Exposure of skin to UV irradiation causes oxidative stress, DNA damage and immune suppression associated with increased incidence of skin cancer. Therefore, protection against UV-induced damages may have a positive skin clinical impact. The efficacy of ectoine and mannitol (0.01% and 0.05%
respectively) were tested on three parameters. First, using UV irradiated keratinocytes, quantification of intracellular reduced glutathione (GSH), an intracellular tripeptide that neutralises reactive oxygen species, was performed following full solar spectrum irradiation (200 J/cm², 750 W/m²). Then, DNA damages induced by UVA was quantified by the phosphorylation of H2Ax, a double strand breaks marker during DNA repair process. The phosphorylation of H2Ax was measured on UVA-irradiated normal human epidermal keratinocytes (15 J/cm², 2.55 mW/cm²) by immunostaining. Finally, the immunosuppressor effect of UVA was revealed through a reduction of the Langerhans cells (LC) ability to present antigen following by a reduction of the T lymphocytes proliferation. The functionality of LC after UVA irradiation was quantified by the proliferation of T lymphocytes induced by coculture with LC after five days. Results showed that the ectoine and mannitol complex restricted GSH UV-induced depletion by 80.8 % (p<0.05) and decreased the H2Ax phosphorylation by 86 % (p<0.001). Conversely, under UV irradiation, this complex increase T lymphocytes proliferation by 64.8 % (p<0.01) indicating the partial maintain of antigen presentation capacity of LC. Our results demonstrate that ectoine and mannitol help the skin to preserve the natural biological system developed against the deleterious effects of sun irradiation. This action is in agreement with ecobiology, a novel scientific approach that is based on the principle that the skin is a constantly changing ecosystem which interacts with its environment and whose natural resources and mechanisms must be preserved.

Photoprotective effect of ectoine and mannitol to preserve the skin according to ecobiology approach.