Protection against chemically induced skin tumorigenesis in SENCAR mice by tannic acid

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

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.

Protective effect of topical application of α-tocopherol and/or N-acetyl cysteine on argemone oil/alkaloid-induced skin tumorigenesis in mice

Since bioantioxidants in plasma of Epidemic Dropsy patients [a condition caused by consumption of adulterated mustard oil with argemone oil (AO)] were found to be significantly decreased, the beneficial effect of N-acetyl cysteine (NAC) and α-tocopherol (TOCO) against AO- or sanguinarine (SANG)-induced tumorigenicity was undertaken in mice. Topical application of TOCO and NAC either alone or in combination showed significant protection against AO/TPA- and SANG/TPA-induced skin tumorigenicity. Histopathological findings suggest that papillomatous growth in AO/TPA- and SANG/TPA-treated animals were substantially protected following topical application of TOCO or NAC. Further, treatment of TOCO and NAC either alone or in combination to AO/TPA- or SANG/TPA-induced mice significantly decreased lipid peroxidation, along with significant revival in glutathione (GSH) content and activities of tyrosinase, histidase, catalase, SOD, GSH peroxidase, and GSH reductase in skin. In vitro studies showed that TOCO and/or NAC significantly decreased the AO and SANG induced cell proliferation and activation of ERK, p38, JNK MAPKs and NF-κB signaling in HaCaT cells. In summary, TOCO and NAC may be useful in preventing the tumorigenic response of AO and SANG probably by acting as scavenger of free radicals and inhibiting MAPKs and NF-κB signaling.

A FRET-based high throughput screening assay to identify inhibitors of anthrax protective antigen binding to capillary morphogenesis gene 2 protein

Anti-angiogenic therapies are effective for the treatment of cancer, a variety of ocular diseases, and have potential benefits in cardiovascular disease, arthritis, and psoriasis. We have previously shown that anthrax protective antigen (PA), a non-pathogenic component of anthrax toxin, is an inhibitor of angiogenesis, apparently as a result of interaction with the cell surface receptors capillary morphogenesis gene 2 (CMG2) protein and tumor endothelial marker 8 (TEM8). Hence, molecules that bind the anthrax toxin receptors may be effective to slow or halt pathological vascular growth. Here we describe development and testing of an effective homogeneous steady-state fluorescence resonance energy transfer (FRET) high throughput screening assay designed to identify molecules that inhibit binding of PA to CMG2. Molecules identified in the screen can serve as potential lead compounds for the development of anti-angiogenic and anti-anthrax therapies. The assay to screen for inhibitors of this protein–protein interaction is sensitive and robust, with observed Z' values as high as 0.92. Preliminary screens conducted with a library of known bioactive compounds identified tannic acid and cisplatin as inhibitors of the PA-CMG2 interaction. We have confirmed that tannic acid both binds CMG2 and has anti-endothelial properties. In contrast, cisplatin appears to inhibit PA-CMG2 interaction by binding both PA and CMG2, and observed cisplatin anti-angiogenic effects are not mediated by interaction with CMG2. This work represents the first reported high throughput screening assay targeting CMG2 to identify possible inhibitors of both angiogenesis and anthrax intoxication.

Astringency: mechanisms and perception

Astringency plays an important role in the sensory experience of many foods and beverages, ranging from wine to nuts. Given the recent trend toward fortifying consumables with astringent compounds and the evidence regarding the health benefits of some astringents, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper reviews the current state of the literature, including consideration of new methods for describing and measuring astringency, and provides an overview of research concerned with elucidating the physical, physiological, and psychological factors that underlie and mediate perception of this sensation.

Differential apoptosis by gallotannin in human colon cancer cells with distinct p53 status

Gallotannin (GT), a plant polyphenol, has shown anticarcinogenic activities in several animal models including colon cancer. In our previous study, we showed that GT inhibits 1,2-dimethylhydrazine-induced colonic aberrant crypt foci and tumors in Balb/c mice, thus supporting a role for GT as a chemopreventive agent in colon cancer. However, at the molecular level, GT's mechanism of chemoprevention is still unclear. In this study, we aim at identifying GT's potential molecular mechanisms of action in in vitro studies. We show that GT differentially inhibits the growth of two isogenic HCT-116 (p53+/+, p53-/-) human colon cancer cells versus normal human intestinal epithelial cells (FHs 74Int). DNA flow cytometric analysis showed that GT induced S-phase arrest in both HCT-116 cell lines. Cell-cycle arrest in p53 (+/+) cells was associated with an increase in p53 protein levels and p21 transcript and protein levels. The inhibition of cell-cycle progression of HCT-116 p53 (+/+) cells by GT correlated with a reduction in the protein levels of cyclin D(1), pRb, and the Bax/Bcl-2 ratio. Although GT did not induce apoptosis in p53 (+/+) cells, a significant induction of apoptosis was observed in p53 (-/-) cells as shown by TUNEL staining and flow cytometry analysis. Apoptosis induction in p53 (-/-) cells was associated with a significant increase in Bax/Bcl-2 protein levels. Our results demonstrate that GT inhibits the growth of HCT-116 colon cancer cells in a p53-independent manner but exhibits differential sensitivity to apoptosis induction in HCT-116 cells with distinct p53 status.

The effect of plant phenols on the expression and activity of phorbol ester-induced PKC in mouse epidermis

Protein kinase C (PKC) is thought to be a major intracellular receptor for the mouse skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). The diversity of PKC isoforms, and their central role in many signaling pathways, makes them important targets for potential chemopreventive agents. Our earlier studies showed that the plant phenols protocatechuic acid, chlorogenic acid and tannic acid alter the activity of enzymes involved in carcinogen activation, inhibit the formation of polycyclic aromatic hydrocarbon (PAH)-DNA adducts in mouse epidermis and decrease the level of lipid peroxidation in the epidermal microsomes. In the present study the effects of protocatechuic acid, chlorogenic acid and tannic acid on TPA-stimulated PKC isozymes alpha, beta(1), beta(2), gamma and zeta activity, and their distribution in mouse epidermis, was examined. The application of these phenolics 15 min before a single dose (3.4 nmol) of TPA resulted in significant inhibition of PKC translocation and a subsequent decrease in classical and novel/atypical PKC isoforms in comparison to a group of mice treated with TPA alone. The most potent inhibitor of PKC translocation and activity was tannic acid. This compound increased the levels of PKCalpha, beta(1), beta(2) in the cytosolic fraction by between 127% and 492% in comparison with TPA treated group of mice. Tannic acid decreased the activities of all three PKC classes by approximately 94% in the membrane fraction in comparison with the TPA treated group of animals. The effect of protocatechuic and chlorogenic acids on the distribution and activity of PKC isozymes was moderate. These compounds mostly affected translocation of PKCalpha and subsequently the activity of classical PKC. The enzyme activity in the particulate fraction was reduced by 59% and 43% in comparison with the TPA group, respectively. Thus, the results of these studies suggest that the subcellular distribution of PKC isoforms, and the activity of PKCs, can be modulated by plant phenolic acids, particularly tannic acid, and that such actions represent a part of the anti-promotional activity of these substances in mouse epidermis.

Correlation of DNA damage in epidemic dropsy patients to carcinogenic potential of argemone oil and isolated sanguinarine alkaloid in mice

In recent times, a higher incidence of gall bladder carcinoma in the Indo-Gangetic basin has been linked with the consumption of contaminated mustard oil. Consumption of mustard oil contaminated with argemone oil (AO) is well known to cause clinical manifestation referred to as "epidemic dropsy." Because sanguinarine, an active alkaloid of AO, has been shown to intercalate DNA, a possible correlation of DNA damage in epidemic dropsy patients to tumorigenic potential of AO and isolated sanguinarine alkaloid in mice was investigated in the present study. Single topical application of AO (0.15-0.3 ml) or isolated sanguinarine (4.5-18 micromol) followed by twice-weekly application of tetradecanoylphorbolmyristate acetate (TPA) for 25 weeks resulted in formation of tumors. Histopathologically these tumors were of squamous cell carcinoma type and similar to those found in the positive control group using dimethylbenzanthracene (DMBA)/TPA. The activities of cutaneous gamma-glutamyl transpeptidase (GGT) and glutathione-S-transferase P (GST-P), marker enzymes of tumorigenesis, were found to exhibit higher expression in AO or isolated sanguinarine/TPA treated groups when compared to control. The higher expression of p53 and p21/WAF1 in skin after single topical application of AO or isolated sanguinarine further confirms the tumorigenic response. Single topical application of AO or isolated sanguinarine alkaloid to mice showed significant DNA damage in terms of Olive tail moment (89-129%), tail length (54%) and tail DNA (153-205%) using Comet assay in skin cells. Further, the extent of DNA damage in blood cells of epidemic dropsy patients in alkaline Comet assay was found to be significantly higher as compared to normal population, indicating the genotoxic response of AO exposure. Although the genotoxic lesions may be repaired to some extent on withdrawal of consumption of AO contaminated mustard oil and the residual genotoxic effects caused by AO may not be expressed as signs of carcinogenesis. Environmental factors or hormonal changes during aging process may lead to stimulate/promote the genetically altered latent cells to form neoplastic lesions and can act as one of the etiological factors responsible for higher incidence of gall bladder carcinoma in the population of Indo-Gangetic basin.

Plant tannins inhibit the induction of aberrant crypt foci and colonic tumors by 1,2-dimethylhydrazine in mice

We have shown that naturally occurring tannins possess antitumor promotion activity in mouse skin. In the present investigation, we studied the ability of a hydrolyzable tannin, gallotannin (GT), and a condensed tannin extracted from red alder (RA) bark to inhibit 1,2-dimethylhydrazine (DMH)-induced colonic aberrant crypt foci (ACF) and tumors in Balb/c mice. In addition, we determined the ability of GT to inhibit the proliferation and to induce apoptosis in a human colon cancer cell line (T-84). Mice were given tannins by intraperitoneal injections, by gavage, or in drinking water before treatment with DMH for 24 weeks. Alternatively, mice were given tannins by intraperitoneal injection or gavage for only 2 weeks before DMH administration, then tannin administration was discontinued and mice were treated with DMH for 24 weeks. The multiplicity, size, and distribution of ACF and tumors were significantly inhibited by GT and RA in the above treatment regimens. The most effective treatments included GT by gavage, RA bark extract by intraperitoneal injection, and either tannin dissolved in drinking water. Extent of inhibition of ACF and tumors was gender independent. In cell culture experiments, GT treatment for three days inhibited the growth of T-84 cells, with a concentration resulting in half-maximal inhibition estimated to be 20 micrograms/ml. The treatment was not cytotoxic to cells at 1-40 micrograms/ml. Interestingly, at 10 micrograms/ml, GT induced apoptosis in T-84 cells as determined by the Hoechst DNA staining technique. Collectively, these findings support a potential role for tannins as chemopreventive agents against colon cancer.

Study on the carcinogenicity of tannic acid in F344 rats

The carcinogenicity of tannic acid, a compound that is used as a food additive, a clarifying agent and a refining agent, was examined in F344 rats of both sexes. Tannic acid was dissolved in distilled water at concentrations of 0.25 and 0.5%. The doses were selected on the basis of results from a 13-wk subchronic study. Groups of 50 male and 50 female rats were given one of these solutions ad lib. as their drinking water for up to 2 yr. The mean body weights of the treated males were essentially comparable with those of the controls, whereas treated females had lower mean body weights than the control group. A variety of tumours developed in all groups, including the control group, but all the neoplasms were histologically similar to those known to occur spontaneously in this strain of rats, and no statistically significant increase in the incidence of any tumour was found in the treated groups of either sex. Thus, it is concluded that, under the conditions of the experiment, tannic acid has neither carcinogenic potential in F344 rats nor modifying effects on spontaneous tumour development.

DNA breakage by tannic acid and Cu(II): generation of active oxygen species and biological activity of the reaction

Tannic acid was shown to reduce oxygen to superoxide anion. In the presence of Cu(II), the hydroxyl radical and hydrogen peroxide were formed. Strand scission reaction was shown to account for the biological activity of tannic acid as assayed by bacteriophage inactivation. The inactivating activity occurs through the Fenton pathway for free radical production and subsequent DNA cleavage by these radicals.

Comfort measures in breastfeeding, primiparous women

OBJECTIVE

To examine various comfort measures and evaluate their effects in alleviating nipple soreness.

DESIGN

Prospectively randomized, experimental study.

SETTING

Postpartum unit of a community teaching hospital.

PATIENTS

Seventy-three primiparous, postpartum, breastfeeding women.

INTERVENTIONS

Subjects were randomly assigned to four groups, with all women receiving instruction about breastfeeding and using one of the following treatments: warm moist tea bag compress, warm water compress, expressed milk massaged into the nipple and areola and air dried, instruction only (control group). The subjects completed a questionnaire each morning for 7 days regarding nipple soreness.

MAIN OUTCOME MEASURE

Effect of treatments on postpartum nipple pain.

RESULTS

Subjects in the warm water compress group demonstrated significantly less pain on Day 3 than did the tea or breast milk group.

CONCLUSIONS

Anticipatory guidance by obstetric nurses may assist breastfeeding women in treating their pain nonpharmacologically.