IN SILICO INHIBITION OF HUMAN PARAPLEGIN WITH NATURAL COMPOUNDS: A POTENTIONAL APPROCH FOR CORONARY ARTERY DISEASE CURE
CHAPTER 1
INTRODUCTION
Heart disease remains a leading cause of death worldwide, with coronary artery disease (CAD) being the most prevalent type. Although considerable progress has been made in understanding and treating CAD, the complexity of the disease and the limited effectiveness of current treatments underline the need for novel therapeutic approaches. Human paraplegin, a mitochondrial protein associated with neurodegenerative diseases, has been implicated in CAD due to its role in oxidative stress and cell death regulation [1]. This study aims to explore the potential of natural compounds to inhibit human paraplegin’s, with a view to developing new treatments for CAD[2]. While traditional drug discovery approaches have relied heavily on empirical testing of large chemical libraries, this study takes a computational approach to screen natural compounds for their ability to inhibit human paraplegin. The use of silicon (computational) methods for drug discovery offers several advantages, including reduced time and cost, and the ability to predict a compound's ability to bind to a target protein. Molecular docking, a widely used in silico method, simulates the interaction between a small molecule (the ligand) and a target protein (the receptor), predicting the most energetically favorable binding poses and estimating binding affinities. Natural compounds have attracted considerable attention as potential drug candidates due to their structural diversity, and historical use in traditional medicine. In addition, natural compounds are often considered safer and more environmentally friendly than synthetic drugs. This study focuses on natural compounds derived from plants, marine organisms, and microorganisms, including flavonoids, polyphenols, and alkaloids, which have been reported to have a variety of biological activities, including anti-inflammatory, antioxidant, and anticancer properties. The specific objectives of this study are to (1) select a representative set of natural compounds with potential for human paraplegin inhibition, (2) identify the binding site(s) on human paraplegin, (3) conduct molecular docking simulations to predict the binding modes and affinities of selected natural compounds, and (4) prioritize the most promising compounds for experimental validation. In summary, this study aims to leverage computational methods to identify natural compounds that can inhibit human paraplegin, with the goal of developing new treatments for CAD. If successful, this approach could provide a cost-effective and sustainable solution to combatting CAD and improving patient outcomes. The following sections of this thesis will outline the methods used in this study, present the results of molecular docking simulations, and discuss the implications of our findings for the development of new CAD treatments. In the quest for novel therapies to combat coronary artery disease (CAD), researchers have been exploring diverse molecular targets and drug development strategies[3].
1.1 Protein and CAD relation
Human paraplegin, a protein primarily found in mitochondria, has recently emerged as a potential target for CAD treatment. While paraplegin is associated with neurodegenerative diseases, its involvement in CAD pathogenesis has gained attention due to its roles in oxidative stress modulation, protein quality control, and cell death regulation. Traditionally, drug discoveries involved time-consuming and costly empirical testing of large chemical libraries. However, recent advancements in computational methods offer a more efficient and cost-effective way to screen potential drug candidates. In silico approaches, particularly molecular docking, enable researchers to predict how small molecules, known as ligands, interact with specific protein targets, such as paraplegin. This computational technique can identify ligands that bind to the target protein with high affinity and predict the most energetically favorable binding modes. Natural compounds have garnered significant interest in drug discovery due to their structural diversity, established safety profiles, and historical use in traditional medicine. In this study, we focus on natural compounds derived from various sources, such as plants, marine organisms, and microorganisms. Compounds like flavonoids, polyphenols, and alkaloids are particularly appealing due to their reported anti-inflammatory, antioxidant, and anticancer properties, which could have implications for CAD treatment [4]. The primary goal of this thesis is to leverage computational methods to identify natural compounds that can inhibit human paraplegin, thus presenting a potential therapeutic avenue for CAD. The primary objective of this study is to explore the potential of natural compounds to inhibit human paraplegin, a protein implicated in coronary artery disease (CAD) pathogenesis. The research will begin with the selection of a diverse set of natural compounds known for their potential therapeutic effects, such as flavonoids, polyphenols, and alkaloids, from various sources including plants, marine organisms, and microorganisms. The next step will involve the identification of the binding sites on the human paraplegin protein, followed by molecular docking simulations to predict the most favorable binding modes and affinities of the selected natural compounds. Finally, the most promising compounds will be prioritized for experimental validation, with the aim of providing a cost-effective and sustainable treatment option for CAD patients, thereby reducing disease burden, and improving patient outcomes.
1.2 History
The Ancient and Medieval Periods (Before 18th Century):
The history of coronary artery disease can be traced back to ancient civilizations. For example, in ancient Egypt (c. 1600 BCE), descriptions of chest pain indicative of heart disease are found in the Ebers Papyrus. Ancient Greek scholars like Hippocrates also documented symptoms and treatments associated with heart conditions. During the Renaissance era, great strides were made in the study of human anatomy. Anatomists such as Leonardo da Vinci and Andreas Vesalius conducted groundbreaking research on the heart and circulatory system. However, the actual causes and mechanisms of coronary artery disease remained largely unknown [5].
18th to 19th Centuries:
It wasn't until the late 18th and early 19th centuries that medical professionals began to gain a better understanding of coronary artery disease. In 1799, British physician Matthew Baillie made the first recorded observation of coronary artery disease during autopsies. He described coronary atherosclerosis, where the arteries become hardened and narrowed due to the buildup of plaque. In the 19th century, advancements in medicine and anatomy continued. William Harvey's work on blood circulation, published in 1628, revolutionized our understanding of cardiovascular physiology. In the mid-1800s, Rudolf Virchow and others made significant contributions to the understanding of atherosclerosis, linking it to inflammation and the buildup of fatty deposits in the arterial walls[4].
20th Century
The 20th century saw a dramatic expansion of knowledge and treatment options for coronary artery disease. In 1912, James B. Herrick published the first description of a heart attack due to a blockage in a coronary artery[6]. This marked a turning point in the understanding of the disease. In the 1950s[7], developments in electrocardiography (ECG) allowed for the non-invasive diagnosis of heart conditions, including coronary artery disease. This was followed by significant surgical innovations, such as the introduction of coronary artery bypass graft (CABG) surgery by Dr. Rene Favaloro in 1967. The 1970s saw the development of percutaneous transluminal coronary angioplasty (PTCA), a minimally invasive procedure to open blocked coronary arteries [8]. This technique was refined over the years and led to the development of modern-day angioplasty and stent procedures[9].
21st Century:
In the 21st century, the focus has shifted towards prevention and early intervention. This includes lifestyle modifications, such as dietary changes, regular physical activity, and smoking cessation, which have been shown to reduce the risk of developing coronary artery disease. Additionally, advances in genetics and personalized medicine have led to targeted treatments based on an individual's genetic profile and risk factors. In conclusion, the history of coronary artery disease is a testament to the progress made in medical science and treatment options over the centuries. From ancient descriptions of chest pain to modern-day interventions, the understanding and management of this complex condition continues to evolve, with an emphasis on prevention, early diagnosis, and personalized care [10].
1.3 Symptoms and diagnosis
Coronary artery disease (CAD) often presents with several key symptoms. The most classic symptom is chest pain or discomfort, known as angina. This might feel like pressure, tightness, squeezing, or a burning sensation centrally in the chest. Physical activity or emotional stress frequently triggers angina, and it can radiate to the arms, neck, jaw, or back. Shortness of breath is another common symptom, particularly during exertion, due to the heart's struggle to circulate enough oxygen-rich blood throughout the body. CAD can also cause persistent fatigue as tissues receive less than their ideal blood supply. Some people might experience dizziness, lightheadedness, or nausea because of the heart not pumping efficiently. Heart palpitations, where you feel skipped heartbeats, a racing heart, or fluttering sensations, can also be associated with CAD. It's important to note that some individuals, particularly women, those with diabetes, and the elderly, might have less typical symptoms of CAD. Instead of classic chest pain, they might experience discomfort in the arms, back, shoulders, neck, jaw, or upper stomach. Sometimes, vague indigestion-like symptoms could be the only presentation. It's essential to remember that symptoms can vary, and some people might not even experience any noticeable signs. If you have concerns about potential CAD symptoms [11].
The accurate diagnosis of coronary artery disease (CAD) is a fundamental step toward risk stratification and the initiation of appropriate therapies aimed at reducing cardiovascular morbidity and mortality. An in-depth medical history and physical examination, focusing on risk factors, symptoms, and clinical signs suggestive of CAD[12], are the starting points for any diagnostic workup. If clinical assessment raises suspicion of CAD, a variety of diagnostic testing modalities will typically be employed to confirm the diagnosis, assess its severity, and guide treatment decisions. Non-invasive modalities represent the initial tier of diagnostic assessments for CAD. An electrocardiogram (ECG) offers critical information regarding the electrical activity of the heart, potentially revealing evidence of arrhythmias, prior myocardial infarction, or ischemia. Exercise stress testing provides insight into cardiac blood flow dynamics during exertion, highlighting areas of reduced perfusion. Echocardiography allows for the visualization of heart structures and function, identifying regional wall motion abnormalities that could indicate areas of inadequate blood supply. Additionally, blood tests measuring cholesterol profiles, blood glucose levels, and inflammatory markers contribute to comprehensive risk assessment[13].
If non-invasive testing establishes a high likelihood of CAD or yields inconclusive results, more advanced imaging studies might be warranted. Nuclear stress testing visualizes cardiac blood flow at rest and under stress, while coronary computed tomography angiography (CTA) utilizes specialized scan technology to provide detailed images of coronary vessels, identifying possible areas of narrowing or occlusion. For definitive diagnosis of blockages or complex cases, the gold standard remains invasive coronary angiography (cardiac catheterization). This approach employs the insertion of a catheter into an artery leading to the heart, followed by dye injection and imaging, for direct assessment of coronary artery patency. The selection of specific diagnostic procedures is tailored to the individual patient. Pre-existing risk factors, symptom severity, and the outcomes of the stepwise evaluation process must be carefully considered by the diagnosing physician to construct the most informative diagnostic sequence. Accurate diagnosis empowers the implementation of evidence-based medical therapies and lifestyle modifications tailored to the patient's needs, significantly improving prognosis, and preventing adverse cardiovascular events[14].
1.4 Paraplegin and MAO: A Contributor to Coronary Artery Disease
The selection of targets for drug discovery is a meticulous process, driven by the need to address unmet medical needs and tackle prevalent diseases effectively. In the context of coronary artery disease (CAD), two proteins have been identified as potential targets: Human Paraplegin protein and Monoamine oxidase (MAO). Human Paraplegin protein [15], encoded by the SPG7 gene, is a metalloprotease located in the inner mitochondrial membrane. It plays a pivotal role in mitochondrial fusion and cellular energy production. Mutations in the SPG7 gene are associated with spastic paraplegia type 7 (SPG7), a condition characterized by progressive spasticity and weakness of the lower limbs. However, studies have shown that human paraplegin protein may also be involved in the pathogenesis of CAD. Given its role in mitochondrial function, targeting human paraplegin protein could potentially mitigate the progression of CAD by restoring mitochondrial dynamics and energy production in the affected cells. Monoamine oxidase (MAO) is an enzyme located in the outer mitochondrial membrane, responsible for the degradation of neurotransmitters such as serotonin, dopamine, and norepinephrine. There are two isoforms of MAO: MAO-A and MAO-B [16]. In the context of CAD, MAO-B has garnered attention due to its role in oxidative stress and vascular dysfunction. Inhibiting MAO-B activity has been proposed as a potential therapeutic strategy for preventing or slowing down the progression of CAD. By targeting MAO-B, it may be possible to reduce the production of reactive oxygen species (ROS) and mitigate oxidative stress in the vascular system, thereby improving endothelial function and reducing the risk of CAD. The rationale behind the selection of these two proteins as potential drug targets for CAD lies in their roles in mitochondrial function and oxidative stress, two key factors implicated in the pathogenesis of CAD. Targeting human paraplegin protein and MAO-B holds promise for developing novel therapeutics that can address the underlying mechanisms of CAD and improve patient outcomes. To assess the feasibility and efficacy of these targets, molecular docking studies can be employed to identify potential small molecule inhibitors that can bind to and modulate the activity of these proteins[17]. These findings can then be validated through in vitro and in vivo experiments to further elucidate their therapeutic potential in CAD management.
1.5 Natural compounds
Natural compounds are chemical substances that are derived from plants, animals, or microorganisms. They are often referred to as secondary metabolites, which means they are produced by living organisms, not as essential for growth, development, or reproduction. Natural compounds have a wide range of structural diversity and biological activities, making them a valuable resource for drug discovery and development[18].
In the field of in silico drug design, natural compounds are frequently used as inhibitors because of their diverse chemical structures and biological activities. The main reasons for using natural compounds as inhibitors in in silico drug design include:
Structural diversity: Natural compounds are structurally diverse, which makes them suitable for screening against a wide range of protein targets. This diversity allows for the identification of novel inhibitors that may not be accessible through synthetic compound libraries alone[19, 20].
Biological activity: Natural compounds have been extensively studied for their biological activities, including their ability to inhibit enzyme activities, modulate cell signaling pathways, and exhibit anti-inflammatory or anti-cancer properties. This wealth of biological data provides a valuable starting point for identifying potential inhibitors of specific protein targets[21].
Availability: Natural compounds are abundant in nature, and many of them can be easily sourced from plants, animals, or microorganisms. This availability makes them an attractive resource for drug discovery efforts, as they can be readily synthesized and tested in in vitro and in vivo assays[22].
Low toxicity: Natural compounds are often perceived as having lower toxicity compared to synthetic compounds, which may make them safer for use in humans. This is particularly important in drug discovery, where the goal is to identify compounds that are both effective and safe for therapeutic use[20].
Overall, natural compounds represent a rich source of chemical diversity and biological activity that can be leveraged in silico drug design to identify novel inhibitors of protein targets implicated in disease[23].
1.6 Treatments
1.6.1 Non medicated treatments
Lifestyle modifications represent the foundation of coronary artery disease (CAD) treatment. A heart-healthy diet emphasizes a wealth of fruits, vegetables, whole grains, lean protein sources, and healthy fats while strictly limiting saturated and trans fats, cholesterol, and sodium. Coupled with this, regular exercise is vital. Aiming for at least 30 minutes of moderate-intensity activity most days of the week strengthens the heart[23], improves blood flow, and combats other CAD risk factors. Maintaining a healthy weight is imperative in minimizing strain on the heart and managing various health conditions linked to CAD. Importantly, smoking cessation is an indispensable step, as smoking drastically increases CAD risk and hinders successful treatment. Stress management techniques can greatly improve long-term outcomes by regulating blood pressure and minimizing the negative impact of stress on heart health [24].
1.6.2 Medication
Medications serve a crucial role in managing CAD alongside lifestyle interventions. Cholesterol-lowering medications, commonly statins, combat a leading contributor to plaque buildup in blood vessels. Various blood pressure medications ensure hypertension is well-controlled, thereby protecting the heart and blood vessels from unnecessary strain. Antiplatelet medications, such as aspirin, are typically recommended to lower the risk of blood clots that could cause blockages in narrowed arteries. In cases of angina (chest pain), nitroglycerin might be prescribed for rapid relief by temporarily dilating blood vessels and improving blood flow to the heart. In more severe cases where lifestyle changes and medications fall short, procedures and surgeries are often critical[25]. Angioplasty with stenting (known as Percutaneous Coronary Intervention or PCI) uses a balloon to open blocked arteries; usually, a permanent stent is put in place to prevent re-narrowing. Coronary artery bypass grafting (CABG) is a major surgery that involves redirecting blood flow around blocked sections of arteries using healthy blood vessels obtained from elsewhere in the body[26].
It's vital to understand that CAD treatment requires a highly personalized approach. The plan developed by a patient's cardiologist is designed with unique health conditions, the severity of CAD, and other factors in mind. Adherence to lifestyle recommendations, medication regimens, and follow-up care are indispensable in controlling CAD and minimizing the risk of future complications, as it remains a chronic condition requiring continual management[27].
1.7 Aim of study
Coronary artery disease (CAD) continues to be a major global health burden. While current treatments address traditional risk factors like high cholesterol and blood pressure, recent research highlights the potential importance of mitochondrial health in CAD development. The human paraplegin protein plays a critical role in maintaining mitochondrial function. Evidence suggests that subtle alterations in paraplegin activity, even without outright dysfunction, could negatively impact mitochondria within heart cells, increasing susceptibility to CAD. This thesis investigates the potential of natural compounds to modulate paraplegin activity as a novel therapeutic strategy for CAD[28, 29]. Natural products harbor a wide array of bioactive molecules with potential health benefits. This study will utilize in silico molecular docking techniques to screen a vast library of natural compounds, evaluating their potential to interact with and influence paraplegin. The central aim of this thesis is to identify promising natural compounds capable of modulating paraplegin activity used in silico molecular docking. The most effective candidates will be further investigated in cell-based models to assess their impact on mitochondrial function within cardiac cells. This project envisions pioneering a new avenue for CAD treatment by using natural compounds to promote mitochondrial health, complementing the existing focus on traditional risk factors.
1.8 Limitations
Molecular docking provides initial predictions about compound-protein interactions, but its accuracy depends on the precision of the models and algorithms used. Even a promising match on computer models doesn't guarantee success in real-world biological systems. Docking can produce 'false positives' where the potential inhibitor ultimately fails to work in cell models or 'false negatives', missing opportunities. Thus, in silico results must always be treated as the starting point for further experimental validation. Natural compounds, while a great source of potential treatments, have their own limitations. Bioavailability is a significant concern. A compound identified through docking might not be well absorbed in the gut or may not reach the heart in sufficient levels for therapeutic effect. Off-target effects must also be considered: natural compounds often interact with numerous cellular systems besides your intended target, potentially leading to side effects or interactions with other medications. Additionally, natural sources present the issue of batch-to-batch variation in compound composition, which would demand extensive quality control in later research phases. Regarding the connection between paraplegin and CAD, further work is needed to definitively establish cause and effect. The link appears suggestive, but coronary artery disease has numerous interconnected causes. Isolating paraplegin's exact role requires more meticulous study. Also, while investigating mitochondrial function in cell models is enlightening, the complexity of real-world heart disease might mean findings don't translate perfectly into clinical benefit[30]. Determining true, long-lasting efficacy in preventing or treating CAD would require further, expansive trials, along with meticulous safety monitoring.
1.9 Literature review:
Over the past decade, there has been a significant shift in our understanding of coronary artery disease (CAD) pathophysiology, which has led to the reevaluation of our clinical approaches to both its chronic and acute phases[31]. Once viewed primarily as a cholesterol storage disorder, we now recognize atherosclerosis as an inflammatory condition. This evolution has broadened our focus from identifying and treating stenotic lesions visible on angiography to considering the biology of nonstenotic plaques, a phenomenon known as arterial remodeling or compensatory enlargement. While revascularization remains effective in relieving ischemia, we have learned that nonobstructive lesions also require attention. Aggressively managing modifiable risk factors in conjunction with appropriate revascularization has been shown to reduce cardiovascular events. Furthermore, we now understand that acute coronary syndromes (ACS) can result from the disruption of plaques that do not necessarily cause critical stenoses. Disrupted plaques serve as a solid-state trigger for thrombosis, while alterations in circulating prothrombotic or antifibrinolytic factors in the blood's fluid phase can also increase the risk of ACS. Recent findings have highlighted the multiplicity of high-risk plaques and the widespread presence of inflammation in individuals prone to ACS[32]. These insights challenge the traditional perception of coronary atherosclerosis as a localized or segmental disease. As a result, the treatment of ACS should involve two complementary phases: addressing the culprit lesion and swiftly stabilizing other vulnerable plaques that could lead to future events [32]. Interventional cardiology must expand beyond mechanical revascularization to encompass preventive interventions aimed at forestalling future cardiovascular incidents. This shift in perspective calls for a more holistic approach to CAD management, one that not only treats the acute event but also addresses the underlying systemic inflammation and arterial remodeling processes[33].
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Figure 1 Simplified schema of diversity of lesions in human coronary atherosclerosis. This schematic depicts 2 morphological extremes of coronary atherosclerotic plaques [34]
The socioeconomic significance of heart disease has greatly stimulated the development of noninvasive imaging tools for evaluating coronary arteries. Current computed tomographic (CT) techniques provide high speed and spatial resolution, combined with advanced electrocardiographic synchronization and ease of use. The research community is actively exploring how to apply these modalities for assessing coronary artery disease. One avenue of exploration is the use of CT to measure coronary artery calcium, which has shown promise in determining the risk of coronary events. However, its precise role in cardiac risk stratification remains uncertain pending the results of population-based studies. In clinical settings, contrast material-enhanced CT coronary angiography is being used to diagnose certain conditions, such as coronary artery anomalies, assess bypass patency, and plan surgeries. While the accuracy of CT coronary angiography for detecting stenoses appears promising, its sensitivity is not yet sufficient for routine diagnostic purposes. Nevertheless, a normal CT coronary angiogram has a high negative predictive value, making it useful for reliably excluding coronary artery stenosis. CT's ability to assess the coronary artery wall noninvasively is also being explored. There is ongoing research to determine whether contrast-enhanced CT coronary angiography can detect, characterize, and quantify atherosclerotic changes and total disease burden in coronary arteries, potentially aiding in cardiac risk stratification [35].
Coronary artery disease (CAD) is the leading cause of cardiovascular mortality worldwide, with more than 4.5 million deaths occurring in the developing world. Despite a recent decline in developed countries[36], both CAD mortality and the prevalence of CAD risk factors continue to rise rapidly in developing countries. The objectives of the current article are to review the literature regarding CAD mortality and the prevalence of CAD risk factors in the developing world and to discuss prevention and control measures[37].
We conducted a MEDLINE search of the English language literature for the years 1990 to 2002 to identify articles pertaining to the prevalence of CAD in developing countries. The search was performed using the following key terms: coronary artery disease, developing countries, ischemic heart disease, incidence, prevalence, prevention, and risk factors. We also obtained relevant statistical information from The World Health Organization's Internet database. There is a paucity of data regarding CAD and its prevalence in the developing world. However, it is projected that CAD mortality rates will double from 1990 to 2020, with approximately 82% of the increase attributable to the developing world. Existing data suggest that rapid socioeconomic growth in developing countries is increasing exposure to risk factors for CAD, such as diabetes, genetic factors, hypercholesterolemia, hypertension, and smoking[38]. There is a relative lack of prevention and control measures to decrease exposure to these risk factors in developing countries [37].
Coronary artery disease (CAD), mainly caused by atherosclerosis of coronary arteries, is a significant cause of mortality in most developed countries. From the 1990s to the 2000s, mortality due to acute myocardial infarction (MI) decreased by up to 50%. The incidence of CAD is influenced by factors such as age, gender, and socioeconomic status[38]. Atherosclerosis is a multifactorial disease process that involves lipid disturbances, thrombosis, inflammation, vascular smooth cell activation, remodeling, platelet activation, endothelial dysfunction, oxidative stress, altered matrix metabolism, and genetic factors[39]. CAD risk factors are prevalent among many individuals and include hypertension, lipid and lipoprotein metabolism disturbances, diabetes mellitus, chronic kidney disease, age, gender, lifestyle factors such as cigarette smoking and diet, obesity, and family history. Angina pectoris is characterized by myocardial ischemia and typically presents as chest pain or discomfort that worsens with exertion. Rest or nitroglycerin can provide relief within minutes. Different grading systems exist for angina pectoris, including the Canadian Cardiovascular Society (CCS) classification, Califf score, and Goldman scale. Patients with ST-segment elevated myocardial infarction (STEMI) may have symptoms of severe angina pectoris and various complications. The combination of sensitive myocardial infarction (MI) biomarkers and precise imaging techniques, including electrocardiography (ECG), computed tomography, and cardiac magnetic resonance imaging, has led to the development of new MI criteria[40]. Complications of acute MI include left ventricular dysfunction, cardiogenic shock, structural complications, arrhythmia, recurrent chest discomfort, recurrent ischemia and infarction[41], pericardial effusion, pericarditis, post-myocardial infarction syndrome, venous thrombosis, pulmonary embolism, left ventricular aneurysm, left ventricular thrombus, and arterial embolism [11].
In the last decade, significant advancements have been made in understanding the genetic underpinnings of coronary artery disease (CAD). The tools employed include large-scale genome-wide association studies (GWAS) involving over 200,000 individuals. These studies have been complemented by bioinformatic techniques like 1000 Genomes imputation, expression quantitative trait locus (eQTL) analyses[42], and the interrogation of various genomic databases, including the Encyclopedia of DNA Elements and Roadmap Epigenomics. Through these efforts, close to 60 common single-nucleotide polymorphisms (SNPs) associated with CAD risk have been identified. These SNPs, with a minor allele frequency above 0.05, have reached genome-wide significance (P<5×10−8). Additionally, a total of 202 independent signals in 109 loci have achieved a false discovery rate (q<0.05) and together explain approximately 28% of the estimated heritability of CAD. These findings have allowed for the development of genetic risk scores that improve the prediction of CAD risk beyond traditional risk factors. They also help identify individuals who are likely to benefit the most from statin therapy. Furthermore, this genetic information has broad applications in clinical medicine and drug discovery[43]. Mendelian randomization, for example, can be used to determine the causal nature of factors associated with CAD risk in epidemiological studies. In contrast to GWAS, whole-exome sequencing has provided valuable insights into genes involved in plasma lipoprotein metabolism. However, it has not yet identified many rare coding variants directly linked to CAD [44].
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Figure 2 Typical Manhattan plot of a significant locus for coronary artery disease (CAD) identified in a meta-analysis of genome-wide association study (GWAS) for myocardial infarction (MI)/CAD[45]
Overall, these recent studies have enhanced our understanding of the genetic basis of CAD. They highlight that CAD's genetic architecture largely comprises multiple common risk alleles, each having a small individual effect size, rather than rare variants with significant effects on CAD risk. Nonetheless, our understanding of the functional roles of the novel loci identified by GWAS remains limited, especially given that most of these loci are in noncoding regions of the genome[46].
The understanding of coronary artery disease (CAD) has improved dramatically in recent years, yet certain aspects of its pathogenesis remain enigmatic. Despite identifying important risk factors for cardiovascular disease (CVD), such as hypertension, hyperlipidemia, diabetes mellitus, and smoking, these do not fully explain why some patients with atherosclerosis are symptomatic and have recurrent symptomatic disease, while others do not. In addition to the extent of coronary atherosclerosis[47], the sensitivity of organs to episodes of ischemia is believed to be important. An organ may be less sensitive to episodes of ischemia if it is supplied with sufficient blood flow through well-developed collateral vessels. Unfortunately, some organs or individuals do not appear to have well-developed collateral vessels, if developed at all. It is not yet clear why there are differences between individuals in their capability of developing a sufficient collateral circulation. The potential of individuals to develop coronary collateral circulation has been largely neglected but may play a significant role in determining myocardial vulnerability. In the current article, we argue for the importance of coronary collaterals and advocate for the consideration of this individual potential to develop collaterals as an additional indicator of cardiac vulnerability. Furthermore, we review the determinants that play a role in collateral coronary blood supply, seeking to deepen our understanding of this underappreciated aspect of CAD [48].
Coronary artery disease (CAD) is one of the major cardiovascular diseases affecting the global human population. This disease has been proved to be the major cause of death in both the developed and developing countries. Lifestyle, environmental factors, and genetic factors pose as risk factors for the development of cardiovascular disease. The prevalence of risk factors among healthy individuals elucidates the probable occurrence of CAD soon. Genome-wide association studies have suggested the association of chromosome 9p21.3 in the premature onset of CAD. The risk factors of CAD include diabetes mellitus, hypertension, smoking, hyperlipidemia, obesity, homocystinuria, and psychosocial stress. The eradication and management of CAD has been established through extensive studies and trials. Antiplatelet agents, nitrates, β-blockers, calcium antagonists, and ranolazine are some of the few therapeutic agents used for the relief of symptomatic angina associated with CAD [49].
In the past, conventional drug discovery strategies have been integral in developing new drugs. However, the process from identifying a promising compound to clinical trials typically takes over 12 years and costs an average of $1.8 billion USD. Given these challenges, there has been a growing interest in silico approaches that leverage computational methods to accelerate the drug discovery process in terms of time, labor, and costs[50]. A number of new drug compounds have been successfully developed using computational methods [51]. Target and lead discovery are pivotal elements of early pharmaceutical research. Target discovery involves identifying and validating suitable drug targets for therapeutic intervention, while lead discovery involves finding novel chemical molecules that act on these targets. The near completion of the human genome sequencing has enabled bioinformatics to establish itself as an essential tool in target discovery. In silico analysis of gene expression and function is now a key part of this process, facilitating the selection of the most relevant targets for a given disease [52]. In lead discovery, advancements in chemoinformatics have led to the development of compound libraries that can be screened virtually. Computational methods are also being developed to predict the drug-likeness of compounds. As a result, drug discovery is increasingly shifting towards electronic R&D[52].
Drug design is a multifaceted endeavor, which can broadly be classified into two main types: rational drug design (RDD) and structure-based drug design (SBDD). Rational drug design (RDD) encompasses a range of computational methods used to identify novel drug compounds, design drugs for selectivity, efficacy, and safety, and develop them into clinical trial candidates. These approaches include structure-based drug design, ligand-based drug design, de novo design, and homology modeling, depending on the available information about drug targets and potential drug compounds. Structure-based drug design (SBDD), on the other hand, utilizes the known three-dimensional (3D) geometrical structure of proteins to design new drug compounds. Typically, the drug targets in SBDD are key molecules involved in specific metabolic or cell signaling pathways associated with a particular disease state[53]. Drug compounds are designed to inhibit, restore, or otherwise modify the structure and behavior of disease-related proteins and enzymes. The 3D structure of these protein targets is usually derived from X-ray crystallography or nuclear magnetic resonance (NMR) techniques. These methods can resolve the structure of proteins to a resolution of a few angstroms, providing researchers with precise insights into the interactions between atoms in protein targets and atoms in potential drug compounds that bind to the proteins. SBDD is a potent tool in drug design, as it allows chemists to design compounds that specifically interact with the target molecule's 3D structure[54], particularly for the development of novel therapeutics that can stimulate or inhibit receptor proteins. Modern drug discovery follows a target-based approach, treating the organism as a series of genes and pathways. The goal is to develop drugs that affect a specific gene or molecular mechanism, known as the target, to selectively treat the underlying cause of the disease without producing side effects. Computers play a crucial role in simulating chemical compounds and designing structures to block enzymes from attaching to a cell's membrane, which causes disease. The modern drug discovery process pipeline consists of seven key steps: target identification, target validation, hit and lead identification, lead optimization, preclinical testing, chemical testing, and new drug application (NDA) and food and drug administration (FDA) approval. These steps ensure that new drugs are thoroughly tested and approved for use in patients[55].
Drug discovery is a critical endeavor in the pharmaceutical industry due to its costliness and time-consuming nature. Identifying drug targets, the first phase in drug discovery, is often a lengthy process. Conventional methods like in vivo and in vitro approaches can yield inefficient results when investigating large-scale data. However, sophisticated in silico approaches have provided pharmaceutical companies with the means to identify new potential drug targets, thereby impacting the success and duration of clinical trials aimed at discovering new drugs[56].
This work aims to review in silico methods for drug discovery, with a particular emphasis on identifying drug targets associated with specific diseases. This review offers a concise overview of recent approaches that leverage bioinformatics for the [57, 58]systematic characterization of the targets of bioactive compounds [59].