Spontaneously Hypertensive Rats Research Articles

Differences in collateral vessel formation after experimental retinal vein occlusion in spontaneously hypertensive rats and wild-type rats

ObjectiveRetinal vein occlusion (RVO) can lead to visual impairment, but the development of collateral vessels can sometimes mitigate significant damage. This study aimed to investigate the relationship between collateral vessels and hypertension, the most common underlying condition associated with RVO, by comparing spontaneously hypertensive rats (SHRs) and wild-type Wister rats (WWRs). We also examined the differences between WWRs and SHRs in terms of sphingosine 1-phosphate receptor 1 (S1PR1) expression and its product nitric oxide synthase 3 (NOS3) expression, which are involved in the formation of collateral vessels after vascular occlusion. MethodsLaser photocoagulation (PC) was used to occlude one randomly selected retinal vein in WWRs and SHRs, and the area surrounding the occluded vessel was examined using optical coherence tomography angiography. If reperfusion of the occluded vessel occurred within 2 weeks, the vessel was re-occluded repeatedly by PC. The number of eyes with successfully occluded vessels accompanied by collateral vessels was recorded. Then, WWRs and SHRs were divided into the following four groups: 1) control (no treatment), 2) vehicle (20% DMSO), 3) S1PR1 agonist (2 mg/mL SEW2871), and 4) S1PR1 antagonist (0.25 mg/mL VPC 23019) groups. The drugs were administered intravitreally in all groups except the control. The number of laser shots required for successful RVO was recorded. Histological evaluation and quantitative real-time PCR of S1PR1 and NOS3 were performed to elucidate the mechanisms underlying collateral vessel formation. ResultsThe proportion of eyes achieving successful vein occlusion was lower in SHRs (4/12 eyes, 33.3%) than in WWRs (8/10 eyes, 80%, p = 0.043). NOS3 expression at 6 h after PC was significantly higher in WWRs than in SHRs (p = 0.021). In WWRs treated with SEW2871, vein occlusion failed in 7 of 10 eyes (70%). The expression of NOS3 was significantly higher in the SEW2871 treatment group than in the untreated group (p < 0.001). Furthermore, NOS3 expression was significantly higher after SEW2871 treatment in WWRs than in SHRs (p = 0.011). ConclusionIn hypertensive environments, collateral vessels are less likely to develop, and S1PR1 may be involved in this phenomenon.

Effects and mechanisms of negative air ions on blood pressure, oxidative stress and inflammation levels in SHR rats

To investigate the effects and possible mechanisms of negative air ions(NAIs) on blood pressure, oxidative stress, and inflammatory status in spontaneous hypertension rats(SHR). A total of 60 SHR(half male and half female) were randomly divided into one-month and three-month groups, 30 rats per groups, based on the duration of the intervention. Each group was further randomized into three groups based on the daily intervention time: SHR control group, 2 h NAIs-SHR group, and 6 h NAIs-SHR group, 10 rats per groups. In addition, 20 Wistar Kyoto(WKY)(half male and half female), were randomized into one-month WKY group and three-month WKY group, 10 rats per groups, based on the intervention time. The 2 h NAIs-SHR group and 6 h NAIs-SHR group were exposed to an environment with NAIs concentrations of 4.5×10~4-5×10~4 cm~3 per day for 2 h and 6 h. The WKY group and SHR group were exposed to normal air on a daily basis. Blood pressure of rats in each group was measured every three days, while weight was measured once a week. After sacrificing the rats in the first month and the third month of rearing, wet weight of the organs was weighed. The enzyme linked immunosorbent assay(ELISA) was used to detect 8-hydroxylated deoxyguanosine(8-OHdG), interleukin-6(IL-6), interleukin-8(IL-8), tumor necrosis factor-α(TNF-α), nitric oxide(NO) and endothelin-1(ET-1) levels. Reactive oxygen species(ROS) detection kit was used to detect ROS level. Malondialdehyde(MDA) and superoxide dismutase(SOD), glutathione(GSH) and glutathione disulfide(GSSG) were measured by colorimetric analysis. HE staining was conducted to observe the histopathological morphological changes of the thoracic aorta in each group, and Western blot was conducted to detect the thoracic aortap38 mitogen-activated protein kinase(p38 MAPK), extracellular signal-regulated kinases(ERK), c-Jun n-terminal kinase(JNK), c-fos proteins, c-jun proteins and their phosphorylated proteins level. The weight of WKY male mice in the same week age group was higher than that of SHR control group, and there was no significant difference in the weight between the other groups. The coefficient of heart in SHR control group(4.66±0.48) was higher than that in WKY group(3.73±0.15)(P&lt;0.05), while there were no significant differences in the coefficients of brain, kidney, liver and spleen among the groups. Blood pressure in WKY group at the same age was lower than that in SHR group, and blood pressure in SHR control group at 2-5 and 8-11 weeks was higher than that in 2 h NAIs-SHR and 6 h NAIs-SHR groups(P&lt;0.05). HE staining showed that the internal, middle and external membranes of thoracic aorta in 2 h NAIs-SHR group and 6 h NAIs-SHR group were improved to varying degrees compared with those in SHR control group, including disordered internal membrane structure, thickened middle membrane and broken external membrane. In terms of oxidative stress levels, compared with the SHR control group, the ROS(0.66%±0.17%, 0.49%±0.32%) and 8-OHdG((48.29±8.00) ng/mL, (33.13±14.67)ng/mL) levels were lower in the 6 h NAIs-SHR group(P&lt;0.05), while the GSH/GSSG ratio was higher in the one-month 6 h NAIs-SHR group(10.08±4.93). Compared with the 2 h NAIs-SHR group, the ROS level(0.99%±0.19%) was lower in the 6 h NAIs-SHR group(P&lt;0.05). In terms of inflammatory factor levels, compared with the SHR control group, the IL-8 levels((160.44±56.54) ng/L, (145.77±38.39) ng/L) were lower in the 6 h NAIs-SHR group(P&lt;0.05), while the ET-1 level((249.55±16.98) ng/L) was higher in the one-month WKY group. There was no significant difference in NO levels among the groups. The relative expression of p-p38 protein in the thoracic aorta of rats in the one-month SHR control group was lower than that in the WKY group(P&lt;0.05). The relative expression of p-p38 and p-c-fos proteins in the thoracic aorta of rats at three-months was higher in the SHR control group than in the 2 h NAIs-SHR and 6 h NAIs-SHR groups(P&lt;0.05). The intervention of NAIs at a concentration of 4.5×10~4-5×10~4/cm~3 may regulate the partial oxidation and inflammatory state of SHR rats through the ROS/MAPK/AP1 signaling pathway, thereby reducing their blood pressure level.

Hemodynamic Parameters in Spontaneously Hypertensive Rats with Obesity and Chemically Induced Colitis during Probiotic Therapy.

We studied the dynamics of the main hemodynamic parameters in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats with visceral obesity and chemically induced colitis (CIC) against the background of probiotic therapy. Systolic BP, HR, and body temperature were recorded over 36 days using a wireless telemetry system. During 8 days (3 days before CIC induction and until the end of the experiment) the animals were intragastrically administered a probiotic based on Lactobacillus delbrueckii D5 strain. At baseline, systolic BP was significantly higher in the SHR group, while HR and body temperature did not differ in SHR and WKY rats. On day 8 after CIC induction, systolic BP, HR, and body temperature in SHR were significantly increased in comparison with the initial values. In the group of WKY rats, all indices at the end of the experiment remained at the initial levels. Probiotic therapy in SHR, in contrast to WKY rats, did not lead to normalization of body temperature and hemodynamic disorders resulting from CIC.

Circadian Rhythms of Body Temperature and Locomotor Activity in Spontaneously Hypertensive Rats under Frequent Changes in Light Conditions.

Changes in lighting accompany modern urbanization trends and can lead to various pathologies based on circadian disturbances. In this study, we assessed the changes in the circadian rhythm of core body temperature (Tcore) and locomotor activity of Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) following exposure to different lighting conditions: extended light phase of the day (16 h-8 h, 20 h-4 h, 24 h-0 h), light pollution, monochromatic light, and bright light therapy. The telemetry data was collected after experimental lighting conditions during periods with standard lighting (12 h of light and 12 h of darkness) and was processed using linear and cosinor analysis. The daily rhythms of rats' parameters persisted in accordance with the standard lighting regime. Tcore changes were observed in both groups compared to the initial period: in WKY, a decrease in Tcore during the darkness and an increase during the light; in SHR, the opposite trend, with Tcore increased during the darkness and decreased during the light phase of the day. A relationship between Tcore and activity was observed with weak correlation. WKY exhibited more pronounced signs of adaptive variation and desynchronization compared to SHR, which could be associated with a wider range of functional capabilities of the organism without cardiovascular pathology.

Study on material basis and anti-hypertensive metabolomics of Zhengan-Xifeng-Tang(ZXT): A comparison between ZXT decoction and granules

High blood pressure is a serious human health problem and one of the leading risk factors for fatal complications in cardiovascular disease. The ZXT granules were prepared based on the Zhengan-Xifeng-Tang (ZXT) decoction. However, the therapeutic effects of ZXT granules on spontaneous hypertension and the metabolic pathways in which they may intervene are unclear. The aim of this study was to investigate the antihypertensive effect of ZXT granules on spontaneously hypertensive rats (SHR) and to analyze the metabolic pathway of intervention through chemical composition characterization, pharmacodynamics, and serum metabolomics analysis. After eight weeks of administration, serum and aortic arch samples were collected for biochemical, histopathology and serum metabolomics analysis to assess the effect of ZXT granules on SHR. The results showed that ZXT granules reduced aortic arch injury and blood pressure in SHR rats. Serum data from rats in each group was collected using LC-MS and 74 potential biomarkers were identified that showed significant differences between the model and control groups. Of these, 18 potential biomarkers were found to be deregulated after intervention with ZXT granules. These 18 potential differential metabolic markers are primarily involved in bile acid biosynthesis, arachidonic acid metabolism pathway, and fatty acid degradation. The results demonstrated that ZXT granules significantly affected blood lipids, aortic arch, and metabolic disorders in SHR rats. ZXT granules offer a new possibility for effective and convenient treatment of hypertensive patients.

Mesenteric artery smooth muscle cells from hypertensive rats have increased microtubule acetylation.

The dynamic nature of the microtubule network is dependent in part by post-translational modifications (PTMs) - particularly through acetylation, which stabilizes the microtubule network. Whether PTMs of the microtubule network in vascular smooth muscle cells (VSMCs) contribute to the pathophysiology of hypertension is unknown. The aim of this study was to determine the acetylated state of the microtubule network in the mesenteric arteries of spontaneously hypertensive rats (SHR). Experiments were performed on male normotensive rats and SHR mesenteric arteries. Western blotting and mass spectrometry determined changes in tubulin acetylation. Wire myography was used to investigate the effect of tubacin on isoprenaline-mediated vasorelaxations. Isolated cells from normotensive rats were used for scanning ion conductance microscopy (SICM). Mass spectrometry and Western blotting showed that tubulin acetylation is increased in the mesenteric arteries of the SHR compared with normotensive rats. Tubacin enhanced the β-adrenoceptor-mediated vasodilatation by isoprenaline when the endothelium was intact, but attenuated relaxations when the endothelium was denuded or nitric oxide production was inhibited. By pre-treating vessels with colchicine to disrupt the microtubule network, we were able to confirm that the effects of tubacin were microtubule-dependent. Using SICM, we examined the cell surface Young's modulus of VSMCs, but found no difference in control, tubacin-treated, or taxol-treated cells. Acetylation of tubulin at Lys40 is elevated in mesenteric arteries from the SHR. Furthermore, this study shows that tubacin has an endothelial-dependent bimodal effect on isoprenaline-mediated vasorelaxation.

Physical exercise is essential for increasing ventricular contractility in hypertensive rats treated with losartan.

The treatment of hypertensive patients with losartan is very common. Despite the reduction in blood pressure, its effects on cardiac contractility and sympathetic autonomic drive are still controversial. In turn, aerobic physical training (APT) also presents an important therapeutic option, providing significant improvements in cardiovascular autonomic control, however little is known about its effects on cardiac contractility, especially when associated with losartan. Therefore, we investigated in spontaneously hypertensive rats (SHR) the effects of losartan and APT on cardiac hemodynamics and functionality, with emphasis on autonomic tonic balance and cardiac contractility. Sixty-four SHR (18 weeks old) were divided into four groups (N = 16): vehicle; vehicle submitted to APT through swimming for 12 weeks; treated with losartan (5 mg·kg-1·d-1) for 12 weeks; and treated with losartan associated with APT. The groups were submitted to cardiac morphological and functional analysis by echocardiography; double blockade of cardiac autonomic receptors with atropine and propranolol; and coronary bed reactivity and left ventricular contractility analyses by the Langendorff technique. APT improved functional parameters and autonomic balance by reducing sympathetic drive and/or increasing vagal drive. In contrast, it promoted a concentric remodeling of the left ventricle (LV). Treatment with losartan reduced sympathetic autonomic drive and cardiac morphological parameters, but there were no significant gains in cardiac functionality and contractility. When combined, the concentric remodeling of the LV to APT was abolished and gains in cardiac functionality and contractility were observed. Our findings suggest that the effects of losartan and APT are complementary and should be applied together in the treatment of hypertension. In spontaneously hypertensive rats, the combination of aerobic physical training with losartan treatment was crucial to greater blood pressure reductions and an increase in left ventricular contractility. Furthermore, losartan treatment prevented the concentric left ventricular remodeling caused by aerobic physical training.

Effects of Chronic Hypertension on the Energy Metabolism of Cerebral Cortex Mitochondria in Normotensive and in Spontaneously Hypertensive Rats During Aging.

In this study the subcellular modifications undergone by cerebral cortex mitochondrial metabolism in chronic hypertension during aging were evaluated. The catalytic properties of regulatory energy-linked enzymes of Tricarboxylic Acid Cycle (TCA), Electron Transport Chain (ETC) and glutamate metabolism were assayed on non-synaptic mitochondria (FM, located in post-synaptic compartment) and on intra-synaptic mitochondria of pre-synaptic compartment, furtherly divided in "light" (LM) and "heavy" (HM) mitochondria, purified form cerebral cortex of normotensive Wistar Kyoto Rats (WKY) versus Spontaneously Hypertensive Rats (SHR) at 6, 12 and 18months. During physiological aging, the metabolic machinery was differently expressed in pre- and post-synaptic compartments: LM and above all HM were more affected by aging, displaying lower ETC activities. In SHR at 6months, FM and LM showed an uncoupling between TCA and ETC, likely as initial adaptive response to hypertension. During pathological aging, HM were particularly affected at 12months in SHR, as if the adaptive modifications in FM and LM at 6months granted a mitochondrial functional balance, while at 18months all the neuronal mitochondria displayed decreased metabolic fluxes versus WKY. This study describes the effects of chronic hypertension on cerebral mitochondrial energy metabolism during aging through functional proteomics of enzymes at subcellular levels, i.e. in neuronal soma and synapses. In addition, this represents the starting point to envisage an experimental physiopathological model which could be useful also for pharmacological studies, to assess drug actions during the development of age-related pathologies that could coexist and/or are provoked by chronic hypertension.

Effects of Gestational Exercise on Nociception, BDNF, and Irisin Levels in an Animal Model of ADHD

Abnormal cognitive and sensorial properties have been reported in patients with psychiatric and neurodevelopmental conditions, such as attention deficit hyperactivity disorder (ADHD). ADHD patients exhibit impaired dopaminergic signaling and plasticity in brain areas related to cognitive and sensory processing. The spontaneous hypertensive rat (SHR), in comparison to the Wistar Kyoto rat (WKY), is the most used genetic animal model to study ADHD. Brain neurotrophic factor (BDNF), critical for midbrain and hippocampal dopaminergic neuron survival and differentiation, is reduced in both ADHD subjects and SHR. Physical exercise (e.g. swimming) promotes neuroplasticity and improves cognition by increasing BDNF and irisin. Here we investigate the effects of gestational swimming on sensorial and behavioral phenotypes, striatal dopaminergic parameters, and hippocampal FNDC5/irisin and BDNF levels observed in WKY and SHR. Gestational swimming improved nociception in SHR rats (p = 0.006) and increased hippocampal BDNF levels (p = 0.02) in a sex-dependent manner in adolescent offspring. Sex differences were observed in hippocampal FNDC5/irisin levels (p = 0.002), with females presenting lower levels than males. Our results contribute to the notion that swimming during pregnancy is a promising alternative to improve ADHD phenotypes in the offspring.

Forgotten Circulation: Reduced Mesenteric Venous Capacitance in Hypertensive Rats Is Improved by Decreasing Sympathetic Activity.

The mesenteric venous reservoir plays a vital role in mediating blood volume and pressure changes and is richly innervated by sympathetic nerves; however, the precise nature of venous sympathetic regulation and its role during hypertension remains unclear. We hypothesized that sympathetic drive to mesenteric veins in spontaneously hypertensive (SH) rats is raised, increasing mean circulatory filling pressure (MCFP), and impairing mesenteric capacitance. Arterial pressure, central venous pressure, mesenteric arterial, and venous blood flow were measured simultaneously in conscious male Wistar and SH rats. MCFP was assessed using an intraatrial balloon. Hemodynamic responses to volume changes (±20%) were measured before and after ganglionic blockade and carotid body denervation. Sympathetic venoconstrictor activity was measured in situ. MCFP in vivo (10.8±1.6 versus 8.0±2.1 mm Hg; P=0.0005) and sympathetic venoconstrictor drive in situ (18±1 versus 10±2 µV; P<0.0001) were higher in SH rats; MCFP decreased in SH rats after hexamethonium and carotid body denervation (7.6±1.4; P<0.0001 and 8.5±1.0 mm Hg; P=0.0045). During volume changes, arterial pressure remained stable. With blood loss, net efflux of blood from the mesenteric bed was measured in both strains. However, during volume infusion, we observed net influx in Wistar (+2.3±2.6 mL/min) but efflux in SH rats (-1.0±1.0 mL/min; P=0.0032); this counterintuitive efflux was abolished by hexamethonium and carotid body denervation (+0.3±1.7 and 0.5±1.6 mL/min, respectively). In SH rats, excessive sympathetic venoconstriction elevates MCFP and reduces capacitance, impairing volume buffering by mesenteric veins. We propose selective targeting of mesenteric veins through sympathetic drive reduction as a novel therapeutic opportunity for hypertension.

Oral Administration of Fermented Milk from Co-Starter Containing Lactobacillus plantarum Y44 Shows an Ameliorating Effect on Hypertension in Spontaneously Hypertensive Rats.

Fermented dairy foods such as yogurt exhibit some beneficial effects on consumers, including relieving the symptoms of hypertension. This study aims to obtain fermented dairy products from a co-starter that have a great flavor and the auxiliary function of reducing blood pressure after longtime consumption. Commercial starter cultures composed of Lactobacillus delbrueckii subsp. bulgaricus CICC 6047 and Streptococcus thermophilus CICC 6038 were combined with Lactobacillus plantarum strains Y44, Y12, and Y16, respectively, as a combined starter culture to ferment the mixed milk of skim milk and soybean milk. The fermented milk produced using the combined starter culture mixed with L. plantarum Y44 showed an angiotensin-converting-enzyme (ACE) inhibitory activity (53.56 ± 0.69%). Some peptides that regulate blood pressure were released in the fermented milk, such as AMKPWIQPK, GPVRGPFPII, LNVPGEIVE, NIPPLTQTPV, and YQEPVL. In spontaneously hypertensive rat (SHR) oral-administration experiments compared with the gavage unfermented milk group, the gavage feeding of SHRs with the fermented milk produced using the combined starter culture mixed with L. plantarum Y44 significantly reduced the blood pressure of the SHRs after long-term intragastric administration, shown with the systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreasing by 23.67 ± 2.49 mmHg and 15.22 ± 2.62 mmHg, respectively. Moreover, the abundance of short-chain fatty acids (SCFA), bacterial diversity in the gut microbiota, and SCFA levels including acetic acid, propionic acid, and butyric acid in the feces of the SHRs were increased via oral administration of the fermented milk produced using the combined starter culture containing L. plantarum Y44. Furthermore, the ACE-angiotensin II (Ang II)-angiotensin type 1 (AT 1) axis was downregulated, the angiotensin-converting-enzyme 2 (ACE 2)-angiotensin(1-7) (Ang1-7)-Mas receptor axis of the SHRs was upregulated, and then the RAS signal was rebalanced. The fermented milk obtained from the combined starter culture shows the potential to be a functional food with antihypertension properties.

Histone deacetylase inhibition by suberoylanilide hydroxamic acid during reperfusion promotes multifaceted brain and vascular protection in spontaneously hypertensive rats with transient ischaemic stroke

Hypertension is the most prevalent modifiable risk factor for stroke and is associated with worse functional outcomes. Pharmacological inhibition of histone deacetylases by suberoylanilide hydroxamic acid (SAHA) modulates gene expression and has emerged as a promising therapeutic approach to reduce ischaemic brain injury. Here, we have tested the therapeutic potential of SAHA administered during reperfusion in adult male spontaneously hypertensive (SHR) rats subjected to transient middle cerebral artery occlusion (tMCAO; 90 min occlusion/24 h reperfusion). Animals received a single dose of SAHA (50 mg/kg) or vehicle i.p. at 1, 4, or 6 h after reperfusion onset. The time-course of brain histone H3 acetylation was studied. After tMCAO, drug brain penetrance and beneficial effects on behavioural outcomes, infarct volume, oedema, angiogenesis, blood-brain barrier integrity, cerebral artery oxidative stress and remodelling, and brain and vascular inflammation were evaluated. SAHA increased brain histone H3 acetylation from 1 to 6 h after injection, reaching the ischaemic brain administered during reperfusion. Treatment given at 4 h after reperfusion onset improved neurological score, reduced infarct volume and oedema, attenuated microglial activation, prevented exacerbated MCA angiogenic sprouting and blood-brain barrier breakdown, normalised MCA oxidative stress and remodelling, and modulated brain and cerebrovascular cytokine expression. Overall, we demonstrate that SAHA administered during early reperfusion exerts robust brain and vascular protection after tMCAO in hypertensive rats. These findings are aligned with previous research in ischaemic normotensive mice and help pave the way to optimise the design of clinical trials assessing the effectiveness and safety of SAHA in ischaemic stroke.

Novel Targets and Potential Mechanisms of Mizuhopecten yessoensis-Derived Tripeptide NCW as Antihypertensive Peptides.

Mizuhopecten yessoensis-derived tripeptide Asn-Cys-Trp (NCW) exhibits a potent antihypertensive effect in vivo. However, a lack of knowledge of the antihypertensive mechanism of tripeptide NCW limits its application for functional foods industrialization. The purpose of this study is to elucidate the corresponding targets and mechanisms of tripeptide NCW in hypertension regulation. Administration of tripeptide NCW for 3 weeks, the blood pressure of spontaneously hypertensive rats (SHRs) is significantly decreased. After sacrifice, the serum sample is analyzed using tandem mass tag (TMT)-based liquid chromatography with tandem mass spectrometry to identify differentially expressed proteins. The proteomic analysis indicates that tripeptide NCW administration alters serum protein profiles in SHR rats, significantly upregulating 106 proteins and downregulating 30 proteins. These proteins enhance the glycolysis, glucose, and TCA cycle, improve amino metabolism, trigger the cAMP/PKA, cGMP/PKG, PI3K/AKT, and AMPK signal pathways, and inhibit Ras-regulated JNK activation, TGF-β/MAPK, and TGF-β/ RhoA/ROCK pathways. Tripeptide NCW supplementation is demonstrated to regulate signal pathways involved in the control of blood pressure and regulate the energy and amino acids metabolic processes in serum, providing important insights into the protective effects of tripeptide NCW on hypertension.

Targeted Affinity Purification and Mechanism of Action of Angiotensin-Converting Enzyme (ACE) Inhibitory Peptides from Sea Cucumber Gonads.

Protein hydrolysates from sea cucumber (Apostichopus japonicus) gonads are rich in active materials with remarkable angiotensin-converting enzyme (ACE) inhibitory activity. Alcalase was used to hydrolyze sea cucumber gonads, and the hydrolysate was separated by the ultrafiltration membrane to produce a low-molecular-weight peptide component (less than 3 kDa) with good ACE inhibitory activity. The peptide component (less than 3 kDa) was isolated and purified using a combination method of ACE gel affinity chromatography and reverse high-performance liquid chromatography. The purified fractions were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the resulting products were filtered using structure-based virtual screening (SBVS) to obtain 20 peptides. Of those, three noncompetitive inhibitory peptides (DDQIHIF with an IC50 value of 333.5 μmol·L-1, HDWWKER with an IC50 value of 583.6 μmol·L-1, and THDWWKER with an IC50 value of 1291.8 μmol·L-1) were further investigated based on their favorable pharmacochemical properties and ACE inhibitory activity. Molecular docking studies indicated that the three peptides were entirely enclosed within the ACE protein cavity, improving the overall stability of the complex through interaction forces with the ACE active site. The total free binding energies (ΔGtotal) for DDQIHIF, HDWWKER, and THDWWKER were -21.9 Kcal·mol-1, -71.6 Kcal·mol-1, and -69.1 Kcal·mol-1, respectively. Furthermore, a short-term assay of antihypertensive activity in spontaneously hypertensive rats (SHRs) revealed that HDWWKER could significantly decrease the systolic blood pressure (SBP) of SHRs after intravenous administration. The results showed that based on the better antihypertensive activity of the peptide in SHRs, the feasibility of targeted affinity purification and computer-aided drug discovery (CADD) for the efficient screening and preparation of ACE inhibitory peptide was verified, which provided a new idea of modern drug development method for clinical use.

Chemical Characterization of Phoenix dactylifera L. Seeds and their Beneficial Effects on the Vascular Response in Hypertensive Rats.

Although Phoenix dactylifera dates are traditionally consumed for their health benefits, no research has been done on the vascular response in hypertensive animals. This study evaluated the vascular relaxation of hydroalcoholic extracts from seeds of three varieties of P. dactylifera; Sukkari seed (SS), Ajwa seed (AS), and Mabroom seed (MS) on L-NAME-induced hypertension and spontaneously hypertensive rats (SHR). Results showed that all extracts (10µg/mL) caused relaxations higher than 60% in the aortic rings precontracted with 10- 6 M phenylephrine in normotensive rats, the SS extract was the most potent. Endothelial nitric oxide (NO) pathway is involved as significantly reduced vascular relaxation in denuded-endothelium rat aorta and with an inhibitor (10- 4 M L-Nω-Nitro arginine methyl ester; L-NAME) of endothelial nitric oxide synthase (eNOS). Confocal microscopy confirmed that 10µg/mL SS extract increases NO generation as detected by DAF-FM fluorescence in intact aortic rings. Consistent with these findings, vascular relaxation in intact aortic rings at 10µg/mL SS extract was significantly decreased in L-NAME-induced hypertensive rats (endothelial dysfunction model), but not in SHR. In both hypertensive models, the denuded endothelium blunted the vascular relaxation. In conclusion, the hydroalcoholic extract of the seed of P. dactylifera (Sukkari, Ajwa and Mabroom varieties) presents a potent endothelium-dependent vascular relaxation, via NO, in normotensive rats as well as in two different models of hypertension. This effect could be mediated by the presence of phenolic compounds identified by UHPLC-ESI-MS/MS, such as protocatechuic acid, and caftaric acid.

Serotonergic and Adrenergic Neuroreceptor Manipulation Ameliorates Core Symptoms of ADHD through Modulating Dopaminergic Receptors in Spontaneously Hypertensive Rats.

The core symptoms of attention deficit hyperactivity disorder (ADHD) are due to the hypofunction of the brain's adrenergic (NE) and dopamine (DA) systems. Drugs that enhance DA and NE neurotransmission in the brain by blocking their transporters or receptors are the current therapeutic strategies. Of late, the emerging results point out the serotonergic (5-HT) system, which indirectly modulates the DA activity in reducing the core symptoms of ADHD. On this basis, second-generation antipsychotics, which utilize 5-HT receptors, were prescribed to children with ADHD. However, it is not clear how serotonergic receptors modulate the DA activity to minimize the symptoms of ADHD. The present study investigates the efficacy of serotonergic and alpha-2 adrenergic receptor manipulation in tackling the core symptoms of ADHD and how it affects the DA neuroreceptors in the brain regions involved in ADHD. Fifteen-day-old male spontaneously hypertensive rats (SHRs) received 5-HT1A agonist (ipsapirone) or 5-HT2A antagonist (MDL 100907) (i.p.) or alpha-2 agonist (GFC) from postnatal days 15 to 42 along with age-matched Wistar Kyoto rats (WKY) (n = 8 in each group). ADHD-like behaviors were assessed using a battery of behavioral tests during postnatal days 44 to 65. After the behavioral tests, rat brains were processed to estimate the density of 5-HT1A, 5-HT2A, DA-D1, and DA-D2 neuroreceptors in the prefrontal cortex, the striatum, and the substantia nigra. All three neuroreceptor manipulations were able to minimize the core symptoms of ADHD in SHRs. The positive effect was mainly associated with the upregulation of 5-HT2A receptors in all three areas investigated, while 5-HT1A was in the prefrontal cortex and the substantia nigra. Further, the DA-D1 receptor expression was downregulated by all three neuroreceptor manipulations except for alpha-2 adrenergic receptor agonists in the striatum and 5-HT2A antagonists in the substantia nigra. The DA-D2 expression was upregulated in the striatum while downregulated in the prefrontal cortex and the substantia nigra. In this animal model study, the 5-HT1A agonist or 5-HT2A antagonist monotherapies were able to curtail the ADHD symptoms by differential expression of DA receptors in different regions of the brain.

Vasodilation and Blood Pressure-Lowering Effect of 3-Demethyl-2-Geranyl-4-Prenylbellidifoline, a Xanthone Obtained from Garcinia achachairu, in Hypertensive Rats.

3-demethyl-2-geranyl-4-prenylbellidifoline (DGP), a natural xanthone isolated from Garcinia achachairu, has previously demonstrated remarkable diuretic and renal protective actions. The present study expands its actions on the cardiovascular system by evaluating its vasorelaxant and blood pressure-lowering effects in spontaneously hypertensive rats (SHRs). Aortic endothelium-intact (E+) preparations of SHRs pre-contracted by phenylephrine and exposed to cumulative concentrations of G. achachairu extract, fractions, and DGP exhibited a significant relaxation compared to vehicle-only exposed rings. The non-selective muscarinic receptor antagonist (atropine), the non-selective inhibitor of nitric oxide synthase (L-NAME), as well as the inhibitor of soluble guanylate cyclase (ODQ) altogether avoided DGP-induced relaxation. Tetraethylammonium (small conductance Ca2+-activated K+ channel blocker), 4-aminopyridine (a voltage-dependent K+ channel blocker), and barium chloride (an influx-rectifying K+ channel blocker) significantly reduced DGP capacity to induce relaxation without the interference of glibenclamide (an ATP-sensitive inward rectifier 6.1 and 6.2 K+ channel blocker). Additionally, administration of DGP, 1 mg/kg i.v., decreased the mean, systolic, and diastolic arterial pressures, and the heart rate of SHRs. The natural xanthone DGP showed promising potential as an endothelium-dependent vasorelaxant, operating through the nitric oxide pathway and potassium channels, ultimately significantly reducing blood pressure in hypertensive rats.

The effects of renal denervation on blood pressure, cardiac hypertrophy, and sympathetic activity during the established phase of hypertension in spontaneously hypertensive rats.

This study aimed to investigate whether renal denervation (RDN) reduces blood pressure and attenuates cardiac hypertrophy with decreasing sympathetic activity in spontaneously hypertensive rats (SHRs), a model of essential hypertension, during the established phase of hypertension. We performed RDN or sham operation in 15-weeks-old SHRs. Thirty days after RDN, mean blood pressure measured by telemetry, heart weight, left ventricular wall thickness assessed by echocardiography, and urinary norepinephrine levels were significantly decreased in the RDN group compared to the Sham group. Furthermore, oxidative stress, as indicated by thiobarbituric acid reactive substances, in the rostral ventrolateral medulla, a pivotal region regulating basal sympathetic tone, was significantly decreased in the RDN group. In conclusion, RDN reduces blood pressure and attenuates cardiac hypertrophy with sympathoinhibition in the established phase of hypertension in SHRs. These findings highlight the sympathoinhibitory effect of RDN and suggest that RDN may be a potential therapy for hypertensive cardiac hypertrophy. Renal denervation reduces blood pressure and attenuates cardiac hypertrophy with sympathoinhibition in the established phase of hypertension in spontaneously hypertensive rats. This study highlights the sympathoinhibitory effect of renal denervation and suggests that renal denervation may be a potential therapy for hypertensive cardiac hypertrophy.

Phasic dopamine signals are reduced in the spontaneously hypertensive rat and increased by methylphenidate.

The spontaneously hypertensive rat (SHR) is a selectively bred animal strain that is frequently used to model attention-deficit hyperactivity disorder (ADHD) because of certain genetically determined behavioural characteristics. To test the hypothesis that the characteristically altered response to positive reinforcement in SHRs may be due to altered phasic dopamine response to reward, we measured phasic dopamine signals in the SHRs and Sprague Dawley (SD) rats using in vivo fast-scan cyclic voltammetry. The effects of the dopamine reuptake inhibitor, methylphenidate, on these signals were also studied. Phasic dopamine signals during the pairing of a sensory cue with electrical stimulation of midbrain dopamine neurons were significantly smaller in the SHRs than in the SD rats. Over repeated pairings, the dopamine response to the sensory cue increased, whereas the response to the electrical stimulation of dopamine neurons decreased, similarly in both strains. However, the final amplitude of the response to the sensory cue after pairing was significantly smaller in SHRs than in the SD rats. Methylphenidate increased responses to sensory cues to a significantly greater extent in the SHRs than in the SD rats, due largely to differences in the low dose effect. At a higher dose, methylphenidate increased responses to sensory cues and electrical stimulation similarly in SHRs and SD rats. The smaller dopamine responses may explain the reduced salience of reward-predicting cues previously reported in the SHR, whereas the action of methylphenidate on the cue response suggests a potential mechanism for the therapeutic effects of low-dose methylphenidate in ADHD.

Effects of physical training on hypothalamic neuronal activation and expressions of vasopressin and oxytocin in SHR after running until fatigue.

To assess the influence of physical training on neuronal activation and hypothalamic expression of vasopressin and oxytocin in spontaneously hypertensive rats (SHR), untrained and trained normotensive rats and SHR were submitted to running until fatigue while internal body and tail temperatures were recorded. Hypothalamic c-Fos expression was evaluated in thermoregulatory centers such as the median preoptic nucleus (MnPO), medial preoptic nucleus (mPOA), paraventricular nucleus of the hypothalamus (PVN), and supraoptic nucleus (SON). The PVN and the SON were also investigated for vasopressin and oxytocin expressions. Although exercise training improved the workload performed by the animals, it was reduced in SHR and followed by increased internal body temperature due to tail vasodilation deficit. Physical training enhanced c-Fos expression in the MnPO, mPOA, and PVN of both strains, and these responses were attenuated in SHR. Vasopressin immunoreactivity in the PVN was also increased by physical training to a lesser extent in SHR. The already-reduced oxytocin expression in the PVN of SHR was increased in response to physical training. Within the SON, neuronal activation and the expressions of vasopressin and oxytocin were reduced by hypertension and unaffected by physical training. The data indicate that physical training counterbalances in part the negative effect of hypertension on hypothalamic neuronal activation elicited by exercise, as well as on the expression of vasopressin and oxytocin. These hypertension features seem to negatively influence the workload performed by SHR due to the hyperthermia derived from the inability of physical training to improve heat dissipation through skin vasodilation.