title: Keratin 4 upregulation by retinoic acid in vivo: a sensitive marker for retinoid bioactivity in human epidermis.
abstract: Retinoids affect keratinocyte differentiation and modulate the expression of many epidermal proteins, among them cellular retinoic acid-binding protein II and the family of cytokeratins. The upregulation of the former protein is a well-known phenomenon, whereas the retinoid-induced regulation of epidermal keratin expression is more complex and only partially understood. We studied the effect of topical retinoids on the expression in healthy skin of cellular retinoic acid-binding protein II, tazarotene-induced genes 1 and 2, several epidermal keratins (K1, K2e, and K10), and two mucous keratins (K4 and K13) known to appear in epidermis under certain abnormal conditions. Reverse transcription-polymerase chain reaction experiments showed that the K4 expression was the one most overtly induced by 2 wk of open treatment with 0.05% of retinoic acid and tazarotene. Using real-time quantitative polymerase chain reaction (TaqMan) and normalization of the mRNA values to beta-actin, the increase in K4 was found to be 100-1000-fold. In comparison, the expression of K13 and cellular retinoic acid-binding protein II was increased 10-50-fold, the K1 and K10 mRNA levels remained unchanged, and the K2e level decreased by a factor of 100-1000. In parallel biopsies, immunohistochemistry showed no change in K1, K2e, or K10 staining, but a strong de novo appearance of K4 in the granular layer after retinoid treatment. In a separate study, occlusive application of 0.025% retinoic acid in four healthy subjects produced a maximal K4 mRNA signal after 48 h and strong K4 staining after 80 h. Finally, a dose-response study showed that the de novo appearance of K4 can be utilized as a sensitive test for retinoid bioactivity in epidermis in vivo.
authors.affiliation: Department of Medical Sciences, Section of Dermatology and Venereology, Uppsala University, Uppsala, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Virtanen
authors.forename: H
authors.initials: H
authors.lastname: Törmä
authors.forename: A
authors.initials: A
authors.lastname: Vahlquist
mesh_terms: D000287:Administration, Topical; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000235:genetics / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009539:Nicotinic Acids / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D018168:Receptors, Retinoic Acid / Q000235:genetics; D012176:Retinoids / Q000008:administration & dosage / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D015415:Biomarkers; D009539:Nicotinic Acids; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D012176:Retinoids; C082928:retinoic acid binding protein II, cellular; D014212:Tretinoin; D007633:Keratins; C086827:tazarotene