Retinoid binding proteins and human skin

Area of Science:

• Biochemistry
• Dermatology
• Molecular Biology

Background:

• Retinoids are crucial for skin health and are used in various therapies.
• Understanding retinoid-binding proteins is key to their therapeutic efficacy and delivery.
• Current methods for analyzing retinoid-protein interactions have limitations.

Purpose of the Study:

• To develop novel techniques for analyzing retinoid-binding proteins in human plasma and skin.
• To investigate the binding of natural and synthetic retinoids to retinol-binding protein (RBP).
• To characterize cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) in human skin and their modulation during retinoid therapy.

Main Methods:

• Polyacrylamide gel electrophoresis (PAGE) coupled with protein blotting using specific antisera.
• Incubation of human skin extracts with radiolabeled retinol or retinoic acid followed by PAGE analysis.
• Competitive binding assays using synthetic retinoid analogs and [3H]retinoic acid with human skin CRABP.

Main Results:

• Retinoic acid binding to RBP caused significant conformational changes.
• Synthetic retinoids used in therapy did not bind to RBP, confirming their non-RBP mediated delivery.
• CRABP was found in higher concentrations in the epidermis than dermis and significantly increased in psoriatic plaques.
• Epidermal CRABP levels were upregulated during systemic or topical synthetic retinoid therapy.
• Pharmacologically active synthetic retinoids competed effectively with [3H]retinoic acid for CRABP binding.

Conclusions:

• Developed PAGE-based techniques offer novel ways to analyze RBP, CRBP, and CRABP.
• Synthetic retinoids bypass RBP for delivery to target tissues.
• CRABP is a key protein in skin, with altered levels in psoriasis and during retinoid treatment.
• CRABP binding assays can predict the pharmacological activity of synthetic retinoids.