Epigenetic regulation of pro-inflammatory cytokine genes in lipopolysaccharide -stimulated peripheral blood mononuclear cells from broilers

The Role of Selected Epigenetic Pathways in Cardiovascular Diseases as a Potential Therapeutic Target

Epigenetics is a rapidly developing science that has gained a lot of interest in recent years due to the correlation between characteristic epigenetic marks and cardiovascular diseases (CVDs). Epigenetic modifications contribute to a change in gene expression while maintaining the DNA sequence. The analysis of these modifications provides a thorough insight into the cardiovascular system from its development to its further functioning. Epigenetics is strongly influenced by environmental factors, including known cardiovascular risk factors such as smoking, obesity, and low physical activity. Similarly, conditions affecting the local microenvironment of cells, such as chronic inflammation, worsen the prognosis in cardiovascular diseases and additionally induce further epigenetic modifications leading to the consolidation of unfavorable cardiovascular changes. A deeper understanding of epigenetics may provide an answer to the continuing strong clinical impact of cardiovascular diseases by improving diagnostic capabilities, personalized medical approaches and the development of targeted therapeutic interventions. The aim of the study was to present selected epigenetic pathways, their significance in cardiovascular diseases, and their potential as a therapeutic target in specific medical conditions.

Correlation Between Inflammatory and Epigenetic Marks With Aerobic Performance in 10-km Runners

Purpose: Our goals were to evaluate the effect of a 10-km running trial on inflammatory and epigenetic markers of 10-km runners and correlate the biochemical findings with anthropometric variables and performance. Methods: Twenty trained 10-km runners and seven sedentary male volunteers were recruited. Venous blood samples were collected at different times: under resting conditions, before the 10 Km race, and immediately after the finish. Inflammatory markers (IL-6, IL-10, and IL-β) and cortisol levels were evaluated in plasma, while DNA methyltransferases (DNMT1 and DNMT3b) contents were measured in peripheral blood mononuclear cells (PBMCs). Results: Higher levels of plasma IL-6 levels were observed in 10-km runners compared to the sedentary group. After the trial, the runners had a significant increase on IL-6, IL-10, and cortisol plasma levels compared to baseline. Conclusion: Our findings suggest that inflammatory profile, but not DNMT content, influences aerobic performance in 10-km runners.

5-aza-2'-deoxycytidine may regulate the inflammatory response of human odontoblast-like cells through the NF-κB pathway

AIM

To explore the role of DNA methylation in the innate immunity of the dental pulp, this study investigated the effect of 5-aza-2'-deoxycytidine (AZA) on lipoteichoic acid (LTA)-induced cytokine production and related intracellular signalling pathways in human odontoblast-like cells (hOBs).

METHODOLOGY

hOBs were cultured and differentiated from human dental pulp tissue, and the odontoblastic phenotype of the cells was detected using immunofluorescence, qRT-PCR and Western blotting. hOBs were pretreated with AZA and then stimulated with 10 μg mL^-1 LTA. The levels of 42 cytokines related to immunity and inflammation were examined using a cytokine antibody array and verified using qRT-PCR and ELISA. The effect of AZA on the LTA-induced NF-κB and MAPK signalling pathways was explored using Western blotting. The cells were treated with the specific NF-κB inhibitor PDTC and MAPK inhibitors (the ERK inhibitor U0126, the p38 inhibitor SB203580, and the JNK inhibitor SP600125) to further confirm the role of the signalling pathways in LTA-treated hOBs. DNA immunoprecipitation-PCR was used to examine the dynamic methylation status of the gene promoters of myeloid differentiation primary response 88 (MyD88) and tumour necrosis factor receptor-associated factor 6 (TRAF6) in the LTA-induced hOBs. Statistical analyses of the differences between two groups were performed using Student's t-test. One-way analysis of variance (anova) or repeated-measures anova with a post hoc Dunnett's test was used to assess the differences between multiple sets of data. P < 0.05 was considered to be statistically significant.

RESULTS

The odontoblastic markers were significantly higher in hOBs than those in human dental pulp cells (hDPCs) (P < 0.05). According to the cytokine antibody array results, hOBs pretreated with AZA had significantly increased production of several inflammatory cytokines (P < 0.05), in which the expression levels of IL-6 and IL-8 were the most dramatically increased upon LTA stimulation (P < 0.01). Furthermore, AZA resulted in the significant upregulation of p-IKKα/β, p-IκBα, p-p65, p-p38 and p-ERK in LTA-stimulated hOBs (P < 0.01). Treatment with the NF-κB pathway inhibitor suppressed both IL-6 and IL-8 expression (P < 0.05), whereas inhibitors of the MAPK pathway (SB203580 and SP600125) did not. In LTA-treated hOBs, AZA significantly increased the expression levels of TRAF6 and MyD88 (P < 0.05). AZA induced MyD88 promoter hypomethylation but did not affect TRAF6 methylation.

CONCLUSION

AZA regulated the LTA-induced inflammatory response through the NF-κB signal pathway in hOBs. This study highlights the important role of DNA methylation in the immunity defence of odontoblasts during the dental pulp immunity response to caries.

Effect of ABCA1 promoter methylation on premature coronary artery disease and its relationship with inflammation

BACKGROUND

ATP-binding cassette transporter A1 (ABCA1) plays a major role in high-density lipoprotein (HDL) metabolism and reverse cholesterol transport (RCT) and exerts anti-inflammatory effects. Increased ABCA1 promoter methylation level may result in the progression of coronary artery disease. Thus, the present study investigated the association between promoter methylation status of ABCA1 and inflammation in the development of premature coronary artery disease (pCAD).

METHODS

PCAD patients and healthy individuals (n = 90 each) were recruited from the Characteristic Medical Center of the Chinese People's Armed Police Force from June to December 2019. Using pyrosequencing, the levels of ABCA1 promoter methylation in their blood samples were evaluated. Serum concentrations of lipids, interleukin 1β (IL-1β), C-reactive protein (CRP), and circulating free DNA/Neutrophil extracellular traps (cfDNA/NETs) were also routinely measured and compared between the two groups. P values < 0.05 were considered statistically significant.

RESULTS

The mean ABCA1 promoter methylation levels were significantly higher in the pCAD group than in the control group (44.24% ± 3.66 vs. 36.05% ± 2.99, P < 0.001). Based on binary logistic regression analysis, ABCA1 promoter methylation level was identified as an independent risk factor for pCAD development (odds ratio = 2.878, 95% confidence interval: 1.802-4.594, P < 0.001). Furthermore, ABCA1 promoter methylation levels were negatively correlated with HDL levels (r =  - 0.488, P < 0.001) and positively correlated with the levels of CRP, cfDNA/NETs, and IL-1β (r = 0.389, 0.404, 0.385, respectively; P < 0.001). Multiple regression analysis showed that the serum levels of CRP, IL-1β, and cfDNA/NETs independently affect ABCA1 promoter methylation.

CONCLUSIONS

Our findings indicate that high methylation levels at the ABCA1 promoter are associated with low HDL cholesterol levels and an increased risk of pCAD. Inflammatory factors and NETs may be involved in the progression of pCAD by affecting ABCA1 promoter methylation levels.

Epigenetic effect of folic acid (FA) on the gene proximal promoter area and mRNA expression of chicken B cell as antigen presenting cells

1. This study evaluated and characterised the effect of folic acid (FA) on chromosomal DNA methylation and the epigenetic result on gene expression control mechanisms in chicken B cells as a model of antigen presenting cells. 2. After FA supplementation, the methylation pattern on the proximal promoter area and mRNA expression of toll-like receptor (TLR) 2b, TLR4, B cell receptor (BCR) immunoglobulin (Ig) β and major histocompatibility complex (MHC) II β chain genes in chicken B cells was observed 3. Chicken B cell line (DT40) cultures were incubated with 0, 1.72 or 3.96 mM of FA for 4 and 8 h and samples were taken at specific time points. After 4 h of incubation, cells were challenged with 0, 1 or 10 µg/ml of lipopolysaccharide (LPS) and samples were collected 4 h post-challenge. 4. FA supplementation modified the methylation patterns of the proximal promoter regions of TLR4, Igß, and MHCII ß chain at 4 and 8 hours of incubation; however, the single CpG dinucleotide of TLR2b remained methylated regardless of the treatment. 5. A positive association was found between FA concentration and percentage DNA methylation on the promoter area of Igβ and TLR2b. However, there was a negative association between FA and MHCII β chain. 6. There were downregulatory effects in TLR4, Igß and MHCII ß chain gene expression after 8 h of incubation, nut not at 4 h. Although incubation time did not affect TLR2b gene expression, FA concentration did, whereby it increased TLR2b expression at 1.72 mM FA (P < 0.05). 7. LPS significant downregulated TLR2b expression, while an interaction between FA and LPS concentration affected TLR4 and Igβ gene expression. 8. In conclusion, the results showed that FA can have an immunomodulatory effect on chicken B cells, possibly affecting their ability to both recognise antigens through the TLR and BCR pathways, and to present it via the MHCII presentation pathway.

5-Aza-2'-deoxycytidine enhances lipopolysaccharide-induced inflammatory cytokine expression in human dental pulp cells by regulating TRAF6 methylation

Dental pulp inflammation is a common bacterially driven inflammation characterized by the local accumulation of inflammatory mediators in human dental pulp. DNA methylation is a crucial epigenetic modification that that plays a fundamental role in gene transcription, and its role in inflammation-related diseases has recently attracted attention. However, its role in dental pulp inflammation is poorly understood. This study is aimed to elucidate the role of DNA methylation in lipopolysaccharide (LPS)-induced inflammatory reaction in human dental pulp cells (hDPCs). hDPCs were pretreated with DNA methylation inhibitor 5-aza-2ʹ-deoxycytidine (5-Aza-CdR) and a cytokine antibody array was used to detect LPS-induced cytokine expression. The results indicated that 5-Aza-CdR significantly increased the expression of several pro-inflammatory cytokines in LPS-treated cells, including IL-6, IL-8, GM-CSF, MCP-2 and RANTES. The increased expression levels of IL-6 and IL-8 were further verified by qRT-PCR and ELISA. Furthermore, pretreatment with 5-Aza-CdR resulted in upregulation of p-IKKα/β, p-IκBα, p-p65 and p-ERK in the NK-κB and MAPK pathways. In addition, the 5mC level of the TRAF6 promoter was significantly decreased following 5-Aza-CdR pretreatment in the LPS-stimulated hDPCs. The findings indicate that 5-Aza-CdR significantly enhances the expression of proinflammatory cytokines and activates the NF-κB and MAPK signaling pathways by eliciting a decline in the 5mc level in the TRAF6 promoter in hDPCs, suggesting that DNA methylation may play an important role in dental pulp inflammation. This study highlights the important role of DNA methylation in the immunity defense of dental pulp infection.

DNA methyltransferase DNMT1 inhibits lipopolysaccharide‑induced inflammatory response in human dental pulp cells involving the methylation changes of IL‑6 and TRAF6

Dental pulp inflammation is a pathological process characterized by local lesions in dental pulp and the accumulation of inflammatory mediators. DNA methylation of cytosine residues is a key epigenetic modification that is essential for gene transcription, and plays pivotal roles in inflammatory reactions and immune responses. However, the function of cytosine DNA methylation in the innate immune defense against the inflammation of dental pulp is poorly understood. To investigate the effect of DNA methylation in inflamed dental pulp upon innate immune responses, expression levels of the DNA methyltransferases (DNMT1, DNMT3a and DNMT3b) in human dental pulp cells (hDPCs) after lipopolysaccharide (LPS) stimulation were evaluated by western blotting and reverse transcription‑quantitative (RT‑q) PCR. Only DNMT1 expression was decreased, while the transcription of inflammatory cytokines was increased. In the immune responses of LPS‑induced hDPCs, the results of RT‑qPCR and ELISA showed that DNMT1 knockdown promoted the production of the pro‑inflammatory cytokines, interleukin (IL)‑6 and IL‑8. Western blotting demonstrated that DNMT1 knockdown increased the phosphorylation levels of IKKα/β and p38 in the NF‑κB and MAPK signaling pathways, respectively. Furthermore, MeDIP and RT‑qPCR analysis demonstrated that the 5‑methylcytosine levels of the IL‑6 and TNF receptor‑associated factor 6 (TRAF6) promoters were significantly decreased in DNMT1‑deficient hDPCs. Taken together, these results indicated that the expression of DNMT1 was decreased after LPS stimulation in hDPCs. DNMT1 depletion increased LPS‑induced cytokine secretion, and activated NF‑κB and MAPK signaling; these mechanisms may involve the decreased methylation levels of the IL‑6 and TRAF6 gene promoters. This study emphasized the role of DNMT1‑dependent DNA methylation on the inflammation of LPS‑infected dental pulp and provides a new rationale for the investigation of the molecular mechanisms of inflamed dental pulps.

DNA hypermethylation does not negatively impact the transcription of the TNF-α gene in an acute T-cell leukemia

Aims: To better understand the roles of DNA methylation and histone acetylation in the transcription of the TNF-α gene (TNFA) in leukemic T cells. Materials & methods: Methylation levels of cytosine-guanosine dinucleotides (CPGs) were assessed by mass spectrometry. The influence of epigenetic modifiers on DNA methylation and TNFA transcription was also determined. Results: CPG at the 5' promoter region, first exon and first intron of TNFA were hypermethylated in leukemic T cells and not impacted by epigenetic drugs. Activation of the class III histone deacetylases but not inhibitors of DNA methylation or histone deacetylases repressed TNFA transcription. Conclusion: These results lend insights into the impact of epigenetic mechanisms on the TNFA transcription in leukemic T cells.

DNA methylation is involved in pro-inflammatory cytokines expression in T-2 toxin-induced liver injury

Currently, T-2 toxin has been reported to cause liver toxicity with the effects of oxidative stress and inflammation; however, the underlying mechanism of T-2 toxin-induced liver injury is not fully understood. Increasing lines of evidence show that DNA methylation affects the expression of inflammatory cytokine, and plays a crucial role in autoimmune diseases. Nevertheless, the potential role of DNA methylation in the hepatotoxicity of T-2 toxin has not been explored. In this study, female Wistar rats were given a single dose of T-2 toxin at 2 mg/kg b.w. and were sacrificed at 1, 3 and 7 days post-exposure. In vitro, a normal rat liver cell line (BRL) was exposed to different concentrations of T-2 toxin. Histopathological analysis was used to investigate damage to the liver, which was detected at the molecular level by RT-PCR, Western blot and immunohistochemical assays, methylation-specific PCR (MSP), bisulfite sequencing (BSP), and flow cytometry. The results showed that T-2 toxin significantly increased the levels of DNA methyltransferases (DNMT1, DNMT3A), which were mainly concentrated at the site of liver injury. The 5-methylcytosine (5-mC) level of genomic DNA was also raised in T-2 toxin-treated rat livers. The expression of inflammatory cytokines (IL-6, IL-1β, IL-11, IL-1α, and TNF-α) increased both in vivo and in vitro under T-2 toxin treatment. Notably, DNA demethylation directly increased the expression of cytokines IL-11, IL-6, IL-α, and TNF-α under T-2 toxin exposure. DNA methylation inhibitors combined with T-2 toxin directly or indirectly induced the production of inflammatory cytokines and aggravate cell apoptosis. Our study uncovered for the first time that DNA methylation is related to the expression of inflammatory cytokines in T-2 toxin-induced liver injury. These findings suggested that DNA methylation is a potential mechanism of T-2 toxin-induced hepatotoxicity.

MyD88 hypermethylation mediated by DNMT1 is associated with LTA-induced inflammatory response in human odontoblast-like cells

Dental caries is a chronic, infectious, and destructive disease that allows bacteria to break into the dental pulp tissue. As caries-related bacteria invade the human dentinal tubules, odontoblasts are the first line of dental pulp that trigger the initial inflammatory and immune responses. DNA methylation is a key epigenetic modification that plays a fundamental role in gene transcription, and its role in inflammation-related diseases has recently attracted attention. However, whether DNA methylation regulates the inflammatory response of human odontoblasts is still unknown. In the present study, we investigated the expression of DNA methyltransferase (DNMT)-1 in lipoteichoic acid (LTA)-stimulated human odontoblast-like cells (hOBs) and found that DNMT1 expression showed a decline that is contrary to the transcription of inflammatory cytokines. Knockdown of the DNMT1 gene increased the expression of several cytokines, including IL-6 and IL-8, in the LTA-induced inflammatory response. DNMT1 knockdown increased the phosphorylation of IKKα/β, IκBα, and p65 in the NF-κB pathway and the phosphorylation of p38 and ERK in the MAPK pathway; however, only the NF-κB pathway inhibitor PDTC suppressed both IL-6 and IL-8 expression, whereas inhibitors of the MAPK pathway (U0126, SB2035580, and SP600125) did not. Furthermore, DNMT1 knockdown upregulated the expression of MyD88 and TRAF6 but only attenuated the MyD88 gene promoter methylation in LTA-treated hOBs. Taken together, these results demonstrated that DNMT1 depletion caused hypomethylation and upregulation of MyD88, which resulted in activation of the NF-κB pathway and the subsequent release of LTA-induced inflammatory cytokines in hOBs. This study emphasizes the critical role of DNA methylation in the immune defense of odontoblasts when dental pulp reacted to caries.

Folic acid contributes to peripheral nerve injury repair by promoting Schwann cell proliferation, migration, and secretion of nerve growth factor

After peripheral nerve injury, intraperitoneal injection of folic acid improves axon quantity, increases axon density and improves electromyography results. However, the mechanisms for this remain unclear. This study explored whether folic acid promotes peripheral nerve injury repair by affecting Schwann cell function. Primary Schwann cells were obtained from rats by in vitro separation and culture. Cell proliferation, assayed using the Cell Counting Kit-8 assay, was higher in cells cultured for 72 hours with 100 mg/L folic acid compared with the control group. Cell proliferation was also higher in the 50, 100, 150, and 200 mg/L folic acid groups compared with the control group after culture for 96 hours. Proliferation was markedly higher in the 100 mg/L folic acid group compared with the 50 mg/L folic acid group and the 40 ng/L nerve growth factor group. In Transwell assays, the number of migrated Schwann cells dramatically increased after culture with 100 and 150 mg/L folic acid compared with the control group. In nerve growth factor enzyme-linked immunosorbent assays, treatment of Schwann cell cultures with 50, 100, and 150 mg/L folic acid increased levels of nerve growth factor in the culture medium compared with the control group at 3 days. The nerve growth factor concentration of Schwann cell cultures treated with 100 mg/L folic acid group was remarkably higher than that in the 50 and 150 mg/L folic acid groups at 3 days. Nerve growth factor concentration in the 10, 50, and 100 mg/L folic acid groups was higher than that in the control group at 7 days. The nerve growth factor concentration in the 50 mg/L folic acid group was remarkably higher than that in the 10 and 100 mg/L folic acid groups at 7 days. In vivo, 80 μg/kg folic acid was intraperitoneally administrated for 7 consecutive days after sciatic nerve injury. Immunohistochemical staining showed that the number of Schwann cells in the folic acid group was greater than that in the control group. We suggest that folic acid may play a role in improving the repair of peripheral nerve injury by promoting the proliferation and migration of Schwann cells and the secretion of nerve growth factors.

Folic Acid Reduced Triglycerides Deposition in Primary Chicken Hepatocytes

Abdominal fat or fatty liver cause huge economic losses in the poultry industry, and nonalcoholic fatty liver disease (NAFLD) is also a global health issue in humans. More than 90% of de novo lipogenesis in humans and chickens is undertaken by the liver, which is proved to be full of lipids in new-born chickens. Folic acid was thought to have correlation with lipid metabolism. Primary hepatocytes from new-born chickens were employed as a natural model of early stage fatty liver in vitro and further to explore whether folic acid could prevent fatty liver in the current study. We found that folic acid addition reduced triglyceride deposition by suppressing de novo fatty acid synthesis and coordinately promoting triglyceride hydrolysis and exportation in primary chicken hepatocytes from new-born chickens. In addition, lipogenesis suppression was through the PI3K/AKT/SREBP pathway mediated by weakening insulin/IGF signal. Our data suggested that folic acid may be considered as a precautionary strategy for abdominal fat deposition in broilers or fatty liver in laying hens and humans. In addition, mechanism regulation also implied that an IGF2 inhibitor and PI3K inhibitor may be used for the NAFLD precautionary measure to reduce TG deposition.

Identification of differentially expressed genes in broiler offspring under maternal folate deficiency

Folate plays an important role in DNA and RNA synthesis by donating methyl groups. To investigate the effects of maternal folate deficiency (FD) on the abdominal adipose transcriptome and on the accumulation of lipid droplets in the liver tissue of chicken offspring, differentially expressed genes (DEGs) of FD were identified with digital gene expression tag profiling. Ultramicroscopy suggested that the size of lipid droplets in hepatocytes increased with FD, while the lipid droplets population number was largely not affected. The serum parameters assay showed that the concentrations of MTHFR (476.57 vs. 395.27), DHFR (45.056 vs. 38.952), LPL (50.408 vs. 48.677), HCY (4.354 vs. 3.836), LEP (9.951 vs. 8.673), and IGF2 (1209.4 vs. 1027.7) in offspring serum of the FD group were significantly higher than those of the normal folate (NF) group ( P < 0.01). The 442 DEGs between NF and FD groups were identified by digital gene expression profiling. Considering the DEGs in the FD groups vs. NF groups, 179 genes were upregulated while 263 downregulated, and in particular, 145 upregulated and 214 downregulated DEGs were successfully annotated with the nonredundant database. Gene Ontology analysis showed that FD mainly affected cellular processes, cell part and binding, cell killing, virions, and receptor regulator activity. With pathway analysis, it indicated that 123 unigenes were assigned to 115 KEGG pathways, but only five of 115 these pathways were significantly enriched with P values ≤ 0.05. Taken together, these results provide a foundation for further studying the responses of offspring to maternal FD in breeding chickens.

The emerging spectrum of early life exposure-related inflammation and epigenetic therapy

Early life exposure to a variety of insults during sensitive windows of development can reprogram normal physiological responses and alter disease susceptibility later in life. During this process, Inflammation triggered by a variety of adverse exposures plays an important role in the initiation and development of many types of diseases including tumorigenesis. This review article summaries the current knowledge about the role and mechanism of inflammation in development of diseases. In addition, epigenome alteration related to inflammation and treatment options using epigenetic modifiers are highlighted and discussed.

Transcriptome analysis of hepatic gene expression and DNA methylation in methionine- and betaine-supplemented geese (Anser cygnoides domesticus)

Dietary methionine (Met) restriction produces a coordinated series of transcriptional responses in the liver that limits growth performance and amino acid metabolism. Methyl donor supplementation with betaine (Bet) may protect against this disturbance and affect the molecular basis of gene regulation. However, a lack of genetic information remains an obstacle to understand the mechanisms underlying the relationship between Met and Bet supplementation and its effects on genetic mechanisms. The goal of this study was to identify the effects of dietary supplementation of Met and Bet on growth performance, transcriptomic gene expression, and epigenetic mechanisms in geese on a Met-deficient diet. One hundred and fifty 21-day-old healthy male Yangzhou geese of similar body weight were randomly distributed into 3 groups with 5 replicates per treatment and 10 geese per replicate: Met-deficient diet (Control), Control+1.2 g/kg of Met (Met), and Control+0.6 g/kg of Bet (Bet). All geese had free access to the diet and water throughout rearing. Our results indicated that supplementation of 1.2 g/kg of Met in Met-deficient feed increased growth performance and plasma homocysteine (HCY) levels, indicating increased transsulfuration flux in the liver. Supplementation of 0.6 g/kg Bet had no apparent sparing effect on Met needs for growth performance in growing geese. The expression of many genes critical for Met metabolism is increased in Met supplementation group. In the Bet-supplemented group, genes involved in energy production and conversion were up-regulated. Dietary supplementation with Bet and Met also altered DNA methylation. We observed changes in the methylation of the LOC106032502 promoter and corresponding changes in mRNA expression. In conclusion, Met and Bet supplementation in geese affects the transcriptional regulatory network and alters the hepatic DNA methylation of LOC106032502.

Lipopolysaccharide Downregulates Kruppel-Like Factor 2 (KLF2) via Inducing DNMT1-Mediated Hypermethylation in Endothelial Cells

KLF2 plays a protective role in antiinflammation and endothelial function, and can be regulated by promoter methylation alteration. Lipopolysaccharide (LPS) is a mediator of inflammatory responses, which causes epigenetic change of certain genes in host cells. We thus aimed to determine whether LPS could control the KLF2 expression by inducing methylation in promoter region. DNA methylation of 16 CpG sites within KLF2 promoter region was detected by bisulfite sequencing PCR. Results showed that methylation at 12 CpG sites were significantly increased in HUVECs after exposure to LPS among the total 16 sites, and the average level was increased by 57%. The KLF2 expressions assessed by reverse transcription quantitative real-time PCR and Western blot were significantly downregulated compared that without LPS simulation. Moreover, both messenger RNA and protein levels of KLF2 in HUVEC co-treated with LPS and DNA methyltransferase (DNMT) 1 small interfering RNA were dramatically higher than that treated with LPS only. Similar result was obtained when the cells were incubated in combination with LPS and 5-aza-2'-deoxycytidine (AZA), suggesting that the reduction of KLF2 expression induced by LPS can be reversed by DNMT1 inhibition. Finally, the presence of AZA changed the expression of genes that depends on KLF2 in LPS-stimulated HUVECs, which downregulated the E-selectin and VCAM and increased the eNOS and thrombomodulin expression. Our data demonstrated that LPS exposure resulted in hypermethylation in KLF2 promoter in HUVECs, which subsequently led to downregulation of the KLF2 expression. The study suggested that epigenetic alteration is involved in LPS-induced inflammatory response and provided a new insight into atherogenesis.