Miroslav Ledvina

Mitochondrial Targeting of Vitamin E Succinate Enhances Its Pro-apoptotic and Anti-cancer Activity via Mitochondrial Complex II

Mitochondrial complex II (CII) has been recently identified as a novel target for anti-cancer drugs. Mitochondrially targeted vitamin E succinate (MitoVES) is modified so that it is preferentially localized to mitochondria, greatly enhancing its pro-apoptotic and anti-cancer activity. Using genetically manipulated cells, MitoVES caused apoptosis and generation of reactive oxygen species (ROS) in CII-proficient malignant cells but not their CII-dysfunctional counterparts. MitoVES inhibited the succinate dehydrogenase (SDH) activity of CII with IC50 of 80 μm, whereas the electron transfer from CII to CIII was inhibited with IC50 of 1.5 μm. The agent had no effect either on the enzymatic activity of CI or on electron transfer from CI to CIII. Over 24 h, MitoVES caused stabilization of the oxygen-dependent destruction domain of HIF1α fused to GFP, indicating promotion of the state of pseudohypoxia. Molecular modeling predicted the succinyl group anchored into the proximal CII ubiquinone (UbQ)-binding site and successively reduced interaction energies for serially shorter phytyl chain homologs of MitoVES correlated with their lower effects on apoptosis induction, ROS generation, and SDH activity. Mutation of the UbQ-binding Ser68 within the proximal site of the CII SDHC subunit (S68A or S68L) suppressed both ROS generation and apoptosis induction by MitoVES. In vivo studies indicated that MitoVES also acts by causing pseudohypoxia in the context of tumor suppression. We propose that mitochondrial targeting of VES with an 11-carbon chain localizes the agent into an ideal position across the interface of the mitochondrial inner membrane and matrix, optimizing its biological effects as an anti-cancer drug.

A Peptide Conjugate of Vitamin E Succinate Targets Breast Cancer Cells with High ErbB2 Expression

Overexpression of erbB2 is associated with resistance to apoptosis. We explored whether high level of erbB2 expression by cancer cells allows their targeting using an erbB2-binding peptide (LTVSPWY) attached to the proapoptotic alpha-tocopheryl succinate (alpha-TOS). Treating erbB2-low or erbB2-high cells with alpha-TOS induced similar levels of apoptosis, whereas alpha-TOS-LTVSPWY induced greater levels of apoptosis in erbB2-high cells. alpha-TOS rapidly accumulated in erbB2-high cells exposed to alpha-TOS-LTVSPWY. The extent of apoptosis induced in erbB2-high cells by alpha-TOS-LTVSPWY was suppressed by erbB2 RNA interference as well as by inhibition of either endocytotic or lysosomal function. alpha-TOS-LTVSPWY reduced erbB2-high breast carcinomas in FVB/N c-neu transgenic mice. We conclude that a conjugate of a peptide targeting alpha-TOS to erbB2-overexpressing cancer cells induces rapid apoptosis and efficiently suppresses erbB2-positive breast tumors.

Mitochondrial targeting of α-tocopheryl succinate enhances its pro-apoptotic efficacy: A new paradigm for effective cancer therapy

Mitochondria are emerging as intriguing targets for anti-cancer agents. We tested here a novel approach, whereby the mitochondrially targeted delivery of anti-cancer drugs is enhanced by the addition of a triphenylphosphonium group (TPP(+)). A mitochondrially targeted analog of vitamin E succinate (MitoVES), modified by tagging the parental compound with TPP(+), induced considerably more robust apoptosis in cancer cells with a 1-2 log gain in anti-cancer activity compared to the unmodified counterpart, while maintaining selectivity for malignant cells. This is because MitoVES associates with mitochondria and causes fast generation of reactive oxygen species that then trigger mitochondria-dependent apoptosis, involving transcriptional modulation of the Bcl-2 family proteins. MitoVES proved superior in suppression of experimental tumors compared to the untargeted analog. We propose that mitochondrially targeted delivery of anti-cancer agents offers a new paradigm for increasing the efficacy of compounds with anti-cancer activity.

Boosting nanodiamond fluorescence: towards development of brighter probes

A novel approach for preparation of ultra-bright fluorescent nanodiamonds (fNDs) was developed and the thermal and kinetic optimum of NV center formation was identified. Combined with a new oxidation method, this approach enabled preparation of particles that were roughly one order of magnitude brighter than particles prepared with commonly used procedures.

Fluorescent Nanodiamonds Embedded in Biocompatible Translucent Shells

High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10-20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells.

Metallochelating liposomes with associated lipophilised norAbuMDP as biocompatible platform for construction of vaccines with recombinant His-tagged antigens: Preparation, structural study and immune response towards rHsp90

Hsp90-CA is present in cell wall of Candida pseudohyphae or hyphae-typical pathogenic morphotype for both systemic and mucosal Candida infections. Heat shock protein from Candida albicans (hsp90-CA) is an important target for protective antibodies during disseminated candidiasis of experimental mice and human. His-tagged protein rHsp90 was prepared and used as the antigen for preparation of experimental recombinant liposomal vaccine. Nickel-chelating liposomes (the size around 100nm, PDI≤0.1) were prepared from the mixture of egg phosphatidyl choline and nickel-chelating lipid DOGS-NTA-Ni (molar ratio 95:5%) by hydration of lipid film and extrusion methods. New non-pyrogenic hydrophobised derivative of MDP (C18-O-6-norAbuMDP) was incorporated into liposomes as adjuvans. rHsp90 was attached onto the surface of metallochelating liposomes by metallochelating bond and the structure of these proteoliposomes was studied by dynamic light scattering, AF microscopy, TEM and GPC. The liposomes with surface-exposed C18-O-6-norAbuMDP were well recognised and phagocyted by human dendritic cells in vitro. In vivo the immune response towards this experimental vaccine applied in mice (i.d.) demonstrated both TH1 and TH2 response comparable to FCA, but without any side effects. Metallochelating liposomes with lipophilic derivatives of muramyl dipeptide represent a new biocompatible platform for construction of experimental recombinant vaccines and drug-targeting systems.

Mitochondrially Targeted α-Tocopheryl Succinate Is Antiangiogenic: Potential Benefit Against Tumor Angiogenesis but Caution Against Wound Healing

AIMS A plausible strategy to reduce tumor progress is the inhibition of angiogenesis. Therefore, agents that efficiently suppress angiogenesis can be used for tumor suppression. We tested the antiangiogenic potential of a mitochondrially targeted analog of α-tocopheryl succinate (MitoVES), a compound with high propensity to induce apoptosis. RESULTS MitoVES was found to efficiently kill proliferating endothelial cells (ECs) but not contact-arrested ECs or ECs deficient in mitochondrial DNA, and suppressed angiogenesis in vitro by inducing accumulation of reactive oxygen species and induction of apoptosis in proliferating/angiogenic ECs. Resistance of arrested ECs was ascribed, at least in part, to the lower mitochondrial inner transmembrane potential compared with the proliferating ECs, thus resulting in the lower level of mitochondrial uptake of MitoVES. Shorter-chain homologs of MitoVES were less efficient in angiogenesis inhibition, thus suggesting a molecular mechanism of its activity. Finally, MitoVES was found to suppress HER2-positive breast carcinomas in a transgenic mouse as well as inhibit tumor angiogenesis. The antiangiogenic efficacy of MitoVES was corroborated by its inhibitory activity on wound healing in vivo. INNOVATION AND CONCLUSION We conclude that MitoVES, a mitochondrially targeted analog of α-tocopheryl succinate, is an efficient antiangiogenic agent of potential clinical relevance, exerting considerably higher activity than its untargeted counterpart. MitoVES may be helpful against cancer but may compromise wound healing.

Solid phase synthesis of glycopeptide dendrimers with Tn antigenic structure and their biological activities. Part I

Multiple antigenic peptides containing dimeric Tn antigen [Ac‐(Tn)2‐γ‐Abu]4‐(Lys‐X)2‐Lys‐β‐Ala (V: X=0; VIII: X=γ‐Abu) and [Ac‐(Tn)2‐γ‐Abu]8‐(Lys‐X)4‐(Lys‐X)2‐Lys‐β‐Ala (XI: X=0; XIV: X=γ‐Abu), immobilized on biocompatible Tenta Gel S NH2 support were prepared by SPPS. Rosetting tests of V, VIII, XI and XIV showed positive reactions with anti‐Tn (DAKO) and Tn+ erythrocytes, with anti‐Tn/A (BRIC 66) and Tn+ and A erythrocytes, other combinations were negative. In all the animals immunized with XIV, we found a remarkable increase in the level of anti‐Tn (titre 2000–64 000, score 105–167) and no change of anti‐A levels (titre 8, score 13–17). Neither non‐immune nor immune sera showed any reactivity with T+, Cad+ and blood group O erythrocytes. Immunized mice did not exhibit any sign of adverse reaction to the administered conjugates. Biological activities were correlated with molecular modelling and molecular dynamic calculations. The biological activities of these synthetic Tn antigen conjugates (good availability for the immunological interactions, highly specific immunogenicity, good biological tolerance) together with their precise chemical characterization seem to be a promising approach to preparation of anti‐tumour vaccine and affinity purification of anti‐Tn antibodies. Copyright

In Vitro Transfection Mediated by Dendrigraft Poly(L-lysines): The Effect of Structure and Molecule Size

Dendritic poly(L-lysines) (DGL) constitute promising nanomaterials applicable as a nonviral gene-delivery vector. In this study, we evaluate the transfection abilities of four DGL generations with special emphasis on the systematic description of the relationship of how generation (i.e., molecule size) affects the transfection efficacy. Using Hep2 cells, we demonstrated that the capability of unmodified DGL to deliver plasmid is of a magnitude lower than that of jetPEI. On the other hand, employing the Hep2 cell line stably transduced with eGFP, we observed that DGL G5 delivers the siRNA oligonucleotide with the same efficiency as Lipofectamine 2000. In further experiments, it was shown that DGL affords excellent ability to bind DNA, protect it against DNase I attack, and internalize it into cells.

Immobilization of histidine-tagged proteins on monodisperse metallochelation liposomes: Preparation and study of their structure

Liposomes represent a biocompatible platform for the construction of self-assembling proteoliposomes using nickel or zinc metallochelation. Potential applications of such structures consist in the development of new biocompatible vaccination nanoparticles and drug delivery nanoparticle systems. Here, we describe the design and construction of a flow-through ultrafiltration cell suitable for the preparation of monodisperse liposomes enabled for metallochelation and, hence, the formation of proteoliposomes. The linkage of the cell with a fast protein liquid chromatography system facilitates automation of the procedure, which fits the criteria for upscaling. Proof-of-concept experiments are performed using a mixture of egg phosphatidyl choline and nickel-chelating lipid DOGS-NTA-Ni (1,2-dioleoyl-sn-glycero-3-{[N(5-amino-1-carboxypentyl)iminodiacetic acid]succinyl}(nickel salt)) to formulate proteoliposomes with proteins attached by metallochelation, including histidine (His)-tagged recombinant green fluorescent protein and rgp120 (derived from HIV-1 Env). These model proteoliposomes are characterized by gel permeation chromatography and by dynamic light scattering. Transmission electron microscopy and immunogold staining are used to characterize surface-bound proteins, revealing the tendency of rgp120 to form microdomains on liposome surfaces. These microdomains possess a two-dimensional crystal-like structure that is seen more precisely by atomic force microscopy.