Cardiospecific Troponins as Laboratory Biomarkers of Myocardial Cell Injury in Hypertension: A Mini-Review

To date, it is well known that a significant number of diseases of cardiovascular genesis (coronary heart disease, myocardial infarction, cardiomyopathy, Takotsubo syndrome, heart failure, etc.) and extra-cardiac genesis (renal failure, chronic obstructive pulmonary disease, sepsis, diabetes mellitus, etc.) cause injury to contractile cells of the heart muscle (myocardial cells). The most sensitive and specific criteria for proving myocardial cell injury are cardiospecific troponins (CSTns) - CSTnI and CSTnT. According to the current clinical recommendations of the European, American, and Russian Cardiological Communities, CSTnI and CSTnT are the main biomarkers for early diagnosis of myocardial infarction. Hypertension is one of the most dangerous and common risk factors for the development of cardiovascular pathologies and is associated with a high risk of dangerous cardiovascular complications. Therefore, there is an urgent need to search for new biomarkers for the timely assessment of the prognosis of patients with hypertension. This mini-review aims to substantiate the possibilities of using the cardiomarkers (CSTnI and CSTnT) to assess the prognosis of patients suffering from hypertension and to discuss potential mechanisms that cause injury to myocardial cells and increase serum levels of CSTnI and CSTnT. This is a narrative mini-review, which was prepared using the following databases: Pubmed/Medline, PubMed Central, Embase, Scopus, and Web of Science. The following keywords were used in the literature search: "myocardial cells", "injury", "damage", and "hypertension" in combination with the terms "mechanisms of injury" "predictive significance", "cardiac troponins", or "cardiospecific troponins".

The Essential Strategies to Mitigate Cardiotoxicity Caused by Doxorubicin

The study of mechanisms underlying cardiotoxicity of doxorubicin and the development of strategies to mitigate doxorubicin-induced cardiotoxicity are the most relevant issues of modern cardio-oncology. This is due to the high prevalence of cancer in the population and the need for frequent use of highly effective chemotherapeutic agents, in particular anthracyclines, for optimal management of cancer patients. However, while being a potent agent to counteract cancer, doxorubicin also affects the cardiovascular systems of patients undergoing chemotherapy in a significant and unfavorable fashion. Consecutively reviewed in this article are risk factors and mechanisms of doxorubicin cardiotoxicity, and the essential strategies to mitigate cardiotoxic effects of doxorubicin treatment in cancer patients are discussed.

The negative effects of statin drugs on cardiomyocytes: current review of laboratory and experimental data (mini-review)

Statin drugs have long been used as a key component of lipid-lowering therapy, which is necessary for the prevention and treatment of atherosclerosis and cardiovascular diseases. Many studies focus on finding and refining new effects of statin drugs. In addition to the main lipid-lowering effect (blocking cholesterol synthesis), statin drugs have a number of pleiotropic effects, including negative effects. The main beneficial effects of statin drugs on the components of the cardiovascular system are: anti-ischemic, antithrombotic, anti-apoptotic, antioxidant, endothelioprotective, anti-inflammatory properties, and a number of other beneficial effects. Due to these effects, statin drugs are considered one of the main therapeutic agents for the management of patients with cardiovascular pathologies. To date, many review manuscripts have been published on the myotoxicity, hepatotoxicity, nephrotoxicity, neurotoxicity and diabetogenic effects of statins. However, there are no review manuscripts considering the negative effect of statin drugs on myocardial contractile cells (cardiomyocytes). The purpose of this review is to discuss the negative effects of statin drugs on cardiomyocytes. Special attention is paid to the cardiotoxic action of statin drugs on cardiomyocytes and the mechanisms of increased serum levels of cardiac troponins. In the process of preparing this review, a detailed analysis of laboratory and experimental data devoted to the study of the negative effects of statin drugs on cardiomyocytes was carried out. The literature search was carried out with the keywords: statin drugs, negative effects, mechanisms, cardiac troponins, oxidative stress, apoptosis. Thus, statin drugs can have a number of negative effects on cardiomyocytes, in particular, increased oxidative stress, endoplasmic reticulum stress, damage to mitochondria and intercalated discs, and inhibition of glucose transport into cardiomyocytes. Additional studies are needed to confirm and clarify the mechanisms and clinical consequences of the negative effects of statin drugs on cardiomyocytes.

Diagnostic Role and Methods of Detection of Cardiac Troponins: An Opinion from Historical and Current Points of View

The laboratory methods for the determination of cardiac troponins (cTnI, cTnT) used nowadays are extremely diverse, which has a significant impact on our understanding of the biology and diagnostic the value of cTnI and cTnT as biomarkers. The main classification of methods for the determination of cTnI and cTnT is based on the sensitivity of the immunoassay. Low- and moderately sensitive detection methods are known to be relatively less sensitive, which leads to a relatively late confirmation of cardiomyocyte death. Due to the new highly sensitive methods used to determine cTnI and cTnT, designated as a highly or ultrasensitive immunoassays (hs-TnT and hs-TnT), we received new, revised data about the biology of cardiac troponin molecules. In particular, it became clear that they can be considered products of normal myocardium metabolism since hs-TnT and hs-TnT are detected in almost all healthy patients. It also turned out that hs-TnT and hs-TnT differ by gender (in men, troponin concentration in the blood is higher than in women), age (in elderly patients, the levels of troponins are higher than in young ones) and circadian cycles (morning concentrations of troponins are higher than in the evening). A large variety of methods for determining cTnI and cTnT, differing in their diagnostic capabilities, creates the need for tests to perform an unbiased assessment of the analytical characteristics of each method. This review focuses on the most pressing issues related to the discussion of the biological characteristics of cardiac troponin and the analytical characteristics of troponin immunoassays from a historical and contemporary point of view.

Modern Concepts of the Role of Fine Particles (PM 2.5) in the Genesis of Atherosclerosis and Myocardial Damage: Clinical and Epidemiological Data, the Main Pathophysiological Mechanisms

Due to the fact that atherosclerotic cardiovascular diseases (CVDs) dominate in the structure of morbidity, disability and mortality of the population, the study of the risk factors for the development of atherosclerotic CVDs, as well as the study of the underlying pathogenetic mechanisms thereof, is the most important area of scientific research in modern medicine. Understanding these aspects will allow improving the set of treatment and preventive measures and activities. One of the important risk factors for the development of atherosclerosis, which has been actively studied recently, is air pollution with fine particulate matter (PM 2.5). According to clinical and epidemiological data, the level of air pollution with PM 2.5 exceeds the normative indicators in most regions of the world and is associated with subclinical markers of atherosclerosis and mortality from atherosclerotic CVDs. The aim of this article is to systematize and discuss in detail the role of PM 2.5 in the development of atherosclerosis and myocardial damage with the consideration of epidemiological and pathogenetic aspects. Materials and Methods: This narrative review is based on the analysis of publications in the Medline, PubMed, and Embase databases. The terms "fine particles" and "PM 2.5" in combination with "pathophysiological mechanisms," "cardiovascular diseases", "atherosclerosis", "cardiac troponins", "myocardial damage" and "myocardial injury" were used to search publications. Conclusion: According to the conducted narrative review, PM 2.5 should be regarded as the significant risk factor for the development of atherosclerotic CVDs. The pro-atherogenic effect of fine particulate matter is based on several fundamental and closely interrelated pathophysiological mechanisms: endothelial dysfunction, impaired lipid metabolism, increased oxidative stress and inflammatory reactions, impaired functioning of the vegetative nervous system and increased activity of the hemostatic system. In addition, PM 2.5 causes subclinical damage to cardiac muscle cells by several mechanisms: apoptosis, oxidative stress, decreased oxygen delivery due to coronary atherosclerosis and ischemic damage of cardiomyocytes. Highly sensitive cardiac troponins are promising markers for detecting subclinical myocardial damage in people living in polluted regions.

Hypertension as One of the Main Non-Myocardial Infarction-Related Causes of Increased Cardiospecific Troponins: From Mechanisms to Significance in Current Medical Practice

It is well known that many pathological conditions of both cardiovascular diseases (CVDs) (coronary heart disease, myocardial infarction, arrhythmias, myocarditis, cardiomyopathy, etc.) and non-cardiac (sepsis, anemia, kidney diseases, diabetes mellitus, etc.) origin in the course of their development cause injury to contractile cardiac muscle cells - myocardial cells (MCs). One of the most sensitive and specific criteria for detecting MC injury are cardiospecific troponins (CTs), which are regulatory protein molecules that are released into the blood serum from MC upon their death or injury. Current methods for determining CTs are called high-sensitive ones, and their main advantage is a very low minimum detectable concentration (limit of detection) (average 1 - 10 ng/L or less), which allows early detection of minor MC injury at the earliest stages of CVDs, and therefore they can change the understanding of disease development mechanisms and open up new diagnostic possibilities. One of the most common and dangerous early diseases of the cardiovascular system is hypertension (HT). The novelty of this article lies in the discussion of a new diagnostic direction - predicting the risk of developing CVDs and their dangerous complications in patients with HT by determining the concentration of CTs. In addition, pathophysiological mechanisms underlying MC injury and the release of CTs into the bloodstream and the elimination of CTs into the urine are proposed. This information will contribute to additional fundamental and clinical research to verify the new diagnostic possibility of using CTs in clinical practice (for the management of patients with HT).

The Role of Fine Particles (PM 2.5) in the Genesis of Atherosclerosis and Myocardial Damage: Emphasis on Clinical and Epidemiological Data, and Pathophysiological Mechanisms

Due to the fact that atherosclerotic cardiovascular diseases (CVDs) dominate in the structure of morbidity, disability and mortality of the population, the study of the risk factors for the development of atherosclerotic CVDs, as well as the study of the underlying pathogenetic mechanisms thereof, is the most important area of scientific research in modern medicine. Understanding these aspects will allow to improve the set of treatment and preventive measures and activities. One of the important risk factors for the development of atherosclerosis, which has been actively studied recently, is air pollution with fine particulate matter (PM 2.5). According to clinical and epidemiological data, the level of air pollution with PM 2.5 exceeds the normative indicators in most regions of the world and is associated with subclinical markers of atherosclerosis and mortality from atherosclerotic CVDs. The aim of this article is to systematize and discuss in detail the role of PM 2.5 in the development of atherosclerosis and myocardial damage.

Cardiac Troponins as Biomarkers of Cardiac Myocytes Damage in Case of Arterial Hypertension: From Pathological Mechanisms to Predictive Significance

Background. Many pathological conditions of both cardiovascular and non-cardiac origin in the course of their development cause damage to contractile cardiac muscle cells—cardiac myocytes (CMCs). One of the most sensitive and specific criteria for detecting CMCs are cardiac troponins (CTs), which are regulatory protein molecules that are released into the blood serum from CMCs upon their death or damage. New (high-sensitive) methods for detecting CTs allow the detection of minor CMCs damages at the earliest stages of cardiovascular diseases and can therefore change the understanding of disease development mechanisms and open up new diagnostic possibilities. One of the most common and dangerous early diseases of the cardiovascular system is arterial hypertension. The purpose of this paper is to summarize the pathophysiological mechanisms underlying CMCs damage and CTs release into the bloodstream in the case of arterial hypertension and to state the clinical significance of increased CTs levels in patients with arterial hypertension. Materials and methods. This is a descriptive review, which was prepared using the following databases: Embase, Pubmed/Medline and Web of Science. The following key words were used in the literature search: “myocardial injury” and “arterial hypertension” in combination with the terms “cardiac troponins” and “mechanisms of increase”. Conclusions. According to a literature analysis, CMCs damage and CTs release in the case of arterial hypertension occur according to the following pathophysiological mechanisms: myocardial hypertrophy, CMCs apoptosis, damage to the CMC cell membrane and increase in its permeability for CTs molecules, as well as changes in the glomerular filtration rate. Most often, increased CTs serum levels in case of arterial hypertension indicate an unfavorable prognosis. Data on the CTs predictive significance in case of arterial hypertension open the prospects for the use of these biomarkers in the choice of patient management plans.

The Metabolic Pathway of Cardiac Troponins Release: Mechanisms and Diagnostic Role

Modern methods of cardiac troponin determination have enabled early diagnosis of acute myocardial infarction (AMI) and selection of optimal treatment tactics for patients early from admission. It has markedly improved the further prognosis of these patients. Unfortunately, there are a number of problems arising from the use of high-sensitivity cardiac troponins: frequent and unexplained increases in serum troponin levels in a number of pathological conditions not associated with AMI; insufficient study of mechanisms of release and increase, features of circulation and elimination of cardiac troponins; inconsistent data on the influence of several factors (circadian, gender and age characteristics), on cardiac troponin levels. All this may be accompanied by difficulties and errors in differential diagnosis as well as insufficient use of the diagnostic potential of cardiac troponins. In general, these problems are due to our insufficient understanding of the metabolic pathway of cardiac troponins. This review briefly discusses the main stages of the metabolic pathway of cardiac troponins and focuses in detail on the first stage of metabolism (the release of cardiac troponins).

On the Effect of Heterophilic Antibodies on Serum Levels of Cardiac Troponins: A Brief Descriptive Review

Serum levels of cardiac troponins can be increased both with myocardial damage and in the absence of myocardial damage. In the second case, this is due to the influence of false-positive factors, among which heterophilic antibodies play a significant role. Understanding the causes of the formation of heterophilic antibodies, the features and mechanisms of their effect on serum levels of cardiac troponins, is an important condition for interpreting a false-positive result due to the influence of heterophilic antibodies. This brief, descriptive review presents the causes of heterophilic-antibodies formation and discusses their effect on serum levels of cardiac troponins.

Current understanding of cardiac troponins metabolism: a narrative review

BACKGROUND AND AIMS

Current methods (highly sensitive and ultra-sensitive) of cardiospecific troponins detection have enabled early diagnosis of myocardial infarction (MI) and selection of optimal treatment tactics for patients early from admission. The use of these methods in real clinical practice helps to choose the most optimal treatment tactics for patients in the early stages after admission, and this significantly improved the further prognosis of patients suffering from MI. However, there are a number of problems that arise when using highly sensitive or ultra-sensitive methods for determining cardiospecific troponins: frequent and unexplained increase in serum levels of cardiospecific troponins in a number of pathological conditions unrelated to MI; insufficient knowledge and understanding of the mechanisms of release and increase in levels of cardiospecific troponins; poorly understood features and mechanisms of circulation and elimination of cardiospecific troponins; the presence of conflicting information about the influence of several factors (gender, age and circadian characteristics) on the levels of cardiospecific troponins in blood serum; undisclosed diagnostic potential of cardiospecific troponins in non-invasive human biological fluids. These problems cause great difficulties and increase the risk of errors in the differential diagnosis of MI, and also do not allow to fully unlock the diagnostic potential of cardiospecific troponins. In general, these problems are associated with a lack of understanding of the fundamental mechanisms of the metabolism of cardiospecific troponins. The main purpose of this narrative review is to summarize and provide detailed information about the metabolism of cardiospecific troponins and to discuss the potential impact of metabolic features on the diagnostic value of cardiospecific troponins and their diagnostic capabilities.

MATERIALS AND METHODS

This narrative review is based on the analysis of publications in the Medline, PubMed, and Embase databases. The terms "cardiac troponins," "troponin T," and "troponin I" in combination with "mechanisms of increase," "mechanisms of release," "circulation," "proteolytic cleavage," "elimination," "circadian rhythms," "saliva," and "urine" were used to search publications.

RESULTS

It has been reported that the metabolic features (mechanisms of release, circulation, and elimination) of cardiospecific troponins may have an important influence on the diagnostic value of cardiospecific troponins in a number of physiological and pathological conditions that cause cardiomyocyte damage. The main mechanisms of cardiac troponin release are: cardiomyocyte apoptosis; myocardial cell regeneration and renewal; increased cell membrane permeability; release of troponins by vesicular transport; increased proteolytic degradation of cardiospecific troponin molecules within the cell which may facilitate their release from intact myocardial cells or in the initial phase of those pathological conditions that increase the activity of enzymes that degrade cardiospecific troponins. Besides, the formation of small fragments (troponin molecules) may facilitate their penetration into other body fluids such as urine and/or oral fluid which may provide researchers and practitioners with a new diagnostic opportunity. It should be noted that in addition to release mechanisms, cardiospecific troponin elimination mechanisms may play an important diagnostic role. The contribution of release and elimination mechanisms in different pathologies may differ significantly. Circadian rhythms of cardiospecific troponins may be associated with fluctuations in the activity of those organ systems which influence the mechanisms of cardiospecific troponin release or elimination. Such major systems include: neuroendocrine, urinary, and hemostasis.

CONCLUSIONS

Cardiospecific troponins metabolism has an important influence on diagnostic value and diagnostic capabilities. Further study of the features of cardiac troponin metabolism (mechanisms of release, circulation and elimination) is required to improve diagnosis and differential diagnosis of diseases causing cardiomyocyte damage. The data on the influence of circadian rhythms of cardiospecific troponins on the diagnostic value and the possibility of determining cardiospecific troponins in body fluids that can be obtained by noninvasive methods are very interesting. However, so far this information and valuable capabilities have not been applied in clinical practice because of the paucity of studies conducted.

False-Positive Causes in Serum Cardiac Troponin Levels

Cardiac troponins (cTns) are the most valuable and specific markers of cardiovascular diseases, including acute myocardial infarction. These biomarkers can also be used to assess the degree of myocardial damage in non-cardiac diseases that can negatively affect the cells of cardiac muscle tissue. However, in everyday clinical practice, doctors often encounter with false-positive cases of increased cTns. False-positive cases of increased cTns can contribute to incorrect diagnosis and subsequent inadequate treatment, which causes significant harm to the patient. This review discusses some common causes of a false-positive increase in the level of cTns in the blood serum. Such causes are fibrin clots, heterophilic antibodies, alkaline phosphatase, rheumatoid factor, and cross-reactions of diagnostic (anti-cTn) antibodies with skeletal troponins. Detailed attention is focused on the mechanisms of false-positive increase, and ways to identify and combat these false-positive causes of increased cTns. This has an important practical significance in modern clinical practice.

Some Common Causes of False Positive Increases in Serum Levels of Cardiac Troponins

Cardiac troponin molecules (cTnI and cTnT) are the most valuable and in-demand biomarkers for detecting various types of myocardial damage (reversible and irreversible, ischemic, inflammatory, toxic, etc.) in current clinical practice. These biomarkers are widely used for early diagnosis of acute myocardial infarction (AMI) and risk stratification of patients suffering from a number of cardiac (such as myocarditis, heart failure, cardiomyopathy, etc.) and extra-cardiac diseases (such as sepsis, renal failure, pulmonary embolism, neurological pathologies, etc.) that negatively affect the cells of cardiac muscle tissue. However, in daily routine clinical activities, internists and cardiologists often encounter cases of false increases in the concentrations of cardiospecific troponins. A false increase in the concentration of troponins contributes to an incorrect diagnosis and incorrect therapy, which can harm the patient. A false increase in the concentration of troponins contributes to an incorrect diagnosis and incorrect therapy, which can harm the patient, therefore, internists and cardiologists should be well aware of the main reasons and mechanisms for false-positive results cTnI and cTnT. This review article mainly focuses on the causes of falsepositive increases in serum levels of cTnI and cTnT, which provide helpful clues for the accurate diagnosis of AMI and evidence for the differential diagnosis.

Cardiac Troponins: Analytical Characteristics and Diagnostic Capabilities of Modern (High-sensitive) Determination Methods

Cardiovascular diseases have a leading role in terms of morbidity, mortality, and disability of the population, causing significant socio-economic damage to all countries of the world. This circumstance requires researchers to constantly seek for new biomarkers and improve methods for determining existing biomarkers, and search for new therapeutic targets to improve diagnostic and treatment strategies. Recently, there have been some important changes in laboratory diagnostics of patients with acute coronary syndrome, due to the introduction into the routine practice of new high and ultrasensitive methods for the determination of biomarkers of injury, specific to cardiac muscle tissue, namely cardiac troponins. A key advantage of highly sensitive immunochemical assays is the ability to detect cardiac troponins in the early stages of myocardial infarction. This allows making the optimal decision on the early choice and conduct of reperfusion therapy, which significantly improves the further prognosis of patients. Among the most significant generally recognised disadvantages of highly sensitive determination methods are low specificity and a huge variety of troponin immunoassays. The decrease in specificity is reflected in the fact that cardiac troponins are no longer considered the “gold standard” of diagnosis related to Acute Myocardial Infarction (AMI) (irreversible ischaemic damage to cardiomyocytes). As a result, any damage to the myocardium, even insignificant and reversible under physiological state (physical activity, stress) and several pathological conditions, can lead to an increase in serum levels of cardiac troponins and affect the accuracy of the diagnosis. Each method for the determination of cardiac troponins, among the existing wide variety of troponin immunoassays, possesses different analytical characteristics, and detects different concentrations of troponins in the same patient. This article provides a view of current data on the biology of cardiac troponins, and defines the analytical characteristics of new high-sensitive methods for the determination of cardiac troponins.

[Clinical and Diagnostic Value of Cardiac Markers in Human Biological Fluids]

The article is devoted to problems of clinical-diagnostic value of determination of cardio-specific troponins in human biological fluids. Improvement of laboratory instrumentation and emergence of high sensitivity methods of analysis have allowed to identify troponins in urine, dialysate, and oral fluid. In the review we present actual information related to measurement of troponins in blood serum, data on testing of cardio-specific troponins in urine, dialysate, and oral fluid. Special attention is paid to determination of some cardiomarkers in oral fluid with thorough analysis of diagnostic value and effectiveness of the conducted studies.