Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in atherosclerosis

Understanding the Mechanisms and Treatment of Heart Failure: Quantitative Systems Pharmacology Models with a Focus on SGLT2 Inhibitors and Sex-Specific Differences

Heart failure (HF), which is a major clinical and public health challenge, commonly develops when the myocardial muscle is unable to pump an adequate amount of blood at typical cardiac pressures to fulfill the body's metabolic needs, and compensatory mechanisms are compromised or fail to adjust. Treatments consist of targeting the maladaptive response of the neurohormonal system, thereby decreasing symptoms by relieving congestion. Sodium-glucose co-transporter 2 (SGLT2) inhibitors, which are a recent antihyperglycemic drug, have been found to significantly improve HF complications and mortality. They act through many pleiotropic effects, and show better improvements compared to others existing pharmacological therapies. Mathematical modeling is a tool used to describe the pathophysiological processes of the disease, quantify clinically relevant outcomes in response to therapies, and provide a predictive framework to improve therapeutic scheduling and strategies. In this review, we describe the pathophysiology of HF, its treatment, and how an integrated mathematical model of the cardiorenal system was built to capture body fluid and solute homeostasis. We also provide insights into sex-specific differences between males and females, thereby encouraging the development of more effective sex-based therapies in the case of heart failure.

Therapeutic Strategies and Chemoprevention of Atherosclerosis: What Do We Know and Where Do We Go?

Despite progress in understanding the pathogenesis of atherosclerosis, the development of effective therapeutic strategies is a challenging task that requires more research to attain its full potential. This review discusses current pharmacotherapy in atherosclerosis and explores the potential of some important emerging therapies (antibody-based therapeutics, cytokine-targeting therapy, antisense oligonucleotides, photodynamic therapy and theranostics) in terms of clinical translation. A chemopreventive approach based on modern research of plant-derived products is also presented. Future perspectives on preventive and therapeutic management of atherosclerosis and the design of tailored treatments are outlined.

The effects of cardiac drugs on human erythrocyte carbonic anhydrase I and II isozymes

Cardiovascular diseases are the leading cause of mortality worldwide. In recent years, the relationship between carbonic anhydrase inhibitors and atherosclerosis has attracted attention. In this study, we aimed to determine the in vitro effects of 35 frequently used cardiac drugs on human carbonic anhydrase I (hCA I) and II (hCA II). The inhibitory effects of the drugs on hCA I and hCA II were determined with both the hydratase and esterase methods. The most potent inhibitors observed were propafenone (hCA I: 2.8 µM and hCA II: 3.02 µM) and captopril (hCA I: 1.58 µM and hCA II: 6.25 µM). Isosorbide mononitrate, propranolol, furosemide, and atorvastatin were also potent inhibitors. The inhibitor constant, Ki, value from the Lineweaver-Burk plot for propafenone was 2.38 µM for hCA I and 2.97 µM for hCA II. The tested cardiac drugs showed potent in vitro inhibition of the hCA I and II isozymes. Especially, in patients with atherosclerotic heart disease, these drugs may be preferred primarily due to the beneficial effects of carbonic anhydrase inhibition on atherosclerosis.

Dose-Effect of Irbesartan on Cyclooxygenase-2 and Matrix Metalloproteinase-9 Expression in Rabbit Atherosclerosis

Irbesartan has previously shown antiatherosclerotic effects on human carotid atherosclerotic plaques. Our study aimed to assess the dose-effect of irbesartan on cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) in rabbit atherosclerotic aorta. New Zealand rabbits were randomly divided into 6 groups: normal control (NC), high cholesterol (HC), low-dose (10 mg·kg·day), medium-dose (20 mg·kg·d), and high-dose (30 mg·kg·d) irbesartan and celecoxib (20 mg·kg·d). Except for the NCs, rabbits were fed a HC diet for 14 weeks to induce atherosclerosis. Aortic atherosclerotic lesions and messenger RNA and protein expression of COX-2, MMP-9, and nuclear factor-κB (NF-κB) were subsequently measured. The surface area of aortic atherosclerotic lesions was visibly larger in the HC group than in NCs (P < 0.01), but showed considerable reduction with medium- and high-dosage irbesartan and celecoxib treatments (P < 0.01). In medium- and high-dosage irbesartan and celecoxib groups, COX-2 and MMP-9 expression and NF-κB activity were significantly lower than in the high-cholesterol group (P < 0.01). No significant differences in treatment effects were observed between the high-dosage irbesartan and celecoxib groups (P > 0.05). Our results indicate that medium and high doses of irbesartan and celecoxib have antiatherosclerotic effects in aortic plaques via inhibition of COX-2 and MMP-9 by suppressing NF-κB activation. High-dose irbesartan has effects similar to celecoxib.

Aortic stenosis at young adult age

Aortic stenosis at young adult age is usually the result of a stenotic bicuspid aortic valve, which is the most common cardiac congenital anomaly. In clinical practice, exercise and pregnancy are important topics. Furthermore, the timing of intervention is under debate, as little information is available on the natural history and outcome after aortic valve replacement in these young adults. In older patients, there is a trend towards earlier intervention. With the increased knowledge of the pathophysiology of aortic stenosis, studies have focused on the dilatation of the ascending aorta with risk of dissection. Recently, it has been suggested that pharmacologic treatment of aortic stenosis could be beneficial for these young adults.

Treating the metabolic syndrome

The metabolic syndrome (MS), a cluster of metabolic abnormalities with insulin resistance as its central component, is increasing in prevalence and is associated with an increased risk of cardiovascular disease and Type 2 diabetes mellitus (T2DM). Current evidence supports an aggressive intervention approach that comprises lifestyle modification in conjunction with drug treatment of the MS components. Healthier eating and regular exercise greatly reduce waistline and body mass index, lower blood pressure and improve lipid profile. Lifestyle modification has been proven to prevent T2DM development. Nevertheless, appropriate treatment of MS components often requires pharmacologic intervention with insulin-sensitizing agents, such as metformin and thiazolidinediones, while statins and fibrates, or angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are the first-line lipid-modifying or antihypertensive drugs. Only severely obese patients require specific drug treatments. Very often, drug combinations will be necessary to manage multiple risk factors. As we progress in the understanding of the pathophysiology of the MS, new targets for therapies will probably be identified and new treatments will prove to be even more efficacious than those currently available for the management of this life-threatening condition.

Effect of Angiotensin-converting enzyme inhibitors and Angiotensin receptor antagonists in atherosclerosis prevention

Atherosclerosis is a highly complex biological process that has become the scourge of modern civilization. Endothelial dysfunction is the first step in the development of atherosclerosis. The renin-angiotensin-aldosterone system (RAAS) plays an important role in the development of endothelial dysfunction and atherosclerosis. Several studies have shown that in vitro blockade of the RAAS is associated with improvement in markers of endothelial dysfunction and inflammation. Many clinical trials have demonstrated a clear benefit of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) manifested by a reduction of cardiovascular events. These findings suggest that ACEIs and ARBs can play an important role in prevention of atherosclerosis and in the delay of its progression. In this review we focus on the importance of RAAS blockade to prevent or delay progression of atherosclerosis and its impact on reduction of cardiovascular events.

Effect of daily fruit ingestion on angiotensin converting enzyme activity, blood pressure, and oxidative stress in chronic smokers

OBJECTIVE

This study examined whether, daily fruit (blueberries) consumption (250 g) for three weeks or acute fruit ingestion (250 g) would attenuate angiotensin converting enzyme (ACE) activity and reduce oxidative stress in chronic cigarette smokers.

METHODS

Twenty subjects were recruited and randomized into fruit or control groups. Blood samples and blood pressure were obtained at baseline and then pre and one hour post when subjects returned to the lab three weeks later. To examine acute effects, the fruit group immediately ingested 250 g of blueberries after returning and at least one hour prior to the post blood draw. Plasma samples were analyzed for ACE activity, F(2)- isoprostanes and lipid hydroperoxides (LH) as measures of oxidative stress, and ferric reducing ability of plasma (FRAP) as a measure of antioxidant potential. A 2 (treatment) x 3 (time) repeated measures ANOVA was used for statistical analysis. If interaction was significant, then Student's t-tests were used to further examine this relationship. For these comparisons, a Bonferroni adjustment was made with statistical significance set at P < 0.025.

RESULTS

The pattern of change between treatments was not significant for any variable except LH (P < 0.001).

CONCLUSION

This study indicates that LH are significantly reduced by daily fruit consumption, but not affected by acute ingestion. This finding could be one way in which fruit consumption contributes to prevention of cardiovascular disease.

Relationship between angiotensin-converting enzyme gene polymorphism and severity of aortic valve calcification

OBJECTIVE

To investigate the role of angiotensin-converting enzyme (ACE) gene polymorphism in patients with degenerative aortic valve calcification (AVC).

PATIENTS AND METHODS

Our study consisted of 305 Turkish patients of European descent (139 male, 166 female; mean plus or minus age, 68 plus or minus 9 years) referred to our echocardiography laboratory for aortic valve evaluation between June 2, 2003, and April 29, 2005. The severity of AVC was graded from 1 to 6 by echocardiography. We used polymerase chain reaction to determine ACE gene polymorphism.

RESULTS

The ACE insertion/deletion genotype distributions for the study population were in Hardy-Weinberg equilibrium (chi square equals 3.5, P equals .18). The study population was divided into 3 groups based on the severity of AVC: those with grade 1 calcification were in group 1, those with grades 2 to 4 in group 2, and those with grades 5 to 6 in group 3. Group 1 patients were significantly younger, less likely to have hypertension and diabetes, and had higher high-density lipoprotein cholesterol levels. The genotype frequencies were significantly different among groups, with the insertion/insertion genotype being less prevalent in group 3 patients. In multivariate analysis, independent predictors of severe AVC were hypertension (odds ratio [OR], 5.6; 95% confidence interval [CI], 2.8 to 11.0; P less than .001), low high-density lipoprotein cholesterol (OR, 2.7; 95 percent CI, 1.5 to 4.9; P equals .001), and the deletion/deletion and insertion/deletion vs insertion/insertion genotype (OR, 3.2; 95 percent CI, 1.5 to 7.2; P equals .004).

CONCLUSION

These results suggest that ACE gene polymorphism may be associated with severe AVC.

Impairment of Endothelium-Dependent Relaxation of Rat Aortas by Homocysteine Thiolactone and Attenuation by Captopril

To explore the effects of angiotensin-converting enzyme (ACE) inhibitors on endothelial dysfunction induced by homocysteine thiolactone (HTL). Both endothelium-dependent relaxation and nondependent relaxation of thoracic aortic rings in rats induced by acetylcholine (Ach) or sodium nitroprusside (SNP) and biochemical parameters including malondialdehyde (MDA) and nitric oxide (NO) were measured in rat isolated aorta. Exposure of aortic rings to HTL (3 to 30 mM) for 90 minutes made a significant inhibition of endothelium-dependent relaxation induced by Ach, decreased contents of NO, and increased MDA concentration in aortic tissue. After incubation of aortic rings with captopril (0.003 to 0.03 mM) attenuated the inhibition of endothelium-dependent relaxation (EDR) and significantly resisted the decrease of NO content and elevation of MDA concentration caused by HTL (30 mmol/L) in aortic tissues, a similarly protective effect was observed when the aortic rings were incubated with both N-acetylcysteine (0.05 mM). Treatment with enalaprilat (0.003 to 0.01 mM) made no significant difference with the HTL (30 mM) group regarding EDR, but enalaprilat (0.03 mM) and losartan (0.03 mM) could partly restore the EDR in response to HTL (30 mM). Captopril was more effective than enalaprilat and losartan in attenuation of the inhibition of on acetylcholine-stimulated aortic relaxation by HTL in the same concentration. Moreover, superoxide dismutase (SOD, 200 U/mL), which is a scavenger of superoxide anions, apocynin (0.03 mM), which is an inhibitor of NADPH oxidase, and l-Arginine (3 mmol/L), a precursor of nitric oxide (NO), could reduce HTL (30 mM)-induced inhibition of EDR. After pretreatment with not only the NO synthase inhibitor Nomega-nitro-l-arginine methyl ester (L-NAME, 0.01 mM) but also the free sulfhydryl group blocking agent p-hydroxymercurybenzoate (PHMB, 0.05 mM) could abolish the protection of captopril and N-acetylcysteine, respectively. These results suggest that mechanisms of endothelial dysfunction induced by HTL may include the decrease of NO and the generation of oxygen free radicals and that captopril can restore the inhibition of EDR induced by HTL in isolated rat aorta, which may be related to scavenging oxygen free radicals and may be sulfhydryl-dependent.

Comparison of captopril and enalapril to study the role of the sulfhydryl-group in improvement of endothelial dysfunction with ACE inhibitors in high dieted methionine mice

To examine the role of sulfhydryl (-SH) group in improvement of endothelial dysfunction with angiotensin-converting enzyme (ACE) inhibitors in experimental high dose of methionine dieted rats. We compared the effects of Captopril (an ACE inhibitor with -SH group), enalapril (an ACE-inhibitor without -SH group), N-acetylcysteine (only -SH group not ACE inhibitor) on endothelial dysfunction injured by methionine-induced hyperhomocysteinemia (HHcy) in rats. Male Sprague-Dawley rats were divided randomly into seven groups: control group, L-methionine group, low dose Captopril (15 mg/kg), middle dose Captopril (30 mg/kg), high dose Captopril (45 mg/kg), enalapril (20 mg/kg), N-acetylcysteine (200 mg/kg); control group were intragastric gavaged by water and others groups were intragastric gavaged by L-methionine and drugs in water one time every day. Acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), sodium nitroprusside (SNP)-induced endothelium-independent relaxation of aortic rings were examined. Paraoxonase1 (PON1) and ACE activity, malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD) in serum were analyzed. It was found that a single intragastric gavage by L-methionine resulted in inhibition of endothelium-dependent relaxation, markedly increased the serum level of malondialdehyde and decreased the activity of PON1 and SOD, similarly decreased the level of NO in the serum; but had no effects on endothelium-independent relaxation and angiotensin-converting enzyme activity compared with the control group. Given the treatment with three doses of Captopril (15 approximately 45 mg/kg) markedly attenuated inhibition of vasodilator responses to ACh, and eliminated the increased level of malondialdehyde, the decreased level of NO, activity of PON1 and SOD in serum by single intragastric gavaged L-methionine. However, there were some significant differences among Captopril (30 mg/kg or 45 mg/kg), enalapril (20 mg/kg), and N-acetylcysteine particular in the activity of PON1 and ACE. These results suggested that Captopril can protect the vascular endothelium against the damages induced by L-methionine in rats, and the beneficial effects of Captopril may be related to attenuating the decrease in PON1 activity and NO levels. Furthermore, this protective effect may be concerned with the sulfhydryl group.

Drug therapy of the metabolic syndrome: minimizing the emerging crisis in polypharmacy

The metabolic syndrome--a collection of factors associated with increased risk for cardiovascular disease and diabetes--is becoming increasingly common, largely as a result of the increase in the prevalence of obesity. Although it is generally agreed that first-line clinical intervention for the metabolic syndrome is lifestyle change, this is insufficient to normalize the risk factors in many patients, and so residual risk could be high enough to justify drug therapy. However, at present there are no approved drugs that can reliably reduce all of the metabolic risk factors over the long term, and so there is growing interest in therapeutic strategies that might target multiple risk factors more effectively, thereby minimizing problems with polypharmacy. This review summarizes current understanding of the nature of the metabolic syndrome, and discusses each of the risk factors of the metabolic syndrome as possible primary drug targets; potential secondary or tertiary targets are also considered.

Role of Blood Cell–Associated AT1 Receptors in the Microvascular Responses to Hypercholesterolemia

OBJECTIVE

Hypercholesterolemia elicits a proinflammatory and prothrombogenic phenotype in the microvasculature that is characterized by activation and adhesion of blood cells. The angiotensin II receptor-1 antagonist Losartan prevents the induction of these responses. The objective of this study was to determine the relative contributions of blood cell-associated versus endothelium-associated AT1a-R to these hypercholesterolemia-induced microvascular alterations.

METHODS AND RESULTS

Leukocyte adhesion and emigration and platelet adhesion were quantified by intravital microscopy in postcapillary venules. C57Bl/6 mice were placed on a normal (ND) or high-cholesterol (HCD) diet for 2 weeks. AT1a-R bone marrow chimeras that express AT1a-R on the vessel wall but not blood cells and AT1a-R knockouts were placed on HCD. Venular shear rate was comparable in all groups. Platelet and leukocyte adhesion and leukocyte emigration were significantly increased in HCD mice versus ND. Leukocyte recruitment was significantly reduced in the HCD-AT1a-R bone marrow chimera group, whereas platelet adhesion remained at HCD levels. However, in HCD-AT1a-R knockout mice, platelet and leukocyte adhesion were reduced to ND levels.

CONCLUSIONS

These data indicate that the platelet-vessel wall adhesion elicited by hypercholesterolemia is mediated by AT1a-R engagement on the endothelial cell rather than the platelet, whereas leukocyte recruitment is mediated by blood cell-associated AT1a-R.

Angiotensin II Type-1 Receptor Antagonism Attenuates the Inflammatory and Thrombogenic Responses to Hypercholesterolemia in Venules

Hypercholesterolemia elicits an inflammatory response in the microvasculature that is accompanied by an increased expression of angiotensin II type-1 receptors (AT1-R) on platelets, leukocytes, and endothelial cells. AT1-R blockade attenuates inflammatory responses to angiotensin II (eg, adhesion molecule expression and reactive oxygen species production). We investigated whether AT1-R antagonism attenuates the platelet and leukocyte recruitment induced by acute hypercholesterolemia in postcapillary venules. Leukocyte and platelet adhesion and oxidative stress were quantified by intravital microscopy in cremaster muscle, and P-selectin and AT1-R expression was determined in mice placed on a normal diet (ND) or high-cholesterol diet (HCD) for 2 weeks. Platelet and leukocyte adhesion was significantly elevated by hypercholesterolemia. In HCD mice receiving losartan (HCD-Los) in drinking water, platelet and leukocyte recruitment was reduced to ND levels. Increased platelet adhesion was observed in HCD mice receiving platelets from HCD-Los mice, consistent with a direct beneficial action of losartan on the vessel wall. Hypercholesterolemia elicited an oxidative stress in venules and an increased expression of P-selectin and AT1-R. The oxidative stress and AT1-R upregulation were reduced by losartan, but the P-selectin response was not. We propose that AT1-R engagement contributes to the prothrombogenic and proinflammatory state induced in venules by hypercholesterolemia.

Inflammation, blood pressure, and stroke: an opportunity to target primary prevention?

Promising findings suggest that systemic inflammation and neuroinflammation are central features in cerebrovascular disease. Inflammatory mechanisms are also important participants in the pathophysiology of hypertension. Markers of inflammation have been shown to be upregulated in different forms of cerebrovascular disease, and to correlate with vascular risk. The inhibitor nuclear factor-kB/nuclear factor-kB system is considered a major intracellular inflammatory pathway, mediating most of the vascular inflammatory responses. Increasing evidence indicates that hypertension, through the vasoactive peptides angiotensin and endothelin-1, promotes and accelerates the atherosclerotic process via inflammatory mechanisms. Proinflammatory properties of angiotensin II have been demonstrated. The identification of useful markers of inflammation, of new therapeutic targets to interfere with these mechanisms, and the evaluation of the efficacy of anti-inflammatory treatments will allow progress in our ability to combat cerebrovascular disease and the complications of hypertension. Whether these targets will be useful in the development of risk prediction strategies or therapies for the treatment of stroke in humans is far from clear.

Is it time for medical therapy for aortic valve disease?

Calcific aortic stenosis is the most common indication for surgical valve replacement. Currently there are no medical therapies approved for the treatment of this disease. This review will summarize the clinical and experimental studies published over the past 5 years that indicate that medical therapy may be an option for this patient population.

The effect of angiotensin-converting enzyme inhibition on endothelial function and oxidant stress

Angiotensin-converting enzyme (ACE) inhibitors effectively interfere with the renin-angiotensin system and exert various beneficial actions on vascular structure and function beyond their blood pressure-lowering effects. Data from experimental studies showed that angiotensin-converting enzyme inhibitors can attenuate the development of atherosclerosis in a wide range of species. The postulated mechanisms of this atheroprotective effect are the antioxidant actions of angiotensin-converting enzyme inhibitors and their enhancement of the endothelial elaboration of bioactive nitric oxide. The aim of this study was to assess the comparative effects of three angiotensin-converting enzyme inhibitors on endothelial nitric oxide production and action, and on endothelial oxidative stress. Using bovine aortic endothelial cells in culture grown to confluence, we examined the effects of 1, 10, 30 and 60 microM of each of captopril, zofenopril and enalapril on nitrite/nitrate accumulation in the media, cyclic GMP accumulation in the cell lysate, and F(2)-isoprostanes in lipid extracts from the cells. Results showed that the sulfhydryl angiotensin-converting enzyme inhibitor zofenopril has unique properties compared with captopril and enalapril. This compound improves nitric oxide production and bioactivity, and does so in conjunction with decreased endothelial cell oxidant stress. The biochemical basis for this protective mechanism is not entirely clear; however, these actions suggest that zofenopril may reduce endothelial effects of risk factors for atherothrombotic disease.

Angiotensin in atherosclerosis

PURPOSE OF REVIEW

While it is well established that angiotensin II promotes cardiovascular and renal disorders, recent evidence has indicated a pivotal role in atherosclerotic disease which is distinguished by the central abnormality of lipid accumulation within the vascular wall.

RECENT FINDINGS

Studies published in the last year show that angiotensin II activity is increased in atherosclerosis, but even a transient elevation in angiotensin II potentiates the disease. The downstream hormone, aldosterone, has vasculopathic effects in conjunction with, as well as independently of, angiotensin II. The mechanism for angiotensin II injury includes potentiation of damage by known risk factors such as hypertension, hyperlipidemia, diabetes and insulin resistance, falling estrogens and inflammation. In addition, angiotensin II has direct effects on cellular proliferation, hypertrophy, apoptosis, and synthesis/degradation of matrix proteins and collagen that underlie development and progression of atherosclerosis as well as stability of the plaque. Antagonism of angiotensin II actions, therefore, offers the possibility of interfering with these direct and indirect effects and lessening the progression of atherosclerosis, stabilizing vulnerable plaques, and even reversing the disease.

SUMMARY

Angiotensin is increased in atherosclerosis, and increased angiotensin II amplifies atherosclerosis by modulating individual risk factors as well as by directly affecting lipid metabolism, the vascular response to lipid accumulation, and plaque stability. Antagonism of angiotensin II actions not only lessens the progression of atherosclerosis, but stabilizes the plaque and may even cause regression of the disease.

From CONSENSUS to CHARM—how do ACEI and ARB produce clinical benefits in CHF?

Two decades of research from CONSENSUS to CHARM using modulators of the renin-angiotensin-aldosterone system (RAAS) in chronic heart failure (CHF) patients have shown convincing clinical benefits, but the majority of clinicians prescribing these drugs are still unclear about what mechanisms are responsible for the observed benefits. Of the candidate mechanisms hitherto proposed, there emerges a theme that best fits the spectrum of known factors from pathophysiology of heart failure to how the drugs enhance longevity of patients. This concept can be summarised as follows: after the onset of heart failure, neurohormones are activated resulting in raised levels of angiotensin, aldosterone and catecholamines, which are all known cardiotoxic agents. Cumulatively over time, they are responsible for accelerated cardiomyocyte attrition, manifesting as a faster reduction of cardiac pumping reserve, leading to worsening heart failure, more neurohormonal activation, thus propagating a vicious cycle spiralling towards an earlier fatality. The vicious cycle can be interrupted by dampening the excessive neurohormonal activities, thereby minimising cardiomyocyte losses and preserving cardiac functional reserve for longer. This culminates in maintenance of a reasonable quality of life and enhanced longevity. Such a mechanistic understanding would enable clinicians to have a better perspective on how to apply data from various clinical trials involving these drugs into clinical practice, to optimise and tailor therapy to the individual patient so that each patient can gain maximal benefits.

Genetic determinants of arterial calcification associated with atherosclerosis

Increasing research interest has focused on arterial calcification in the setting of atherosclerosis. Many features of atherosclerosis-related calcification provide useful clinical information. For example, calcium mineral deposits frequently form in atherosclerotic plaque, and intimal arterial calcification can be used as a surrogate marker for atherosclerosis; also, calcium deposits are readily and noninvasively quantified, which is useful because greater amounts of coronary calcification predict a higher risk of myocardial infarction and death. Several mechanisms leading to calcification associated with atherosclerosis have been proposed; however, no direct testing of proposed mechanisms has yet been reported. Studies in genetically altered animals and in humans have shed light on potential genetic determinants, which in turn could form the basis for a more comprehensive understanding of the factors affecting calcification within plaque and the associated pathobiologic implications. We review proposed molecular and cellular mechanisms of atherosclerosis-associated arterial calcification, summarize genetic influences, and suggest areas in which further investigation is needed. Understanding the molecular and genetic determinants of specific structural plaque components such as calcification can provide a solid foundation for the development of novel therapeutic approaches to favorably alter plaque structure and minimize vulnerability to arterial rupture.