The omega-3 postbiotic trans-10-cis-15-octadecadienoic acid attenuates contact hypersensitivity in mice through downregulation of vascular endothelial growth factor A.

Intestinal bacteria metabolize dietary substances to produce bioactive postbiotics, among which some are recognized for their role in promoting host health. We here explored the postbiotic potential of two omega-3 α-linolenic acid-derived metabolites: trans-10-cis-15-octadecadienoic acid (t10,c15-18:2) and cis-9-cis-15-octadecadienoic acid (c9,c15-18:2). Dietary intake of lipids rich in omega-3 α-linolenic acid elevated levels of t10,c15-18:2 and c9,c15-18:2 in the serum and feces of mice, an effect dependent on the presence of intestinal bacteria. Notably, t10,c15-18:2 mitigated skin inflammation in mice that became hypersensitive after exposure to 2,4-dinitrofluorobenzene, an experimental model for allergic contact dermatitis. In particular, t10,c15-18:2-but not c9,c15-18:2-attenuated ear swelling and edema, characteristic symptoms of contact hypersensitivity. The anti-inflammatory effects of t10,c15-18:2 were due to its ability to suppress the release of vascular endothelial growth factor A from keratinocytes, thereby mitigating the enhanced vascular permeability induced by hapten stimulation. Our study identified retinoid X receptor as a functional receptor that mediates the downregulation of skin inflammation upon treatment with t10,c15-18:2. Our results suggest that t10,c15-18:2 holds promise as an omega-3 fatty acid-derived postbiotic with potential therapeutic implications for alleviating the skin edema seen in allergic contact dermatitis-induced inflammation.

Mead acid inhibits retinol-induced irritant contact dermatitis via peroxisome proliferator-activated receptor alpha.

Retinol is widely used in topical skincare products to ameliorate skin aging and treat acne and wrinkles; however, retinol and its derivatives occasionally have adverse side effects, including the induction of irritant contact dermatitis. Previously, we reported that mead acid (5,8,11-eicosatrienoic acid), an oleic acid metabolite, ameliorated skin inflammation in dinitrofluorobenzene-induced allergic contact hypersensitivity by inhibiting neutrophil infiltration and leukotriene B4 production by neutrophils. Here, we showed that mead acid also suppresses retinol-induced irritant contact dermatitis. In a murine model, we revealed that mead acid inhibited keratinocyte abnormalities such as keratinocyte hyperproliferation. Consistently, mead acid inhibited p38 MAPK (mitogen-activated protein kinase) phosphorylation, which is an essential signaling pathway in the keratinocyte hyperplasia induced by retinol. These inhibitory effects of mead acid were associated with the prevention of both keratinocyte hyperproliferation and the gene expression of neutrophil chemoattractants, including Cxcl1 and Cxcl2, and they were mediated by a PPAR (peroxisome proliferator-activated receptor)-α pathway. Our findings identified the anti-inflammatory effects of mead acid, the use of which can be expected to minimize the risk of adverse side effects associated with topical retinoid application.

Role of Plant-Derived Flavonoids in Cancer Treatment.

Flavonoids are polyphenolic phytochemicals, which occur naturally in plants and possess both anti-oxidant and pro-oxidant properties. Flavonoids are gaining increasing popularity in the pharmaceutical industry as healthy and cost-effective compounds. Flavonoids show beneficial pharmacological activities in the treatment and prevention of various types of diseases. They are natural and less toxic agents for cancer chemotherapy and radiotherapy via regulation of multiple cell signaling pathways and pro-oxidant effects. In this review, we have summarized the mechanisms of action of selected flavonoids, and their pharmacological implications and potential therapeutic applications in cancer therapy.

Intestinal microbe-dependent ω3 lipid metabolite αKetoA prevents inflammatory diseases in mice and cynomolgus macaques.

Dietary ω3 fatty acids have important health benefits and exert their potent bioactivity through conversion to lipid mediators. Here, we demonstrate that microbiota play an essential role in the body's use of dietary lipids for the control of inflammatory diseases. We found that amounts of 10-hydroxy-cis-12-cis-15-octadecadienoic acid (αHYA) and 10-oxo-cis-12-cis-15-octadecadienoic acid (αKetoA) increased in the feces and serum of specific-pathogen-free, but not germ-free, mice when they were maintained on a linseed oil diet, which is high in α-linolenic acid. Intake of αKetoA, but not αHYA, exerted anti-inflammatory properties through a peroxisome proliferator-activated receptor (PPAR)γ-dependent pathway and ameliorated hapten-induced contact hypersensitivity by inhibiting the development of inducible skin-associated lymphoid tissue through suppression of chemokine secretion from macrophages and inhibition of NF-κB activation in mice and cynomolgus macaques. Administering αKetoA also improved diabetic glucose intolerance by inhibiting adipose tissue inflammation and fibrosis through decreased macrophage infiltration in adipose tissues and altering macrophage M1/M2 polarization in mice fed a high-fat diet. These results collectively indicate that αKetoA is a novel postbiotic derived from α-linolenic acid, which controls macrophage-associated inflammatory diseases and may have potential for developing therapeutic drugs as well as probiotic food products.

ω3 fatty acid metabolite, 12-hydroxyeicosapentaenoic acid, alleviates contact hypersensitivity by downregulation of CXCL1 and CXCL2 gene expression in keratinocytes via retinoid X receptor α.

ω3 fatty acids show potent bioactivities via conversion into lipid mediators; therefore, metabolism of dietary lipids is a critical determinant in the properties of ω3 fatty acids in the control of allergic inflammatory diseases. However, metabolic progression of ω3 fatty acids in the skin and their roles in the regulation of skin inflammation remains to be clarified. In this study, we found that 12-hydroxyeicosapentaenoic acid (12-HEPE), which is a 12-lipoxygenase metabolite of eicosapentaenoic acid, was the prominent metabolite accumulated in the skin of mice fed ω3 fatty acid-rich linseed oil. Consistently, the gene expression levels of Alox12 and Alox12b, which encode proteins involved in the generation of 12-HEPE, were much higher in the skin than in the other tissues (eg, gut). We also found that the topical application of 12-HEPE inhibited the inflammation associated with contact hypersensitivity by inhibiting neutrophil infiltration into the skin. In human keratinocytes in vitro, 12-HEPE inhibited the expression of two genes encoding neutrophil chemoattractants, CXCL1 and CXCL2, via retinoid X receptor α. Together, the present results demonstrate that the metabolic progression of dietary ω3 fatty acids differs in different organs, and identify 12-HEPE as the dominant ω3 fatty acid metabolite in the skin.

17(S),18(R)-epoxyeicosatetraenoic acid generated by cytochrome P450 BM-3 from Bacillus megaterium inhibits the development of contact hypersensitivity via G-protein-coupled receptor 40-mediated neutrophil suppression.

Dietary intake of ω3 polyunsaturated fatty acids such as eicosapentaenoic acid and docosahexaenoic acid is beneficial for health control. We recently identified 17,18-epoxyeicosatetraenoic acid (17,18-EpETE) as a lipid metabolite endogenously generated from eicosapentaenoic acid that exhibits potent anti-allergic and anti-inflammatory properties. However, chemically synthesized 17,18-EpETE is enantiomeric due to its epoxy group-17(S),18(R)-EpETE and 17(R),18(S)-EpETE. In this study, we demonstrated stereoselective differences of 17(S),18(R)-EpETE and 17(R),18(S)-EpETE in amelioration of skin contact hypersensitivity and found that anti-inflammatory activity was detected in 17(S),18(R)-EpETE, but not in 17(R),18(S)-EpETE. In addition, we found that cytochrome P450 BM-3 derived from Bacillus megaterium stereoselectively converts EPA into 17(S),18(R)-EpETE, which effectively inhibited the development of skin contact hypersensitivity by inhibiting neutrophil migration in a G protein-coupled receptor 40-dependent manner. These results suggest the new availability of a bacterial enzyme to produce a beneficial lipid mediator, 17(S),18(R)-EpETE, in a stereoselective manner. Our findings highlight that bacterial enzymatic conversion of fatty acid is a promising strategy for mass production of bioactive lipid metabolites.

Flavonoids sensitize tumor cells to radiation: molecular mechanisms and relevance to cancer radiotherapy.

Purpose: Radiobiological research continues to focus on finding newer strategies for enhanced killing of tumor cells by ionizing radiation. In recent years, chemotherapeutic drugs have been found to possess the capabilities to sensitize tumor cells without affecting the normal cells. There have been increasing research efforts to identify novel and nontoxic compounds which cause minimal or no harm to normal cells but maximize tumor toxicity response to radiation exposure. Extensive researches on flavonoids that are compounds derived from plants have shown that these have promising abilities as radioprotectors and radiosensitizers.Conclusions: In this review, we examine the role of flavonoids as potential radiosensitizers, review the underlying molecular mechanisms and discuss their potential usefulness in improving cancer radiotherapy. It is emphasized that obtaining a deeper insight into the molecular mechanisms underlying the combined action of flavonoids and ionizing radiation may provide new directions for radiobiological research applicable to the much needed enhanced selective tumor cytotoxicity to treatment agents.

Dietary coconut oil ameliorates skin contact hypersensitivity through mead acid production in mice.

Coconut oil is used as a dietary oil worldwide, and its healthy effects are recognized by the fact that coconut oil is easy to digest, helps in weight management, increases healthy cholesterol, and provides instant energy. Although topical application of coconut oil is known to reduce skin infection and inflammation, whether dietary coconut oil has any role in decreasing skin inflammation is unknown. In this study, we showed the impact of dietary coconut oil in allergic skin inflammation by using a mouse model of contact hypersensitivity (CHS). Mice maintained on coconut oil showed amelioration of skin inflammation and increased levels of cis-5, 8, 11-eicosatrienoic acid (mead acid) in serum. Intraperitoneal injection of mead acid inhibited CHS and reduced the number of neutrophils infiltrating to the skin. Detailed mechanistic studies unveiled that mead acid inhibited the directional migration of neutrophils by inhibiting the filamentous actin polymerization and leukotriene B4 production required for secondary recruitment of neutrophils. Our findings provide valuable insights into the preventive roles of coconut oil and mead acid against skin inflammation, thereby offering attractive therapeutic possibilities.

The 17,18-epoxyeicosatetraenoic acid-G protein-coupled receptor 40 axis ameliorates contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques.

BACKGROUND: Metabolites of eicosapentaenoic acid exert various physiologic actions. 17,18-Epoxyeicosatetraenoic acid (17,18-EpETE) is a recently identified new class of antiallergic and anti-inflammatory lipid metabolite of eicosapentaenoic acid, but its effects on skin inflammation and the underlying mechanisms remain to be investigated. OBJECTIVE: We evaluated the effectiveness of 17,18-EpETE for control of contact hypersensitivity in mice and cynomolgus macaques. We further sought to reveal underlying mechanisms by identifying the responsible receptor and cellular target of 17,18-EpETE. METHODS: Contact hypersensitivity was induced by topical application of 2,4-dinitrofluorobenzene. Skin inflammation and immune cell populations were analyzed by using flow cytometric, immunohistologic, and quantitative RT-PCR analyses. Neutrophil mobility was examined by means of imaging analysis in vivo and neutrophil culture in vitro. The receptor for 17,18-EpETE was identified by using the TGF-α shedding assay, and the receptor's involvement in the anti-inflammatory effects of 17,18-EpETE was examined by using KO mice and specific inhibitor treatment. RESULTS: We found that preventive or therapeutic treatment with 17,18-EpETE ameliorated contact hypersensitivity by inhibiting neutrophil mobility in mice and cynomolgus macaques. 17,18-EpETE was recognized by G protein-coupled receptor (GPR) 40 (also known as free fatty acid receptor 1) and inhibited chemoattractant-induced Rac activation and pseudopod formation in neutrophils. Indeed, the antiallergic inflammatory effect of 17,18-EpETE was abolished in the absence or inhibition of GPR40. CONCLUSION: 17,18-EpETE inhibits neutrophil mobility through GPR40 activation, which is a potential therapeutic target to control allergic inflammatory diseases.

Activation-induced cytidine deaminase auto-activates and triggers aberrant gene expression.

DNA methylation is a well-characterized epigenetic landmark involved in transcriptional regulation; however, mechanisms underlying its regulation remain poorly characterized. Recent studies demonstrate that activation-induced cytidine deaminase (AID) is involved in active DNA demethylation. AID is aberrantly expressed in inflammation-associated cancers and generates point mutations; however, cellular disorders attributed to its demethylation function are largely unexplored. Here we demonstrate that ectopic AID expression perturbs tumor-related gene expression. AID (with Gadd45) activated a methylated paired box gene 5 (Pax5) reporter construct, and induced expression and association of endogenous Pax5 with the AID promoter, suggesting that aberrant AID expression triggers an auto-activation circuit to consolidate self-expression.

Prediction and experimental validation of a putative non-consensus binding site for transcription factor STAT3 in serum amyloid A gene promoter.

We previously demonstrated that though the human SAA1 gene shows no typical STAT3 response element (STAT3-RE) in its promoter region, STAT3 and the nuclear factor (NF-κB) p65 first form a complex following interleukin IL-1 and IL-6 (IL-1+6) stimulation, after which STAT3 interacts with a region downstream of the NF-κB RE in the SAA1 promoter. In this study, we employed a computational approach based on indirect read outs of protein-DNA contacts to identify a set of candidates for non-consensus STAT3 transcription factor binding sites (TFBSs). The binding of STAT3 to one of the predicted non-consensus TFBSs was experimentally confirmed through a dual luciferase assay and DNA affinity chromatography. The present study defines a novel STAT3 non-consensus TFBS at nt -75/-66 downstream of the NF-κB RE in the SAA1 promoter region that is required for NF-κB p65 and STAT3 to activate SAA1 transcription in human HepG2 liver cells. Our analysis builds upon the current understanding of STAT3 function, suggesting a wider array of mechanisms of STAT3 function in inflammatory response, and provides a useful framework for investigating novel TF-target associations with potential therapeutic implications.

Silibinin-induced apoptosis in MCF7 and T47D human breast carcinoma cells involves caspase-8 activation and mitochondrial pathway.

Silibinin, a natural flavonoid, under phase I/II clinical trial in prostate cancer patients was aimed to evaluate its chemotherapeutic potential in human breast cancer cell MCF7 and T47D. Results showed that T47D cells were found to be more sensitive to silibinin than MCF7 as observed by proliferation, clonogenic, and apoptotic assays, which was abrogated by pan-caspase inhibitor but remained unaffected by p53 inhibitor. Apoptotic events in both cell types differ temporally and also by magnitude that involved mitochondrial and caspase-8 activation pathway. These results have relevance in understanding silibinin treatment to breast tumor.

Radiobiological basis in management of accidental radiation exposure.

PURPOSE: With increasing utilisation of nuclear technologies in power production, medical and industrial applications, and in a scenario of nuclear terrorism/war, there is an enhanced likelihood of accidental radiation exposure to occupational workers, patients and public. The consequent health effects of the radiation exposure are resultant of interaction of radiation with biological systems and subsequent radiation injury. The present review discusses the knowledge gained in radiation biology that can be exploited for better treatment and management of radiation accident victims. RESULTS: In comparison with planned radiation exposure during diagnosis/therapy, the management of accidental radiation exposure is quite complicated due to uncertainties in dose, duration, organs involved and radionuclides internalised, and hence, require multi-faceted approaches. However, the options available for dosimetry, decorporation of radionuclides and therapeutic protocols of patients are limited, which provides substantial scope in these areas of research. Moreover, there is a need to fill the gaps in knowledge of radiation action in different dose ranges and post-irradiation windows, which would help in improving therapeutic approaches. Cytogenetic approaches are 'gold standard' for biodosimetry but with limited applications in mass casualty scenario. State-of-the-art technological advancement and high throughput in metabolomics, proteomics and genomics could be employed successfully in developing better biodosimetry for triage in accidental radiation exposure. Furthermore, identification of targets at organs/organelles level of internalised radionuclides would be helpful to develop effective decorporation strategies. Despite substantial research investigating several agents, which could modify radiation effects, only a few could reach up to practical application due to poor bioavailability or toxicity. CONCLUSIONS: Deeper insight into the mechanisms of radiation injury under accidental radiation conditions would be helpful in achieving better biodosimetry, decorporation strategies and improvement in prevention/post-irradiation management of radiation accident patients.

Radioprotection of plasmid and cellular DNA and Swiss mice by silibinin.

The radioprotective effect of a non-toxic bioactive component in plant milk thistle, silibinin against genotoxicity induced by gamma-irradiation was investigated in vivo/in vitro. Under in vitro conditions of irradiation, silibinin protected plasmid pBR322 DNA against gamma-radiation-induced strand breaks in a concentration dependent manner (0-200microM). Under cellular conditions of radiation exposure (3Gy), silibinin offered protection to lymphocyte DNA as evidenced from reduction in DNA damage and micronuclei formation, which showed correlation to the extent of intracellular reactive oxygen species reduction. Our extended animal studies suggest that oral administration of silibinin (70mg/kg for 3 days) to mice prior to whole-body gamma-exposure (7.5Gy) resulted in significant protection to radiation-induced mortality and DNA damage in blood leukocytes. However, silibinin treatment after irradiation was not as effective as pre-administration. In conclusion, present study indicated that silibinin has a strong potential to prevent radiation-induced DNA damage under both in vitro and in vivo.

Radiation-induced micronucleus formation and DNA damage in human lymphocytes and their prevention by antioxidant thiols.

Thiol family of antioxidants has been considered to be the most effective class of radio protective agents. Present study reports a comparative evaluation of antioxidant thiols, namely N-acetyl cysteine (NAC), glutathione (GSH) and thioproline (TP), on gamma radiation-induced damage to human lymphocytes DNA as assessed by micronucleus (MN) formation and comet assay parameters. Pretreatment of cells with NAC, GSH and TP showed significant protection against DNA damage and MN frequency in irradiated lymphocytes (2-4 Gy). The magnitude of DNA damage protection was found to be concentration dependent (100-300 microM) which followed the order GSH>NAC>TP. Further, antioxidant thiols mediated protection against DNA damage in irradiated lymphocyte showed significant correlation with their ability to decrease intracellular ROS but not to the increase in intracellular GSH. Experiments on the effect of antioxidant thiols on plasmid DNA irradiated under cell free aqueous conditions showed that NAC exerts greater protection than GSH against radiation damage. TP showed similar responses in cellular and plasmid DNA. Greater protection of plasmid DNA by NAC is ascribable to its more potential hydrogen donor ability as revealed by radical chromogen 2,2-diphenyl-1-picrylhydrazyl (DPPH) photometric assay. Thus, present study indicated that radioprotection of lymphocytes DNA by antioxidant thiols are closely correlated to the reduction of cellular oxidative stress, which seems to involve multiple mechanisms.

Correlation of FBX dosimeter and micronucleus assay in radiation dosimetry of gamma chambers.

The aim of the present study is to determine the dose distribution in gamma irradiation chambers by chemical dosimetry and to establish its correlation with biological dosimetry. The dose-distribution studies of these two gamma chambers show that compared to the center point of the chambers, the dose rate was 17%-22% higher at the circumference. Moreover, the dose rate was 12%-18% lower at the bottom and top positions compared to the center point. It was interesting to observe that the dose rate determined by chemical dosimetry was well correlated with the number of micro-nucleus (MN) formations at different positions of the chamber. Our results suggest that the formation of the single MN/cell was better correlated with the dose rate than the double MN/cell, suggesting that the number of single MN/cells could be better biomarkers for determining the dose rate. These results provide a correlation between chemical and biological dosimetry, which may have relevance in the development of better bioassay techniques for radiation exposure.