SKIN PROTECTION 91 superoxide, not singlet oxygen.13 The
increase of ROS production could result in an increase of DNA damage.14, 15 It has also been proven that oxidative damage due to LED exposure would induce an increase of ROS generation, leading to the inhibition of cell proliferation and the induction of cell apoptosis, mainly through PKC inactivation and caspase-3 activation.16
The irradiation of the human skin with blue-violet light would, at least, result in a dose-dependent significant degradation of the epidermal antioxidants with the depletion of higher content of cutaneous carotenoids.17 We demonstrated that SA inhibits the
production of ROS caused by blue light as the chosen standards (vitamins C and E). It reduces by 71% the ROS production caused by blue light at 5 J/cm² at 0.025% (significant effect) and by 28% at 0.005% (Fig 2).
Thanks to its richness in carotenoids, it
can provide skin in antioxidants and therefore may contribute to restore cutaneous carotenoid levels after their degradation by blue light.
SA preserves the elastin capital under blue light exposure Elastin shows numerous age-related changes, including slow degradation and accumulation of damages in existing elastin with intrinsic ageing, an increase of
a 8000 6000 4000
-54% *
p=0.108
-71% **
2000
-55% ***
0 No treated Vitamin C Vitamin E Without stress SA Irradiated Vitamin C Vitamin E Blue light (5j/cm2 ) Figure 2: Release of free radicals without any stress and under blue light exposure.
apparently abnormal elastin synthesis in photo-exposed areas and abnormal localisation of elastin in the upper dermis of photodamaged skin. UV irradiation increases the expression of matrix metalloproteinases (MMPs), which cause degradation of extracellular matrix such as elastin, and especially the expression of human elastase (MMP-12) within 16h after UV exposure.18 It also causes a disruption in the regular array of elastic fibres that appear shorter, highly fragmented, and thinner after UVA treatment.19
Blue light exposure also induces the release of enzymes metalloproteinases
b
(MMPs), in particular MMP-1 and MMP-9 (that degrade dermal fibres and therefore cause premature ageing1
), the increase of
MMP-1 and MMP-9 expression, the decrease of Type I procollagen expression in the skin20
and the increase of MMP-12
(elastase) expression.21 The results relative to specific
immunolabelling on irradiated human skin explants treated with 2.5% SA are presented in Figure 3. Cell nuclei are coloured in blue and elastin fibres in green. These results give new information
relating to the effects of blue light irradiation on the structure of the elastic fibres: blue light exposure is able, as UV rays, to induce important microstructural changes of elastin fibres after low repetitive doses of irradiation.
At the dose of 2.5%, SA in a basic gel is
able to prevent elastin fragmentation and rupture of fibres after blue light irradiation. Therefore it safeguards elastin capital and counteracts the loss of skin elasticity.
SA protects against protein carbonylation under blue light exposure Reactive oxygen species can modify proteins in tissue to form carbonyl derivatives.22
c d
irreversible oxidative damage leading to a loss of protein function due to the implication of the proteasome complex. Photoageing induced by UVA/UVB
A Explants non irradiated and non treated : elastin fibres well apparent and regularly arranged. B Explants irradiated and non treated : disruption and fragmentation of elastin fibres. C Explants irradiated and treated by placebo : elastin fibres thin and less oriented. D Explants irradiated and treated by 2.5% SA : elastin fibres long and arranged in a regular fashion.
Figure 3: Immunolabelling of skin human explants submitted to blue light exposure. November 2019
exposures is linked to protein oxidation in human skin, due to a depleting of anti- oxidant enzymes.23 Carbonylated proteins are also excited by absorbing blue light. They would result in the generation of superoxide anion radicals through a particular photosensitising reaction.24 The images presented in Figure 4 show
the expression of oxidised proteins in different experiments. Cell nuclei are coloured in blue and oxidised proteins in characteristics red points. It clearly appears that blue light
PERSONAL CARE ASIA PACIFIC SA 500 µM 200 µM 0.025% 0.005% 500 µM 200 µM 0.025% 0.005%
-28%
Carbonylation of proteins is an
RFU
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