The retinoids are a class of chemical compounds that are vitamers of vitamin A or are chemically related to it. Retinoids have found use in medicine where they regulate epithelial cell growth.
Retinoids have many important functions throughout the body including roles in vision, regulation of cell proliferation and differentiation, growth of bone tissue, immune function, and activation of tumor suppressor genes.
Research is also being done into their ability to treat skin cancers. Currently, alitretinoin (9-cis-retinoic acid) may be used topically to help treat skin lesions from Kaposi's sarcoma, and tretinoin (all-trans- retinoic acid) is used to treat acute promyelocytic leukemia.
There are four generations of retinoids:
First generation include retinol, retinal, tretinoin (retinoic acid), isotretinoin, and alitretinoin
Second generation include etretinate and its metabolite acitretin
Third generation include adapalene, bexarotene, and tazarotene
Fourth generation includes Trifarotene
The basic structure of the hydrophobic retinoid molecule consists of a cyclic end group, a polyene side chain and a polar end group. The conjugated system formed by alternating C=C double bonds in the polyene side chain are responsible for the color of retinoids (typically yellow, orange, or red). Hence, many retinoids are chromophores. Alternation of side chains and end groups creates the various classes of retinoids.
First and second generation retinoids are able to bind with several retinoid receptors due to the flexibility imparted by their alternating single and double bonds.
Third generation retinoids are less flexible than first- and second-generation retinoids and therefore, interact with fewer retinoid receptors.
Fourth generation retinoid, Trifarotene, binds selectively to the RAR-y receptor. It was approved for use in the US in 2019.
The major source of retinoids from the diet are plant pigments such as carotenes and retinyl esters derived from animal sources. Retinyl esters are hydrolyzed in the intestinal lumen to yield free retinol and the corresponding fatty acid (i.
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Tazarotene, sold under the brand name Tazorac, among others, is a third-generation prescription topical retinoid. It is primarily used for the treatment of plaque psoriasis and acne. Tazarotene is also used as a therapeutic for photoaged and photodamaged skin. Tazarotene is a member of the acetylenic class of retinoids. It is available as a generic medication. Tazarotene is most commonly used topically to treat acne vulgaris and psoriasis.
A comedo is a clogged hair follicle (pore) in the skin. Keratin (skin debris) combines with oil to block the follicle. A comedo can be open (blackhead) or closed by skin (whitehead) and occur with or without acne. The word "comedo" comes from the Latin comedere, meaning "to eat up", and was historically used to describe parasitic worms; in modern medical terminology, it is used to suggest the worm-like appearance of the expressed material. The chronic inflammatory condition that usually includes comedones, inflamed papules, and pustules (pimples) is called acne.
Isotretinoin, also known as 13-cis-retinoic acid and sold under the brand name Accutane among others, is a medication primarily used to treat severe acne. It is also used to prevent certain skin cancers (squamous-cell carcinoma), and in the treatment of other cancers. It is used to treat harlequin-type ichthyosis, a usually lethal skin disease, and lamellar ichthyosis. It is a retinoid, meaning it is related to vitamin A, and is found in small quantities naturally in the body. Its isomer, tretinoin, is also an acne drug.
A series of bifunctional ruthenium(II) arene compounds modified with bexarotene, a retinoid that selectively activates retinoid X receptors inducing cell differentiation and apoptosis and preventing drug resistance, are described. The bexarotene is tethere ...
The intracellular fatty acid content of insulin-sensitive target tissues determines in part their insulin sensitivity. Uptake of fatty acids into cells is a controlled process determined in part by a regulated import/export system that is controlled at lea ...
Hypertriglyceridemia is a frequent complication accompanying the treatment of patients with either retinoids or rexinoids, [retinoid X receptor (RXR)-selective retinoids]. To investigate the cellular and molecular basis for this observation, we have studie ...