Patrícia M. R. Pereira

Amphiphilic phthalocyanine-cyclodextrin conjugates for cancer photodynamic therapy.

Three phthalocyanines (Pcs) conjugated with α-, β- and γ-cyclodextrins (CDs) were prepared and their application as photosensitizer (PS) agents was assessed by photophysical, photochemical and in vitro photobiological studies. The photoactivity of Pc-α-CD and Pc-γ-CD ensures their potential as PDT drugs against UM-UC-3 human bladder cancer cells.

Porphyrins and Phthalocyanines Decorated with Dendrimers: Synthesis and Biomedical Applications

In medical applications such as drug delivery, gene transfection and imaging the formation of systems with well-defined sizes and shapes are of significant interest. For this reason the design of dendrimers with modulated size, shape, branching length/density, and their surface functionality, clearly distinguishes these structures as unique and optimum carriers for medical applications. The bioactive agents may be encapsulated into the interior of the dendrimers or chemically attached/physically adsorbed onto the dendrimer surface, with the option of tailoring the carrier to the specific needs of the active material and its therapeutic applications. In this regard one area with growing attention is photodynamic therapy (PDT) where a photosensitizer combined with light and molecular oxygen can easily cause irreversible damage to the target tissue. Nevertheless most of the photosensitizers have solubility issues when attempts are made to dissolve them in aqueous environments, hampering in most cases their medical applicability. Currently, investigations are running towards the combination of these photosensitizers with dendrimers increasing their organization, solubility and specificity to the target tissues. In this communication we review the latest advancements in the synthesis of porphyrin and phthalocyanine dendrimer architectures, regarding their utility as biomedical agents.

Galactodendritic Phthalocyanine Targets Carbohydrate-Binding Proteins Enhancing Photodynamic Therapy

Photosensitizers (PSs) are of crucial importance in the effectiveness of photodynamic therapy (PDT) for cancer. Due to their high reactive oxygen species production and strong absorption in the wavelength range between 650 and 850 nm, where tissue light penetration is rather high, phthalocyanines (Pcs) have been studied as PSs of excellence. In this work, we report the evaluation of a phthalocyanine surrounded by a carbohydrate shell of sixteen galactose units distributed in a dendritic manner (PcGal16) as a new and efficient third generation PSs for PDT against two bladder cancer cell lines, HT-1376 and UM-UC-3. Here, we define the role of galacto-dendritic units in promoting the uptake of a Pc through interaction with GLUT1 and galectin-1. The photoactivation of PcGal16 induces cell death by generating oxidative stress. Although PDT with PcGal16 induces an increase on the activity of antioxidant enzymes immediately after PDT, bladder cancer cells are unable to recover from the PDT-induced damage effects for at least 72 h after treatment. PcGal16 co-localization with galectin-1 and GLUT1 and/or generation of oxidative stress after PcGal16 photoactivation induces changes in the levels of these proteins. Knockdown of galectin-1 and GLUT1, via small interfering RNA (siRNA), in bladder cancer cells decreases intracellular uptake and phototoxicity of PcGal16. The results reported herein show PcGal16 as a promising therapeutic agent for the treatment of bladder cancer, which is the fifth most common type of cancer with the highest rate of recurrence of any cancer.

Porphyrin conjugated with serum albumins and monoclonal antibodies boosts efficiency in targeted destruction of human bladder cancer cells

The synthesis of a novel PS conjugated with bovine and human serum albumin (BSA and HSA) and a monoclonal antibody anti-CD104 is reported, as well as their biological potential against the human bladder cancer cell line UM-UC-3. No photodynamic effect was detected when the non-conjugated porphyrin was used. Yet, when it was coupled covalently with the mAb anti-CD104, BSA and HSA, the resulting photosensitizer conjugates demonstrated high efficacy in destroying the cancer cells, the mAb anti-CD104 efficacy overruling the albumins.

New platinum(II)-bipyridyl corrole complexes: Synthesis, characterization and binding studies with DNA and HSA.

A simple methodology giving access to the metal-free corroles of trans-A2B type, 5,15-bis(pentafluorophenyl)-10-{3-[2-(pyridin-4-yl)vinyl]phenyl}corrole and 5,15-bis(pentafluorophenyl)-10-{4-[2-(pyridin-4-yl)vinyl]phenyl}corrole, and to the corresponding bipyridyl platinum(II) complexes is described. These new positional isomers were fully characterized and spectroscopic studies demonstrated the ability of Pt(II)-corrole complexes to establish non-covalent interactions with calf-thymus DNA (ct-DNA) and human serum albumin (HSA). Additionally, gel electrophoresis experiments demonstrated that Pt(II)-corrole complexes are able to bind plasmid pMT123 DNA, inducing alterations on its secondary structure.

Galactodendritic Porphyrinic Conjugates as New Biomimetic Catalysts for Oxidation Reactions

This work employed [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin] ([H2(TPPF20)], H2P1) as the platform to prepare a tetrasubstituted galactodendritic conjugate porphyrin (H2P3). After metalation with excess copper(II) acetate, H2P3 afforded a new solid porphyrin material, Cu4CuP3S. This work also assessed the ability of the copper(II) complex (CuP3) of H2P3 to coordinate with zinc(II) acetate, to yield the new material Zn4CuP3S. UV-visible, Fourier transform infrared, and electron paramagnetic resonance spectroscopies aided full characterization of the synthesized solids. (Z)-Cyclooctene epoxidation under heterogeneous conditions helped to evaluate the catalytic activity of Cu4CuP3S and Zn4CuP3S. The efficiency of Cu4CuP3S in the oxidation of another organic substrate, catechol, was also investigated. According to the results obtained in the heterogeneous process, Cu4CuP3S mimicked the activity of cytochrome P-450 and catecholase. In addition, Cu4CuP3S was reusable after recovery and reactivation. The data obtained herein were compared with the results achieved for the copper complex (CuP1) of [H2(TPPF20)] and for CuP3 under homogeneous conditions.

Dual functionality of phosphonic-acid-appended phthalocyanines: inhibitors of urokinase plasminogen activator and anticancer photodynamic agents

Phthalocyanines (Pcs) bearing phosphonic acid groups at the periphery exhibit a potential photodynamic effect to induce phototoxicity on human bladder cancer epithelial cells (UM-UC-3). In vitro photophysical and biological studies show high intrinsic ability to inhibit the activity of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9).

Carbon-1 versus Carbon-3 Linkage of d-Galactose to Porphyrins: Synthesis, Uptake, and Photodynamic Efficiency

The use of glycosylated compounds is actively pursued as a therapeutic strategy for cancer due to the overexpression of various types of sugar receptors and transporters on most cancer cells. Conjugation of saccharides to photosensitizers such as porphyrins provides a promising strategy to improve the selectivity and cell uptake of the photosensitizers, enhancing the overall photosensitizing efficacy. Most porphyrin-carbohydrate conjugates are linked via the carbon-1 position of the carbohydrate because this is the most synthetically accessible approach. Previous studies suggest that carbon-1 galactose derivatives show diminished binding since the hydroxyl group in the carbon-1 position of the sugar is a hydrogen bond acceptor in the galectin-1 sugar binding site. We therefore synthesized two isomeric porphyrin-galactose conjugates using click chemistry: one linked via the carbon-1 of the galactose and one linked via carbon-3. Free base and zinc analogs of both conjugates were synthesized. We assessed the uptake and photodynamic therapeutic (PDT) activity of the two conjugates in both monolayer and spheroidal cell cultures of four different cell lines. For both the monolayer and spheroid models, we observe that the uptake of both conjugates is proportional to the protein levels of galectin-1 and the uptake is suppressed after preincubation with an excess of thiogalactose, as measured by fluorescence spectroscopy. Compared to that of the carbon-1 conjugate, the uptake of the carbon-3 conjugate was greater in cell lines containing high expression levels of galectin-1. After photodynamic activation, MTT and lactate dehydrogenase assays demonstrated that the conjugates induce phototoxicity in both monolayers and spheroids of cancer cells.

The ubiquitin proteasome pathway - Repair or degradation of damaged proteins

Purpose Accumulation of methylglyoxal (MGO), a highly reactive side-product of glycolysis can modify proteins. Increased levels of MGO in cells have been implicated in diabetic vascular complications. In physiological conditions, proteolytic systems and chaperones together ensure maintenance of protein quality control. We hypothesize that MGO impairs the function of UPS and on molecular chaperones. Methods Rats with moderate type 2 diabetes (GK) and retinal epithelium pigment cell line were used. Protein oxidation was assessed by formation of carbonyl groups. Production of intracellular ROS was assessed in frozen sections of diabetic retinas by DHE incorporation. 20S proteasome activities were assessed by fluorogenic peptides. Ubiquitin (Ub) conjugation activity was determined by the ability of retinal extracts to conjugate 125I-Ub to endogenous substrates. Ub conjugates, Hsp90, Hsc70, Hsp40 and CHIP levels were assessed by WB. Cell viability was determined by MTT while proliferation was assessed by BrdU-incorporation. Results Data show that accumulation of endogenous Ub conjugates in the presence of MGO is associated with an increased ability of retinal extracts to conjugate 125I-Ub to endogenous substrates. Moreover, MGO significantly decreases the 20S ptoteasome activity. Data further show that MGO decreases the levels of the molecular chaperones Hsp90 and Hsc70 and promotes aggregation of Hsp40 and CHIP. Moreover, these aggregates revealed immunoreactivity against Ub. Consistently, these effects are associated with increased cell protein oxidation, decreased cell proliferation and viability. Conclusion In diabetes, accumulation of MGO may impair the UPP and the protein quality control, leading to accumulation of obsolete proteins and cell injury.