Expressional changes in the intracellular melanogenesis pathways and their possible role the pathogenesis of vitiligo (original) (raw)
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Gene expression analysis of melanocortin system in vitiligo
Journal of Dermatological Science, 2007
Background: The melanocortin system in the skin coordinates pigmentation and immune response and could be implicated in the pathogenesis of vitiligo. Objectives: We aimed to analyze changes in expression of genes involved in skin pigmentation (melanocortin system and enzymes involved in melanin synthesis). Methods: With quantitative RT-PCR we measured the mRNA expression levels of eight genes from the melanocortin system and two enzymes involved in melanogenesis. RNA was extracted from both lesional and non-lesional skin of vitiligo patients and in nonsun-exposed skin of healthy subjects. Results: POMC (proopiomelanocortin) expression was lower in lesional skin compared to non-lesional skin. Expression of melanocortin receptors was increased in unaffected skin of vitiligo patients compared to healthy subjects and decreased in lesional skin compared to uninvolved skin of vitiligo patients, the differences were statistically significant in the cases of MC1R (melanocortin receptor 1) and MC4R (melanocortin receptor 4). TRP1 and DCT genes were down-regulated in lesional skin compared to non-lesional vitiligo skin or skin of healthy controls and up-regulated in uninvolved vitiligo skin compared to healthy control samples. In non-lesional skin, POMC expression was not elevated, possibly indicating that systemic influences are involved in up-regulation of MC receptor genes. Decreased expression of the analyzed genes in the lesional skin is not surprising, but statistically significant increased
Human Immunology, 2012
The expression pattern of several genes associated with different processes in melanocytes, including melanogenesis, is changed in vitiligo patients. We evaluated possible changes in the expression of interleukin (IL)-10 family cytokines (IL26, IL-28A, IL28B, IL29), their receptor subunits (IL20RB, IL22RA2, IL28RA), and genes potentially related to functioning of melanocytes (MDM1, IFNA1, IFNB1, IFNG, and ICAM1) in the case of vitiligo. We observed mRNA expression in vitiligo patients' and controls' skin and peripheral blood mononuclear cells using quantitative real-time polymerase chain reaction. The mRNA expression pattern of IL20RB,
Mechanisms regulating melanogenesis*
Anais Brasileiros de Dermatologia, 2013
Skin pigmentation is an important human phenotypic trait whose regulation, in spite of recent advances, has not yet been fully understood. The pigment melanin is produced in melanosomes by melanocytes in a complex process called melanogenesis. The melanocyte interacts with endocrine, immune, inflammatory and central nervous systems, and its activity is also regulated by extrinsic factors such as ultraviolet radiation and drugs. We have carried out a review of the current understanding of intrinsic and extrinsic factors regulating skin pigmentation, the melanogenesis stages and related gene defects. We focused on melanocyte-keratinocyte interaction, activation of melanocortin type 1 receptor (MC1-R) by peptides (melanocyte-stimulating hormone and adrenocorticotropic hormone) resulting from proopiomelanocortin (POMC) cleavage, and mechanisms of ultraviolet-induced skin pigmentation. The identification and comprehension of the melanogenesis mechanism facilitate the understanding of the pathogenesis of pigmentation disorders and the development of potential therapeutic options.
Journal of Investigative Dermatology, 2015
Vitiligo affects 1% of the worldwide population. Halting disease progression and repigmenting the lesional skin represent the two faces of therapeutic challenge in vitiligo. We performed transcriptome analysis on lesional, perilesional, and non-depigmented skin from vitiligo patients and on matched skin from healthy subjects. We found a significant increase in CXCL10 in non-depigmented and perilesional vitiligo skin compared with levels in healthy control skin; however, neither CXCL10 nor other immune factors were deregulated in depigmented vitiligo skin. Interestingly, the WNT pathway, which is involved in melanocyte differentiation, was altered specifically in vitiligo skin. We demonstrated that oxidative stress decreases WNT expression/activation in keratinocytes and melanocytes. We developed an ex vivo skin model and confirmed the decrease activation of the WNT pathway in human skin subjected to oxidative stress. Finally, using pharmacological agents that activate the WNT pathway, we treated ex vivo depigmented skin from vitiligo patients and successfully induced differentiation of resident stem cells into pre-melanocytes. Our results shed light on the previously unrecognized role of decreased WNT activation in the prevention of melanocyte differentiation in depigmented vitiligo skin. Furthermore, these results support further clinical exploration of WNT agonists to repigment vitiligo lesions.
The Melanocortin-1 Receptor is a Key Regulator of Human Cutaneous Pigmentation
Pigment Cell Research, 2000
MC1R revealed the following. Human melanocytes homelanocytes respond to the melanocortins, a-melanocyte stim-mozygous for Arg160Trp mutation in the MC1R demonulating hormone (a-MSH) and adrenocorticotrophic hormone strated a significantly reduced response to a-MSH. Also, this culture responded poorly to ASP and exhibited an exagger-(ACTH), with increased proliferation and eumelanogenesis ated cytotoxic response to UVR. Another culture, which was had put an end to a long-standing controversy about the role homozygous for Val92Met mutation in the MC1R, demon-of melanocortins in regulating human cutaneous pigmentation. strated a normal response to a-MSH. Heterozygous muta-We have shown that a-MSH and ACTH bind the human tions that are frequently expressed in various melanocyte MC1R with equal affinity, and are equipotent in their mitocultures did not disrupt MC1R function. These results begin genic and melanogenic effects on human melanocytes. We also to elucidate the significance of MC1R variants in the function showed that the activation of the MC1R is important for the of the receptor. Our data emphasize the significance of a melanogenic response of human melanocytes to ultraviolet normally functioning MC1R in the response of melanocytes to radiation (UVR). The MC1R is also the principal mediator of melanocortins, ASP, and UVR. the inhibitory effects of agouti signaling protein (ASP) on melanogenesis. Expression of the MC1R is subject to regulation by its own ligands a-MSH and ACTH, as well as by Key words: Melanocortin 1 receptor, Human melanocytes, Ultraviolet radiation, Melanocortins, Agouti signaling protein, UVR and endothelin-1. Recent studies that we conducted on the expression of MC1R variants by human melanocytes and Eumelanin, Pheomelanin that have an extensive amino acid sequence homology. These peptides include a-melanocyte stimulating hormone (a-MSH), b-MSH, g-MSH, and adrenocorticotrophic hormone (ACTH), all of which are derived from a large precursor peptide, pro-opiomelanocortin (POMC) (1). The 4-10 carboxy teminus amino acid residues of a-MSH, b-MSH,
Journal of Investigative Dermatology, 2015
Vitiligo affects 1% of the worldwide population. Halting disease progression and repigmenting the lesional skin represent the two faces of therapeutic challenge in vitiligo. We performed transcriptome analysis on lesional, perilesional, and non-depigmented skin from vitiligo patients and on matched skin from healthy subjects. We found a significant increase in CXCL10 in non-depigmented and perilesional vitiligo skin compared with levels in healthy control skin; however, neither CXCL10 nor other immune factors were deregulated in depigmented vitiligo skin. Interestingly, the WNT pathway, which is involved in melanocyte differentiation, was altered specifically in vitiligo skin. We demonstrated that oxidative stress decreases WNT expression/activation in keratinocytes and melanocytes. We developed an ex vivo skin model and confirmed the decrease activation of the WNT pathway in human skin subjected to oxidative stress. Finally, using pharmacological agents that activate the WNT pathway, we treated ex vivo depigmented skin from vitiligo patients and successfully induced differentiation of resident stem cells into pre-melanocytes. Our results shed light on the previously unrecognized role of decreased WNT activation in the prevention of melanocyte differentiation in depigmented vitiligo skin. Furthermore, these results support further clinical exploration of WNT agonists to repigment vitiligo lesions.
The Arg160Trp Allele of Melanocortin-1 Receptor Gene Might Protect Against Vitiligo
Photochemistry and Photobiology, 2008
Melanocortin-1 receptor (MC1R) and agouti signaling protein (ASIP) play pivotal roles in the regulation of human pigmentation. We aimed to study whether single nucleotide polymorphisms (SNPs) of the MC1R and ASIP genes contribute to the pathogenesis of the polygenic pigment skin disorder, vitiligo. The PCR-amplified, full-length MC1R gene was studied with sequence analysis, and the 3¢ untranslated region (3¢ UTR) SNP of ASIP was detected using restriction fragment length polymorphism. The allele frequency of the ASIP SNP did not show any difference between the skin type, hair color and eye color-matched 97 vitiligo patients and the 59 healthy control individuals. As one of the MC1R polymorphisms showed significantly higher incidence among fair-skinned individuals (Fitzpatrick I + II, n = 140) than among dark-skinned individuals (Fitzpatrick III + IV, n = 90), both vitiligo patients and controls were divided into two groups and the frequency of the MC1R alleles was studied separately in fair-skinned and dark-skinned subgroups of diseased and healthy groups. C478T, one of the MC1R SNPs studied in 108 fair-skinned vitiligo patients and in 70 fair-skinned healthy control individuals, showed a significant difference (P = 0.0262, odds ratio [95% confidence interval] = 3.6 [0.0046-0.1003]) in allele frequency between the two groups: the allele frequency was higher in the control group, suggesting protection against vitiligo. Computer prediction of antigenicity has revealed that the Arg160Trp amino acid change caused by this SNP results in a decrease in antigenicity of the affected peptide epitope.
New Insights into the Pathogenesis of Vitiligo: Imbalance of Epidermal Cytokines at Sites of Lesions
PIGMENT CELL RESEARCH, 2002
Vitiligo is a skin disease that is caused by selective destruction of melanocytes and is characterized by white spots. Melanocytes and keratinocytes seem to exhibit a functional close relationship, mediated at least in part by keratinocyte-derived cytokines, which seem important for survival and activity of melanocytic cells. We wanted to investigate the hypothesis that in vitiligo the expression of epidermal cytokines may be modified compared with normal skin. In 15 patients with active, non-segmental vitiligo, biopsies were obtained from lesional, perilesional and non-lesional skin; normal skin from five healthy donors was also tested. Tissue sections were tested using immunohistochemistry for the expression of keratinocyte-derived cytokines with stimulating activity, such as granulocyte-monocyte colony stimulating factor (GM-CSF), basic fibroblastic growth factor (bFGF), and stem cell factor (SCF) or with inhibiting activity, such as interleukin 6 (IL-6) and tumour necrosis factor a (TNF-a) on melanocytes.
Cytokines: the yin and yang of vitiligo pathogenesis
Expert Review of Clinical Immunology, 2018
Introduction: Dysregulation of melanocyte function is associated with vitiligo, an idiopathic autoimmune hypopigmentary skin disorder, caused by the selective destruction of melanocytes. Cytokines, the key mediators of immune response, which are pivotal in maintaining immune homeostasis, are crucial in vitiligo pathogenesis. Several studies indicate that there is an imbalance between pro-and anti-inflammatory cytokines in the skin and serum of vitiligo patients. Areas covered: In this comprehensive review, we have summarized the correlation of cytokine imbalance and vitiligo pathogenesis, its role in melanocyte biology and its impact on vitiligo treatment. We have integrated various published reports on the levels of major cytokines from skin and serum samples of vitiligo patients. We have also discussed the role of endoplasmic reticulum (ER) and oxidative stress on cytokine imbalance and vice-versa leading to destruction of melanocytes. Expert commentary: The review reflects that dysregulation of cytokines is multi-factorial, ranging from genetic predisposition to altered protein expression relevant to vitiligo pathogenesis. We emphasize that cytokine imbalance in systemic and skin microenvironment plays a crucial role in vitiligo pathogenesis and has promising potential as therapeutic targets for vitiligo.
Melan-A expression related to apoptosis of melanocytes in segmental and non-segmental vitiligo
F1000Research, 2022
Background Vitiligo is a progressive depigmentation of the skin with unclear etiology. Cell-mediated immunity has been suggested to play an important role in the pathogenesis of vitiligo's progression. Melan-A has a high affinity for specific CD8+ T cells and is one of the critical markers for detecting damage to melanocytes. Our study aims to demonstrate the differences in Melan-A expression associated with apoptosis of melanocytes in patients with segmental vitiligo (SV) and those with non-segmental vitiligo (NSV). Methods A cross-sectional study with 64 patients diagnosed with vitiligo, of whom 33 had NSV and 31 had SV. Skin biopsy and direct immunofluorescence were used to examine Melan-A, and the TUNEL staining method was performed to examine melanocyte apoptosis in both groups. Group comparisons were conducted using appropriate statistical methods. Results Melan-A expression was significantly higher in the NSV group than in the SV group, and there was a significant difference between the two groups (p=0.001). The median of melanocyte apoptosis in the NSV group was relatively higher than in the SV group, and a significant difference was found between the two groups (p=0.001). The Spearman's rank correlation test between Melan-A expression and melanocyte apoptosis in the NSV group was 0.767 (76.7%) and showed a significant relationship (p<0.05). The same test in the SV group was 0.583 (58.3%) and showed a significant relationship (p<0.05). In both groups, the higher the Melan-A expression, the higher the melanocyte Open Peer Review Approval Status AWAITING PEER REVIEW Any reports and responses or comments on the article can be found at the end of the article.