The sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid photosensitizes the formation of oxidized guanines in cellulo after UV-A or UV-B exposure

A Bioinspired Skin UV Filter with Broadband UV Protection, Photostability, and Resistance to Oxidative Damage

In recent years, sunscreens' adverse impacts on the environment and biology have gained wide attention. The improvement of sunscreen safety has become one of the major priorities in skin photoprotection research. It is an effective strategy to develop bionic photoprotective materials by simulating the photoprotective mechanism existing in nature. Inspired by the photoprotective mechanisms of skin and plant leaves, the bionic photoprotective material CS-SA-PDA nanosheet was developed using the free radical grafting method and Michael addition, with natural melanin analogue polydopamine (PDA) nanoparticles and plant sunscreen molecular sinapic acid (SA) as sun protection factors and natural polymer chitosan (CS) as the connecting arm. The results show that CS-SA-PDA can effectively shield UVB and UVA due to the possible synergistic effect between PDA and SA. The introduction of polymer CS significantly improved the photostability of SA and reduced the skin permeability of PDA nanoparticles. The CS-SA-PDA nanosheet can also effectively scavenge photoinduced free radicals. Furthermore, in vivo toxicity and anti-UV evaluations confirm that CS-SA-PDA has no skin irritation and is excellent against skin photodamage, which makes it an ideal skin photoprotective material.

The Role of Acetyl Zingerone and Its Derivatives in Inhibiting UV-Induced, Incident, and Delayed Cyclobutane Pyrimidine Dimers

Cyclobutane pyrimidine dimers (CPDs) are ultraviolet radiation (UV)-induced carcinogenic DNA photoproducts that lead to UV signature mutations in melanoma. Previously, we discovered that, in addition to their incident formation (iCPDs), UV exposure induces melanin chemiexcitation (MeCh), where UV generates peroxynitrite (ONOO^-), which oxidizes melanin into melanin-carbonyls (MCs) in their excited triplet state. Chronic MeCh and energy transfer by MCs to DNA generates CPDs for several hours after UV exposure ends (dark CPD, dCPDs). We hypothesized that MeCh and the resulting dCPDs can be inhibited using MeCh inhibitors, and MC and ONOO^- scavengers. Here, we investigated the efficacy of Acetyl Zingerone (AZ), a plant-based phenolic alkanone, and its chemical analogs in inhibiting iCPDs and dCPDs in skin fibroblasts, keratinocytes, and isogenic pigmented and albino melanocytes. While AZ and its methoxy analog, 3-(4-Methoxy-benzyl)-Pentane-2,4-dione (MBPD) completely inhibited the dCPDs, MBPD also inhibited ~50% of iCPDs. This suggests the inhibition of ~80% of total CPDs at any time point post UV exposure by MBPD, which is markedly significant. MBPD downregulated melanin synthesis, which is indispensable for dCPD generation, but this did not occur with AZ. Meanwhile, AZ and MBPD both upregulated the expression of nucleotide excision repair (NER) pathways genes including Xpa, Xpc, and Mitf. AZ and its analogs were non-toxic to the skin cells and did not act as photosensitizers. We propose that AZ and MBPD represent "next-generation skin care additives" that are safe and effective for use not only in sunscreens but also in other specialized clinical applications owing to their extremely high efficacy in blocking both iCPDs and dCPDs.

Ecotoxicological Evaluation of Sunscreens on Marine Plankton

In recent years, a large number of sunscreens have emerged to protect our skin. Most of them are made up of simple or compound aromatic structures, which can pose a threat to marine ecosystems. In order to understand their effects on the marine environment, different ecotoxicological bioassays were carried out using planktonic organisms from three phyla and two different trophic levels: larvae of the sea urchin Paracentrotus lividus, the copepod Acartia tonsa, and the microalga Tisochrysis lutea. The aim of these tests was to expose these organisms to leachates from eight sunscreen formulations. All of them showed a great variability in toxicity on the different plankton organisms. The highest toxicity level was found for cream number 4 when tested on sea urchin, exhibiting an EC50 = 122.4 mg/L. The toxicity of the UV filter 2-phenyl-5-benzimidazolesulfonic acid, exclusively present in that cream, was evaluated in sea urchin, where an EC10 = 699.6 mg/L was obtained under light exposure. According to our results, all tested creams become nontoxic to plankton upon 30,000-fold dilution in seawater; thus, only local effects are expected. This study highlights the need to understand the toxic effects generated by solar protection products, as well as their ingredients, on marine organisms.

A sunscreen nanoparticles polymer based on prolonged period of protection

UV rays are one of the most dangerous factors that harm the skin. There is continuous improvement in getting an effective sunscreen that protects the skin from excessive exposure to UV rays. Typically, phenylbenzimidazole-5-sulfonic acid (PBSA) is used as a sun blocking agent, but its disadvantage is that it can photodegrade and cause cell damage. In our work, PBSA was encapsulated in niosomes nanoparticles then coated with chitosan-aloe vera (CS-nio-aloe/PBSA) to form a carrier polymer with novel and potent properties. This polymer controls PBSA release and epidermal penetration. Characterization of CS-nio-aloe/PBSA polymer nanoparticles through transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and dynamic light scattering (DLS). The carrier polymer release rate was studied in vitro and epidermal permeability to coated PBSA was assessed using mouse skin. The nanoparticle polymer containing sunscreen was effectively prepared with an encapsulation efficiency of 80%. The formulation (CS-nio-aloe/PBSA) was completely deposited on the surface of the skin. This supports its use to protect the skin, and its nanostructures stimulate the release of PBSA for a longer period. Encapsulation of PBSA in CS-nio-aloe nanoparticles could allow for further cellular preservation, UV protection, control of free PBSA, and limited penetration through the mouse skin epidermis.

Elucidating the Photoluminescence Quenching in Ensulizole: an Artificial Water Soluble Sunscreen

Employing natural or artificial sunscreens is essential to protect the skin from ultraviolet radiations that cause premature aging and develop melanoma and other forms of skin cancer. The 2-Phenylbenzimidazole-5-sulfonic acid, commonly known as ensulizole is a water-soluble artificial sunscreen that absorb UV-B (280 nm - 315 nm) radiations and protects the skin against the harmful effects of these radiations. We have measured steady-state photoluminescence (SSPL) spectra and photoluminescence (PL) kinetics of this compound in various conditions. Steady-state absorption indicates a strong absorption feature at 303 nm and a weak one at 316 nm that have been identified as π → π* and n → π* transitions, respectively. The spectra of PL induced by these absorptions indicate that the PL of ensulizole is less Stokes-shifted in polar solvents and more Stokes-shifted in non-polar solvents. The average PL lifetime of ensulizole is longer in non-polar solvents than in polar solvents and it exhibits the shortest PL lifetime in aqueous medium that maximize its transition efficiency in water. This suggests in non-polar solvents intersystem crossing is the dominant mode of relaxation of the excited ππ* state. Furthermore, an increase of pH of ensulizole solution decreases the PL intensity and the lifetime. Stern-Volmer equation is employed to evaluate bimolecular quenching rate constant kq. The evaluation result suggests the diffusional dynamic mode of PL quenching is operative.

Antimicrobial activity and metabolite profiling of endophytic fungi in Digitaria bicornis (Lam) Roem. and Schult. and Paspalidium flavidum (Retz.) A. Camus

Endophytic fungal occurrences were studied in aerial regions of Digitaria bicornis and Paspalidium flavidum by three isolation methods: potato dextrose agar (PDA), malt extract agar (MEA), and moist blotters. Seventy species of 29 genera of endophytic fungi in D. bicornis and 71 species of 30 genera in P. flavidum were documented. Endophytic fungal communities were grouped into 40 and 43 anamorphic ascomycetes (21 and 23 genera) and 20 teleomorphic ascomycetes (6 and 7 genera) in D. bicornis and P. flavidum, respectively. PDA supported the expression of larger number of fungal communities than MEA and MB; and P. flavidum hosted more number of endophytic fungi than D. bicornis. Seasons played an important role in supporting the assemblage of fungal endophytes. Endophytic fungal species richness and assemblages in plant regions were determined for alpha, beta, and gamma diversities. The ethyl acetate followed by methanolic extracts of certain fungal species showed good antagonistic and antibacterial activities. Among fungal endophytes, Curvularia protuberata and Penicillium citrinum exhibited high antagonistic and antibacterial activities. The high-resolution orbitrap liquid chromatography-mass spectrometry of ethyl acetate crude extracts of C. protuberata and P. citrinum revealed the presence of antifungal and antimicrobial, besides a host of compounds in the extracts. The present study indicated that grass endophytes are the sources of compounds with antimicrobial and other pharmacological activities.

Suppression of Pax3-MITF-M Axis Protects from UVB-Induced Skin Pigmentation by Tetrahydroquinoline Carboxamide

Paired box gene 3 (Pax3) and cAMP responsive element-binding protein (CREB) directly interact with the cis-acting elements on the promoter of microphthalmia-associated transcription factor isoform M (MITF-M) for transcriptional activation in the melanogenic process. Tyrosinase (Tyro) is a target gene of MITF-M, and functions as a key enzyme in melanin biosynthesis. Tetrahydroquinoline carboxamide (THQC) was previously screened as an antimelanogenic candidate. In the current study, we evaluated the antimelanogenic activity of THQC in vivo and elucidated a possible mechanism. Topical treatment with THQC mitigated ultraviolet B (UVB)-induced skin pigmentation in guinea pig with decreased messenger RNA (mRNA) and protein levels of melanogenic genes such as MITF-M and Tyro. Moreover, THQC inhibited cAMP-induced melanin production in α-melanocyte-stimulating hormone (α-MSH)- or histamine-activated B16-F0 cells, in which it suppressed the expression of the MITF-M gene at the promoter level. As a mechanism, THQC normalized the protein levels of Pax3, a transcriptional activator of the MITF-M gene, in UVB-exposed and pigmented skin, as well as in α-MSH-activated B16-F0 culture. However, THQC did not affect UVB- or α-MSH-induced phosphorylation (activation) of CREB. The results suggest that suppression of the Pax3–MITF-M axis might be a potential strategy in the treatment of skin pigmentary disorders that are at high risk under UVB radiation.

Insights and controversies on sunscreen safety

Although sunlight provides several benefits, ultraviolet (UV) radiation plays an important role in the development of various skin damages such as erythema, photoaging, and photocarcinogenesis. Despite cells having endogenous defense systems, damaged DNA may not be efficiently repaired at chronic exposure. In this sense, it is necessary to use artificial defense strategies such as sunscreen formulations. UV filters should scatter, reflect, or absorb solar UV radiation in order to prevent direct or indirect DNA lesions. However, the safety of UV filters is a matter of concern due to several controversies reported in literature, such as endocrine alterations, allergies, increased oxidative stress, phototoxic events, among others. Despite these controversies, the way in which sunscreens are tested is essential to ensure safety. Sunscreen regulation includes mandatory test for phototoxicity, but photogenotoxicity testing is not recommended as a part of the standard photosafety testing program. Although available photobiological tests are still the first approach to assess photosafety, they are limited. Some existing tests do not always provide reliable results, mainly due to limitations regarding the nature of the assessed phototoxic effect, cell UV sensitivity, and the irradiation protocols. These aspects bring queries regarding the safety of sunscreen wide use and suggest the demand for the development of robust and efficient in vitro screening tests to overcome the existing limitations. In this way, Saccharomyces cerevisiae has stood out as a promising model to fill the gaps in photobiology and to complete the mandatory tests enabling a more extensive and robust photosafety assessment.

Novel functions for 2-phenylbenzimidazole-5-sulphonic acid: Inhibition of ovarian cancer cell responses and tumour angiogenesis

In this study, we investigated the effects and molecular mechanisms of 2-phenylbenzimidazole-5-sulphonic acid (PBSA), an ultraviolet B protecting agent used in sunscreen lotions and moisturizers, on ovarian cancer cell responses and tumour angiogenesis. PBSA treatment markedly blocked mitogen-induced invasion through down-regulation of matrix metalloproteinase (MMP) expression and activity in ovarian cancer SKOV-3 cells. In addition, PBSA inhibited mitogen-induced cell proliferation by suppression of cyclin-dependent kinases (Cdks), but not cyclins, leading to pRb hypophosphorylation and G1 phase cell cycle arrest. These anti-cancer activities of PBSA in ovarian cancer cell invasion and proliferation were mediated by the inhibition of mitogen-activated protein kinase kinase 3/6-p38 mitogen-activated protein kinase (MKK3/6-p38MAPK ) activity and subsequent down-regulation of MMP-2, MMP-9, Cdk4, Cdk2 and integrin β1, as evidenced by treatment with p38MAPK inhibitor SB203580. Furthermore, PBSA suppressed the expression and secretion of vascular endothelial growth factor in SKOV-3 cells, leading to inhibition of capillary-like tubular structures in vitro and angiogenic sprouting ex vivo. Taken together, our results demonstrate the pharmacological effects and molecular targets of PBSA on modulating ovarian cancer cell responses and tumour angiogenesis, and suggest further evaluation and development of PBSA as a promising chemotherapeutic agent for the treatment of ovarian cancer.

Manganese Oxide Nanoclusters for Skin Photoprotection

An ultraviolet (UV) filter is the core component of sunscreen and protects skin from various photo damages. Current UV filters are hampered by skin penetration, poor photostability, photocatalytic generation of harmful reactive oxygen species (ROS), and potential environmental risks. In this work, manganese dioxide nanoclusters were developed as an eco-friendly UV filter by a facile two-step synthesis, using colloid silica as support under ambient conditions. These nanoclusters show a better UV-shielding profile than commercial titanium dioxide nanoparticles and capability to scavenge various ROS. They can be easily incorporated by a sunscreen formula and demonstrate an excellent skin photoprotection performance both in vitro and in vivo.

Nanolayered composite with enhanced ultraviolet ray absorption properties from simultaneous intercalation of sunscreen molecules

Introduction

The potential of layered double hydroxide (LDH) as a host of multiple ultraviolet-ray absorbers was investigated by simultaneous intercalation of benzophenone 4 (B4) and Eusolex^® 232 (EUS) in Zn/Al LDH.

Methods

The nanocomposites were prepared via coprecipitation method at various molar ratios of B4 and EUS.

Results

At equal molar ratios, the obtained nanocomposite showed an intercalation selectivity that is preferential to EUS. However, the selectivity ratio of intercalated anions was shown to be capable of being altered by adjusting the molar ratio of intended guests during synthesis. Dual-guest nanocomposite synthesized with B4:EUS molar ratio 3:1 (ZEB [3:1]) showed an intercalation selectivity ratio of B4:EUS =53:47. Properties of ZEB (3:1) were monitored using powder X-ray diffractometer to show a basal spacing of 21.8 Å. Direct-injection mass spectra, Fourier transform infrared spectra, and ultraviolet–visible spectra confirmed the dual intercalation of both anions into the interlayer regions of dual-guest nanocomposite. The cytotoxicity study of dual-guest nanocomposite ZEB (3:1) on human dermal fibroblast cells showed no significant toxicity until 25 μg/mL.

Conclusion

Overall, the findings demonstrate successful customization of ultraviolet-ray absorbers composition in LDH host.

A sunblock based on bioadhesive nanoparticles

The majority of commercial sunblock preparations use organic or inorganic ultraviolet (UV) filters. Despite protecting against cutaneous phototoxicity, direct cellular exposure to UV filters has raised a variety of health concerns. Here, we show that the encapsulation of padimate O (PO)--a model UV filter--in bioadhesive nanoparticles (BNPs) prevents epidermal cellular exposure to UV filters while enhancing UV protection. BNPs are readily suspended in water, facilitate adherence to the stratum corneum without subsequent intra-epidermal or follicular penetration, and their interaction with skin is water resistant yet the particles can be removed via active towel drying. Although the sunblock based on BNPs contained less than 5 wt% of the UV-filter concentration found in commercial standards, the anti-UV effect was comparable when tested in two murine models. Moreover, the BNP-based sunblock significantly reduced double-stranded DNA breaks when compared with a commercial sunscreen formulation.

Photophysical and photosensitizing characters of 2-phenylbenzimidazole-5-sulfonic acid. A theoretical study

The sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid (PBSA) has been reported to exhibit photosensitizing activity. In the present study, the photophysical and photosensitizing properties of PBSA were investigated by means of quantum chemical calculations with the aim to gain deeper insights into the underlying photosensitizing mechanisms. The results indicate that singlet oxygen may be generated spontaneously through direct energy transfer from triplet excited state PBSA to (3)O2, and superoxide anion radical is formed through electron transfer between the anion of PBSA and (3)O2. This offers some deeper insights into the photosensitizing mechanisms of PBSA.

Formation of cyclobutane pyrimidine dimers at dipyrimidines containing 5-hydroxymethylcytosine

Much of the cancer-causing effects of ultraviolet radiation from the sun have been linked to the formation of dimerized DNA bases. These dimeric DNA photoproducts include the cyclobutane pyrimidine dimers (CPDs) and the pyrimidine(6-4)pyrimidone photoproducts [(6-4)PPs]. CPDs are highly mutagenic and are produced in substantial quantities by UVB radiation. These dimers can form between any two adjacent pyrimidines and can involve thymine, cytosine, or 5-methylcytosine. Very recently, a sixth DNA base, 5-hydroxymethylcytosine (5hmC) has been identified and characterized as a normal component of mammalian DNA. Here, we investigated the formation of CPDs at different DNA sequences containing 5hmC following irradiation with UVA, UVB, or UVC light sources. We show that the formation of CPDs at dipyrimidines containing 5hmC occurs at different DNA sequences but is not enhanced relative to cytosine or 5-methylcytosines at the same sequence positions. In fact, in some sequence contexts, CPDs containing 5hmC are formed at very low levels. Nonetheless, CPD formation at 5hmC pyrimidines is expected to be biologically relevant since three types of human skin-derived cells, fibroblasts, keratinocytes and melanocytes, all contain detectable levels of this modified base.