Discovery of matrix metalloproteinase inhibitors as anti-skin photoaging agents

Photodamage is the result of prolonged exposure of the skin to sunlight. This exposure causes an overexpression of matrix metalloproteinases (MMPs), leading to the abnormal degradation of collagen in the skin tissue and resulting in skin aging and damage. This review presents a detailed overview of MMPs as a potential target for addressing skin aging. Specifically, we elucidated the precise mechanisms by which MMP inhibitors exert their anti-photoaging effects. Furthermore, we comprehensively analyzed the current research progress on MMP inhibitors that demonstrate significant inhibitory activity against MMPs and anti-skin photoaging effects. The review also provides insights into the structure-activity relationships of these inhibitors. Our objective in conducting this review is to provide valuable practical information to researchers engaged in investigations on anti-skin photoaging.

Kappaphycus alvarezii as a renewable source of kappa-carrageenan and other cosmetic ingredients

Kappa-carrageenan is one of the most traded marine-derived hydrocolloids used in the food-and-beverage, pharmaceuticals, and personal care/cosmetics industries. K. alvarezii (previously known as Kappaphycus alvarezii) is arguably the most important natural producer based on annual production size and near-homogeneity of the product (i.e., primarily being the kappa-type). The anticipated expansion of the kappa-carrageenan market in the coming years could easily generate >100,000 MT of residual K. alvarezii biomass per year, which, if left untreated, can severely affect the environment and economy of the surrounding area. Among several possible valorization routes, turning the biomass residue into anti-photoaging cosmetic ingredients could potentially be the most sustainable one. Not only optimizing the profit (thus better ensuring economic sustainability) relative to the biofuels- and animal feed-routes, the action could also promote environmental sustainability. It could reduce the dependency of the current cosmetic industry on both petrochemicals and terrestrial plant-derived bioactive compounds. Note how, in contrast to terrestrial agriculture, industrial cultivation of seaweeds does not require arable land, freshwater, fertilizers, and pesticides. The valorization mode could also facilitate the sequestration of more greenhouse gas CO2 as daily-used chemicals, since the aerial productivity of seaweeds is much higher than that of terrestrial plants. This review first summarizes any scientific evidence that K. alvarezii extracts possess anti-photoaging properties. Next, realizing that conventional extraction methods may prevent the use of such extracts in cosmetic formulations, this review discusses the feasibility of obtaining various K. alvarezii compounds using green methods. Lastly, a perspective on several potential challenges to the proposed valorization scheme, as well as the potential solutions, is offered.

Photosynthetic performance of symbiont-bearing foraminifera Heterostegina depressa affected by sunscreens

Foraminifera are abundant unicellular organisms that play an important role in marine element cycles. A large benthic foraminifer obligatory bearing photosymbionts is Heterostegina depressa. We studied potential impacts of sunscreens available on the market on the activity of photosymbionts on H. depressa by means of pulse-amplitude modulated (PAM) fluorescence microscopy. We included four different sunscreens, with two of them sold as “conventional” and two more stated as “eco-friendly”. Further, the impact of pure Ensulizole (phenylbenzimidazole sulfonic acid) was tested, which is a common agent of sunscreens. Foraminifera were incubated at varying concentrations (10, 50 and 200 mgL⁻¹) of different sunscreens and the pure Ensulizole for 14 days. The photosynthetic performance was measured after 1,3, 7 and 14 days. Pure Ensulizole had a strong negative impact on the photobionts, which was reflected by a significant reduction of the areal fluorescence signal. “Eco-friendly” sunscreens affected the health of foraminifera more severely compared to “conventional” ones. We assume that metal nanoparticles like titanium dioxide or zinc oxide of “eco-friendly” sunscreens are causing this impact, because these substances were already classified as toxic for several microorganisms.

Pigmentation effects of blue light irradiation on skin and how to protect against them

Background

Visible light, in particular blue light, has been identified as an additional contributor to cutaneous photoageing. However, clinical studies demonstrating the clear effect of blue light on photoageing are still scarce, and so far, most studies have focused on broad‐spectrum visible light. Although there is evidence for increased skin pigmentation, the underlying mechanisms of photoageing in vivo are still unclear. Furthermore, there is still a need for active ingredients to significantly protect against blue light‐induced hyperpigmentation in vivo.

Our study had two aims: to detect visible changes in skin pigmentation following repeated irradiation of the skin with LED‐based blue light and to reduce pigmentation using suitable active ingredients.

Method

We conducted a randomized, double‐blind and placebo‐controlled clinical study on 33 female volunteers with skin phototypes III and IV. We used a repetitive blue light (4 × 60 J cm⁻², 450 nm) irradiation protocol on the volunteers’ inner forearms. Using hyperspectral imaging, we assessed chromophore status. In addition, we took chromameter measurements and photographs to assess visible hyperpigmentation.

Results

We measured significant changes in chromophore status (P < 0.001 vs baseline), that is of melanin, haemoglobin and oxygen saturation, immediately after blue light irradiation. In addition, we found visible skin colour changes which were expressed by a significant decrease in ITA° values (delta ITA° = −16.89, P < 0.001 vs baseline for the placebo group) and an increase in a* (delta a* = +3.37, P < 0.001 vs baseline for the placebo group) 24 h post‐irradiation. Hyperpigmentation and skin reddening were mitigated by both a formulation containing 3% of a microalgal product and a formulation containing 3% niacinamide.

Conclusion

Our study sets out an efficient and robust protocol for investigating both blue light‐induced cutaneous alterations, such as changes in skin chromophores, and signs of photoageing, such as hyperpigmentation. Moreover, we have shown evidence that both an extract of the microalga Scenedesmus rubescens and niacinamide (vitamin B3) have the potential to protect against blue light‐induced hyperpigmentation.

Current opinion on risk assessment of cosmetics

Risk assessment of cosmetic ingredients is a useful scientific method to characterize potential adverse effects resulting from using cosmetics. The process of risk assessment consists of four steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization. Hazard identification of chemicals refers to the initial stage of risk assessment and generally utilizes animal studies to evaluate toxicity. Since 2013, however, toxicity studies of cosmetic ingredients using animals have not been permitted in the EU and alternative toxicity test methods for animal studies have momentum to be developed for cosmetic ingredients. In this paper, we briefly review the alternative test methods that are available for cosmetic ingredients including read-across, in silico, in chemico, and invitro methods. In addition, new technologies such as omics and artificial intelligence (AI) have been discussed to expand or improve the knowledge and hazard identification of cosmetic ingredients. Aggregate exposure of cosmetic ingredients is another safety issue and methods for its improvement were reviewed. There have been concerns over the safety of nano-cosmetics for a long time, but the risk of nano-cosmetics remains unclear. Therefore, current issues of cosmetic risk assessment are discussed and expert opinion will be provided for the safety of cosmetics.

Coexistence effect of UVA absorbers to increase their solubility and stability of supersaturation

OBJECTIVE

Sunscreens containing UVA absorbers in high concentrations are expected to be developed, since recent studies have suggested the possibility of involvement of UVA ray in skin cancer and early skin aging. Solubility and stability of supersaturation of UVA absorbers in UVB absorber were determined in the absence and the presence of cosmetic oil. Coexistence effect of UVA absorbers was analyzed to dissolve them in high concentrations.

METHODS

Two UVA absorbers, diethylamino hydroxybenzoyl hexyl benzoate (DHHB) and butyl methoxydibenzoylmethane (BMDM), a UVB absorber, 2-ethylhexyl methoxycinnamate (EHMC), and a cosmetic oil, 2-ethylhexyl ester of oligomer of hydroxystearic acid (EH-O-HSA), were used. Their solutions were prepared at 80°C and cooled to 5°C. The solid DHHB and/or BMDM were added to it, and the time evolution of concentrations of the UVA absorbers in the solution phase was monitored.

RESULTS

At the saturation in the absence of EH-O-HSA at 5°C, weight ratio of DHHB and BMDM to EHMC was 0.39/1.00 and 0.22/1.00, respectively. Addition of EH-O-HSA slightly changed the solubility of DHHB and BMDM. When the weight ratio of EH-O-HSA to EHMC was 0.20/1.00, weight ratio of DHHB and BMDM to EHMC was 0.35/1.00 and 0.25/1.00, respectively at the saturation at 5°C. In the presence of EH-O-HSA, a strong coexistence effect of DHHB and BMDM was found on their solubility. A thermodynamically stable saturated solution at 5°C having the composition that DHHB: BMDM: EHMC: EH-O-HSA = 0.47: 0.46: 1.00: 0.20 was obtained by the simultaneous addition of solid DHHB and BMDM into the initial solution.

CONCLUSION

The solution type composite having the highest concentrations of DHHB and BMDM prepared in this study exhibited critical wavelength at 368 nm that was just below the border for sunscreens being qualified as 'Broad Spectrum' protection under the new rule launched by US FDA.

Toxicity of ZnO nanoparticles to the copepod Acartia tonsa, exposed through a phytoplankton diet

Zinc oxide (ZnO) nanoparticles are being increasingly utilized in a variety of products and applications and are therefore commonly discharged into aquatic environments, increasing exposure and potentially impacting aquatic organisms. Zinc oxide nanoparticles can depress growth of some marine phytoplankton, and several examples of nanoparticle trophic transfer have been documented, although not within planktonic communities. The authors test whether feeding on ZnO-exposed phytoplankton could cause toxic effects in a widespread and ecologically important marine grazer, the copepod Acartia tonsa. The authors exposed the diatom Thalassiosira weissflogii to ZnO nanoparticles for 7 d and measured growth, zinc accumulation, and zinc distribution within the algal cells to elucidate bioavailability to grazing copepods. Thalassiosira weissflogii cultured with nano-ZnO were continuously fed to A. tonsa for 7 d, and reproduction and survival were quantified. A dose-dependent growth reduction was observed in T. weissflogii exposed to nano-ZnO, with a 20% effective concentration (EC20) of 70 µg/L Zn and a lowest observed effect concentration (LOEC) of 99 µg/L Zn. Zinc accumulation in the algae occurred dose-dependently over time, with the majority of the zinc partitioning into the cell wall fraction. Feeding on ZnO-exposed diatoms led to a decrease in copepod survival and reproduction. The EC20s corresponding to the dissolved zinc concentration in the T. weissflogii exposure media were 112 µg/L (13 µg/g dry wt) and 143 µg/L (16 µg/g dry wt), and the LOECs were 168 µg/L (17 µg/g dry wt) and 263 µg/L (21 µg/g dry wt) for copepod survival and reproduction, respectively. These results provide evidence of trophic transfer of metal contaminants associated with metal oxide nanomaterials within a marine plankton community, leading to a reduction in individual demographic performance of an important coastal marine grazer.

Solubility of nano-zinc oxide in environmentally and biologically important matrices

Increasing manufacture and use of engineered nanoparticles is leading to a greater probability for release of engineered nanoparticles into the environment and exposure to organisms. In particular, zinc oxide (ZnO) is toxic, although it is unclear whether this toxicity is due to the zinc oxide nanoparticles, dissolution to Zn(2+) , or some combination thereof. The goal of this study was to determine the relative solubilities of both commercially available and in-house synthesized ZnO in matrices used for environmental fate and transport or biological toxicity studies. Dissolution of ZnO was observed in nanopure water (7.18-7.40 mg/L dissolved Zn, as measured by filtration) and Roswell Park Memorial Institute medium (RPMI-1640) (∼5 mg/L), but much more dissolution was observed in Dulbecco's modified Eagle's medium, in which the dissolved Zn concentration exceeded 34 mg/L. Moderately hard water exhibited low Zn solubility, likely because of precipitation of a Zn carbonate solid phase. Precipitation of a Zn-containing solid phase in RPMI also appeared to limit Zn solubility. Equilibrium conditions with respect to ZnO solubility were not apparent in these matrices, even after more than 1,000 h of dissolution. These results suggest that solution chemistry exerts a strong influence on ZnO dissolution and can result in limits on Zn solubility from precipitation of less soluble solid phases.

Photostabilization effect of quercetin on the UV filter combination, butyl methoxydibenzoylmethane-octyl methoxycinnamate

The aim of the study was to investigate the effect of the natural antioxidant quercetin on the photostability of the most widely used combination of UVA (320-400 nm) and UVB (290-320 nm) filters, respectively butyl methoxydibenzoylmethane (BMDBM) and octyl methoxycinnamate (OMC). In order to reproduce the conditions prevalent in commercial sunscreen products, the stabilizing efficacy of quercetin was evaluated in model creams containing BMDBM (3%, wt/wt) together with OMC (4%, wt/wt) and exposed to a solar simulator at an irradiance corresponding to natural sunlight. Quercetin was found to enhance the photostability of the two UV filters in a concentration-dependent way. Addition of quercetin to the sunscreen formulation significantly reduced the photodegradation of BMDBM and OMC from 40.3 +/- 2.4 to 27.7 +/- 2.6% and from 51.3 +/- 2.1 to 42.2 +/- 2.0%, respectively. Moreover, comparative photodegradation studies demonstrated that quercetin was much more effective and at a lower concentration than commonly used stabilizer (octocrylene) and antioxidants (vitamin E, butylated hydroxyanisole). In vitro determination of the UVB and UVA protection parameters showed that the quercetin-based formulation fulfilled the official requirements on sunscreen products. Because of its photostabilizing and multiple antioxidant properties, quercetin represents a useful additive for the formulation of effective broad-spectrum sunscreens containing BMDBM and OMC.

Comparative evaluation of different substrates for the in vitro determination of sunscreen photostability: spectrophotometric and HPLC analyses

Polymethylmethacrylate (PMMA) plates and Transpore(TM) tapes were compared as substrates for the in vitro evaluation of photostability of commercial sunscreen products. The sun care preparations were applied respectively on Transpore(TM) tapes and PMMA plates and their sun protection factors (SPF) and UVA protection parameters [UVA/UVB ratio, critical wavelength, UVA protection factor (UVA-PF)] were measured by transmission spectroscopy, before and after irradiation with simulated sunlight. No significant differences were observed in the UV protection parameters measured on Transpore(TM) tapes or PMMA plates, before exposure to the solar simulator. Conversely, after irradiation, the SPF values of the sun care products exhibited marked variations between the two substrates, the decrease in SPF being greater on PMMA plates (31.3-63.1%) than on Transpore(TM) tapes (10.4-23.8%). Differences between the two substrates were detected also for the UVA protection parameters, although they were significant only for the UVA-PF. The tested samples were assayed also by high-performance liquid chromatography (HPLC) to assess the extent of photodegradation of the UV filters present in the examined formulations. The results showed that for the PMMA plates, the light-induced decrease in SPF, as determined by spectrophotometry, fitted well with the percentage loss of ethyl hexyl methoxycinnamate (the only photounstable UVB filter present) measured by HPLC. Moreover, for the PMMA substrate, the UVA-PF percentage reduction was consistent with the percentage degradation of butyl methoxydibenzoylmethane (the only photounstable UVA filter present) determined by HPLC. On the other hand, poor correlation between spectrophotometric and HPLC analyses was observed on Transpore(TM) tapes. Therefore, PMMA plates are more reliable than Transpore(TM) tapes as substrates for in vitro photodegradation tests of sunscreen products by transmission spectroscopy.

Incorporation in lipid microparticles of the UVA filter, butyl methoxydibenzoylmethane combined with the UVB filter, octocrylene: effect on photostability

The aim of this study was to reduce the photoinstability of butyl methoxydibenzoylmethane (BMDBM), the most widely used UVA filter, by incorporating it in lipid microparticles (LMs) alone or together with the UVB filter octocrylene (OCR), acting also as photostabilizer. Microparticles loaded with BMDBM or with combined BMDBM and OCR were produced by the hot emulsion technique, using glyceryl behenate as lipid material and poloxamer 188 as surfactant. The LMs were characterized by release studies, scanning electron microscopy, and powder X-ray diffractometry. The BMDBM and OCR loading was 15.2% and 10.6%, respectively. In order to reproduce the conditions prevalent in commercial sunscreen products, the photoprotective efficacy of the LMs was evaluated after their introduction in a model cream (oil-in-water emulsion) containing a mixture of UVA and UVB filters. A small but statistically significant decrease in BMDBM photodegradation was obtained when the UVA filter was encapsulated alone into the LMs (the extent of degradation was 28.6% +/-2.4 for non-encapsulated BMDBM and 26.0% +/-2.5 for BMDBM-loaded microparticles). On the other hand, the co-loading of OCR in the LMs produced a more marked reduction in the light-induced decomposition of microencapsulated BMDBM (the UVA filter loss was 21.5% +/-2.2). Therefore, incorporation in lipid microparticles of BMDBM together with the sunscreen OCR is more effective in enhancing the UVA filter photostability than LMs loaded with BMDBM alone.

Influence of liposphere preparation on butyl-methoxydibenzoylmethane photostability

The incorporation of butyl-methoxydibenzoylmethane (BMDBM), one of the most efficient and frequently used UV-A blockers, into lipospheres was examined in order to decrease the light-induced sunscreen degradation. Lipospheres, obtained by the melt technique and using tristearin as the lipid material and hydrogenated phosphatidylcholine as the emulsifier, showed proper features in terms of size (10-40 microm), BMDBM loading level (21.63% +/- 0.90%, w/w) and physical state. Photolysis studies, involving irradiation of lipospheres with simulated sunlight before and after their introduction in emulsion formulations, demonstrated a relevant enhancement of the encapsulated sunscreen photostability in comparison with unencapsulated BMDBM.

Reactive oxygen species produced upon photoexcitation of sunscreens containing titanium dioxide (an EPR study)

Commercial sunscreen products containing titanium dioxide were irradiated with lambda>300 nm and the formation of oxygen- (.OH, O2.-/.OOH) and carbon-centered radicals was monitored by EPR spectroscopy and spin trapping technique using 5,5-dimethyl-1-pyrroline N-oxide, alpha-phenyl-N-tert-butylnitrone (PBN), alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone as spin traps, and free nitroxide radical 4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxyl. The photoinduced production of singlet oxygen was shown by 4-hydroxy-2,2,6,6-piperidine. The generation of reactive oxygen radical species upon irradiation of sunscreens significantly depends on their composition, as the additives present (antioxidants, radical-scavengers, solvents) can transform the reactive radicals formed to less harmful products. The continuous in situ irradiation of titanium dioxide powder, recommended for cosmetic application, investigated in different solvents (water, dimethyl sulfoxide, isopropyl myristate) resulted in the generation of oxygen-centered reactive radical species (superoxide anion radical, hydroxyl and alkoxyl radicals).

Prediction of sun protection factors and UVA parameters of sunscreens by using a calibrated step film model

At the stage of screening of new sun protection formulations, quick and inexpensive methods for estimation of the ultraviolet (UV) screening performance are highly desirable. It has been shown recently that apart from measurements of sun protection factors in vitro, calculations using a calibrated step film model are also a possibility. In the present investigation, further evidence for the usefulness of the step film model in terms of prediction of the sun protection factor is shown. In addition, it is demonstrated that parameters, which characterize the protection in the UVA range such as the UVA/UVB ratio and the critical wavelength can be calculated in good accordance with experimental data. Although with less accuracy, the estimation of UVA protection factors is also possible, if the photodegradation some filters undergo upon irradiation is taken into consideration.