Endothelial nitric oxide synthase-independent effects of an ACE inhibitor on coronary flow response to bradykinin in aged mice

Pathophysiology and Outcomes of Endothelium Function in Coronary Microvascular Diseases: A Systematic Review of Randomized Controlled Trials and Multicenter Study

BACKGROUND

Coronary macrovascular disease is a concept that has been well-studied within the literature and has long been the subject of debates surrounding coronary artery bypass grafting (CABG) vs. Percutaneous Coronary Intervention (PCI). ISCHEMIA trial reported no statistical difference in the primary clinical endpoint between initial invasive management and initial conservative management, while in the ORBITA trial PCI did not improve angina frequency score significantly more than placebo, albeit PCI resulted in more patient-reported freedom from angina than placebo. However, these results did not prove the superiority of the PCI against OMT, therefore do not indicate the benefit of PCI vs. the OMT. Please rephrase the sentence. We reviewed the role of different factors responsible for endothelial dysfunction from recent randomized clinical trials (RCTs) and multicentre studies.

METHODS

A detailed search strategy was performed using a dataset that has previously been published. Data of pooled analysis include research articles (human and animal models), CABG, and PCI randomized controlled trials (RCTs). Details of the search strategy and the methods used for data pooling have been published previously and registered with Open-Source Framework.

RESULTS

The roles of nitric oxide (NO), endothelium-derived contracting factors (EDCFs), and vasodilator prostaglandins (e.g., prostacyclin), as well as endothelium-dependent hyperpolarization (EDH) factors, are crucial for the maintenance of vasomotor tone within the coronary vasculature. These homeostatic mechanisms are affected by sheer forces and other several factors that are currently being studied, such as vaping. The role of intracoronary testing is crucial when determining the effects of therapeutic medications with further studies on the horizon.

CONCLUSION

The true impact of coronary microvascular dysfunction (CMD) is perhaps underappreciated, which supports the role of medical therapy in determining outcomes. Ongoing trials are underway to further investigate the role of therapeutic agents in secondary prevention.

Endothelium in Coronary Macrovascular and Microvascular Diseases

ABSTRACT

The endothelium plays a pivotal role in the regulation of vascular tone by synthesizing and liberating endothelium-derived relaxing factors inclusive of vasodilator prostaglandins (eg, prostacyclin), nitric oxide (NO), and endothelium-dependent hyperpolarization factors in a distinct blood vessel size-dependent manner. Large conduit arteries are predominantly regulated by NO and small resistance arteries by endothelium-dependent hyperpolarization factors. Accumulating evidence over the past few decades has demonstrated that endothelial dysfunction and coronary vasomotion abnormalities play crucial roles in the pathogenesis of various cardiovascular diseases. Structural and functional alterations of the coronary microvasculature have been coined as coronary microvascular dysfunction (CMD), which is highly prevalent and associated with adverse clinical outcomes in many clinical settings. The major mechanisms of coronary vasomotion abnormalities include enhanced coronary vasoconstrictive reactivity at epicardial and microvascular levels, impaired endothelium-dependent and endothelium-independent coronary vasodilator capacities, and elevated coronary microvascular resistance caused by structural factors. Recent experimental and clinical research has highlighted CMD as the systemic small artery disease beyond the heart, emerging modulators of vascular functions, novel insights into the pathogenesis of cardiovascular diseases associated with CMD, and potential therapeutic interventions to CMD with major clinical implications. In this article, we will summarize the current knowledge on the endothelial modulation of vascular tone and the pathogenesis of coronary macrovascular and microvascular diseases from bench to bedside, with a special emphasis placed on the mechanisms and clinical implications of CMD.

Gender Differences in Endothelial Function and Coronary Vasomotion Abnormalities

Introduction:

Structural and functional abnormalities of coronary microvasculature, referred to as coronary microvascular dysfunction (CMD), have been implicated in a wide range of cardiovascular diseases and have gained growing attention in patients with chest pain with no obstructive coronary artery disease, especially in females. The central mechanisms of coronary vasomotion abnormalities encompass enhanced coronary vasoconstrictive reactivity (ie, coronary spasm), reduced endothelium-dependent and -independent coronary vasodilator capacities, and increased coronary microvascular resistance. The 2 major endothelium-derived relaxing factors, nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) factors, modulate vascular tone in a distinct vessel size–dependent manner; NO mainly mediates vasodilatation of relatively large, conduit vessels, while EDH factors in small resistance vessels. Endothelium-dependent hyperpolarization–mediated vasodilatation is more prominent in female resistance arteries, where estrogens exert beneficial effects on endothelium-dependent vasodilatation via multiple mechanisms. In the clinical settings, therapeutic approaches targeting NO are disappointing for the treatment of various cardiovascular diseases, where endothelial dysfunction and CMD are substantially involved.

Significance:

In this review, we will discuss the current knowledge on the pathophysiology and molecular mechanisms of endothelial function and coronary vasomotion abnormalities from bench to bedside, with a special reference to gender differences.

Results:

Recent experimental and clinical studies have demonstrated distinct gender differences in endothelial function and coronary vasomotion abnormalities with major clinical implications. Moreover, recent landmark clinical trials regarding the management of stable coronary artery disease have questioned the benefit of percutaneous coronary intervention, supporting the importance of the coronary microvascular physiology.

Conclusion:

Further characterization and a better understanding of the gender differences in basic vascular biology as well as those in cardiovascular diseases are indispensable to improve health care and patient outcomes in cardiovascular medicine.

Atorvastatin improves left ventricular remodeling and cardiac function in rats with congestive heart failure by inhibiting RhoA/Rho kinase-mediated endothelial nitric oxide synthase

The aim of the present study was to investigate the effects and possible mechanisms of atorvastatin (Ato) against chronic heart failure (CHF). A rat model of CHF was established and cardiac functions were assessed using Echocardiography. The expression of RhoA/Rho kinase and endothelial nitric oxide synthase (eNOS) was assessed using western blotting and reverse transcription polymerase chain reaction following 4 weeks of treatment. The three groups assessed in the present study were as follows: The control group (no treatment), the Ato + isopropylnoradrenaline (ISO) group (subcutaneous injections of 340 mg/kg ISO + orally administered 50 mg/kg Ato dissolved in saline; administered once daily) and the ISO group (subcutaneous injections of 340 mg/kg ISO + orally administered with an equal volume of saline; administered once daily). Heart volume and weight in the ISO group were significantly increased compared with the control (C) group (P<0.01), whereas contractility was decreased. The results were reverse for the Ato group when compared with the ISO group (P<0.05). Levels of RhoA/Rho kinase protein and mRNA were significantly increased in the ISO group (P<0.01); however. The mRNA and protein expression of eNOS was significantly decreased (P<0.05) when compared with the C group. The mRNA and protein expression of RhoA/Rho kinase was significantly reduced in the Ato+ISO group compared with the ISO group (P<0.01), whereas the mRNA and protein expression of eNOS was significantly increased (P<0.05). RhoA protein expression was increased in the cytoplasm of the C group and on the cell membrane of the ISO group; however, in the Ato+ISO group, RhoA protein expression on the cell membrane was significantly downregulated when compared with the ISO group (P<0.05). The results of the present study suggest that Ato upregulates eNOS by inhibiting RhoA/Rho kinase overexpression in the myocardial tissue of rats with CHF, thus improving left ventricular remodeling and cardiac function.

Endothelial nitric oxide synthase gene polymorphisms and renal responsiveness to RAS inhibition therapy in type 2 diabetic Asian Indians

AIM

To investigate the association of functional single nucleotide polymorphisms (SNPs) of the endothelial nitric oxide synthase gene (eNOS) gene (T-786C, G894T) and one variable number tandem repeat polymorphism (aa 27VNTR bb) with reno-protective response to angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) therapy in North Indian type 2 diabetic mellitus (T2DM) subjects with cases having diabetic nephropathy (DN) and controls without DN.

METHOD

We genotyped three polymorphisms of eNOS (two SNPs: T-786C, G894T and one 27 VNTR) in T2DM patients with overt nephropathy (cases: n=320) and T2DM patients without overt nephropathy (controls: n=490), using validated PCR-RFLP assays. These 810 North Indian T2DM patients treated with ACEI or ARB after diagnosis were followed up for 3 years. Percent changes in eGFR, urinary albumin excretion (UAE), serum creatinine at the end of 3 years of treatment were taken as end points of renoprotective response.

RESULT

We observed that in normoalbuminuric patients, eNOS -786 CC genotype and haplotypes C-b-G and C-b-T were associated with lesser renoprotective response to ACEI. While, in macroalbuminurics, eNOS -786 CC genotype, haplotypes C-b-G and C-b-T and 27VNTR aa were associated with better renoprotective response to ACEI/ARB.

CONCLUSION

Our results showed that eNOS T-786C CC genotype and 27VNTR individually and in interaction with other eNOS SNPs modulate renoprotective efficacy of ACEI and ARB in T2DM patients, depending on the status of proteinuria.

eNOS is required for acute in vivo ischemic preconditioning of the heart: effects of ischemic duration and sex

Ischemic preconditioning (IPC) is a powerful phenomenon that provides potent cardioprotection in mammalian hearts; however, the role of endothelial nitric oxide (NO) synthase (eNOS)-mediated NO in this process remains highly controversial. Questions also remain regarding this pathway as a function of sex and ischemic duration. Therefore, we performed extensive experiments in wild-type (WT) and eNOS knockout (eNOS(-/-)) mice to evaluate whether the infarct-limiting effect of IPC depends on eNOS, ischemic periods, and sex. Classical IPC was induced by three cycles of 5 min of regional coronary ischemia separated by 5 min of reperfusion and was followed by 30 or 60 min of sustained ischemia and 24 h of reperfusion. The control ischemia-reperfusion protocol had 30 or 60 min of ischemia followed by 24 h of reperfusion. Protection was evaluated by measuring the myocardial infarct size as a percentage of the area at risk. The major findings were that regardless of sex, WT mice exhibited robust IPC with significantly smaller myocardial infarction, whereas eNOS(-/-) mice did not. IPC-induced cardiac protection was absent in eNOS(-/-) mice of both Jackson and Harvard origin. In general, female WT mice had smaller infarctions compared with male WT mice. Although prolonged ischemia caused significantly larger infarctions in WT mice of both sexes, they were consistently protected by IPC. Importantly, prolonged myocardial ischemia was associated with increased mortality in eNOS(-/-) mice, and the survival rate was higher in female eNOS(-/-) mice compared with male eNOS(-/-) mice. In conclusion, IPC protects WT mice against in vivo myocardial ischemia-reperfusion injury regardless of sex and ischemic duration, but the deletion of eNOS abolishes the cardioprotective effect of classical IPC.

Ameliorative effect of Captopril and Valsartan on an animal model of diabetic cardiomyopathy

The objective of this study was to clarify the relationship between angiotensin II and the pathogenesis of diabetic cardiomyopathy by observing the effects of related drugs on diabetic cardiomyopathy in rats. Captopril and Valsartan, an automatic biochemical analyzer, and radioimmunoassay technology were used to an experimental rat model of diabetic cardiomyopathy to dynamically measure the levels of creatine kinase-MB, lactate dehydrogenase-1 in the serum, and angiotensin I and II in the plasma, and to observe changes in the myocardial ultrastructure. The content of angiotensin I and II was increased and the renin-angiotensin system was in a hyperfunctional state in experimental rats with myocardial damage. Angiotensin-converting enzyme inhibitors and angiotensin II receptor 1 antagonists improved the myocardial structure and cardiac function. It is concluded that hyperfunction of the renin-angiotensin system is involved in the pathogenesis of diabetic cardiomyopathy, with an increase in angiotensin being a key factor. Preventing the increase in angiotensin II or the action of angiotensin II on its receptor can prevent the occurrence and development of diabetic cardiomyopathy.

In Vivo Characterization of Murine Myocardial Perfusion With Myocardial Contrast Echocardiography

Background— The ability to noninvasively evaluate murine myocardial blood flow (MBF) in vivo would provide an important tool for cardiovascular research. Myocardial contrast echocardiography (MCE) has been used to measure MBF; however, it has not been validated in mice. This study assesses whether MCE can evaluate MBF at rest and after vasodilation and measure the maximal augmentation (coronary reserve) of MBF in mice. Wild-type (WT) and nitric oxide synthase 3 (NOS3)–deficient (NOS3 −/− ) mice were studied.

Methods and Results— MCE was performed at baseline and after intravenous infusion of acetylcholine or adenosine. Definity contrast agent was infused, and parasternal views were acquired in real-time mode. Replenishment curves of myocardial contrast were obtained, and rates of signal rise (β) and plateau intensity (A) were calculated. MBF estimated by the product of A and β (Aβ) was compared with that measured with fluorescent microspheres. MCE analysis was feasible in 98% (52/53) of mice. MBF measured by microspheres increased with adenosine and correlated closely with Aβ. There was no difference in MCE-derived MBF between WT and NOS3 −/− mice at rest. Adenosine infusion increased MBF by 3.0±0.6-fold in NOS3 −/− mice and 2.5±0.3-fold in WT ( P =0.58 between genotypes). Acetylcholine induced an increase of 2.4±0.2-fold in MBF in WT mice but did not increase MBF in NOS3 −/− mice ( P <0.0005 versus WT).

Conclusions— MBF, coronary reserve, and vasodilator responses can be evaluated accurately in the intact mouse by MCE. This method demonstrated a preserved coronary response to adenosine but an impaired acetylcholine-induced vasodilation in NOS3 −/− mice compared with WT mice.

Interaction of Endothelial Nitric Oxide and Angiotensin in the Circulation

Discovery of the unexpected intercellular messenger and transmitter nitric oxide (NO) was the highlight of highly competitive investigations to identify the nature of endothelium-derived relaxing factor. This labile, gaseous molecule plays obligatory roles as one of the most promising physiological regulators in cardiovascular function. Its biological effects include vasodilatation, increased regional blood perfusion, lowering of systemic blood pressure, and antithrombosis and anti-atherosclerosis effects, which counteract the vascular actions of endogenous angiotensin (ANG) II. Interactions of these vasodilator and vasoconstrictor substances in the circulation have been a topic that has drawn the special interest of both cardiovascular researchers and clinicians. Therapeutic agents that inhibit the synthesis and action of ANG II are widely accepted to be essential in treating circulatory and metabolic dysfunctions, including hypertension and diabetes mellitus, and increased availability of NO is one of the most important pharmacological mechanisms underlying their beneficial actions. ANG II provokes vascular actions through various receptor subtypes (AT1, AT2, and AT4), which are differently involved in NO synthesis and actions. ANG II and its derivatives, ANG III, ANG IV, and ANG-(1-7), alter vascular contractility with different mechanisms of action in relation to NO. This review article summarizes information concerning advances in research on interactions between NO and ANG in reference to ANG receptor subtypes, radical oxygen species, particularly superoxide anions, ANG-converting enzyme inhibitors, and ANG receptor blockers in patients with cardiovascular disease, healthy individuals, and experimental animals. Interactions of ANG and endothelium-derived relaxing factor other than NO, such as prostaglandin I2 and endothelium-derived hyperpolarizing factor, are also described.

Temocapril, an Angiotensin converting enzyme inhibitor, ameliorates age-related increase in carotid arterial stiffness in normotensive subjects

BACKGROUND/AIMS

Oxidative stress plays an important role in vascular ageing. The close relationship of the renin-angiotensin system with mechanisms of oxidative stress suggests its possible involvement in the deleterious effects of ageing. The present study was designed to investigate whether inhibition of the renin-angiotensin system improves the age-related increase in arterial stiffness.

METHODS

Normotensive elderly subjects in a geriatric nursing home (n = 24; male/female = 7/17; 86 +/- 9 years, mean +/- SD) were randomly assigned to receive either an angiotensin converting enzyme inhibitor, temocapril (n = 12, 1 mg daily) or nothing (n = 12). Carot id arterial stiffness parameter beta and circulating levels of malondialdehyde-modified low-density lipoprotein were measured before and 6 months after randomization.

RESULTS

Temocapril decreased beta (from 7.0 +/- 1.0 to 4.9 +/- 0.9, p < 0.05) and malondialdehyde-modified low-density lipoprotein levels (from 73.2 +/- 19.9 to 61.3 +/- 18.4 U/l, p < 0.05) without changing the blood pressure. The changes in beta and malondialdehyde-modified low-density lipoprotein levels were significantly correlated (rho = 0.600, p < 0.05).

CONCLUSION

These results suggest that temocapril ameliorates the age-related increase in carotid arterial stiffness in healthy, normotensive elderly subjects.