Coexistence of 2282del4 FLG gene mutation and IL-18 -137G/C gene polymorphism enhances the risk of atopic dermatitis

Association between polymorphisms and atopic dermatitis susceptibility: A systematic review and meta-analysis

AIM

Atopic dermatitis (AD) is a chronic pruritic inflammatory skin disease that is closely linked to genetic factors. Previous studies have revealed numerous single nucleotide polymorphisms (SNPs) that been related to susceptibility to AD; however, the results are conflicting. Therefore, a meta-analysis was conducted to assess the associations of these polymorphisms and AD risk.

MATERIAL AND METHODS

PubMed, Web of Science, Embase, Cochrane Library, and China National Knowledge Infrastructure databases were retrieved to identify eligible studies, with selected polymorphisms being reported in a minimum of three separate studies. The Newcastle-Ottawa Scale (NOS) was used to evaluate study quality. Review Manager 5.3 and STATA 14.0 were used to perform the meta-analysis.

RESULTS

After screening, 64 studies involving 13 genes (24 SNPs) were selected for inclusion in the meta-analysis. Nine SNPs were positively correlated with AD susceptibility [filaggrin (FLG) R501X, FLG 2282del4, chromosome 11q13.5 rs7927894, interleukin (IL)-17A rs2275913, IL-18 -137 G/C, Toll-like receptor 2 (TLR2) rs5743708, TLR2 A-16934 T, serine protease inhibitor Kazal type-5 (SPINK5) Asn368Ser, interferon-γ (IFN-γ) T874A] and one was negatively associated with AD susceptibility (IL-4 -1098 T/G). The 14 remaining SNPs were not significantly associated with AD susceptibility.

CONCLUSIONS

Nine SNPs that may be risk factors and one SNP that may be a protective factor for AD were identified, providing a reference for AD prediction, prevention, and therapy.

Genotype Study of Filaggrin Gene Loss-of-Function Mutations in Central India Population with Atopic Dermatitis and Ichthyosis Vulgaris

Background

A genotype study of filaggrin gene loss-of-function mutations in central India can provide valuable insights into the prevalence and association of these mutations with atopic dermatitis (AD) and ichthyosis vulgaris (IV) in the region. The FLG R501X and 2282del4 are both genetic variants in the human gene called filaggrin gene (FLG), which encodes a protein that plays an important role in the formation and maintenance of the skin barrier. In this study, we determined the FLG R501X and 2282del4 variants association with both AD and IV in Central Indian populations.

Materials and Methods

This case-control study was conducted in the Departments of Dermatology and Molecular and Virology Research and Diagnostic Laboratory at Sri Aurobindo Medical College and Post Graduate Institute, Indore (Madhya Pradesh). The study was approved by the Clinical Research and Ethics Committee. A total of 180 patients aged between 3 months - 60 years who attended the skin outpatient department between March-2021 to June-2022 were recruited in this study. Among them, 60 patients were in AD-group, 60 patients in IV-group, and 60 patients were in the healthy control group. Polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) was used in genotyping for FLG mutations (R501X and 2282del4).

Results

The most common FLG mutations were R501X (31.6% and 23.3%) and 2282del4 (18.3% and 13.3%) in AD and IV patients with heterozygous (AT) genotype, respectively. The combined mutation (FLG R501X and 2282del4) association was 10% and 5% in the AD and IV groups with heterozygous (AT) genotype, respectively, and in all the patients of control group with wild genotype (AA). There were no significant (P = 0.09) associations found with 2282del14 genotype.

Conclusion

The R501X mutation in the gene encoding filaggrin is one of the robust genetic associations of AD and IV. The 2282del4 polymorphism was marginally less as compared to R501X.

Candidate Gene Association Studies in Atopic Dermatitis in Participants of European and Asian Ancestry: A Systematic Review and Meta-Analysis

Atopic dermatitis (AD) has been extensively investigated for genetic associations utilizing both candidate gene approaches and genome-wide scans. Here, we comprehensively evaluated the available literature to determine the association of candidate genes in AD to gain additional insight into the etiopathogenesis of the disease. We systematically screened all studies that explored the association between polymorphisms and AD risks in cases of European and Asian ancestry and synthesized the available evidence through a random-effects meta-analysis. We identified 99 studies that met our inclusion/exclusion criteria that examined 17 candidate loci in Europeans and 14 candidate genes in Asians. We confirmed the significant associations between FLG variants in both European and Asian populations and AD risk, while synthesis of the available data revealed novel loci mapped to IL18 and TGFB1 genes in Europeans and IL12RB1 and MIF in Asians that have not yet been identified by genome-wide association studies. Our findings provide comprehensive evidence for AD risk loci in cases of both European and Asian ancestries, validating previous associations as well as revealing novel loci that could imply previously unexplored biological pathways.

Interleukin-18 and IL-18BP in inflammatory dermatological diseases

Interleukin (IL)-18, an interferon-γ inducer, belongs to the IL-1 family of pleiotropic pro-inflammatory factors, and IL-18 binding protein (IL-18BP) is a native antagonist of IL-18 in vivo, regulating its activity. Moreover, IL-18 exerts an influential function in host innate and adaptive immunity, and IL-18BP has elevated levels of interferon-γ in diverse cells, suggesting that IL-18BP is a negative feedback inhibitor of IL-18-mediated immunity. Similar to IL-1β, the IL-18 cytokine is produced as an indolent precursor that requires further processing into an active cytokine by caspase-1 and mediating downstream signaling pathways through MyD88. IL-18 has been implicated to play a role in psoriasis, atopic dermatitis, rosacea, and bullous pemphigoid in human inflammatory skin diseases. Currently, IL-18BP is less explored in treating inflammatory skin diseases, while IL-18BP is being tested in clinical trials for other diseases. Thereby, IL-18BP is a prospective therapeutic target.

Structure and function of the epidermal barrier in patients with atopic dermatitis - treatment options. Part one

Atopic dermatitis is a chronic, recurrent inflammatory skin disease, which is frequently familial. The main cause of the disease seems to be a defect of the epidermal barrier resulting from a genetic predisposition concerning the epidermis, functioning of the immune system as well as environmental factors (which are not related to the immune system). Genes responsible for encoding protein S100, filaggrin, proteases and their inhibitors are the main genes related to the problem of epidermal barrier dysfunction. There is a close connection between structural and immunological processes. Increased expression of cytokine Th2 profile belongs to the latter category. The objective of the present paper is to describe the influence of aforementioned factors on epidermis structure and dysfunction which leads to clinical symptoms of atopic dermatitis.

Association of Genetic Polymorphisms with Atopic Dermatitis, Clinical Severity and Total IgE: A Replication and Extended Study

Purpose

Atopic dermatitis (AD) is a common and chronic inflammatory skin disease affecting up to 20% of children and 3% of adults worldwide. Although previous reports including genome-wide association study (GWAS) approaches have identified several risk factors that appear to be associated with AD development, replication studies are lacking. In our current study, we replicated the associations between candidate susceptibility loci and AD.

Methods

A total of 885 Korean subjects (425 AD patients and 460 unaffected controls) were genotyped for 17 single nucleotide polymorphisms (SNPs) from previous GWASs and meta-analyses of AD and from immune-related genes.

Results

Several SNPs showed significant associations with AD in the case-control analysis (minimum P=0.005 at rs17389644), suggesting that these polymorphisms may be related to this disease. In addition, several SNPs showed significant signals (minimum P=0.004 at rs6473227) in severe AD compared to unaffected controls. In additional linear regression analysis, a few genotypes appeared to have potential effects on the SCORing AD (SCORAD) values (minimum P=0.003 at rs13361382 on TMEM232) and immunoglobulin E (IgE) levels (minimum P<0.0001 at rs4713555 near HLA-DRB1 and HLA-DQA1) in AD patients.

Conclusions

Our replication and extended study provide additional supporting information on the genetic associations (especially, variants in TMEM232 and nearby to IL21 and HLA-DRB1/HLA-DQA1) related to AD, its clinical severity and IgE involvement.