UVB-induced Hyperpigmentation Research Articles

Non-invasive high-intensity focused ultrasound for UV-induced hyperpigmentation in Fitzpatrick skin types III and IV: a prospective, randomized, controlled, evaluator-blinded trial.

Skin hyperpigmentation is a frequently encountered problem, particularly in darker skin types. Unfortunately, standard treatments for this condition have shown disappointing results. High-intensity focused ultrasound (HIFU) is commonly indicated for skin laxity, but recently was used to treat UV-induced hyperpigmentation in animal models. This study is aimed to evaluate the efficacy and safety of high-intensity focused ultrasound for UVB-induced hyperpigmentation in human subjects. A randomized, evaluator-blinded pilot study was conducted on 20 subjects. Each subject was induced three hyperpigmentary spots by local broadband UVB. After 2weeks, each spot was randomly allocated to control, low-energy, and high-energy HIFU. Subjects were instructed to follow up weekly for a duration of 1month. Lightness index measurements, mean improvement scores, subjects' satisfaction, pain scores, and side effects were evaluated. All 20 subjects completed the study. Fourteen subjects had Fitzpatrick (FPT) skin type III and six subjects had FPT skin type IV. Twelve subjects showed greater improvement at control sites while eight subjects showed greater improvement at HIFU-treated sites. In FPT skin type III, HIFU appeared to be inferior to control in both lightness index and mean improvement scores, but in FPT skin type IV, HIFU had greater lightness index improvement and higher improvement scores than control. Side effects were more frequent in high-energy-treated areas. Focused ultrasound may be offered in some patients with hyperpigmentary conditions. More research is needed to determine proper energy settings for optimal outcome.

Anti-Melanogenic Potentials of Nanoparticles from Calli of Resveratrol-Enriched Rice against UVB-Induced Hyperpigmentation in Guinea Pig Skin

We already reported that genetically engineered resveratrol-enriched rice (RR) showed to down-regulate skin melanogenesis. To be developed to increase the bioactivity of RR using calli from plants, RR was adopted for mass production using plant tissue culture technologies. In addition, high-pressure homogenization (HPH) was used to increase the biocompatibility and penetration of the calli from RR into the skin. We aimed to develop anti-melanogenic agents incorporating calli of RR (cRR) and nanoparticles by high-pressure homogenization, examining the synergistic effects on the inhibition of UVB-induced hyperpigmentation. Depigmentation was observed following topical application of micro-cRR, nano-calli of normal rice (cNR), and nano-cRR to ultraviolet B (UVB)-stimulated hyperpigmented guinea pig dorsal skin. Colorimetric analysis, tyrosinase immunostaining, and Fontana-Masson staining for UVB-promoted melanin were performed. Nano-cRR inhibited changes in the melanin color index caused by UVB-promoted hyperpigmentation, and demonstrated stronger anti-melanogenic potential than micro-cRR. In epidermal skin, nano-cRR repressed UVB-promoted melanin granules, thereby suppressing hyperpigmentation. The UVB-enhanced, highly expressed tyrosinase in the basal layer of the epidermis was inhibited by nano-cRR more prominently than by micro-cRR and nano-cNR. The anti-melanogenic potency of nano-cRR also depended on pH and particle size. Nano-cRR shows promising potential to regulate skin pigmentation following UVB exposure.

High intensity focused ultrasound as a potential new modality for the treatment of pigmentary skin disorder.

The clinical skin tightening benefits of high intensity focused ultrasound (HIFU) have been established, but its mechanism of action in pigmented skin disorders remains unknown. We macroscopically and histopathologically investigated dermatological changes after HIFU at different exposure doses in a UVB-induced guinea pig model of hyperpigmentation. We applied HIFU irradiation at 0.1 and 0.2J/cm(2) to UVB-induced spotty hyperpigmentation in guinea pig skin. The therapeutic effects of HIFU were judged based on gross appearance using photography, dermoscopy, and chromametry during a period of 3weeks after HIFU irradiation. Histological assessments were performed using Fontana-Masson staining 1day before and 3weeks after HIFU irradiation. Macroscopically, UVB-induced hyperpigmentation was significantly reduced 2weeks after HIFU with 0.2J/cm(2) , and 3weeks after HIFU with 0.1J/cm(2) . Histopathologically, the heavy deposition of melanin in the epidermis induced by UVB exposure was reduced 3weeks after HIFU irradiation. We confirmed that HIFU has a positive effect on UVB-induced hyperpigmentation as well as mechanical destructive activity. We suggest that HIFU may be useful as an alternative modality for human patients suffering from skin pigmentary conditions.

Astaxanthin and withaferin A block paracrine cytokine interactions between UVB-exposed human keratinocytes and human melanocytes via the attenuation of endothelin-1 secretion and its downstream intracellular signaling

BackgroundParacrine interactions between keratinocytes and melanocytes via cytokines play an essential role in regulating pigmentation in epidermal hyperpigmentary disorders. There is an urgent need for a human epidermal model in which melanogenic paracrine interactions between UVB-exposed keratinocytes and melanocytes can be precisely evaluated because human epidermal equivalents consisting of multilayered keratinocytes and melanocytes have significant limitations in this respect. ObjectiveTo resolve this challenge, we established a co-culture system with cell inserts using human keratinocytes and human melanocytes that serves as an appropriate new model for UVB-induced hyperpigmentation. Using that new model, we examined the blocking effects of two natural chemicals, astaxanthin and withaferin A, on paracrine cytokine interactions between UVB-exposed keratinocytes and melanocytes and characterized their mechanisms of action. Methods and ResultsRT-PCR analysis showed that co-culture of human keratinocytes that had been exposed to UVB significantly stimulated human melanocytes to increase their expression of genes encoding microphthalmia-associated transcription factor, tyrosinase and tyrosinase-related protein 1. The catalytic activity of tyrosinase was also increased. ELISA assays revealed that UVB significantly increased the secretion of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1 but not α-melanocyte stimulating hormone. The addition of an endothelin-1 neutralizing antibody significantly abrogated the increase of tyrosinase activity. Post-irradiation treatment with astaxanthin or withaferin A significantly abolished the up-regulation of tyrosinase activity induced by UVB. Treatment with astaxanthin or withaferin A significantly reduced the increased levels of interleukin-1α, interleukin-6/8, granulocyte macrophage stimulatory factor and endothelin-1. Withaferin A but not astaxanthin also significantly abrogated the endothelin-1-stimulated activity of tyrosinase in melanocytes. Western blot analysis of intracellular signaling factors revealed that withaferin A but not astaxanthin significantly abolished the endothelin-1-stimulated phosphorylation of Raf-1, MEK, ERK, MITF and CREB in human melanocytes. ConclusionsThese results demonstrate that this co-culture system is an appropriate model to characterize melanogenic paracrine interactions and that astaxanthin and withaferin A serve as potent inhibitors of those interactions. Their effects are caused not only by down-regulating the increased secretion of an intrinsic melanogenic cytokine, endothelin-1, by UVB-exposed human keratinocytes, but also by interrupting the endothelin-1-triggered downstream intracellular signaling between protein kinase C and Raf-1 in human melanocytes (only for withaferin A).

Inhibitory effects of salidroside and paeonol on tyrosinase activity and melanin synthesis in mouse B16F10 melanoma cells and ultraviolet B-induced pigmentation in guinea pig skin

Salidroside, the major active component of Rhodiola rosea, a herb with antioxidant, free radical scavenging and tyrosinase inhibitory effects, has been recently reported in protecting the kerationcytes from the UV radiation, suggesting the potential of this component in depigmentation. Paeonol is isolated from Moutan Cortex Radicis with anti-inflammation/microbial activities, was reported to induce the down-regulation of microphthalmia-associated transcription factor and subsequently tyrosinase. To testify the potential of these compounds as melanin formation inhibitors for hyperpigmentation therapy, the influence of salidroside and paeonol on pigmentation was investigated. With arbutin as a positive control, salidroside and paeonol were evaluated for their inhibitory effect on the cell viability, tyrosinase activity and melanin synthesis in B16F10 melanoma cells, as well as their effects in UVB-induced hyperpigmentation in brown guinea pig skins. It was demonstrated that the significant inhibition of salidroside (33.0%) and paeonol (22.2–30.9%) on the tyrosinase activity is slightly lower than that of arbutin (18.4–44.7%). However, salidroside exhibited the dose-dependent inhibition (30.6–42.0%) in melanin synthesis at a low concentration of 100μM, paeonol and arbutin expressed inhibition rates of 27.4–37.2% and 25.8–45.6% within 500–1000μM. The in vivo topical application of these compounds was demonstrated to obviously decrease the hyperpigmentation on UVB stimulated guinea pig skin. This study provided the original evidence for the salidroside and paeonol as therapeutic agents for pigmentation disorder and skin lightening, with further clinical investigation of these compounds in the field of depigmentation was suggested.

In vitro and in vivo studies disclosed the depigmenting effects of gallic acid: A novel skin lightening agent for hyperpigmentary skin diseases

Gallic acid (GA) is a phenolic compound, which has been reported to suppress melanogenesis in melanoma cells. However, the molecular mechanism underlying this inhibitory effect was poorly understood. In this article, we revealed that GA down-regulated melanogenic regulatory genes including tyrosinase, tyrosinase related protein-1 (TRP-1), and dopachrome tatamerase (Dct) expression at transcriptional and translational level. In addition, GA effectively suppressed the microphthalmia-associated transcription factor (MITF) expression by down-regulating the cAMP-mediated PKA/CREB signaling cascades. To delineate the inhibition of MITF by GA, the activation of extracellular signal-regulated protein kinase (ERK) and AKT was investigated. GA caused significant increase of ERK and AKT phosphorylation, while ERK (PD98059) or AKT (LY294002) inhibitor prevents their phosphorylation and increased melanin biosynthesis. In addition, pre-treatment of MITF-siRNA significantly reduced melanin production from 100 to 40%, and even decreased into 10% by combination treatment with GA. Furthermore, UVB-induced hyperpigmentation in the mice skin was significantly rescued by topical application of GA for 4 weeks. Immunohistochemical analyses also confirmed that GA significantly inhibited melanin production followed by the down-regulation of MITF, tyrosinase and their regulatory proteins. In addition, when compared with control zebrafish, GA caused a remarkable inhibition on the endogenous pigmentation in the zebrafish. Results presented in this study strongly suggest that GA is an effective de-pigmenting or skin lightening cosmetics for topical application.

Liver X receptor activation inhibits melanogenesis through the acceleration of ERK-mediated MiTF degradation

Liver X receptors(LXRs) are nuclear receptors that act as ligand-activated transcription factors regulating lipid metabolism and inflammation. In the skin, activation of LXRs stimulates differentiation of keratinocytes and augments lipid synthesis in sebocytes. However, function of LXRs in melanocytes has not been elucidated. Here we investigated if LXR activation might affect melanogenesis, the representative function of melanocytes. In human primary melanocytes and B16 melanoma cells, TO901317, a synthetic LXR ligand inhibited melanin synthesis. Enzymatic activities of tyrosinase were unaffected but the expression of melanogenesis-related proteins such as tyrosinase, tyrosinase related protein(TRP)-1 and -2 was suppressed by TO901317. Expression of microphthalmia-associated transcription factor(MiTF), a master transcriptional regulator of melanogenesis, and upstream event, cAMP responsive element-binding activation were not affected. Of note, the degradation of MiTF was substantially accelerated by TO901317. Extracellular signal-regulated kinase(ERK) contributed to TO901317-induced anti-melanogenesis, which was supported by recovery of melanogenesis with an ERK inhibitor. Other LXR ligands like 22(R)-hydroxycholesterol and GW3965 also activated ERK and suppressed melanogenesis. Anti-melanogenic effects of TO901317 were confirmed in vivo in UVB-tanning model in brownish guinea pigs where topical application of TO901317 significantly reduced UVB-induced hyper-pigmentation, providing the first line of evidence that LXRs may be a novel target for anti-melanogenesis. JSID AbstractsJournal of Dermatological ScienceVol. 69Issue 2Preview Full-Text PDF

Saponified Evening Primrose Oil Reduces Melanogenesis in B16 Melanoma Cells and Reduces UV‐Induced Skin Pigmentation in Humans

This study was conducted to determine whether saponified evening primrose oil (sap-EPO) has the potential for use as a whitening agent and to investigate its underlying mechanisms of action. In B16 melanoma cells, sap-EPO dose-dependently inhibited isobutylmethylxanthine-induced melanogenesis with no cytotoxicity. This decrease in melanin production was correlated with reduced enzyme activity and decreased mRNA and protein levels of tyrosinase. The mRNA levels of tyrosinase-related proteins 1 and 2 decreased in response to treatment with sap-EPO, indicating that it regulated tyrosinase at the transcriptional level. Expression of microphthalmia-associated transcription factor was also decreased by sap-EPO as evidenced by decreased mRNA and protein levels. Additionally, topical application of sap-EPO resulted in efficient whitening of UVB-induced hyperpigmentation of human skin. Taken together, these results suggest that sap-EPO has the potential for use as a cosmetic whitening agent.

The Essential Role of p53 in Hyperpigmentation of the Skin via Regulation of Paracrine Melanogenic Cytokine Receptor Signaling

Hyperpigmentation of the skin is characterized by increases in melanin synthesis and deposition. Although considered a significant psychosocial distress, little is known about the detailed mechanisms of hyperpigmentation. Recently, the tumor suppressor protein p53 has been demonstrated to promote ultraviolet B-induced skin pigmentation by stimulating the transcription of a melanogenic cytokine, POMC (pro-opiomelanocortin), in keratinocytes. Given that p53 can be activated by various kinds of diverse stresses, including sun exposure, inflammation, and aging, this finding led us to examine the involvement of p53 in cytokine receptor signaling, which might result in skin hyperpigmentation. Immunohistochemical and reverse transcription-PCR analyses revealed the increased expression and phosphorylation of p53 in the epidermis of hyperpigmented spots, accompanied by the higher expression of melanogenic cytokines, including stem cell factor, endothelin-1, and POMC. The involvement of p53 in hyperpigmentation was also indicated by the significantly higher expression of p53 transcriptional targets in the epidermis of hyperpigmented spots. Treatment of human keratinocytes and melanocytes with known p53 activators or inhibitors, including pifithrin-alpha (PFT), demonstrated significant increases or decreases, respectively, in the expression of melanogenic factors, including cytokines and their receptors. Additionally, PFT administration abolished stem cell factor-induced phosphorylation of mitogen-activated protein kinase in human melanocytes. Furthermore, when organ-cultured hyperpigmented spots, in vitro human skin substitutes, and mouse skin were treated with PFT or p53 small interfering RNA, the expression of melanogenic cytokines and their receptors was significantly decreased, as were levels of tyrosinase and melanogenesis. Taken together, these data reveal the essential role of p53 in hyperpigmentation of the skin via the regulation of paracrine-cytokine signaling, both in keratinocytes and in melanocytes.

Skin-Lightening Effect of a Polyphenol Extract from Acerola (Malpighia emarginataDC.) Fruit on UV-Induced Pigmentation

To investigate the physiological functions of polyphenols from acerola (Malpighia emarginata DC.) fruit, the effects on melanogenesis were studied. The crude polyphenol concentrated extract from acerola (C-AP) was used to examine the skin-lightening effect on brownish guinea pigs which had been subjected to controlled UVB irradiation. The results show that C-AP significantly lightened the UVB-irradiated skin pigmentation. Furthermore, treatment with C-AP reduced the content of melanin in B16 melanoma cells, suggesting that the in vivo skin-lightening effect of C-AP was due to the suppression of melanin biosynthesis in melanocytes. In addition, we found that C-AP could effectively inhibit mushroom tyrosinase activity, the main constituents responsible for this effect being thought to be such anthocyanins as cyanidin-3-alpha-O-rhamnoside (C3R) and pelargonidin-3-alpha-O-rhamnoside (P3R). This result indicates that the skin-lightening effect of C-AP can be partly attributed to the suppression of melanogenesis through the inhibition of tyrosinase activity in melanocytes. An oral ingestion of C-AP may therefore be efficacious for reducing UVB-induced hyper-pigmentation by inhibiting the tyrosinase in melanocytes.

Synthesis, discovery and mechanism of 2,6-dimethoxy- N-(4-methoxyphenyl)benzamide as potent depigmenting agent in the skin

In this study, a new skin-depigmenting agent, 2,6-dimethoxy- N-(4-methoxyphenyl)benzamide (DMPB), was synthesized using a combination of benzoic acid and aniline. DMPB exhibited significant depigmentation ability on the UV B-induced hyperpigmentation of the brown guinea pig skin. In addition, the 100 ppm treatment with this compound had a 30% inhibitory effect on melanin pigment generation in the melan-a cell line without significant cell toxicity. To search for relationship with the depigmentation, the effects of DMPB on the tyrosinase and dopachrome tautomerase were evaluated. DMPB had no effect on tyrosinase. However, it accelerated dopachrome transformation into 5,6-dihydroxyindole-2-carboxylic acid (DHICA) in the presence of dopachrome tautormerase. In addition, intracellular level of dopachrome tautomerase in melan-a cells was increased by treatment of DMPB. These results suggest that the pigment-lightening effects of DMPB might be due to biased production of DHICA-eumelanin induced by dopachrome tautormerase activation.

Benzylamide derivative compound attenuates the ultraviolet B-induced hyperpigmentation in the brownish guinea pig skin

This study evaluated the effects of synthetic benzylamide compound I (2,6-dimethoxy- N-phenylbenzamide) on the ultraviolet B (UV B)-induced hyperpigmentation of the skin. UV B-induced hyperpigmentation was elicited on brownish guinea pig skin according to the method reported by Hideya et al. [Arch Dermatol Res 290 (1998) 375] with minor modifications. A lightening effect was observed following the topical application of compound I on UV-stimulated hyperpigmentation. The skin returned to its original color after treatment with compound I. Fontana-Masson staining indicated that melanin level in the hyperpigmented area was significantly decreased in the compound I-treated animals. However, the number of melanocytes were not changed in the compound I-treated groups using the S-100 stain, which is an immunohistochemical method. In vitro experiments using the cultured melanoma cells showed a 31.7% inhibition of melanin production by compound I at 100 μM. In addition, this compound had no effect on the tyrosinase enzyme function. However, it exhibited a catalyzing effect on the dopachrome transformation into 5,6-dihydroxyindole-2-carboxylic acid. Overall, the pigment-lightening effects of the compound I may due to the dopachrome tautomerase stimulation.

The Degrees of UVB-Induced Erythema and Pigmentation Correlate Linearly and Are Reduced in a Parallel Manner by Topical Anti-Inflammatory Agents

To examine whether it is possible to evaluate the degree of ultraviolet B (UVB)-induced inflammation by measuring the degree of hyperpigmentation, we investigated the relationship between UVB-induced erythema and the subsequent pigmentation quantitatively. At 24 h and 7 d after irradiation with erythemogenic doses of UVB to the backs of 16 Japanese subjects, the degree of induced erythema (delta erythema index) and that of pigmentation (delta melanin index) were examined by an image analytic method using a videomicroscope interfaced with a computer. The relationship between two indices was linear in each subject, and the correlation coefficient was 0.83 when evaluated using whole data. The slope of the regression line for the delta melanin index against delta erythema index tended to become steeper as non-irradiated skin color became darker (r = 0.63), suggesting that more efficient melanogenesis takes place after the same level of inflammation in the subject with darker skin. Both erythema and hyperpigmentation were suppressed significantly and in a parallel manner by corticosteroids and indomethacin applied topically immediately after UVB irradiation. These results imply that the post-inflammatory hyperpigmentation correlates closely with the severity of the prior inflammation and that chemical mediators released in the inflammatory process have considerable influence on the melanogenesis. We conclude that the measurement of UVB-induced hyperpigmentation can be utilized for the assessment of topical anti-inflammatory agents, unless these have direct actions on the tyrosinase activity of melanocytes.