Evidence for quinol oxidase activity of ImoA, a novel NapC/NirT family protein from the neutrophilic Fe(II) oxidizing bacterium Sideroxydans lithotrophicus ES-1

The freshwater chemolithoautotrophic Gram-negative bacterium Sideroxydans lithotrophicus ES-1 oxidizes Fe(II) at the cell surface. In this organism, it is proposed that the monoheme cytochrome MtoD from the Mto pathway transfer electrons across the periplasm to an inner membrane NapC/NirT family tetraheme cytochrome encoded by Slit_2495, for which we propose the name ImoA (inner membrane oxidoreductase). ImoA has been proposed to function as the quinone reductase, receiving electrons from iron oxidizing extracellular electron uptake pathway to reduce the quinone pool. In this study, ImoA was cloned on a pBAD plasmid vector and overexpressed in Escherichia coli. Biochemical and spectroscopic characterization of the purified ImoA reveals that this 26.5 kDa cytochrome contains one high-spin and three low-spin hemes. Our data show that ImoA can function as a quinol oxidase and is able to functionally replace CymA, a related NapC/NirT family tetraheme cytochrome required for anaerobic respiration of a wide range of substrates by Shewanella oneidensis. We demonstrate that ImoA can transfer electrons to different periplasmic proteins from S. oneidensis including STC and FccA, but in a manner that is distinct from that of CymA. Phylogenetic analysis shows that ImoA is clustered closer to NirT sequences than to CymA. This study suggests that ImoA functions as a quinol oxidase in S. oneidensis and raises questions about the directionality and/or reversibility of electron flow through the Mto pathway in S. lithotrophicus ES-1.

Cancer chemopreventive and antioxidant activities of seed, skin, and pulp of Maximo hybrid grapes (IAC 138-22) at five different ripening stages

ABSTRACT: This study evaluated the composition and the cancer chemopreventive and antioxidant activities of the seed, skin, and pulp of Maximo hybrid grapes (IAC 138-22) harvested at different ripening stages. The content of total phenolic compounds and tannins were determined by the Folin-Ciocaulteau method, and total anthocyanins were determined using the differential pH method. Different chemical methods assessed the antioxidant activity. Cell viability (macrophage and melanoma skin cancer) and cancer chemopreventive activity were tested in cell lines by quinone reductase induction assay, TNF-α-induced NF-κB inhibitory activity assay, and aromatase inhibitory activity assay. The hybrid grape had high phenolic contents in both seeds and skin, significantly reduced upon ripening. The results showed that fruit ripening significantly affected both the composition and the antioxidant and cancer chemopreventive activities. Except for the anthocyanin content, the most significant results were observed for green seeds, with the greenest stage showing the best results. The green seeds showed the highest antioxidant activity, even when compared to free resveratrol. In the assessment of cancer chemopreventive activity, the green seeds showed the ability to inhibit N-FκB and aromatase activity, important factors for the early stage of cancer development. Besides, no extracts showed cytotoxicity. Therefore, this grape’s green seeds showed strong antioxidant and cancer chemopreventive activities confirmed herein, suggesting beneficial health effects.

Neuroprotective Properties of Quinone Reductase 2 Inhibitor M-11, a 2-Mercaptobenzimidazole Derivative

The ability of NQO2 to increase the production of free radicals under enhanced generation of quinone derivatives of catecholamines is considered to be a component of neurodegenerative disease pathogenesis. The present study aimed to investigate the neuroprotective mechanisms of original NQO2 inhibitor M-11 (2-[2-(3-oxomorpholin-4-il)-ethylthio]-5-ethoxybenzimidazole hydrochloride) in a cellular damage model using NQO2 endogenous substrate adrenochrome (125 µM) and co-substrate BNAH (100 µM). The effects of M-11 (10–100 µM) on the reactive oxygen species (ROS) generation, apoptosis and lesion of nuclear DNA were evaluated using flow cytometry and single-cell gel electrophoresis assay (comet assay). Results were compared with S29434, the reference inhibitor of NQO2. It was found that treatment of HT-22 cells with M-11 results in a decline of ROS production triggered by incubation of cells with NQO2 substrate and co-substrate. Pre-incubation of HT-22 cells with compounds M-11 or S29434 results in a decrease of DNA damage and late apoptotic cell percentage reduction. The obtained results provide a rationale for further development of the M-11 compound as a potential neuroprotective agent.

Cytotoxicity Profile of Calix[4]pyrrole Derivatives on HeLa and MCF-7 Human Cancer Cell Lines via In vitro Study and Molecular Modelling

Amongst significant macromolecules, the cytotoxic activity of calixarene analogs is significant due to their unique biomedical properties. Recently, calix[4]pyrrole have shown remarkable efficacy and have extended new dimensions towards different biomedical and therapeutic applications. Herein, meso-tetra (methyl) meso-tetra (3-methoxy 4-hydroxy phenyl) calix[4]pyrrole (HMCP) have been studied for their remarkable cytotoxic activity against HeLa and human breast adenocarcinoma (MCF-7) cancer cell lines in comparison to its hydrazide derivative, meso-tetra (methyl) meso-tetra (3-methoxy 4-hydroxy phenoxy acetatohydrazide) calix[4]pyrrole (MCPTH). Cytotoxicity assays were studied at varying concentrations where HMCP molecule was very active against cancer cell lines with G150 values less than 10. The cell viability has been examined by SRB assay. The anti-cancerous activity results of HMCP can be potentially extended with applications in cancer therapies. Furthermore, the structure and anti-cancer activity relationship has been supported by molecular docking study of the active compounds against quinone reductase-2 (PDB ID 4ZVM) protein.

MdaB and NfrA, two novel reductases important in the survival and persistence of the major enteropathogen Campylobacter jejuni

The paralogues RrpA and RrpB which are members of MarR family of DNA binding proteins are important for the survival of the global bacterial foodborne pathogen Campylobacter jejuni under redox stress. We report that RrpA is a positive regulator of mdaB , encoding a flavin-dependent quinone reductase that contributes to the protection from redox stress mediated by structurally diverse quinones, whilst RrpB negatively regulates the expression of cj1555c (renamed nfrA for NADPH-flavin reductase A), encoding a flavin reductase. NfrA reduces riboflavin at a greater rate than its derivatives, suggesting exogenous free flavins are the natural substrate. MdaB and NfrA both prefer NADPH as an electron donor. Cysteine substitution and post-translational modification analyses indicated that RrpA and RrpB employ a cysteine-based redox switch. Complete genome sequence analyses revealed mdaB is frequently found in Campylobacter and related Helicobacter spp ., whilst nfrA is predominant in C. jejuni strains. Quinones and flavins are redox cycling agents secreted by a wide range of cell-types that can form damaging superoxide by one-electron reactions. We propose a model for stress adaptation where MdaB and NfrA facilitate a two-electron reduction mechanism to the less toxic hydroquinones, thus aiding survival and persistence of this major pathogen. Importance Changes in cellular redox potential results in alteration in the oxidation state of intracellular metabolites and enzymes, consequently, cells make adjustments that favor growth and survival. The work we present here answers some of the many questions that have remained elusive over the years of investigation into the enigmatic microaerophile bacterium, Campylobacter jejuni . We employed molecular approaches to understand the regulation mechanisms and functional analyses to reveal the roles of two novel quinone and flavin reductases, both serve as major pools of cellular redox-active molecules. This work extends our knowledge on bacterial redox sensing mechanisms and the significance of hemostasis.

The Analysis of NADPH Quinone Reductase 1 (NQO1) Polymorphism in Polish Patients with Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignancies in Poland. Based on the findings of clinical trials, it is safe to conclude that genetic predisposition and environmental factors are the main factors responsible for the formation of colorectal cancer.The NQO1 gene plays an important role in reducing endogenous and exogenous quinones as well as quinone compounds to hydroquinones. It is an enzyme which is a part of the body’s antioxidant defense system. The aim of the study was to evaluate the correlation between the 609C > T polymorphism of the NQO1 gene and colorectal cancer risk in the Polish population. A total of 512 people were recruited for the study, including 279 patients with colorectal cancer, diagnosed at the University Hospital, Pomeranian Medical University in Szczecin. Genomic DNA was isolated from peripheral blood and the analyzed polymorphism was determined by PCR-RFLP. In the present study, we analyzed the clinical valuesand frequency of NQO1 609C > T polymorphism in patients diagnosed with colorectal cancer and controls. In case of the carriers of the TT genotype of the NQO1 polymorphism, an elevated risk for colorectal cancer was observed (OR = 2.96; 95% CI: 1.02–10.40). The analysis of the clinical parameters concerning the location and characteristics of the tumor stage revealed a statistically significant increase in the risk for colorectal cancer in the carriers of the TT genotype of the NQO1 polymorphism.

Reversal of Insulin Resistance in Overweight and Obese Subjects by trans-Resveratrol and Hesperetin Combination—Link to Dysglycemia, Blood Pressure, Dyslipidemia, and Low-Grade Inflammation

The dietary supplement, trans-resveratrol and hesperetin combination (tRES-HESP), induces expression of glyoxalase 1, countering the accumulation of reactive dicarbonyl glycating agent, methylglyoxal (MG), in overweight and obese subjects. tRES-HESP produced reversal of insulin resistance, improving dysglycemia and low-grade inflammation in a randomized, double-blind, placebo-controlled crossover study. Herein, we report further analysis of study variables. MG metabolism-related variables correlated with BMI, dysglycemia, vascular inflammation, blood pressure, and dyslipidemia. With tRES-HESP treatment, plasma MG correlated negatively with endothelial independent arterial dilatation (r = −0.48, p < 0.05) and negatively with peripheral blood mononuclear cell (PBMC) quinone reductase activity (r = −0.68, p < 0.05)—a marker of the activation status of transcription factor Nrf2. For change from baseline of PBMC gene expression with tRES-HESP treatment, Glo1 expression correlated negatively with change in the oral glucose tolerance test area-under-the-curve plasma glucose (ΔAUGg) (r = −0.56, p < 0.05) and thioredoxin interacting protein (TXNIP) correlated positively with ΔAUGg (r = 0.59, p < 0.05). Tumor necrosis factor-α (TNFα) correlated positively with change in fasting plasma glucose (r = 0.70, p < 0.001) and negatively with change in insulin sensitivity (r = −0.68, p < 0.01). These correlations were not present with placebo. tRES-HESP decreased low-grade inflammation, characterized by decreased expression of CCL2, COX-2, IL-8, and RAGE. Changes in CCL2, IL-8, and RAGE were intercorrelated and all correlated positively with changes in MLXIP, MAFF, MAFG, NCF1, and FTH1, and negatively with changes in HMOX1 and TKT; changes in IL-8 also correlated positively with change in COX-2. Total urinary excretion of tRES and HESP metabolites were strongly correlated. These findings suggest tRES-HESP counters MG accumulation and protein glycation, decreasing activation of the unfolded protein response and expression of TXNIP and TNFα, producing reversal of insulin resistance. tRES-HESP is suitable for further evaluation for treatment of insulin resistance and related disorders.

Quinone reductase activity is widespread in lichens

In our earlier work, we demonstrated that the oxidases tyrosinase (TYR), laccase (LAC), and a heme peroxidase (POX) occur widely in lichens. Here we report on the occurrence of another oxidoreductase enzyme, quinone reductase (QR) (EC 1.6.5.5). While QR has been reported to occur widely in other organisms, there is currently no information on QR activities in lichens. Here we present a survey of QR activity in 14 species of lichens. Results demonstrate that QR activity is readily detectable in all lichen species tested. However, activities vary greatly, with ‘jelly’ lichens in the genera Collema and Leptogium having the highest activities. QR, LAC and POX are all believed to have a role in extracellular hydroxyl radical production. However, in this study no correlation was found between the activities of these enzymes and the rates at which hydroxyl radicals were produced. Possible roles for QR in lichen biology are discussed.