Skin aging is an extremely complex multifactorial process that disrupts the functions and structure of epidermal and dermal cells and extracellular matrix components and has multiple causes including extrinsic phenomena (UV radiation, exposure to pollution, etc.).~It has important effects on the skin and is particularly apparent on the face. Indeed, sunlight, in particular ultraviolet light, is an important factor that contributes to cutaneous photoaging by inducing the photo-chronic generation of reactive oxygen species (ROS). Although skin has its own antioxidant system against ROS, these antioxidant defenses are not fully effective during sun exposure and weaken over time. Photoaging of the skin is characterized by the development of pigmentary disorders, such as actinic lentigos (AL), as well as benign skin tumors such as actinic keratosis (AK), both of which are target pathologies for this study.~AL usually occur in the elderly. They are usually benign but can cause aesthetic problems. They are commonly seen on the hands but can appear on all areas of the body, especially on sun-exposed areas such as the face, back, arms, feet, shoulders and skull. There are different treatment approaches, including physical therapy such as laser therapy, pulsed light, chemical peeling, bleaching and cryotherapy or topical therapy such as hydroquinone (HQ). Although topical therapies are generally more time consuming compared to physical therapies, patients can control their own treatment and side effects can be decreased.~AK is a very common skin lesion caused by chronic sun damage that typically measure less than 1 cm in diameter. KA is considered a premalignant epithelial skin lesion that may progress to squamous cell carcinoma. For this reason, all KA should be treated and clinical follow-up is recommended. The goals of treatment are: (i) to clinically eradicate obvious and subclinical lesions, (ii) to prevent their progression to EC, and (iii) to reduce the number of relapses and consequently increase the quality of life of patients.~Medical treatment with antioxidant properties/actions that would allow the reduction of damaged cells seems to play a role in both the prevention and treatment of AL and KA (Nashan et al., 2013).~In addition, a paper published in early 2020 highlighted a major role for carbonylation in the progression of this type of skin lesion (Tramutola et al., 2020). Based on these elements, we hypothesize that our cosmetic active ingredient - MRB - which has antioxidant activity and a specific and original chaperone effect giving it a strong capacity to fight against protein carbonylation- will be effective in the treatment of photo-induced signs of aging: keratoses and actinic lentigo, by a mechanism that acts on the oxidative stress pathway and the maintenance of cellular proteostasis.
The aim of this study is to evaluate effectiveness of a serum containing 0.3% of MRB, a cosmetic active ingredient, against actinic lentigo and actinic keratosis.