Microbiota and photoageing: COSSMA

In recent years, the role of the cutaneous microbiota in modulating skin homeostasis has been described. Less well known is the role of the microbiome in protecting the skin from sun exposure. A healthy and balanced skin microbiota helps to protect the skin from the harmful effects of solar radiation. A microbiome that is out of balance can exacerbate photo-induced skin ageing. Researcher Òscar Expósito explains how a new ingredient can rebalance the skin and protect it from photo-induced ageing.

Nowadays, we are aware that the cutaneous microbiota plays a key role in skin homeostasis and that the skin microbial ecosystem evolves with age^{1, 2, 3}. Furthermore, the microbiome is highly relevant regarding the regulation of skin functions when the skin is exposed to sun radiation.

Various microorganisms of the skin microbiota have been identified for having especially important functions in protecting the skin in front of UV radiation^4,5: Staphylococcus epidermidis, Micrococcus luteus, Bifidobacterium spp. and Malassezia furfur. The metabolism of these microorganisms contributes in the protection of our skin against the exposure to sun radiation.

S. epidermidis can produce Short Chain Fatty Acids (SCFA) which inhibit the sun erythema, reducing the pro-inflammatory cytokine IL-6, as well as increasing the collagen expression in fribroblasts⁶, thus improving the skin firmness and elasticity.
M. luteus can resist high dosages of UV radiation thanks to the production of a high amount of carotenoids^7,8, at the same time it synthesiszes UV endonuclease, which eliminates Cyclo-Pyrimidine Dimers (CPD) in damaged DNA, repairing it⁹.
Bifidobacterium spp. also produce SCFA, such as lactate, which protect from free radicals (Reactive Oxygen Species, ROS)¹⁰, preventing UV radiation-induced damage in collagen¹¹, as well as reducing pro-inflammatory cytokines (IL-6, IL-1b and TNFα) and modulating metalloproteases MMP-1, MMP-3 and MMP-9 which degrade skin collagen. Finally, these bacteria synthesize urolithins¹², natural microbial antioxidants highly beneficial for the skin^{13, 14, 15, 16}.
M. furfur, and other species of Malasseziaceae, can produce melanin and melanin-like pigments^{17, 18, 19}.

The role of the solar postbiotics

These microorganisms are affected by the sun radiation, and if their environment is not the most suitable, the loss of homeostasis will impact our skin, potentially leaving it defenseless in front of the harmful effect of sun exposure. The skin microbiome and its state in front of sun radiation, including the microbial metabolic behaviour, is the Photobiome Factor. These microorganisms can interact with sun radiation and produce specific metabolites: the solar postbiotics (metabiotics)the metabiotics.

Among these metabiotics, microbial melanin and urolithins stand out. Both compounds photo-protect cutaneous microbiota and are part of the skin’s natural photo-defense system. If the conditions are not favourable, like with an excessive sun exposure, the population of these protecting microbes is dramatically reduced, the production of urolithins and melanin is decreased, and the cutaneous synthesis of harmful metabolites (ROS, IL-6) gets higher, worsening the skin photo-induced damage and the photo-ageing.

Prevention of photoageing through the skin's microbiota

Therefore, we present a new axis in cosmetics: Sun-Microbiota-Skin. This biological axis allows prevention ofto prevent the photo-ageing with a totally new approach: we can prevent the photo-ageing from excessive sun radiation exposure by protecting our skin microbiota.

The new natural active ingredient20 combines the mode of action of stem cells from pomegranate (Punica granatum) and cotton from desert and semi-arid areas of the Near and Middle East (Gossypium herbaceum). Through a new technological platform of phyto-cell fusion, a phyto-lipid fraction (PLF) of P. granatum is combined with a plasma rich in cell factors (PRCF) of G. herbaceum. In this way, a synergistic effect is achieved to prevent photo-ageing by protecting the skin’s microbiota (Figure 1).

The membrane lipids of de P. granatum (phospholipids, glycolipids, etc.) have been maximized in this active ingredient, together with the plant’s antioxidants, the polyphenols and the hydroxybenzoic acids like ellagic acid. Furthermore, the Phyto-Lipidic Fraction helps to encapsulate these antioxidants, and by fusing this fraction with the PRCF of G. herbaceum, the active molecules of this extremophile cotton (mainly, plant chromophores like polyphenols and other defense molecules) are also encapsulated in the lipids from P. granatum.

This Phyto-Cell Fusion is complemented with two more plant-derived substances: the fructooligosaccharides and the trehalose, sugars that help protecting the cell membranes of the skin microbiome against adverse conditions like dehydration. Therefore, the fructoologisaccharides and the trehalose also contribute to protecting the microbiota in front of sun radiation and as a consequence, to protecting our skin against its harmful effects.

In vitro tests

Protection of skin microbiota against sun radiation: The bacterial population (CFU) of different microorganisms was quantified (S. epidermidis, M. luteus and B. pseudocatenolatum), each cultured in its specific culture médium in Petri plates (serial dilutions followed by CFU count), in different conditions: non irradiated, and irradiating at 6J (broad spectrum: UV, visible and IR) in absence or presence of the active (at a 20% dosage, as the bacterial populations were very high, between 200,000 and 5,000,000 CFU).

The sun radiation reduced the bacterial populations, while the active could maintain higher rates of survival. S. epidermidis was the bacteria with highest CFU count reduction in front of sun radiation, and in this case the ingredient increased the bacterial survival by 7-fold versus the irradiated untreated control. With M. luteus and B. pseudocatenolatum, more than the 100% of the CFU count was recovered compared to the irradiated untreated control.In another assay, the effect of sun radiation on a co-culture of various microorganisms in plates was analysed. The microorganisms cultured were: S. epidermidis, Staphylococcus capitis, Streptococcus mitis, Corynebacterium tuberculostearicum, Corynebacterium simulans, Cutibacterium acnes, Malassezia pachydermatis). A total reduction of the microbiota was observed when irradiating 2.69J (UV) and applying a lotion without any SPF. But with the same irradiation plus a lotion with a 3% of of the active substance, the co-culture could maintain a 43% of survival (Figure 1).

Effect of the sund radiation, and the active, in the microbial metabolism: Furthermore, for the first time, research to understand the effects of sun radiation in the microbial metabolism of skin microbiome, and to study the effect of microbial secretome after sun exposure (photo-secretome, PS) on keratinocytes.

When irradiating B. pseudocatenolatum (6J; UV, visible and IR), a reduction by 29% in the production of urolithins compared to the non-irradiated control was observed (quantification by UPLC in the bacterial supernatant, i.e., the photo-secretome, PS). With the same irradiation in the presence of a 10% of the active, though, the opposite effect was obtained: the synthesis of urolithins increased by 34% versus the non-irradiated control.²

In parallel, we observed that sun radiation caused some increase in the melanin production in M. furfur, but if in addition to sun radiation, the M. furfur culture is treated with 20% of the ingredient, the increase is 18-fold higher (Figure 2).

In a flow cytometry assay, cultures of S. epidermidis and M. luteus exposed to sun radiation produced more ROS than their non-irradiated controls. But under the same exposure in the presence of 20% of the active, a reduction of ROS production was observed, by 67% in S. epidermidis, and by 19% in M. luteus, compared to the irradiated controls which were not treated with the ingredient.

Finally, we analysed the effect of the microbial photo-secretome (PS) on ROS and IL-6 production on keratinocytes, in different condition: effect of the treatment of keratinocytes with 1% of each PS, effect of irradiating the keratinocytes at the same time they were treated with 1% of each PS, and effect of the active on keratinocytes irradiated and at the same time treated with 1% of each PS (Figure 3).

Clinical evaluation

In vivo test performed with 20 volunteers with signs of photo-ageing, summer tan and ages between 49 and 67. Double-blind and placebo-controlled assay, hemi-facial application, 1% of the ingredient PhotoBiome dosage, with two daily applications during 28 and 56 days. The test was carried out in Italy atin the end of the summer season so the sun exposure and the damage on the volunteers’ skin were maximiszed.

The variation in the Individual Tipology Angle (ITA) was measured in order to study the skin pigmentation during the treatment, both in the face and in the dark hyperpigmented spots (CM-700D colorimeter from Konica Minolta). Furthermore, the skin firmness and elasticity were assessed by cutometry, and by skin profilometry and PRIMOS 3D analysis, the variation in wrinkle depth in the crow’s feet and in the nasolabial regions (eye contour and bar code areas) were also analysed (Figure 4).

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