Pharmacology of RALGA, a Mixture of Retinaldehyde and Glycolic Acid

In situ antioxidant activity of a dermo-cosmetic product: A randomized controlled clinical study

Ultraviolet light enhances the generation of reactive oxygen species that are responsible for skin photoageing. The aim of this randomized, vehicle- and active-controlled double-blind, intra-individual monocentric study was to evaluate in situ the antioxidant activity of a dermo-cosmetic product in photoaged skin. Twenty healthy volunteers had defined skin areas randomized to receive a topical product containing 3 antioxidants (pre-tocopheryl® , retinaldehyde and glycylglycine ole-amide), its vehicle and a positive antioxidant control cream. The products were applied daily for 30-day period. The skin areas were exposed to a controlled dose of UVA rays, and the skin oxidative status was evaluated 4 and 24 hours post-UVA exposure at D0 (basal value) and after 15 and 30 days of product application. Skin layers were collected by stripping, and antioxidant capacity was measured using the ferric reducing ability of a plasma assay. Lipid peroxidation (LPO) was assessed using the malonyldialdehyde test. The tested product significantly improved the skin antioxidant capacity after 15 and 30 days and significantly decreased the basal level of the skin LPO. The skin LPO level significantly decreased 4 and 24 hours after UVA exposure at 15 and 30 days. These findings were comparable to positive control treated sites and were significantly different from the vehicle and untreated sites. This minimally invasive methodology enabled a quantitative evaluation of potent antioxidant activity in situ in the stratum corneum reflecting real-life skin conditions and confirming the benefits of the topical application of a product containing 3 antioxidants in the prevention of UVA-induced oxidative damage.

Efficacy and tolerability of a double-conjugated retinoid cream vs 1.0% retinol cream or 0.025% tretinoin cream in subjects with mild to severe photoaging

BACKGROUND

Topical retinoids are used to treat the visible signs of photoaging. While efficacious, they are irritating.

OBJECTIVE

Evaluate the effectiveness and tolerability of a double-conjugate retinoid cream (AlphaRet Overnight Cream; AHA-Ret) in improving visible signs of photoaging vs 1.0% retinol or 0.025% tretinoin.

METHODS

A 12-week, split-face, randomized trial was conducted in 48 female subjects, aged 30-65 years with mild to severe photodamage. AHA-Ret was applied to one side of the face and either retinol (n=24) or tretinoin (n=24) to the other side (PM). Expert blinded evaluation of images and Nova measurements occurred at 4, 8, and 12 weeks. Tolerability was assessed throughout the study.

RESULTS

Forty-seven subjects completed the study. AHA-Ret demonstrated significant reductions in average severity from baseline: Fine Lines/Wrinkles (P<.001; all time points); Erythema (P=.004, P<.0001; 8 and 12 weeks, respectively); Dyschromia (P<.0001; all time points); Skin Tone (P<.0001; all time points), and Pore Size (P=.035, P<.0001; 8 and 12 weeks, respectively). AHA-Ret induced less Erythema vs retinol at 8 (P=.008) and 12 (P<.02) weeks. AHA-Ret was noninferior to prescription tretinoin in all categories at 4 and 8 weeks, and for Fine Lines/Wrinkles, Erythema, Dyschromia, and Skin Tone at 12 weeks. Improvements in Hydration occurred at every time point with AHA-Ret only (P<.04, P<.03, P<.01). Less irritation was reported with AHA-Ret vs retinol or tretinoin.

CONCLUSIONS

Treatment with a double-conjugate retinoid cream demonstrated early reductions in photodamage and improvements in Hydration. AHA-Ret induced less Erythema vs retinol and was more tolerable vs retinol and tretinoin.

Topical retinoids in skin ageing: a focused update with reference to sun-induced epidermal vitamin A deficiency

Vitamin A is an important constituent of the epidermis, where it plays a crucial role in epidermal turnover. A deficiency of epidermal vitamin A may be the consequence of nutritional vitamin A deficiency, exposure to sunlight or any UV source, oxidative stress or chronological ageing. As a consequence, any treatment aiming at increasing epidermal vitamin A would exert a protective effect against these deleterious conditions. Retinoids may counteract some deleterious actions of UV radiation by physical and biological mechanisms. Topical natural retinoic acid precursors such as retinaldehyde or retinol are less irritant than acidic retinoids and may prevent epidermal vitamin A deficiency due to nutritional deficiency, exposure to sunlight or any condition leading to free radical production. Retinoids may be combined with other compounds with complementary actions against ageing, nutritional deficiency and cancer, such as antioxidants, to potentiate their beneficial effects in the skin.

Proposed mechanisms of action for retinoid derivatives in the treatment of skin aging

Skin aging (intrinsic aging) and photoaging (extrinsic aging) involve a similar process that leads to the typical creased appearance of the skin, with the progressive loss of its physical and biologic properties. Photoaging is a premature skin aging caused by long-term exposure to the ultraviolet B radiations of the sun, and is more frequently associated to skin cancer than intrinsic aging. Retinoids are natural and synthetic vitamin A derivatives. They are lipophilic molecules and penetrate the epidermis easily. Their biologically active forms can modulate gene expression by binding to nuclear receptors and then to specific DNA sequences. Because of their ability to modulate genes involved in cellular differentiation and proliferation, they appear as good candidates to treat and prevent photoaging. Hyaluronate and collagen, two major constituents of the dermis, are progressively decreased and altered during aging. Various retinoids were shown to increase their synthesis and concentration in the skin and reduce their rate of degradation. Furthermore, retinoids share a common chemical structure containing several conjugated double bonds that enable them to trap free radicals and absorb UV radiations from the sun, thereby protecting cellular targets such as DNA, lipid membranes, or proteins by preventing direct photochemical damage or UV-induced oxidative stress. Therefore, retinoids may be beneficial in treating skin aging and photoaging because of their biologic, chemical, and physical properties, which act at several levels.

Effective over-the-counter acne treatments

Acne is the most common disease of the skin, yet only a fraction of acne sufferers are treated with prescription products by physicians. There is, however, a large and expanding market for over-the-counter (OTC) medications, many of which are not only effective but also well tolerated and cosmetically elegant. Given the presence of OTC acne medications on the television, the Internet, and store shelves, patients will be acutely aware of these OTC remedies and will have questions. Patients will expect dermatologists to advise them regarding products to use either as a sole therapy or in combination with prescription drugs. Recently, combinations of OTC acne medications in treatment regimens or "kits" have gained popularity and appear to have increased patient compliance. Quality-of-life outcomes from OTC medication use, in at least one study, have demonstrated good benefit. The most common OTC ingredients include benzoyl peroxide, a potent antibacterial agent, and salicylic acid, a mild comedolytic and antiinflammatory medication. Other, less-common OTC ingredients include sulfur, sodium sulfacetamide, and alpha hydroxy acids. Zinc, vitamin A, tea tree oil, and ayurvedic therapies also are available OTC for acne. Additional and better studies are needed to clarify the benefit of these latter medications.

Retinoids in cosmeceuticals

Retinoids are natural and synthetic vitamin A derivatives. They are lipophilic molecules and easily penetrate the epidermis. Their biologically active forms can modulate the expression of genes involved in cellular differentiation and proliferation. Retinoic acid (tretinoin), its 13-cis isomer isotretinoin, as well as various synthetic retinoids are used for therapeutic purposes, whereas retinaldehyde, retinol, and retinyl esters, because of their controlled conversion to retinoic acid or their direct receptor-independent biologic action, can be used as cosmeceuticals. These natural retinoic acid precursors are thus expected to be helpful in (i) renewing epidermal cells, (ii) acting as UV filters, (iii) preventing oxidative stress, (iv) controlling cutaneous bacterial flora, and (v) improving skin aging and photoaging. Retinol and retinyl esters are not irritant, whereas demonstrating only a modest clinical efficiency. On the other hand, retinaldehyde, which is fairly well tolerated, seems to be the most efficient cosmeceutical retinoid; it has significant efficiency toward oxidative stress, cutaneous bacterial flora, epidermis renewing, and photoaging.

Spectral properties of topical retinoids prevent DNA damage and apoptosis after acute UV-B exposure in hairless mice

We showed in a recent study that topical retinyl palmitate prevented UV-B-induced DNA damage and erythema in humans. Given that retinyl palmitate is a precursor of retinoic acid, the biological form of vitamin A that acts through nuclear receptors, we wondered whether these protective effects toward UV-B exposure were either receptor dependent or linked to other properties of the retinoid molecule such as its spectral properties. We determined the epidermal retinoid profile induced by topical retinoic acid in hairless mice and analyzed its effect on markers of DNA photodamage (thymine dimers) and apoptosis following acute UV-B exposure; we compared these effects to those induced by other natural topical retinoids (retinaldehyde, retinol and retinyl palmitate) which do not directly activate the retinoid receptors. We then analyzed the direct action of these retinoids on UV-B-induced DNA damage and apoptosis in cultured A431 keratinocytes. Topical retinoic acid significantly decreased (approximately 50%) the number of apoptotic cells, as well as the formation of thymine dimers in the epidermis of mice exposed to acute UV-B. Interestingly, the other topical retinoids decreased apoptosis and DNA damage in a similar way. On the other hand, neither retinoic acid nor the other retinoids interfered with the apoptotic process in A431 keratinocytes exposed to UV-B, whereas DNA photodamage was slightly decreased. We conclude that the decrease of apoptotic cells in hairless mouse epidermis following topical retinoids and UV-B irradiation reflects a protection of the primary targets of UV-B (DNA) by a mechanism independent of the activation of retinoid nuclear receptors, rather than a direct inhibition of apoptosis.

The Depigmenting Effect of RALGA in C57BL/6 Mice

BACKGROUND

It has been known for a long time that the topical use of retinoic acid (RA) produces mild depigmentation of human skin. However, RA has two major disadvantages for its utilisation as a topical depigmenting compound. First, RA can act as an irritant and can produce considerable erythema and exfoliation of skin. Second, RA has a relatively weak depigmenting ability compared to other known depigmenting chemicals.

OBJECTIVE

In this study, we show that RALGA, a combination of the less irritant retinoid retinaldehyde (RAL; 0.1%) and glycolic acid (6.4%), has a higher skin-depigmenting potential than RA 0.05% in the tail skin of C57BL/6 mice. This effect was observed in reducing the number of functioning melanocytes and/or in inhibiting their ability to synthesise melanin. In addition, the visually recognisable depigmenting effect of RALGA was evident earlier than that of RA, i.e. only after 1 week of application. RALGA may therefore serve as a depigmenting product for the treatment of skin hyperpigmentary disorders. Postacne hyperpigmented lesions represent a very common pigmentary problem among acne patients. RALGA may thus act as an anti-acne product, due to the presence of RAL--an RA precursor--which could simultaneously remove the postacne hyperpigmented lesions in such patients.

Topical Retinaldehyde with Glycolic Acid: Study of Tolerance and Acceptability in Association with Anti-Acne Treatments in 1,709 Patients

BACKGROUND

Retinaldehyde (RAL), a key metabolite between vitamin A and retinoic acid, acts by modulating differentiation and proliferation of keratinocytes, which is of interest in acne lesions, mainly retentional lesions. Glycolic acid increases the exfoliation of corneocytes explaining its mild activity on retentional lesions. Thus, RAL and glycolic acid combined in the same product (Diacneal) have complementary activities which can be of interest for acne patients. The aim of this study was to evaluate the tolerance of Diacneal used by 1,709 acne patients in combination with their usual acne products except retinoids.

RESULTS

This study demonstrated a very good tolerance of Diacneal when used with other acne treatments for 90 days. Complaints about side-effects were rare. Moreover, the significant decrease in both inflammatory and retentional lesions between day 0 and day 90 indicates that Diacneal could amplify the efficiency of other anti-acne products used at the same time by the patients. The subjective evaluation of the preparation's efficacy by investigators and patients was strongly favourable.

CONCLUSION

These data show that a combination of RAL 0.1% and glycolic acid 6% may be used in association with other topical anti-acne treatments (benzoyl peroxide and topical antibiotics) with an excellent tolerance.