Singlet oxygen detection in vivo is hindered by nonspecific SOSG staining.

Singlet oxygen is considered an important cell damaging agent due to its propensity to react with organic compounds. This drives the interest in developing methods for determination of O. Simplicity of application and high sensitivity makes fluorescent probes a popular choice for in vivo O detection.

Effect of the nature of the chelated metal on the photodynamic activity of metalloporphyrins.

Coordination of metal ions by the tetrapyrrolic macrocyclic ring of porphyrin-based photosensitizers (PSs) affects their photophysical properties and consequently, their photodynamic activity. Diamagnetic metals increase the singlet oxygen quantum yield while paramagnetic metals have the opposite effect. Since singlet oxygen is considered the main cell-damaging species in photodynamic therapy (PDT), the nature of the chelated cation would directly affect PDT efficacy.

Improved Formazan Dissolution for Bacterial MTT Assay.

The MTT assay, based on the enzymatic reduction of the water-soluble, yellowish tetrazolium salt 3-(4,5-dimethylthiazol)-2,5-diphenyl-tetrazolium bromide (MTT) to purple formazan, is commonly used for assessment of cell viability and proliferation. Accurate performance by the MTT assay depends on complete solubilization of cells and formazan and stability of the colored solution. Comparison of different solubilization solutions revealed that dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), buffered with ammonia buffer, pH 10, and containing 5% SDS, produced the best results.

Ascorbate-dependent and ascorbate-independent Mn porphyrin cytotoxicity: anticancer activity of Mn porphyrin-based SOD mimics through ascorbate-dependent and -independent routes.

Objective: The aim of this study was to investigate how modifications at the periphery of the porphyrin ring affect the anticancer activity of Mn porphyrins (MnPs)-based SOD mimics.

Methods: Six compounds: MnTE-2-PyP with a short ethyl chain on the pyridyl ring; MnTnHexOE-2-PyP and MnTnOct-2-PyP with linear 8-atom alkyl chains, but the former with an oxygen atom within the alkyl chain; MnTE-2-PyPhP and MnTPhE-2-PyP with pyridyl and phenyl substituents, were investigated. Cytotoxicity was studied using pII and MDA-MB-231 cancer cell lines.

Antibacterial Activity of Synthetic Cationic Iron Porphyrins.

Widespread antibiotic resistance demands new strategies for fighting infections. Porphyrin-based compounds were long ago introduced as photosensitizers for photodynamic therapy, but light-independent antimicrobial activity of such compounds has not been systematically explored. The results of this study demonstrate that synthetic cationic amphiphilic iron -alkylpyridylporphyrins exert strong bactericidal action at concentrations as low as 5 μM.

Methylene blue induces the soxRS regulon of Escherichia coli.

Extensive application of methylene blue (MB) for therapeutic and diagnostic purposes, and reports for unwanted side effects, demand better understanding of the mechanisms of biological action of this thiazine dye. Because MB is redox-active, its biological activities have been attributed to transfer of electrons, generation of reactive oxygen species, and antioxidant action. Results of this study show that MB is more toxic to a superoxide dismutase-deficient Escherichia coli mutant than to its SOD-proficient parent, which indicates that superoxide anion radical is involved.

Effect of growth media on the MTT colorimetric assay in bacteria.

Reduction of tetrazolium salts to colored formazan products by metabolically active cells is widely used for assessment of cell viability. Among the tetrazolium compounds most commonly used is MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide]. Numerous studies about sites and mechanisms of cellular reduction of MTT, performed in mammalian cell cultures, have identified various parameters that affect formazan production and can lead to overestimation/underestimation of viable cells or effects of treatment.

Sublethal Photodynamic Treatment Does Not Lead to Development of Resistance.

A promising new alternative approach for eradication of antibiotic-resistant strains is to expose microbes to photosensitizers, which upon illumination generate reactive oxygen species. Among the requirements for a potent, medically applicable photosensitizer, are high efficacy in killing microbes and low toxicity to the host. Since photodynamic treatment is based on production of reactive species which are potentially DNA damaging and mutagenic, it might be expected that under selective pressure, microbes would develop resistance.

Radiation-Mediated Tumor Growth Inhibition Is Significantly Enhanced with Redox-Active Compounds That Cycle with Ascorbate.

Aims: We aim here to demonstrate that radiation (RT) enhances tumor sensitization by only those Mn complexes that are redox active and cycle with ascorbate (Asc), thereby producing HO and utilizing it subsequently in protein S-glutathionylation in a glutathione peroxidase (GPx)-like manner. In turn, such compounds affect cellular redox environment, described by glutathione disulfide (GSSG)/glutathione (GSH) ratio, and tumor growth. To achieve our goal, we tested several Mn complexes of different chemical and physical properties in cellular and animal flank models of 4T1 breast cancer cell.

Post-illumination cellular effects of photodynamic treatment.

Increased interest in clinical application of photodynamic therapy (PDT) in various medical fields poses a demand for better understanding of processes triggered by photo-treatment. Most of the work on PDT performed so far has focused on the immediate effects of photo-treatment. It is generally accepted that cellular damage occurs during light exposure and within a short period thereafter.

Cationic amphiphilic Zn-porphyrin with high antifungal photodynamic potency.

Photodynamic therapy (PDT) is a promising alternative approach particularly attractive for treatment of localized fungal infections. It is based on compounds, photosensitizers (PSs), which when excited with visible light, generate reactive species that ultimately cause cell death. Such species have short lifespans; as a consequence, efficiency and selectivity of the PDT treatment depend mainly on the properties of the PSs.

Possible role of antioxidative capacity of (-)-epigallocatechin-3-gallate treatment in morphological and neurobehavioral recovery after sciatic nerve crush injury.

OBJECTIVE This study examined the capacity of the major polyphenolic green tea extract (-)-epigallocatechin-3-gallate (EGCG) to suppress oxidative stress and stimulate the recovery and prompt the regeneration of sciatic nerve after crush injury. METHODS Adult male Wistar rats were randomly assigned to one of 4 groups: 1) Naïve, 2) Sham (sham injury, surgical control group), 3) Crush (sciatic nerve crush injury treated with saline), and 4) Crush+EGCG (sciatic nerve crush injury treated with intraperitoneally administered EGCG, 50 mg/kg). All animals were tested for motor and sensory neurobehavioral parameters throughout the study.

The Contribution of Superoxide Radical to Cadmium Toxicity in E. coli.

Numerous reports suggest the involvement of oxidative stress in cadmium toxicity, but the nature of the reactive species and the mechanism of Cd-induced oxidative damage are not clear. In this study, E. coli mutants were used to investigate mechanisms of Cd toxicity.

Optimizing Zn porphyrin-based photosensitizers for efficient antibacterial photodynamic therapy.

Introduction: Efficient photodynamic inactivation of microbes requires highly efficient photosensitizers which kill microbial cells, but spare host tissues. One way to achieve such selectivity is to use photosensitizers that are rapidly taken up by microbes and, when applied at low concentrations, efficiently kill them after a short illumination. Design of such photosensitizers requires insight into molecular properties which are critical for antimicrobial photo-efficiency.

Important cellular targets for antimicrobial photodynamic therapy.

The persistent problem of antibiotic resistance has created a strong demand for new methods for therapy and disinfection. Photodynamic inactivation (PDI) of microbes has demonstrated promising results for eradication of antibiotic-resistant strains. PDI is based on the use of a photosensitive compound (photosensitizer, PS), which upon illumination with visible light generates reactive species capable of damaging and killing microorganisms.

Synthesis and biological evaluation of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives.

Research activities on the oxazolidinone antibacterial class of compounds continue to focus on developing newer derivatives with improved potency, broad-spectrum activity and safety profiles superior to linezolid. Among the safety concerns with the oxazolidinone antibacterial agents is inhibition of monoamine oxidases (MAO) resulting from their structural similarity with toloxatone, a known MAO inhibitor. Diverse substitution patterns at the C-5 position of the oxazolidinone ring have been shown to significantly affect both antibacterial activity and MAO inhibition to varying degrees.

Is there a role for neurotrophic factors and their receptors in augmenting the neuroprotective effect of (-)-epigallocatechin-3-gallate treatment of sciatic nerve crush injury?

This study analyzed and compared the effects of EGCG treatment on the expression of NTFs and NTF receptors expression in the sciatic nerve and the L3-L6 spinal cord segments at the early phase of regeneration following sciatic nerve crush injury. Analysis of BDNF, GDNF and NT3 neurotropic factors and Trk-B, Trk-C and NGFR-p75 receptors in neurons in the spinal cord of CRUSH and CRUSH + EGGC rats showed significant (p < 0.0001) decrease compared to NAÏVE and SHAM at day 1, 3, 7 and 14 after nerve injury.

Anticancer therapeutic potential of Mn porphyrin/ascorbate system.

Ascorbate (Asc) as a single agent suppressed growth of several tumor cell lines in a mouse model. It has been tested in a Phase I Clinical Trial on pancreatic cancer patients where it exhibited no toxicity to normal tissue yet was of only marginal efficacy. The mechanism of its anticancer effect was attributed to the production of tumoricidal hydrogen peroxide (H2O2) during ascorbate oxidation catalyzed by endogenous metalloproteins.

A comprehensive evaluation of catalase-like activity of different classes of redox-active therapeutics.

Because of the increased insight into the biological role of hydrogen peroxide (H2O2) under physiological and pathological conditions and the role it presumably plays in the action of natural and synthetic redox-active drugs, there is a need to accurately define the type and magnitude of reactions that may occur with this intriguing and key species of redoxome. Historically, and frequently incorrectly, the impact of catalase-like activity has been assigned to play a major role in the action of many redox-active drugs, mostly SOD mimics and peroxynitrite scavengers, and in particular MnTBAP(3-) and Mn salen derivatives. The advantage of one redox-active compound over another has often been assigned to the differences in catalase-like activity.

Amphiphilic cationic Zn-porphyrins with high photodynamic antimicrobial activity.

Aim: Photodynamic inactivation of microbes can efficiently eradicate antibiotic-resistant strains. Systematic structural modification was used to investigate how porphyrin-based photosensitizers (PSs) could be designed for improved antibacterial activity.

Materials & Methods: Zinc(II)5,10,15,20-tetrakis(N-alkylpyridinium-2(3,4)-yl)porphyrins presenting systematic modifications at the periphery of the porphyrin ring were evaluated for toxicity and antimicrobial photodynamic activity by measuring metabolic activity, cell membrane integrity and viability using antibiotic-sensitive and resistant Escherichia coli strains as model Gram-negative targets.

Evaluation of the monoamine oxidases inhibitory activity of a small series of 5-(azole)methyl oxazolidinones.

Oxazolidinone class of compounds continue to generate interest as promising agents effective against sensitive and resistant Gram-positive pathogenic bacteria strains. Recent focus is to develop new potent derivatives with improved broad-spectrum activity and safety profile superior to linezolid. An important toxicity issue for this class of compounds arises from the structural similarity with toloxatone, a known MAO inhibitor.

Rational design of superoxide dismutase (SOD) mimics: the evaluation of the therapeutic potential of new cationic Mn porphyrins with linear and cyclic substituents.

Our goal herein has been to gain further insight into the parameters which control porphyrin therapeutic potential. Mn porphyrins (MnTnOct-2-PyP(5+), MnTnHexOE-2-PyP(5+), MnTE-2-PyPhP(5+), and MnTPhE-2-PyP(5+)) that bear the same positive charge and same number of carbon atoms at meso positions of porphyrin core were explored. The carbon atoms of their meso substituents are organized to form either linear or cyclic structures of vastly different redox properties, bulkiness, and lipophilicities.

Targeting mitochondria by Zn(II)N-alkylpyridylporphyrins: the impact of compound sub-mitochondrial partition on cell respiration and overall photodynamic efficacy.

Mitochondria play a key role in aerobic ATP production and redox control. They harness crucial metabolic pathways and control cell death mechanisms, properties that make these organelles essential for survival of most eukaryotic cells. Cancer cells have altered cell death pathways and typically show a shift towards anaerobic glycolysis for energy production, factors which point to mitochondria as potential culprits in cancer development.

Photodynamic therapy: current status and future directions.

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality used for the management of a variety of cancers and benign diseases. The destruction of unwanted cells and tissues in PDT is achieved by the use of visible or near-infrared radiation to activate a light-absorbing compound (a photosensitizer, PS), which, in the presence of molecular oxygen, leads to the production of singlet oxygen and other reactive oxygen species. These cytotoxic species damage and kill target cells.

Effect of molecular characteristics on cellular uptake, subcellular localization, and phototoxicity of Zn(II) N-alkylpyridylporphyrins.

Tetra-cationic Zn(II) meso-tetrakis(N-alkylpyridinium-2 (or -3 or -4)-yl)porphyrins (ZnPs) with progressively increased lipophilicity were synthesized to investigate how the tri-dimensional shape and lipophilicity of the photosensitizer (PS) affect cellular uptake, subcellular distribution, and photodynamic efficacy. The effect of the tri-dimensional shape of the molecule was studied by shifting the N-alkyl substituent attached to the pyridyl nitrogen from ortho to meta and para positions. Progressive increase of lipophilicity from shorter hydrophilic (methyl) to longer amphiphilic (hexyl) alkyl chains increased the phototoxicity of the ZnP PSs.