Deleterious effect of angiotensin-converting enzyme gene polymorphism in vitiligo patients

Identification of TNF-α as Major Susceptible Risk Locus for Vitiligo: A Systematic Review and Meta-Analysis Study in the Asian Population

INTRODUCTION

Vitiligo is a common depigmentation disorder characterized by defined white patches on the skin and affecting around 0.5% to 2% of the general population. Genetic association studies have identified several pre-disposing genes and single nucleotide polymorphisms (SNPs) for vitiligo pathogenesis; nonetheless, the reports are often conflicting and rarely conclusive. This comprehensive meta-analysis study was designed to evaluate the effect of the risk variants on vitiligo aetiology and covariate stratified vitiligo risk in the Asian population, considering all the studies published so far.

METHODS

We followed a systematic and comprehensive search to identify the relevant vitiligo-related candidate gene association studies in PubMed using specific keywords. After data extraction, we calculated, for the variants involved, the study-level unadjusted odds ratio, standard errors, and 95% confidence intervals by using logistic regression with additive, dominant effect, and recessive models using R software package (R, 3.4.2) "metafor." Subgroup analysis was performed using logistic regression (generalized linear model; "glm") of disease status on subgroup-specific genotype counts. For a better understanding of the likely biological function of vitiligo-associated variant obtained through the meta-analysis, in silico functional analyses, through standard publicly available web tools, were also conducted.

RESULTS

Thirty-one vitiligo-associated case-control studies on eleven SNPs were analysed in our study. In the fixed-effect meta-analysis, one variant upstream of TNF-α gene: rs1800629 was found to be associated with vitiligo risk in the additive (p = 4.26E-06), dominant (p = 1.65E-7), and recessive (p = 0.000453) models. After Benjamini-Hochberg false discovery rate (FDR) correction, rs1800629/TNF-α was found to be significant at 5% FDR in the dominant (padj = 1.82E-6) and recessive models (padj = 0.0049). In silico characterization revealed the prioritized variant to be regulatory in nature and thus having potential to contribute towards vitiligo pathogenesis.

CONCLUSION

Our study constitutes the first comprehensive meta-analysis of candidate gene-based association studies reported in the whole of the Asian population, followed by an in silico analysis of the vitiligo-associated variant. According to the findings of our study, TNF-α single nucleotide variant rs1800629G>A has a risk association, potentially contributing to vitiligo pathogenesis in the Asian population.

Prevalence and burden of vitiligo in Africa, the Middle East and Latin America

Vitiligo is a common chronic autoimmune disorder characterized by skin and hair depigmentation that affects 0.5%-2.0% of the global population. Vitiligo is associated with diminished quality of life (QoL) and psychosocial burden. The burden of vitiligo may vary based on skin tone and cultural differences as well as geographical variations in disease awareness, societal stigma, healthcare systems and treatment options. Data on the burden and management of vitiligo in Africa, the Middle East and Latin America are scarce. Literature searches using terms covering vitiligo in Africa, the Middle East and Latin America were conducted using PubMed to identify relevant publications that focused on disease prevalence and burden, QoL and psychosocial impact and disease management between 2011 and 2021. Most of the reviewed studies were conducted in the Middle East, and most Latin American studies were from Brazil. Most studies involved small patient numbers and may not be generalizable. Reported prevalence of vitiligo ranged from 0.18% to 5.3% in Africa and the Middle East, and from 0.04% to 0.57% in Latin America. In several studies, prevalence was higher among female participants. Generally, non-segmental vitiligo was the dominant clinical variant identified and the age at onset varied widely across studies. Common comorbidities include autoimmune diseases such as Hashimoto's thyroiditis, alopecia areata and diabetes. Few treatment guidelines exist in these regions, with the exceptions of guidelines published by the Brazilian and Argentinian Societies of Dermatology. There is a clear unmet need for large epidemiological studies with uniform methodology to accurately ascertain the true prevalence of vitiligo in Africa, the Middle East and Latin America. Additional data on vitiligo burden and management in Africa and Latin America are also needed, along with local disease management guidelines that consider genetic variation, psychosocial burden and socioeconomic diversity in all 3 regions.

The Renin-Angiotensin System: The Challenge behind Autoimmune Dermatological Diseases

Autoimmune dermatological diseases (AIDD) encompass a diverse group of disorders characterized by aberrant immune responses targeting the skin and its associated structures. In recent years, emerging evidence suggests a potential involvement of the renin-angiotensin system (RAS) in the pathogenesis and progression of these conditions. RAS is a multicomponent cascade, primarily known for its role in regulating blood pressure and fluid balance. All of the RAS components play an important role in controlling inflammation and other immune responses. Angiotensin II, the main effector, acts on two essential receptors: Angiotensin Receptor 1 and 2 (AT1R and AT2R). A disturbance in the axis can lead to many pathological processes, including autoimmune (AI) diseases. AT1R activation triggers diverse signaling cascades involved in inflammation, fibrosis and tissue remodeling. Experimental studies have demonstrated the presence of AT1R in various cutaneous cells and immune cells, further emphasizing its potential contribution to the AI processes in the skin. Furthermore, recent investigations have highlighted the role of other RAS components, beyond angiotensin-converting enzyme (ACE) and Ang II, that may contribute to the pathophysiology of AIDD. Alternative pathways involving ACE2, Ang receptors and Ang-(1-7) have been implicated in regulating immune responses and tissue homeostasis within the skin microenvironment. Understanding the intricate involvement of the RAS in AIDD may provide novel therapeutic opportunities. Targeting specific components of the RAS, such as angiotensin receptor blockers (ARBs), ACE inhibitors (ACEIs) or alternative RAS pathway modulators, could potentially ameliorate inflammatory responses, reduce tissue damage and lessen disease manifestations. Further research is warranted to outline the exact mechanisms underlying RAS-mediated immune dysregulation in AIDD. This abstract aims to provide a concise overview of the intricate interplay between the RAS and AIDD. Therefore, we elaborate a systematic review of the potential challenge of RAS in the AIDD, including psoriasis, systemic sclerosis, vitiligo, lupus erythematosus and many more.

Effect of the Angiotensin-Converting Enzyme (ACE) (I/D) Polymorphism in COVID-19 Patients and Their Healthy Contacts

Introduction The quest to understand the pathophysiology behind the deleterious effects of the coronavirus disease 2019 (COVID-19) outbreak took a turn when involvement of the angiotensin converting enzyme (ACE) receptors in different organs, especially the lungs, could explain all the clinical manifestations and adverse events in patients. The I/D polymorphism in the ACE gene, having been attributed in various studies, was also seen to have an effect in this pandemic. Present study aimed to analyze the effect of this I/D mutation in COVID-19 patients and in their healthy contacts. Methods Patients with past history of COVID-19 infection and their healthy contacts were enrolled in the study after obtaining ethical clearance and informed consent. The polymorphism was studied by real-time polymerase chain reaction (PCR). Data was analyzed in SPSS version 20 (IBM Corp., Armonk, NY, USA). p value less than 0.05 was taken as significant. Results The allelic distribution followed the Hardy-Weinberg equilibrium, with the wild 'D' allele being dominant in the population. Between the case and controls, the mutant 'I' allele was observed more in the controls, and the association was statistically significant. Conclusion From the results of the present study, it could be concluded that while the wild 'D' allele led to higher chances of being affected with COVID-19, the polymorphism to 'I' allele was relatively protective in nature.

Association of genetic variants of the vitamin D receptor gene with vitiligo in a tertiary care center in a Saudi population: a case-control study

BACKGROUND

Vitiligo is a common cutaneous disorder of the skin and hair caused by a systemic depigmentation disorder that affects 1% of the population or less due to its onset in early adulthood. Meta-analyses have documented a linkage between vitiligo and the vitamin D receptor (VDR) gene.

OBJECTIVE

Investigate the relationship between the ApaI, BsmI, FokI and TaqI genetic variants in the VDR gene with vitiligo in a Saudi population.

DESIGN

Case-control.

SETTING

Single tertiary care center.

PATIENT AND METHODS

The case-control study was carried out between January 2015-December 2015 in Saudi vitiligo patients and healthy controls. VDR genetic variants or polymorphisms (ApaI, BsmI, FokI and TaqI) were genotyped by polymerase chain reaction-restriction fragment length analysis followed by 3% agarose gel electrophoresis. Applicable statistical methods were used to assess relationships between vitiligo cases and controls.

MAIN OUTCOM MEASURE

Effect of genotype distribution among four single nucleotide polymorphisms.

SAMPLE SIZE

152 vitiligo (median [IQR] 23 [19] years) patients and 159 healthy controls (45 [28.5] years).

RESULTS

We found an association of vitiligo with ApaI and BsmI polymorphisms (P<.05). However, a decreased risk was noted in vitiligo patients with FokI and TaqI polymorphisms and in the diplotype and haplotype analysis within males and females. A positive association with vitiligo was observed in ACAC and AC (adjusted by gender) haplotypes (P<.05). The strongest linkage disequilibrium was observed between rs79785232 (ApaI) and rs731236 (TaqI) polymorphisms (r²=.83), followed by rs2228570 (FokI) and rs1544410 (BsmI) polymorphisms (r²=.53).

CONCLUSIONS

Our results confirm an association of vitiligo with ApaI and BsmI polymorphisms and fail to show an association in TaqI and FokI polymorphism with vitiligo. Additional studies need to be carried out in different Arab populations to determine whether the polymorphisms are present.

LIMITATIONS

Controls not age matched, small sample size, lack of biochemical parameters.

CONFLICT OF INTEREST

None.

Genetic variants affecting chemical mediated skin immunotoxicity

The skin is an immune-competent organ and this function may be impaired by exposure to chemicals, which may ultimately result in immune-mediated dermal disorders. Interindividual variability to chemical-induced skin immune reactions is associated with intrinsic individual characteristics and their genomes. In the last 30-40 years, several genes influencing susceptibility to skin immune reactions were identified. The aim of this review is to provide information regarding common genetic variations affecting skin immunotoxicity. The polymorphisms selected for this review are related to xenobiotic-metabolizing enzymes (CYPA1 and CYPB1 genes), antioxidant defense (GSTM1, GSTT1, and GSTP1 genes), aryl hydrocarbon receptor signaling pathway (AHR and ARNT genes), skin barrier function transepidermal water loss (FLG, CASP14, and SPINK5 genes), inflammation (TNF, IL10, IL6, IL18, IL31, and TSLP genes), major histocompatibility complex (MHC) and neuroendocrine system peptides (CALCA, TRPV1, ACE genes). These genes present variants associated with skin immune responses and diseases, as well as variants associated with protecting skin immune homeostasis following chemical exposure. The molecular and association studies focusing on these genetic variants may elucidate their functional consequences and contribution in the susceptibility to skin immunotoxicity. Providing information on how genetic variations affect the skin immune system may reduce uncertainties in estimating chemical hazards/risks for human health in the future.