Sunlight damage to cellular DNA: Focus on oxidatively generated lesions

RHOAming Through the Nucleotide Excision Repair Pathway as a Mechanism of Cellular Response Against the Effects of UV Radiation

Typical Rho GTPases include the enzymes RhoA, Rac1, and Cdc42 that act as molecular switches to regulate essential cellular processes in eukaryotic cells such as actomyosin dynamics, cell cycle, adhesion, death and differentiation. Recently, it has been shown that different conditions modulate the activity of these enzymes, but their functions still need to be better understood. Here we examine the interplay between RhoA and the NER (Nucleotide Excision Repair) pathway in human cells exposed to UVA, UVB or UVC radiation. The results show high levels and accumulation of UV-induced DNA lesions (strand breaks and cyclobutane pyrimidine dimers, CPDs) in different cells with RhoA loss of function (LoF), either by stable overexpression of negative dominant RhoA (RhoA-N19 mutant), by inhibition with C3 toxin or by transient silencing with siRNA. Cells under RhoA LoF showed reduced levels of γH2AX, p-Chk1 (Ser345) and p-p53 (Ser15) that reflected causally in their accumulation in G1/S phases, in low survival rates and in reduced cell proliferation, also in accordance with the energy of applied UV light. Even NER-deficient cells (XPA, XPC) or DNA translesion synthesis (TLS)-deficient cells (XPV) showed substantial hypersensitivity to UV effects when previously submitted to RhoA LoF. In contrast, analyses of apoptosis, necrosis, autophagy and senescence revealed that all cells displaying normal levels of active RhoA (RhoA-GTP) are more resistant to UV-promoted cell death. This work reaffirms the role of RhoA protein signaling in protecting cells from damage caused by UV radiation and demonstrates relevant communicating mechanisms between actin cytoskeleton and genomic stability.

Solar ultraviolet-induced DNA damage response: Melanocytes story in transformation to environmental melanomagenesis

Exposure to sunlight is both beneficial, as it heats the planet to a comfortable temperature, and potentially harmful, since sunlight contains ultraviolet radiation (UVR), which is deemed detrimental for living organisms. Earth's ozone layer plays a vital role in blocking most of the extremely dangerous UVC; however, low frequency/energy UVR (i.e., UVB and UVA) seeps through in minute amount and reaches the Earth's surface. Both UVB and UVA are physiologically responsible for a plethora of skin ailments, including skin cancers. The UVR is readily absorbed by the genomic DNA of skin cells, causing DNA bond distortion and UV-induced DNA damage. As a defense mechanism, the DNA damage response (DDR) signaling in skin cells activates nucleotide excision repair (NER), which is responsible for the removal of UVR-induced DNA photolesions and helps maintain the genomic integrity of the cells. Failure of proper NER function leads to mutagenesis and development of skin cancers. One of the deadliest form of skin cancers is melanoma which originates upon the genetic transformation of melanocytes, melanin producing skin cells. NER is a well-studied DNA repair system in the whole skin, as a tissue, but not much is known about it in melanocytes. Therefore, this review encapsulates NER in melanocytes, with a specific focus on its functional regulators and their cross talks due to skin heterogeneity and divulging the potential knowledge gap in the field.

DNA Damage Induced by Late Spring Sunlight in Antarctica

Sunlight ultraviolet (UV) radiation constitutes an important environmental genotoxic agent that organisms are exposed to, as it can damage DNA directly, generating pyrimidine dimers, and indirectly, generating oxidized bases and single-strand breaks (SSBs). These lesions can lead to mutations, triggering skin and eye disorders, including carcinogenesis and photoaging. Stratospheric ozone layer depletion, particularly in the Antarctic continent, predicts an uncertain scenario of UV incidence on the Earth in the next decades. This research evaluates the DNA damage caused by environmental exposure to late spring sunlight in the Antarctic Peninsula, where the ozone layer hole is more pronounced. These experiments were performed at the Brazilian Comandante Ferraz Antarctic Station, at King's George Island, South Shetlands Islands. For comparison, tropical regions were also analyzed. Samples of plasmid DNA were exposed to sunlight. Cyclobutane pyrimidine dimers (CPDs), oxidized base damage and SSBs were detected using specific enzymes. In addition, an immunological approach was used to detect CPDs. The results reveal high levels of DNA damage induced by exposure under the Antarctic sunlight, inversely correlated with ozone layer thickness, confirming the high impact of ozone layer depletion on the DNA damaging action of sunlight in Antarctica.

Imaging of metabolic activity adaptations to UV stress, drugs and differentiation at cellular resolution in skin and skin equivalents - Implications for oxidative UV damage

The epidermis is a multi-layered epithelium that consists mainly of keratinocytes which proliferate in its basal layer and then differentiate to form the stratum corneum, the skin's ultimate barrier to the environment. During differentiation keratinocyte function, chemical composition, physical properties, metabolism and secretion are profoundly changed. Extrinsic or intrinsic stressors, like ultraviolet (UV) radiation thus may differently affect the epidermal keratinocytes, depending on differentiation stage. Exposure to UV elicits the DNA damage responses, activation of pathways which detoxify or repair damage or induction of programmed cell death when the damage was irreparable. Recently, rapid diversion of glucose flux into the pentose phosphate pathway (PPP) was discovered as additional mechanism by which cells rapidly generate reduction equivalents and precursors for nucleotides - both being in demand after UV damage. There is however little known about the correlation of such metabolic activity with differentiation state, cell damage and tissue localization of epidermal cells. We developed a method to correlate the activity of G6PD, the first and rate-limiting enzyme of this metabolic UV response, at cellular resolution to cell type, differentiation state, and cell damage in human skin and in organotypic reconstructed epidermis. We thereby could verify rapid activation of G6PD as an immediate UVB response not only in basal but also in differentiating epidermal keratinocytes and found increased activity in cells which initiated DNA damage responses. When keratinocytes had been UVB irradiated before organotypic culture, their distribution within the skin equivalent was abnormal and the G6PD activity was reduced compared to neighboring cells. Finally, we found that the anti-diabetic and potential anti-aging drug metformin strongly induced G6PD activity throughout reconstructed epidermis. Activation of the protective pentose phosphate pathway may be useful to enhance the skin's antioxidant defense systems and DNA damage repair capacity on demand.

Redox Regulation in the Base Excision Repair Pathway: Old and New Players as Cancer Therapeutic Targets

BACKGROUND

Reactive Oxygen Species (ROS) are by-products of normal cellular metabolic processes, such as mitochondrial oxidative phosphorylation. While low levels of ROS are important signalling molecules, high levels of ROS can damage proteins, lipids and DNA. Indeed, oxidative DNA damage is the most frequent type of damage in the mammalian genome and is linked to human pathologies such as cancer and neurodegenerative disorders. Although oxidative DNA damage is cleared predominantly through the Base Excision Repair (BER) pathway, recent evidence suggests that additional pathways such as Nucleotide Excision Repair (NER) and Mismatch Repair (MMR) can also participate in clearance of these lesions. One of the most common forms of oxidative DNA damage is the base damage 8-oxoguanine (8-oxoG), which if left unrepaired may result in G:C to A:T transversions during replication, a common mutagenic feature that can lead to cellular transformation.

OBJECTIVE

Repair of oxidative DNA damage, including 8-oxoG base damage, involves the functional interplay between a number of proteins in a series of enzymatic reactions. This review describes the role and the redox regulation of key proteins involved in the initial stages of BER of 8-oxoG damage, namely Apurinic/Apyrimidinic Endonuclease 1 (APE1), human 8-oxoguanine DNA glycosylase-1 (hOGG1) and human single-stranded DNA binding protein 1 (hSSB1). Moreover, the therapeutic potential and modalities of targeting these key proteins in cancer are discussed.

CONCLUSION

It is becoming increasingly apparent that some DNA repair proteins function in multiple repair pathways. Inhibiting these factors would provide attractive strategies for the development of more effective cancer therapies.

A large family with CYLD cutaneous syndrome: medical genetics at the community level

Germline mutations in the cylindromatosis gene (CYLD) are associated with a rare autosomal dominant disease known as CYLD cutaneous syndrome (CCS). Patients present multiple neoplasms originating from skin appendages. Here, we investigated the main clinical and molecular features of a large family with CCS having lived in a small Brazilian town for 6 generations, making its prevalence significantly high. We observed a predominance of the disease among males and a wide phenotypic variation. A high frequency of basal cell carcinomas among affected people was found. The mutation c.2806C>T, p.Arg936* in the CYLD gene was detected in all patients. In this work, a geographical cluster of CCS was found, which raised some community genetics issues related not only to the high prevalence of a rare disease in a limited area but also to the strong social stigma associated with the disease.

The early local and systemic Type I interferon responses to ultraviolet B light exposure are cGAS dependent

Most systemic lupus erythematosus (SLE) patients are photosensitive and ultraviolet B light (UVB) exposure worsens cutaneous disease and precipitates systemic flares of disease. The pathogenic link between skin disease and systemic exacerbations in SLE remains elusive. In an acute model of UVB-triggered inflammation, we observed that a single UV exposure triggered a striking IFN-I signature not only in the skin, but also in the blood and kidneys. The early IFN-I signature was significantly higher in female compared to male mice. The early IFN-I response in the skin was almost entirely, and in the blood partly, dependent on the presence of cGAS, as was skin inflammatory cell infiltration. Inhibition of cGAMP hydrolysis augmented the UVB-triggered IFN-I response. UVB skin exposure leads to cGAS-activation and both local and systemic IFN-I signature and could contribute to acute flares of disease in susceptible subjects such as patients with SLE.

Rhus coriaria L. Fruit Extract Prevents UV-A-Induced Genotoxicity and Oxidative Injury in Human Microvascular Endothelial Cells

Rhus coriaria L. (sumac) is a small plant widely diffused in the Mediterranean region. Its fruit are often consumed as a spice but are also present in traditional medicine of several countries. Recently, interest in this plant has increased and many scientific works reported its beneficial effects including antioxidant and anti-inflammatory properties. Plant extracts can be successfully used against ultraviolet rays, which are able to reach and damage the human skin; however, sumac extracts were never applied to this usage. Thus, in this study, we used a macerated ethanol extract of Rhus coriaria L. dried fruit (mERC) to demonstrate its preventive role against the damage induced by ultraviolet-A rays (UV-A) on microvascular endothelial cells (HMEC-1). In vitro effects of the extract pre-treatment and UV-A exposure were evaluated in detail. The antioxidant capacity was assessed by reactive oxygen species (ROS) formation and cellular antioxidant activity measurement. Genoprotective effects of mERC were investigated as well. Our findings indicate that the extract acts as a cell cycle inhibitor or apoptosis inducer, according to the level of damage. The present work provides new insights into the usage of Rhus coriaria extracts against skin injuries.

A dose of experimental hormesis: When mild stress protects and improves animal performance

The adaptive response characterized by a biphasic curve is known as hormesis. In a hormesis framework, exposure to low doses leads to protective and beneficial responses while exposures to high doses are damaging and detrimental. Comparative physiologists have studied hormesis for over a century, but our understanding of hormesis is fragmented due to rifts in consensus and taxonomic-specific terminology. Hormesis has been and is currently known by multiple names; preconditioning, conditioning, pretreatment, cross tolerance, adaptive homeostasis, and rapid stress hardening (mostly low temperature: rapid cold hardening). These are the most common names used to describe adaptive stress responses in animals. These responses are mechanistically similar, while having stress-specific responses, but they all can fall under the umbrella of hormesis. Here we review how hormesis studies have revealed animal performance benefits in response to changes in oxygen, temperature, ionizing radiation, heavy metals, pesticides, dehydration, gravity, and crowding. And how almost universally, hormetic responses are characterized by increases in performance that include either increases in reproduction, longevity, or both. And while the field can benefit from additional mechanistic work, we know that many of these responses are rooted in increases of antioxidants and oxidative stress protective mechanisms; including heat shock proteins. There is a clear, yet not fully elucidated, overlap between hormesis and the preparation for oxidative stress theory; which predicts part of the responses associated with hormesis. We discuss this, and the need for additional work into animal hormetic effects particularly focusing on the cost of hormesis.

Mechanisms of UV-induced mutations and skin cancer

Ultraviolet (UV) irradiation causes various types of DNA damage, which leads to specific mutations and the emergence of skin cancer in humans, often decades after initial exposure. Different UV wavelengths cause the formation of prominent UV-induced DNA lesions. Most of these lesions are removed by the nucleotide excision repair pathway, which is defective in rare genetic skin disorders referred to as xeroderma pigmentosum. A major role in inducing sunlight-dependent skin cancer mutations is assigned to the cyclobutane pyrimidine dimers (CPDs). In this review, we discuss the mechanisms of UV damage induction, the genomic distribution of this damage, relevant DNA repair mechanisms, the proposed mechanisms of how UV-induced CPDs bring about DNA replication-dependent mutagenicity in mammalian cells, and the strong signature of UV damage and mutagenesis found in skin cancer genomes.

Whole-exome sequencing reveals the impact of UVA light mutagenesis in xeroderma pigmentosum variant human cells

UVA-induced mutagenesis was investigated in human pol eta-deficient (XP-V) cells through whole-exome sequencing. In UVA-irradiated cells, the increase in the mutation frequency in deficient cells included a remarkable contribution of C>T transitions, mainly at potential pyrimidine dimer sites. A strong contribution of C>A transversions, potentially due to oxidized bases, was also observed in non-irradiated XP-V cells, indicating that basal mutagenesis caused by oxidative stress may be related to internal tumours in XP-V patients. The low levels of mutations involving T induced by UVA indicate that pol eta is not responsible for correctly replicating T-containing pyrimidine dimers, a phenomenon known as the ‘A-rule’. Moreover, the mutation signature profile of UVA-irradiated XP-V cells is highly similar to the human skin cancer profile, revealing how studies involving cells deficient in DNA damage processing may be useful to understand the mechanisms of environmentally induced carcinogenesis.

Understanding the role of p38 and JNK mediated MAPK pathway in response to UV-A induced photoaging in Caenorhabditis elegans

Premature aging of the skin, principally induced by the UV radiations is called as photoaging, characterized by an increase in the level of ROS and the damage of the collagen layer leading to the damage of the cells. Mitogen activated Protein kinase (MAPK) pathway is known to mediate photoaging by controlling the level of ROS and initiating detoxification. Caenorhabditis elegans, a known model to analyze photoaging was used to understand the role of MAPK pathway (p38 and JNK) during UV-A mediated photoaging. Gene specific mutants of p38 MAPK pathway showed reduced survival when exposed to UV-A suggesting that UV-A mediated photoaging was dependent on this pathway. Also, the role of SKN-1 in eliciting response against UV-A was analyzed with the help of GFP tagged strains and qPCR analysis. Further, UV-A did not have any impact on the lifespan of JNK pathway mutants suggesting the importance of the pathway in eliciting a response against UV-A exposure, which was further validated by Western blot analysis. Overall, this study suggests that MAPK pathway could play an important part in initiating and eliciting a response by the host against UV-A exposure, by which it could be used as a marker to analyze the effects of photoaging.

Cooperation and interplay between base and nucleotide excision repair pathways: From DNA lesions to proteins

Base and nucleotide excision repair (BER and NER) pathways are normally associated with removal of specific types of DNA damage: small base modifications (such as those induced by DNA oxidation) and bulky DNA lesions (such as those induced by ultraviolet or chemical carcinogens), respectively. However, growing evidence indicates that this scenario is much more complex and these pathways exchange proteins and cooperate with each other in the repair of specific lesions. In this review, we highlight studies discussing the involvement of NER in the repair of DNA damage induced by oxidative stress, and BER participating in the removal of bulky adducts on DNA. Adding to this complexity, UVA light experiments revealed that oxidative stress also causes protein oxidation, directly affecting proteins involved in both NER and BER. This reduces the cell’s ability to repair DNA damage with deleterious implications to the cells, such as mutagenesis and cell death, and to the organisms, such as cancer and aging. Finally, an interactome of NER and BER proteins is presented, showing the strong connection between these pathways, indicating that further investigation may reveal new functions shared by them, and their cooperation in maintaining genome stability.

Silk peptide production from whole silkworm cocoon using ultrasound and enzymatic treatment and its suppression of solar ultraviolet-induced skin inflammation

Silk fibroin, which is derived from sericin through degumming, is mainly used as a biomaterial. However, interest in functional verification and industrial applications of sericin has been growing for several years. We used ultrasonication to simplify the extraction process of the silk peptide under low salt conditions at 20 °C, instead of using the conventional conditions of high salt and temperature. The concentration of the silk peptide was measured to determine the optimized extraction time and solvent, which were 4 h and 0.1 N NaOH, respectively. The molecular weight of the enzyme-treated silk peptide was measured using SDS-PAGE and GPC. Silk peptide treated with papain after ultrasound had a molecular weight of less than 5 kDa, and the papain treated-silk peptide reduced solar ultraviolet-induced COX-2 expression through inhibition of ERK phosphorylation. This is the first study investigating simultaneous extraction of fibroin and sericin, which can be used for mass production of food materials.

Balance between Health Risks and Benefits for Outdoor Workers Exposed to Solar Radiation: An Overview on the Role of Near Infrared Radiation Alone and in Combination with Other Solar Spectral Bands

Near infrared or infrared A (IRA) accounts for over 40% of the solar spectrum (SS) and is able to reach subcutaneous tissue as well as the retina. Outdoor workers are occupationally exposed to solar radiation (SR), but the level of exposure may differ widely depending on the job performed, time spent outdoors, latitude, altitude, season, personal protection, etc. Until now, risk assessment and management for outdoor workers has focused on the prevention of both acute and long-term effects on the eye and the skin due to solar ultraviolet radiation (UVR) with little consideration of the other components of the SS (a possible exception is represented by visible radiation with reference to the eye). A growing body of evidence coming from in vitro studies indicates that IRA is involved in cellular reactive oxygen species (ROS) production and may interfere with the respiratory chain in the mitochondria. Moreover, it can modulate gene expression and some metabolic pathways. The biological action of IRA is only partly attributable to a thermal mechanism, should it be also involved in photochemical ones. The cellular and molecular pathways affected by IRA are partly similar and partly different with respect to those involved in the case of visible ultraviolet A (UVA) and ultraviolet B (UVB) radiation. Consequently, the net effect of the SS is very difficult to predict at different levels of the biological organization, making more difficult the final balance of health risk and benefits (for the skin, eye, immune system, blood pressure, etc.) in a given exposure situation. Moreover, few in vivo studies and no epidemiological data are presently available in this regard. Investigating this topic may contribute to better defining the individual exposome. More practically, it is expected to bring benefits to the risk assessment and management for outdoor workers exposed to SS, contributing to: (1) better definition of the individual profiles of susceptibility, (2) more focused preventive and protective measures, (3) better implementation of the health surveillance and (4) a more effective information and training.

Experimental evaluation of genomic DNA degradation rates for the pathogen Pseudogymnoascus destructans (Pd) in bat guano

Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in bats (WNS), has led to dramatic declines of bat populations in eastern North America. In the spring of 2016, WNS was first detected at several locations in Washington State, USA, which has prompted the need for large scale surveillance efforts to monitor the spread of Pd. Pd is typically detected in bats using invasive methods requiring capturing and swabbing individual bats. However, Pd can also be detected in guano, which may provide an efficient, affordable, and noninvasive means to monitor Pd in bats across North America. The widespread implementation of Pd surveillance in guano is hindered by substantial uncertainty about the probability of detecting Pd when present, and how this probability is influenced by the time since defecation, local environmental conditions, the amount of guano sampled, and the original concentration of DNA shed in the guano. In addition, the expected degradation rate of Pd DNA depends on whether the Pd DNA found in guano represents extracellular DNA fragments, intracellular DNA from dead Pd fungal cells, or from intracellular and viable Pd cells. While this is currently unknown, it has been posited that most environmental DNA, such as Pd found in guano long after defecation, is fragmented extracellular DNA. Using non-viable isolated DNA at precise quantities, we experimentally characterized the degradation rates of Pd DNA in guano samples. We spiked 450 guano samples with Pd gDNA in a 10-fold dilution series from 1 million to 1,000 fg and placed them in variable environmental conditions at five sites at Mount Rainier National Park in Washington State, which is a priority location for Pd surveillance. We evaluated DNA degradation over 70 days by quantifying the amount of DNA in samples collected every 14 days using real-time quantitative PCR (qPCR). Our sampling period was from July 10th to September 17th 2018 which overlaps with bat movement between summer roosts as well as movement from maternity colonies fall swarms. We detected Pd DNA in guano 56 and 70 days after inoculation with 1 million and 100,000 fg respectively, while the lowest quantity (1,000 fg) was detected until 42 days. Detection probability was variable among sites and lower where samples were left exposed without overhead cover. If Pd is shed as extracellular DNA in guano at quantities above 1,000 fg, then guano collection is likely to provide an effective tool for environmental screening of Pd that can be employed in an early detection and rapid response framework throughout Washington and other regions where this disease is rapidly emerging.

Riboflavin Plays a Pivotal Role in the UVA-Induced Cytotoxicity of Fibroblasts as a Key Molecule in the Production of H2O2 by UVA Radiation in Collaboration with Amino Acids and Vitamins

To investigate environmental factors that contribute to ultraviolet A (UVA)-induced oxidative stress, which accelerates the senescence and toxicity of skin cells, we irradiated human fibroblasts cultured in commonly used essential media with UVA and evaluated their viability and production of reactive oxygen species. The viability of fibroblasts exposed to a single dose of 3.6 J/cm² UVA was not reduced when cultured in Hanks balanced salt solution, but it was significantly decreased when cultured in Dulbecco’s modified Eagle’s medium (DMEM), which contains various amino acids and vitamins. Furthermore, cell viability was not reduced when fibroblasts were cultured in DMEM and treated with a hydrogen peroxide (H₂O₂) scavenger such as glutathione or catalase added after UVA irradiation. In addition, we confirmed that the production of H₂O₂ was dramatically increased by UVA photosensitization when riboflavin (R) coexisted with amino acids such as tryptophan (T), and found that R with folic acid (F) produced high levels of H₂O₂ after UVA irradiation. Furthermore, we noticed that R and F or R and T have different photosensitization mechanisms since NaN₃, which is a singlet oxygen quencher, suppressed only R and T photosensitization. Lastly, we examined the effects of antioxidants (L-ascorbic acid, trolox, L-cysteine, and L-histidine), which are singlet oxygen or superoxide or H₂O₂ scavengers, on R and F or on R and T photosensitization, and found that 1 mM ascorbic acid, Trolox, and L-histidine were strongly photosensitized with R, and produced significant levels of H₂O₂ during UVA exposure. However, 1 mM L-cysteine dramatically suppressed H₂O₂ production by UVA photosensitization. These data suggest that a low concentration of R-derived photosensitization is elicited by different mechanisms depending on the coexisting vitamins and amino acids, and regulates cellular oxidative stress by producing H₂O₂ during UVA exposure.

Autophagy: Multiple Mechanisms to Protect Skin from Ultraviolet Radiation-Driven Photoaging

Autophagy is an essential cellular process that maintains balanced cell life. Restriction in autophagy may induce degenerative changes in humans. Natural or pathological aging of susceptible tissues has been linked with reduced autophagic activity. Skin photoaging is an example of such pathological condition caused by ambient solar UV radiation exposure. The UV-induced production of reaction oxygen species (ROS) has been linked to the promotion and progression of the photoaging process in exposed tissues. Accordingly, it has been suggested that autophagy is capable of delaying the skin photoaging process caused by solar ultraviolet (UV), although the underlying mechanism is still under debate. This review highlights several plausible mechanisms by which UV-induced ROS activates the cellular signaling pathways and modulates the autophagy. More specifically, the UV-mediated regulation of autophagy and age-related transcription factors is discussed to pinpoint the contribution of autophagy to antiphotoaging effects in the skin. The outcome of this review will provide insights into design intervention strategies for delaying the phenomenon of sunlight-induced photodamage, photoaging, and other aging-related chronic diseases based on factors that activate the autophagy process in the skin.

Andrographolide sodium bisulfate attenuates UV‑induced photo‑damage by activating the keap1/Nrf2 pathway and downregulating the NF‑κB pathway in HaCaT keratinocytes

Oxidative and inflammatory damage has been suggested to play important roles in the pathogenesis of skin photoaging. Andrographolide sodium bisulfate (ASB) is a soluble derivative of andrographolide and has known antioxidant and anti‑inflammatory properties. In the present study, cellular experiments were designed to investigate the molecular mechanisms underlying the effect of ASB in relieving ultraviolet (UV)‑induced photo‑damage. Following ASB pretreatment and UV irradiation, the apoptosis and necrosis of HaCaT cells were investigated by Hoechst 33342/propidium iodide staining. Reactive oxygen species (ROS) production was investigated using a DCFH‑DA fluorescence probe. Furthermore, the protein expression levels of p65, NF‑κB inhibitor‑α, nuclear factor E2‑related factor 2 (Nrf2) and kelch‑like ECH‑associated protein 1 (keap1) were measured via western blotting and immunofluorescence analyses. Furthermore, NF‑κB‑mediated cytokines were assessed by ELISA, and Nrf2‑mediated genes were detected by reverse transcription‑quantitative PCR. Pretreatment with ASB markedly increased cell viability, decreased cell apoptosis and decreased UV‑induced excess ROS levels. In addition, ASB activated the production of Nrf2 and increased the mRNA expression levels of glutamate‑cysteine ligase catalytic subunit and NAD(P)H quinone oxidoreductase 1, while ASB downregulated the protein expression of p65 and decreased the production of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α. These results suggested that ASB attenuates UV‑induced photo‑damage by activating the keap1/Nrf2 pathway and downregulating the NF‑κB pathway in HaCaT keratinocytes.

Cell aging and cellular senescence in skin aging - Recent advances in fibroblast and keratinocyte biology

The aging of the skin is the most visible and obvious manifestation of organismal aging and may serve as a predictor of life expectancy and health. It is, however, also the human desire for long-lasting beauty that further raises interests in the topic, and thus considerable means and efforts are put into studying the mechanisms of skin aging in basic and applied research. Both medical und non-medical interests are of benefit for skin research in general because the results from these studies help to deepen our understanding of the complex molecular, biological, cell signaling, developmental and immunological processes in this organ. In fact, the skin is an ideal organ to observe and analyze the impact of extrinsic and intrinsic drivers of aging. Within the past five years technological advances like lineage tracing of cells in model organisms, intra-vital microscopy, nucleic acid sequencing at the single cell level, and high resolution mass spectrometry have allowed to study aging and senescence of individual skin cells within the tissue context, their signaling and communication, and to derive new hypotheses for experimental studies in vitro. In this short review we will discuss very recent developments that promise to extend the existing knowledge on cell aging and senescence of dermal fibroblasts and epidermal keratinocytes in skin aging.

Dose and time effects of solar-simulated ultraviolet radiation on the in vivo human skin transcriptome

Background

Terrestrial ultraviolet (UV) radiation causes erythema, oxidative stress, DNA mutations and skin cancer. Skin can adapt to these adverse effects by DNA repair, apoptosis, keratinization and tanning.

Objectives

To investigate the transcriptional response to fluorescent solar‐simulated radiation (FSSR) in sun‐sensitive human skin in vivo.

Methods

Seven healthy male volunteers were exposed to 0, 3 and 6 standard erythemal doses (SED). Skin biopsies were taken at 6 h and 24 h after exposure. Gene and microRNA expression were quantified with next generation sequencing. A set of candidate genes was validated by quantitative polymerase chain reaction (qPCR); and wavelength dependence was examined in other volunteers through microarrays.

Results

The number of differentially expressed genes increased with FSSR dose and decreased between 6 and 24 h. Six hours after 6 SED, 4071 genes were differentially expressed, but only 16 genes were affected at 24 h after 3 SED. Genes for apoptosis and keratinization were prominent at 6 h, whereas inflammation and immunoregulation genes were predominant at 24 h. Validation by qPCR confirmed the altered expression of nine genes detected under all conditions; genes related to DNA repair and apoptosis; immunity and inflammation; pigmentation; and vitamin D synthesis. In general, candidate genes also responded to UVA1 (340–400 nm) and/or UVB (300 nm), but with variations in wavelength dependence and peak expression time. Only four microRNAs were differentially expressed by FSSR.

Conclusions

The UV radiation doses of this acute study are readily achieved daily during holidays in the sun, suggesting that the skin transcriptional profile of ‘typical’ holiday makers is markedly deregulated.

What's already known about this topic?

The skin's transcriptional profile underpins its adverse (i.e. inflammation) and adaptive molecular, cellular and clinical responses (i.e. tanning, hyperkeratosis) to solar ultraviolet radiation.

Few studies have assessed microRNA and gene expression in vivo in humans, and there is a lack of information on dose, time and waveband effects.

What does this study add?

Acute doses of fluorescent solar‐simulated radiation (FSSR), of similar magnitude to those received daily in holiday situations, markedly altered the skin's transcriptional profiles.

The number of differentially expressed genes was FSSR‐dose‐dependent, reached a peak at 6 h and returned to baseline at 24 h.

The initial transcriptional response involved apoptosis and keratinization, followed by inflammation and immune modulation. In these conditions, microRNA expression was less affected than gene expression.

Linked Comment:Hart. Br J Dermatol 2020; 182:1328–1329.

Plain language summary available online

Respond to this article

Supplementation with 5-formyltetrahydrofolate alleviates ultraviolet B-inflicted oxidative damage in folate-deficient zebrafish

Ultraviolet (UV) is an omnipresent environmental carcinogen transmitted by sunlight. Excessive UV irradiation has been correlated to an increased risk of skin cancers. UVB, the most mutagenic component among the three UV constituents, causes damage mainly through inducing DNA damage and oxidative stress. Therefore, strategies or nutrients that strengthen an individual's resistance to UV-inflicted harmful effects shall be beneficial. Folate is a water-soluble B vitamin essential for nucleotides biosynthesis, and also a strong biological antioxidant, hence a micronutrient with potential of modulating individual's vulnerability to UV exposure. In this study, we investigated the impact of folate status on UV sensitivity and the protective activity of folate supplementation using a zebrafish model. Elevated reactive oxygen species (ROS) level and morphological injury were observed in the larvae exposed to UVB, which were readily rescued by supplementing with folic acid, 5-formyltetrahydrofolate (5-CHO-THF) and N-acetyl-L-cysteine (NAC). The UVB-inflicted abnormalities and mortality were worsened in Tg(hsp:EGFP-γGH) larvae displaying folate deficiency. Intriguingly, only supplementation with 5-CHO-THF, as opposed to folic acid, offered significant and consistent protection against UVB-inflicted oxidative damage in the folate-deficient larvae. We concluded that the intrinsic folate status correlates with the vulnerability to UVB-induced damage in zebrafish larvae. In addition, 5-CHO-THF surpassed both folic acid and NAC in preventing UVB-inflicted oxidative stress and injury in our current experimental zebrafish model.

UV-B Induces Chloroplast Movements in a Phototropin-Dependent Manner

We examined the impact of UV-B irradiation on chloroplast movements in Arabidopsis leaves. Directional chloroplast movements induced by blue light have been described in multiple plant species. In weak light, chloroplasts accumulate at periclinal cell walls to increase light capture. In strong light, chloroplasts exhibit the avoidance response, as they move towards anticlinal walls to protect the photosynthetic apparatus from light-induced damage. In Arabidopsis, chloroplast movements are triggered by phototropins, phot1 and phot2, which are known as blue/UV-A photoreceptors. We found that irradiation with UV-B of 3.3 µmol·m-2·s-1 induced chloroplast accumulation in wild-type plants. UV-B-triggered accumulation was dependent on the presence of phototropins, especially phot1, but not on UVR8 (the canonical UV-B photoreceptor). Irradiation with strong UV-B of 20 µmol·m-2·s-1 did not induce substantial chloroplast relocations in wild-type leaves. However, in the jac1 mutant, which is defective in chloroplast accumulation, strong UV-B elicited chloroplast avoidance. This indicated that UV-B can also activate signaling to the avoidance response. To assess the possibility of indirect effects of UV-B on chloroplast movements, we examined the impact of UV-B on the actin cytoskeleton, which serves as the motile system for chloroplast movements. While irradiation with UV-B of 3.3 µmol·m-2·s-1 did not affect the actin cytoskeleton, strong UV-B disrupted its structure as shown using an Arabidopsis line expressing Lifeact-green fluorescent protein (GFP). In wild-type plants, pretreatment with strong UV-B attenuated chloroplast responses triggered by subsequent blue light irradiation, further indicating that this UV-B intensity also indirectly affects chloroplast movements. Taken together, our results suggest that the effect of UV-B on chloroplast movement is twofold: it directly induces phototropin-mediated movements; however, at higher intensities, it attenuates the movements in a nonspecific manner.

Treatment of Basal Cell Cancer With a Pulsed Copper Vapor Laser: A Case Series

Introduction: Basal cell carcinoma (BCC) is the most prevalent form of non-melanoma skin cancer commonly arising in elderly patients. Currently, many laser systems are applied for the treatment of BCC. However, up to the present, there have been several reports concerning ocular side effects due to the laser procedure in the borders of the periorbital area. This determines the feasibility of testing new laser surgical modes for the management of periorbital BCC. This stuay aimed to estimate both the efficacy, the early post-radiated side effects and long-term outcomes of the CVL treatment of periorbital BCC. Patients and Methods: Two men and 6 women aged 50 to 77 years were diagnosed with periorbital BCC according to the data of both the clinical evaluation and histological examination of the tissue samples taken from the involved area. Six months after the laser treatment, the histological examination of skin samples from the borderline of the irradiated area was made again. All patients were followed for 24 months after the laser treatment of BCC. The laser treatment was administered during one session of copper vapor laser (CVL) (Yakhroma-Med model). The treatment included CVL radiation with a wavelength of 511 nm and 578 nm, in the ratio of 3:2. The power level was set up to 3 W, and the exposure time was equal from 200 to 600 ms. The pulse duration accounted for 15 ns. The diameter of the light spot on the skin surface amounted to 1 mm. Results: Dual-wavelengths CVL treatment of periorbital BCC provided a complete elimination of malignant cells and dysplastic vessels during one procedure. The duration of skin healing amounted to 2-4 weeks. There were neither ocular injuries or pronounced skin side effects nor relapses within 24 months after the laser procedure. Conclusion: CVL treatment of periorbital BCC provides relevant cosmetic results without ocular injuries and relapses.

Effects of Lyse-It on endonuclease fragmentation, function and activity

Nucleases are enzymes that can degrade genomic DNA and RNA that decrease the accuracy of quantitative measures of those nucleic acids. Here, we study conventional heating, standard microwave irradiation, and Lyse-It, a microwave-based lysing technology, for the potential to fragment and inactivate DNA and RNA endonucleases. Lyse-It employs the use of highly focused microwave irradiation to the sample ultimately fragmenting and inactivating RNase A, RNase B, and DNase I. Nuclease size and fragmentation were determined visually and quantitatively by SDS polyacrylamide gel electrophoresis and the mini-gel Agilent 2100 Bioanalyzer system, with a weighted size calculated to depict the wide range of nuclease fragmentation. Enzyme activity assays were conducted, and the rates were calculated to determine the effect of various lysing conditions on each of the nucleases. The results shown in this paper clearly demonstrate that Lyse-It is a rapid and highly efficient way to degrade and inactivate nucleases so that nucleic acids can be retained for down-stream detection.

Mechanism of unprecedented hydroxyl radical production and site-specific oxidative DNA damage by photoactivation of the classic arylhydroxamic acid carcinogens

The carcinogenicity of N-hydroxy-2-acetamidofluorene (N-OHAAF), the major genotoxic metabolite of the classic model aromatic amine (AA) carcinogen 2-acetylaminofluorene, has been attributed mainly to the formation of DNA adducts via arylnitrenium upon enzymatic activation. Here, we show, unexpectedly, that exposure of N-OHAAF to UV or sunlight irradiation can not only induce the formation of the well-known covalent DNA adducts, but, more interestingly, simultaneous generation of oxidative DNA damage was also observed as measured by the formation of DNA single-/double-strand breaks (SSBs/DSBs) and 8-oxo-2'-deoxyguanosine (8-oxodG), which were partly inhibited by the typical hydroxyl radical (•OH) scavengers. Electron spin resonance spin-trapping and fluorescent studies unequivocally confirmed that the highly reactive •OH was generated from photolysis of N-OHAAF. Further DNA sequencing investigations suggest that photoactivation of N-OHAAF caused preferential cleavage at guanine, thymine and cytosine sites. More importantly, the formation of 8-oxodG and DSBs were also observed when fibroblast Balb/c-3T3 cells were co-exposed to N-OHAAF/UV irradiation as measured by double immunofluorescence staining. Taken together, we propose that both •OH and amidyl radicals can be readily produced via N-OH homolysis in N-OHAAF by photoirradiation, which can induce both oxidative and covalent DNA damage. This represents the first report of •OH production and site-specific DNA damage via photoactivation of the genotoxic hydroxamic acid intermediate, which provides a new free radical perspective to better understand the molecular mechanism for the carcinogenicity of AAs.

Fluorescence imaging of Cys in keratinocytes upon UVB exposure using phenyl doped graphitic carbon nitride Nanosheets-Au nanoparticles nanocomposite

Ultraviolet B (UVB) irradiation induces the generation of reactive oxygen species (ROS) and causes damages to human skin. The depletion of glutathione (GSH) to scavenge ROS can protect skin cells from oxidative damage. However, little is known about the concentration level changes of cysteine (Cys), a precursor of GSH in skin cells after exposure to UVB irradiation. Herein, phenyl doped graphitic carbon nitride nanosheets-Au nanoparticles nanocomposite was prepared by in situ deposition of Au nanoparticles on the surface of phenyl doped graphitic carbon nitride nanosheets and showed a turn-on fluorescence response toward Cys over homocysteine, glutathione under physiological conditions. In the presence of Cys, remarkable enhancement of green fluorescence was observed. This nanocomposite was successfully applied for fluorescence imaging of Cys in human skin epidermal cells and monitoring the changes of Cys concentration level under the oxidative stress upon exposure to UVB irradiation in keratinocytes. It was found that the concentration of Cys was increased in the initial period after exposure to UVB irradiation and then gradually decreased to the normal level for the synthesis of GSH to defense the oxidative stress. Our result helps to understand the physiological function of Cys in human skin cells under UVB exposure.

Protective Effects of Sesamin against UVB-Induced Skin Inflammation and Photodamage In Vitro and In Vivo

Ultraviolet (UV) exposure has been demonstrated as the most critical factor causing extrinsic skin aging and inflammation. This study explored the protective effects and mechanisms of sesamin against skin photodamage. Sesamin reduced intracellular reactive oxygen species production after UVB irradiation in human dermal fibroblasts. The sesamin treatment attenuated mitogen-activated protein (MAP) kinase phosphorylation and matrix metalloproteinase (MMPs) overexpression induced by UVB exposure, and it significantly enhanced the tissue inhibitor of metalloproteinase-1 protein expression. Sesamin also elevated the total collagen content in human fibroblasts by inhibiting UVB-induced mothers against decapentaplegic homolog 7 (Smad7) protein expression. Sesamin reduced UVB-induced inducible nitric oxide synthase (i-NOS) and cyclooxygenase-2 (COX-2) overexpression and inhibited nuclear factor-kappa B (NF-κB) translocation. Moreover, sesamin may regulate the c-Jun N-terminal kinases (JNK) and p38 MAP kinase pathways, which inhibit COX-2 expression. Sesamin could reduce UVB-induced inflammation, epidermal hyperplasia, collagen degradation, and wrinkle formation in hairless mice. It also reduced MMP-1, interleukin (IL-1), i-NOS, and NF-κB in the mouse skin. These results demonstrate that sesamin had antiphotodamage and anti-inflammatory activities. Sesamin has potential for use as a skin protection agent in antiphotodamage and skin care products.

Apocynin protects retina cells from ultraviolet radiation damage via inducing sirtuin 1

Direct exposure to Ultraviolet (UV) radiation causes progressive damages in retinal cells, which is one of the hypothetical mechanisms underlying age-related retinopathy or macular degeneration. The protective effects of Apocynin against UV damages were firstly tested in retinal pigment epithelium cells (RPEs) and retinal ganglion cells (RGCs). Subsequently the beneficial effect of Apocynin on mouse retinas against light damage were examined. Next, microarray profiling was used to identify the genes regulated by Apocynin in both RPEs and RGCs. A candidate gene was isolated for functional characterisation by knock-down study. Apocynin was shown to inhibit cell death, reduce oxidative stress and deoxyribonucleic acid damages in both RPEs and RGCs challenged with UV. Intravitreal application of Apocynin also improved retinal dysfunction caused by light damage. Sirtuin 1 (SIRT1) was identified as induced by Apocynin by microarray study. The induction was confirmed by realtime-PCR and western blotting. Knocking down SIRT1 antagonised the protective effect of Apocynin against UV damages in both RPEs and RGCs. Apocynin is a novel agent that shows both in vitro and in vivo efficacies against UV radiation induced retina damages. SIRT1 pathway is implicated in UV radiation protection of Apocynin in retinal cells.

Saccharomyces cerevisiae strains as bioindicators for titanium dioxide sunscreen photoprotective and photomutagenic assessment

Although several short-term assays are available for cosmetic photosafety assessment, cell models are usually highly sensitive to UV radiation, tending to overestimate both phototoxic and photomutagenic risks. In addition, these assays are performed with UV doses/fluences that do not correspond to actual environmental conditions. In this sense, Saccharomyces cerevisiae has already proved to be an interesting tool to predict photomutagenic potential of several compounds, including sunscreens. Yeast can support environmental UVB doses compatible with human daily sunlight exposure, allowing the use of irradiation sources to faithfully mimic the external conditions of ambient sunlight. Herein, we used a set of S. cerevisiae mutant strains sensitive to UVA, UVB and Solar Simulated Light sources in order to evaluate their potential as bioindicators for sunscreen development. The bioindicator potential of the strains was tested with the widely-used titanium dioxide inorganic sunscreen. The AWP001 (yno1) and LPW002 (ogg1yno1) strains obtained in this study stood out as promising experimental tools for the validation of this assay. Overall, our results evidenced a set of S. cerevisiae strains particularly useful for evaluating both photoprotective (efficacy) and photo/antiphotomutagenic (safety) potential of UV filters, meeting the industries and regulatory agencies demand for robust and efficient in vitro screening tests.

Cyanidin-3-o-glucoside inhibits UVA-induced human dermal fibroblast injury by upregulating autophagy

BACKGROUND/PURPOSE

Ultraviolet (UV) A (315-400 nm) is the UV light that most frequently reaches the Earth's surface and can penetrate the epidermis through to the dermis, causing various issues, including skin aging and skin cancer. The results of our previous studies have shown that the flavonoid monomer cyanidin-3-o-glucoside (C3G) can effectively inhibit primary human dermal fibroblast (HDF) oxidative damage and apoptosis caused by UVA radiation. Many flavonoids can regulate the level of autophagy. However, whether C3G inhibits UVA-induced oxidative damage to primary HDFs by regulating autophagy levels remains unclear.

METHODS AND RESULTS

In this study, we used different doses (0-12 J/cm² ) of UVA to irradiate cells and showed that the expression levels of autophagy-related gene 5 (Atg5) and microtubule-associated protein 1 light chain 3 (LC3)-II in primary HDFs first increased and then decreased. The expression of Atg5 and LC3-II was significantly decreased under 12 J/cm² (light-damage model). C3G increased the levels of Atg5 and LC3-II. Primary HDFs were pretreated with C3G, followed by treatment with the autophagy inhibitor 3-methyladenine (3-MA) after 12 J/cm² UVA irradiation. The inhibitory effects of C3G on morphological changes, oxidative damage, and apoptosis in primary HDFs induced by UVA were significantly decreased.

CONCLUSION

C3G can inhibit UVA-induced damage to primary HDFs by inducing autophagy. These results provide a theoretical basis for the application of natural compounds to resist light damage to the skin in the future.

A perspective on ecologically relevant plant-UV research and its practical application

Plants perceive ultraviolet-B (UV-B) radiation through the UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8), and initiate regulatory responses via associated signalling networks, gene expression and metabolic pathways. Various regulatory adaptations to UV-B radiation enable plants to harvest information about fluctuations in UV-B irradiance and spectral composition in natural environments, and to defend themselves against UV-B exposure. Given that UVR8 is present across plant organs and tissues, knowledge of the systemic signalling involved in its activation and function throughout the plant is important for understanding the context of specific responses. Fine-scale understanding of both UV-B irradiance and perception within tissues and cells requires improved application of knowledge about UV-attenuation in leaves and canopies, warranting greater consideration when designing experiments. In this context, reciprocal crosstalk among photoreceptor-induced pathways also needs to be considered, as this appears to produce particularly complex patterns of physiological and morphological response. Through crosstalk, plant responses to UV-B radiation go beyond simply UV-protection or amelioration of damage, but may give cross-protection over a suite of environmental stressors. Overall, there is emerging knowledge showing how information captured by UVR8 is used to regulate molecular and physiological processes, although understanding of upscaling to higher levels of organisation, i.e. organisms, canopies and communities remains poor. Achieving this will require further studies using model plant species beyond Arabidopsis, and that represent a broad range of functional types. More attention should also be given to plants in natural environments in all their complexity, as such studies are needed to acquire an improved understanding of the impact of climate change in the context of plant-UV responses. Furthermore, broadening the scope of experiments into the regulation of plant-UV responses will facilitate the application of UV radiation in commercial plant production. By considering the progress made in plant-UV research, this perspective highlights prescient topics in plant-UV photobiology where future research efforts can profitably be focussed. This perspective also emphasises burgeoning interdisciplinary links that will assist in understanding of UV-B effects across organisational scales and gaps in knowledge that need to be filled so as to achieve an integrated vision of plant responses to UV-radiation.

UV cell stress induces oxidative cyclization of a protective reagent for DNA damage reduction in skin explants

UV irradiation is a major driver of DNA damage and ultimately skin cancer. UV exposure leads to persistent radicals that generate ROS over prolonged periods of time. Toward the goal of developing long-lasting antioxidants that can penetrate skin, we have designed a ROS-initiated protective (RIP) reagent that, upon reaction with ROS (antioxidant activity), self-cyclizes and then releases the natural product apocynin. Apocynin is a known antioxidant and inhibitor of NOX oxidase enzymes. A key phenol on the compound 1 controls ROS-initiated cyclization and makes 1 responsive to ROS with a EC50 comparable to common antioxidants in an ABTS assay. In an in vitro DNA nicking assay, the RIP reagent prevented DNA strand breaks. In cell-based assays, the reagent was not cytotoxic, apocynin was released only in cells treated with UVR, reduced UVR-induced cell death, and lowered DNA lesion formation. Finally, topical treatment of human skin explants with the RIP reagent reduced UV-induced DNA damage as monitored by quantification of cyclobutane dimer formation and DNA repair signaling via TP53. The reagent was more effective than administration of a catalase antioxidant on skin explants. This chemistry platform will expand the types of ROS-activated motifs and enable inhibitor release for potential use as a long-acting sunscreen.

Rat Glioma Cell-Based Functional Characterization of Anti-Stress and Protein Deaggregation Activities in the Marine Carotenoids, Astaxanthin and Fucoxanthin

Stress, protein aggregation, and loss of functional properties of cells have been shown to contribute to several deleterious pathologies including cancer and neurodegeneration. The incidence of these pathologies has also been shown to increase with age and are often presented as evidence to the cumulative effect of stress and protein aggregation. Prevention or delay of onset of these diseases may prove to be unprecedentedly beneficial. In this study, we explored the anti-stress and differentiation-inducing potential of two marine bioactive carotenoids (astaxanthin and fucoxanthin) using rat glioma cells as a model. We found that the low (nontoxic) doses of both protected cells against UV-induced DNA damage, heavy metal, and heat-induced protein misfolding and aggregation of proteins. Their long-term treatment in glioma cells caused the induction of physiological differentiation into astrocytes. These phenotypes were supported by upregulation of proteins that regulate cell proliferation, DNA damage repair mechanism, and glial differentiation, suggesting their potential for prevention and treatment of stress, protein aggregation, and age-related pathologies.

Photoprotection assessment of olive (Olea europaea L.) leaves extract standardized to oleuropein: In vitro and in silico approach for improved sunscreens

Olive leaves contain higher amount of polyphenols than olive oil and represent a waste product from olive harvest and pruning of olive trees. The most abundant compound in olive leaves is oleuropein. Benefits of the topical application of olive leaves extract were previously reported, but little information is available on its photoprotective potential and the result of the association of this extract with organic UV filters in topical sunscreen formulations. The olive leaves extract photoprotective potential is less explored for both oral and topical photoprotection in comparison with other plants extracts and polyphenols, such as Polypodium leucotomos extract and resveratrol. There are increasing efforts towards developing more efficient sunscreens and a photoprotection assessement along with a better understanding of the photochemistry of naturally occurring sunscreens could aid the design of new and improved commercial sunscreen formulations. This study was designed to investigate the photoprotective potential of olive leaves extract standardized for oleuropein performing a set of in vitro and in silico tools as an innovative approach, highlighting yeast assays, in vitro Sun Protection Factor (SPF) and molecular modelling studies of UV absorption. This study supports the use of olive leaves extract for photoprotection, as an effective photoprotective, anti-mutagenic and antioxidant active, also showing a synergistic effect in association with UV filters with an improvement on in vitro SPF of sunscreen formulations.

Anti-Wrinkling and Anti-Melanogenic Effect of Pradosia mutisii Methanol Extract

Ultraviolet (UV) exposure causes skin photoaging leading to skin wrinkling and sagging via production of reactive oxygen species (ROS). For this reason, protection from photoaging is an important feature in cosmeceutical and dermatological products. Natural product-derived biomaterials are highly desired as future possible ingredients, because these biomaterials are often safe and effective. In this study, we aimed to characterize the skin protective activity of Pradosia mutisii, traditionally used to treat sunburn and erythema. We determined the free radical scavenging, anti-melanogenic, and moisturizing effects of a methanol extract of Pradosia mutisii (Pm-ME) in keratinocytes (HaCaT cells), melanocytes (B16F10 cells), and fibroblasts (human dermal fibroblasts (HDFs)) at non-cytotoxic concentrations. Pradosia mutisii methanol extract contains coumaric acid as a major component, and the extract exhibited protective activity against UVB- and H₂O₂-induced cytotoxicity. This extract also suppressed the expression of metalloproteinases (MMPs) and cyclooxygenase (COX)-2 in HaCaT cells. A reduction of Sirt-1 expression under UVB- and H₂O₂-treated conditions was recovered in HaCaT cells by Pm-ME. This extract displayed significant free radical scavenging activity according to the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) assay. The Pm-ME also upregulated the expression levels of hyaluronic acid synthase (HAS) and transglutaminase-1 (TGM-1) in HaCaT cells, indicating a putative moisturizing activity. Interestingly, the expression of collagen type 1 (Col1A1) gene and its promoter activity, as assessed by a reporter gene assay, were found to be increased in HDF and HEK293 cells. Similarly, Pm-ME helped recover collagen levels after UVB and H₂O₂ treatment in HDFs as well as decreased the synthesis and secretion of melanin from B16F10 melanoma cells, which may indicate a beneficial whitening cosmetic value. The p38 inhibitor SB203580 and the JNK inhibitor SP600125 suppressed MMP-9 and COX-2 expression in H₂O₂-treated HaCaT cells. Similarly, the ERK inhibitor U0126 inhibited HAS-2 in Pm-ME/H₂O₂-treated HaCaT cells. These findings suggested that inhibition of JNK and p38 and activation of ERK could be targeted by Pm-ME. Therefore, Pm-ME may exert anti-photoaging and anti-melanogenic properties via the regulation of mitogen-activated protein kinase, which could be beneficial in the cosmeceutical industry.

Defense potential of secondary metabolites in medicinal plants under UV-B stress

Ultraviolet-B (UV-B) radiation has, for many decades now, been widely studied with respect to its consequences on plant and animal health. Though according to NASA, the ozone hole is on its way to recovery, it will still be a considerable time before UV-B levels reach pre-industrial limits. Thus, for the present, excessive UV-B reaching the Earth is a cause for concern, and UV-B related human ailments are on the rise. Plants produce various secondary metabolites as one of the defense strategies under UV-B. They provide photoprotection via their UV-B screening effects and by quenching the reactive oxygen- and nitrogen species produced under UV-B influence. These properties of plant secondary metabolites (PSMs) are being increasingly recognized and made use of in sunscreens and cosmetics, and pharma- and nutraceuticals are gradually becoming a part of the regular diet. Secondary metabolites derived from medicinal plants (alkaloids, terpenoids, and phenolics) are a source of pharmaceuticals, nutraceuticals, as well as more rigorously tested and regulated drugs. These metabolites have been implicated in providing protection not only to plants under the influence of UV-B, but also to animals/animal cell lines, when the innate defenses in the latter are not adequate under UV-B-induced damage. The present review focuses on the defense potential of secondary metabolites derived from medicinal plants in both plants and animals. In plants, the concentrations of the alkaloids, terpenes/terpenoids, and phenolics have been discussed under UV-B irradiation as well as the fate of the genes and enzymes involved in their biosynthetic pathways. Their role in providing protection to animal models subjected to UV-B has been subsequently elucidated. Finally, we discuss the possible futuristic scenarios and implications for plant, animal, and human health pertaining to the defense potential of these secondary metabolites under UV-B radiation-mediated damages.

Light-triggered release of photocaged therapeutics - Where are we now?

The current available therapeutics face several challenges such as the development of ideal drug delivery systems towards the goal of personalized treatments for patients benefit. The application of light as an exogenous activation mechanism has shown promising outcomes, owning to the spatiotemporal confinement of the treatment in the vicinity of the diseased tissue, which offers many intriguing possibilities. Engineering therapeutics with light responsive moieties have been explored to enhance the bioavailability, and drug efficacy either in vitro or in vivo. The tailor-made character turns the so-called photocaged compounds highly desirable to reduce the side effects of drugs and, therefore, have received wide research attention. Herein, we seek to highlight the potential of photocaged compounds to obtain a clear understanding of the mechanisms behind its use in therapeutic delivery. A deep overview on the progress achieved in the design, fabrication as well as current and possible future applications in therapeutics of photocaged compounds is provided, so that novel formulations for biomedical field can be designed.