Epinephrine induction of white hair in ACI rats

A functional single-nucleotide polymorphism in the catechol-O-methyltransferase gene alter vitiligo risk in a Chinese population

Vitiligo is an acquired hypomelanotic skin disorder resulting from the loss of functional melanocytes. The COMT-158 polymorphism can reduce COMT enzyme activity and may thus lead to the overproduction of toxic radicals in the melanocyte microenvironment. To determine whether this polymorphism in the COMT gene is associated with an increased risk of vitiligo in Chinese populations, we used a polymerase chain reaction sequence-specific primer (PCR-SSP) technique to determine the frequency of the polymorphism COMT-158 G > A in 749 vitiligo patients and 763 healthy controls. We found that compared to the COMT-158 GG genotype, the COMT-158 GA genotype (adjusted odds ratio [OR], 1.39; 95% confidence interval [CI], 1.13-1.72) and the combined GA + AA genotype (adjusted OR, 1.41; 95% CI, 1.15-1.74) were associated with an increased risk of generalized vitiligo. The association was more pronounced in patients with early-onset vitiligo (adjusted OR, 1.95; 95% CI, 1.45-2.60), those with a family history of vitiligo (adjusted OR, 3.84; 95% CI, 2.47-5.96), and female patients (adjusted OR, 1.74; 95% CI, 1.29-2.36). When we further clinically stratified the vitiligo patients according to their disease types, we found that the combined GA + AA genotype was associated with vitiligo vulgaris (adjusted OR, 1.31; 95% CI, 1.02-1.68), focal vitiligo (adjusted OR, 1.62; 95% CI, 1.17-2.25), and universal vitiligo (adjusted OR, 1.50; 95% CI, 0.98-2.30), but not with acrofacial vitiligo (adjusted OR, 1.53; 95% CI, 0.86-2.73) or segmental vitiligo (adjusted OR, 1.35; 95% CI, 0.72-2.51). In conclusion, this COMT gene polymorphism may have contributed to the etiology of vitiligo in our Chinese population. Larger population-based studies are required to verify our findings.

A critical appraisal of vitiligo etiologic theories. Is melanocyte loss a melanocytorrhagy?

Common generalized vitiligo is an acquired depigmenting disorder characterized by a chronic and progressive loss of melanocytes from the epidermis and follicular reservoir. However, the mechanism of melanocyte disappearance has never been clearly understood, and the intervention of cellular and humoral autoimmune phenomena as primary events remains unproven. In this review, is discussed the data supporting the major theories of vitiligo, namely melanocyte destruction (autoimmune, neural and impaired redox status) and melanocyte inhibition or defective adhesion. Based on recent morphologic findings in vivo supporting a chronic detachment and transepidermal loss of melanocytes in common generalized vitiligo, a new theory is suggested proposing melanocytorrhagy as the primary defect underlying melanocyte loss, integrating most of the possible triggering/precipitating/enhancing effects of other known factors.

Impact of life events on the onset of vitiligo in adults: preliminary evidence for a psychological dimension in aetiology

The present study retrospectively examines the role of stressful life events in the onset of vitiligo in adults. A matched clinical sample of patients with other forms of disfigurement or skin disease (dystrophic epidermolysis bullosa and naevi, not thought to be associated with stress) served as a control group. Newly diagnosed patients and matched controls were thus asked to complete the 12-month version of the Schedule of Recent Experience, a questionnaire which measures the frequency and number of stressful life events occurring over a specified period. The results suggest that such patients endure a significantly higher number of stressful life events than do controls, suggesting that psychological distress may have contributed to the onset of their condition. The implications of the results are discussed and suggestions made for future research.

Neuropeptide and neuronal marker studies in vitiligo

Neuropeptide and neuronal marker immunoreactivity was studied in skin biopsies from lesional and marginal areas in 12 patients with vitiligo, and in seven normal controls. The vitiligo was active in seven, static in two, and of unknown activity in three. Antibodies against general neuronal marker PGP 9.5 (PGP 9.5), substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY), were used. The epidermis, dermo-epidermal junction, papillary and reticular dermis, and appendages, were assessed semiquantitatively for reactivity with each antibody. Staining with PGP 9.5 in the upper dermis was assessed quantitatively by image analysis. An increase in reactivity against NPY antibody was seen in five of 10 cases (three with active vitiligo) in the marginal areas, and in three of 12 subjects (all with active vitiligo) in the lesional vitiligo areas. VIP antibody reactivity showed a minimal increase in the marginal and lesional vitiligo areas (in two cases each, both of whom had active vitiligo). SP and CGRP reactivities did not differ from normal. PGP 9.5 staining was minimally increased at the dermo-epidermal junction and lower Malpighian layer in biopsies from marginal areas in three of 10 subjects (all with active vitiligo). Quantitative analysis of PGP 9.5 reactivity in the upper dermis showed no difference between vitiligo and normal biopsies. These findings support the concept of neuronal or neuropeptide involvement in vitiligo, and in particular suggest that NPY may have a role in the pathogenesis of the disease.

Catechol-O-methyltransferase in vitiligo

Catechol-O-methyltransferase (COMT) is involved in the metabolism of neurotransmitters such as epinephrine, norepinephrine and dopamine. For melanocytes, the enzyme is of particular importance in preventing the formation of toxic o-quinones during melanin synthesis. It has been suggested that COMT plays a regulatory role in melanin synthesis. Indeed, when the melanin precursor molecule DHI(2C) is methylated by COMT it is no longer available for incorporation into melanin. Auto-destruction by intermediates of melanin metabolism has been implicated in the aetiology of vitiligo. Therefore enzyme activities in vitiligo patients and in healthy controls were compared. Systemic COMT activities were measured using red blood cells (RBC) as starting material. However, as local alterations in COMT activity may be specifically involved in vitiligo, the enzyme activity was also measured in epidermal homogenates. Finally, to ascribe epidermal COMT activity to the responsible cell type(s), enzyme activity was measured in cultured vitiligo non-lesional melanocytes and melanocytes from healthy controls as well as in cultured keratinocytes from lesional skin and in purified keratinocytes from control skin. It was found that epidermal homogenates from vitiligo patients expressed higher levels of COMT activity than homogenates from healthy controls. Such differences were not found at the systemic level (i.e. in RBC) nor could they be explained by measurements on separately cultured epidermal cell types, indicating that the COMT activity was induced at the tissue level by extracellular factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of the etiopathomechanism of vitiligo: a convergence theory

Vitiligo is an acquired melanin pigmentary disorder manifesting itself by expanding depigmented lesions of the skin. To date, the etiopathomechanism of vitiligo has not been convincingly elucidated and a number of seemingly mutually opposed hypotheses with equal likelihood still coexist. Concurrent theories on vitiligo etiology, together with supportive evidence, are reviewed here. Due to the observed variation in clinical manifestations of the disease, it seems likely that the etiology of vitiligo may differ among patients. Therefore several theories on vitiligo etiopathogenesis have been combined to formulate a convergence theory for vitiligo, also presented in this article. This theory states that stress, accumulation of toxic compounds, infection, autoimmunity, mutations, altered cellular environment and impaired melanocyte migration and/or proliferation can all contribute to vitiligo etiopathogenesis in varying proportions.

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.

Vitiligo and dysgammaglobulinemia. A case report and family study

This report concerns an 8 year old female with vitiligo and dysgammaglobulinemia characterized by absent IgA, very low IgG, and normal IgM. The t-cell immune system was intact but other family members had low levels or absence of IgA. The possible relationship of dysgammaglobulinemia and vitiligo is discussed along with the classification and inheritance of the immune cell defects.

Skin melanin concentrations in the affective disorders: possible relationships to the catecholamine hypothesis

SYNOPSIS Skin melanin concentrations were measured by reflectance spectrophotometry in patients during the active phase of a primary affective illness and in normal subjects. There were no significant differences between 27 females with depression (unipolar illness) and 17 females with mania (bipolar illness) or between a mixed group of 30 male patients with mania and depression (predominantly mania) and a normal sample of 27 male subjects. These negative results are discussed in terms of the catecholamine hypothesis of the affective disorders. A study of brain pigmentation is suggested as being a potentially useful investigation in manic-depressive psychosis.