Identification of TYR, TYRP1, DCT and LARP7 as related biomarkers and immune infiltration characteristics of vitiligo via comprehensive strategies.

This study aims to explore biomarkers associated with vitiligo and analyze the pathological role of immune cell infiltration in the disease. We used the robust rank aggregation (RRA) method to integrate three vitiligo data sets downloaded from gene expression omnibus database, identify the differentially expressed genes (DEGs) and analyze the functional correlation. Then, the comprehensive strategy of combined weighted gene coexpression network analysis (WGCNA) and logical regression of the selection operator (LASSO), support vector machine recursive feature elimination (SVM-RFE), and random forest (RF) machine learning algorithm are employed to screen and biomarkers associated with vitiligo. Finally, the immune cell infiltration of vitiligo was evaluated by CIBERSORT, and the correlation between biomarkers and infiltrating immune cells was analyzed. Herein, we identified 131 robust DEGs, and enrichment analysis results showed that robust DEGs and melanogenesis were closely associated with vitiligo development and progression. TYR, TYRP1, DCT and LARP7 were identified as vitiligo-related biomarkers. Immune infiltration analysis demonstrated that CD4 T Cell, CD8 T Cell, Tregs, NK cells, dendritic cells, and macrophages were involved in vitiligo's pathogenesis. In summary, we adopted a comprehensive strategy to screen biomarkers related to vitiligo and explore the critical role of immune cell infiltration in vitiligo.Abbreviations: TYR, Tyrosinase; TYRP1, Tyrosinase-related protein-1; DCT, dopachrome tautomerase; LARP7, La ribonucleoprotein domain family, member-7; RRA, robust rank aggregation; DEGs, differentially expressed genes; WGCNA, weighted gene coexpression network analysis; LASSO, logical regression of the selection operator; SVM-RFE, support vector machine recursive feature elimination; RF, random forest; GWAS, Genome-wide association study; FasL, Fas-Fas ligand; Tregs, T-regulatory cells; NK, natural killer; GEPCs, gene expression profiling chips; GO, gene ontology; GSEA, gene set enrichment analysis; FDR, false discovery rate; AUC, area under the curve; ROC, receiver-operating characteristic; BP, biological process; CC, cellular component; MF, molecular function.

Vitexin protects melanocytes from oxidative stress via activating MAPK-Nrf2/ARE pathway.

INTRODUCTION: Vitiligo is the most common type of depigmented skin disease. Cellular oxidative stress caused by reactive oxygen species (ROS) has been implicated in the pathogenesis of vitiligo. Nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway plays an important role in melanocytes against hydrogen peroxide (H2O2) induced oxidative stress. In addition, vitexin may protect vitiligo by inhibiting oxidative stress and inflammation. OBJECTIVE: In the present study, we aimed to investigate the antioxidant effect of vitexin-activated mitogen-activated protein kinase (MAPK)-Nrf2/ARE axis in vitiligo. METHODS: MTT assay identified cell viability of human melanocyte PIG1. Cell apoptosis was evaluated by flow cytometry. Gene and protein expression levels were analyzed by quantitative real-time PCR (qPCR) and Western blotting. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expressions of inflammatory factors and ROS production. RESULTS: Vitexin inhibited H2O2-induced melanocyte apoptosis and promoted cell proliferation. Moreover, vitexin decreased expression of interleukin-1ß (IL-1ß), IL-17A, and ROS in melanocytes induced by H2O2. Subsequently, activation of MAPK-Nrf2/ARE signaling was readily induced by vitexin treatment, as evidenced by the upregulation of antioxidant genes including heme oxygenase 1 (HO-1) and superoxide dismutase (SOD). Knockdown of Nrf2 reversed the protective effect of vitexin on H2O2-induced melanocytes. And, knockdown of Nrf2 increased the expression of IL-1ß, IL-17A and ROS, and reduced HO-1 and SOD expression. CONCLUSIONS: Vitexin protected melanocytes from oxidative stress by activating MAPK-Nrf2/ARE signaling pathway. Our results suggested that the role of the Nrf2/ARE axis in the antioxidant defense of melanocytes, and the potential therapeutic strategy for vitiligo.

Effects of six compounds with different chemical structures on melanogenesis.

Several chemical compounds can restore pigmentation in vitiligo through mechanisms that vary according to disease etiology. In the present study, we investigated the melanogenic activity of six structurally distinct compounds, namely, scopoletin, kaempferol, chrysin, vitamin D3, piperine, and 6-benzylaminopurine. We determined their effectiveness, toxicity, and mechanism of action for stimulating pigmentation in B16F10 melanoma cells and in a zebrafish model. The melanogenic activity of 6-benzylaminopurine, the compound identified as the most potent, was further verified by measuring green fluorescent protein concentration in tyrp1 a: eGFP (tyrosinase-related protein 1) zebrafish and mitfa: eGFP (microphthalmia associated transcription factor) zebrafish and antioxidative activity. All the tested compounds were found to enhance melanogenesis responses both in vivo and in vitro at their respective optimal concentration by increasing melanin content and expression of TYR and MITF. 6-Benzyamino-purine showed the strongest re-pigmentation action at a concentration of 20 µmol·L-1in vivo and 100 µmol·L-1in vitro, and up-regulated the strong fluorescence expression of green fluorescent protein in tyrp1a: eGFP and mitfa: eGFP zebrafish in vitro. However, its relative anti-oxidative activity was found to be very low. Overall, our results indicated that 6-benzylaminopurine stimulated pigmentation through a direct mechanism, by increasing melanin content via positive regulation of tyrosinase activity in vitro, as well as up-regulating the expression of the green fluorescent protein in transgenic zebrafish in vivo.

The catalase gene promoter and 5'-untranslated region variants lead to altered gene expression and enzyme activity in vitiligo.

BACKGROUND: Oxidative stress is considered to be the initial event in the course of vitiligo. The enzyme catalase (CAT) is mainly involved in cellular defence against oxidizing agents through detoxifying H2 O2 . OBJECTIVES: The aims were (i) to assess erythrocyte CAT enzyme activity and lipid peroxidation (LPO) levels as well as CAT mRNA expression in skin and blood; (ii) to investigate CAT gene promoter rs7943316, rs1001179, 5'-untranslated region rs1049982, and exon (rs17886350, rs11032709, rs17880442, rs35677492) polymorphisms; and (iii) to perform genotype/haplotype-phenotype correlation analyses in patients with vitiligo and controls from Gujarat. METHODS: CAT activity and LPO levels were measured spectrophotometrically. CAT mRNA levels were estimated using real-time polymerase chain reaction (PCR) by the SYBR Green method. Single-nucleotide polymorphism genotyping was performed using PCR-restriction fragment length polymorphism and amplification-refractory mutation system-PCR analyses. RESULTS: Patients with vitiligo showed significantly decreased CAT mRNA expression in lesional and nonlesional skin and in blood, with reduced CAT activity compared with that of controls. CAT -89A/T and -20T/C polymorphisms were significantly associated with patients, especially with active and generalized vitiligo, whereas no association was observed for -262G/A and exon polymorphisms. The A-262 T-89 C-20 haplotype with variant alleles was found to be associated with 6·4-fold risk of vitiligo. Genotype/haplotype-phenotype correlation analyses revealed that individuals with susceptible genotypes/haplotype for CAT -89A/T and -20T/C polymorphisms showed significantly decreased CAT mRNA/activity, and only -89A/T polymorphisms showed significantly increased LPO levels compared with wild-type genotypes/haplotype. CONCLUSIONS: The present study proposes the crucial role of CAT and its allelic variants in oxidative stress-mediated pathogenesis of vitiligo.

JAK inhibitors in dermatology: The promise of a new drug class.

New molecularly targeted therapeutics are changing dermatologic therapy. Janus kinase-signal transducer and activator of transcription (JAK-STAT) is an intracellular signaling pathway upon which many different proinflammatory signaling pathways converge. Numerous inflammatory dermatoses are driven by soluble inflammatory mediators, which rely on JAK-STAT signaling, and inhibition of this pathway using JAK inhibitors might be a useful therapeutic strategy for these diseases. Growing evidence suggests that JAK inhibitors are efficacious in atopic dermatitis, alopecia areata, psoriasis, and vitiligo. Additional evidence suggests that JAK inhibition might be broadly useful in dermatology, with early reports of efficacy in several other conditions. JAK inhibitors can be administered orally or used topically and represent a promising new class of medications. The use of JAK inhibitors in dermatology is reviewed here.

Effect of different types of therapeutic trauma on vitiligo lesions.

New treatment modalities for vitiligo acting by changing certain cytokines and metalloproteinases are newly emerging. The aim of this work is to To assess the efficacy of trichloroacetic acid (TCA) chemical peel, dermapen, and fractional CO2 laser in treatment of stable non-segmental vitiligo and to detect their effects on IL-17 and MMP-9 levels. Thirty patients with stable vitiligo were recruited in a randomized controlled study. They were randomly categorized into three equal groups. Group 1: TCA peel, Group 2: dermapen machine, and Group 3: Fractional CO2 laser. Skin biopsies were taken from treated areas and from control areas for which MMP-9 and IL-17 tissue levels were measured using ELISA. The 30 vitiligo patients had low basal tissue MMP-9 levels and high baseline IL-17 tissue levels. As regards the three different used modalities, all of them caused rise in MMP-9 as well as IL-17 levels and almost their levels were much more elevated with repetition of the previously mentioned traumatic procedures. TCA 25% peel proved to be the most effective modality both clinically and laboratory and it can be used prior or with other conventional therapies in the treatment of vitiligo.

Analysis of Manganese Superoxide Dismutase and Glutathione Peroxidase 1 Gene Polymorphisms in Vitiligo.

Vitiligo is a hereditary/acquired progressive pigmentation disorder characterized by discoloration of skin as a result of melanocyte dysfunction. Recent studies have proposed that oxidant/antioxidant status plays an important role in vitiligo pathogenesis because of the toxic effects on melanocytes. In this study, we aimed to investigate possible associations of MnSOD Ala-9Val and GPx1 Pro198Leu polymorphisms with vitiligo with in Turkish population. The study group consists of 57 patients with vitiligo and 69 healthy controls. Genotyping is performed to identify MnSOD Ala-9Val and GPx1 Pro198Leu polymorphisms. The method used for genotyping was based on the PCR amplification and detection of polymorphisms by hybridization probes labeled with fluorescent dyes. Both the genotype and allele frequencies of MnSOD Ala-9Val (p = 0.817 and p = 0.553, respectively) and GPx1 Pro198Leu polymorphisms (p = 0.422 and p = 0.673, respectively) were not significantly different between vitiligo patients and the control group. Although no significant difference was found, this is the first report investigating the possible associations between the MnSOD Ala-9Val and GPx1 Pro198Leu polymorphisms in Turkish population. Further studies with large populations will be able to clarify the association better.

Oxidized tyrosinase: A possible antigenic stimulus for non-segmental vitiligo autoantibodies.

BACKGROUND: Vitiligo is a common pigmentary disorder, the precise etiology of which remains obscure. Tyrosinase, a key enzyme involved in melanin synthesis, has now been implicated as an autoantigen for vitiligo patients, but it is not clear how this prevalent protein becomes antigenic in vitiligo. OBJECTIVE: To investigate the status and contribution of oxidized tyrosinase in vitiligo and to explore whether oxidized tyrosinase has a role in disease progression. METHODS: Tyrosinase was modified by reactive-oxygen-species (ROS). Binding characteristics of antibodies in vitiligo patients (n=25) with varying disease duration (DD) and disease severity were screened against ROS-modified tyrosinase (ROS-tyrosinase) by immunoassays and their results were compared with healthy controls (n=23). RESULTS: The ROS caused extensive alterations in conformation and function of tyrosinase. Protein-A purified IgGs from vitiligo patients (Vt-IgG) showed strong binding to ROS-tyrosinase in comparison with IgGs from healthy controls (p<0.001). Interestingly, not only was there an increased number of subjects positive for anti-ROS-tyrosinase-IgGs, but also the levels of these IgGs were significantly higher among vitiligo patients, whose DD were ≥10 years as compared to patients with short DD (<10 years). In addition, a significant correlation was observed between the levels of anti-ROS-tyrosinase-IgGs and the patients' ages or with disease severity. Experimentally induced anti-ROS-tyrosinase-IgGs show reactivity with tyrosinase from vitiligo patients. Furthermore, vitiligo patients had lower levels of tyrosinase activity compared with healthy controls. Not only these, levels of carbonylation were also higher among vitiligo patients whose DD were ≥10 years as compared to patients with DD<10 years. CONCLUSIONS: This is the first study to demonstrate the role of oxidized tyrosinase in vitiligo. Our novel results support an association between oxidized tyrosinase and vitiligo autoimmunity. The stronger antibodies response to oxidized tyrosinase in vitiligo patients with higher DD or with severe patients suggests that oxidized tyrosinase may be a useful biomarker in evaluating the progression of vitiligo and in elucidating the mechanisms of disease pathogenesis.

Treatment with low-dose cytokines reduces oxidative-mediated injury in perilesional keratinocytes from vitiligo skin.

BACKGROUND: Vitiligo is a systemic dermatological disorder characterized by the loss of skin pigmentation due to melanocyte injury or aberrant functioning. Recent data underline its multifactorial etiology with significant involvement of autoimmune and redox alterations. The major role in vitiligo cellular immunity is displayed by augmented Th1 and Th17 and suppressed TREGs and Th2 lymphocyte populations. Our previous studies indicate a marked redox imbalance in perilesional ("PL", i.e. obtained from visibly unaffected skin surrounding the depigmented area in vitiligo patients) keratinocytes where the massive infiltration of inflammatory cells takes place. No defined therapy exists for vitiligo. Although a number of approaches have been used for the induction of TREGs and Th2 cells, they may be associated with significant off-target effects. OBJECTIVE: In order to identify a targeted approach for vitiligo treatment we, first, aimed to investigate the possible source of ROS overproduction in PL keratinocytes. Second, we tested the effect of low-dose selected cytokines, on intra- and extracellular ROS production, cell viability and cell cycle of PL keratinocytes. METHODS: The in vitro study was conducted on primary PL keratinocytes obtained from the skin of vitiligo patients in our previous studies. The activity of NADPH oxidase was measured on intact PL and control keratinocytes, treated or not with cytokines, by luminometric assay. The following cytokines were selected for PL keratinocytes treatment: IL-10 and IL-4 (produced by TREGs and Th2, respectively), basic fibroblasts growth factor (bFGF) and neuropeptide ß-endorphin (modulating the cellular resistance to oxidative stress and the immune response, respectively). All cytokines were used at concentration of 10fg/ml and were prepared by sequential-kinetic-activation (SKA). Intracellular ROS production and cell cycle were analyzed by flow cytometry using H2DCFDA and propidium iodide dyes, respectively. Cell viability was measured by fluorometric resazurin reduction method. RESULTS: Our results suggest that NADPH oxidase represents one of the main sources of ROS overproduction by PL keratinocytes. Further, SKA low-dose IL-10, ß-endorphin and, particularly, IL-4 and bFGF display a positive effect on redox dyshomeostasis and viability and, in our experimental conditions, don't affect the cell cycle of PL keratinocytes. CONCLUSION: Our preliminary data suggest that low-dose IL-10, IL-4, ß-endorphin and bFGF can be proposed as a new therapeutic tool for vitiligo treatment.

Low glutathione peroxidase activity levels in patients with vitiligo.

BACKGROUND: Vitiligo is an idiopathic skin disease characterized by white areas on the skin due to loss of the functional melanocytes, with possible involvement of oxidative stress. Glutathione peroxidase (GPx) is an antioxidant enzyme that protects cells against oxidative damage. AIM: To examine serum GPx levels in patients with vitiligo and to relate the findings to the clinical features. PATIENTS AND METHODS: The study group included 60 patients with vitiligo and 30 matching healthy controls. GPx activity was evaluated using enzyme-linked immunosorbent assay. RESULTS: We found a significant decrease in serum GPx activity level in the patients with vitiligo compared to the healthy controls (0.29 ± 0.14 versus 0.47 ± 0.13, p < .001). The levels were significantly low in skin phenotypes III and IV (p < .001). Higher levels were also observed with increasing age (≥ 14 years), prolonged disease duration (≥ 3 years), and generalized and extensive vitiligo (< 50%). However, these variations were statistically insignificant. CONCLUSIONS: Low levels of serum GPx activity, indicative of a disturbed oxidant-antioxidant system, may contribute to the development of vitiligo.

Association of Angiotensin-Converting Enzyme ACE Gene Polymorphism with ACE Activity and Susceptibility to Vitiligo in Egyptian Population.

AIM: The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene is associated with vitiligo in the Indians and Koreans, but not in those of English or Turkish background. We investigated the ACE (I/D) polymorphism in vitiligo patients for the first time in Egypt and compared serum ACE levels between vitiligo patients and controls. The present study was carried out in 100 vitiligo patients (40 males and 60 females) and in 100 healthy controls of an Egyptian population using the polymerase chain reaction genotyping method. RESULTS: The ACE genotype and allele frequency was significantly different between vitiligo patients and controls. Our results revealed a significant increase in the frequency of the ACE I allele (p=0.002; odds ratio: 1.99; 95% confidence intervals: 1.207-3.284) with an overrepresentation of I/D genotype in the vitiligo patient group. Furthermore, there was a significant difference between the segmental, nonsegmental, and focal vitiligo in ACE gene genotype distribution. Serum ACE levels were significantly increased in vitiligo patients compared to controls (p=0.034). CONCLUSION: This study suggests that, for the first time, ACE gene polymorphism confers susceptibility to vitiligo in the Egyptian population.

Analysis of oxidative stress status, catalase and catechol-O-methyltransferase polymorphisms in Egyptian vitiligo patients.

Vitiligo is the most common depigmentation disorder of the skin. Oxidative stress is implicated as one of the probable events involved in vitiligo pathogenesis possibly contributing to melanocyte destruction. Evidence indicates that certain genes including those involved in oxidative stress and melanin synthesis are crucial for development of vitiligo. This study evaluates the oxidative stress status, the role of catalase (CAT) and catechol-O-Methyltransferase (COMT) gene polymorphisms in the etiology of generalized vitiligo in Egyptians. Total antioxidant capacity (TAC) and malondialdehyde (MDA) levels as well as CAT exon 9 T/C and COMT 158 G/A polymorphisms were determined in 89 patients and 90 age and sex-matched controls. Our results showed significantly lower TAC along with higher MDA levels in vitiligo patients compared with controls. Meanwhile, genotype and allele distributions of CAT and COMT polymorphisms in cases were not significantly different from those of controls. Moreover, we found no association between both polymorphisms and vitiligo susceptibility. In conclusion, the enhanced oxidative stress with the lack of association between CAT and COMT polymorphisms and susceptibility to vitiligo in our patients suggest that mutations in other genes related to the oxidative pathway might contribute to the etiology of generalized vitiligo in Egyptian population.

Association of the 389 C/T polymorphism of the catalase gene with susceptibility to vitiligo: a meta-analysis.

BACKGROUND: The 389 C/T polymorphism in the catalase gene, CAT, has been reported to be associated with the risk of vitiligo. AIM: To evaluate the association of the CAT 389 C/T polymorphism with susceptibility to vitiligo. METHODS: We undertook a literature search and included the relevant studies passing the selection criteria. After the relevant data were extracted from each study, we statistically analysed the strength of association between the CAT gene and vitiligo risk. RESULTS: In total, 7 relevant studies were identified, comprising 1531 patients with vitiligo and 1608 controls. The genotype distribution in the controls of all studies complied with Hardy-Weinberg equilibrium. After pooling all studies, the results indicated that the 389 C/T polymorphisms in CAT were not associated with the risk of vitiligo in Asians and Turks; however the CT genotype might be a genetic risk factor for susceptibility to vitiligo (OR = 1.77, 95% CI 1.30-2.43, P < 0.001) and the CC genotype might decrease the risk of vitiligo (OR = 0.63, 95% CI 0.47-0.86, P < 0.01) in western Europeans. CONCLUSIONS: The 389 C/T polymorphisms in the CAT gene may be associated with vitiligo in western Europeans. Further studies with larger sample sizes are warranted to confirm our findings.

Genetic polymorphisms in the methylenetetrahydrofolate reductase gene (MTHFR) and risk of vitiligo in Han Chinese populations: a genotype-phenotype correlation study.

BACKGROUND: Recent evidence has revealed an elevation of total homocysteine (tHcy) in patients with vitiligo. Methylenetetrahydrofolate reductase (MTHFR) is one of the main enzymes regulating homocysteine (Hcy) metabolism. Thus, polymorphisms of MTHFR could potentially contribute to the development of vitiligo by affecting MTHFR activity and tHcy levels. OBJECTIVES: To evaluate the potential association between MTHFR polymorphisms and vitiligo susceptibility. METHODS: In total, 1000 patients with vitiligo and 1000 age- and sex-matched controls were enrolled in this hospital-based case-control study. Two single-nucleotide polymorphisms of the MTHFR gene (rs1801133 C>T and rs1801131 A>C) were selected and genotyped using polymerase chain reaction (PCR)-restriction fragment length polymorphism and allele-specific PCR, respectively. The MTHFR activity concentration and tHcy level in serum were measured by enzyme-linked immunosorbent assay. RESULTS: We found that allele T of rs1801133 in the MTHFR gene was associated with a significantly reduced risk of vitiligo (adjusted odds ratio 0·58, 95% confidence interval 0·43-0·76, P < 0·001). In addition, the patients with vitiligo had a lower activity concentration of MTHFR and higher level of tHcy than the controls. Correlation between these markers and the risk of vitiligo was also observed. Furthermore, the individuals with a no-risk genotype (CT + TT) of rs1801133 and higher activity concentration of MTHFR or lower level of tHcy had a significantly decreased risk of vitiligo. CONCLUSIONS: Our data suggest that MTHFR gene polymorphisms may play a vital role in genetic susceptibility to vitiligo.

Stress-induced RNASET2 overexpression mediates melanocyte apoptosis via the TRAF2 pathway in vitro.

The recent genome-wide association study identified a link between vitiligo and genetic variants in the ribonuclease T2 (RNASET2) gene; however, the functional roles of RNASET2 in vitiligo pathogenesis or in melanocyte apoptosis have yet to be determined. The current study was designed to investigate the vitiligo-related expression pattern of RNASET2 and its molecular function involving apoptosis-related signaling proteins and pathways. The results showed overexpression of RNASET2 in epidermis specimens from 40 vitiligo patients compared with that from matched healthy controls. In addition, in vitro analyses indicated that overexpression of RNASET2 was inducible in cultured primary human melanocytes and keratinocytes by stress conditions, that is, exposure to UV irradiation, hydrogen peroxide, and inflammatory factors, respectively, and led to increased cell apoptosis via the tumor necrosis factor receptor-associated factor 2 (TRAF2)-caspases pathway through the physical interaction of RNASET2 with TRAF2. Thus, RNASET2 may contribute to vitiligo pathogenesis by inhibiting TRAF2 expression and, as such, RNASET2 may represent a potential therapeutic target of vitiligo.

SIRT1 regulates MAPK pathways in vitiligo skin: insight into the molecular pathways of cell survival.

Vitiligo is an acquired and progressive hypomelanotic disease that manifests as circumscribed depigmented patches on the skin. The aetiology of vitiligo remains unclear, but recent experimental data underline the interactions between melanocytes and other typical skin cells, particularly keratinocytes. Our previous results indicate that keratinocytes from perilesional skin show the features of damaged cells. Sirtuins (silent mating type information regulation 2 homolog) 1, well-known modulators of lifespan in many species, have a role in gene repression, metabolic control, apoptosis and cell survival, DNA repair, development, inflammation, neuroprotection and healthy ageing. In the literature there is no evidence for SIRT1 signalling in vitiligo and its possible involvement in disease progression. Here, biopsies were taken from the perilesional skin of 16 patients suffering from non-segmental vitiligo and SIRT1 signalling was investigated in these cells. For the first time, a new SIRT1/Akt, also known as Protein Kinase B (PKB)/mitogen-activated protein kinase (MAPK) signalling has been revealed in vitiligo. SIRT1 regulates MAPK pathway via Akt-apoptosis signal-regulating kinase-1 and down-regulates pro-apoptotic molecules, leading to decreased oxidative stress and apoptotic cell death in perilesional vitiligo keratinocytes. We therefore propose SIRT1 activation as a novel way of protecting perilesional vitiligo keratinocytes from damage.

Involvement of superoxide dismutase isoenzymes and their genetic variants in progression of and higher susceptibility to vitiligo.

Oxidative stress has been implicated as the initial triggering event in vitiligo pathogenesis leading to melanocyte destruction. Here, we report a significant increase in oxidative stress in vitiligo patients as evidenced by high lipid peroxidation levels suggesting an imbalance in the antioxidant enzyme system as reported in our previous studies. This study examined the role of the enzymatic antioxidant SOD, which converts the pro-oxidant superoxide into H2O2, in vitiligo pathogenesis. The activity of three isoforms of SOD, i.e., SOD1, SOD2, and SOD3, was significantly higher in vitiligo patients. To identify the underlying mechanism for the increase in activities of SOD isoforms, we explored the SOD1, SOD2, and SOD3 genes for their genetic variations and transcript levels. The SOD2 Thr58Ile (rs35289490) and Leu84Phe (rs11575993) polymorphisms were significantly associated with vitiligo patients, and the Val16Ala (rs4880) polymorphism was associated with active vitiligo patients. Interestingly, SOD2 activity was contributed by these polymorphisms along with its increase in transcript levels in patients. SOD3 activity was associated with the Arg213Gly (rs8192291) polymorphism. The SOD3 transcript levels were also increased in patients, which might contribute to the increased SOD3 activity. However, we could not establish the genotype-phenotype correlation for SOD1 as we could not detect any novel or reported SNPs in SOD1. In addition, both transcript and protein levels of SOD1 were unchanged between patients and controls, though SOD1 activity was increased in patients. Activities of SOD isoforms also correlated with progression of the disease as the activity was higher in active cases of vitiligo compared to stable cases. Here, we report that SOD2 and SOD3 polymorphisms may be genetic risk factors for susceptibility and progression of vitiligo and hence the genetic makeup of an individual may form a basis for the effective treatment of the disease. Overall, our results suggest that increased activity of SOD isoforms under the influence of genetic factors may lead to accumulation of H2O2 in cytoplasmic, mitochondrial, and extracellular compartments resulting in oxidative damage to the melanocytes.

Inherited catalase deficiency: is it benign or a factor in various age related disorders?

Hydrogen peroxide was - and is still - considered toxic for a wide range of living organisms. Oxidative stress occurs when there is an excess of pro-oxidants over antioxidants and it has been implicated in several diseases. Catalase is involved in hydrogen peroxide catabolism and is important in defense against oxidative stress. Acatalasemia means the inherited near-total deficiency of catalase activity, usually in reference to red cell catalase. Acatalasemia was thought at first to be an asymptotic disorder. In the absence of catalase, neither the Japanese, or Hungarian acatalasemics nor acatalasemic mice had significantly increased blood glutathione peroxidase activity. In animal models, catalase deficient tissues show much slower rates of removal of extracellular hydrogen peroxide. In catalase knock-out mice, a decreased hydrogen peroxide removing capacity and increased reactive oxygen species formation were reported. Hydrogen peroxide may cause methemoglobinemia in patients with catalase deficiency. During anesthesia for a Japanese acatalasemic patient the disinfection with hydrogen peroxide solution caused severe methemoglobinemia. Patients with inherited catalase deficiency, who are treated with uric acid oxidase (rasburicase) may experience very high concentrations of hydrogen peroxide and may suffer from methemoglobinemia and hemolysis. The high (18.5%) prevalence of diabetes mellitus in inherited catalase deficient individuals and the earlier (10 years) manifestation of the disease may be attributed to the oxidative damage of oxidant sensitive, insulin producing pancreatic beta-cells. Ninety-seven of 114 acatalasemics had diseases related to oxidative stress and aging. The oxidative stress due to catalase deficiency could contribute to the manifestation of diabetes while for the other diseases it may be one of the factors in their causations. In summary, inherited catalase deficiency is associated with clinical features, pathologic laboratory test results, age and oxidative stress related disorders. Rather than considering it a benign condition, it should be considered as a complicating condition for aging and oxidative stress.