Green tea polyphenolic antioxidants and skin photoprotection (Review)

Green tea is consumed as a popular beverage worldwide particularly in Asian countries like China, Korea, Japan and India. It contains polyphenolic compounds also known as epicatechins, which are antioxidant in nature. Many laboratories have shown that topical treatment or oral consumption of green tea polyphenols inhibits chemical carcinogen- or ultraviolet radiation-induced skin tumorigenesis in different animal models. Studies have shown that green tea extract also possesses anti-inflammatory activity. These anti-inflammatory and anti-carcinogenic properties of green tea are due to their polyphenolic constituents present therein. The major and most chemopreventive constituent in green tea responsible for these biochemical or pharmacological effects is (-)-epigallocatechin-3-gallate (EGCG). Understanding the molecular mechanisms of these effects of green tea is a subject of investigation in many laboratories. Treatment of green tea polyphenols to skin has been shown to modulate the biochemical pathways involved in inflammatory responses, cell proliferation and responses of chemical tumor promoters as well as ultraviolet (UV) light-induced inflammatory markers of skin inflammation. Topical treatment with EGCG on mouse skin also results in prevention of UVB-induced immunosuppression, and oxidative stress. The protective effects of green tea treatment on human skin either topically or consumed orally against UV light-induced inflammatory or carcinogenic responses are not well understood. Based on documented extensive beneficial effects of green tea on mouse skin models and very little in human skin, many pharmaceutical and cosmetic companies are supplementing their skin care products with green tea extracts. Therefore, the focus of this communication is to review and analyze the photoprotective effects of green tea polyphenols to skin.

Aspergillus fumigatus CYP51 sequence: potential basis for fluconazole resistance

We have cloned and sequenced the Aspergillus fumigatus CYP51 gene which encodes the target of azole antifungal agents, namely cytochrome P450 sterol 14alpha-demethylase. Since A. fumigatus is intrinsically resistant to the widely used azole fluconazole, we compared its predicted CYP51 sequence to the CYP51 sequences from fluconazole-susceptible and resistant Candida albicans. This analysis generated specific hypotheses regarding the basis for A. fumigatus fluconazole resistance; in particular, A. fumigatus residue Ile301 corresponds to C. albicans residue Thr315 which is mutated to Ala in resistant strains and is proposed to hydrogen bond with the sterol substrate.

Green tea polyphenol (-)-epigallocatechin-3-gallate treatment to mouse skin prevents UVB-induced infiltration of leukocytes, depletion of antigen-presenting cells, and oxidative stress

Ultraviolet (UV) radiation-induced infiltrating leukocytes, depletion of antigen-presenting cells, and oxidative stress in the skin play an important role in the induction of immune suppression and photocarcinogenesis. Earlier we have shown that topical application of polyphenols from green tea or its major chemopreventive constituent (-)-epigallocatechin-3-gallate (EGCG) prevents UV-B-induced immunosuppression in mice. To define the mechanism of prevention, we found that topical application of EGCG (3 mg/mouse/3 cm(2) of skin area) to C3H/HeN mice before a single dose of UV-B (90 mJ/cm(2)) exposure inhibited UV-B-induced infiltration of leukocytes, specifically the CD11b+ cell type, and myeloperoxidase activity, a marker of tissue infiltration of leukocytes. EGCG treatment was also found to prevent UV-B-induced depletion in the number of antigen-presenting cells when immunohistochemically detected as class II MHC+ Ia+ cells. UV-B-induced infiltrating cell production of H2O2 and nitric oxide (NO) was determined as a marker of oxidative stress. We found that pretreatment of EGCG decreased the number of UV-B-induced increases in H2O2-producing cells and inducible nitric oxide synthase-expressing cells and the production of H2O2 and NO in both epidermis and dermis at a UV-B-irradiated site. Together, these data suggest that prevention of UV-B-induced infiltrating leukocytes, antigen-presenting cells, and oxidative stress by EGCG treatment of mouse skin may be associated with the prevention of UV-B-induced immunosuppression and photocarcinogenesis.

Green tea polyphenol (-)-epigallocatechin-3-gallate treatment of human skin inhibits ultraviolet radiation-induced oxidative stress

The use of naturally occurring botanicals with substantial antioxidant activity to afford protection to human skin against UV damage is receiving increasing attention. The green tea constituent (-)-epigallocatechin-3-gallate (EGCG) is a potent antioxidant and has shown remarkable preventive effects against photocarcinogenesis and phototoxicity in mouse models. In this study we have investigated the effects of topical application of EGCG, the major polyphenol present in green tea, to human skin before UV irradiation on UV-induced markers of oxidative stress and antioxidant enzymes. Using immunohistochemistry and analytical enzyme assays, we found that application of EGCG (mg/cm(2) skin) before a single UV exposure of 4x minimal erythema dose (MED) markedly decreases UV-induced production of hydrogen peroxide (68-90%, P < 0.025-0.005) and nitric oxide (30-100%, P < 0.025-0.005) in both epidermis and dermis in a time-dependent manner. EGCG pretreatment also inhibits UV-induced infiltration of inflammatory leukocytes, particularly CD11b(+) cells (a surface marker of monocytes/macrophages and neutrophils), into the skin, which are considered to be the major producers of reactive oxygen species. EGCG treatment was also found to inhibit UV-induced epidermal lipid peroxidation at each time point studied (41-84%, P < 0.05). A single UV exposure of 4x MED to human skin was found to increase catalase activity (109-145%) and decrease glutathione peroxidase (GPx) activity (36-54%) and total glutathione (GSH) level (13-36%) at different time points studied. Pretreatment with EGCG was found to restore the UV-induced decrease in GSH level and afforded protection to the antioxidant enzyme GPx. Further studies are warranted to study the preventive effects of EGCG against multiple exposures to UV light of human skin.

Identification and expression of multidrug resistance-related ABC transporter genes in Candida krusei

Infections with Candida krusei have increased in recent years as a consequence of its intrinsic resistance to fluconazole, an antifungal azole widely used in immunocompromised individuals to suppress infections due to azole-susceptible C. albicans. One established mechanism for azole resistance is drug efflux by ATP binding cassette (ABC) transporters. Since these transporters recognize structurally diverse drugs, their overexpression can lead to multidrug resistance (MDR). To identify C. krusei genes potentially involved in azole resistance, PCR was performed with primers corresponding to conserved sequences of MDR-related ABC transporters from other fungi. Two genes, ABC1 and ABC2, were identified; Southern blots suggested that both have one or two related gene copies in the C. krusei genome. ABC1 RNA was constitutively expressed at low levels in log phase cells while ABC2 RNA was undetectable. However, both genes were upregulated as cultures approached stationary phase, and this upregulation was correlated with decreased susceptibility to the lethal activity of the azole derivative miconazole. Furthermore, ABC1 was upregulated following brief treatment of C. krusei with miconazole and clotrimazole (but not other azoles), and the unrelated compounds albendazole and cycloheximide. The latter two compounds antagonized fluconazole activity versus C. krusei, supporting a role for the ABC1 transporter in azole efflux. Finally, miconazole-resistant mutants selected in vitro demonstrated increased constitutive expression of ABC1. Based on these expression data, genetic and functional characterization of the ABC1 transporter to directly test its role in C. krusei azole resistance would appear to be warranted.

Kinetics of UV light-induced cyclobutane pyrimidine dimers in human skin in vivo: an immunohistochemical analysis of both epidermis and dermis

It is well known that UV exposure of human skin induces DNA damage, and the cumulative effect of such repeated damage is an important contributor to the development of skin cancer. Here, we demonstrate UV dose- and time-dependent induction of DNA damage in the form of cyclobutane pyrimidine dimers (CPD) in skin cells following a single exposure of human skin to UV radiation. CPD+ cells were identified by an immunohistochemical technique using monoclonal antibodies to thymine dimers. The percentage of CPD+ cells was UV dose-dependent, even a suberythemal (0.5 minimal erythemal dose [MED]) dose resulted in detectable level of cells that contained pyrimidine dimers. Forty-eight hours after irradiation the percent of total epidermal cells positive for CPD ranged from 19 +/- 8, 36 +/- 10, 57 +/- 12 and 80 +/- 10, and total percent dermal cells positive for CPD ranged from 1 +/- 1, 7 +/- 3, 16 +/- 3 and 20 +/- 5, respectively, following 0.5, 1.0, 2.0 and 4.0 MED. CPD were also observed in deeper reticular dermis, which suggest the penetrating ability of UV radiation into the skin. The change in CPD+ cells from 0.5 to 240 h post-UV exposure in both epidermal and dermal compartments of the skin was also quantitated. CPD+ cells were observed in skin biopsies at early time points after UV exposure which remained elevated for 48 h, then declined significantly by 3 days post-UV. A close examination of the skin at and after 3 days following UV exposure indicates the significant removal of DNA damaged cells from the epidermis. Ten days after UV exposure the levels of CPD+ cells in both epidermis and dermis were not significantly different from that in unirradiated skin.

Green tea polyphenol treatment to human skin prevents formation of ultraviolet light B-induced pyrimidine dimers in DNA

Cancer chemopreventive effects of polyphenols from green tea (GTP) in mouse models of photocarcinogenesis are established. The present study is extended from mouse model to human system in vivo to determine the effect of topical application of GTP to human individuals against UV light-induced DNA damage in the form of cyclobutane pyrimidine dimers (CPDs) in the skin. UVB-induced CPDs were detected by immunohistochemical technique using monoclonal antibodies to thymine dimers. With the gradual increase in UVB dose, both erythema response and CPD formation in the skin was increased. GTP treatment inhibited both UVB-induced erythema response as well as CPD formation. Topical treatment with GTP (approximately 1 mg/cm2 of skin area) 20 min before human buttock skin (sun-protected site) exposure to UVB inhibited CPD formation in epidermis by 81, 70, 60, and 60% at 0.5, 1.0, 2.0, and 4.0 minimal erythema dose of UV exposure, respectively. Treatment of human skin with varying doses of GTP (1-4 mg/2.5 cm2 of skin area) before a single dose of UVB exposure (4.0 minimal erythema dose) decreased dose dependently the formation of UVB-induced CPDs in both epidermis and dermis. The inhibition of UVB-induced CPDs by GTP treatment may be, at least in part, responsible for the inhibition of photocarcinogenesis. Our data suggest that GTP may be used as a novel chemopreventive candidate and possible strategy to reduce UV-induced skin cancer risk in the human population.

Green tea and skin

OBJECTIVE

To discuss the current knowledge of polyphenolic compounds present in green tea as anti-inflammatory, antioxidant, and anticarcinogenic in skin.

DATA SOURCES

References identified from bibliographies of pertinent articles, including our work in related fields.

STUDY SELECTION AND DATA EXTRACTION

Articles were selected based on the use of green tea or its polyphenolic constituents for prevention against inflammation and cancer in the skin. Also discussed is the possible use of green tea to treat various inflammatory dermatoses.

DATA SYNTHESIS

The polyphenolic compounds from green tea were tested against chemical carcinogenesis and photocarcinogenesis in murine skin. These green tea polyphenols were found to afford protection against chemical carcinogenesis as well as photocarcinogenesis in mouse skin. A few experimental studies were conducted in human skin in our laboratory. Analysis of published studies demonstrates that green tea polyphenols have anti-inflammatory and anticarcinogenic properties. These effects appear to correlate with antioxidant properties of green tea polyphenols.

CONCLUSIONS

The outcome of the several experimental studies suggests that green tea possess anti-inflammatory and anticarcinogenic potential, which can be exploited against a variety of skin disorders. Although more clinical studies are needed, supplementation of skin care products with green tea may have a profound impact on various skin disorders in the years to come. Arch Dermatol. 2000;136:989-994

Biodiversity of Asian rice gall midge (Orseolia oryzae Wood Mason) from five countries examined by AFLP analysis

Amplified fragment length polymorphism (AFLP) analysis was used to assess the biodiversity of one of the most important dipteran pests of cereals, the Asian rice gall midge (Orseolia oryzae Wood Mason). Larvae and pupae were collected at 15 locations in five Asian countries and preserved in 95% ethanol for storage, shipment, and DNA extraction using cetyltrimethylammonium bromide (CTAB). Although only approximately 1 microg of DNA was extracted from a single pupa or larva, the use of several AFLP primers in various combinations meant that this amount of DNA was sufficient to allow many DNA fingerprints to be made per individual. Fingerprints were sufficiently reproducible, especially during selective amplification, to allow the genetic diversity within a field population to be characterized. Extraction of DNA from a pool of 20 insects yielded AFLP fingerprints in which variation among individuals was sacrificed in favor of detecting differences among populations. For each location, pooled DNA was amplified with three primer pairs. A total of 261 distinct AFLP bands were identified for the 45 fingerprints. Cluster analysis, performed by the unweighted pair-group method (UPGMA), separated the populations into two distinct groups. Group I included two populations from Guangdong province of southern China and one each from Laos and Imphal in northeastern India, while group II was comprised of eleven populations from elsewhere in India (Assam, Orissa, Madhya Pradesh, Andhra Pradesh, and Kerala) and from Nepal and Sri Lanka. AFLP analysis provided insight into the origins of gall midge biotypes. In 1992, the prevailing biotype in Imphal changed from Indian biotype 3 to a new biotype 3M. Our data show that biotype 3M belongs to group I and did not arise by a recent mutation from biotype 3, which belongs to group II. By contrast, Indian biotypes 2 and 4 are likely to have diverged through recent mutation and selection, as are Chinese biotypes 1 and 4. The almost simultaneous emergence of new biotypes in Kerala and Sri Lanka during 1985-1988 was most probably coincidental, because these biotypes are not closely related. AFLP fingerprints were also able to detect sexual dimorphism in the DNA of adult gall midges and to distinguish gall midge from its major parasite Platygaster oryzae.

Biodiversity of Asian rice gall midge (Orseolia oryzae Wood Mason) from five countries examined by AFLP analysis

Amplified fragment length polymorphism (AFLP) analysis was used to assess the biodiversity of one of the most important dipteran pests of cereals, the Asian rice gall midge (Orseolia oryzae Wood Mason). Larvae and pupae were collected at 15 locations in five Asian countries and preserved in 95% ethanol for storage, shipment, and DNA extraction using cetyltrimethylammonium bromide (CTAB). Although only ~1 µg of DNA was extracted from a single pupa or larva, the use of several AFLP primers in various combinations meant that this amount of DNA was sufficient to allow many DNA fingerprints to be made per individual. Fingerprints were sufficiently reproducible, especially during selective amplification, to allow the genetic diversity within a field population to be characterized. Extraction of DNA from a pool of 20 insects yielded AFLP fingerprints in which variation among individuals was sacrificed in favor of detecting differences among populations. For each location, pooled DNA was amplified with three primer pairs. A total of 261 distinct AFLP bands were identified for the 45 fingerprints. Cluster analysis, performed by the unweighted pair-group method (UPGMA), separated the populations into two distinct groups. Group I included two populations from Guangdong province of southern China and one each from Laos and Imphal in northeastern India, while group II was comprised of eleven populations from elsewhere in India (Assam, Orissa, Madhya Pradesh, Andhra Pradesh, and Kerala) and from Nepal and Sri Lanka. AFLP analysis provided insight into the origins of gall midge biotypes. In 1992, the prevailing biotype in Imphal changed from Indian biotype 3 to a new biotype 3M. Our data show that biotype 3M belongs to group I and did not arise by a recent mutation from biotype 3, which belongs to group II. By contrast, Indian biotypes 2 and 4 are likely to have diverged through recent mutation and selection, as are Chinese biotypes 1 and 4. The almost simultaneous emergence of new biotypes in Kerala and Sri Lanka during 1985-1988 was most probably coincidental, because these biotypes are not closely related. AFLP fingerprints were also able to detect sexual dimorphism in the DNA of adult gall midges and to distinguish gall midge from its major parasite Platygaster oryzae.

Key words: biotypes, Cecidomyiidae, insect, Oryza sativa, Platygaster oryzae, population, sexual dimorphism.

Ultraviolet-B exposure of human skin induces cytochromes P450 1A1 and 1B1

The cytochromes P450 belong to a multigene superfamily and are responsible for the metabolic activation of both xenobiotics and endobiotics. The expression of cytochrome P450 genes in target cells is an important determinant of human susceptibility to cancers and other chemically initiated diseases. In this study using immunohistochemistry, reverse transcription polymerase chain reaction, and western blot analysis, we investigated the cellular distribution and localization of cytochrome P450 1A1 and cytochrome P450 1B1 in human skin, and their induction by ultraviolet-B. Through the use of immunohistochemistry, cytochrome P450 1A1 was found to be primarily localized in the basal cell layer of the epidermis in non-ultraviolet-B exposed skin, whereas cytochrome P450 1B1 was localized in the epidermal cells other than the basal cell layer. Thus, localizations of cytochrome P450 1A1 and cytochrome P450 1B1 in human skin are different and may be related to keratinocyte differentiation. Ultraviolet-B exposure to solar-ultraviolet-protected skin (buttock site) resulted in an ultraviolet-B dose-dependent (0-4 minimal erythema doses) and time-dependent (0-48 h) induction of both cytochrome P450 1A1 and cytochrome P450 1B1 in the epidermis. Reverse transcription polymerase chain reaction and western blot analyses revealed that exposure of human skin to ultraviolet-B (4 minimal erythema doses) resulted in enhanced expression of mRNA and protein of both cytochrome P450 1A1 and cytochrome P450 1B1 in the epidermis. Ultraviolet-B induction of both cytochrome P450 1A1 and cytochrome P450 1B1 in human skin will probably result in enhanced bioactivation of polycyclic aromatic hydrocarbons and other environmental pollutants to which humans are exposed, which in turn could make the human skin more susceptible to ultraviolet-B-induced skin cancers or allergic and irritant contact dermatitis.

Prevention of UVB-induced immunosuppression in mice by the green tea polyphenol (-)-epigallocatechin-3-gallate may be associated with alterations in IL-10 and IL-12 production

UV exposure of the skin, particularly UVB (290-320 nm), causes adverse biological effects, including alterations in cutaneous immune cells, photoaging and photocarcinogenesis. Several studies have shown that polyphenolic compounds isolated from green tea afford protection against UVB-induced inflammatory responses and photocarcinogenesis in murine models. In this study we show that topical application of (-)-epigallocatechin-3-gallate (EGCG) (3 mg/mouse), a major polyphenolic component of green tea, before a single low dose UVB exposure (72 mJ/cm(2)) to C3H/HeN mice prevented UVB-induced inhibition of the contact hypersensitivity response and tolerance induction to the contact sensitizer 2, 4-dinitrofluorobenzene. Topical application of EGCG before UVB exposure reduced the number of CD11b+ monocytes/macrophages and neutrophils infiltrating into skin inflammatory lesions, which are considered to be responsible for creating the UV-induced immunosuppressive state. In addition, application of EGCG before UVB exposure decreased UVB-induced production of the immunomodulatory cytokine interleukin (IL)-10 in skin as well as in draining lymph nodes (DLN), whereas production of IL-12, which is considered to be a mediator and adjuvant for induction of contact sensitivity, was found to be markedly increased in DLN when compared with UVB alone-exposed mice. Taken together, our data demonstrate that EGCG protects against UVB-induced immunosuppression and tolerance induction by: (i) blocking UVB-induced infiltration of CD11b+ cells into the skin; (ii) reducing IL-10 production in skin as well as in DLN; (iii) markedly increasing IL-12 production in DLN. Protection against UVB-induced immunosuppression by EGCG may be associated with protection against UVB-induced photocarcinogenesis.

Antagonism of azole activity against Candida albicans following induction of multidrug resistance genes by selected antimicrobial agents

Antifungal azoles (e.g., fluconazole) are widely used for prophylaxis or treatment of Candida albicans infections in immunocompromised individuals, such as those with AIDS. These individuals are frequently treated with a variety of additional antimicrobial agents. Potential interactions between three azoles and 16 unrelated drugs (antiviral, antibacterial, antifungal, and antiprotozoal agents) were examined in vitro. Two compounds, tested at concentrations achievable in serum, demonstrated an antagonistic effect on azole activity against C. albicans. At fluconazole concentrations two to four times the 50% inhibitory concentration, C. albicans growth (relative to treatment with fluconazole alone) increased 3- to 18-fold in the presence of albendazole (2 microg/ml) or sulfadiazine (50 microg/ml). Antagonism (3- to 78-fold) of ketoconazole and itraconazole activity by these compounds was also observed. Since azole resistance has been correlated with overexpression of genes encoding efflux proteins, we hypothesized that antagonism results from drug-induced overexpression of these same genes. Indeed, brief incubation of C. albicans with albendazole or sulfadiazine resulted in a 3-to->10-fold increase in RNAs encoding multidrug transporter Cdr1p or Cdr2p. Zidovudine, trimethoprim, and isoniazid, which were not antagonistic with azoles, did not induce these RNAs. Fluphenazine, a known substrate for Cdr1p and Cdr2p, strongly induced their RNAs and, consistent with our hypothesis, strongly antagonized azole activity. Finally, antagonism was shown to require a functional Cdr1p. The possibility that azole activity against C. albicans is antagonized in vivo as well as in vitro in the presence of albendazole and sulfadiazine warrants investigation. Drug-induced overexpression of efflux proteins represents a new and potentially general mechanism for drug antagonism.

A flavonoid antioxidant, silymarin, affords exceptionally high protection against tumor promotion in the SENCAR mouse skin tumorigenesis model

In cancer chemoprevention studies, the identification of better antitumor-promoting agents is highly desired because they may have a wider applicability against the development of clinical cancers. Both epidemiological and animal studies have suggested that microchemicals present in the diet and several herbs and plants with diversified pharmacological properties are useful agents for the prevention of a wide variety of human cancers. Silymarin, a flavonoid isolated from milk thistle, is used clinically in Europe and Asia as an antihepatotoxic agent, largely due to its strong antioxidant activity. Because most antioxidants afford protection against tumor promotion, in this study, we assessed the protective effect of silymarin on tumor promotion in the SENCAR mouse skin tumorigenesis model. Application of silymarin prior to each 12-O-tetradecanoylphorbol 13-acetate (TPA) application resulted in a highly significant protection against tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated mouse skin. The protective effect of silymarin was evident in terms of reduction in tumor incidence (25, 40, and 75% protection, P < 0.001, X2 test), tumor multiplicity (76, 84, and 97% protection, P < 0.001, Wilcoxon rank sum test), and tumor volume (76, 94, and 96% protection, P < 0.001, Student's t test) at the doses of 3, 6, and 12 mg per application, respectively. To dissect out the stage specificity of silymarin against tumor promotion, we next assessed its effect against both stage I and stage II of tumor promotion. Application of silymarin prior to that of TPA in stage I or mezerein in stage II tumor promotion in dimethylbenz(a)anthracene-initiated SENCAR mouse skin resulted in an exceptionally high protective effect during stage I tumor promotion, showing 74% protection against tumor incidence (P < 0.001, X2 test), 92% protection against tumor multiplicity (P < 0.001, Wilcoxon rank sum test), and 96% protection against tumor volume (P < 0.001, Student's t test). With regard to stage II tumor promotion, silymarin showed 26, 63, and 54% protection in tumor incidence, multiplicity, and volume, respectively. Similar effect of silymarin to that in anti-stage I studies, were also observed when applied during both stage I and stage II protocols. In other studies, silymarin significantly inhibited: (a) TPA-induced skin edema, epidermal hyperplasia, and proliferating cell nuclear antigen-positive cells; (b) DNA synthesis; and (c) epidermal lipid peroxidation, the early markers of TPA-caused changes that are associated with tumor promotion. Taken together, these results suggest that silymarin possesses exceptionally high protective effects against tumor promotion, primarily targeted against stage I tumors, and that the mechanism of such effects may involve inhibition of promoter-induced edema, hyperplasia, proliferation index, and oxidant state.

Polyphenolic antioxidant (-)-epigallocatechin-3-gallate from green tea reduces UVB-induced inflammatory responses and infiltration of leukocytes in human skin

Identification of natural products capable of affording protection against UVB radiation-induced inflammatory responses and generation of oxidative stress may have important human health implications. The UVB exposure-induced skin injury and oxidative stress has been associated with a variety of skin disease conditions including photoaging, inflammation and cancer. Tea is a popular beverage consumed worldwide. In several mouse skin models, topical application as well as oral consumption of green tea has been shown to afford protection against chemical and UVB-induced carcinogenesis and inflammatory responses. In the present study, we investigated in human skin, whether topical application of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent in green tea, inhibits UVB-induced infiltration of leukocytes (macrophage/neutrophils), a potential source of generation of reactive oxygen species (ROS), and generation of prostaglandin (PG) metabolites. Human subjects were UVB irradiated on sun-protected skin to four times their minimal erythema dosage (MED) and skin biopsies or keratomes were obtained either 24 h or 48 h later. We found that topical application of EGCG (3 mg/2.5 cm2) before UVB (4 MED) exposure to human skin significantly blocked UVB-induced infiltration of leukocytes and reduced myeloperoxidase activity. These infiltrating leukocytes are considered to be the major source of generation of ROS. In the same set of experiments we found that topical application of EGCG before UVB exposure decreased UVB-induced erythema. In additional experiments, we found that microsomes from EGCG pretreated human skin and exposed to UVB, compared to UVB exposure alone, produced significantly reduced PG metabolites, particularly PGE2. The PG metabolites play a critical role in free radical generation and skin tumor promotion in multistage skin carcinogenesis. Careful microscopic examination of skin sections, stained with hematoxylin and eosin, under higher magnification (x400) also revealed that EGCG pretreated and UVB-exposed human skin contained fewer dead cells in the epidermis with comparison to nonpretreated UVB-exposed skin. Taken together, our data demonstrate that EGCG has the potential to block the UVB-induced infiltration of leukocytes and the subsequent generation of ROS in human skin. This may explain the possible mechanism involved in anti-inflammatory effects of green tea. We suggest that EGCG may be useful as a topical agent for protection against UVB-induced ROS-associated inflammatory dermatoses, photoaging and photocarcinogenesis. Further studies are warranted in this direction.

Tea antioxidants in cancer chemoprevention

In recent years, the concept of cancer chemoprevention has matured greatly. Significant reversal or suppression of premalignancy in several sites by chemopreventive agents appears achievable. This article summarizes experimental data on chemopreventive effects of tea polyphenols in different tumor bioassay systems. Tea (Camellia sinensis) is cultivated in about 30 countries, and is the most widely consumed beverage in the world. Three main commercial tea varieties--green, black, and oolong--are usually consumed, but most experimental studies demonstrating the antimutagenic and anticarcinogenic effects of tea have been conducted with water extract of green tea, or a polyphenolic fraction isolated from green tea (GTP). The majority of these studies have been conducted in a mouse skin tumor model system where tea is fed either as water extract through drinking water, or as purified GTP. GTP has been shown to exhibit antimutagenic activity in vitro, and inhibit carcinogen- as well as UV-induced skin carcinogenesis in vivo. Tea consumption has also been shown to afford protection against chemical carcinogen-induced stomach, lung, esophagus, duodenum, pancreas, liver, breast, and colon carcinogenesis in specific bioassay models. Several epicatechin derivatives (polyphenols) present in green tea have been shown to possess anticarcinogenic activity; the most active is (-)-epigallocatechin-3-gallate, which is also the major constituent of GTP. The mechanisms of tea's broad cancer chemopreventive effects are not completely understood. Several theories have been put forward, including inhibition of UV- and tumor promoter-induced ornithine decarboxylase, cyclo-oxygenase, and lipoxygenase activities, antioxidant and free radical scavenging activity; enhancement of antioxidant (glutathione peroxidase, catalase, and quinone reductase) and phase II (glutathione-S-transferase) enzyme activities; inhibition of lipid peroxidation, and anti-inflammatory activity. These properties of tea polyphenols make them effective chemopreventive agents against the initiation, promotion, and progression stages of multistage carcinogenesis.

Activated complement component 3 (C3) is required for ultraviolet induction of immunosuppression and antigenic tolerance

Complement component 3 (C3), a critical regulator of innate immunity, may also play a role in the regulation of cognate immunity, such as contact sensitivity responses. Because ultraviolet (UV) radiation also activates C3 in the skin, we determined whether the immunosuppressed state that results when a contact sensitizer is applied through UVB-exposed skin requires the presence and activation of C3. This question was addressed through the use of C3-deficient mice, blockade of C3 cleavage to C3b, and accelerated degradation of iC3b by soluble complement receptor 1 (sCR1). Both C3-modulated systems totally reversed the failure to induce a contact sensitivity response to dinitrofluorobenzene (DNFB) upon primary sensitization at the UV-exposed site, as well as immunologic tolerance to a second DNFB immunization through normal skin. Treatment with sCR1 reduced the infiltration of CD11b+ leukocytes into the epidermis and dermis of UV-irradiated skin but did not reverse the UV-induced depletion of epidermal class II MHC+CD11blo Langerhans cells. These data, taken together with previous results showing abrogation of locally induced UV immunosuppression by in vivo anti-CD11b treatment, suggest a novel mechanism by which ligation of the leukocyte beta2 integrin, CD11b, by iC3b molecules formed from C3 activation in UV-exposed skin, modifies cutaneous CD11b+ cells such that skin antigen-presenting cells are unable to sensitize in a primary immune response, but actively induce antigenic tolerance.

Genetic variation in low-dose UV-induced suppression of contact hypersensitivity and in the skin photocarcinogenesis response

Two of the major cutaneous consequences of ultraviolet (UV) radiation exposure are immunosuppression and the development of skin cancer. This study examined whether these effects are genetically determined. Suppression of contact hypersensitivity by local, low-dose UV radiation was examined in what have been termed "UV-susceptible" and "UV-resistant" strains of mice. C3H/HeJ mice ("UV resistant") were resistant to the adverse effects of low-dose UV radiation when normal doses of hapten were applied to UV-irradiated skin; however, they were sensitive when the amount of hapten used for sensitization was reduced. A similar effect was observed in BALB/c mice ("UV resistant") and when the hapten was dimethylbenz(a)anthracene, thus indicating that the genetic variation was not strain or hapten specific. Despite the fact that some strains were sensitive and some were resistant to low-dose UV radiation when high doses of hapten were employed, all strains initially sensitized to hapten through UV-irradiated skin were found to be unresponsive when rechallenged on normal skin, no matter what the initial sensitizing dose of hapten was. To determine whether other biologic effects of UV also exhibited genetic variation, C3H/HeN and C3H/HeJ mice were compared for susceptibility to UVB-induced skin cancer formation. C3H/HeJ mice developed significantly more tumors than C3H/HeN mice when subjected to a single dose of UV radiation followed by repeated exposure to the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. These studies provide strong evidence that genetic factors influence individual susceptibility to the biologic effects of UV radiation.

In vitro susceptibilities of the AIDS-associated microsporidian Encephalitozoon intestinalis to albendazole, its sulfoxide metabolite, and 12 additional benzimidazole derivatives

Recent reports have described the successful treatment of Encephalitozoon intestinalis infection in AIDS patients with albendazole. However, this compound is rapidly metabolized in vivo to albendazole sulfoxide, and furthermore it is only 1 of about 15 commercially developed benzimidazole derivatives. To compare the activities of albendazole, albendazole sulfoxide, and other benzimidazoles, an in vitro system involving infection of green monkey kidney cell (E6) monolayers with E. intestinalis spores was developed. After 14 days, the effects of benzimidazoles on spore production were determined. Ten of fourteen derivatives tested, including albendazole, were inhibitory at concentrations of 1 to 10 ng/ml. Derivatives modified at the 1 or 2 position were less active. Albendazole sulfoxide was 1.7-fold more inhibitory than albendazole but significantly less toxic to E6 cells, a finding that explains the clinical efficacy of this compound. Potential alternatives to albendazole are discussed. No albendazole-resistant E. intestinalis mutants were obtained following in vitro selection.

Inhibition of phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate-caused inflammatory responses in SENCAR mouse skin by black tea polyphenols

Over the past 10 years many studies from several laboratories defined anticarcinogenic and anti-inflammatory effects of tea, a widely consumed beverage by the human population. Much of such work has been conducted with green tea or its polyphenolic constituents. Regarding black tea, studies have shown that its water extract affords protection against tumor promotion caused by chemical carcinogens or ultraviolet B radiation in murine skin carcinogenesis models. Several studies have shown that topical application of chemical tumor promoters to murine skin results in the induction of epidermal edema, hyperplasia and ornithine decarboxylase (ODC) and cyclo-oxygenase activities, and interleukin-1 alpha (IL-1alpha) and ODC mRNA expression. In this study, we assessed whether topical application of polyphenols isolated from black tea leaves (hereafter referred to as BTP) mainly consisting of theaflavine gallates and (-)-epigallocatechin-3-gallate, inhibits phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)-caused induction of these markers of inflammatory responses in murine skin. Topical application of BTP (6 mg in 0.2 ml acetone/animal) 30 min prior to TPA application on to the mouse skin resulted in significant inhibition against TPA-caused induction of epidermal edema (40%, P < 0.01), hyperplasia (57%, P < 0.005), leukocytes infiltration (50%), and induction of epidermal ODC (57%) and pro-inflammatory cytokine IL-1alpha mRNA expression (69%). Pre-application of BTP to that of TPA also resulted in significant inhibition of TPA-caused induction of epidermal ODC (23-73%, P < 0.005-0.0001), and cyclo-oxygenase, in terms of prostaglandins metabolites formation (38-65%, P < 0.01-0.0005), enzyme activities. Our data indicate that the inhibition of TPA-caused changes in these markers of inflammatory responses in murine skin by BTP may be one of the possible mechanisms of chemopreventive effects associated with black tea against tumorigenesis. The results of this study suggest that black tea, specifically polyphenols present therein, may be useful against cutaneous inflammatory responses in human population.

Protective effects of silymarin against photocarcinogenesis in a mouse skin model

BACKGROUND

Nonmelanoma skin cancer is the most common cancer among humans; solar UV is its major cause. Therefore, it is important to identify agents that can offer protection against this cancer.

PURPOSE

We evaluated the protective effects of silymarin, a flavonoid compound isolated from the milk thistle plant, against UVB radiation-induced nonmelanoma skin cancer in mice and delineated the mechanism(s) of its action.

METHODS

For long-term studies, three different protocols of treatment were employed, each evaluating protection by silymarin at a different stage of carcinogenesis. Female SKH-1 hairless mice were subjected to 1) UVB-induced tumor initiation followed by phorbol ester-mediated tumor promotion, 2) 7,12-dimethylbenz[a]anthracene-induced tumor initiation followed by UVB-mediated tumor promotion, and 3) UVB-induced complete carcinogenesis. Forty mice were used in each protocol and were divided into control and treatment groups. Silymarin was applied topically at a dose of 9 mg per application before UVB exposure, and its effects on tumor incidence (% of mice with tumors), tumor multiplicity (number of tumors per mouse), and average tumor volume per mouse were evaluated. In short-term studies, the following parameters were measured: formation of sunburn and apoptotic cells, skin edema, epidermal catalase and cyclooxygenase (COX) activities, and enzymatic activity and messenger RNA (mRNA) expression for ornithine decarboxylase (ODC), a frequently observed marker at tumor promotion stage. Fisher's exact test was used to evaluate differences in tumor incidence, two-sample Wilcoxon rank sum test was used for tumor multiplicity and tumor volume, and Student's t test was used for all other measurements. All statistical tests were two-sided.

RESULTS

In the protocol with UVB-induced tumor initiation, silymarin treatment reduced tumor incidence from 40% to 20% (P = .30), tumor multiplicity by 67% (P = .10), and tumor volume per mouse by 66% (P = .14). In the protocol with UVB-induced tumor promotion, silymarin treatment reduced tumor incidence from 100% to 60% (P<.003), tumor multiplicity by 78% (P<.0001), and tumor volume per mouse by 90% (P<.003). The effect of silymarin was much more profound in the protocol with UVB-induced complete carcinogenesis, where tumor incidence was reduced from 100% to 25% (P<.0001), tumor multiplicity by 92% (P<.0001), and tumor volume per mouse by 97% (P<.0001). In short-term experiments, silymarin application resulted in statistically significant inhibition in UVB-caused sunburn and apoptotic cell formation, skin edema, depletion of catalase activity, and induction of COX and ODC activities and ODC mRNA expression.

CONCLUSIONS AND IMPLICATION

Silymarin can provide substantial protection against different stages of UVB-induced carcinogenesis, possibly via its strong antioxidant properties. Clinical testing of its usefulness is warranted.

Protection against induction of mouse skin papillomas with low and high risk of conversion to malignancy by green tea polyphenols

We earlier showed that a polyphenolic fraction isolated from green tea (GTP) affords protection against tumor promotion and tumor progression in SENCAR mouse skin. The present study was designed to further evaluate the protective effect of GTP against the induction and subsequent progression of papillomas to squamous cell carcinomas (SCCs) in experimental protocols where papillomas were developed with a low or high probability of their malignant conversion. Topical application of GTP (6 mg/animal) 30 min prior to that of 12-O-tetradecanoylphorbol-13-acetate (TPA) either once a week for 5 weeks (high risk TPA protocol) or once a week for 20 weeks (low risk TPA protocol) or mezerein (MEZ) twice a week for 20 weeks (high risk MEZ protocol) in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin resulted in significant protection against skin tumor promotion in terms of tumor incidence (32-60%), multiplicity (49-63%) and tumor volume/mouse (73-90%) at the termination of the experiment at 20 weeks. In three separate malignant progression experiments when papilloma yield in DMBA-initiated and TPA or MEZ promoted low and high risk protocols was stabilized at 20 weeks, animals were divided into two subgroups. These animals were either topically treated twice weekly with acetone (0.2 ml/animal, spontaneous malignant conversion group) or with GTP (6 mg/animal in 0.2 ml acetone) for an additional period of 31 weeks. During these treatment regimens, all suspected carcinomas were recorded and each one was verified histopathologically either at the time when tumor-bearing mouse died/moribund or at the termination of the experiment at 51 weeks. GTP resulted in significant protection against the malignant conversion of papillomas to SCC in all the protocols employed. At the termination of the experiment at 51 weeks, these protective effects were evident in terms of mice with carcinomas (35-41%), carcinomas per mouse (47-55%) and percent malignant conversion of papillomas to carcinomas (47-58%). The kinetics of malignant conversion suggest that a subset of papillomas formed in the early phase of tumor promotion in all the protocols had a higher probability of malignant conversion into SCCs because all the positive control groups (acetone treated) produced nearly the same number of carcinomas (33-38 in a group of 20 animals) at the end of the progression period. In the GTP-treated group of animals the number of carcinomas formed was less (14-20 in a group of 20 animals), which shows the ability of GTP to protect against the malignant conversion of papillomas of higher probability of malignant conversion to SCCs. The results of this study suggest that irrespective of the risk involved, GTP may be highly useful in affording protection against skin cancer risk.

Cultivation of Mycobacterium tuberculosis from pleural tissue and its histopathology in suspected cases of tuberculous pleural effusion

The majority of idiopathic pleural effusion are considered to be of tuberculous etiology. The culture of bacilli provide most authentic evidence of disease process. This study was carried out on 21 cases of suspected tuberculous pleural effusion. The pleural fluid and tissue was subjected for smear examination, and cultivation of tubercle bacilli along with pleural biopsy. Overall the diagnosis could be made out of 8 (38.09%) cases. The cultivation of Mycobacterium tuberculosis from pleural tissue was more sensitive (33.33%) as compared to histopathology (19.05%). However, the triad of cultivation of Mycobacterium tuberculosis from pleural tissue, pleural histopathology and pleural fluid smear examination or culture should be done in each suspected case of tuberculous effusion.