Oxidative stress level and tyrosinase activity in vitiligo patients

Mitochondria-Melanocyte cellular interactions: An emerging mechanism of vitiligo pathogenesis

Mitochondria has emerged as a potential modulator of melanocyte function other than just meeting its cellular ATP demands. Mitochondrial DNA defects are now an established cause of maternal inheritance diseases. Recent cellular studies have highlighted the mitochondrial interaction with other cellular organelles that lead to disease conditions such as in Duchenne muscular dystrophy, where defective mitochondria was found in melanocytes of these patients. Vitiligo, a depigmentory ailment of the skin, is another such disorder whose pathogenesis is now found to be associated with mitochondria. The complete absence of melanocytes at the lesioned site in vitiligo is a fact; however, the precise mechanism of this destruction is still undefined. In this review we have tried to discuss and link the emerging facts of mitochondrial function or its inter- and intra-organellar communications in vitiligo pathogenesis. Mitochondrial close association with melanosomes, molecular involvement in melanocyte-keratinocyte communication and melanocyte survival are new paradigm of melanogenesis that could ultimately account for vitiligo. This definitely adds the new dimensions to our understanding of vitiligo, its management and designing of future mitochondrial targeted therapy for vitiligo.

Tetrahydrobiopterin as a Trigger for Vitiligo: Phototransformation during UV Irradiation

Vitiligo is a type of hypomelanosis. Tetrahydrobiopterin (H4Bip), the coenzyme of the initial stage of melanogenesis, appears to be a trigger for vitiligo. H4Bip is present in vitiligo in 3-5-fold excess and causes oxidative stress by triggering an autocatalytic cycle of excess hydrogen peroxide synthesis. Using quantum-chemical calculations, we have evaluated the possibility of H4Bip reactions occurring in the dark and under ultraviolet (UV) irradiation, including the formation of dihydropterin dimers. In order to simulate the oxidative stress, oxidative modification of human serum albumin (HSA) has been carried out in the presence of excessive H4Bip using the fluorescence method. The fraction of oxidized protein (FOP) has been calculated. It has been established that there is a strong oxidative modification of amino acids chromophores (tryptophan and tyrosine) in the protein (FOP 0.64). Under UV irradiation of the system (HSA + H4Bip), FOP is reduced to 0.39. Apparently, a part of H4Bip transforms into dihydropterin dimers and does not participate in the oxidative modification of the protein. The data on oxidative modification of HSA are consistent with dynamic light scattering: H4Bip promotes HSA aggregation with the formation of particles with a hydrodynamic radius Rh ≥ 2000 nm, which can become immunogenic.

Detection of melanocyte lineage-specific genes in vitiligo lesions

Vitiligo is an acquired pigmentary disorder characterized by the loss of skin color and functional melanocytes. The pathogenesis of vitiligo remains unclear, which means that effective clinical treatment is difficult. However, if melanocyte linkage-specific genes are identified in vitiligo lesions, the appropriate treament for melanocytes may be implemented. The current study aimed to detect the expression of melanocyte lineage-specific genes in vitiligo lesion needle biopsies and to predict the occurrence of perifollicular repigmentation in depigmented macules. A total of 6 patients with stable vitiligo and 4 healthy volunteers were recruited from the Department of Dermatology, Wuhan Third Hospital. Total RNA was extracted from skin tissue needle biopsies from the periphery and center of depigmented macules, and adjacent normal skin. The expression of dopachrome tautomerase (Dct), tyrosinase (Tyr) and β-actin (ACTB) genes were detected using a reverse transcription (RT)-semi quantitative polymerase chain reaction (PCR) assay. RNA extracted from 7 mg of skin samples was sufficient to amplify all three genes. The expression profile of each patient was then observed in the center of vitiligous lesions and were deemed to be Dct+Tyr-ACTB+, Dct-Tyr-ACTB+ or Dct+Tyr+ACTB+. At 5 months, patient follow-up indicated that perifollicular repigmentation was efficaciously induced by 308 nm eximer light radiation in a patient who had a Dct+Tyr-ACTB+ gene expression. The results demonstrated that needle skin biopsy and RT-semi quantitative PCR may be used as a less traumatic and reliable method to detect the expression profiles of melanocyte lineage-specific genes in needle biopsies, which may have the potential to predict the occurrence of perifollicular repigmentation in vitiligo.

Critical appraisal of the oxidative stress pathway in vitiligo: a systematic review and meta-analysis

BACKGROUND

The pathogenesis of vitiligo remains a topic of extensive debate. This is partly due to the moderate efficacy of current treatments. The role of the oxidative stress pathway in vitiligo is a popular although controversial research topic.

OBJECTIVE

To clarify the role of the oxidative stress pathway in vitiligo compared to other inflammatory skin disorders and to assess the therapeutic role of antioxidants.

METHODS

We conducted a systematic search of the existing literature on the aberrancies of the oxidative stress pathway in vitiligo. Subsequently, the efficacy of both topical and oral antioxidants in clinical trials was investigated.

RESULTS

A deregulated oxidative pathway is clearly evident with elevated superoxide dismutase, decreased catalase and increased lipid peroxidation. However, similar results have been obtained in other inflammatory skin diseases such as psoriasis, atopic dermatitis, lichen planus and urticaria. This questions the unique role of oxidative stress in the development of vitiligo. Some isolated successes have been reported with oral ginkgo biloba, polypodium leucotomos and vitamin C and E preparations, while other clinical trials have failed to show reproducible results. The use of topical antioxidants delivers in general no beneficial results.

CONCLUSION

The oxidative pathway is affected in vitiligo, but its unique initiating or contributory role in the pathogenesis is less evident. Interesting data support the added value of oral antioxidants in vitiligo although confirmatory studies are missing.

Antroquinonol Exerts Immunosuppressive Effect on CD8+ T Cell Proliferation and Activation to Resist Depigmentation Induced by H2O2

Antroquinonol was investigated as antioxidant and inhibition of inflammatory responses. Our study was to evaluate its immunosuppressive effect on CD8⁺ T cells and protective effect on depigmentation. CD8⁺ T cells were treated with antroquinonol in vitro, and C57BL/6 mice were treated with antroquinonol with or without H₂O₂in vivo for 50 consecutive days. We found antroquinonol could inhibit proliferation of CD8⁺ T cells and suppress the production of cytokines IL-2 and IFN-γ and T cell activation markers CD69 and CD137 in vitro. H₂O₂ treatment induced depigmentation and reduced hair follicle length, skin thickness, and tyrosinase expression in vivo. Whereas, antroquinonol obviously ameliorated depigmentation of mice skin and resisted the reduction of hair follicle length, skin thickness, and tyrosinase expression induced by H₂O₂. Antroquinonol decreased CD8⁺ T cell infiltration in mice skin, inhibited the production of IL-2 and IFN-γ, and decreased the expression of CXCL10 and CXCR3. Summarily, our data shows antroquinonol inhibits CD8⁺ T cell proliferation in vitro. It also reduces CD8⁺ T cell infiltration and proinflammatory cytokine secretion and suppresses the thinning of epidermal layer in vivo. Our findings suggest that antroquinonol exerts immunosuppressive effects on CD8⁺ T cell proliferation and activation to resist depigmentation induced by H₂O₂.

[Vitiligo occurring on dermal melanocytosis (nevus of Ota) in a dark-skinned patient]

BACKGROUND

Nevus of Ota is a rare disease most frequently found in Asians. It presents clinically as a bluish gray hyperpigmentation of one side of the face. Transformation into melanoma and glaucoma are the main risks. The appearance of vitiligo lesions with poliosis within a nevus of Ota is exceptional.

PATIENTS AND METHODS

A 22-year-old female patient with a nevus of Ota consulted for depigmentation of the eyelashes. Physical examination revealed hyperpigmentation in the right orbitofrontal part of her face, achromic macules and eyelash poliosis. A diagnosis was made of vitiligo developing on a nevus of Ota. Ophthalmologic examination showed hyperpigmentation of the sclera. Regular dermatologic and ophthalmologic follow-up was instituted.

DISCUSSION

Vitiligo is a condition characterized by the development of depigmented lesions secondary to chronic degradation of the melanocytes of the epidermis and the follicles. Its occurrence on congenital nevus and melanoma has already been reported. However, its appearance in dermal melanocytosis is very rare. Since the first observation of this association in 1979, only 4 other cases have been reported. The pathogenic mechanisms of this association are still poorly understood. Histopathological examination generally shows a loss of epidermal melanocytes, especially in the basal layer, while dermal melanocytes remain unaffected. In this context, vitiligo developed on dermal melanosis appears to result from the difference between the properties of normal (epidermal) melanocytes and ectopic (dermal) melanocytes.

CONCLUSION

Association of vitiligo with nevus of Ota is rare. Herein, we report a new case in a dark-skinned subject.

Prospective Analytical Controlled Study Evaluating Serum Biotin, Vitamin B12, and Folic Acid in Patients with Premature Canities

Background:

Premature canities is a common yet unfathomed disorder. The evidence for the role of micronutrient deficiency in premature canities is not well established.

Aim:

The present study was undertaken to evaluate the micronutrient levels in Indian patients with premature canities as compared to controls.

Materials and Methods:

We conducted a case–control study in 52 self-reporting patients with premature canities (<20 years age). Micronutrient levels including serum Vitamin B₁₂, biotin, and folic acid were assessed and compared among the patients and controls.

Results:

We observed that mean serum Vitamin B₁₂ (198.07 ± 88.98 pg/ml in cases vs. 343.07 ± 143.06 pg/ml in controls, P = 0.000), folic acid (6.22 ± 2.46 ng/ml in cases vs. 8.49 ± 4.18 ng/ml in controls, P = 0.01), and biotin (252.71 ± 18.79 pg/ml in cases vs. 266.47 ± 30.44 pg/ml in controls, P = 0.013) levels were significantly lower in cases as compared to the controls.

Conclusion:

In view of the dark hair and many prevailing myths, premature canities is a significant problem in Asians with profound psychosocial impact. This study unveils the association with Vitamin B₁₂, folic acid, and biotin deficiencies. Larger studies are recommended to arrive on a logical conclusion.

Formulation, characterization, and geno/cytotoxicity studies of galbanic acid-loaded solid lipid nanoparticles

CONTEXT

Galbanic acid (GBA) is a sesquiterpene coumarin with different medicinal properties and anticancer effects.

OBJECTIVE

To improve the anticancer activities of GBA, in the current study, we aimed to fabricate GBA-loaded solid lipid nanoparticles (GBA-SLNs) and study their biological activities in vitro.

MATERIALS AND METHODS

Hot homogenization was used for preparation of GBA-SLNs. The encapsulation efficiency (EE) and drug loading (DL) and in vitro release were determined. MTT, DAPI, DNA fragmentation, comet, and Anexin V apoptosis assays were used to compare the anti-cell proliferation and genotoxicity properties of GBA and GBA-SLNs against A549 cells and HUVEC to detect apoptosis and DNA damage in the final concentration of 100 µM after 48 h treatment.

RESULTS

Scanning electron microscopy (SEM) and particle size analysis showed spherical SLNs (92 nm), monodispersed distribution, and zeta potential of -23.39 mV. High EE (>98%) and long-term in vitro release were achieved. The stability of GBA-SLNs in aqueous medium was approved after 3 months in terms of size and polydispersity index. GBA was able to inhibit A549 growth with an IC50 value of 62 µM at 48 h. Although GBA-SLNs could also inhibit the growth rate of A549 cells, the effect is perceived after 48 h, as approved by the quantitative expression of Bcl-xL and Casp 9 genes, and also genotoxicity assays.

CONCLUSION

Long-term apoptotic effect of GBA-SLNs compared with GBA may be due to the accumulation of GBA-SLNs in the tumor site because of deviant tumor pathology. Our data confirmed that SLNs could be exploited for sustained lipophilic GBA delivery.

Oxidative stress and immune system in vitiligo and thyroid diseases

Vitiligo is an acquired dermatological disease frequently associated with autoimmune thyroid disorders. Several theories have been proposed so far to unravel the complex vitiligo pathogenesis. Currently, the autocytotoxic and the autoimmune theories are the most accredited hypothesis, since they are sustained by several important clinical and experimental evidences. A growing body of evidences shows that autoimmunity and oxidative stress strictly interact to finally determine melanocyte loss. In this scenario, associated thyroid autoimmunity might play an active and important role in triggering and maintaining the depigmentation process of vitiligo.

Geno/cytotoxicty and Apoptotic Properties of Phenolic Compounds from the Seeds of Dorema Glabrum Fisch. C.A

Introduction: Dorema glabrum (Apiaceae) is a rare and monocarpic species distributed in Transcaucasia and North West of Iran. We aimed to explore anti-cancer potency of bioactive compounds from the seeds of Dorma glabrum.

Methods: Methanol extract was subjected to phytochemical investigation using normal phase Sep-pak and reversed-phase HPLC, and cytotoxic effect of isolated compounds on CAOV-4 cell line was evaluated. Furthermore, Annexin V/PI staining and comet assay were used to study genotoxicity of compounds.

Results: Diglucosyl caffeoyl ester (1), Glucopyranosylcaffeic acid (2) and skimmin (3), were identified. MTT cytotoxicity assay showed growth inhibition of CAOV-4 cells due to treatment with compunds (1), (2) and (3) with an IC₅₀ of 99.7, 87.3 and 70.03 μg/ml at 48 h, respectively. Annexin V-FITC/PI staining showed occurrence of early/late apoptosis in the (1)-treated cells, while (2)-and (3)-treated cells necrosis/late apoptosis was dominant event. Single/double strands DNA breakages were observed by comet assay in all treatments.

Conclusion: This work provides sufficient information about anti-cancer properties of the diglucosyl caffeoyl ester from the seeds of D. glabrum.

Antioxidant, antityrosinase, anticholinesterase, and nitric oxide inhibition activities of three malaysian macaranga species

The methanol extracts of three Macaranga species (M. denticulata, M. pruinosa, and M. gigantea) were screened to evaluate their total phenolic contents and activities as cholinesterase inhibitors, nitric oxide (NO) production inhibitors, tyrosinase inhibitors, and antioxidants. The bark of M. denticulata showed the highest total phenolic content (2682 mg gallic acid equivalent (GAE)/100 g) and free radical scavenging activity (IC₅₀ = 0.063 mg/mL). All of the samples inhibited linoleic acid peroxidation by greater than 80%, with the leaves of M. gigantea exhibiting the highest inhibition of 92.21%. Most of the samples exhibited significant antioxidant potential. The bark of M. denticulata and the leaves of both M. pruinosa and M. gigantea exhibited greater than 50% tyrosinase inhibition, with the bark of M. denticulata having the highest percentage of inhibition (68.7%). The bark and leaves of M. denticulata exhibited greater than 50% inhibition (73.82% and 54.50%, resp.) of the acetylcholinesterase enzyme (AChE), while none of the samples showed any significant inhibition of butyrylcholinesterase (BChE). Only the bark of M. denticulata and M. gigantea displayed greater than 50% inhibition of nitric oxide production in cells (81.79% and 56.51%, resp.). These bioactivities indicate that some Macaranga spp. have therapeutic potential in medicinal research.

Cyto/Genotoxicity study of polyoxyethylene (20) sorbitan monolaurate (tween 20)

Polyoxyethylene (20) sorbitan monolaurate (tween 20) is a non-ionic surfactant that is widely used as an emulsifier and stabilizer in pharmaceutical formulations, food and cosmetic industries. Although a number of studies have showed its non-toxic impacts on target cells, still, it is essential to investigate its effect on target cells. Therefore, in the present study, the anti-cell proliferation and cyto/genotoxicity effects of tween 20 are reported to address the possible mechanism for induction of apoptosis. At 40%-50% confluency, A549 cells and human umbilical vein endothelial cells were exposed to tween 20 at a recommended concentration for 24 h. After 24 h, to detect apoptosis and DNA damage, the treated cells were subjected to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, fluorescein isothiocyanate (FITC)-labeled annexin V flow cytometry, DAPI staining, comet, and DNA ladder assays. Tween 20 decreased the growth of treated cells dose and time dependently, and single-strand DNA cleavage has been confirmed by comet assay. In addition, morphological alteration of DAPI-stained cells showed clear fragmentation in the chromatin and DNA rings within the nucleus of tween 20-treated cells. In addition, flow cytometry and DNA fragmentation assays confirmed DAPI staining assay results and indicated the occurrence of a programmed cell death (apoptosis) in the treated cells. These results demonstrate that, despite consideration of tween 20 as a safe non-ionic surfactant, it can induce apoptosis in target cells.

Two Cases of Vitiligo Developed on the Persisting Dermal Melanocytosis: Is There a Difference between Epidermal Melanocytes and Dermal Melanocytes?

Vitiligo is one of the most common pigmentary skin disorders; it is characterized by circumscribed depigmented macules due to the destruction of melanocytes. Although the etiology of vitiligo has not been fully elucidated, multiple factors including autoimmune and oxidative stress have been implicated in the pathogenesis of vitiligo. In contrast, dermal melanocytosis is histologically characterized by the presence of dermal melanocytes. It has been described that there are ectopic dermal melanocytes, which have failed to reach their proper location. A literature search revealed very few reports of patients with vitiligo developing vitiligo within dermal melanocytosis. Here, we report two cases of patients with vitiligo that occurred at pre-existing sites of dermal pigmented lesions. The histopathology showed the loss of epidermal melanocytes in spite of the existence of melanocytes in the dermis. There was no significant infiltration of inflammatory cells in the dermis. These cases illustrate unknown environmental factors as well as heterogeneity.

Vitiligo: an update on current pharmacotherapy and future directions

INTRODUCTION

Vitiligo is a common pigmentary skin disorder, characterized by the appearance of white macules on the skin, mucosal or hair. Treatment is often a tough challenge and involves a wide range of therapies.

AREAS COVERED

This review focuses on available first- and second-line pharmacological treatments for vitiligo. In particular, the mechanisms of action, the main indications, the efficacy and the most important side effects are reviewed. Moreover, a brief discussion is provided, regarding other nonpharmacological treatments, such as phototherapy and surgical options, due to their importance and successful outcomes in vitiligo treatment. Finally, a concise overview regarding the future directions in vitiligo therapy is presented.

EXPERT OPINION

The promising outcomes reported here demonstrate that it is possible to achieve a satisfactory and often stable repigmentation of vitiligo lesions. Topical corticosteroids, calcineurin inhibitors, phototherapy and photochemotherapy represent the first-line therapeutic options, due to their safety and efficacy, whereas vitamin D analogues, targeted phototherapy, oral corticosteroids and surgery should be used as second-line therapies. Other therapies, such as antioxidants, can be used in association with other therapeutic options, whereas depigmenting agents should be used only in cases of extensive vitiligo, recalcitrant to other treatments.

The association of functional polymorphisms in the aryl hydrocarbon receptor (AHR) gene with the risk of vitiligo in Han Chinese populations

BACKGROUND

Vitiligo is an acquired depigmentation disorder resulting from selective destruction of melanocytes. The aryl hydrocarbon receptor (AHR) is vital to the regulation of melanogenesis and melanocyte proliferation and differentiation through modulating the expressions of melanogenesis-related genes. AHR mutations may negatively affect AHR proteins and its target genes. Therefore, we hypothesized that AHR polymorphisms might be involved in vitiligo by impacting the transcriptional activities of related genes as mentioned above.

OBJECTIVES

  To evaluate the potential association between AHR polymorphisms and vitiligo susceptibility.

METHODS

We performed a hospital-based, case-control study of 1000 patients with vitiligo and 1000 vitiligo-free but age- and gender-matched controls. Two single nucleotide polymorphisms of the AHR gene (rs10249788 and rs2066853) were selected and genotyped using a polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

A statistically significantly decreased risk of vitiligo was found to be associated with the TT and CT genotypes of rs10249788 [odds ratio (OR) 0·59, 95% confidence interval (CI) 0·38-0·93; P = 0·028 and OR 0·82, 95% CI 0·68-0·98; P = 0·032, respectively] as well as among subgroups: male, active, nonsegmental vitiligo, and onset age ≤ 20 years. Moreover, subjects with the combined (CT + TT)/GG genotype or T/G haplotype (rs10249788/rs2066853) showed a decreased risk for vitiligo (OR 0·57, 95% CI 0·37-0·87, P = 0·009 and OR 0·78, 95% CI 0·64-0·96, P = 0·033, respectively).

CONCLUSIONS

These results suggest that the T allele of rs10249788 located in the promoter of the AHR gene is associated with a protective effect on vitiligo in Han Chinese populations.

Comet assay: a method to evaluate genotoxicity of nano-drug delivery system

INTRODUCTION

Drug delivery systems could induce cellular toxicity as side effect of nanomaterials. The mechanism of toxicity usually involves DNA damage. The comet assay or single cell gel electrophoresis (SCGE) is a sensitive method for detecting strand damages in the DNA of a cell with applications in genotoxicity testing and molecular epidemiology as well as fundamental research in DNA damage and repair.

METHODS

In the current study, we reviewed recent drug delivery researches related to SCGE.

RESULTS

We found that one preference for choosing the assay is that comet images may result from apoptosis-mediated nuclear fragmentation. This method has been widely used over the last decade in several different areas. Overall cells, such as cultured cells are embedded in agarose on a microscope slide, lysed with detergent, and treated with high salt. Nucleoids are supercoiled DNA form. When the slide is faced to alkaline electrophoresis any breakages present in the DNA cause the supercoiling to relax locally and loops of DNA extend toward the anode as a ''comet tail''.

CONCLUSION

This article provides a relatively comprehensive review upon potentiality of the comet assay for assessment of DNA damage and accordingly it can be used as an informative platform in genotoxicity studies of drug delivery systems.