Novel pathway of endothelin-1 and reactive oxygen species in coronary vasospasm with endothelial dysfunction

Endothelin-1 potentiates TRPV1-mediated vasoconstriction of human adipose arterioles in a protein kinase C-dependent manner

BACKGROUND AND PURPOSE

The TRPV cation channels have emerged as important regulators of vascular tone. TRPV1 channels and endothelin-1 are independently associated with the pathophysiology of coronary vasospasm, but the relationship between their vasomotor functions remains unclear. We characterized the vasomotor function of TRPV1 channels in human arterioles and investigated regulation of their vasomotor function by endothelin-1.

EXPERIMENTAL APPROACH

Human arterioles (mainly from adipose tissue) were threaded on two metal wires, equilibrated in a physiological buffer at 37°C and exposed to increasing concentrations of capsaicin, with or without SB366791 (TRPV1-selective inhibitor) or GF109203X (PKC-selective inhibitor). Some arterioles were pre-constricted with endothelin-1 or phenylephrine or high potassium buffer. TRPV1 mRNA and protein expression in human arteries were also assessed.

KEY RESULTS

TRPV1 transcripts and proteins were detected in human resistance arteries. Capsaicin (1 μM) induced concentration-dependent constriction of endothelium-intact and endothelium-denuded human adipose arterioles (HAA), which was significantly inhibited by SB366791. Pre-constriction of HAA with endothelin-1, but not high potassium buffer or phenylephrine, significantly potentiated capsaicin (0.1 μM)-induced constriction. GF109203X significantly inhibited potentiation of capsaicin-induced constriction by endothelin-1.

CONCLUSION AND IMPLICATIONS

TRPV1 channels are expressed in the human vasculature and affect vascular tone of human arterioles on activation. Their vasomotor function is modulated by endothelin-1, mediated in part by PKC. These findings reveal a novel interplay between endothelin-1 signalling and TRPV1 channels in human VSMC, adding to our understanding of the ion channel mechanisms that regulate human arteriolar tone and may also contribute to the pathophysiology of coronary vasospasm.

Endothelin Receptor Antagonists: Status Quo and Future Perspectives for Targeted Therapy

The endothelin axis, recognized for its vasoconstrictive action, plays a central role in the pathology of pulmonary arterial hypertension (PAH). Treatment with approved endothelin receptor antagonists (ERAs), such as bosentan, ambrisentan, or macitentan, slow down PAH progression and relieves symptoms. Several findings have indicated that endothelin is further involved in the pathogenesis of certain other diseases, making ERAs potentially beneficial in the treatment of various conditions. In addition to PAH, this review summarizes the use and perspectives of ERAs in cancer, renal disease, fibrotic disorders, systemic scleroderma, vasospasm, and pain management. Bosentan has proven to be effective in systemic sclerosis PAH and in decreasing the development of vasospasm-related digital ulcers. The selective ERA clazosentan has been shown to be effective in preventing cerebral vasospasm and delaying ischemic neurological deficits and new infarcts. Furthermore, in the SONAR (Study Of Diabetic Nephropathy With Atrasentan) trial, the selective ERA atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease. These data suggest atrasentan as a new therapy in the treatment of diabetic nephropathy and possibly other renal diseases. Preclinical studies regarding heart failure, cancer, and fibrotic diseases have demonstrated promising effects, but clinical trials have not yet produced measurable results. Nevertheless, the potential benefits of ERAs may not be fully realized.

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Statins ameliorate pulmonary hypertension secondary to left ventricular dysfunction through the Rho-kinase pathway and NADPH oxidase

BACKGROUND

Pulmonary hypertension (PH) is a devastating disorder, for which no therapy is curative. It has been reported that pulmonary vascular remodeling, associated with increasing mean pulmonary arterial pressure and upregulated expression of endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1), RhoA/RhoH-kinase results in the development of PH. Oxidative stress and the RhoA/Rho-kinase pathway are also thought to be involved in the pathophysiology of PH. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (HMG-CoA reductase inhibitors) with pleiotropic effects and are potential agents for the treatment of PH. In this study, we investigated the beneficial effects of simvastatin on the development of PH secondary to left ventricular dysfunction.

METHODS

A PH secondary to left ventricular dysfunction model was established in 6-week-old aortic-banded rats. The pulmonary expression of Rho kinase, ET-1, eNOS, p-eNOS, nitrite/nitrate (NOx), cGMP, p47^Phox , and p67^Phox were investigated in the early-treatment group, to which was administered simvastatin (30 mg/kg/day) from days 1 to 42 or the late-treatment group, to which was administered simvastatin (30 mg/kg/day) from days 29 to 42.

RESULTS

Simvastatin attenuated the mean pulmonary artery pressure, pulmonary arteriolar remodeling, plasma brain natriuretic peptide, ET-1, reactive oxygen species, and the NADPH oxidase 2 regulatory subunits, p47^Phox and p67^Phox , and upregulated pulmonary p-eNOS, NOx, and cGMP in both the early- and late-treated groups.

CONCLUSIONS

Inhibiting HMG-CoA reductase may have therapeutic potential for preventing and attenuating the development of PH in left ventricular dysfunction through the Rho-kinase pathway and NADPH oxidase. A translational study in humans is needed to substantiate these findings. Pediatr Pulmonol. 2017;52:443-457. © 2016 Wiley Periodicals, Inc.

Methamphetamine induces the release of endothelin

Methamphetamine is a potent psychostimulant drug of abuse that increases release and blocks reuptake of dopamine, producing intense euphoria, factors that may contribute to its widespread abuse. It also produces severe neurotoxicity resulting from oxidative stress, DNA damage, blood-brain barrier disruption, microgliosis, and mitochondrial dysfunction. Intracerebral hemorrhagic and ischemic stroke have been reported after intravenous and oral abuse of methamphetamine. Several studies have shown that methamphetamine causes vasoconstriction of vessels. This study investigates the effect of methamphetamine on endothelin-1 (ET-1) release in mouse brain endothelial cells by ELISA. ET-1 transcription as well as endothelial nitric oxide synthase (eNOS) activation and transcription were measured following methamphetamine treatment. We also examine the effect of methamphetamine on isolated cerebral arteriolar vessels from C57BL/6 mice. Penetrating middle cerebral arterioles were cannulated at both ends with a micropipette system. Methamphetamine was applied extraluminally, and the vascular response was investigated. Methamphetamine treatment of mouse brain endothelial cells resulted in ET-1 release and a transient increase in ET-1 message. The activity and transcription of eNOS were only slightly enhanced after 24 hr of treatment with methamphetamine. In addition, methamphetamine caused significant vasoconstriction of isolated mouse intracerebral arterioles. The vasoconstrictive effect of methamphetamine was attenuated by coapplication of the endothelin receptor antagonist PD145065. These findings suggest that vasoconstriction induced by methamphetamine is mediated through the endothelin receptor and may involve an endothelin-dependent pathway.

Reactive oxygen species and the pathogenesis of radiocontrast-induced nephropathy

Experimental findings in vitro and in vivo illustrate enhanced hypoxia and the formation of reactive oxygen species (ROS) within the kidney following the administration of iodinated contrast media, which may play a role in the development of contrast media-induced nephropathy. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging or reduced ROS formation with the administration of N-acetyl cysteine and bicarbonate infusion, respectively. Furthermore, most risk factors, predisposing to contrast-induced nephropathy are prone to enhanced renal parenchymal hypoxia and ROS formation. In this review, the association of renal hypoxia and ROS-mediated injury is outlined. Generated during contrast-induced renal parenchymal hypoxia, ROS may exert direct tubular and vascular endothelial injury and might further intensify renal parenchymal hypoxia by virtue of endothelial dysfunction and dysregulation of tubular transport. Preventive strategies conceivably should include inhibition of ROS generation or ROS scavenging.

Working under pressure: coronary arteries and the endothelin system

Endogenous endothelin-1-dependent (ET-1) tone in coronary arteries depends on the balance between ET(A) and ET(B) receptor-mediated effects and on parameters such as receptor distribution and endothelial integrity. Numerous studies highlight the striking functional interactions that exist between nitric oxide (NO) and ET-1 in the regulation of vascular tone. Many of the cardiovascular complications associated with cardiovascular risk factors and aging are initially attributable, at least in part, to endothelial dysfunction characterized by a dysregulation between NO and ET-1. The contribution of the imbalance between smooth muscle ET(A/B) and endothelial ET(B) receptors to this process is poorly understood. An increased contribution of ET-1 that is associated with a proportional decrease in that of NO accompanies the development of coronary endothelial dysfunction, coronary vasospasm, and atherosclerosis. These data form the basis for the rationale of testing therapeutic approaches counteracting ET-1-induced cardiovascular dysfunction. It remains to be determined whether the beneficial role of endothelial ET(B) receptors declines with age and risk factors for cardiovascular diseases, revealing smooth muscle ET(B) receptors with proconstricting and proinflammatory activities.

Endothelium-derived endothelin-1

One year after the revelation by Dr. Furchgott in 1980 that the endothelium was obligatory for acetylcholine to relax isolated arteries, it was clearly shown that the endothelium could also promote contraction. In 1988, Dr. Yanagisawa's group identified endothelin-1 (ET-1) as the first endothelium-derived contracting factor. The circulating levels of this short (21-amino acid) peptide were quickly determined in humans, and it was reported that, in most cardiovascular diseases, circulating levels of ET-1 were increased, and ET-1 was then tagged as "a bad guy." The discovery of two receptor subtypes in 1990, ET(A) and ET(B), permitted optimization of the first dual ET-1 receptor antagonist in 1993 by Dr. Clozel's team, who entered clinical development with bosentan, which was offered to patients with pulmonary arterial hypertension in 2001. The revelation of Dr. Furchgott opened a Pandora's box with ET-1 as one of the actors. In this brief review, we will discuss the physiological and pathophysiological role of endothelium-derived ET-1 focusing on the regulation of the vascular tone, and as much as possible in humans. The coronary bed will be used as a running example in this review because it is the most susceptible to endothelial dysfunction, but references to the cerebral and renal circulation will also be made. Many of the cardiovascular complications associated with aging and cardiovascular risk factors are initially attributable, at least in part, to endothelial dysfunction, particularly dysregulation of the vascular function associated with an imbalance in the close interdependence of nitric oxide and ET-1.