agents, stimulate an immune response and promote anti-tumor immunity. Unfortunately, rapid and selective intracellular inactivation of CTSB has not been possible. However, here we report on the synthesis and characterization of photochemical and biological properties of BODIPY-caged inhibitors of CTSB that are cell permeable, highly selective and activated rapidly upon exposure to visible light. Intriguingly, these compounds display tunable photophysical and biological properties based on substituents bound directly to boron. Me2BODIPY-caged compound 8 displays the dual-action capability of light-accelerated CTSB inhibition and singlet oxygen production from a singular molecular entitiy. The dual-action capacity of 8 leads to a rapid necrotic response in MDA-MB-231 triple negative breast cancer cells with high phototherapeutic indexes (\u3e30) and selectivity vs. non-cancerous cells that neither CTSB inhibition nor photosensitization gives alone. Our work confirms that singlet oxygen production and CTSB inactivation is highly synergistic and a promising method for killing cancer cells. Furthermore, our ability to trigger intracellular inactivation of CTSB with light will provide researchers with a powerful photochemical tool for probing biochemical processes on short timescales

BODIPY-Caged Photoactivated Inhibitors of Cathepsin B Flip the Light Switch on Cancer Cell Apoptosis

Acquired resistance to apoptotic agents is a long-standing challenge in cancer treatment. Cathepsin B (CTSB) is an enzyme which, among many essential functions, promotes apoptosis during cellular stress through regulation of intracelllular proteolytic networks on the minute timescale. Recent data indicate that CTSB inhibition may be a promising method to steer cells away from apoptotic death towards necrosis, a mechanism of cell death that can overcome resistance to apoptotic agents, stimulate an immune response and promote anti-tumor immunity. Unfortunately, rapid and selective intracellular inactivation of CTSB has not been possible. However, here we report on the synthesis and characterization of photochemical and biological properties of BODIPY-caged inhibitors of CTSB that are cell permeable, highly selective and activated rapidly upon exposure to visible light. Intriguingly, these compounds display tunable photophysical and biological properties based on substituents bound directly to boron. Me2BODIPY-caged compound 8 displays the dual-action capability of light-accelerated CTSB inhibition and singlet oxygen production from a singular molecular entitiy. The dual-action capacity of 8 leads to a rapid necrotic response in MDA-MB-231 triple negative breast cancer cells with high phototherapeutic indexes (>30) and selectivity vs. non-cancerous cells that neither CTSB inhibition nor photosensitization gives alone. Our work confirms that singlet oxygen production and CTSB inactivation is highly synergistic and a promising method for killing cancer cells. Furthermore, our ability to trigger intracellular inactivation of CTSB with light will provide researchers with a powerful photochemical tool for probing biochemical processes on short timescales.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Chemical Biology, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acschembio.9b00711. Posted with permission.</p

Photosensitive Ru(II) Complexes as Inhibitors of the Major Human Drug Metabolizing Enzyme CYP3A4

We report the synthesis and photochemical and biological characterization of the first selective and potent metal-based inhibitors of cytochrome P450 3A4 (CYP3A4), the major human drug metabolizing enzyme. Five Ru(II)-based derivatives were prepared from two analogs of the CYP3A4 inhibitor ritonavir, 4 and 6: [Ru(tpy)(L)(6)]Cl(2) (tpy = 2,2′:6′,2″-terpyridine) with L = 6,6′-dimethyl-2,2′-bipyridine (Me(2)bpy; 8), dimethylbenzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (Me(2)dppn; 10) and 3,6-dimethyl-10,15-diphenylbenzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (Me(2)Ph(2)dppn; 11), [Ru(tpy)(Me(2)bpy)(4)]Cl(2) (7) and [Ru(tpy)(Me(2)dppn)(4)]Cl(2) (9). Photochemical release of 4 or 6 from 7–11 was demonstrated, and the spectrophotometric evaluation of 7 showed that it behaves similarly to free 4 (type II heme ligation) after irradiation with visible light but not in the dark. Unexpectedly, the intact Ru(II) complexes 7 and 8 were found to inhibit CYP3A4 potently and specifically through direct binding to the active site without heme ligation. Caged inhibitors 9–11 showed dual action properties by combining photoactivated dissociation of 4 or 6 with efficient (1)O(2) production. In prostate adenocarcinoma DU-145 cells, compound 9 had the best synergistic effect with vinblastine, the anticancer drug primarily metabolized by CYP3A4 in vivo. Thus, our study establishes a new paradigm in CYP inhibition using metalated complexes and suggests possible utilization of photoactive CYP3A4 inhibitory compounds in clinical applications, such as enhancement of therapeutic efficacy of anticancer drugs