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Clinical and histological effects of blue light on normal skin
Abstract
Phototherapy with visible light is gaining interest in dermatological practice. Theoretically, blue light could induce biological effects comparable to ultraviolet A (UVA) radiation.
To study the effects of blue light on normal skin in terms of photodamage, skin ageing and melanogenesis.
Eight healthy volunteers were included and irradiation with visible blue light was given on five consecutive days. Skin biopsies were analysed with respect to photodamage (p53, vacuolization, sunburn cells), skin ageing (elastosis, MMP-1) and melanogenesis (Melan-A).
No inflammatory cells and sunburn cells were visible before or after irradiation. A significant increase in the perinuclear vacuolization of keratinocytes was demonstrated during treatment (P=0.02) with a tendency towards significance after cessation of treatment (P=0.09). No significant change in p53 expression was seen. Signs of elastosis and changes in MMP-1 expression were absent. Minimal clinical hyperpigmentation of the irradiated skin was confirmed histologically with a significant increase in Melan-A-positive cells (P=0.03).
Visible blue light, as given in the present study, does not cause deoxyribonucleic acid damage or early photo-ageing. The biological effects of blue light on normal skin are transient melanogenesis and inexplicable vacuolization without resulting apoptosis. In conclusion, the (short-term) use of visible blue light in dermatological practice is safe.
... To be precise, blue light is characterized as high-energy visible light with a short wavelength within the range of 400 to 490 nm [4]. Blue light is close to the UVA spectrum and results in similar cutaneous disorders to those observed in photo-aged skin [5]. These disorders are now well described, and numerous studies have reported that blue light generates reactive oxygen species and thus causes oxidative damage, DNA damage, mitochondrial stress, hyperpigmentation in darker skin types, inflammation, and barrier disruption [1][2][3][4][5], all of which lead to premature aging. ...
... Blue light is close to the UVA spectrum and results in similar cutaneous disorders to those observed in photo-aged skin [5]. These disorders are now well described, and numerous studies have reported that blue light generates reactive oxygen species and thus causes oxidative damage, DNA damage, mitochondrial stress, hyperpigmentation in darker skin types, inflammation, and barrier disruption [1][2][3][4][5], all of which lead to premature aging. ...
... Digital stress is mainly represented by exposure to blue light through radiation close to UVA that is emitted by the screens of electronic devices such as mobile phones, computers, or televisions [4] The consequences for the skin are well known, some of which are similar to those of UVA exposure. Numerous studies have related premature photo-aging to an increase in oxidative stress, DNA damage, and mitochondrial stress, among other conditions [1,2,5]. The aim of our work was to reveal the beneficial properties of the Gardenia jasminoides extract, regarding its ability to protect the skin against these direct deleterious effects of blue light irradiation. ...
Digital stress is a newly identified cosmetic stress that is mainly characterized by blue light exposure. The effects of this stress have become increasingly important with the emergence of personal digital devices, and its deleterious effects on the body are now well-known. Blue light has been observed to cause perturbation of the natural melatonin cycle and skin damage similar to that from UVA exposure, thus leading to premature aging. “A melatonin-like ingredient” was discovered in the extract of Gardenia jasminoides, which acts as a filter against blue light and as a melatonin-like ingredient to prevent and stop premature aging. The extract showed significant protective effects on the mitochondrial network of primary fibroblasts, a significant decrease of −86% in oxidized proteins on skin explants, and preservation of the natural melatonin cycle in the co-cultures of sensory neurons and keratinocytes. Upon analysis using in silico methods, only the crocetin form, released through skin microbiota activation, was found to act as a melatonin-like molecule by interacting with the MT1-receptor, thus confirming its melatonin-like properties. Finally, clinical studies revealed a significant decrease in wrinkle number of −21% in comparison to the placebo. The extract showed strong protection against blue light damage and the prevention of premature aging through its melatonin-like properties.
... Exposing human skin to the blue light contained in sunlight depressed Flavin autofluorescence. It has been suggested that blue light could contribute to the same biological effects (skin ageing and an increase in pigmentation) as UVA radiation because wavelengths of blue light are closely related to the UVA spectrum [76,77]. However, it has been stated in some earlier studies that visible blue light does not cause DNA damage or early photo-ageing and that the use thereof in dermatological practice was safe (420 nm at 20 J/cm 2 on five consecutive days) [77]. ...
... It has been suggested that blue light could contribute to the same biological effects (skin ageing and an increase in pigmentation) as UVA radiation because wavelengths of blue light are closely related to the UVA spectrum [76,77]. However, it has been stated in some earlier studies that visible blue light does not cause DNA damage or early photo-ageing and that the use thereof in dermatological practice was safe (420 nm at 20 J/cm 2 on five consecutive days) [77]. Recent studies, however, have shown that visible blue light (450-465 nm at a power density of 42.05 mW/cm 2 ) at higher fluences (38 J/cm 2 ) has a negative impact on cellular morphology, hyperpigmentation, mitochondrial hyperpolarisation, and oxidative stress [78]. ...
... Kleinpenning et al. [77] Wavelength/s selection is frequently based on tissue penetration depth, whereby longer wavelengths penetrate tissue more deeply. Combination treatments with different wavelengths for optimal wound management have been suggested. ...
Diabetes is a serious threat to global health and is among the top 10 causes of death. The Diabetic foot ulcer (DFU) is among the most common and severe complications of the disease. Bacterial infections are common; therefore, timely aggressive management, using multidisciplinary management approaches is needed to prevent complications, morbidity, and mortality, particularly in view of the growing cases of antibiotic-resistant bacteria. Photobiomodulation (PBM) involves the application of low-level light at specific wavelengths to induce cellular photochemical and photophysical responses. Red and near-infrared (NIR) wavelengths have been shown to be beneficial, and recent studies indicate that other wavelengths within the visible spectrum could be helpful as well, including blue light (400–500 nm). Reports of the antimicrobial activity and susceptibility of blue light on several strains of the same bacterium show that many bacteria are less likely to develop resistance to blue light treatment, meaning it is a viable alternative to antibiotic therapy. However, not all studies have shown positive results for wound healing and fibroblast proliferation. This paper presents a critical review of the literature concerning the use of PBM, with a focus on blue light, for tissue healing and diabetic ulcer care, identifies the pros and cons of PBM intervention, and recommends the potential role of PBM for diabetic ulcer care.
... Sinar biru merupakan golongan sinar tampak yang dipancarkan dari perangkat elektronik seperti layar komputer dan ponsel pintar (Bernstein, et al., 2019). Efek sinar biru pada kulit normal orang sehat diketahui dapat menyebabkan melanogenesis, penuaan kulit, photodamage seperti efek sunburn (Kleinpenning et al., 2010), dan pigmentasi kulit (Mahmoud et al., 2010) Salah satu cara yang dapat dilakukan untuk mencegah efek tersebut adalah dengan menggunakan tabir surya. Menurut Trullas et al. (2020) dan Bissonnette et al. (2008 jenis tabir surya yang dapat memberikan proteksi terhadap sinar biru adalah mineral sunscreen dengan kandungan besi oksida tinggi (3,2%) dan titanium oksida. ...
... Namun karena semakin banyaknya peneliltian tentang radiasi yang dipancarakan oleh gawai yang sering digunakan saat berada didalam ruangan dan juga bahaya yang ditimbulkan, sehingga mewajibkan kita untuk tetap menggunakan tabir surya didalam ruangan saat menggunakan gawai yang mana semakin sering kita gunakan saat pembelajaran secara daring. Efek sinar biru pada kulit normal orang sehat diketahui dapat menyebabkan melanogenesis, penuaan kulit, photodamage seperti efek sunburn (Kleinpenning et al. 2010), dan pigmentasi kulit (Mahmoud et al. 2010) Ketiga, penggunaan tabir surya dan komposisi bahan dari produk tabir surya yang mampu mengatasi efek radiasi sinar biru (sinar tampak). Bahan aktif tabir surya terbagi menjadi 2 yaitu bahan kimia dan bahan fisika. ...
... Akan tetapi, di lain sisi sejumlah 55 responden menyatakan bahwa mereka tidak merasa perlu untuk menggunakan produk tabir surya sebelum menggunakan gawai dan 4 orang merasa sangat tidak perlu. Padahal jika tidak menggunakan tabir surya dapat menyebabkan melanogenesis, penuaan kulit dan photodamage seperti efek sunburn (Kleinpenning et al., 2010). Dari data tersebut terlihat adanya ketidakcocokan dalam menjawab pertanyaan satu sama lain. ...
Pandemi COVID-19 telah mengubah semua sektor kehidupan termasuk pada sektor pendidikan yaitu perubahan metode pembelajaran menjadi daring. Pembelajaran daring mengharuskan mahasiswa berhadapan dengan gawai yang memancarkan sinar biru. Sinar biru diketahui berbahaya bagi kulit dan harus dilakukan perlindungan dengan mineral sunscreen. Penelitian ini dilakukan untuk mengetahui tingkat pengetahuan, sikap, dan tindakan mahasiswa mengenai penggunaan tabir surya dalam mengatasi dampak sinar biru gawai. Studi ini bersifat cross-sectional dengan analisis kuantitatif menggunakan kuesioner yang disebarkan secara online dengan teknik pengambilan sampel accidental sampling. Kuesioner disebarkan melalui ruang chat media sosial. Dari 106 responden, 76% responden memiliki pengetahuan baik, 59% responden memiliki sikap baik dan 72% memiliki tindakan baik. Masih ada beberapa pertanyaan yang belum dijawab benar. Dari analisis hubungan pengetahuan dan tindakan didapatkan nilai p > 0,05 yang menunjukkan bahwa pengetahuan yang dimiliki oleh responden tidak ada korelasi dengan tindakannya. Responden memiliki tingkat pengetahuan, sikap, tindakan yang baik dalam pemakaian tabir surya saat menggunakan gawai selama pembelajaran daring.
... While numerous studies have documented that irradiation with blue light and green light can induce a dose-dependent hyperpigmentation response [6,11,43,45,[49][50][51], the skin phototype plays a crucial role in this process. For instance, it has been proved that blue light (453 nm,18 J/cm 2 ) can induce IPD in type I-III healthy skins [52], which is in line with the findings of Kleinpenning et al., who explored the clinical and histological effects of blue light (420 nm, 20 J/cm 2 ) on normal skin types I-III. ...
... For instance, it has been proved that blue light (453 nm,18 J/cm 2 ) can induce IPD in type I-III healthy skins [52], which is in line with the findings of Kleinpenning et al., who explored the clinical and histological effects of blue light (420 nm, 20 J/cm 2 ) on normal skin types I-III. The authors observed transient melanogenesis and inexplicable vacuolization without melanocyte apoptosis [51]. Likewise, Moreiras et al. demonstrated that both blue light (450 nm) and green light (530 nm) induced melanin production in healthy human skin of types II and III ex vivo, without any detectable increase in DNA damage or cell apoptosis, even under fairly high doses of exposure (140 J/cm 2 ) [53]. ...
Electromagnetic radiation, notably visible light (VL), has complicated effects on human skin, particularly pigmentation, which have been largely overlooked. In this review, we discuss the photobiological mechanisms, pathological effects, clinical applications and therapeutic strategies of VL at varying wavelengths on melanocyte biology and skin pigmentary disorders. Different VL wavelengths may impose positive or negative effects, depending on their interactions with specific chromophores, photoaging, ROS production, circadian rhythm and other photon-mediated reactions. Further in vivo and in vitro studies are required to establish the pathologic mechanisms and application principles of VL in pigmentary disorders, as well as optimal photoprotection with coverage against VL wavelengths.
... Creators such as Philips are currently developing devices and technologies that emit a blue visible spectrum for use in the treatment of skin diseases [8][9][10]. The presence of blue light has also been reported in a number of studies that have been effective in killing bacteria associated with periodontal disease, such as Pg and Aa [11][12][13] Periodontal disease, also known as gum disease, is a group of inflammatory conditions that affect the tissues surrounding the teeth [14]. The disease start as acute tenderness of the gum tissue and untreated cases can develop to form dental pockets, and finally tooth death [14]. ...
... In addition, it is well accepted that aBL is less harmful to host cells than UVC irradiation. [12,13]. The objectives of this study were to determine the phototoxic effect of visible blue light on Pg and Aa isolates of chronic gingivitis patients, and to study their antibiotic sensitivity against selected antibiotics. ...
ABSTRACT Chronic periodentitis is a quite common disease in adult patients characterized by pocket formation and/or recession while progressive loss of periodontal attachment occurs slowly to moderately local risk factors, e.g. bacterial plaque. Wide array of microorganisms have been associated with periodontal disease, out of which Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) have been predominantly associated with periodontal diseases. The objectives of this study were to determine phototoxic effect of visible blue light on Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis clinical isolates from chronic periodentitis patients, and to study their antibiotic sensitivity against selected antibiotics. The test was carried out on 15 strains of Aggregatibacter actinomycetemcomitans and 15 strains of Porphyromonas gingivalis isolated from pockets of chronic periodentitis patients aged between 30-50 years old with pocket depths of 5-6 mm. The bacteria cultured, isolated, and identified by standard bacteriological methods, then subjected to visible blue light at different periods of time exposures. After light exposure, the bacterial killing rates were calculated from colony forming unit (CFU) counts after 48hours of anaerobic incubation. There was a decrease in CFU for both microorganisms as we proceeded from zero, 20, 40 and 60 seconds of blue light exposure. In conclusions, there was a phototoxic effect for the visible blue light emitted from the light curing device against the anaerobic periodontal pathogens and blue light exposure is effective in reducing periodontal pathogens. It is recommended that an adjunctive exogenous photosensitizer be used and that pathogens be exposed to visible light for clinical antimicrobial periodontal therapy. Keywords: Anaerobic periodontal pathogen, blue light, CFU.
... LED technology is based on semiconductors that emit selected ranges of wavelengths within the visible-light spectrum. Compared with UV illumination and conventional sources of light, LEDs, in terms of spectral properties and radiation pattern, show numerous advantages, including being environmentally friendly, energy-saving, safe, having a long lifespan, and being effective at causing a lethal photobiological response [2,24], without the concerns of harmful impacts on human health and deleterious effect on treated foods [28][29][30][31]. ...
Increasing antibiotic resistance is one of the world’s greatest health problems, and biocide use in food disinfection, alongside other application fields, could increase antibiotic resistance. Effective and eco-friendly food decontamination treatment with minimal chemical intervention in food production is urgently needed. Synergistic antimicrobial interaction of photoactive compounds and blue-light-emitting diodes have recently been proven effective in agricultural and environmental applications. Curcumin-based non-thermal treatment has been reviewed in this work for the development of a safe and effective decontamination tool that could be adapted to the food industry. The antimicrobial mechanism of the synergistic interaction and the inhibitory efficacy against foodborne pathogens (bacteria in both vegetative form and spore, as well as in biofilms) are discussed. Further studies on curcumin and its derivative, as well as light illumination patterns, were compared for enhanced bactericidal efficacy. Moreover, studies relating to photodynamic inactivation treatment for food sanitation and food quality enhancement (cereal grains and other food products) were summarized, as well as the impact on food organoleptic and nutritional quality.
... Furthermore, light in the blue spectrum effectively inactivates viruses, including coronaviruses [15,16] and several fungal species [17]. Despite having lower germicidal capacity than ultraviolet (UV) light, blue light benefits from its safety on mammalian cells, allowing its widespread use in various applications for extended exposure times without harming human cells [18]. In addition, blue light is equally effective against drug-sensitive and drug-resistant microorganisms [19,20]. ...
Blue light in the visible spectrum naturally fights bacteria and effectively deactivates various Gram-positive and Gram-negative bacteria and fungi using photodynamic processes. It works against drug-resistant strains within these species and is gentler on mammalian cells than ultraviolet rays or chemicals. This study evaluated blue light as an affordable way to sanitize surfaces in poultry settings, such as eggs and litter. The study used an light-emitting diode array to remove harmful Esche¬richia coli and Staphylococcus aureus from these items and observed how blue light affected their survival rates. Blue light (455 nm) at 30 mW/cm2 for one hour decreased the survival of S. aureus and E. coli on solid agar plates to 29.88% and 21.04%, respectively, compared to non-irradiated cultures. Similarly, on untreated surfaces (such as plastic used for feeding and drinking), the survival rates dropped to 25.8% and 15.6%, respectively. The survival percentages on treated eggs were 50% (S. aureus) and 48.2% (E. coli) and 59% (S. aureus) and 36.46% (E. coli) on treated litter. Hence, blue light technology offers a promising alternative to traditional antimicrobial methods by leveraging specific wavelengths to target microbial cells. This approach can significantly reduce the microbial load in poultry environments, enhancing food safety and animal health. This paper reports the first use of blue light as an antibacterial within poultry research in Iraq, offering a fresh approach to disinfection in this field.
... Therefore, aBL is attracting increased attention as an alternative that is safer for workers in industrial settings. The results of studies in animal models and volunteers suggest that exposure to blue light, at an effective antimicrobial dose, does not cause significant DNA damage to keratinocytes, inflammatory reactions or skin burns [38,39]. The effectiveness of E. coli eradication using aBL has been demonstrated for nonpathogenic and pathogenic strains, including the seven main Shiga-like toxin-producing E. coli (STEC) pathotypes, which are among the most serious threats in the food industry [40,41]. ...
Background
Escherichia coli is an integral part of the colonic microflora, though its pathogenic intestinal strains can contaminate animal and plant products and cause significant challenges in the food industry. Thermal processing is one of the most common methods used to preserve food. Nevertheless, non-thermal antibacterial methods, such as antibacterial blue light (aBL), are attracting more interest due to the growing demand for minimally processed products. Thus, the current study was aimed at assessment whether the risk of co-selection for these two food processing approaches exist.
Results
The development of E. coli tolerance to both selective factors was observed after repeated exposure to sublethal doses of heat and aBL, and the observed adaptations were confirmed to be phenotypically stable. The results demonstrated that populations with increased tolerance to aBL also exhibited increased tolerance to temperature, while the sensitivity of temperature-tolerant populations to aBL did not change. We also identified 11 genes that could be involved in cross-stress tolerance. Neither adaptation changed the antibiotic sensitivity of the tolerant strains. Finally, short- and long-term pre-incubation at elevated temperatures significantly increased the tolerance of E. coli BW25113 to aBL.
Conclusions
The results obtained clearly demonstrate that aBL may serve as a complementary approach in food industry lacking resistance development and exerting no impact on microbial drug susceptibility. Nevertheless, the phenomenon of cross-tolerance should be considered an issue when designing food processing including sequential use of aBL and high temperature.
Graphical Abstract
... However, the low human tissue permeability due to the short wavelength of blue light is underutilized [22,25,36,37]. Blue light can damage not only bacteria but also host cells [21,38,39]. This study showed that certain natural phytochemicals could be active according to the energy of light, not because they were active at a specific wavelength or time among the four wavelengths used in the experiment. ...
As the risk of antibiotic-resistant bacteria increases, interest in non-antibiotic treatment is also increasing. Among the methods used in non-antibiotic therapy, natural antibiotics such as essential oils have disadvantages such as low efficiency. In the case of phototherapy, the light used for antibacterial activities has low penetration into the human body because of its short wavelength, making it of low medical utility. To solve this problem, this study aimed to determine conditions for enhancing the antibacterial activity of natural phytochemicals and visible light. Four natural phytochemical extracts that showed high antibacterial properties in previous studies were analyzed. Synergistic effects on antibacterial activity and cytotoxicity were determined when natural phytochemical extracts and visible light were simultaneously used. As a result, it was confirmed that the antibacterial activity increased by four times when Sanguisorba officinalis L. was irradiated with 465 nm for 10 min and 520 nm for 40 min, and Uncaria gambir Roxb. was irradiated with 465 nm for 10 min and 520 nm for 60 min compared to when Sanguisorba officinalis L. and Uncaria gambir Roxb. were used alone. The synergistic effect on antibacterial activity was independent of the absorption peak of the natural phytochemical extracts. In addition, in the case of natural phytochemical extracts with improved antibacterial activity, it was confirmed that the improvement of antibacterial activity was increased in inverse proportion to the light irradiation wavelength and in proportion to the light irradiation time. The antibacterial activity was enhanced regardless of antibiotic resistance. In the case of cytotoxicity, it was confirmed that there was no toxicity to A549 cells when treated with 465 nm, the shortest wavelength among the natural phytochemical extracts. These results show how to replace blue light, which has been underutilized due to its low transmittance and cytotoxicity. They also demonstrate the high medical potential of using natural phytochemical and visible light as a combination therapy.
... 25 In contrast, BLT alone, at doses of less than 100 J/cm2 leads to no detrimental effects of human tissues both on gross inspection and at a histologic level allowing this treatment to be employed in a perioperative setting. 22 Given that C. acnes naturally expresses porphyrins, particularly when grown in culture for at least 3 days, we did not find it necessary to use photosensitizers in this work. 3 Although the growth phase of commensal organisms on human skin has not been well defined, it can be postulated that bacteria on skin may be in various stages of their growth cycle. ...
Background
Blue light therapy (BLT) is a Food and Drug Administration cleared modality used in dermatology as an effective treatment of acne. The primary purpose of this study is to determine if there are dose-dependent antimicrobial effects of BLT against Cutibacterium acnes (C. acnes).
Methods
A known strain of C. acnes was grown on chocolate agar in a controlled laboratory environment under anaerobic conditions for 1 week. After 1 week, 2-3 colonies of C. acnes were isolated and transferred to broth medium to incubate for 2 or 7 days. Broth vials (treatment arm) then underwent 1 of 6 different blue light dosing treatment regimens and a duplicate broth vial served as a control left open to the same environment. The BLT regimens were a single treatment of 25 J/cm², 50 J/cm², 75 J/cm², 100 J/cm², 2 serial treatments of 50 J/cm² separated by 24 hours, or 2 serial treatments of 75 J/cm² separated by 24 hours. The Omnilux Blue device (415 nm wavelength) was used for all BLT treatments and delivered, on average, 1.68 ± 0.004 J/min. Following treatment, the control and treatment broth samples were plated on chocolate agar and allowed to grow for 7 days. After 7 days, plates were counted and colony forming units (CFUs) were calculated. Six trials were completed for each BLT dosing regimen based on an a priori power analysis of 6 individual 2-sided t-tests. Comparisons in the primary outcome were made via mixed-effects analysis of variance with replicate as a random effect.
Results
All BLT treatment regimens resulted in significantly fewer CFUs than their aggregate control plate CFUs (P < .05 for all). Furthermore, in 2-way comparison of CFUs between BLT treatment groups, a single treatment of 75 J/cm² did lead to significantly less growth than 25 J/cm² (P = .017) and 50 J/cm² (P = .017). There were no improved antimicrobial effects with serial treatments when comparing 2 doses of 50 J/cm² with a single dose of 100J/cm², nor were 2 doses of 75 J/cm² more efficacious than 100 J/cm². Using the Omnilux Blue device, it took 44.8 minutes to deliver a 75 J/cm² dose.
Conclusion
BLT is an effective antimicrobial agent against this single virulent strain of C. acnes. Treatment dosing of 75 J/cm² was identified to be the most effective dose per unit time. Serial treatments did not lead to superior antimicrobial effects over a single, high-dose treatment.
... Thus, blue light in the spectral range of 400-470 nm, with its closeness to the strongly antibacterially effective UV-light, but without its possibly damaging effect, has garnered great scientific interest because of its corresponding high photon energy. [26][27][28][29] There are already in vitro and in vivo successes in the fight against gram(+) as well as gram(-) pathogens, whereby various authors disagree with one another about the question which bacteria form reacts more sensitively to blue light disinfection. 26 Propionibacterium acnes, Helicobacter pylori, Pseudomonas aeruginosa and Staphylococcus aureus 13,26 have been shown to be just as photosensitive as P. intermedia and P. gingivalis, 25,30 which could be significantly reduced, depending on the power, through irradiation with blue laser light (405 nm). ...
Introduction: Cavity disinfection is necessary to prevent a progressive infection of the crown dentin and pulp. Increasing intolerance and resistance to antiseptics and antibiotics as well as the controversy over the effects of those on the dental hard tissue and composite have prompted the investigation of alternative treatment options. The objective of this pilot study is to evaluate the antibacterial potential of a diode laser with a wavelength of 445 nm in the cavity preparation using the bacterium Streptococcus salivarius associated with caries in conjunction with the characteristics and influences of dentin on light transmission.
Methods: The bactericidal effect of the laser irradiation was determined in culture experiments by using caries-free human dentin samples on bacteria-inoculated agar. For this, dentin discs (horizontally cut coronal dentin) of 500 μm and 1000 μm thicknesses were produced and irradiated with the laser with irradiation parameters of 0.7-1 W in a cw-mode and exposure times of between 5-30 s. Based on the different sample thicknesses, the penetration depth effect of the irradiation was ascertained after the subsequent incubation of the bacteria-inoculated agar. Additional influential parameters on the irradiation transmission were investigated, including surface moisture, tooth color as well as the presence of a smear layer on the dentin surface.
Results: The optical transmission values of the laser radiation for dentin were significantly dependent on the sample thickness (P = 0.006) as well as its moisture content (P = 0.013) and were independent of the presence of a smear layer. There was a 40% reduction in bacteria after the radiography of the 500-μm-thick dentin samples, which was shown as the lowest laser dose (443 J/cm2).
Conclusion: These findings indicate that the diode laser with light emission at a wavelength of 445 nm is interesting for the supportive cavity disinfection within the scope of caries therapy and show potential for clinical applications.
... Studies on osteoblasts suggest that exposure of cells to light at 405 nm up to a dose of 36 J/cm 2 has no observable effect on cell viability, function, proliferation rate and morphology. Conversely, when the effects of exposure to this wavelength on bacterial cells are studied, results show that the same doses induce significant bactericidal effects [47][48][49]. ...
Effective disinfection procedures in healthcare facilities are essential to prevent transmission. Chemical disinfectants, hydrogen peroxide vapour (HPV) systems and ultraviolet (UV) light are commonly used methods. An emerging method, violet-blue light at 405 nm, has shown promise for surface disinfection. Its antimicrobial properties are based on producing reactive oxygen species (ROS) that lead to the inactivation of pathogens. Studies have shown significant efficacy in reducing bacterial levels on surfaces and in the air, reducing nosocomial infections. The aim of this study was to evaluate the antimicrobial effectiveness of violet-blue (405 nm) LED lamps on high-contact surfaces in a hospital infection-control laboratory. High-contact surfaces were sampled before and after 7 days of exposure to violet-blue light. In addition, the effect of violet-blue light on MRSA-contaminated surfaces was investigated. Exposure to violet-blue light significantly reduced the number of bacteria, yeasts and moulds on the sampled surfaces. The incubator handle showed a low microbial load and no growth after irradiation. The worktable and sink showed an inconsistent reduction due to shaded areas. In the second experiment, violet-blue light significantly reduced the microbial load of MRSA on surfaces, with a greater reduction on steel surfaces than on plastic surfaces. Violet-blue light at 405 nm has proven to be an effective tool for pathogen inactivation in healthcare settings Violet-blue light shows promise as an additional and integrated tool to reduce microbial contamination in hospital environments but must be used in combination with standard cleaning practices and infection control protocols. Further research is needed to optimise the violet-blue, 405 nm disinfection method.
... The fact is also established that blue light is much less harmful to human cells than UV irradiation. 6 Topical BPO has antimicrobial, keratolytic and comedolytic properties, with no fear of antibiotic resistance. Topical preparations are currently available at concentrations of 2.5%, 4%, 5%, 10% and 20 %. ...
Objective To determine the efficacy and safety of blue light in comparison with 4% topical benzoyl peroxide (BPO) in mild to moderate acne. Methods This randomized controlled trial, carried out in the, included 124 patients age ranging from 14-35 years having mild to moderate acne. Patients were randomized to receive blue light therapy (group I) or topical 4% BPO twice daily (group II). Efficacy was determined at week 8 by comparing % reduction in number of lesions. Side effects were noted during treatment period. Results Total 124 patients were randomly divided into two groups. Group I, 62 (50%) patients were treated with blue light therapy and group B, 62 (50%) patients were treated with 4% topical BPO. 52 patients were male (41.9%) whereas 72 were females (58.1%). The mean age of the patient was 23.02 ± 6.3 years. The efficacy of the treatment in term of % reduction in the number of lesions was more in blue light group as compared to 4% topical BPO group, (76% vs. 60%), P <0.05. Blue light group was safer as compared to 4% topical BPO group (100% vs. 91%). Conclusion Blue light is more effective and safe therapy for mild to moderate acne patients as compared to 4% topical benzoyl peroxide.
... However, concerns regarding potential health risks associated with UV radiation have restricted its widespread application, requiring a safer alternative. When absorbed the blue light, the endogenous photosensitizer in the presence of oxygen is precisely activated, generating ROS that primarily affects the bacteria while minimizing harm to surrounding healthy tissues compared to UV irradiation [21,22]. Blue light at the wavelength of 405 nm has been demonstrated to induce less than approximately tenfold DNA damage [23] compared to UV light at 365 nm, which is widely used for bactericidal effects [24]. ...
Staphylococcus aureus is one of the most common bacteria in the human skin and causes various severe infections. Methicillin-resistant Staphylococcus aureus (MRSA) has raised significant concerns and challenges because they are difficult to kill due to their ability to resist many antibiotics. In the present study, a blue light-emitting diode with a wavelength of 405 nm was designed and applied for inactivating S. aureus. We investigated the dependence of the S. aureus inactivation rate on the irradiation factors, including time, distance, and energy dose. The results indicated that irradiation time and distance were observed to significantly affect the growth of S. aureus. In particular, the energy dose of 322.2 J/cm2 at a distance of 5 cm for 35 min was recommended to inactivate S. aureus growth completely. The study also proposes the DNA self-repair mechanism causing the delaying time during inactivating S. aureus. Therefore, energy dose is a reliable parameter for designing a single-factor experiment to optimize the irradiation time and distance to obtain a suitable range of values. The comparison between red and blue LED also confirmed the ability of the blue LED to inhibit bacterial growth, while red LED enhances the growth of bacteria. Briefly, our research suggested that blue LED at the wavelength of 405 nm has the potential to be applied in clinical hygiene and food processing as an antimicrobial technique to prevent the development of antibiotic resistance.
... A study conducted by Kleinpenning et al. [212] tested the effect of blue 420 nm light (100 J cm −2 per day) on eight healthy volunteers by illuminating them over 5 consecutive days at 20 J cm −2 . From skin biopsies, the results were the following: no DNA damage, no inflammatory processes of the cells and no sunburn before and after the test, although they observed transient melanogenesis and vacuolization of keratinocytes even though these alterations did not lead to cell apoptosis. ...
Blue light is an emerging technology used for the decontamination of food contact surfaces and products. It is based on the activation of photosensitizers by light, determining the release of reactive oxygen species (ROS). ROS causes damage to bacterial cells leading to cell death. Several types of microbes may be treated, such as bacteria, yeasts, moulds and viruses, in planktonic or biofilm form. Blue light technology is affected by several factors: light parameters (i.e., irradiance, dose, wavelength), microbial parameters (i.e., pH, temperature, initial inoculum, grade of biofilm maturation) and surface parameters (i.e., material, roughness, and optical properties). In addition, it may be used alone or coupled with other technologies. The use of blue light shows several advantages, such as safety for food operators, and a lower release of chemicals in the environment. Moreover, it seems unlikely for bacteria to develop resistance to the blue light application.
... 13,14 These effects can be observed in all skin types, including in patients with pigmentation diseases. 10,15 The reason for this effect of blue light is that melanocyte opsin 3 activates calmodulin-dependent protein kinase II, transcription factor cAMP-responsive element-binding protein, mitogen-activated protein kinase P38, and extracellular regulated protein kinase by sensing external blue light and induces melanin synthesis. 16 In ex vivo skin specimens, gene expression and tyrosinase activity are increased by visible light. ...
Background
The difference in skin pigmentation induced by blue light between melasma patients and healthy people has not been reported. This study aimed to explore the impact of different doses of blue light irradiation on the pigmentation of the skin of non‐exposed areas in female melasma patients with III‐IV‐type skin and healthy women.
Materials and methods
This observational study enrolled patients with melasma and healthy people at the First Affiliated Hospital of Kunming Medical University between January and April 2021. The outcomes were the degree of pigmentation, ΔL*, and ΔITA* values.
Results
Forty‐two (21/group) participants were enrolled. After irradiation with different doses of blue light, different degrees of pigmentation could be observed in the irradiated area of the skin of female melasma patients and healthy women. The △L* and △ITA* values in the irradiated area of the skin of healthy women were higher than in female melasma patients after blue light irradiation at 20 J/cm² (p < 0.05). There were no significant differences in the pigmentation scores, △L* values, and △ITA* values in the irradiated areas of skin at different time points after irradiation with the other doses of blue light (p > 0.05).
Conclusion
Blue light at 20 J/cm² induced a smaller change in pigmentation in melasma patients than in healthy women, but the effect of blue light at 40–80 J/cm² was similar.
... Both Gram-positive and Gram-negative bacteria can perceive blue light at 405-470 nm to respond physiologically [11]. Blue light has antibacterial or bactericidal abilities with little to no harmful effects on mammalian cells [12]. In an in vitro study, blue light exposure killed 15.7% of the tested Propionibacterium acnes immediately and 24.4% after 60 min [13]. ...
Vibrio parahaemolyticus is a typical marine bacterium, which often contaminates seafood and poses a health risk to consumers. Some non-thermal sterilization technologies, such as ultrasonic field (UF) and blue light (BL) irradiation, have been widely used in clinical practice due to their efficiency, safety, and avoidance of drug resistance, but their application in food preservation has not been extensively studied. This study aims to investigate the effect of BL on V. parahaemolyticus in culture media and in ready-to-eat fresh salmon, and to evaluate the killing effectiveness of the UF combined with BL treatment on V. parahaemolyticus. The results showed that BL irradiation at 216 J/cm2 was effective in causing cell death (close to 100%), cell shrinkage and reactive oxygen species (ROS) burst in V. parahaemolyticus. Application of imidazole (IMZ), an inhibitor of ROS generation, attenuated the cell death induced by BL, indicating that ROS were involved in the bactericidal effects of BL on V. parahaemolyticus. Furthermore, UF for 15 min enhanced the bactericidal effect of BL at 216 J/cm2 on V. parahaemolyticus, with the bactericidal rate of 98.81%. In addition, BL sterilization did not affect the color and quality of salmon, and the additive UF treatment for 15 min did not significant impact on the color of salmon. These results suggest that BL or UF combined with BL treatment has potential for salmon preservation, however, it is crucial to strictly control the intensity of BL and the duration of UF treatment to prevent reducing the freshness and brightness of salmon.
... Important findings suggesting the hypothesis of an UV-ray involvement in certain types of tumors are the association between lesions and concomitant histopathological changes that universally correlate with photoaging in humans [25][26][27] and in veterinary medicine [28][29][30]. In this case report, the areas adjacent to the two tumors showed photoinduced changes such as epidermal hyperplasia, epithelial stratification disorders, the squamatization of the basal layer and the presence of proliferation nests of keratinocytes. ...
As with human species, recent studies also suggest a photoinduced etiopathology for non-epithelial cutaneous tumors in feline species. We report a recent case of a ten-year-old male cat with a white-hair coat and mesenchymal neoplasms of both auricles. Cytology, complete blood count (CBC), serum biochemistry and imaging examinations were performed. After surgery, the samples underwent routinary histopathology and were additionally stained with orcein. A routine analysis yielded values within a normal range and the imaging examination showed no abnormalities, suggesting that the bilateral presentation of neoplasms was primary rather than metastatic. The cytology was inconclusive, but, through histopathology, two well-differentiated fibrosarcomas were diagnosed and histopathological changes related to chronic UV exposure (such as epidermal hyperplasia, stratification disorders, keratinocyte dysplasia and an accumulation of elastotic material) were documented in the skin adjacent to the lesions. An orcein stain succeeded in highlighting elastosis. The elastic fibers lost their regular structure and orientation and appeared to be fragmented, wavy to branched and knotted. A morphometric analysis showed that the amount of elastotic material in the dermis close to the tumors was more than double compared with the more distant areas. Elastosis is considered to be a hallmark of photodamage; thus, an involvement of UV rays in the carcinogenic process of the tumors may be suspected.
... Moreover, no bacterial resistance has been reported yet [10]. However, blue irradiation does not damage the normal host cell compared to ultraviolet light which is very harmful [12][13][14]. Besides this, herbal compounds with fewer side effects can potentially decrease the resistance. ...
Nowadays, with increasing resistance of microorganisms to drugs, it is necessary to look for new solutions beside antibiotic therapy. One of these effective approaches is the use of plant compounds and blue LED Irradiation. Berberine (an alkaloid compound) has several properties, including antibacterial effect. This compound destroys bacterial cells by producing reactive oxygen species (ROS). In this study, the combined effect of blue LED Irradiation and berberine on Pseudomonas aeruginosa (Gram-negatives) and Staphylococcus aureus (Gram-positive) and also their effect on human dermal fibroblast (HDF) cells were investigated. The obtained results showed that the combination of berberine and blue light irradiation had a better effect on both bacteria and this antimicrobial effect was higher in Gram-positive bacteria. These compounds also prevented the formation of biofilms and were able to destroy the created biofilms. Therefore, this method can be suggested to treat infection in chronic wounds, such as diabetic wounds.
... The antibacterial effects of aBL are based on the well-known mechanisms of photodynamic therapy, the generation of intracellular reactive oxygen species (ROS) by the excitation of light-activated photosensitizers, but aBL uses endogenous photosensitizers, such as porphyrins and flavins inside the cells instead of exogenously applied ones [27,28]. As the effects of aBL on mammalian cells are reported to be less detrimental than with UV light, further research is necessary [29,30]. ...
The increase in antibiotic resistance represents a major global challenge for our health systems and calls for alternative treatment options, such as antimicrobial light-based therapies. Blue light has shown promising results regarding the inactivation of a variety of microorganisms; however, most often, antimicrobial blue light (aBL) therapy is performed using wavelengths close to the UV range. Here we investigated whether inactivation was possible using blue light with a wavelength of 475 nm. Both Gram-positive and -negative bacterial strains were treated with blue light with fluences of 7.5–45 J/cm2. Interestingly, only some bacterial strains were susceptible to 475 nm blue light, which was associated with the lack of RecA, i.e., a fully functional DNA repair mechanism. We demonstrated that the insertion of the gene recA reduced the susceptibility of otherwise responsive bacterial strains, indicating a protective mechanism conveyed by the bacterial SOS response. However, mitigating this pathway via three known RecA inhibiting molecules (ZnAc, curcumin, and Fe(III)-PcTs) did not result in an increase in bactericidal action. Nonetheless, creating synergistic effects by combining a multitarget therapy, such as aBL, with an RecA targeting treatment could be a promising strategy to overcome the dilemma of antibiotic resistance in the future.
... The principal advantage of light-based therapies is the equal killing effectiveness regardless of antibiotic resistance. When comparing blue light to ultraviolet irradiation (another light-based therapy), blue light is less detrimental against mammalian cells [28]. ...
Resistance or multi-resistance to antibiotics by microorganisms has generated one of the most emerging problems of public health due to the loss of susceptibility to drugs. The World Health Organization (WHO) publishes the groups of bacteria considered antibiotic-resistant "priority pathogens", and for these microbes new antimicrobials or strategic combinations are urgently needed. A novel strategy to control resistance is the application of combined antimicrobials with synergistic effect to destroy priority pathogens, but also against parasites, fungi, even viral particles. Therefore, it is important to expand the scientific knowledge regarding to antimicrobial combinations and the pharmacological treatments to preserve human health because paradoxically, the former solution to the spread of infectious diseases found in antibiotics, is now the main cause of a new problem: antimicrobial resistance.
... While both UV and blue light cause hyperpigmentation via ROS generation, only blue light causes hyperpigmentation via opsin stimulation [10]. In skin biopsies from healthy volunteers, blue light irradiation over 5 consecutive days re-DOI: 10.1159/000526720 sulted in increased perinuclear vacuolization in keratinocytes and an increased number of melan-A-positive cells [10,33]. Blue light irradiation increased melanin production, oxygen saturation, and hemoglobin content in female volunteers [29]. ...
The growing use of electronic devices and other artificial light sources in recent decades has changed the pattern of exposure to blue light (400–500 nm). Although some progress has been made in the study of the biological effects of blue light on the skin, many questions in this field remain unexplored. The aim of this article was to review the currently available evidence on the deleterious effects of blue light on the skin, as well as the methods and strategies designed to protect from the detrimental effects of blue light. PubMed and ProQuest databases were searched in January 2022. Search results were supplemented by articles considered relevant by the authors. The results of in vitro, in vivo and clinical studies show that blue light produces direct and indirect effects on the skin. The most significant direct effects are the excessive generation of reactive oxygen and nitrogen species, and hyperpigmentation. Reactive oxygen and nitrogen species cause DNA damage and modulate the immune response. Indirect effects of blue light include disruption of the central circadian rhythm regulation via melatonin signaling and local circadian rhythm regulation via direct effects on skin cells. Antioxidants and sunscreens containing titanium dioxide, iron oxides, and zinc oxide can be used to protect against the detrimental effects of blue light as part of a strategy that combines daytime protection and night-time repair. Blue light produces a wide variety of direct and indirect effects on the skin. As exposure to blue light from artificial sources is likely to continue to increase, this area warrants further investigation.
... All of these radicals damage cell structures such as DNA, proteins or membranes [9][10][11][12][13][14][15] and can thus lead to cell death. If the irradiation dose is high enough, visible light appears to be effective against bacteria, fungi and even viruses [16][17][18] without endangering humans or human cells [19,20]. ...
The spread of infections, as in the coronavirus pandemic, leads to the desire to perform disinfection measures even in the presence of humans. UVC radiation is known for its strong antimicrobial effect, but it is also harmful to humans. Visible light, on the other hand, does not affect humans and laboratory experiments have already demonstrated that intense visible violet and blue light has a reducing effect on bacteria and viruses. This raises the question of whether the development of pathogen-reducing illumination is feasible for everyday applications. For this purpose, a lighting device with white and violet LEDs is set up to illuminate a work surface with 2,400 lux of white light and additionally with up to 2.5 mW/cm² of violet light (405 nm). Staphylococci are evenly distributed on the work surface and the decrease in staphylococci concentration is observed over a period of 46 hours. In fact, the staphylococci concentration decreases, but with the white illumination, a 90% reduction occurs only after 34 hours; with the additional violet illumination the necessary irradiation time is shortened to approx. 3.5 hours. Increasing the violet component probably increases the disinfection effect, but the color impression moves further away from white and the low disinfection durations of UVC radiation can nevertheless not be achieved, even with very high violet emissions.
... Over the last decade, an innovative light-based approach, antimicrobial blue light therapy (aBL), has emerged as a potent microbicide that does not require the application of exogenous photosensitizers [19,[25][26][27][28][29][30]. Notably, aBL has been found to be far less damaging to human cells when compared to UVC [31,32]. Mechanistically, aBL excites endogenous chromophores (porphyrins and/or flavins) that are present in microbial cells, resulting in the generation of ROS, which has potent microbicidal properties [33,34]. ...
... Over the last decade, an innovative light-based approach, antimicrobial blue light therapy (aBL), has emerged as a potent microbicide that does not require the application of exogenous photosensitizers [19,[25][26][27][28][29][30]. Notably, aBL has been found to be far less damaging to human cells when compared to UVC [31,32]. Mechanistically, aBL excites endogenous chromophores (porphyrins and/or flavins) that are present in microbial cells, resulting in the generation of ROS, which has potent microbicidal properties [33,34]. ...
... These were either found within the epidermal layer (hyperkeratosis and/or parakeratosis, mild to severe hyperplasia, stratification disorders, squamatization of epidermal basal cells, atypia or apoptosis of keratinocytes) and in the dermis (fibrosis and elastosis). Similar histological features are described in the photodamaged skin of humans and are related to the type and amount of UV radiation [5,11,30]. Interestingly, solar-induced lesions observed in the skin adjacent to the epithelioid melanoma were limited to the dermis (solar dermatosis) without the typical epidermal involvement seen for actinic keratosis [9]. This could be linked to the total amount of UV radiation that reaches the skin, which is directly influenced by the quantity of hair, amount of cutaneous pigment, and duration of exposure [9]. ...
The photoinduced etiopathology of actinic keratosis and squamous cell carcinoma in feline species is well known. This etiology has also been reported for non-epithelial cutaneous tumors in other species. To date, no cases of auricular non-epithelial cutaneous neoplasms erased in a contest of actinic keratosis in cats have been reported. The aim of this study was to describe feline auricular non-epithelial cutaneous neoplasms associated with typical UV-induced cutaneous lesions and solar elastosis. The study was conducted on five feline cases diagnosed with auricular non-epithelial cutaneous tumors (two fibrosarcomas, one mixosarcoma, one epithelioid melanoma and one hemangiosarcoma), selected from the Tumor Registry of the Department of Veterinary Sciences of the University of Pisa (1998-2018). Ten and six feline auricular biopsies of normal skin and skin with actinic keratosis, respectively, were used as controls. Orcein stain was used to investigate solar elastosis. Histological changes related to chronic solar irradiation were documented in the skin adjacent to the neoplastic lesions in the five cats. Considering the anatomical localization and the results of histopathology, this study suggests that non-epithelial cutaneous neoplasms may have a UV-induced etiopathogenesis in the feline species.
... These intracellular reactive oxygen species attack DNA, proteins or membranes and, if the produced damage becomes too great, the cell dies. Human cells also contain such photosensitizers, but they have nevertheless proven to be very resistant to visible light [16][17][18][19][20][21][22][23][24]. ...
The COVID-19 pandemic is driving the search for new antiviral techniques. Bacteria and fungi are known to be inactivated not only by ultraviolet radiation but also by visible light. Several studies have recently appeared on this subject, in which viruses were mainly irradiated in media. However, it is an open question to what extent the applied media, and especially their riboflavin concentration, can influence the results. A literature search identified appropriate virus photoinactivation publications and, where possible, viral light susceptibility was quantitatively determined in terms of average log-reduction doses. Sensitivities of enveloped viruses were plotted against assumed riboflavin concentrations. Viruses appear to be sensitive to visible (violet/blue) light. The median log-reduction doses of all virus experiments performed in liquids is 58 J/cm2. For the non-enveloped, enveloped and coronaviruses only, they were 222, 29 and 19 J/cm2, respectively. Data are scarce, but it appears that (among other things) the riboflavin concentration in the medium has an influence on the log-reduction doses. Experiments with DMEM, with its 0.4 mg/L riboflavin, have so far produced results with the greatest viral susceptibilities. It should be critically evaluated whether the currently published virus sensitivities are really only intrinsic properties of the virus, or whether the medium played a significant role. In future experiments, irradiation should be carried out in solutions with the lowest possible riboflavin concentration.
... It is commonly accepted that b-LED is much less harmful to host cells than UV irradiation [28]. The DNA damage caused by UV results in (i) misincorporation of bases during replication process, (ii) hydrolytic damage, which results in deamination of bases, depurination, and depyrimidination, and (iii) oxidative damage through ROS induction [29]. ...
While blue LED (b-LED) light is increasingly being studied for its cytotoxic activity towards bacteria in therapy of skin-related infections, its effects on eukaryotic cells plasticity are less well characterized. Moreover, since different protocols are often used, comparing the effect of b-LED towards both microorganisms and epithelial surfaces may be difficult. The aim of this study was to analyze, in the same experimental setting, both the bactericidal activity and the effects on human keratinocytes. Exposure to b-LED induced an intense cytocidal activity against Gram-positive (i.e, Staphylococcus aureus) and Gram-negative (i.e., Pseudomonas aeruginosa) bacteria associated with catheter-related infections. Treatment with b-LED of a human keratinocyte cell line induced a transient cell cycle arrest. At the molecular level, exposure to b-LED induced a transient downregulation of Cyclin D1 and an upregulation of p21, but not signs of apoptosis. Interestingly, a transient induction of phosphor-histone γ-H2Ax, which is associated with genotoxic damages, was observed. At the same time, keratinocytes underwent a transient epithelial to mesenchymal transition (EMT)-like phenotype, characterized by E-cadherin downregulation and SNAIL/SLUG induction. As a functional readout of EMT induction, a scratch assay was performed. Surprisingly, b-LED treatment provoked a delay in the scratch closure. In conclusion, we demonstrated that b-LED microbicidal activity is associated with complex responses in keratinocytes that certainly deserve further analysis.
... In consequence, blue light could reduce wound infections and probably contribute to a better wound healing in these difficult wounds. All these findings suggest that irradiation with blue light might serve as a promising alternative wound healing therapy, especially for wound infections (and burn wound infections) and chronic inflammatory skin diseases with only minor side effects, since short-term irradiation with visible blue light in dermatological practice is regarded to be safe [23]. ...
Phototherapy is gaining more attention in the treatment of various diseases. Especially, blue light seems to be a promising approach for wound healing promotion due to its antimicrobial and immune-modulating properties. Despite this, there is only little research focusing on the immune-modulating properties of blue light and its possible effects on wound healing. Therefore, we investigated the effects of blue light irradiation on peripheral blood mononuclear cells (PBMC) and the influence on reepithelization in vitro. PBMCs were irradiated with DermoDyne® (DermoDyne HealthCare, Berlin, Germany) and effects on cell viability, cytokine expression, and scratch wound closure were evaluated afterwards. Irradiated cells showed a higher Interleukin-γ concentration while irradiation reduced resazurin concentration in a time-dependent manner. No differences in reepithelization were detectable when keratinocytes were treated with the supernatant of these blue light irradiated PBMCs. Blue light–mediated ex vivo stimulation of PBMCs does not cause faster reepithelization in an in vitro setting. Further research is needed to investigate the wound healing effects of phototherapy with blue light.
... HEV light and UVA induce photo-oxidation of melanogenic precursors leading to immediate pigment darkening (IPD) and persistent pigment darkening (PPD). IPD is characterized by a greyish darkening observed immediately after irradiation and fading shortly afterward, whereas a brownish-black pigmentation can develop over several weeks in PPD without the involvement of melanogenesis processes (99). Staying indoors gives a false sense of security against harmful ultraviolet radiation, so less care is taken in closed environments, such as the use of photoprotective substances. ...
A new coronavirus emerged in 2019 in Wuhan, China named Severe Acute Respiratory Syndrome type 2 coronavirus (SARS-CoV-2). Later, this virus spread worldwide, causing a disease called coronavirus disease (COVID-19). To control the outbreak, many countries announced mandatory quarantine; thus, people changed their lifestyles and started engaging in most activities from home. This review explains how some dermatological pathologies may be precipitated by prolonged stays at home, considering that quarantine was a widely used public health measure during 2020. Most of these dermatoses had to be seen, diagnosed, and treated through tele-dermatology, a remote health care system that took force during the COVID-19 pandemic because of its ease and efficiency in connecting health care professionals and their patients; therefore, reducing the risk of contagion and costs associated to medical care. This review of the principal dermatologic conditions during confinement could allow for a better preparation of health professionals.
... Stimulation of immune system and promotion of wound healing are some of the UV-light's effects [10]. Conversely, blue light is less harmful than the UV radiation and induces lower levels of photodegradation than UV light [14]. LED blue (470 nm) light treats superficial conditions due to its smaller penetration ability -1mm the most [3]. ...
Due to their effects, similar to low-intensity therapy light sources such as light-emitting diodes (LED) and broadband spectrum lamps have recently become commonly used in the diagnosis and treatment of neurodegenerative pathologies, cancer, as well as ageing. Despite the proven positive effects of such therapies, deeper understanding of the light therapies’ biological effects remains unclear. Even more, the molecular mechanisms through which different neurotransmitters, namely serotonin (5-hydroxytryptamine, 5-HT), mediate the organism’s response to radiation are yet indistinct. In this paper, we present the design and development of a specialized system for irradiation of biological objects, which is composed of LED 365 nm and LED 470 nm and a broadband lamp source of UVA/B (350 nm) with intensity, power density and direction, which can be optimized experimentally. The system, named a “water organ bath (wob)”, is used in the current work to irradiate smooth muscle stomach strips of rats. The obtained results prove that the modulation of the spontaneous contractile smooth muscle activity and the potentiation of the effects of major neurotransmitters are executed by the emitted light. The probable explanation for the neurotransmitters photoactivation is that it is the resultant effect of electromagnetic radiation on intracellular enzymes signaling systems.
... More recently, it has been demonstrated that repeated VL exposure increases pigmentation more significantly than single exposures, with increased tyrosinase activity signifying a response comparable to that of UVR-induced DT [19]. Pigmentation induced by longwave UVR/blue light (λ Max = 420 nm) has also been demonstrated histologically through a substantial increase in melan-A positive cells (a melanocyte differentiation antigen) after 5 days of irradiation with a cumulative dose of 100 J/cm 2 [20]. Differences in pigmentation response between UVR (λ max = 311 nm), blue (λ max = 450 nm) and green (λ max = 530 nm) light have also been assessed in FST I-III ex vivo skin cultures. ...
Skin pigmentation by solar ultraviolet radiation (UVR; ~295–400 nm) is well established. More recently, visible light (VL; 400–740 nm) has been shown to induce rapid pigmentation. Such pigmentation is thought to be caused by oxidative stress, which has associations with skin cancer and photoageing. However, the UVR-VL boundary region has been less well studied. The lower back of healthy Fitzpatrick skin type II-IV individuals was irradiated with increasing doses of narrow-band 385 nm and 405 nm radiation. Pigmentation change was measured immediately, 6 h and 24 h post-irradiation using two reflectance spectroscopy devices and visual grading. Pigmentation was dose-dependently increased in all skin types and time points for both spectra. Two sunscreens, both labelled SPF 15 and UVA protective in the EU and USA (but with different Boots star rating in the UK, 2* vs 5*) were compared. Their formulations were the same apart from the addition of a new organic filter bis-(diethylaminohydroxybenzoyl benzoyl) piperazine (BDBP) that absorbs between 385 and 405 nm. The product that lacked BDBP provided minimal protection against pigmentation, but its addition provided almost complete protection. This demonstrates the needs to improve photoprotection at the UVR-visible border and for sunscreens to act as neutral density filters.
Low-level light therapy (LLLT) employs athermal and atraumatic levels of illumination, typically in the visible or near-infrared (NIR) regions of the electromagnetic spectrum, to target tissue and stimulate a clinically useful local or systemic effect. LLLT has demonstrated beneficial applications in the areas of wound healing, pain management, and various musculoskeletal conditions as well as skin rejuvenation. This chapter dives into the benefits of using LED-based devices in aesthetic applications, resulting in a safer and more convenient approach to benefit patients.
Cutaneous pythiosis is a life-threatening infectious disease. Low-level laser therapy (LLLT) and ozone (O3) have been used individually in the treatment of infected wounds. The goals of the study were a) to characterize the antimicrobial action of the photo-ozone therapy (LLLT-O3) against equine Pythium insidiosum, and b) to assess the cytotoxic potential of the LLLT-O3 in keratinocytes. Specimens of pathogen were isolated from 10 horses. After culturing, 120 hyphae plugs were distributed among four groups (n=30 hyphae plugs/group): LLLT (laser irradiation for 160 sec;), O3 (exposition to O3 for 15 min;), LLLT-O3 (LLLT and O3 treatments in sequence) and control (untreated plugs). The hyphae growth was measured during the first 14 days post-treatment. In case of absence of hyphae growth, the plug was recultured for an additional 14 days. The cytotoxic potential of the treatments against HaCaT keratinocytes was accessed by colorimetric assays. The LLLT-O3 and O3 treatments inactivated, respectively, 92.3% (28/30) and 30% (9/30) of the samples. In addition, no growth was detected after the reculture of the respective plugs retrospectively. Similar growth rate was detected in all untreated and laser-irradiated hyphae plugs (control and LLT groups, respectively). The viability of HaCaT cells was not affected by the isolated treatments (LLLT and O3), while the LLLT-O3 showed slight cytotoxic effect (20%) when compared to the control group (P<0.05). A single LLLT-O3 treatment showed germicidal action against P. insidiosum. Moreover, the marked viability of skin cells previously exposed to photo-ozone therapy suggests its topical biosafety.
Introduction
Exposure to solar radiation can cause a range of skin damage, including sunburn, erythema, skin carcinogenesis, the release of reactive oxygen species (ROS), inflammation, DNA damage, and photoaging. Other wavelengths beyond UVB, such as UVA, blue light, and infrared radiation, can also contribute to the harmful effects of solar radiation. Reconstructed full-thickness human skin has the potential to serve as effective predictive in vitro tools for evaluating the effects of solar radiation on the skin. The aim of this work was to evaluate the damaging effects of UVA, blue light, and infrared radiation in a full-thickness skin model in terms of viability, inflammation, photoaging, tissue damage, photocarcinogenesis.
Methods
Full thickness skin models were purchased from Henkel (Phenion FT; Düsseldorf, Germany), and irradiated with increasing doses of UVA, blue light, or infrared radiation. Different endpoints were analyzed on the tissues: Hematoxylin-eosin staining, inflammation mediators, photoaging-related dermal markers and oxidative stress marker GPX1, evaluated by real-time quantitative PCR, as well as photocarcinogenesis markers by Western Blot.
Results and Discussion
The results showed differential responses in cytokine release for each light source. In terms of photoaging biomarkers, collagen, metalloproteinases 1 and 9, elastin, and decorin were modulated by UVA and blue light exposure, while not all these markers were affected by infrared radiation. Furthermore, exposure to UVA and blue light induced loss of fibroblasts and modulation of the photocarcinogenesis markers p53 and p21. In conclusion, the presented results suggest that the various wavelengths of solar light have distinct and differential damaging effects on the skin. Understanding the differential effects of UVA, blue light, and infrared radiation can serve as a valuable tool to investigate the efficacy of photoprotective agents in full thickness skin models.
Introduction: While a wound caused by a minor cutaneous incision routinely heals in a short time, wounds from major surgical operations might need numerous days to heal and may leave an obvious cicatrix. The use of blue light therapy (BLT) to destroy infectious microorganisms and disrupt biofilm formation could be an efficient method for healing ulcers. This systematic review focused on the effects of BLT in different preclinical in vivo studies and clinical models of skin wound healing. Furthermore, this study attempted to determine what main light parameters should be tested in preclinical and clinical studies.
Methods: The online databases PubMed.gov, Google Scholar, Scopus, Web of Science, and Cochrane were searched using the keywords “blue light” and “wound healing” according to PRISMA guidelines. No publication time limit was enforced.
Results: A total of 858 articles were identified, and 17 articles in three distinct categories were included for review. They comprised two articles on humans, fourteen articles on healthy animals, and one article on diabetic animals.
Conclusion: Some studies have shown that the application of BLT on preclinical and clinical models of wound healing in vivo is able to significantly accelerate the healing process. Few studies, however, have explored the bactericidal effect of BLT on skin injury repair in burn patients. Further preclinical investigations designed to provide a better understanding of the bactericidal effect of BLT using standardized protocols, different BLT wavelengths, and different stages of the wound-healing process of infected wounds and ulcers in healthy and diabetic animals should be carried out before clinical trials can be considered. BLT could eventually be a good option for treating infected chronic wounds, including those in diabetic patients.
Aims:
The aim of this study was to investigate dual far-UVC (Ultraviolet-C) (222 nm) and blue LED (Light Emitting Diode) (405 nm) light on the inactivation of extended spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) and to determine if repetitive exposure to long pulses of light resulted in changes to light tolerance, and antibiotic susceptibility.
Methods and results:
Antimicrobial efficiency of dual and individual light wavelengths and development of light tolerance in E. coli was evaluated through a spread plate method after exposure to light at 25 cm. Dual light exposure for 30 min resulted in a 5-6 log10 CFU mL-1 reduction in two ESBL-Ec and two antibiotic-sensitive control E. coli strains. The overall inhibition achieved by dual light treatment was always greater than the combined reductions (log10 CFU) observed from exposure to individual light wavelengths (combined 222-405 nm), indicating a synergistic relationship between blue LED and far-UVC light when used together. Repetitive long pulses of dual and individual far-UVC light exposure resulted in light tolerance in two ESBL-Ec strains but not the antibiotic-sensitive E. coli strains. Subsequent passages of repetitive light-treated ESBL-Ec strains continued to exhibit light tolerance. Antibiotic susceptibility was determined through a standard disk diffusion method. No changes were observed in the antibiotic susceptibility profiles for any of the four strains after exposure to either dual or individual wavelengths.
Conclusions:
Dual light exposure was effective in the disinfection of ESBL-Ec in solution; however, antibiotic-resistant E. coli were able to develop light tolerance after repetitive exposure to light.
Blue light has garnered attention, because of its ability to penetrate deeper into the skin layers, induce cellular dysfunction, and DNA damage. Photoaging, hyperpigmentation and melasma are some of the cutaneous changes, developing on exposure to blue light. Till date, the therapeutic role of blue light have been evaluated in dermatological conditions like psoriasis, eczema, acne vulgaris, actinic keratosis and cutaneous malignancies, amongst others. In this review, we have attempted to present an evidence based compilation of the effects of blue light on the skin.
Since recent global pandemic started, there has been a high demand for establishing an inexpensive but effective method to interfere with the spread of infectious diseases. Here, we have tested several combinations of violet light (V, 405 nm) with infra-red (IR, 850 nm) to identify an optimal light for suppressing pathogens. Our results demonstrate that both violet only (4 V) and 3V-1IR (3:1 ratio in combination of violet and infra-red) effectively suppressed all the bacterial growth tested, including Gram-negative and -positive multi-drug resistant (MDR) strains. Both 4 V and 3V-1IR equally terminated standard strains of Escherichia coli and Staphylococcus aureus, as well as MDR-strains (E. coli, Salmonella enterica and S. aureus from ATCC) effectively. In mechanism, the violet light enhanced the level of reactive oxygen species (ROS) for bactericidal effects, however, we have observed a slightly higher potency from 3V-1IR at a shorter distance, probably due to mild heat-derived dehydration by IR. Therefore, we suggest to expose 3V-1IR for short distance applications (≤1 meter) and both 4 V and 3V-1IR for longer distance (≥1 m). Notably, our results strongly suggest that the exposure of safe violet light or with infra-red can be an effective method to suppress the potential spread of bacteria-derived infectious diseases.
The efficacy of blue light therapy in dermatology relies on numerous clinical studies. The safety remains to be a topic of controversy, where potentially deleterious effects were derived from in vitro rather than in vivo experiments. The objectives of this work were 1) to highlight the nuances behind ‘colors’ of blue light, light propagation in tissue and the plurality of modes of action; and 2) to rigorously analyze studies on humans reporting both clinical and histological data from skin biopsies with focus on DNA damage, proliferation, apoptosis, oxidative stress, impact on collagen, elastin, immune cells, and pigmentation. We conclude that blue light therapy is safe for human skin. It induces intriguing skin pigmentation, in part mediated by photoreceptor Opsin‐3, which might have a photoprotective effect against ultraviolet irradiation. Future research needs to unravel photochemical reactions and the most effective and safe parameters of blue light in dermatology. This article is protected by copyright. All rights reserved.
Nanotechnology has unlocked new horizon in the field of agriculture and food sectors. Food spoilage can lead to sensory options alteration, loss of quality, production of harmful chemicals and growth of food borne pathogens. Synthetic preservatives, traditional preservation methods, and food packaging (FP) processes enable
effective control of food spoilage. They do not allow real-time control of food quality during storage and transportation and allow for a relatively short shelf life. In addition, FP can protect food from spoilage caused by external contamination but is ineffective against food borne microorganisms. The functionalities of FP preservatives could be enhanced by adding edible natural antimicrobials and antioxidants,
but these chemicals are easily degradable.Nowadays, because of the rise of
various nanotechnology techniques, it's potential to enhance the FP performances using
nanotechnology. In this paper, the recent progresses within the field of nanomaterial-
based improved FP are discussed. Several progresses are made recently in different areas like nanofood, nano-sensors, nano-packaging, nano-fertilizers, and nano-pesticides. Nowadays food quality, food safety and food packaging areas reflect high-spirited impacts of nano- science based technologies. The application of nanotechnology in the food industry has opened a new direction for the people.
Background
Red and blue light therapies are safe and effective treatments for mild to moderate acne vulgaris. However, very few previous studies have directly compared the characteristics of these two methods.
Objective
To compare the efficacy and side effects of red light (RL) and blue light (BL) for acne vulgaris and to assess these two therapies in different types of lesions.
Materials and Methods
A total of 28 subjects with mild to moderate acne vulgaris were randomized into the RL group or the BL group. Subjects in each group received different light treatments, and they were followed up regularly until 2 weeks after the last treatment. The improvement rates of different types of acne lesions were compared between the 2 groups, as well as the incidence of adverse reactions.
Results
At the 2-week follow-up, the average improvement rate of total acne lesions was 36.2% in the RL group and 30.7% in the BL group (P>0.05). The average improvement rate of inflammatory and non-inflammatory lesions was 51.5% and 17.3% in the RL group, compared with 26.4% and 10.0% in the BL group (all P>0.05). Treatment-related adverse reactions were observed distinctly in the BL group.
Conclusions
RL and BL therapies have similar efficacy in mild to moderate acne vulgaris, especially for inflammatory lesions. RL had advantages with fewer adverse reactions compared with BL.
Bacteria belonging to the group of ESKAPE pathogens are responsible for the majority of nosocomial infections. Due to the increase of antibiotic resistance, alternative treatment strategies are of high clinical relevance. In this context visible light as disinfection technique represents an interesting option as microbial pathogens can be inactivated without adjuvants. However cytotoxic effects of visible light on host cells have also been reported. We compared the cytotoxicity of violet and blue light irradiation on monocytic THP-1 and alveolar epithelium A549 cells with the inactivation effect on ESKAPE pathogens. THP-1 cells displayed a higher susceptibility to irradiation than A549 cells with first cytotoxic effects occurring at 300 J cm ⁻² (405 nm) and 400 J cm ⁻² (450 nm) in comparison to 300 J cm ⁻² and 1000 J cm ⁻² , respectively. We could define conditions in which a significant reduction of colony forming units for all ESKAPE pathogens, except Enterococcus faecium , was achieved at 405 nm while avoiding cytotoxicity. Irradiation at 450 nm demonstrated a more variable effect which was species and medium dependent. In summary a significant reduction of viable bacteria could be achieved at subtoxic irradiation doses, supporting a potential use of visible light as an antimicrobial agent in clinical settings.
Curcumin, a phytochemical derived from the rhizome of turmeric (Curcuma longa L.), has a broad group of substances with antibacterial, anti-inflammatory, anti-oxidant, anticancer activities. The anticancer activity of curcumin and its derivatives are mainly related to its regulation of signal transduction pathways. However, due to the low oral availability of curcumin, fast metabolism and other pharmacokinetic properties limit the application of curcumin in the treatment of cancer. Evidence suggests that curcumin combined with photodynamic therapy can overcome the limitation of curcumin's low bioavailability by acting on apoptosis pathways, such as B-cell lymphoma 2 (Bcl-2) and caspase family, and affecting cell cycle. This paper reviews the structure and pharmacokinetics of curcumin, focusing on the anticancer activity of curcumin combined with photodynamic therapy and the effects on cancer-related signal pathways.
New developments in the field of the commonly used photodiagnostic and phototherapeutic methods help to continuously improve the results in the daily practise. Edited by internationally renowned experts, the new edition offers up-to-date, comprehensive and clinically relevant information on every aspect of photodiagnostic and phototherapy. The book is structured in following parts:Photochemotherapy in daily practice, special phototherapeutic modalities and photoprotection in daily practice. Due to the detailed structure this new edition is even more reader-friendly and has a strong focus on clinical aspects. It includes: Guidelines for the treatment selections of specific diseases, practical guidelines for phototherapy with information about basic principles of photobiology, standardized test protocols for photodermatoses and diagnosis for skin tumors.
Sunlight influences the physiology of the human skin in beneficial as well as harmful ways, as has been shown for UV light. However, little is known about the effects of other wavelengths of solar irradiation. In this study we irradiated human keratinocytes and skin-derived endothelial cells with light-emitting-diode devices of distinct wavelengths to study the effects on cell physiology. We found that light at wavelengths of 632-940 nm has no effect, but irradiation with blue light at 412-426 nm exerts toxic effects at high fluences. Light at 453 nm is nontoxic up to a fluence of 500 J/cm(2). At nontoxic fluences, blue light reduces proliferation dose dependently by up to 50%, which is attributable to differentiation induction as shown by an increase of differentiation markers. Experiments with BSA demonstrate that blue-light irradiation up to 453 nm photolytically generates nitric oxide (NO) from nitrosated proteins, which is known to initiate differentiation in skin cells. Our data provide evidence for a molecular mechanism by which blue light may be effective in treating hyperproliferative skin conditions by reducing proliferation due to the induction of differentiation. We observed a photolytic release of NO from nitrosated proteins, indicating that they are light acceptors and signal transducers up to a wavelength of 453 nm.
Photodynamic therapy (PDT) consists of the combination of photosensitizers absorbing light mainly in the red spectral region and irradiation with light of corresponding wavelengths. We analysed its effects on the cytokine secretion (IL-1 beta, TNF alpha, IL-6) of freshly isolated peripheral mononuclear cells from six patients with chronic plaque-stage psoriasis in comparison with PUVA. PUVA treatment resulted in a decreased production of all three cytokines, but most pronounced in the case of IL-6. PDT caused a similar change in the cytokine pattern, but its effectiveness was lower. In vivo fluorescence recordings were performed on psoriatic plaque lesions after topical application of the photosensitizer Photosan-3. Under irradiation, progressive photobleaching was noted with increasing radiation dosage. This is the first reported study of photochemical reactions using on-line fluorescence recordings during PDT of psoriatic lesions in vivo. Our results demonstrate the capacity of PDT to cause immunomodulatory effects similar to PUVA, thus indicating its potential application to the treatment of this common disease.
The temporo-spatial expression of fibrillin and elastin in skin regenerating from autologous keratinocyte grafts was studied in three burned children. Skin biopsies taken between 5 days and 17 months after grafting were investigated by conventional immunofluorescence, confocal laser scanning, and electron microscopy. Fibrillin, the major component of 10-12nm microfibrils, appeared 5 days after grafting in a band-like fashion similar to collagen VII at the prospective basement membrane, and the formed the characteristic microfibrillar candelabra at the dermo-epidermal junction by fusion of several fine microfibrils to communicating microfibrils projecting downward into the reticular layer of the neodermis. Four to five months after grafting, several communicating microfibrils were connected to a web of horizontally undulating microfibrils of the neodermis which had developed independently. Elastin was first identified in the deeper neodermis 1 month after grafting as granular aggregates and 4 months after grafting on fibrillar structures and surrounding capillaries of the upper neodermis. Association of elastin with microfibrils in the papillary dermis was not detectable before month 17. Our findings suggest that the cutaneous microfibrillar apparatus develops simultaneously at both the dermo-epidermal junction and the reticular dermis and is a prerequisite for elastic fiber formation. In addition, it might be a driving force for the formation of the papilla-rete ridge pattern.
The tumor suppressor protein, p53, is part of the cell's emergency team that is called upon following cellular insult. How do cells sense DNA damage and other cellular stresses and what signal transduction pathways are used to alert p53? How is the resulting nuclear accumulation of p53 accomplished and what determines the outcome of p53 induction? Many posttranslational modifications of p53, such as phosphorylation, dephosphorylation, acetylation and ribosylation, have been shown to occur following cellular stress. Some of these modifications may activate the p53 protein, interfere with MDM2 binding and/or dictate cellular localization of p53. This review will focus on recent findings about how the p53 response may be activated following cellular stress.
New developments in the field of the commonly used photodiagnostic and phototherapeutic methods help to continuously improve the results in the daily practice. Edited by internationally renowned experts, the new edition offers again up-to-date, comprehensive and clinically relevant information on every aspect of photodiagnostics and phototherapy.
This eagerly awaited 2nd edition will become the bible of this field. It is structured in following parts: Photochemotherapy in daily practice, special phototherapeutic modalities and photoprotection.
Due to the detailed structure the book is more reader-friendly and has a strong focus on clinical aspects. It includes: Guidelines for the treatment selections of specific diseases, practical guidelines for phototherapy with information about basic principles of photobiology, standardized test protocols for photodermatoses and diagnosis for skin tumors.
The book is an invaluable resource for dermatologists, oncologists and all other physicians treating dermatological patients.
DNA damage induced by UV radiation and visible light (290-500 nm) in AS52 Chinese hamster cells was analysed by an alkaline elution assay with specific repair endonucleases. Cells were exposed to extensively filtered monochrome or broad-band radiation. Between 290 and 315 nm, the ratio of base modifications sensitive to Fpg protein (i.e. 8-hydroxyguanine and formamidopyrimidines) and T4 endonuclease V (i.e. cyclobutane pyrimidine dimers) was constant (approximately 1:200), indicating that the direct excitation of DNA is responsible for both types of damage in this range of the spectrum. While the yield of pyrimidine dimers per unit dose continued to decrease exponentially beyond 315 nm, the yield of Fpg-sensitive modifications increased to a second maximum between 400 and 450 nm. The damage spectrum in this wavelength range consisted of only a few other modifications (strand breaks, abasic sites and pyrimidine modifications sensitive to endonuclease III) and is attributed to endogenous photosensitizers that give rise to oxidative DNA damage via singlet oxygen and/or type I reactions. The generation of Fpg-sensitive modifications by visible light was not linear with dose but followed a saturation curve. It is calculated that the exposure of the cells to low doses of solar radiation results in the formation of cyclobutane pyrimidine dimers and Fpg-sensitive modifications in a ratio of 10:1.
The stratum corneum and DNA repair do not completely protect keratinocytes from ultraviolet B. A third defense prevents cells with DNA photoproducts from becoming precancerous mutant cells: apoptosis of ultraviolet-damaged keratinocytes ("sunburn cells"). As signals for ultraviolet-induced apoptosis, some studies implicate DNA photoproducts in actively transcribed genes; other studies implicate non-nuclear signals. We traced and quantitated the in vivo DNA signal through several steps in the apoptosis-signaling pathway in haired mice. Homozygous inactivation of Xpa, Csb, or Xpc nucleotide excision repair genes directed the accumulation of DNA photoproducts to specific genome regions. Repair-defective Xpa–/– mice were 7–10-fold more sensitive to sunburn cell induction than wild-type mice, indicating that 86–90% of the ultraviolet B signal for keratinocyte apoptosis involved repairable photoproducts in DNA; the remainder involves unrepaired DNA lesions or nongenomic targets. Csb–/– mice, defective only in excising photoproducts from actively transcribed genes, were as sensitive as Xpa–/–, indicating that virtually all of the DNA signal originates from photoproducts in active genes. Conversely, Xpc–/– mice, defective in repairing the untranscribed majority of the genome, were as resistant to apoptosis as wild type. Sunburn cell formation requires the Trp53 tumor suppressor protein; 90–96% of the signal for its induction in vivo involved transcribed genes. Mdm2, which regulates the stability of Trp53 through degradation, was induced in vivo by low ultraviolet B doses but was suppressed at erythemal doses. DNA photoproducts in actively transcribed genes were involved in 89% of the Mdm2 response.Keywords: apoptosis, Cockayne syndrome, mdm2 protein, MeSH, protein p53, ultraviolet rays, xeroderma pigmentosum
Oncogene is one of the world’s leading cancer journals. It is published weekly and covers all aspects of the structure and function of Oncogenes. Oncogene also publishes 8 Reviews issues a year, on a broad range of topics.
DNA damage by UV radiation plays an essential role in skin cancer induction. We report that even sub-erythemal doses of solar simulating radiation, are capable of inducing substantial nuclear damage, namely pyrimidine dimers and p53 induction in human skin in situ. The quantity and distribution of p53 induced in human skin by UV radiation depended highly on the waveband and dose of UV used. Solar simulating radiation induced very high levels of p53 throughout all layers in epidermal keratinocytes 24 hr following an erythemal dose (230+/-15.9/1000 cells), and the induction followed a dose response. Following UVA I + II and UVA I radiations, p53 expression was approximately half of that seen with equivalent biological doses of solar simulating radiation (63.5+/-28.5 and 103+/-15.9, respectively). Expression of p53 was seen in basal cell keratinocytes at lower doses of UVA, but all layers of the epidermis were affected at higher doses. Pyrimidine dimer induction, however, was seen to be the same for equivalent biological doses of UVA I, UVA I + II and solar simulating radiations, which coincides with previous findings that pyrimidine dimers initiate the erythemal response and are implicated in skin carcinogenesis. When equivalent biological doses of pure UVA are used with no UVB contamination, significant nuclear alterations occur in human skin in situ, which can approach those seen with UVB radiation. Our results suggest that DNA damage assessed in vivo by immunohistochemistry could provide a very sensitive endpoint for determining the efficacy of protective measures, such as sunscreens or protective clothing, against both UVB- and UVA-induced damage in human skin.
Photodynamic therapy (PDT) using 5-aminolevulinic acid (5-ALA) or its methyl ester (MAL) is a very effective method to treat actinic keratosis (AK). New developments will contribute to optimization of this treatment modality. This will partly be based on a better understanding of the nature of AKs. Since pain during treatment is a frequent side effect of PDT, new methods of alleviating pain are of high interest, especially when large areas are treated. A better understanding of the underlying mechanism of specific protoporphyrin IX (PPIX) accumulation can lead to further increase the response rates. New formulations might contribute to a wider acceptance of the treatment, for example a self-adhesive patch containing 5-ALA, promises easy handling, while maintaining high efficacy. New concepts in illumination, such as ambulatory PDT or daylight illumination might contribute to the further acceptance of this method.
Acne is common and can lead to scarring of the skin, as well as to psychological distress and reduced self-esteem. Most topical or oral treatments for acne are inconvenient and have side-effects. Laser and other light therapies have been reported to be convenient, safe and effective in treating acne.
To carry out a systematic review of randomized controlled trials of light and laser therapies for acne vulgaris.
We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, PsycInfo, LILACS, ISI Science Citation Index and Dissertation Abstracts International for relevant published trials.
We identified 25 trials (694 patients), 13 of light therapy and 12 of light therapy plus light-activated topical cream (photodynamic therapy, PDT). Overall, the results from trials of light alone were disappointing, but the trials of blue light, blue-red light and infrared radiation were more successful, particularly those using multiple treatments. Red-blue light was more effective than topical 5% benzoyl peroxide cream in the short term. Most trials of PDT showed some benefit, which was greater with multiple treatments, and better for noninflammatory acne lesions. However, the improvements in inflammatory acne lesions were not better than with topical 1% adapalene gel, and the side-effects of therapy were unacceptable to many participants.
Some forms of light therapy were of short-term benefit. Patients may find it easier to comply with these treatments, despite the initial discomfort, because of their short duration. However, very few trials compared light therapy with conventional acne treatments, were conducted in patients with severe acne or examined long-term benefits of treatment.
Chronic wounds resistant to conventional therapy have been treated successfully with low energy lasers and light emitting diodes (LEDs) in the visible and near IR region. It has been proposed that production of low level reactive oxygen species (ROS) following illumination is the first step of photobiomodulation. It was also shown that white light (400-800 nm) has similar stimulatory effects as lasers and LEDs. ROS at higher levels are toxic to cells and bacteria.
In the present study, we examined the phototoxicity of broadband (400-800 nm, 120 J/cm(2)) visible light on the survival of several pathogenic bacteria: Staphylococcus aureus 195, Pseudomonas aeruginosa 1316, Escherichia coli 1313, and Serratia marcescens. These bacteria were chosen due to their high prevalence in infected wounds. The survival of bacterial cells following illumination was monitored by counting the number of colony forming units before and after exposure to light.
Illumination with white light, 120 J/cm(2), caused a reduction of 62%, 83%, and 56% in the colony count of E. coli 1313, S. aureus 195 and S. marcescens, respectively, though no reduction in the viability of P. aeruginosa 1316 was demonstrated. The phototoxic effect was found to involve induction of ROS production by the bacteria. It was also found that illumination of S. aureus 195 and E. coli 1313 in the presence of pyocyanin, known to be secreted by P. aeruginosa, had a stronger bactericidal effect compared to illumination alone.
Visible light at high intensity can kill bacteria in infected wounds. Thus, illumination of infected wounds with intense visible light, prior to low intensity illumination for stimulating wound closure, may reduce infection and promote healing.
Emollients, moisturizers, and keratolytic agents are essential in the topical treatment of psoriasis. They are adjuvants for classic treatments and help to reduce the scale load of individual patients. The major role for emollients and moisturizers is the supportive role in normalizing hyperproliferation, differentiation, and apoptosis; furthermore, they exert anti-inflammatory effects, for example, through physiologic lipids. Subsequently, an improved barrier function and stratum corneum hydration makes the epidermis more resistant to external stressors and reduces the induction of Koebner phenomena. Most of the emollients are lipid-rich (sometimes oily). The keratolytic agents, especially salicylic acid, and higher concentration of urea should be used in the initial keratolytic phase, whereas moisturizing products and emollients are especially suitable in the intermediate phase and the chronic/remission phase of psoriasis. They should be combined with bath oils.
Exposure of normal skin to visible light (400-700 nm) resulted in the induction of immediate pigment darkening (IPD), immediate erythema and a persistent (delayed) tanning reaction. The intensity of pigmentation and time course of the reaction were monitored by measuring chromaticity coordinates. Both IPD and immediate erythema faded over a 24-h period but, unlike erythema, the pigmentation did not totally disappear and the residual tanning response remained unchanged for the rest of the 10-day observation period. The threshold dose for IPD with visible light was between 40 and 80 J/cm2, while the threshold dose for "persistent" pigmentation was greater than or equal to 80 J/cm2.
We find a dramatic difference in the efficiency of removal of UV-induced pyrimidine dimers from the transcribed and nontranscribed strands of the dihydrofolate reductase (DHFR) gene in cultured hamster and human cells. In hamster cells, 80% of the dimers are removed from the transcribed strand in 4 hr, but little repair occurs in the nontranscribed strand even after 24 hr. In human cells, repair is significantly faster in the transcribed strand than in the other strand. Furthermore, in the 5' flanking region of the human DHFR gene, selective rapid repair occurs in the opposite DNA strand relative to the transcribed strand of the DHFR gene. This strand is thought to serve as a template for transcription of a divergent transcript. These results have important implications for excision repair pathways and mutagenesis in mammalian cells.
—Propionibacterium acnes (P. acnes), grown on Eagles medium with different pH. were irradiated with monochromatic light in the range 320 to 440 nm. Different pH leads to different porphyrin concentrations in the cells. The light sensitivity of the bacteria was estimated from the reduction in their ability to form colonies after radiation. The sensitivity was highest for the lowest wavelength (320 nm). and decreased continuously with increasing wavelength up to 380 nm. In the region between 380 and 440 nm there was a second maximum (at 415 nm) which corresponds to the maximum absorption ol the fluorescing porphyrins in P. acnes. The sensitivity to 415 nm light was found to be dependent on the endogenous porphyrin concentration in the cells. while the sensitivity to 320 nm radiation was independent of the amount of porphyrin present. These results indicate that porphyrins produced by the bacteria are important for the light sensitivity of these bacteria.
An integrated review of the transfer of optical radiation into human skin is presented, aimed at developing useful models for photomedicine. The component chromophores of epidermis and stratum corneum in general determine the attenuation of radiation in these layers, moreso than does optical scattering. Epidermal thickness and melanization are important factors for UV wavelengths less than 300 nm, whereas the attenuation of UVA (320-400 nm) and visible radiation is primarily via melanin. The selective penetration of all optical wavelengths into psoriatic skin can be maximized by application of clear lipophilic liquids, which decrease regular reflectance by a refractive-index matching mechanism. Sensitivity to wavelengths less than 320 nm can be enhanced by prolonged aqueous bathing, which extracts urocanic acid and other diffusible epidermal chromophores. Optical properties of the dermis are modelled using the Kubelka-Munk approach, and calculations of scattering and absorption coefficients are presented. This simple approach allows estimates of the penetration of radiation in vivo using noninvasive measurements of cutaneous spectral remittance (diffuse reflectance). Although the blood chromophores Hb, HbO2, and bilirubin determine dermal absorption of wavelengths longer than 320 nm, scattering by collagen fibers largely determines the depths to which these wavelengths penetrate the dermis, and profoundly modifies skin colors. An optical "window" exists between 600 and 1300 nm, which offers the possibility of treating large tissue volumes with certain long-wavelength photosensitizers. Moreover, whenever photosensitized action spectra extend across the near UV and/or visible spectrum, judicious choice of wavelengths allows some selection of the tissue layers directly affected.
Squamous cell carcinoma of the skin (SCC) can progress by stages: sun-damaged epidermis, with individual disordered keratinocytes; actinic keratosis (AK), spontaneously regressing keratinized patches having aberrant cell differentiation and proliferation; carcinoma in situ; SCC and metastasis. To understand how sunlight acts as a carcinogen, we determined the stage at which sunlight mutates the p53 tumour-suppressor gene and identified a function for p53 in skin. The p53 mutations induced by ultraviolet radiation and found in > 90% of human SCCs were present in AKs. Inactivating p53 in mouse skin reduced the appearance of sunburn cells, apoptotic keratinocytes generated by overexposure to ultraviolet. Skin thus appears to possess a p53-dependent 'guardian-of-the-tissue' response to DNA damage which aborts precancerous cells. If this response is reduced in a single cell by a prior p53 mutation, sunburn can select for clonal expansion of the p53-mutated cell into the AK. Sunlight can act twice: as tumour initiator and tumour promoter.
DNA damage induced by UV radiation and visible light (290-500 nm) in AS52 Chinese hamster cells was analysed by an alkaline elution assay with specific repair endonucleases. Cells were exposed to extensively filtered monochrome or broad-band radiation. Between 290 and 315 nm, the ratio of base modifications sensitive to Fpg protein (i.e. 8-hydroxyguanine and formamidopyrimidines) and T4 endonuclease V (i.e. cyclobutane pyrimidine dimers) was constant (approximately 1:200), indicating that the direct excitation of DNA is responsible for both types of damage in this range of the spectrum. While the yield of pyrimidine dimers per unit dose continued to decrease exponentially beyond 315 nm, the yield of Fpg-sensitive modifications increased to a second maximum between 400 and 450 nm. The damage spectrum in this wavelength range consisted of only a few other modifications (strand breaks, abasic sites and pyrimidine modifications sensitive to endonuclease III) and is attributed to endogenous photosensitizers that give rise to oxidative DNA damage via singlet oxygen and/or type I reactions. The generation of Fpg-sensitive modifications by visible light was not linear with dose but followed a saturation curve. It is calculated that the exposure of the cells to low doses of solar radiation results in the formation of cyclobutane pyrimidine dimers and Fpg-sensitive modifications in a ratio of 10:1.
The narrow-band UVB (TL01) lamp (311 nm emission) was developed for use in phototherapy, as an alternative to a broad-band UVB source and to photochemotherapy, both of which have significant side effects and carry a risk of carcinogenesis. This new lamp has proved to be particularly effective at clearing psoriasis. It is now acknowledged that the TL01 lamp is probably 2-3 times more carcinogenic per minimum erythema dose than broad-band UVB, but the cumulative dose required in therapy is considerably less than when using broad-band UVB sources. In terms of irradiation dose, the TL01 lamp is about 5-10-fold less potent than broad-band UVB for erythema induction, hyperplasia, oedema, sunburn cell formation and Langerhans cell depletion from skin. However, the broad-band UVB to TL01 potency ratio for cis-urocanic acid formation in the skin is approximately unity. In addition, the TL01 lamp, as used in phototherapy, has relatively more suppressive effects than broad-band UVB on systemic immune responses as judged by natural killer cell activity, lymphoproliferation and cytokine responses. However, the TL01 lamp is less effective at reducing epidermal antigen presentation, inducing dendritic cell migration to lymph nodes draining irradiated sites and suppressing contact hypersensitivity at the doses tested. Therefore the use of the TL01 lamp in phototherapy should be considered carefully after weighing up its diverse effects on the skin and immune system.
Long-term exposure to ultraviolet irradiation from sunlight causes premature skin aging (photoaging), characterized in part by wrinkles, altered pigmentation, and loss of skin tone. Photoaged skin displays prominent alterations in the collagenous extracellular matrix of connective tissue. We investigated the role of matrix-degrading metalloproteinases, a family of proteolytic enzymes, as mediators of collagen damage in photoaging.
We studied 59 whites (33 men and 26 women, ranging in age from 21 to 58 years) with light-to-moderate skin pigmentation, none of whom had current or prior skin disease. Only some of the participants were included in each of the studies. We irradiated their buttock skin with fluorescent ultraviolet lights under standard conditions and obtained skin samples from irradiated and nonirradiated areas by keratome or punch biopsy. In some studies, tretinoin and its vehicle were applied to skin under occlusion 48 hours before ultraviolet irradiation. The expression of matrix metalloproteinases was determined by in situ hybridization, immunohistology, and in situ zymography. Irradiation-induced degradation of skin collagen was measured by radioimmunoassay of soluble cross-linked telopeptides. The protein level of tissue inhibitor of matrix metalloproteinases type 1 was determined by Western blot analysis.
A single exposure to ultraviolet irradiation increased the expression of three matrix metalloproteinases -- collagenase, a 92-kd gelatinase, and stromelysin -- in skin connective tissue and outer skin layers, as compared with nonirradiated skin. The degradation of endogenous type I collagen fibrils was increased by 58 percent in irradiated skin, as compared with nonirradiated skin. Collagenase and gelatinase activity remained maximally elevated (4.4 and 2.3 times, respectively) for seven days with four exposures to ultraviolet irradiation, delivered at two-day intervals, as compared with base-line levels. Pretreatment of skin with tretinoin (all-trans-retinoic acid) inhibited the induction of matrix metalloproteinase proteins and activity (by 70 to 80 percent) in both connective tissue and outer layers of irradiated skin. Ultraviolet irradiation also induced tissue inhibitor of matrix metalloproteinases-1, which regulates the enzyme. Induction of the inhibitor was not affected by tretinoin.
Multiple exposures to ultraviolet irradiation lead to sustained elevations of matrix metalloproteinases that degrade skin collagen and may contribute to photoaging. Treatment with topical tretinoin inhibits irradiation-induced matrix metalloproteinases but not their endogenous inhibitor.
We have investigated the clinical response of 22 patients with plaque psoriasis to photodynamic therapy using topical application of 5-aminolaevulinic acid followed by a single exposure to broad-band visible radiation. Light doses in the range 2-16 J/cm2 delivered at dose of 10-40 mW/ cm2 resulted in a variable clinical response. Seven (35%) patients showed clearing of psoriasis at some treated sites. The intensity of protoporphyrin IX fluorescence was recorded before, during and after treatment. Pre-illumination fluorescence intensity varied considerably between sites on the same patient and between patients. Protoporphyrin IX fluorescence recovered and persisted after treatment for up to 14 days and became higher than preillumination levels at 25% of sites. The rate of protoporphyrin IX photo-oxidation during treatment was proportional to both initial fluorescence intensity and incident light dose rate and was almost complete after 16 J/cm2. We have defined the photodynamic dose as the product of time-dependent protoporphyrin IX concentration and light dose and demonstrated that only in those patients who showed clearance of psoriasis was there a relationship between photodynamic dose and clinical response. Discomfort ranged from stinging through to burning, was significant in some patients and tended to be more severe with increasing photodynamic dose but was not predictable. Efficacy may improve by achieving consistent protoporphyrin IX levels or by using multiple treatments.
Several mechanisms are likely to be involved in the solar radiation-mediated modifications of cellular DNA. Direct excitation of DNA bases by the UVB component (290-320 nm) of solar light gives rise, mostly through oxygen independent reactions, to the formation of dimeric pyrimidine lesions including cyclobutadipyrimidines, pyrimidine (6-4) pyrimidone photoproducts and related valence Dewar isomers. In addition, photoexcitation of cytosine and guanine may lead to the formation in relatively minor yields of 6-hydroxy-5,6-dihydrocytosine and 8-oxo-7,8-dihydroguanine, respectively. A second mechanism that requires the participation of endogenous photosensitizers together with oxygen is at the origin of most of the DNA damage generated by the UVA (320-400 nm) and visible light. Singlet oxygen, which arises from a type II mechanism, is likely to be mostly involved in the formation of 8-oxo-7,8-dihydroguanine that was observed within both isolated and cellular DNA. However, it may be expected that the latter oxidized purine lesion together with DNA strand breaks and pyrimidine base oxidation products are also generated with a lower efficiency through Fenton type reactions. A more definitive assessment of these mechanisms would require further studies aimed at the identification and quantification of the different DNA photolesions including both dimeric pyrimidine photoproducts and photooxidized lesions.
Understanding the mechanisms responsible for photodamage to the skin is most important for dermatology. 3-D cultures have been used as tools to mimic the in vivo situation for several years. We irradiated such a system containing human dermal fibroblasts cultured in collagen gels, a well-known model considered to be a dermal equivalent, which reproduces the interaction between cells and the surrounding extracellular matrix. The effects of solar irradiation (315-800 nm) on the steady-state levels of the mRNAs of extracellular matrix components (type I and III collagens) and their degrading enzymes (interstitial collagenase, MMP-1 and stromelysin 1, MMP-3) were measured. Exposure to low levels of solar radiation (0-10 J cm-2 in the UVA, i.e. suberythemal UVA doses) caused a transient decrease in type I procollagen mRNA, an increase in MMP-mRNA, and no change in type III procollagen mRNA steady-state levels. These results describe the early changes in the connective tissue of the skin following exposure to low-level solar stimulation, and may help explain the long-term changes in photodamaged skin.
In evaluating the autofluorescence properties of normal and diseased skin we discovered that psoriatic plaques can emit a distinct red fluorescence when illuminated with UVA or blue light. Using a macrospectrofluorometer equipped with a 442 nm excitation laser, a sharp in vivo fluorescence emission peak around 635 nm could be demonstrated within the plaques of 34 of 75 (45%) patients with psoriasis. This peak was absent from normal appearing skin of psoriatic patients and also from the skin of 66 patients with other dermatologic diseases. A microspectrofluorometer coupled with the same excitation laser was used to obtain emission spectra of separated epidermal sheets and dermis from plaques demonstrating macroscopic red autofluorescence. An emission peak around 635 nm was observed in all three patients thus studied, but only on spectra obtained from the epidermis. Additional spectra of vertical microscopic sections of intact psoriatic skin from five other patients revealed that the peak originated from the stratum corneum. Emission spectra from other microlocations including the mid-epidermis and dermis of psoriatic and normal skin, as well as the stratum corneum of normal skin, failed to demonstrate a 635 nm peak. The excitation and emission fluorescence spectra of acid extracts of psoriatic scale from five patients were all similar to those of protoporphyrin IX in acid solution. High performance liquid chromatography identified the presence of protoporphyrin IX in the acid extracts from psoriatic scale of the same patients. We conclude that native psoriatic plaques can exhibit red autofluorescence that is due to elevated levels of protoporphyrin IX within scales.
In 1998 it is appropriate to commemorate the 50th anniversary of el Mofty's use of purified 8-methoxypsoralen (8-MOP) in the treatment of vitiligo (el Mofty AM. A preliminary clinical report on the treatment of leukoderma with Ammi majus linn. J R Egypt Med Assn 1948,31:651 65. el Mofty AM, el Sawalhy H, el Mofty M. Clinical study of a new preparation of 8-methoxypsoralen in photochemotherapy. Int J Dermatol 1994;8:588 92). Two young American dermatologists (Aaron Lerner and Thomas Fitzpatrick) were intrigued by the potency of this material. After Lerner determined that artificial long wavelength ultraviolet (320-400 nm, UVA) radiation was the most efficient for activating 8-MOP. the development of artificial sources enabled the efficient delivery of these photons to skin containing 8-MOP. Their initial studies for vitiligo led to further development of this therapy for the treatment of psoriasis (Parrish JA, Fitzpatrick TB, Tannenbaum L, et al. Photochemotherapy of psoriasis with oral methoxsalen and long-wave ultraviolet light. New Engl J Med 1974;291:1207-11. Honigsmann H, Fitzpatrick TB, Pathak MA, et al. Oral photochemotherapy with psoralen and UVA (PUVA): principles and practice. In: Fitzpatrick TB, Eisen AZ, Wolf K, editors. Dermatology in General Medicine. New York: McGraw-Hill, 1987:1728-54). This photochemotherapy came to be called 'PUVA' (psoralen + UVA). The position PUVA holds today as one of the most common procedures performed in dermatology can be traced to their initial curiosity and their subsequent ingenuity. Further developments in more recent years capitalized on their seminal work. The therapy met with unprecedented success from the outset, leaving little perceived need to understand underlying science. However, in recent years there has been a new found interest in the basic aspects of psoralen photobiology and molecular mechanistic events contributing to therapeutic responses as well as to the development of skin cancers in PUVA patients. These will be surveyed in this review commemorating the 50 years of modern psoralen photobiology and photomedicine.
The adverse outcome of increased ultraviolet (UV) irradiation on human health is currently of concern. While many experiments have been carried out in rodent models, fewer have been designed to test the effects of UV exposure in human subjects. This review concentrates on the modulations induced in the human immune system by UV, and outlines changes in antigen presentation by Langerhans cells and macrophages, in the activities of natural killer cells and T cells, and in cytokine regulation. Precautionary measures which might be taken to help protect people against the immunosuppressive action of UV irradiation are considered.
Cytochrome c oxidase is discussed as a possible photoacceptor when cells are irradiated with monochromatic red to near-IR radiation. Four primary action mechanisms are reviewed: changes in the redox properties of the respiratory chain components following photoexcitation of their electronic states, generation of singlet oxygen, localized transient heating of absorbing chromophores, and increased superoxide anion production with subsequent increase in concentration of the product of its dismutation, H2O2. A cascade of reactions connected with alteration in cellular homeostasis parameters (pHi, [Cai], cAMP, Eh, [ATP] and some others) is considered as a photosignal transduction and amplification chain in a cell (secondary mechanisms).
We investigated the clinical response of 10 patients with plaque psoriasis to multiple treatments with photodynamic therapy, using topical application of 5-aminolaevulinic acid followed by exposure to broad-band visible radiation. Treatment was performed up to 3 times per week, with a maximum of 12 treatments, using a light dose of 8 Jcm(-2) delivered at a dose-rate of 15 mW cm(-2). Eight patients showed a clinical response. Out of 19 treated sites, 4 cleared, 10 responded but did not clear and 5 showed no improvement. Of the 4 sites that cleared only 1 did so fully, after 7 treatments, 45 days after the start of therapy. Of the 10 sites that responded partially, the greatest reduction in scale, erythema and induration index occurred after a minimum of 3 and a maximum of 8 treatments. The intensity of 5-aminolaevulinic acid-induced protoporphyrin IX fluorescence, recorded prior to the first treatment, varied between sites on the same patient as well as between patients. There was also a variation in fluorescence intensity recorded from the same site immediately prior to subsequent treatments, although the pretreatment levels generally decreased as the study progressed and then increased as psoriasis relapsed. Biopsies confirmed that fluorescence was localized throughout the epidermis and stratum corneum, but the level was not consistent between sections taken within the same biopsy. We also observed fluorescence at sites distant from the ones that received 5-aminolaevulinic acid, which was not present prior to the start of the treatment programme, but found no evidence of elevated levels of plasma porphyrins. The level of discomfort associated with this therapy increased with increasing values of the calculated photodynamic dose, defined as the product of the initial photosensitizer concentration and the percentage reduction in fluorescence following irradiation. Therefore, although clinical efficacy improved with multiple treatments, unpredictable response and patient discomfort make ALA-PDT unsuitable for the treatment of psoriasis.
Actinic elastosis is characterized by an accumulation of elastotic material in the upper dermis and is considered to be a manifestation of ultraviolet-induced skin aging. To compare the structural components of the elastotic material in actinic elastosis with those in normal skin, skin specimens were stained with antibodies raised against various elastin-related proteins. Elastotic materials exhibited a strong reaction to the antibodies for elastin, microfibril-associated glycoprotein-1 (MAGP-1), MAGP-4, matrix metalloproteinase 1 (MMP-1), MMP-2 and MMP-3, but a diminished reaction to anti-MMP-9 antibody. Fibroblast cell lines from the upper dermis of affected and unaffected skin were established, and the mRNA levels of MMPs were determined. MMP-1 and -2 mRNA levels were found to be elevated approximately twofold in the fibroblasts from actinic elastosis. Since MMP-1 and -2 are considered to be major enzymes involved in the degradation of matrix components, the accumulation of elastotic materials in actinic elastosis may be related to the degradation process.
The effects of low-level laser light irradiation are still highly contested, and the mechanisms of its action still unclear. This study was conducted to test the effects of low-level laser irradiation at 660 nm on human lymphocytes and to investigate the possible mechanisms by which these effects are produced.
Whole blood obtained by phlebotomy was irradiated at 660 nm by using energy fluences between 0 and 5.0 J/cm(2). The lymphocytes were isolated after irradiation of the whole blood. For the control experiment, the lymphocytes were first isolated and then irradiated at the same wavelength and energy fluence for comparison. The proliferation of lymphocytes and the formation of free radicals and lipid peroxides were monitored. Hemoglobin was also irradiated in a cell-free environment to test for the production of lipid peroxides.
Lymphocyte proliferation was significantly higher (P<0.05) as expressed by a Stimulation Index in samples irradiated in the presence of whole blood compared with lymphocytes irradiated after isolation from whole blood. Free radical and lipid peroxide production also increased significantly when samples were irradiated in the presence of red blood cells.
The present study supports the hypothesis that one mechanism for the photobiostimulation effect after irradiation at 660 nm is the reaction of light with hemoglobin, resulting in oxygen radical production.
Chronic sun exposure causes photoaging of human skin, a process that is characterized by clinical, histological and biochemical changes which differ from alterations in chronologically aged but sun-protected skin. Within recent years, substantial progress has been made in unraveling the underlying mechanisms of photoaging. Induction of matrix metalloproteinases as a consequence of activator protein (AP)-1 and nuclear factor (NF)-KB activation as well as mutations of mitochondrial DNA have been identified recently. This has increased our understanding of photoaging significantly and has led to new prophylactic and therapeutic strategies aimed at the prevention and repair of the detrimental effects of chronic sun-exposure on the skin.