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Home , Direct DNA damage, Sunburn, Sunscreen, UV filter

7-2013

English Edition International Journal for Applied Science • Personal Care • Detergents • Specialties

J. Vollhardt, A. Janssen, Ch. Saecker Modern that Protect from more than just CARE

J. Vollhardt, A. Janssen, Ch. Saecker* Modern Sunscreens that Protect from more than just Sunburn

■ Sunburn and what happens at duced damage level and undergo the ing level of on the affected spot. The lower UV dosages? programmed cellular death, a distinct corresponding energy dosage necessary to buildup of inflammatory cytokines oc- induce this answer is called one min- If our skin receives UV light with the first curs. The thus initiated imal erythemal dosage (1 MED). Dosages ray damaging effects will happen to vari- process causes blood vessels to widen, below this value usually do not induce ous cellular and extracellular constituents. and this turns the skin red. A sunburn be- any visible skin redness, with the excep- For keratinocytes, after »enough« cells comes manifest macroscopically not on- tion they are received subsequently for have been »disabled« by a certain UV-in- ly in skin reddening but also in a grow- a longer period of days. If a single UV

Introduction

fter 3 decades of intense episodes. But to draw the whole and therefore represents a strong public campaigns sun pro- picture: more than half of the UV driver to apply sun protection Atection is in the mind of al- dosage is not linked to vacation products. Most people consider most every consumer in particular times but rather to day by day ac- the avoidance of sunburn as a suc- if it concerns holiday or sport ac- tivities such as gardening, grill cess signal for their personal pro- tivities. Does this mean that in- parties or lunch breaks. People tection strategy and feel on the dustry stakeholders and con- have significantly lower aware- save side if they succeeded in do- sumers can lean back? Surely not. ness for sun protection in those ing so. But is this really true? Are There is still a lot more work and situations which might result in dosages below the erythemal education on safe sun to occasional localized sunburn, e.g. dose level (1 MED) well compen- do, in particular because only one the facial area. In holiday sated in our body? This article country so far, (1), has episodes most consumers have looks at such dosages in a few di- achieved a beginning decline of learnt how to avoid sunburn of mensions, e.g. DNA damage as the incidence. Holidays larger skin areas; however, quite mutagenic marker, oxidative and sport themes are often com- frequently they still have localized stress as anti-aging initiator and municated together with sun pro- weak on super-exposed immunosuppression as a cancer tection messages – with a com- skin parts or areas which had enhancement marker. It also gives pelling reason: a significant por- been treated only sparsely with recommendations based on the tion of the annual UV exposure . Sunburn does cause findings to protect people of UV dose is collected in these pain and significant discomfort beyond sunburn.

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dosage does not cause sunburn it is called suberythemal. UVB : UVA The energy or duration of UV radiation Natural day light, noon, noon time, June 1 : 25 necessary to induce sunburn is not con- Natural day light, tropics noon 1 : 18 stant and can vary a lot from person to person mainly depending on skin type. Solar Simulated Radiation Sunburn is also wavelength dependent (SSR, artificial light for SPF measurements) 1 : 10 as UVB is more damaging than UVA. Be- Table 1 Light sources: Proportional energy ratios between UVB and UVA light ing in a holiday location in the tropics makes our skin faster, not only be- cause of a general higher radiation in- tensity but also because at that latitude due to absorption and some back scat- represent one major route to carcino- contains more UVB than e.g. in tering. The absorbed energy allows the genesis. The complex repair process, par- Europe (Table 1). But it is important to base pairs of the DNA to undergo a va- ticularly for the CPDs, takes place with- keep in mind that sunburn is not 100% riety of reactions which lead to alter- in hours and days and is therefore gen- UVB based. There is also an energy level ations in the structure of DNA. The ge- erally much slower than the time to pro- or time point at which pure UVA radia- netic code at that structurally altered lo- duce the damage under solar radiation. tion would cause as well if UVB cation is not correctly readable anymore Different molecular biological markers were filtered out (Table 2). This situation and thus could give rise to mutations. are known to track the buildup of this may evolve with sunscreens providing no Two neighboring thymines in the DNA damage and repair process, which hap- or little UVA protection. strand are prone to a particular muta- pens unnoticed by the consumer until When reporting on human trials involv- tion: they form in a photo-catalyzed re- the skin shows visible signs of redness ing UV radiation, the wavelength and in- action a dimer, called cyclobutane pyri- due to exposure to erythemal UV dosages dividual sensitivity dependency of the midine dimer (CPD) or more specific, (> 1 MED). Indicative damage markers MED is less suitable and may lead to con- thymine dimer (TT). Fortunately, our cells after UV radiation can be: relative num- fusion in data comparisons. Additional have evolved several DNA repair mecha- ber of SBCs and CPDs. Also monitoring parameters would have to be measured nisms such as the nucleotide excision re- of p53 by immunofluorescence can be and reported to make experiments com- pair (NER). While it is well known that helpful, as it indicates the cells’ begin of parable. The Standard Erythemal Dosage UVB is the major source of DNA damage, repair. In addition to molecular biologi- (SED) has therefore been introduced (2) only recently it has been shown that UVA cal methods requiring biopsies, measure- to avoid or define dependencies. For a could also induce direct DNA damage ment of the erythemal index represents reference example: 1 MED for a skin type particularly in deeper layers of the skin a sensitive technology to follow up the 2 person is about 2 SED. Table 2 (3-6) lists (7). UVA light interacts also with DNA in subsequent rise towards sunburn before average energy values to induce 1 MED in more indirect mechanism through for- it is really visible to the human eye. a skin type 2 person of some commonly mation of excited oxygen species which used light sources, note the much higher finally might lead to the formation of number for UVA to induce sunburn. CPDs, 8-oxoguanine and strand breaks. ■ Damages revealed before onset p53, a key , orchestrates the re- of sunburn after single and subse- pair process. It also initiates , quent suberythemal UV Exposure ■ Molecular components related the programmed death to protect to sunburn and evolvement of against mutagenesis. Such affected cells UV damage until sunburn are called sunburn cells (SBCs). Damage Fig. 1 shows the slow evolvement of skin on p53 itself and persisting mutations of redness by a series of subsequent subery- It is widely accepted that sunburn is that protein are very critical as they can themal dosages (11 x 0.6 MED of SSR) linked with DNA damage in the cellular nucleus, followed by apoptosis of the keratinocytes and in consequence in- Type of Light Energy necessary to induce duction of an inflammation, which leads 1 MED in a skin type II finally to skin redness. However not all 2 connections in this cascade of events are Monochromatic UVB (300 nm) median 25 mJ/cm fully understood. The most prominent Monochromatic UVA (360 nm) median 32 J/cm2 primary target for UV interaction with Simulated Day Light (SDL) 15.2 J/cm2 skin is DNA. UVB light gets physically ab- Sun (295–400 nm) ~5–12 J/cm2 sorbed e.g. by the thymine chromophore. Solar Simulated Radiation (SSR) as used for SPF measurement ~2 J/cm2 The is densely packed with cells and therefore UVB does not pene- Table 2 Energy values of certain light sources to induce 1 MED in a skin type 2 person trate much deeper than the basal layer

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volunteers of skin type I and II were ex- of either SSR or SDL was enough to gen- uneven skin tone (13) delivers informa- posed to (8). At a value of about 80 skin erate p53 upregulated cells. SBCs were tion for a visional judgment on age. The redness gets visually perceivable. Over present at a significant level already at desire to look attractive is high, being the the whole period of 11 days there seems only 0.25 MED SSR, while SDL needed 0.5 main driver of the global demand for to be a gradually rising level of damage MED to generate a similar number. effective treatment concepts. A second indicated by progressing skin redness strategy, which actually should be the (blue line, Fig. 1). During the first 8 – 10 primary one to fight signs of aging is to days this damage goes on unnoticed, on- ■ UVA radiation is setting an aging protect skin against their origin before ly at the last day it seemed to have be- process into motion aging signs appear or get worse. In par- come finally manifest in sunburn ap- ticular UVA induces a multitude of ef- pearance. A low level sunscreen (SPF of Visible signs of skin aging become evi- fects which lead to visual skin aging phe- 7.5) was enough to suppress a major dent as wrinkles, in particular around the nomena. Most often UVA-induced changes evolvement of skin redness, but - is this so called »crow feet« area, but also an start by UVA light generating oxidative really an indication for the complete ab- sence of DNA damage? We therefore in- vestigated the CPD level with biopsies (Fig. 2). Fig. 1 also suggests that there seems to be not much damage for a single radia- tion period, e.g. at day 1. This aspect has been addressed by several authors (5, 8-10), who analyzed biopsies of skin type I, II or III volunteers after a single radia- tion of 0.5 MED with several light sources, including also pure UVA light (11). CPDs could already be detected in keratinocytes and , as an in- dicator of DNA damage. Also p53 seems to be up-regulated, indicating the switch on of the repair signal in skin type II and III. We therefore investigated the CPD level with biopsies. Fig. 2 shows significantly elevated DNA damage levels after 5, 11 and 12 days of suberythemal radiation Fig. 1 Erythema index during 11 subsequent suberythemal dosages of 0.6 MED. The for the untreated area. This means the sunscreen used was broadspectrum and had an SPF of 7.5 erythema index does not parallel the presence of CPDs. The DNA repair is al- ready leading to a balance of newly in- coming and already repaired damage. After the last radiation (day 12) the CPD value is going down, which is indicating successful repair. A broadspectrum sun- screen having only an SPF of 7.5 is able to cause a significant protection against DNA damage. However, the low protec- tion level was not fully sufficient to sup- press CPD formation completely com- pared to the non-radiated site, so a still small level of DNA damage persists. Similar observations had also been made in a study with 9 times subsequent suberythemal UV at 0.25, 0.5 and 0.75 MED (12), in which also the dif- ference of SSR used for SPF testing and Fig. 2 Evolvement of CPDs with 11 subsequent suberythemal treatments with 0.6 a simulated day light (SDL) had been MED. Pictures represent day 12, a (unprotected), b (sunscreen SPF 7.5) compared. A radiation of only 0.25 MED

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stress in the tissue. An action spectrum has been measured for this. Multiplied with the solar radiation spectrum the re- sulting solar generation spectrum shows the strongest peak around 360 nm (14), which indicates that most oxidative stress caused by UV originates from UVA. Unfortunately UVA penetrates deep into the dermis and can there initiate partly irreversible damage of cell constituents and matrix . Over the years mod- ified proteins could build up as they are hard to metabolize and form e.g. the ba- sis solar elastosis. The inhomogeneity of protein distribution causes also an un- even whiteness distribution of the skin. Considering that UVA is present much longer during the day time than UVB, sunscreens should therefore be all equipped with a sufficiently strong UVA Fig. 4 Influence of 11 subsequent suberythemal radiations with 0.6 MED on the num- protection. Day care formulas may even ber of Langerhans cells go over the recommended minimum guidelines to achieve an extra benefit in fighting the face changing effects of UVA. mation. It detects mutated cells and de- allergens (and in essence also towards stroys them. However, the immune sys- mutated cells). The Mantoux reaction tem reacts very sensitive to UV stress. Re- against tuberculin has been utilized to ■ Suberythemal UV radiation leads cently an action spectrum for immuno- measure this effect (16) (Fig. 3, blue to immunosuppression suppression has been established (15). It bars). We were also able to see disap- shows two peaks, a smaller one at 300 nm pearance of Langerhans cells upon sub- Our skin has several lines of defense and a huge one in the UVA region peak- sequent radiation of 0.6 MED (8) (Fig. 4, against deleterious UV effects. The skin’s ing at 370 nm. It has been shown that blue bars). Seité (4) had observed an sig- immune system can be seen as a last only 0.3 MED is enough to damage the nificant immunosuppressive effect al- fortress in the fight against cancer for- immune response of the skin towards ready at 0.25 MED. A SPF 7.5 broadband sunscreen protected the Langerhans cells significantly against the suberythemal UV radiation (Fig. 4, pink bars). Interest- ingly, it was found that topical Niaci- namide, also known as Vitamin B3, al- most completely preserved the immune status of the volunteers exposed to 0.3 to 1 MED SSR (Fig. 3, pink bars).

■ Two typical UV exposure scenar- ios – is there a need for more pro- tection?

1st Scenario – Shorter periods of exposure in summer Many leisure activities including lunch breaks happen around and at the zenith of sun, where the UVB intensity is the highest. During lunch people are often Fig. 3 Immunosuppressive effect of erythemal and suberythemal SSR. Protection can facing the same angle towards the sun, be achieved with Niacinamide (15) so that there is little relief by changing exposure to other body areas. Some parts,

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e.g. the nose tip or ears can actually be hit perpendicular by the sun, which means reception of the full UV dosage compared if the sun had a certain angle to the plain of the skin. The risk of get- ting sunburn varies of course with the skin type. Skin type I and II, both partic- ularly sensitive, would have most likely no longer than 0.5 h under those condi- tions until they reach 1 MED and exhib- ited a slight sunburn. Skin Type III would have eventually about 15 - 30 minutes longer and Type IV would most likely have no burn symptoms during a lunch break. Easily sunburn can be avoided during outdoor lunch or other shorter outdoor activities by utilizing a SPF 15 UVB based sunscreen, a formula type often realized in former generations of day care formu- las. However, such a formulation principle would leave the door open for UVA based premature aging effects. In addition there could also be a UVA based sunburn. In solar radiation the UVB contribution is only 80-85 %. UVA light is clearly much less effective in causing sunburns, but on has developed powerful anti-oxidant emulsions, like Phenylbenzimidazole Sul- the other side it is 25 times more abun- defense systems to survive in this habi- fonic (PARSOL® HS), show very good dant. At the French Riviera e.g., if some- tat. The constituents are able to protect performance with no oily or greasy skin body were solely protected against UVB too (17). It is a protected wild feel. Polysilicone-15 (PARSOL® SLX) adds it would take about 2-3 h in noon time life species; however, due to high alti- not only synergistically UV protection for a UVA sunburn of a non-tanned per- tude alpine cultivations according to Bio performance to such a system, but also son with skin type II (4). UVA is still very Suisse organic standards this material a silky skin feel. The high-spreading sili- much present in morning and afternoon (ALPAFLOR® EDELWEISS) is available to cone feature of this UVB filter implies an hours, when it is »UVB safe«. Even more the personal care industry. auto-rearrange on the skin to correct lo- concerning are the devastating prema- The design and realization of facial day cal film irregularities and weak coverage ture aging effects of UVA light. Therefore care formulas can be particularly chal- spots. Formulas with Polysilicone-15 day care formulas need to be equipped lenging to comprise all above-described (PARSOL® SLX) therefore perform usual- with a functional UVA protection screen. functionality and together with desir- ly much better on human skin than on in On top of that should be also an im- able sensory features. Day creams should vitro plates. The high SPF boosting syn- muno-protective agent, e.g. Niacinamide, neither be too greasy or too glossy nor ergy between Phenylbenzimidazole Sul- because already lower levels of radiation should the play time too long. After a fonic Acid (PARSOL® HS) and Polysili- could cause damage here as shown above. rather quick dry-out, there should be a cone-15 (PARSOL® SLX) had been clear- People typically apply significantly less nice, silky and matt finish. Extra care ly demonstrated by in vivo SPF determi- than 2 mg/cm2, which call for addition- claim formulas could purposely leave a nations (18). al measures for facial care products. The perceivable film with a little thick- residual oxidative stress by still transmit- er residue. Usually most UV filters add an ted UVA light needs to be taken care of. oily and greasy feature to the formula, 2nd Scenario – Summer holiday Therefore a day care formula should and generate a lot of shine in the residue exposure also contain an anti-oxidant complex. on the skin after the rub out. For broad This 2nd scenario includes beach holidays Combinations of Vitamins and plant ex- UV spectrum functionality UVA and UVB with quite intense and consecutive UV tracts offer good solutions here. A sig- filters are a must but careful selection of exposure with a typical length of about nature plant associated with blue sky the UV filters and building on the SPF 1-3 weeks. A skin type II person could and high sunshine radiation is Edelweiss contributing synergy between the UV fil- theoretically easily gather 10-15 MED on (Leontopodium nivale, subsp. alpinum). ters will help to tweak the formulas to- a clear day in Southern Europe in the It grows only in high altitudes up to wards a drier, less greasy direction. UV summer. But as even sun worshipper on 3000 m with a lot of UV radiation and filters occupying the water phase of a deck chair move and turn their bodies

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and the angle of the plain of the skin is are pleasing sensory features. Most like- tool box need to be considered. It starts often not 90° towards the sun the actu- ly it is a sensory endpoint which tells with the right UV filter combinations for al daily UV dosage received is rather the consumers to stop applying more sun- a maximized performance, an optimal half of the theoretical maximum. How- screen at a certain optical or touch sen- use level of non-oily, skin pleasing UV ever, certain skin areas, let us name them sation (23). filters like Phenylbenzimidazole Sulfon- super-exposed areas, e.g. head, top of What improved sensory features can do ic Acid (PARSOL® HS), Polysilicone-15 the ears or shoulders and the nose tip for the application amount shows a (PARSOL® SLX) and could receive a significant higher UV study, in which we investigated the right (PARSOL® TX) and in addition the right dosage due to a preferred orientation. It balance of inorganic and Poly- choice of texture builders. The use of the is strongly recommended to use addi- silicone-15 (PARSOL® SLX) by comparing emulsifier Potassium Cetyl Phosphate tional sun protection for these super-ex- the voluntary use level in a consumer (AMPHISOL® K) especially ensures the posed skin parts. Very recently a sun ex- study. Participants received two sun- stability of these complex emulsion sys- posure investigation concluded on Tener- screens; one contained next to other UV tems with relatively high oil loading and ife (19). The participants wore wrist dosi- filters 6% Titanium Dioxide, the other a high content of pigments and UV filters. meters, and in only 6 days each of the 25 mix of 3% Titanium Dioxide and 3% subjects picked up 57 SED in total on av- Polysilicone-15 (PARSOL® SLX). Both had erage, which is about 43% of the annu- similar SPFs, 26 and 27 respectively. The ■ Conclusions al dosage of a Danish indoor worker. This participants had to apply the test creams quite intense and highly cumulated UV to a defined skin area for 14 days and Sunlight is a factor of setting good mood dose calls for good sun protections mea- thereafter the weight of the used sun- to people. It doesn’t wonder that this sures. A SPF 15 product, as recommend- screen was measured. It turned out that creates a sun seeking behavior, not just ed by authorities e.g. in UK or US would the sunscreen with a mix of Titanium only in holiday situations but also in our protect against sunburn in those cir- Dioxide and Polysilicone-15 (PARSOL® daily life, whenever the sun is shining. cumstances if applied according to guide- SLX) was unconsciously used at a 29% Unfortunately sunlight comes also with line, with 2 mg/cm2 and with re-applica- higher level. This trial can be considered a downside, that can create significant tions. But there is more to consider than as principal to demonstrate that appeal- aging and effects, which call for only sunburn. The fully correct usage of ing sensory features can enhance the to- protective strategies. Avoidance of sun- such a SPF 15 sunscreen would still re- tal amount applied on the skin leading burn turns out to be not enough to en- sult in 0.3-0.5 MED of suberythemal UV to a better ultimate protection of sun- sure successful and sufficient protection. radiation on average and super-exposed burn and of damages due to suberythe- Dosages below sunburn can still affect sites would receive even a higher dosage mal UV exposure. health and beauty. For shorter exposures with all the consequences and risks de- Creating high broad spectrum perfor- a minimum of SPF 15 with an excellent scribed above. Products with much high- mance and well accepted textures allur- UVA coverage and further protective in- er SPF are therefore recommended for ing for more product usage represents a gredients is recommended. Longer and beach holidays or other full-day outdoor tough challenge for the formulator. All subsequent exposures, e.g. beach holi- activities. options of the sunscreen formulation days call for very high SPF numbers with It is a well-known fact that people apply a smaller amount of sunscreen than rec- ommended and required to achieve the labeled SPF factor (20). The SPF that ma- terializes then for the consumer is there- fore often only a fraction of the labeled SPF (21, 22). Typical application amounts vary between 0.4 to 0.8 mg/cm2, which is reducing the (labeled) SPF by about 5 to 2.5 times. To nevertheless cope with the significant UV radiation dosages on the beach, the call is for highest protec- tion products (21) and additional shading strategies to avoid localized sunburns and significant suberythemal damage. In ad- dition, active such as niacin- amide might help to reduce the harmful damage by protecting or by stimulating intrinsic cellular repair mechanisms. A key driver for applying higher amounts of those high performance sunscreens

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broadspectrum coverage and additional (8) Young, A. R., Orchard, G. E., Harrison, G. I., and different structural and biochemical barriers shade seeking strategies. The sensory Klock, J. L. (2006) The Detrimental Effects of of the skin. Proceedings 27th Congress IFSCC/ profiles of those high performance for- Daily Sub-Erythemal Exposure on Human Skin South Africa In Vivo Can Be Prevented by a Daily-Care mulas should be adapted to the con- Broad-Spectrum Sunscreen. J Invest Derma- (18) Mendrok-Edinger, C., Janssen, A., Smith, K., sumer’s expectations driving the sun tol 127, 975-978 Lenz, D., and Vollhardt, J. (2009) Maximizing seekers to use plenty amount for a bet- Efficiency of Sunscreens to achieve High SPF/ ter ultimate UV protection. A reduced (9) Young, A. R., Potten, C. S., Nikaido, O., Parsons, UVAPF and maintain an optimal Skin Feel. th health risk and a long time young look- P. G., Boenders, J., Ramsden, J. M., and Chad- Proceedings 10 International Sun Protection wick, C. 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