A Protective Mechanism of Visible Red Light in Normal Human Dermal Fibroblasts: Enhancement of GADD45A-Mediated DNA Repair Activity

5-aminolevulinic acid photodynamic therapy protects against UVB-induced skin photoaging: A DNA-repairing mechanism involving the BER signalling pathway

Low-dose 5-aminolevulinic acid photodynamic therapy (ALA-PDT) has been used to cope with skin photoaging, and is thought to involve DNA damage repair responses. However, it is still unknown how low-dose ALA-PDT regulates DNA damage repair to curb skin photoaging. We established a photoaging model using human dermal fibroblasts (HDFs) and rat skin. RNA-sequencing (RNA-seq) analysis was conducted to identify differentially expressed genes (DEGs) in HDFs before and after low-dose ALA-PDT treatment, followed by bioinformatics analysis. Senescence-associated β-galactosidase (SA-β-gal) staining was employed to assess skin aging-related manifestations and Western blotting to evaluate the expression of associated proteins. A comet assay was used to detect cellular DNA damage, while immunofluorescence to examine the expression of 8-hydroxy-2'-deoxyguanosine (8-oxo-dG) in cells and skin tissues. In both in vivo and in vitro models, low-dose ALA-PDT alleviated the manifestations of ultraviolet B (UVB)-induced skin photoaging. Low-dose ALA-PDT significantly reduced DNA damage in photoaged HDFs. Furthermore, low-dose ALA-PDT accelerated the clearance of the photoproduct 8-oxo-dG in photoaged HDFs and superficial dermis of photoaged rat skin. RNA-seq analysis suggested that low-dose ALA-PDT upregulated the expression of key genes in the base excision repair (BER) pathway. Further functional validation showed that inhibition on BER expression by using UPF1069 significantly suppressed SA-β-gal activity, G2/M phase ratio, expression of aging-associated proteins P16, P21, P53, and MUTYH proteins, as well as clearance of the photoproduct 8-oxo-dG in photoaged HDFs. Low-dose ALA-PDT exerts anti-photoaging effects by activating the BER signalling pathway.

Phototoxicity of low doses of light and influence of the spectral composition on human RPE cells

Light is known to induce retinal damage affecting photoreceptors and retinal pigment epithelium. For polychromatic light, the blue part of the spectrum is thought to be the only responsible for photochemical damage, leading to the establishment of a phototoxicity threshold for blue light (445 nm). For humans it corresponds to a retinal dose of 22 J/cm2. Recent studies on rodents and non-human primates suggested that this value is overestimated. In this study, we aim at investigating the relevance of the current phototoxicity threshold and at providing new hints on the role of the different components of the white light spectrum on phototoxicity. We use an in vitro model of human induced pluripotent stem cells (hiPSC)-derived retinal pigment epithelial (iRPE) cells and exposed them to white, blue and red lights from LED devices at doses below 22 J/cm2. We show that exposure to white light at a dose of 3.6 J/cm2 induces an alteration of the global cellular structure, DNA damage and an activation of cellular stress pathways. The exposure to blue light triggers DNA damage and the activation of autophagy, while exposure to red light modulates the inflammatory response and inhibits autophagy.

The blue light hazard and its use on the evaluation of photochemical risk for domestic lighting. An in vivo study

BACKGROUND

Nowadays artificial light highly increases human exposure to light leading to circadian rhythm and sleep perturbations. Moreover, excessive exposure of ocular structures to photons can induce irreversible retinal damage. Meta-analyses showed that sunlight exposure influences the age of onset and the progression of Age-related macular degeneration (AMD), the leading cause of blindness in people over fifty-year old. Currently, the blue-light hazard (BLH) curve is used in the evaluation of the phototoxicity of a light source for domestic lighting regulations.

OBJECTIVES

Here, we analyze the phototoxicity threshold in rats and investigate the role played by the light spectrum, assessing the relevance of the use of the BLH-weighting to define phototoxicity.

METHODS

We exposed albino rats to increasing doses of blue and white light, or to lights of different colors to evaluate the impact of each component of the white light spectrum on phototoxicity. Cellular mechanisms of cell death and cellular stress induced by light were analyzed.

RESULTS

Our results show that the phototoxicity threshold currently accepted for rats is overestimated by a factor of 50 when considering blue light and by a factor of 550 concerning white light. This is the result of the toxicity induced by green light that increases white light toxicity by promoting an inflammatory response. The content of green in white light induces 8 fold more invasion of macrophages in the retina than the content of blue light. Moreover, the use of BLH-weighting does not evaluate the amount of red radiations contained in white light that mitigates damage by inhibiting the nuclear translocation of L-DNase II and reducing by 33% the number of TUNEL-positive cells.

DISCUSSION

These findings question the current methods to determine the phototoxicity of a light source and show the necessity to take into account the entire emission spectrum. As current human phototoxicity thresholds were estimated with the same methods used for rats, our results suggest that they might need to be reconsidered.

Low energy multiple blue light-emitting diode light Irradiation promotes melanin synthesis and induces DNA damage in B16F10 melanoma cells

Visible light is present everywhere in our lives. Widespread use of computers and smartphones has increased the daily time spent in front of screens. What effect does this visible light have on us? Recent studies have shown that short-wavelength blue light (400-450nm) irradiation, similar to UV, inhibits the cell proliferation and differentiation, induces the intracellular oxidative stress, promotes the cell apoptosis and causes some other negative effects. However, it's unusual that directly face to such short-wavelength and high-energy blue light in daily life. Therefore, the effects of blue light with longer wavelength (470nm), lower energy (1, 2 J/cm2) and multiple times (simulated daily use) exposure on cells have been studied in this experiment. In our results, low energy density multiple blue light inhibited cell proliferation and metastatic capability with a weak phototoxicity. Blue light also promoted intracellular reactive oxygen species and caused DNA damage. Furthermore, the melanin synthesis was also promoted by low energy density multiple blue light exposure. Together, these results indicate that longer wavelength and low energy density blue light multiple exposure is still harmful to our cells. Furthermore, prolonged exposure to screens likely induces dull skin through induction of melanin synthesis. These results further mentioned us should paid more attention to controlling the daily use of digital device.

The Protective Effects of EMF-LTE against DNA Double-Strand Break Damage In Vitro and In Vivo

With the rapid growth of the wireless communication industry, humans are extensively exposed to electromagnetic fields (EMF) comprised of radiofrequency (RF). The skin is considered the primary target of EMFs given its outermost location. Recent evidence suggests that extremely low frequency (ELF)-EMF can improve the efficacy of DNA repair in human cell-lines. However, the effects of EMF-RF on DNA damage remain unknown. Here, we investigated the impact of EMF-long term evolution (LTE, 1.762 GHz, 8 W/kg) irradiation on DNA double-strand break (DSB) using the murine melanoma cell line B16 and the human keratinocyte cell line HaCaT. EMF-LTE exposure alone did not affect cell viability or induce apoptosis or necrosis. In addition, DNA DSB damage, as determined by the neutral comet assay, was not induced by EMF-LTE irradiation. Of note, EMF-LTE exposure can attenuate the DNA DSB damage induced by physical and chemical DNA damaging agents (such as ionizing radiation (IR, 10 Gy) in HaCaT and B16 cells and bleomycin (BLM, 3 μM) in HaCaT cells and a human melanoma cell line MNT-1), suggesting that EMF-LTE promotes the repair of DNA DSB damage. The protective effect of EMF-LTE against DNA damage was further confirmed by attenuation of the DNA damage marker γ-H2AX after exposure to EMF-LTE in HaCaT and B16 cells. Most importantly, irradiation of EMF-LTE (1.76 GHz, 6 W/kg, 8 h/day) on mice in vivo for 4 weeks reduced the γ-H2AX level in the skin tissue, further supporting the protective effects of EMF-LTE against DNA DSB damage. Furthermore, p53, the master tumor-suppressor gene, was commonly upregulated by EMF-LTE irradiation in B16 and HaCaT cells. This finding suggests that p53 plays a role in the protective effect of EMF-LTE against DNA DSBs. Collectively, these results demonstrated that EMF-LTE might have a protective effect against DNA DSB damage in the skin, although further studies are necessary to understand its impact on human health.

The interplay between ATF2 and NEAT1 contributes to lung adenocarcinoma progression

Background

Activating transcription factor 2 (ATF2), a member of the activator protein 1 (AP-1) transcription factor family, has been shown to be involved in the pathobiology of numerous cancers. However, the biological role and mechanism of ATF2 in lung adenocarcinoma (LUAD) remains to be elucidated.

Methods

The expression of ATF2, NEAT1 and miR-26a-5p in LUAD tissues and cell lines was detected by qRT-PCR and western blotting. The interaction between ATF2, NEAT1, and miR-26a-5p was validated by chromatin immunoprecipitation, luciferase reporter assay and RNA immunoprecipitation. Cell proliferation, invasion and tumorigenesis of LUAD cells were analyzed by using CCK8, transwell invasion assay and xenograft tumor model.

Results

We confirmed that ATF2 expression was increased in LUAD tissues compared with normal adjacent lung tissues. Functional experiments showed that ATF2 positively regulated cell proliferation and invasion in LUAD cells. Moreover, we identified that NEAT1 expression was increased in LUAD tissues and positively correlated with ATF2 expression. Mechanistically, ATF2 could bind to the promoter of NEAT1 to promote its transcription. Rescue experiments showed that ATF2 exerted its oncogenic function in LUAD, at least, partly through NEAT1 upregulation. In turn, NEAT1 could positively regulate ATF2 expression and form a positive feedback loop in LUAD cells. Furthermore, we demonstrated that NEAT1 positively regulated ATF2 expression via sponging miR-26a-5p.

Conclusion

ATF2 and NEAT1 form a positive feedback loop mediated by miR-26a-5p and coordinately contribute to LUAD progression.

Various biological effects of solar radiation on skin and their mechanisms: implications for phototherapy

The skin protects our body from various external factors, such as chemical and physical stimuli, microorganisms, and sunlight. Sunlight is a representative environmental factor that considerably influences the physiological activity of our bodies. The molecular mechanisms and detrimental effects of ultraviolet rays (UVR) on skin have been thoroughly investigated. Chronic exposure to UVR generally causes skin damage and eventually induces wrinkle formation and reduced elasticity of the skin. Several studies have shown that infrared rays (IR) also lead to the breakdown of collagen fibers in the skin. However, several reports have demonstrated that the appropriate use of UVR or IR can have beneficial effects on skin-related diseases. Additionally, it has been revealed that visible light of different wavelengths has various biological effects on the skin. Interestingly, several recent studies have reported that photoreceptors are also expressed in the skin, similar to those in the eyes.

Based on these data, I discuss the various physiological effects of sunlight on the skin and provide insights on the use of phototherapy, which uses a specific wavelength of sunlight as a non-invasive method, to improve skin-related disorders.

Cytotoxicity studies of an optoacoustic stimulation strategy for the development of laser-based hearing aids

SIGNIFICANCE

Worldwide, ∼460  million people suffer from disabling hearing impairment. Many of these patients are still not sufficiently supplied with currently available auditory technologies. Optical stimulation of the hearing organ offers a promising alternative for a new generation of auditory prostheses.

AIM

To assess the biocompatibility margins of our laser pulse amplitude strategy in vitro, we designed a protocol and present the effects on normal human dermal fibroblasts, human chondrocytes, and human osteoblasts.

APPROACH

Laser pulses of 532 nm were applied over 120 s using our laser pulse amplitude modulation strategy. We then assessed cell viability and cytotoxicity through fluorescence staining and quantitative polymerase chain reaction-analysis regarding 84 key player-genes for cytotoxicity and stress response.

RESULTS

The first in vitro biocompatibility margins for our stimulation parameters applied to cells of the peripheral hearing organ were between 200 and 223 mW (3348  J/cm2). After irradiation with a subphototoxic laser power of 199 mW (2988  J/cm2), only the fibroblasts showed a significant upregulation of GADD45G.

CONCLUSION

Further studies are underway to optimize parameters for the optoacoustic stimulation of the auditory system. Our protocol and results on laser-tissue interactions can be useful for translational laser applications in various other irradiated biological tissues.

Transcriptomic analysis of human dermal fibroblast cells reveals potential mechanisms underlying the protective effects of visible red light against damage from ultraviolet B light

BACKGROUND

Ultraviolet B (UVB) radiation is a major cause of skin photodamage, including the damage associated with photodermatoses, aging, and cancer. Although many studies have shown that red light has photoprotective effects on skin, the mechanisms underlying these effects are still poorly understood.

OBJECTIVE

The aim of this study was to identify the photoprotective effects of visible red light against UVB-induced skin damage in normal human dermal fibroblast cells using a transcriptomic approach.

METHODS

Next-generation sequencing-based transcriptomic analyses were used to profile transcriptomic alterations and identify genes that are differentially expressed by visible red light and by UVB exposure. To understand the biological networks among identified genes, a literature-based biological pathway analysis was performed. Quantitative real-time polymerase chain reaction assays were used for mRNA-level validation of selected key genes.

RESULTS

We observed that visible red light contributes to skin cell protection against UVB by modulating gene expression that enhances the adaptive response to redox and inflammatory balancing and by upregulating genes involved in DNA excision repair processes. We also identified that several key genes in the red light-induced biological network were differentially regulated.

CONCLUSIONS

Visible red light enhanced the UVB-protective effects in normal human skin cells via the transcriptomic modulation of genes involved in cell-protective processes. Our findings from this next-generation sequencing analysis may lead to a better understanding of the cytoprotective effects of visible red light and provide direction for further molecular or mechanistic studies.