Resveratrol protects human keratinocytes HaCaT cells from UVA-induced oxidative stress damage by downregulating Keap1 expression

Phytochemicals for the Prevention of Photocarcinogenesis

Ultraviolet (UV) exposure has an array of damaging effects and is the main cause of skin cancer in humans. Nonmelanoma skin cancer (NMSC), including basal cell carcinoma and squamous cell carcinoma, is the most common type of cancer. Incidence of NMSC has increased due to greater UV radiation, increased life expectancy and other changes in lifestyle; the annual cost of skin cancer treatment in the United States has increased concurrently to around eight billion dollars. Because of these trends, novel approaches to skin cancer prevention have become an important area of research to decrease skin cancer morbidity and defray the costs associated with treatment. Chemoprevention aims to prevent or delay the development of skin cancer through the use of phytochemicals. Use of phytochemicals as chemopreventive agents has gained attention due to their low toxicity and anticarcinogenic properties. Phytochemicals also exhibit antioxidant, anti-inflammatory and antiproliferative effects which support their use as chemopreventive agents, particularly for skin cancer. Preclinical and human studies have shown that phytochemicals decrease UV-induced skin damage and photocarcinogenesis. In this review article, we discuss the selected phytochemicals that may prevent or delay UV-induced carcinogenesis and highlight their potential use for skin protection.

Diet phytochemicals and cutaneous carcinoma chemoprevention: A review

Cutaneous carcinoma, which has occupied a peculiar place among worldwide populations, is commonly responsible for the considerably increasing morbidity and mortality rates. Currently available medical procedures fail to completely avoid cutaneous carcinoma development or to prevent mortality. Cancer chemoprevention, as an alternative strategy, is being considered to reduce the incidence and burden of cancers through chemical agents. Derived from dietary foods, phytochemicals have become safe and reliable compounds for the chemoprevention of cutaneous carcinoma by relieving multiple pathological processes, including oxidative damage, epigenetic alteration, chronic inflammation, angiogenesis, etc. In this review, we presented comprehensive knowledges, main molecular mechanisms for the initiation and development of cutaneous carcinoma as well as effects of various diet phytochemicals on chemoprevention.

Towards therapeutic advances in melanoma management: An overview

Melanoma is one of the most aggressive types of skin cancer with rapidly increasing incidence rate. The disease is largely considered incurable and the patients diagnosed with metastatic melanoma have a survival of not more than five years. Despite of the recent advances in anti-melanoma chemo- and immunotherapies, the available drugs are relatively toxic and responsive to only a limited subset of lesions. Currently, topical pharmacotherapy is demonstrated as an effective approach for the treatment of various skin cancers. Also, in vitro testing of melanoma cell lines and murine melanoma models has identified a number of relatively safe and effective phytochemicals. In this review, we described the use of topical pharmacotherapy for the treatment of skin cancers. Melanoma treatment by drugs targeting MAPK-pathway has also been discussed. Long non-coding RNAs and therapeutics targeting ER-associated pathways looks quite promising for the treatment of melanoma. Moreover, some natural anticancer compounds that have been reported to have anti-melanoma effects have also been described. At present a better understanding of genetics and epigenetics of initiation and progression of melanoma is needed for the identification of novel biomarkers and development of targeted therapeutics against melanoma.

Nrf2- and Bach1 May Play a Role in the Modulation of Ultraviolet A-Induced Oxidative Stress by Acetyl-11-Keto-β-Boswellic Acid in Skin Keratinocytes

BACKGROUND

Exposure of human skin to solar ultraviolet A (UVA) irradiation causes severe oxidative stress with damage to various cellular components and concomitant inflammation and carcinogenesis.

OBJECTIVE

The aim of this study is to investigate the protective effect of acetyl-11-keto-β-boswellic acid (AKBA) against UVA radiation on human skin keratinocytes.

METHODS

HaCaT cells were pretreated with AKBA followed by UVA irradiation. Radiation effects on cell morphology, cell viability, intracellular reactive oxygen species (ROS) levels, and antioxidant enzymes were examined.

RESULTS

AKBA reduces UVA irradiation-induced cell viability loss, accompanied by a decreased production of UVA-induced ROS, decreased malondialdehyde, and increased superoxide dismutase expression. In addition, AKBA increased basal and UVA-induced levels of Nrf2 (NF-E2-related factor 2), the redox-sensitive factor, and its target genes NQO1 and heme oxygenase-1 (HO-1), whereas expression of the transcriptional repressor Bach1 (BTB and CNC homology 1) was reduced. Furthermore, the cytoprotective effects of AKBA against UVA-derived oxidative damage were accompanied by modulating expression of inflammatory mediators (i.e., cyclooxygenase-2 and nuclear factor-κB) and NOX1.

CONCLUSIONS

AKBA protects skin cells from UVA-induced damage by modulating inflammatory mediators and/or ROS production. Therefore, AKBA has potential in the development of skin care products.

Rutin as a Mediator of Lipid Metabolism and Cellular Signaling Pathways Interactions in Fibroblasts Altered by UVA and UVB Radiation

Background. Rutin is a natural nutraceutical that is a promising compound for the prevention of UV-induced metabolic changes in skin cells. The aim of this study was to examine the effects of rutin on redox and endocannabinoid systems, as well as proinflammatory and proapoptotic processes, in UV-irradiated fibroblasts. Methods. Fibroblasts exposed to UVA and UVB radiation were treated with rutin. The activities and levels of oxidants/antioxidants and endocannabinoid system components, as well as lipid, DNA, and protein oxidation products, and the proinflammatory and pro/antiapoptotic proteins expression were measured. Results. Rutin reduced UV-induced proinflammatory response and ROS generation and enhanced the activity/levels of antioxidants (SOD, GSH-Px, vitamin E, GSH, and Trx). Rutin also normalized UV-induced Nrf2 expression. Its biological activity prevented changes in the levels of the lipid mediators: MDA, 4-HNE, and endocannabinoids, as well as the endocannabinoid receptors CB1/2, VR1, and GPR55 expression. Furthermore, rutin prevented the protein modifications (tyrosine derivatives formation in particular) and decreased the levels of the proapoptotic markers—caspase-3 and cytochrome c. Conclusion. Rutin prevents UV-induced inflammation and redox imbalance at protein and transcriptional level which favors lipid, protein, and DNA protection. In consequence rutin regulates endocannabinoid system and apoptotic balance.

Plant Phenols and Autophagy

Many plant phenols (stilbenes, curcumins, catechins, flavonoids, etc.) are effective antioxidants and protect cells during oxidative stress. Extensive clinical studies on the potential of phenolic compounds for treatment of cardiovascular, neurodegenerative, oncological, and inflammatory diseases are now being conducted. In addition to direct antioxidant effect, plant phenols may provide a protective effect via activation of the Keap1/Nrf2/ARE redox-sensitive signaling system and regulation of autophagy. In this review, mechanisms of effects of the most common plant phenols on autophagy are presented.

Activation of Nrf2 Reduces UVA-Mediated MMP-1 Upregulation via MAPK/AP-1 Signaling Cascades: The Photoprotective Effects of Sulforaphane and Hispidulin

UVA irradiation plays a role in premature aging of the skin through triggering oxidative stress-associated stimulation of matrix metalloproteinase-1 (MMP-1) responsible for collagen degradation, a hallmark of photoaged skin. Compounds that can activate nuclear factor E2-related factor 2 (Nrf2), a transcription factor regulating antioxidant gene expression, should therefore serve as effective antiphotoaging agents. We investigated whether genetic silencing of Nrf2 could relieve UVA-mediated MMP-1 upregulation via activation of mitogen-activated protein kinase (MAPK)/activator protein 1 (AP-1) signaling using human keratinocyte cell line (HaCaT). Antiphotoaging effects of hispidulin (HPD) and sulforaphane (SFN) were assessed on their abilities to activate Nrf2 in controlling MMP-1 and collagen expressions in association with phosphorylation of MAPKs (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38), c-Jun, and c-Fos, using the skin of BALB/c mice subjected to repetitive UVA irradiation. Our findings suggested that depletion of Nrf2 promoted both mRNA expression and activity of MMP-1 in the UVA-irradiated HaCaT cells. Treatment of Nrf2 knocked-down HaCaT cells with MAPK inhibitors significantly suppressed UVA-induced MMP-1 and AP-1 activities. Moreover, pretreatment of the mouse skin with HPD and SFN, which could activate Nrf2, provided protective effects against UVA-mediated MMP-1 induction and collagen depletion in correlation with the decreased levels of phosphorylated MAPKs, c-Jun, and c-Fos in the mouse skin. In conclusion, Nrf2 could influence UVA-mediated MMP-1 upregulation through the MAPK/AP-1 signaling cascades. HPD and SFN may therefore represent promising antiphotoaging candidates.

Antioxidant capacity of phytochemicals and their potential effects on oxidative status in animals - A review

Oxidative stress suppresses animal health, performance, and production, subsequently impacting economic feasibility; hence, maintaining and improving oxidative status especially through natural nutrition strategy are essential for normal physiological process in animals. Phytochemicals are naturally occurring antioxidants that could be considered as one of the most promising materials used in animal diets in various forms. In this review, their antioxidant effects on animals are discussed as reflected by improved apparent performance, productivity, and the internal physiological changes. Moreover, the antioxidant actions toward animals further describe a molecular basis to elucidate their underlying mechanisms targeting signal transduction pathways, especially through the antioxidant response element/nuclear factor (erythroid-derived 2)-like 2 transcription system.

Use of Polyphenolic Compounds in Dermatologic Oncology

Polyphenols are a widely used class of compounds in dermatology. While phenol itself, the most basic member of the phenol family, is chemically synthesized, most polyphenolic compounds are found in plants and form part of their defense mechanism against decomposition. Polyphenolic compounds, which include phenolic acids, flavonoids, stilbenes, and lignans, play an integral role in preventing the attack on plants by bacteria and fungi, as well as serving as cross-links in plant polymers. There is also mounting evidence that polyphenolic compounds play an important role in human health as well. One of the most important benefits, which puts them in the spotlight of current studies, is their antitumor profile. Some of these polyphenolic compounds have already presented promising results in either in vitro or in vivo studies for non-melanoma skin cancer and melanoma. These compounds act on several biomolecular pathways including cell division cycle arrest, autophagy, and apoptosis. Indeed, such natural compounds may be of potential for both preventive and therapeutic fields of cancer. This review evaluates the existing scientific literature in order to provide support for new research opportunities using polyphenolic compounds in oncodermatology.

Resveratrol-Loaded Liquid-Crystalline System Inhibits UVB-Induced Skin Inflammation and Oxidative Stress in Mice

Evidence shows beneficial effects of resveratrol (RES) on human health. However, its poor aqueous solubility limits therapeutic effectiveness. Thus, the use of nanostructured delivery systems for RES, such as a liquid-crystalline system (LCS), could be viable. The purpose of this study was to develop, characterize, and determine the in vivo effectiveness of a RES-loaded LCS. We studied an LCS containing silicon glycol copolymer, polyether functional siloxane, and the polymeric dispersion carbomer homopolymer type B (C974) in the ratio 20:55:25 with and without RES. Results obtained using polarized light microscopy, small-angle X-ray scattering, and rheology analysis showed that the RES-loaded LCS system presents a lamellar structure and behaves as a non-Newtonian fluid presenting pseudoplastic (the apparent viscosity decreases as the stress increases) and thixotropic (the apparent viscosity decreases with the duration of stress) behaviors. Cytotoxicity studies showed that the formulation components are noncytotoxic. Topical application of a RES-loaded LCS protected hairless mice from UVB-irradiation-induced skin damage by inhibiting edema, neutrophil recruitment, lipid hydroperoxide and superoxide anion production, gp91phox mRNA expression, and oxidative stress. The RES-loaded LCS maintained 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing abilities, catalase activity, reduced glutathione levels, and mRNA expression of glutathione peroxidase 1 and glutathione reductase. The RES-loaded LCS also up-regulated matrix metalloproteinase-9 activity, IL-10 production, and mRNA expression of transcription factor Nrf2 and heme oxygenase-1. Therefore, a RES-loaded LCS is a promising new therapeutic approach to mitigate skin photodamage.

Cancer prevention and therapy through the modulation of the tumor microenvironment

Cancer arises in the context of an in vivo tumor microenvironment. This microenvironment is both a cause and consequence of tumorigenesis. Tumor and host cells co-evolve dynamically through indirect and direct cellular interactions, eliciting multiscale effects on many biological programs, including cellular proliferation, growth, and metabolism, as well as angiogenesis and hypoxia and innate and adaptive immunity. Here we highlight specific biological processes that could be exploited as targets for the prevention and therapy of cancer. Specifically, we describe how inhibition of targets such as cholesterol synthesis and metabolites, reactive oxygen species and hypoxia, macrophage activation and conversion, indoleamine 2,3-dioxygenase regulation of dendritic cells, vascular endothelial growth factor regulation of angiogenesis, fibrosis inhibition, endoglin, and Janus kinase signaling emerge as examples of important potential nexuses in the regulation of tumorigenesis and the tumor microenvironment that can be targeted. We have also identified therapeutic agents as approaches, in particular natural products such as berberine, resveratrol, onionin A, epigallocatechin gallate, genistein, curcumin, naringenin, desoxyrhapontigenin, piperine, and zerumbone, that may warrant further investigation to target the tumor microenvironment for the treatment and/or prevention of cancer.

Intestinal immune function, antioxidant status and tight junction proteins mRNA expression in young grass carp (Ctenopharyngodon idella) fed riboflavin deficient diet

This study investigated the effects of riboflavin on intestinal immunity, tight junctions and antioxidant status of young grass carp (Ctenopharyngodon idella). Fish were fed diets containing graded levels of riboflavin (0.63-10.04 mg/kg diet) for 8 weeks. The study indicated that riboflavin deficiency decreased lysozyme, acid phosphatase, copper/zinc superoxide dismutase, glutathione reductase and glutathione peroxidase activities, and contents of complement component 3 and reduced glutathione in the intestine of fish (P < 0.05). Meanwhile, riboflavin deficiency increased reactive oxygen species, malondialdehyde and protein carbonyl contents and catalase activity (P < 0.05) in the intestine of fish. Furthermore, real-time polymerase chain reaction analysis was used to investigate mRNA expression patterns and found that the mRNA levels of interleukin 10 and transforming growth factor β1, Occludin, zonula occludens 1, Claudin-b and Claudin-c, inhibitor protein κBα, target of rapamycin, ribosomal S6 protein kinase 1 and NF-E2-related factor 2, copper/zinc superoxide dismutase, glutathione peroxidase and glutathione reductase were decreased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. Conversely, the mRNA levels of tumor necrosis factor α, interleukin 1β, interleukin 8, nuclear factor kappa B p65, Ikappa B kinase β, Ikappa B kinase γ, Kelch-like-ECH-associated protein 1b, p38 mitogen-activated protein kinase, myosin light chain kinase and Claudin-12 were increased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. In conclusion, riboflavin deficiency decreased immunity and structural integrity of fish intestine. The optimum riboflavin level for intestinal acid phosphatase activity of young grass carp was estimated to be 6.65 mg/kg diet.

Nrf2--A regulator of keratinocyte redox signaling

The skin is frequently exposed to environmental challenges, such as UV irradiation, toxic chemicals, and mechanical wounding. These insults cause an increase in the levels of reactive oxygen species, resulting in oxidative stress and concomitant inflammation, skin aging, and even cancer development. Therefore, an efficient antioxidant defense strategy is of major importance in this tissue. Since the Nrf2 transcription factor regulates a battery of genes involved in the defense against reactive oxygen species and in compound metabolism, it plays a key role in skin homeostasis, repair, and disease. In this review we summarize current knowledge on the expression and function of Nrf2 in normal skin and its role in the acute and chronic UV response as well as in the pathogenesis of epithelial skin cancer and of different inflammatory skin diseases. Finally, we discuss the potential of Nrf2-activating compounds for skin protection under stress conditions and for the treatment of major human skin disorders.

Dermato-protective properties of ergothioneine through induction of Nrf2/ARE-mediated antioxidant genes in UVA-irradiated Human keratinocytes

UVA irradiation-induced skin damage and redox imbalance have been shown to be ameliorated by ergothioneine (EGT), a naturally occurring sulfur-containing amino acid. However, the responsible molecular mechanism with nanomolar concentrations of EGT remains unclear. We investigated the dermato protective efficacies of EGT (125-500nM) against UVA irradiation (15J/cm(2)), and elucidated the underlying molecular mechanism in human keratinocyte-derived HaCaT cells. We found that EGT treatment prior to UVA exposure significantly increased the cell viability and prevented lactate dehydrogenase release into the medium. UVA-induced ROS and comet-like DNA formation were remarkably suppressed by EGT with a parallel inhibition of apoptosis, as evidenced by reduced DNA fragmentation (TUNEL), caspase-9/-3 activation, and Bcl-2/Bax dysregulation. Furthermore, EGT alleviated UVA-induced mitochondrial dysfunction. Dose-dependent increases of antioxidant genes, HO-1, NQO-1, and γ-GCLC and glutathione by EGT were associated with upregulated Nrf2 and downregulated Keap-1 expressions. This was confirmed by increased nuclear accumulation of Nrf2 and inhibition of Nrf2 degradation. Notably, augmented luciferase activity of ARE may explain Nrf2/ARE-mediated signaling pathways behind EGT dermato-protective properties. We further demonstrated that Nrf2 translocation was mediated by PI3K/AKT, PKC, or ROS signaling cascades. This phenomenon was confirmed with suppressed nuclear Nrf2 activation, and consequently diminished antioxidant genes in cells treated with respective pharmacological inhibitors (LY294002, GF109203X, and N-acetylcysteine). Besides, increased basal ROS by EGT appears to be crucial for triggering the Nrf2/ARE signaling pathways. Silencing of Nrf2 or OCTN1 (EGT carrier protein) signaling with siRNA showed no such protective effects of EGT against UVA-induced cell death, ROS, and apoptosis, which is evidence of the vitality of Nrf2 translocation and protective efficacy of EGT in keratinocytes. Our findings conclude that EGT at nanomolar concentrations effectively ameliorated UVA-induced skin damage, and may be considered as a desirable food supplement for skin protection and/or preparation of skin care products.

Topical treatment with pterostilbene, a natural phytoalexin, effectively protects hairless mice against UVB radiation-induced skin damage and carcinogenesis

The aim of our study was to investigate in the SKH-1 hairless mouse model the effect of pterostilbene (Pter), a natural dimethoxy analog of resveratrol (Resv), against procarcinogenic ultraviolet B radiation (UVB)-induced skin damage. Pter prevented acute UVB (360 mJ/cm(2))-induced increase in skin fold, thickness, and redness, as well as photoaging-associated skin wrinkling and hyperplasia. Pter, but not Resv, effectively prevented chronic UVB (180 mJ/cm(2), three doses/week for 6 months)-induced skin carcinogenesis (90% of Pter-treated mice did not develop skin carcinomas, whereas a large number of tumors were observed in all controls). This anticarcinogenic effect was associated with (a) maintenance of skin antioxidant defenses (i.e., glutathione (GSH) levels, catalase, superoxide, and GSH peroxidase activities) close to control values (untreated mice) and (b) an inhibition of UVB-induced oxidative damage (using as biomarkers 8-hydroxy-2'-deoxyguanosine, protein carbonyls, and isoprostanes). The molecular mechanism underlying the photoprotective effect elicited by Pter was further evaluated using HaCaT immortalized human keratinocytes and was shown to involve potential modulation of the Nrf2-dependent antioxidant response.

Photoprotective effects of oxyresveratrol and Kuwanon O on DNA damage induced by UVA in human epidermal keratinocytes

Ultraviolet A not only plays a major part in photoaging and skin tanning but also induces genetic damage and mutation in the epidermal basal layer of human skin. The photoprotective effect of oxyresveratrol and kuwanon O, two phenolic compounds from the root extract of Morus australis, in human primary epidermal keratinocytes was investigated in this study. Both of them were nontoxic to cells at a concentration less than 10 and 0.5 μM, respectively. After pretreatment at the concentrations of 5 and 10 μM, oxyresveratrol increased cell viability, exhibited significant suppressions on UVA- or H2O2-induced cellular ROS. UVA-enhanced nitrotyrosine was also reduced by post-treatment with oxyresveratrol at theses concentrations. Kuwanon O presented similar inhibitions on cellular ROS and nitrotyrosine with lower concentrations (0.25 and 0.5 μM), but there is no significant protection on cell survival after UVA irradiation. Their photoprotective effects also involved the enhanced repair of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and cyclobutane pyrimidine dimers (CPDs) as mediated by the augment of p53 expression after UVA radiation.

Anticedants and natural prevention of environmental toxicants induced accelerated aging of skin

Skin is frequently exposed to a variety of environmental and chemical agents that accelerate ageing. External stress such as UV radiations (UVR) and environmental pollutants majorly deteriorate the skin morphology, by activating certain intrinsic factors such as Reactive Oxygen Species (ROS) which trigger the activation of Matrix Metalloproteinases (MMPs) and inflammatory responses hence damaging the extracellular matrix (ECM) components. To counter this, an exogenous supply of anti-oxidants, is required since the endogenous anti-oxidant system cannot alone suffice the need. Bio-prospecting of natural resources for anti-oxidants has hence been intensified. Immense research is being carried out to identify potential plants with potent anti-oxidant activity against skin ageing. This review summarizes the major factors responsible for premature skin ageing and the plants being targeted to lessen the impact of those.

Skin resistance to oxidative stress induced by resveratrol: from Nrf2 activation to GSH biosynthesis

Skin is particularly exposed to oxidative stress, either from environmental insults such as sunlight or pollution or as a consequence of specific impairments in antioxidant status resulting from pathologies or aging. Traditionally, antioxidant products are exogenously provided to neutralize pro-oxidant species. However, another approach based on stimulation of endogenous antioxidant defense pathways is more original. Resveratrol (RSV) was reported to display such a behavior in various tissues, but data about the mechanisms of action in skin are scarce. We show here that, in primary culture of normal human keratinocytes (NHKs) or in full-thickness reconstructed human skin, RSV activated the Nrf2 pathway at nontoxic doses, from 20 µM up to 100µM. Among the Nrf2 downstream genes, glutamylcysteinyl ligase and glutathione peroxidase-2 were induced at the mRNA and protein levels. In parallel, a significant increase in glutathione content, assessed by LC/MS analysis, was observed in both models. Nrf2 gene silencing experiments performed in NHKs confirmed that Nrf2 was involved in RSV-induced modulation of cellular antioxidant status, in part by increasing cellular glutathione content. Finally, improvement of endogenous defenses induced in RSV-pretreated reconstructed skin ensured protection against the toxic oxidative effects of cumene hydroperoxide (CHP). In fact after RSV pretreatment, in response to CHP stress, glutathione content did not decrease as in unprotected samples. Cellular alterations at the dermal-epidermal junction were clearly prevented. Together, these complementary experiments demonstrated the beneficial effects of RSV on skin, beyond its direct antioxidant properties, by upregulation of a cutaneous endogenous antioxidant pathway.

Antioxidant and anti-inflammatory effects of selected natural compounds contained in a dietary supplement on two human immortalized keratinocyte lines

Several advantages may derive from the use of dietary supplements containing multiple natural antioxidants and/or anti-inflammatory agents. At present, however, there is scarce information on the properties and potential of combined supplements. To fill the gap, the antioxidant and anti-inflammatory activities exerted by a combination of seven natural components (coenzyme Q10, krill oil, lipoic acid, resveratrol, grape seed oil, α-tocopherol, and selenium) contained in a dietary supplement used for the prevention of skin disorders were investigated in vitro. Each component was administered, alone or in combination, to human keratinocytes, and the inhibition of Reactive Oxygen Species production and lipid peroxidation as well as the ability to reduce inflammatory cytokine secretion and to modulate Nuclear Factor-κB pathway was evaluated. The combination exhibited high antioxidant activity and in specific conditions the combination's efficiency was higher than that of the most powerful components administered individually. Moreover, the combination showed remarkable anti-inflammatory properties. It reduced more efficiently than each component the secretion of Monocyte Chemoattractant Protein-1, a crucial cytokine for the development of chronic inflammation in skin, and inhibited Nuclear Factor-κB molecular pathway. Overall, our findings suggest that the combined formulation may have the potential to powerfully inhibit oxidative stress and inflammation at skin level.

Resveratrol induces antioxidant and heat shock protein mRNA expression in response to heat stress in black-boned chickens

This study investigated the effects of dietary resveratrol at 0, 200, 400, or 600 mg/kg of diet on the performance, immune organ growth index, serum parameters, and expression levels of heat shock protein (Hsp) 27, Hsp70, and Hsp90 mRNA in the bursa of Fabricius, thymus, and spleen of 42-d-old female black-boned chickens exposed to heat stress at 37 ± 2°C for 15 d. The results showed that heat stress reduced daily feed intake and BW gain; decreased serum glutathione (GSH), growth hormone, and insulin-like growth factor-1 levels; and inhibited GSH peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities compared with birds subjected to thermo-neutral circumstances. Chickens that were fed diets supplemented with resveratrol exhibited a linear increase in feed intake and BW gain (P < 0.001); serum GSH, growth hormone, and insulin-like growth factor-1 levels (P ≤ 0.01); and GSH-Px, SOD, and CAT activities (P < 0.001) compared with chickens that were fed diets without resveratrol during heat stress. In contrast, serum malonaldehyde concentrations were decreased (P < 0.001) in the chickens fed a resveratrol-supplemented diet. Heat stress also reduced (P < 0.05) the growth index of the bursa of Fabricus and spleen; however, it had no effect on the growth index of the thymus. The growth index of the bursa of Fabricius and spleen increased (P < 0.05) upon heat stress and coincided with an increase in supplemental resveratrol levels. The expression of Hsp27, Hsp70, and Hsp90 mRNA in the bursa of Fabricius and spleen were increased (P < 0.01), but those of Hsp27 and Hsp90 mRNA in thymus were decreased (P < 0.01) under heat stress compared with no heat stress. Resveratrol attenuated the heat stress-induced overexpression of Hsp27, Hsp70, and Hsp90 mRNA in the bursa of Fabricius and spleen and increased the low expression of Hsp27 and Hsp90 mRNA in thymus upon heat stress. The results suggest that supplemental resveratrol improves growth performance and reduces oxidative stress in heat-stressed black-boned chickens by increasing serum growth hormone concentrations and modulating the expression of heat shock genes in organs of the immune system.

Combating oxidative stress in diabetic complications with Nrf2 activators: how much is too much?

Diabetes is increasing at an alarming rate and, despite anti-hypertensive and insulin therapies, diabetic patients are still at risk of developing complications such as chronic kidney disease, cardiovascular disease, and retinopathy. There is therefore an urgent need for more effective therapies to prevent the development and progression of diabetic complications. Oxidative stress is a major player in the aetiology of diabetic complications. However, results from clinical trials thus far using general antioxidants have been disappointing. Mechanism-based antioxidants have gained considerable attention due to their more targeted approach at reducing oxidative stress and associated complications in diabetes. The transcription factor, NFE2-related factor 2 (Nrf2), is a master regulator of redox homeostasis and the cellular detoxification response. Instead of relying on a single antioxidant, activation of Nrf2 results in the concerted upregulation of several antioxidant enzymes and cytoprotective genes, making it an attractive therapeutic target for diabetic complications. Several Nrf2 activators have been discovered and have proven effective at activating Nrf2 signalling through different mechanisms in both in vitro and in vivo models of diabetes. This review will address some of the most promising and well-known Nrf2 activators and their roles in preventing the development and progression of diabetic complications. Challenges facing the advancement of this drug class into the clinic will be discussed, as will be the future of Nrf2 activation as a therapeutic strategy in preventing the development of diabetic complications.

Activation of Nrf2 in keratinocytes causes chloracne (MADISH)-like skin disease in mice

The transcription factor Nrf2 is a key regulator of the cellular stress response, and pharmacological Nrf2 activation is a promising strategy for skin protection and cancer prevention. We show here that prolonged Nrf2 activation in keratinocytes causes sebaceous gland enlargement and seborrhea in mice due to upregulation of the growth factor epigen, which we identified as a novel Nrf2 target. This was accompanied by thickening and hyperkeratosis of hair follicle infundibula. These abnormalities caused dilatation of infundibula, hair loss, and cyst development upon aging. Upregulation of epigen, secretory leukocyte peptidase inhibitor (Slpi), and small proline-rich protein 2d (Sprr2d) in hair follicles was identified as the likely cause of infundibular acanthosis, hyperkeratosis, and cyst formation. These alterations were highly reminiscent to the phenotype of chloracne/“metabolizing acquired dioxin-induced skin hamartomas” (MADISH) patients. Indeed, SLPI, SPRR2, and epigen were strongly expressed in cysts of MADISH patients and upregulated by dioxin in human keratinocytes in an NRF2-dependent manner. These results identify novel Nrf2 activities in the pilosebaceous unit and point to a role of NRF2 in MADISH pathogenesis.

The protective effects of bilberry and lingonberry extracts against UV light-induced retinal photoreceptor cell damage in vitro

Bilberry extract (B-ext) and lingonberry extract (L-ext) are currently used as health supplements. We investigated the protective mechanisms of the B-ext and L-ext against ultraviolet A (UVA)-induced retinal photoreceptor cell damage. Cultured murine photoreceptor (661W) cells were exposed to UVA following treatment with B-ext and L-ext and their main constituents (cyanidin, delphinidin, malvidin, trans-resveratrol, and procyanidin). B-ext, L-ext, and constituents improved cell viability and suppressed ROS generation. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and protein kinase B (Akt) were analyzed by Western blotting. B-ext and cyanidin inhibited phosphorylation of p38 MAPK, and B-ext also inhibited phosphorylation of JNK by UVA. L-ext, trans-resveratrol, and procyanidin alleviated the reduction of phosphorylated Akt levels by UVA. Finally, a cotreatment with B-ext and L-ext showed an additive effect on cell viability. Our findings suggest that both B-ext and L-ext endow protective effects against UVA-induced retinal damage.

Polydatin, a natural precursor of resveratrol, induces β-defensin production and reduces inflammatory response

It is well known that human keratinocytes produce the anti-microbial peptide β-defensin 2. Its production is enhanced by pathogenic microorganisms or other environmental stressors. In this study, we evaluated the effect of resveratrol, a polyphenol found in several dietary source as grape seed, and its natural precursor, polydatin on heat-stressed human keratinocytes. By reverse transcription-polymerase chain reaction and enzyme-linked immunoadsorbent assay, we demonstrated that resveratrol used in combination with polydatin was able to modulate interleukin (IL)-6, IL-8 and tumor necrosis factor-alpha gene expression. In addition, our data show that resveratrol and polydatin increased the heat shock protein (Hsp)70B' gene expression, a Hsp that plays an important role in the cytoprotection and repair of cells and tissues. Worthy of note, polydatin used alone or in combination with resveratrol, increased the release of human β-defensin 2. These results highlighted the ability of polydatin and resveratrol to reinforce cytoprotective response in stress conditions and suggest their use in cosmetic or pharmaceutical preparations.

Nutritional strategies to modulate inflammation and oxidative stress pathways via activation of the master antioxidant switch Nrf2

The nuclear factor E2-related factor 2 (Nrf2) plays an important role in cellular protection against cancer, renal, pulmonary, cardiovascular and neurodegenerative diseases where oxidative stress and inflammation are common conditions. The Nrf2 regulates the expression of detoxifying enzymes by recognizing the human Antioxidant Response Element (ARE) binding site and it can regulate antioxidant and anti-inflammatory cellular responses, playing an important protective role on the development of the diseases. Studies designed to investigate how effective Nrf2 activators or modulators are need to be initiated. Several recent studies have shown that nutritional compounds can modulate the activation of Nrf2-Keap1 system. This review aims to discuss some of the key nutritional compounds that promote the activation of Nrf2, which may have impact on the human health.

Photoprotective and antioxidant effects of Rhubarb: inhibitory action on tyrosinase and tyrosine kinase activities and TNF-α, IL-1α and α-MSH production in human melanocytes

BACKGROUND

Exposure to ultraviolet (UV) radiation causes various forms of acute and chronic skin damage, including immunosuppression, inflammation, premature aging and photodamage. Furthermore, it induces the generation of reactive oxygen species, produces proinflammatory cytokines and melanocyte-stimulating hormone (MSH) and increases tyrosinase activity. The aim of this study was to evaluate the potential photoprotective effects of Rheum rhaponticum L. rhizome extract on human UV-stimulated melanocytes.

METHODS

The effects of Rheum rhaponticum rhizome extract on tyrosine kinase activity, and on interleukin-1α (IL-1α), tumour necrosis factor α (TNF-α), and α-MSH production in human epidermal melanocytes were evaluated under UV-stimulated and non-stimulated conditions. Antioxidant activity was evaluated by lipid peroxidation and 1,1-dyphenyl-2-picryl-hydrazyl (DPPH) assays, while anti-tyrosinase activity was evaluated by the mushroom tyrosinase method.

RESULTS

Rheum rhaponticum L. rhizome extract showed in vitro antioxidant properties against lipid peroxidation, free radical scavenging and anti-tyrosinase activities, and inhibited the production of IL-1α, TNF-α, α-MSH, and tyrosine kinase activity in melanocytes subjected to UV radiation.

CONCLUSIONS

These results support the inclusion of Rheum rhaponticum L. rhizome extract into cosmetic, sunscreen and skin care products for the prevention or reduction of photodamage.

Trichostatin A inhibits transforming growth factor-β-induced reactive oxygen species accumulation and myofibroblast differentiation via enhanced NF-E2-related factor 2-antioxidant response element signaling

Trichostatin A (TSA) has been shown to prevent fibrosis in vitro and in vivo. The present study aimed at investigating the role of reactive oxygen species (ROS) scavenging by TSA on transforming growth factor-β (TGF-β)-induced myofibroblast differentiation of corneal fibroblasts in vitro. Human immortalized corneal fibroblasts were treated with TGF-β in the presence of TSA, the NAD(P)H oxidase inhibitor diphenyleneiodonium (DPI), the antioxidant N-acetyl-cysteine (NAC), the NF-E2-related factor 2-antioxidant response element (Nrf2-ARE) activator sulforaphane, or small interfering RNA. Myofibroblast differentiation was assessed by α-smooth muscle actin (α-SMA) expression, F-actin bundle formation, and collagen gel contraction. ROS, H(2)O(2), intracellular glutathione (GSH) level, cellular total antioxidant capacity, and the activation of Nrf2-ARE signaling were determined with various assays. Treatment with TSA and the Nrf2-ARE activator resulted in increased inhibition of the TGF-β-induced myofibroblast differentiation as compared with treatment with DPI or NAC. Furthermore, TSA also decreased cellular ROS and H(2)O(2) accumulation induced by TGF-β, whereas it elevated intracellular GSH level and cellular total antioxidant capacity. In addition, TSA induced Nrf2 nuclear translocation and up-regulated the expression of Nrf2-ARE downstream antioxidant genes, whereas Nrf2 knockdown by RNA interference blocked the inhibition of TSA on myofibroblast differentiation. In conclusion, this study provides the first evidence implicating that TSA inhibits TGF-β-induced ROS accumulation and myofibroblast differentiation via enhanced Nrf2-ARE signaling.

Ethanol extract of peanut sprout induces Nrf2 activation and expression of antioxidant and detoxifying enzymes in human dermal fibroblasts: implication for its protection against UVB-irradiated oxidative stress

A peanut sprout is known to contain a significant level of resveratrol, which was reported to have beneficial effects in our body due to its antioxidant activities. The purpose of this study was to evaluate the cytoprotective activity of ethanol extract of peanut sprout (EPS) from ultraviolet B (UVB)-induced oxidative stress in human dermal fibroblasts (HDF). EPS was revealed to contain 54.2 μg g(-1) of trans-resveratrol. The DCF-DA-positive reactive oxygen species level was increased by 50 mJ cm(-2) of UVB irradiation (2150 ± 450% of nonirradiated control), which was markedly suppressed by EPS treatment (180 ± 42% of control). Annexin V-positive apoptotic cell death induced by UVB irradiation (16.4 ± 4.5%) was also significantly inhibited by EPS treatment (6.7 ± 2.5%). EPS induced up-regulation and nuclear translocation of Nrf2, a transcription factor for antioxidant and detoxifying enzymes, in HDF as a dose-dependent manner. UVB irradiation up-regulated Nrf2-dependent enzymes of heme oxygenase-1, NAD(P)H:quinine oxidoreductase-1 and glutathione-S-transferase pi, and they were further stimulated by EPS treatment. Taken together, EPS is an efficient cytoprotective agent against UVB-induced oxidative stress by activation of Nrf2 and upregulation of Nrf2-relating antioxidant and detoxifying enzymes in HDF.

Anti-inflammatory effects of concentrated ethanol extracts of Edelweiss (Leontopodium alpinum Cass.) callus cultures towards human keratinocytes and endothelial cells

Edelweiss (Leontopodium alpinum Cass.) is traditionally employed in folk medicine as an anti-inflammatory remedy. In nature, the plant is sparsely available and protected; therefore production of callus cultures was established. A concentrated ethanolic extract of culture homogenate, with leontopodic acid representing 55 ± 2% of the total phenolic fraction (ECC55), was characterized for anti-inflammatory properties in primary human keratinocytes (PHKs) and endotheliocytes (HUVECs). Inflammatory responses were induced by UVA+UVB, lipopolysaccharide (LPS), oxidized low-density lipoprotein (oxLDL), and a mixture of proinflammatory cytokines. Trichostatin A, a sirtuin inhibitor, was used to induce keratinocyte inflammatory senescence. ECC55 (10–50 μg/mL) protected PHK from solar UV-driven damage, by enhancing early intracellular levels of nitric oxide, although not affecting UV-induced expression of inflammatory genes. Comparison of the dose-dependent inhibition of chemokine (IL-8, IP-10, MCP-1) and growth factor (GM-CSF) release from PHK activated by TNFα + IFNγ showed that leontopodic acid was mainly responsible for the inhibitory effects of ECC55. Sirtuin-inhibited cell cycle, proliferation, and apoptosis markers were restored by ECC55. The extract inhibited LPS-induced IL-6 and VCAM1 genes in HUVEC, as well as oxLDL-induced selective VCAM1 overexpression. Conclusion. Edelweiss cell cultures could be a valuable source of anti-inflammatory substances potentially applicable for chronic inflammatory skin diseases and bacterial and atherogenic inflammation.

Resveratrol enhances solar UV-induced responses in normal human epidermal keratinocytes

Resveratrol (RV) differentially affects UV-induced death/pro-survival pathways in normal and tumor cells. On these grounds, RV-containing topical products have been developed to prevent UV-associated tumorigenesis/damage to human skin. In this study, we evaluated mechanisms of combined effects of RV and low-dose solar simulated UVA+UVB or 6-formylindo[3,2-b]carbazole (FICZ), a product of tryptophan photo-oxidation known to mediate UV effects, on the inflammatory, metabolic and proliferative responses of cultured normal human epidermal keratinocytes (HEK). Applied alone, RV, UV and FICZ induced time- and dose-dependent activation of aryl hydrocarbon receptor (AhR) pathway followed by over-expression of Cyp1A1 (metabolic response), UV and RV induced IL-8 expression (inflammatory response), while RV enhanced also HEK proliferation revealed by MTT assay and (3)H-thymidine incorporation. In the combined treatment, RV synergized with both UV and FICZ, leading to further activation of AhR machine, Cyp1A1 transcription and IL-8 expression, the latter partly AhR-dependent as assessed by AhR silencing. RV enhanced UV-induced NFkappaB activation and nuclear translocation of epidermal growth factor receptor. By contrast, proliferative effect of RV was abolished in the presence of UV, whereas synergic anti-proliferative action of RV+UV was observed in the Nrf2-silenced HEK. Our data suggest cooperative effects of RV-specific and UV-/FICZ-activated transcription factors leading to deregulated inflammatory, metabolic and proliferative responses of HEK.

The prospective role of plant products in radiotherapy of cancer: a current overview

Treatment of cancer often requires exposure to radiation, which has several limitations involving non-specific toxicity toward normal cells, reducing the efficacy of treatment. Efforts are going on to find chemical compounds which would effectively offer protection to the normal tissues after radiation exposure during radiotherapy of cancer. In this regard, plant-derived compounds might serve as “leads” to design ideal radioprotectors/radiosensitizers. This article reviews some of the recent findings on prospective medicinal plants, phytochemicals, and their analogs, based on both in vitro and in vivo tumor models especially focused with relevance to cancer radiotherapy. Also, pertinent discussion has been presented on the molecular mechanism of apoptotic death in relation to the oxidative stress in cancer cells induced by some of these plant samples and their active constituents.

Ageing skin: oestrogen receptor β agonists offer an approach to change the outcome

Oestrogen (17β estradiol) and the dietary antioxidants resveratrol, genistein and S-equol, an isoflavone produced from the gut biotransformation of soy daidzein, are effective agents to reduce ageing in skin. It is widely held that these antioxidants scavenge free radicals to prevent skin damage. However, the evidence to date suggests that the primary mechanism of action of these antioxidants is to activate oestrogen receptor β (ERβ), which in turn enhances the expression of antioxidant enzymes and inhibits the expression of snail, a transcription factor that regulates keratinocyte cell proliferation and migration. Based on their selectivity, ERβ agents provide a treatment option for ageing skin without the potential safety issues associated with oestrogen therapy.

Hyperoside attenuates hydrogen peroxide-induced L02 cell damage via MAPK-dependent Keap₁-Nrf₂-ARE signaling pathway

The flavonoid hyperoside has been reported to elicit cytoprotection against oxidative stress partly by increasing the activity of antioxidant enzymes, such as glutathione peroxidase, superoxide dismutase and catalase. However, the cellular and molecular mechanisms underlying this effect remain unclear. Here, hepatic L02 cells exposed to H(2)O(2) (100 μM) were used to demonstrate that hyperoside protected cells by significantly inhibiting overproduction of intracellular ROS, depletion of the mitochondrial membrane potential and leakage of lactate dehydrogenase. Hyperoside further enhanced the cellular antioxidant defense system through increasing the activity of heme oxygenase-1 (HO-1), and by up-regulating HO-1 expression. Meanwhile, real time PCR, western blot and immunofluorescence studies revealed that hyperoside stimulated nuclear translocation of the Nrf(2) transcription factor in a dose-dependent manner, and this effect was significantly suppressed by pharmacological inhibition of the mitogen-activated protein kinases (MAPK) p38 and ERK. Collectively, our data provide the first description of the mechanism underlying hyperoside's ability to attenuate H(2)O(2)-induced cell damage, namely this compound interacts with the MAPK-dependent Keap(1)-Nrf(2)-ARE signaling pathway to up-regulate HO-1 expression and enhance intracellular antioxidant activity.

The grape antioxidant resveratrol for skin disorders: promise, prospects, and challenges

Resveratrol, a phytoalexin antioxidant found in red grapes, has been shown to have both chemopreventive and therapeutic effects against many diseases and disorders, including those of the skin. Studies have shown protective effects of resveratrol against ultraviolet radiation-mediated oxidative stress and cutaneous damages including skin cancer. Because many of the skin conditions stem from ultraviolet radiation and oxidative stress, this antioxidant appears to have promise and prospects against a wide range of cutaneous disorders including skin aging and skin cancers. However, there are a few roadblocks in the way of this promising agent regarding its translation from the bench to the bedside. This review discusses the promise and prospects of resveratrol in the management of skin disorders and the associated challenges.