Hypertension (HTN) is a chronic illness with uncertain etiology. It is a common cardiovascular risk factor that contributes to the likelihood of cardiovascular events (1,2). Severe myocardial injury, heart failure, chronic kidney disease, peripheral vascular disease, stroke and derived complications affecting organ systems, such as the brain and eyes, are known to be associated with HTN (3-5). According to the latest report in December 2022 conducted by the Korea Centers for Disease Control and Prevention, HTN affects 33.2% of the Korean population aged >30 years and 62.3% of the population aged >65 years (6). Similar to other vascular conditions, HTN has been characterized by the aberrant expression of microRNAs (miRNAs/miRs), which can induce translational repression or mRNA degradation (2,4). Since the pathophysiology of HTN constitutes an intricate combination of environmental and genetic factors, our understanding of the molecular mechanism underlying this condition remains incomplete (4).

miRNAs are a conserved class of small, non-coding RNAs that mainly function to block the translation of or accelerating the degradation of mRNAs by binding to their 3'-untranslated regions (3'-UTRs) (7-9). Through this function, they have been documented to, in turn, regulate endothelial function, the renin-angiotensin-aldosterone system and the pathogenesis of HTN (10). Investigations into these miRNAs have the potential to contribute to our understanding of the pathological mechanisms underlying HTN and may lead to the development of therapeutic medicine against this condition (4). A previous study by Yin et al (5) analyzed miR-128 expression in the peripheral blood of patients with HTN in China; they found that upregulation of this miRNA was associated with the progression of myocardial injury in the HTN group, particularly stage III/IV HTN. Other previous studies have shown the expression of members of the miR-29 family to be upregulated in patients with HTN, whilst also showing a positive association with their blood pressure (2). Zhang et al (10) previously suggested that miR-122 bound to the 3'-UTR of cationic amino acid transporter 1 mRNA may lead to the decreased metabolism of L-arginine and nitric oxide in vascular endothelial cells. This can eventually lead to the dysfunction of vascular endothelial cells, which have been reported to be a significant cause of HTN (10). In miRNA biology, although a single miRNA can target multiple genes, it can also be targeted by other genes. Owing to this feature, miRNAs can potentially serve an important role in a regulatory network controlling the pathological mechanisms of various cardiovascular diseases, such as HTN (4).

Previous studies have suggested that miRNA polymorphisms can contribute to a genetic predisposition to HTN (1,2,5,11). Members of the miR-200 family, including miR-200b, have been reported to serve an important role in processes associated with hypoxia, such as angiogenic responses in microvascular endothelial cells and the apoptosis of cardiomyocytes (12). They have also been found to have a significant relationship with tumorigenesis, cancer metastasis and recurrence (13). miR-200b expression has been shown to be increased in renal tissues of patients with hypertensive nephrosclerosis when accompanied by expression in heart ventricles with salt-sensitive hypertension (11). In addition, the dynamic expression of miRNAs, a genetic regulatory mechanism for platelet formation and activation, has been reported to be linked with the pathogenesis of thrombotic disorders (14). A prior study examining miRNA expression in platelets reported that the expression of miR-200b and miR-495 may be significantly downregulated during the maturation of megakaryocytes into platelets (15). These miRNA shave also been shown to reduce the expression of platelet-specific functional proteins, protein kinase cAMP-dependent type II regulatory subunit β (PRKAR2B) and Kelch-like family member 5 (KLHL5) (16). Therefore, the target genes of miR-200b and miR-495 may modulate platelet functions during the activation, aggregation and proinflammatory reaction of platelets (14).

Polymorphisms of miR-200bT>C (rs7549819) in chromosome 1 and miR-495A>C (rs2281611) in chromosome 14 were previously found in their corresponding promoter regions (14,17). Their genetic variant allele frequencies in the global population from the Allele Frequency Aggregator dataset were documented to be 0.099 for miR-200bT>C and 0.236 for miR-495A>C (17). In a study by Kim et al (14), susceptibility to ischemic stroke and post-stroke mortality was investigated among cohorts with various miRNA genotypes. The study did not find a significant difference in the distribution of miRNA single nucleotide polymorphisms (SNPs; miR-200bT>C and miR-495A>C) between the patient and control groups, but the miR-200b CC genotype was less frequently found in patients with large-artery atherosclerotic stroke (14). Furthermore, Qin et al (18) previously suggested that the miR-200bT>C and miR-495A>C variants were significantly associated with genes and pathways that can regulate ischemic stroke pathogenesis in a Chinese population. In addition, their evidence has also supported the notion that alterations in the miR-200b and miR-495 genetic structure were associated with the promotion of neovascularization in ischemia and myocardial infarction mouse models (18).

However, although miR-200b and miR-495 are likely to be involved in several diseases, including lung, prostate, breast, colon and endometrial cancer, to the best of our knowledge, no studies on the association of the polymorphisms of miR-200bT>C and miR-495A>C with HTN. Therefore, the present study aimed to test the hypothesis of the potential association between miR-200bT>C and/or miR-495A>C polymorphisms and susceptibility to HTN in a Korean cohort.

Previous studies have reported that miRNAs in the human genome act as unknown multifactorial factors in the development of various diseases, such as ischemic stroke and thrombotic disorders, since they work as genetic modulators affecting target gene expression (4,14). This is due to miRNAs having been found to be associated with several physiological and pathological processes, such as oncogenesis and cardiovascular diseases, including coronary artery disease, stroke, acute myocardial infarction and heart failure (19). In particular, circulating miRNAs targeting other miRNAs as intercellular signaling mediators, for instance, circulating levels of miR-181a and miR-122 were higher in hypertensive individuals than in controls, have been proposed to serve a role in HTN according to tissue-based studies (1,4,10). According to results from the present study, miRNA polymorphisms miR-200bT>C and miR-495A>C are likely to be associated with the development of HTN in a cohort of Korean patients. Located in the promoters of the respective miRNAs, these miR-200b and miR-495 SNPs can influence their expression levels, which can in turn affect the expression levels of their target genes (20).

The results of the present study suggested an association of the miR-495 CC genotype and C allele with an increased risk of HTN. However, the risk of HTN was not associated with the miR-200b TC and CC genotypes, dominant and recessive models or the miR-200b variant T and C allele. miR-495 has been previously shown to be associated with susceptibility to blood-related diseases, such as pre-eclampsia (21), ischemic stroke and post-stroke prognosis (14), by inhibiting cell proliferation, migration, invasion and angiogenesis. Hu et al (22) previously reported that miR-495 leads to the pathogenesis of type 2 diabetes since it could increase the blood glucose content and insulin resistance by a targeted negative regulatory effect on fat mass and the obesity-associated gene FTO, which encodings the α-ketoglutarate-dependent dioxygenase FTO protein. Data from a previous genome-wide study has shown that the expression of miR-495 targets KLHL5 expression, and is positively associated with changes and subsequent organization involving platelet activation and aggregation in platelet microtubules and cytoskeleton in humans (14). In addition, several reports have suggested that inhibiting the expression of miR-495 can improve hemodynamics and angiogenesis in hypertensive conditions. Fu et al (23) demonstrated that the inhibition of miR-495 can promote hemodynamics and vascular remodeling, whose effects were involved in increasing angiogenic transcription factor (vascular endothelial zinc finger 1) and marked upregulation of angiogenic genes in pulmonary hypertension according to the analysis on the biological function of miR-495 in cultured pulmonary arterial endothelial cells under hypoxic conditions. Furthermore, attenuation of miR-495 has been documented to promote PTEN expression to protect against cardiomyocyte hypertrophy (24). It has also been reported that myocardial infarction-associated transcript, also known as retinal non-coding RNA 2 or Gomafu, can promote the progression of acute myeloid leukemia through suppression of miR-495 target genes (PBX3 and MEIS1) by not only promoting cell proliferation and cell cycle progression, but also decreasing apoptosis (25). In a study investigating the regulatory role of miR-200b in cor pulmonale model mice, miR-200b has been previously shown to potentially suppress protein kinase C (PKC)-α expression, which can modulate the proliferation and contraction of vascular smooth muscle cells evoked by the expression of endothelin 1 through the activation of protein kinases and transcription factors (11). The suppression of PKC-α can attenuate pathological fibrosis and restore cardiac function (26), indicating an association between miR-200b and protection against heart failure.

Analysis of the genotype combination for SNPs in the present study revealed that the TC/CC and CC/CC combined genotypes of miR-200bT>C and miR-495A>C polymorphisms were associated with susceptibility to HTN. Several previous studies have reported that members of the miR-200 family can promote the pathogenesis of atherosclerosis by targeting ZEB2 and RPS6KB1 gene expression to promote foam-cell formation (18,27,28). Although the present study did not cover the experimental evidence at the cellular level, Piperigkou et al (28) demonstrated that the difference in miRNA distributions implicated that miR-200b from five miRNA sequences of the miR-200 family (miR-200a, miR-200b, miR-200c, miR-141, and miR-429) might be involved in the regulation of epithelial-to-mesenchymal transition and cell proliferation, which can affect growth deformity and in turn the development of vascular diseases. A previous study into the role of miR-200b in the mechanism underlying stroke has reported that it can promote lipid accumulation whilst inhibiting cholesterol efflux by downregulating the expression of ATP binding cassette subfamily A member 1, an integrated membrane protein (29). When the expression of miR-200b was physiologically changed during hypoxia through manipulation of the miRNA level using miR-200b mimics and antagomirs, the expression of endothelial nitric oxide synthase (eNOS) was reduced, which limited the bioavailability of nitric oxide (NO) (18).

According to the haplotype results in the present study, the allele combination of miR-200bT>C and miR-495A>C in the haplotype of C-A significantly differed between the HTN and control groups. The regulatory miRNA SNPs in the promoter regions of miR-200b and miR-495 can affect the expression of their corresponding mature miRNAs, which can cause a significant impact on the expression of their target genes (14). The present study found interactive effects between miR-200b and miR-495 according to the SNP-SNP interaction analysis in a cohort of Korean patients. Through a combinatorial gene-environment analysis, Kim et al (20) previously reported that the combination of miR-495 CC genotype and low plasma folate contributed to an increased risk of rectal cancer according to a gene-environment combinatorial analysis. Using miRNA-miRNA co-expression profiling, Gatsiou et al (30) also found that there were possible associations between miRNA expression in platelets and their reactivity. Knockdown experiments revealed that miR-200b and miR-495 can target the expression of PRKAR2B and KLHL5, respectively. The regulatory subunit encoded by PRKAR2B is considered to control protein kinase A activity to regulate the activation and aggregation of platelets. When cAMP concentration increases, the catalytic subunit dissociates from the regulatory complex, to phosphorylate its target substrates, which suppresses platelet activation (31,32). The role of KLHL5, encoding a Kelch-like protein that binds actin and serves as a signaling molecule scaffold, in platelet function is reported to involve cytoskeletal reorganization and subsequent cell shape changes, which is an essential feature of platelet activation (16). According to these previous findings, it is possible that both miR-200b and miR-495 are involved in the activation of platelets, which have been reported to robustly influence the pathophysiology of coronary artery disease (33).

Based on the stratified analysis of the miR-200bT>C and miR-495A>C polymorphisms according to the HTN risk factors, the miR-200b TC+CC was associated with the BMI of <28.12 kg/m² and FBG levels of <106.26 mg/dl. By contrast, the miR-495 AA+CC was associated with HDL-C levels <44.29 mg/dl, whilst also being associated with SBP levels of ≥132.67 mmHg. These findings are similar to those of Motawi et al (21), who previously conducted a study on a cohort of Egyptian patients with pre-eclampsia and found a significant positive association between miR-495 expression and the parameters of systolic and diastolic blood pressure, and cholesterol level. In addition, a negative association was found with high density lipoprotein level and miR-495 expression (21).

The present study has several limitations. The study population was confined to a cohort of middle-aged Korean patients who visited the Jeju National University Hospital. The subjects, therefore, may not be representative of the general population from various contexts including age, ethnicity, place of residence and sampling period. For additional verification, it will be necessary to conduct further studies on larger sample sizes containing more diverse patient cohorts. The functional mechanisms regarding how the miRNA polymorphisms may affect HTN remains unclear. Since the present study did not assess the expression levels of the miRNAs of interest on either molecular and functional levels, it is likely that the miR-200bT>C and miR-495A>C polymorphisms are associated with HTN risk by targeting the expression of genes involved in HTN induction. However, this requires experimental confirmation.

In conclusion, the present study investigated the relationship between HTN susceptibility and miR-200bT>C and miR-495A>C polymorphisms. It was found that the miR-495A>C polymorphism may be associated with HTN susceptibility. Although there have been studies describing the relationship between the miR-200 family and the incidence of tumorigenesis and cancer, the present study specifically demonstrated the association between the miR-200bT>C and miR-495A>C polymorphisms with HTN risk; to the best of our knowledge, this has not yet been reported. Therefore, results of the present study may provide evidence that miR-495A>C polymorphism is a potential candidate as a biomarker for HTN diagnosis and prevention in Korean populations.