title: Reaction kinetics and targeting to cellular glutathione S-transferase of the glutathione peroxidase mimetic PhSeZnCl and its D,L-polylactide microparticle formulation.
abstract: Catalytic properties and cellular effects of the glutathione peroxidase (GPx)-mimetic compound PhSeZnCl or its d,l-lactide polymer microencapsulation form (M-PhSeZnCl) were investigated and compared with the prototypical Se-organic compounds ebselen and diselenide (PhSe)2. PhSeZnCl was confirmed to catalyze the ping-pong reaction of GPx with higher Vmax than ebselen and (PhSe)2, but the catalytic efficiency calculated for the cosubstrates glutathione (GSH) and H2O2, and particularly the high reactivity against thiols (lowest KM for GSH in the series of test molecules), suggested poor biological applicability of PhSeZnCl as a GPx mimetic. Cytotoxicity of PhSeZnCl was demonstrated in various cancer cell lines via increased reactive oxygen species (ROS) generation, depletion of intracellular thiols, and induction of apoptosis. Experiments carried out in GSH S-transferase P (GSTP)-overexpressing K562 human erythroleukemia cells and in GSTP1-1-knockout murine embryonic fibroblasts (MEFs) demonstrated that this cytosolic enzyme represents a preferential target of the redox disturbances produced by this Se-compound with a key role in controlling H2O2 generation and the perturbation of stress/survival kinase signaling. Microencapsulation was adopted as a strategy to control the thiol reactivity and oxidative stress effects of PhSeZnCl, then assessing applications alternative to anticancer. The uptake of this "depowered" GPx-mimetic formulation, which occurred through an endocytosis-like mechanism, resulted in a marked reduction of cytotoxicity. In MCF-7 cells transfected with different allelic variants of GSTP, M-PhSeZnCl lowered the burst of cellular ROS induced by the exposure to extracellular H2O2, and the extent of this effect changed between the GSTP variants. Microencapsulation is a straightforward strategy to mitigate the toxicity of thiol-reactive Se-organic drugs that enhanced the antioxidant and cellular protective effects of PhSeZnCl. A mechanistic linkage of these effects with the expression pattern and signaling properties of GSTP . This has overcome the GPx-mimetic paradigm proposed for Se-organic drugs with a more pragmatic concept of GSTP signaling modulators.
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Bartolini
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Piroddi
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Tidei
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Giovagnoli
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Pietrella
authors.affiliation: Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29401, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Manevich
authors.affiliation: Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29401, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Tew
authors.affiliation: Department of Life Sciences, University of Siena, Siena, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Giustarini
authors.affiliation: Department of Life Sciences, University of Siena, Siena, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Rossi
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29401, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Townsend
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Santi
authors.affiliation: Department of Pharmaceutical Sciences, University of Perugia, 06126 Perugia, Italy. Electronic address: francesco.galli@unipg.it.
authors.forename: F
authors.initials: F
authors.lastname: Galli
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001393:Azoles / Q000494:pharmacology; D032701:Biomimetics; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002626:Chemistry, Pharmaceutical; D004339:Drug Compounding; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000737:chemistry* / Q000378:metabolism; D051549:Glutathione S-Transferase pi / Q000037:antagonists & inhibitors* / Q000502:physiology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D054833:Isoindoles; D020014:K562 Cells; D007700:Kinetics; D061986:MCF-7 Cells; D051379:Mice; D018345:Mice, Knockout; D016566:Organoselenium Compounds / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D011091:Polyesters / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000378:metabolism; D018036:Selenium Compounds / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D000975:Antioxidants; D001393:Azoles; D054833:Isoindoles; D016566:Organoselenium Compounds; D011091:Polyesters; D017382:Reactive Oxygen Species; D018036:Selenium Compounds; D013438:Sulfhydryl Compounds; C042986:ebselen; C033616:poly(lactide); D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D051549:Glutathione S-Transferase pi; C496557:Gstp1 protein, mouse; D005978:Glutathione
keywords: Antioxidants; Cell signaling; Diphenyl diselenide; Ebselen; Glutathione S-transferase Pi; Glutathione peroxidase; Peroxiredoxins; PhSeZnCl; Selenium; Seleno-organic compound; Thiols