Radical decisions in cancer: Redox control of cell growth and death

Free radicals play a key role in many physiological decisions in cells. Since free radicals are toxic to cellular components, it is known that they cause DNA damage, contribute to DNA instability and mutation and thus favor carcinogenesis. However, nowadays it is assumed that free radicals play a further complex role in cancer. Low levels of free radicals and steady state levels of antioxidant enzymes are responsible for the fine tuning of redox status inside cells. A change in redox state is a way to modify the physiological status of the cell, in fact, a more reduced status is found in resting cells while a more oxidative status is associated with proliferative cells. The mechanisms by which redox status can change the proliferative activity of cancer cells are related to transcriptional and posttranscriptional modifications of proteins that play a critical role in cell cycle control. Since cancer cells show higher levels of free radicals compared with their normal counterparts, it is believed that the anti-oxidative stress mechanism is also increased in cancer cells. In fact, the levels of some of the most important antioxidant enzymes are elevated in advanced status of some types of tumors. Anti-cancer treatment is compromised by survival mechanisms in cancer cells and collateral damage in normal non-pathological tissues. Though some resistance mechanisms have been described, they do not yet explain why treatment of cancer fails in several tumors. Given that some antitumoral treatments are based on the generation of free radicals, we will discuss in this review the possible role of antioxidant enzymes in the survival mechanism in cancer cells and then, its participation in the failure of cancer treatments

Antitumor bioactivity and gut microbiota modulation of polyhydroxybutyrate (PHB) in a rat animal model for colorectal cancer

Polyhydroxybutyrate (PHB) is a non-toxic polyhydroxyalkanoate polymer produced by several microorganisms, widely used as a biological substitute for plastics derived from fossil hydrocarbons. In this work, PHB polymer has been tested in an animal model for colorectal cancer. In the animal model, PHB has been able to reduce the number of polyps by 48,1%, and the tumoral extension area by 58,1%. Also, PHB induces a selective increase in beneficial gut bacterial taxons in this animal model, and a selective reduction in pro-inflammatory taxons, demonstrating its value as a nutraceutical compound. This antitumor effect is caused by gut production of 3hydroxybutyrate and butyrate. In this animal model, 3-hydroxybutyrate is also observed in plasma and in brain tissue, after PHB consumption, making PHB supplementation interesting as a bioactive compound in other extraintestinal conditions, as 3-hydroxybutyrate has been reported to enhance brain and cognitive function, cardiac performance, appetite suppression and diabetes. Therefore, PHB could be postulated as an interesting non-polysaccharide antitumor prebiotic, paving the way towards its future use in functional foods

Optimization of flavanonols heterologous biosynthesis in Streptomyces albidoflavus, and generation of auronols

Aromadendrin and taxifolin are two flavanonols (derived from the precursor naringenin) displaying diverse beneficial properties for humans. The carbon skeleton of these flavonoids may be transformed by the human gastrointestinal microbiota into other compounds, like auronols, which exert different and interesting biological activities. While research in flavonoids has become a certainly extensive field, studies about auronols are still scarce. In this work, different versions of the key plant enzyme for flavanonols biosynthesis, The flavanone 3-hydroxylase (F3H), has been screened for selecting the best one for the de novo production of these compounds in the bacterial factory Streptomyces albidoflavus UO-FLAV-004-NAR, a naringenin overproducer strain. This screening has rendered 2.6 μg/L of aromadendrin and 2.1 mg/L of taxifolin final production titers. Finally, the expression of the chalcone isomerase (CHI) from the gut bacterium Eubacterium ramulus has rendered a direct conversion (after feeding experiments) of 38.1% of (+)-aromadendrin into maesopsin and 74.6% of (+)-taxifolin into alphitonin. Moreover, de novo heterologous biosynthesis of 1.9 mg/L of alphitonin was accomplished by means of a co-culture strategy of a taxifolin producer S. albidoflavus and a CHI-expressing Escherichia coli, after the observation of the high instability of alphitonin in the culture medium. This study addresses the significance of culture time optimization and selection of appropriate enzymes depending on the desired final product. To our knowledge, this is the first time that alphitonin de novo production has been accomplished

Functional anthocyanin-rich sausages diminish colorectal cancer in an animal model and reduce pro-inflammatory bacteria in the intestinal microbiota

Colorectal cancer is the fourth most common neoplasia in Europe, where it accounts for 28.2 new cases per 100,000 inhabitants. In an effort to decrease the incidence of this disease, various prevention measures are being studied, one of which are anthocyanin-rich foods. Anthocyanins are potent antioxidant flavonoids mainly found in flowers and colorful fruits and vegetables. These nutraceuticals have diverse biological functions once ingested, including immunomodulatory, anti-inflammatory and antitumor functions. In order to test the preventive effect of these flavonoids against colorectal cancer, an animal model (Rattus norvegicus F344) was developed. In this model two doses of azoxymethane (10 mg/kg) and two treatments with dextran sodium sulfate (DSS) were administered to the animals. For 20 weeks they were fed either control rat feed, control sausages, or functional sausages containing 0.1% (w/w) of anthocyanins from a mixture of dehydrated blackberries and strawberries. At the end of that period, the animals were sacrificed and their antioxidant plasma levels and digestive tract tissues were analyzed. The results revealed a statistically significant reduction in the number of colon tumors in the functional sausages cohort with respect to the control animals and an increase in the FRAP (ferric reducing ability of plasma) total antioxidant activity in that same cohort. Colon microbiota differences were also examined via metagenomics 16S ribosomal RNA (rRNA) sequencing, revealing a significant reduction in populations of the pro-inflammatory Bilophila wadsworthia. Therefore, the design of functional processed meat products, such as ones enriched with anthocyanins, may be an effective strategy for preventing inflammatory digestive diseases and colorectal cancer in human populations

Healthy effects of prebiotics and their metabolites against intestinal diseases and colorectal cancer

A specific group of plant and animal oligosaccharides does not suffer enzymatic digestion in the human upper intestinal tract, achieving the colon microbial ecosystem in intact form. The reason for that is their diverse glycosidic bond structure, in comparison with common energetic polysaccharides as starch or glycogen. In this complex ecosystem, these molecules serve as energy sources, via fermentation, of distinctive beneficial bacterial groups, mainly belonging to the Anaerostipes, Bifidobacterium, Coprococcus, Faecalibacterium, Lactobacillus, Roseburia and other genera. The main catabolic products of these fermentations are short-chain fatty acids (SCFA) as acetate, propionate and butyrate, which appear in high concentrations in the lumen around the colon mucosa. Acetate and propionate are associated to energetic purposes for enterocytes, hepatocytes and other cells. Butyrate is the preferred energy source for colonocytes where it controls their cell cycle; butyrate is able to induce cell cycle arrest and apoptosis in tumor colonocytes. These oligosaccharides that increase beneficial colon bacterial populations and induce SCFA production in this ecosystem are called prebiotics. Here, different sources and chemical structures for prebiotics are described, as well as their modulatory effect on the growth of specific probiotic bacterial groups in the colon, and how their fermentation renders diverse SCFA, with beneficial effects in gut healt

Development of a biosensor protein bullet as a fluorescent method for fast detection of Escherichia coli in drinking water

Drinking water can be exposed to different biological contaminants from the source, through the pipelines, until reaching the final consumer or industry. Some of these are pathogenic bacteria and viruses which may cause important gastrointestinal or systemic diseases. The microbiological quality of drinking water relies mainly in monitoring three indicator bacteria of faecal origin, Escherichia coli, Enterococcus faecalis and Clostridium perfringens, which serve as early sentinels of potential health hazards for the population. Here we describe the analysis of three chimeric fluorescent protein bullets as biosensor candidates for fast detection of E. coli in drinking water. Two of the chimeric proteins (based on GFP-hadrurin and GFP-pb5 chimera proteins) failed with respect to specificity and/or sensitivity, but the GFP-colS4 chimera protein was able to carry out specific detection of E. coli in drinking water samples in a procedure encompassing about 8 min for final result and this biosensor protein was able to detect in a linear way between 20 and 103 CFU of this bacterium. Below 20 CFU, the system cannot differentiate presence or absence of the target bacterium. The fluorescence in this biosensor system is provided by the GFP subunit of the chimeric protein, which, in the case of the better performing sensor bullet, GFP-colS4 chimera, is covalently bound to a flexible peptide bridge and to a bacteriocin binding specifically to E. coli cells. Once bound to the target bacteria, the excitation step with 395 nm LED light causes emission of fluorescence from the GFP domain, which is amplified in a photomultiplier tube, and finally this signal is converted into an output voltage which can be associated with a CFU value and these data distributed along mobile phone networks, for example. This method, and the portable fluorimeter which has been developed for it, may contribute to reduce the analysis time for detecting E. coli presence in drinking water

Multiplex detection of nine food-borne pathogens by mPCR and capillary electrophoresis after using a universal pre-enrichment medium

Routine microbiological quality analyses in food samples require, in some cases, an initial incubation in pre-enrichment medium. This is necessary in order to assure that small amounts of pathogenic strains are going to be detected. In this work, a universal pre-enrichment medium has been developed for simultaneous growth of Bacillus cereus, Campylobacter jejuni, Clostridium perfringens, Cronobacter sakazakii, Escherichia coli, Enterobacteriaceae family (thirty eight species, twenty seven genera), Listeria monocytogenes, Staphylococcus aureus, Salmonella spp. (two species, thirteen strains). Growth confirmation for all these species was achieved in all cases, with excellent enrichments. This was confirmed by plating on the corresponding selective agar media for each bacterium. This GVUM universal pre-enrichment medium could be useful in food microbiological analyses, where different pathogenic bacteria must be detected after a pre-enrichment step. Following, a mPCR reaction for detection of all these pathogens was developed, after designing a set of nine oligonucleotide pairs from specific genetic targets on gDNA from each of these bacteria, covering all available strains already sequenced in GenBank for them. The detection limits have been 1 Genome Equivalent, with the exception of Fam. Enterobacteriaceae (5 GEs). We obtained amplification for all targets (from 70 to 251 bp, depending on the bacteria type), showing the capability of this method to detect the most important industrial and sanitary food-borne pathogens from a universal pre-enrichment medium. This method includes an initial pre-enrichment step (18 h), followed by a mPCR (2 h) and a capillary electrophoresis (30 min); avoiding the tedious and long lasting growing on solid media required in traditional analysis (1 to 4 days, depending on the specific pathogen and verification procedure). An external testing of this method was conducted in order to compare classical and mPCR methods. This evaluation was carried out on five types of food matrixes (meat, dairy products, prepared foods, canned fish and pastry products), which were artificially contaminated with each one of the microorganisms, demonstrating the equivalence between the two methods (coincidence percentages between both methods ranged from 78% to 92%)