UNLABELLED: BACKGROUND & SCOPE OF THE REVIEW: This review focuses on the UV radiation effects on skin, emphasizing the photoaging process, and the photoprotection conferred by tretinoin (all-trans retinoic acid or ATRA). Tretinoin is still the best tested retinoid to reverse photoaged skin. MAJOR CONCLUSIONS: Tretinoin can be used for photoaging treatment or combined treatment by different mechanisms. It binds to and activates retinoic acid receptors, inducing changes in gene expression that leads to cell differentiation, decreased cell proliferation, and inhibition of tumourigenesis. It has been demonstrated that photoaging resulting from UV-B radiation can be treated by retinoid formulations. Pretreatment of human skin with tretinoin blocks dermal matrix degradation followed by sun exposure, inhibiting the induction of the activated protein-1 (AP-1) transcription factor and AP-1 regulated matrix-degrading metalloproteinases. GENERAL SIGNIFICANCE AND INTEREST: Tretinoin should be considered as a key factor as it is the most potent and best-studied retinoid. In addition, the development of advanced drug delivery systems, especially novel nanoformulations, has contributed to overpass some technical drawbacks besides the skin irritation potential. The triple combination of tretinoin, hydroquinone and corticosteroids is still considered the gold standard for melasma. Although there are other novel therapeutic approaches, more high-quality clinical trials are still needed.
UNLABELLED: BACKGROUND & SCOPE OF THE REVIEW: This review focuses on the UV radiation effects on skin, emphasizing the photoaging process, and the photoprotection conferred by tretinoin (all-trans retinoic acid or ATRA). Tretinoin is still the best tested retinoid to reverse photoaged skin. MAJOR CONCLUSIONS:Tretinoin can be used for photoaging treatment or combined treatment by different mechanisms. It binds to and activates retinoic acid receptors, inducing changes in gene expression that leads to cell differentiation, decreased cell proliferation, and inhibition of tumourigenesis. It has been demonstrated that photoaging resulting from UV-B radiation can be treated by retinoid formulations. Pretreatment of human skin with tretinoin blocks dermal matrix degradation followed by sun exposure, inhibiting the induction of the activated protein-1 (AP-1) transcription factor and AP-1 regulated matrix-degrading metalloproteinases. GENERAL SIGNIFICANCE AND INTEREST: Tretinoin should be considered as a key factor as it is the most potent and best-studied retinoid. In addition, the development of advanced drug delivery systems, especially novel nanoformulations, has contributed to overpass some technical drawbacks besides the skin irritation potential. The triple combination of tretinoin, hydroquinone and corticosteroids is still considered the gold standard for melasma. Although there are other novel therapeutic approaches, more high-quality clinical trials are still needed.