Spontaneously Hypertensive Rats Animals Research Articles

Non-clinical investigations about cytotoxic and anti-platelet activities of gamma-terpinene.

Gamma-terpinene (γ-TPN) is a cyclohexane monoterpene isolated from plant essential oils, such as tea tree (Melaleuca alternifolia), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis L.), thyme (Thymus vulgaris Marchand), and eucalyptus (Eucalyptus sp.). Terpenes are widely studied molecules pharmacologically active on the cardiovascular system, hemostasis, and antioxidant actions. Herein, it was investigated the cytotoxic and antiplatelet activity of γ-TPN using different non-clinical laboratory models. For in silico evaluation, the PreADMET, SwissADME, and SwissTargetPrediction softwares were used. Molecular docking was performed using the AutoDockVina and BIOVIA Discovery Studio databases. The cytotoxicity of γ-TPN was analyzed by the MTT assay upon normal murine endothelial SVEC4-10 and fibroblast L-929 cells. Platelet aggregation was evaluated with platelet-rich (PRP) and platelet-poor (PPP) plasma from spontaneously hypertensive rats (SHR), in addition to SVEC4-10 cells pre-incubated with γ-TPN (50, 100, and 200 µM) for 24 h. SHR animals were pre-treated by gavage with γ-TPN for 7 days and divided into four groups (negative control, 25, 50, and 100 mg/kg). Blood samples were collected to measure nitrite using the Griess reagent. Gamma-TPN proved to be quite lipid-soluble (Log P = +4.50), with a qualified profile of similarity to the drug, good bioavailability, and adequate pharmacokinetics. It exhibited affinity mainly for the P2Y12 receptor (6.450 ± 0.232 Kcal/mol), moderate cytotoxicity for L-929 (CC50 = 333.3 µM) and SVEC 4-10 (CC50 = 366.7 µM)cells. The presence of γ-TPN in SVEC 4-10 cells was also able to reduce platelet aggregation by 51.57 and 44.20% at lower concentrations (50 and 100 µM, respectively). Then, γ-TPN has good affinity with purinergic receptors and an effect on the reversal of platelet aggregation and oxidative stress, being promising and safe for therapeutic targets and subsequent studies on the control of thromboembolic diseases.

Differential expression of alpha-synuclein in the hippocampus of SHR and SLA16 isogenic rat strains

Two inbred strains, Lewis (LEW) and Spontaneously Hypertensive Rats (SHR), are well-known for their contrasting behavior related to anxiety/emotionality. Studies with these two strains led to the discovery of the Quantitative Trait Loci (QTL) on chromosome 4 (Anxrr16). To better understand the influences of this genomic region, the congenic rat strain SLA16 (SHR.LEW-Anxrr16) was developed. SLA16 rats present higher hyperactivity/impulsivity, deficits in learning and memory, and lower basal blood pressure than the SHR strain, even though genetic differences between them are only in chromosome 4. Thus, the present study proposed the alpha-synuclein and the dopaminergic system as candidates to explain the differential behavior of SHR and SLA16 strains. To accomplish this, beyond the behavioral analysis, we performed (I) the Snca gene expression and (II) quantification of the alpha-synuclein protein in the hippocampus (HPC), prefrontal cortex (PFC), and striatum (STR) of SHR and SLA16 strains; (III) sequencing of the 3′UTR of the Snca gene; and (IV) evaluation of miRNA binding in the 3′UTR site. A Single Nucleotide Polymorphism (SNP) was identified in the 3′UTR of the Snca gene, which exhibited upregulation in the HPC of SHR compared to SLA16 females. Alpha-synuclein protein was higher in the HPC of SHR males compared to SLA16 males. The results of this work suggested that differences in alpha-synuclein HPC content could be influenced by miRNA regulation and associated with behavioral differences between SHR and SLA16 animals.

P2X7 receptor antagonist improves gastrointestinal disorders in spontaneously hypertensive rats.

The purinergic system participates in the control of blood pressure. Hypertension promotes the occurrence of gastrointestinal disorders such as intestinal inflammation and gastric emptying delay. This study aimed i) to investigate the participation of the P2X7 receptor blocker Brilliant Blue G (BBG) on gastric emptying of solids and changes in oxidative stress in the gastric fundus, duodenum, and colon of spontaneously hypertensive rats (SHR) and ii) to study the putative relationship of this effect with the renin-angiotensin system. Rats were divided into five groups: Control, SHR, SHR+BBG, SHR+BBG+ATP, and SHR+BBG+ANG II. In the gastrointestinal tract, we assessed gastric emptying (GE) and oxidative stress markers (NOx, MPO, GSH, SOD). We observed a decrease in the GE rate (P<0.05) in SHR vs control rats (21.8±2.0% vs 42.8±3.5%). The decrease in GE was returned (P<0.05) to control levels by BBG in SHR rats (21.8±2.0% vs 41.6±3.2%). Co-administration of ATP or ANG II together with BBG bypassed the effect of the P2X7 antagonist on GE in SHR (P<0.05) (21.9±5.0% vs 25.6±3.0% vs 41.6±3.2%). The MPO activity increased (P<0.05) in the gastric fundus of SHR compared to control rats (6.12±2.26 vs 0.077±0.02 UMPO/mg tissue); this effect was prevented (P<0.05) by BBG (0.55±0.15 vs 6.12±2.26 UMPO/mg tissue). Data demonstrated that blockage of P2X7 receptors with BBG can improve the GE delay and oxidative stress biomarkers in SHR animals. This preventive effect of BBG on GE delay was abrogated by ANG II and ATP, thus prompting crosstalk between renin-angiotensin and the purinergic signaling systems underlying this phenomenon.

VH-4-A Bioactive Peptide from Soybean and Exercise Training Constrict Hypertension in Rats through Activating Cell Survival and AMPKα1, Sirt1, PGC1α, and FoX3α.

Hypertension is a chronic disease related to age, which affects tens of millions of people around the world. It is an important risk factor that causes myocardial infarction, heart failure, stroke, and kidney damage. Bioactive peptide VHVV (VH-4) from soybean has shown several biological activities. Physical exercise is a cornerstone of non-pharmacologic treatment for hypertension and has established itself as an effective and complementary strategy for managing hypertension. The present study evaluates the efficacy of VH-4 supplement and swimming exercise training in preventing hypertension in spontaneously hypertensive rats (SHR). SHR animals were treated with VH-4 (25 mg/kg by intraperitoneal administration) and swimming exercise (1 h daily) for eight weeks, and the hemodynamic parameters, histology, and cell survival pathway protein expression were examined. In SHR rats, increased heart weight, blood pressure, and histological aberrations were observed. Cell survival protein p-PI3K and p-AKT and antiapoptosis proteins Bcl2 and Bcl-XL expression decreased in SHR animals. SIRT1 and FOXO3 were decreased in hypertensive rats. Both bioactive peptide VH-4 treatment and swimming exercise training in hypertensive rats increased the cell survival proteins p-PI3K and p-AKT and AMPKα1, Sirt1, PGC1α, and FoX3α proteins. Soy peptide VH-4, along with exercise, acts synergistically and prevents hypertension by activating cell survival and AMPKα1, Sirt1, PGC1α, and FoX3α proteins.

Sex-Dependent Mechanical Allodynia in Co-Morbid Hypertension and Osteoarthritis

Despite the common comorbid presentation of hypertension and osteoarthritis (OA), the relationship between these two diseases is often over-simplified as a result of limited physical activity in these populations. However, in the clinical population, there is a significant relationship between hypertension and both symptomatic and radiographic knee OA. Interestingly, aged spontaneously hypertensive rats (SHR) have spontaneous joint damage shown through micro-CT and histopathology compared to age matched non-hypertensive controls; however, the pain phenotype in these animals is unknown. Thus, the purpose of this study was to characterize the 50% withdrawal threshold in SHR animals to explore the pathophysiological interactions between hypertension and OA. OA was induced in female and male SHR animals via medial collateral ligament transection and medial meniscus transection (MCLT+MMT), with skin incision used as a sham control (n=7-8/group/sex). Mechanical allodynia was assessed at the ipsilateral hind paw at baseline, then every other week for 8 weeks post-op. The 50% withdrawal threshold was calculated using Chaplan's up-down application method of von Frey filaments. In female MCLT+MMT animals, 50% withdrawal threshold decreased from baseline to weeks 2 and 4 (p's<0.05). In female sham animals, this decrease was only seen at week 4 (p<0.05). No week-to-week differences were observed in male animals of either group. In the MCLT+MMT group, sex differences were observed at weeks 2, 4 and 6 (p's<0.05) while in the sham group, sex differences were only seen at week 4 (p<0.05). Finally, at this sample size, no effects due to OA were observed for either sex. Female hypertensive animals experience lower withdrawal thresholds compared to males, regardless of joint pathophysiology. Interestingly, sex differences were more prevalent in the MCLT+MMT group, indicating a possible sex-dependent interaction between hypertension and OA progression; however, further research should implement more sensitive pain-assessment techniques to determine these interactions. Supported by National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Numbers R01AR071431 and F31 AR077996.

High-intensity interval training attenuates the effects caused by arterial hypertension in the ventral prostate.

The prostatic effects induced by arterial hypertension is very controversial and its mechanism is unclear. High-intensity interval training (HIIT) is an exercise considered to be hypotensive. The objective of this work was to investigate the molecular, biochemical, and morphological effects of 8 weeks of HIIT in the prostatic tissue of spontaneously hypertensive rats (SHR). Twenty male SHR rats, 51.4 weeks old, were used. The SHR animals were divided into two groups: spontaneously sedentary hypertensive and spontaneously hypertensive submitted to HIIT. We analyze androgens receptor and glucocorticoid receptors in the prostate. Still, we verify effects of the hypertension and HIIT on the physiopathology prostatic, for immunohistochemistry investigated BCL-2, BAX, IGF-1, FAS/CD95, data's inflammatory tumour necrosis factor α, nuclear factor kappa B and interleukin (IL)-6, anti-inflammatory IL-10. The echocardiographic evaluation was performed at the baseline and after the training period. Arterial hypertension promote high prostatic intraepithelial neoplasia incidence in the prostate, increases IGF-1, BCL-2 (p < 0.05), and inflammatory proteins (p < 0.05). Eight weeks of HIIT training reduced the arterial pressure and increase the concentration of tissue collagen and intracellular glycogen and showed a higher expression of BAX, FAS/CD95, and IL-10 proteins (p < 0.05), coinciding with a lower incidence of lesions and lower prostate weight (p < 0.05) and reduction of the BCL-2 and IGF-1. Our data suggested that arterial hypertension suppressed apoptosis and increased damage prostatic. On other hand, HIIT promotes morphology and function improves in the prostatic environment, inhibited inflammation, and increased apoptosis.

EFFECTS OF THE INGESTION OF FLAXSEED (LINUM USITATISSIMUM L.) OIL AND PHYSICAL EXERCISE ON THE BODY WEIGHT, GLYCEMIC AND LIPID PROFILES OF A RAT MODEL DEVELOPED FOR THE STUDY OF METABOLIC SYNDROME

Metabolic syndrome (MetSyn) is a disorder that involves a series of symptoms that are associated to obesity and metabolic modifications, and increases the risk of developing cardiovascular disease and type 2 diabetes Mellitus. The study of new possibilities of non-drug therapies is fundamental for the primary prevention of MetSyn. The aim of this work was to evaluate the responses of spontaneously hypertensive rats (SHR) with lipid changes induced by the administration of dexamethasone (DEXA) to the ingestion of flaxseed oil associated or not associated with physical exercise regarding the body weight, and glycemic and lipid profiles, in comparison with the drug treatment with metformin. After 24 days of experiment, the 20-week-old animals were submitted to the glucose tolerance test (GTT) and lipid profile evaluation. The results showed that the administration of DEXA in SHR animals promoted a framework of hyperglycemia, dyslipidemia and attenuated the insulin resistance common in the SHR, thus producing an experimental model with several components of the human MetSyn. The effects on weight gain indicated an important preventive action of flaxseed oil and exercise on the weight evolution of SHR-DEXA animals. Furthermore, the ingestion of flaxseed oil associated or not with exercise promoted significant improvements on hyperglycemia and glucose intolerance in these animals. Regarding the lipid profile, the treatments with flaxseed oil and exercise promoted reductions in triglyceride levels and HDL-c increase; however, the combination of these two non-drug interventions was more effective than the isolated treatments.

Abstract MP23: Arterial Depressor Responses Induced By Neuromodulation Of Deep Peroneal Nerve In Spontaneously Hypertensive Rats

Hypertension affects nearly half of the US population but only 43% achieved blood pressure control with medication alone. Medical devices for hypertension include implantable lead electrodes that stimulate the carotid baroreceptors with promising results, albeit with significant adverse complications. To address these limitations, we have proposed the use of deep peroneal nerve stimulation (DPNS), which elicited a depressor response in anesthetized, breathing supported, spontaneously hypertensive rats (SHR). In this study, we further define the electrical stimulation parameters that optimize the DPNS depressor response, and demonstrated that increasing the pulse duration from 0.15 ms to 1ms, of 1.0 mA pulses at 2 Hz for 10 sec, significantly reduced the mean arterial pressure (MAP) by 8±4 mmHg (p&lt;0.005; n=4) in this animal model. DPNS also caused an immediate increase in renal nerve activity (RNA; p&lt; 0.004, n=5), which may represent afferent sensory axons from the kidney, although this possibility needs to be further investigated. In a separate cohort of anesthetized SHR animals, breathing spontaneously, we demonstrated that optimal DPNS stimulation reduced the MAP from 121±3 to 108±4; p=0.02; n=10). To confirm if DPNS is able to evoke a depressor response in fully awake SHR animals, we developed a novel miniaturized wireless microchannel electrode (w-μCE) with a L-shaped microchannel, through which the DPN slides and locks into a recording/stimulation chamber, causing no discomfort to the animal during locomotion. Two weeks after implantation of the w-μCE neural stimulation device, animals were movement-retrained to received wireless DPNS for 10 min daily for 2 weeks. Blood pressure was measured by tail-cuff at baseline, 10 days after device implantation, and 1 and 2-hr 15 days after DPNS. After two weeks of DPNS, the acute neuromodulation treatment reduced the initial systolic BP of 154±20 mmHg to 127±7 and 119±2 mmHg at 1 and 2 hr; respectively (p&lt; 0.001, n=15-19 measurements; n=2 animals). These results provide evidence of the effectiveness and reliability of DPN neuromodulation as a possible treatment for drug-resistant hypertension.

Изменения морфофункциональных параметров сердечно-сосудистой системы на фоне рациона питания с повышенной калорийностью у спонтанно гипертензивных крыс

Introduction. Hypertension with left ventricular hypertrophy (LVH) is a major independent risk factor for cardiovascular-related morbidity. Diet plays an essential role in the prevention and treatment of chronic cardiovascular disease. The aim of our study was to analyze the influence of 10-week diets consisting of different high fats and carbohydrates on the myocardium in spontaneously hypertensive rats (SHR). Materials and methods. The SHR (n=34) and WKY (n=34) were randomly divided into five groups (n=6 or 7 per group). For 10 weeks, the control group was fed the standard diet; the experimental groups were fed the standard chow diet with the different fats and sucrose (11% of the calorie intake). Systolic blood pressure (SBP) was measured before the experiment and 10 weeks after by the non-invasive tail-cuff method. After the experiment, the animals were humanely sacrificed. The heart specimens after routine processing were stained with hematoxylin and eosin. We determined the thickness of the left ventricle and the number of cardiomyocyte nuclei per unit area using morphometry. Results. An increase in SBP at the end of the experiment was found in SHR animals in groups receiving trans-fat and sucrose by 10.9 mm Hg and 13.4 mm Hg, respectively. Myocardial hypertrophy was observed in the SHR Butter group. Conclusion. We found that the increased content of trans-fats and sucrose in the diet leads to an increase in SBP in spontaneously hypertensive rats; saturated fatty acids – to myocardial hypertrophy in spontaneously hypertensive rats without aggravation of systolic hypertension. In normotensive animals, no negative effect of the high-fat diet on the cardiovascular system was observed. Keywords: myocardial hypertrophy, arterial hypertension, high fat diets, palm oil, carbohydrates

SPONTANEOUSLY HYPERTENSIVE RATS ARE RESISTANT TO 4NQO-INDUCED ORAL CARCINOGENESIS

Objective: This study aimed to investigate the incidence and progression of chemically-induced oral cancer in spontaneously hypertensive rats (SHR). Study Design: Thirty SHR and 30 Wistar rats (control) were treated with 4-nitroquinoline N-oxide (4NQO) carcinogen for 5 months. After euthanasia, tongue specimens were microscopically analyzed. P16/CDKN2A, vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNFα), interleukin (IL)-6, matrix metalloproteinase (MMP)-2, and MMP-9 expressions were verified by reverse transcription polymerase chain reaction (RT-PCR). The anxiety levels of rats were verified by the opened-field (OPF) test before carcinogenic induction, 75 and 150 days after tumor induction. Results: Oral cancer incidence was significantly lower in SHR animals (28% vs 60%; P = .003). Tumor volume was 2 times lower in SHR animals, but this result was not significant. MMP-9 expression was reduced in the tumors from SHR rats while P16/CDKN2A, VEGF, TNFα, IL-6, and MMP-2 levels did not differ statistically. SHR rats spent more time and had more frequency at the central area of the OPF test than Wistar rats in the 3 periods. The OPF test showed a progressive increase in anxiety levels of both groups during 4NQO treatment. Conclusion: SHR rats were resistant to the chemically induced oral carcinogenesis and displayed a decreased tumor progression. Support: Sao Paulo Research Foundation (FAPESP Process: 14/25393-8).

Dipeptide IF prevents the effects of hypertension-induced Alzheimer's disease on long-term memory in the cortex of spontaneously hypertensive rats.

Hypertension (HTN) is one of the most prevalent chronic conditions; it can damage blood vessels and rupture blood vessels can trap in small vessels. This blockage can prevent blood flow and oxygen delivery to brain cells and can result in Alzheimer's disease (AD). HTN- and AD-mediated long-time memory loss and its treatment remain poorly understood. Plant-derived natural compounds are alternative solutions for effectively treating diseases without any side effects. This study revealed that bioactive peptides extracted from potato hydrolysis suppress HTN-mediated long-term memory (LTM) loss and cell apoptosis, thus improving memory formation and neuronal cell survival in the spontaneously hypertensive rat (SHR) rat model. SHR rats were treated with bioactive peptide IF (10 mg/kg orally) and angiotensin-converting enzyme inhibitors (5 mg/kg orally). In this study, we evaluated the molecular expression levels of BDNF-, GluR1-, and CREB-mediated markers protein expression in 24-week-old SHR rats. The study result showed that HTN-induced AD regulated long-term memory (LTM) loss and neuronal degeneration in the SHR animals. The bioactive peptide-treated animals showed an elevated level of survival proteins. Bioactive peptide IF activate CREB-mediated downstream proteins to regulate synaptic plasticity and neuronal survival in the SHR rat model.

Bioactive Peptide VHVV Upregulates the Long-Term Memory-Related Biomarkers in Adult Spontaneously Hypertensive Rats.

Hypertension is one of the growing risk factors for the progression of long-term memory loss. Hypertension-mediated memory loss and treatment remain not thoroughly elucidated to date. Plant-based natural compounds are an alternative solution to treating human diseases without side effects associated with commercial drugs. This study reveals that bioactive peptides extracted from soy hydrolysates mimic hypertension-mediated memory loss and neuronal degeneration and alters the memory molecular pathway in spontaneously hypertensive rats (SHR). The SHR animal model was treated with bioactive peptide VHVV (10 mg/kg/oral administration) and angiotensin-converting-enzyme (ACE) inhibitors (5 mg/kg/oral administration) for 24 weeks. We evaluated molecular level expression of brain-derived neurotrophic factor (BDNF), cAMP response element binding protein (CREB), and survival markers phospho-protein kinase B (P-AKT) and phosphoinositide 3-kinase (PI3K) after 24 weeks of treatment for SHR in this study. Western blotting, hematoxylin and eosin (H&E) staining, and immunohistochemistry showed long-term memory loss and neuronal degeneration in SHR animals. Bioactive peptide VHVV-treated animals upregulated the expression of long-term memory-relate proteins and neuronal survival. Spontaneously hypertensive rats treated with oral administration of bioactive peptide VHVV had activated CREB-mediated downstream proteins which may reduce hypertension-mediated long-term memory loss and maintain neuronal survival.

LOW-INTENSITY ENDURANCE TRAINING AND RIGHT VENTRICULAR MYOCYTES OF HYPERTENSIVE RATS

ABSTRACT Introduction The structural and mechanical adaptations of the right ventricular (RV) myocytes in response to hypertension associated with low-intensity endurance training (LIET) have not been studied in experimental models. Objective To determine the effects of LIET on the structural and mechanical properties of RV myocytes in spontaneously hypertensive rats (SHRs). Methods Male SHRs and normotensive Wistar rats (age: 16 weeks) were allocated to groups (n=7): WIS (Wistar Controls); SHR-C (SHR Controls) and SHR-T (SHR Trained; 60 min/day, 50-60% of maximal exercise capacity, 5 days/week for 8 weeks). Systolic arterial pressure (SAP), isolated RV myocyte dimensions, contractility, intracellular Ca2+ transient ([Ca2+]i), and ventricular Ca2+ regulatory proteins were measured. The statistical analysis was performed by one-way ANOVA followed by the Tukey post hoc test (α=5%). Results LIET reduced the SAP in SHR animals (SHR-C, 164 ± 2 mmHg vs. SHR-T, 152 ± 4 mmHg; P&lt;0.05). Hypertension increased cell length (WIS, 156.8 ± 2.7 µm; SHR-C, 166.6 ± 3.1 µm; P&lt;0.05) but did not affect cell width or volume (P&gt;0.05). LIET did not change the cell dimensions in the SHR-T. Neither hypertension nor LIET affected myocyte contractility or the expression of Ca2+ regulatory proteins in the RV of the SHR-C and SHR-T groups. Hypertension did not affect the amplitude of the [Ca2+]i transient or the time to half resting level (P&gt;0.05), but increased the time to peak (WIS, 58 ± 1 ms vs. SHR-C, 79 ± 2 ms; P&lt;0.05). LIET increased the amplitude of the [Ca2+]i transient (WIS, 2.28 ± 0.07 F/F0 and SHR-C, 2.48 ± 0.08 F/F0 vs. SHR-T, 2.87 ± 0.08 F/F0 P&lt;0.05), but did not alter the times to peak or to half resting level. Conclusion LIET had no effect on the structural and mechanical properties of RV myocytes in the SHRs, although it increased the amplitude of the [Ca2+]i transient and reduced the SAP. Level of evidence I, Therapeutic Studies - Investigating the Results of Treatment.

Essential oil of the leaves of Eugenia sulcata preserve myocardial contractility and does not present immunotoxicity

The essential oil of the leaves of Eugenia sulcata, in the Myrtaceae family, has a demonstrated antihypertensive effect, but its effects on heart muscle and its toxicity have not yet been elucidated. Little chemical or biological data are available for E. sulcata, whether emphasizing the beneficial effects or the pharmacological security of this species. This study aims to evaluate myocardial contractility and to analyze angiotensin converting enzyme (ACE) and myosin ATPase activities associated with use of this essential oil. In addition, we evaluated the immunotoxicity of E. sulcata essential oil. Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were treated daily for 30 days (10 mg/kg of oil) to evaluate the isometric force of the papillary muscle, ACE measured by fluorimetry, and myosin ATPase activities by inorganic phosphate. Lymphocyte cultures were used to evaluate cytotoxicity, DNA damage, and mutagenicity of the essential oil. The results demonstrate that the treatment did not change the cardiac contraction force and did not alter the functioning of the sarcoplasmic reticulum, extrusion of the membrane calcium, or modify the membrane calcium channels or β-adrenergic receptor activity. Tetanic contractions were potentiated in the SHR animals. Myosin ATPase activity was also increased in the SHR animals. Cardiac ACE activity was reduced in both animal strains, and the serum ACE was reduced only in the SHR animals. The essential oil did not cause cytotoxicity or mutagenicity and presented low DNA damage. Our results demonstrated that the essential oil does not change myocardial contractility and does not present relevant immunotoxicity.

Influence of pre-existing hypertension on neuroendocrine and cardiovascular changes evoked by chronic stress in female rats

This study investigated neuroendocrine, autonomic, and cardiovascular changes evoked by daily exposure to the same type of stressor (homotypic) or different aversive stressor stimuli (heterotypic) in 60-days-old female normotensive Wistar rats and female spontaneously hypertensive rats (SHR). Both strains of rats were exposed for 10 consecutive days to either the homotypic stressor repeated restraint stress (RRS) or the heterotypic stressor chronic unpredictable stress (CUS). As expected, SHR had higher baseline blood pressure values and impaired baroreflex activity in relation to normotensive animals. Besides, SHR presented higher plasma corticosterone levels and decreased thymus weight. Both RRS and CUS increased baseline plasma corticosterone concentration and decreased body weight gain in both normotensive and SHR rats. In addition, both stress protocols caused hypertrophy of adrenal glands in normotensive rats. Regarding the cardiovascular effects, RRS increased basal heart rate in both rat strains, which was mediated by an increase in sympathetic tone to the heart. Besides, RRS increased baroreflex-mediated tachycardia in SHR animals, while CUS increased cardiac parasympathetic activity and pacemaker activity in normotensive rats. Taken together, these results indicate a stress type-specific effect, as identified by a vulnerability of both strains to the deleterious cardiovascular effects evoked by the homotypic stressor and a resilience to the impact of the heterotypic stressor. Vulnerability of hypertensive rats was evidenced by the absence of CUS-evoked adaptive cardiovascular responses and an increase of baroreflex tachycardia in SHR animals subjected to RRS. The somatic and HPA axis changes were overall independent of the chronic stress regimen and pre-existing hypertension.

COMPARATIVE PROTEOMIC ANALYSIS IN MICRODISSECTED RENAL VESSELS OF HYPERTENSIVE AND NORMOTENSIVE RATS

Objective: Systemic hypertension has a profound impact on the renal vascular physiology and functionality. Our goal was to identify the biological pathways and macromolecules of the renal arteriolar wall, which are involved with the development of hypertrension. Design and method: Tissue derived exclusively from renal vessels of 4 Spontaneously Hypertensive Rat (SHR) and 4 normotensive controls (Wistar Kyoto,WKY) at 20 weeks using Laser Capture Microdissection on 14 micrometer cryosections was used. High sensitivity proteomic analysis was performed in the microdissected homogenized material in order to detect early molecular alterations associated with hypertension of the renal vessels before the onset of vascular damage. Results: Proteomic analysis revealed 688 proteins; 550 proteins were found in both groups, of which 58 proteins were differentially expressed (15 proteins were up-regulated and 43 proteins were down-regulated in SHR). 71 proteins were found exclusively in control WKY rats and 67 exclusively in SHR rats. Pathway enrichment analysis revealed 114 and 111 pathways in WKY and SHR, respectively and 106 common pathways in both groups. Many of the interesting differentially expressed proteins identified in our study are relevant to vascular tone regulation. Thus proteins involved with NO and vasodilation and affecting eNOS include Xaa-Pro aminopeptidase 1 (XPP1), N (G) N (G)-dimethylarginine dimethylaminohydrolase 1 (DDAH1), Dehydropteridine reductase (DHPR), whereas proteins involved with blood pressure regulation by the renin-angiotensin system include Glutamyl aminopeptidase / Aminopeptidase A (AMPE) and Aminopeptidase N (AMPN). Moreover, pathway enrichment analysis revealed that the eNOS activation pathway is disregulated only in the hypertensive SHR animals. Conclusions: Our study demonstrates that hypertension causes early proteomic changes in the renal vessels of SHR compared to WKY. These changes are relevant to vascular tone regulation and consequently may be involved in the development of vascular damage and hypertensive nephrosclerosis. Further studies are required to explore whether these pathways and molecules are involved with hypertensive nephrosclerosis and to identify components that could be considered new therapeutic targets

Anti-Apoptosis and Anti-Fibrosis Effects of Eriobotrya Japonica in Spontaneously Hypertensive Rat Hearts.

Myocardial apoptosis and fibrosis represent important contributing factors for development of hypertension-induced heart failure. The present study aims to investigate the potential effects of Eriobotrya japonica leaf extract (EJLE) against hypertension-induced cardiac apoptosis and fibrosis in spontaneously hypertensive rats (SHRs). Twelve-week-old male rats were randomly divided into four different groups; control Wistar Kyoto (WKY) rats, hypertensive SHR rats, SHR rats treated with a low dose (100 mg/kg body weight) of EJLE and SHR rats treated with a high dose (300 mg/kg body weight) of EJLE. Animals were acclimatized for 4 weeks and thereafter were gastric fed for 8 weeks with two doses of EJLE per week. The rats were then euthanized following cardiac functional analysis by echocardiography. The cardiac tissue sections were examined by Terminal Deoxynucleotidyl Transferase-Mediated Deoxyuridine Triphosphate (dUTP) Nick End-Labeling (TUNEL) assay, histological staining and Western blotting to assess the cardio-protective effects of EJ in SHR animals. Echocardiographic measurements provided convincing evidence to support the ability of EJ to ameliorate crucial cardiac functional characteristics. Furthermore, our results reveal that supplementation of EJLE effectively attenuated cardiac apoptosis and fibrosis and also enhanced cell survival in hypertensive SHR hearts. Thus, the present study concludes that EJLE potentially provides cardio-protective effects against hypertension-induced cardiac apoptosis and fibrosis in SHR animals.

Prolonged diuretic and saluretic effect of nothofagin isolated from Leandra dasytricha (A. Gray) Cogn. leaves in normotensive and hypertensive rats: Role of antioxidant system and renal protection

Although the acute diuretic effect of nothofagin has been recently demonstrated, its effects after dose-repeated treatment have not yet been explored. For that, male Wistar normotensive (NTR) and spontaneously hypertensive rats (SHR) were orally treated, once a day, with vehicle (VEH: distilled water; 1 ml/kg), hydrochlorothiazide (HCTZ; 10 mg/kg) or nothofagin (NOT; 1 mg/kg). The cumulative diuretic index and urinary electrolytes excretion were measured each 24 h. On the last day of the experiment (7th day), urine, blood and kidney samples were collected for biochemical and molecular analyzes. The urinary volume of both NTR and SHR were significantly increased with the treatment with NOT (from the second to the seventh day of treatment), with final values reaching an increase of 56% and 82%, respectively, when compared with VEH-treated group. This effect was associated with increased levels of urinary excretion of Na+ and Cl−, without any changes on K+ excretion. None of the treatments modified urinary pH or density values. Importantly, neither the NOT nor the HCTZ caused any change in body weight following the dose-repeated treatment, and also did not provoke an electrolytic disturbance. Regarding the renal analyzes, when compared with the vehicle-treated NTR group, the activity of superoxide dismutase (SOD) and the reduced glutathione (GSH) levels in kidney homogenates of the SHR group were decreased, while the generation of lipid hydroperoxides were significantly increased. The daily treatment with NOT was able to restore the GSH levels and SOD activity, as well as reduced the lipoperoxidation in the kidney homogenates obtained from SHR animals. Finally, NOT significantly augmented the levels of nitrite, a marker of nitric oxide production, in the plasma obtained from SHR group when compared with the vehicle-treated only NTR. This study revealed the prolonged diuretic and saluretic effect of nothofagin in normotensive and hypertensive rats. Our data also showed the renal protective effects of nothofagin by the improvement of antioxidative capacity, as well as by the augmented bioavailability of plasma nitric oxide in the hypertensive group.

Mineralocorticoid receptor associates with pro-inflammatory bias in the hippocampus of spontaneously hypertensive rats.

Damage observed in the hippocampus of the adult spontaneously hypertensive rat (SHR) resembles the neuropathology of mineralocorticoid-induced hypertension, supporting a similar endocrine dysfunction in both entities. In the present study, we tested the hypothesis that increased expression of the hippocampal mineralocorticoid receptor (MR) in SHR animals is associated with a prevalent expression of pro-inflammatory over anti-inflammatory factors. Accordingly, in the hippocampus, we measured mRNA expression and immunoreactivity of the MR and glucocorticoid receptor (GR) using a quantitative polymerase chain reaction and histochemistry. We also measured serum-glucocorticoid-activated kinase 1 (Sgk1 mRNA), the number and phenotype of Iba1+ microglia, as well as mRNA expression levels of the pro-inflammatory factors cyclo-oxygenase 2 (Cox2), Nlrp3 inflammasome and tumour necrosis factor α (Tnfα). Expression of anti-inflammatory transforming growth factor (Tgf)β mRNA and the NADPH-diaphorase activity of nitric oxide synthase (NOS) were also determined. The results showed that, in the hippocampus of SHR rats, expression of MR and the number of immunoreactive MR/GR co-expressing cells were increased compared to Wistar-Kyoto control animals. Expression of Sgk1, Cox2, Nlrp3 and the number of ramified glia cells positive for Iba1+ were also increased, whereas Tgfβ mRNA expression and the NADPH-diaphorase activity of NOS were decreased. We propose that, in the SHR hippocampus, increased MR expression causes a bias towards a pro-inflammatory phenotype characteristic for hypertensive encephalopathy.

Activation of α1A -adrenoceptors desensitizes the rat aorta response to phenylephrine through a neuronal NOS pathway, a mechanism lost with ageing.

A NO-mediated desensitization of vasoconstrictor responses evoked by stimulation of α1 -adrenoceptors has been reported in different vessels. We investigated the involvement of each α1 -adrenoceptor subtype and constitutive NOS isoforms and the influence of ageing and hypertension on this process. Wistar and spontaneously hypertensive rats (SHR), 16, 32, 52 and 72weeks-old, were used to evaluate the desensitization process. Expression of α1 -adrenoceptor subtypes, endothelial NOS (eNOS) and neuronal NOS (nNOS) were determined in rat aorta and left ventricle (LV). Expression levels were also evaluated in LV of a group of heart failure patients with a wide age range. Repeated application of phenylephrine decreased subsequent α1 -adrenoceptor-mediated vasoconstriction by increasing nNOS protein expression in aorta, but not in tail or mesenteric resistance arteries, where mRNA levels of nNOS were undetectable. This desensitization process disappeared in the absence of endothelium or in the presence of L-NAME (100μM), nNOS inhibitors, SMTC (1μM) and TRIM (100μM), and 5-methylurapidil (100nM, α1A -antagonist), but not BMY7378 (10nM, α1D -antagonist). The α1A /nNOS-mediated desensitization was absent in aged SHR and Wistar animals, where the expression of α1A -adrenoceptors was reduced in aorta and LV. In human LV, a negative correlation was found between age and α1A -adrenoceptor expression. The α1A -adrenoceptor subtype, through endothelial nNOS-derived NO, may act as a physiological 'brake' against the detrimental effects of excessive α1 -adrenoceptor-mediated vasoconstriction. Reduced α1A -adrenoceptor- and nNOS-mediated desensitization in aged patients could be involved in the age-dependent elevation of adrenergic activity.