ET-1 induces IL-6 gene expression in human umbilical vein endothelial cells: synergistic effect of IL-1

NLRP3 activation contributes to endothelin-1-induced erectile dysfunction

In the present study, we hypothesized that endothelin (ET) receptors (ET_A and ET_B ) stimulation, through increased calcium and ROS formation, leads to Nucleotide Oligomerization Domain-Like Receptor Family, Pyrin Domain Containing 3 (NLRP3) activation. Intracavernosal pressure (ICP/MAP) was measured in C57BL/6 (WT) mice. Functional and immunoblotting assays were performed in corpora cavernosa (CC) strips from WT, NLRP3^-/- and caspase^-/- mice in the presence of ET-1 (100 nM) and vehicle, MCC950, tiron, BAPTA AM, BQ123, or BQ788. ET-1 reduced the ICP/MAP in WT mice, and MCC950 prevented the ET-1 effect. ET-1 decreased CC ACh-, sodium nitroprusside (SNP)-induced relaxation, and increased caspase-1 expression. BQ123 an ET_A receptor antagonist reversed the effect. The ET_B receptor antagonist BQ788 also reversed ET-1 inhibition of ACh and SNP relaxation. Additionally, tiron, BAPTA AM, and NLRP3 genetic deletion prevented the ET-1-induced loss of ACh and SNP relaxation. Moreover, BQ123 diminished CC caspase-1 expression, while BQ788 increased caspase-1 and IL-1β levels in a concentration-dependent manner (100 nM-10 μM). Furthermore, tiron and BAPTA AM prevented ET-1-induced increase in caspase-1. In addition, BAPTA AM blocked ET-1-induced ROS generation. In conclusion, ET-1-induced erectile dysfunction depends on ET_A - and ET_B -mediated activation of NLRP3 in mouse CC via Ca²⁺ -dependent ROS generation.

The innate face of Giant Cell Arteritis: Insight into cellular and molecular innate immunity pathways to unravel new possible biomarkers of disease

Giant cell arteritis (GCA) is an inflammatory chronic disease mainly occurring in elderly individuals. The pathogenesis of GCA is still far from being completely elucidated. However, in susceptible arteries, an aberrant immune system activation drives the occurrence of vascular remodeling which is mainly characterized by intimal hyperplasia and luminal obstruction. Vascular damage leads to ischemic manifestations involving extra-cranial branches of carotid arteries, mostly temporal arteries, and aorta. Classically, GCA was considered a pathological process resulting from the interaction between an unknown environmental trigger, such as an infectious agent, with local dendritic cells (DCs), activated CD4 T cells and effector macrophages. In the last years, the complexity of GCA has been underlined by robust evidence suggesting that several cell subsets belonging to the innate immunity can contribute to disease development and progression. Specifically, a role in driving tissue damage and adaptive immunity activation was described for dendritic cells (DCs), monocytes and macrophages, mast cells, neutrophils and wall components, such as endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). In this regard, molecular pathways related to cytokines, chemokines, growth factors, vasoactive molecules and reactive oxygen species may contribute to the inflammatory process underlying GCA. Altogether, innate cellular and molecular pathways may clarify many pathogenetic aspects of the disease, paving the way for the identification of new biomarkers and for the development of new treatment targets for GCA. This review aims to deeply dissect past and new evidence on the innate immunological disruption behind GCA providing a comprehensive description of disease development from the innate perspective.

Inhibitory effects of Syzygium jambos extract on biomarkers of endothelial cell activation

Background

Disordered endothelial cell activation plays an important role in the pathophysiology of atherosclerosis, cancer, sepsis, viral infections, and inflammatory responses. There is interest in developing novel therapeutics to regulate endothelial cell function in atherothrombotic, metabolic, vascular, and hematological diseases. Extracts from leaves of the Syzygium jambos (L.) Alston (S. jambos) trees have been proposed to treat cardiovascular diseases and diabetes through unclear mechanisms. We investigated the effects of the S. jambos extract on biomarkers of endothelial dysfunction and immune responses in the human endothelial cell line, EA.hy926.

Methods

Leaves of S. jambos were collected, concocted and lyophilized. To study the effects of S. jambos on endothelial cell activation, we used the human endothelial cell line. IL-6 levels were measured using qPCR and ELISA. PDI activity was measured using Insulin Turbidity and Di-E-GSSG assays. CM-H2DCFDA was used to study ROS levels. Migration assay was used to study S. jambos effect on ex vivo human polymorphonuclear and human mononuclear cells.

Results

Our results show that incubation of EA.hy926 cells with ET-1 led to a 6.5 ± 1.6 fold increase in IL-6 expression by qPCR, an event that was blocked by S. jambos. Also, we observed that ET-1 increased extracellular protein disulfide isomerase (PDI) activity that was likewise dose-dependently blocked by S. jambos (IC₅₀ = 14 μg/mL). Consistent with these observations, ET-1 stimulated ex vivo human polymorphonuclear and mononuclear cell migration that also was dose-dependently blocked by S. jambos. In addition, ET-1 stimulation led to significant increases in ROS production that were sensitive to S. jambos.

Conclusion

Our results suggest that the S. jambos extract represents a novel cardiovascular protective pharmacological approach to regulate endothelial cell activation, IL-6 expression, and immune-cell responses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03572-7.

Endothelin-1-induced endothelial microvesicles impair endothelial cell function

The aim of this study was to determine the effects of endothelin-1 (ET-1)-generated endothelial microvesicles (EMVs) on endothelial cell inflammation, apoptosis, and endothelial nitric oxide synthase (eNOS). Human umbilical vein endothelial cells (HUVECs) were treated with ET-1 for 24 h. EMVs released into the supernatant from cells treated with ET-1 or vehicle were isolated and quantified. EMV release was higher (P < 0.05) in cells treated with ET-1 compared with control (95 ± 15 vs. 54 ± 5 EMV/µL). Fresh HUVECs were then treated with either ET-1, ET-1-induced EMVs, or control EMVs for 24 h. ET-1-generated EMVs induced significantly higher release of IL-6 (181.0 ± 16.0 vs. 132.1 ± 8.1 pg/mL) and IL-8 (303.4 ± 37.4 vs. 211.8 ± 10.0 pg/mL), as well as greater total NF-κB p65 (76.0 ± 7.6 vs. 57.1 ± 2.1 AU) and active NF-κB p65 (Ser-536) (11.6 ± 0.9 vs. 6.8 ± 1.0 AU) expression than control EMVs. There were no significant differences in expression of caspase-9 (230.1 ± 24.3 vs. 243.6 ± 22.3 AU), caspase-3 (271.9 ± 22.7 vs. 265.1 ± 30.5 AU), and active caspase-3 (4.4 ± 0.4 vs. 4.3 ± 0.1 AU) in cells treated with ET-1-EMVs versus control EMVs. Total eNOS (108.4 ± 11.4 vs. 158.8 ± 1.6 AU) and activated eNOS (4.7 ± 0.5 vs. 9.6 ± 1.4 AU) were significantly lower in endothelial cells treated with ET-1-generated EMVs compared with control EMVs. The effects of ET-1-generated EMVs on cellular markers and mediators of endothelial inflammation, as well as eNOS function, was comparable to the effects of ET-1. In summary, ET-1 induces an EMV phenotype that adversely affects endothelial cell function. ET-1-generated EMVs may contribute to the atherogenic effect of ET-1.NEW & NOTEWORTHY Endothelin-1 (ET-1) is a potent vasoconstrictor peptide released by the endothelium that contributes to the regulation of vascular tone. Overexpression of ET-1 has been implicated in the etiology of atherosclerotic vascular disease. Endothelial cell-derived microvesicles (EMVs) play a pivotal role in vascular health and disease. Their functional phenotype is largely dictated by the stimulus for release. EMVs released in response to various pathological conditions have been shown to elicit deleterious vascular effects. In the present study, we determined, in vitro, the effect of ET-1 on EMV release from endothelial cells and the effects of ET-1-generated EMVs on endothelial cell inflammation, apoptosis, and endothelial nitric oxide synthase (eNOS). ET-1 induced a marked increase in EMV release. ET-1-generated EMVs significantly increased endothelial cell inflammation and reduced eNOS protein expression and activation. Moreover, the endothelial effects of ET-1-derived EMVs were similar to the direct effects of ET-1. ET-1-generated EMVs may contribute to the proatherogenic profile of ET-1.

Endothelin receptor antagonists in sickle cell disease: A promising new therapeutic approach

Sickle cell disease (SCD) is a genetic hematologic disorder that is characterized by a variety of potentially life threatening acute and chronic complications. Currently, hydroxyurea is the only clinically approved pharmacological therapy for the treatment of SCD, and the continued prevalence of severe disease complications underscores the desperate need for the development of new therapeutic agents. Central features of the sickle cell disease milieu, including hypoxia, oxidative stress, and thrombosis, are established enhancers of endothelin-1 (ET-1) synthesis. This conceptual connection between ET-1 and SCD was confirmed by multiple studies that demonstrated markedly elevated plasma and urinary levels of ET-1 in SCD patients. Direct evidence for the involvement of ET-1 signaling in the development of SCD pathologies has come from studies using endothelin receptor antagonists in SCD mice. This review summarizes recent studies that have implicated ET-1 signaling as a mechanistic contributor to renal, vascular, pulmonary, and nociceptive complications of sickle cell disease and discusses the potential for the use of ET receptor antagonists in the treatment of SCD.

Skeletal Muscle Vascular Function: A Counterbalance of Insulin Action

Insulin is a vasoactive hormone that regulates vascular homeostasis by maintaining balance of endothelial-derived NO and ET-1. Although there is general agreement that insulin resistance and the associated hyperinsulinemia disturb this balance, the vascular consequences for hyperinsulinemia in isolation from insulin resistance are still unclear. Presently, there is no simple answer for this question, especially in a background of mixed reports examining the effects of experimental hyperinsulinemia on endothelial-mediated vasodilation. Understanding the mechanisms by which hyperinsulinemia induces vascular dysfunction is essential in advancing treatment and prevention of insulin resistance-related vascular complications. Thus, we review literature addressing the effects of hyperinsulinemia on vascular function. Furthermore, we give special attention to the vasoregulatory effects of hyperinsulinemia on skeletal muscle, the largest insulin-dependent organ in the body. This review also characterizes the differential vascular effects of hyperinsulinemia on large conduit vessels versus small resistance microvessels and the effects of metabolic variables in an effort to unravel potential sources of discrepancies in the literature. At the cellular level, we provide an overview of insulin signaling events governing vascular tone. Finally, we hypothesize a role for hyperinsulinemia and insulin resistance in the development of CVD.

Endothelin-1-mediated vasoconstriction alters cerebral gene expression in iron homeostasis and eicosanoid metabolism

Endothelins are potent vasoconstrictors and signaling molecules. Their effects are broad, impacting processes ranging from neurovascular and cardiovascular health to cell migration and survival. In stroke, traumatic brain injury or subarachnoid hemorrhage, endothelin-1 (ET-1) is induced resulting in cerebral vasospasm, ischemia, reperfusion and the activation of various pathways. Given the central role that ET-1 plays in these patients and to identify the downstream molecular events specific to transient vasoconstriction, we studied the consequences of ET-1-mediated vasoconstriction of the middle cerebral artery in a rat model. Our observations demonstrate that ET-1 can lead to increases in gene expression, including genes associated with the inflammatory response (Ifnb, Il6, Tnf) and oxidative stress (Hif1a, Myc, Sod2). We also observed inductions (>2 fold) of genes involved in eicosanoid biosynthesis (Pla2g4a, Pla2g4b, Ptgs2, Ptgis, Alox12, Alox15), heme metabolism (Hpx, Hmox1, Prdx1) and iron homeostasis (Hamp, Tf). Our findings demonstrate that mRNA levels for the hormone hepcidin (Hamp) are induced in the brain in response to ET-1, providing a novel target in the treatment of multiple conditions. These changes on the ipsilateral side were also accompanied by corresponding changes in a subset of genes in the contralateral hemisphere. Understanding ET-1-mediated events at the molecular level may lead to better treatments for neurological diseases and provide significant impact on neurological function, morbidity and mortality.

Vascular effects of glycoprotein130 ligands--part I: pathophysiological role

The vessel wall is no longer considered as only an anatomical barrier for blood cells but is recognized as an active endocrine organ. Dysfunction of the vessel wall occurs in various disease processes including atherosclerosis, hypertension, peripheral artery disease, aneurysms, and transplant and diabetic vasculopathies. Different cytokines were shown to modulate the behavior of the cells, which constitute the vessel wall such as immune cells, endothelial cells and smooth muscle cells. Glycoprotein 130 (gp130) is a common cytokine receptor that controls the activity of a group of cytokines, namely, interleukin (IL)-6, oncostatin M (OSM), IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine (CLC), IL-27, and neuropoietin (NP). Gp130 and associated cytokines have abundantly diverse functions. Part I of this review focuses on the pathophysiological functions of gp130 ligands. We specifically describe vascular effects of these molecules and discuss the respective underlying molecular and cellular mechanisms.

Epidermal Growth Factor–Like Domain 7 Is a Novel Inhibitor of Neutrophil Adhesion to Coronary Artery Endothelial Cells Injured by Calcineurin Inhibition

Background—

We investigated the effect of epidermal growth factor–like domain 7 (Egfl7) on nuclear factor-κB activation, intercellular adhesion molecule-1 expression, and neutrophil adhesion to human coronary artery endothelial cells after calcineurin-inhibition–induced injury.

Methods and Results—

Human coronary endothelial cells were incubated with cyclosporine (CyA) 10 μg/mL with or without Egfl7 (100 ng/mL) or the Notch receptor activator Jagged1 (200 ng/mL) for 6 to 48 hours. CyA upregulated nuclear factor-κB (p65) activity (128±2% of control, P <0.001) in nuclear extracts, as determined with a DNA-binding activity ELISA. This activity was inhibited by Egfl7 (86±3% of control; P <0.001 versus CyA alone). Jagged1 blocked Egfl7-induced nuclear factor-κB inhibition (105±4% of control; P <0.05 versus CyA plus Egfl7). CyA upregulated cell-surface intercellular adhesion molecule-1 expression (215±13% of control; P <0.001), as determined by flow cytometry. This expression was suppressed by Egfl7 (148±5%; P <0.001 versus CyA alone). Jagged1 attenuated the intercellular adhesion molecule-1–suppressive effect of Egfl7 when administered with CyA (193±3% versus 148±5%; P <0.01). CyA increased neutrophil adhesion to human coronary endothelial cells (control 20±5%, CyA 37±3%; P <0.001 versus control) in a nonstatic neutrophil adhesion assay. This increase was attenuated by Egfl7 (22±6%; P <0.001 versus CyA alone). Jagged 1 attenuated the effect of Egfl7 on neutrophil adhesion (31±3%; P <0.001 versus Egfl7 plus CyA).

Conclusions—

Our study reveals that Egfl7 is a potent inhibitor of neutrophil adhesion to human coronary endothelial cells subsequent to calcineurin-inhibition–induced injury. Mechanistically, Egfl7 blocked nuclear factor-κB pathway activation and intercellular adhesion molecule-1 expression, which suggests that it may have significant antiinflammatory properties. Because Jagged1 blocked the effect of Egfl7, Notch receptor antagonism may contribute to the mechanism of action of Egfl7.

The interaction between endothelin-1 and nitric oxide in the vasculature: new perspectives

Nitric oxide (NO) and endothelin-1 (ET-1) are natural counterparts in vascular function, and it is becoming increasingly clear that an imbalance between these two mediators is a characteristic of endothelial dysfunction and is important in the progression of vascular disease. Here, we review classical and more recent data that suggest that ET-1 should be regarded as an essential component of NO signaling. In particular, we review evidence of the role of ET-1 in models of acute and chronic NO synthase blockade. Furthermore, we discuss the possible mechanisms by which NO modulates ET-1 activity. On the basis of these studies, we suggest that NO tonically inhibits ET-1 function, and in conditions of diminished NO bioavailability, the deleterious effects of unmitigated ET-1 actions result in vasoconstriction and eventually lead to vascular remodeling and dysfunction.

The endothelin axis stimulates the expression of pro-inflammatory cytokines and pro-migratory molecules in breast cancer

We investigated the effects of the endothelin-1 (ET-1) receptor dual antagonist (Bosentan®) on the inflammatory cytokines and the chemoattractant molecules associated with breast cancer growth and the development of tumor infiltration in bone explants. Immunocompetent mice implanted with the murine mammary carcinoma 4T1 cells in a skin-fold chamber and treated with Bosentan® had reduced tumor growth (p < .05). ET-1 promoted the secretion of the anti-inflammatory soluble tumor necrosis factor (TNF) receptor and IL12 p40 in vitro. The Bosentan® treatment in vivo was associated with a local increase of the anti-inflammatory IL-1α cytokine concentration and decrease of the pro-inflammatory TNF-α and IL-17 cytokine concentrations (p < .05).

Increased tissue endothelin-1 and endothelin-B receptor expression in temporal arteries from patients with giant cell arteritis

PURPOSE

Endothelin (ET)-1 has been implicated in the atherosclerotic process and during inflammation. Similarity in the development process of giant cell arteritis (GCA) and atherosclerosis exists. Several ET receptor antagonists have been developed, principally to target cardiovascular disease states. High doses of corticosteroids currently are used in the treatment of GCA, whereas other treatments are not as reliably effective. The present study was performed to elucidate the role for ET-1, ET(A), and ET(B) receptors in GCA.

DESIGN

Experimental, retrospective immunohistochemical study of temporal arteries using archival formalin-fixed, paraffin-embedded tissue.

PARTICIPANTS

The study included 10 patients with GCA and 10 control patients with clinically suspected GCA but diagnosed not to have GCA.

METHODS

Immunohistochemistry, with anti ET-1, anti-ET(A), and anti-ET(B) antibodies, was performed on formalin-fixed and paraffin-embedded temporal arteries.

MAIN OUTCOME MEASURES

Endothelin-1, ET(A), and ET(B) receptor immunostaining intensities were quantified.

RESULTS

Temporal arteries from the patients with GCA showed the typical histologic features, including intimal thickening, disruption or loss of the elastic lamina, and inflammatory infiltrates of lymphocytes, macrophages, and multinucleated giant cells. These features were associated with increased ET-1 and ET(B) receptor immunoreactivity in the medial layer of the temporal arteries and endothelial cells in patients with GCA compared with the controls. The increased ET-1 and ET(B) receptor immunoreactivity occurred in vascular smooth muscle cells (SMCs) and multinucleated giant cells. The ET-1 and ET(B) receptor immunoreactivity correlated with the degree of systemic inflammation. No changes were observed in ET(A) receptor expression in SMCs or endothelial cells compared with controls.

CONCLUSIONS

The results suggest a role for ET-1 and ET(B) receptors in GCA. Inhibiting the ET system may provide a corticosteroid-sparing alternative in the treatment of GCA.

The role of endothelin-1 in myocarditis and inflammatory cardiomyopathy: old lessons and new insights

Endothelin-1 has emerged as an important participant in the pathophysiology of a variety of cardiovascular diseases, where it may act on endocrine, paracrine and autocrine bases. Here we review its regulated biosynthesis, receptor-mediated signaling, and functional consequences in the heart, with particular emphasis on cardiac development and disease. Exploring published data employing molecular genetic mouse models of endothelin dysregulation, we highlight its heretofore underappreciated role as a pro-inflammatory cytokine. We also present novel micro-array data from one such mouse model, which implicate the specific downstream pathways that may mediate endothelin-1's effects.Key words: endothelin-1, cardiac development, inflammation, transgenic mice, gene expression profiling.

Altered endothelin-1 levels in acute lower limb ischemia and reperfusion

Tourniquet-induced ischemia is often used in orthopedic and reconstructive procedures. This is associated with muscle damage and dysfunction, which limits tourniquet application time. Endothelin-1 (ET-1) is a potent vasoconstrictor, which has been implicated in ischemic conditions and ischemia-reperfusion injury. This study aimed to investigate the role of ET-1 in human skeletal muscle subjected to tourniquet-induced acute ischemia and reperfusion. Thirteen patients undergoing total knee replacement were studied. Plasma and muscle ET-1 concentrations were measured at the start of surgery, after an hour of acute ischemia, and 15 minutes following reperfusion. ET-1 receptor binding was also studied by use of autoradiography, and ET-1 mRNA expression investigated by use of real-time polymerase chain reaction (RT-PCR). Tissue ET-1 increased following the period of acute ischemia and persisted during reperfusion. ET-1 was associated with microvessels and macrophages in the muscle. No changes in circulating ET-1 levels, ET-1 mRNA expression, or ET-1 receptor binding were found. It is concluded that the ET-1 pathway is involved in acute ischemia and reperfusion and it may contribute to the muscle injury that occurs during surgical procedures.

Hydroxyurea downregulates endothelin-1 gene expression and upregulates ICAM-1 gene expression in cultured human endothelial cells

The clinical efficacy of oral hydroxyurea (HU) in adults and children with sickle cell anemia (SCA) cannot solely be explained by its ability to enhance fetal hemoglobin (HbF) expression. Since increased adherence of sickle red blood cells to vascular endothelium is a possible contributing factor to vaso-occlusive crisis (VOC), we explored the effect of HU on human endothelial cell (EC) lines (TrHBMEC and EA-hy 926). We demonstrated that HU, in a dose-dependent and reversible manner, significantly decreased (up to three-fold) the release of endothelin-1 (ET-1), a vasoconstrictor peptide through downregulation (up to three-fold) of ET-1 gene expression. This finding is of therapeutic relevance as SCA patients exhibit elevated serum levels of ET-1 during episodes of VOC and levels correlate with disease severity. Unexpectedly, HU upregulated (up to three-fold) the expression of membrane-bound intercellular cell adhesion molecule 1 (mbICAM-1) and its soluble form (sICAM-1) with a parallel increase in ICAM-1 mRNA expression. Although ICAM-1 does not appear to be involved in the sickle cell adhesion to vascular endothelium, it may exacerbate vaso-occlusion by promoting leukocyte adhesion. The HU-induced increase in mbICAM-1 may appear inconsistent with the clinical benefits confered by HU. However, both the increase in sICAM-1- and HU-induced leukocyte reduction in patients, may counteract the potentially detrimental effect of elevated mbICAM-1 expression. Also HU reduces the expression of vascular cell adhesion molecule (VCAM-1) on EC. Since HU reduces the very late antigen 4-positive reticulocytes in SCA patients, a ligand for VCAM-1, HU-induced downregulation of VCAM-1 on EC will very likely decrease the reticulocyte-endothelium adhesion. Thus, HU, apart from inducing HbF expression in the red cell, also affects the expression profile of EC compartment.

Conditional Cardiac Overexpression of Endothelin-1 Induces Inflammation and Dilated Cardiomyopathy in Mice

Background— Myocardial expression of endothelin-1 (ET-1) and its receptors ET A and ET B is increased in heart failure. However, the role of ET-1 and its signaling pathways in the pathogenesis of myocardial diseases is unclear.

Methods and Results— Human ET-1 cDNA was placed downstream of a promoter responsive to a doxycycline (DOX)-regulated transcriptional activator (tTA). This line (ET + ) was bred with one harboring cardiac myocyte-restricted expression of tTA (αMHC-tTA). Myocardial ET-1 peptide levels were significantly increased in binary transgenic (BT, ET + /tTA + ) compared with nonbinary transgenic (NBT, ET + /tTA − ; ET − /tTA + ; ET − /tTA − ) or DOX-treated BT littermates (40.1±4.7 versus 2.6±1.2 fmol/mL, P <0.003). BT mice demonstrated progressive mortality between 5 and 11 weeks after DOX withdrawal, associated with left ventricular dilatation and contractile dysfunction (peak +dP/dT, 4673±468 versus 5585±658 mm Hg/s, P <0.05). An interstitial inflammatory infiltrate, including macrophages and T lymphocytes, was evident in the myocardium of BT mice, associated with sequential increases in nuclear factor-κB translocation and expression of tumor necrosis factor-α, interferon-γ, interleukin-1 and interleukin-6. Significant prolongation of survival was observed with the combined ET A /ET B antagonist LU420627 (n=8, P <0.05) in BT mice but not the ET A -selective antagonist LU135252 (n=5, P =0.9), consistent with an important role for ET B in this model.

Conclusions— These are the first data to demonstrate that cardiac overexpression of ET-1 is sufficient to cause increased expression of inflammatory cytokines and an inflammatory cardiomyopathy leading to heart failure and death.

Shear flow attenuates serum-induced STAT3 activation in endothelial cells

Vascular endothelial cells (ECs) are constantly exposed to flow-induced shear stress. Shear stress is known to induce signaling cascades, including the extracellular signal-regulated protein kinase (ERK) pathway. STAT3 transcription factor plays a key role in cytokine stimulation. Recent studies indicate that STAT3 is involved in growth factor-induced cell cycle. In the present study, we have examined STAT3 activation of ECs under conditions of shear flow. Bovine aortic ECs cultured with serum at static state show a serum concentration-dependent phosphorylation at Tyr-705 of STAT3, whereas there is a constant basal phosphorylation at Ser-727. In ECs subjected to shear flow, a shear dose-dependent phosphorylation of Ser-727 and ERK1/2 was observed. In contrast, a concomitantly shear dose-dependent inhibition of phosphorylation at Tyr-705 was exhibited. Shear stress on ECs increased the association of ERK1/2 to STAT3. ECs treated with MEK inhibitor (U0126 or PD98059) consistently and significantly reduced the shear-induced ERK1/2 and Ser-727 phosphorylation, indicating that ERK1/2 is upstream of Ser-727 phosphorylation. Interestingly, shear-induced inhibition in Tyr-705 phosphorylation was abolished in these same inhibitor-treated ECs. Similarly, ECs transfected with a dominant positive mutant of MEK1 enhanced the phosphorylation of Ser-727 with the attenuation of the Tyr-705 phosphorylation. In contrast, when ECs were transfected with dominant positive mutant of MEKK1, JNK upstream, no change in the phosphorylation of Ser-727 and Tyr-705 was observed. These results indicate that shear flow induces the phosphorylation of Ser-727 via ERK1/2 pathway, and this Ser-727 phosphorylation inhibits Tyr-705 phosphorylation in STAT3. As a result, shear flow reduced the translocation of STAT3 into nucleus. This study shows for the first time that shear flow may play a significant role by attenuating STAT3 activation and thus may reduce inflammatory responses and/or serum-induced endothelial proliferation.

Evidence for the involvement of endothelin-1 but not urotensin-II in chronic lower limb ischaemia in man

BACKGROUND

endogenous vasoconstrictor peptides may play a role in the pathophysiology of critical limb ischaemia (CLI). This study investigated endothelin-1 (ET-1) and urotensin-II (U-II) mRNA expression, peptide distribution and ET receptor subtype binding in chronically ischaemic muscle.

METHODS

open muscle biopsies were taken from patients undergoing amputations for CLI and from patients undergoing coronary artery bypass surgery (controls). ET-1 and U-II mRNA expression in muscle biopsies was studied using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). ET-1 and U-II immunohistochemistry was performed on muscle sections and ET receptor binding studied using in vitro autoradiography.

RESULTS

ET-1 mRNA expression was significantly increased in CLI compared to controls (p<0.05) whilst no significant change in U-II expression occurred. ET-1 immunoreactivity was also increased in CLI with no difference in U-II immunostaining observed. ET(B) receptor binding was significantly increased in CLI (median 4, range 1-8 vs 2, range 1-3, dpm x 10(3)/mm(2), p=0.01, Mann-Whitney test) whilst ET(A) receptor binding was not significantly raised. Binding was associated with microvessels and macrophages.

CONCLUSIONS

in CLI, the ET-1 pathway is upregulated but U-II is unaffected. ET-1 may vasoconstrict microvessels and mediate inflammation in chronically ischaemic muscle. ET-1 binding to ET(B) receptors in particular may play an important role in the pathophysiology of CLI underscoring the therapeutic potential of ET(B) receptor antagonists in the management of CLI.

Plasma and synovial fluid endothelin-1 and nitric oxide concentrations in horses with and without joint disease

OBJECTIVE

To compare plasma and synovial fluid endothelin-1 (ET-1) and nitric oxide (NO) concentrations in clinically normal horses and horses with joint disease.

ANIMALS

36 horses with joint disease, and 15 horses without joint disease.

PROCEDURE

Horses with joint disease were assigned to 1 of the 3 groups (ie, synovitis, degenerative joint disease [DJD], or joint sepsis groups) on the basis of findings on clinical and radiographic examination and synovial fluid analysis. Endothelin-1 and NO concentrations were measured in plasma from blood samples, collected from the jugular vein and ipsilateral cephalic or saphenous vein of the limb with an affected or unaffected joint, as well as in synovial fluid samples obtained via arthrocentesis from the involved joint.

RESULTS

Plasma ET-1 concentrations between affected and unaffected groups were not significantly different. Median concentration and concentration range of ET-1 in synovial fluid obtained from the joint sepsis group (35.830 pg/mL, 7926 to 86.614 pg/mL; n = 7) were significantly greater than values from the synovitis (17.531 pg/mL, 0.01 to 46.908 pg/mL; 18), DJD (22.858 pg/mL, 0.01 to 49.990 pg/mL; 10), and unaffected (10.547 pg/mL, 0.01 to 35.927 pg/mL; 10) groups. Plasma and synovial fluid NO concentrations between affected and unaffected groups were not significantly different.

CONCLUSIONS AND CLINICAL RELEVANCE

Endothelin-1 is locally synthesized in the joints of horses with various types of joint disease. Synovial fluid concentrations of ET-1 varied among horses with joint disease, with concentrations significantly higher in the synovial fluid of horses with joint sepsis. These results indicate that ET-1 may play a role in the pathophysiologic mechanism of joint disease in horses.

Endothelin-1 as a target for therapeutic intervention in prostate cancer

The endothelins, a family of potent vasoconstricting peptides, have been implicated in the pathophysiology of advanced prostate cancer. Two endothelin receptors, ET-A and ET-B are found in normal prostate tissue. Malignant prostate cells are notable for the loss of ET-B receptors and increased levels of endothelin-1 [ET-1]; this distortion of the endothelin system may be a significant factor in the progression of prostate cancer. Proposed roles for endothelin in prostate cancer include growth promotion, apoptosis inhibition, bone formation, and stimulation of nociceptive receptors. ET-1 can act alone as a mitogen, but its effects are greatest as a comitogen with a variety of growth factors, including basic fibroblast growth factor, insulin-like growth factors, and platelet derived growth factor. Although their exact functions are unclear, ET-1, in conjunction with vascular endothelial growth factor, appears to play a major role in tumor angiogenesis. By a variety of methods, ET-1 alters the balance of osteoblast and osteoclasts to the favor new bone formation that is characteristic of metastatic disease. Several studies indicate that the refractory pain of metastatic cancer is related to the direct nociceptive effects ET-1. These findings suggest that ET receptors are promising therapeutic targets for pharmacologic intervention. Early clinical trials indicate that the ET-A receptor antagonist used in prostate cancer is reasonably well tolerated with mild but pervasive symptoms related to ET-1's vasoconstrictive effects. Results of ongoing clinical trials are eagerly awaited in order to see if the hypothetical promise of ET antagonism will result in clinical success.

Cerebrovascular inflammation following subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage frequently results in complications including intracranial hypertension, rebleeding and vasospasm. The extravasated blood is responsible for a cascade of reactions involving release of various vasoactive and pro-inflammatory factors (several of which are purported to induce vasospasm) from blood and vascular components in the subarachnoid space. The authors review the available evidence linking these factors to the development of inflammatory lesions of the cerebral vasculature, emphasizing: 1) neurogenic inflammation due to massive release of sensory nerve neuropeptides; 2) hemoglobin from lysed erythrocytes, which creates functional lesions of endothelial and smooth muscle cells; 3) activity, expression and metabolites of lipoxygenases cyclooxygenases and nitric oxide synthases; 4) the possible role of endothelin-1 as a pro-inflammatory agent; 5) serotonin, histamine and bradykinin which are especially involved in blood-brain barrier disruption; 6) the prothrombotic and pro-inflammatory action of complement and thrombin towards endothelium; 7) the multiple actions of activated platelets, including platelet-derived growth factor production; 8) the presence of perivascular and intramural macrophages and granulocytes and their interaction with adhesion molecules; 9) the evolution, origins, and effects of pro-inflammatory cytokines, especially IL-1, TNF-alpha and IL-6. Human and animal studies on the use of anti-inflammatory agents in subarachnoid hemorrhage include superoxide and other radical scavengers, lipid peroxidation inhibitors, iron chelators, NSAIDs, glucocorticoids, and serine protease inhibitors. Many animal studies claim reduced vasospasm, but these effects are not always confirmed in human trials, where symptomatic vasospasm and outcome are the major endpoints. Despite recent work on penetrating vessel constriction, there is a paucity of studies on inflammatory markers in the microcirculation.

Endothelin-1 and smooth muscle cells: induction of jun amino-terminal kinase through an oxygen radical-sensitive mechanism

Endothelin-1 (ET-1) has been proposed to contribute to atherogenesis and plaque rupture in coronary heart disease through activation of mitogen-activated protein kinases (MAPKs) in smooth muscle cells (SMCs). Reactive oxygen species (ROS) have been shown to be important signal transduction molecules in SMCs. Thus, the present study aimed to assess the role of ROS in ET-1-mediated activation of c-Jun amino-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) 1/2. Rat SMCs were exposed to ET-1 over time at concentrations from 10(-6) to 10(-10) mol/L, and MAPK activity was quantified. Activation of JNK and ERK was observed with a maximum stimulation at 10(-7) mol/L ET-1. JNK and ERK were activated by ET-1 binding to a single receptor (ET-1A) but differed in their downstream mechanisms: only JNK activation was sensitive to the radical scavenger N-acetylcysteine and diphenylene iodonium, an inhibitor of NADPH oxidase, indicating a role for ROS. The downstream MAPK effector and proinflammatory transcription factor, the activator protein-1 complex, was maximally activated 2 hours after the addition of ET-1. It was mainly composed of the JNK substrate c-Jun, and activation was also dependent on ROS formation. We suggest that plaque activation by ET-1 can be mediated through ROS. It can be hypothesized that the clinical benefit of antioxidants in the treatment of atherogenesis may partially depend on neutralization of ET-1-mediated ROS production.

Endothelin-1-induced ET(A) receptor-mediated nociception, hyperalgesia and oedema in the mouse hind-paw: modulation by simultaneous ET(B) receptor activation

Endothelin-1 causes ET(A) receptor-mediated enhancement of capsaicin-induced nociception in mice. We have assessed if this hyperalgesic effect of endothelin-1 is also accompanied by other pro-inflammatory effects, namely nociception and oedema, and characterized the endothelin ET receptors involved. Intraplantar (i. pl.) hind-paw injection of endothelin-1 (0.3 - 30 pmol) induced graded nociceptive responses (accumulated licking time: vehicle, 20. 5+/-3.3 s; endothelin-1 at 30 pmol, 78.1+/-9.8 s), largely confined to the first 15 min. Endothelin-1 (1 - 10 pmol) potentiated ipsilateral capsaicin-induced (0.1 microgram, i.pl.; at 30 min) nociception (vehicle, 40.2+/-2.6 s; endothelin-1 at 10 pmol, 98.4+/-5.8 s, but 30 pmol was inactive), and caused oedema (increase in paw weight 5 min after capsaicin: vehicle, 46.3+/-2.3 mg; endothelin-1 at 30 pmol, 100.3+/-6.1 mg). Selective ET(B) receptor agonists sarafotoxin S6c (up to 30 pmol) and IRL 1620 (up to 100 pmol) were inactive, whereas endothelin-3 (up to 30 pmol) induced only modest oedema. ET(A) receptor antagonists BQ-123 (1 nmol, i.pl. ) or A-127722-5 (6 micromol kg(-1), i.v.) prevented all effects of endothelin-1 (10 pmol), but the ET(B) receptor antagonist BQ-788 (1 or 10 nmol, i.pl.) was ineffective. BQ-788 (10 nmol, i.pl.) unveiled hyperalgesic effects of 30 pmol endothelin-1 and endothelin-3. Sarafotoxin S6c (30 pmol, i.pl.) did not modify endothelin-1-induced (10 pmol) nociception or oedema, but abolished hyperalgesia. Thus, endothelin-1 triggers ET(A) receptor-mediated nociception, hyperalgesia and oedema in the mouse hind-paw. Simultaneous activation of ET(B) receptors by endothelin-1 or selective agonists can limit the hyperalgesic, but not the nociceptive or oedematogenic, effects of the peptide.

Essential role for endothelin ET(B) receptors in fever induced by LPS (E. coli) in rats

1. The influence of endothelin receptor antagonists on febrile responses to E. coli lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and endothelin-1 (ET-1) was assessed in conscious rats. 2. Intravenous (i.v.) LPS (5.0 microg kg(-1)) markedly increased rectal temperature to a peak of 1.30 degrees C over baseline at 2.5 h. Pretreatment with the mixed endothelin ET(A)/ET(B) receptor antagonist bosentan (10 mg kg(-1), i.v.) or the selective endothelin ET(B) receptor antagonist BQ-788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D -1-methoxycarboyl-D-norleucine; 3 pmol, into a lateral cerebral ventricle-i.c.v.) reduced the peak response to LPS to 0.90 and 0.75 degrees C, respectively. The selective endothelin ET(A) receptor antagonist BQ-123 (cyclo[D-Trp-D-Asp-Pro-D-Val-Leu]; 3 pmol, i.c.v.) was ineffective. 3. Increases in temperature caused by IL-1beta (180 fmol, i.c.v.), TNF-alpha (14.4 pmol, i.c.v.) or IL-1beta (150 pmol kg(-1), i.v.) were unaffected by BQ-788 (3 pmol, i.c.v.). 4. Central injection of endothelin-1 (0.1 to 3 fmol, i.c.v.) caused slowly-developing and long-lasting increases in rectal temperature (starting 2 h after administration and peaking at 4-6 h between 0.90 and 1.15 degrees C) which were not clearly dose-dependent. The response to endothelin-1 (1 fmol, i.c.v.) was prevented by BQ-788, but not by BQ-123 (each at 3 pmol, i.c.v.). Intraperitoneal pretreatment with the cyclo-oxygenase inhibitor indomethacin (2 mg kg(-1)), which partially reduced LPS-induced fever, did not modify the hyperthermic response to endothelin-1 (3 fmol, i.c.v.). 5. Therefore, central endothelin(s) participates importantly in the development of LPS-induced fever, via activation of a prostanoid-independent endothelin ET(B) receptor-mediated mechanism possibly not situated downstream from IL-1beta or TNF-alpha in the fever cascade.

Effects of endothelin-1 on capsaicin-induced nociception in mice

The influence of endothelin-1 on nociception induced by capsaicin was assessed in the mouse hindpaw. Local endothelin-1 injection (1 to 20 pmol/paw) 30 min prior to ipsilateral injection of capsaicin (0.1 microg/paw) increased, in a graded fashion, the time spent licking the injected paw. Maximal hyperalgesia was obtained with 10 pmol/paw of endothelin-1 (capsaicin-induced hindpaw licking time increased from 43 +/- 3 s to 114 +/- 7 s, n = 6), but no hyperalgesia was evident following 30 pmol/paw of endothelin-1. The selective endothelin ET(B) receptor agonists sarafotoxin S6c (< or = 30 pmol/paw) and IRL 1620 (i.e., Suc[Glu9,Ala11,15]endothelin-1-(10-21); < or = 100 pmol/paw) failed to induce hyperalgesia. Local treatment with BQ-123 (i.e., cyclo[DTrp-DAsp-Pro-DVal-Leu] 1 nmol/paw selective endothelin ET(A) receptor antagonist), 10 min before endothelin-1 (10 pmol/paw), fully blocked the hyperalgesic response, whereas similar treatment with the selective endothelin ET(B) receptor antagonist BQ-788 (i.e., N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D- 1-methoxy-carboyl-D-norleucine) was ineffective. Intravenous injection of bosentan (17 and 52 micromol/kg a non-peptidic mixed endothelin ET(A)/ET(B) receptor antagonist) or BMS 182874 (i.e., 5-[dimethylamino]-N-[3,4-dimethyl-5-isoxazolyl]-1-naphthalenesulph onamide; 10 and 30 micromol/kg; a non-peptidic selective endothelin ET(A) receptor antagonist), 1 h before endothelin-1, inhibited its hyperalgesic effect in a graded fashion and abolished the response at the higher doses. None of the antagonists modified nociception induced by capsaicin alone or the hyperalgesia induced by local injection of 5-hydroxytryptamine (5-HT; 2 nmol/paw, 30 min before capsaicin). Hyperalgesia induced by 5-HT was abolished by simultaneous injection of endothelin-1 or the endothelin ET(B) receptor agonist IRL 1620 (each at 30 pmol/paw). Therefore, local endothelin-1 exerts a dual influence in this model: at low doses it causes endothelin ET(A) receptor-mediated hyperalgesia (i.e., it potentiates capsaicin-induced nociception), whereas at higher doses it induces an anti-hyperalgesic effect against 5-HT which seems to be mediated via distinct endothelin ET (possibly ET(B)) receptors.

Endothelin B receptor-mediated increase of cerebral blood flow in experimental pneumococcal meningitis

Study investigates the role of endothelin (ET) receptors in mediating early changes in cerebral blood flow--as measured by laser Doppler flowmetry (CBFLDF)--during experimental pneumococcal meningitis. Meningitis was induced with heat-killed pneumococci and confirmed by a significant increase in CBFLDF (baseline 100%; 225.3 +/- 21.8% after 6 hours; mean +/- SD), intracranial pressure (ICP), brain water content, and white blood cell count in the CSF. Intravenous administration of the selective endothelin B (ETB) receptor antagonist BQ-788 immediately before pneumococcal challenge (but not 4 hours afterward) significantly attenuated these pathophysiologic alterations (e.g., CBFLDF 6 hours after pneumococcal challenge: 116.7 +/- 17.4%). Pretreatment with BQ-123, a selective endothelin A receptor antagonist, had no significant effect on ICP and brain water content, but augmented the increase in CBFLDF and CSF white blood cell count. Since ET is known to trigger the release of nitric oxide (NO) by ETB receptor activation, we examined specific ET-NO interactions in primary rat cerebromicrovascular endothelial cells after stimulation with heat-killed pneumococci. Pneumococci induced a significant increase in both ET and NO concentrations in endothelial cell culture medium. Treatment with phosphoramidon, an inhibitor of the endothelin-converting enzyme, prevented the production of endothelin and markedly reduced NO generation. Our data provide evidence that ET is involved as a mediator in early pneumococcal meningitis in the rat and contributes to the increase in CBFLDF, ICP, brain water content, and CSF pleocytosis, presumably through ETB receptor-mediated NO production.

Plasma phospholipid transfer protein. Adenovirus-mediated overexpression in mice leads to decreased plasma high density lipoprotein (HDL) and enhanced hepatic uptake of phospholipids and cholesteryl esters from HDL

In vitro studies have shown that plasma phospholipid transfer protein (PLTP) converts isolated human high density lipoprotein-3 (HDL3) into larger HDL particles and generates lipid-poor apoA-I containing nascent HDL. To evaluate the role of PLTP in vivo we generated recombinant adenovirus vectors containing either human PLTP cDNA (rPLTP.AdV) or the reporter luciferase cDNA as a control. After intravenous infusion of 4 x 10(7) plaque-forming units (low dose) and 4 x 10(8) plaque-forming units (high dose) of rPLTP.AdV into mice, PLTP activity in plasma increased from base-line levels of 8.4 +/- 0.2 to 108 +/- 17 and from 8.9 +/- 0.6 to 352 +/- 31 micromol/ml/h, respectively, on day 4 (both p < 0.001). Thus, both low and high doses of rPLTP.AdV led to pronounced overexpression of human PLTP in mice. On day 4 after treatment, mice treated with low and high doses of rPLTP.AdV showed decreased HDL cholesterol (-54% and -91%) and apoA-I (-64% and -98%) (all p < 0.05). Kinetic studies revealed that the fractional catabolic rates of HDL labeled with [3H]phosphatidylcholine, [14C]phosphatidylcholine ether, [3H]cholesteryl ether, and 125I-labeled mouse apoA-I were increased by 8.5-, 8.7-, 3.8-, and 2.8-fold, respectively, in mice treated with low dose rPLTP.AdV (all p < 0.001). After injection of labeled HDL, mice treated with rPLTP.AdV showed an increased accumulation of labeled PC ether (+304%) and cholesteryl ether (+92%) in the liver (both p < 0.05). Two-dimensional gel electrophoresis of plasma 5 min after injection of HDL labeled with 125I-apoA-I demonstrated increased levels of newly generated pre-beta-HDL in mice overexpressing PLTP. In conclusion, HDL remodeling mediated by PLTP generates nascent, lipid-poor apoA-I in vivo and accelerates the hepatic uptake of HDL surface and core lipids in mice treated with rPLTP.AdV. Accelerated catabolism of HDL in mice overexpressing PLTP leads to low HDL levels. Our data indicate an important role for PLTP in modulating reverse cholesterol transport in vivo.