Retinoic Acid - An Overview

Introduction:

Retinoic acid belongs to retinoids, and the term retinoid refers to the synthetic and natural analogs of vitamin A. Retinoids are derived from vitamin A or structure and function similarly to vitamin A. Retinoids are compounds that bind to and activate the relevant nuclear receptors and generate a transcription of appropriate genes either directly or after metabolic transformation. Retinoids are used in cosmetics as a concentrated dermatological agent in psoriasis, acne, and other skin diseases. These are the compounds of both natural and biologically active forms of vitamin A (retinol, retinal, and retinoic acid) as well as synthetic analogs of retinol. Retinoic acid has the same biological characteristics as vitamin A.

Retinol does not have a considerable biological effect on tissues but evolves after modification into more active metabolites. The most significant one is retinoic acid, depicted by its multilateral action. Retinoic acid is present in two isomers: the fully transformed and the 9-cis form. This affects the multiplication and differentiation of cells by controlling the respective genes. Retinoids are implicated in various biological actions, including cellular cohesion, growth, immunomodulatory effects, and antitumor functions.

What Is Retinol?

One useful form of vitamin A for skin care is retinol. In addition to its anti-aging properties, it treats acne. Since retinol is a topical therapy, it is applied topically to the skin. Creams are among the several forms that retinol can take. Cosmetic goods occasionally contain retinol as a component.

How Does Retinoic Acid Work?

Retinoids such as vitamin A and its derivatives are involved in embryogenesis. They play a role in developing the liver, nervous system, heart, kidneys, eyes, intestine, and limbs. The conversion of retinol to its active form, retinoic acid, happens in the target organ through the two-step oxidation process. Retinol dehydrogenase (RDH) or alcohol dehydrogenase (ADH), after entering the cell, catalyzes the oxidation of retinol to the retinal. The reaction can be reversed by the same enzyme as the oxidation of retinol to retinoic aldehyde, which is reversible.

Moreover, many enzymes can catalyze the reverse reaction: the conversion from retinamide to retinol. This suggests a different mechanism that controls the local retinol concentration in the tissues. After that, retinol is oxidized to retinoid acid by retinaldehyde dehydrogenase (RALDH) or some enzymes of the cytochrome P450 family. This reaction is irreversible. The outcome formed is a natural ligand of nuclear receptors and reflects vitamin A's activity. Also, the oxidation of the retinoic acid by the CYP26 enzyme results in the receiving of inactive vitamin A metabolites.

What Does Retinol Treat?

Numerous retinol solutions available without a prescription are advertised as improving skin appearance. Studies show topical retinoids can treat stretch marks, acne, and acne scars. Retinol also has anti-aging properties.

How Is Retinoic Acid Formed?

Vitamin A is derived from food and cannot be made in the body. It is specified and stored in the liver. Retinoic acid is synthesized from retinol by two enzymatic reactions. The first of them is a reversible oxidation of retinol to the retina. A second irreversible oxidation reaction to retinoic acid follows the next.

Retinoic acid is a light-sensitive compound due to the alternating double bonds between the carbon atoms in its hydrophobic tail, which is attached to a 6-carbon ring. The low molecular weight of the compound also makes it highly fat-soluble, which means it readily diffuses across cell membranes.

What Are the Functions of Retinoic Acid?

The functions of retinoic acid are:

• Reduces Sebum and Inflammation: Retinoic acid (all-trans retinoic acid, tretinoin) accelerates the elimination of sebum remaining in ducts, stimulates epidermal cell proliferation, thus reducing inflammation in sebaceous glands, loosens connections among cells in stratum corneum, and inhibits keratosis. It can be used for psoriasis, acne, and chronic inflammation of hair follicles and sebaceous glands.

• Anti-Acne Therapy: Tretinoin (all-trans-retinoic acid) is a considerably bioactive form among retinoids used topically on the skin. It causes the dispersion of melanin granules and increases epidermal cellular turnover. Generally, the tretinoin concentration in anti-acne therapy varies from 0.01 to 0.4 percent. It is available as gel or cream and is applied topically. Retinoic acid can be present in different formulas- cream (0.025, 0.05, and 0.1 percent), gel (0.01 and 0.25 percent), new technology microspheres (0.04 and 0.1 percent), emollient (0.05 percent), and solution (0.05 percent). Retinoic acid firmly affects epithelial differentiation and proliferation. In vitro cultivated keratinocytes in media with retinoic acid deficiency have reduced motility. They do not form distinct patterns and have increased adhesiveness.

• Regulation of Keratin Production: The production of keratins is controlled by the concentration of retinoids. In cells cultured without retinoic acid, keratin 1 (67 kiloDalton) production, characteristic of terminally differentiating keratinocytes, increases. In contrast, the synthesis of keratin 8/18 (52 kiloDalton) and keratin 19 (40 kiloDalton) is decreased. Supplementation of retinoids in cultured human epidermal keratinocytes results in increased expression of keratin 7, keratin 13, keratin 15, and keratin 19 and the reduced expression of keratin 1, keratin 5, keratin 6, keratin 10, and keratin 14. Most affected genes regulate the cell cycle, DNA synthesis and repair, translation, transcription factors, adhesion, RNA metabolism, receptor expression, apoptosis, membrane proteins, and protein kinase. Retinoic acid controls its bioavailability. Retinoic acid also proved to be essential in preadipocyte differentiation in adipose tissues.

• Treatment of Basal Cell Carcinoma: Regression of basaliomatous cells is associated with reduced proliferation and increased apoptosis, which occurs in basal cell carcinoma—unresponsive tumors after administration of retinoic acid show keratotic differentiation. Keratotic BBCs display overexpression of retinol-binding protein-1 (RBP-1) and p53 compared to undifferentiated tumors.

• Regulating Cell Growth and Differentiation: Retinoic acid helps to control cell growth and differentiation, particularly in developing embryos. It also forms organs, limbs, and the central nervous system.

Can You Use Retinol While Pregnant or Breastfeeding?

1. Retinol Use During Pregnancy: Retinoids can result in birth malformations (congenital disorders) when taken orally. According to some research, topically applying a drug may reduce its absorption and bloodstream penetration. However, there are examples of newborns who were born with congenital problems as a result of their birth parents using topical retinoid creams. Pregnant women are advised not to use retinoids as there are safer and more effective alternatives to address skin issues.

1. Retinol Use During Breastfeeding: Minimal topical retinoid is absorbed into your bloodstream because it is applied topically. According to medical professionals, there is little risk for nursing babies. While breastfeeding, you should always talk to your healthcare professional about all your medications and supplements, including topical ones. If topical retinoids are something you do use, avoid putting them on your breasts and be cautious not to get any on your baby's skin.

How Often Can You Use Retinol?

It is advisable to start slowly because retinol might irritate your skin. Following a patch test, you may use a product once every few days and then progressively increase it to once or twice daily. Redness, itching, or burning may occur initially, but these symptoms diminish as your skin adjusts to the treatment.

What Are the Side Effects of Retinol?

The majority of topical retinol side effects are transient. Among them are:

• Itchy, dry skin.

• Burning or itching.

• Skin that is flaky, scaly, red, or peeling.

• Sunburned skin.

As the new treatment settles in and your skin adjusts, these adverse effects should eventually disappear.

How Can You Manage the Side Effects of Retinol?

Modest changes to your skincare regimen could lessen the redness and irritation that retinol use can cause.

• One retinol product should be used at a time.

• Instead of using retinol daily, use it every other day.

• After cleansing your skin, wait half an hour before using a retinol product.

• Stay away from retinol products if you have damaged skin, sunburned skin, or other skin irritations.

• Wear hats and clothes that protect you from the sun, along with SPF 30, to minimize your exposure to the sun.

Conclusion

Treatment with retinoic acid derivatives is very effective in basal cell carcinomas. Tazarotene is effective in treating basal cell carcinoma. Retinoic acid is an active form of retinoids and vitamin A. It can treat various skin diseases, such as acne and psoriasis. However, retinoid acid therapy cannot be used in pregnancy as it can have negative effects on the fittest development. Also, using retinoic acid leads to a buildup of tolerance and the development of adverse effects such as rash, erythema, scaling, dryness, and desquamation, which leads to epidermal barrier dysfunction.