Evaluation of plasma endothelin-1 levels in patients with cerebral infarction

Candidate neuroinflammatory markers of cerebral autoregulation dysfunction in human acute brain injury

The loss of cerebral autoregulation (CA) is a common and detrimental secondary injury mechanism following acute brain injury and has been associated with worse morbidity and mortality. However patient outcomes have not as yet been conclusively proven to have improved as a result of CA-directed therapy. While CA monitoring has been used to modify CPP targets, this approach cannot work if the impairment of CA is not simply related to CPP but involves other underlying mechanisms and triggers, which at present are largely unknown. Neuroinflammation, particularly inflammation affecting the cerebral vasculature, is an important cascade that occurs following acute injury. We hypothesise that disturbances to the cerebral vasculature can affect the regulation of CBF, and hence the vascular inflammatory pathways could be a putative mechanism that causes CA dysfunction. This review provides a brief overview of CA, and its impairment following brain injury. We discuss candidate vascular and endothelial markers and what is known about their link to disturbance of the CBF and autoregulation. We focus on human traumatic brain injury (TBI) and subarachnoid haemorrhage (SAH), with supporting evidence from animal work and applicability to wider neurologic diseases.

C-Terminal-Pro-Endothelin-1 Adds Incremental Prognostic Value for Risk Stratification After Ischemic Stroke

Background and Aims: Endothelins have shown to play a role in the pathophysiology of ischemic stroke. We aimed at evaluating the incremental prognostic value of C-terminal-pro-endothelin-1 (CT-pro-ET-1) in a well-described cohort of acute stroke patients. Methods: We performed serial measurements of CT-pro-ET-1 in 361 consecutively enrolled ischemic stroke patients and assessed functional outcome and mortality after 90 days. As we found peak levels of CT-pro-ET-1 and the most prominent association with mortality on day 1 after admission (n = 312), we focused on this time point for further outcome analyses. We calculated logistic regression and cox proportional hazards models to estimate the association of CT-pro-ET-1 with our outcome measures after adjusting for demographic and clinical risk factors. To evaluate the incremental value of CT-pro-ET-1, we calculated the area under the receiver operating characteristics (AUC) curve and the continuous net reclassification index (cNRI) comparing the model with and without the biomarker CT-pro-ET-1. Results: In the univariate analysis CT-pro-ET-1 with a peak on day 1 after admission was associated with unfavorable outcome with an OR of 1.32 (95% CI, 1.16-1.51, p < 0.001) and with mortality with a HR of 1.45 (95% CI, 1.29-1.63, p < 0.001). After adjusting, CT-pro-ET-1 remained an independent predictor of mortality with an adjusted HR of 1.50 (95% CI, 1.29-1.74, p < 0.001), but not for functional outcome. Adding CT-pro-ET-1 to the cox-regression model for mortality, the discriminatory accuracy improved from 0.89 (95% CI, 0.84-0.94) to 0.92 (95% CI, 0.88-0.96) p < 0.001, and the cNRI was 0.72 (95% CI, 0.17-1.13). Conclusion: CT-pro-ET-1 with a peak level on day 1 was an independent predictor of mortality adding incremental prognostic value beyond traditional risk factors.

Modulating effects of preconditioning exercise in the expression of ET-1 and BNP via HIF-1α in ischemically injured brain

It is well-known that in ischemia-induced hypoxia, hypoxia-inducible factor -1α (HIF-1α) is critical in triggering expression of its downstream target genes to produce several products, such as erythropoietin (EPO), vascular endothelial growth factor (VEGF), nitric oxide synthesis (NOS), glucose transportor-1 (GLUT-1), insulin-like growth factor (IGF), which further promote erythropoiesis, angiogenesis, vasodilation and capitalization of glucose to overcome hypoxia. Meanwhile, as the factors with opposite effects on blood vessels, endothelin-1 (ET-1) and brain natriuretic peptide (BNP) also stand out strikingly in ischemic pathophysiology. To this day, several preconditioning manners have been used to induce tolerance to ischemia. During our research, exercise preconditioning was applied and it was demonstrated that HIF-1α triggered expression of ET-1 and BNP, which confirmed their downstream target genes for HIF-1α. And ET-1 may influcence expression of BNP to some degree but not the only factor which regulates BNP expression. Therefore, our findings suggest exercise preconditioning may provide protection to the ischemic brain tissue via HIF-1α which in turn increases expression of BNP to cause vasodilation in cooperation with some other factors, such as VEGF and EPO, to increase the blood flow in the ischemic area and then relieve the injuries induced by ischemia.

Maternal hypertension programs increased cerebral tissue damage following stroke in adult offspring

The maternal system is challenged with many physiological changes throughout pregnancy to prepare the body to meet the metabolic needs of the fetus and for delivery. Many pregnancies, however, are faced with pathological stressors or complications that significantly impact maternal health. A shift in this paradigm is now beginning to investigate the implication of pregnancy complications on the fetus and their continued influence on offspring disease risk into adulthood. In this investigation, we sought to determine whether maternal hypertension during pregnancy alters the cerebral response of adult offspring to acute ischemic stroke. Atrial natriuretic peptide gene-disrupted (ANP(-/-)) mothers exhibit chronic hypertension that escalates during pregnancy. Through comparison of heterozygote offspring born from either normotensive (ANP(+/-WT)) or hypertensive (ANP(+/-KO)) mothers, we have demonstrated that offspring exposed to maternal hypertension exhibit larger cerebral infarct volumes following middle cerebral artery occlusion. Observation of equal baseline cardiovascular measures, cerebrovascular structure, and cerebral blood volumes between heterozygote offspring suggests no added influences on offspring that would contribute to adverse cerebral response post-stroke. Cerebral mRNA expression of endothelin and nitric oxide synthase vasoactive systems demonstrated up-regulation of Et-1 and Nos3 in ANP(+/-KO) mice and thus an enhanced acute vascular response compared to ANP(+/-WT) counterparts. Gene expression of Na(+)/K(+) ATPase channel isoforms, Atp1a1, Atp1a3, and Atp1b1, displayed no significant differences. These investigations are the first to demonstrate a fetal programming effect between maternal hypertension and adult offspring stroke outcome. Further mechanistic studies are required to complement epidemiological evidence of this phenomenon in the literature.

Molecular adaptations in vasoactive systems during acute stroke in salt-induced hypertension

Investigations regarding hypertension and dietary sodium, both factors that influence stroke risk, have previously been limited to using genetically disparate treatment and control groups, namely the stroke-prone, spontaneously hypertensive rat and Wistar-Kyoto rat. In this investigation, we have characterized and compared cerebral vasoactive system adaptations following stroke in genetically identical, salt-induced hypertensive, and normotensive control mice. Briefly, ANP(+/-) (C57BJ/6 × SV129 background) mice were fed chow containing either 0.8% NaCl (NS) or 8.0% NaCl (HS) for 7 weeks. Transient cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Infarct volumes were measured 24-h post-reperfusion and the mRNA expression of five major vasoactive systems was characterized using qPCR. Along with previous publications, our data validate a salt-induced hypertensive state in ANP(+/-) mice fed HS chow as they displayed left ventricular hypertrophy, increased systolic blood pressure, and increased urinary sodium excretion. Following MCAO, mice fed HS exhibited larger infarct volumes than their dietary counterparts. In addition, significant up-regulation in Et-1 and Nos3 mRNA expression in response to salt and stroke suggests implications with increased cerebral damage in this group. In conclusion, our data demonstrate increased cerebral susceptibility to stroke in salt-induced hypertensive mice. More importantly, however, we have characterized a novel method of investigating hypertension and stroke with the use of genetically identical treatment and control groups. This is the first investigation in which genetic confounding variables have been eliminated.

Endothelin-1 in peripheral arterial disease: a potential role in muscle damage

The evidence for the role of endothelin-1 (ET-1) in endothelial dysfunction and atherosclerosis has been growing since its discovery. However most studies have focussed on cardiac disease and its role in peripheral arterial disease (PAD) is less clear. In addition to its role in the development and progression of atherosclerotic lesions in lower limb arteries, there is evidence that ET-1 adversely affects microvessels within the muscle and the viability of the ischemic muscle itself. This review summarises some of these findings which underscore the potential use of ET antagonists as an adjunct in the treatment of PAD.

Neuroprotection in focal cerebral ischemia owing to delayed treatment with melanocortins

In gerbils subjected to transient global cerebral ischemia, melanocortin peptides produce long-lasting protection with a broad time window, and through the activation of central nervous system melanocortin MC(4) receptors. Here we aimed to investigate whether melanocortins are neuroprotective also in a rat model of focal cerebral ischemia induced by intrastriatal microinjection of endothelin-1. The vasoconstrictor agent endothelin-1 caused a significant impairment in spatial learning and memory, as well as in sensory-motor orientation and limb use, associated with severe striatal morphological damage including intense neuronal death and an almost complete myelin degradation. Treatment of ischemic rats with a nanomolar dose (340 microg/kg/day i.p. for 11 days, beginning 3 h or 9 h after endothelin-1 microinjection) of the melanocortin analog [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH) significantly reduced striatal damage, and improved subsequent functional recovery, with all scheduled NDP-alpha-MSH treatments. Pharmacological blockade of melanocortin MC(4) receptors prevented the protective effect of NDP-alpha-MSH. Our findings give evidence that melanocortins are neuroprotective, with a broad time window, also in a severe model of focal cerebral ischemia, and suggest that melanocortin MC(4) receptor agonists could produce neuroprotection in different experimental models of ischemic stroke.

Enrasentan, an antagonist of endothelin receptors

Endothelins are powerful vasoconstrictor agents produced by endothelial cells and identified by Yanagisawa et al. in 1988. Two types of receptors for endothelins have been identified: ET(A) receptors are located on smooth muscle cells of the vascular wall and are responsible for endothelin-induced vasoconstriction while ET(B) receptors are located on endothelial cells and induce these cells to release NO and prostacyclin. Moreover, these peptides not only cause a potent and prolonged vasoconstriction but are also known to enhance cell proliferation and to stimulate extracellular matrix accumulation. High levels of plasma or tissue endothelins have been found in patients with heart failure, diabetes, stroke, primary pulmonary hypertension, liver cirrhosis and other diseases. Given these effects of endothelins, blocking their receptors might be a new way to reduce blood pressure and to treat other illnesses. Accordingly, many endothelin antagonists have been developed and evaluated in animals and humans. Enrasentan is a mixed ET(A) and ET(B) receptor antagonist with a higher affinity for ET(A) receptors, although it cannot be considered a selective antagonist. In an animal model of hypertension and cardiac hypertrophy the drug has reduced blood pressure, prevented cardiac hypertrophy and preserved myocardial function. In rats with hyperinsulinemia and hypertension enrasentan normalized blood pressure and prevented cardiac and renal damage. In rats with stroke the drug reduced the ischemic area in the brain. Enrasentan has been added to conventional treatment in patients with heart failure (NYHA Class 2-3) and no addictive effect of the drug has been observed. This is in contrast with results obtained in animal models and still has not been explained. In conclusion, many possible clinical applications can be suggested for this drug, but further studies are necessary to better evaluate its therapeutic efficacy.