Enzyme plus light therapy to repair DNA damage in ultraviolet-B-irradiated human skin

Sunscreens: Updates on Sunscreen Filters and Formulations

BACKGROUND/PURPOSE

Sunscreens are a critical component of photoprotection, shielding the skin from the harmful effects of solar radiation. However, current sunscreens have limitations, including insufficient filters with long-wavelength ultraviolet A (UVA) and visible light (VL) coverage. This review briefly discusses the mechanisms of sunscreen filters, newly developed filters that improve broad-spectrum protection, and examines recent advances in sunscreen formulations that enhance efficacy.

METHODS

A targeted literature review was conducted using databases such as Pubmed to identify recent studies published on advancements in sunscreen filters.

RESULTS

Recent developments include novel filters with extended UVA and VL coverage. Additives such as antioxidants and anti-inflammatory agents are also being integrated to bolster skin protection.

CONCLUSION

Although traditional sunscreens have limitations, ongoing innovations in filter development and formulation science are progressively addressing existing gaps in photoprotection.

Variation in ultraviolet-B (UV-B)-induced DNA damage repair mechanisms in plants and humans: an avenue for developing protection against skin photoaging

PURPOSE

The increasing amounts of ultraviolet-B (UV-B) light in our surroundings have sparked worries about the possible effects on humans and plants. The detrimental effects of heightened UV-B exposure on these two vital elements of terrestrial life are different due to their unique and concurrent nature. Understanding common vulnerabilities and distinctive adaptations of UV-B radiation by exploring the physiological and biochemical responses of plants and the effects on human health is of huge importance. The comparative effects of UV-B radiation on plants and animals, however, are poorly studied. This review sheds light on the sophisticated web of UV-B radiation effects by navigating the complex interaction between botanical and medical perspectives, drawing upon current findings.

CONCLUSION

By providing a comprehensive understanding of the complex effects of heightened UV-B radiation on plants and humans, this study summarizes relevant adaptation strategies to the heightened UV-B radiation stress, which offer new approaches for improving human cellular resilience to environmental stressors.

Understanding Active Photoprotection: DNA-Repair Enzymes and Antioxidants

The detrimental effects of ultraviolet radiation (UVR) on human skin are well-documented, encompassing DNA damage, oxidative stress, and an increased risk of carcinogenesis. Conventional photoprotective measures predominantly rely on filters, which scatter or absorb UV radiation, yet fail to address the cellular damage incurred post-exposure. To fill this gap, antioxidant molecules and DNA-repair enzymes have been extensively researched, offering a paradigm shift towards active photoprotection capable of both preventing and reversing UV-induced damage. In the current review, we focused on "active photoprotection", assessing the state-of-the-art, latest advancements and scientific data from clinical trials and in vivo models concerning the use of DNA-repair enzymes and naturally occurring antioxidant molecules.

A recombinant fungal photolyase autonomously enters human cell nuclei to fix UV-induced DNA lesions

Solar ultraviolet radiations induced DNA damages in human skin cells with cyclobutane pyrimidine dimers (CPD) and (6-4) photoproducts (6-4PPs) as the most frequent lesions. CPDs are repaired much slower than 6-4PPs by the nucleotide excision repair pathway, which are thus the major lesions that interfere with key cellular processes and give rise to gene mutations, possibly resulting in skin cancer. In prokaryotes and multicellular eukaryotes other than placental mammals, CPDs can be rapidly repaired by CPD photolyases in one simple enzymatic reaction using the energy of blue light. In this study, we aim to construct recombinant CPD photolyases that can autonomously enter human cell nuclei to fix UV-induced CPDs. A fly cell penetration peptide and a viral nucleus localization signal peptide were recombined with a fungal CPD photolyase to construct a recombinant protein. This engineered CPD photolyase autonomously crosses cytoplasm and nuclear membrane of human cell nuclei, which then efficiently photo-repairs UV-induced CPD lesions in the genomic DNA. This further protects the cells by increasing SOD activity, and decreasing cellular ROSs, malondialdehyde and apoptosis.

Enzymes for dermatological use

Skin is the ultimate barrier between body and environment and prevents water loss and penetration of pathogens and toxins. Internal and external stressors, such as ultraviolet radiation (UVR), can damage skin integrity and lead to disorders. Therefore, skin health and skin ageing are important concerns and increased research from cosmetic and pharmaceutical sectors aims to improve skin conditions and provide new anti-ageing treatments. Biomolecules, compared to low molecular weight drugs and cosmetic ingredients, can offer high levels of specificity. Topically applied enzymes have been investigated to treat the adverse effects of sunlight, pollution and other external agents. Enzymes, with a diverse range of targets, present potential for dermatological use such as antioxidant enzymes, proteases and repairing enzymes. In this review, we discuss enzymes for dermatological applications and the challenges associated in this growing field.

Recombinant production of a highly efficient photolyase from Thermus thermophilus

Ultraviolet (UV) radiation from sunlight can damage DNA, inducing mutagenesis and eventually leading to skin cancer. Topical sunscreens are used to avoid the effect of UV irradiation, but the topical application of DNA repair enzymes, such as photolyase, can provide active photoprotection by DNA recovery. Here we produced a recombinant Thermus thermophilus photolyase expressed in Escherichia coli, evaluated the kinetic parameters of bacterial growth and the kinetics and stability of the enzyme. The maximum biomass (𝑋𝑚𝑎𝑥 ) of 2.0 g L-1 was reached after 5 h of cultivation, corresponding to 𝑃X  = 0.4 g L-1 h. The µ𝑚𝑎𝑥 corresponded to 1.0 h-1 . Photolyase was purified by affinity chromatography and high amounts of pure enzyme were obtained (3.25 mg L-1 of cultivation). Two different methods demonstrated the enzyme activity on DNA samples and very low enzyme concentrations, such as 15 µg mL-1 , already resulted in 90% of CPD photodamage removal. We also determined photolyase kM of 9.5 nM, confirming the potential of the enzyme at very low concentrations, and demonstrated conservation of enzyme activity after freezing (-20°C) and lyophilization. Therefore, we demonstrate T. thermophilus photolyase capacity of CPD damage repair and its potential as an active ingredient to be incorporated in dermatological products.

The Immune Microenvironment in Basal Cell Carcinoma

The immune system plays a key role in the suppression and progression of basal cell carcinoma (BCC). The primary aetiological factor for BCC development is exposure to ultraviolet radiation (UVR) which, particularly in lighter Fitzpatrick skin types, leads to the accumulation of DNA damage. UVR has roles in the generation of an immunosuppressive environment, facilitating cancer progression. Rates of BCC are elevated in immunosuppressed patients, and BCC may undergo spontaneous immune-mediated regression. Histologic and immunohistochemical profiling of BCCs consistently demonstrates the presence of an immune infiltrate and associated immune proteins. Early studies of immune checkpoint inhibitors reveal promising results in BCC. Therefore, the host immune system and tumor responses to it are important in BCC pathogenesis. Understanding these interactions will be beneficial for disease prognostication and therapeutic decisions.

Short-Term UVB Irradiation Leads to Persistent DNA Damage in Limbal Epithelial Stem Cells, Partially Reversed by DNA Repairing Enzymes

The cornea is frequently exposed to ultraviolet (UV) radiation and absorbs a portion of this radiation. UVB in particular is absorbed by the cornea and will principally damage the topmost layer of the cornea, the epithelium. Epidemiological research shows that the UV damage of DNA is a contributing factor to corneal diseases such as pterygium. There are two main DNA photolesions of UV: cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4) photoproducts (6-4PPs). Both involve the abnormal linking of adjacent pyrimide bases. In particular, CPD lesions, which account for the vast majority of UV-induced lesions, are inefficiently repaired by nucleotide excision repair (NER) and are thus mutagenic and linked to cancer development in humans. Here, we apply two exogenous enzymes: CPD photolyase (CPDPL) and T4 endonuclease V (T4N5). The efficacy of these enzymes was assayed by the proteomic and immunofluorescence measurements of UVB-induced CPDs before and after treatment. The results showed that CPDs can be rapidly repaired by T4N5 in cell cultures. The usage of CPDPL and T4N5 in ex vivo eyes revealed that CPD lesions persist in the corneal limbus. The proteomic analysis of the T4N5-treated cells shows increases in the components of the angiogenic and inflammatory systems. We conclude that T4N5 and CPDPL show great promise in the treatment of CPD lesions, but the complete clearance of CPDs from the limbus remains a challenge.

Preparation of CPD Photolyase Nanoliposomes Derived from Antarctic Microalgae and Their Effect on UVB-Induced Skin Damage in Mice

UVB radiation is known to trigger the block of DNA replication and transcription by forming cyclobutane pyrimidine dimer (CPD), which results in severe skin damage. CPD photolyase, a kind of DNA repair enzyme, can efficiently repair CPDs that are absent in humans and mice. Although exogenous CPD photolyases have beneficial effects on skin diseases, the mechanisms of CPD photolyases on the skin remain unknown. Here, this study prepared CPD photolyase nanoliposomes (CPDNL) from Antarctic Chlamydomonas sp. ICE-L, which thrives in harsh, high-UVB conditions, and evaluated their protective mechanisms against UVB-induced damage in mice. CPDNL were optimized using response surface methodology, characterized by a mean particle size of 105.5 nm, with an encapsulation efficiency of 63.3%. Topical application of CPDNL prevented UVB-induced erythema, epidermal thickness, and wrinkles in mice. CPDNL mitigated UVB-induced DNA damage by significantly decreasing the CPD concentration. CPDNL exhibited antioxidant properties as they reduced the production of reactive oxygen species (ROS) and malondialdehyde. Through activation of the NF-κB pathway, CPDNL reduced the expression of pro-inflammatory cytokines including IL-6, TNF-α, and COX-2. Furthermore, CPDNL suppressed the MAPK signaling activation by downregulating the mRNA and protein expression of ERK, JNK, and p38 as well as AP-1. The MMP-1 and MMP-2 expressions were also remarkably decreased, which inhibited the collagen degradation. Therefore, we concluded that CPDNL exerted DNA repair, antioxidant, anti-inflammation, and anti-wrinkle properties as well as collagen protection via regulation of the NF-κB/MAPK/MMP signaling pathways in UVB-induced mice, demonstrating that Antarctic CPD photolyases have the potential for skincare products against UVB and photoaging.

Photo-repair effect of a bacterial Antarctic CPD-photolyase on UVC-induced DNA lesions in human keratinocytes

Exposure to ultraviolet radiation from sunlight induces oxidative DNA lesions and bipyrimidine photoproducts that can lead to photo-aging and skin carcinogenesis. CPD-photolyases are flavoproteins that repair cyclobutane pyrimidine dimers using blue light as an energy source. In the present work, we evaluated the photo-repair effect of the recombinant CPD-photolyase PhrAHym from the Antarctic bacterium Hymenobacter sp. UV11 on DNA lesions in human keratinocytes induced by UVC light. By performing immunochemistry assays we observed that PhrAHym repairs in a highly efficient way the CPD-photoproducts and reduces the γH2AX formation. Since this enzyme is non-cytotoxic and repairs UVC-induced DNA lesions in human keratinocytes, we propose that PhrAHym could be used as a biotherapeutic agent against UV-induced skin cancer, photoaging, and related diseases.

The Double-Edged Sword of Oxidative Stress in Skin Damage and Melanoma: From Physiopathology to Therapeutical Approaches

The skin is constantly exposed to exogenous and endogenous sources of reactive oxygen species (ROS). An adequate balance between ROS levels and antioxidant defenses is necessary for the optimal cell and tissue functions, especially for the skin, since it must face additional ROS sources that do not affect other tissues, including UV radiation. Melanocytes are more exposed to oxidative stress than other cells, also due to the melanin production process, which itself contributes to generating ROS. There is an increasing amount of evidence that oxidative stress may play a role in many skin diseases, including melanoma, being the primary cause or being a cofactor that aggravates the primary condition. Indeed, oxidative stress is emerging as another major force involved in all the phases of melanoma development, not only in the arising of the malignancy but also in the progression toward the metastatic phenotype. Furthermore, oxidative stress seems to play a role also in chemoresistance and thus has become a target for therapy. In this review, we discuss the existing knowledge on oxidative stress in the skin, examining sources and defenses, giving particular consideration to melanocytes. Therefore, we focus on the significance of oxidative stress in melanoma, thus analyzing the possibility to exploit the induction of oxidative stress as a therapeutic strategy to improve the effectiveness of therapeutic management of melanoma.

The Aryl Hydrocarbon Receptor in the Pathogenesis of Environmentally-Induced Squamous Cell Carcinomas of the Skin

Cutaneous squamous cell carcinoma (SCC) is one of the most frequent malignancies in humans and academia as well as public authorities expect a further increase of its incidence in the next years. The major risk factor for the development of SCC of the general population is the repeated and unprotected exposure to ultraviolet (UV) radiation. Another important risk factor, in particular with regards to occupational settings, is the chronic exposure to polycyclic aromatic hydrocarbons (PAH) which are formed during incomplete combustion of organic material and thus can be found in coal tar, creosote, bitumen and related working materials. Importantly, both exposomal factors unleash their carcinogenic potential, at least to some extent, by activating the aryl hydrocarbon receptor (AHR). The AHR is a ligand-dependent transcription factor and key regulator in xenobiotic metabolism and immunity. The AHR is expressed in all cutaneous cell-types investigated so far and maintains skin integrity. We and others have reported that in response to a chronic exposure to environmental stressors, in particular UV radiation and PAHs, an activation of AHR and downstream signaling pathways critically contributes to the development of SCC. Here, we summarize the current knowledge about AHR's role in skin carcinogenesis and focus on its impact on defense mechanisms, such as DNA repair, apoptosis and anti-tumor immune responses. In addition, we discuss the possible consequences of a simultaneous exposure to different AHR-stimulating environmental factors for the development of cutaneous SCC.

[Sunscreens of the future: challenges and opportunities]

Sunscreens provide excellent protection against erythema and against chronic damage such as photoaging and skin cancer. Today's challenges concern safety of the products and improved methods for standardizing the evaluation of their efficacy. Other important topics are the further development of sunscreen products, as well as personalization of use. Personalized sun protection based on the phenotype, the genetic profiles and moreover the skin's microbiome - all linked to the identification of certain consumer susceptibility factors - is an exciting new area of research. In particular, the expansion with innovative topical agents such as DNA repair liposomes in improved galenic formulations with UV filters tailored to the skin phototype and new topical antioxidants could in future provide even more comprehensive sun protection. New antioxidants and other agents such as nicotinamide could increase systemic photoprevention. Sustainability will also be an important aspect to protect consumers, but also the environment (i.e. especially marine wildlife) from toxic effects of sunscreens.

UV Protection in the Cornea: Failure and Rescue

Simple Summary

The sun is a deadly laser, and its damaging rays harm exposed tissues such as our skin and eyes. The skin’s protection and repair mechanisms are well understood and utilized in therapeutic approaches while the eye lacks such complete understanding of its defenses and therefore often lacks therapeutic support in most cases. The aim here was to document the similarities and differences between the two tissues as well as understand where current research stands on ocular, particularly corneal, ultraviolet protection. The objective is to identify what mechanisms may be best suited for future investigation and valuable therapeutic approaches.

Abstract

Ultraviolet (UV) irradiation induces DNA lesions in all directly exposed tissues. In the human body, two tissues are chronically exposed to UV: the skin and the cornea. The most frequent UV-induced DNA lesions are cyclobutane pyrimidine dimers (CPDs) that can lead to apoptosis or induce tumorigenesis. Lacking the protective pigmentation of the skin, the transparent cornea is particularly dependent on nucleotide excision repair (NER) to remove UV-induced DNA lesions. The DNA damage response also triggers intracellular autophagy mechanisms to remove damaged material in the cornea; these mechanisms are poorly understood despite their noted involvement in UV-related diseases. Therapeutic solutions involving xenogenic DNA-repair enzymes such as T4 endonuclease V or photolyases exist and are widely distributed for dermatological use. The corneal field lacks a similar set of tools to address DNA-lesions in photovulnerable patients, such as those with genetic disorders or recently transplanted tissue.

PHOTOPROTECTION FOR ALL: CURRENT GAPS AND OPPORTUNITIES

The effects of solar radiation on human skin differ based on skin phototype, the presence or absence of photodermatoses, biological capacity to repair DNA damage, wavelength, intensity of sun exposure, geographic latitude, and other factors, underscoring the need for a more tailored approach to photoprotection. To date, the focus of photoprotection guidelines has been to prevent sunburn and DNA damage induced by ultraviolet (UV) radiation, both UVB and UVA; however, several recent studies have shown that visible light (VL) also generates reactive oxygen and nitrogen species that can contribute to skin damage and pigmentation on the skin, particularly in people of color. Therefore, dark-skinned individuals, while naturally better protected against UVB radiation by virtue of high eumelanin content in melanocytes, may need additional protection from VL-induced skin damage. The current options for photoprotection products need to expand, and potential strategies against VL include the addition of iron oxide, titanium dioxide, and biologically relevant antioxidants to sunscreen formulations, as well as supplementation with orally active antioxidants.

UV Radiation in DNA Damage and Repair Involving DNA-Photolyases and Cryptochromes

Prolonged exposure to ultraviolet radiation on human skin can lead to mutations in DNA, photoaging, suppression of the immune system, and other damage up to skin cancer (melanoma, basal cell, and squamous cell carcinoma). We reviewed the state of knowledge of the damaging action of UVB and UVA on DNA, and also the mechanisms of DNA repair with the participation of the DNA-photolyase enzyme or of the nucleotide excision repair (NER) system. In the course of evolution, most mammals lost the possibility of DNA photoreparation due to the disappearance of DNA photolyase genes, but they retained closely related cryptochromes that regulate the transcription of the NER system enzymes. We analyze the published relationships between DNA photolyases/cryptochromes and carcinogenesis, as well as their possible role in the prevention and treatment of diseases caused by UV radiation.

Reducing non-melanoma skin cancer risk in renal transplant recipients

With an increasing number of renal transplant recipients (RTRs) and improving patient survival, a higher incidence of non-melanoma skin cancer (NMSC) has been observed. NMSC in RTRs are often more numerous and biologically more aggressive than the general population, thus contributing towards an increase in morbidity and to a lesser degree, mortality. The resultant cumulative health and financial burden is a recognized concern. Proposed strategies in mitigating risks of developing NMSC and early therapeutic options thereof include tailored modification of immunosuppressants in conjunction with sun protection in all transplant patients. This review highlights the clinical and financial burden of transplant-associated skin cancers, carcinogenic mechanisms in association with immunosuppression, importance of skin cancer awareness campaign and integrated transplant skin clinic, and the potential role of chemoprotective agents. A scheme is proposed for primary and secondary prevention of NMSC based on the available evidence.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Challenging Cosmetic Innovation: The Skin Microbiota and Probiotics Protect the Skin from UV-Induced Damage

Many studies performed in the last decade have focused on the cutaneous microbiota. It has been shown that this microbiota plays a key role in skin homeostasis. Considered as “a second barrier” to the environment, it is very important to know how it reacts to exogenous aggressions. The cosmetics industry has a started to use this microbiota as a source of natural ingredients, particularly ones that confer photoprotection against ultraviolet (UV) rays. Interestingly, it has been demonstrated that bacterial molecules can block UV rays or reverse their harmful effects. Oral probiotics containing living microorganisms have also shown promising results in restoring skin homeostasis and reversing the negative effects of UV rays. Microbial-based active sunscreen compounds have huge potential for use as next-generation photoprotection products.

DNA photolyase from Antarctic marine bacterium Rhodococcus sp. NJ-530 can repair DNA damage caused by ultraviolet

Marine bacterium Rhodococcus sp. NJ-530 has developed several ultraviolet (UV) adaptive characteristics for survival and growth in extreme Antarctic environment. Rhodococcus sp. NJ-530 DNA photolyase encoded by a 1146 bp photolyase-homologous region (phr) was identified in genome. Quantitative real-time PCR demonstrated that transcriptional levels of phr were highly up-regulated by ultraviolet-B (UV-B) radiation (90 μW·cm^-2) and increased to a maximum of 149.17-fold after exposure for 20 min. According to the results of SDS-PAGE and western blot, PHR was effectively induced by isopropyl-β-d-1-thiogalactopyranoside (IPTG) at the genetically engineered BL21(DE3)-pET-32a( +)-phr construct under the condition of 15 °C for 16 h and 37 °C for 4 h. In terms of in vivo activity, compared with a phr-defective E. coli strain, phr-transformed E. coli exhibited higher survival rate under high UV-B intensity of 90 μW·cm^-2. Meanwhile, the purified PHR, with blue light, presented obvious photorepair activity toward UV-induced DNA damage in vitro assays. To sum up, studying the mechanisms of Rhodococcus sp. NJ-530 photolyase is of great interest to understand the adaptation of polar bacteria to high UV radiation, and such data present important therapeutic value for further UV-induced human skin and genetic damage diseases.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02660-8.

Focus on UV-Induced DNA Damage and Repair-Disease Relevance and Protective Strategies

The protective ozone layer is continually depleting due to the release of deteriorating environmental pollutants. The diminished ozone layer contributes to excessive exposure of cells to ultraviolet (UV) radiation. This leads to various cellular responses utilized to restore the homeostasis of exposed cells. DNA is the primary chromophore of the cells that absorbs sunlight energy. Exposure of genomic DNA to UV light leads to the formation of multitude of types of damage (depending on wavelength and exposure time) that are removed by effectively working repair pathways. The aim of this review is to summarize current knowledge considering cellular response to UV radiation with special focus on DNA damage and repair and to give a comprehensive insight for new researchers in this field. We also highlight most important future prospects considering application of the progressing knowledge of UV response for the clinical control of diverse pathologies.

DNA repair enzymes in sunscreens and their impact on photoageing-A systematic review

BACKGROUND

DNA damage is one of the main factors responsible for photoageing and is predominantly attributed to ultraviolet irradiation (UV-R). Photoprotection by conventional sunscreens is exclusively prophylactic, and of no value, once DNA damage has occurred. As a result, the demand for DNA repair mechanisms inhibiting, reversing or delaying the pathologic events in UV-exposed skin has sparked research on anti-photoageing and strategies to improve the effect of conventional sunscreens. This review provides an overview of recent developments in DNA repair enzymes used in sunscreens and their impact on photoageing.

METHODS

A systematic review of the literature, up to March 2019, was conducted using the electronic databases, PubMed and Web of Science. Quality assessment was carried out using the Newcastle-Ottawa scale (NOS) to ensure inclusion of adequate quality studies only (NOS > 5).

RESULTS

Out of the 352 publications, 52 were considered relevant to the key question and included in the present review. Two major enzymes were found to play a major role in DNA damage repair in sunscreens: photolyase and T4 endonuclease V. These enzymes are capable of identifying and removing UV-R-induced dimeric photoproducts. Clinical studies revealed that sunscreens with liposome-encapsulated types of photolyase and/or T4 endonuclease V can enhance these repair mechanisms.

CONCLUSION

There is a lack of randomized controlled trials demonstrating the efficacy of DNA repair enzymes on photoageing, or a superiority of sunscreens with DNA repair enzymes compared to conventional sunscreens. Further studies are mandatory to further reveal pathogenic factors of photoageing and possible therapeutic strategies against it.

How It Works: The Immunology Underlying Phototherapy

Phototherapeutic modalities induce apoptosis of keratinocytes and immune cells, impact cytokine production, downregulate the IL-23/Th17 axis, and induce regulatory T cells. As in anti-IL-17 or anti-IL-23 antibody treatment, the dual action of phototherapy on skin and the immune system is likely responsible for sustained resolution of lesions in diseases such as psoriasis. In cutaneous T cell lymphoma, phototherapy may function by causing tumor cell apoptosis and eliminating the neoplastic and inflammatory infiltrate. Further research on phototherapeutic mechanisms will help advance, optimize, and refine dermatologic treatments and may open up novel avenues for treatment strategies in dermatology and beyond.

Pruritus secondary to primary biliary cholangitis: a review of the pathophysiology and management with phototherapy

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune hepatobiliary disorder characterized by destruction of liver bile ducts leading to intrahepatic cholestasis. It causes intractable pruritus for which ultraviolet (UV)B phototherapy is an experimental treatment when alternative therapies fail. The pathophysiology of cholestatic itch and the mechanism of action of narrowband UVB in this condition remains poorly understood.

OBJECTIVES

To summarize the current literature and propose testable hypotheses for the mechanism of action of phototherapy in attenuating itch.

METHODS

A focused PubMed search for articles relating to the pathogenesis of itch in cholestatic disease was performed. A total of 3855 articles were screened and 50 were found suitable for literature review. Evidence from this literature review was combined with author expertise in the area.

RESULTS

Formulated hypotheses focus on the role of bile salts, autotaxin and specific receptors including G-protein-coupled bile acid receptor, Gpbar1 (also known as TGR5) and the nuclear transcription factor farnesoid X receptor.

CONCLUSIONS

Several testable mechanisms through which phototherapy may exert its effects are discussed in this review. The next steps are to carry out an objective assessment of the efficacy of phototherapy in cholestatic pruritus, gain further knowledge on the underlying pathways, and subsequently trial its use against current licensed therapies. Such studies could lead to increased mechanistic understanding, identification of novel therapeutic targets and the potential to refine phototherapy protocols, leading to improved control of itch and quality of life in patients with PBC. What's already known about this topic? Primary biliary cholangitis (PBC) is frequently associated with intractable pruritus for which current treatment options are often unsuccessful. Phototherapy is used as an experimental treatment for PBC-associated pruritus when alternative better-studied treatments fail. What does this study add? This study reviews the current literature on the pathophysiology and management of cholestatic pruritus, an area which remains poorly understood. We propose testable hypotheses of the mechanisms behind the attenuation of cholestatic pruritus with phototherapy.

Role of the Aryl Hydrocarbon Receptor in Environmentally Induced Skin Aging and Skin Carcinogenesis

The skin is constantly exposed to a variety of environmental threats, including solar electromagnetic radiation, microbes, airborne particulate matter, and chemicals. Acute exposure to these environmental factors results in the activation of different signaling pathways that orchestrate adaptive stress responses to maintain cell and tissue homeostasis. Chronic exposure of skin to these factors, however, may lead to the accumulation of damaged macromolecules and loss of cell and tissue integrity, which, over time, may facilitate aging processes and the development of aging-related malignancies. One transcription factor that is expressed in all cutaneous cells and activated by various environmental stressors, including dioxins, polycyclic aromatic hydrocarbons, and ultraviolet radiation, is the aryl hydrocarbon receptor (AHR). By regulating keratinocyte proliferation and differentiation, epidermal barrier function, melanogenesis, and immunity, a certain degree of AHR activity is critical to maintain skin integrity and to adapt to acute stress situations. In contrast, a chronic activation of cutaneous AHR signaling critically contributes to premature aging and the development of neoplasms by affecting metabolism, extracellular matrix remodeling, inflammation, pigmentation, DNA repair, and apoptosis. This article provides an overview of the detrimental effects associated with sustained AHR activity in chronically stressed skin and pinpoints AHR as a promising target for chemoprevention.

Recent Trends of Sunscreen Cosmetic: An Update Review

Ultraviolet (UV) radiation has been demonstrated to cause skin disorders, including sunburn and relative symptoms of prolonged exposure. It has been reported that sunscreens have beneficial effects in reducing the incidence of skin disorders (sunburn, skin aging, and immunosuppression) through their ability to absorb, reflect, and scatter UV. Many commercial products have recently been manufactured from not only usual organic and inorganic UV filters, but also hybrid and botanical ingredients using typical formulations (emulsion, gel, aerosol, and stick). Particularly, these products have been supplemented with several preeminent properties to protect against the negative effects of not only UVB, but also UVA. However, the use of sunscreen has faced many challenges, including inducing photoallergic dermatitis, environment pollution, and deficiency of vitamin D production. Therefore, consumers should efficiently apply suitable products to improve sun protection. as well as to avoid the side effects of sunscreen.

Six critical questions for DNA repair enzymes in skincare products: a review in dialog

Concerns over existing sunscreen filters have reinforced the need to examine supplemental sun protection or repair of sun damage. Technology to enhance DNA repair has been available in skincare and sunscreen products for several decades, but skepticism and lack of familiarity with the supporting data remain prevalent. Here, we address six of the main questions raised by medical professionals regarding the efficacy of DNA repair enzymes in sun protection. These include the mode of delivery and mechanism of action, the effect on cellular responses and the amelioration of pre-cancers, cancers and photoaging. The conclusions are that topical DNA repair enzymes do enhance removal of DNA damage and reduce the appearance of new actinic keratoses as well as increase regression of existing lesions. Support for prevention of photoaging and skin cancer is significant but could be strengthened or disproven with additional research.

Photoimmunology: how ultraviolet radiation affects the immune system

Ultraviolet (UV) radiation is a ubiquitous component of the environment that has important effects on a wide range of cell functions. Short-wavelength UVB radiation induces sunburn and is a potent immunomodulator, yet longer-wavelength, lower-energy UVA radiation also has effects on mammalian immunity. This Review discusses current knowledge regarding the mechanisms by which UV radiation can modify innate and adaptive immune responses and how this immunomodulatory capacity can be both beneficial in the case of inflammatory and autoimmune diseases, and detrimental in the case of skin cancer and the response to several infectious agents.

Review of Clinical Evidence over 10 Years on Prevention and Treatment of a Film-Forming Medical Device Containing Photolyase in the Management of Field Cancerization in Actinic Keratosis

Abstract

Actinic keratosis (AK) is a common pathology that afflicts sun-exposed areas of the skin. It predominantly affects older and fair-skinned individuals suggesting an accumulative damage attributable to chronic sun exposure. The prevalence of AK has risen in the past decades and is expected to continue to rise. Apart from visible hyperkeratotic, hyperplastic lesions, AK is also associated with the presence of subclinical lesions adjacent to tumor tissue, which has led to the use of the concept “cancerization field”. Although lesion- and field-targeting treatments are currently available, many are associated with local side effects and recurrence of new lesions. This review provides information on AK pathophysiology and treatment options and summarizes the available clinical evidence supporting the use of Eryfotona AK-NMSC, a film-forming medical device with SPF 100+ containing the DNA repair enzyme photolyase, for managing AK, based on the analysis of the results of 228 patients treated with the product.

Funding

ISDIN funded the Article Processing Charges.

Electronic supplementary material

The online version of this article (10.1007/s13555-019-0294-1) contains supplementary material, which is available to authorized users.

Skin cancer prevention: a review of current topical options complementary to sunscreens

The incidence of non-melanoma skin cancer (NMSC) is dramatically increasing worldwide, despite the increased use of improved sunscreens. In 2014, the Surgeon General estimated that 2.2-5.0 million people were treated annually for NMSC. As the number of newly diagnosed skin cancers continues to rise, there is a need for additional preventative measures beyond sunscreens. Several newer topical products that focus on boosting DNA repair, modulating DNA transcription, decreasing inflammation and selectively targeting precancerous cells may play an important role in future skin cancer prevention.

Exploring Cycloreversion Reaction of Cyclobutane Pyrimidine Dimers Quantum Mechanically

The cyclobutane pyrimidine dimer (CPD) is a major photoproduct of deoxyribonucleic acid (DNA) that is damaged by ultraviolet light. This DNA lesion can be repaired by DNA photolyase with the aid of UV light and two cofactors. To understand the repair mechanism of CPD and whether protonation of CPD participates in the DNA repair process, the cycloreversion reactions of four CPD models and proton transfers between the adjacent residue Glu283 and CPD models were explored through the quantum mechanical method. Two-dimensional maps of potential energy surface in a vacuum and in implicit water solution were calculated at the ωB97XD/6-311++G(2df,2pd) level. One-dimensional potential energy profiles were computed for proton transfer reactions. Among the models that have been considered, both in a vacuum and in water solution, the results indicate that the most likely repair mechanism involves CPD^•2- radical anion splitting in a stepwise manner. C5-C5' splits first, and C6-C6' splits later. The computed free energies of activation of the two splitting steps are 0.9 and 3.1 kcal/mol, respectively. The adjacent Glu283 may stabilize the CPD^•2- radical anion through hydrogen bond and increase the quantum yield; however, protonating the CPD radical anion by Glu283 cannot accelerate the rate of ring opening.

Ultraviolet-A1 phototherapy in Asian skin: A review of 159 cases in Singapore

Background

Ultraviolet-A1 phototherapy has been used to treat many inflammatory dermatoses.

Aims

To determine the efficacy and safety of ultraviolet-A1 phototherapy in Asian skin.

Materials and Methods

We performed a review of records of patients undergoing ultraviolet-A1 phototherapy at our dermatology unit in Singapore from January 2007 to January 2011. Their electronic medical records were reviewed and a standardized questionnaire was filled up for data collection and tabulation. Chi-square or Fisher's exact tests were used to compare the difference in response between various groups for each characteristic. P value of < 0.05 was considered statistically significant.

Results

Our study comprised of 159 patients, of which 103 were patients with hand and foot eczema, 21 with atopic dermatitis, 17 with scleroderma and the remaining with miscellaneous dermatoses. Of these patients, 47.6% of patients with hand and feet eczema had good response after 10 sessions, which increased to 75% after 20 sessions and to 84.6% after 30 sessions. After 10 sessions, 47.6% of patients with atopic dermatitis had good response, which increased to 66.7% after 20 sessions. After 30 sessions, all the three remaining patients with atopic dermatitis experienced good response. For patients with scleroderma, only 11.8 and 10% had good response after 10 and 20 sessions, respectively, which increased to 40% after 30 sessions.

Limitations

Limitations of our study include its retrospective design and, consequently, the lack of standardized treatment protocol, as well as subjective assessment in terms of clinical improvement.

Conclusions

Ultraviolet-A1 phototherapy appears to be efficacious for the treatment of hand and foot eczema as well as atopic dermatitis. However, in patients with scleroderma, the response was partial and needed a longer duration of treatment.

What's New in Photoprotection: A Review of New Concepts and Controversies

Cumulative ultraviolet exposure plays a critical role in photodamage. Recent advancements in photomedicine have resulted in a more thorough understanding of these mechanisms. Despite this, the adoption of routine sun protective practices is commonly not undertaken regularly by a large proportion of the public. Various obstacles exist that contribute to the public's nonadherence to these practices. Sunscreens, which are an integral component in all photoprotective regimens, have been questioned recently in terms of their safety. The aim of this article is to provide an overview of new concepts in photoprotection and also address current controversies pertaining to sunscreens.

New Vision in Photoprotection and Photorepair

Chronic exposure to solar radiation is associated with an increased incidence of skin cancer worldwide and more specifically with non-melanoma skin cancers and actinic keratosis. At the cellular level DNA damage is the main event following ultraviolet (UV) exposure. The kind of lesions produced depends on the wavelength and the energy profile of the radiation, with different photoproducts being formed as a result. Although endogenous DNA repair mechanisms are somewhat effective in repairing DNA, some DNA damage persists and can accumulate with chronic exposure. UV protection strategies, such as sunscreen use, are important in limiting further DNA damage. Several published studies have demonstrated the protective effect that regular use of sunscreen can have against the development of skin cancers. Newer options that aim to help repair damaged DNA may have an important role in reducing the incidence of chronic sun exposure-related photoaging and non-melanoma skin cancers. Photolyase, which is capable of repairing cyclobutane dimers formed as a result of DNA irradiation, is one such novel ingredient. In the first part of this paper we review the rationale for a combined treatment approach of photoprotection and photorepair with photolyase. In the second part we evaluate several published clinical studies, which suggest a beneficial effect in preventing new skin lesions in photodamaged skin. A strategy of photoprotection plus photorepair appears to be relevant for all persons with a high level of solar exposure and those at a higher risk for developing skin cancers.

Novel Means for Photoprotection

Due to changes in human lifestyle (expanded sunbathing, the use of solaria, etc.) and, most importantly, increasing lifetime and thus higher cumulative exposure to solar radiation, skin aging and skin cancer have become major health issues. As a consequence effective photoprotection is of outmost importance to humans. In this regard a lot has been learned in the past about the cellular and molecular basis underlying ultraviolet (UV) radiation-induced skin damage and, based on this knowledge, numerous skin protective approaches including organic and inorganic UV-filters, but also topically applicable antioxidants, DNA repair enzymes and compatible solutes as well as oral photoprotective strategies based on nutritional supplements have been developed. A new aspect is here that sun protection of human skin might even be possible after solar radiation-induced skin damage has occurred. A second, very important development was prompted by the discovery that also wavelengths beyond the UV spectrum can damage human skin. These include the blue light region of visible light (VIS) as well as the near infrared range (IRA) and corresponding sunprotection strategies have thus recently been or are still being developed. In this article we will provide a state of the art summary of these two novel developments and, at the end, we will also critically discuss strengths and weaknesses of the current attempts, which mainly focus on the prevention of skin damage by selected wavelengths but greatly ignore the possibility that wavelengths might interfere with each other. Such combined effects, however, need to be taken into account if photoprotection of human skin is intended to be global in nature.

Codon usage analysis of photolyase encoding genes of cyanobacteria inhabiting diverse habitats

Nucleotide and amino acid compositions were studied to determine the genomic and structural relationship of photolyase gene in freshwater, marine and hot spring cyanobacteria. Among three habitats, photolyase encoding genes from hot spring cyanobacteria were found to have highest GC content. The genomic GC content was found to influence the codon usage and amino acid variability in photolyases. The third position of codon was found to have more effect on amino acid variability in photolyases than the first and second positions of codon. The variation of amino acids Ala, Asp, Glu, Gly, His, Leu, Pro, Gln, Arg and Val in photolyases of three different habitats was found to be controlled by first position of codon (G1C1). However, second position (G2C2) of codon regulates variation of Ala, Cys, Gly, Pro, Arg, Ser, Thr and Tyr contents in photolyases. Third position (G3C3) of codon controls incorporation of amino acids such as Ala, Phe, Gly, Leu, Gln, Pro, Arg, Ser, Thr and Tyr in photolyases from three habitats. Photolyase encoding genes of hot spring cyanobacteria have 85% codons with G or C at third position, whereas marine and freshwater cyanobacteria showed 82 and 60% codons, respectively, with G or C at third position. Principal component analysis (PCA) showed that GC content has a profound effect in separating the genes along the first major axis according to their RSCU (relative synonymous codon usage) values, and neutrality analysis indicated that mutational pressure has resulted in codon bias in photolyase genes of cyanobacteria.

[New approaches for the prevention of actinic keratosis]

Actinic keratosis is one of the most common skin diseases. Because of the ongoing demographic changes, it is anticipated that the incidence will further increase. Prevention of actinic keratoses is thus of great importance. By far the most important cause of actinic keratoses is the chronic cumulative irradiation of human skin with ultraviolet B and A radiation from natural sunlight. There is no doubt that use of sunscreens is effective in preventing actinic keratoses. Recent studies indicate that in high-risk groups the regular use of medical devices which are characterized by a very high SPF and which contain liposomally encapsulated DNA repair enzymes are effective in preventing the development of new actinic keratoses even when field cancerization is already present in human skin. There is also evidence that oral photoprotective strategies based on the regular intake of vitamin B₃ may be used to prevent actinic keratoses.

Crosstalk Among UV-Induced Inflammatory Mediators, DNA Damage and Epigenetic Regulators Facilitates Suppression of the Immune System

The suppression of the immune system by overexposure to ultraviolet (UV) radiation has been implicated in the initiation and progression of photocarcinogenesis. Numerous changes occur in the skin on UVB exposure, including the generation of inflammatory mediators, DNA damage, epigenetic modifications, and migration and functional alterations in the antigen-presenting dendritic cells. Although each of these alterations can elicit a cascade of events that have the potential to modulate immune sensitivity alone, there is emerging evidence that there is considerable crosstalk between these cascades. The development of an understanding of UV-induced changes in the skin that culminate in UV-induced immunosuppression, which has been implicated in the risk of nonmelanoma skin cancer, as a network of events has implications for the development of more effective chemopreventive strategies. In the current review article, we discuss the evidence of interactions between the various molecular targets and signaling mechanisms associated with UV-induced immunosuppression.

Protein oxidation, UVA and human DNA repair

Solar UVB is carcinogenic. Nucleotide excision repair (NER) counteracts the carcinogenicity of UVB by excising potentially mutagenic UVB-induced DNA lesions. Despite this capacity for DNA repair, non-melanoma skin cancers and apparently normal sun-exposed skin contain huge numbers of mutations that are mostly attributable to unrepaired UVB-induced DNA lesions. UVA is about 20-times more abundant than UVB in incident sunlight. It does cause some DNA damage but this does not fully account for its biological impact. The effects of solar UVA are mediated by its interactions with cellular photosensitizers that generate reactive oxygen species (ROS) and induce oxidative stress. The proteome is a significant target for damage by UVA-induced ROS. In cultured human cells, UVA-induced oxidation of DNA repair proteins inhibits DNA repair. This article addresses the possible role of oxidative stress and protein oxidation in determining DNA repair efficiency - with particular reference to NER and skin cancer risk.

Phototherapy for sclerosing skin conditions

Phototherapy is an effective treatment strategy for a variety of sclerosing skin conditions. There are a number of phototherapeutic modalities used for the treatment of sclerosing skin conditions, including ultraviolet (UV)A1, broadband UVA, psoralen plus UVA, and narrowband UVB phototherapy. As controlled trials with validated outcome measures are lacking for these therapies, existing evidence is largely level II for morphea and is even more minimal for scleroderma and other sclerosing disorders (scleroderma, lichen sclerosus, and chronic graft-versus-host disease, among others). Studies do suggest that phototherapy may be effective for many of these disorders, including those that have been unresponsive to other therapies. Phototherapy remains an attractive therapeutic option for patients due to its efficacy and favorable risk-versus-benefit profile. Phototherapy also offers a therapeutic alternative to systemic immunosuppressives for patients who cannot tolerate these medications.

Ultraviolet light-emitting diode irradiation-induced cell death in HL-60 human leukemia cells in vitro

Ultraviolet (UV) radiation is considered to be a potent cell-damaging agent in various cell lineages; however, the effect of UV light‑emitting diode (LED) irradiation on human cells remains unclear. The aim of the present study was to examine the effect of UV LED irradiation emitting at 280 nm on cultured HL‑60 human leukemia cells, and to explore the underlying mechanisms. HL‑60 cells were irradiated with UV LED (8, 15, 30 and 60 J/m2) and incubated for 2 h after irradiation. The rates of cell proliferation and apoptosis, the cell cycle profiles and the mRNA expression of B‑cell lymphoma 2 (Bcl‑2) were detected using cell counting kit‑8, multicaspase assays, propidium iodide staining and reverse transcription‑quantitative polymerase chain reaction, respectively. The results showed that UV LED irradiation (8‑60 J/m2) inhibited the proliferation of HL‑60 cells in a dose‑dependent manner. UV LED at 8‑30 J/m2 induced dose‑dependent apoptosis and G0/G1 cell cycle arrest, and inhibited the expression of Bcl‑2 mRNA, while UV LED at 60 J/m2 induced necrosis. In conclusion, 280 nm UV LED irradiation inhibits proliferation and induces apoptosis and necrosis in cultured HL‑60 cells. In addition, the cell cycle arrest at the G0/G1 phase and the downregulation of Bcl‑2 mRNA expression were shown to be involved in UV LED-induced apoptosis.