SKIN CARE 145
Figure 2: Schematic representation of the senolytic study concept. The desired senolytic activity depicted on the right results in the depletion of senescent cells while not affecting the healthy cell number.
senolytics has not yet been applied in the cosmetic field despite its great potential for skin rejuvenation.
Protein carbonylation Environmental stress factors, such as UV light, infrared radiation, tobacco smoke, and pollution, generate reactive oxygen species (ROS). ROS oxidise proteins and lipids, which are the main components of cell membranes. This leads to carbonylation, which is one of the most harmful irreversible modifications of protein structure. Under normal conditions, the resulting carbonylated proteins are recycled by the proteasome. However, age and an increase in oxidative stress factors impair the proteasome activity, which leads to a further addition of lipid aldehydes to these carbonylated proteins resulting in their crosslinking. These high-molecular-weight superstructures resist degradation and accumulate over time, and they become cytotoxic and accelerate ageing by promoting cellular senescence. Therefore, the content of carbonylated proteins is the major indicator of oxidative damage and a hallmark of ageing.
An extract from organic Swiss alpine rose leaves Rhododendron ferrugineum, which is also known as alpine rose, is one of the most typical and iconic plants of the Swiss Alps. To produce an active ingredient for cosmetics, the leaves of alpine roses were handpicked by organic farmers in the Swiss Alps through controlled wildcrafting. The extract from these leaves (INCI: Rhododendron Ferrugineum Extract (and) Glycerin (and) Aqua / Water, from here on alpine rose extract) inhibits the formation of carbonylated proteins and
April 2020
therefore protects the skin against the formation of premature senescent cells. Where cellular senescence has already occurred, the alpine rose extract can help to clear these cells from the tissue thanks to its senolytic activity.
Materials and methods Senolytic assay In order to distinguish between the prevention of senescence and true senolytic activity, Normal Human Dermal Fibroblasts were first stressed with 500 µM H2
O2 for 2
hours to induce premature senescence through oxidative stress. The medium was then exchanged, and the cells were grown for 3 days to fully establish the senescent phenotype in a subpopulation of the cells. This mixture of senescent and healthy fibroblasts was then treated for 48 hours with
n Senescent fibroblasts n Healthy fibroblasts
120 100 80 60 40 20 0
Control * **
20 15 10 5 0
Navitoclax 3 uM
1% Alpine Rose Extract
*p<0.005 versus control **p<0.0005 versus control
-10
Figure 3: The alpine rose extract exhibits senolytic activity. Cell numbers of senescent and non-senescent cells are shown normalised to control cells in which senescence was induced with hydrogen peroxide.
*p<0.05 versus placebo
Figure 4: Prevention of protein carbonyl formation by the alpine rose extract upon UVA stress in vivo.
PERSONAL CARE EUROPE -5 *
either 1% alpine rose extract or Navitoclax (Cayman Chemical, Ann Arbor, USA), a known senolytic drug, or not treated (control). Following fixation with 2% formaldehyde and 0.2% glutaraldehyde, cells were stained with DAPI and the relative total cell number was determined by fluorescence measurement. Senescence-Associated β-galactosidase activity assay was performed according to (6) and a total of 400 cells were counted. Counting the β-gal-positive cells as a marker for senescence and calculating the percentage compared to the total cell number revealed the treatment efficacy.
In vivo protein carbonylation assay A double-blind, placebo-contolled clinical study was performed with 12 volunteers (9 female/3 male, 40 - 54 years) who applied a placebo cream and 2% alpine rose extract in
n Placebo n 2% Alpine Rose Extract
Cell number compared to control cells (=100) in %
Carbonyl protein concentration compared to unirradiated/untreated
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