Pollution is there, but the skin can now be protected

By Alicia Gimenez, Cristina Davi, Elena Canadas, Nuria Alminana, Raquel Delgado

Alarming levels of environmental pollution are widely present around the world. Besides, the deleterious effects of contaminants on the skin are very clear and consumers are more and more aware of those. In order to minimise these negative consequences, Pollushield functional ingredient has been developed, helping to prevent accumulation of particles in the epidermis and to replenish the skin with antioxidants, increasing its capacity to resist damage.

Environmental Pollution

Environmental pollution is very widespread and basi­cally disturbs the air, water and land. Atmospheric pol­lution affects the outdoor air of many cities and is mainly due to fuel burning for transportation, but it is also very present indoors, resulting from household activities such as biomass combustion for cooking or heating. Water pollution frequently derives from agricultural and industrial work. However, by-products of water purifica­tion procedures, such as chlorine or ozone, are some­times found in potable water.

Pollution consists of a complex mixture of chemicals. Among the most prominent is particulate matter (PM), formed by harmful micro-particles and liquid droplets that are classified according to their size (e.g. PM10 and PM2.5). Toxic metals, such as cadmium, mercu­ry, lead and nickel, can persist and accumulate in the environment. Finally, volatile organic compounds and gaseous pollutants have to be considered as well.

The harm caused in the skin

The constant contact of air and water contaminants with the skin results in detrimental effects, such as pre­mature ageing or irritation. In the skin, pollutants drive the production of free radicals that react with biological molecules leading to loss of function (e.g. peroxidation of lipids).

In addition, when toxic substances or oxidative stress are present, the skin displays specific responses, like the synthesis of metal-binding proteins known as metal and migrate away from the epidermis to initiate the immune response. The result is a lower number of Langerhans cells in the epidermis, with the consequent decline in skin immunity.

Natural skin protection and cosmetic solutions

The skin has a certain ability to defend itself from pollution. Its physical barrier helps minimise penetration of pollutants. Also, the skin has endogenous antioxidative defences consisting of vitamins and enzymes. However, when exposed to high levels of contaminants, the protecting capacity of the skin is surpassed, leading to damage and accelerated ageing with their visible consequences.

Some additional shielding strate­gies can be adopted. By topically applying molecules such as metal chelators, it is possible to reduce the direct interaction of pollution particles with the skin.

In addition, it is essential to provide antioxidants to complement the loss of endogenous ones caused by overexposure to harmful sub­stances or the ageing process. Antioxidants can act within the skin to block the effects of free radicals regardless of the type of pollutant that produces them.

Pollushield functional ingredient is the combination of a metal-chelating polymer with a powerful antioxidant. As a result, this anti-pollution ingredient can limit the accumulation of toxic particles and also enhance the self-defensive capability of the skin, as various studies have proven.

Urban dust in epidermal cells

To evaluate the protective effect on skin cells, human epidermal kerati­nocytes from adult (HEKa) were in­cubated for 24 hours with the poly­mer (acrylic acid/acrylamidomethyl propane sulfonic acid copolymer) and the antioxidant (dimethylme­thoxychromanol) at concentrations equivalent to 0.5 percent Pollush­ield functional ingredient, while non-treated cells were used as a control.

Then, 100 μg/ml urban dust, consisting of atmospheric particulate material collected in a city, were added and incubated with the cells. After 24 hours, cellular viability was evaluated through the colorimetric method based on the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT). Epidermal cells were protected despite the presence of urban dust, with a viability that was 47.9 percent higher when treated with the cosmetic ingredient.

Skin explants exposed to pollution

Human skin explants maintained with culture medium were treated with 5 percent Pollushield func­tional ingredient in carboxymethyl cellulose (CMC) aqueous gel or with CMC aqueous gel alone. The CMC gel is used because it pro­vides the appropriate viscosity for the ingredient to stay in contact with the skin. The explants were treated once a day for four days whereas non-treated explants were used as a control. After four hours from the last treatment, the explants were ex­posed to a pollution mix containing heavy metals, hydrocarbons and diesel particles, for an additional 24 hours.

Skin morphology

Skin sections were stained with the Masson’s trichrome, Goldner variant method. Then, cell and tissue morphology were visually evaluated by a trained expert. The application of Pollushield functional ingredient to the explants helped preserve normal morphology in pollution-exposed skin.

Expression of metallothionein

Protein metallothionein (MT-1H) was used as a marker of exposure to metals and oxidative stress. This protein was detected on skin tissue sections by means of immu­nostaining and its levels were visually evaluated by trained experts. With the active ingredient, MT-1H was not increased despite the presence of toxic substances, suggesting skin protection.

Number of Langerhans cells

Glycoprotein CD1a, which is spe­cifically expressed by Langerhans cells, was detected through immune staining and quantified on skin tissue sections. The total amount of Langerhans cells dimin­ished significantly in skin exposed to pollution. However, with the anti-pollution ingredient, the number of these cells was higher (32.4 per­cent) compared to non-treated skin.

Lipid peroxidation

The degree of oxidation of skin lipids was assessed using an en­hanced method of the thiobarbituric acid reactive substances (TBARS) assay. The concentration of the marker for oxidative stress malondi­aldehyde (MDA) in the explants me­dium was quantified and it was 37.4 percent lower in pollution-exposed skin pretreated with the ingredient compared with non-treated skin.

In Vivo test in a highly polluted city

In order to evaluate the protective effect of the ingredient in an urban environment, a clinical test was performed in a panel of 20 Asian female volunteers, between 26- 62 years old, who were outdoor workers in Beijing, China. The subjects applied a cream containing 5 percent Pollushield functional ingredient to half face and a placebo cream to the other half, according to a randomization scheme.

Build-up of metals

At the beginning of the study, skin samples obtained through tape stripping were obtained to measure basal levels of metals. Then, the volunteers applied the creams and spent six hours in the city traffic. Finally, skin stripping was performed to obtain new samples of the epidermis. Metals were extracted from skin samples and, by means of graphite furnace atomic absorption spectroscopy, the following were analysed: iron, lead, chromium, nickel, and zinc. Variations in metal levels with respect to basal conditions were calculated.

All metals evaluated increased significantly after exposure to pollution. However, this was not observed in skin treated with the active cream, where there was a significant difference in metal levels compared to placebo (p<0.001).

Antioxidative capacity and lipid peroxidation

After 15 and 30 days of product application and regular exposure of the volunteers to city pollution, skin samples were taken by means of tape stripping and analysed. The antioxidant capacity of the skin was assessed by the ferric reducing antioxidant power (FRAP) method, while lipid peroxidation was determined by means of the MDA assay.

In the skin that was treated with the active cream, the antioxidative capacity improved and the level of lipid peroxides decreased. Differences in these measurements were statistically significant also when compared to placebo, both after 15 (p<0.01) and 30 days (p<0.001).

Conclusion

Pollushield functional ingredient is a cosmetic ingredient that offers the benefits of a polymer that can bind toxic metals and the aid of a powerful antiox­idant. The ingredient has been shown to maintain the viability of epidermal cells in contact with urban dust. Furthermore, it protects the skin, with a preservation of morphology and reduced peroxidation, together with lower levels of damage markers. A single application of Pollushield functional ingredient in volunteers exposed to urban pollution provided quick protection against heavy metals deposition in the skin, while its continued use replenished the antioxidative pool of the skin suggesting a better capacity to resist oxida­tive stress, which was also revealed with reduced lipid peroxidation.

Source: Lipotec SAU Pollushield™ is owned by The Lubrizol Corporation or its affiliates.

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