Cutaneous interaction with visible light: What do we know?

Visible light has been used therapeutically in dermatology for years for a variety of cosmetic and medical indications, including skin rejuvenation and the treatment of inflammatory and neoplastic conditions, among others. Until recently, visible light was thought to be relatively inert compared to its spectral neighbors, ultraviolet and infrared radiation. However, recent literature has described the ability of visible light to cause erythema in light skin and pigmentary changes in individuals with darker skin types. Concern surrounding its potentially damaging cutaneous effects has been raised in both the medical community and social media outlets. In this article, we provide an evidenced-based review describing what is currently known about visible light, focusing on its role in dermatologic diseases including disorders of hyperpigmentation such as melasma and postinflammatory hyperpigmentation.

Hyperspectral imaging to accurately segment skin erythema and hyperpigmentation in cutaneous chronic graft-versus-host disease

In 51 lesions from 15 patients with the inflammatory skin condition chronic graft-versus-host-disease, hyperspectral imaging accurately delineated active erythema and post-inflammatory hyperpigmentation. The method was validated by dermatologist-approved confident delineations of only definitely affected and definitely unaffected areas in photographs. A prototype hyperspectral imaging system acquired a 2.5 × 3.5 cm2 area of skin at 120 wavelengths in the 450-850 nm range. Unsupervised extraction of unknown absorbers by endmember analysis achieved a comparable accuracy to that of supervised extraction of known absorbers (melanin, hemoglobin) by chromophore mapping: 0.78 (IQR: 0.39-0.85) vs. 0.83 (0.53-0.91) to delineate erythema and 0.74 (0.57-0.87) vs. 0.73 (0.52-0.84) to delineate hyperpigmentation. Both algorithms achieved higher specificity than sensitivity. Whereas a trained human confidently marked a median of 7% of image pixels, unsupervised and supervised algorithms delineated a median of 14% and 27% pixels. Hyperspectral imaging could overcome a fundamental practice gap of distinguishing active from inactive manifestations of inflammatory skin disease.

Photoprotective activities of Lignosus rhinocerus in UV-irradiated human keratinocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Lignosus rhinocerus, also known as Tiger Milk Mushroom has been used traditionally to treat a variety of human conditions, including asthma, diabetes, respiratory disease, skin allergy, and food poisoning. The reported activities of Lignosus rhinocerus extracts include anti-inflammatory, anti-oxidant, anti-asthmatic, anti-microbial, anti-cancer, neuroprotection, and immune modulation effects. However, its effect on human skin is not well documented, including human skin exposed to ultraviolet light (UV). Exposure to UV can trigger various cellular responses, including inflammation, oxidative stress, DNA damage, cell death, and cellular aging.

AIM OF THE STUDY

The study aims to investigate the effects of methanolic extract prepared from cultured Lignosus rhinocerus (herein referred to as TM02 and its methanol extract as TM02-ME) on UV-irradiated human keratinocytes.

MATERIALS AND METHODS

Powdered stock of TM02 was dissolved and sequentially extracted with different solvents to prepare the extracts and the methanol extract was subsequently characterized based on its bio-activities on HaCaT human keratinocytes. The keratinocytes were pre-treated with the methanol extract followed by UV-irradiation. Cellular responses of the HaCaT cells such as cell viability, DNA damage, as well as gene and protein expressions that were responsive to the treatments, were characterized by using bio-assays, including reverse-transcription based PCR, Western blot, cell viability, and mitochondrial Cytochrome C release assays.

RESULTS

TM02-ME protected HaCaT cells from UV-induced DNA damage and cell death in a dose-dependent manner. Pre-treatment of HaCaT cells with TM02-ME led to a 39% reduction of cyclobutane pyrimidine dimers (CPD) and up-regulated the gene expression of REV1 and SPINK5 in UVB-irradiated HaCaT cells when compared to the control. In addition, TM-02-ME treated HaCaT cells increased the expression of BCL-XL and BCL-2 proteins which coincided with the down-regulation of mitochondrial Cyt. C release in the UV-B irradiated HaCaT cells. The results were further supported by data that showed the stable clones of HaCaT cells stably expressed BCL-XL were resistant to UVB-induced cell death.

CONCLUSIONS

^__The results showed that TM02-ME confers photoprotective activities to UVB-irradiated HaCaT cells, leading to a reduction in DNA damage and cell death as well as up-regulated the expression of REV1 and SPINK5 which are involved in DNA repair and skin barrier function, respectively. The up-regulation of pro-survival members of the BCL-2 family by TM02-ME confers protection against UVB-induced cell death.

Effects of topical application of different molecular weight marine fish skin collagen oligopeptides on UVB-induced photoaging rat skin

OBJECTIVE

The objective of this work was to develop a peptide production process of the exact molecular weight propitious to topical application for cosmetics and to investigate the effects of enzymolysis-derived peptide on UVB-induced photoaging rat skin.

METHODS

The chum salmon fish skins were hydrolyzed by alkaline protease and neutral protease and spray-dried at different conditions, and three kinds of molecular weight peptide (MFSOP) were obtained. A total of 66 ICR rats (female, 20 ± 1 g) were randomly divided into eleven groups, including the normal, model, and experimental groups. The three kinds of MFSOP were dissolved at different dosages (5‰, 2.5%, and 5%) and then applied on the ICR hairless back skins prior to exposing UVB irradiation of 3000mJ/cm² to them 4 h later. After 8 weeks, the rats were killed and the hair-shaved skins were tested for skin moisture, hyaluronic acid, hydroxyproline, antioxidant activity, and RNA expression.

RESULTS

Three kinds of MFSOP were obtained, with the average molecular weights of 495.16, 1194.00, and 2032.46 Dalton, respectively. The MFSOPs, especially the MFSOP of average molecular weight of 1194.00 Dalton, played an important role in the recovery of the UVB-injured skin tissue in lock in moisture, in antioxidant activity and in promotion in collagen and elastin protein to some extent.

CONCLUSION

MFSOPs, especially MFSOP of average molecular weight of 1194.00 Dalton, derived from enzymolysis are potential materials to apply in cosmetics for the UVB9-induced anti-photoaging activity (lock in moisture, antioxidant activity, and promotion in collagen and elastin protein).

Possible treatment for UVB-induced skin injury: Anti-inflammatory and cytoprotective role of metformin in UVB-irradiated keratinocytes

BACKGROUND

Excessive inflammation and cell death induced by ultraviolet (UV) cause skin photodamage. Metformin possesses anti-inflammatory and cytoprotective effects. However, whether metformin inhibits inflammation and cell death in UVB-induced acute skin damage is unclear.

OBJECTIVE

To evaluate the anti-inflammatory and cytoprotective effects of metformin in vitro and in vivo. Furthermore, its potential mechanism has been explored.

METHODS

Transcriptome sequencing and multiplex cytokines analysis were used to evaluate the validity of in vitro UVB-induced acute damage keratinocyte model and anti-inflammatory effects of metformin. We also determined the expression and nuclear translocation of CCAAT/enhancer-binding protein beta (C/EBPβ), an important transcriptional factor of Interleukin-1beta (IL-1β). Cell viability and cell death of keratinocytes were evaluated upon UVB irradiation in the presence or absence of metformin. 0.6% metformin cream was applied on UVB-irradiated mice to explore its pharmacological effects in vivo.

RESULTS

Transcriptional landscape of 50 mJ/cm² UVB-irradiated HaCaT cells is typical of UVB-induced acute damage keratinocyte model in vitro. Metformin alleviated transcription and secretion of IL-1β, Tumor Necrosis Factor-alpha, and Fibroblast Growth Factor 2, expression and nuclear translocation of C/EBPβ in this model. Metformin also protected keratinocytes from cell death caused by UVB-induced cellular secretions, which contributed to its cytoprotective effects. Topical administration of 0.6% metformin cream alleviated UVB-induced skin damage in mice.

CONCLUSION

We proved the protective roles of metformin in UVB-challenged keratinocytes and UVB-irradiated mice, which indicated the potential value of metformin in topical therapy against skin photodamage.

The regulation of protein kinase casein kinase II by apigenin is involved in the inhibition of ultraviolet B-induced macrophage migration inhibitory factor-mediated hyperpigmentation

Ultraviolet (UV) radiation elicits melanogenesis and pigmentation in the skin. Apigenin (4',5,7-trihydroxyflavone [AGN]) is a plant flavone contained in various herbs, fruits, and vegetables. We herein investigated antimelanogenic properties of AGN and the molecular mechanisms of the action of AGN. In UVB-treated mice, AGN inhibited cutaneous hyperpigmentation and macrophage migration inhibitory factor (MIF) expression as a melanogenesis-related key factor. In mouse keratinocytes, AGN inhibited the expression of MIF and also the related factors (e.g., stem cell factor and proteinase-activated receptor 2) induced by MIF. In addition to ellagic acid as a casein kinase II (CK2) inhibitor, AGN suppressed CK2 enzymatic activity and UVB-induced CK2 expression and subsequent phosphorylation of IκB and MIF expression. These results suggest that AGN inhibits UVB-induced hyperpigmentation through the regulation of CK2-mediated MIF expression in keratinocytes.

Irradiation-Enhanced Cytotoxicity of Zinc Oxide Nanoparticles

Zinc oxide (ZnO) nanoparticles (NPs) are being widely utilized in industry due to their versatile properties. The in vitro cytotoxicity findings and the potential for exposures to ZnO NP from different sources via different routes of entry into the body have raised public health concerns. Although recent studies have shown the cytotoxic effects of these NPs, including oxidative stress, apoptosis and necrosis induction, genotoxicity, and others, irradiation-induced cytotoxicity has not been systematically studied. The goal of this study was to determine whether irradiation in the forms of visible light (approximately 400-600 nm), ultraviolet (UV) A (366 nm), and UVC (254 nm) would affect ZnO NPs-induced cytotoxicity. The results of this study demonstrated that the cytotoxicity of 60 to 80 nm ZnO NPs to A549 cells is dosage, time, and wavelength dependent. Nuclear decomposition by ZnO NPs, prior to membrane deformation, was found to be enhanced when exposed to irradiation. This study suggests that this phenomenon may be attributed to the irradiation-induced formation of positively charged sites on the ZnO NPs, which enhances nuclear affinity and generation of reactive oxygen species. Finally, the data demonstrated that while ZnO NPs act preferentially toward nuclear regions, destructions of cell membrane and the cytosol have also been observed. The photocatalytic properties of ZnO NPs play a critical role during the early stages of cell death, and their effects were reduced through the use of an antioxidant, N-acetylcysteine. In conclusion, both visible light and UV irradiations have been found to enhance the cytotoxic effect of ZnO NPs on the A549 cell line. This finding supports the need for further in vivo exposure studies relevant to actual conditions to confirm whether combined irradiation and ZnO NP exposure could enhance the nanotoxicity of ZnO NPs.

Antiinflammatory effects of Viola tricolor gel in a model of sunburn in rats and the gel stability study

ETHNOPHARMACOLOGICAL RELEVANCE

Viola tricolor, popularly known as heartsease has been empirically used in several skin disorders, including burns.

AIM OF THE STUDY

The objective of this study was investigate the antinociceptive and antiinflammatory effect of a gel containing extract of Viola tricolor flowers on thermal burn induced by UVB irradiation and to perform gel stability study.

METHODS

The antinociceptive and antiinflammatory effect were evaluated by static and dynamic mechanical allodynia model, paw edema, and neutrophilic cell infiltration. Metabolites compounds were quantified by HPLC. The gel stability study was performed analyzing organoleptical aspects, besides pH, viscosity, and quantification of rutin by HPLC.

RESULTS

In the results were evidenced changes in threshold in statical and dynamic mechanical allodynia (I(max)=100 ± 10% and 49 ± 10%, respectively), paw edema (I(max)=61 ± 6%), and myeloperoxidase activity (I(max)=89 ± 5%). Such effects may be attributed, in part, to rutin, salicylic and chlorogenic acids, and others compounds found in this species. No important changes were detected in the stability study, in all aspects analyzed in temperature below 25 °C.

CONCLUSION

These findings suggest that Viola tricolor gel has an antinociceptive and antiinflammatory effect in the ultraviolet-B-induced burn, since maintain the temperature below 25 °C.

Effects of ultraviolet radiation, visible light, and infrared radiation on erythema and pigmentation: a review

The effects of ultraviolet radiation, visible light, and infrared radiation on cutaneous erythema, immediate pigment darkening, persistent pigment darkening, and delayed tanning are affected by a variety of factors. Some of these factors include the depth of cutaneous penetration of the specific wavelength, the individual skin type, and the absorption spectra of the different chromophores in the skin. UVB is an effective spectrum to induce erythema, which is followed by delayed tanning. UVA induces immediate pigment darkening, persistent pigment darkening, and delayed tanning. At high doses, UVA (primarily UVA2) can also induce erythema in individuals with skin types I-II. Visible light has been shown to induce erythema and a tanning response in dark skin, but not in fair skinned individuals. Infrared radiation produces erythema, which is probably a thermal effect. In this article we reviewed the available literature on the effects of ultraviolet radiation, visible light, and infrared radiation on the skin in regards to erythema and pigmentation. Much remains to be learned on the cutaneous effects of visible light and infrared radiation.