Spontaneously Hypertensive Rats Research Articles

Exercise-induced neuroplasticity in autonomic nuclei restores the cardiac vagal tone and baroreflex dysfunction in aged hypertensive rats.

Aging is accompanied by considerable deterioration of homeostatic systems, such as autonomic imbalance characterized by heightened sympathetic activity, lower parasympathetic tone, and depressed heart rate (HR) variability, which are aggravated by hypertension. Here, we hypothesized that these age-related deficits in aged hypertensive rats can be ameliorated by exercise training, with benefits to the cardiovascular system. Therefore, male 22-mo-old spontaneously hypertensive rats (SHRs) and age-matched Wistar Kyoto (WKY) submitted to moderate-intensity exercise training (T) or kept sedentary (S) for 8 wk were evaluated for hemodynamic/autonomic parameters, baroreflex sensitivity, cardiac sympathetic/parasympathetic tone and analysis of dopamine β-hydroxylase (DBH+) and oxytocin (OT+) pathways of autonomic brain nuclei. Aged SHR-S versus WKY-S exhibited elevated mean arterial pressure (MAP: +51%) and HR (+20%), augmented pressure/HR variability, no cardiac vagal tone, and depressed reflex control of the heart (HR range, -28%; gain, -49%). SHR-T exhibited a lower resting HR, a partial reduction in the MAP (-14%), in the pressure/HR variabilities, and restored parasympathetic modulation, with improvement of baroreceptor reflex control when compared with SHR-S. Exercise training increased the ascending DBH+ projections conveying peripheral information to the paraventricular nucleus of hypothalamus (PVN), augmented the expression of OT+ neurons, and reduced the density of DBH+ neurons in the rostral ventrolateral medulla (RVLM) of SHR-T. Data indicate that exercise training induces beneficial neuroplasticity in brain autonomic circuitry, and it is highly effective to restore the parasympathetic tone, and attenuation of age-related autonomic imbalance and baroreflex dysfunction, thus conferring long-term benefits for cardiovascular control in aged hypertensive individuals.NEW & NOTEWORTHY Exercise training reduces high blood pressure and cardiovascular autonomic modulation in aged hypertensive rats. The dysfunction in the baroreflex sensitivity and impaired parasympathetic tone to the heart of aged hypertensive rats are restored by exercise training. Exercise induces beneficial neuroplasticity in the brain nuclei involved with autonomic control of cardiovascular function of aged hypertensive rats.

Effects of Long-Term Administration of Bovine Bone Gelatin Peptides on Myocardial Hypertrophy in Spontaneously Hypertensive Rats.

The research purpose was to investigate the effects and the underlying molecular mechanisms of bovine bone gelatin peptides (BGP) on myocardial hypertrophy in spontaneously hypertensive rats (SHR). BGP relieved myocardial hypertrophy and fibrosis in SHR rats in a dose-dependent manner by reducing the left ventricular mass index, myocardial cell diameter, myocardial fibrosis area, and levels of myocardial hypertrophy markers (atrial natriuretic and brain natriuretic peptide). Label-free quantitative proteomics analysis showed that long-term administration of BGP changed the left ventricle proteomes of SHR. The 37 differentially expressed proteins in the high-dose BGP group participated in multiple signaling pathways associated with cardiac hypertrophy and fibrosis indicating that BGP could play a cardioprotective effect on SHR rats by targeting multiple signaling pathways. Further validation experiments showed that a high dose of BGP inhibited the expression of phosphoinositide 3-kinase (Pi3k), phosphorylated protein kinase B (p-Akt), and transforming growth factor-beta 1 (TGF-β1) in the myocardial tissue of SHR rats. Together, BGP could be an effective candidate for functional nutritional supplements to inhibit myocardial hypertrophy and fibrosis by negatively regulating the TGF-β1 and Pi3k/Akt signaling pathways.

Sustained activation of 12/15 lipoxygenase (12/15 LOX) contributes to impaired renal recovery post ischemic injury in male SHR compared to females

BackgroundAcute kidney injury (AKI) due to ischemia-reperfusion (IR) is a serious and frequent complication in clinical settings, and mortality rates remain high. There are well established sex differences in renal IR, with males exhibiting greater injury following an ischemic insult compared to females. We recently reported that males have impaired renal recovery from ischemic injury vs. females. However, the mechanisms mediating sex differences in renal recovery from IR injury remain poorly understood. Elevated 12/15 lipoxygenase (LOX) activity has been reported to contribute to the progression of numerous kidney diseases. The goal of the current study was to test the hypothesis that enhanced activation of 12/15 LOX contributes to impaired recovery post-IR in males vs. females.Methods13-week-old male and female spontaneously hypertensive rats (SHR) were randomized to sham or 30-minute warm bilateral IR surgery. Additional male and female SHR were randomized to treatment with vehicle or the specific 12/15 LOX inhibitor ML355 1 h prior to sham/IR surgery, and every other day following up to 7-days post-IR. Blood was collected from all rats 1-and 7-days post-IR. Kidneys were harvested 7-days post-IR and processed for biochemical, histological, and Western blot analysis. 12/15 LOX metabolites 12 and 15 HETE were measured in kidney samples by liquid chromatography–mass spectrometry (LC/MS).ResultsMale SHR exhibited delayed recovery of renal function post-IR vs. male sham and female IR rats. Delayed recovery in males was associated with activation of renal 12/15 LOX, increased renal 12-HETE, enhanced endoplasmic reticulum (ER) stress, lipid peroxidation, renal cell death and inflammation compared to females 7-days post-IR. Treatment of male SHR with ML355 lowered levels of 12-HETE and resulted in reduced renal lipid peroxidation, ER stress, tubular cell death and inflammation 7-days post-IR with enhanced recovery of renal function compared to vehicle-treated IR male rats. ML355 treatment did not alter IR-induced increases in plasma creatinine in females, however, tubular injury and cell death were attenuated in ML355 treated females compared to vehicle-treated rats 7 days post-IR.ConclusionOur data demonstrate that sustained activation 12/15 LOX contributes to impaired renal recovery post ischemic injury in male and female SHR, although males are more susceptible on this mechanism than females.

Inhibition of the STIM1/Orai1 Signaling Pathway by Glycine Betaine Mitigates Myocardial Hypertrophy in Spontaneous Hypertension Rats.

Spontaneous hypertension is a leading risk factor for cardiovascular diseases morbidity and mortality. Glycine betaine (GB) is a natural vitamin that has the potential to lower blood pressure. This work attempted to investigate the role and mechanisms of GB in spontaneous hypertension. Spontaneously hypertensive rats (SHRs) were administrated with 100, 200, or 400 mg/kg of GB by gavage or combined with by injection of lentivirus-mediated STIM1 overexpression vector. The heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart weight/body weight (HW/BW) of rats were monitored. The pathological changes in myocardium were examined by hematoxylin and eosin staining and Masson staining. The expression of genes and proteins was detected by quantitative real-time PCR, western blotting, and immunohistochemistry. GB at 200 and 400 mg/kg reduced the HR, SBP, DBP and HW/BW in SHRs. GB decreased the cross-sectional area and fibrotic area in the myocardium and downregulated the expression of atrial natriuretic peptide (ANP) and β-myosin heavy chain (β-MHC) in the myocardium of SHRs. It indicated that GB treatment effectively alleviated myocardial hypertrophy in SHRs. Additionally, GB treatment repressed the expression of stromal interaction molecule 1 (STIM1) and calcium release-activated calcium channel protein 1 (Orai1) in the myocardium of SHRs. STIM1 overexpression reversed GB treatment-mediated inhibition of myocardial hypertrophy in SHRs. In conclusion, GB repressed STIM1/Orai1 signaling pathway, which contributed to alleviating myocardial hypertrophy in SHRs. Thus, our study provides a theoretical basis for GB as an antihypertensive drug.

Subdiaphragmatic vagal nerve stimulation attenuates the development of hypertension and alters nucleus of the solitary tract transcriptional networks in the spontaneously hypertensive rat.

Augmented vagal signaling may be therapeutic in hypertension. Most studies to date have used stimulation of the cervical vagal branches. Here, we investigated the effects of chronic intermittent electric stimulation of the ventral subdiaphragmatic vagal nerve branch (sdVNS) on long-term blood pressure, immune markers, and gut microbiota in the spontaneously hypertensive rat (SHR), a rodent model of hypertension characterized by vagal dysfunction, gut dysbiosis, and low-grade inflammation. We evaluated the effects of sdVNS on transcriptional networks in the nucleus of the solitary tract (NTS), a major cardioregulatory brain region with direct gut vagal projections. Male juvenile SHRs were implanted with radiotelemetry transmitters and vagal nerve cuffs for chronic intermittent electric sdVNS, applied three times per day for 7 consecutive weeks followed by 1 wk of no stimulation. Blood pressure was measured once a week using telemetry in the sdVNS group as well as age-matched sham-stimulated SHR controls. At the endpoint, colonic and circulating inflammatory markers, corticosterone, and circulating catecholamines were investigated. Bacterial 16 s sequencing measured gut bacterial abundance and composition. RNA sequencing evaluated the effects of sdVNS on transcriptional networks in the NTS. SHRs that received sdVNS exhibited attenuated development of hypertension compared with sham animals. No changes in peripheral inflammatory markers, corticosterone, or catecholamines and no major differences in gut bacterial diversity and composition were observed following sdVNS, apart from decreased abundance of Defluviitaleaceale bacterium detected in sdVNS SHRs compared with sham animals. RNA sequencing revealed significant sdVNS-dependent modulation of select NTS transcriptional networks, including catecholaminergic and corticosteroid networks.NEW & NOTEWORTHY We show that stimulation of the ventral subdiaphragmatic vagal nerve branch may be a promising potential approach to treating hypertension. The data are especially encouraging given that rodents received only 30 min per day of intermittent stimulation therapy and in view of the potential of long-term blood pressure effects that are not stimulus-locked.

Protective effect of novel angiotensin receptor neprilysin inhibitor S086 on target organ injury in spontaneously hypertensive rats

BackgroundHypertension is a clinical syndrome characterized by elevated systemic arterial blood pressure associated with injury to the heart, kidney, brain, and other organs. Angiotensin receptor neprilysin inhibitors (ARNi), including angiotensin receptor blockers (ARBs) and neprilysin inhibitors (NEPi), have been shown to be safe and effective at reducing blood pressure and alleviating development of target organ injury. This study was used to develop S086 as a novel ARNi and conducted preclinical studies in animal models to evaluate the protective effects of S086 on target organs. MethodsThis study used a 14-month-old spontaneously hypertensive rat (SHR) model to evaluate the protective effects of S086 on the cardiovascular system and organs such as heart and kidney by blood pressure monitoring, urine and blood examination, pathological examination, and immunological index detection. ResultsAfter administering S086 orally to the SHR, their blood pressure and levels of renal injury indicators such as serum creatinine and urinary microalbumin were reduced, and myocardial cell necrosis and cardiac fibrosis of the heart were significantly improved. In addition, there were also significantly improvements in the histological lesions of blood vessels and the kidneys. ConclusionsThe findings showed that S086 effectively reduced the blood pressure of SHR and had effects on alleviating development of heart, blood vessels and kidney.

Vasorelaxant and Antihypertensive Effects of (3β)-ursen-12-en-3,28-diol by NO/cGMP System

Objective: The aim of this study was to determine the vasorelaxant effect of semisynthetic derivatives of ursolic acid, establish the mode of action, and determine the antihypertensive effect of the most active compound. Methods: Isolated aorta rat rings (ex vivo assay), with and without endothelium, were used to determine the vasorelaxant effect of seven semisynthetic derivatives of ursolic acid (UA-01 to UA-07). Then, the effect of the most active compound was studied in ex vivo assay using L-NAME, ODQ and indomethacin to determine its mode action. Finally, the in vivo cardiovascular effect and molecular docking of the most active compound were determined. Results: UA-07 was the most potent compound of the derivatives, since UA-07 induced significant relaxant effect in concentration- and endothelium-dependent manners (Emax = 79.09% and EC50 = 110 μM) on aortic rat rings pre-contracted with noradrenaline (NA, 0.1 μM). Also, endothelium-derived nitric oxide seems to be involved in the mechanism of action of UA-07, because pre-incubation with L-NAME (a NOS inhibitor) and ODQ (a soluble guanylate cyclase inhibitor) significantly reduced its vasorelaxant effect. Further, UA-07 showed a similar binding affinity as ursolic acid on eNOS C1 binding pocket in in silico studies. Finally, treatment with UA-07 (50 mg/Kg) on spontaneously hypertensive rats (SHR) significantly decreased diastolic blood pressure for seven hours. Conclusion: These results demonstrate the significant antihypertensive effect of UA-07, possibly through the NO/cGMP system.

In silico screening and characterization, inhibition mechanism on ACE, and stability of antihypertensive peptides with Zn-chelating capacity identified from millet bran albumin hydrolysates

To obtain Angiotensin-I-Converting Enzyme (ACE) inhibition peptides with Zn-chelating capacity, millet bran albumin hydrolysates (MBAH) were subjected to Sephadex G-15 gel and reverse phase-high liquid performance chromatography, and UPLC-ESI-MS/MS analysis. Five oligopeptides including Val-Gly-Ser-Asp-Gly-Leu (VGSDGL), Thr-Gly-His-Gly-Val-Ala (TGHGVA), Gly-Cys-His-His-Tyr (GCHHY), Leu-Val-Glu-Ala-Val-Pro-Arg-Gly (LVEAVPRG) and Val-Leu-Ala-Gln-Glu-Glu (VLAQEE) were identified in MBAH. Of these, only pentapeptide GCHHY showed both ACE-inhibitory activity (IC50: 134.78 μmol/L) and Zn-chelating capacity (14.16 mg/g). Molecular docking and inhibition kinetics showed that GCHHY was a competitive inhibitor of ACE, because it could bind with Lys511 of ACE which belongs to the central S2 pocket. Moreover, GCHHY can affect zinc tetrahedral coordination in ACE through binding with Glu411 and His383. The sulfhydryl, amino and carboxyl groups of GCHHY can bind with zinc ions. Under the gastrointestinal digestion, the ACE-inhibitory activity of GCHHY was relatively stable, and the zinc solubility of GCHHY-Zn complexes was more stable than zinc sulfate (P < 0.05). In addition, both GCHHY and GCHHY-Zn complexes lowered the diastolic blood pressure and systolic blood pressure of spontaneous hypertensive rats at dose of 50–200 mg/kg body weight. These results suggested the potential applications of millet albumin peptides as ingredients for antihypertension or zinc fortification.

Acute poisoning by chlorpyrifos differentially impacts survival and cardiorespiratory function in normotensive and hypertensive rats

Hypertension is the most important and well-known risk factor for cardiovascular disease (CVD). Recently, acute organophosphate (OP) poisoning has also been pointed as a CVD risk factor. Despite this evidence, no studies have contrasted the acute toxicosis and cardiovascular (CV) effects of OP poisoning under conditions of normotension and hypertension. In this work, adult male normotensive Wistar and Spontaneously Hypertensive rats (SHR) were intraperitoneally injected with saline or chlorpyrifos (CPF), an OP compound, monitored for acute toxicosis signs and 24-h survival. After poisoning, blood pressure, heart rate and ventilation were recorded, the Bezold-Jarisch Reflex (BJR), the Chemoreflex (CR) were chemically activated, as well as the cardiac autonomic tone (AUT) was assessed. Erythrocyte and brainstem acetylcholinesterase and plasmatic butyrylcholinesterase (BuChE) activities were measured as well as lipid peroxidation, advanced oxidation protein products (AOPP), nitrite/nitrate levels, expression of catalase, TNFα and angiotensin-I converting enzyme (ACE-1) within the brainstem. CPF induced a much more pronounced acute toxicosis and 33 % lethality in SHR. CPF poisoning impaired ventilation in SHR, the BJR reflex responses in Wistar rats, and the chemoreflex tachypneic response in both strains. CPF inhibited activity of cholinesterases in both strains, increased AOPP and nitrite/nitrate levels and expression of TNFα and ACE-1 in the brainstem of Wistar rats. Interestingly, SHR presented a reduced intrinsic BuChE activity, an important bioscavenger. Our findings show that, CPF at sublethal doses in normotensive rats lead to lethality and much more pronounced acute toxicity signs in the SHR. We also showed that cardiorespiratory reflexes were differentially impacted after CPF poisoning in both strains and that the cardiorespiratory disfunction seems to be associated with interference in cholinergic transmission, oxidative stress and inflammation. These results points to an increased susceptibility to acute toxicosis in hypertension, which may impose a significant risk to vulnerable populations.

Astragalus (Astragalus mongholicus) Improves Ventricular Remodeling via ESR1 Downregulation RhoA/ROCK Pathway.

Astragalus (Astragalus mongholicus) alleviates myocardial remodeling caused by hypertension. However, the detailed molecular mechanism is unclear. This study aims to investigate the effect of Astragalus on ventricular remodeling in ovariectomized spontaneous hypertensive rats (OVX-SHR).Female SHR/NCrl rats were subjected to bilateral ovariectomy to establish the OVX-SHR model and treated with Astragalus extract by gavage. The hemodynamics and cardiac function parameters were measured. HE and Masson staining were used to detect the pathological structure of myocardial remodeling and observe the hyperplasia of myocardial collagen fibers. The immunohistochemistry tested the level of α-SMA. The expression levels of inflammatory cytokines, IκB, p65, Cleaved-Caspase3, RhoA, and ROCK1/2 were detected using Western blot. The method of qRT-PCR measured the expression of matrix metalloproteinase (MMP-2 and MMP-9).Hemodynamic and cardiac function parameters were significantly improved after a high dose of Astragalus extract and Valsartan treatment. The myocardial integrity of the model group was significantly reduced, arranged loosely, and disordered, while the expression of α-SMA was increased. However, Astragalus extract and Valsartan treatments significantly reduced the pathological damage and α-SMA. The levels of TNF-α, IL-1β, IL-6, TGF-β, MMP-2, and MMP-9 in the model group were increased but decreased after Astragalus extract treatment. Adding an ESR1 inhibitor attenuated the improvement effect of Astragalus extract on myocardial remodeling and restored the expression of RhoA and ROCK1/2.Astragalus extract attenuates the cardiac damage in OVX-SHR by downregulating the RhoA/ROCK pathway through ESR1.

Hypotensive and Endothelium-Dependent Vasorelaxant Effects of Grayblue Spicebush Ethanol Extract in Rats.

Hypertension is one of the most common chronic diseases, and its prevalence is increasing worldwide. Lindera glauca (Siebold & Zucc.) Blume, known as grayblue spicebush (GS), has been used as food and for medicinal purposes; however, studies about its hypotensive or vasorelaxant effects are lacking. Therefore, the hypotensive effect of an ethanolic extract of the GS branch (GSE) was investigated in 15-week-old spontaneously hypertensive rats (SHRs) using the tail cuff method. The GSE administration group (1000 mg/kg SHR body weight) showed a decrease in their systolic and diastolic blood pressure measured 4 h after its administration. In addition, we investigated its vasorelaxant effect using the thoracic aorta dissected from Sprague-Dawley rats. The GSE (0.5, 1, 2, 5, 10, and 20 μg/mL) showed an endothelium-dependent vasorelaxant effect, and its mechanisms were found to be relevant to the inward rectifier, voltage-dependent, and non-selective K+ channels. Moreover, the GSE (20 μg/mL) showed an inhibitory effect on aortic rings constricted with angiotensin II. Considering its hypotensive and vasorelaxant effects, GSE has potential as a functional food to help treat and prevent high blood pressure. However, further studies on the identification of the active components of GSE and safety evaluations of its use are needed.

Mild traumatic brain injury-induced persistent blood–brain barrier disruption is prevented by cyclosporine A treatment in hypertension

IntroductionMild traumatic brain injury (mTBI) and hypertension synergize to induce persistent disruption of the blood–brain barrier (BBB), neuroinflammation and cognitive decline. However, the underlying mechanisms are not known. Cerebral production of Cyclophilin A (CyPA) is induced in hypertension and after TBI, and it was demonstrated to activate the nuclear factor-κB (NF-kB)- matrix-metalloproteinase-9 (MMP-9) pathway in cerebral vessels leading to BBB disruption.MethodsTo test the role of CyPA in mTBI- and hypertension-induced BBB disruption we induced mTBI in normotensive and spontaneously hypertensive rats (SHR), then the animals were treated with cyclosporine A (a specific inhibitor of CyPA production) or vehicle for 7 days. We assessed BBB permeability and integrity, cerebral expression and activity of the CyPA-NF-kB-MMP-9 pathway, extravasation of fibrin and neuroinflammation.ResultsWe found that mild TBI induced BBB disruption and upregulation of the CyPA-NF-kB-MMP-9 pathway in hypertension, which were prevented by blocking CyPA. Cyclosporine treatment and preservation of BBB function prevented accumulation of blood-derived fibrin in the brain parenchyma of hypertensive rats after mTBI and reversed increased neuroinflammation.DiscussionWe propose that mTBI and hypertension interact to promote BBB disruption via the CyPA-NF-kB-MMP-9 pathway, and inhibition of cyclophilin production after mTBI may exert neuroprotection and improve cognitive function in hypertensive patients.

Role of LncMALAT1-miR-141-3p/200a-3p-NRXN1 Axis in the Impairment of Learning and Memory Capacity in ADHD.

As a prevalent neurodevelopmental disease, attention-deficit hyperactivity disorder (ADHD) impairs the learning and memory capacity, and so far, there has been no available treatment option for long-term efficacy. Alterations in gene regulation and synapse-related proteins influence learning and memory capacity; nevertheless, the regulatory mechanism of synapse-related protein synthesis is still unclear in ADHD. LncRNAs have been found participating in regulating genes in multiple disorders. For instance, lncRNA Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) has an essential regulatory function in numerous psychiatric diseases. However, how MALAT1 influences synapse-related protein synthesis in ADHD remains largely unknown. Here, our study found that MALAT1 decreased in the hippocampus tissue of spontaneously hypertensive rats (SHRs) compared to the standard controls, Wistar Kyoto (WKY) rats. Subsequent experiments revealed that MALAT1 enhanced the expression of neurexin 1 (NRXN1), which promoted the synapse-related genes (SYN1, PSD95, and GAP43) expression. Then, the bioinformatic analyses predicted that miR-141-3p and miR-200a-3p, microRNAs belonging to miR-200 family and sharing same seed sequence, could interact with MALAT1 and NRXN1 mRNA, which were further confirmed by luciferase report assays. Finally, rescue experiments indicated that MALAT1 influenced the expression of NRXN1 by sponging miR-141-3p/200a-3p. All data verified our hypothesis that MALAT1 regulated synapse-related proteins (SYN1, PSD95, and GAP43) through the MALAT1-miR-141-3p/200a-3p-NRXN1 axis in ADHD. Our research underscored a novel role of MALAT1 in the pathogenesis of impaired learning and memory capacity in ADHD and may shed more light on developing diagnostic biomarkers and more effective therapeutic interventions for individuals with ADHD.

Memory deficits and hippocampal cytokine expression in a rat model of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder characterized by hyperactivity, impulsivity, inattention, and deficits in working memory and time perception. While animal models have advanced our neurobiological understanding of this condition, there are limited and inconsistent data on working and elapsed time memory function. Inflammatory signaling has been identified as a key factor in memory and cognitive impairments, but its role in ADHD remains unclear. Additionally, the disproportionate investigation of male subjects in ADHD research has contributed to a poor understanding of the disorder in females. This study sought to investigate the potential connections between memory, neuroimmunology, and ADHD in both male and female animals. Specifically, we utilized the spontaneously hypertensive rat (SHR), one of the most extensively studied animal models of ADHD. Compared to their control, the Wistar-Kyoto (WKY) rat, male SHR are reported to exhibit several behavioral phenotypes associated with ADHD, including hyperactivity, impulsivity, and poor sustained attention, along with impairments in learning and memory. As the hippocampus is a key brain region for learning and memory, we examined the behavior of male and female SHR and WKY rats in two hippocampal-dependent memory tasks. Our findings revealed that SHR have delay-dependent working memory deficits that were similar to, albeit less severe than, those seen in hippocampal-lesioned rats. We also observed impairments in elapsed time processing in female SHR, particularly in the discrimination of longer time durations. To investigate the impact of inflammatory signaling on memory in these rats, we analyzed the levels of several cytokines in the dorsal and ventral hippocampus of SHR and WKY. Although we found some sex and genotype differences, concentrations were generally similar between groups. Taken together, our results indicate that SHR exhibit deficits in spatial working memory and memory for elapsed time, as well as some differences in hippocampal cytokine concentrations. These findings contribute to a better understanding of the neurobiological basis of ADHD in both sexes and may inform future research aimed at developing effective treatments for the disorder. Nonetheless, the potential mediating role of neuroinflammation in the memory symptomatology of SHR requires further investigation.

A novel heat-stable angiotensin-converting enzyme zinc-binding motif inhibitory peptide identified from corn silk

Ethnopharmacological relevanceHypertension is the most common and chronic severe health problem globally. Corn silk (CS), the silky fibers of corn (Zea mays L.), has a long history of traditional usage as a remedy for edema and hypertension. Aim of the studyThe aim of the study was to explore the underlying mechanism by which CS exerts its anti-hypertensive effects and investigate the presence of bioactive molecules in CS aqueous extract. Materials and methodsWe analyzed the effects of boiling water extract of CS on angiotensin-converting enzyme (ACE) activities, the critical enzyme involved in the regulation of blood pressure. ACE inhibitory peptides from CS extract were identified using proteomics and bioinformatics tools. The binding interfaces between these peptides and ACE were defined by hydrogen-deuterium exchange mass spectrometry (HDX-MS). Subsequently, the anti-hypertensive effects of peptides were further investigated in spontaneously hypertensive rats (SHR). ResultsOur data showed that CS extract exhibited dose-dependent inhibition of ACE activity. Liquid chromatography-tandem mass spectrometry identified a heat-stable peptide bank with 1313 distinct peptide fragments within the CS boiling water extract. Among these, CS-1 (LVPGWTKPICIGR) was selected through PeptideRanker and BIOPEP-UWM analyses. In vitro ACE inhibitory assays confirmed that CS-1 exhibited dose-dependent ACE inhibition, with IC50 values of 10.32 ± 0.41 μmol/L (using HHL as the substrate) and 13.74 ± 1.87 μmol/L (using ZFHL as the substrate). Oral administration of CS-1 led to a significant dose-dependent reduction in blood pressure, with the maximal decrease (42.33 ± 13.08 mmHg) occurring 0.5 h after ingestion. HDX-MS analysis revealed that CS-1 interacted with the zinc-binding motif of ACE, and hydrogen bond interactions were predicted between CS-1 and specific residues, including His361 in the N-domain, as well as His382, Gly386, and His387 in the C-domain of ACE. These findings suggested that the interaction of CS-1 with the residues in the zinc-binding motif of ACE led to ACE activity inhibition and a subsequent decrease in blood pressure in rats. ConclusionsA novel heat-stable ACE inhibitory peptide, which interacted with the zinc-binding motif of ACE and reduced blood pressure in SHR, was identified in the CS extract. The presence of ACE inhibitory peptides in the CS extract supports its traditional use in ethnopharmacology for hypertension.

Acupuncture Alleviates Chronic Ischemic White Matter Injury in SHR Rats via JNK-NMDAR Circuit.

To study the protective mechanism of acupuncture at "Jiangya Recipe" on chronic ischemic white matter injury in spontaneously hypertensive rats (SHR) and the regulation of Jun N-terminal kinase-N-methyl-D-aspartate receptor (JNK-NMDAR) loop. A hypertensive white matter injury model was established in 46 male SHR rats aged 11 weeks by bilateral common carotid artery tapering (SHR-2VGO). In the SHR sham operation group, only bilateral common carotid arteries were isolated and in the SHR-2VGO modeling group, 36 rats were used for microcoil spring clip implantation to narrow the common carotid arteries and then, after 2 weeks of modeling, rats with impaired motor function were removed, and SHR-2VGO rats with successful final models were randomly divided into the model group, JNK blocking group, and acupuncture group. The sham operation group, model group, and JNK blocking group underwent the same grasping fixation, and the acupuncture group received acupuncture at acupoints "Jiangya Fang" once daily. In the JNK blocker group, an injection cannula was implanted into the lateral ventricle and sp600125 was injected into the lateral ventricle at 4.5 ul/day for 4 weeks. One week after the end of the intervention, white matter lesions were detected by MRI DWI and T2 imaging, and the learning and memory ability of rats was tested by Y-Maze and Passive Avoidance. Myelin density was detected by luxol fast blue (LFB) staining, also axon arrangement, myelin integrity, and thickness of neurons were detected by electron microscopy; neuronal morphology and the number of Nissl bodies in the hippocampus were detected by Nissl staining, dendritic spine density changes were detected by Golgi staining, and JNK, NMDAR1, and N-methyl-D-receptor 2B (NMDAR2B) in DG, CA3 region of hippocampus were detected by immunohistochemistry, protein expression of p-JNK/JNK, p-NMDAR1/NMDAR1, NMDAR2B, GSK3β protein expression in the fimbria of hippocampus was detected by Western blot. The Y maze test of SHR-2VGO+Acu and SHR-2VGO+ sp600125 group showed that the spontaneous alternating reaction rate increased significantly. At the same time, the incubation period increased significantly and the number of errors decreased significantly in Passive Avoidance. MRI T2WI showed that the white matter high signal of the corpus callosum, internal capsule and hippocampal fimbria in the SHR-2VGO+ sp600125 and SHR-2VGO+Acu groups was significantly lower than that in the SHR-2VGO model group, and the striatum and anterior commissure were not obvious. DWI showed that the SHR-2VGO model group had scattered high signal and limited diffusion movement in both the internal capsule and striatum, but the difference between groups was not obvious. Compared with SHR-2VGO rats, LFB staining of SHR-2VGO + sp600125 and SHR-2VGO +Acu groups showed significant relaxation of myelin porosity in corpus callosum, striatum, inner capsule, anterior commissure and hippocampal fimbria, and electron microscopy showed improved axonal myelin integrity and thickness in corpus callosum region. Also, the number of blue patchy Nissl bodies increased, and the number and complexity of dendritic spines increased significantly in Golgi staining. Immunohistochemical detection showed that JNK levels in DG and CA3 region were increased and NMDAR1 and NMDAR2B levels were decreased in SHR-2VGO+Acu and SHR-2VGO+ sp600125 groups. Meanwhile, protein expressions of GSK3β, NMDAR1/p-NMDAR1 and NMDAR2B in fimbria of hippocampus were increased, and JNK/P-JNK protein expression decreased. Acupuncture can increase the density and thickness of myelin sheath in white matter areas of corpus callosum, anterior commissure and hippocampal fimbria, increase the number and length of hippocampal neuronal dendrites, and improve hypertensive white matter injury and cognitive decline through JNK-NMDAR pathway.

Role of K+ and Ca2+ Channels in the Vasodilator Effects of Plectranthus barbatus (Brazilian Boldo) in Hypertensive Rats.

Plectranthus barbatus, popularly known as Brazilian boldo, is used in Brazilian folk medicine to treat cardiovascular disorders including hypertension. This study investigated the chemical profile by UFLC-DAD-MS and the relaxant effect by using an isolated organ bath of the hydroethanolic extract of P. barbatus (HEPB) leaves on the aorta of spontaneously hypertensive rats (SHR). A total of nineteen compounds were annotated from HEPB, and the main metabolite classes found were flavonoids, diterpenoids, cinnamic acid derivatives, and organic acids. The HEPB promoted an endothelium-dependent vasodilator effect (~100%; EC50 ~347.10 μg/mL). Incubation of L-NAME (a nonselective nitric oxide synthase inhibitor; EC50 ~417.20 μg/mL), ODQ (a selective inhibitor of the soluble guanylate cyclase enzyme; EC50 ~426.00 μg/mL), propranolol (a nonselective α-adrenergic receptor antagonist; EC50 ~448.90 μg/mL), or indomethacin (a nonselective cyclooxygenase enzyme inhibitor; EC50 ~398.70 μg/mL) could not significantly affect the relaxation evoked by HEPB. However, in the presence of atropine (a nonselective muscarinic receptor antagonist), there was a slight reduction in its vasorelaxant effect (EC50 ~476.40 μg/mL). The addition of tetraethylammonium (a blocker of Ca2+-activated K+ channels; EC50 ~611.60 μg/mL) or 4-aminopyridine (a voltage-dependent K+ channel blocker; EC50 ~380.50 μg/mL) significantly reduced the relaxation effect of the extract without the interference of glibenclamide (an ATP-sensitive K+ channel blocker; EC50 ~344.60 μg/mL) or barium chloride (an influx rectifying K+ channel blocker; EC50 ~360.80 μg/mL). The extract inhibited the contractile response against phenylephrine, CaCl2, KCl, or caffeine, similar to the results obtained with nifedipine (voltage-dependent calcium channel blocker). Together, the HEPB showed a vasorelaxant effect on the thoracic aorta of SHR, exclusively dependent on the endothelium with the participation of muscarinic receptors and K+ and Ca2+ channels.

Lactobacillus induced by irbesartan on spontaneously hypertensive rat contribute to its antihypertensive effect.

Hypertension is linked to gut dysbiosis. Here, the impact of the angiotensin receptor antagonist irbesartan on the gut microbiota of spontaneously hypertensive rats (SHR) were investigated. In addition, we assessed their contribution to its antihypertensive effect. Eight-week-old Wistar-Kyoto (WKY) rats and SHR were administered irbesartan for 8 weeks. Fecal microbiota transplantation (FMT) was performed from SHR treated with irbesartan or untreated SHR to recipient untreated SHR. The preventive effect of Lactobacillus on hypertension in SHR was evaluated. Blood pressure (BP) was calculated using a tail-sleeve sphygmomanometer. To better assess the composition of the gut microbiota, the V3-V4 region of the 16S rRNA gene was amplified while short-chain fatty acids (SCFAs) in feces were tested by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Irbesartan restored gut dysbiosis, increased the abundance of Lactobacillus , and improved anti-inflammatory ability, antioxidative ability, intestinal integrity, and intestinal inflammation in SHR. The microbiota in SHR-treated irbesartan could reduce BP and improve antioxidative ability and gut integrity in SHR. Lactobacillus johnsonii ( L. johnsonii ) and Lactobacillus reuteri ( L. reuteri ) reduced BP, restored gut dysbiosis and improved anti-inflammatory ability, antioxidative ability, intestinal integrity in SHR. Most notably, irbesartan, L. johnsonii , and L. reuteri can significantly increase SCFA content in SHR feces. The current study demonstrated that irbesartan treatment ameliorated gut dysbiosis in SHR. Irbesartan induced alterations in gut microbiota, with increased prevalence of Lactobacillus .

Herbal medicine (Oryeongsan) for fluid and sodium balance in renal cortex of spontaneously hypertensive rats

BackgroundHerbal medicine Oryeongsan (ORS), also known as Wulingsan in Chinese, has been used for the treatment of impaired body fluid balance. However, the mechanisms involved are not clearly defined. The purpose of the present study was to identify the actions of ORS on the renal excretory function and blood pressure (BP) and to define the mechanisms involved in association with renin-angiotensin system (RAS) and natriuretic peptide system (NPS) in spontaneously hypertensive rats (SHR), an animal model of human essential hypertension. MethodsChanges in urine volume (UV), excretion of electrolytes including Na+ (urinary excretion of Na+ (UNaV)) were measured. RT-PCR was performed to trace the changes in expression of RAS, NPS and sodium (Na+)-hydrogen (H+) exchanger 3 (NHE3) in the renal cortex. ResultsIn the SHR treated with vehicle (SHR-V) group, UV and UNaV were suppressed and the Na+ balance was maintained at the higher levels leading to an increase in BP compared to WKY-V group. These were accompanied by an increase in NHE3 expression with an accentuation of angiotensin I converting enzyme-angiotensin II type 1 (ACE-AT1) receptor and concurrent suppression of angiotensin II type 2 (AT2) receptor/ACE2-Mas receptor expression in the renal cortex. Chronic treatment with ORS increased UV and UNaV, and decreased the Na+ and water balance with a decrease in BP in the ORS-treated SHR-ORS group compared to SHR-V. These were accompanied by a decrease in NHE3 expression with a suppression of ACE-AT1 receptor and concurrent accentuation of AT2/ACE2-Mas receptor. ConclusionThe present study shows that ORS reduced BP with a decrease in Na+ and water retention by a suppression of NHE3 expression via modulation of RAS and NPS in SHR. The present study provides pharmacological rationale for the treatment of hypertension with ORS in SHR.

Follistatin-like 1 protects endothelial function in the spontaneously hypertensive rat by inhibition of endoplasmic reticulum stress through AMPK-dependent mechanism

ABSTRACT Objective Endothelial dysfunction is a critical initiating factor in the development of hypertension and related complications. Follistatin-like 1 (FSTL1) can promote endothelial cell function and stimulates revascularization in response to ischemic insult. However, it is unclear whether FSTL1 has an effect on ameliorating endothelial dysfunction in spontaneously hypertensive rats (SHRs). Methods Wistar Kyoto (WKY) and SHRs were treated with a tail vein injection of vehicle (1 mL/day) or recombinant FSTL1 (100 μg/kg body weight/day) for 4 weeks. Blood pressure was measured by tail-cuff plethysmograph, and vascular reactivity in mesenteric arteries was measured using wire myography. Results We found that treatment with FSTL1 reversed impaired endothelium-dependent relaxation (EDR) in mesenteric arteries and lowered blood pressure of SHRs. Decreased AMP-activated protein kinase (AMPK) phosphorylation, elevated endoplasmic reticulum (ER) stress markers, increased reactive oxygen species (ROS), and reduction of nitric oxide (NO) production in mesenteric arteries of SHRs were also reversed by FSTL1 treatment. Ex vivo treatment with FSTL1 improved the impaired EDR in mesenteric arteries from SHRs and reversed tunicamycin (ER stress inducer)-induced ER stress and the impairment of EDR in mesenteric arteries from WKY rats. The effects of FSTL1 were abolished by cotreatment of compound C (AMPK inhibitor). Conclusions These results suggest that FSTL1 prevents endothelial dysfunction in mesenteric arteries of SHRs through inhibiting ER stress and ROS and increasing NO production via activation of AMPK signaling.