Molecular and cellular effects of ultraviolet light-induced genotoxicity

Essential roles of Rad6 in conidial property, stress tolerance, and pathogenicity of Beauveria bassiana

Rad6 functions as a ubiquitin-conjugating protein that regulates cellular processes in many fungal species. However, its role in filamentous entomopathogenic fungi remains poorly understood. This study characterizes Rad6 in Beauveria bassiana, a filamentous fungus widely employed as a critical fungicide globally. The results demonstrate a significant association between Rad6 and conidial properties, heat shock response, and UV-B tolerance. Concurrently, the mutant strain exhibited heightened sensitivity to oxidative stress, cell wall interfering agents, DNA damage stress, and prolonged heat shock. Furthermore, the absence of Rad6 significantly extended the median lethal time (LT50) of Galleria mellonella infected by B. bassiana. This delay could be attributed to reduced Pr1 proteases and extracellular cuticle-degrading enzymes, diminished dimorphic transition rates, and dysregulated antioxidant enzymes. Additionally, the absence of Rad6 had a more pronounced effect on genetic information processing, metabolism, and cellular processes under normal conditions. However, its impact was limited to metabolism in oxidative stress. This study offers a comprehensive understanding of the pivotal roles of Rad6 in conidial and hyphal stress tolerance, environmental adaptation, and the pathogenesis of Beauveria bassiana.

Photoreactivation Activities of Rad5, Rad16A and Rad16B Help Beauveria bassiana to Recover from Solar Ultraviolet Damage

In budding yeast, Rad5 and Rad7-Rad16 play respective roles in the error-free post-replication repair and nucleotide excision repair of ultraviolet-induced DNA damage; however, their homologs have not yet been studied in non-yeast fungi. In the fungus Beauveria bassiana, a deficiency in the Rad7 homolog, Rad5 ortholog and two Rad16 paralogs (Rad16A/B) instituted an ability to help the insect-pathogenic fungus to recover from solar UVB damage through photoreactivation. The fungal lifecycle-related phenotypes were not altered in the absence of rad5, rad16A or rad16B, while severe defects in growth and conidiation were caused by the double deletion of rad16A and rad16B. Compared with the wild-type and complemented strains, the mutants showed differentially reduced activities regarding the resilience of UVB-impaired conidia at 25 °C through a 12-h incubation in a regime of visible light plus dark (L/D 3:9 h or 5:7 h for photoreactivation) or of full darkness (dark reactivation) mimicking a natural nighttime. The estimates of the median lethal UVB dose LD50 from the dark and L/D treatments revealed greater activities of Rad5 and Rad16B than of Rad16A and additive activities of Rad16A and Rad16B in either NER-dependent dark reactivation or photorepair-dependent photoreactivation. However, their dark reactivation activities were limited to recovering low UVB dose-impaired conidia but were unable to recover conidia impaired by sublethal and lethal UVB doses as did their photoreactivation activities at L/D 3:9 or 5:7, unless the night/dark time was doubled or further prolonged. Therefore, the anti-UV effects of Rad5, Rad16A and Rad16B in B. bassiana depend primarily on photoreactivation and are mechanistically distinct from those for their yeast homologs.

Recovery of insect-pathogenic fungi from solar UV damage: Molecular mechanisms and prospects

Molecular mechanisms underlying insect-pathogenic fungal tolerance to solar ultraviolet (UV) damage have been increasingly understood. This chapter reviews the methodology established to quantify fungal response to solar UV radiation, which consists of UVB and UVA, and characterize a pattern of the solar UV dose (damage) accumulated from sunrise to sunset on sunny summer days. An emphasis is placed on anti-UV mechanisms of fungal insect pathogens in comparison to those well documented in model yeast. Principles are discussed for properly timing the application of a fungal pesticide to improve pest control during summer months. Fungal UV tolerance depends on either nucleotide excision repair (NER) or photorepair of UV-induced DNA lesions to recover UV-impaired cells in the darkness or the light. NER is a slow process independent of light and depends on a large family of anti-UV radiation (RAD) proteins studied intensively in model yeast but rarely in non-yeast fungi. Photorepair is a rapid process that had long been considered to depend on only one or two photolyases in filamentous fungi. However, recent studies have greatly expanded a genetic/molecular basis for photorepair-dependent photoreactivation that serves as a primary anti-UV mechanism in insect-pathogenic fungi, in which photolyase regulators required for photorepair and multiple RAD homologs have higher or much higher photoreactivation activities than do photolyases. The NER activities of those homologs in dark reactivation cannot recover the severe UV damage recovered by their activities in photoreactivation. Future studies are expected to further expand the genetic/molecular basis of photoreactivation and enrich principles for the recovery of insect-pathogenic fungi from solar UV damage.

Rad2, Rad14 and Rad26 recover Metarhizium robertsii from solar UV damage through photoreactivation in vivo

Rad2, Rad14 and Rad26 recover ultraviolet (UV) damage by nucleotide excision repair (NER) in budding yeast but their functions in filamentous fungi have not been elucidated. Here, we report mechanistically different anti-UV effects of nucleus-specific Rad2, Rad14 and Rad26 orthologs in Metarhizium robertsii, an insect-pathogenic fungus. The null mutants of rad2, rad14 and rad26 showed a decrease of ∼90% in conidial resistance to UVB irradiation. When conidia were impaired at a UVB dose of 0.15 J/cm2, they were photoreactivated (germinated) by only 6-13% through a 5-h light plus 19-h dark incubation, whereas 100%, 80% and 70% of the wild-type conidia were photoreactivated at 0.15, 0.3 and 0.4 J/cm2, respectively. The dose-dependent photoreactivation rates were far greater than the corresponding 24-h dark reactivation rates and were largely enhanced by the overexpression (OE) of rad2, rad14 or rad26 in the wild-type strain. The OE strains exhibited markedly greater activities in photoreactivation of conidia inactivated at 0.5-0.7 J/cm2 than did the wild-type strain. Confirmed interactions of Rad2, Rad14 and Rad26 with photolyase regulators and/or Rad1 or Rad10 suggest that each of these proteins could have evolved into a component of the photolyase regulator-cored protein complex to mediate photoreactivation. The interactions inhibited in the null mutants resulted in transcriptional abolishment or repression of those factors involved in the complex. In conclusion, the anti-UV effects of Rad2, Rad14 and Rad26 depend primarily on DNA photorepair-dependent photoreactivation in M. robertsii and mechanistically differ from those of yeast orthologs depending on NER.

High photoreactivation activities of Rad2 and Rad14 in recovering insecticidal Beauveria bassiana from solar UV damage

Anti-ultraviolet (UV) roles of Rad2 and Rad14 depend on nucleotide excision repair (NER) of UV-induced DNA lesions in budding yeast but remain unexplored yet in filamentous fungi. Here, nucleus-specific Rad2 and Rad14 orthologs are shown to recover Beauveria bassiana, a main source of wide-spectrum mycoinsecticides, from solar UV damage through photorepair-depending photoreactivation. As a photorepair index, photoreactivation (germination) rates of lethal UVB dose-irradiated conidia via a 3- or 5-h light plus 9- or 7-h dark incubation at 25 °C were drastically reduced in the Δrad2 and Δrad14 mutants versus a wild-type strain. As an NER index, nighttime-mimicking 12-h dark reactivation rates of low UVB dose-impaired conidia decreased sharply compared to the corresponding photoreactivation rates in the presence or absence of either ortholog, indicating that its extant NER activity was limited to recovering light UVB damage in the field. The high photoreactivation activity of either Rad2 or Rad14 was derived from its tight link to a large protein complex formed by photolyase regulators and other anti-UV proteins through multiple protein-protein interactions revealed by yeast two-hybrid assays. Therefore, Rad2 and Rad14 recover B. bassiana from solar UV damage through photoreactiovation in vivo that depends primarily on photorepair, although they contribute little to the fungal lifecycle-related phenotypes. These findings unveil a novel scenario distinguished from the NER-depending anti-UV roles of Rad2 and Rad14 in the model yeast and broaden a biological basis crucial for rational application of fungal insecticides to improve pest control efficacy via feasible recovery of solar UV damage.

Divergent roles of Rad4 and Rad23 homologs in Metarhizium robertsii's resistance to solar ultraviolet damage

The anti-ultraviolet (UV) role of a Rad4-Rad23-Rad33 complex in budding yeast relies on nucleotide excision repair (NER), which is mechanistically distinct from photorepair of DNA lesions generated under solar UV irradiation but remains poorly known in filamentous fungi. Here, two nucleus-specific Rad4 paralogs (Rad4A and Rad4B) and nucleocytoplasmic shuttling Rad23 ortholog are functionally characterized by multiple analyses of their null mutants in Metarhizium robertsii, an entomopathogenic fungus lacking Rad33. Rad4A was proven to interact with Rad23 and contribute significantly more to conidial UVB resistance (90%) than Rad23 (65%). Despite no other biological function, Rad4A exhibited a very high activity in photoreactivation of UVB-impaired/inactivated conidia by 5-h light exposure due to its interaction with Rad10, an anti-UV protein clarified previously to have acquired a similar photoreactivation activity through its interaction with a photolyase in M. robertsii. The NER activity of Rad4A or Rad23 was revealed by lower reactivation rates of moderately impaired conidia after 24-h dark incubation but hardly observable at the end of 12-h dark incubation, suggesting an infeasibility of its NER activity in the field where nighttime is too short. Aside from a remarkable contribution to conidial UVB resistance, Rad23 had pleiotropic effect in radial growth, aerial conidiation, antioxidant response, and cell wall integrity but no photoreactivation activity. However, Rad4B proved redundant in function. The high photoreactivation activity of Rad4A unveils its essentiality for M. robertsii's fitness to solar UV irradiation and is distinct from the yeast homolog's anti-UV role depending on NER. IMPORTANCE Resilience of solar ultraviolet (UV)-impaired cells is crucial for the application of fungal insecticides based on formulated conidia. Anti-UV roles of Rad4, Rad23, and Rad33 rely upon nucleotide excision repair (NER) of DNA lesions in budding yeast. Among two Rad4 paralogs and Rad23 ortholog characterized in Metarhizium robertsii lacking Rad33, Rad4A contributes to conidial UVB resistance more than Rad23, which interacts with Rad4A rather than functionally redundant Rad4B. Rad4A acquires a high activity in photoreactivation of conidia severely impaired or inactivated by UVB irradiation through its interaction with Rad10, another anti-UV protein previously proven to interact with a photorepair-required photolyase. The NER activity of either Rad4A or Rad23 is seemingly extant but unfeasible under field conditions. Rad23 has pleiotropic effect in the asexual cycle in vitro but no photoreactivation activity. Therefore, the strong anti-UV role of Rad4A depends on photoreactivation, unveiling a scenario distinct from the yeast homolog's NER-reliant anti-UV role.

Standardized Extract from Wastes of Edible Flowers and Snail Mucus Ameliorate Ultraviolet B-Induced Damage in Keratinocytes

Several studies have highlighted the ability of snail mucus in maintaining healthy skin conditions due to its emollient, regenerative, and protective properties. In particular, mucus derived from Helix aspersa muller has already been reported to have beneficial properties such as antimicrobial activity and wound repair capacity. In order to enhance the beneficial effects of snail mucus, a formulation enriched with antioxidant compounds derived from edible flower waste (Acmella oleracea L., Centaurea cyanus L., Tagetes erecta L., Calendula officinalis L., and Moringa oleifera Lam.) was obtained. UVB damage was used as a model to investigate in vitro the cytoprotective effects of snail mucus and edible flower extract. Results demonstrated that polyphenols from the flower waste extract boosted the antioxidant activity of snail mucus, providing cytoprotective effects in keratinocytes exposed to UVB radiation. Additionally, glutathione content, reactive oxygen species (ROS), and lipid peroxidation levels were reduced following the combined treatment with snail mucus and edible flower waste extract. We demonstrated that flower waste can be considered a valid candidate for cosmeceutical applications due to its potent antioxidant activity. Thus, a new formulation of snail mucus enriched in extracts of edible flower waste could be useful to design innovative and sustainable broadband natural UV-screen cosmeceutical products.

Co-Regulatory Roles of WC1 and WC2 in Asexual Development and Photoreactivation of Beauveria bassiana

The white collar proteins WC1 and WC2 interact with each other to form a white collar complex acting as a well-known transcription regulator required for the operation of the circadian clock in Neurospora, but their roles in insect-pathogenic fungal lifecycles remain poorly understood. Here, we report that WC1 and WC2 orthologs co-regulate the conidiation capacity and conidial resistance to solar ultraviolet-B (UVB) irradiation in Beauveria bassiana, after their high activities in the photorepair of UVB-induced DNA damages were elucidated previously in the insect mycopathogen, which features non-rhythmic conidiation and high conidiation capacity. The conidial yield, UVB resistance, and photoreactivation rate of UVB-impaired conidia were greatly reduced in the null mutants of wc1 and wc2 compared to their control strains. However, many other lifecycle-related phenotypes, except the antioxidant response, were rarely affected in the two mutants. Transcriptomic analysis revealed largely overlapping roles for WC1 and WC2 in regulating the fungal gene networks. Most of the differentially expressed genes identified from the null mutants of wc1 (1380) and wc2 (1001) were co-downregulated (536) or co-upregulated (256) at similar levels, including several co-downregulated genes required for aerial conidiation and DNA photorepair. These findings expand a molecular basis underlying the fungal adaptation to solar UV irradiation and offer a novel insight into the genome-wide co-regulatory roles of WC1 and WC2 in B. bassiana's asexual development and in vivo photoreactivation against solar UV damage.

Use of Natural Agents and Agrifood Wastes for the Treatment of Skin Photoaging

Photoaging is the premature aging of the skin caused by repeated exposure to ultraviolet (UV) rays. The harmful effects of UV rays-from the sun or from artificial sources-alter normal skin structures and cause visible damage, especially in the most exposed areas. Fighting premature aging is one of the most important challenges of the medical landscape. Additionally, consumers are looking for care products that offer multiple benefits with reduced environmental and economic impact. The growing requests for bioactive compounds from aromatic plants for pharmaceutical and cosmetic applications have to find new sustainable methods to increase the effectiveness of new active formulations derived from eco-compatible technologies. The principle of sustainable practices and the circular economy favor the use of bioactive components derived from recycled biomass. The guidelines of the European Commission support the reuse of various types of organic biomass and organic waste, thus transforming waste management problems into economic opportunities. This review aims to elucidate the main mechanisms of photoaging and how these can be managed using natural renewable sources and specific bioactive derivatives, such as humic extracts from recycled organic biomass, as potential new actors in modern medicine.

Comparative Roles of Rad4A and Rad4B in Photoprotection of Beauveria bassiana from Solar Ultraviolet Damage

The Rad4-Rad23-Rad33 complex plays an essential anti-ultraviolet (UV) role depending on nucleotide excision repair (NER) in budding yeast but has been rarely studied in filamentous fungi, which possess two Rad4 paralogs (Rad4A/B) and orthologous Rad23 and rely on the photorepair of UV-induced DNA lesions, a distinct mechanism behind the photoreactivation of UV-impaired cells. Previously, nucleocytoplasmic shuttling Rad23 proved to be highly efficient in the photoreactivation of conidia inactivated by UVB, a major component of solar UV, due to its interaction with Phr2 in Beauveria bassiana, a wide-spectrum insect mycopathogen lacking Rad33. Here, either Rad4A or Rad4B was proven to localize exclusively in the nucleus and interact with Rad23, which was previously shown to interact with the white collar protein WC2 as a regulator of two photorepair-required photolyases (Phr1 and Phr2) in B. bassiana. The Δrad4A mutant lost ~80% of conidial UVB resistance and ~50% of activity in the photoreactivation of UVB-inactivated conidia by 5 h light exposure. Intriguingly, the reactivation rates of UVB-impaired conidia were observable only in the presence of rad4A after dark incubation exceeding 24 h, implicating extant, but infeasible, NER activity for Rad4A in the field where night (dark) time is too short. Aside from its strong anti-UVB role, Rad4A played no other role in B. bassiana's lifecycle while Rad4B proved to be functionally redundant. Our findings uncover that the anti-UVB role of Rad4A depends on the photoreactivation activity ascribed to its interaction with Rad23 linked to WC2 and Phr2 and expands a molecular basis underlying filamentous fungal adaptation to solar UV irradiation on the Earth's surface.

Efficient Photoreactivation of Solar UV-Injured Metarhizium robertsii by Rad1 and Rad10 Linked to DNA Photorepair-Required Proteins

Nucleotide excision repair (NER) of ultraviolet (UV)-induced DNA lesions known as cyclobutane pyrimidine dimer (CPD) and (6-4)-pyrimidine-pyrimidone (6-4PP) photoproducts depends on the activities of multiple anti-UV radiation (RAD) proteins in budding yeast. However, NER remains poorly known in filamentous fungi, whose DNA lesions are photorepaired by one or two photolyases, namely CPD-specific Phr1 and/or 6-4PP-specific Phr2. Previously, the white collar proteins WC1 and WC2 were proven to regulate expressions of phr2 and phr1 and photorepair 6-4PP and CDP DNA lesions, respectively, in Metarhizium robertsii, a filamentous entomopathogenic-phytoendophytic fungus. We report here high activities of orthologous Rad1 and Rad10 in 5-h photoreactivation of UVB-injured or UVB-inactivated conidia but a severely compromised capability of their reactivating those conidia via 24-h dark incubation in M. robertsii. The null mutants of rad1 and rad10 were much more compromised in conidial UVB resistance and photoreactivation capability than the previous null mutants of phr1, phr2, wc1 and wc2. Multiple protein-protein (Rad1-Rad10, Rad1-WC2, Rad10-Phr1, WC1-Phr1/2 and WC2-Phr1/2) interactions detected suggest direct/indirect links of Rad1 and Rad10 to Phr1/2 and WC1/2 and an importance of the links for their photoreactivation activities. Conclusively, Rad1 and Rad10 photoreactivate UVB-impaired M. robertsii through their interactions with the DNA photorepair-required proteins.

Optional strategies for low-risk and non-risk applications of fungal pesticides to avoid solar ultraviolet damage

BACKGROUND

Solar ultraviolet (UV) irradiation is harmful to formulated conidia as active ingredients of fungal pesticides and hence restrains their field application in sunny days of summer, a season requiring frequent pest controls. This conflict makes it necessary to explore optimal strategies for the application of fungal pesticides to suppress pest populations but avoid solar UV damage during summer.

RESULTS

The conidia of Beauveria bassiana, a wide-spectrum fungal pesticide, were tolerable to UVB (major solar UV wavelengths) damage of ≤0.5 J cm^-2 . The damage of this upper limit caused a loss of conidial viability and infectivity if not photoreactivated by light exposure after irradiation. Intriguingly, the light exposure resulted in a high photoreactivation rate of UVB-inactivated conidia and an insignificant or marginal difference in insecticidal activity between normal conidia and those photoreactivated. Modeling analysis of solar UVB intensity recorded hourly over the daylight of five sunny summer days from 5:00 am to 7:00 pm at 30° 17'57'' N and 120°5'7'' E revealed a variation of daily accumulated UVB dose from 2.07 to 2.78 J cm^-2 , which was far beyond the upper limit. A more tolerable dose of ~0.2 J cm^-2 appeared between 3:00 pm and 5:00 pm, and no harmful dose accumulated between 5:00 pm and 7:00 pm.

CONCLUSION

Fungal UVB tolerance, fungal photoreactivation capability and the daily accumulation pattern of solar UV irradiation are based to propose an optional strategy for low-risk or non-risk application of fungal pesticides after 3:00 or 5:00 pm during summer. © 2022 Society of Chemical Industry.

Rad1 and Rad10 Tied to Photolyase Regulators Protect Insecticidal Fungal Cells from Solar UV Damage by Photoreactivation

Beauveria bassiana serves as a main source of global fungal insecticides, which are based on the active ingredient of formulated conidia vulnerable to solar ultraviolet (UV) irradiation and restrained for all-weather application in green agriculture. The anti-UV proteins Rad1 and Rad10 are required for the nucleotide excision repair (NER) of UV-injured DNA in model yeast, but their anti-UV roles remain rarely exploredin filamentous fungi. Here, Rad1 and Rad10 orthologues that accumulated more in the nuclei than the cytoplasm of B. bassiana proved capable of reactivating UVB-impaired or UVB-inactivated conidia efficiently by 5h light exposure but incapable of doing so by 24 h dark incubation (NER) if the accumulated UVB irradiation was lethal. Each orthologue was found interacting with the other and two white collar proteins (WC1 and WC2), which proved to be regulators of two photolyases (Phr1 and Phr2) and individually more efficient in the photorepair of UVB-induced DNA lesions than either photolyase alone. The fungal photoreactivation activity was more or far more compromised when the protein-protein interactions were abolished in the absence of Rad1 or Rad10 than when either Phr1 or Phr2 lost function. The detected protein-protein interactions suggest direct links of either Rad1 or Rad10 to two photolyase regulators. In B. bassiana, therefore, Rad1 and Rad10 tied to the photolyase regulators have high activities in the photoprotection of formulated conidia from solar UV damage but insufficient NER activities in the field, where night (dark) time is too short, and no other roles in the fungal lifecycle in vitro and in vivo.

Phytocomplex of a Standardized Extract from Red Orange (Citrus sinensis L. Osbeck) against Photoaging

Excessive exposure to solar radiation is associated with several deleterious effects on human skin. These effects vary from the occasional simple sunburn to conditions resulting from chronic exposure such as skin aging and cancers. Secondary metabolites from the plant kingdom, including phenolic compounds, show relevant photoprotective activities. In this study, we evaluated the potential photoprotective activity of a phytocomplex derived from three varieties of red orange (Citrus sinensis (L.) Osbeck). We used an in vitro model of skin photoaging on two human cell lines, evaluating the protective effects of the phytocomplex in the pathways involved in the response to damage induced by UVA-B. The antioxidant capacity of the extract was determined at the same time as evaluating its influence on the cellular redox state (ROS levels and total thiol groups). In addition, the potential protective action against DNA damage induced by UVA-B and the effects on mRNA and protein expression of collagen, elastin, MMP1, and MMP9 were investigated, including some inflammatory markers (TNF-α, IL-6, and total and phospho NFkB) by ELISA. The obtained results highlight the capacity of the extract to protect cells both from oxidative stress—preserving RSH (p < 0.05) content and reducing ROS (p < 0.01) levels—and from UVA-B-induced DNA damage. Furthermore, the phytocomplex is able to counteract harmful effects through the significant downregulation of proinflammatory markers (p < 0.05) and MMPs (p < 0.05) and by promoting the remodeling of the extracellular matrix through collagen and elastin expression. This allows the conclusion that red orange extract, with its strong antioxidant and photoprotective properties, represents a safe and effective option to prevent photoaging caused by UVA-B exposure.

MaAts, an Alkylsulfatase, Contributes to Fungal Tolerances against UV-B Irradiation and Heat-Shock in Metarhizium acridum

Sulfatases are commonly divided into three classes: type I, type II, and type III sulfatases. The type III sulfatase, alkylsulfatase, could hydrolyze the primary alkyl sulfates, such as sodium dodecyl sulfate (SDS) and sodium octyl sulfate. Thus, it has the potential application of SDS biodegradation. However, the roles of alkylsulfatase in biological control fungus remain unclear. In this study, an alkylsulfatase gene MaAts was identified from Metarhizium acridum. The deletion strain (ΔMaAts) and the complemented strain (CP) were constructed to reveal their functions in M. acridum. The activity of alkylsulfatase in ΔMaAts was dramatically reduced compared to the wild-type (WT) strain. The loss of MaAts delayed conidial germination, conidiation, and significantly declined the fungal tolerances to UV-B irradiation and heat-shock, while the fungal conidial yield and virulence were unaffected in M. acridum. The transcription levels of stress resistance-related genes were significantly changed after MaAts inactivation. Furthermore, digital gene expression profiling showed that 512 differential expression genes (DEGs), including 177 up-regulated genes and 335 down-regulated genes in ΔMaAts, were identified. Of these DEGs, some genes were involved in melanin synthesis, cell wall integrity, and tolerances to various stresses. These results indicate that MaAts and the DEGs involved in fungal stress tolerances may be candidate genes to be adopted to improve the stress tolerances of mycopesticides.

Molecular basis and regulatory mechanisms underlying fungal insecticides' resistance to solar ultraviolet irradiation

Resistance to solar ultraviolet (UV) irradiation is crucial for field-persistent control efficacies of fungal formulations against arthropod pests, because their active ingredients are formulated conidia very sensitive to solar UV wavelengths. This review seeks to summarize advances in studies aiming to quantify, understand and improve conidial UV resistance. One focus of studies has been on the many sets of genes that have been revealed in the postgenomic era to contribute to or mediate UV resistance in the insect pathogens serving as main sources of fungal insecticides. Such genetic studies have unveiled the broad basis of UV-resistant molecules including cytosolic solutes, cell wall components, various antioxidant enzymes, and numerous effectors and signaling proteins, that function in developmental, biosynthetic and stress-responsive pathways. Another focus has been on the molecular basis and regulatory mechanisms underlying photorepair of UV-induced DNA lesions and photoreactivation of UV-impaired conidia. Studies have shed light upon a photoprotective mechanism depending on not only one or two photorepair-required photolyases, but also two white collar proteins and other partners that play similar or more important roles in photorepair via interactions with photolyases. Research hotspots are suggested to explore a regulatory network of fungal photoprotection and to improve the development and application strategies of UV-resistant fungal insecticides. © 2021 Society of Chemical Industry.

Mechanically robust hybrid hydrogels of photo-crosslinkable gelatin and laminin-mimetic peptide amphiphiles for neural induction

Self-assembling bio-instructive materials that can provide a biomimetic tissue microenvironment with the capability to regulate cellular behaviors represent an attractive platform in regenerative medicine. Herein, we develop a hybrid neuro-instructive hydrogel that combines the properties of a photo-crosslinkable gelatin methacrylate (GelMA) and self-assembling peptide amphiphiles (PAs) bearing a laminin-derived neuro-inductive epitope (PA-GSR). Electrostatic interaction and ultraviolet light crosslinking mechanisms were combined to create dual-crosslinked hybrid hydrogels with tunable stiffness. Spectroscopic, microscopic and theoretical techniques show that the cationic PA-GSR(+) electrostatically co-assembles with the negatively charged GelMA to create weak hydrogels with hierarchically ordered microstructures, which were further photo-crosslinked to create mechanically robust hydrogels. Dynamic oscillatory rheology and micromechanical testing show that photo-crosslinking of the co-assembled GelMA and PA-GSR(+) hydrogel results in robust hydrogels displaying improved stiffness. Gene expression analysis was used to show that GelMA/PA-GSR(+) hydrogels can induce human mesenchymal stem cells (hMSCs) into neural-lineage cells and supports neural-lineage specification of neuroblast-like cells (SH-SY5Y) in a growth-factor-free manner. Also, metabolomics analysis suggests that the hydrogel alters the metabolite profiles in the cells by affecting multiple molecular pathways. This work highlights a new approach for the design of PA-based hybrid hydrogels with robust mechanical properties and biological functionalities for nerve tissue regeneration.

A Global Analysis of Photoreceptor-Mediated Transcriptional Changes Reveals the Intricate Relationship Between Central Metabolism and DNA Repair in the Filamentous Fungus Trichoderma atroviride

Light provides critical information for the behavior and development of basically all organisms. Filamentous fungi sense blue light, mainly, through a unique transcription factor complex that activates its targets in a light-dependent manner. In Trichoderma atroviride, the BLR-1 and BLR-2 proteins constitute this complex, which triggers the light-dependent formation of asexual reproduction structures (conidia). We generated an ENVOY photoreceptor mutant and performed RNA-seq analyses in the mutants of this gene and in those of the BLR-1, CRY-1 and CRY-DASH photoreceptors in response to a pulse of low intensity blue light. Like in other filamentous fungi BLR-1 appears to play a central role in the regulation of blue-light responses. Phenotypic characterization of the Δenv-1 mutant showed that ENVOY functions as a growth and conidiation checkpoint, preventing exacerbated light responses. Similarly, we observed that CRY-1 and CRY-DASH contribute to the typical light-induced conidiation response. In the Δenv-1 mutant, we observed, at the transcriptomic level, a general induction of DNA metabolic processes and strong repression of central metabolism. An analysis of the expression level of DNA repair genes showed that they increase their expression in the absence of env-1. Consistently, photoreactivation experiments showed that Δenv-1 had increased DNA repair capacity. Our results indicate that light perception in T. atroviride is far more complex than originally thought.

The impact of ultraviolet radiation on skin photoaging - review of in vitro studies

Background

Photoaging, ultra violet (UV) induced skin aging is a gradual process that depends on the time and intensity of solar radiation.

Aim

The aim of this paper was to review of the literature focused on in vitro studies explaining the mechanisms of photoaging.

Methods

Electronic databases, including PubMed and MEDLINE, were searched for in vitro studies on the importance of UV radiation in the skin photoaging process of peer‐reviewed scientific journals. Only articles available in English and full version publications were considered for this review.

Results

Three main modes of UV radiation action on skin cells which lead to photoaging, there are changes in cell metabolism, induction of oxidative stress due to the change in enzyme activity.

Conclusion

The information gathered in this publication will help to better understand the complex and multidirectional mechanism of skin photoaging, which will contribute to the development of research on potential cosmetic products that provide effective and safe sun protection or repair damage caused by UV radiation.

Two white collar proteins protect fungal cells from solar UV damage by their interactions with two photolyases in Metarhizium robertsii

The photolyases PHR1 and PHR2 enable photorepair of fungal DNA lesions in the forms of UV-induced cyclobutane pyrimidine dimer (CPD) and (6-4)-pyrimidine-pyrimidone (6-4PP) photoproducts, but their regulation remains mechanistically elusive. Here, we report that the white collar proteins WC1 and WC2 mutually interacting to form a light-responsive transcription factor regulate photolyase expression required for fungal UV resistance in the insect-pathogenic fungus Metharhizum robertsii. Conidial UVB resistance decreased by 54% in Δwc1 and 67% in Δwc2. Five-hour exposure of UVB-inactivated conidia to visible light resulted in photoreactivation rates of 30% and 9% for the Δwc1 and Δwc2 mutants, contrasting to 79%-82% for wild-type and complemented strains. Importantly, abolished transcription of phr1 in Δwc-2 and of phr2 in Δwc1 resulted in incapable photorepair of CDP and 6-4PP DNA lesions in UVB-impaired Δwc2 and Δwc1 cells respectively. Yeast two-hybrid assays revealed interactions of either WC protein with both PHR1 and PHR2. Therefore, the essential roles for WC1 and WC2 in both photorepair of UVB-induced DNA lesions and photoreactivation of UVB-inactivated conidia rely upon their interactions with, and hence transcriptional activation of, PHR1 and PHR2. These findings uncover a novel WC-cored pathway that mediates filamentous fungal response and adaptation to solar UV irradiation.

Omega-3 fatty acid intake and decreased risk of skin cancer in organ transplant recipients

PURPOSE

Organ transplant recipients have over 100-fold higher risk of developing skin cancer than the general population and are in need of further preventive strategies. We assessed the possible preventive effects of omega-3 polyunsaturated fatty acid (PUFA) intake from food on the two main skin cancers, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) in kidney and liver transplant recipients.

METHODS

Adult kidney or liver transplant recipients transplanted for at least 1 year and at high risk of skin cancer were recruited from the main transplant hospital in Queensland, 2012-2014 and followed until mid-2016. We estimated their dietary total long-chain omega-3 PUFAs and α-linolenic acid intakes at baseline using a food frequency questionnaire and ranked PUFA intakes as low, medium, or high. Relative risks (RRs_adj) of skin cancer adjusted for confounding factors with 95% confidence intervals (CIs) were calculated.

RESULTS

There were 449 transplant recipients (mean age, 55 years; 286 (64%) male). During follow-up, 149 (33%) patients developed SCC (median 2/person; range 1-40) and 134 (30%), BCC. Transplant recipients with high total long-chain omega-3 PUFA compared with low intakes showed substantially reduced SCC tumour risk (RR_adj 0.33, 95% CI 0.18-0.60), and those with high α-linolenic acid intakes experienced significantly fewer BCCs (RR_adj 0.40, 95% CI 0.22-0.74). No other significant associations were seen.

CONCLUSION

Among organ transplant recipients, relatively high intakes of long-chain omega-3 PUFAs and of α-linolenic acid may reduce risks of SCC and BCC, respectively.

Photoprotective Role of Photolyase-Interacting RAD23 and Its Pleiotropic Effect on the Insect-Pathogenic Fungus Beauveria bassiana

RAD23 can repair yeast DNA lesions through nucleotide excision repair (NER), a mechanism that is dependent on proteasome activity and ubiquitin chains but different from photolyase-depending photorepair of UV-induced DNA damages. However, this accessory NER protein remains functionally unknown in filamentous fungi. In this study, orthologous RAD23 in Beauveria bassiana, an insect-pathogenic fungus that is a main source of fungal insecticides, was found to interact with the photolyase PHR2, enabling repair of DNA lesions by degradation of UVB-induced cytotoxic (6-4)-pyrimidine-pyrimidine photoproducts under visible light, and it hence plays an essential role in the photoreactivation of UVB-inactivated conidia but no role in reactivation of such conidia through NER in dark conditions. Fluorescence-labeled RAD23 was shown to normally localize in the cytoplasm, to migrate to vacuoles in the absence of carbon, nitrogen, or both, and to enter nuclei under various stresses, which include UVB, a harmful wavelength of sunlight. Deletion of the rad23 gene resulted in an 84% decrease in conidial UVB resistance, a 95% reduction in photoreactivation rate of UVB-inactivated conidia, and a drastic repression of phr2 A yeast two-hybrid assay revealed a positive RAD23-PHR2 interaction. Overexpression of phr2 in the Δrad23 mutant largely mitigated the severe defect of the Δrad23 mutant in photoreactivation. Also, the deletion mutant was severely compromised in radial growth, conidiation, conidial quality, virulence, multiple stress tolerance, and transcriptional expression of many phenotype-related genes. These findings unveil not only the pleiotropic effects of RAD23 in B. bassiana but also a novel RAD23-PHR2 interaction that is essential for the photoprotection of filamentous fungal cells from UVB damage.IMPORTANCE RAD23 is able to repair yeast DNA lesions through nucleotide excision in full darkness, a mechanism distinct from photolyase-dependent photorepair of UV-induced DNA damage but functionally unknown in filamentous fungi. Our study unveils that the RAD23 ortholog in a filamentous fungal insect pathogen varies in subcellular localization according to external cues, interacts with a photolyase required for photorepair of cytotoxic (6-4)-pyrimidine-pyrimidine photoproducts in UV-induced DNA lesions, and plays an essential role in conidial UVB resistance and reactivation of UVB-inactivated conidia under visible light rather than in the dark, as required for nucleotide excision repair. Loss-of-function mutations of RAD23 exert pleiotropic effects on radial growth, aerial conidiation, multiple stress responses, virulence, virulence-related cellular events, and phenotype-related gene expression. These findings highlight a novel mechanism underlying the photoreactivation of UVB-impaired fungal cells by RAD23 interacting with the photolyase, as well as its essentiality for filamentous fungal life.

Sunbeds and melanoma risk: time to close the debate

PURPOSE OF REVIEW

In spite of the established scientific evidence on the association of sunbed use with melanoma risk, some have recently expressed scepticism about the carcinogenicity of indoor tanning. This may have raised confusion among both physicians and patients. The purpose of this review is to make the point about the real impact of sunbed use on melanoma risk in light of the most recently published evidence.

RECENT FINDINGS

Seven themes were covered: recent studies on age at first sunbed exposure and melanoma risk; sunbed use and melanoma at different body sites; sunbed use and development of additional primary melanomas; new studies on proportion of melanomas attributable to sunbed use; sunbed use and melanoma risk factors; economic burden of sunbed use; and recent debate over whether indoor tanning contributes to melanoma.

SUMMARY

We were able to apply all epidemiological criteria for causality to the relationship between sunbed use and melanoma. Together with the new evidence on the strength, dose response, and temporality of the association of sunbeds with melanoma, this will hopefully close the debate over whether indoor tanning contributes to melanoma.

Cost-Effective Cosmetic-Grade Hyaluronan Hydrogels for ReNcell VM Human Neural Stem Cell Culture

Hyaluronic acid (HA) is a polysaccharide polymer frequently used as a starting material to fabricate hydrogels, especially for recapitulating the brain's extracellular matrix (ECM) for in vitro neural stem cell (NSC) cultures. Here, we report the successful synthesis of a methacrylated HA (MeHA) polymer from an inexpensive cosmetic-grade hyaluronan starting material. The MeHA polymers synthesized from cosmetic-grade HA yielded similar chemical purity to those from pharmaceutical/research-grade HA reported in the literature. Crosslinked MeHA (x-MeHA) hydrogels were formed using radical polymerization which resulted in mechanical properties matching previously reported mechanical property ranges for enhanced neuronal differentiation of NSCs. We assessed cellular adhesion, spreading, proliferation, and stiffness-dependent neuronal differentiation properties of ReNcell VM human neural stem cells (hNSCs) and compared our results to studies reported in the literature (that utilized non-human and human pluripotent cell-derived NSCs).

Dietary Fat Intake and the Risk of Skin Cancer: A Systematic Review and Meta-Analysis of Observational Studies

We conducted a meta-analysis to evaluate the association between fat intake and the risk of three major types of skin cancer including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM). A comprehensive search of PubMed and EMBASE was performed to identify all relevant observational studies published up to December 1, 2018. Specific odds ratio (OR) or relative risk (RR) estimates for the highest versus the lowest intake of dietary fat and 95% confidence intervals (CI) from the included studies were pooled using random effect model. Three prospective cohort studies (175,675 participants and 30,915 BCC cases, 4,106 SCC cases and 1,638 CMM cases) and nine case-control studies (328 BCC cases, 493 SCC cases, 1,547 CMM cases and 2,660 controls) were identified. The pooled results indicated that dietary consumption of total fat and saturated fat were not associated with three major types of skin cancer. High consumption of monounsaturated fat was significantly associated with a decreased risk of BCC (RR: 0.90, 95% CI: 0.85-0.96) and high level of polyunsaturated fat intake was potentially positively associated with SCC (RR: 1.19, 95% CI: 1.06-1.33). Our findings should be confirmed by further evidence from well-designed and large-scale prospective cohort studies.

The phosphatase gene MaCdc14 negatively regulates UV-B tolerance by mediating the transcription of melanin synthesis-related genes and contributes to conidiation in Metarhizium acridum

Reversible phosphorylation of proteins regulated by protein kinases and phosphatases mediate multiple biological events in eukaryotes. In this study, a dual-specificity cell division cycle 14 phosphatase, MaCdc14, was functionally characterized in Metarhizium acridum. Deletion of MaCdc14 decreased branch numbers, affected septum formation and resulted in multiple nuclei in each hyphal compartment, indicating nuclear division and cytokinesis defects. The spore production capacity was severely impaired with decreased conidial yield and delayed conidiation in MaCdc14-deletion mutant (ΔMaCdc14). The transcription levels of conidiation-related genes were significantly changed after MaCdc14 inactivation. The morphology of conidia was uneven in size and the germination rate of conidia was increased in ΔMaCdc14. In addition, ΔMaCdc14 displayed significantly enhanced conidial tolerance to ultraviolet (UV) irradiation but had no significant effect on the thermotolerance, the sensitivities to cell wall damage reagents, osmotic and oxidative stresses, and virulence compared to the wild-type strain and complementary transformant. Furthermore, the pigmentation of ΔMaCdc14 was increased by the upregulated expression of melanin synthesis-related genes, which may result in the enhanced UV-B tolerance of ΔMaCdc14. In summary, MaCdc14 negatively regulated UV-B tolerance by mediating the transcription of melanin synthesis-related genes, contributed to conidiation by regulating the expression levels of conidiation-related genes and also played important roles in cytokinesis and morphogenesis in Metarhizium acridum.

Two Photolyases Repair Distinct DNA Lesions and Reactivate UVB-Inactivated Conidia of an Insect Mycopathogen under Visible Light

Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobutane pyrimidine dimers (CPDs) and (6-4)-pyrimidine-pyrimidine photoproducts (6-4PPs). This study aims to elucidate how CPD photolyase (Phr1) and 6-4PP photolyase (Phr2) repair DNA damage and photoreactivate UVB-inactivated cells in Beauveria bassiana, a main source of fungal insecticides. Both Phr1 and Phr2 are proven to exclusively localize in the fungal nuclei. Despite little influence on growth, conidiation, and virulence, singular deletions of phr1 and phr2 resulted in respective reductions of 38% and 19% in conidial tolerance to UVB irradiation, a sunlight component most harmful to formulated conidia. CPDs and 6-4PPs accumulated significantly more in the cells of Δphr1 and Δphr2 mutants than in those of a wild-type strain under lethal UVB irradiation and were largely or completely repaired by Phr1 in the Δphr2 mutant and Phr2 in the Δphr1 mutant after optimal 5-h exposure to visible light. Consequently, UVB-inactivated conidia of the Δphr1 and Δphr2 mutants were much less efficiently photoreactivated than were the wild-type counterparts. In contrast, overexpression of either phr1 or phr2 in the wild-type strain resulted in marked increases in both conidial UVB resistance and photoreactivation efficiency. These findings indicate essential roles of Phr1 and Phr2 in photoprotection of B. bassiana from UVB damage and unveil exploitable values of both photolyase genes for improved UVB resistance and application strategy of fungal insecticides.IMPORTANCE Protecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in Beauveria bassiana, a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition of cytotoxic cyclobutane pyrimidine dimers and (6-4)-pyrimidine-pyrimidine photoproducts, hence reactivating UVB-inactivated cells effectively under visible light. Our findings shed light on the high potential of both photolyase genes for use in improving UVB resistance and application strategy of fungal insecticides.

Efficiency of natural substances to protect Beauveria bassiana conidia from UV radiation

BACKGROUND

Solar radiation is assumed to be a major factor limiting the efficacy of entomopathogenic fungi used as biocontrol agents in open field applications. We evaluated 12 natural UV-protective co-formulants for their effect on the survival of UV-exposed Beauveria bassiana spores on agar plates, colza leaf discs and in the field.

RESULTS

Colony-forming unit (CFU) counts of unformulated conidia on agar plates and leaf discs dropped to ≤ 50% after exposure to UV radiation. The highest UV protection was achieved with humic acid, which provided > 90% protection of UV-B-exposed conidia in laboratory experiments. In the field, 10% humic acid increased spore persistence up to 87% at 7 days after application. Sesame and colza oil also provided high UV protection in both assays (> 73% and > 70%, respectively).

CONCLUSIONS

This study shows that it is possible to increase the persistence of B. bassiana spores under exposure to UV radiation by formulation with natural UV-protective additives. UV protectants might, therefore, increase the efficacy of entomopathogenic fungi as biocontrol agents in open field applications. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Exploring major signaling cascades in melanomagenesis: a rationale route for targetted skin cancer therapy

Although most melanoma cases may be treated by surgical intervention upon early diagnosis, a significant portion of patients can still be refractory, presenting low survival rates within 5 years after the discovery of the illness. As a hallmark, melanomas are highly prone to evolve into metastatic sites. Moreover, melanoma tumors are highly resistant to most available drug therapies and their incidence have increased over the years, therefore leading to public health concerns about the development of novel therapies. Therefore, researches are getting deeper in unveiling the mechanisms by which melanoma initiation can be triggered and sustained. In this context, important progress has been achieved regarding the roles and the impact of cellular signaling pathways in melanoma. This knowledge has provided tools for the development of therapies based on the intervention of signal(s) promoted by these cascades. In this review, we summarize the importance of major signaling pathways (mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)-Akt, Wnt, nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB), Janus kinase (JAK)-signal transducer and activator of transcription (STAT), transforming growth factor β (TGF-β) and Notch) in skin homeostasis and melanoma progression. Available and developing melanoma therapies interfering with these signaling cascades are further discussed.

Riboflavin induces Metarhizium spp. to produce conidia with elevated tolerance to UV-B, and upregulates photolyases, laccases and polyketide synthases genes

AIMS

The effect of nutritional supplementation of two Metarhizium species with riboflavin (Rb) during production of conidia was evaluated on (i) conidial tolerance (based on germination) to UV-B radiation and on (ii) conidial expression following UV-B irradiation, of enzymes known to be active in photoreactivation, viz., photolyase (Phr), laccase (Lac) and polyketide synthase (Pks).

METHODS AND RESULTS

Metarhizium acridum (ARSEF 324) and Metarhizium robertsii (ARSEF 2575) were grown either on (i) potato dextrose agar medium (PDA), (ii) PDA supplemented with 1% yeast extract (PDAY), (iii) PDA supplemented with Rb (PDA+Rb), or (iv) PDAY supplemented with Rb (PDAY+Rb). Resulting conidia were exposed to 866·7 mW m^-2 of UV-B Quaite-weighted irradiance to total doses of 3·9 or 6·24 kJ m^-2 . Some conidia also were exposed to 16 klux of white light (WL) after being irradiated, or not, with UV-B to investigate the role of possible photoreactivation. Relative germination of conidia produced on PDA+Rb (regardless Rb concentration) or on PDAY and exposed to UV-B was higher compared to conidia cultivated on PDA without Rb supplement, or to conidia suspended in Rb solution immediately prior to UV-B exposure. The expression of MaLac3 and MaPks2 for M. acridum, as well as MrPhr2, MrLac1, MrLac2 and MrLac3 for M. robertsii was higher when the isolates were cultivated on PDA+Rb and exposed to UV-B followed by exposure to WL, or exposed to WL only.

CONCLUSIONS

Rb in culture medium increases the UV-B tolerance of M. robertsii and M. acridum conidia, and which may be related to increased expression of Phr, Lac and Pks genes in these conidia.

SIGNIFICANCE AND IMPACT OF THE STUDY

The enhanced UV-B tolerance of Metarhizium spp. conidia produced on Rb-enriched media may improve the effectiveness of these fungi in biological control programs.

Varying susceptibility of clinical and environmental Scedosporium isolates to chemical oxidative stress in conidial germination

Scedosporium species are opportunistic pathogens causing a great variety of infections in both immunocompetent and immunocompromised individuals. The Scedosporium genus ranks the second among the filamentous fungi colonizing the airways of patients with cystic fibrosis (CF), after Aspergillus fumigatus, and most species are capable to chronically colonize the respiratory tract of these patients. Nevertheless, few data are available regarding evasion of the inhaled conidia to the host immune response. Upon microbial infection, macrophages and neutrophils release reactive oxygen species (ROS). To colonize the respiratory tract, the conidia need to germinate despite the oxidative stress generated by phagocytic cells. Germination of spores from different clinical or environmental isolates of the major Scedosporium species was investigated in oxidative stress conditions. All tested species showed susceptibility to oxidative stress. However, when comparing clinical and environmental isolates, differences in germination capabilities under oxidative stress conditions were seen between species as well as within each species. Among environmental isolates, Scedosporium aurantiacum isolates were the most resistant to oxidative stress whereas Scedosporium dehoogii were the most susceptible. Overall, the differences observed between Scedosporium species in the capacity to germinate under oxidative stress conditions could explain their varying prevalence and pathogenicity.

Mechanisms of aging and development-A new understanding of environmental damage to the skin and prevention with topical antioxidants

Recent research has given us new insights into the molecular biology of extrinsic aging of the skin. Not only does UV irradiation directly cause photoaging of the skin, but also environmental pollutants significantly damage exposed skin by several mechanisms. Exposure to the noxious gases of air pollution with simultaneous exposure to UVA can act synergistically to initiate skin cancer. Also ozone generated from pollutants reacting with UV induces oxidative stress of the skin's surface via formation of lipid peroxidation products, with cascading consequences to deeper layers. Furthermore, new studies have demonstrated that particulate matter (PM) pollutants can penetrate the skin transepidermally and through hair follicles to induce skin aging via the aryl hydrocarbon receptor (AHR), a recently discovered ligand-activated transcription factor that regulates and protects keratinocytes, melanocytes, and fibroblasts. With this understanding that extrinsic aging of the skin is not only due to photoaging, we realize the necessity of protection beyond sunscreen. Fortunately, correctly formulated topical antioxidants can prevent damage inflicted by both UV and environmental pollution.

Immunostaining of UVA-induced DNA damage in erythrocytes of medaka (Oryzias latipes)

Some authors have recently reported that UVA induces double-strand breaks (DSBs) in DNA. Only a few researchers have reported on the induction of DSBs upon UVA exposure, as measured using the Comet assay and γ-H2AX as markers of DSB formation. In the present study, we have investigated for the first time the dose-dependent induction of DSBs by UVA in medaka (Oryzias latipes) erythrocytes. Adult female medaka fish were exposed to UVA for 15, 30, and 60min/day for three continuous days; an unirradiated control group was kept in the same laboratory conditions. At 0h and 24h after UVA exposure, blood was collected to detect DNA damage and repair. The number of γ-H2AX foci was higher than the control value at 0h after UVA exposure and decreased within a 24h. the comet assay showed that DNA repair began during the recovery period. These findings confirm our pervious findings of genotoxic effects after UVA exposure in medaka erythrocytes and suggest that the replication-independent formation of UVA-induced DSBs is mediated through the generation of reactive oxygen species. In conclusion, these results suggest that DNA damage and repair occur after UVA exposure in medaka fish. UVA is the main component of solar UV radiation and is used for artificial UV exposure. Our results may have implications for skin cancer research.

Chlorin e6 mediated photodynamic inactivation for multidrug resistant Pseudomonas aeruginosa keratitis in mice in vivo

Following corneal epithelium scratches, mouse corneas were infected with the multidrug resistant (MDR) P. aeruginosa strain PA54. 24 hours later, 0% (for control group), 0.01%, 0.05% or 0.1% Chlorin e6 (Ce6), a second generation photosensitizer derived from chlorophyll, was combined with red light, for photodynamic inactivation (PDI). 1 hour or 2 days later, entire mouse eyes were enucleated and homogenized for counting colony forming units (CFU) of P. aeruginosa. For comparison, 0.1% Ce6 mediated PDI was started at 12 hours post infection, and 0.005% methylene blue mediated PDI 24 hours post infection. Clinical scores of corneal manifestation were recorded daily. Compared to the control, CFU 1 hour after PDI started 24 hours post infection in the 0.01% Ce6 and 0.05% Ce6 groups were significantly lower (more than one log₁₀ reduction), the CFU 2 days post PDI higher in the 0.1% Ce6 group, clinical score lower in the 0.1% Ce6 group at 1 day post PDI. These findings suggest that PDI with Ce6 and red light has a transient efficacy in killing MDR-PA in vivo, and repetitive PDI treatments are required to fully resolve the infection. Before its clinical application, the paradoxical bacterial regrowth post PDI has to be further studied.

Stress tolerance and virulence of insect-pathogenic fungi are determined by environmental conditions during conidial formation

The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects.

Ultraviolet radiation and systemic lupus erythematosus

Exposure to ultraviolet (UV) radiation is among the environmental factors that have been proposed and studied in association with systemic lupus erythematosus (SLE). While it is known that UV radiation exposure may exacerbate pre-existing lupus, it remains unclear whether UV exposure is a risk factor for the development of SLE. Experimental studies show a significant immunomodulatory role for UV radiation, but strong epidemiologic data regarding its role in triggering SLE onset are lacking. Further studies are needed to assess the role of UV radiation in relation to development of incident SLE, yet they are challenging to design due to difficulties in accurate exposure assessment, the heterogeneous nature of SLE, and the challenge of assessing photosensitivity, a feature of SLE, which often precedes its diagnosis.

Preventive Long-Term Effects of a Topical Film-Forming Medical Device with Ultra-High UV Protection Filters and DNA Repair Enzyme in Xeroderma Pigmentosum: A Retrospective Study of Eight Cases

Skin cancer is common in xeroderma pigmentosum (XP) due to a DNA repair mechanisms genetic defect. Ultraviolet (UV) exposure is the main cause of increased incidence of actinic keratosis (AK), basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) observed in XP subjects. Photoprotection is therefore a mandatory strategy in order to reduce skin damage. A topical DNA repair enzyme has been shown to slow down the development of skin lesions in XP. However, there are no data regarding the effects of photoprotection combined with DNA repair strategies in this clinical setting. A film-forming medical device containing the DNA repair enzyme photolyase and very high-protection UV filters (Eryfotona AK-NMSC, Ery) is currently available. We report retrospective data regarding the use of Ery in 8 patients (5 women, 3 men) with a diagnosis of XP treated for at least 12 consecutive months, comparing the rate of new skin lesions (AK, BCC and SCC) during active treatment with Ery and during 12 months just before the use of the product. New AK, BCC and SCC mean lesion numbers during the 1-year Ery treatment were 5, 3 and 0, respectively in comparison with 14, 6.8 and 3 lesions, respectively during the 1-year pre-treatment period. Ery use was associated with a 65% reduction in appearance of new AK lesions and with 56 and 100% reductions in the incidence of new BCC and SCC lesions, respectively. These data suggest that topical use of photoprotection and DNA repair enzyme could help lower skin cancer lesions in XP. Control prospective trials are advisable in this clinical setting.

Simultaneous irradiation with different wavelengths of ultraviolet light has synergistic bactericidal effect on Vibrio parahaemolyticus

Ultraviolet (UV) irradiation is an increasingly used method of water disinfection. UV rays can be classified by wavelength into UVA (320-400 nm), UVB (280-320 nm), and UVC (<280 nm). We previously developed UVA sterilization equipment with a UVA light-emitting diode (LED). The aim of this study was to establish a new water disinfection procedure using the combined irradiation of the UVA-LED and another UV wavelength. An oxidative DNA product, 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased after irradiation by UVA-LED alone, and the level of cyclobutane pyrimidine dimers (CPDs) was increased by UVC alone in Vibrio parahaemolyticus. Although sequential irradiation of UVA-LED and UVC-induced additional bactericidal effects, simultaneous irradiation with UVA-LED and UVC-induced bactericidal synergistic effects. The 8-OHdG and CPDs production showed no differences between sequential and simultaneous irradiation. Interestingly, the recovery of CPDs was delayed by simultaneous irradiation. The synergistic effect was absent in SOS response-deficient mutants, such as the recA and lexA strains. Because recA- and lexA-mediated SOS responses have crucial roles in a DNA repair pathway, the synergistic bactericidal effect produced by the simultaneous irradiation could depend on the suppression of the CPDs repair. The simultaneous irradiation of UVA-LED and UVC is a candidate new procedure for effective water disinfection.

Effects of oral administration of Lonicera caerulea berries on UVB-induced damage in SKH-1 mice. A pilot study

Solar ultraviolet radiation is a major environmental factor that has serious adverse effects on the structure and function of the skin. Although the UVB waveband (295-315 nm) represents only 5-10% of incoming UV light, it is very damaging to the skin. The aim of this study was to investigate the effect of Lonicera caerulea berries on UVB-induced damage to SKH-1 hairless mice. Mice were fed a L. caerulea berry-enriched diet (10%, w/w) for 14 days before a single UVB (1000 mJ cm(-2)) treatment. Effects on health status, antioxidant enzyme activity and expression, and DNA damage were evaluated. The bioavailability of L. caerulea phenolic components was also assessed. We found that feeding with L. caerulea berries prevented a decrease in catalase activity and stimulated NADPH quinone oxidoreductase-1, heme oxygenase-1, and gamma-glutamylcysteine synthetase catalytic and modulatory subunit expression in UVB exposed mice. Administration of the L. caerulea berry-enriched diet led to an increase in UVB-reduced interleukin-17 levels and a decrease in keratinocyte-derived chemokine protein expression that was enhanced after UVB treatment. Further, L. caerulea berries reduced UVB-induced DNA damage evaluated as number of single strand breaks, cyclobutane-pyrimidine dimer formation and H2AX phosphorylation, a marker of double strand breaks. Taken together, we provide evidence that oral administration of L. caerulea berries to mice affords at least partial protection from the adverse effects of a single UVB exposure via modulation of antioxidant enzyme activity/expression and reduction of DNA damage.

Structural insights into DNA repair by RNase T--an exonuclease processing 3' end of structured DNA in repair pathways

DNA repair mechanisms are essential for preservation of genome integrity. However, it is not clear how DNA are selected and processed at broken ends by exonucleases during repair pathways. Here we show that the DnaQ-like exonuclease RNase T is critical for Escherichia coli resistance to various DNA-damaging agents and UV radiation. RNase T specifically trims the 3' end of structured DNA, including bulge, bubble, and Y-structured DNA, and it can work with Endonuclease V to restore the deaminated base in an inosine-containing heteroduplex DNA. Crystal structure analyses further reveal how RNase T recognizes the bulge DNA by inserting a phenylalanine into the bulge, and as a result the 3' end of blunt-end bulge DNA can be digested by RNase T. In contrast, the homodimeric RNase T interacts with the Y-structured DNA by a different binding mode via a single protomer so that the 3' overhang of the Y-structured DNA can be trimmed closely to the duplex region. Our data suggest that RNase T likely processes bulge and bubble DNA in the Endonuclease V-dependent DNA repair, whereas it processes Y-structured DNA in UV-induced and various other DNA repair pathways. This study thus provides mechanistic insights for RNase T and thousands of DnaQ-like exonucleases in DNA 3'-end processing.

Consumption of omega-3 fatty acids and the risk of skin cancers: a systematic review and meta-analysis

Skin cancers have a higher incidence than all other cancers combined and are a major cause of morbidity worldwide. Laboratory data suggest certain dietary constituents, notably omega-3 polyunsaturated fatty acids (n-3 PUFAs), could potentially protect against skin malignancy, although no large-scale review has been conducted in humans. The objective of this review and meta-analysis was to determine the relationship between dietary n-3 PUFAs and skin cancer incidence. It considered all published randomized controlled trials and observational studies up to March 2013. Five studies (two case-control and three cohort) were identified pertaining to oral n-3 PUFA consumption and incidence of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), melanoma (or a combination) and were included in a random-effects meta-analysis. A further six studies considering nondietary n-3 PUFA exposure (e.g., by tissue analysis) and/or recognized biological markers of skin cancer risk (e.g., p53 expression) were analyzed qualitatively. Dietary n-3 PUFAs were not associated with BCC (pooled OR 1.05, 95% CIs 0.86-1.28). Consumption of high levels of n-3 PUFAs were inversely associated with melanoma, although with only one estimate available (OR 0.52, 95% CI 0.34-0.78), and SCC, although nonsignificantly (pooled OR 0.86, 95% CIs 0.59-1.23). Available evidence is suggestive, but currently inadequate, to support the hypothesis that n-3 PUFAs protect against skin malignancy.

The role of optical radiations in skin cancer

Purpose. Electromagnetic radiation with wavelength in the range 100 nm to 1 mm is known as optical radiation and includes ultraviolet radiation, the visible spectrum, and infrared radiation. The deleterious short- and long-term biological effects of ultraviolet radiation, including melanoma and other skin cancers, are well recognized. Infrared radiation may also have damaging biological effects. Methods. The objective of this review was to assess the literature over the last 15 years and to summarize correlations between exposure to optical radiation and the risk of melanoma and other cancers. Results. There is a clear correlation between exposure to UV radiation and the development of skin cancer. Most importantly, a strong association between artificial UV radiation exposure, for example, tanning devices, and the risk of melanoma and squamous cell carcinoma has been clearly demonstrated. There is no clear evidence that exposure to IR and laser radiation may increase the risk of skin cancer, although negative health effects have been observed. Conclusions. Preventative strategies that involve provision of public information highlighting the risks associated with exposure to sunlight remain important. In addition, precautionary measures that discourage exposure to tanning appliances are required, as is legislation to prevent their use during childhood.