1. Introduction
The prevalence of metabolic risk factors and aging of the population in developed countries lead to persistence of high mortality rates from non-communicable diseases, and from coronary artery disease (CAD) in the world [
1]. According to World Health Organization (WHO) in 2021, the mortality rate from CAD reached 17.9 million people [
2]. Among patients with CAD there are phenotypes with ischemia/angina and non-obstructive coronary arteries (INOCA/ANOCA), the prevalence of which in the population with CAD, according to some studies, reaches 13% [
3]. At the same time, INOCA/ANOCA is significantly more common in women (61%, and, in accordance with other data – 65%) than in men (32%) [
4,
5,
6,
7]. The development of different types of CA lesions is regulated by many various factors, among which proinflammatory agents play a significant role. According to a study by Karakayali M. et al., the systemic immuno-inflammatory index (SII, platelet × neutrophil/lymphocyte ratio) is independently associated with the presence of INOCA [
8]. It is known that in case of INOCA, an increase in the systemic inflammation response index (SIRI) plays a potentially important role in the diagnosis of the slow coronary flow phenomenon [
9]. Additionally, numerous factors—including pro-inflammatory cytokines (IL, TNF-α), reactive oxygen species (ROS), an imbalance between vasodilation (NO) and vasoconstriction mediators, several zinc-dependent endopeptidases (matrix metalloproteinases, MMP), and growth factors (such as VEGF)—influence the progression of CA atherosclerosis. This effect was particularly demonstrated in the study by Beatty et al., which showed that TNF-α induces activation of macrophages, T-helper 1 lymphocytes, and endothelial cells in atherosclerosis. Activated endothelial cells produce receptors and adhesion molecules that promote abnormal leukocyte migration into the vascular wall, leading to dysregulated secretion of pro-inflammatory cytokines. The authors conclude that TNF-α and IL-6 play significant roles as risk factors for the development of CAD [
10].
MMP are zinc-dependent endopeptidases, which are multi-domain proteins with a highly conserved signal peptide, a propeptide domain, and a catalytic domain [
11]. The expression of MMPs as inactive zymogens is transcriptionally regulated by a variety of proinflammatory signals, and MMPs are involved in the destruction of the extracellular matrix [
12].
MMPs can be divided into six groups based on substrate specificity and sequence similarity: collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMP and others [
13,
14]. It is known that foamy and smooth muscle cells (SMC) synthesize MMPs, which play a key role in the formation and growth of atherosclerotic plaques [
15]. At the same time, MMPs produced by macrophages are actively involved in the process of the fibrous cap thinning and plaque destabilization [
16]. Thus, increased expression of activated MMP-13 is associated with increased collagenolysis in vivo, mainly in atheromatous plaques, and a decrease in the accumulation of SMC at different stages of atherogenesis, in particular, at the preclinical stage [
17]. The investigation by Lehrke M. et al. demonstrated that the level of circulating MMP-1 can be used as a predictive marker of the presence of atherosclerotic plaques [
18].
The study of the role of circulating microRNAs (miRs) in the epigenetic regulation of the development and progression of atherosclerosis is also of considerable interest. MiRs are short non-coding RNA molecules that regulate gene expression by inhibiting translation or enhancing mRNA degradation. Recent research highlights the significance of miRNAs as promising diagnostic biomarkers for assessing the degree of CA obstruction. In particular, the expression of miR-34a increases in the heart during myocardial hypertrophy caused by stretch, adrenergic stimulation and hypoxia, that has been shown to contribute to the disruption of angiogenesis by uncoupling hypoxia-inducible factor 1-α – VEGF (HIF-1α-VEGF) signaling [
19]. In addition, it is known that miR-34a, miR-92a, miR-181c and miR-210 are involved in the regulation of vascular endothelial function by inducing or reducing the level of oxidative stress markers [
20,
21].
The expression of miR-145 decreases in acute coronary syndrome (ACS), what makes it possible to consider this miR as a potential diagnostic biomarker. A negative correlation of miR-145 with markers of endothelial damage (von Willebrand factor (vWF), heart-type fatty acid-binding protein (H-FABP)) and proinflammatory cytokines (IL-6 and TNF-α) was also found [
22]. In turn, miR-221 and miR222 are involved in the regulation of endothelial inflammation, angiogenesis and apoptosis of endothelial cells [
23].
According to the literature data, there are isolated evidence on the expression of miR-34a, miR-145 and miR-222 in patients with CAD, including those with INOCA/ANOCA. It should be noted that in patients with CAD (including non-obstructive phenotype), no investigation was conducted of the possible association of the expression of these miRs with proinflammatory cytokines (TNF-α), MMPs and growth factors (VEGF). The study of miR expression levels in such patients can clarify some aspects of the pathogenesis of atherosclerotic lesions of the CA and, in consequence, may be important for determining their potential as possible diagnostic biomarkers and for the development of new therapies with antagomiRs.
3. Discussion
The development and progression of CA atherosclerosis in stable CAD is influenced by many independent factors that play a crucial role in the formation of different variants of CA lesion. One of these factors is angiogenesis, in the regulation of which VEGF is actively involved. There are six variants of VEGF, each has structurally similar proteins included in the regulation and differentiation of the vascular system. In the previous studies, it has been demonstrated that VEGF can influence plaque growth and instability through angiogenesis-independent processes [
24,
25].
It is known that in metabolic syndrome, the activity of angiogenesis processes in CA may be reduced, despite the increased expression of VEGF, which is associated with an altered VEGF signaling pathway – VEGF/VEGFR signaling [
26] VEGF is involved not only in angiogenesis, stimulating the proliferation and growth of endothelial cells, but also affects pro-inflammatory cytokines and cells: it increases the levels of TNF-α and IL-1 in monocytes and reduces IL-6. Similar results were obtained in our study in plasma samples with obstructive CAD [
27].
TNF-α is mainly produced by activated macrophages and many other types of cells. Recent studies have demonstrated that TNF-α and VEGFA gene expression was significantly lower in patients with INOCA compared to patients with obstructive CAD [
28].
In addition, VEGF induces the expression of MMP-1, MMP-3 and MMP-13 [
29]. Changes in MMP levels may also be associated with an increased risk of CAD and various severity of the disease. Our study revealed significant differences between levels of MMP-9 and MMP-14 in samples with obstructive CAD and INOCA/ANOCA compared with the control group. Direct correlations of VEGF with MMP-1, MMP-9 and MMP-14 were found in obstructive CA lesions, and only MMP-1 and MMP-14 non–obstructive ones.
According to Buchler A., et al. and Quillard T., et al., increased expression of activated MMP-13 is associated with increased collagenolysis in vivo, which accelerates vascular remodeling processes in atherosclerotic lesions [
17,
30]. In the study of Gaubatz J. W. et al. a positive relationship between plasma levels of MMP-1 and calcification of the carotid arteries was revealed [
31]. At the same time, although in the study Polonskaya Y.V. et al. the levels of MMP-1 and MMP-9 were higher in calcified plaques. According to logistic regression analysis, the relative risk of calcification formation in the CA was associated only with MMP-9 [
32].
MMP-9 is a strong predictor of plaque instability, whereas MMP-13 can act in both ways: in the early stages of atherosclerosis, MMP-13 cleaves ICAM-1, thereby preventing the adhesion of circulating monocytes to the lesion site [
33], while in the later stages MMP-13 promotes degradation of the extracellular matrix, thus leading to plaque destabilization [
30,
34].
Currently, the role of MMP-14 in the development of CAD has been proven in many studies. Thus, high levels of MMP-14 were independently associated with CVD [
35]. Increased expression of MMP-14 was detected by Johnson J.L. et al. in the foamy cells of unstable atherosclerotic plaques [
36].
In our study the absence of significant differences between the groups in MMP-1 and MMP-13 levels may be due to the fact that MMP activity was determined only in stable CAD and inclusion of a group with ACS may help reveal these differences.
It has been established that miRs are involved in the regulation of various processes, among which the most important in atherogenesis are endothelial damage, inflammation development, activation of macrophages, the formation of foam cells in the vascular wall, proliferation, migration and apoptosis of SMCs, and, as a consequence, vascular remodeling [
16,
37].
In the present study, the level of expression of miR-145 in the groups significantly differed and reached the highest values in patients with INOCA/ANOCA. It should be noted that a negative high-strength correlation was found between miR-145 and MMP-13. According to available scientific data, miR-145-5p can act as a “cardioprotective” molecule in patients with myocardial ischemia and, through negative regulation of CD40, is involved in reducing the activity of the inflammatory response and apoptosis caused by hypoxia [
38]. Overexpression of miR-145 can eliminate endothelial damage and reduce the activity of abnormal inflammation, which makes it possible to consider this miR as a potential candidate for targeted therapy of ACS [
22].
Non-obstructive and obstructive phenotypes of CAD can be united by the presence of endothelial dysfunction. It can be hypothesized that INOCA/ANOCA represents an initial stage in the progression of classical CAD. The anti-atherogenic miRNA-145 may function as part of a compensatory mechanism protecting vascular walls against stenotic atherosclerosis.
In the study of Wu S. et al., a negative relationship between miR-145 expression and levels of vWF, H-FABP, IL-6 and TNF-α was demonstrated. Thus, the authors concluded that the reduced expression of miR-145 in serum can serve as a potential diagnostic biomarker of ACS [
22]. In our study, similar results were obtained in INOCA/ANOCA group: a moderate negative correlation between miR-145 and TNF-a was revealed. According to the work of Zhang X. et al., miR-145-5p expression was reduced in blood samples and arterial walls of patients with stenotic atherosclerosis of the coronary arteries [
39]. Kumar A. et al. found that lower levels of miR-145 and miR-155, along with endothelial dysfunction, were associated with the severity of CKD and were associated with a higher risk of CVD development [
40]. Thus, our data support the assumption that a lower level of miR-145 expression in obstructive CAD, in contrast to INOCA, may be associated with a more severe atherosclerotic lesion of the CA.
As for the analysis of miR-34a, the minimal level of expression of this miR was observed in the control group, represented by healthy volunteers without CVD risk factors, while in obstructive and non-obstructive CA lesions the expression was significantly higher. Similar results were obtained by Gatsiou, A. et al.: high miR-34a levels were independently associated with the presence of CAD, while simultaneous high expression of miR-34-a/c or all three miR-34a/b/c was associated with increased stiffness of aorta [
41].
MiR-34a promotes downregulation of SIRT1 and VEGF protein expression, causing disruption of angiogenesis processes and inducing cell death [
19]. A study of the role of miR-21, -34a, -146a, -146b-5p and -210 demonstrated a significant increase in their expression in atherosclerotic plaques compared to intact arteries [
42]. All these data confirm a significant upregulation in miR-34a expression levels in the plasma of patients with CAD compared with the control group [
43].
Similar results were obtained when studying miR-222, the expression of which was significantly higher in both study groups when compared with the control. According to available scientific data, miR-222 also takes part in atherogenesis, being involved in the regulation of many processes. MiR-221/222 and miR-155 suppress the inflammatory response induced by angiotensin II in endothelial cells, affecting the transcription factor Ets-1 and the genes vascular cell adhesion molecule 1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP1) [
44]. Overexpression of miR-19b-3p, miR-221-3p, and miR-222-3p induced by inflammatory cytokines TNF-α and IFNγ resulted in intracellular ROS accumulation, leading to cell apoptosis [
45]. In obstructive CAD a moderate association between miR-222 and TNF-α expression was found, as well as a high-strength correlation with MMP-1 and MMP-14 [
46]. Karere G.M. et al. identified vascular miRs expressed in baboons and humans and potential novel miRs associated with atherosclerosis. The expression of miR-144-3p, miR-146a-5p, miR-21, miR-221/222-3p was increased in fibrous plaques, while miR-195-5p was decreased. These results indicate that some miRs are not only lesion type specific but also exhibit differential expression at different stages of the disease, indicating their importance in the initiation and progression of atherosclerosis [
47].
In our study potential non-invasive diagnostic marker of stable CAD were found among investigated miRs. Based on the results of the multivariate regression analysis, we can assume miR-145 as independent predictors of the non-obstructive phenotype of stable CAD.
In accordance with the results of the ROC analysis, it was concluded that various miRs can be considered as potential diagnostic noninvasive markers of CAD. Multivariate logistic regression analysis revealed that levels of circulating miR-145 and miR-155 were associated with CAD and may be powerful markers for detecting CAD [
48]. O'Sullivan et. al. concluded that four miRNAs (miR-15a-5p, miR-146a-5p, miR-16-5p, and miR-93-5p) were predictors of the stable CAD development [
49]. Zhang et. al. suggested another miRs (miR-29a-3p, miR-574-3p, and miR-574-5p with AUCs 0.83, 0.792, and 0.789, respectively) as potential markers for noninvasive diagnosis of CAD [
50]. Recent data suggest that plasma levels of miR-23b and miR-143 could be useful as noninvasive biomarkers of in-stent restenosis [
51]. Gholipour, A. et al. established potential suitability of miR-6721-5p as a biomarker for CAD [
52].
Our results can be useful in comprehension of potential roles of miRs and we are planning to continue further studies on the mechanisms of epigenetic regulation of the pathogenesis of different phenotypes of CAD. Investigation of the pathogenesis of atherosclerotic CA lesions may be important for determining the potential role of miRs as possible diagnostic biomarkers and in development of new treatment methods using antagomiRs. It is necessary to continue careful study and fundamental research to solve this complicated problem.
4. Materials and Methods
4.1. Patient Population
A cross-sectional observational study included 127 subjects, who were eligible according to the inclusion criteria and signed informed consent from 2020 to 2024. The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethic Committee of the Sechenov University (Number: 01–21, 22 January 2021). The study included men and women aged 45–75 years with a verified CAD diagnosis.
The myocardial ischemia in hospitalized patients with stable angina or its analogs was confirmed by using instrumental diagnostic methods, namely stress echocardiography (echo-CG) or single-photon emission computed tomography (myocardial scintigraphy), against the background of the exercise testing. Depending on the results of coronary angiogram (CAG) or multispiral computed tomography (CT), the patients were divided into two groups: 51 patients with non-obstructive CA lesions (stenosis <50% or unchanged CA); 76 patients with obstructive CAD (presence of hemodynamically significant CA stenosis). The control group (n = 30) included healthy volunteers without CVD and risk factors. Exclusion criteria were the following: diabetes mellitus, acute coronary syndrome, myocardial infarction, and stroke in the previous 3 months, chronic heart failure III-IV functional class (NYHA), autoimmune and oncological diseases, signs and symptoms of liver disease in the decompensation stage, portal hypertension, uncontrolled bronchial asthma and chronic obstructive pulmonary disease, gastric or duodenal ulcer in the exacerbation stage, chronic pancreatitis in the exacerbation stage, malignant neoplasms, thyroid diseases, Cushing’s syndrome, acute renal failure, terminal renal failure (GFR < 15 mm/min/1.73 m2 ), mental illness, alcoholism, drug addiction, substance abuse, pregnancy, and breastfeeding.
4.2. Collection of Blood Samples and ELISA
Blood plasma samples were collected in tubes with EDTA K3 as an anticoagulant, centrifuged for 20 min at 1000 × g (1000 RCF), and further frozen in cryotubes at −80 ◦ C. To estimate the MMPs levels, VEGF and TNF-α enzyme immunoassay (ELISA) was performed on the ELISA analyzer Adaltis Personal Lab (Rome, Italy) using Wuhan Fine Biotech Co., Ltd. kits (Wuhan, Hubei, China) (catalogue numbers: Cat. No.: EH0232, EH0238, EH0234, EH0369, EH0302, EH0327). The coefficient of variation (CV) for the sets was 10% and 12%, respectively. All patients have undergone standard biochemical tests, including indicators of the lipid spectrum, glucose, and uric acid.
4.3. RNA Extraction and Reverse Transcription-Polymerase Chain Reaction (RT-PCR) Assay
Blood total RNA, including miRNA, was extracted from samples using Qiazol (Qiagen, Germany) following the manufacturers’ protocols. The concentration and purity of the obtained RNA were estimated on the NanoDrop 2000 microvolume spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA). The process of extraction was repeated for each sample until a sufficient amount of RNA was obtained for the next steps.
cDNA was synthesized using MiScript II RT Kit (Qiagen, Hilden, Germany) according to the recommended protocol. To obtain cDNA, 300 ng of total RNA isolated from each sample was used.
The expression level for each analyzed miRNA and the control was quantified in three repetitions on the CFX96 Real-Time PCR Detection System (Bio-Rad, Hercules, CA, USA) by using the MiScript SYBR Green PCR Kit (Qiagen, Hilden, Germany; Catalogue number: 218073) according to the manufacturer’s recommended program (15 min at 95 ◦ C, followed by 40 cycles of 94 ◦ C for 15 s, 55 ◦ C for 30 s, and 70 ◦ C for 30 s). Primers for miRNAs were designed according to the instructions [
53] and their sequences are listed in
Table 6. The presynthesized MiScript Primer Assay (Ce_miR-39_1, identification code MS00019789, Qiagen, Germany) was used for the control. The obtained Ct values were normalized to the exogenous control cel-miR-39-3p and analyzed using the 2
−∆Ct method. The results are presented as REU (relative units of expression).
4.4. Statistical Analysis
Statistical analysis of the results was performed using the program StatTech v.v. 3.1.10 (StatTech, Russia) and the free Python computing software environment (v.3.11). The normality of sample distribution was evaluated using the Shapiro–Wilk (n < 50) or Kolmogorov-Smirnov (n > 50) tests. Quantitative variables with normal distribution were described using arithmetic averages (M) and standard deviations (SD) with a 95% confidence interval (95% CI). When the distribution of variables differed from the normal, quantitative data were described using the median (Me) and the lower and upper quartiles (Q1; Q3). The two groups were compared quantitatively with an abnormal distribution using the Mann-Whitney U-test. Three or more groups were compared quantitatively with an abnormal distribution using the Kruskal–Wallis test; the post-hoc testing was performed using the Dunn test with Bonferroni adjustment. To estimate the diagnostic significance of quantitative variables in predicting a certain outcome, the ROC curve analysis method was used. The cut-off value of the quantitative variable was determined to correspond to the maximum Youden index.
Multiple logistic regression (MLR) was used to build a model for predicting the presence/absence of a characteristic. The choice of the method was based on the dichotomy of the dependent variable and the fact that independent variables characterize both categorical and quantitative characteristics. The independent variables were selected by step-by-step reverse selection using Wald statistics as an exclusion criterion. The statistical significance of the obtained model was determined using the criterion χ 2. To balance the training dataset for a more stable predictive model, the SMOTE (Synthetic Minority Over-sampling Technique) method was employed. To estimate the quality of the constructed model, the following criteria were used: ROC-AUC, accuracy, sensitivity, specificity, and DCA analysis (decision curve analysis). Metrics were calculated together with 95% CI. The 95% CI was calculated using the bootstrap method with a sample of 1000 instances. The threshold value was chosen in accordance with the maximization of sensitivity and specificity.