Category: receptor_pharmacology
Retinoic acid (all-trans + 9-cis) is the bioactive form of vitamin A; binds nuclear RAR (α/β/γ) + RXR (α/β/γ) heterodimers that bind RARE/RXRE on DNA → modulate transcription of genes governing keratinocyte differentiation, sebum production, melanocyte function, and epidermal cell-cycle. Therapeutic retinoids: tretinoin (all-trans RA — topical acne + photoaging; APL induction agent in oncology); isotretinoin (13-cis RA — oral severe nodulocystic acne + sebaceous-gland atrophy; iPLEDGE pregnancy program for teratogenicity); adapalene (RARβ/γ-selective — Differin OTC); tazarotene (RARβ/γ — psoriasis + acne); trifarotene (RARγ-selective — Aklief, truncal acne); bexarotene (RXR-selective — CTCL). Mechanism crosses both DERM + ONC use cases.