Inhibition of microRNA-429 in the renal medulla increased salt sensitivity of blood pressure in Sprague Dawley rats

Integrated analysis of the lncRNA-associated competing endogenous RNA network in salt sensitivity of blood pressure

Accumulating evidence showed that competing endogenous RNA (ceRNA) mechanism plays a pivotal role in salt sensitivity of blood pressure (SSBP). We constructed a ceRNA network based on SSBP-related differently expressed lncRNAs (2), mRNAs (73) and miRNAs (18). Bioinformatic analyses were utilized to analyze network and found network genes participate in biological pathways related to SSBP pathogenesis such as regulation of nitric oxide biosynthetic process (GO:0045,428) and cellular response to cytokine stimulus (GO:0071,345). Fourteen candidate ceRNA pathways were selected from network to perform qRT-PCR validation and found nine RNAs (KCNQ1OT1, SLC8A1-AS1, IL1B, BCL2L11, KCNJ15, CX3CR1, KLF2, hsa-miR-362-5p and hsa-miR-423-5p) differently expressed between salt-sensitive (SS) and salt-resistant (SR) groups (P < 0.05). Four ceRNA pathways were further validated by luciferase reporter assay and found KCNQ1OT1→hsa-miR-362-5p/hsa-miR-423-5p→IL1B pathways may influence the pathogenic mechanism of SS. Our findings suggested the ceRNA pathway and network may affect SS occurrence mainly through endothelial dysfunction and inflammatory activation.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

MicroRNAs in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading causes of death and disability worldwide, despite the wide diversity of molecular targets identified and the development of therapeutic methods. MicroRNAs (miRNAs) are a class of small (about 22 nucleotides) non-coding RNAs (ncRNAs) that negatively regulate gene expression at the post-transcriptional level in the cytoplasm and play complicated roles in different CVDs. While miRNA overexpression in one type of cell protects against heart disease, it promotes cardiac dysfunction in another type of cardiac cell. Moreover, recent studies have shown that, apart from cytosolic miRNAs, subcellular miRNAs such as mitochondria- and nucleus-localized miRNAs are dysregulated in CVDs. However, the functional properties of cellular- and subcellular-localized miRNAs have not been well characterized. In this review article, by carefully revisiting animal-based miRNA studies in CVDs, we will address the regulation and functional properties of miRNAs in various CVDs. Specifically, the cell-cell crosstalk and subcellular perspective of miRNAs are highlighted. We will provide the background for attractive molecular targets that might be useful in preventing the progression of CVDs and heart failure (HF) as well as insights for future studies.

The hypoxia-inducible factor prolyl hydroxylase inhibitor FG4592 promotes natriuresis through upregulation of COX2 in the renal medulla

The renal medulla is a key site for the regulation of renal sodium excretion. However, the molecular mechanism remains unclear. Cyclooxygenase 2 (COX2) is specifically expressed in the renal medulla and contributes to the maintenance of the electrolyte/water balance in the body. Hypoxia-inducible factors (HIFs) have also been found to be expressed in the renal medulla, probably owing to the hypoxic conditions in the renal medulla. This study was designed to test the effects of HIF activation on renal sodium handling and renal medullary COX2 expression. Our data showed that HIF activation by the prolyl hydroxylase inhibitor (PHI) FG4592 enhanced natriuresis in mice challenged with a high-salt diet. In addition, FG4592 upregulated the expression of COX2 in the renal medulla. An in vitro study further supported the finding that HIF can induce the expression of COX2 and that this induction is mediated through direct binding to the promoter region of the Cox2 gene, facilitating its transcription. In addition, the COX2 inhibitor celecoxib diminished the natriuretic effect of FG4592. Together, these results suggest that HIF activation promotes sodium excretion through upregulation of COX2 in the renal medulla and therefore maintains sodium homeostasis in the body.

Overexpression of MicroRNA-429 Transgene Into the Renal Medulla Attenuated Salt-Sensitive Hypertension in Dahl S Rats

BACKGROUND

We have previously shown that high salt stimulates the expression of miR-429 in the renal medulla, which induces mRNA decay of HIF prolyl-hydroxylase 2 (PHD2), an enzyme to promote the degradation of hypoxia-inducible factor (HIF)-1α, and increases the HIF-1α-mediated activation of antihypertensive genes in the renal medulla, consequently promoting extra sodium excretion. Our preliminary results showed that high salt-induced increase of miR-429 was not observed in Dahl S rats. This present study determined whether correction of this impairment in miR-429 would reduce PHD2 levels, increase antihypertensive gene expression in the renal medulla and attenuate salt-sensitive hypertension in Dahl S rats.

METHODS

Lentiviruses encoding rat miR-429 were transfected into the renal medulla in uninephrectomized Dahl S rats. Sodium excretion and blood pressure were then measured.

RESULTS

Transduction of lentiviruses expressing miR-429 into the renal medulla increased miR-429 levels, decreased PHD2 levels, and upregulated HIF-1α target gene NOS-2, which restored the adaptive mechanism to increase the antihypertensive gene after high-salt intake in Dahl S rats. Functionally, overexpression of miR-429 transgene in the renal medulla significantly improved pressure natriuretic response, enhanced urinary sodium excretion, and reduced sodium retention upon extra sodium loading, and consequently, attenuated the salt-sensitive hypertension in Dahl S rats.

CONCLUSIONS

Our results suggest that the impaired miR-429-mediated PHD2 inhibition in response to high salt in the renal medulla may represent a novel mechanism for salt-sensitive hypertension in Dahl S rats and that correction of this impairment in miR-429 pathway could be a therapeutic approach for salt-sensitive hypertension.

Impact of Nutritional Epigenetics in Essential Hypertension: Targeting microRNAs in the Gut-Liver Axis

PURPOSE OF REVIEW

To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis.

RECENT FINDINGS

There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

CeRNA network analysis and functional enrichment of salt sensitivity of blood pressure by weighted-gene co-expression analysis

Background

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular disease. The pathogenic mechanisms of SSBP are still uncertain. This study aimed to construct the co-regulatory network of SSBP and data mining strategy based on the competitive endogenous RNA (ceRNA) theory.

Methods

LncRNA and mRNA microarray was performed to screen for candidate RNAs. Four criteria were used to select the potential differently expressed RNAs. The weighted correlation network analysis (WGCNA) package of R software and target miRNA and mRNA prediction online databases were used to construct the ceRNA co-regulatory network and discover the pathways related to SSBP. Gene ontology enrichment, gene set enrichment analysis (GSEA) and KEGG pathway analysis were performed to explore the functions of hub genes in networks.

Results

There were 274 lncRNAs and 36 mRNAs that differently expressed between salt-sensitive and salt-resistant groups (P < 0.05). Using WGCNA analysis, two modules were identified (blue and turquoise). The blue module had a positive relationship with salt-sensitivity (R = 0.7, P < 0.01), high-density lipoprotein (HDL) (R = 0.53, P = 0.02), and total cholesterol (TC) (R = 0.55, P = 0.01). The turquoise module was positively related with triglyceride (TG) (R = 0.8, P < 0.01) and low-density lipoprotein (LDL) (R = 0.54, P = 0.01). Furthermore, 84 ceRNA loops were identified and one loop may be of great importance for involving in pathogenesis of SSBP. KEGG analysis showed that differently expressed mRNAs were mostly enriched in the SSBP-related pathways. However, the enrichment results of GSEA were mainly focused on basic physical metabolic processes.

Conclusion

The microarray data mining process based on WGCNA co-expression analysis had identified 84 ceRNA loops that closely related with known SSBP pathogenesis. The results of our study provide implications for further understanding of the pathogenesis of SSBP and facilitate the precise diagnosis and therapeutics.

miR-429 and miR-424-5p inhibit cell proliferation and Ca2+ influx by downregulating CaSR in pulmonary artery smooth muscle cells

Cytosolic free Ca²⁺ concentration is a key factor in pulmonary vasoconstriction and vascular remodeling of pulmonary artery smooth muscle cells (PASMCs). These processes contribute to pulmonary arterial hypertension and are influenced by expression of calcium-sensing receptor (CaSR). Although regulation of CaSR expression is precisely controlled, the contribution of microRNAs (miR) is incompletely understood. Here, we demonstrate that miR-429, miR-424-5p, miR-200b-3p, and miR-200c-3p regulate CaSR by targeting specific 3'-untranslated region, suggesting that these miRNAs function as CaSR inhibitors in PASMCs. Moreover, miR-429 and miR-424-5p inhibit proliferation of PASMCs by downregulating CaSR, resulting in reduced Ca²⁺ influx under both normoxia and hypoxia. These findings indicate miR-429 and miR-424-5p target CaSR and may function as Ca²⁺ influx suppressors in pulmonary arterial hypertension-associated diseases.

Sodium Reduction, miRNA Profiling and CVD Risk in Untreated Hypertensives: a Randomized, Double-Blind, Placebo-Controlled Trial

Sodium reduction decreases blood pressure (BP) and cardiovascular mortality. However, the underlying molecular mechanisms are not well understood. We tested the hypothesis that reduction of sodium intake would change miRNA expression in hypertensive patients, and those changes would be associated with improved cardiovascular phenotypes. A whole genome RNA sequencing was performed in paired serum samples collected at the end of usual sodium intake and reduced sodium intake periods from 10 (age 56.8 ± 8.9) untreated black male hypertensives, selected from a randomized crossover trial of sodium reduction as the discovery cohort. Validation was carried out by the PCR Serum/Plasma Focus panel profiling in paired samples in all 64 (50% males, age 50.2 ± 9.5) untreated black hypertensives from the same trial. Fifteen respondent miRNAs were identified in the discovery stage. miR-143-3p was replicated. Sodium reduction up-regulated miR-143-3p. The increase in miR-143-3p was associated with the reduction of BP and arterial stiffness and the increase in skin capillary density. In conclusion, dietary sodium reduction alters circulating miRNA expressions, and those miRNA changes are associated with reduced BP and improved arterial compliance in untreated black hypertensives, suggesting that miRNA regulation may be one of the underlying mechanisms that dietary sodium regulates cardiovascular health.

Recombinant Adeno-Associated Virus-Mediated Delivery of MicroRNA-21-3p Lowers Hypertension

Hypertension is the most important risk factor for cardiovascular diseases worldwide. However, the underlying molecular mechanisms of hypertension are complex and remain largely elusive. Here, we described a novel, microRNA-dependent therapeutic strategy for hypertension. First, we found that plasma microRNA-21-3p (miR-21-3p) levels were significantly reduced both in hypertensive patients and spontaneously hypertensive rats (SHRs) when compared with normal controls. In a series of experiments to dissect the role of miR-21-3p in hypertension, we showed that intravenous delivery of recombinant adeno-associated virus (rAAV)-mediated miR-21-3p expression induced a persistent attenuation of hypertension, with marked amelioration of target organ damages, including cardiac hypertrophy and fibrosis and artery and kidney fibrosis in SHRs, whereas miR-21-3p tough decoys (TuDs) counteracted the above effects. Computational prediction coupled with biochemical experiments revealed that the miR-21-3p-mediated hypotensive reduction effect was accomplished by regulating phenotypic switch of vascular smooth muscle cells (VSMCs) via suppression of the adrenal α2B-adrenergic receptor (ADRA2B) in arteries. Furthermore, we observed that activation of transcription factor NF-κB and SRF significantly increased the expression of miR-21-3p in VSMCs. In summary, our study is the first to identify a novel role and mechanism of miR-21-3p in blood pressure control and provides a possible strategy for hypertension therapy using rAAV-miR-21-3p.