Retinoic

Retinoic refers to retinoids, a class of compounds derived from vitamin A (retinol) or synthetic analogs. The most biologically active member is retinoic acid, a transcriptionally active metabolite produced from retinol through a two-step oxidation pathway: retinol is oxidized to retinal by retinol dehydrogenases, then to retinoic acid by retinaldehyde dehydrogenases. Among retinoic acids, both all-trans-retinoic acid and 9-cis-retinoic acid are well studied for their distinct isomeric forms and receptor affinities.

Biological action centers on nuclear receptors. Retinoic acid binds to retinoic acid receptors (RARα, RARβ, RARγ), which form heterodimers with retinoid X receptors (RXR). This receptor complex attaches to retinoic acid response elements in DNA to regulate transcription, influencing genes involved in cell differentiation, proliferation, and apoptosis. Retinoic acid signaling is essential for embryonic development and the maintenance of epithelial tissues; disrupted signaling is linked to developmental disorders and cancer.

Medical uses and safety considerations vary by agent. All-trans-retinoic acid is a cornerstone in the treatment of acute promyelocytic leukemia, where it promotes differentiation of malignant cells. In dermatology, topical tretinoin and systemic isotretinoin are used for acne, while acitretin and alitretinoin are employed for certain psoriasis and dermatoses. Retinoids can be teratogenic; pregnancy is contraindicated, and contraception is advised during therapy. Common adverse effects include mucocutaneous irritation, hepatotoxicity, and lipid abnormalities; monitoring of liver enzymes and lipids is recommended.

Dietary sources include animal-derived retinol and provitamin A carotenoids, such as beta-carotene, found in fruits and vegetables. Adequate intake varies by age and sex.