Current insights and future perspectives of ultraviolet radiation (UV) exposure: Friends and foes to the skin and beyond the skin.

Ultraviolet (UV) radiation is ubiquitous in the environment, which has been classified as an established human carcinogen. As the largest and outermost organ of the body, direct exposure of skin to sunlight or UV radiation can result in sunburn, inflammation, photo-immunosuppression, photoaging and even skin cancers. To date, there are tactics to protect the skin by preventing UV radiation and reducing the amount of UV radiation to the skin. Nevertheless, deciphering the essential regulatory mechanisms may pave the way for therapeutic interventions against UV-induced skin disorders. Additionally, UV light is considered beneficial for specific skin-related conditions in medical UV therapy. Recent evidence indicates that the biological effects of UV exposure extend beyond the skin and include the treatment of inflammatory diseases, solid tumors and certain abnormal behaviors. This review mainly focuses on the effects of UV on the skin. Moreover, novel findings of the biological effects of UV in other organs and systems are also summarized. Nevertheless, the mechanisms through which UV affects the human organism remain to be fully elucidated to achieve a more comprehensive understanding of its biological effects.

UV radiation-induced peptides in frog skin confer protection against cutaneous photodamage through suppressing MAPK signaling.

Overexposure to ultraviolet light (UV) has become a major dermatological problem since the intensity of ultraviolet radiation is increasing. As an adaption to outside environments, amphibians gained an excellent peptide-based defense system in their naked skin from secular evolution. Here, we first determined the adaptation and resistance of the dark-spotted frogs (Pelophylax nigromaculatus) to constant ultraviolet B (UVB) exposure. Subsequently, peptidomics of frog skin identified a series of novel peptides in response to UVB. These UV-induced frog skin peptides (UIFSPs) conferred significant protection against UVB-induced death and senescence in skin cells. Moreover, the protective effects of UIFSPs were boosted by coupling with the transcription trans-activating (TAT) protein transduction domain. In vivo, TAT-conjugated UIFSPs mitigated skin photodamage and accelerated wound healing. Transcriptomic profiling revealed that multiple pathways were modulated by TAT-conjugated UIFSPs, including small GTPase/Ras signaling and MAPK signaling. Importantly, pharmacological activation of MAPK kinases counteracted UIFSP-induced decrease in cell death after UVB exposure. Taken together, our findings provide evidence for the potential preventive and therapeutic significance of UIFSPs in UV-induced skin damage by antagonizing MAPK signaling pathways. In addition, these results suggest a practicable alternative in which potential therapeutic agents can be mined from organisms with a fascinating ability to adapt.