Team:Tartu TUIT/Description

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DESCRIPTION

Toxicity of modern sunscreen

Sunlight is very important for maintaining human health: it boosts vitamin D production,increases blood level of endorphins, induces the release of the alpha melanocyte-stimulating hormone[1]. However, along with positive effects of sunlight, Sun’s UV may cause sunburns, photoaging, photosensitivity, age spots and skin cancer[2]. These risks can be significantly reduced by the use of sunscreen. There are two types of sunscreen – organic and inorganic. The former contains chemical filters such as Oxybenzone and Octinoxate. They absorb UV radiation resulting in the emission of light with a longer wavelength, which is less damaging to the skin. Inorganic sunscreen, such as zinc oxide and titanium dioxide, act as physical sun blockers, which scatter, absorb and reflect UVA and UVB rays[3].

However, the use of sunscreen currently available at the market can be harmful to nature. In particular, UV – absorbents negatively affect marine environment:

1. Oxybenzone and octinoxate cause coral bleaching by promoting viral infections in coral’s endosymbiotic algae[4]. DNA damage, resulting in reproductive diseases and endocrine disruption [5].
2. Nanoparticles of titanium dioxide and zinc oxide exert harmful ecotoxicological effects such as bleaching and, inhibition of algal growth along with the increase of the lipid peroxidation of the cell membrane, resulting in the deformation of the membrane structure[6][7].

Every year up to 14,000 tons of sunscreen is being washed into the oceans and seas, resulting in a dramatic increase of the toxicity level and causing a variety of pathologies to corals[5].

Mycosporine-Like Amino Acids(MAA)

Considering all the negative effects on the environment mentioned above, our team decided to look for safer sunscreen options. The possible alternative to current synthetic UV filters might be Mycosporine-Like Amino Acids (MAA). MAAs are small, water-soluble, colorless molecules [8] produced by a variety of marine organisms, including cyanobacteria, fungi, microalgae, and macroalgae [9]. Nowadays, more than 30 different types of MAAs have been identified [10]. MAAs consist of cyclohexanone or cyclohexenimine chromophore attached to the nitrogen substituent of an amino acid or amino alchohol[11].

Two types of MAAs , Shinorine and Porphyra-334 (Figure 1), were originally isolated from red algae Porphyra Umbilicalis. These MAAs have relatively high UV – absorption in the range from 310 to 365 nm that covers UV-A and UV-B parts of the light spectrum[10]. While both substances are efficient UV-sunscrening compounds, Porphyra-334 also possesses anti-aging effects [12] and even works as an antioxidant [13]. Therefore, the use of Shinorire and Porphyra as ingredients in cosmetic products has potential advantages to humans. In addition to that, these MAAs are safe to the marine environment, since they are both parts of naturally – existing light protective mechanism in algae [14]

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  Figure 1.1.
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  Figure 1.2.

Currently, the only source of MAAs for the industry is their extraction from red algae. This process is time- and cost-consuming since red algae have a long life cycle and they require specific conditions for artificial cultivation (temperature, nutrients, etc.). Specific light is also essential for the optimal MAA production resulting in the variations of Shinorine and Porphyra-334 yield from harvest to harvest [15][16].To date, Helioguard 365 is the first commercially produced natural sunscreen, which incorporates MAAs as UV absorbents. Helioguard 365, protects skin from photo-aging and helps to prevent the appearance of lines and wrinkles [17].

MAA production

Our team was inspired by the work of researchers from the University of Florida, who used Synechocystis sp PCC6803 – as a host for the heterologous production of Shinorine. Shinorine gene cluster was taken from filamentous cyanobacterium Fisherella sp. PCC9339. By optimizing gene expression, researchers managed to get the yield of Shinorine comparable to that obtained from the commercially used Shinorine producer.

The work has proved that it is possible to efficiently produce MAA under laboratory conditions using a synthetic biology approach, which is cheaper and faster than farming [18].

Two obtain two natural UV-protecting compounds, Shinorine and Porphyra-334, we decided to use as gene sources two different organisms, which synthesize target MAAs in vivo. Enzymes of MAAs biosynthesis are encoded either by MysA, MysB, MysC, MysD or amir4256, amir4257, amir4258, amir4259 in cyanobacterium Nostoc Punctiforme and actinobacterium Actinosynnema Mirum, respectively. Two different organisms were chosen to increase a chance of successful heterologous expression in yeast..

Shinorine and Porphyra-334 biosynthetic pathway comprises four enzymatic reactions catalyzed by 4 different enzymes:

1. The intermediate of the pentose phosphate pathway, sedoheptulose-7-phosphate, is converted into dimethyl 4-deoxygadusol (DDG) by demethyl-4-deoxygadusol synthase encoded by mysA/amir4259.
2. DDG is then converted to 4-deoxygadusol (4-DG) by demethyl-4-deoxygadusol methyltransferase(O-MT family) encoded by mysB/amir4258.
3. The (ATP-grasp family) encoded by mysC/amir4257 catalyzes the addition of glycine to 4-DG to form mycosporine-glycine.
4. D-ala-D-ala ligase homolog (ATP-grasp family) encoded by mysD/amir4256 catalyzes the last reaction, in which serine and threonine are added to mycosporine-glycine forming Shinorine and Porphyra-334, respectively [10, 19, 20,21,22].

Figure 2

Yeast and yeast extract

Our team decided to synthesize MAAs in S.cerevisiae, since yeast cultures have some valuable properties. First of all, S. cerevisiae is a standard model organism and there are a lot of well-developed lab techniques for yeast cultivation and genome manipulation. Yeast is widely used as producers since they have high growth rate and production of the target compound can be relatively easy optimized [23][24].

Our idea is to produce MAA-enriched yeast extract.

There are several reasons why we think that yeast extract is a good component for our sunscreen:

1. It does not cause irritation [25].
2. It was proven to be an efficient antioxidant due to the presence of beta-glucan [25].
3. It can moisturize and nourish the skin and is able to activate both, collagen production in the skin and cell regeneration processes [26].

These properties would make the sunscreen healing, so it not only protects the skin from the sun but also helps to fight the consequences of sunburns.In addition to that, use of MAA-enriched yeast extract allows skipping purification of the target compounds, which is often time- and cost-consuming.

Therefore, we believe that the combination of MAAs and yeast extract will be advantageous and will make our product multifunctional and attractive for further development.

References:

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