Evaluation of DNA methylation status of toll‐like receptors 2 and 4 promoters in Behcet's disease

Abstract

Background: Altered innate immune function plays an important role in the initiation of inflammatory response in Behcet's disease (BD). Toll-like receptors (TLRs) are the master regulators of the innate immune system. Because the role of TLRs remains unknown in the pathogenesis of BD, the present study aimed to evaluate the expression levels and methylation status of the TLR2 and TLR4 promoters in patients with BD. Methods: In the present study, Iranian Azeri BD patients (n = 47) with an active (n = 22) and inactive (n = 25) period, and healthy controls (n = 61), were matched according to age, sex and ethnicity. TLR2 and TLR4 genes promoter CpG islands were predicted with the Eukaryotic Promoter Database (https://epd.vital-it.ch). Methylated DNA immunoprecipitation (MeDIP) was conducted. Results: The results showed that mRNA of TLR4 was significantly increased in the peripheral blood mononuclear cells (PBMCs) of BD patients with an active phase compared to the control group. Differences in mRNA of TLR4 between the inactive BD and control groups were not significant. Differences in TLR2 mRNA levels in the PBMCs of the active and inactive phase BD and control groups were not significant. The methylation rate of TLR4 gene promoter was significantly lower in the active and inactive BD groups compared to the control group. The difference between the active and inactive BD groups was not significant. There was no significant difference in the methylation rates of the TLR2 gene between studied groups. Conclusions: Our preliminary findings suggest that the hypomethylation of TLR4 gene may be involved in the pathogenesis of BD via increasing TLR4 expression.

Critical Role of Gut Microbiota and Epigenetic Factors in the Pathogenesis of Behçet’s Disease

“…As mentioned earlier, TLR4 showed hypomethylation and increased expression in Iranian BD patients (Horie et al, 2009;Kolahi et al, 2020). In addition, the researchers detected and analyzed the association between nine SNPs in TLR4 and BD through direct sequencing, and found that the TLR4 polymorphism may increase the risk of BD in the Japanese population (Meguro et al, 2008), which has also been confirmed in the Korean and Italian populations (Meguro et al, 2008;Boiardi et al, 2009).…”

“…At the same time, this process induces the overexpression of the corresponding pattern recognition receptor (TLR2/TLR4), which leads to a series of inflammatory reactions, including systemic vasculitis of BD (Ye et al, 2018). In another study, hypomethylated TLR4 promoter and increased TLR4 expression were found in BD patients, which suggests that there may be a common pathogenic pathway between GM and epigenetic factors (Kolahi et al, 2020). To determine whether GM play a role in the development of BD, researchers transplanted mixed fecal samples from patients with active BD into mice with experimental autoimmune uveitis (EAU) and observed increased intraocular inflammation; a large amount of inflammatory cell infiltration throughout the retina, choroid, and vitreous cavity; and increased production of inflammatory cytokines including IL-17 and interferon gamma (IFN-γ) (Ye et al, 2018).…”

“…The epigenetic mechanism, especially DNA methylation, controls TLR-related immunity (Muhammad et al, 2019). The expression of TLR4 mRNA in the PBMCs of patients with active BD was significantly higher than that of the control group, and the methylation rate of the TLR4 gene promoter in the active and inactive BD groups was significantly lower than that in the control group (Kolahi et al, 2020). Studies have shown that TLR4 can promote the differentiation of initial CD4 + T cells into Th17 cells, so the hypomethylation of TLR4 gene may participate in the pathogenesis of BD by increasing the expression of TLR4 (Bartlett et al, 2018).…”

Epigenetic Modifications and Therapy in Uveitis

“…In addition, Zhu Y et al revealed that the hypermethylation of GATA3 and TGF-β may lead to gene transcriptional silencing, which may play a role in the pathogenesis of BD ( Zhu et al, 2017a ). Kolahi S et al suggested that hypomethylation of the TLR4 gene may be involved in the pathogenesis of BD by increasing TLR4 expression ( Kolahi et al, 2020 ). Alipour S et al found that the expression level of the IL-10 gene in BD patients was significantly decreased, while the promoter methylation rate in patients with low IL-10 mRNA expression was significantly higher than that in controls ( Alipour et al, 2018 ).…”

“…),Yu et al (2019),Zhu et al (2017a) had uveitis. In the other studies, such as studies performed byHughes et al (2014),Kolahi et al (2020),Alipour et al (2018),Alipour et al (2020),Aziz et al (2020), only part of the BD patients had ocular symptoms which presumably involved uveitis.…”