AVE3085 protects coronary endothelium from the impairment of asymmetric dimethylarginine by activation and recoupling of eNOS. Cardiovasc Drugs Ther. 2012;26:383-392. [PMID: 22890813 DOI: 10.1007/s10557-012-6404-2]

Endothelial dysfunction: developmental mechanisms and therapeutic strategies

Introduction: Every year the importance of the normal functioning of the endothelial layer of the vascular wall in maintaining the health of the body becomes more and more obvious.

The physiological role of the endothelium: The endothelium is a metabolically active organ actively involved in the regulation of hemostasis, modulation of inflammation, maintenance of hemovascular homeostasis, regulation of angiogenesis, vascular tone, and permeability.

Risk factors for the development of endothelial dysfunction: Currently, insufficient bioavailability of nitric oxide is considered the most significant risk factor for endothelial dysfunction.

Mechanisms of development of endothelial dysfunction: The genesis of endothelial dysfunction is a multifactorial process. Among various complex mechanisms, this review examines oxidative stress, inflammation, hyperglycemia, vitamin D deficiency, dyslipidemia, excess visceral fat, hyperhomocysteinemia, hyperuricemia, as well as primary genetic defect of endotheliocytes, as the most common causes in the population underlying the development of endothelial dysfunction.

Markers of endothelial dysfunction in various diseases: This article discusses the main biomarkers of endothelial dysfunction currently used, as well as promising biomarkers in the future for laboratory diagnosis of this pathology.

Therapeutic strategies: Therapeutic approaches to the endothelium in order to prevent or reduce a degree of damage to the vascular wall are briefly described.

Conclusion: Endothelial dysfunction is a typical pathological process involved in the pathogenesis of many diseases. Thus, pharmacological agents with endothelioprotective properties can provide more therapeutic benefits than a drug without such an effect.

Endothelial nitric oxide synthase enhancer AVE3085 reverses endothelial dysfunction induced by homocysteine in human internal mammary arteries

Homocysteine (Hcy) is an independent risk factor for endothelial dysfunction in cardiovascular diseases. We hypothesized that the eNOS transcription enhancer AVE3085 may protect the endothelial function damaged by Hcy in the human internal mammary artery (IMA). Cumulative concentration-relaxation curves to acetylcholine (-10 to -4.5 log mol/L) or sodium nitroprusside were established in IMA from patients undergoing coronary artery surgery precontracted by U46619 (-8 log mol/L) in the absence/presence of Hcy (100 μmol/L) with/without AVE3085 (30 μmol/L) in vitro in a myograph. RT-qPCR and ELISA were used to quantify the mRNA and protein levels of eNOS. Colorimetric assay method was used to detect the production of nitric oxide (NO). Maximal relaxation was significantly attenuated by Hcy in human IMA. Co-incubation with AVE3085 protected endothelium from the impairment by Hcy and increased the production of NO. Exposure to Hcy for 24 h downregulated eNOS protein expression (P < 0.05) whereas it upregulated the expression of eNOS at mRNA levels (P < 0.05). The presence of AVE3085 in addition to Hcy significantly increased the eNOS protein (P < 0.05) and slightly decreased the mRNA level. The study for the first time revealed that in the human blood vessels (IMA) the clinically-relevant high concentration of Hcy directly causes endothelial dysfunction by downregulating eNOS protein that may be reversed by AVE3085. These findings not only provide new direction for protecting endothelium during coronary artery bypass grafting and improving long-term patency of the grafts, but also provide evidence to the use of eNOS enhancer in the patients with endothelial dysfunction in various pathological conditions.

Vascular endothelial dysfunction and pharmacological treatment

The endothelium exerts multiple actions involving regulation of vascular permeability and tone, coagulation and fibrinolysis, inflammatory and immunological reactions and cell growth. Alterations of one or more such actions may cause vascular endothelial dysfunction. Different risk factors such as hypercholesterolemia, homocystinemia, hyperglycemia, hypertension, smoking, inflammation, and aging contribute to the development of endothelial dysfunction. Mechanisms underlying endothelial dysfunction are multiple, including impaired endothelium-derived vasodilators, enhanced endothelium-derived vasoconstrictors, over production of reactive oxygen species and reactive nitrogen species, activation of inflammatory and immune reactions, and imbalance of coagulation and fibrinolysis. Endothelial dysfunction occurs in many cardiovascular diseases, which involves different mechanisms, depending on specific risk factors affecting the disease. Among these mechanisms, a reduction in nitric oxide (NO) bioavailability plays a central role in the development of endothelial dysfunction because NO exerts diverse physiological actions, including vasodilation, anti-inflammation, antiplatelet, antiproliferation and antimigration. Experimental and clinical studies have demonstrated that a variety of currently used or investigational drugs, such as angiotensin-converting enzyme inhibitors, angiotensin AT1 receptors blockers, angiotensin-(1-7), antioxidants, beta-blockers, calcium channel blockers, endothelial NO synthase enhancers, phosphodiesterase 5 inhibitors, sphingosine-1-phosphate and statins, exert endothelial protective effects. Due to the difference in mechanisms of action, these drugs need to be used according to specific mechanisms underlying endothelial dysfunction of the disease.

Central obesity, type 2 diabetes and insulin: exploring a pathway full of thorns

The prevalence of type 2 diabetes (T2D) is rapidly increasing. This is strongly related to the contemporary lifestyle changes that have resulted in increased rates of overweight individuals and obesity. Central (intra-abdominal) obesity is observed in the majority of patients with T2D. It is associated with insulin resistance, mainly at the level of skeletal muscle, adipose tissue and liver. The discovery of macrophage infiltration in the abdominal adipose tissue and the unbalanced production of adipocyte cytokines (adipokines) was an essential step towards novel research perspectives for a better understanding of the molecular mechanisms governing the development of insulin resistance. Furthermore, in an obese state, the increased cellular uptake of non-esterified fatty acids is exacerbated without any subsequent β-oxidation. This in turn contributes to the accumulation of intermediate lipid metabolites that cause defects in the insulin signaling pathway. This paper examines the possible cellular mechanisms that connect central obesity with defects in the insulin pathway. It discusses the discrepancies observed from studies organized in cell cultures, animal models and humans. Finally, it emphasizes the need for therapeutic strategies in order to achieve weight reduction in overweight and obese patients with T2D.

Mechanistic studies of AVE3085 against homocysteine in endothelial protection

PURPOSE

Homocysteine (Hcy) is an independent risk factor for cardiovascular diseases that impairs endothelial function. We investigated whether the impaired endothelial function can be restored by the eNOS transcription enhancer AVE3085 in porcine coronary arteries. The effects of AVE3085 against Hcy on eNOS-NO function were studied and further investigations were conducted to reveal the role of arginase and the signaling pathway of eNOS activation in the effect of AVE3085 on endothelial dysfunction caused by Hcy.

METHODS

Myograph study of vasorelaxation, electrochemical measurement of NO, RT-PCR and Western blot analysis of eNOS, iNOS expression, and eNOS phosphorylation were performed. Arginase activity was determined by urea production and O2 (.-) generation by lucigenin-enhanced chemiluminenscence.

RESULTS

Exposure to Hcy for 24 h attenuated bradykinin-induced relaxation and NO release, downregulated eNOS mRNA expression and protein expressions of eNOS and p-eNOS(Ser1177) whereas it upregulated iNOS expression. AVE3085 restored NO release and relaxation, enhanced eNOS but decreased iNOS expression. Inhibition of protein kinase Akt or PI3 kinase attenuated the effect of AVE3085 on relaxation and eNOS phosphorylation. Arginase activity and O2 (.-) production were inhibited by AVE3085 in Hcy-exposed vessels.

CONCLUSIONS

AVE3085 prevents Hcy-induced endothelial dysfunction in coronary arteries by preservation of NO production and suppression of O2 (.-) generation. Preservation of NO is attributed to upregulation of eNOS expression, activation of eNOS via phosphorylation of Ser1177 through a PI3 kinase/Akt-dependent pathway, and inhibition of arginase. Reduction of O2 (.-) generation results from reversal of eNOS uncoupling and inhibition of arginase and iNOS.