Cultured cells of Arachis hypogaea susceptible to induction of stilbene synthase (resveratrol-forming)

Resveratrol as sensitizer in colorectal cancer plasticity

Despite tremendous medical treatment successes, colorectal cancer (CRC) remains a leading cause of cancer deaths worldwide. Chemotherapy as monotherapy can lead to significant side effects and chemoresistance that can be linked to several resistance-activating biological processes, including an increase in inflammation, cellular plasticity, multidrug resistance (MDR), inhibition of the sentinel gene p53, and apoptosis. As a consequence, tumor cells can escape the effectiveness of chemotherapeutic agents. This underscores the need for cross-target therapeutic approaches that are not only pharmacologically safe but also modulate multiple potent signaling pathways and sensitize cancer cells to overcome resistance to standard drugs. In recent years, scientists have been searching for natural compounds that can be used as chemosensitizers in addition to conventional medications for the synergistic treatment of CRC. Resveratrol, a natural polyphenolic phytoalexin found in various fruits and vegetables such as peanuts, berries, and red grapes, is one of the most effective natural chemopreventive agents. Abundant in vitro and in vivo studies have shown that resveratrol, in interaction with standard drugs, is an effective chemosensitizer for CRC cells to chemotherapeutic agents and thus prevents drug resistance by modulating multiple pathways, including transcription factors, epithelial-to-mesenchymal transition-plasticity, proliferation, metastasis, angiogenesis, cell cycle, and apoptosis. The ability of resveratrol to modify multiple subcellular pathways that may suppress cancer cell plasticity and reversal of chemoresistance are critical parameters for understanding its anti-cancer effects. In this review, we focus on the chemosensitizing properties of resveratrol in CRC and, thus, its potential importance as an additive to ongoing treatments.

Resveratrol and p53: How are they involved in CRC plasticity and apoptosis?

BACKGROUND

Colorectal cancer (CRC), which is mainly caused by epigenetic and lifestyle factors, is very often associated with functional plasticity during its development. In addition, the malignant plasticity of CRC cells underscores one of their survival abilities to functionally adapt to specific stresses, including inflammation, that occur during carcinogenesis. This leads to the generation of various subsets of cancer cells with phenotypic diversity and promotes epithelial-mesenchymal transition (EMT), formation of cancer cell stem cells (CSCs) and metabolic reprogramming. This can enhance cancer cell differentiation and facilitate tumorigenic potential, drug resistance and metastasis.

AIM OF REVIEW

The tumor protein p53 acts as one of the central suppressors of carcinogenesis by regulating its target genes, whose proteins are involved in the plasticity of cancer cells, autophagy, cell cycle, apoptosis, DNA repair. The aim of this review is to summarize the latest published research on resveratrol's effect in the prevention of CRC, its regulatory actions, specifically on the p53 pathway, and its treatment options.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Resveratrol, a naturally occurring polyphenol, is a potent inducer of a variety of tumor-controlling. However, the underlying mechanisms linking the p53 signaling pathway to the functional anti-plasticity effect of resveratrol in CRC are still poorly understood. Therefore, this review discusses novel relationships between anti-cellular plasticity/heterogeneity, pro-apoptosis and modulation of tumor protein p53 signaling in CRC oncogenesis, as one of the crucial mechanisms by which resveratrol prevents malignant phenotypic changes leading to cell migration and drug resistance, thus improving the ongoing treatment of CRC.

New Highlights of Resveratrol: A Review of Properties against Ocular Diseases

Eye diseases are currently a major public health concern due to the growing number of cases resulting from both an aging of populations and exogenous factors linked to our lifestyles. Thus, many treatments including surgical pharmacological approaches have emerged, and special attention has been paid to prevention, where diet plays a preponderant role. Recently, potential antioxidants such as resveratrol have received much attention as potential tools against various ocular diseases. In this review, we focus on the mechanisms of resveratrol against ocular diseases, in particular age-related macular degeneration, glaucoma, cataract, diabetic retinopathy, and vitreoretinopathy. We analyze, in relation to the different steps of each disease, the resveratrol properties at multiple levels, such as cellular and molecular signaling as well as physiological effects. We show and discuss the relationship to reactive oxygen species, the regulation of inflammatory process, and how resveratrol can prevent ocular diseases through a potential epigenetic action by the activation of sirtuin-1. Lastly, various new forms of resveratrol delivery are emerging at the same time as some clinical trials are raising more questions about the future of resveratrol as a potential tool for prevention or in therapeutic strategies against ocular diseases. More preclinical studies are required to provide further insights into RSV's potential adjuvant activity.

Myb14, a direct activator of STS, is associated with resveratrol content variation in berry skin in two grape cultivars

High and low resveratrol (Res) contents in two cultivars are correlated with the expression abundance of Myb14 , which could directly activate transcriptional expression of stilbene synthase gene ( STS ). Resveratrol (3,5,4'-trihydroxystilbene) is one of the natural polyphenols produced by secondary metabolism in some plants. Stilbene synthase (STS) is the key enzyme for the final step of precursor formation of resveratrol (Res) in grapevines. In this study, we found that Res contents in ripe berry skin were completely different in two grape cultivars, namely, 'Z168' (Vitis monticola × Vitis riparia) with high-Res and 'Jingzaojing' (Vitis vinifera) with low-Res. Moreover, the level of expression of STS gene was higher in the ripe berry skin of 'Z168' than in that of 'Jingzaojing'. To further investigate the underlying mechanisms, we conducted a co-expression analysis through transcriptomic data. We confirmed that Myb14, an R2R3 Myb transcription factor, is the direct regulator of STS by binding to Box-L5 motif. Moreover, the expression pattern of Myb14 is associated with the variation of Res content. To test this prediction, we conducted a number of experiments in vivo and in vitro. The expression patterns of Myb14 and STS in grapevine leaves were identical under a series of stimulus. Myb14 showed higher expression in the ripe berry skin of 'Z168' than in that of 'Jingzaojing'. Yeast one-hybrid assay indicated that grapevine Myb14 could interact with the promoter of STS in vitro, and the transient overexpression of Myb14 promoted the expression of STS. Furthermore, co-expressing 35S::Myb14 in transgenic Arabidopsis could activate GUS expression promoted by STS promoter. Thus, Myb14 is the direct activator of STS, and its expression pattern is associated with Res content variation in grapes.

Elicitation studies in cell suspension cultures of Cannabis sativa L

Cannabis sativa L. plants produce a diverse array of secondary metabolites. Cannabis cell cultures were treated with biotic and abiotic elicitors to evaluate their effect on secondary metabolism. Metabolic profiles analysed by (1)H NMR spectroscopy and principal component analysis (PCA) showed variations in some of the metabolite pools. However, no cannabinoids were found in either control or elicited cannabis cell cultures. Tetrahydrocannabinolic acid (THCA) synthase gene expression was monitored during a time course. Results suggest that other components in the signaling pathway can be controlling the cannabinoid pathway.

Production of stilbenoids from the callus of Arachis hypogaea: a novel source of the anticancer compound piceatannol

A new source to produce a significant quantity of a naturally occurring polyphenol, piceatannol, was investigated in this study. Both resveratrol and piceatannol are recognized as important ingredients in functional foods due to their beneficial health effects. However, unlike resveratrol, the piceatannol concentration in plants is very low. Thus, calluses of peanuts, an easily obtainable source, were chosen as the material to induce piceatannol production under controlled conditions. To induce resveratrol and piceatannol, calluses were exposed to the ultraviolet (UV) irradiation. Significant quantities of resveratrol and piceatannol were produced by calluses upon UV irradiation in both static and suspension culture conditions. The amounts of piceatannol and resveratrol produced in 1 g of calluses ranged from 2.17 to 5.31 microg and from 0.25 to 11.97 microg, respectively, in static culture. In suspension culture, the amounts of induced piceatannol and resveratrol were somewhat lower. The quantities of induced piceatannol and resveratrol reached a maximum at 18 h after UV irradiation treatment in static culture. In contrast, the levels of resveratrol and piceatannol remained almost constant throughout the experiments in suspension culture. The piceatannol produced by calluses in all studies was much higher than the values reported in the literature, whereas the resveratrol produced was comparable to reported values.

A family of polyketide synthase genes expressed in ripening Rubus fruits

Quality traits of raspberry fruits such as aroma and color derive in part from the polyketide derivatives, benzalacetone and dihydrochalcone, respectively. The formation of these metabolites during fruit ripening is the result of the activity of polyketide synthases (PKS), benzalcetone synthase and chalcone synthase (CHS), during fruit development. To gain an understanding of the regulation of these multiple PKSs during fruit ripening, we have characterized the repertoire of Rubus PKS genes and studied their expression patterns during fruit ripening. Using a PCR-based homology search, a family of ten PKS genes (Ripks1-10) sharing 82-98% nucleotide sequence identity was identified in the Rubus idaeus genome. Low stringency screening of a ripening fruit-specific cDNA library, identified three groups of PKS cDNAs. Group 1 and 2 cDNAs were also represented in the PCR amplified products, while group 3 represented a new class of Rubus PKS gene. The Rubus PKS gene-family thus consists of at least eleven members. The three cDNAs exhibit distinct tissue-specific and developmentally regulated patterns of expression. RiPKS5 has high constitutive levels of expression in all organs, including developing flowers and fruits, while RiPKS6 and RiPKS11 expression is consistent with developmental and tissue-specific regulation in various organs. The recombinant proteins encoded by the three RiPKS cDNAs showed a typical CHS-type PKS activity. While phylogenetic analysis placed the three Rubus PKSs in one cluster, suggesting a recent duplication event, their distinct expression patterns suggest that their regulation, and thus function(s), has evolved independently of the structural genes themselves.

Resveratrol: a molecule whose time has come? And gone?

OBJECTIVES

Resveratrol (3,5,4'-trihydroxystilbene) is the parent compound of a family of molecules, including glucosides and polymers, existing in cis and trans configurations in a narrow range of spermatophytes of which vines, peanuts and pines are the prime representatives. Its synthesis from p-coumaroyl CoA and malonyl CoA is induced by stress, injury, infection or UV-irradiation, and it is classified as a phytoalexin anti-fungicide conferring disease resistance in the plant kingdom.

RESULTS

In vitro, ex vivo and animal experiments have shown that it possesses many biological attributes that favour protection against atherosclerosis, including antioxidant activity, modulation of hepatic apolipoprotein and lipid synthesis, inhibition of platelet aggregation as well as the production of pro-atherogenic eicosanoids by human platelets and neutrophils. Red wine represents its main source in the human diet, and it has been proposed as a major constituent of the polyphenol fraction to which the health benefits of red wine consumption have been attributed.

CONCLUSIONS

The past several years have witnessed intense research devoted to its measurement in wine and the factors likely to promote its enrichment in this beverage. Up to the present, conclusive evidence for its absorption by human subjectsin biologically significant amounts is lacking, and it is questionable (but not yetexcluded) that its powerful and beneficial in vitro activities are reproduced as a consequence of sustained moderate red wine consumption.

Elicitor-specific induction of one member of the chitinase gene family in Arachis hypogaea

Chitinases are believed to play an important role in plant defence against bacterial and fungal attack. In peanut (Arachis hypogaea) chitinase genes form a small multigene family. Four chitinase cDNAs (chit 1-4) were isolated from cultured peanut cells. Expression of individual chit genes was assayed by the polymerase chain reaction (PCR) followed by analysis of restriction fragment length polymorphisms (RFLP). UV irradiation, dilution of cell cultures and treatment with Phytophthora megasperma (Pmg) elicitor or yeast extract were used to induce expression of chit genes. The chit 3 gene is constitutively expressed at a low level in untreated as well as in treated cultures; the expression of chit 4 gene is induced by each of the stimuli tested, whereas the chit 1 gene is activated by cell culture dilution and by yeast extract treatment. The chit 2 gene is strongly activated by treatment with cell wall components from the fungus Phytophthora megasperma but not by the other stimuli. These results indicate that chit 2 gene expression may be controlled by pathogen-specific regulatory elements.

Expression of a stilbene synthase gene in Nicotiana tabacum results in synthesis of the phytoalexin resveratrol

A gene from groundnut (Arachis hypogaea) coding for stilbene synthase was transferred together with a chimaeric kanamycin resistance gene. It was found to be rapidly expressed after induction with UV light and elicitor in tobacco cells (Nicotiana tabacum). Comparative studies of stilbene synthase mRNA synthesis in groundnut and transgenic tobacco suspension cultures revealed the same kinetics of gene expression. Stilbene synthase specific mRNA was detectable 30 minutes after elicitor induction and 10 minutes after UV irradiation. The maximum of mRNA accumulation was between 2 and 8 hours post induction. 24 hours after induction stilbene synthase mRNA accumulation ceased. Furthermore, in transgenic tobacco plants, the gene was found to be inducible in sterile roots, stems and leaves. Stilbene synthase was demonstrated in crude protein extracts from transgenic tobacco cell cultures using specific antibodies. Resveratrol, the product of stilbene synthase, was identified by HPLC and antisera raised against resveratrol.

Differential regulation of genes for resveratrol synthase in cell cultures ofArachis hypogaea L

Resveratrol synthase (RS; EC 2.3.1.-) catalyzes the formation of the phytoalexin resveratrol from 4-coumaroyl-CoA and malonyl-CoA. We present the characterization of new genomic RS sequences (RS3, RS4), and describe studies with gene-specific oligonucleotides on the expression of four different RS sequences (RScDNA, RS1, RS2, RS3) during growth of a cell culture fromArachis hypogaea L. and after application of various inducers (elicitor fromPhytophtora megasperma, yeast extract, and dilution of the cultures). Transcripts from RScDNA were induced by all of the factors tested, and they represented the majority of all identified RS RNAs. Expression from RS1 and RS3 was much lower than from RScDNA, and transcripts from RS2 were never detected. Both RS1 and RS3 were induced by elicitor, but they reacted differently from the other inducers: RS1 was induced by yeast extract, but RS3 was not, and RS3 was induced by dilution of the cultures, but RS1 was not. The results indicate that the RS genes inA. hypogaea represent a gene family, and that some of the members are regulated by different signals. The quantitative data also show that the sum of the transcripts identified with gene-specific oligonucleotides was lower than the total amount of RS-specific transcripts, indicating that the cells contain active genes which have not yet been identified.

Vanadate mimics effects of fungal cell wall in eliciting gene activation in plant cell cultures

Cell-suspension cultures of peanut (Arachis hypogaea L.) can be used as a very sensitive and rapidly responding physiological system for monitoring extracellular signals. Elicitors effect the activation of the genes that code for a set of enzymes synthesizing stilbenes. Within 2-6 h after administering micromolar, concentrations of orthovanadate to the suspended cells, the enzyme activities of phenylalanine ammonia-lyase, stilbene synthase, and cinnamate 4-hydroxylase increased 10-to 100-fold. The transient time course of induction, and the quality and quantity of gene expression found with vanadate as artificial elicitor were very similar to those observed after biotic stress generated by fungal cell walls. The dose-response of vanadate as an elicitor of gene expression in intact cells matched precisely its inhibitory effect on the ATPase activity of isolated plasma membrane. By concentrating, on the profiles of cinnamate 4-hydroxylase activity, we observed differences between the effects elicited by fungal cell wall or vanadate when different stages of cell development were analyzed. Unlike the fungal elicitor, vanadate did not induce the hydroxylase activity when cells at the stationary phase of the cell cycle were used. This lack of response was not the result of a decrease in membrane biosynthesis. The finding, that the effects of vanadate and fungal elicitor are additive indicates that vanadate does not interfere negatively with the perception of the biotic signal but rather addresses the same intracellular intermediate of the signalling process. We hypothesize that membrane potentials created or modulated by ATPases may be intermediates in the signal chain, starting with the recognition process at the plasma membrane and eventually leading to the production of stilbenes as low-molecular-weight plant-defence products.

Control of gene expression during induction of cultured peanut cells: mRNA levels, protein synthesis and enzyme activity of stilbene synthase

Stilbene synthase is an inducible enzyme occurring in a small number of plants. The enzyme is amenable to analysis and biochemical studies only after the cells are subjected to induction. Cell suspension cultures of peanut react very selectively if elicited with biotic inducers. Just as intact peanut plants produce stilbene phytoalexins when attacked by fungi so also do sterile cultured cells when treated with sterilized insoluble fungal cell walls. Both systems react by synthesizing stilbene synthase. The time courses of increase in enzyme activity, protein synthesis and mRNA activity were studied, and their relation to other activities of the cells was elaborated. The results show that, after applying the fungal elicitor, the system responds very quickly and selectively: within 2 hours the synthesis rate of stilbene synthase protein is increased more than 30-fold, the increase being detectable 40 min after induction. The first increase in translatable mRNA for stilbene synthase can be seen 20 min after application of the stimulus. Stilbene synthase synthesized in vivo was compared to stilbene synthase prepared by translation in vitro. There was no difference in size, and limited proteolysis did not indicate significant differences in the peptide structure of the primary translation product and the active enzyme.

Molecular analysis of resveratrol synthase. cDNA, genomic clones and relationship with chalcone synthase

Resveratrol synthase (RS), a key enzyme in biosynthesis of stilbene-type phytoalexins, catalyzes the formation of resveratrol from coumaroyl-CoA and malonyl-CoA. Two cDNA clones, pGSC1 and pGSC2, have been isolated from cDNA libraries established with poly(A)-rich RNA from peanut (Arachis hypogaea) cell cultures specifically induced for RS. These cDNAs were used to identify two genomic clones (pGSG10 and pGSG11). Sequence analysis shows that the two clones overlap in a large stretch of nearly identical sequences, and that pGSG10 contains the 5' and pGSG11 the 3' end of RS genes. The sequences reveal a single intron, and the size of the predicted protein is 42.7 kDa, in close agreement with that observed in polyacrylamide gels (43 kDa). Chalcone synthase (CHS), a key enzyme of flavonoid biosynthesis, utilizes the same substrates as RS, but the product is different (naringenin chalcone). Comparison of RS with CHS consensus sequences shows that the two genes are related. Homology extends throughout the coding region, and the intron in RS is at the same position as a conserved intron in CHS. However, RS reveals a substantial number of amino acid differences to CHS in positions highly conserved in all CHS enzymes. It is proposed that the two proteins possess a common scaffold necessary for binding of the substrates and the type of enzyme reaction, and that the differences are responsible for the formation of different products.

Cell-suspension culture of Arachis hypogaea L.: model system of specific enzyme induction in secondary metabolism

A peanut (Arachis hypogaea L.) cell-suspension culture susceptible to selective induction of stilbene formation was established. The principles of defense responses of the whole plant were found to be retained in the artificial system. The suspension culture was characterized by its growth curve and by various biochemical parameters. In the stationary phase, reached 8 d after transfer to a new medium, the formation of stilbenes and stilbene synthase could be induced without altering the levels of other enzymes. Eighteen hours after applying an artificial elicitor (ultraviolet-C light) or 4 h after eliciting with a crude preparation of Phytophthora cambivora cell walls, phenylalanineammonia-lyase activity was increased eightfold and stilbene-synthase activity 20-fold. The activity of phenylalanine ammonia-lyase reached its peak at a slightly different time from that of stilbene synthase. The main products of L-phenylalanine metabolism in the induced cells were resveratrol, 3,3',5-trihydroxy-4'-methoxystilbene and isopentenylresveratrol. Likewise, feruloyl-CoA reductase, as a parameter of lignin formation, was enhanced following induction, albeit with a different time course and with a less steep increase than found for phenylalanine ammonia-lyase and stilbene synthase.

Action of ultraviolet-C on stilbene formation in callus ofArachis hypogaea

The action of light on the formation of stilbenes and the induction of stilbene synthase in dark-grown and light-grown callus of peanut (Arachis hypogaea) was investigated over the wavelength range from 250 to 400 nm. Ultraviolet light of 260-270 nm had a significant and selective effect on the formation of resveratrol and isopentenylresveratrol. The callus responded by the production of stilbene synthase, with maximal activity appearing 4 h after irradiation with a fluence rate of 1 W m(-2) (270 nm) applied for 10 min. At lower fluence rates, maximal responses in enzyme activity were shifted to longer induction periods. The efficiency of the biosynthetic pathway, and the form and maxima of enzyme profiles depended on the duration of exposure. We failed to demonstrate any significant influence of red light at low energy irradiation (672 nm, 726 nm and 753 nm).