FIELD OF THE INVENTION

The present invention relates to the use of film formers to prevent pollution damage to the skin of an individual. More specifically it relates to the use of resin-based film formers for the prevention of lipoperoxidation-based damage to the skin.

BACKGROUND OF THE INVENTION

Air pollution is known to have major effects on the human skin. Pollutants such as polycyclic aromatic hydrocarbons, volatile organic compounds, oxides, particulate matter, ozone and cigarette smoke affect the skin as it is the outermost barrier, causing damage by inducing oxidative stress.

Human skin acts as a biological shield against pro-oxidative chemicals and physical air pollutants and as such, exposure to these pollutants has serious effects. For example, smoke contributes to premature aging and an increase in the incidence of psoriasis, acne and skin cancers and is also implicated in allergic skin conditions such as atopic dermatitis and eczema. Polyaromatic hydrocarbons are associated with extrinsic skin aging, pigmentation, cancers and acneiform eruptions. Volatile organic compounds have been associated with atopic dermatitis.

Many strategies are therefore recommended to address the damage caused to skin by pollution. A recent review by Mistry (Cosmetics 2017, 4, 57) lists the following possible approaches to address the effects of pollution on the skin: Reducing particle load by cleansing or exfoliation; Preventing deposition and penetration of pollutants on skin; Restoring and strengthening the skin’s protective barrier structure and function; Reducing trans epidermal water loss to improve skin hydration; Replenishing antioxidant reserves; Reducing inflammation; Controlling melanogenesis; Promoting collagen/elastin synthesis; Protect skin from UV.

Lipid peroxidation (lipoperoxidation) is known to be caused by pollution and is a crucial step in the pathogenesis of several disease states in adult and infants. Lipid peroxidation is a process generated mainly by the effect of several reactive oxygen species (hydroxyl radical, hydrogen peroxide etc.). It can also be generated by the action of several phagocytes. The reactive oxygen species readily attack the polyunsaturated fatty acids of the fatty acid membrane, initiating a self-propagating chain reaction. The destruction of membrane lipids and the end-products of such lipid peroxidation reactions are especially dangerous for the viability of cells, even tissues. Enzymatic (catalase, superoxide dismutasse) and nonenzymatic (vitamins A and E) natural antioxidant defence mechanisms exist; however, these mechanisms may be overcome, causing lipid peroxidation to take place. Since lipid peroxidation is a self-propagating chain-reaction, the initial oxidation of only a few lipid molecules can result in significant tissue damage. It can therefore be appreciated that pollution can be addressed in many different ways and the present invention is directed to the prevention of lipoperoxidation-based damage to the skin through the use of barriers, specifically film formers.

In a study by Portugal-Cohen et al. (Clinical, Cosmetic and Investigational Dermatology 2017:10 185-193), two representative pollution models were studied using reconstructed epidermis: 1 ) mixture of pollutants containing heavy metals and atmospheric particulate matter and 2) ozone exposure. Dead Sea mineral-rich water and anionic polysaccharide film former (PolluStop) were topically applied alone or in combination, and their protection against pollution was assessed by testing the levels of the inflammation markers interleukin 1a (IL-1 a) and prostaglandin E2 (PGE2). It was found that exposure to the mixture of pollutants induced IL-1 a release, which was attenuated following pre-application with Dead Sea mineral-rich water and anionic polysaccharide alone or in combination. Ozone exposure induced IL-1 a and PGE2 release. Pre-application with Dead Sea mineral-rich water or anionic polysaccharide film former alone did not inhibit IL-1 a and PGE2 overproduction. However, when they were mixed together, inhibition of these inflammatory markers was observed.

US201710031 1 generally relates to a skin treatment composition comprising an emulsion (e.g., a water-in-oil emulsion) comprising an oil phase comprising (a) an acrylate polymer and (b) a silicone resin, wherein (a) and (b) are dissolved in a nonvolatile emollient oil, and wherein the composition is essentially free of any additional emulsifiers (i.e., beyond any already listed above). The composition can be configured to dry to a coating comprising at least 60 wt percent of the emollient oil. However, this disclosure does not deal with the prevention of lipoperoxidation-based damage to the skin through the use of a specific film former.

It can therefore be appreciated that although film formers may be capable of protecting the skin against pollution, mention has not been made of an application for such materials to prevent lipoperoxidation-based damage to the skin.

SUMMARY OF THE INVENTION

The present invention has surprisingly found that a specific type of film former has enhanced efficacy in preventing lipoperoxidation-based damage to the skin, especially damage caused by pollution.

Accordingly, in a first aspect, the invention provides the use of a resin-based film former for the prevention of lipoperoxidation-based damage to the skin, preferably the prevention of lipoperoxidation-based damage due to pollution, more preferably the prevention of lipoperoxidation-based damage caused by particulate matter.

Preferably the resin-based film former comprises trimethylsiloxysilicate and polypropylsilsesquioxane.

Most preferably the resin-based film former is MQ1640.

DETAILED DESCRIPTION OF THE INVENTION

Air pollution is a heterogeneous mixture of chemicals and solid particles, in which chemical composition, size, and sources of origin differ in each microenvironment. Both organic and inorganic compounds are found in the core and surface of airborne particulate matter. Such matter is emitted into the atmosphere from natural and anthropogenic sources and so particulate matter, specially particles on the nanosize range, are of major concern from a health perspective to both susceptible and healthy members of the population.

The skin is one of the most common routes by which organisms enter in contact with different ambient pollutants. Because of its barrier function, skin provides a major interface between the body and the environment, and offers a protection against airborne particulate matter.

However, the skin’s defensive capacity is limited. Environmental stressors may exceed the protective potential and disturb the skin structure leading to skin diseases, such as erythema, edema, hyperplasia, skin aging, contact dermatitis, atopic dermatitis, psoriasis, and carcinogenesis. Epidemiological studies suggest that particulate matter negatively affects human skin and exacerbates pre-existing skin diseases. In vitro and in vivo studies have shown a variety of biological effects after both chronic and acute exposures and the mechanisms by which particulate matter exerts its detrimental effects are believed to involve oxidative stress and inflammation which are both important contributors to extrinsic skin aging. Injury mechanisms after particulate matter exposure have been suggested to involve local reactive oxygen species production which could, in part, be generated from the particles themselves. Moreover, smaller particles provide a higher surface area, in which different compounds could be adsorbed. The oxidative capacity of particulate matter has been attributed to transition metal constituents, which typically include Fe, V, Cr, Mn, Co, Ni, Cu, Zn, and Ti, most of which can catalyze Fenton- like reactions and generate reactive oxygen species (ROS) initiating oxidative damage mechanisms. In addition, particles can serve as organic compound carriers like polycyclic aromatic hydrocarbons, which are highly lipophilic, and capable of localizing in mitochondria contributing to ROS production. Furthermore, oxygen-derived free radicals may also be generated by the interaction of particle pollutants and their components, with cellular enzymes and organelles in particular in relation to lipid peroxidation.

Lipid peroxidation is therefore a critical mechanism that drives pollution damage in the skin. Lipid peroxidation is the oxidative degradation of lipids. It is the process in which free radicals sequester electrons from lipids in cell membranes, resulting in cell damage. Lipid peroxidation proceeds by a free radical chain reaction mechanism which affects the polyunsaturated fatty acids. These acids contain multiple double bonds with methylene bridges between which carry reactive hydrogen atoms. The chemical products of this oxidation are known as lipid peroxides or lipid oxidation products. A fatty acid radical is produced in the initiation step with initiators in living cells being reactive oxygen species such as OH- and HOO. These combine with a hydrogen atom to make water and a fatty acid radical. The end products of lipid peroxidation are reactive aldehydes, such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE). When lipid peroxidation is not terminated the cell membrane, which consists mainly of lipids, is damaged. Moreover, end-products of lipid peroxidation may be mutagenic and carcinogenic, for example, the MDA reacts with deoxyadenosine and deoxyguanosine in DNA, forming DNA adducts such as M1 G. Indeed, the toxicity of lipid hydroperoxides to animals is illustrated by the lethal phenotype of glutathione peroxidase 4 knockout mice which do not survive past embryonic day 8, indicating that the removal of lipid hydroperoxides is essential for mammalian life.

There is therefore clearly a need to address the lipoperoxidation damage to skin caused by the aforementioned pollutants and biological mechanisms.

As discussed above with reference to the study by Portugal-Cohen et al., film formers can be used to address pollution damage to skin.

Film formers are used extensively in personal care formulations. In hair care applications they can be used to aid styling and enhance shine; in skin care and sun care they can protect the skin, add water-resistance and ensure the even distribution and adherence of active ingredients. Film-formers are particularly important in colour cosmetics where they can increase the wear properties of formulations such as lipsticks, mascaras, eyeliners, eyeshadows and foundations. They can have a significant effect on the ease of application of a cosmetic product as well as the appearance of the product on the skin, and the length of the time that the product remains on the skin.

There are three main types of film formers.

The first is polysaccharide-based (such as those used in the Portugal-Cohen et al. study above), examples of which include the anionic polysaccharide-based film former “PolluStop”, and other starch-based polymers.

The second is acrylate-based film formers containing acrylate monomers which form acrylate polymers based on the structure of acrylic acid, which consists of a vinyl group and a carboxylic acid ester terminus or a nitrile. Other typical acrylate monomers are derivatives of acrylic acid, such as methyl methacrylate in which one vinyl hydrogen and the carboxylic acid hydrogen are both replaced by methyl groups, and acrylonitrile in which the carboxylic acid group is replaced by the related nitrile group. The third is resin-based film formers which can be silicon-based and typically comprise dimethicone, trimethylsiloxysilicate, cyclomethicone, polypropylsilsesquioxane, isododecane, trimethylsiloxysilicate/dimethiconol crosspolymer, cyclopentasiloxane or a combination thereof. The present invention has surprisingly found that resin-based film formers have enhanced efficacy in preventing lipoperoxidation-based damage to the skin, especially lipoperoxidation-based damage caused by pollution and therefore provides the use of a resin-based film former for the prevention of lipoperoxidation-based damage to the skin. Resin-based film formers according to the invention can contain dimethicone, trimethylsiloxysilicate, cyclomethicone, polypropylsilsesquioxane, isododecane, trimethylsiloxysilicate/dimethiconol crosspolymer, cyclopentasiloxane or a combination thereof. Resin-based film formers containing trimethylsiloxysilicate (IUPAC Name: trimethyl-[oxo(trimethylsilylperoxy)silyl]peroxysilane, Canonical SMILES:

C[Si](C)(C)00[Si](=0)00[Si](C)(C)C) and polypropylsilsesquioxane have been found to be particularly effective. An example of such a film former is MQ1640 which can be obtained from Dow chemicals. The INCI Name for MQ1640 is Trimethylsiloxy silicate (and) Polypropyl silsesquioxane. MQ1640 is a combination of MQ and T propyl silicone resin and has been developed to address a different problem to pollution, namely to provide both transfer and wash resistance combined with a flexible film and comfort of wear in skin and cosmetics applications. Additionally, in sunscreens it has been found to enhance the SPF wash off resistance. However, its efficacy in the prevention of lipoperoxidation-based damage has not previously been elucidated.

Resins suitable for the present invention can include any copolymeric silicone resins that comprise M and Q groups, e.g., MQ silicone resins (e.g. trialkylsiloxysilicates, such as trlmethylsiloxysilicates), MQD silicone resins, and MQT silicone resins, which can have a number average molecular weight of from about 100 to about 50,000 preferably 500 to about 20,000, and generally have methyl substituents. MQ silicone resins may include both non-functional and functional resins, the functional resins having one or more functionalities including, for example, silicon-bonded hydrogen, silicon-bonded alkenyl and silanol. MQ silicone resins are copolymeric silicone resins having R3SIO1/2 units (M units) and SIO4/2 units (Q units). MQ resins comprise clusters of quadrafunctional silicate Q groups end-capped with monofunctional trialkylsiloxy M groups. Such resins are described in Encyclopedia of Polymer Science and Engineering, vol. 15, John Wiley & Sons, New York, (1989), pp. 265 to 270. Commercially available MQ resins include SR- 545 MQ resin in toluene available from General Electric Co., Silicone Resins Division (Waterford, N.Y), MQOH resins which are MQ silicone resins in toluene are available from PCR, Inc. (Gainesville, Fla.). Such resins are generally supplied in organic solvent and may be dried by any number of techniques known in the art including, e.g., spray drying, oven drying, and steam separation, to provide a MQ silicone resin at 100 percent non-volatile content. The MQ silicone resin can also include blends of two or more silicone resins. Other suitable MQ resins for compositions of the present disclosure include alkylsiloxysilicates, such as trialkylsiloxysilicates (e.g., trimethylsiloxysilicates). Trimethylsiloxysilicates are available under the trade designation "MQ 1600 solid resin" (or the trade designation "TI-7012 solid resin" healthcare grade) from Dow Corning Corporation, Midland, Mich.

T resins of the present disclosure can include any silicone resin comprising (or predominantly comprising) T groups, which are often referred to as silsesquioxanes. Particularly suitable T resins for compositions of the present disclosure include alkylsilsesquioxanes, such as alkylsilsesquioxanes (e.g., propylsilsesquioxanes) and arylsilsesquioxanes (e.g., phenylsilsesquioxanes). T resins are generally characterized by the empirical chemical formula RS1O _3/2 and a cage-like structure, which can be in the general structure of a cube, a hexagonal prism, an octagonal prism, a decagonal prism, a dodecagonal prism, or another suitable three-dimensional structure.

Silicone resins of the present disclosure can also include silicone resins comprising metals, e.g., aluminosilicates, borosilicates, and combinations thereof. The silicone resins of the present disclosure can have a variety of shapes or structures, including, but not limited to, flake, rod, sphere, porous, other suitable shapes or structures, or combinations thereof. In the present invention, resin-based film formers have been found to perform better than the other categories of film formers at preventing pollution driven oxidative damage to the skin, specifically lipid peroxidation. Particularly effective are those resin-based film formers with trimethylsiloxysilicate and/or polypropylsilsesquioxane.

As used herein the term“comprising” encompasses the terms“consisting essentially of” and“consisting of”. Where the term“comprising” is used, the listed steps or options need not be exhaustive.

Unless otherwise specified, numerical ranges expressed in the format "from x to y" are understood to include x and y.

In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount.

Except in the examples and comparative experiments, or where otherwise explicitly indicated, all numbers are to be understood as modified by the word“about”.

All percentages and ratios contained herein are calculated by weight unless otherwise indicated.

As used herein, the indefinite article“a” or“an” and its corresponding definite article“the” means at least one, or one or more, unless specified otherwise. The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only, and are not intended to limit the disclosure in any way.

The examples are intended to illustrate the invention and are not intended to limit the invention to those examples per se. EXAMPLES

The following film formers were tested:

Kobo50N (Cyanoacrylate-based)

- MQ1640 (Resin-based)

Structure XL (Polysaccharide-based)

Skin Explant Collection

Human skin explants of an average diameter of 14 mm (±1 mm) were prepared on an abdoplasty coming from a 35-year-old Caucasian woman. The explants were kept in survival in BEM culture medium at 37°C in a humid, 5 %-CC>2 atmosphere. 4 explants were used for each sample treatment as shown in Table 1 - i.e. the samples were prepared in quadruplicate:

Table 1 - Samples

On day 0 and day 1 , each of the 3 film formers shown in Table 1 were applied topically on to the explants for samples 2-4 and 6-8 (10 pi per cm ² ). The explants were then held for two hours at room temperature before being put back in the incubator.

Samples 1 and 4 did not receive any treatment except the renewal of culture medium. The culture medium was half renewed (1 ml per well) on day 2.

On days 2 and 3, explants for samples 5 to 8 were placed outside the incubator for two hours and placed in a PolluBox system with 900 pi per well of HBSS, and exposed by vaporization to a mixture of pollutants supplemented with NaCI 0.9% (150 mI of NaCI 0.9% per ml of pollutant solution) for 1 .5 hours.

At the end of the exposure, explants were put back in the incubator under standard culture conditions.

The pollutant applied on the explants was composed of:

Heavy metals

Solution ICP multi-element standard V Certi Pur ® (Merck ; Ref. : 1.10714.0500 ; Batch:: HC309202)

- Al 0.01 mg/ml

- AS 0.01 mg/ml

B 0.001 mg/ml

Ba 0.001 mg/ml

- Be 0.0005mg/ml

Ca 0.005mg/ml

Cd 0.001 mg/ml

Cr 0.001 mg/ml

Cu 0.001 mg/ml

- Fe 0.001 mg/ml

Hg 0.0025mg/ml

K 0.0495mg/ml

Li 0.001 mg/ml

Mg 0.0005mg/ml

- Mn 0.0005mg/ml

Na 0.01 mg/ml

Ni 0.0025mg/ml

P 0 .005mg/ml

Pb 0.01 mg/ml Sc 0.0005mg/ml

Sa 0.01 mg/ml

Sr 0.0005mg/ml

- Te 0.01 mg/ml

- Ti 0.001 mg/ml

- Y 0.0005mg/ml

- Zn 0.001 mg/ml

Hydrocarbons

- Benzene 1 mI_/GhI (Fluka, Ref. 12550)

- Xylene 1 pL/ml (Fluka, Ref. 95673)

Toluen 1 mI_/hΊΐ (Sigma, Ref. 34866)

Diesel particles

Nist, ref. SRM1650b

Diesel particles 0.01%

The concentration of the pollutant in the chamber was consistent with the environment of a polluted city.

Malondialdehyde Assay

As discussed above, malondialdehyde (MDA) is an end product of lipid peroxidation with serious potential to cause damage as a direct consequence of pollution exposure. An assay was therefore performed to assess the ability of the various film formers to prevent pollution driven damage utilising MDA as a marker of that damage.

On day 4, levels of MDA in the samples were assessed with an enhanced method of the TBARs (ThioBarbituric Acid Reactive substances) assay. The MDA was assayed in HBSS medium by addition of TBARs solution (thiobarbituric acid, hydrochloric acid and tricholoroacetic acid) and placed in a water bath (80°C for 15 minutes). Substances such as glucose which are not related with lipoperoxidation are known to react with thiobarbituric acid. Therefore, to enhance the specificity of the assay, the MDA was extracted by a liquid/liquid extraction with butanol. The MDA in the butanol extraction was measured in spectrofluorimetry (excitation: 515 nm, emission: 550 nm) using a Tecan Infinite M200 Pro microplate reader. The MDA concentration (nmol/l) in the culture medium of the different batches on day 4 is shown in Table 2.

Table 2 - MDA Levels

As can be seen, at the end of the experiment the concentration of MDA in the samples not exposed to pollution was:

No film former applied: 82.3 nmol/l

Kobo50N applied: 96.3 nmol/l

MQ1640 applied: 81.5 nmol/l

Structure XL applied: 83.9 nmol/l

In contrast, the concentration of MDA in the samples exposed to pollution was:

- No film former applied: 1 13.3 nmol/l

Kobo50N applied: 133.7 nmol/l

MQ1640 applied: 97.4 nmol/l

Structure XL applied: 106.1 nmol/l It can therefore be appreciated that exposure to pollution caused an increase in the levels of MDA (and therefore lipid peroxidation). It was also possible to calculate the difference between the MDA levels of the various samples to assess which, if any, film formers provided protection against the damage caused by the pollution. This was assessed by calculating the“delta” - i.e. the increase in MDA in the pollution exposed samples as shown in Table 3.

Table 3 - Calculation of deltas

The deltas for the film formers in Table 3 were compared against the delta for no film former. It was found that the delta for the resin-based film former MQ1640 (15.9) was 49% less than the delta for no film former (31 ). This result was found to be significant

(P<0.05, Student’s T-test).

In contrast, the delta for the cyanoacrylate-based film former Kobo50N was actually higher than the delta for no film former, and the delta for the polysaccharide-based film former Structure XL was only 29% less than the delta for no film former and was therefore not significant.

It can therefore be seen that the inventors have surprisingly found that resin-based film formers are uniquely enhanced in their ability to prevent the lipoperoxidation-based damage caused to skin by pollution.

In addition to the Malondialdehyde Assay, the following assessments were also carried out to test the efficacy of the film formers for preventing other forms of damage. Histological processing

After fixation for 24 hours in buffered formalin, the samples were dehydrated and impregnated in paraffin using a Leica PEARL dehydration automat. The samples were embedded using a Leica EG 1160 embedding station. 5pm thick sections were made using a Leica RM 2125 Minot-type microtome, and the sections were mounted on Superfrost® histological glass slides. The frozen samples were cut into 7pm thick sections using a Leica CM 3050 cryostat. Sections were then mounted on Superfrost® plus silanized glass slides. The microscopical observations were realized using a Leica DMLB or Olympus BX43 microscope. Pictures were digitized with a numeric DP72 Olympus camera with CellD storing software.

Cellular viability control

Cellular viability was observed on paraffinized sections after Masson’s trichrom staining, Goldner variant. Cellular viability was assessed by microscopical observation.

Nrf2 immunostaining

Nrf2 immunostaining was done on paraffinized sections with a monoclonal anti-Nrf2 antibody (Abeam, ref. ab76026, clone EP1809Y) diluted at 1 :200 in PBS-BSA 0.3%- Tween 20 at 0.05% and incubated for 1 hour at room temperature using a Vectastain Kit Vector amplifier system avidin/biotin, and revealed by VIP, a substrate of peroxydase (Vector laboratories, Ref. SK-4600). Immunostaining was performed using an automated slide processing system (Autostainer, Dako) and assessed by microscopical observation.

HO-1 immunostaining

HO-1 immunostaining was done on paraffin sections with a monoclonal anti-HO-1 antibody (Novus biologicals, ref. NBP1 -97507) diluted at 1 :25 in PBS-BSA 0.3% -Tween 20 at 0.05% for 1 h at room temperature, amplified using a biotin/ streptavidin system (RTU, Kit vector PK-7200) and revealed by VIP (Vector SK-4600). Immunostaining was assessed by microscopical observation.

Results

It was surprisingly found that none of the film formers tested had any significant effect on the cell viability of the samples. Moreover, although both the Nrf2 and HO-1 assays are recognised determinants of oxidative stress, it was also surprisingly found that none of the film formers tested had any significant effect in these assays.

Summary It can therefore be concluded that resin-based film formers are uniquely capable of specifically preventing lipoperoxidation-based damage to skin, in particular lipoperoxidation-based damage caused by pollution.