Detection of environmental depigmenting substances

Para-tertiary butyl catechol (PTBC), an industrial antioxidant induces human platelet apoptosis

The catecholic derivative para-tertiary butyl catechol (PTBC) is a conventional antioxidant and polymerization inhibitor, which exhibits melanocytotoxic effects and contact dermatitis often leading to occupational leucoderma or vitiligo. Although numerous industrial workers will be in constant exposure to PTBC and its chances of getting entry into blood are most expected, its effect on blood components is still undisclosed. As platelets play a prominent role in dermatitis, inflammation, and immunity, in this study we have evaluated the effect of PTBC on human platelets in vitro. Exposure of platelets to PTBC showed increased reactive oxygen species (ROS), intracellular calcium, cardiolipin oxidation, mitochondrial permeability transition pore (MPTP) formation, activation of caspases, phosphatidylserine (PS) externalization and decreased mitochondrial membrane potential. In addition, there was a significant decrease in cellular glutathione level, increased γ-glutamyltransferase (GGT) activity and cell death. These findings demonstrate that PTBC could induce toxic effects on blood components, which is often ignored field of research. Since dermal exposure of humans to toxic chemicals covers an important issue in various industries, there is a need of such work to understand and update the long-term toxicities induced by PTBC usage in industrial sectors and public domain.

Chemical-Induced Vitiligo

Chemical-induced depigmentation of the skin has been recognized for more than 75 years, first as an occupational hazard but then extending to those using household commercial products as common as hair dyes. Since their discovery, these chemicals have been used therapeutically in patients with severe vitiligo to depigment their remaining skin and improve their appearance. Because chemical-induced depigmentation is clinically and histologically indistinguishable from nonchemically induced vitiligo, and because these chemicals appear to induce melanocyte autoimmunity, this phenomenon should be known as "chemical-induced vitiligo," rather than less accurate terms that have been previously used.

The Effect of Butin on the Vitiligo Mouse Model Induced by Hydroquinone

Vernonia anthelmintica (L.) Willd has been traditionally used in the treatment of vitiligo in Uyghur medicine. This study used butin, the main component of V. anthelmintica, to study the influence on hydroquinone-induced vitiligo in mice. The animals were randomly divided into six groups: control, model, 8-methoxypsoralen (8-MOP, 4.25 mg/kg), and butin (0.425, 4.25, and 42.5 mg/kg) groups. The number of melanin-containing hair follicles, basal layer melanocytes, melanin-containing epidermal cells, the expression of tyrosinase (TYR) and tyrosinase-related protein-1 (TRP-1), the malondialdehyde (MDA), and cholinesterase (CHE) activity in serum were measured. Our results indicated that compared with the model group, the melanin-containing hair follicles, the expression of TYR and TRP-1 increased, the activity of CHE decreased after treatment with 8-MOP and all doses of butin (p < 0.05, p < 0.01), the basal layer melanocytes and melanin-containing epidermal cells increased significantly after treatment with butin 4.25 and 42.5 mg/kg (p < 0.05, p < 0.01), and the MDA activity decreased after using butin 4.25 and 42.5 mg/kg and 8-MOP (p < 0.05, p < 0.01). Our results support the use of butin on vitiligo, and its possible mechanisms may be related to increase the TYR and TRP-1 protein expression and decrease the activity of MDA and CHE in hydroquinone-induced vitiligo model in mice. Copyright © 2017 John Wiley & Sons, Ltd.

2 Final Report on the Safety Assessment of Propyl Gallate

Propyl Gallate acid is used as an antioxidant in cosmetic products at concentrations normally less than 0.1 percent. Propyl Gallate is absorbed when ingested, methylated, conjugated, and excreted in the urine. Acute animal toxicity studies indicate that Propyl Gallate is slightly toxic when ingested and practically nontoxic when applied to the skin. Numerous chronic oral toxicity studies indicate that Propyl Gallate at concentrations up to 5 percent is practically nontoxic to rats, mice, dogs, and guinea pigs.

Propyl Gallate is nonirritating to human skin at concentrations up to 10 percent; however, it is sensitizing at this and higher concentrations. Propyl Gallate was nonphototoxic. It is concluded that Propyl Gallate is safe as a cosmetic ingredient at concentrations not exceeding 1 percent.

4: Final Report on the Safety Assessment of Hydroquinone and Pyrocatechol

Hydroquinone and Pyrocatechol, two benzenediol isomers, are used as couplers in oxidative hair dyes at concentrations of less than 1.0%. Both compounds are absorbed from the gastrointestinal tract; Pyrocatechol is also readily absorbed through the skin. Both compounds are excreted in the urine, mainly as the ethereal sulfate. In acute oral studies Hydroquinone is practically nontoxic to moderately toxic; the data from subchronic feeding studies of Hydroquinone indicated that it was not toxic at 1% but was at higher concentrations. Pyrocatechol was moderately toxic in acute studies. Subchronic oral studies of Pyrocatechol at 0.25% produced hepatic cell hyperplasia in rats. Hydroquinone was a weak depigmenter but not an irritant when tested at 1.0%. Theingredient was a sensitizer when injected at 2.0%. The acute dermal LD50 of Pyrocatechol was 0.8 g/kg. Pyrocatechol did not depigment rabbit skin at 1.0% but did at 3.0%; skin irritation was observed at 5.0%. Guinea pigs were sensitized when Pyrocatechol was injected at concentrations above 0.2 μM. Undiluted product formulation containing 2.0% Hydroquinone produced mild conjunctivitis in 3 of 6 animals; undiluted Pyrocatechol is an extreme ocular irritant.

Hydroquinone was not teratogenic in three separate studies. The results of mutagenesis assays of Hydroquinone varies with the assay system used. In four Salmonella typhimurium strains, both with and without activation, the mutagenesis assay was negative. Hydroquinone produced positive results both with and without activation in the HeLa DNA synthesis test but was not considered mutagenic in assays using Chinese hamster cells. Hydroquinone induced SCE and delayed cell-turnover time in human lymphocyte studies. Oral doses of Hydroquinone did not inhibit testicular DNA synthesis in male mice, and was nonmutagenic in the mouse sperm-head abnormality test. In multigeneration studies with rats, topically applied hair dyes containing 0.2% Hydroquinone had no effect on reproduction; the dye was neither embryotoxic or teratogenic. Dermally applied hair dyes containing Hydroquinone were not carcinogenic. Hydroquinone when applied topically was neither a tumor promoter nor a cocarcinogen in mice. The mutagenicity of Pyrocatechol also varies with the test system used. In most studies, Pyrocatechol was nonmutagenic, both with and without metabolic activation, in the Ames' assay. The compound was negative in the Escherichia coli DNA polymerase assay, but was positive in the yeast, Saccharomyces cerevisiae. Pyrocatechol was negative in the HeLa DNA synthesis test and with Chinese Hamster V79 cells. The compound increased the numbers of chromatid breaks and exchanges in Chinese hamster ovary cells and induced SCE and delayed cell turnover time in human lymphocyte cultures. The compound given by intraperitoneal injection to mice was negative in the sperm-head abnormality test but was positive in the bone marrow assay.

In three studies in mice, topically applied Pyrocatechol was not a tumor promotor. However, topically applied Pyrocatechol was a cocarcinogen for mouse skin in two other studies. Positive sensitization reactions to Hydroquinone were reported in 8.9% of 536 dermatologic patients. Two of 38 patients treated with an ointment containing 5.4% Hydroquinone became sensitized. A cosmetic formulation containing 2% Hydroquinone produced one or more mild irritation reactions in 69 of 90 subjects in the induction phase of a sensitization test; 22 of the 69 subjects were mildly sensitized when challenged. The use of ointments containing 2, 3, and 5% Hydroquinone produced at least minimal depigmentation in white but not black subjects. It is concluded that Hydroquinone and Pyrocatechol are safe for cosmetic use at concentrations of ≤ 1.0% in formulations that are designed for discontinuous, brief use followed by rinsing from the skin and hair.

2 Final Report on the Safety Assessment of Butylated Hydroxyanisole

Butylated hydroxyanisole (BHA) is used in cosmetic formulations as a chemical preservative and as an antioxidant. Both animal and human studies have shown that BHA is absorbed from the gastrointestinal tract and metabolized. Tissue storage may occur with BHA because of its lipid solubility. However, the amount stored is limited by rapid metabolism and excretion. Reported acute oral LD50 values for BHA in rats varied from 2.0 to > 5.0 g/kg. Formulations containing BHA elicited, at most, minimal or moderate skin and eye irritation in rabbits. An extensive number of subchronic and chronic oral studies have been conducted and are reviewed.

BHA given orally or parenterally to mice and rats was shown to inhibit the carcinogenic effects of a broad range of chemical carcinogens. BHA has been shown to inhibit mutagenesis and was not a mutagenic agent in standard in vitro tests. No evidence of carcinogenicity was observed when BHA was administered to mice by subcutaneous injection, by intraperitoneal injection, or by topical application. No carcinogenesis was demonstrated following dietary administration of BHA to either rats or dogs. An increased incidence of forestomach papillomas and squamous cell carcinomas has been observed in rats fed BHA. Studies with pregnant rabbits, mice, rats, and hamsters receiving BHA during gestation by a variety of oral dosage regimens revealed no significant embryotoxic or teratogenic effects.

Clinical data for BHA in cosmetic formulations indicated that they were generally nonsensitizing, nonphotosensitizing, and only minimally or mildly irritating. It is concluded that BHA is safe as a cosmetic ingredient in the present practices of use.

Depigmentation caused by application of the active brightening material, rhododendrol, is related to tyrosinase activity at a certain threshold

BACKGROUND

Tyrosinase, the rate-limiting enzyme required for melanin production, has been targeted to develop active brightening/lightening materials for skin products. Unexpected depigmentation of the skin characterized with the diverse symptoms was reported in some subjects who used a tyrosinase-competitive inhibiting quasi-drug, rhododendrol.

OBJECTIVE

To investigate the mechanism underlying the depigmentation caused by rhododendrol-containing cosmetics, this study was performed.

METHODS

The mechanism above was examined using more than dozen of melanocytes derived from donors of different ethnic backgrounds. The RNAi technology was utilized to confirm the effect of tyrosinase to induce the cytotoxicity of rhododendrol and liquid chromatography-tandem mass spectrometry was introduced to detect rhododendrol and its metabolites in the presence of tyrosinase.

RESULTS

Melanocyte damage was related to tyrosinase activity at a certain threshold. Treatment with a tyrosinase-specific siRNA was shown to dramatically rescue the rhododendrol-induced melanocyte impairment. Hydroxyl-rhododendrol was detected only in melanocytes with higher tyrosinase activity. When an equivalent amount of hydroxyl-rhododendrol was administered, cell viability was almost equally suppressed even in melanocytes with lower tyrosinase activity.

CONCLUSION

The generation of a tyrosinase-catalyzed hydroxyl-metabolite is one of the causes for the diminishment of the melanocyte viability by rhododendrol.

Chemical leucoderma: Indian scenario, prognosis, and treatment

Chemical leucoderma is an industrial disorder in developed countries and the common causative chemicals are phenols and catechols. Due to stringent controls and preventive measures the incidence has come down. In the recent past various chemicals in consumer products have also been documented to produce depigmentation. In India due to lax quality control measures chemical leucoderma due to consumer items is not uncommon.The various consumer items documented to cause contact depigmentation are sticker bindis, rain shoes, plastic chappals, hair dye/ black henna(kali mehndi), alta, wallets and even mobile plastic covers.

Modifying skin pigmentation - approaches through intrinsic biochemistry and exogenous agents

Rates of skin cancer continue to increase despite the improved use of traditional sunscreens to minimize damage from ultraviolet radiation. The public perception of tanned skin as being healthy and desirable, combined with the rising demand for treatments to repair irregular skin pigmentation and the desire to increase or decrease constitutive skin pigmentation, arouses great interest pharmaceutically as well as cosmeceutically. This review discusses the intrinsic biochemistry of pigmentation, details mechanisms that lead to increased or decreased skin pigmentation, and summarizes established and potential hyper- and hypo-pigmenting agents and their modes of action.

Final report on the amended safety assessment of Propyl Gallate

Propyl Gallate is the n-propyl ester of gallic acid (3,4,5-trihydroxybenzoic acid). It is soluble in ethanol, ethyl ether, oil, lard, and aqueous solutions of polyethylene glycol (PEG) ethers of cetyl alcohol, but only slightly soluble in water. Propyl Gallate currently is used as an antioxidant in a reported 167 cosmetic products at maximum concentrations of 0.1%. Propyl Gallate is a generally recognized as safe (GRAS) antioxidant to protect fats, oils, and fat-containing food from rancidity that results from the formation of peroxides. Data on dermal absorption are not available, but Propyl Gallate is absorbed when ingested, then methylated, conjugated, and excreted in the urine. The biological activity of Propyl Gallate is consistent with its free-radical scavenging ability, with effects that include antimicrobial activity, enzyme inhibition, inhibition of biosynthetic processes, inhibition of the formation of nitrosamines, anesthesia, inhibition of neuromuscular response to chemicals, ionizing/ultraviolet (UV) radiation protection, chemoprotection, antimutagenesis, anticarcinogenesis and antitumorigenesis, antiteratogenesis, and anticariogenesis. Animal toxicity studies indicate that Propyl Gallate was slightly toxic when ingested, but no systemic effects were noted with dermal application. Propyl Gallate is a strong sensitizer when tested intradermally, less sensitizing when tested topically, and nonsensitizing topically at 0.1% in one study. In a second study, Propyl Gallate (15 mg dissolved in 8 ml vehicle) was sensitizing to guinea pigs. Acute eye irritation tests conducted on nine cosmetic formulations, each containing less than 1% Propyl Gallate, were negative. A phototoxicity study conducted on a cosmetic formulation containing 0.003% Propyl Gallate determined that the product was not phototoxic to guinea pigs. In one study, female rats fed 0.5 g Propyl Gallate had substantially increased fetal resorption rates when compared to controls, but in four other studies, Propyl Gallate at doses up to 2.04 g/kg was nonteratogenic in rats, rabbits, mice, and hamsters. In clinical cumulative irritancy tests, Propyl Gallate was nonirritating at concentrations up to 10%. Patch tests at concentrations less than 1% yielded positive elicitation responses. Repeat-insult patch tests using cosmetic formulations with 0.003% Propyl Gallate produced no irritation or sensitization. Propyl Gallate at a concentration of 10% in alcohol was nonphototoxic in 25 subjects. Cosmetic formulations, each containing 0.003% Propyl Gallate, produced no signs of photosensitization or phototoxicity in a total of 371 subjects. Although Propyl Gallate is not a skin irritant in clinical tests, the available data demonstrate that it is a skin sensitizer and that it may be a sensitizer at lower concentrations than originally thought, i.e., at concentrations less than 1%. In actual practice, cosmetic formulations contain Propyl Gallate at concentrations up to 0.1% and usage has increased over the past 20 years. In spite of the increased exposure associated with increased use, it is the clinical experience of the Panel that the use of Propyl Gallate in cosmetics has not resulted in sensitization reactions. Therefore, the Panel believes that a concentration limitation of 0.1% in cosmetics is necessary (given the evidence of sensitization at concentrations less than 1%) and sufficient (given that current products are not producing adverse reactions).

On the Etiology of Contact/Occupational Vitiligo

Vitiligo is an acquired depigmentary disorder of the skin that results from the selective destruction of melanocytes, generally during the second decade of life and affecting approximately 1% of the population worldwide. Loss of cutaneous pigment appears to render the skin susceptible to premature aging and cancer. In addition this disease can be socially devastating for afflicted individuals. The etiology of vitiligo is poorly understood. The present dogma suggests that genetic factors render the melanocyte fragile thus predisposing individuals to developing vitiligo. When subjected to instigating factors, these susceptible, fragile melanocytes undergo apoptosis. Autoimmune factors then perpetuate the removal of the melanocyte component from the skin. In the majority of cases the instigating factors are not known (idiopathic vitiligo), however a small sub-set of individuals develop contact/occupational vitiligo following exposure to particular chemicals. Many of these chemicals have been implicated in both contact/occupational vitiligo and chemical leukoderma. Both conditions present with well-defined, depigmented skin lesions that develop following exposure. Only in the case of vitiligo does the depigmentation spread beyond the areas of contact, probably via an immune-mediated mechanism. The largest class of chemicals known to trigger contact/occupational vitiligo is the phenolic/catecholic derivatives. Many have been demonstrated to be preferentially cytotoxic to melanocytes, with high-dose exposure resulting in the initiation of apoptosis. Phenolic/catecholic derivatives are structurally similar to the melanin precursor tyrosine, and therefore tyrosinase was originally implicated as a mediator of cytotoxicity. However, our data suggests that tyrosinase-related protein-1, rather than tyrosinase, facilitates toxicity, possibly by catalytic conversion of the compounds, which results in the generation of radical oxygen species. The ensuing oxidative stress then triggers activation of cellular free radical scavenging pathways to prevent cell death. Genetic inability of melanocytes to tolerate and/or respond to the oxidative stress may underlie the etiology of contact/occupational vitiligo.

Depigmenting action of phenylhydroquinone, an O-phenylphenol metabolite, on the skin of JY-4 black guinea-pigs

The effects of o-phenylphenol (OPP) and its metabolite, phenylhydroquinone (PHQ) on the skin of JY-4 black guinea-pigs were studied. Topical application of 1 or 5% PHQ on the black skin of the back caused marked depigmentation and hypopigmentation of the skin after 5 weeks, whereas OPP applied at the same concentrations had little effect. Depigmented skin had an increased L* (lightness) value in the CIE-L*a*b* color system. This corresponded with a decreased number of melanocytes and melanosomes in the melanocytes and keratinocytes, the disruption of melanosomes in the melanocytes, and destruction of the membranous organelles of the melanocytes. These morphological and numerical changes in epidermal melanocytes indicate that selective melanocyte toxicity occurred. Furthermore, application of PHQ to the skin of white guinea-pigs caused skin irritation, as shown by a colorimetric increase in a* value (redness) and by histological observation of inflammation. This study confirmed that OPP, which is a reported depigmenter, has little depigmenting action, while its metabolite, PHQ, is a potent depigmenter preferentially affecting melanocytes.

Vitiligo: a manifestation of apoptosis?

Vitiligo is a common cutaneous disorder that has significant biological and social consequences for those affected. It is characterized by a loss of melanocytes from the epidermis, which results in the absence of melanin, i.e. depigmentation. There are numerous hypotheses about the etiology of vitiligo, but no data to definitively prove one theory over another. It is likely that there are numerous causes for the loss of these melanocytes. One way to approach the identification of the etiology is to determine the mechanism by which the melanocytes are destroyed. The two known mechanisms for the destruction of cells are necrosis and apoptosis. One purpose of this paper is to review the extant data that might suggest which of the two mechanisms is operative against melanocytes in patients with vitiligo. The histological data, and some laboratory data, support apoptosis, rather than necrosis, as the mechanism for removal of melanocytes. Apoptosis can be induced by a variety of factors, including immune cytokines, some environmental chemicals (for example substituted hydroquinones such as monobenzone) or other molecular mechanisms. Current therapies, such as corticosteroids and ultraviolet light, do affect apoptosis in a variety of ways. Confirmation of apoptosis as a mechanism, and identification of how apoptosis is initiated to produce vitiligo, can serve as a basis for devising medications that might stop the progression of the disorder. The problem of vitiligo would be essentially solved if there was a medication that is well tolerated in children, adults and pregnant women, and that would halt the progression of the depigmentation. The study of apoptosis, mechanisms of its induction, and the ways to block apoptosis, is one possible way to find both the causes of depigmentation and medications to prevent its progression.

The cytotoxicity and apoptosis induced by 4-tertiary butylphenol in human melanocytes are independent of tyrosinase activity

It has been known for several decades that cutaneous depigmentation, i.e., contact/occupational vitiligo, can be caused by some phenolic derivatives that have a similar structure to tyrosine. Among these phenolic depigmenting agents, 4-tertiary butylphenol is the most potent. The cutaneous depigmentation induced by phenolic derivatives results from the loss of functional melanocytes. Tyrosinase is a melanocyte specific copper-containing enzyme that catalyzes the conversion of the amino acid tyrosine, through a complex series of intermediates, to melanin. In this study we tested the hypothesis that the cytotoxicity induced by 4-tertiary butylphenol is mediated by tyrosinase and occurs via an apoptotic process. Melanocyte cultures derived from African-American and Caucasian donors exhibiting a 3-fold difference in tyrosinase activity and 14-fold difference in melanin content demonstrate comparable concentration-dependent sensitivity to 4-tertiary butylphenol. In addition, cultures of dermal fibroblasts and epidermal keratinocytes exhibited similar and reduced sensitivity, respectively, to 4-tertiary butylphenol compared with autologous melanocytes. Two melanoma cell lines, one melanotic and one amelanotic lacking the expression of both tyrosinase protein and activity, when transfected with the tyrosinase cDNA, exhibited no alteration in its sensitivity to 4-tertiary butylphenol. These data suggest that 4-tertiary butylphenol cytotoxicity is not mediated via tyrosinase. Melanocytes treated with 4-tertiary butylphenol, however, did exhibit plasma membrane blebbing, DNA fragmentation, and phosphatidylserine relocalization indicating that 4-tertiary butylphenol induced melanocyte destruction occurs by an apoptotic process.

Effects of 4-tertiary butylphenol on the tyrosinase activity in human melanocytes

Vitiligo is a common dermatological disorder characterized by the development of complete pigment loss from focal lesions that tends to increase in size over time. The etiology of vitiligo, resulting in the disappearance of functional melanocytes from involved skin, is not clearly understood. As a consequence, no satisfactory therapy has been developed. A subtype of vitiligo, termed 'occupational' or 'contact' vitiligo, is increased in individuals who are exposed to materials containing phenolic derivatives, such as 4-tertiary butylphenol (4-TBP). Phenolic derivatives are structurally similar to tyrosine, the initial substrate of tyrosinase in the biochemical synthesis of melanin. Therefore, it has been proposed that phenolic derivatives compete with tyrosine for hydroxylation by tyrosinase and interfere with the completion of melanin synthesis and/or generate cytotoxic intermediates. Our results demonstrated that 4-TBP competitively inhibited both tyrosine hydroxylase and dihydroxyphenylalanine (DOPA) oxidase activities of tyrosinase, i.e., the first two catalytic steps in the biochemical conversion of tyrosine to melanin in cultured human melanocytes. This inhibition occurred at concentrations that did not influence the viability of melanocytes. The tyrosinase activity inhibited by 4-TBP was recovered after removing the treatment. 4-TBP did not affect the function of other enzymes, such as succinate-tetrazolium reductase, acid phosphatase and sulfatase. Since depigmentation occurred without a cytotoxic response after exposure of melanocytes to low concentration of 4-TBP, it is unclear whether the interaction between 4-TBP and tyrosinase leads to the destruction of the melanocytes in 'contact/occupational' vitiligo.

Depigmentation with tert-butyl hydroquinone using black guinea pigs

tert-Butyl hydroquinone (TBHQ) has important and functional uses in consumer and commercial applications, some of which involve human exposure primarily through dermal contact. To assist in the safety evaluation of TBHQ, this study was conducted to determine whether TBHQ would produce changes in skin pigmentation after repeated dermal application to black guinea pigs. Hydroquinone (HQ) and hydroquinone monomethyl ether (HQMME) were used as positive controls. TBHQ and HQ were tested at concentrations of 0.1, 1.0 and 5.0%, while HQMME was tested at a concentration of 10.0%. Groups of five males and five females were dosed with TBHQ, HQ, or the vehicle (hydrophilic ointment) daily (M-F) for 13 weeks. In addition, animals (five males, five females) treated with HQMME received 13 doses over a 3-week period. The application site was evaluated weekly for degree of pigmentation loss and irritation. Twenty-four hours after final application, sites were evaluated for depigmentation, irritation and hyperpigmentation. Subsequently, the application site was depilated and re-evaluated for the same endpoints. Repetitive exposure to concentrations of 1.0% and 5.0% TBHQ and HQ were slightly to moderately irritating, while 0.1% of each of these test materials produced only weak irritant responses. No irritant responses to hydrophilic ointment were observed and HQMME produced weak irritant responses after 2 weeks. Neither 0.1% TBHQ nor HQ produced depigmentation, while 20% of animals dosed with 1.0% TBHQ and 30% of animals dosed with 1.0% HQ had spotty or uniform loss of pigment at the site of treatment. Approximately 40% of animals dosed with 5% TBHQ or HQ were depigmented at the treatment site at the final evaluation. HQMME produced complete depigmentation of the skin and hair in all animals. Hyperpigmentation of the treatment site was observed in 80-100% of animals in all groups (with the exception of HQMME-treated animals, treated for only 3 weeks), which may be attributable to the use of hydrophilic ointment as the vehicle, the application procedure, or simply clipping hair from the skin. Thus, this study showed that TBHQ causes depigmentation in black guinea pigs at concentrations of 1% or greater, but that a no-effect threshold for this endpoint exists at a concentration between 0.1 and 1.0%.

Contact depigmentation caused by an azo dye in alta

Alta, a scarlet-red solution used by some Indian women as a cosmetic to colour their feet, was found to be associated with depigmentation at the site of application. Chromatographic and spectroscopic analysis of 3 brands of alta confirmed the presence of 2 dyes: Crocein Scarlet MOO (CSM) (brilliant crocein) and rhodamine B (tetraethyl rhodamine). Patch testing produced depigmentation at the site of application of alta, CSM and para-phenylenediamine (PPD). Although PPD has been reported to produce leukoderma, azo dyes have not previously been reported as depigmenting agents.

Structural aberration of the rough endoplasmic reticulum and melanosome compartmentalization in long-term cultures of melanocytes from vitiligo patients

Long-term cultures of melanocytes were established from 14 subjects with vitiligo and from five normal controls and analyzed ultrastructurally. Cultured melanocytes from 78.6% of the vitiligo patients demonstrated abnormalities that consisted of 1) dilation of the rough endoplasmic reticulum (RER), 2) circular RER profiles, and/or 3) membrane bound compartments of melanosomes. Cultured melanocytes from control subjects were predominantly normal with only one of the normal cultures demonstrating minimal circular RER profiles. The three unique abnormal structures in cultured vitiligo melanocytes were not always concomitantly expressed and could not be associated with any specific clinical feature of vitiligo. Quantitative analysis of the RER demonstrated that the profiles of dilated RER in cultured vitiligo melanocytes expressed a significant 1.5-2.8-times increase in mean cisternal area over cultured control melanocytes (i.e., 5.41-9.92 microns 2 versus 3.53 microns 2, respectively). The cisterna of the dilated RER profiles frequently contained floccular material that appeared to originate from the ribosomes, an indication that the floccular material may be translation products. The dilation of RER in melanocytes from the same patient persisted through repeated subculturing for up to 14.75 months. Epidermal melanocytes in biopsied skin from a patient whose cultured melanocytes were aberrant also demonstrated dilated and circular RER profiles. These results demonstrate that melanocytes from most vitiligo patients express an innate defect when cultured. Although this defect does not appear to be cytotoxic in vitro, this abnormality may be the primary defect that elicits melanocyte destruction in vivo.

Interaction of several mono- and dihydroxybenzene derivatives of various depigmenting potencies with L-3,4-dihydroxyphenylalanine-melanin

Certain mono- and dihydroxybenzene derivatives cause depigmentation of skin and hair, and appear to be selectively cytotoxic for melanized pigment cells. As direct physical and/or chemical interaction between depigmenter (DP) and pigment melanin may play a role in depigmentation, we have carried out preliminary studies in model systems where such interactions may easily be separated from effects due to tyrosinase, melanosomal proteins, and other components. We have used synthetic L-3,4-hydroxyphenylalanine (L-DOPA)-melanin as a protein-free model pigment and potassium ferricyanide as a model electron acceptor. Compounds studied were catechol, 4-t-butylcatechol, 4-methylcatechol, 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid, hydroquinone, 4-methoxyphenol, 4-t-butylphenol, and 2,6, di-t-butyl-4-methylphenol (BHT) in 0.1 M phosphate buffer, pH 7.4. These compounds vary widely in their ability to depigment hair and skin. Ferricyanide reduction by DP in the presence and absence of melanin was monitored spectrophotometrically. The sparingly soluble BHT and 4-t-butylphenol did not reduce ferricyanide in the absence or presence of melanin. For the other compounds, kinetic analysis demonstrated direct interaction between each DP and melanin. Except for dihydroxyphenylacetic acid, reduction kinetics were consistent with a mechanism involving noninteractive binding of both DP and ferricyanide to melanin prior to coupled electron transfer through the melanin backbone. Kinetic analysis afforded KB, a thermodynamic constant (M-1) for DP-melanin binding, and k', a rate parameter (M s-1) for electron transfer. A dimensionless enhancement factor (EF) was defined as k'KB/ks, with ks a pseudo-first-order constant (s-1) for ferricyanide reduction in the absence of melanin. Depending on the reductant, melanin either retards (EF less than 1) or accelerates (EF greater than 1) the rate of ferricyanide reduction. There appears to be a direct relationship between EF and depigmenting potency. There is no relationship between depigmenting power and the ability per se of the DP to bind to melanin or to reduce ferricyanide.

Contact allergy and depigmentation from alstroemeria

Alstroemeria plants have increased in popularity in recent years, but surprisingly few cases of contact allergy have been reported. Observations of combined sensitivity between Alstroemeria and Tulipa have given support to the assumption that they contain identical sensitizing agents. A patient working as a gardner developed a dermatitis from Alstroemeria. Patch tests with Alstroemeria were positive, but patch tests with Tulipa were negative. 2 months after test application, the patient showed depigmented areas at the test sites and at the sites of a previous dermatitis. The depigmented test areas remained unchanged at least a year after test application. Whether the depigmentation was due to some unique character of the molecular structure of the unknown Alstroemeria allergen, or to a unique biological characteristic of the patient, remains to be determined.

Screening for occupational vitiligo in workers exposed to hydroquinone monomethyl ether and to paratertiary-amyl-phenol

Two men reported previously with vitiligo after occupational exposure to hydroquinone monomethyl ether (HMME) have been reviewed after eight years. Repigmentation of significant degree was found in one man and of limited degree in the other. One hundred and sixty-nine men in the same works have been screened with Wood's light for evidence of vitiligo. No cases were found in the 148 men exposed to HMME (colleagues who screened 100 men exposed to HMME in two other factories also found no case) or in the 129 who had been exposed to paratertiary-amyl-phenol. Loss of light reflection on Wood's light examination was observed in 13 men due to scars or to other skin disorders.