Protective effect of Fucoxanthin against UVB-induced skin photoaging in hairless mice

Fucoxanthin, a major carotenoid in brown algae, has various beneficial effects. In this study, we evaluated the effect of topical fucoxanthin on UVB-induced skin photoaging in hairless mice. The dorsal skins were treated topically with a 0.001% fucoxanthin solution 2 h each time before UVB irradiation (5 times a week) for 10 weeks. The formation of wrinkles in UVB-irradiated skin treated with vehicle alone significantly increased, as compared with the non-irradiated control. Treatment with fucoxanthin tended to suppress UVB-induced wrinkle formation, but there was no significant difference between wrinkle formation in the control group and the fucoxanthin treatment group. However, topical treatment with fucoxanthin significantly lessened UVB-induced epidermal hypertrophy, VEGF, and MMP-13 expression in the epidermis and thiobarbituric acid reactive substances (TBARS) in the skin. These results indicate that topical treatment with fucoxanthin prevents skin photoaging in UVB-irradiated hairless mice, possibly via antioxidant and antiangiogenic effects.     

Docosahexaenoic acid inhibits UVB-induced activation of NF-κB and expression of COX-2 and NOX-4 in HR-1 hairless mouse skin by blocking MSK1 signaling

Exposure to ultraviolet-B (UVB) radiation induces inflammation and photocarcinogenesis in mammalian skin. Docosahexaenoic acid (DHA), a representative ω-3 polyunsaturated fatty acid, has been reported to possess anti-inflammatory and chemopreventive properties. In the present study, we investigated the molecular mechanisms underlying the inhibitory effects of DHA on UVB-induced inflammation in mouse skin. Our study revealed that topical application of DHA prior to UVB irradiation attenuated the expression of cyclooxygenase-2 (COX-2) and NAD(P)H:oxidase-4 (NOX-4) in hairless mouse skin. DHA pretreatment also attenuated UVB-induced DNA binding of nuclear factor-kappaB (NF-κB) through the inhibition of phosphorylation of IκB kinase-α/β, phosphorylation and degradation of IκBα and nuclear translocation of p50 and p65. In addition, UVB-induced phosphorylation of p65 at the serine 276 residue was significantly inhibited by topical application of DHA. Irradiation with UVB induced phosphorylation of mitogen and stress-activated kinase-1 (MSK1), extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinase, and all these events were attenuated by pretreatment with DHA. Blocking ERK and p38 MAP kinase signaling by U0126 and SB203580, respectively, diminished MSK1 phosphorylation in UVB-irradiated mouse skin. Pretreatment with H-89, a pharmacological inhibitor of MSK1, abrogated UVB-induced activation of NF-κB and the expression of COX-2 and NOX-4 in mouse skin. In conclusion, topically applied DHA inhibits the UVB-induced activation of NF-κB and the expression of COX-2 and NOX-4 by blocking the phosphorylation of MSK1, a kinase downstream of ERK and p38 MAP kinase, in hairless mouse skin.     

Anti-photoaging effect of skin cream manufactured with ziyuglycoside I isolated from Sanguisorba officinalis on ultraviolet B-induced hairless mice

In this study, skin cream containing ziyuglycoside I isolated from Sanguisorba officinalis was manufactured and examined the protective effects of the skin cream against UVB-induced hairless mice. UVB-induced hairless mice were topically treated with the skin cream once a day for 5 weeks. Application of the skin cream did not exhibit side effect on body growth showing normal body weight and food efficiency in the mice. The skin cream treatment also was inhibited mRNA expression of interleukin (IL)-1β, matrix metalloproteinase (MMP)-2, MMP-9, and MMP-2 protein expression in the mice. Furthermore, the skin cream treatment inhibits epidermal wrinkle formation, wrinkle depth, wrinkle thickness, and collagen degradation in UVB-induced hairless mice. Therefore, the skin cream was able to play a role in the attenuation of photoaging caused by UVB irradiation via downregulation of mRNA expression of inflammatory cytokine IL-1β, MMP-2, MMP-9, and suppression of MMP-2 proteins expression.     

Rice bran supplement prevents UVB-induced skin photoaging in vivo

Although rice bran consumption is reportedly has numerous beneficial effects on human health, the relationship between rice bran and the prevention of photoaging has not been investigated in detail. We sought to investigate whether consumption of rice bran supplement (RBS) can elicit preventive effects against UVB-induced photoaging in vivo. Dorsal skin sections of hairless mice were exposed to UVB over 16 weeks. RBS consumption suppressed UVB-induced wrinkle formation and inhibited the loss of water content and epidermal thickening in the mouse skin. Western blot and immunohistochemical analyses revealed that repeated exposure to UVB upregulated matrix metalloproteinase-13 (MMP-13) and cyclooxygenase-2 (COX-2) expression, while consumption of RBS suppressed MMP-13 and COX-2 expression, as well as mitogen-activated protein kinase (MAPK) signaling pathways. These findings suggest that RBS could be a potential bioactive ingredient in nutricosmetics to inhibit wrinkle formation and water content loss via the suppression of COX-2 and MMP-13 expression.     

Coenzyme Q_{10} effects on manganese superoxide dismutase and glutathione peroxidase in the hairless mouse skin induced by ultraviolet B irradiation

Coenzyme Q_{10} (CoQ_{10}) is a naturally occurring antioxidant and a prominent component of mitochondrial electron transport chain. In the present study, we investigated the effect of CoQ_{10} nanoparticle against photoaging using immunohistochemistry and Western blot analysis in the hairless mouse skin induced by ultraviolet B (UVB) irradiation (300 mJ/cm;{2}, 3 min/day for 21 days). In the UVB-irradiated distilled water (DW)-treated group, manganese superoxide dismutase (SOD2) and glutathione peroxidase (GPx) immunoreactivity and their protein levels in the skin were significantly lower than those in the control group. However, SOD2 and GPx immunoreactivity and their protein levels in the skin of the UVB-irradiated CoQ_{10}-treated group were higher than those in the UVB-irradiated DW-treated group. GPx activity in the skin in the UVB-irradiated DW-treated group significantly decreased compared to that in the control group; whereas GPx activity in the UVB-irradiated CoQ_{10}-treated group was similar to that in the control group. These results suggest that CoQ_{10} strongly inhibits oxidative stress in the skin induced by UVB via increasing SOD2 and GPx.     

Involvement of NADPH oxidase 1 in UVB-induced cell signaling and cytotoxicity in human keratinocytes

Members of NADPH oxidase (Nox) enzyme family are important sources of reactive oxygen species (ROS) and are known to be involved in several physiological functions in response to various stimuli including UV irradiation. UVB-induced ROS have been associated with inflammation, cytotoxicity, cell death, or DNA damage in human keratinocytes. However, the source and the role of UVB-induced ROS remain undefined.Here, we show that Nox1 is involved in UVB-induced p38/MAPK activation and cytotoxicity via ROS generation in keratinocytes. Nox1 knockdown or inhibitor decreased UVB-induced ROS production in human keratinocytes. Nox1 knockdown impaired UVB-induced p38 activation, accompanied by reduced IL-6 levels and attenuated cell toxicity. Treatment of cells with N-acetyl-L-cysteine (NAC), a potent ROS scavenger, suppressed p38 activation as well as consequent IL-6 production and cytotoxicity in response to UVB exposure. p38 inhibitor also suppressed UVB-induced IL-6 production and cytotoxicity. Furthermore, the blockade of IL-6 production by IL-6 neutralizing antibody reduced UVB-induced cell toxicity.In vivo assay using wild-type mice, the intradermal injection of lysates from UVB-irradiated control cells, but not from UVB-irradiated Nox1 knockdown cells, induced inflammatory swelling and IL-6 production in the skin of ears. Moreover, administration of Nox1 inhibitor suppressed UVB-induced increase in IL-6 mRNA expression in mice skin.Collectively, these data suggest that Nox1-mediated ROS production is required for UVB-induced cytotoxicity and inflammation through p38 activation and inflammatory cytokine production, such as IL-6. Thus, our findings suggest Nox1 as a therapeutic target for cytotoxicity and inflammation in response to UVB exposure.     

The osmolyte taurine protects against ultraviolet B radiation-induced immunosuppression

Organic osmolytes, such as taurine, are involved in cell volume homeostasis and cell protection. Epidermal keratinocytes possess an osmolyte strategy, i.e., they take up taurine upon hyperosmotic stress and express the corresponding transporter TAUT. UVB irradiation also triggers taurine uptake and TAUT expression in this cell type. We therefore asked whether taurine plays a role in photoprotection. By using a TAUT-deficient mouse model, lack of taurine in the skin was found to cause a significantly higher sensitivity to UVB-induced immunosuppression. This was not due to an increased generation or decreased repair of UVB-induced DNA photoproducts in the skin of these animals. Instead, decreased skin taurine levels were associated with an increased formation of the soluble immunosuppressive molecule platelet-activating factor (PAF) from the membranes of UVB-irradiated epidermal cells. Blocking PAF activity in taut-deficient mice with a PAF receptor antagonist abrogated their increased sensitivity to UVB-induced immunosuppression. Moreover, taut -/- mice were more sensitive to PAF-mediated immunosuppression than taut +/+ mice. These data suggest that taurine uptake by epidermal cells prevents undue PAF formation, and thereby photoimmunosuppression. Thus, similar to nucleotide excision repair, taurine uptake is critically involved in photoprotection of the skin.     

UV-induced skin carcinogenesis in xeroderma pigmentosum group A (XPA) gene-knockout mice with nucleotide excision repair-deficiency

Nucleotide excision repair (NER) removes a wide variety of lesions from the genome and is deficient in the genetic disorder, xeroderma pigmentosum (XP). In this paper, an in vitro analysis of the XP group A gene product (XPA protein) is reported. Results of an analysis on the pathogenesis of ultraviolet (UV)-B-induced skin cancer in the XPA gene-knockout mouse are also described: (1) contrary to wild type mice, significant bias of p53 mutations to the transcribed strand and no evident p53 mutational hot spots were detected in the skin tumors of XPA-knockout mice. (2) Skin cancer cell lines from UVB-irradiated XPA-knockout mice had a decreased mismatch repair activity and an abnormal cell cycle checkpoint, suggesting that the downregulation of mismatch repair helps cells escape killing by UVB and that mismatch repair-deficient clones are selected for during the tumorigenic transformation of XPA (-/-) cells. (3) The XPA-knockout mice showed a higher frequency of UVB-induced mutation in the rpsL transgene at a low dose of UVB-irradiation than the wild type mice. CC-->TT tandem transition, a hallmark of UV-induced mutation, was detected at higher frequency in the rpsL transgene in the XPA-knockout mice than the wild type mice. This rpsL/XPA mouse system will be useful for further analysing the role of NER in the mutagenesis induced by various carcinogens. (4) The UVB-induced immunosuppression was greatly enhanced in the XPA-knockout mice. It is possible that an enhanced impairment of the immune system by UVB irradiation is involved in the high incidence of skin cancer in XP.     

Changes in the proliferative activity of epidermal melanocytes in serum-free primary culture during the development of ultraviolet radiation B-induced pigmented spots in hairless mice

Long-term exposure to ultraviolet radiation B (UVB) induced pigmented spots in the dorsal skin of hairless mice of strain (HR-1 X HR/De)F1. To clarify the cellular mechanism for the development of these UVB-induced pigmented spots, we investigated changes in the proliferative activity of epidermal melanoblasts and melanocytes in the dorsal skin at various weeks after UVB irradiation. Epidermal cell suspensions from the dorsal skin of hairless mice were cultured in a serum-free medium supplemented with dibutyryl adenosine 3':5'-cyclic monophosphate (DBcAMP) and basic fibroblast growth factor (bFGF). The suspensions were prepared from dorsal skins of mice exposed to UVB for 4 weeks (the stage of hyperpigmentation). Suspensions were also prepared from mice at 3 (the stage of depigmentation), 8 (the stage of appearance of pigmented spots), 20 (the stage of development of small-sized pigmented spots) and 37 (the stage of development of medium-sized pigmented spots) weeks after the cessation of 8-week UVB exposure. At the stage of hyperpigmentation the proliferative activity of melanoblasts and melanocytes was suppressed. With the development of pigmented spots, the proliferative activity of undifferentiated melanoblasts gradually increased, and then followed the increase in the proliferative activity of differentiated melanocytes. These results suggest that the proliferative activity of epidermal melanoblasts and melanocytes in UVB-irradiated skin increases with the development of pigmented spots.     

UVA and UVB wavebands modulate expression of fasL in mouse skin epidermis

In our previous report, we observed different cytokine modulation in mouse epidermis by the UVA and UVB wavebands. In the present investigations, the effects of irradiation with UVA and UVB on the Fas(CD95)/FasL system have been studied because apoptosis mediated by the interaction between Fas and FasL has been suggested recently to be associated with UVB-induced immunosuppression in mouse skin. Our results show that UVA irradiation following UVB irradiation has the ability to reduce the up-regulation of FasL expression in mouse skin resulting from the UVB irradiation.     

The effect of cilostazol on the expression of matrix metalloproteinase-1 and type I procollagen in ultraviolet-irradiated human dermal fibroblasts

AimCilostazol is a selective inhibitor of type III phosphodiesterase that inhibits platelet aggregation. Cilostazol is a useful vasodilator, antithrombotic, and cardiotonic agent. Ultraviolet B (UVB) irradiation increases the production of matrix metalloproteinase-1 (MMP-1) during skin photoaging. The UVB-induced increase of MMP-1 results in connective tissue damage, and the skin becomes wrinkled and aged. Here, we investigated the capacity of cilostazol to inhibit MMP-1 expression in UVB-irradiated human dermal fibroblasts.Main methodsCultured human dermal fibroblasts were irradiated with UVB, followed by the addition of cilostazol to the culture medium.Key findingsPost-treatment with cilostazol attenuated UVB-induced production of MMP-1 and prevented the reduction of type I procollagen. Cilostazol inhibited UVB irradiation-induced phosphorylation of the mitogen-activated protein kinase (MAPK) signaling molecules Jun-N-terminal kinase (JNK) and p38 kinase, as well as activator protein-1 (AP-1) in dermal fibroblasts.SignificanceOverall, these results demonstrate that cilostazol regulates UVB-induced MMP-1 expression and type I procollagen synthesis by inhibiting MAPK signaling and AP-1 activity. Therefore, we suggest that cilostazol may be useful for the prevention and treatment of skin photodamage caused by UVB-irradiation.     

Protective effect of inositol hexaphosphate against UVB damage in HaCaT cells and skin carcinogenesis in SKH1 hairless mice

UVB radiation damages keratinocytes, potentially inducing chronic skin damage, cutaneous malignancy, and suppression of the immune system. Naturally occurring agents have been considered for prevention and treatment of various kinds of cancer, including skin cancer. Inositol hexaphosphate (IP6), an antioxidant, is a naturally occurring polyphosphorylated carbohydrate that has shown a strong anticancer activity in several experimental models. We assessed the protective effects of IP6 against UVB irradiationinduced injury and photocarcinogenesis by using HaCaT cells (human immortalized keratinocytes) and SKH1 hairless mice. We found that IP6 counteracts the harmful effects of UVB irradiation and increases the viability and survival of UVB-exposed cells. Treatment with IP6 after UVB irradiation (30 mJ/cm(2)) arrested cells in the G(1) and G(2) M phases while decreasing the S phase of the cell cycle. Treatment with IP6 also decreased UVB-induced apoptosis and caspase 3 activation. Topical application of IP6 followed by exposure to UVB irradiation in SKH1 hairless mice decreased tumor incidence and multiplicity as compared with control mice. Our results suggest that IP6 protects HaCaT cells from UVB-induced apoptosis and mice from UVB-induced tumors.     

UVA and UVB wavebands modulate expression of FasL in mouse skin epidermis

Abstract

In our previous report, we observed different cytokine modulation in mouse epidermis by the UVA and UVB wavebands. In the present investigations, the effects of irradiation with UVA and UVB on the Fas(CD95)/FasL system have been studied because apoptosis mediated by the interaction between Fas and FasL has been suggested recently to be associated with UVB-induced immunosuppression in mouse skin. Our results show that UVA irradiation following UVB irradiation has the ability to reduce the up-regulation of FasL expression in mouse skin resulting from the UVB irradiation.     

Protective Effect of Indole-3-Pyruvate against Ultraviolet B-Induced Damage to Cultured HaCaT Keratinocytes and the Skin of Hairless Mice

Previous investigations demonstrated that pyruvate protects human keratinocytes against cell damage stemming from exposure to ultraviolet B (UVB) radiation. This study endeavoured to elucidate the protective capacity of aromatic pyruvates (e.g., phenylpyruvate (PPyr), 4-hydroxyphenylpyruvate (HPPyr), and indole-3-pyruvate (IPyr)) against UVB-induced injury to skin cells, both in vitro and in vivo. Cultured human HaCaT keratinocytes were irradiated with UVB light (60 mJ/cm²) and maintained with or without test compounds (1–25 mM). In addition, the dorsal skin of hairless mice (HR-1) was treated with test compounds (100 µmol) and exposed to UVB light (1 J/cm²) for two times. The ability of the test compounds to ameliorate UVB-induced cytotoxicity and inflammation was then assessed. Aromatic pyruvates reduced cytotoxicity in UVB-irradiated HaCaT keratinocytes, and also diminished the expression of interleukin 1β (IL-1β) and interleukin 6 (IL-6). IPyr was more efficacious than either PPyr or HPPyr. Furthermore, only IPyr inhibited cyclooxygenase-2 (Cox-2) expression at both the mRNA and the protein level in UVB-treated keratinocytes. Topical application of IPyr to the dorsal skin of hairless mice reduced the severity of UVB-induced skin lesions, the augmentation of dermal thickness, and transepithelial water loss. Overproduction of IL-1β and IL-6 in response to UVB radiation was also suppressed in vivo by the topical administration of IPyr. These data strongly suggest that IPyr might find utility as a UVB-blocking reagent in therapeutic strategies to lessen UVB-induced inflammatory skin damage.     

Estrogen receptor-beta signaling protects epidermal cytokine expression and immune function from UVB-induced impairment in mice.

A previous study in the hairless mouse, in which the photoimmune protective properties of a topical phytoestrogen or 17-beta-estradiol were abrogated by the estrogen receptor antagonist ICI 182,780, revealed that estrogen receptor (Er) signaling is involved in the regulation of the suppression of immune function by UVB (290-320 nm) radiation. Here we identify the expression of Er-beta but not Er-alpha mRNA in hairless mouse skin, whereas Er-alpha and Er-beta mRNA were present in normal haired mouse skin. This suggests that the non-classical estrogen target Er-beta is involved in the photoimmune modulation, and is consistent with Er-alpha being more closely associated with hair growth control, as indicated by other studies. In mice with a null mutation for Er-beta, there was a significant exacerbation of the solar simulated UV (290-400 nm)-induced suppression of contact hypersensitivity. Immunohistochemical analysis revealed that the Er-beta deficiency inhibited the normally immunoprotective upregulation by the UVA (320-400 nm) waveband of the epidermal expression of the cytokines IFN-gamma and IL-12. Er-beta deficiency also significantly increased the UVB-induced expression of the immunosuppressive cytokine IL-10. Thus Er signalling via the Er-beta is evidently a major regulator of the UVA and UVB waveband interactions that determine the skin's immune functional status, and achieves this by normalization of the cutaneous cytokine array in the UV-irradiated skin.     

Anti-wrinkle and anti-inflammatory effects of a combination of topically applied horse oil and dietary enzyme hydrolysates from horse bone

This study investigated the anti-wrinkle and anti-inflammatory effects of horse bone hydrolysates of <3 kDa (HL) and topically applied horse oil (HO) on UVB-induced photoaging and inflammation in hairless mice. Forty-nine mice were divided into seven groups: −NC, chow without UVB irradiation; +UC, chow with UVB irradiation, +HLL, chow with low dose (500 mg/kg body weight (BW)) HL and UVB irradiation; +HLH, chow with high dose (1000 mg/kg BW) HL and UVB irradiation; +HO, chow and combined with topical application of HO and UVB irradiation; +HOHLL, treated with a combination of dietary HLL and topical application of HO with UVB irradiation; +HOHLH, treated with a combination of dietary HLH and topical application of HO with UVB irradiation. The transepidermal water loss in mice of all treatment groups was lower than that of mice in the +UC group. Furthermore, the wrinkle depth in the +HLH group was significantly lower than that in the +UC group. In addition, HO and low level of HL significantly decreased the level of tumor necrosis factor-α, interleukin-6, and matrix metalloproteinase-9, thereby down-regulating inflammation, including the cyclooxygenase-2 synthesis. In the future, human trials are needed to confirm the efficacy and synergistic effect of HL and HO.     

Oral administration of Aloe vera gel powder prevents UVB-induced decrease in skin elasticity via suppression of overexpression of MMPs in hairless mice

This study reports the effects of oral Aloe vera gel powder (AVGP) containing Aloe sterols on skin elasticity and the extracellular matrix in ultraviolet B (UVB)-irradiated hairless mice. Ten-week-old hairless mice were fed diets containing 0.3% AVGP for 8 weeks and irradiated UVB for 6 weeks. Mice treated with AVGP showed significant prevention of the UVB-induced decrease in skin elasticity. To investigate the mechanism underlying this suppression of skin elasticity loss, we measured the expression of matrix metalloproteinase (MMP)-2, -9, and -13. AVGP prevented both the UVB-induced increases in MMPs expressions. Moreover, we investigated hyaluronic acid (HA) content of mice dorsal skin and gene expression of HA synthase-2 (Has2). In the results, AVGP oral administration prevented UVB-induced decreasing in skin HA content and Has2 expression and attenuates the UVB-induced decrease in serum adiponectin, which promotes Has2 expression. These results suggested that AVGP has the ability to prevent the skin photoaging.