Endothelin Receptor Blockade Blunts the Pressor Response to Acute Stress in Obese Men and Women

Obesity is associated with dysregulation of the endothelin system. In obese individuals, an exaggerated pressor response to acute stress is accompanied by increased circulating endothelin-1. The impact of combined endothelin A/B receptor (ETA/B) antagonism on the stress-induced pressor response in overweight/obese individuals is unknown. Objective: To test the hypothesis that treatment with an ETA/B antagonist (bosentan) would reduce the stress-induced pressor response and arterial stiffness in overweight/obese compared to normal weight individuals. Methods: 40 participants [Normal weight (NW): n=20, BMI: 21.7 ± 2.4 kg/m2 & Overweight/obese (OB): n=20, BMI: 33.8 ± 8.2 kg/m2] were randomized to placebo or 125 mg of bosentan twice a day (250 mg total) for 3 days. Hemodynamics were assessed before, during, and after a cold pressor test (CPT). Endothelin-1 was assessed at baseline and immediately after CPT. Following a washout period, the same protocol was repeated with the opposite treatment. Results: The change from baseline in mean arterial pressure (MAP) during CPT following bosentan was significantly lower (p=0.039) in the OB group, compared to the NW group (OB: 28±12 vs LN: 34±15 mm Hg). Conclusions: These results suggest that ETA/B antagonism favorably blunts the pressor response to acute stress in overweight/obese individuals.

Kidney Response to Chemotherapy-Induced Heart Failure: mRNA Analysis in Normotensive and Ren-2 Transgenic Hypertensive Rats

The aim of the present study was to perform kidney messenger ribonucleic acid (mRNA) analysis in normotensive, Hannover Sprague–Dawley (HanSD) rats and hypertensive, Ren-2 renin transgenic rats (TGR) after doxorubicin-induced heart failure (HF) with specific focus on genes that are implicated in the pathophysiology of HF-associated cardiorenal syndrome. We found that in both strains renin and angiotensin-converting enzyme mRNA expressions were upregulated indicating that the vasoconstrictor axis of the renin–angiotensin system was activated. We found that pre-proendothelin-1, endothelin-converting enzyme type 1 and endothelin type A receptor mRNA expressions were upregulated in HanSD rats, but not in TGR, suggesting the activation of endothelin system in HanSD rats, but not in TGR. We found that mRNA expression of cytochrome P-450 subfamily 2C23 was downregulated in TGR and not in HanSD rats, suggesting the deficiency in the intrarenal cytochrome P450-dependent pathway of arachidonic acid metabolism in TGR. These results should be the basis for future studies evaluating the pathophysiology of cardiorenal syndrome secondary to chemotherapy-induced HF in order to potentially develop new therapeutic approaches.

Endothelial dysfunction in cancer patients before and after chemotherapy: focus on biomarkers

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The reported study was funded by Russian Foundation for Basic Research (RFBR) project number 19-315-90034 Background. Nowadays gastric cancer is one of the leading causes of world cancer mortality. Modern chemotherapy (CT) significantly improves survival and quality of life among these patients. Unfortunately, anticancer drugs induce some biomolecular disorders, which influence endothelial dysfunction and microcirculation lesions, subsequently leading to vasculo- and cardiotoxicity. The aim To study the dynamics of endothelial dysfunction’s (ED) biomarkers (endothelin-1 (ET-1), von Willebrand factor (VWF)) in patients with gastric cancer before and after CT. Material and methods The study included 25 patients with histologically confirmed gastric cancer (adenocarcinoma) stage II - IV, who have been treated by CT including platinum compound (oxaliplatin, cisplatin) and fluoropyrimidine group (5-fluorouracil, capecitabine) and are proven to be cardiovasculotoxic. All patients underwent blood tests, computer nailfold capillaroscopy and finger photoplethysmography (non-invasive assessment of vascular wall stiffness and endothelial function), electrocardiography (ECG), 24-hour ECG, echocardiography before CT and within a month after the last course. Results The median patients’ age was 64 ± 13 years; 68% were male; 52% had a prior cardiac illness: arterial hypertension (n = 12, 48%), coronary artery disease (n = 7, 28%), chronic heart failure (n = 3, 12%). The data obtained showed that ET-1 median levels were below normal values and did not change during CT: 0,95pg/ml (0,6;1,4) vs. 0,94pg/ml (0,7;1,4), р<0,9 (N = 1–3pg/ml), before and after CT respectively. The level of VWF remained within normal ranges and did not significantly differ in cancer patients before and after treatment 0,75IU/ml (0,7;0,9) vs. 0,8IU/ml (0,74;0,9), р<0,6 (N = 0,5–1,5IU/ml). Even before CT, endothelial dysfunction was detected, which significantly worsened after the treatment (occlusion index (IO) before and after CT 1.7 (1.38; 1.9) vs. 1.3 (1.2; 1.5), p < 0.0002, respectively). During data analysis, significant correlations were found: between ET-1 level and IO (r = 0.554, p = 0,006), ET-1 and percentage of capillary recovery (r= -0.7, p = 0,029) [both parameters characterize functional abnormalities of the microvasculature], ET-1 and the quantity of supraventricular extrasystoles (r=-0.48, p = 0,032). Conclusion In this study, the dynamics of ED biomarkers in patients with gastric cancer were studied. Even though reliable changes were not proven for the assessed molecular parameters ET-1 and VWF during CT (supposing depletion of endothelin system, small patient cohort), the above parameters may be used for identifying early signs of close and long-term cardio/vasculotoxicity due to significant positive correlations with microvasculature lesions. Further bigger trials for identification of other accurate and effective laboratory methods of detecting early features of vasculotoxicity are required.

MO096ROLE OF THE ENDOTHELIN SYSTEM IN THE INTERACTIONS OF THE VASOPRESSOR SYSTEMS IN VIVO IN MEN - IMPORTANCE OF GENETIC HOST FACTORS

Background and Aims Arterial hypertension is one of the most common diseases of the cardiovascular system worldwide and is still the cause of most deaths in Germany. Data on interactions of the endothelin-system with the renin-angiotensin- and the sympathoadrenergic system in the regulation of systemic hemodynamics in humans are lacking. In our present investigation we study the effects of Endothelin A-, Alpha1- and Angiotensin II-type-1-receptor antagonization on the systemic pressor effects of intravenous Endothelin-1-application in young, healthy men. In addition, we analyzed the effects of the genetic variations of the GNB3 C825T-polymorphism on hemodynamic changes. GNB3 825CT/TT-allele-carriers are considered to have a higher risk for multiple diseases with structural, vascular degeneration, such as arterial hypertension, diabetes mellitus and obesity. Method 21 healthy male volunteers were included in this double- blind, randomized, placebo-controlled cross-over study and were studied on four days. Endothelin-1 (ET-1) (0.5, 1, 2.5, 5 ng/kg/min for 20 min each) was given intravenous 2.0 hours after oral application of either placebo or Doxazosin, 3.5 hours after oral application of Candesartan (Candesartan 8 mg) or in the presence of a continuous infusion of the ET-A-selective antagonist BQ123 (60 μg/min). Blood pressure (BP) and heart rate (HR) were recorded and total peripheral resistance (TPR) was measured using impedance cardiography. ET-1-dose-response curves were analyzed with ANOVA. Data are presented as mean ± SD. Since we suspected an effect of the GNB3 C825T-polymorphism we divided the overall collective into 2 sub-collectives according to the GNB3 C825T-genotypes (n = 21, GNB3 825CC: n = 10, GNB3 825CT/TT: n = 11). Our analyses considered the overall collective and compared the sub-collectives intraday and interday. Results ET-1 increased systolic blood pressure (SBD) (p ≤ 0,01), diastolic blood pressure (DBD) and mean arterial pressure (MBP) as well as total peripheral resistance (TPR) (each p ≤ 0,001) with decreasing heart rate (HR5) (p ≤ 0,05). Elevation of blood pressure existed in both sub-collectives (GNB3 825CC: SBD & MBD: p ≤ 0,01, DBP & TPR: p ≤ 0,05, GNB3 825CT/TT: DBD, MBD & TPR: p ≤ 0,01, SBP p ≤ 0,05). Antagonization of ETA-receptors reversed the effect in the overall collective as well as in the sub-collectives. Both, Doxazosin, as well as Candesartan led to a decrease in blood pressure, however, dose-response relationship was influenced more by doxazosin (DBD: p ≤ 0,001, MBD: p ≤ 0,01) than by candesartan (all values: p > 0,05). For both drugs, blood pressure and TPR remained elevated under maximum ET-1-application compared to baseline measurement. Blood pressure dependent heart rate changes were observed in the overall collective and in GNB3 825CC-allele-carriers under sole ET-1-therapy (p ≤ 0.05) (Fig. 1). Candesartan reversed the effect of ET-1 on the sub-collectives (p > 0.05). GNB3 825CT/TT-allele-carriers showed no reduction in heart rate under ET-1-application, but with accompanying candesartan therapy (p ≤ 0.01) (Fig. 2). The genotype collectives thus behaved oppositely to the drugs in this respect. Conclusion In summary, ET-1 increased systolic, diastolic and mean arterial blood pressure as well as systemic vascular resistance. Doxazosin, Candesartan and BQ123 led to a decrease in blood pressure. Blood pressure and TPR remained elevated under maximum ET-1 application plus Candesartan or Doxazosin. The heart rate changes of the genotype-separated sub-collectives were opposite when ET-1 was administered compared to ET-1 and Candesartan.

Interplay of the Circadian Clock and Endothelin System

The peptide hormone endothelin-1 and its receptors are linked to several disease states. Pharmacological inhibition of this pathway has proven beneficial in pulmonary hypertension, yet its potential in other disease states remains to be realized. This review considers an often understudied aspect of endothelin biology, circadian rhythm regulation and how understanding the intersection between endothelin signaling and the circadian clock may be leveraged to realize the potential of endothelin-based therapeutics.

Monitoring Endothelin-A Receptor Expression during the Progression of Atherosclerosis

Cardiovascular disease remains the most frequent cause of death worldwide. Atherosclerosis, an underlying cause of cardiovascular disease, is an inflammatory disorder associated with endothelial dysfunction. The endothelin system plays a crucial role in the pathogenesis of endothelial dysfunction and is involved in the development of atherosclerosis. We aimed to reveal the expression levels of the endothelin-A receptor (ETAR) in the course of atherogenesis to reveal possible time frames for targeted imaging and interventions. We used the ApoE−/− mice model and human specimens and evaluated ETAR expression by quantitative rtPCR (qPCR), histology and fluorescence molecular imaging. We found a significant upregulation of ETAR after 22 weeks of high-fat diet in the aortae of ApoE−/− mice. With regard to translation to human disease, we applied the fluorescent probe to fresh explants of human carotid and femoral artery specimens. The findings were correlated with qPCR and histology. While ETAR is upregulated during the progression of early atherosclerosis in the ApoE−/− mouse model, we found that ETAR expression is substantially reduced in advanced human atherosclerotic plaques. Moreover, those expression changes were clearly depicted by fluorescence imaging using our in-house designed ETAR-Cy 5.5 probe confirming its specificity and potential use in future studies.

1195. Influence of Histoplasma capsulatum Infection on Endothelin-1 mRNA Gene Expression in Bone Marrow Derived Macrophages

Background Endothelin-1 (ET-1) is increasingly recognized as an immune modulator; it exerts a pro-inflammatory effect by increasing the release of cytokines like interferon gamma. ET-1 is secreted by a variety of cells such as macrophages, neurons and endothelial cells. Activation of the endothelin system has been implicated in the pathogenesis of sepsis caused by bacteria, viruses and even parasites. However, there are no published studies that have explored the role of ET-1 in Histoplasma capsulatum infection. Studying the role of ET-1 in histoplasmosis is important because understanding its role in the host defense mechanism may serve as the foundation for future discovery of novel therapeutic options. Methods Bone marrow cells were isolated from mice and set up for tissue culture. Bone marrow derived macrophages (BMDM) were harvested after 5-7 days of incubation, and infected with varying ratios (0.5,1 and 5) of yeasts to macrophages. RNA was extracted from the BMDM after 3, 6, 24 and 48 hours of infection. For comparison, RNA was also extracted from uninfected BMDM at the same time points. Real-time PCR (polymerase chain reaction) was performed on complementary DNA. ET-1 (Edn1) messenger RNA (mRNA) gene expression was quantified relative to the expression of the house keeping /endogenous control gene that encodes for beta-2 microglobulin (B2m). Results In BMDM infected with H. capsulatum there was upregulation of Edn1 after 3, 6 and 24 hours of infection. During this same time points, the expression of ET-1 mRNA in the uninfected BMDM remained constant. Expression of Edn1 was highest in the BMDM infected with 5x H. capsulatum after 3 and 6 hours of infection. After 24 hours, the expression of ET-1 mRNA decreased markedly in all concentrations of H. capsulatum. At 48 hours post-infection the Edn1 was downregulated in the 0.5,1 and 5-fold quantities of H. capsulatum across all time the time intervals. Figure 1 Conclusion Results from this study indicate that H. capsulatum infection induced an upregulation of the Edn-1 in BMDM. This may correlate with an increase in levels of ET-1 production by the BMDM in the face of H. capsulatum infection. These results provide a platform in which to examine the influence of ET-1 on the host response to this fungus. Disclosures All Authors: No reported disclosures

Abstract P001: Diurnal Dysfunction Of The Renal Endothelin System Is Associated With Obesity-induced Hypertension In Rats

Loss of endothelin (ET) control of Na + reabsorption results in salt-sensitive hypertension. Diet-induced obesity such as via high fat (HF) diet can produce salt-sensitive hypertension. The goal of this study was to determine if obesity produced by HF diet impairs the renal ET system. Male SD rats were fed either HF (45 Kcal% fat) or normal fat (10 Kcal% fat, NF) diet at 6 weeks of age and for 8 weeks duration. Telemetry transmitters were implanted for systolic blood pressure (SBP) and activity monitoring. During the last 2 weeks of the diet, HF and NF rats were sub-divided into 2 groups to receive an additional high salt (4% NaCl, HS) diet or continue on normal salt (0.3% NaCl, NS) diet. Urine was collected and food and water intakes monitored in 12-hr increments the final 2 days. All groups maintained a diurnal BP pattern. However, rats on HF had significantly higher SBP compared to NF (146 ± 1 vs 138 ± 2 mmHg during the active period, p=0.003, n= 12/group). 12-hr urine volume or Na + excretion values were similar between groups. However, urinary ET-1, a measure of intrarenal ET-1 production, was significantly lower in the HF compared to NF controls (0.92 ± 0.15 vs 1.52 ± 0.09 pg/12hrs, p= 0.0007, n= 12/group). Relative mRNA expression of ET-1 in the renal cortex collected at ZT12 was significantly lower in the HF vs. NF (0.8 ± 0.1 vs 1.3 ± 0.2, p= 0.008, n= 6/group). A similar reduction of ET-1 mRNA was observed in the OM of HF rats. However, there was no change in ET-1 mRNA in the IM of HF rats compared to NF (0.8 ± 0.1 vs 1.0 ± 0.2, p= 0.28, n= 8/group). HS diet led to a further increase in SBP in HF vs the HF/NS group (152 ± 2 vs 147 ± 1 mmHg, p=0.04, n= 8/group) while addition of HS to the NF group showed no significant increase in SBP (145 ± 2 vs 140 ± 3 mmHg, p=0.37 n= 6/group). The NF/HS group had a significant increase in active-time ET-1 excretion compared to NF/NS (4.0 ± 0.4 vs 1.5 ± 0.2 pg/12hrs, p<0.0001, n= 6/group). ET-1 excretion was elevated in the HF/HS vs HF/NS rats (2.6 ± 0.3 vs 1.1 ± 0.1 pg/12hrs, p= 0.02, n= 8/group), but was significantly lower than NF/HS rats (4.0 ± 0.4 pg/12hrs p=0.009). These findings demonstrate that HF diets impair the renal ET-1 system and are consistent with our hypothesis that loss of renal ET-1 contributes to salt-sensitive hypertension in diet-induced obesity.

Vascular toxicity associated with anti-angiogenic drugs

Over the past two decades, the treatment of cancer has been revolutionised by the highly successful introduction of novel molecular targeted therapies and immunotherapies, including small-molecule kinase inhibitors and monoclonal antibodies that target angiogenesis by inhibiting vascular endothelial growth factor (VEGF) signaling pathways. Despite their anti-angiogenic and anti-cancer benefits, the use of VEGF inhibitors (VEGFi) and other tyrosine kinase inhibitors (TKIs) has been hampered by potent vascular toxicities especially hypertension and thromboembolism. Molecular processes underlying VEGFi-induced vascular toxicities still remain unclear but inhibition of endothelial NO synthase (eNOS), reduced nitric oxide (NO) production, oxidative stress, activation of the endothelin system, and rarefaction have been implicated. However, the pathophysiological mechanisms still remain elusive and there is an urgent need to better understand exactly how anti-angiogenic drugs cause hypertension and other cardiovascular diseases (CVDs). This is especially important because VEGFi are increasingly being used in combination with other anti-cancer dugs, such as immunotherapies (immune checkpoint inhibitors (ICIs)), other TKIs, drugs that inhibit epigenetic processes (histone deacetylase (HDAC) inhibitor) and poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors, which may themselves induce cardiovascular injury. Here, we discuss vascular toxicities associated with TKIs, especially VEGFi, and provide an up-to-date overview on molecular mechanisms underlying VEGFi-induced vascular toxicity and cardiovascular sequelae. We also review the vascular effects of VEGFi when used in combination with other modern anti-cancer drugs.

Intricacies of the endothelin system in human obesity: role in the development of complications and potential as a therapeutic target

Activation of the vascular endothelin-1 (ET-1) system is a key abnormality in vascular dysfunction of human obesity, especially in patients developing complications, such as the metabolic syndrome, diabetes, and atherosclerosis. Vascular insulin resistance, an increased insulin-stimulated endothelial production of ET-1 combined with impaired nitric oxide availability, is the hallmark of obesity-related vasculopathy, but dysregulated adipokine release from obese adipose tissue may contribute to the predominance of ET-1-dependent vasoconstriction. ET-1, in turn, might determine unhealthy obese adipose tissue expansion, with visceral and perivascular adipose tissue changes driving the release of inflammatory cytokines and atherogenic chemokines. In addition, ET-1 might also play a role in the development of the metabolic complications of obesity. Studies have shown inhibition of lipoprotein lipase activity by ET-1, with consequent hypertriglyceridemia. Also, ET-1 in pancreatic islets seems to contribute to beta cell dysfunction, hence affecting insulin production and development of diabetes. Moreover, ET-1 may play a role in nonalcoholic steatohepatitis. Recent clinical trials using innovative design have demonstrated that antagonism of ET-type A receptors protects against some complications of obesity and diabetes, such as nephropathy. These findings encourage further investigation to evaluate whether targeting the ET-1 system could afford better protection against other consequences of the obesity epidemic.