The Depigmenting Effect of RALGA in C57BL/6 Mice

Retinaldehyde/hyaluronic acid fragments: a synergistic association for the management of skin aging

BACKGROUND

Retinaldehyde (RAL) was proven effective in treating photodamaged skin. Topical treatments with specific intermediate-size hyaluronate fragments (HAFi, 50-400 kDa) have been shown to stimulate keratinocytes proliferation and epidermal hyperplasia. The aim of this open, multicentric, international study was to assess the efficacy of the combination RAL-HAFi in the correction of skin photoaging.

PATIENTS/METHODS

Either RAL 0.05%-HAFi 0.5% (Eluage® cream; group 1) or RAL 0.05%-HAFi 1% (Eluage® antiwrinkle concentrate; group 2) or both products (group 3) were applied daily to the 1462 subjects during 90 days. Overall photoaging severity was evaluated in the three groups by the dermatologists at D0, D30, and D90 based on the Larnier's scale. Wrinkles and/or furrows and clinical signs of aging were evaluated using a 4-point scale. The skin microrelief of the crow's feet, evaluated by optical profilometry, was performed in subjects from group 3.

RESULTS

The 3-month application significantly improved overall photoaging through decrease of the Larnier's score in the three groups (P<0.001). At D90, significant improvement of wrinkles was shown in groups 2 and 3 [forehead wrinkles (-19% and -10%, respectively, P<0.001), nasolabial folds (-20% and -16%, P<0.001), crow's feet (-27% in the two groups, P<0.001), and perioral wrinkles (-34% and -23%, P<0.001)]. Clinical signs of photoaging on the entire face improved significantly in groups 1 and 3 [elasticity (-32% and -33%, respectively, P<0.001), hyperpigmentation (-34% and -31%, P<0.001), and ptosis (-18% and -22%; P<0.001)]. Results were confirmed using an optical profilometry technique. Products were very well tolerated.

CONCLUSION

This clinical study showed the efficacy and value of the RAL-HAFi combination in the management of aging skin in a large cohort of patients.

Inhibition of melanogenesis and oxidation by protocatechuic acid from Origanum vulgare (oregano)

Antioxidant and antimelanogenesis activities of protocatechuic acid (1) from Origanum vulgare (oregano) were investigated. The antioxidative capacity of 1 was confirmed from its free-radical-scavenging activities, inhibition of lipid peroxidation, and suppression of reactive oxygen species in H(2)O(2)-induced BNLCL2 cells. The inhibition by 1 of tyrosinase and DOPA oxidase activity and melanin production was possibly related to the down-regulation of melanocortin-1 receptor, microphthalmia-associated transcription factor, tyrosinase, tyrosinase-related proteins-2, and tyrosinase-related proteins-1 expression in α-melanocyte-stimulating hormone-induced B16 cells. After a gel containing 1 was applied to mice, the values of L* slightly increased, and a* and erythema-melanin levels of skin were reduced by comparing the values of untreated control groups, indicating 1 can reduce melanin production. These results suggest that 1 may act as an effective quencher of oxidative attackers with antimelanogenesis properties.

Hypopigmenting agents: an updated review on biological, chemical and clinical aspects

An overview of agents causing hypopigmentation in human skin is presented. The review is organized to put forward groups of biological and chemical agents. Their mechanisms of action cover (i) tyrosinase inhibition, maturation and enhancement of its degradation; (ii) Mitf inhibition; (iii) downregulation of MC1R activity; (iv) interference with melanosome maturation and transfer; (v) melanocyte loss, desquamation and chemical peeling. Tyrosinase inhibition is the most common approach to achieve skin hypopigmentation as this enzyme catalyses the rate-limiting step of pigmentation. Despite the large number of tyrosinase inhibitors in vitro, only a few are able to induce effects in clinical trials. The gap between in-vitro and in-vivo studies suggests that innovative strategies are needed for validating their efficacy and safety. Successful treatments need the combination of two or more agents acting on different mechanisms to achieve a synergistic effect. In addition to tyrosinase inhibition, other parameters related to cytotoxicity, solubility, cutaneous absorption, penetration and stability of the agents should be considered. The screening test system is also very important as keratinocytes play an active role in modulating melanogenesis within melanocytes. Mammalian skin or at least keratinocytes/melanocytes co-cultures should be preferred rather than pure melanocyte cultures or soluble tyrosinase.

Retinoid therapy of pigmentary disorders

Topical retinoids such as all-trans-retinoic acid (RA), 13-cis-retinoic acid (isotretinoin), retinol, retinaldehyde, tazarotene, and adapalene have been shown to improve dyspigmentation of photodamaged skin including mottling and actinic lentigines. RA monotherapy has also been demonstrated to improve melasma and postinflammatory hypermelanosis. Furthermore, RA in combination with hydroquinone or 4-hydroxyanisole, or azelaic acid increases the potency of depigmenting agents for the treatment of melasma, actinic lentigines, and postinflammatory hypermelanosis. The basic mechanisms underlying these effects are not completely identified. Topical retinoids stimulate the cell turn-over of epidermal keratinocytes and promote a decrease in melanosome transfer and a rapid loss of melanins via epidermopoiesis. Topical retinoids are also involved in the control of cell differentiation. Retinoid-induced changes in the stratum corneum and the permeability barrier may also facilitate the penetration of depigmenting agents in the epidermis and increase their bioavailability, leading to increased depigmentation. In addition, several in vitro studies demonstrate that cis and trans-retinoic acid inhibit UV-B stimulated melanogenesis in term of tyrosinase activity and melanin synthesis. It is likely that topical retinoids modulate epidermal melanin count via a direct action on melanocytes and epidermal keratinocytes.

Retinoic acid synergistically enhances the melanocytotoxic and depigmenting effects of monobenzylether of hydroquinone in black guinea pig skin

Monobenzylether of hydroquinone (MBEH) has long been utilized for the depigmentation therapy of patients with extensive vitiligo. In this approach, the normally pigmented areas surrounding vitiligo lesions are depigmented to achieve a uniform skin tone. One of the important disadvantages of MBEH therapy, however, is the resistance of a considerable number of vitiligo patients against the depigmenting effect of this agent. We have previously proposed that the glutathione-dependent cytoprotection of melanocytes can be impaired through the inhibition of the enzyme glutathione S-transferase by retinoic acid (RA). The combination of RA with melanocytotoxic agents could thus lead to increased susceptibility of melanocytes to such compounds. In this study we have shown, for the first time, that the melanocytotoxic and depigmenting effects of MBEH are synergistically enhanced when it is combined with RA. The treatment of black guinea pig skin with RA (0.025%) alone induced no significant changes in the number of epidermal melanocytes and no skin depigmentation. On the other hand, MBEH (10%) produced mild to moderate skin depigmentation and reduced the average number of melanocytes from 76 (+/-5)/field (magnification: x 40) in control sites, to 42 (+/-6)/field in the depigmented skin. The RA (0.025%)-MBEH (10%) combination, however, produced a complete degree of depigmentation in the majority of treated sites after 10 days of application and reduced the average number of melanocytes to only 6 (+/-6)/field. RA-MBEH combination serves as a very potent skin depigmenting formula and now awaits future assessments of its potential use for the treatment of extensive vitiligo.

RALGA (Diacnéal®), a Retinaldehyde and Glycolic Acid Association and Postinflammatory Hyperpigmentation in Acne – A Review

Acne vulgaris affects 3 out of 4 adolescents and usually vanishes at the end of puberty with either no sequelae or mild to moderate sequelae, such as postinflammatory hyperpigmenation (PIH), which may result in psychological and emotional damages. The poor tolerability of the actual treatments (secondary inflammation) is a hindrance to therapy. Retinaldehyde (RAL), a precursor of retinoic acid, has shown depigmenting activity. Glycolic acid (GA) decreases the excess of pigment by a wounding and re-epithelization process. Thus, a synergistic effect was expected from the combination of RAL 0.1% and GA 6% RALGA (Diacneal) in the treatment of acne vulgaris and PIH. Efficacy results of preclinical and clinical trials tend to confirm the expectations for both acne and PIH treatment. A good tolerability was observed. In conclusion, the cosmetic cream Diacneal is a well-tolerated treatment for the prevention and healing of PIH in acne patients.