Hypomethylation of interleukin-6 (IL-6) gene increases the risk of essential hypertension: a matched case–control study

Association of Interleukin-6 Genetic Polymorphisms (rs1800795, -174C > G and rs1800796, -572G > C) With Risk of Essential Hypertension in the Chinese Population

Background Interleukin-6 (IL-6) plays a critical role in essential hypertension (EH) and cardiovascular disease. Evidence suggests two hotspot single nucleotide polymorphisms (SNPs) of the IL-6 gene (rs1800795, -174C > G and rs1800796, -572G > C) might be associated with the susceptibility of EH. However, no consensus has yet been established. Thus, we aimed to investigate the potential association between IL-6 gene polymorphisms and the risk of EH based on a case-control study in a Chinese population. Materials and methods A total of 479 subjects (272 healthy controls and 207 EH patients) were randomly enrolled in our study. After extracting the genomic DNA, two SNPs of the IL-6 gene (rs1800795, -174C > G and rs1800796, -572G > C) were genotyped to analyze the potential association between these genetic variants and EH risk. Multiple genetic models were performed to investigate the strength of association by calculating the odds ratio (OR) and 95% confidence interval (95% CI). The potential effect of SNPs on gene expression was evaluated using expression quantitative trait loci (eQTL) analysis. Results The genotyping findings of IL-6 rs1800795, -174C > G polymorphism showed three study participants with CG genotype and 204 with GG genotype in the EH patients. The IL-6 -174C > G polymorphism was significantly associated with EH risk (P = 0.046) and conferred a reduced risk of EH development (OR = 0.99, 95%CI = 0.97-1.00). Conversely, no substantial association between IL-6 rs1800796, -572G > C polymorphism and the risk of EH was found in all genetic models (P > 0.05). Moreover, the eQTL analysis indicated that the -174C > G polymorphism was significantly associated with gene expression of IL-6 (P = 0.006), and the G allele corresponded to a reduced IL-6 gene expression (Beta = -0.397). Compared with -174C > G, the -572G > C polymorphism was not found to be significantly associated with IL-6 gene expression (Beta = -0.120, P = 0.560). Conclusions Our findings provide evidence that the rs1800795, -174C > G polymorphism can affect the expression levels of IL-6, and the risk of EH occurrence. However, the rs1800796, -572G > C polymorphism does not regulate the IL-6 gene expression levels and the susceptibility of EH.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

The role of interleukin-6 in the development of cardiovascular diseases: A review

Currently, the search and study of new biological markers that can provide early diagnosis of cardiovascular diseases, serve as a laboratory tool for assessing the effectiveness of treatment, or be used as prognostic markers and risk stratification criteria is ongoing. Our literature review indicates the potentially important diagnostic and prognostic value of assessing members of the interleukin-6 family. It is expected that further scientific and clinical studies will demonstrate the possibility of using members of the interleukin-6 family as an additional laboratory tool for the diagnosis, risk stratification and prediction of cardiovascular events in cardiac patients. It is necessary to evaluate in detail the possibilities of blockade of these interleukin-6 molecules in patients with cardiovascular diseases in vitro and in vivo.

Summary of Known Genetic and Epigenetic Modification Contributed to Hypertension

Hypertension is a multifactorial disease due to a complex interaction among genetic, epigenetic, and environmental factors. Characterized by raised blood pressure (BP), it is responsible for more than 7 million deaths per annum by acting as a leading preventable risk factor for cardiovascular disease. Reports suggest that genetic factors are estimated to be involved in approximately 30 to 50% of BP variation, and epigenetic marks are known to contribute to the initiation of the disease by influencing gene expression. Consequently, elucidating the genetic and epigenetic mediators associated with hypertension is essential for better discernment of its pathophysiology. By deciphering the unprecedented molecular hypertension basis, it could help to unravel an individual's inclination towards hypertension which eventually could result in an arrangement of potential strategies for prevention and therapy. In the present review, we discuss known genetic and epigenetic drivers that contributed to the hypertension development and summarize the novel variants that have currently been identified. The effect of these molecular alterations on endothelial function was also presented.

Deeper insight into the role of IL-17 in the relationship beween hypertension and intestinal physiology

With the incidence of hypertension increasing worldwide, more and more the mechanisms of hypertension from the perspective of immunity have found. Intestinal microbiota as well as its metabolites relationship with hypertension has attracted great attention from both clinicians and investigators. However, the associations of hypertension with lesions of a large number of immune factors including IL-17, MCP-1, IL-6, TGF-β, IL-10 and others have not been fully characterized. In this review, after introducing the immune factors as the most potent anti/pro-hypertension agents known, we provide detailed descriptions of the IL-17 involved in the pathology of hypertension, pointing out the underlying mechanisms and suggesting the clinical indications.

The Role of Interleukin-6 Family Members in Cardiovascular Diseases

Cardiovascular disease is one of the main causes of human mortality. Cytokines play crucial roles in the development of cardiovascular disease. Interleukin (IL)-6 family members are a series of cytokines, including IL-6, IL-11, IL-30, IL-31, OSM, LIF, CNTF, CT-1, CT-2, and CLC, that regulate multiple biological effects. Experimental and clinical evidence shows that IL-6 family members are closely related to cardiovascular diseases such as atherosclerosis, hypertension, aortic dissection, cardiac fibrosis, and cardiomyopathy. This review mainly discusses the role of IL-6 family members in cardiovascular disease for the sake of identifying possible intervention targets for cardiovascular disease prevention and treatment.

Novel methylation mark and essential hypertension

Background

Essential hypertension (EH) is an important risk factor for various cardiovascular, cerebral and renal disorders. It is a multi-factorial trait which occurs through complex interplay between genetic, epigenetic, and environmental factors. Even after advancement of technology and deciphering the involvement of multiple signalling pathways in blood pressure regulation, it still remains as a huge global concern.

Main body of the abstract

Genome-wide association studies (GWAS) have revealed EH-associated genetic variants but these solely cannot explain the variability in blood pressure indicating the involvement of additional factors. The etiopathogenesis of hypertension has now advanced to the level of epigenomics where aberrant DNA methylation is the most defined epigenetic mechanism to be involved in gene regulation. Though role of DNA methylation in cancer and other mechanisms is deeply studied but this mechanism is in infancy in relation to hypertension. Generally, 5-methylcytosine (5mC) levels are being targeted at both individual gene and global level to find association with the disease. But recently, with advanced sequencing techniques another methylation mark, N6-methyladenine (6mA) was found and studied in humans which was earlier considered to be absent in case of eukaryotes. Relation of aberrant 6mA levels with cancer and stem cell fate has drawn attention to target 6mA levels with hypertension too.

Conclusion

Recent studies targeting hypertension has suggested 6mA levels as novel marker and its demethylase, ALKBH1 as probable therapeutic target to prevent hypertension through epigenetic programming. This review compiles different methylation studies and suggests targeting of both 5mC and 6mA levels to cover role of methylation in hypertension in broader scenario.

Hypertension and its management in COVID-19 patients: The assorted view

BACKGROUND

Coronavirus disease 2019 (COVID-19) is suspected to mainly be more deleterious in patients with underlying cardiovascular diseases (CVD). There is a strong association between hypertension and COVID-19 severity. The binding of SARS-CoV-2 to the angiotensin-converting enzyme 2 (ACE2) leads to deregulation of the renin-angiotensin-aldosterone system (RAAS) through down-regulation of ACE2 with subsequent increment of the harmful Ang II serum levels and reduction of the protective Ang-(1-7). Both angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) are commonly used to manage hypertension.

OBJECTIVE

Objective was to illustrate the potential link between hypertension and COVID-19 regarding the role of angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) in hypertensive patients with COVID-19.

METHODS

We carried out comprehensive databases search from late December 2019 to early January 2021 by using online engines of Web of Science, Research gate, Scopus, Google Scholar, and PubMed for published and preprinted articles.

RESULTS

The present study's findings showed that hypertension is regarded as an independent risk factor for COVID-19 severity. Both ACEIs and ARBs are beneficial in managing hypertensive patients.

CONCLUSION

This study concluded that hypertension increases COVID-19 severity due to underlying endothelial dysfunctions and coagulopathy. COVID-19 might augment the hypertensive complications due to down-regulation of ACE2. The use of ACEIs or ARBs might be beneficial in the management of hypertensive patients with COVID-19.

Roles and Mechanisms of DNA Methylation in Vascular Aging and Related Diseases

Vascular aging is a pivotal risk factor promoting vascular dysfunction, the development and progression of vascular aging-related diseases. The structure and function of endothelial cells (ECs), vascular smooth muscle cells (VSMCs), fibroblasts, and macrophages are disrupted during the aging process, causing vascular cell senescence as well as vascular dysfunction. DNA methylation, an epigenetic mechanism, involves the alteration of gene transcription without changing the DNA sequence. It is a dynamically reversible process modulated by methyltransferases and demethyltransferases. Emerging evidence reveals that DNA methylation is implicated in the vascular aging process and plays a central role in regulating vascular aging-related diseases. In this review, we seek to clarify the mechanisms of DNA methylation in modulating ECs, VSMCs, fibroblasts, and macrophages functions and primarily focus on the connection between DNA methylation and vascular aging-related diseases. Therefore, we represent many vascular aging-related genes which are modulated by DNA methylation. Besides, we concentrate on the potential clinical application of DNA methylation to serve as a reliable diagnostic tool and DNA methylation-based therapeutic drugs for vascular aging-related diseases.

Intracranial VCAM1 at time of mechanical thrombectomy predicts ischemic stroke severity

Background

Emergent large vessel occlusion (ELVO) strokes are devastating ischemic vascular events for which novel treatment options are needed. Using vascular cell adhesion molecule 1 (VCAM1) as a prototype, the objective of this study was to identify proteomic biomarkers and network signaling functions that are potential therapeutic targets for adjuvant treatment for mechanical thrombectomy.

Methods

The blood and clot thrombectomy and collaboration (BACTRAC) study is a continually enrolling tissue bank and registry from stroke patients undergoing mechanical thrombectomy. Plasma proteins from intracranial (distal to clot) and systemic arterial blood (carotid) were analyzed by Olink Proteomics for N=42 subjects. Statistical analysis of plasma proteomics used independent sample t tests, correlations, linear regression, and robust regression models to determine network signaling and predictors of clinical outcomes. Data and network analyses were performed using IBM SPSS Statistics, SAS v 9.4, and STRING V11.

Results

Increased systemic (p<0.001) and intracranial (p=0.013) levels of VCAM1 were associated with the presence of hypertension. Intracranial VCAM1 was positively correlated to both infarct volume (p=0.032; r=0.34) and edema volume (p=0.026; r=0.35). The %∆ in NIHSS from admittance to discharge was found to be significantly correlated to both systemic (p=0.013; r = −0.409) and intracranial (p=0.011; r = −0.421) VCAM1 levels indicating elevated levels of systemic and intracranial VCAM1 are associated with reduced improvement of stroke severity based on NIHSS from admittance to discharge. STRING-generated analyses identified biologic functional descriptions as well as function-associated proteins from the predictive models of infarct and edema volume.

Conclusions

The current study provides novel data on systemic and intracranial VCAM1 in relation to stroke comorbidities, stroke severity, functional outcomes, and the role VCAM1 plays in complex protein-protein signaling pathways. These data will allow future studies to develop predictive biomarkers and proteomic targets for drug development to improve our ability to treat a devastating pathology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02157-4.

H2S releasing Sodium sulfide protects from acute stress-induced hypertension by increasing the activity of endothelial nitric oxide synthase enzyme

Acute stress is a feature of our daily events that affects cardiovascular system and predisposes to hypertension. H₂S is now considered as a vasorelaxant gasotransmitter although it was considered as a toxic agent. In present work we studied the effect of H₂S releasing Na₂S in acute stress induced hypertension and cardiac damage. Rats were divided into five groups: control, Na₂S, acute stress, half dose of Na₂S (6  mg/kg), and finally full dose of Na₂S (12  mg/kg) to acute stressed rats. BP was measured then blood samples were taken for estimation of cortisol, cardiac enzymes markers, IL-6 and H₂S. Finally, animals were sacrificed, hearts and thoracic aortae were excised for histological assessment, estimation of MDA, SOD and RNA extraction of CSE. Acute stress significantly elevated BP, cortisol, cardiac enzymes markers, IL-6, and tissue levels of MDA. It also, induced cardiac cell damage with congested B.V., extravasation of blood and decreased eNOs. Moreover, acute stress reduced H₂S levels, RNA expression of CSE and SOD in cardiac tissues. Na₂S significantly decreased BP, serum levels of cortisol, cardiac enzymes markers, IL-6, and tissue levels of MDA. Also, Na₂S elevated serum H₂S, RNA expression of CSE, SOD in cardiac tissue and increased eNOs activity.

Angiotensin-converting enzyme 2, the complement system, the kallikrein-kinin system, type-2 diabetes, interleukin-6, and their interactions regarding the complex COVID-19 pathophysiological crossroads

Because of the current COVID-19-pandemic, the world is currently being held hostage in various lockdowns. ACE2 facilitates SARS-CoV-2 cell-entry, and is at the very center of several pathophysiological pathways regarding the RAAS, CS, KKS, T2DM, and IL-6. Their interactions with severe COVID-19 complications (e.g. ARDS and thrombosis), and potential therapeutic targets for pharmacological intervention, will be reviewed.

The up-regulated hsa-circRNA9102-5 may be a risk factor for essential hypertension

Background

The present study was aimed to investigate the expression levels of circular RNAs (circRNAs) in the peripheral blood of essential hypertension (EH) patients and healthy controls (HC). On this basis, we tried to explain the possible role of circRNAs in the progression of EH and their potential as diagnostic biomarkers of EH.

Methods

First, we analyzed the differentially expressed circRNAs in peripheral blood obtained from the finished microarray analysis and selected four circRNAs under strict standards. Then, quantitative real‐time polymerase chain reaction (qRT‐PCR) was performed to measure the expression levels of the selected circRNAs in a total of 192 blood samples, consisting of 96 HC and 96 diagnosed EH patients. Bioinformatics prediction of the target microRNAs (miRNAs) was performed for differentially expressed circRNAs, and the circulating vascular‐related miRNAs were selected for qRT‐PCR analysis to determine their expression levels.

Results

Hsa‐circRNA9102‐5 (11.7 ± 1.06 vs 12.13 ± 1.11, P = .007) was up‐regulated in the patients group which was diagnosed with EH, as compared to the HC group, and was involved in the regulation of EH by sponging hsa‐miR‐150‐5p. The area under the ROC curve (AUC) of the model was 0.620, using hsa‐circRNA9102‐5 as an independent predictor. Furthermore, the AUC was increased to 0.728 when hsa‐circRNA9102‐5 was combined with hsa‐miR‐150‐5p and multiple other factors, as a combined predictor.

Conclusions

The present results suggested that hsa‐circRNA9102‐5 may have played a crucial role in the development of EH by sponging hsa‐miR‐150‐5p, which showed great potential as a novel target.

Leucocytic DNA Methylation of Interleukin-6 Promoter Reduction in Pre-Hypertensive Young Adults

Background

Pre-hypertension is associated with increased risk of cardiovascular disease. Chronic inflammation plays an important role in the pathophysiology of essential hypertension, with epigenetic dysregulation involvement. Nevertheless, the role of DNA methylation in prehypertensive state is unknown. The aim of this study was to investigate the association between DNA methylation level of interleukin-6 (IL-6) promoter in pre-hypertensive (PreHT) and normotensive (NT) young adults.

Methods

A total of 80 NT and 80 PreHT healthy subjects aged between 18-45 years were recruited in Kuantan, Pahang, Malaysia using an observational cross-sectional study approach. DNA methylation level of IL-6 promoter in peripheral leukocytes were measured using bisulphite conversion and MethyLight assay.

Results

There was no significant difference in age between NT and PreHT (P = 0.655). The mean blood pressure was 110(8)/73(5) mmHg in NT and 125(7)/82(5) mmHg in PreHT subjects. The IL-6 promoter methylation level was significantly lower in PreHT compared to NT subjects (P < 0.001).

Conclusion

The current study demonstrates that hypomethylation of IL-6 promoter was associated with pre-hypertension in young adults. Thus, IL-6 methylation could be used as an early indicator for predicting hypertension and related risk of cardiovascular diseases in prehypertensive subjects. Gene expression and longitudinal studies are warranted to examine the methylation effect on IL-6 expression over time.

DNA Methylation of Candidate Genes (ACE II, IFN-γ, AGTR 1, CKG, ADD1, SCNN1B and TLR2) in Essential Hypertension: A Systematic Review and Quantitative Evidence Synthesis

Physical, chemical, and social environments adversely affect the molecular process and results in cell signal transduction and the subsequent transcription factor dysregulation, leading to impaired gene expression and abnormal protein synthesis. Stressful environments such as social adversity, isolation, sustained social threats, physical inactivity, and highly methylated diets predispose individuals to molecular level alterations such as aberrant epigenomic modulations that affect homeostasis and hemodynamics. With cardiovascular disease as the leading cause of mortality in the US and blacks/African Americans being disproportionately affected by hypertension (HTN) which contributes substantially to these deaths, reflecting the excess mortality and survival disadvantage of this sub-population relative to whites, understanding the molecular events, including epigenomic and socio-epigenomic modulations, is relevant to narrowing the black-white mortality risk differences. We aimed to synthesize epigenomic findings in HTN namely (a) angiotensin-converting enzyme 2 (ACE II) gene, (b) Toll-like receptor 2 (TLR2) gene, (c) interferon γ (IFN-γ) gene, and (d) Capping Actin Protein, Gelosin-Like (CAPG) gene, adducin 1(ADD1) gene, (e) Tissue inhibitor of metalloproteinase 3 (TIMP3), (f) mesoderm specific transcript (MEST) loci, (g) sodium channel epithelial 1 alpha subunit 2 (SCNN1B), (h) glucokinase (CKG) gene (i) angiotensin II receptor, type1 (AGTR1), and DNA methylation (mDNA). A systematic review and quantitative evidence synthesis (QES) was conducted using Google Scholar and PubMed with relevant search terms. Data were extracted from studies on: (a) Epigenomic modulations in HTN based on ACE II (b) TLR2, (c) IFN-γ gene, (d) CAPG, ADD1, TIMP3, MEST loci, and mDNA. The random-effect meta-analysis method was used for a pooled estimate of the common effect size, while z statistic and I^2 were used for the homogeneity of the common effect size and between studies on heterogeneity respectively. Of the 642 studies identified, five examined hypermethylation while seven studies assessed hypomethylation in association with HTN. The hypermethylation of ACE II, SCNN1B, CKG, IFN-γ gene, and miR-510 promoter were associated with hypertension, the common effect size (CES) = 6.0%, 95% CI, −0.002–11.26. In addition, the hypomethylation of TLR2, IFN-γ gene, ADD1, AGTR1, and GCK correlated with hypertension, the CES = 2.3%, 95% CI, −2.51–7.07. The aberrant epigenomic modulation of ACE II, TLR2, IFN-γ, AGTR1, and GCK correlated with essential HTN. Transforming the environments resulting from these epigenomic lesions will facilitate early intervention mapping in reducing HTN in the US population, especially among socially disadvantaged individuals, particularly racial/ethnic minorities.

The role of DNA methylation and histone modifications in blood pressure: a systematic review

Epigenetic mechanisms might play a role in the pathophysiology of hypertension, a major risk factor for cardiovascular disease and renal failure. We aimed to systematically review studies investigating the association between epigenetic marks (global, candidate-gene or genome-wide methylation of DNA, and histone modifications) and blood pressure or hypertension. Five bibliographic databases were searched until the 7th of December 2018. Of 2984 identified references, 26 articles based on 25 unique studies met our inclusion criteria, which involved a total of 28,382 participants. The five studies that assessed global DNA methylation generally found lower methylation levels with higher systolic blood pressure, diastolic blood pressure, and/or presence of hypertension. Eighteen candidate-gene studies reported, in total, 16 differentially methylated genes, including renin-angiotensin-system-related genes (ACE promoter and AGTR1) and genes involved in sodium homeostasis and extracellular fluid volume maintenance system (NET promoter, SCNN1A, and ADD1). Between the three identified epigenome-wide association studies (EWAS), lower methylation levels of SULF1, EHMT2, and SKOR2 were found in hypertensive patients as compared with normotensive subjects, and lower methylation levels of PHGDH, SLC7A11, and TSPAN2 were associated with higher systolic and diastolic blood pressure. In summary, the most convincing evidence has been reported from candidate-gene studies, which show reproducible epigenetic changes in the interconnected renin-angiotensin and inflammatory systems. Our study highlights gaps in the literature on the role of histone modifications in blood pressure and the need to conduct high-quality studies, in particular, hypothesis-generating studies that may help to elucidate new molecular mechanisms.

Impact of interleukin-6 gene polymorphisms and its interaction with obesity on osteoporosis risk in Chinese postmenopausal women

AIMS

To investigate the association of four single-nucleotide polymorphisms (SNPs) of the IL-6 gene with osteoporosis (OST) susceptibility.

METHODS

PCR restriction fragment length polymorphism (PCR-RFLP) was carried out for SNPs detection. Generalized multifactor dimensionality reduction (GMDR) model and logistic regression model were used to examine the interaction between SNP and obesity on OST.

RESULTS

Logistic regression model revealed that G allele of rs1800796 and the T allele of rs2069849 were associated with increased OST risk, compared to those with wild genotype. However, no significant correlations were found when analyzing the association of rs1800795 and rs1554606 with OST risk. GMDR analysis suggested that the interaction model composed of the rs1800796 and obesity was the best model with statistical significance (P value from sign test [Psign] = 0.012), indicating a potential gene-environment interaction between rs1800796 and obesity. Overall, the two-locus models had a cross-validation consistency of 10/10 and had the testing accuracy of 0.641. We also conducted stratified analysis for rs1800796 genotype and obesity, and found that obese subjects with CG or GG genotype have the highest OST risk, compared to subjects with CC genotype, and normal BMI OR (95% CI) = 2.21 (1.52-3.49), after adjustment for age, smoke, and alcohol consumption status.

CONCLUSIONS

Our results suggested that the C allele of rs1800796 and the C allele of rs2069849 of IL-6 gene interaction between rs1800796 and abdominal obesity were all associated with increased OST risk.

Arterial Hypertension and Interleukins: Potential Therapeutic Target or Future Diagnostic Marker?

Hypertension as a multifactorial pathology is one of the most important cardiovascular risk factors, affecting up to 30-40% of the general population. Complex immune responses are involved in the inflammatory mechanism of hypertension, with evidence pointing to increased inflammatory mediators even in prehypertensive patients. Increased vascular permeability, thrombogenesis, and fibrosis, effects that are associated with sustained hypertension, could be attributed to chronic inflammation. Chronic inflammation triggers endothelial dysfunction via increased production of ROS through proinflammatory cytokines. Increased serum level of proinflammatory cytokines such as IL-1β, IL-6, IL-8, IL-17, IL-23, TGFβ, and TNFα in hypertensive patients has been associated with either increased blood pressure values and/or end-organ damage. Moreover, some cytokines (i.e., IL-6) seem to determine a hypertensive response to angiotensin II, regardless of blood pressure values. Understanding hypertension as an inflammatory-based pathology gives way to new therapeutic targets. As such, conventional cardiovascular drugs (statins, calcium channels blockers, and ACEIs/ARBs) have shown additional anti-inflammatory effects that could be linked to their blood pressure lowering properties. Moreover, anti-inflammatory drugs (mycophenolate mofetil) have been shown to decrease blood pressure in hypertensive patients or prevent its development in normotensive individuals. Further research is needed to evaluate whether drugs targeting hypertensive-linked proinflammatory cytokines, such as monoclonal antibodies, could become a new therapeutic option in treating arterial hypertension.

Epigenetic modification: a regulatory mechanism in essential hypertension

Essential hypertension (EH) is a multifactorial disease of the cardiovascular system that is influenced by the interplay of genetic, epigenetic, and environmental factors. The molecular dynamics underlying EH etiopathogenesis is unknown; however, earlier studies have revealed EH-associated genetic variants. Nevertheless, this finding alone is not sufficient to explain the variability in blood pressure, suggesting that other risk factors are involved, such as epigenetic modifications. Therefore, this review highlights the potential contribution of well-defined epigenetic mechanisms in EH, specifically, DNA methylation, post-translational histone modifications, and microRNAs. We further emphasize global and gene-specific DNA methylation as one of the most well-studied hallmarks among all epigenetic modifications in EH. In addition, post-translational histone modifications, such as methylation, acetylation, and phosphorylation, are described as important epigenetic markers associated with EH. Finally, we discuss microRNAs that affect blood pressure by regulating master genes such as those implicated in the renin-angiotensin-aldosterone system. These epigenetic modifications, which appear to contribute to various cardiovascular diseases, including EH, may be a promising research area for the development of novel future strategies for EH prevention and therapeutics.

Circular RNA hsa_circ_0014243 may serve as a diagnostic biomarker for essential hypertension

Circular RNAs (circRNAs) have a great potential as clinical biomarkers; however, specific circRNAs with a diagnostic value for essential hypertension (EH) largely remain to be identified. In the present study, the potential application of Homo sapiens (hsa)_circ_0014243, which was identified to be significantly upregulated in whole blood samples of EH patients in a previous microarray profiling study by our group, in the diagnosis of EH was evaluated. Reverse transcription-quantitative polymerase chain reaction analysis was performed to determine the expression levels of hsa_circ_0014243 and hsa-microRNA (miR)-10a-5p in a total of 178 blood samples collected from 89 healthy controls and 89 patients diagnosed with EH. Divergent primers were designed for circRNAs, while conventional primers were used for miRs. Independent-samples t-tests and bivariate correlation analyses were performed to analyze the association between clinical factors influencing EH and hsa_circ_0014243 expression levels. A receiver operating characteristics (ROC) curve was generated to estimate the diagnostic value of hsa_circ_0014243 for EH. Finally, the expression levels of circRNAs and miRNAs were combined to propose a possible prediction model for EH. The results indicated that hsa_circ_0014243 was upregulated in whole blood samples of EH patients compared with that in the controls (P<0.001). Furthermore, the relative expression levels of hsa_circ_0014243 (Δ quantification cycle) were identified to be significantly correlated with age (r=-0.259, P<0.001), high-density lipoprotein levels (r=0.196, P=0.009) and glucose levels (r=-0.204, P=0.006). The area under the ROC curve (AUC) of the model using hsa_circ_0014243 as a predictor was 0.732. Of note, the AUC increased to 0.781 when hsa_circ_0014243 levels were combined with hsa-miR-10a-5p levels as predictors. The present results suggest that hsa_circ_0014243 has a crucial role in the genesis and development of EH, and presents a certain diagnostic capability for EH.

Serine hydroxymethyltransferase 1 promoter hypermethylation increases the risk of essential hypertension

BACKGROUND

Serine hydroxymethyltransferase 1 (SHMT1) is an enzyme involved in folic acid metabolism and is known to contribute to the development of hypertension. We evaluated the relationship between SHMT1 promoter methylation and essential hypertension (EH).

METHODS

Quantitative methylation-specific polymerase chain reaction was used to measure the SHMT1 promoter methylation level in 241 EH patients and 288 age- and gender-matched healthy individuals. The diagnostic value of SHMT1 promoter hypermethylation was analyzed using a receiver operating characteristic (ROC) curve. The Gene Expression Omnibus (GEO) database and dual-luciferase reporter assay were used to validate our findings.

RESULTS

Compared with the control group, significant differences in SHMT1 promoter methylation were found in both EH and hyperhomocysteinemia groups (P < 0.001 and P = 0.029, respectively). The area under the curve of the diagnosis of SHMT1 promoter hypermethylation for EH was 0.808, with a sensitivity and specificity of 73.9% and 77.8%, respectively. The risk of SHMT1 promoter hypermethylation was significantly higher in the >65-year group than in the ≤65-year group (odds ratio = 3.925; 95% confidence interval = 2.141-7.196). In addition, GEO database analysis showed that 5-aza-deoxycytidine increased gene expression in several carotid endothelial cell lines. A dual-luciferase reporter assay revealed that the target sequence in the SHMT1 promoter upregulated gene expression.

CONCLUSION

Our findings indicate that SHMT1 promoter hypermethylation increases the risk of EH and may be a promising biomarker for EH.

Maternal protein malnutrition induced-hypertension: New evidence about the autonomic and respiratory dysfunctions and epigenetic mechanisms

Maternal protein malnutrition during the critical stages of development (pregnancy, lactation and first infancy) can lead to adult hypertension. Studies have shown that renal and cardiovascular dysfunctions can be associated to the development of hypertension in humans and rats exposed to maternal protein malnutrition. The etiology of hypertension, however, includes a complex network involved in central and peripheral blood pressure control. Recently, the hyperactivity of the sympathetic nervous system in protein-restricted rats has been reported. Studies have shown that protein malnutrition during pregnancy and/or lactation alters blood pressure control through mechanisms that include central sympathetic-respiratory dysfunctions and epigenetic modifications, which may contribute to adult hypertension. Thus, this review will discuss the historical context, new evidences of neurogenic disruption in respiratory-sympathetic activities and possible epigenetic mechanisms involved in maternal protein malnutrition induced- hypertension.