Lack of association between the 389C>T polymorphism (rs769217) in the catalase (CAT) gene and the risk of vitiligo: An update by meta-analysis

Evaluation of CAT Variants A-89T, C389T, and C419T in Patients with Vitiligo in the Saudi Population

Background and Objectives: Vitiligo is a chronic autoimmune and depigmentation disorder in humans that manifests as whitening lesions. Reactive oxygen species (ROS) are involved in cell damage. Catalase (CAT) is a well-known oxidative stress regulator and is primarily responsible for the catalytic decomposition of hydrogen peroxide into water and oxygen. Based on previous case-control and meta-analysis studies, we assessed the prevalence of three single-nucleotide polymorphisms (SNPs) of the CAT genes A-89T (rs7943316), C389T (rs769217) and C419T (rs11032709) in participants with vitiligo and healthy controls in the Saudi population. Materials and Methods: We recruited 152 participants with vitiligo and 159 healthy controls for A-89T, C389T, and C419T SNP genotyping studies using PCR and RFLP analysis. Additionally, we performed linkage disequilibrium and haplotype analyses between vitiligo cases and controls. Results: The rs7943316 and rs11032709 SNPs of the CAT genes showed a positive association with vitiligo for both heterozygous genotypes and dominant genetic models (TT + AT vs. AA in A-89T and TT + CT vs. CC in C389T), in the CAT gene. Linkage disequilibrium analysis revealed a moderate linkage between rs7943316 and rs11032709 SNPs in vitiligo cases and controls. Haplotype frequency estimation revealed a significant association (p = 0.003) among the three SNP alleles. Conclusions: The rs7943316 and rs11032709 SNPs of the CAT genes were strongly associated with susceptibility to vitiligo.

The Genetic Diversity and Dysfunctionality of Catalase Associated with a Worse Outcome in Crohn's Disease

Chronic gut inflammation in Crohn’s disease (CD) is associated with an increase in oxidative stress and an imbalance of antioxidant enzymes. We have previously shown that catalase (CAT) activity is permanently inhibited by CD. The purpose of the study was to determine whether there is any relationship between the single nucleotide polymorphisms (SNPs) in the CAT enzyme and the potential risk of CD associated with high levels of oxidative stress. Additionally, we used protein and regulation analyses to determine what causes long-term CAT inhibition in peripheral white mononuclear cells (PWMCs) in both active and inactive CD. We first used a retrospective cohort of 598 patients with CD and 625 age-matched healthy controls (ENEIDA registry) for the genotype analysis. A second human cohort was used to study the functional and regulatory mechanisms of CAT in CD. We isolated PWMCs from CD patients at the onset of the disease (naïve CD patients). In the genotype-association SNP analysis, the CAT SNPs rs1001179, rs475043, and rs525938 showed a significant association with CD (p < 0.001). Smoking CD patients with the CAT SNP rs475043 A/G genotype had significantly more often penetrating disease (p = 0.009). The gene expression and protein levels of CAT were permanently reduced in the active and inactive CD patients. The inhibition of CAT activity in the PWMCs of the CD patients was related to a low concentration of CAT protein caused by the downregulation of CAT-gene transcription. Our study suggests an association between CAT SNPs and the risk of CD that may explain permanent CAT inhibition in CD patients together with low CAT gene and protein expression.

A comprehensive meta-analysis and prioritization study to identify vitiligo associated coding and non-coding SNV candidates using web-based bioinformatics tools

Vitiligo is a prevalent depigmentation disorder affecting around 1% of the general population. So far, various Genome Wide Association Studies (GWAS) and Candidate Gene Association Studies (CGAS) have identified several single nucleotide variants (SNVs) as a risk factor for vitiligo. Nonetheless, little has been discerned regarding their direct functional significance to the disease pathogenesis. In this study, we did extensive data mining and downstream analysis using several experimentally validated datasets like GTEx Portal and web tools like rSNPBase, RegulomeDB, HaploReg and STRING to prioritize 13 SNVs from a set of 291SNVs that have been previously reported to be associated with vitiligo. We also prioritized their underlying/target genes and tried annotating their functional contribution to vitiligo pathogenesis. Our analysis revealed genes like FGFR10P, SUOX, CDK5RAP1 and RERE that have never been implicated in vitiligo previously to have strong potentials to contribute to the disease pathogenesis. The study is the first of its kind to prioritize and functionally annotate vitiligo-associated GWAS and CGAS SNVs and their underlying/target genes, based on functional data available in the public domain database.

Catalase but not vitamin D receptor gene polymorphisms are associated with nonsegmental vitiligo in Northwestern Mexicans

BACKGROUND

Vitiligo is an acquired pigmentation disorder characterized by melanocyte loss via autoimmune mechanisms triggered by oxidative stress. Gene polymorphisms in antioxidant enzymes and immunomodulators such as catalase (CAT) and vitamin D receptor (VDR), respectively, have been linked to vitiligo in European and Asian populations. Our aim was to evaluate the role of CAT and VDR gene polymorphisms as well as CAT and vitamin D in nonsegmental vitiligo in Northwestern Mexicans.

METHODS

A total of 357 subjects, 173 nonsegmental vitiligo patients and 184 age-gender matched healthy controls, were genotyped by PCR-restriction fragment length polymorphism. CAT activity was determined in 39 patients and in 39 controls and vitamin D (VitD) levels in 35 individuals per group.

RESULTS

CAT 419 C/T gene polymorphism was not informative, -89 A/T was associated with risk (P = 0.02), and 389 C/T conferred protection against vitiligo along with AT haplotype (P < 0.01 in both cases). VDR BsmI, ApaI, and TaqI gene polymorphisms were not associated with vitiligo, but BsmI was more prevalent in patients with Koebner phenomenon (P = 0.02). Serum CAT activity and VitD levels were lower in patients than in controls, but they showed no association with any vitiligo clinical characteristics neither with their gene polymorphisms.

CONCLUSIONS

Our results suggest a role for CAT gene polymorphisms in vitiligo susceptibility in the Mexican population and a lack of association with VDR gene polymorphisms.

Vitiligo: How do oxidative stress-induced autoantigens trigger autoimmunity?

Vitiligo is a common depigmentation disorder characterized by a loss of functional melanocytes and melanin from epidermis, in which the autoantigens and subsequent autoimmunity caused by oxidative stress play significant roles according to hypotheses. Various factors lead to reactive oxygen species (ROS) overproduction in the melanocytes of vitiligo: the exogenous and endogenous stimuli that cause ROS production, low levels of enzymatic and non-enzymatic antioxidants, disturbed antioxidant pathways and polymorphisms of ROS-associated genes. These factors synergistically contribute to the accumulation of ROS in melanocytes, finally leading to melanocyte damage and the production of autoantigens through the following ways: apoptosis, accumulation of misfolded peptides and cytokines induced by endoplasmic reticulum stress as well as the sustained unfolded protein response, and an 'eat me' signal for phagocytic cells triggered by calreticulin. Subsequently, autoantigens presentation and dendritic cells maturation occurred mediated by the release of antigen-containing exosomes, adenosine triphosphate and melanosomal autophagy. With the involvement of inducible heat shock protein 70, cellular immunity targeting autoantigens takes the essential place in the destruction of melanocytes, which eventually results in vitiligo. Several treatments, such as narrow band ultraviolet, quercetin and α-melanophore-stimulating hormone, are reported to be able to lower ROS thereby achieving repigmentation in vitiligo. In therapies targeting autoimmunity, restore of regulatory T cells is absorbing attention, in which narrow band ultraviolet also plays a role.