Lack of Association Between Polymorphism rs4986791 in TLR4 and Primary Open-Angle Glaucoma in a Saudi Cohort

Single-nucleotide polymorphisms of TLR4 and GAS7 linked to primary open-angle glaucoma among patients of Shenyang, China

The potential for adverse outcomes and classifications of glaucoma differ among race, country, gender, and family medical history. Nearly, 50 represent candidate genes are considered as potential contributors to the happening for the primary open-angle glaucoma (POAG) since the advent of GWASs. Our investigation is the first to report the Toll-like receptor 4 (TLR4) and growth arrest-specific 7 (GAS7) among people in Shenyang, China; to investigate whether single-nucleotide polymorphisms (SNPs) in (TLR4) or GAS7 gene are risk factors for POAG among people in Shenyang, China; and also to explore their potential pathogenic mechanisms. POAG patients from July 2015 to June 2019 at Shenyang Fourth People's Hospital were selected. A total of 218 POAG patients and 252 controls were enrolled. Eight potentially functional SNPs of TLR4 (rs7868859, rs7873784, rs77358523, and rs752998) and GAS7 (rs8012311, rs11656696, rs74629981, and rs9900085) were genotyped. Multifactor analysis was conducted to evaluate the correlation between TLR4, GAS7, and POAG. The allele frequency of rs7873784 of TLR4 demonstrated that the GC (P = 0.030), CC (P = 0.040), and GC + CC genotypes (P = 0.009) were significantly higher compared with CC genotype for POAG patients than that for controls. The rs8072311 and rs9900085 of GAS7 gene also were significantly associated with POAG. Haplotype analysis found that the C-A-T-A haplotype (order: rs7873784-rs77358523-rs752998-rs7868859) of TLR4 gene and the two haplotypes A-C-C-A and C-C-A-C of GAS7 (order: rs9900085-rs74629981-rs8072311-rs11656696) were associated with an elevated susceptibility to POAG (P < 0.05). In this study, rs7868859 of TLR4 and rs8012311 and rs9900085 polymorphisms of GAS7 were first identified to be related to POAG among people in Shenyang, China.

Molecular Effect of Variants in Toll-like Receptor 4 Gene in Saudi Patients with Type 2 Diabetes Mellitus

Single-nucleotide polymorphisms (SNPs) in the Toll-like receptor 4 (TLR4) gene have been documented in type 2 diabetes mellitus (T2DM) and other diseases in the Saudi population. We investigated the relationship between rs11536889, rs4986790, and rs4986791 SNPs in the TLR4 gene and T2DM in the Saudi population; 105 patients with T2DM and 105 healthy controls were analyzed. The TLR4 gene was amplified through PCR, followed by restriction fragment length polymorphism analysis for rs4986791 and Sanger sequencing for rs11536889 and rs4986790 SNPs. The clinical and biochemical characteristics were associated with T2DM (p < 0.05). The rs11536889, rs4986790, and rs4986791 SNPs in control subjects followed the Hardy-Weinberg equilibrium (p > 0.05). Alleles were associated with rs11536889, rs4986791, heterozygous codominant, and dominant models (p < 0.05). However, the rs4986790 SNP was not associated with T2DM (p > 0.05). Logistic regression analysis showed that high-density lipoprotein cholesterol (HDLc) levels were associated with T2DM (p < 0.001). Analysis of variance showed that waist (p = 0.0005) and hip circumferences (p = 0.002) in rs4986790 and rs4986791 SNPs, in SBP (p = 0.001), DBP (p = 0.002), and HDLc levels (p = 0.003), were associated with T2DM subjects. T2DM was also associated with the haplotype (p < 0.001) but not with linkage disequilibrium. The gene-gene interaction was associated with the three SNPs studied in patients with T2DM according to the generalized multifactor dimensionality reduction model (p < 0.0001). Dendrogram and graphical depletion analysis revealed a moderate association in patients with T2DM. The results suggest that rs11536889 and rs4986790 SNPs are genotypically and allelically associated with T2DM in Saudi patients. Future functional studies are recommended to validate the genetic roles of these SNPs in the pathogenesis and progression of diseases.

Microbiome Dysbiosis: A Pathological Mechanism at the Intersection of Obesity and Glaucoma

The rate at which obesity is becoming an epidemic in many countries is alarming. Obese individuals have a high risk of developing elevated intraocular pressure and glaucoma. Additionally, glaucoma is a disease of epidemic proportions. It is characterized by neurodegeneration and neuroinflammation with optic neuropathy and the death of retinal ganglion cells (RGC). On the other hand, there is growing interest in microbiome dysbiosis, particularly in the gut, which has been widely acknowledged to play a prominent role in the etiology of metabolic illnesses such as obesity. Recently, studies have begun to highlight the fact that microbiome dysbiosis could play a critical role in the onset and progression of several neurodegenerative diseases, as well as in the development and progression of several ocular disorders. In obese individuals, gut microbiome dysbiosis can induce endotoxemia and systemic inflammation by causing intestinal barrier malfunction. As a result, bacteria and their metabolites could be delivered via the bloodstream or mesenteric lymphatic vessels to ocular regions at the level of the retina and optic nerve, causing tissue degeneration and neuroinflammation. Nowadays, there is preliminary evidence for the existence of brain and intraocular microbiomes. The altered microbiome of the gut could perturb the resident brain-ocular microbiome ecosystem which, in turn, could exacerbate the local inflammation. All these processes, finally, could lead to the death of RGC and neurodegeneration. The purpose of this literature review is to explore the recent evidence on the role of gut microbiome dysbiosis and related inflammation as common mechanisms underlying obesity and glaucoma.

Association of single-nucleotide polymorphisms in TLR4 gene and gene-environment interaction with primary open angle glaucoma in a Chinese northern population

BACKGROUND

The present study aimed to investigate the association of several single nucleotide polymorphisms (SNPs) within the Toll-like receptor 4 (TLR4) gene and additional gene-environment interaction with primary open angle glaucoma (POAG) risk.

METHODS

Tests for Hardy-Weinberg equilibrium in controls and haplotype analysis were performed using SNPstats (https://www.snpstats.net). Generalized multifactor dimensionality reduction (GMDR) was performed to test the interaction effects among four SNPs within the TLR4 gene and environmental factors. Logistic regression was performed to calculate the odds ratios (ORs) (95% confidence interval [CI]) for association between four SNPs within the TLR4 gene and POAG risk.

RESULTS

The POAG risk was significantly higher in carriers with the T allele of rs4986791 and the T allele of rs2149356 within the TLR4 gene than in those with the wild-type genotype, adjusted ORs (95% CI) were 1.65 (1.23-2.12) and 1.70 (1.16-2.31). The GMDR model suggested a significant two-locus model (p = 0.0010) involving rs2149356 and alcohol drinking. Alcohol drinkers with the rs2149356-GT+TT genotype within the TLR4 gene have the highest POAG risk compared to never alcohol drinkers with the rs2149356-GG genotype (OR = 2.62; 95% CI = 1.48-3.78) after covariates adjustment. However, the study did not find a significant any-locus model involving SNP and smoking. In all samples, the haplotype rs2149356-G-rs7873784-C was observed most frequently in two groups (47.47% and 48.21% for the POAG patients and controls, respectively). The results also indicated that no significant haplotype was associated with POAG risk.

CONCLUSIONS

The minor alleles of rs4986791 and rs2149356 within the TLR4 gene, as well as interaction between rs2149356 and alcohol drinking, were associated with an increased POAG risk.

Associations between TLR4 Polymorphisms and Open Angle Glaucoma: A Meta-Analysis

Background

Previous studies exploring the association between toll-like receptor 4 (TLR4) polymorphisms and open angle glaucoma (OAG) presented inconsistent results. We aimed to investigate the association between TLR4 polymorphisms and OAG.

Methods

A systematic literature search was conducted in PubMed, EMBASE, ISI Web of Knowledge, and the Cochrane Library up to 31 December 2018. Odds ratio (OR) and 95% confidence interval (95%CI) were calculated, followed by stratification analyses according to ethnicity and glaucoma subtype.

Results

TLR4 rs7037117 polymorphism had significant associations with increased risk of OAG in allelic model (OR=1.25; 95%CI: 1.09-1.44; P=0.002) and recessive model (OR=1.49; 95%CI: 1.08-2.04; P=0.01). With regard to rs10759930, rs12377632, and rs2149356, the results showed significant increased risks in all genetic models (all P<0.05), whereas, for rs1927914, rs11536889, and rs7045953, no significant associations were identified in any genetic model (all P>0.05). Furthermore, the association of rs1927911 with OAG risk was found to be significant in recessive model (OR=1.34; 95%CI: 1.06-1.71; P=0.02). As for rs4986790 and rs4986791, meta-analyses were not performed due to the limited number of studies and the ethnic differences. Subgroup analysis indicated that the above polymorphisms with significant differences might increase the susceptibility in POAG patients. As for the ethnicity, rs7037117, rs10759930, and rs1927911 might increase the risk in Asians, while rs12377632 and rs2149356 might increase the risk in Asians and Mexicans.

Conclusion

The meta-analysis highlighted that certain mutations of some TLR4 polymorphisms might increase the susceptibility of OAG. However, TLR4 polymorphisms are still far from being candidate genetic biomarkers for OAG. Additional researches involving larger scale epidemiological studies are warranted to validate our results.

The association of toll-like receptor 4 gene polymorphisms with primary open angle glaucoma susceptibility: a meta-analysis

Primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) cause irreversible blindness while current medications cannot completely inhibit disease progression. An understanding of immunopathogenesis is thus a keystone to develop novel drug targets and genetic markers are still required for early diagnosis. Toll-like receptor 4 (TLR4) is an essential player in inflammation in various diseases. However, the TLR4 polymorphisms have not been completely elucidated in both types of glaucoma. The aim of the present study was to identify the association between TLR4 polymorphism and glaucoma (POAG and NTG) via the use of a comprehensive review and meta-analysis. The relevant studies were collected from PubMed, Excerpta Medica Database (EMBASE), and Web of Science to identify eight included articles, assessed for quality by a modified Newcastle-Ottawa Scale (NOS) for gene association study. A meta-analysis was applied to calculate the pooled odds-ratio and 95% confidence intervals (CIs) to evaluate the association between TLR4 polymorphism and glaucoma. The results revealed that TLR4 rs1927911 A/G, rs12377632 C/T, and rs2149356 G/T significantly decrease the risk of POAG and NTG in allele contrast models 0.71-, 0.71-, and 0.67-fold, respectively. Moreover, rs4986790 A/G and rs4986791 C/T showed a stringent association with POAG in allele contrast, heterozygous, recessive, and overdominant models. In conclusion, this meta-analysis represented a significant correlation between TLR4 polymorphisms and both types of glaucoma suggesting that TLR4 might be involved in the pathogenesis of glaucoma and may be applied as a genetic marker for disease screening.

Modulation of the Immune System for the Treatment of Glaucoma

Background:

At present intraocular pressure (IOP) lowering therapies are the only approach to treat glaucoma. Neuroprotective strategies to protect the retinal ganglion cells (RGC) from apoptosis are lacking to date. Substantial amount of research concerning the role of the immune system in glaucoma has been performed in the recent years. This review aims to analyse changes found in the peripheral immune system, as well as selected local changes of retina immune cells in the glaucomatous retina.

Methods:

By dividing the immune system into the innate and the adaptive immune system, a systematic literature research was performed to find recent approaches concerning the modulation of the immune system in the context of glaucoma. Also ClinicalTrials.gov was assessed to identify studies with a translational context.

Results:

We found that some aspects of the immune system, such as changes in antibody levels, changes in toll like receptor signalling, T cells and retinal microglial cells, experience more research activity than other areas such as changes in dendritic cells or macrophages. Briefly, results from clinical studies revealed altered immunoreactivities against retinal and optic nerve antigens in sera and aqueous humor of glaucoma patients and point toward an autoimmune involvement in glaucomatous neurodegeneration and RGC death. IgG accumulations along with plasma cells were found localised in human glaucomatous retinae in a pro-inflammatory environment possibly maintained by microglia. Animal studies show that antibodies (e.g. anti- heat shock protein 60 and anti-myelin basic protein) elevated in glaucoma patients provoke autoaggressive RGC loss and are associated with IgG depositions and increased microglial cells. Also, studies addressing changes in T lymphocytes, macrophages but also local immune responses in the retina have been performed and also hold promising results.

Conclusions:

This recapitulation of recent literature demonstrates that the immune system definitely plays a role in the pathogenesis of glaucoma. Multiple changes in the peripheral innate as well as adaptive immune system have been detected and give room for further research concerning valuable therapeutic targets. We conclude that there still is a great need to bring together the results derived from basic research analysing different aspects of the immune system in glaucoma to understand the immune context of the disease. Furthermore local immune changes in the retina of glaucoma patients still leave room for further therapeutic targets