TNF-α Gene Promoter -238G>A and -308G>A Polymorphisms Alter Risk of Psoriasis Vulgaris: A Meta-Analysis

Tumour necrosis factor α-308 G/a and -238 G/a polymorphisms as predicator of diabetic retinopathy in Egyptians

BACKGROUND

Diabetic retinopathy (DR) is a duration dependent serious micro vascular insult of diabetes mellitus. Inflammation has a critical role in the development of early and late stage of DR. Tumour necrosis factor alpha (TNF-α) is an inflammatory cytokine that promoteup regulation of adhesion molecule expression, leukocyte recruitment and monocyte attraction. TNF-α levels are increased in retinas or vitreous of diabetic animals. A cross-sectional, observational study was performed in a sample of diabetic patients who attend diabetes polyclinic of RIO Hospital, Giza, Egypt, between October 2016 and December 2019. Three hundred diabetic patients were studied (150 males and 150 females). 100 diabetic patients without retinopathy, 100 diabetic patients with proliferative retinopathy (PDR), 100diabetic patients with non-proliferative retinopathy (NPDR), also 100 healthy subjects as a control group All patients and subjects were analysed for serum TNF-α levels by ELISA assay and -308 G/A and -238 G/A polymorphism by using Restriction fragment length polymorphisms.

AIM

Evaluating the role of tumour necrosis factor α and -308 G/A, -238 G/A polymorphisms in the pathogenesis of proliferative diabetic retinopathy among Egyptian patients.

RESULTS

A statistically significant increase in TNF-α levels was detected in diabetic without retinopathy, NPDR and PDR groups compared to control group (p > .001). There were no significant different in Genotype and allele frequencies of the -308G/A, and -238 G/A, polymorphisms in both NPDR and PDR. However, the G/G genotype of the -308 G/A polymorphism occurred more frequently in PDR patients with than NPDR patients (0.74% vs 0.68%).

CONCLUSION

The present study clearly demonstrated increased levels of TNF-α, in diabetic patients with diabetic without retinopathy, NPDR and PDR. Furthermore, this study suggested that TNF-α assay could be used as diagnostic tools to predict the initiation and progression of diabetic retinopathy. They could serve as biomarkers not only for an early detection of the disease, but also to monitor the effects of therapy. Also, the G/G genotype of the -308 G/A polymorphism and the G allele of TNF-α gene were more frequent in PDR patients than with NPDR.

Association between tumor necrosis factor-alpha polymorphisms (rs361525, rs1800629, rs1799724, 1800630, and rs1799964) and risk of psoriasis in studies following Hardy-Weinberg equilibrium: A systematic review and meta-analysis

Objective

Psoriasis is a disease with an immunogenetic background in which cytokines have important effects on its prevalence and incidence. The present meta-analysis evaluated the relationship between tumor necrosis factor-alpha (TNF-α) polymorphisms (rs361525, rs1800629, rs1799724, 1800630, and rs1799964) and psoriasis risk in studies following Hardy-Weinberg equilibrium (HWE).

Materials and methods

Four databases were searched to retrieve relevant studies reporting the distributions of TNF-α polymorphisms in psoriasis cases compared to controls. The effect sizes were the 95% confidence intervals (CIs) and odds ratios (ORs). Subgroup analysis, sensitivity analyses, publication bias, trial sequential analysis (TSA), and meta-regression were performed on the initial pooled results of TNF-α polymorphisms.

Results

Thirty-six articles with 71 studies were included in the meta-analysis (twenty-six: rs361525, twenty-seven: rs1800629, nine: rs1799724, four: 1800630, and five: rs1799964). The pooled ORs for -238 G/A rs361525 polymorphism were 2.33 (p < 0.00001), 2.79 (p < 0.0001), 2.35 (p < 0.00001), 2.44 (p < 0.00001), and 2.45 (p < 0.00001), as well as 1.57 (p < 0.00001), 1.98 (p = 0.01), 1.61 (p < 0.00001), 1.64 (p < 0.00001), and 1.79 (p < 0.00001) for -857 C/T rs1799724 polymorphism in allelic, homozygous, heterozygous, dominant, and recessive models, respectively. Ethnicity, psoriasis type, and sample size affected the pooled results of rs361525, rs1800629, and rs1799724 polymorphisms. Based on TSA, there were just sufficient cases for -238 G/A rs361525 polymorphism in five genetic models and -857C/T rs1799724 polymorphism in allelic, heterozygous, and dominant models.

Conclusions

The A allele and GA and GG genotypes of -238 G/A rs361525 polymorphism and T allele, TT and CT genotypes of -857C/T rs1799724 polymorphism were related to increased risks in psoriasis cases. Well-designed studies (with no deviation from HWE in controls) with more cases are recommended in the future.

TNFα gene -238G>A polymorphism is associated with psoriasis patients

BACKGROUND

Tumor Necrosis Factor α (TNFα) is a protein that plays a key role in the pathophysiology of chronic inflammatory disorders like psoriasis.

AIMS

The goal of this study was to see if the TNFα gene -238G>A polymorphism was linked to psoriasis susceptibility.

METHODS

This study comprised ninety psoriasis patients and ninety healthy controls. For the TNFa gene -238G>A polymorphism, genomic DNA was extracted and genotyped using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) studies.

RESULTS

Psoriasis patients had higher frequencies of the A allele and the AA genotype than the control group, and psoriasis was linked to the AA genotype (OR = 4.25, 95% CI = 1.37-13.1, p = 0.008) and the A allele (OR = 1.55, 95% CI = 1.01-2.34, p = 0.04). Patients with a family history of psoriasis showed an increase in the frequency of the AA genotype compared to GG and GA genotypes (respectively, 46.7%, 36.7%, and 16.7%, p = 0.003). Furthermore, psoriasis patients with the AA genotype were discovered more commonly among those under 30 years old and male patients than those with the GG and GA genotypes, but the differences were not statistically significant.

CONCLUSION

The TNFa gene -238G>A polymorphism has been related to an increased incidence of psoriasis.

Psoriasis: An Immunogenetic Perspective

Psoriasis is an erythematous-squamous dermatosis with a polygenic inheritance history. Both environmental and genetic factors play a role in the etiology of the disease. Over the past two decades, numerous linkage analyzes and genome-wide association studies have been conducted to investigate the role of genetic variation in disease pathogenesis and progression. To date, >70 psoriasis susceptibility loci have been identified, including HLA-Cw6, IL12B, IL23R, and LCE3B/3C. Some genetic markers are used in clinical diagnosis, prognosis, treatment, and personalized new drug development that can further explain the pathogenesis of psoriasis. This review summarizes the immunological mechanisms involved in the etiopathogenesis of psoriasis and recent advances in susceptibility genes and highlights new potential targets for therapeutic intervention.

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.

Tumor necrosis factor-α gene promoter -308 and -238 polymorphisms and its serum level in psoriasis

BACKGROUND

Psoriasis is a chronic, immune-mediated, inflammatory skin disease affecting genetically predisposed individuals and requiring long-term treatment. The etiology of psoriasis is not fully understood. This article aimed to determine association between genetic polymorphisms in tumor necrosis factor-α (TNF -α) promoter -308 (rs1800629) and -238 (rs 361,525) and its serum level in psoriasis patients.

METHODS

The study was conducted on 70 patients with psoriasis and 70 age and sex-matched, healthy individuals. All patients were subjected to history taking and complete medical examination. The polymorphisms of TNF -α promoter gene -308 (rs1800629) and -238 (rs 361,525) were detected by real time PCR and Serum levels of TNF -α were measured by ELISA technique.

RESULTS

AG polymorphism and A allele of TNF-α -238 G/A (rs 361,525) were significantly more in patients than controls, whereas AG polymorphism and A allele of TNF-α -308 G/A (rs1800629) were significantly more in controls than patients. There were significant high levels of TNF-α in serum of patients in comparison to controls.

CONCLUSIONS

The AG polymorphism and A allele of TNF-α -238G/A (rs 361,525) may act as a risk factor for occurrence of psoriasis, whereas AG polymorphism and A allele of TNF-α -308G/A (rs1800629) may have protective role. There is pivotal role of TNF-α as a pro-inflammatory mediator in pathogenesis of psoriasis.

Tumor Necrosis Factor-α 308 G/A polymorphism and psoriasis risk: A pooled analysis in different populations

More and more researches have been carried out on the association between the tumor necrosis factor-α (TNF-α) 308 G/A polymorphism and psoriasis, however, controversial results have emerged in these studies. This meta-analysis was performed to quantitatively clarify the relationship between TNF-α 308 G/A polymorphism and the risk of psoriasis in different populations. Databases of PubMed, Springer Link, Ovid, Chinese Wanfang Data Bases, Chinese National Knowledge Infrastructure and Chinese Biology Medicine were investigated until June 2019. The association between the TNF-α 308 G/A polymorphism and psoriasis was evaluated by calculating the pooled odds ratio (OR) and 95% confidence intervals (CIs). A total of 26 studies including 3657 patients and 3197 controls were screened out. In the overall population, the pooled results showed a reduced psoriasis risk with the TNF-α 308 G/A polymorphism (A vs G: OR = 0.77, 95% CI = 0.67-0.89; AA+GA vs GG: OR = 0.72, 95% CI = 0.61-0.86). In the subgroup analysis stratified by geographic locations, the TNF-α 308 G/A polymorphism was significantly associated with a reduced risk of psoriasis in Germany (A vs G: OR = 0.67, 95% CI = 0.57-0.78; AA+GA vs GG: OR = 0.62, 95% CI = 0.52-0.75), as well as in China (AA+GA vs GG: OR = 0.71, 95% CI = 0.52-0.98) and Poland (A vs G: OR = 0.61, 95% CI = 0.38-0.97; AA+GA vs GG: OR = 0.59, 95% CI = 0.35-0.99). This study indicated a significantly reduced psoriasis risk associated with the TNF-α 308 G/A polymorphism in Germans, as well as in Chinese and Poles populations compared with other populations. Ethnicity and geographic locations probably play a pivotal role in the genetic association of psoriasis.

Cytokines in psoriasis

Psoriasis is chronic, immune-mediated, inflammatory disease with a multifactorial etiology that affects the skin tissue and causes the appearance of dry and scaly lesions of anywhere on the body. The study of the pathophysiology of psoriasis reveals a network of immune cells that, together with their cytokines, initiates a chronic inflammatory response. Previously attributed to T helper (Th)1 cytokines, currently the Th17 cytokine family is the major effector in the pathogenesis of psoriatic disease and strongly influences the inflammatory pattern established during the disease activity. In addition, the vast network of cells that orchestrates the pathophysiology makes psoriasis complex to study. Along with this, variations in genes that code the cytokines make psoriasis more clinically heterogeneous and present a challenge for the development of drugs that can be used in the treatment of the patients with this disease. Therefore, it is important to clarify the mechanisms by which the cytokines are involved in the pathophysiology of psoriasis and how this knowledge is translated to the medical practice.

Association Analysis of Tumor Necrosis Factor Alpha Promoter Polymorphisms and Vitiligo Susceptibility in South Indian Tamils

Tumor necrosis factor alpha (TNF-α) has been associated with the pathogenesis of several autoimmune diseases. Also, various studies in different ethnics showed an association between TNF-α gene polymorphisms and susceptibility to vitiligo. The paucity of genetic data led us to undertake this study to evaluate the association of five TNF-α SNPs (rs1799964, rs1800630, rs1799724, rs1800629, and rs361525) with the development of vitiligo in South Indian Tamils. A total of 264 vitiligo patients and 264 healthy controls were recruited and TNF-α genotyping was performed using amplification-refractory mutation system polymerase chain reaction and TaqMan allele discrimination assay. Circulatory TNF-α levels were measured by enzyme-linked immunosorbent assay. We observed that a single polymorphic allele A in the promoter region -308 (rs1800629) conferred significant risk to develop vitiligo (p = 0.0002, OR = 1.70, 95% CI = 1.28-2.25), whereas the other polymorphisms failed to contribute to disease risk (p > 0.05). From the constructed haplotypes, TCCAG was found to be a significant risk factor for vitiligo (p < 0.05). Also, a strong linkage disequilibrium was observed between the following SNPs: (1) rs1799964 and rs1800629 (2) rs1800630 and rs1799724 (D' = 0.90). Analysis of the influence of genotype on phenotypes revealed that the A allele of rs361525 was a risk factor for vitiligo in females (p = 0.04, OR = 0.45, 95% CI = 0.21-0.95), whilst the rs1800629 allele conferred protection against early disease onset (p < 0.05). A statistically significant difference in plasma TNF-α levels was found between cases and controls (p < 0.05). The TNF-α -308A allele and TCCAG haplotype were identified as genetic risk factors for vitiligo susceptibility in South Indian Tamils.

Genetic polymorphism in psoriasis and its meaning for the treatment efficacy in the future

The concept of personalized medicine is a new individualized approach which helps application of the targeted therapy. In fact, tailored medicine is mostly present in the field of life-threatening diseases such as oncology. However, skin diseases as such might be regarded as a potential area of implementation of this approach in the future. Stratified medicine in polygenetic and heterogeneous diseases, such as psoriasis, is more complex. Rapid development of science and novel molecular techniques led to better understanding of molecular pathogenetic pathways of many diseases including psoriasis. Identification of the particular immunopathogenetic pathways led to further development of targeted therapies such as biologic drugs. Actually the goal of individualized therapy is to determine the identical homogenous subgroups of patients, according to a biomarker, in which the response to that therapy will be the best and will carry the lowest risk of side effects. This review attempts to analyze the associations between polymorphisms of certain genes and the increased risk of developing psoriasis or psoriatic arthritis. The review of literature has also included the studies investigating the associations between gene polymorphisms and response to biologic therapy in psoriasis and psoriatic arthritis patients.

Profile of Tumour Necrosis Factor Alpha -308 G/A Gene Polymorphism in Psoriatic Patients in Karnataka, India

INTRODUCTION

Tumour necrosis factor-alpha (TNFα) gene -308G/A polymorphism (rs1800629) are associated with psoriasis in several populations worldwide. Presently, there is no literature on the status of this polymorphism in the South Indian population.

AIM

To determine the profile of TNFα -308G/A polymorphism among psoriatic patients.

MATERIALS AND METHODS

This case-control study involved 74 patients with Psoriasis Vulgaris (PsV) and 74 age and gender matched healthy individuals. Patients were recruited from the Department of Dermatology of R.L. Jalappa Hospital and Research Center, Tamaka, Kolar, Karnataka, India, from March 2014 to March 2016. TNFα -308G/A polymorphism was genotyped by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method.

RESULTS

The frequency of TNFα -308A allele 7.4% among psoriatic and 8.8% among non-psoriatic individuals. The difference was not statistically significant (p=0.82).

CONCLUSION

Our results indicate that TNFα gene -308G/A polymorphism is not a significant marker for the risk of developing PsV among South Indian (Karnataka) psoriatic patients.

Tumor necrosis factor alpha gene promoter -238G/A polymorphism increases the risk of psoriasis vulgaris in Indian patients

BACKGROUND

Tumor necrosis factor alpha (TNFα) gene -238G/A polymorphism (rs361525) is associated with psoriasis in several populations worldwide. To the best of our knowledge, there is no information about this polymorphism in Indian psoriatic patients. This study was undertaken to fill the gap in knowledge.

METHODS

This case-control study involved 72 patients with psoriasis vulgaris (PsV) and 72 age and gender matched healthy individuals. TNFα -238G/A polymorphism was genotyped by PCR-RFLP method.

RESULTS

TNFα -238A allele was 5 times commoner in PsV patients than in the control group (P = 4.1 × 10^-7 ; odds ratio [OR] = 6.5 [0.95 CI: 2.9-14.6]). Distribution of the genotypes in the two groups showed statistically significant difference in dominant genetic model (P = 2.3 × 10^-7 ) and not in recessive genetic model (P = 2.5 × 10^-1 ). Odds ratio for the occurrence of -238A genotype in PsV patients was 8.8 (0.95 CI: 3.5-20.2). The association showed no major difference when PsV patients were subgrouped into type I and type II categories and tested separately. Subgroup analysis on the basis of disease severity showed higher association with the moderate-severe subgroup (P = 2.4 × 10^-9 , OR 15.4 [0.95 CI: 5.8-41.0]) than with mild subgroup (P = 1.3 × 10^-2 , OR 3.8 [0.95 CI: 1.3-10.9]).

CONCLUSIONS

Our results indicate that TNFα gene -238G/A polymorphism increases the risk of developing psoriasis vulgaris among Indians. Also, the data show that severity and not the type affects the strength of association in this population.

Is there any increased risk of hypertension, diabetes and cardiac diseases in psoriatic patients with TNF-α G238A and G308A polymorphism?

Introduction

Psoriasis is regarded as a complex autoimmune disease with strong genetic background. Psoriatic patients suffer from many comorbidities including hypertension, diabetes and cardiovascular diseases. Cytokines such as tumor necrosis factor α (TNF-α) may be a key player that triggers psoriasis and diabetes, hypertension and cardiac disease at the same time.

Aim

To evaluate genetic variations in the TNF-α region and its association with psoriasis and related comorbidities.

Material and methods

The study covered 129 psoriasis patients with three main subgroups with coronary artery disease (n = 41), hypertension (n = 35), and diabetes (n = 21). DNA samples were genotyped for TNF-α G308A and G238A polymorphisms by real-time polymerase chain reaction melting-curve analysis and results were compared statistically.

Results

Psoriatic patients with both TNF-α-298 and TNF-α-308 polymorphisms showed no statistically significant increase in the risk of hypertension (OR = 0.425, χ² = 1.76, p = 0.18 and OR = 1.87, χ² = 1.33, p = 0.25), coronary artery disease (OR = 1.97, χ² = 1.91, p = 0.17 and OR = 2.63, χ² = 1.35, p = 0.25), or diabetes (OR = 1.35, χ² = 0.24, p = 0.62 and OR = 1.53, χ² = 0.24, p = 0.62).

Conclusions

The current preliminary results suggested that there was no correlation between TNF-α promoter polymorphism and diabetes, hypertension and cardiac disease among psoriatic patients in the Turkish population.

The Risk of Chronic Pancreatitis in Patients with Psoriasis: A Population-Based Cohort Study

Background

Psoriasis is a chronic systemic inflammatory disorder, and studies have revealed its association with a variety of comorbidities. However, the risk of chronic pancreatitis (CP) in psoriasis has not been studied. This study aimed to investigate the risk of CP among patients with psoriasis.

Methods

Using the Taiwan National Health Insurance Research Database, this population-based cohort study enrolled 48430 patients with psoriasis and 193720 subjects without psoriasis. Stratified Cox proportional hazards models were used to compare the risks of CP between the patients with and without psoriasis.

Results

The incidence of CP was 0.61 per 1000 person-years in patients with psoriasis and 0.34 per 1000 person-years in controls during a mean 6.6-year follow-up period. Before adjustment, patients with psoriasis had a significantly higher risk of CP (crude hazard ratio (HR) = 1.81; 95% confidence interval (CI) = 1.53–2.15), and the risk remained significantly higher after adjustments for gender, age group, medications, and comorbidities (adjusted HR (aHR) = 1.76; 95% CI = 1.47–2.10). All psoriasis patient subgroups other than those with arthritis, including those with mild and severe psoriasis and those without arthritis, had significantly increased aHRs for CP, and the risk increased with increasing psoriasis severity. Psoriasis patients taking nonsteroidal anti-inflammatory drugs (aHR = 0.33; 95% CI = 0.22–0.49) and methotrexate (aHR = 0.28; 95% CI = 0.12–0.64) had a lower risk of developing CP after adjustments.

Conclusions

Psoriasis is associated with a significantly increased risk of CP. The results of our study call for more research to provide additional insight into the relationship between psoriasis and CP.

HLA-C and TNF gene polymorphisms are associated with psoriasis in Brazilian patients

BACKGROUND

Polymorphisms at the human leukocyte antigens (HLA-C) and tumor necrosis factor (TNF) genes have been associated with susceptibility to psoriasis in several worldwide populations. In this study, HLA-C and TNF (-238/-308) polymorphisms were performed in 125 Brazilian patients and 202 healthy controls.

METHODS

HLA-C and TNF promoter region alleles were typed by polymerase chain reaction using sequence-specific primer-polymerase chain reaction.

RESULTS

The presence of HLA-C*06 was associated with psoriasis onset, particularly in younger patients, being more frequent for patients with disease onset before the age of 20 years (P = 0.03), 25 years (P = 0.01), or 30 years (P = 0.03). No association between HLA-C*06 and psoriasis was observed for patients older than 35 years. Susceptibility to psoriatic arthritis was associated with the TNF -238 G/A genotype (P = 0.02). The TNF -308A allele was overrepresented in patients (P = 0.0061), and the TNF -308 G/A genotype was increased in generalized forms (erythrodermic and generalized pustular psoriasis) compared to plaque psoriasis (P < 0.001). The TNF -238A/HLA-C*06 haplotype was overrepresented in patients (P = 0.025), while the TNF -238G/HLA-C*15 haplotype was increased in controls (P = 0.037).

CONCLUSIONS

The strong association of HLA-C*06 allele with disease susceptibility, particularly in early onset psoriasis, indicates that younger ages could be considered to stratify psoriasis into early and late types. TNF -308 polymorphisms can be associated with psoriasis susceptibility and severity. Potential genetic markers of psoriasis in populations with a complex mixture of ethnicities should be investigated.

A Comprehensive Study of Tumor Necrosis Factor-Alpha Genetic Polymorphisms, its Expression in Skin and Relation to Histopathological Features in Psoriasis

BACKGROUND

Tumor necrosis factor-alpha (TNFα) is an important inflammatory mediator in psoriasis and several genetic polymorphisms of this cytokine have been reported. Majority of studies have focused on the increased G- A polymorphism at the -308 position in psoriasis. There has been no comprehensive study evaluating the genetic polymorphisms, TNFα expression in the skin and histopathology. We are undertaking this study to outline TNFα genetic polymorphisms, its skin expression and histopathological correlation to help determine its role at the genetic and protein level.

MATERIALS AND METHODS

112 patients of psoriasis and 243 healthy controls were included in this prospective study. 5 ml of peripheral blood was collected to study the TNFα genetic polymorphisms by polymerase chain reaction and restriction fragment length polymorphism analysis. Histopathological analysis of biopsies from the 112 patients were done using visual analogue scale and correlated with the findings. 61 of these cases were analyzed for TNFα expression by immunohistochemistry. The results of study were statistically analyzed using SPSS 13.0 statistical package program.

RESULTS

A strong association of TNFα -308 G/A polymorphism in psoriasis cases was detected. The A allele of the TNFα -308 G/A polymorphism occurs rarely in the Indian population, however there is an over representation of this allele in psoriatic patients. There was no association seen between TNFα genotype and histopathological severity of psoriasis.

CONCLUSION

The study emphasized the central role of TNFα in the pathogenesis of psoriasis. TNFα genotyping may be helpful in identifying subjects in whom anti-TNFα therapeutic strategies may be tried.

TNF, IL12B, and IFNG Gene Polymorphisms in Serbian Patients with Psoriasis

Background

Psoriasis is a common chronic inflammatory skin disease with a strong genetic basis. Cytokines such as tumor necrosis factor alpha (TNF-α), interleukins (ILs) such are IL-12 and IL-23, and interferon gamma (IFN-γ) are released from various inflammatory and resident cells, and have been implicated in the initiation/maintenance of inflammation. Certain alleles of the aforementioned cytokines may be associated with disease susceptibility/severity.

Objective

To investigate the association of three common functional gene polymorphisms, namely TNF -308 G/A (rs1800629), IL12B (encoding the p40 subunit of IL-12/23) +1188 A/C (rs3212227), and IFNG +874 T/A (rs2430561) with psoriasis development and severity in Serbian patients.

Methods

We genotyped 130 patients with psoriasis (26 of whom also had psoriatic arthritis) and 259 controls; rs1800629 and rs3212227, and rs2430561, by real-time PCR assay.

Results

The TNF GG genotype was detected at a higher frequency in patients with psoriasis compared to control subjects (OR, 1.420; 95% CI, 0.870~2.403) without statistical significance (p=0.191). Lack of the TNF G allele was associated with lower psoriasis severity (p=0.007). The IL12B AC genotype was underrepresented in the patients with psoriatic arthritis compared to healthy subjects (OR, 0.308; 95% CI, 0.090~1.057; p=0.049). The distribution of the rs2430561 allele and genotype frequencies was similar between patients with psoriasis and controls.

Conclusion

Our study demonstrates an effect of the rs1800629 on psoriasis severity, and a marginal impact of the rs3212227 on susceptibility to psoriatic arthritis. Collectively, our results obtained in a Serbian cohort expand current knowledge regarding individual predisposition to psoriatic disease.

Four polymorphisms of VEGF (+405C>G, -460T>C, -2578C>A, and -1154G>A) in susceptibility to psoriasis: a meta-analysis

The contribution of genetic polymorphisms in the vascular endothelial growth factor (VEGF) gene to psoriasis risk is a controversial topic. The aim of this meta-analysis was to investigate large-scale evidence to determine the degree to which four common VEGF polymorphisms (+405C>G [dbSNP: rs2010963], -460T>C [dbSNP: rs833061], -2578C>A [dbSNP: rs699947], and -1154G>A [dbSNP: rs1570360]) are associated with susceptibility to psoriasis. A literature search of PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure, and Chinese Biomedical Literature Database was conducted to identify all eligible studies published before September 15, 2013. The principal outcome measure for evaluating the strength of the association was crude odds ratios (ORs) along with their corresponding 95% confidence intervals (95% CIs). Two thousand five hundred thirty-one patients and 2670 controls from nine case-control studies detailing a possible association between the VEGF genotypes and psoriasis risk were selected. Our meta-analysis provides evidence that two independent alleles +405G and -460C may be a protective factor for psoriasis in Asians, whereas the -1154A allele had a slight but statistically significant preventive effect on the development of psoriasis in Caucasians. The -2578C>A polymorphism, however, did not correlate with any significant difference between patients and healthy controls, even when the groups were stratified by ethnicity. Results from the meta-analysis do support the hypothesis that single-nucleotide polymorphism markers at +405C>G, -460C>T, and -1154G>A of the VEGF gene may serve as biological markers of psoriasis. Future studies should investigate interactions among multiple genotypes and environmental exposures to identify the role of proangiogenic markers in psoriasis and to delineate the underlying mechanisms of psoriasis.

Polymorphisms in the TNF-α and IL-10 gene promoters and risk of psoriasis and correlation with disease severity

Several cytokines were assumed to play an essential role in the induction and the pathogenesis of psoriasis. The aim of this work was to investigate the role of TNF-α-308 and IL-10-1082 polymorphisms and their serum levels in the pathogenesis of psoriasis and determine their relation to disease severity. 110 Psoriasis patients and 120 healthy volunteers were genotyped for TNF-α-308 and IL-10-1082 polymorphism by polymerase chain reaction. Serum level of TNF-α and IL-10 were measured by ELISA. Our study demonstrated an association of IL-10-1082 polymorphism and psoriasis and between TNF α-308 polymorphism and psoriasis disease and severity. Serum TNF α increased in patients, while serum IL-10 decreased in patients with significant correlation between serum TNF-α and psoriasis severity. These results indicated that TNF-α-308 and IL-10-1082 polymorphisms imparted significant risk towards the development of psoriasis.

[Psoriasis: physiopathology and immunogenetics]

Psoriasis is a multifactorial disease that involves genetic, immunological and environmental factors. During the last decade, several studies by genome scan on families or cases/controls helped to highlight more than ten loci "PSORS" located on different chromosomes and containing several candidate genes. Psoriasis appears as a genetic disease that follows the mixed model with the involvement of a major gene (PSORS1) and a set of minor genes with a variable penetrance depending on the locus. Genetic data have focused on the involvement of the immune system in the pathogenesis of psoriasis. It is now accepted that psoriasis is an immunological disease involving the response profiles TH1 and TH17. Much remains to be done to better elucidate the mechanisms involved in the genesis of psoriatic lesions to find new therapeutic targets.

Genetics of psoriasis and pharmacogenetics of biological drugs

Psoriasis is a chronic inflammatory disease of the skin. The causes of psoriasis are unknown, although family and twin studies have shown genetic factors to play a key role in its development. The many genes associated with psoriasis and the immune response include TNFα, IL23, and IL12. Advances in knowledge of the pathogenesis of psoriasis have enabled the development of new drugs that target cytokines (e.g., etanercept, adalimumab, and infliximab, which target TNFα, and ustekinumab, which targets the p40 subunit of IL23 and IL12). These drugs have improved the safety and efficacy of treatment in comparison with previous therapies. However, not all patients respond equally to treatment, possibly owing to interindividual genetic variability. In this review, we describe the genes associated with psoriasis and the immune response, the biological drugs used to treat chronic severe plaque psoriasis, new drugs in phase II and III trials, and current knowledge on the implications of pharmacogenomics in predicting response to these treatments.

Single nucleotide polymorphisms in the tumor necrosis factor-alpha gene promoter region alter the risk of psoriasis vulgaris and psoriatic arthritis: a meta-analysis

BACKGROUND

It has been confirmed that tumor necrosis factor-alpha (TNFα), a macrophage-derived pro-inflammatory cytokine, plays an important role in the pathogenesis of psoriasis vulgaris and psoriatic arthritis (PsV&PsA). In contrast, the reported association of TNFα gene promoter region single nucleotide polymorphisms (SNPs) and PsV&PsA has remained controversial. Accordingly, we performed a meta-analysis to provide new evidence that SNPs in the TNFα gene promoter region alter not only the risk of psoriasis vulgaris (PsV) or psoriatic arthritis (PsA) but also of PsV&PsA.

METHODS

Interrelated literature dated to October 2012 was acquired from the PubMed, ScienceDirect, and SpringerLink databases. The number of the genotypes and/or alleles for the TNFα promoter in the PsV and PsA and control subjects was obtained. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to calculate the risk of PsV and/or PsA with TNFα promoter SNPs.

RESULTS

A total of 26 papers of 2159 for PsV (2129 normal controls) and 2360 for PsA (2997 normal controls) were included in our meta-analysis. The results showed that the variant genotype and allele of TNFα -308A/G was protective in pooled groups of patients with PsV&PsA (OR = 0.682, 0.750; 95% CI, 0.596-0.779, 0.653-0.861). However, the variant genotypes and alleles of TNFα -238A/G and -857T/C had an increased risk of PsV&PsA (OR = 2.493, 2.228, 1.536, 1.486, 95% CI, 1.777-3.498, 1.628-3.049, 1.336-1.767, 1.309-1.685). Moreover, the meta-analysis revealed a significant association between TNFα -238A/G and -857T/C polymorphism and PsA susceptibility (OR = 2.242, 2.052, 1.419, 1.465; 95% CI, 1.710-2.941, 1.614-2.610, 1.214-1.658, 1.277-1.681). In contrast, the variant genotypes and alleles of TNFα -308A/G proved to be protective against PsV (OR = 0.574, 0.650, 95% CI, 0.478-0.690, 0.556-0.759), whereas TNFα -238A/G was found to have a risk association (OR = 2.636, 2.223, 95% CI, 1.523-4.561, 1.317-3.751).

CONCLUSIONS

SNPs in the TNFα gene promoter region alter the risk of PsV and/or PsA.

Increased Tumor Necrosis Factor (TNF)-α and its promoter polymorphisms correlate with disease progression and higher susceptibility towards vitiligo

Tumor Necrosis Factor (TNF)-α, is a paracrine inhibitor of melanocytes, which plays a critical role in the pathogenesis of several autoimmune diseases including vitiligo, as abnormal immune responses have frequently been observed in vitiligo patients. Moreover, vitiligo patients show higher lesion levels of TNF-α. Genetic polymorphisms in the promoter region of TNF-α are involved in the regulation of its expression. The present study explores TNF-α promoter polymorphisms and correlates them with TNF-α transcript and protein levels in vitiligo patients and controls of Gujarat along with its effect on disease onset and progression. PCR-RFLP technique was used for genotyping of these polymorphisms in 977 vitiligo patients and 990 controls. TNF-α transcript and protein levels were measured by Real time PCR and ELISA respectively. The genotype and allele frequencies for the investigated polymorphisms were significantly associated with vitiligo patients. The study revealed significant increase in TNF-α transcript and protein levels in vitiligo patients compared to controls. In particular, haplotypes: AATCC, AACCT, AGTCT, GATCT, GATCC and AGCCT were found to increase the TNF-α levels in vitiligo patients. Analysis of TNF-α levels based on the gender and disease progression suggests that female patients and patients with active vitiligo had higher levels of TNF-α. Also, the TNF-α levels were high in patients with generalized vitiligo as compared to localized vitiligo. Age of onset analysis of the disease suggests that the haplotypes: AACAT, AACCT, AATCC and AATCT had a profound effect in the early onset of the disease. Moreover, the analysis suggests that female patients had an early onset of vitiligo. Overall, our results suggest that TNF-α promoter polymorphisms may be genetic risk factors for susceptibility and progression of the disease. The up-regulation of TNF-α transcript and protein levels in individuals with susceptible haplotypes advocates the crucial role of TNF-α in autoimmune pathogenesis of vitiligo.

Lack of association between TNF-α promoter polymorphisms and multiple myeloma: a meta-analysis

Results of available literatures, which concerned the association between TNF-α promoter -238/-308 gene polymorphisms and multiple myeloma (MM), are of great controversy. A review was performed in studies reporting on the association between them. Odds ratios (ORs) with 95% confidence interval (CI) were used to evaluate the association. The pooled ORs indicated that there was no association between TNF-α -238/-308 polymorphisms and MM susceptibility in overall population. Sub-group analysis also confirmed that no evidence supported the relevance of TNF-α promoter -238/-308 gene polymorphisms with MM. Studies with large sample size and multi-ethnics may be needed to further explore the association between them.

Lack of association between TNF-α gene promoter polymorphisms and pancreatitis: a meta-analysis

BACKGROUND/AIMS

Tumor necrosis factor alpha (TNF-α) is a major proinflammatory cytokine involved in the etiology of pancreatitis. The association between pancreatitis and the -308G>A and -238G>A polymorphisms in TNF-α gene has been analyzed in several studies, but results have been inconsistent. The purpose of this study was to integrate previous findings and explore whether these polymorphisms are associated with susceptibility and severity to pancreatitis.

METHODS

A meta-analysis was performed by searching PubMed, Cochrane Library, and ScienceDirect databases. Data were extracted using predefined form and odds ratios (OR) with 95% confidence intervals (CI) were calculated.

RESULTS

Our meta-analysis of a total of 1569 pancreatitis cases and 1330 control subjects from twelve published case-control studies for the -308G>A polymorphism (OR 0.98; 95% CI 0.83-1.17), and of 480 cases and 302 controls from four studies for the -238G>A polymorphism (OR 0.92; 95% CI 0.58-1.47) did not show any significant associations of susceptibility to pancreatitis with the variant GA+AA genotypes compared with the GG genotype. An association between severity of acute pancreatitis and -308G>A polymorphism was not found either (OR 0.93; 95% CI 0.69-1.24).

CONCLUSION

Polymorphisms in two sites of TNF-α gene promoter do not alter the risk of pancreatitis.

Tumour necrosis factor gene polymorphism and disease prevalence

Tumour necrosis factor (TNF), an important proinflammatory cytokine, plays a role in the regulation of cell differentiation, proliferation and death, as well as in inflammation, innate and adaptive immune responses, and also implicated in a wide variety of human diseases. The presence of DNA sequence variations in regulatory region might interfere with transcription of TNF gene, influencing the circulating level of TNF and thus increases the susceptibility to human diseases (infectious, cancer, autoimmune, neurodegenerative and other diseases). In this review, we have comprehensively analysed various published case-control studies of different types of human diseases, in which TNF gene polymorphism played a role, and computationally predicted several single nucleotide polymorphisms (SNPs) lie in transcription factor-binding sites (TFBS) of transcription factors (TFs). It has been observed that TNF enhancer polymorphism is implicated in several diseases, and TNF rs1800629 and rs361525 SNPs are the most important in human disease susceptibility as these might influence the transcription of TNF gene. Thirty-two SNPs lies in TFBS of 20 TFs have been detected in the TNF upstream region. It has been found that TNF enhancer polymorphism influences the serum level of TNF in different human diseases and thus affects the susceptibility to diseases. The presence of DNA sequence variation in TNF gene causes the modification of transcriptional regulation and thus responsible for association of susceptibility/resistance with human diseases.

[Study of genetic polymorphisms in the tumor necrosis factor α promoter region in Spanish patients with psoriasis]

BACKGROUND

Several studies have reported an association between tumor necrosis factor α (TNF-α) polymorphisms and inflammatory diseases such as psoriasis vulgaris and psoriatic arthritis, although the results vary according to the population studied. No studies have been performed in the Spanish population.

OBJECTIVE

To analyze the polymorphisms of the promoter region of the TNF-α gene in patients with moderate to severe psorasis and to identify potential differences in genotype compared to a group of healthy volunteers.

MATERIAL AND METHODS

Eighty-nine patients with moderate to severe psoriasis and 76 healthy controls with no personal or family history of psoriasis were selected. Polymorphisms of the TNF-α promoter region of both groups were genotyped.

RESULTS

We observed a higher prevalence of the genotype with both wild-type alleles at positions -238 (GG genotype, 86.5% vs 70.4%, respectively) and -1031 (TT genotype, 80.2% vs 45.8%, respectively) in patients compared to the healthy control group. The differences at positions -308 and -857 were not significant.

CONCLUSION

There are differences in polymorphisms at positions -238 and -1031 in patients with moderate to severe psoriasis compared to healthy volunteers. This observation provides further support for the importance of the part that TNF-α plays in the pathophysiology of this disease.

Genetic profile of psoriasis patients

The article systematizes information about genetic polymorphisms associated with the risk of psoriasis and psoriatic arthritis development. Gene variants that are potentially essential for their inclusion in genetic tests were sampled taking into consideration polymorphism localization. The presented data are sufficient to prepare the genetic profile of psoriatic patients, forecast the clinical course of the disease and potential efficacy of treatment, and calculate the risk of the disease development in the patients relatives.

How genetic variation affects patient response and outcome to therapy for psoriasis

Psoriasis is a prevalent chronic inflammatory condition that affects the skin. There are many treatments available for psoriasis but they are not universally effective and some have associated toxicities. Pharmacogenetics and pharmacogenomics explore the relationship between individual genetic variation and drug effect to allow targeted 'personalized' therapy for patients. There has been very limited pharmacogenetic research regarding psoriasis, with most limited to small retrospective case-control studies looking at single-nucleotide polymorphisms in candidate genes involved in drug pharmacokinetics. We review the pharmacogenetic investigation of treatments for psoriasis to date, including emerging pharmacogenomic studies. In addition, we discuss how such genetic data could be incorporated into routine clinical practice and future areas for development in this field.

Genetics of psoriasis and psoriatic arthritis

It is well established that psoriasis and psoriatic arthritis (PsA) have a strong genetic component. Recent advances in genetics have confirmed previous associations and new loci have been discovered. However, these loci do not fully account for the high heritability of psoriasis and PsA and therefore many genetic as well as environmental factors remain to be identified. This paper reviews the current status of genetic studies in psoriasis and PsA.

Role of the TNF-α promoter polymorphisms for development of multiple myeloma and clinical outcome in thalidomide plus dexamethasone

The role of TNF-α promoter polymorphisms in the development of multiple myeloma (MM) were tested in 210 patients and 218 healthy individuals and their impact on the clinical outcome were evaluated in 98 patients treated with thalidomide and dexamethasone (Thal+Dex) regimen. MM patients carrying the GA genotype (P=0.01) or GA+AA genotypes (P=0.02) at the TNF-α -308 polymorphism were associated with a reduced risk for MM. The TNF-α -238 GA+AA genotypes were associated with a significant enhancement in the progression-free survival (PFS) (P=0.009) and a better overall survival (OS) (P=0.088).

Multiple Loci within the major histocompatibility complex confer risk of psoriasis

Psoriasis is a common inflammatory skin disease characterized by thickened scaly red plaques. Previously we have performed a genome-wide association study (GWAS) on psoriasis with 1,359 cases and 1,400 controls, which were genotyped for 447,249 SNPs. The most significant finding was for SNP rs12191877, which is in tight linkage disequilibrium with HLA-Cw*0602, the consensus risk allele for psoriasis. However, it is not known whether there are other psoriasis loci within the MHC in addition to HLA-C. In the present study, we searched for additional susceptibility loci within the human leukocyte antigen (HLA) region through in-depth analyses of the GWAS data; then, we followed up our findings in an independent Han Chinese 1,139 psoriasis cases and 1,132 controls. Using the phased CEPH dataset as a reference, we imputed the HLA-Cw*0602 in all samples with high accuracy. The association of the imputed HLA-Cw*0602 dosage with disease was much stronger than that of the most significantly associated SNP, rs12191877. Adjusting for HLA-Cw*0602, there were two remaining association signals: one demonstrated by rs2073048 (p = 2×10⁻⁶, OR = 0.66), located within c6orf10, a potential downstream effecter of TNF-alpha, and one indicated by rs13437088 (p = 9×10⁻⁶, OR = 1.3), located 30 kb centromeric of HLA-B and 16 kb telomeric of MICA. When HLA-Cw*0602, rs2073048, and rs13437088 were all included in a logistic regression model, each of them was significantly associated with disease (p = 3×10⁻⁴⁷, 6×10⁻⁸, and 3×10⁻⁷, respectively). Both putative loci were also significantly associated in the Han Chinese samples after controlling for the imputed HLA-Cw*0602. A detailed analysis of HLA-B in both populations demonstrated that HLA-B*57 was associated with an increased risk of psoriasis and HLA-B*40 a decreased risk, independently of HLA-Cw*0602 and the C6orf10 locus, suggesting the potential pathogenic involvement of HLA-B. These results demonstrate that there are at least two additional loci within the MHC conferring risk of psoriasis.

Psoriasis (Ps) is a chronic inflammatory disease of the skin, affecting approximately 2% of Europeans. The HLA-C gene, located within the major histocompatibility complex (MHC) region on chromosome 6, is the major genetic determinant of psoriasis. However, multiple susceptibility genes within MHC are also hypothesized. Recently, we carried out a genome-wide association scan (GWAS) on psoriasis with 1,359 patients and 1,400 healthy controls, which identified seven psoriasis loci in the human genome and confirmed the effect of HLA-C. This dataset contains densely distributed genetic variations, single nucleotide polymorphisms (SNPs), which were then further analyzed in search for additional susceptibility genes within the MHC region. Using the SNP data, we imputed in all samples the HLA-C risk allele with high accuracy. Adjusting for the HLA-C, two additional loci, one near C6orf10 and one near HLA-B/MICA, have significant associations with psoriasis, which were also observed in an independent Han Chinese dataset, suggesting that within the MHC there are at least three genes moderating susceptibility to psoriasis.

Interleukin-1 receptor antagonist and tumour necrosis factor-alpha gene polymorphisms in Turkish patients with allergic contact dermatitis

BACKGROUND

It has been shown that the family of interleukin-1 receptor antagonist (IL-1 RA) and tumour necrosis factor-alpha (TNFalpha) genes are polymorphic and related to some inflammatory diseases. Allergic contact dermatitis is the classic presentation of delayed-type hypersensitivity responses to exogenous agents. A number of genes playing role in inflammatory response may be associated with allergic contact dermatitis.

OBJECTIVES

To investigate whether there is an association between IL-1RA and TNFalpha gene polymorphisms and allergic contact dermatitis in Turkish patients with allergic contact dermatitis.

METHODS

This study was performed by the collaboration of Departments of Dermatology and Medical Genetics, Ege University, Faculty of Medicine. A total of 50 patients (31 females and 19 males) with allergic contact dermatitis, and 100 age- and sex-matched controls (58 females and 42 males) were included in the study. IL-1RA Variable Number of Tandem Repeats (VNTR) polymorphism in intron 2 and TNFalpha-308G-A polymorphism were genotyped by using polymerase chain reaction and agarose gel electrophoresis.

RESULTS

The frequency of IL-1RA 1/2 (48%) genotype was significantly higher (P = 0.002) in patient group than that is found in control group (22%). The frequency of TNFalpha (TNF G-308A) G/G genotype was significantly higher in patient group (68%) than that is found in control group (31%) (P = 0.008).

CONCLUSIONS

Our findings suggest that TNFalpha (G/G) gene polymorphism may play role in susceptibility to allergic contact dermatitis in Turkish patients.

Implications of cytokine gene polymorphisms on the orchestration of the immune response: lessons learned from oral diseases

Over the past 10 years, a plethora of information concerning the influence of gene polymorphisms on cytokine expression has been made available in the literature. Significant contribution to this field has come from studies of oral diseases, one of the widest spread health problems in the world, affecting hundreds of millions worldwide. Here we will discuss the importance of studies of gene polymorphism towards the identification of susceptible groups or prognostic indicators of oral disease. Additionally, we will highlight the differences in data obtained from genetically diverse populations and review the application of cytokine gene polymorphisms studies in oral diseases in autoimmune processes and parasitic infections.

Tumor necrosis factor-alpha inhibitor-induced psoriasis or psoriasiform exanthemata: first 120 cases from the literature including a series of six new patients

Tumor necrosis factor-alpha (TNFalpha) inhibition is effective in the treatment of moderate-to-severe psoriasis. We report on 120 patients from the literature including six new patients (three women and three men) who developed pustular lesions during treatment with TNFalpha inhibitors. We identified 72 women and 36 men (several papers did not specify the gender of patients) with an age range of 13-78 years (mean 42.3 years). The primary diagnoses were rheumatoid arthritis (n = 61), ankylosing spondylitis (n = 21), psoriasis (n = 10), Crohn disease (n = 8), SAPHO (synovitis acne pustulosis hyperostosis osteitis) syndrome (n = 3), psoriatic arthritis (n = 2), and other diagnoses (n = 15). Psoriasis (except palmoplantar pustular type) was the most common adverse effect during anti-TNFalpha treatment (n = 73), followed by palmoplantar pustular psoriasis (n = 37) and psoriasis of the nail (n = 6), sometimes combined in the same patient. Palmoplantar pustulosis and psoriasiform exanthema was the diagnosis in ten patients each. A positive personal history of psoriasis was recorded in 25 patients. A positive family history was noted in eight patients. No data about personal (n = 7) or family history (n = 46) were available in a number of patients. Newly induced psoriasis was diagnosed in 74 patients whereas an exacerbation or aggravation of a pre-existing psoriasis was noted in another 25 patients. All three TNFalpha inhibitors available on the market were involved: infliximab (63 patients), etanercept (37 patients), and adalimumab (26 patients). Several patients were treated with more than a single TFNalpha inhibitor. The timing of cutaneous adverse effects (psoriasis and psoriasiform rash) varied considerably among patients, ranging from after a single application to a delayed response of up to 63 months after initiation of treatment. The mean time to appearance of the cutaneous adverse effect for all TNFalpha inhibitors was 9.5 months. Cessation of the responsible TNFalpha inhibitor was carried out in 47 patients either alone or in association with adjuvant anti-psoriatic therapy (mostly topical). This resulted in complete remission in 21 patients, partial remission in 20 patients, and stable disease in another three patients; in the other three patients, the outcome was not reported. TNFalpha inhibition was continued in 47 patients but anti-psoriatic adjuvant therapy was introduced. The outcome in this group was complete remission in 22 patients, partial remission in 25 patients, and stable disease in 2 patients. The response rate (complete remission plus partial remission) was 93.2% and 95.9%, respectively, in each group. In six patients, switching from one TNFalpha inhibitor to another one immediately after cutaneous adverse effects occurred resulted in an improvement in five patients. In nine patients, a second TNFalpha inhibitor was initiated after a break in TNFalpha inhibition. The response to a second or third drug in these patients was mixed. The underlying pathomechanisms of induction of psoriasis or psoriasiform exanthemata by TNFalpha inhibitors remain elusive but there is reason to assume that induction of such adverse events has more than one pathophysiology.