Behrooz Kasraee

Topical Methimazole as a New Treatment for Postinflammatory Hyperpigmentation: Report of the First Case

We have previously shown that the peroxidase inhibitor methimazole (1-methyl-2-mercapto imidazole; MMI) is a noncytotoxic inhibitor of melanin production in cultured B16 melanocytes. It was further demonstrated that the topical application of 5% MMI on brown guinea pig skin for 6 weeks causes a significant reduction in the amount of epidermal melanin, resulting in visually recognizable cutaneous depigmentation. Herein, we report a 27-year-old male with postinflammatory hyperpigmentation (due to acid burn), successfully treated with topical MMI as a new skin depigmenting agent. Topical 5% MMI caused a moderate to marked improvement of the hyperpigmented lesions within 6 weeks of once-daily application. Topical MMI was well tolerated by the patient and did not affect the level of serum thyroid hormones (free thyroxin, free triiodothyronine and the thyroid-stimulating hormone). Unlike most known depigmenting agents, such as hydroquinone and kojic acid, MMI is a noncytotoxic, nonmutagenic compound, and it is possible that MMI could serve as a novel agent for the treatment of hyperpigmentary disorders in human.

Correlation between Protoporphyrin IX Fluorescence Intensity, Photobleaching, Pain and Clinical Outcome of Actinic Keratosis Treated by Photodynamic Therapy

Background: Photodynamic therapy (PDT) with Metvix® is a good therapeutic option to treat actinic keratosis, but it presents drawbacks (pain, lesion recurrences, heterogeneous outcome), emphasizing the possible need to individualize treatment. Objective: We assessed whether PDT clinical outcome and pain during treatment were correlated with protoporphyrin IX fluorescence intensity and photobleaching. Methods: 25 patients were treated by Metvix PDT. The outcome was evaluated after 1.3 (±0.4), 7.6 (±1.8), 13.2 (±1.2) and 33.6 (±3.0) months. After administration of Metvix, red light (632 ± 10 nm) was delivered with a light-emitting diode panel device. The outcome was assessed on a cosmetoclinical scale. Results: All patients who showed a fluorescence level before PDT treatment above a certain threshold had a complete recovery at 33.6 (±3.0) months. Conclusion: Our approach could be used to individualize PDT treatment based on the pretreatment fluorescence level, and to predict its long-term outcome.

Safety of Topical Methimazole for the Treatment of Melasma Transdermal Absorption, the Effect on Thyroid Function and Cutaneous Adverse Effects

Methimazole is an oral antithyroid compound that exhibits a skin-depigmenting effect when used topically. However, the effect of topical methimazole on thyroid function has not been reported. This study was aimed at assessing the safety of topical methimazole used to treat pigmented lesions, without affecting thyroid hormones due to systemic delivery. The pharmacokinetics of methimazole, either applied in the form of a 5% topical formulation to facial skin or taken orally in the form of a 5-mg tablet by 6 volunteers, were determined. In addition, the effect of long-term topical applications of 5% methimazole on the function of the thyroid gland in 20 patients with epidermal melasma was determined following 6 weeks of once-daily application. Cutaneous adverse effects of topical methimazole were determined. From 15 min up to 24 h after application, methimazole was undetectable in the serum of the individuals receiving single topical methimazole dosing. Methimazole, however, was detected in serum after 15 min of oral administration and remained detectable in serum up to 24 h after administration. Long-term topical methimazole applications in melasma patients did not induce any significant changes in serum TSH, free thyroxine and free triiodothyronine levels. Topical methimazole was well tolerated by the patients and did not induce any significant cutaneous side effects. Present data together with the previously shown non-cytotoxic and non-mutagenic characteristics of methimazole indicate that this agent could be considered as a safe skin-depigmenting compound for topical treatment of skin hyperpigmentary disorders in humans.

Ebselen is a new skin depigmenting agent that inhibits melanin biosynthesis and melanosomal transfer

Abstract:  We assessed the ability of ebselen, a glutathione peroxidase mimic, to reduce pigmentation in various models. In murine B16 melanocytes, 25 μm ebselen inhibited melanogenesis and induced a depolymerisation of actin filaments. In co‐cultures of B16 melanocytes with BDVII keratinocytes, a pretreatment of melanocytes with ebselen resulted in a strong inhibition of melanosome transfer to keratinocytes, as shown under optical and electron microscopy. In reconstructed epidermis, topical 0.5% ebselen led to a twofold decrease of melanin without affecting the density of active melanocytes. A similar result was obtained with topical 0.5% ebselen in black guinea pig ears. Ebselen induced a decrease of epidermal melanin parallel to a localisation of melanin and melanosomes in the basal layer. Ebselen appears as a new depigmenting compound that inhibits melanin synthesis and melanosome transfer to keratinocytes.

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

Abstract:  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: × 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.

Pharmacology of RALGA, a Mixture of Retinaldehyde and Glycolic Acid

Background: Retinoids and α-hydroxy acids (AHAs) are major compounds in topical therapy. They exert distinct but potentially complementary activities. However, their association is limited by their respective irritating potential. Recently, the first association between a retinoid and an AHA has been achieved; this formulation (RALGA) associates retinaldehyde (RAL) – a precursor of retinoic acid (RA) – and glycolic acid (GA) – an AHA. Objective: To study the pharmacological properties of RALGA. Methods: The bioavailability of RAL into the skin after topical RALGA was studied by HPLC, and its bioconversion to RA was analysed by measuring the enzyme activity of retinaldehyde dehydrogenase and the RA content in the epidermis and dermis. The retinoid activity of RALGA was studied on the modulation of Hhb4 keratin mRNA on the tail of C57BL/6 mice, and its comedolytic properties on the size and density of dermal cysts and the morphology of sebaceous glands in hairless mice. Results: Epidermal and dermal concentrations of RAL and RA were higher after RALGA treatment, as compared to both RAL 0.1% alone and RA 0.05% alone; this indicates that the presence of GA favours the bioavailability and biotransformation of RAL into RA. The retinoid activity of RALGA (suppression of Hhb4 mRNA keratin) was similar to that of RAL alone, indicating that the presence of GA does not interfere with specific retinoid activity; GA alone had no effect in this test, which confirms the specificity of Hhb4 mRNA keratin modulation for retinoid activity. The diameter and the density of dermal cysts as well as the size of sebaceous glands were significantly decreased by RALGA. Conclusion: These observations indicate that the addition of an AHA such as GA to a retinoid such as RAL results in a better bioavailability of the retinoid, thus a higher delivery of RA, which potentiates the biological activities of the retinoid. This combination allows a delivery of high amounts of RA in the skin while preventing the side-effects usually observed with high concentrations of topical RA.

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.

The Potential Depigmenting Activity of Retinaldehyde

Background: Retinoids have been reported to exert depigmenting activity. Unlike most depigmenting agents that target tyrosinase, they are not phenolic agents and may act via different mechanisms. Objectives: We analysed the properties of retinaldehyde (RAL), a precursor of retinoic acid (RA), as a skin-lightening agent in various models. Methods: The viability and the depigmenting properties of RAL were assessed in murine melanocytes, in human reconstructed epidermis, and in mice and guinea pigs. The melanin content and cytotoxicity were assessed in melanocytes; in 3-dimensional models, the melanin concentration and the number of active melanocytes were determined. Results: RAL was taken up by melanocytes and mostly metabolised to retinol and retinyl esters, and to a lesser extent to RA. RAL decreased the melanin concentration of guinea pig ears and mouse tails by 54 and 74%, respectively, and decreased the number of active melanocytes by 42 and 77%, respectively. In reconstructed epidermis the melanin concentration was increased by 52%, whereas the number of active melanocytes decreased by 44%. Conclusion: RAL exerts a significant depigmenting activity with a mode of action that looks different from that of RA. Our data suggest a skin-lightening effect related to a melanolytic action (i.e. a decrease in melanin concentration, whatever the mechanism) rather than to melanocytotoxicity, besides other still unknown actions of RAL on melanocytes.

The Combination of a Retinoid, a Phenolic Agent and an Antioxidant Improves Tolerance while Retaining an Optimal Depigmenting Action in Reconstructed Epidermis

Background: Cutaneous pigmented lesions urge the need to find safe and effective treatments to lighten the skin. Objective: The aim of this study was to combine a retinoid (retinaldehyde), a new phenolic agent (4-(1-phenylethyl)-resorcinol) and a proreducing agent (δ-tocopheryl-β-D-glucopyranoside) to achieve synergistic actions for skin lightening. Methods: The tolerance profile and the depigmenting properties of these agents were assessed in murine keratinocyte and melanocyte cell lines, as well as in a 3-dimensional model of reconstructed epidermis. Results: Retinaldehyde and 4-(1-phenylethyl)-resorcinol induced a significant decrease of tissue viability in reconstructed epidermis, but this cytotoxicity was prevented by the addition of δ-tocopheryl-β-D-glucopyranoside. The combination of the three agents was, however, efficient in decreasing the specific melanin content and the density of active melanocytes. Conclusion: A combination of various chemicals acting via different mechanisms allows a decrease in the toxicity of each compound alone while retaining optimal skin-lightening properties.

A new spectrophotometric method for simple quantification of melanosomal transfer from melanocytes to keratinocytes

Abstract:  Three major difficulties must be overcome to establish a quantitative method for melanosomal transfer analysis: (i) establishing a three‐dimensional co‐culture reassuring direct melanocyte to keratinocyte transfer, (ii) separation of melanocytes and keratinocytes following co‐culture and (iii) melanosome quantification in each cell population. Melanocytes and keratinocytes are cultured on the opposite sides of the porous membrane of hanging cell inserts (1 μm pores, 2 × 106 pores/cm2). Cell separation is performed after 3 days of co‐culture by simple trypsinisation. Melanosome quantification in separated cell populations was accomplished by an ELISA‐like method using gp‐100 as the antigen. Melanocytes and keratinocytes come into ‘direct’ contact through the pores, and melanosomal transfer is accomplished without cell passage through the membrane. Cell separation by simple trypsinisation results in pure melanocyte and keratinocyte populations. Melanosome quantification by the ELISA‐like method proved to be sensitive and specific to distinguish the known inhibitors and inducers of melanosomal transfer.