Development Of Hypertension In Rats Research Articles

MiR-1249 on Endothelial Extracellular Vesicles Mediates Cigarette Smoke-Induced Pulmonary Hypertension by Inhibiting HDAC10 (Histone Deacetylase 10)-NFκB (Nuclear Factor κB)-CaSR (Calcium-Sensing Receptor) Cascade.

Overproduction of endothelial extracellular vesicles (eEVs) is correlated with pulmonary hypertension progression, but the precise mechanism remains largely unclear. MicroRNA-chip and real-time polymerase chain reaction were conducted to screen and validate microRNA profiles in blood plasma eEVs of rats and human with or without cigarette smoking. Pulmonary artery smooth muscle cells were cultured to study signaling pathways. Pulmonary hypertension phenotypes were evaluated in wild-type and calcium-sensing receptor knockout rats to identify the pathophysiological significance of the microRNA pathway. MicroR-1249 was predominant highly expressed in eEVs from plasma of rats exposed to cigarette smoking, and confirmed in eEVs from plasma of human smokers as well as in eEVs from cigarette smoke extract-treated pulmonary artery endothelial cells, but not in cigarette smoke extract-treated pulmonary artery smooth muscle cells. In cultured pulmonary artery smooth muscle cells, microR-1249 downregulated the expression of histone deacetylase 10, which in turn enhanced the acetylated form of NFκB (nuclear factor κB) level and its nuclear translocation leading to increased expression of calcium-sensing receptor. In rats, the repression of microR-1249 in eEVs by microR-1249 inhibitor, histone deacetylase 10 overexpression, or calcium-sensing receptor knockout profoundly inhibited the proliferative capacities and diminished apoptosis-resistance of pulmonary artery smooth muscle cells and pulmonary hypertension development in rats intravenously administrated with eEVs preparation from cigarette smoke extract-treated pulmonary artery endothelial cells. Cigarette smoke-enriched microR-1249 in endothelial extracellular vesicles facilitates the hyperproliferative and antiapoptotic status of pulmonary artery smooth muscle cells promoting pulmonary hypertension evolution through the inhibition of histone deacetylase 10-NFκB-calcium-sensing receptor cascade.

Model difference in the effect of cilostazol on the development of experimental pulmonary hypertension in rats

BackgroundPreventing pulmonary vascular remodeling is a key strategy for pulmonary hypertension (PH). Causes of PH include pulmonary vasoconstriction and inflammation. This study aimed to determine whether cilostazol (CLZ), a phosphodiesterase-3 inhibitor, prevents monocrotaline (MCT)- and chronic hypoxia (CH)-induced PH development in rats.MethodsFifty-one male Sprague–Dawley rats were fed rat chow with (0.3% CLZ) or without CLZ for 21 days after a single injection of MCT (60 mg/kg) or saline. Forty-eight rats were fed rat chow with and without CLZ for 14 days under ambient or hypobaric (air at 380 mmHg) CH exposure. The mean pulmonary artery pressure (mPAP), the right ventricle weight-to-left ventricle + septum weight ratio (RV/LV + S), percentages of muscularized peripheral pulmonary arteries (%Muscularization) and medial wall thickness of small muscular arteries (%MWT) were assessed. Levels of the endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (peNOS), AKT, pAKT and IκB proteins in lung tissue were measured using Western blotting. Monocyte chemotactic protein (MCP)-1 mRNA in lung tissue was also assessed.ResultsmPAP [35.1 ± 1.7 mmHg (MCT) (n = 9) vs. 16.6 ± 0.7 (control) (n = 9) (P < 0.05); 29.1 ± 1.5 mmHg (CH) (n = 10) vs. 17.5 ± 0.5 (control) (n = 10) (P < 0.05)], RV/LV + S [0.40 ± 0.01 (MCT) (n = 18) vs. 0.24 ± 0.01 (control) (n = 10) (P < 0.05); 0.41 ± 0.03 (CH) (n = 13) vs. 0.27 ± 0.06 (control) (n = 10) (P < 0.05)], and %Muscularization and %MWT were increased by MCT injection and CH exposure. CLZ significantly attenuated these changes in the MCT model [mPAP 25.1 ± 1.1 mmHg (n = 11) (P < 0.05), RV/LV + S 0.30 ± 0.01 (n = 14) (P < 0.05)]. In contrast, these CLZ effects were not observed in the CH model. Lung eNOS protein expression was unchanged in the MCT model and increased in the CH model. Lung protein expression of AKT, phosphorylated AKT, and IκB was downregulated by MCT, which was attenuated by CLZ; the CH model did not change these proteins. Lung MCP-1 mRNA levels were increased in MCT rats but not CH rats.ConclusionsWe found model differences in the effect of CLZ on PH development. CLZ might exert a preventive effect on PH development in an inflammatory PH model but not in a vascular structural change model of PH preceded by vasoconstriction. Thus, the preventive effect of CLZ on PH development might depend on the PH etiology.

Peptide Blocking Self-Polymerization of Extracellular Calcium-Sensing Receptor Attenuates Hypoxia-Induced Pulmonary Hypertension.

[Figure: see text].

Baicalin prevents pulmonary arterial remodeling in vivo via the AKT/ERK/NF-κB signaling pathways.

Pulmonary arterial hypertension is a rapidly progressive and often fatal disease. As the pathogenesis of pulmonary arterial hypertension remains unclear, there is currently no good drug for pulmonary arterial hypertension and new therapy is desperately needed. This study investigated the effects and mechanism of baicalin on vascular remodeling in rats with pulmonary arterial hypertension. A rat pulmonary arterial hypertension model was constructed using intraperitoneal injection of monocrotaline, and different doses of baicalin were used to treat these rats. The mean pulmonary arterial pressure (mPAP) and right ventricular systolic pressure (RVSP) were measured with a right heart catheter. Moreover, the hearts were dissected to determine the right ventricular hypertrophy index (RVHI). The lung tissues were stained with H&E and Masson's staining to estimate the pulmonary vascular remodeling and collagen fibrosis, and the expression of proteins in the AKT, ERK, and NF-κB p65 phosphorylation (p-AKT, p-ERK, p-p65) was examined by Western blot analysis. We found that compared with untreated pulmonary arterial hypertension rats, baicalin ameliorated pulmonary vascular remodeling and cardiorespiratory injury, inhibited p-p65 and p-ERK expression, and promoted p-AKT and p-eNOS expression. In conclusion, baicalin interfered with pulmonary vascular remodeling and pulmonary arterial hypertension development in rats through the AKT/eNOS, ERK and NF-κB signaling pathways.

DL0108 suppresses the development of pulmonary arterial hypertension in rats through its protective effect on pulmonary arteries

BackgroundPulmonary arterial hypertension (PAH) is a severe disease but in short of an effective drug. DL0108 is a flavonoid discovered by our lab, and is recently found useful in the treatment of PAH. The present study aims to evaluate the potency of DL0108 in PAH rats induced by monocrotaline (MCT).MethodThe PAH rat model was established by subcutaneous injection of 50 mg/kg MCT on day 0. From the second day, 3, 10, or 30 mg/kg DL0108 was respectively administrated (i.p.) daily for 4 weeks in three tested groups, while the model and control group were treated with normal saline. During the experiment, the survival rate and body weight were recorded. At the end of the study, the right ventricular systolic pressure (RVSP) was measured through right cardiac catheterization. The heart ventricle was isolated to calculate the Fulton index (RV/LV+S). The contraction and relaxation of pulmonary artery rings were tested in a classical isolated vessel experiment.ResultOn day 28, the survival rate of the model group was 66.7%. Treatment with 3, 10, or 30 mg/kg DL0108 increased the survival rate to 73.3%, 86.7% and 86.7%, respectively. However, the decrease of body weight induced by PAH was not improved by DL0108. The RVSP of PAH rats in the model group increased from 21.73 to 49.61 mmHg, while the treatment with DL0108 reduced the RVSP to 30.56, 27.42 or 24.9 mmHg, respectively. Meanwhile, DL0108 significantly reduced the right ventricular hypertrophy in a dose‐dependent manner. In the isolated vessel experiment, it was found that 3 and 10 mg/kg DL0108 improved the contraction response of pulmonary artery rings to 10−6 M phenylephrine and the relaxant effect induced by the accumulation of acetylcholine (10−8–10−4 M Ach).ConclusionEarly intervention of PAH rats with DL0108 can delay the progression of the disease and increase the survival rate. The preliminary study indicates that DL0108 protects the function of pulmonary arteries, relieves the remodeling of vessels to control the pressure, and in turn attenuates the injury of heart ventricle. This study contributes to the further development of DL0108 for the treatment of PAH.Support or Funding InformationThis project was supported by grants from the Nation Natural Science Foundation of China (No. 81603101, 81773935, 81573645), Natural Science Foundation of Beijing (No. 7174322) and CAMS Innovation Fund for Medical Sciences (2016‐I2M‐1‐010, 2017‐I2M‐1‐010). The survival rates of PAH rats treated by DL0108.imageThe survival rates of PAH rats treated by DL0108.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Examining the Role of Gut Dysbiosis in Neuroinflammation and Hypertension in a Model of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA), characterized by repeated closure of the upper airway during sleep, is a significant clinical problem and an independent risk factor for systemic hypertension. The importance of a healthy gut microbiota, and detriment of a dysbiotic microbiota, on host physiology is becoming increasingly evident. We have previously demonstrated that gut dysbiosis is associated with the development of hypertension in a rat model of OSA. Transplanting the dysbiotic microbiota from a hypertensive OSA rat into a normotensive rat induces hypertension, demonstrating a causal relationship between gut dysbiosis and hypertension. The mechanisms linking gut dysbiosis to hypertension are unknown. We tested the hypothesis that OSA‐induced gut dysbiosis impairs gut barrier function, causing systemic inflammation and neuroinflammation, which is linked to hypertension. Using an in vivo model of OSA, we exposed high fat fed rats to 2 weeks of sham or OSA (60 apneas/hr). Relative to sham rats, OSA led to a significant increase in TNFα mRNA expression in the cecum wall as well as decreased goblet cells/crypt in the cecum and colon (n=6, p&lt;0.05). OSA resulted in a 3‐fold increase in gut permeability (n=6, p&lt;0.05). Consistent with impaired gut barrier function and bacterial translocation, we observed increased bacterial 16S rRNA signatures in the mesenteric lymph node and visceral adipose tissue following OSA (n=4–7, p&lt;0.05). Flow cytometric analysis using whole brain revealed a significant increase in the number of activated microglia following OSA (n=4–6, p&lt;0.05). Short chain fatty acids play a key role in maintaining gut barrier integrity and regulating immune responses. We found that OSA significantly reduced the acetate concentraction in the cecum (n=5, p&lt;0.05). To increase short chain fatty acid production in the gut, rats were treated with a prebiotic (diet enriched with 20% resistant starch), or probiotic (Clostridium butyricum; 109 CFU by gavage every three days) during the 2 weeks of sham or OSA. Pre‐ and probiotics each prevented OSA‐induced decrease in cecal acetate concentration, prevented OSA‐induced loss of goblet cells, and prevented increased TNFα expression in the cecum of OSA rats (n=5–6, p&lt;0.05 for each). Additionally, pre‐ and probiotics prevented OSA‐induced activation of microglia in brain (n=6–8, p&lt;0.05). Importantly, both the pre‐ and probiotic successfully prevented the development of hypertension in OSA rats. To test the direct effects of acetate, we chronically infused 20μmol/(kg‐min) acetate into the cecum during the 2 weeks of sham or OSA. Cecal acetate infusion prevented OSA‐induced hypertension. These data demonstrate a causal role for gut dysbiosis in the development of hypertension, which involves reduced acetate production, gut barrier disruption, bacterial translocation, and neuroinflammation. Our data suggest that manipulation of the gut microbiota may serve as a novel therapy in the prevention of hypertension.Support or Funding InformationThis project was funded by NINDS R01NS080531 (RMB), AHA 16SDG29970000 (DJD), and by Public Health Service grant DK56338, which funds the Texas Medical Center Digestive Diseases Center (DJD).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Diagnostics of erythrocytes' microrheological features and early abnormalities of rats in the model of experimental hypertension development

Difficulties of the earliest stages' detection of erythrocytes' microrheological abnormalities' development at hypertension are connected with falling out of clinicians' field of view of persons with first signs of this pathology. It dictates the necessity of experimental investigations' fulfillment on laboratory animals with just developed hypertension in them. 87 of healthy male-rats of Vistar line at the age of 2,5-3 months were taken into investigation. 29 animals of them had experienced no impacts and composed the control group. 58 rats had hypertension developed by prescribing them cardioangionefopathogenic semisynthetic diet. There were used biochemical, hematological and statistical methods of investigation. As the result of hypertension development the rats turned out to have stable developing increase of systolic and diastolic pressure. At regular exercise on the treadmill the rats were noted to have gradual decrease of their values during 60 days of investigation to the level of norm. During hypertension development lipids' peroxidation activated in rats' erythrocytes because of activity weakening of their antioxidant protection. At hypertension development in rats there was found reliable decrease of erythrocytes-discocytes quantity in blood. It was accompanied by increase of reversibly and irreversibly changed erythrocytes' quantity in examined animals' blood. At hypertension development in rats there was found quick rise of erythrocytes' sum in aggregate and these aggregates' quantity at lowering of free erythrocytes' number. During experimental hypertension modelling we noticed very early in rats' blood decrease of erythrocytes-discocytes' quantity, level rise of their reversibly and irreversibly varieties with strengthening of their aggregative ability. It takes place on the background of weakening of erythrocytes' antioxidant protection and activation of lipids' peroxidation in them.

The Role of Gut Dysbiosis in Obstructive Sleep Apnea Induced Hypertension

Obstructive sleep apnea (OSA), characterized by repeated closure of the upper airway during sleep, is a significant clinical problem. OSA is an independent risk factor for systemic hypertension, and the most common underlying cause of resistant hypertension. The importance of a healthy gut microbiota, and detriment of a dysbiotic microbiota, on host physiology is becoming increasingly evident. We have previously observed that gut dysbiosis is associated with the development of hypertension in a rat model of OSA. Furthermore we have shown that transplantation of the dysbiotic microbiota from a hypertensive OSA rat into a normotensive rat is capable of inducing hypertension. These studies demonstrate, for the first time, a causal relationship between gut dysbiosis and hypertension. The mechanisms linking gut dysbiosis to hypertension are unknown. We tested the hypothesis that OSA‐induced gut dysbiosis leads to impaired gut barrier function, systemic inflammation, and inflammation of the brain, which is linked to hypertension. Using an in vivo model of OSA, we exposed high fat fed rats to 2 weeks of sham or OSA (60 apneas/hr). Relative to sham rats, OSA led to a significant increase in TNFα mRNA expression in the cecum wall as well as decreased goblet cells/crypt in the cecum and colon (n=4, p&lt;0.05). Consistent with impaired gut barrier function and bacterial translocation, we observed bacterial 16S rRNA signatures in the mesenteric lymph node and visceral adipose tissue, as well as elevated adipose IL‐6 mRNA expression following OSA (n=4–7, p&lt;0.05). Flow cytometric analysis revealed a significant decrease in the number of anti‐inflammatory T‐regulatory cells in the brain of OSA vs. sham rats. This was associated with an increase in the number of activated microglia following OSA (n=3, p&lt;0.05). Short chain fatty acids play a key role in maintaining gut barrier integrity and regulating immune responses. To further examine the role of gut dysbiosis in the development of OSA‐induced hypertension we treated sham and OSA rats with a prebiotic (diet enriched with 20% resistant starch) or probiotic (Clostridium butyricum; 109 CFU by gavage every three days) to increase short chain fatty acids and improve gut barrier function. Pre‐ and probiotics successfully prevented OSA‐induced loss of goblet cells and TNFα expression in the cecum and colon. Compared to vehicle treated rats, the probiotic C. butyricum prevented the OSA‐induced increase in adipose IL‐6 expression, increased total T‐regulatory cells in the brain, and decreased activated microglia (n=3–6, p&lt;0.05). Importantly, both the pre‐ and probiotic successfully prevented the development of hypertension in OSA rats. These data demonstrate a causal role for gut dysbiosis in the development of hypertension, which involves gut barrier disruption, bacterial translocation, and brain inflammation. Our data suggest that manipulation of the gut microbiota, through pre‐ or probiotics, may serve as a novel therapy in the prevention of hypertension.Support or Funding InformationNINDS R01NS080531 (RMB), PHS DK56338 and AHA 16SDG29970000 (DJD)

ANTXR2 Knock-Out Does Not Result in the Development of Hypertension in Rats.

Our recent genetic study as well as robust evidences reported by previous genome-wide association studies (GWASs) have indicated that the single nucleotide polymorphism rs16998073, located near gene anthrax toxin receptor 2 (ANTXR2), was significantly associated with hypertension in Asians and Europeans. The aim of the present study was to determine whether ANTXR2 is the causal gene of hypertension at the 4q21 locus using an ANTXR2 knock-out model. Relative expression of ANTXR2 in Wistar-Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) were determined by real-time quantitative polymerase chain reaction and western blot analysis. ANTXR2 knock-out rats were created using CRISPR/Cas9-mediated genome editing and blood pressure values were measured in ANTXR2-/- and wild type (WT) rats by tail-cuff method and carotid arterial catheterization method. Neither the mRNA nor protein levels of ANTXR2 were significantly different between tissues from SHRs and WKYs. To create ANTXR2-/- rats, 67 base pairs were deleted in exon 1 of ANTXR2 using CRISPR/Cas9-mediated genome editing. ANTXR2 protein decreased significantly in aortas of ANTXR2-/- rats, suggesting sufficient efficiency of ANTXR2 knock-out in this model. However, ANTXR2-/- rats exhibited nearly the same blood pressure as WT rats at baseline conditions as well as during Angiotensin II (400ng/kg/min) infusion or high-salt diet treatment. These findings suggest that ANTXR2 might not be associated with hypertension and thus further functional analysis is warranted to identify the causal gene at this locus.

OS 11-03 Role of renal nervous activity in the development of renovascular hypertension in rats

OS 11-03 Role of renal nervous activity in the development of renovascular hypertension in rats

Renal denervation attenuates NADPH oxidase-mediated oxidative stress and hypertension in rats with hydronephrosis.

Hydronephrosis is associated with the development of salt-sensitive hypertension. Studies have suggested that increased sympathetic nerve activity and oxidative stress play important roles in hypertension and the modulation of salt sensitivity. The present study primarily aimed to examine the role of renal sympathetic nerve activity in the development of hypertension in rats with hydronephrosis. In addition, we aimed to investigate if NADPH oxidase (NOX) function could be affected by renal denervation. Partial unilateral ureteral obstruction (PUUO) was created in 3-wk-old rats to induce hydronephrosis. Sham surgery or renal denervation was performed at the same time. Blood pressure was measured during normal, high-, and low-salt diets. The renal excretion pattern, NOX activity, and expression as well as components of the renin-angiotensin-aldosterone system were characterized after treatment with the normal salt diet. On the normal salt diet, rats in the PUUO group had elevated blood pressure compared with control rats (115 ± 3 vs. 87 ± 1 mmHg, P < 0.05) and displayed increased urine production and lower urine osmolality. The blood pressure change in response to salt loading (salt sensitivity) was more pronounced in the PUUO group compared with the control group (15 ± 2 vs. 5 ± 1 mmHg, P < 0.05). Renal denervation in PUUO rats attenuated both hypertension (97 ± 3 mmHg) and salt sensitivity (5 ± 1 mmHg, P < 0.05) and normalized the renal excretion pattern, whereas the degree of renal fibrosis and inflammation was not changed. NOX activity and expression as well as renin and ANG II type 1A receptor expression were increased in the renal cortex from PUUO rats and normalized by denervation. Plasma Na(+) and K(+) levels were elevated in PUUO rats and normalized after renal denervation. Finally, denervation in PUUO rats was also associated with reduced NOX expression, superoxide production, and fibrosis in the heart. In conclusion, renal denervation attenuates hypertension and restores the renal excretion pattern, which is associated with reduced renal NOX and components of the renin-angiotensin-aldosterone system. This study emphasizes a link between renal nerves, the development of hypertension, and modulation of NOX function.

Abstract 11711: Valproic Acid, a Class [[Unable to Display Character: &amp;#1030;]] Histone Deacetylase Inhibitor, Suppresses the Development of Severe Pulmonary Hypertension in Rats

Introduction: Pulmonary hypertension (PH) is a progressive vascular remodeling disease characterized by exuberant cell proliferation, apoptosis resistance, and inflammation that contributes to increased pulmonary arterial resistance. Histone deacetylases (HDACs) and histone acetyltransferases shift acetyl groups from histone and non-histone proteins and enhance gene transcription by post-translational modifications. Valproic acid, a class I HDAC inhibitor, is a widely used antiepileptic drug with low toxicity and also shows supportive efficacy in cancer treatment by inhibiting cancer cell proliferation and inflammation. Hypothesis: We assessed the hypothesis that HDAC inhibition may attenuate excessive cell proliferation and inflammation and improve vascular remodeling in a severe PH rat model. Methods: To compare the development of vascular remodeling, we assessed 6 rats that underwent a single monocrotaline injection, chronic hypoxic exposure, or a combination of both treatments. Valproic acid or vehicle was administered in rats with severe PH induced by the combination method to assess whether valproic acid has the ability to prevent severe PH development in the first 3 weeks or to reverse disease progression at 3-5 weeks. Results: The combination method induced PH of greater severity than that induced by any single stimulation in rats after 3 weeks. Compared with the vehicle-treated rats, valproic acid treatment blocked the elevation of right ventricular systolic pressure and right ventricle hypertrophy index (from 57 ± 3 to 49 ± 3 mmHg and from 46 ± 4 to 37 ± 3 %) in both the first 3 weeks and in the late treatment group (from 75 ± 2 to 61 ± 5mmHg and from 61 ± 7 to 48 ± 3 %, respectively; P &lt; 0.01). Valproic acid attenuated the muscularization ratio of peripheral pulmonary vascular, repressed proliferation and inflammation marker expression (PCNA and ED1), and enhanced apoptosis (cleaved caspase 3) in severe PH rats. Conclusions: These data indicate that a selective HDAC inhibitor may be effective in the treatment of PH.

Renal Nerve Ablation for Resistant Hypertension

Sympathetic renal denervation, or renal nerve ablation (RNA), has become the new buzz word in hypertension and interventional cardiology. Recent advances in catheter-based approaches have allowed sympathetic fiber interruption through transvascular techniques that are minimally invasive and can be delivered expeditiously and safely. Radiofrequency (RF) energy sources are currently the preferred modalities, but other sources of energy, such as cryoablation, microwave, high-intensity focus ultrasound, and local neurotoxic agent infusion, are under intense investigation. Results thus far have been encouraging and offer promise for the future. The role of the sympathetic nervous system (SNS) in the development of resistant hypertension and cardiovascular disease has long been known, and a great deal of work has been done through the years trying to explore potential interventions to interrupt the sympathetic influence on systemic vasculature and target organs. In this article we attempt an overview of time-dependent interventions on the SNS and examine approaches used in humans and in the many experimental models that offer a better understanding of the role of sympathetic activity in cardiovascular disease. Naturally we focus on methods and techniques addressing sympathetic renal denervation in patients with drug-resistant hypertension, examine the current state of the art, and attempt a look into the future. In 1889, after meticulous experiments on dogs, Bradford1 reported that stimulation of dorsal and splanchnic nerves causes changes in blood pressure (BP) and kidney size measured by plethysmography. Whether BP increased or decreased depended on the anatomic area stimulated, as well as the electric impulse frequency, but outcomes were consistent and reproducible. Neurosurgical treatment of hypertension was independently suggested by researchers in 1923.2 Adson, however, was the first to performed surgical sympathectomy for the treatment of malignant hypertension in 1925.3 During the following years and in the 1930s, Peet in Ann Arbor, Page and …

Effect of Captopril and Melatonin on Fibrotic Rebuilding of the Aorta in 24 Hour Light-Induced Hypertension

Chronic continuous light exposure leads to melatonin deficiency along with complex neurohumoral activation resulting in hypertension development in rats. The aim of this study was to show, whether continuous light induces fibrotic rebuilding of the aorta and whether the treatment with melatonin or angiotensin converting enzyme inhibitor captopril can prevent these potential alterations. In a six-week experiment, 3-month-old Wistar rats were divided into 4 groups (ten per group): controls, rats exposed to continuous light, exposed to continuous light plus treated with captopril (100 mg/kg/24 h) and exposed to continuous light plus treated with melatonin (10 mg/kg/24 h). Systolic blood pressure (SBP) and collagen type I and III in the media of thoracic aorta were measured. Continuous light induced hypertension and fibrotic rebuilding of the aorta in terms of enhancement of collagen I and III concentration in the aortic media. Both captopril and melatonin prevented SBP rise and reduced collagen III concentration in the aorta. However, only melatonin reduced collagen I and the sum of collagen I and III in the aortic tissue. We conclude that in continuous light-induced hypertension, administration of melatonin, along with SBP reduction, decreases collagen I and III concentration in the aorta. It is suggested that antifibrotic effect of melatonin may reduce the stiffness of the aorta and small arteries and beneficially influence the nature of the pulse wave and peripheral vascular resistance.

Cyclooxygenase-1 inhibition attenuates angiotensin II-salt hypertension and neurogenic pressor activity in the rat

Cyclooxygenase (COX)-derived prostanoids contribute to angiotensin II (ANG II) hypertension (HTN). However, the specific mechanisms by which prostanoids act are unclear. ANG II-induced HTN is caused partly by increased sympathetic nervous system activity, especially in a setting of high dietary salt intake. This study tested the hypothesis that COX-derived prostanoids cause ANG II-salt sympathoexcitation and HTN. Experiments were conducted in conscious rats. Infusion of ANG II (150 ng·kg(-1)·min(-1) sc) caused a marked HTN in rats on 2% salt diet, but a much smaller increase in blood pressure in rats on 0.4% salt diet. The nonselective COX inhibitor ketoprofen (2 mg/kg sc) given throughout the ANG-II infusion period attenuated HTN development in rats on 2% NaCl diet, but not in rats on 0.4% NaCl diet. The acute depressor response to ganglion blockade was used to assess neurogenic pressor activity in rats on 2% NaCl diet. Ketoprofen-treated rats showed a smaller fall in arterial pressure in response to ganglion blockade during ANG-II infusion than did nontreated controls. In additional experiments, ketoprofen-treated rats exhibited smaller increases in plasma norepinephrine levels and whole body norepinephrine spillover than we previously reported in ANG II-salt HTN. Finally, the effects of the selective COX-1 inhibitor SC560 (10 mg·kg(-1)·day(-1) ip) and the selective COX-2 inhibitor nimesulide (10 mg·kg(-1)·day(-1) ip) were investigated. Treatment with SC560 but not nimesulide significantly reduced blood pressure and the depressor response to ganglion blockade in ANG II-salt HTN rats. The results suggest that COX-1 products are critical for sympathoexcitation and the full development of ANG II-salt HTN in rats.

Estrogen Metabolite 2-methoxyestradiol Prevents Hypertension in Deoxycorticosterone Acetate-salt Rats

Our early work showed that the estrogen metabolite 2-methoxyestradiol (2ME) inhibits proliferation of vascular smooth muscle cells (SMCs) and vascular contractility through an endothelium-dependent mechanism. The aim of this study was to examine whether 2ME prevents the development of hypertension in rats. A hypertensive model was established in uninephrectomized rats using deoxycorticosterone acetate (DOCA)-salt. Blood pressure in response to 2ME (treatment up to 10 weeks or single bolus) was monitored. Our results showed that systolic blood pressure, as measured by tail-cuff plethysmography, was significantly increased in conscious rats treated with DOCA-salt for 3-10 weeks. Co-treatment with 2ME (100-300 μg/kg), but not dimethyl sulfoxide (DMSO), completely prevented the increase in blood pressure of DOCA-salt rats. After 10-week treatment, the mean arterial blood pressure (MABP) of anesthetized rats measured using PowerLab Data Acquisition System was: 84 ± 16 mmHg in normotensive control rats and 150 ± 9 mmHg in DOCA-salt rats, which was similar to that of DMSO-treated rats. Treatment with 2ME at low or high doses reduced MABP of DOCA-salt rats close to that of control normotensive rats. In addition, MABP of hypertensive DOCA-salt rats was significantly reduced in response to a single injection of 2ME. Delayed administration of 2ME reduced the further increase of blood pressure in DOCA-salt rats. However, inhibition of 2ME production by entacapone did not significantly affect blood pressure in either control or DOCA-salt rats. 2ME treatment prevents the development of hypertension in DOCA-salt rats, implicating a therapeutic potential of 2ME in hypertension treatment.

The role of repeatedly heated soybean oil in the development of hypertension in rats: association with vascular inflammation

Thermally oxidized oil generates reactive oxygen species that have been implicated in several pathological processes including hypertension. This study was to ascertain the role of inflammation in the blood pressure raising effect of heated soybean oil in rats. Male Sprague-Dawley rats were divided into four groups and were fed with the following diets, respectively, for 6months: basal diet (control); fresh soybean oil (FSO); five-time-heated soybean oil (5HSO); or 10-time-heated soybean oil (10HSO). Blood pressure was measured at baseline and monthly using tail-cuff method. Plasma prostacyclin (PGI(2) ) and thromboxane A(2) (TXA(2) ) were measured prior to treatment and at the end of the study. After sixmonths, the rats were sacrificed, and the aortic arches were dissected for morphometric and immunohistochemical analyses. Blood pressure was increased significantly in the 5HSO and 10HSO groups. The blood pressure was maintained throughout the study in rats fed FSO. The aortae in the 5HSO and 10HSO groups showed significantly increased aortic wall thickness, area and circumferential wall tension. 5HSO and 10HSO diets significantly increased plasma TXA(2) /PGI(2) ratio. Endothelial VCAM-1 and ICAM-1 were significantly increased in 5HSO, as well as LOX-1 in 10HSO groups. In conclusion, prolonged consumption of repeatedly heated soybean oil causes blood pressure elevation, which may be attributed to inflammation.

Angiotensin-(1–7) upregulates central nitric oxide synthase in spontaneously hypertensive rats

Increased blood pressure in hypertension is hypothesized to be caused by high sympathetic nervous system (SNS) activity. Since Ang (1–7) exerts an inhibitory neuromodulatory effect on the SNS through a NO-mediated mechanism, we tested the hypothesis that Ang (1–7) alters centrally nitric oxide synthase (NOS) activity and expression in spontaneously hypertensive rats (SHR). Since NOS activity is altered in relation to the development of hypertension in rats, we evaluated the effect of Ang-(1–7) on hypothalamic NOS activity in two different ages in SHR, corresponding to a prehypertensive phase (3–4weeks) and a established hypertension (13–14weeks) and compared with age-matched Wistar-Kyoto (WKY) rats. NOS activity was measured by the conversion of [3H]l-arginine to citrulline . Ang-(1–7) caused an impairment in NOS activity in prehypertensive SHR (26±4% reduction), while it induced an increase in NOS activity at established hypertension (48±9% increase). In contrast, Ang-(1–7) did not modify NOS activity in age-matched WKY rats. In another set of experiments, Ang-(1–7) was injected into the anterior hypothalamic area, mean arterial blood pressure (MAP) was registered and after 30, 60 and 180min nNOS expression was evaluated by Western-blot. Ang-(1–7) decreased MAP after 10min of injection and this effect was blocked by a NOS inhibitor. nNOS expression increased after 180min of Ang-(1–7) intrahypothalamic injection in both WKY and SHR (WKY: 3.6-fold increase above basal; SHR: 1.85-fold increase above basal). Our results suggest that Ang-(1–7) upregulates hypothalamic NOS in a hypertensive state as a compensatory and protective mechanism to combat hypertension.

Simvastatin protects against the development of monocrotaline-induced pulmonary hypertension in rats via a heme oxygenase-1–dependent pathway

ABSTRACTHeme oxygease-1 (HO-1) is the rate-limiting enzyme in heme catabolism. Induction of HO-1 has been shown to have vasodilatory, anti-inflammatory, and proapoptotic effects. More recently, experimental studies suggested the potential of simvastatin as a novel therapy for pulmonary hypertension (PH); however, the underlying mechanism remains to be investigated. The aim of this study was to evaluate whether HO-1 is required for the pulmonary vascular protective effects of simvastatin. Simvastatin (2 mg/kg/day) was administered once daily to rats for 4 weeks after monocrotaline (MCT) injection. Zn-protoporphyrin (Znpp), a potent inhibitor of HO, was used to confirm the role of HO-1. The hemodynamic changes, right heart hypertrophy, interleukin-6 (IL-6) level, and HO-1 protein expression in lungs were measured at day 28. Simvastatin significantly ameliorated mean pulmonary arterial hypertension (20.6 mm Hg). In addition, perivascular infiltration of inflammatory cells and the level of IL-6 were decreased in simvastatin treatment group. Simvastatin also increased significantly lung HO-1 protein expression. Inhibiting HO-1 using Znpp resulted in a loss of the effect of simvastatin in MCT rats. These results suggest that HO-1 expression is critical for the vascular protective effects of simvastatin in MCT-induced PH rats.

Progressive increase in renal sympathetic nerve activity during development of cold-induced hypertension in rats

Progressive increase in renal sympathetic nerve activity during development of cold-induced hypertension in rats