Experimental Models Of Hypertension Research Articles

CACNB2 expression is positively associated to the Ras/MAPK pathway in vitro and in an experimental model of hypertension

Several independent genome‐wide association studies highlighted the strong association of voltage‐dependent L‐type calcium channel subunit beta‐2 (CACNB2) gene with hypertension. One such study showed that hypertensive individuals who carry a promoter polymorphism (rs2357928) in CACNB2 exhibited adverse effects during treatment with calcium channel blocker (CCB) ‐ verapamil but responded well to treatment with the β‐blocker‐ atenolol. However, the exact molecular signature of CACNB2 during the pathophysiology of hypertension is currently remains to be explored. In the clinical setting, CCBs are widely used to treat hypertensive individuals, and the inhibition of L‐type Ca2+ channels with CCBs significantly increases the glomerular filtration rate and renal blood flow. Hence, the goal of this present study is to understand the molecular signaling of CACNB2 during hypertension via in vitro and in vivo approaches using HEK293 cells and genetically hypertensive, Dahl Salt‐Sensitive (SS) rats. The over‐expression of CACNB2 in HEK293 cells increased cell proliferation and upregulated the Ras‐MAPK pathway significantly when compared to the controls. These results were consistent with a recent study showing that overexpression of CACNB2, activate Ras/ERK/CREB pathways in vitro. Additionally, the ER stress markers IRE‐1α and PERK were upregulated by CACNB2 over expression compared to the control cells. In contrast, treatment with the L‐type CCB‐ nifidepine in CACNB2 overexpressed cells did not abolish upregulation of Ras‐MAPK and ER stress pathway genes. Similarly, we observed an increase in apoptotic signaling exemplified by the downregulation of Bcl‐2 and upregulation of Caspase 7 and Caspase 9, which were also insensitive to nifidepine treatment. Correspondingly, we investigated whether CACNB2 levels were altered using the SS rats under low salt (0.3% NaCl) and high (2% NaCl) diet fed conditions. We observed higher CACNB2 levels in high salt fed SS rat kidneys compared to SS rats maintained on low salt diet (n=4, p<0.05). In addition, our gene expression studies showed that Mapk1 and Mapk4 levels were upregulated in the kidneys of SS rats under high salt diet (n=4, p<0.05). In summary, our study reveals that CACNB2 significantly associated with the activation of Ras‐MAPK pathway in SS rats. In summary, understanding the regulation of CACNB2 and associated Ras‐MAPK pathway could help in expanding the knowledge of molecular mechanism of hypertension and may help in identifying novel drug targets.Support or Funding InformationFunding support for this study was met from the American Heart Association grant 16SDG27700030 (to S. Kumarasamy) and funding from UT‐COMLS.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Renal Sensory Nerves Increase Blood Pressure and Sympathetic Nerve Activity in 2‐Kidney 1‐Clip Hypertensive Mice

Renal denervation lowers arterial blood pressure (ABP) in multiple clinical trials and some experimental models of hypertension. These antihypertensive effects have been attributed to the removal of renal afferent nerves. The purpose of the present study was to determine whether renal sensory nerves contribute to the 2‐Kidney‐1‐Clip (2K1C) model of hypertension. 2K1C hypertension was produced in male C57B16 mice (12–14 weeks, Jackson Laboratories) by placement of a 0.5mm length of PTFE tubing (ID: 0.008” x OD: 0.014”) around the left renal artery. 2K1C mice (n=10) displayed an elevated ABP measured via telemetry (Day 0: 96 ± 1mmHg vs Day 14: 120 ± 3mmHg; P<0.01). Ganglionic blockade with hexamethonium (30mg/kg, ip) produced a greater fall in mean ABP at Day 14 vs Day 0 (Day 0: −35 ± 2mmHg vs Day 14: −57 ± 5mmHg; P<0.01). 2K1C‐clipped kidneys vs 2K1C‐unclipped kidneys had lower mass (105 ± 14mg vs 173 ± 8mg, respectively; P<0.05) and higher mRNA levels of several pro‐inflammatory cytokines (IL1B, IL2, IL10, TNFa; P<0.05). Renal afferent discharge was significantly higher in 2K1C‐clipped kidneys vs 2K1C‐unclipped vs sham mice (2K1C‐clipped: 3.4 ± 0.9 Hz vs 2K1C‐unclipped: 0.7 ± 0.3Hz vs control: 0.3 ± 0.1 Hz, n=6/group; P<0.05). Furthermore, electrical stimulation of renal afferent nerves in control mice (n=6) produced a frequency‐dependent increase in ABP (5Hz: 4 ± 1mmHg, 10Hz: 6 ± 1mmHg, 20Hz: 11 ± 2mmHg; P<0.05). These responses were eliminated after ganglionic blockade with 5mg/kg chlorisondamine (5Hz: 1 ± 1mmHg, 10Hz: 1 ± 1mmHg, 20Hz: 1 ± 1mmHg, n=4/group; P<0.05). Stimulus‐triggered averaging of SNA during stimulation of renal afferent nerves (1 Hz, 200uA) revealed significant (P<0.05, n=4/group) increases in splanchnic (179 ± 11%), renal (195 ± 15%), and lumbar (167 ± 9%) SNA. Interestingly, the latency to the peak SNA (142 ± 10ms) suggests supraspinal pathways mediate the sympathoexcitatory response. Finally, both total renal denervation (10% phenol) or selective denervation of renal afferent nerves (periaxonal application of 33mM capsaicin) at time of clipping resulted in lower ABP than 2K1C mice at Day 14 (2K1C: 120 ± 3mmHg, phenol: 106 ± 3mmHg, capsaicin: 108 ± 3mmHg, n=6–10/group; P<0.05). These findings suggest 2K1C hypertension depends on renal sensory nerves and elevated SNA via supraspinal pathways.Support or Funding InformationNIH grant HL113270, AHA Undergraduate Research FellowshipThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hypertensive Neuropathy: A New Clinical Entity?

Hypertension is a main risk factor for stroke and vascular dementia and may cause important changes to the cerebrovascular tree, turning the brain more susceptible to infarcts, microaneurysms and ischemia. In spite of the well documented influence of hypertension on the brain, data on the sensitivity of peripheral nerves in hypertension is scarce. Our laboratory has been working for decades to help understanding how hypertension affects peripheral nerve morphology and function, using the spontaneously hypertensive rats (SHR) model. Spontaneously hypertensive rats (SHR), first inbred from Wistar Kyoto rats (WKY), are considered a good experimental model of human essential hypertension. The purpose of this study was to investigate the alterations on the morphology and morphometric data on sural, phrenic, vagus and recurrent laryngeal nerves of SHR, previous to the development of hypertension and with well‐established hypertension. Male and female SHR and normotensive WKY rats aged 5, 8 and 20 weeks (N = 6 in each group) were investigated. After arterial pressure and heart rate recordings in anesthetized animals, right and left sural, vagus, phrenic and recurrent laryngeal nerves were removed and prepared for epoxy resin embedding and light microscopy. Morphometric analysis was performed with the aid of computer software, and took into consideration the fascicle area and diameter, as well as myelinated fiber number, density, area and diameter. Nerves from young animals did not show differences between sides and genders. Significant differences were observed for the myelinated fiber number and density, comparing different genders of WKY and SHR in all nerves. Also, significant differences for the morphological (thickening of the endoneural blood vessel walls and lumen reduction) and morphometric (myelinated fibers diameter and G ratio) parameters of myelinated fibers were identified in nerves from adult hypertensive animals. Morphological exam of the myelinated fibers suggested the presence of a neuropathy due to hypertension in both SHR genders. These results indicate that hypertension altered important morphometric parameters related to nerve conduction in hypertensive animals. Moreover the comparison between males and females of WKY and SHR showed that the morphological and morphometric alterations due to hypertension are not gender related. The presence of a so called “hypertensive neuropathy” is documented with endoneural vascular lesions, axonal atrophy and loss of small myelinated fibers.Support or Funding InformationSupport: CNPq, FAPESP and FAEPAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of Diminazene aceturate treatment on some cardiovascular parameters and antioxidant status of apparently healthy horses

IntroductionApart from being a widely used antiprotozoal drug in many parts of Africa, Diminazene aceturate (DIZE), has been shown to have beneficial effects in experimental murine models of hypertension, pulmonary hypertension, myocardial infarction, stroke, atherosclerosis, type 1 diabetes, and eye disease. In this study, we investigated the effect of diminazene aceturate treatment after a single intramuscular administration on some cardiovascular parameters and antioxidant status in apparently healthy Nigerian horses.Materials and methodsTen male horses were divided into two groups comprising 5 horses each. Group A was the control group with no drug administered. Group B was treated with DIZE at 3.5 mg/kg, single dose. Baseline data were collected before the commencement of the experiment and thereafter, post‐administration at 0hrs, 24hrs, 48hrs and 96hrs. Base apex electrocardiogram was recorded using a computer ECG machine while oscillometric blood pressure measurement was recorded using a veterinary blood pressure monitor. Markers of oxidative stress were determined in the serumResultSingle intramuscular treatment caused a significant (p<0.05) increase in the systolic, diastolic and mean arterial blood pressure values when compared with the controls. From the electrocardiogram, sinus rhythm was recorded in both groups however, significant (p<0.05) increase in heart rate, p‐wave duration, QRS complex duration and QTc were observed in the treated group when compared with the control. Oxidative stress markers (malondialdehyde and hydrogen peroxide) significantly (p<0.05) increased while antioxidant enzymes (catalase, glutathione peroxidase and glutathione) were decreased when compared to the control.ConclusionThis study indicates that the use of DIZE in horses should be with great caution because of the associated cardiovascular physiological alterations, reduction in activities of antioxidant enzymes and increase in markers of oxidative stress.Support or Funding InformationNoneThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Samchulkunbitang regulates blood pressure and renal function in L‐NAME‐induced hypertensive rat

Hypertension is a risk factor for cardiovascular diseases and endothelial dysfunction was found in humans as well as in various animal experimental models of arterial hypertension. Samchulkunbitang (SCT) is Korean traditional medicine. Traditionally, the SCT was used in gastritis, gastric ulcers, and gastroptosis. This study was performed to evaluate the effect of SCT on vascular dysfunction in NG‐nitro‐L‐arginine methyl ester (L‐NAME)‐induced hypertension model. Sprague Dawley rats were divided into 5 groups; Control group, L‐NAME induced hypertension group (40 mg/kg/day), L‐NAME with olmetec (10 mg/kg/day), L‐NAME with SCT (100 or 200 mg/kg/day). L‐NAME was treated as drinking water for 3 weeks to induce hypertension in rats. Simultaneously treated L‐NAME, SCT was injected to rats by oral intake for 2 weeks. The systolic blood pressure was decreased in SCT treated groups compared with L‐NAME induced hypertension group. SCT restored vasorelaxation of response to acetylcholine, cGMP production in thoracic aorta. SCT decreased intima‐media thickness and maintained smooth and soft intimal endothelial layers in aorta of L‐NAME induced hypertension rats. SCT restored the reduction eNOS expression and decreased ET‐1 expression. Also, in western blot, SCT increased p‐eNOS and p‐Akt expression in aorta of L‐NAME hypertensive rat. Furthermore, in renal functional parameters, SCT has recovered osmolality, blood urea nitrogen (BUN), and serum creatinine level.Taken together, these results showed that recovering relaxation and cGMP production in thoracic aorta by treated SCT, which is associated with NO/cGMP pathway. In addition, SCT suppresses increase of blood pressure in the L‐NAME induced hypertensive model as well as ameliorates in renal function.Support or Funding InformationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Effect of Different Antihypertensive Classes on the Complexity of Heart Rate and Blood Pressure Variability

Hypertension is associated with several physiological dysfunctions, including changes in the neurohumoral control of heart and vessels. Different classes of antihypertensive drugs may have distinct effects on the autonomic system and body homeostasis, but their individual effects on the complexity of cardiovascular regulation are still not established. We investigated the effect of five different classes of antihypertensive on the complexity of pulse interval (PI) and arterial pressure (AP) variability in an experimental model of renal hypertension (2 kidney 1 clip, 2K1C) in the rat. Hypertensive rats were treated (by gavage) during 15 days with: water (N=12), ramipril (2 mg/kg/day; N=7), losartan (10 mg/kg/day; N=8), atenolol (90 mg/kg/day; N=9), amlodipine (10 mg/kg/day; N=7) or hydrochlorothiazide (20 mg/kg/day; N=8). A normotensive (sham‐operated) control group (N=10) received water for the same period. After the treatment, rats had their raw AP recorded and beat‐by‐beat series of systolic AP and PI were created. The complexity of AP and PI was assessed by multiscale entropy (MSE) and detrended fluctuation analysis (DFA). For PI series, hypertensive rats treated with water showed decreased MSE and increased DFA in the middle range of scales. For AP series, hypertensive rats untreated or treated with amlodipine have lower MSE at short and middle time scales. Hypertensive rats treated with amlodipine also showed altered DFA in comparison to the other groups. All antihypertensive drugs were efficient to restore AP to normal levels. Moreover, 2K1C untreated (water) rats presented the lowest cardiovascular complexity and all antihypertensive drugs, except for amlodipine, were capable to restore the cardiovascular complexity to normal levels. Therefore, amlodipine seems to have a deleterious effect on the cardiovascular integrative control, probably due to the increased sympathetic activity induced by amlodipine.Support or Funding InformationThis study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ‐ Brasil (CAPES) ‐ Finance Code 001, São Paulo Research Foundation (FAPESP, Proc. 2013/20549‐7) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Proc. 402076/2016‐8).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Decrease in Tregs Exacerbates DOCA‐Salt Hypertension and Renal Injury in Female Rats

BackgroundT regulatory cells (Tregs) have previously been shown to protect against increases in blood pressure (BP) in male experimental models of hypertension, however less is known regarding the role of Tregs in BP control in females. Our lab has previously reported that there is a sex difference in the renal T cell profile in DOCA, where DOCA results in a decrease in Tregs in males while females maintain their Tregs. The current study tested the hypothesis that Treg maintenance attenuates the increase in blood pressure (BP) to DOCA‐salt in females.MethodsFemale (n=4–7) 13‐week‐old Sprague Dawley rats underwent an uninephrectomy followed by the implantation of a time release 200mg Deoxycorticosterone Acetate (DOCA) pellet and 0.9% saline to drink ad libitum. Rats were then randomized to receive a vehicle or anti‐CD25 injection (IP 250 μg/week) weekly for 3 weeks and BP was measured by telemetry. 24‐hour urinary protein excretion was measured via Bradford Assay at baseline and weekly thereafter for the duration of the study. At the end of the study, kidneys were isolated for flow cytometric analysis of T cells and a terminal plasma sample was collected to measure the kidney injury marker Tim1/Kim1.ResultsAnti‐CD25 injections in DOCA hypertensive females significantly decreased renal (4.2 ± 0.6 vs. 6 ± 0.7; p=0.03) and circulating Tregs compared to DOCA alone (3.6 ± 0.5 vs. 5.5 ± .6 p=0.05). 3 weeks of DOCA‐salt treatment significantly increased BP (101 ± 3 to 160 ± 5; p=<.0001), and decreasing Tregs exacerbated the DOCA‐salt induced increase in BP (109 ± 1 to 188 ± 4; p=0.002). We calculated area under the curve for each BP tracing, and the overall BP load in the rats treated with anti‐CD25 was significantly greater than in rats with DOCA‐salt alone (3327 ± 37 vs. 3662 ± 39; p=0.033). DOCA‐salt also increased urinary protein excretion from baseline to week 3 (3 mg/day ± 0.4 to 34 mg/day ± 9; p=0.01) and this increase was exacerbated with anti‐CD25 treatment (2 mg/day ± 0.5 to 86 mg/day ± 17; p=0.003). Tim1/Kim1 was also increased in DOCA hypertensive females compared to uninephrectomized controls, and this increase was greater in rats treated with anti‐CD25 (control: 292 ± 25 pg/ml; DOCA: 415 ± 57pg/ml; DOCA+anti‐CD25: 589 ± 105; p=0.04).DiscussionOur data suggests that the maintenance of Tregs in DOCA‐salt hypertensive females attenuates increases in BP and renal injury. Future studies will determine if this effect if mediated by the anti‐inflammatory and anti‐hypertensive effects of IL‐10.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Behavioral, electrophysiological and neuropathological characteristics of the occurrence of hypertension in pregnant rats

Pre-eclampsia (PE) affects approximately 2 to 8% of pregnant women, causing blood pressure above 140 × 90 mmHg and proteinuria, normally after the 20th gestation week. If unsuccessfully treated, PE can lead to self-limited seizures (Eclampsia) that could eventually result in death of the mother and her fetus. The present study reports an experimental model of preeclampsia hypertension in pregnant (HP) and non-pregnant (H) Wistar rats by partially clamping one of their renal arteries. Pregnant (P) and non-pregnant (C) controls were provided. Differently from controls (C and P), H and HP animals presented a steady rise in BP two weeks after renal artery clamping. Injection of pentylenetetrazol (PTZ) induced behavioral and electroencephalographic seizures in all groups, which were increased in number, duration, amplitude and power accompanied by decreased latency in HP animals (p < 0.05). Consistent results were obtained in in vitro experimentation. Immunohistochemistry of hippocampus tissue in HP animals showed decreased density of neurons nuclei in CA1, CA3 and Hilus and increased density of astrocytes in CA1, CA3 and gyrus (p < 0.05). The present findings show that the clamping of one renal arteries to 0.15 mm and PTZ administration were able to induce signs similar to human PE in pregnant Wistar rats.

Paying the Toll for Inflammation

Paying the Toll for Inflammation

The gut microbiota and blood pressure in experimental models.

To summarize evidence supporting that microorganisms colonizing our gastrointestinal tract, collectively known as the gut microbiota, are implicated in the development and maintenance of hypertension in experimental models. The use of gnotobiotic (germ-free) mice has been essential for advancement in this area: they develop higher blood pressure (BP) if they receive faecal transplants from hypertensive patients compared to normotensive donors, and germ-free mice have a blunted response to angiotensin II. Experimental hypertension is consistently accompanied by changes in the composition of the gut microbiota. This is combined with a shift in microbial diversity and the deterioration of the gut epithelial barrier commonly referred to as gut dysbiosis. Restoration of normal gut biosis and microbiota alleviates and protects against the development of hypertension in both genetic and pharmacological models. This has been achieved by the use of antibiotics, faecal transplants between normotensive and hypertensive strains, and the use of prebiotics (i.e. food stuff that feeds the microbiota), probiotics (i.e. live bacteria) and gut metabolites (i.e. short-chain fatty acids). Research into experimental hypertension supports that the gut microbiota contributes to the regulation of BP. Manipulation of the microbiota might represent a new tool to prevent hypertension.

Alterations in cardiovascular function in an experimental model of lung fibrosis and pulmonary hypertension.

What is the central question of this study? We have evaluated changes in cardiovascular physiology using echocardiography in an experimental model of lung fibrosis. What is the main finding and its importance? Remarkably, we report changes in cardiovascular function as early as day7, concomitant with evidence of vascular remodelling. We also report that isolated pulmonary arteries were hypercontractile in response to a thromboxane A2 agonist. These findings are significant because the development of pulmonary hypertension is one of the most significant predictors of mortality in patients with lung fibrosis, where there are no available therapies and a lack of animal models. Group III pulmonary hypertension is observed in patients with chronic lung diseases such as chronic obstructive pulmonary disease or idiopathic pulmonary fibrosis. Pulmonary hypertension (PH) develops as a result of extensive pulmonary vascular remodelling and resultant changes in vascular tone that can lead to right ventricle hypertrophy. This eventually leads to right heart failure, which is the leading indicator of mortality in patients with idiopathic pulmonary fibrosis. Treatments for groupIII PH are not available, in part owing to a lack of viable animal models. Here, we have evaluated the cardiovascular changes in a model of lung fibrosis and PH. Data obtained from this study indicated that structural alterations in the right heart, such as right ventricular wall hypertrophy, occurred as early as day14, and similar increases in right ventricle chamber size were seen between days21 and 28. These structural changes were correlated with decreases in the systolic function of the right ventricle and right ventricular cardiac output, which also occurred between the same time points. Characterization of pulmonary artery dynamics also highlighted that PH might be occurring as early as day21, indicated by reductions in the velocity-time integral; however, evidence for PH is apparent as early as day 7, indicated by the significant reduction in pulmonary acceleration time values. These changes are consistent with evidence of vascular remodelling observed histologically starting on day 7. In addition, we report hyperactivity of bleomycin-exposed pulmonary arteries to a thromboxaneA2 receptor (Tbxa2r) agonist.

Novel Potent Decameric Peptide of Spirulina platensis Reduces Blood Pressure Levels Through a PI3K/AKT/eNOS-Dependent Mechanism.

Considered as a superfood of the future, Spirulina platensis matrix has been extensively used because of its beneficial effect on the management of cardiovascular diseases. However, its nutraceutical properties, bioactive compounds, and molecular mechanisms are unknown. Here, we demonstrate that S platensis matrix processed in vitro by simulated gastrointestinal digestion induces direct endothelial nitric oxide (NO)-mediated vasorelaxation of resistance vessels in mice. To gain insight into the bioactive compounds responsible for this effect, we used a complex multistep peptidomic approach to fractionate the crude digest: of the 5 peptide fractions identified (A-E), only fraction E evoked vasorelaxation. High-resolution mass spectrometry-based screening revealed in E the presence of 4 main peptides (SP3-SP6 [spirulina peptides]), of which only SP6 (GIVAGDVTPI) exerted direct endothelium-dependent vasodilation of ex vivo vessels, an effect occurring via a PI3K (phosphoinositide-3-kinase)/AKT (serine/threonine kinase Akt) pathway converging on NO release. In vivo, administration of SP6 evoked a significant hemodynamic effect, reducing blood pressure, an action absent in eNOS (endothelial NO synthase)-deficient mice. Of note, although lower doses of SP6 had no hemodynamic effects, it still enhanced endothelial NO vasorelaxation. Finally, in an experimental model of arterial hypertension, SP6 exerted an antihypertensive effect, improving endothelial vasorelaxation associated with enhanced serum nitrite levels. Based on our results, this novel decameric peptide may extend the possible fields of application for spirulina-derived peptides and could be developed into a promising nonpharmacological approach for the containment of pathologies associated with vascular NO misregulation.

Wnt/β-catenin regulates blood pressure and kidney injury in rats

Activation of the renin-angiotensin system (RAS) plays a pivotal role in mediating hypertension, chronic kidney and cardiovascular diseases. As Wnt/β-catenin regulates multiple RAS genes, we speculated that this developmental signaling pathway might also participate in blood pressure (BP) regulation. To test this, we utilized two rat models of experimental hypertension: chronic angiotensin II infusion and remnant kidney after 5/6 nephrectomy. Inhibition of Wnt/β-catenin by ICG-001 blunted angiotensin II-induced hypertension. Interestingly, angiotensin II was able to induce the expression of multiple Wnt genes in vivo and in vitro, thereby creating a vicious cycle between Wnt/β-catenin and RAS activation. In the remnant kidney model, renal β-catenin was upregulated, and delayed administration of ICG-001 also blunted BP elevation and abolished the induction of angiotensinogen, renin, angiotensin-converting enzyme and angiotensin II type 1 receptor. ICG-001 also reduced albuminuria, serum creatinine and blood urea nitrogen, and inhibited renal expression of fibronectin, collagen I and plasminogen activator inhibitor-1, and suppressed the infiltration of CD3+ T cells and CD68+ monocytes/macrophages. In vitro, incubation with losartan prevented Wnt/β-catenin-mediated fibronectin, α-smooth muscle actin and Snail1 expression, suggesting that the fibrogenic action of Wnt/β-catenin is dependent on RAS activation. Taken together, these results suggest an intrinsic linkage of Wnt/β-catenin signaling with BP regulation. Our studies also demonstrate that hyperactive Wnt/β-catenin can drive hypertension and kidney damage via RAS activation.

Pharmacological Characterization of Aprocitentan, a Dual Endothelin Receptor Antagonist, Alone and in Combination with Blockers of the Renin Angiotensin System, in Two Models of Experimental Hypertension.

The endothelin (ET) system has emerged as a novel target for hypertension treatment where a medical need persists despite availability of several pharmacological classes, including renin angiotensin system (RAS) blockers. ET receptor antagonism has demonstrated efficacy in preclinical models of hypertension, especially under low-renin conditions and in hypertensive patients. We investigated the pharmacology of aprocitentan (N-[5-(4-bromophenyl)-6-[2-[(5-bromo-2-pyrimidinyl)oxy]ethoxy]-4-pyrimidinyl]-sulfamide), a potent dual ETA/ETB receptor antagonist, on blood pressure (BP) in two models of experimental hypertension: deoxycorticosterone acetate (DOCA)-salt rats (low-renin model) and spontaneously hypertensive rats [(SHR), normal renin model]. We also compared the effect of its combination with RAS blockers (valsartan and enalapril) with that of the combination of the mineraloreceptor antagonist spironolactone with the same RAS blockers on BP and renal function in hypertensive rats. Aprocitentan was more potent and efficacious in lowering BP in conscious DOCA-salt rats than in SHRs. In DOCA-salt rats, single oral doses of aprocitentan induced a dose-dependent and long-lasting BP decrease and 4-week administration of aprocitentan dose dependently decreased BP (statistically significant) and renal vascular resistance, and reduced left ventricle hypertrophy (nonsignificant). Aprocitentan was synergistic with valsartan and enalapril in decreasing BP in DOCA-salt rats and SHRs while spironolactone demonstrated additive effects with these RAS blockers. In hypertensive rats under sodium restriction and enalapril, addition of aprocitentan further decreased BP without causing renal impairment, in contrast to spironolactone. In conclusion, ETA/ETB receptor antagonism represents a promising therapeutic approach to hypertension, especially with low-renin characteristics, and could be used in combination with RAS blockers, without increasing the risk of renal impairment.

Antihypertensive effects of Moringa oleifera leaf extract Lam. (Moringaceae) in NG-nitro-L-arginine-methyl ester-induced hypertensive rats

Background: The use of natural products such as Moringa oleifera (MO) for the improvement of resistance artery relaxation is a potential strategy for the prevention and treatment of hypertension. Aims and Objective: The present study was designed to evaluate the protective effect of MO hydro-ethanol extract on NG-nitro-L-arginine-methyl ester (L-NAME)-induced hypertension and the toxicity profile in Wistar rats and shrimp larvae. Materials and Methods: An experimental hypertensive model was established by administration of L-NAME at 40 mg/kg body weight (BW) by oral gavages to male Wistar rats for 2 weeks and treated with hydro-ethanol extract of MO leaves and losartan. The control group received distilled water. L-NAME group was treated with L-NAME and distilled water. L-NAME-Losartan group was treated with L-NAME and losartan at 100 mg/kg BW. L-NAME-MO group was treated with L-NAME and the hydroethanol extract of MO leaves at 500 mg/kg BW. Blood pressure (BP) was measured by tail cuff method. In vitro toxicity study of the extract was performed on Artemia salina larvae using a biological test for the determination of shrimp lethality. A 14 days acute oral toxicity study was evaluated in female rats on a single dose of 2000 mg/kg BW of hydro-ethanol extract of MO. Results: L-NAME treated rats developed significantly increased BP from 110.20 ± 4.46 mmHg to 159.60 ± 4.38 mmHg. Concurrent oral treatment with hydro-ethanol extract of MO leaves decreased the high BP from 159.60 ± 4.38 mmHg to 102.40 ± 5.07 mmHg. No harm was observed at the tested doses in vitro and in vivo toxicity studies. Conclusion: These findings suggest that MO leaves may be potentially useful as a natural product against hypertension.

Effects of hypertension and antihypertensive treatments on sulfatide levels in serum and its metabolism.

Serum sulfatides are critical glycosphingolipids present in lipoproteins that work as modulators of thrombosis and hemostasis. Decreased serum sulfatide levels are suggested by our previous work to be related to cardiovascular disease (CVD). Hypertension, known to be an important risk factor for CVD, may affect serum sulfatide levels. However, how hypertension affects serum sulfatides directly and mechanistically is unknown. To elucidate these possible mechanisms, we investigated changes in serum sulfatide levels and their metabolism using an established experimental model of hypertension that uses continuous infusion of angiotensin II (AngII) into mice. Furthermore, we also examined the effects of four different antihypertensive drugs (losartan, irbesartan, nifedipine, and hydralazine) on serum sulfatide metabolism. Serum levels of sulfatides were found to be decreased in groups in which only hypertension was induced (AngII only), whereas they were increased in groups with reduced blood pressure (antihypertensives only) and ameliorated to increasingly normal levels in groups with induced hypertension that were also treated (AngII+antihypertensives). Changes in serum sulfatides were strongly related to hepatic expression levels of cerebroside sulfotransferase (CST), which is a key enzyme involved in sulfatide synthesis. Furthermore, the current study suggests that the primary factors affecting CST expression are oxidative stress, peroxisome proliferator-activated receptor α activity and blood pressure itself. This study demonstrates that hypertension significantly decreases levels of serum sulfatides by reducing hepatic CST expression via various effects mediated by AngII. Antihypertensive treatments can ameliorate abnormalities in serum sulfatide levels and may partially prevent hypertension related CVD by positively affecting sulfatide metabolism.

Efficacy and safety of a novel nitric oxide generator for the treatment of neonatal pulmonary hypertension: Experimental and clinical studies

Persistent pulmonary hypertension of the newborn (PPHN) is a complex pathology resulting from a failure of the post-natal reduction in pulmonary vascular resistance leading to hypoxemia. The standard therapy is inhaled Nitric Oxide (NO) improving oxygenation but its availability is limited, especially in hospitals with restricted financial resources. We evaluated the efficacy and safety of a new device generating NO (TAS + PLUS), in three experimental piglet models of pulmonary hypertension (PH), and we later tested its application in a pilot study of newborn patients suffering from PPHN.Piglets with experimentally induced PH showed a decrease in pulmonary arterial pressure (PAP) after breathing NO. Both acute and chronic exposure of piglets and rats did not cause any adverse effect in blood gas levels and biological parameters. A pilot study including 32 patients suffering from PPHN showed an increase in oxygen saturation (SatO2) and partial pressure of oxygen in arterial blood (PaO2) leading to a decrease of Oxygenation Index (OI) after compassionate treatment with NO from TAS + PLUS device.The device showed effectiveness and safety both in experimental PH and in the clinical setting. Therefore, it represents an excellent alternative for PPHN management in conditions where commercial NO is unavailable.

Equilin displays similar endothelium-independent vasodilator potential to 17β-estradiol regardless of lower potential to inhibit calcium entry

Conjugated equine estrogens (CEE) have been widely used by women who seek to relieve symptoms of menopause. Despite evidence describing protective effects against risk factors for cardiovascular diseases by naturally occurring estrogens, little is known about the vascular effects of equilin, one of the main components of CEE and not physiologically present in women. In this regard, the present study aims to compare the vascular effects of equilin in an experimental model of hypertension with those induced by 17β-estradiol. Resistance mesenteric arteries from female spontaneously hypertensive rats (SHR) were used for recording isometric tension in a small vessel myograph. As effectively as 17β-estradiol, equilin evoked a concentration-dependent relaxation in mesenteric arteries from female SHRs contracted with KCl, U46619, PDBu or ET-1. Equilin-induced vasodilation does not involve classical estrogen receptor activation, since the estrogen receptor antagonist (ICI 182,780) failed to inhibit relaxation in U46619-precontracted mesenteric arteries. Vasorelaxation was not affected by either endothelium removal or by inhibiting the release or action of endothelium-derived factors. Incubation with L-NAME (NOS inhibitor), ODQ (guanylyl cyclase inhibitor) or KT5823 (inhibitor of protein kinase G) did not affect equilin-induced relaxation. Similarly, indomethacin (COX inhibitor) or blockage of potassium channels with tetraethylammonium, glibenclamide, 4-aminopyridine, or ouabain did not affect equilin-induced relaxation. Inhibitors of adenylyl cyclase SQ22536 or protein kinase A (KT5720) also had no effects on equilin-induced relaxation. While 17β-estradiol inhibited calcium (Ca2+) -induced contractions in high-K+ depolarization medium in a concentration-dependent manner, equilin induced a slight rightward-shift in the contractile responses to Ca2+. Comparable pattern of responses were observed in the concentration-response curves to (S)-(−)-Bay K 8644, a L-type Ca2+ channel activator. Equilin was unable to block the transitory contraction produced by caffeine-induced Ca2+ release from intracellular stores. In conclusion, equilin blocks L-type Ca2+ channels less effectively than 17β-estradiol. Despite its lower effectiveness, equilin equally relaxes resistance mesenteric arteries by blocking Ca2+ entry on smooth muscle.

Inflammation in Salt-Sensitive Hypertension and Renal Damage.

Low-grade inflammation drives elevations in blood pressure (BP) and consequent target organ damage in diverse experimental models of hypertension. Here, we discuss recent advances elucidating immune-mediated mechanisms of BP elevation and associated target organ damage. Inflammatory mediators produced by immune cells or target organs act on the kidney, vasculature, skin, and nervous system to modulate hypertension. For example, cells of the innate immune system, including monocytes, neutrophils, and dendritic cells (DCs), can all promote BP elevation via actions in the vasculature and kidney. Macrophages expressing VEGF-C impact non-osmotic sodium storage in the skin that in turn regulates salt sensitivity. Within the adaptive immune system, activated T cells can secrete tumor necrosis factor-alpha (TNF-α), interleukin-17a (IL-17a), and interferon-gamma (IFN-γ), each of which has augmented BP and renal damage in pre-clinical models. Inversely, deficiency of IL-17a in mice blunts the hypertensive response and attenuates renal sodium retention via a serum- and glucocorticoid-regulated kinase 1 (SGK1)-dependent pathway. Linking innate and adaptive immune responses, dendritic cells activated by augmented extracellular sodium concentrations stimulate T lymphocytes to produce pro-hypertensive cytokines. By contrast, regulatory T cells (Tregs) can protect against hypertension and associated kidney injury. Rodent studies reveal diverse mechanisms via which cells of the innate and adaptive immune systems drive blood pressure elevation by altering the inflammatory milieu in the kidney, vasculature, and brain.

Combined Aerobic and Resistance Exercise Training Improve Hypertension Associated With Menopause.

The prevalence of hypertension sharply increases in menopausal women. Recent studies have demonstrated that aerobic or resistance training may help control hypertension. In this study, we report that combining aerobic and resistance training may provide an effective therapeutic approach for hypertension control, attenuating inflammation and oxidative stress in ovariectomized rats. Female Wistar and spontaneous hypertensive rats (SHR) were distributed into four groups: sedentary control (C), sedentary hypertensive (HR), sedentary hypertensive ovariectomized (HR-O), and combined trained hypertensive ovariectomized (T-HR-O). Combined exercise training was performed on a motor treadmill (aerobic training) and on a ladder adapted to rats (resistance training), in alternate days for 8 weeks. Direct arterial pressure was recorded and oxidative stress and inflammation were evaluated in cardiac and renal tissue. Ovariectomy increases increased mean arterial blood pressure, sympathetic modulation, and oxidative stress in SHR. Combining aerobic and resistance training reduced mean arterial blood pressure (12% vs. HR-O), heart rate (8% vs. HR-O), vascular sympathetic modulation (40% vs. HR-O), and improved baroreflex sensitivity. Combined training reduced cardiac inflammation (TNF and IL-6) and cardiac and renal lipoperoxidation (59% and 57%, respectively vs. HR-O). It also enhanced cardiac (71%) and renal (76%) total antioxidant capacity when compared to HR-O group. In conclusion, combining aerobic and resistance training improves mean arterial blood pressure, cardiovascular autonomic control, preventing cardiac and renal oxidative stress and inflammation in an experimental hypertension model with surgical menopause induced with ovariectomy.