A novel interaction between sympathetic overactivity and aberrant regulation of renin by miR-181a in BPH/2J genetically hypertensive mice

Non-coding RNAs and hypertension-unveiling unexpected mechanisms of hypertension by the dark matter of the genome

Hypertension is a major risk factor of cardiovascular diseases and a most important health problem in developed countries. Investigations on pathophysiology of hypertension have been based on gene products from coding region that occupies only about 1% of total genome region. On the other hand, non-coding region that occupies almost 99% of human genome has been regarded as "junk" for a long time and went unnoticed until these days. But recently, it turned out that noncoding region is extensively transcribed to non-coding RNAs and has various functions. This review highlights recent updates on the significance of non-coding RNAs such as micro RNAs and long non-coding RNAs (lncRNAs) on the pathogenesis of hypertension, also providing an introduction to basic biology of noncoding RNAs. For example, microRNAs are associated with hypertension via neuro-fumoral factor, sympathetic nerve activity, ion transporters in kidneys, endothelial function, vascular smooth muscle phenotype transformation, or communication between cells. Although reports of lncRNAs on pathogenesis of hypertension are scarce at the moment, new lncRNAs in relation to hypertension are being discovered at a rapid pace owing to novel techniques such as microarray or next-generation sequencing. In the clinical settings, clinical use of non-coding RNAs in identifying cardiovascular risks or developing novel tools for treating hypertension such as molecular decoy or mimicks is promising, although improvement in chemical modification or drug delivery system is necessary.

Epigenetics and arterial hypertension: the challenge of emerging evidence

Epigenetic phenomena include DNA methylation, post-translational histone modifications, and noncoding RNAs, as major marks. Although similar to genetic features of DNA for their heritability, epigenetic mechanisms differ for their potential reversibility by environmental and nutritional factors, which make them potentially crucial for their role in complex and multifactorial diseases. The function of these mechanisms is indeed gaining interest in relation to arterial hypertension (AH) with emerging evidence from cell culture and animal models as well as human studies showing that epigenetic modifications have major functions within pathways related to AH. Among epigenetic marks, the role of DNA methylation is mostly highlighted given the primary role of this epigenetic feature in mammalian cells. A lower global methylation was observed in DNA of peripheral blood mononuclear cells of hypertensive patients. Moreover, DNA hydroxymethylation appears modifiable by salt intake in a Dahl salt-sensitive rat model. The specific function of DNA methylation in regulating the expression of AH-related genes at promoter site was described for hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2), somatic angiotensin converting enzyme (sACE), Na+/K+/2Cl- cotransporter 1 (NKCC1), angiotensinogen (AGT), α-adducin (ADD1), and for other crucial genes in endocrine hypertension. Post-translational histone methylation at different histone 3 lysine residues was also observed to control the expression of genes related to AH as lysine-specific demethylase-1(LSD1), HSD11B2, and epithelial sodium channel subunit α (SCNN1A). Noncoding RNAs including several microRNAs influence genes involved in steroidogenesis and the renin-angiotensin-aldosterone pathway. In the present review, the current knowledge on the relationship between the main epigenetic marks and AH will be presented, considering the challenge of epigenetic patterns being modifiable by environmental factors that may lead toward novel implications in AH preventive and therapeutic strategies.

microRNAs in Essential Hypertension and Blood Pressure Regulation

Unravelling the complete genetic predisposition to high blood pressure (BP) has proven to be challenging. This puzzle and the fact that coding regions of the genome account for less than 2 % of the entire human DNA support the hypothesis that mechanisms besides coding genes are likely to contribute to BP regulation. Non-coding RNAs, especially microRNAs, are emerging as key players of transcription regulation in both health and disease states. They control basic functions in virtually all cell types relevant to the cardiovascular system and, thus, a direct involvement with BP regulation is highly probable. Here we review the literature about microRNAs associated with regulation of BP and hypertension, highlighting investigations, methodology and difficulties arising in the field. These molecules are being studied for exploitation in diagnostics, prognostics and therapeutics in many diseases. There have been some studies that examined biological fluid microRNAs as biomarkers for hypertension, but most remain inconclusive due to the small sample sizes and differences in methodological standardisation. Fewer studies have analysed tissue microRNA levels in vascular smooth muscle cells and the kidney. Others focused on the interaction between single nucleotide polymorphisms and microRNA binding sites. Studies in animals have shown that angiotensin II, high-salt diet and exercise change microRNA levels in hypertension. Treatment of spontaneously hypertensive rats with a miR-22 inhibitor and treatment of hypertensive Schlager BPH/2J mice with a miR-181a mimic decreased their BP. This supports the use of microRNAs as therapeutic targets in hypertension, and future studies should test the use of other microRNAs found in human association studies. In conclusion, there is a clear need of increased pace of human, animal and functional studies to help us understand the multifaceted roles of microRNAs as critical regulators of the development and physiology of BP.

The emerging role of non-coding RNA in essential hypertension and blood pressure regulation

Unravelling the complete genetic predisposition to high blood pressure (BP) has proven to be challenging. This puzzle and the fact that coding regions of the genome account for less than 2% of the entire human DNA support the hypothesis that genetic mechanism besides coding genes are likely to contribute to BP regulation. Non-coding RNAs (ncRNAs) are emerging as key players of transcription regulation in both health and disease states. They control basic functions in virtually all cell types relevant to the cardiovascular system and, thus, a direct involvement with BP regulation is highly probable. Here, we review the literature about ncRNAs associated with human BP and essential hypertension, highlighting investigations, methodology and difficulties arising in the field. The most investigated ncRNAs so far are microRNAs (miRNAs), small ncRNAs that modulate gene expression by posttranscriptional mechanisms. We discuss studies that have examined miRNAs associated with BP in biological fluids, such as blood and urine, and tissues, such as vascular smooth muscle cells and the kidney. Furthermore, we review the interaction between miRNA binding sites and single nucleotide polymorphisms in genes associated with BP. In conclusion, there is a clear need for more human and functional studies to help elucidate the multifaceted roles of ncRNAs, in particular mid- and long ncRNAs in BP regulation.

Identification of genes with altered expression in male and female Schlager hypertensive mice

Background

Numerous studies have shown sex differences in the onset and severity of hypertension. Despite these sex-differences the majority of animal studies are carried out in males. This study investigated expression changes in both male and female hypertensive mouse kidneys to identify common mechanisms that may be involved in the development of hypertension.

Methods

The Schlager hypertensive mouse model (BPH/2J) and its normotensive control (BPN/3J) were used in this study. Radiotelemetry was performed on 12 to 13 week old BPH/2J and BPN/3J male and female animals. Affymetrix GeneChip Mouse Gene 1.0 ST Arrays were performed in kidney tissue from 12 week old BPH/2J and BPN/3J male and female mice (n = 6/group). Genes that were differentially expressed in both male and female datasets were validated using qPCR.

Results

Systolic arterial pressure and heart rate was significantly higher in BPH/2J mice compared with BPN/3J mice in both males and females. Microarray analysis identified 153 differentially expressed genes that were common between males and females (70 upregulated and 83 downregulated). We validated 15 genes by qPCR. Genes involved in sympathetic activity (Hdc, Cndp2), vascular ageing (Edn3), and telomere maintenance (Mcm6) were identified as being differentially expressed between BPH/2J and BPN/3J comparisons. Many of these genes also exhibited expression differences between males and females within a strain.

Conclusions

This study utilised data from both male and female animals to identify a number of genes that may be involved in the development of hypertension. We show that female data can be used to refine candidate genes and pathways, as well as highlight potential mechanisms to explain the differences in prevalence and severity of disease between men and women.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-014-0101-x) contains supplementary material, which is available to authorized users.

Let-7 in cardiovascular diseases, heart development and cardiovascular differentiation from stem cells

The let-7 family is the second microRNA found in C. elegans. Recent researches have found it is highly expressed in the cardiovascular system. Studies have revealed the aberrant expression of let-7 members in cardiovascular diseases, such as heart hypertrophy, cardiac fibrosis, dilated cardiomyopathy (DCM), myocardial infarction (MI), arrhythmia, angiogenesis, atherosclerosis, and hypertension. Let-7 also participates in cardiovascular differentiation of embryonic stem cells. TLR4, LOX-1, Bcl-xl and AGO1 are by now the identified target genes of let-7. The circulating let-7b is suspected to be the biomarker of acute MI and let-7i, the biomarker of DCM. Further studies are necessary for identifying the gene targets and signaling pathways of let-7 in cardiovascular diseases. Let-7 might be a potential therapeutic target for cardiovascular diseases. This review focuses on the research progresses regarding the roles of let-7 in cardiovascular development and diseases.