Associations of B-Type Natriuretic Peptide and Its Coding Gene Promoter Methylation With Functional Outcome of Acute Ischemic Stroke: A Mediation Analysis

Natriuretic peptide system in hypertension: Current understandings of its regulation, targeted therapies and future challenges

The natriuretic peptide system (NPS) is the key driving force of the heart's endocrine function. Recent developments in NPS-targeted therapies have been found promising and effective against cardiovascular diseases, including hypertension. Notably, after discovering crosstalk between NPS and the renin-angiotensin-aldosterone system (RAAS), various combinations such as neprilysin/angiotensin II receptor type 1 AT1 receptor inhibitors and neprilysin/renin inhibitors have been preclinically and clinically tested against various cardiac complications. However, the therapeutic effects of such combinations on the pathophysiology of hypertension are poorly understood. Furthermore, the complicated phenomena underlying NPS regulation and function, particularly in hypertension, are still unexplored. Mounting evidence suggests that numerous regulatory mechanisms modulate the expression of NPS, which can be used as potential targets against hypertension and other cardiovascular diseases. Therefore, this review will specifically focus on epigenetic and other regulators of NPS, identifying prospective regulators that might serve as new therapeutic targets for hypertension. More importantly, it will shed light on recent developments in NPS-targeted therapies, such as M-atrial peptides, and their latest combinations with RAAS modulators, such as S086 and sacubitril-aliskiren. These insights will aid in the development of effective therapies to break the vicious cycle of high blood pressure during hypertension, ultimately addressing the expanding global heart failure pandemic.

Identification of significant m6A regulators and immune microenvironment characterization in ischemic stroke

The role of m6A modification in the regulation of the immune microenvironment (IME) of ischemic stroke (IS) is barely known. Thus, we aim to investigate the impact of m6A modification on the IME of IS and its diagnostic value in IS. We comprehensively assessed the m6A modification patterns, the relationship between these modification patterns and the characteristics of the IME. The m6A modification patterns of individual IS sample were quantified by m6Ascore. The performance of m6A phenotype-related genes as potential biomarkers was evaluated by the area under the receiver operating characteristic curve. Experimental validation was also performed by qRT-PCR. Six dysregulated m6A regulators were identified and a classification model consisting of four key m6A regulators (METLL3, RBMX, RBM15B, YTDHF3) could distinguish IS and healthy control samples well. METTL3 and YTHDF3 are closely related to circulating neutrophil abundance. Two distinct m6A modification patterns were determined which differed in immunocyte abundance. We also identified six m6A phenotype-related genes (APOBEC3A, PTMA, FCGR3A, LOC440926, LOC649946, and FTH1L11), and further explored their biological function. Among them, APOBEC3A, FCGR3A, and FTH1L11 were positively associated with neutrophil abundance. APOBEC3A and FCGR3A were stable diagnostic m6A-associated genes in both the discovery and validation cohorts. This study reveals that m6A modification plays a non-negligible role in the formation of a diversified and complex IME in IS. The m6A phenotype-related genes could be diagnostic biomarkers of IS.

Epigenetic mechanisms and potential therapeutic targets in stroke

Accumulating evidence indicates a central role for epigenetic modifications in the progression of stroke pathology. These epigenetic mechanisms are involved in complex and dynamic processes that modulate post-stroke gene expression, cellular injury response, motor function, and cognitive ability. Despite decades of research, stroke continues to be classified as a leading cause of death and disability worldwide with limited clinical interventions. Thus, technological advances in the field of epigenetics may provide innovative targets to develop new stroke therapies. This review presents the evidence on the impact of epigenomic readers, writers, and erasers in both ischemic and hemorrhagic stroke pathophysiology. We specifically explore the role of DNA methylation, DNA hydroxymethylation, histone modifications, and epigenomic regulation by long non-coding RNAs in modulating gene expression and functional outcome after stroke. Furthermore, we highlight promising pharmacological approaches and biomarkers in relation to epigenetics for translational therapeutic applications.

DNA Methylation of the Natriuretic Peptide System Genes and Ischemic Stroke: Gene-Based and Gene Set Analyses

Background and Objectives

The natriuretic peptide (NP) system has been considered an important regulator for ischemic stroke (IS) with a limited clinical implication. A better understanding of the underlying molecular mechanisms is urgent. Here, we aimed to examine the role of DNA methylation of NP system genes in IS.

Methods

DNA methylation at promoter regions of 4 core NP system genes, e.g., CORIN, FURIN, NPPA, and NPPB, was measured by targeted bisulfite sequencing in 853 patients with IS and 918 controls. We first examined the association between DNA methylation at each single CpG and IS, followed by gene-based and gene set analyses to examine the joint associations of DNA methylation at multiple CpGs in a gene or all 4 genes as a pathway with IS.

Results

After control of covariates and multiple testing, DNA methylation at 19 of the 36 assayed CpGs was individually associated with IS at q < 0.05. Higher average methylation levels at the targeted regions of CORIN (odds ratio [OR] = 0.64, 95% confidence interval [CI]: 0.56–0.73), FURIN (OR = 0.78, 95% CI: 0.69–0.88), and NPPA (OR = 0.78, 95% CI: 0.69–0.88) were associated with a lower odds of IS (all q < 0.05). The truncated product method revealed the same gene-based associations (all q < 0.05) and found that DNA methylation at all 4 NP system genes together was jointly associated with IS (p = 0.0001).

Discussion

DNA methylation at NP system genes was downregulated in patients with IS. Our results may unravel a molecular mechanism underlying the regulating effect of the NP system on IS and highlight the relevance of testing the joint effect of multiple CpGs in the epigenetic analysis.

Circulating N-Terminal Probrain Natriuretic Peptide Levels in Relation to Ischemic Stroke and Its Subtypes: A Mendelian Randomization Study

Mendelian randomization was used to evaluate the potential causal association between N-terminal probrain natriuretic peptide (NT-proBNP) and ischemic stroke based on summary statistics data from large-scale genome-wide association studies. Three single-nucleotide polymorphisms (SNPs) rs198389, rs13107325, and rs11105306 associated with NT-proBNP levels found in large general populations and in patients with acute heart disease were used as instrumental variables. The results of genetic association analysis of each single SNP show that there is no significant association between NT-proBNP levels and ischemic stroke or its subtypes, whereas rs198389 alone has a suggestive association with large-artery atherosclerosis stroke. The MR analysis of three SNPs shows that NT-proBNP levels may reduce the risk of small-vessel occlusion stroke suggestively. This genetic analysis provides insights into the pathophysiology and treatment of ischemic stroke.

Heart Failure in Breast Cancer Survivors: Focus on Early Detection and Novel Biomarkers

PURPOSE OF REVIEW

Breast cancer survival rate has greatly improved in the last two decades due to the emergence of next-generation anti-cancer agents. However, cardiotoxicity remains a significant adverse effect arising from traditional and emerging chemotherapies as well as targeted therapies for breast cancer patients. In this review, we will discuss cardiotoxicities of both traditional and emerging therapies for breast cancer. We will discuss current practices to detect cardiotoxicity of these therapies with the focus on new and emerging biomarkers. We will then focus on 'omics approaches, especially the use of epigenetics to discover novel biomarkers and therapeutics to mitigate cardiotoxicity.

RECENT FINDINGS

Significant cardiotoxicities of conventional chemotherapies remain and new and unpredictable new forms of cardiac and/or vascular toxicity emerge with the surge in novel and targeted therapies. Yet, there is no clear guidance on detection of cardiotoxicity, except for significant left ventricular systolic dysfunction, and even then, there is no uniform definition of what constitutes cardiotoxicity. The gold standard for detection of cardiotoxicity involves a serial echocardiography in conjunction with blood-based biomarkers to detect early subclinical cardiac dysfunction. However, the ability of these tests to detect early disease remains limited and not all forms of toxicity are detectable with these modalities. There is an unprecedented need to discover novel biomarkers that are sensitive and specific for early detection of subclinical cardiotoxicity. In that space, novel echocardiographic techniques, such as strain, are becoming more common-place and new biomarkers, discovered by epigenetic approaches, seem to become promising alternatives or adjuncts to conventional non-specific cardiac biomarkers.

Associations of B-Type Natriuretic Peptide and Its Coding Gene Promoter Methylation With Functional Outcome of Acute Ischemic Stroke: A Mediation Analysis

Background

The prognostic role of B‐type natriuretic peptide (BNP) in stroke has been suggested, but limited studies have shown mixed results and unknown underlying mechanisms. DNA methylation, a molecular modification that alters gene expression, may represent a candidate mechanism for this purpose. We aimed to examine the associations of BNP and methylation of its coding gene (natriuretic peptide B [NPPB]) with the functional outcome in a large sample of patients with acute ischemic stroke from CATIS (China Antihypertensive Trial in Acute Ischemic Stroke).

Methods and Results

Leveraging participants from CATIS with available specimens, serum proBNP (equimolarly produced with BNP) was measured in 3216 patients (mean age, 62 years; 64% men), and peripheral blood DNA methylation of the NPPB promoter was quantified by targeted bisulfite sequencing in 806 patients (mean age, 62 years; 54% men). The functional outcome was defined as an ordered modified Rankin Scale score assessed at 14 days or hospital discharge after stroke onset. Mediation analysis was conducted to test the potential mediating effect of proBNP on the relationship between NPPB methylation and functional outcome. The results showed that a higher level of proBNP was significantly associated with a higher risk of having a poorer functional outcome (odds ratio [OR], 1.14; P=0.006). Every 5% of hypermethylation at 2 (Chr1:11919160 [OR, 0.93; P=0.022] and Chr1:11918989 [OR, 0.92; P=0.032]) of 11 CpG loci assayed was associated with 7% and 8% lower risk, respectively, of having a poor functional outcome. In addition, proBNP was negatively correlated to hypermethylation at 1 CpG (Chr1:11918989 [β=−0.029; P=0.009]) and mediated approximately 7.69% (95% CI, 2.50%–13.82%) of the association between this CpG methylation and the functional outcome.

Conclusions

Hypermethylation at the NPPB promoter is associated with the functional outcome after ischemic stroke, at least partially by suppressing BNP expression or excretion.