Control Spontaneously Hypertensive Rats Research Articles

Chronic inhibition of angiotensin converting enzyme lowers blood pressure in spontaneously hypertensive rats by attenuation of sympathetic tone: The role of enhanced baroreflex sensitivity

Spontaneously hypertensive rats (SHR) are characterized by sympathetic hyperactivity and insufficient parasympathetic activity, and their high blood pressure (BP) can be lowered by long-term inhibition of the renin-angiotensin system. The aim of our study was to determine the influence of chronic inhibition of angiotensin converting enzyme (ACE) by captopril on cardiovascular regulation by the sympathetic and parasympathetic nervous system. Implanted radiotelemetric probes or arterial cannulas were used to measure mean arterial pressure (MAP), heart rate (HR), and arterial baroreflex in adult SHR and Wistar-Kyoto (WKY) rats under basal or stress conditions. MAP and the low-frequency component of systolic blood pressure variability (LF-SBPV, marker of sympathetic activity) were greater in SHR than in WKY rats. Under basal conditions chronic captopril treatment reduced both parameters more effectively in SHR, and the same was true during acute restraint stress. HR was similar in control rats of both strains, but WKY rats showed greater heart rate variability (HRV), indicating higher parasympathetic activity. Captopril administration increased HR in both strains, whereas HRV was decreased only in WKY. Chronic captopril treatment improved the impaired baroreflex-HR control in SHR by increasing the sensitivity but not the capacity of vagal arm of arterial baroreflex. Captopril treatment attenuated BP changes elicited by dimethylphenylpiperazinium (DMPP, agonist of nicotinic acetylcholine receptors), especially in SHR, indicating that sympathetic nerve transmission is facilitated by angiotensin II more in hypertensive than in normotensive animals. Thus, chronic ACE inhibition improves baroreflex sensitivity and lowers BP through both central and peripheral attenuation of sympathetic tone.

Hepatoprotective and cardioprotective effects of empagliflozin in spontaneously hypertensive rats fed a high-fat diet

A combination of liver and heart dysfunction worsens the prognosis of human survival. The aim of this study was to investigate whether empagliflozin (a sodium-glucose transporter-2 inhibitor) has beneficial effects not only on cardiac and renal function but also on hepatic function. Adult (6-month-old) male spontaneously hypertensive rats (SHR) were fed a high-fat diet (60% fat) for four months to induce hepatic steatosis and mild heart failure. For the last two months, the rats were treated with empagliflozin (empa, 10 mg.kg-1.day-1 in the drinking water). Renal function and oral glucose tolerance test were analyzed in control (n=8), high-fat diet (SHR+HF, n=10), and empagliflozin-treated (SHR+HF+empa, n=9) SHR throughout the study. Metabolic parameters and echocardiography were evaluated at the end of the experiment. High-fat diet feeding increased body weight and visceral adiposity, liver triglyceride and cholesterol concentrations, and worsened glucose tolerance. Although the high-fat diet did not affect renal function, it significantly worsened cardiac function in a subset of SHR rats. Empagliflozin reduced body weight gain but not visceral fat deposition. It also improved glucose sensitivity and several metabolic parameters (plasma insulin, uric acid, and HDL cholesterol). In the liver, empagliflozin reduced ectopic lipid accumulation, lipoperoxidation, inflammation and pro-inflammatory HETEs, while increasing anti-inflammatory EETs. In addition, empagliflozin improved cardiac function (systolic, diastolic and pumping) independent of blood pressure. The results of our study suggest that hepatoprotection plays a decisive role in the beneficial effects of empagliflozin in preventing the progression of cardiac dysfunction induced by high-fat diet feeding.

Danhong formula alleviates endothelial dysfunction and reduces blood pressure in hypertension by regulating MicroRNA 24 - Phosphatidylinositol 3-Kinase-Serine/Threonine Kinase- Endothelial Nitric Oxide Synthase axis

Ethnopharmacological relevanceEssential hypertension (EH) is one of the important risk factors of cardio-cerebrovascular diseases, and it can significantly increase the incidence and mortality of acute myocardial infarction, cerebral infarction and hemorrhage. Danhong Formula (DHF) was consisting of Radix et Rhizoma Salviae Miltiorrhizae (Salvia miltiorrhiza Bge., Labiatae, Danshen in Chinese) and Flos Carthami (Carthamus tinctorius L., Compositae, Honghua in Chinese) (Plant names have been checked with http://www.the plant list.org on June 28th, 2023) was approved by State Food and Drug Administration of China, that has been used for thousands of years in the treatment of cardiovascular diseases in China with proven safety and efficacy. Though our previous studies have found that DHF improved endothelial dysfunction (ED) and decreased high blood pressure (BP), the underlying mechanisms of its antihypertensive effect still remain unclear. Aim of the studyThis study investigated whether DHF regulated MicroRNA 24- Phosphatidylinositol 3-Kinase-Serine/Threonine Kinase- Endothelial Nitric Oxide Synthase (miR-24 - PI3K/AKT/eNOS) axis to produce antihypertensive effect and improve endothelial dysfunction. Materials and methodsFirstly, the chemical components of DHF were analyzed by UHPLC-MS. After that, BP was continuously monitored within the 1st, 3rd, and 4th week in SHR to evaluate the antihypertensive effect of DHF intraperitoneal injection. In addition, not only the contents of serum nitric oxide (NO), prostacyclin (PGI2), and angiotensin II (Ang II) were detected, but also the isolated aorta ring experiment was conducted to evaluate the vasomotoricity to evaluate of DHF on improving endothelial dysfunction. Key proteins or mRNA expression associated with miR-24 - PI3K/AKT/eNOS axis in aorta were detected by capillary Western blot, immunohistochemistry or RT-PCR to explore the underlying mechanisms. Index of NO, Ang II PGI2 and key proteins or mRNA expression were also conducted in miR-24-3p over-expression HUVECs model. ResultsCompared with SHR control group, DHF (4 mL/kg/day, 2 mL/kg/day, 1 mL/kg/day) treatment significantly reduced high BP in SHR and selectively increased acetylcholine (Ach) induced vasodilation, but not sodium nitroprusside (SNP) in a manner of concentration dependency in isolated aorta ring. DHF (4 mL/kg/day, 1 mL/kg/day) treatment was accompanying an increment of NO and PGI2, and lowering AngII in SHR. Moreover, DHF treatment significantly up-regulated expression of p-PI3K, p-AKT, mTOR, eNOS and p-eNOS, but down-regulated miR-24-3p expression in aorta. Compared with miR-24-3p over-expression HUVECs model group, DHF treatment inhibited miR- 24-3p expression and up-regulated p-PI3K, p-AKT, mTOR and eNOS mRNA expression. Similarly, DHF treatment increased PI3K, AKT, mTOR and eNOS protein expression in HUVECs by Western blot. ConclusionsThese findings suggest that DHF alleviates endothelial dysfunction and reduces high BP in SHR mediated by down-regulating miR-24 via ultimately facilitating up-regulation of PI3K/AKT/eNOS axis. This current study firstly demonstrates a potential direction for antihypertensive mechanism of DHF from microRNA aspect and will promote its clinical applications.

Rewiring of IGF1 secretion and enhanced IGF1R signaling induced by co-chaperone carboxyl-terminus of Hsp70 interacting protein in adipose-derived stem cells provide augmented cardioprotection in aging-hypertensive rats.

Aging-associated cardiovascular diseases depend on the longitudinal deterioration of stem cell dynamics. The entire mechanism behind it is not completely understood. However, many studies suggest that endocrine pathways, particularly the insulin-like growth factor-1(IGF1) signaling pathway are involved in cardioprotection, especially in stem-cell treatments. Here, we investigated the role of a co-chaperone, carboxyl-terminus of Hsp70 interacting protein (CHIP) in the aspects of growth factor secretion and receptor stabilization in mesenchymal stem cells (MSCs). Briefly, we overexpressed CHIP in rat adipose-derived stem cells (rADSCs) and explored the consequences in vitro, and in vivo, in spontaneously hypertensive rats (SHR). Our data revealed that CHIP overexpression in rADSCs promoted the secretion of insulin-like growth factor-1 (IGF1) and IGF binding protein-3 (IGFBP3) as per immunoblot/cytokine array analysis. We also found that these results were dependent on the nuclear translocation of signal transducer and activator of transcription 3 (STAT3) in rADSCs. Further, the CHIP co-chaperone was also involved in the stabilization of the receptor of IGF1 (IGF1R); interactions between the beta transmembrane region of IGF1R, and the tetracopeptide repeat (TPR) domain of CHIP were evident. Importantly, after the transplantation of lentiviral CHIP overexpression of rADSCs (rADSCsCHIP-WT) into nine months aging-SHR led to an increase in their cardiac function - increased ejection fraction and fractional shortening (≈15% vs. control SHR) - as well as a decrease in their heart size and heart rate, respectively. Altogether, our results support the use of CHIP overexpressing stem cells for the mitigation of cardiac hypertrophy and remodeling associated with late-stage hypertension.

Subdiaphragmatic Vagal Nerve Stimulation Attenuates the Development of Hypertension and Alters NTS Transcriptional Networks in the SHR.

Augmented vagal signaling may be therapeutic in hypertension. Most studies to date employed 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 (BP), 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 SHR were implanted with radiotelemetry transmitters and vagal nerve cuffs for chronic intermittent electric sdVNS, applied three times per day for seven consecutive weeks followed by one week of no stimulation. BP was measured once a week using telemetry in the sdVNS group as well as the age-matched Sham-stimulated SHR controls. At endpoint, colonic and circulating inflammatory markers and corticosterone, and circulating catecholamines were investigated. Bacterial 16s sequencing measured gut bacterial abundance and composition. RNAseq evaluated the effects of sdVNS on transcriptional networks in the NTS. SHRs that received sdVNS exhibited attenuated development of hypertension compared to the Sham. 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 the sdVNS SHR compared to the Sham. RNAseq revealed significant sdVNS-dependent modulation of select NTS transcriptional networks, including catecholaminergic and corticosteroid networks.

Correlational Study of Aminopeptidase Activities between Left or Right Frontal Cortex versus the Hypothalamus, Pituitary, Adrenal Axis of Spontaneously Hypertensive Rats Treated with Hypotensive or Hypertensive Agents.

It has been suggested that the neuro-visceral integration works asymmetrically and that this asymmetry is dynamic and modifiable by physio-pathological influences. Aminopeptidases of the renin-angiotensin system (angiotensinases) have been shown to be modifiable under such conditions. This article analyzes the interactions of these angiotensinases between the left or right frontal cortex (FC) and the same enzymes in the hypothalamus (HT), pituitary (PT), adrenal (AD) axis (HPA) in control spontaneously hypertensive rats (SHR), in SHR treated with a hypotensive agent in the form of captopril (an angiotensin-converting enzyme inhibitor), and in SHR treated with a hypertensive agent in the form of the L-Arginine hypertensive analogue L-NG-Nitroarginine Methyl Ester (L-NAME). In the control SHR, there were significant negative correlations between the right FC with HPA and positive correlations between the left FC and HPA. In the captopril group, the predominance of negative correlations between the right FC and HPA and positive correlations between the HPA and left FC was maintained. In the L-NAME group, a radical change in all types of interactions was observed; particularly, there was an inversion in the predominance of negative correlations between the HPA and left FC. These results indicated a better balance of neuro-visceral interactions after captopril treatment and an increase in these interactions in the hypertensive animals, especially in those treated with L-NAME.

Experimental control for the spontaneously hypertensive rat: Wistar or Wistar Kyoto? A systematic review and meta-analysis

This study aimed to carry out a systematic review and meta-analysis of studies that measured the blood pressure (BP) and body mass (BM) of the Wistar (WIS), Wistar Kyoto (WKY) and spontaneously hypertensive rat (SHR) strains. The methods followed the criteria established by the PRISMA guidelines. A systematic search in PubMed, Web of Science and EMBASE was performed. After analysis, 83 studies were included for systematic review, and of those, 74 were applicable for BP meta-analysis and 39 for BM meta-analysis. The SHR had higher BP compared to control strains, while WKY had higher systolic BP compared to WIS. The WIS are heavier, followed by the WKY and the SHR. The WIS and WKY strains exhibit similarities and differences, and the choice of the strain to be used as the SHR control requires a deep analysis. However, our results support this theory that both strains can be used as SHR controls.

Abstract 089: Periodontitis Accelerates The Onset Of Arterial Hypertension In SHR, While The Electrical Activation Of The Carotid Sinus Nerve Delays The Beginning Of The Increase In Blood Pressure.

Background: We demonstrated that electrical stimulation of thecarotid sinus nerve (CSN) has a protective effect on the development ofPeriodontitis (PER). However, whether PER accelerates the onset ofhypertension in SHR is unknown. If this is true, it could be expected that theactivation of the CSN would retard the onset of hypertension. Objective: To evaluate whether PER accelerates the onset of hypertension inSHR; and whether the electrical stimulation of the CSN in SHR would delay theonset of this outcome. Methods: Three weeks old male SHRs were implanted with electrodes aroundthe CSN for daily electrical stimulation (3V; 1 ms; 30Hz; 10 minutes per day, fortwo weeks), combined with bilateral ligation of the lower first molar with a silksuture for PER induction. Besides, PER induction was combined with theadministration, p.o., of Porphyromonas gingivalis (strain W83) injected threetimes a week. The femoral artery of a five-week-old SHR was cannulated, and 24hours later, with the animals awakened, the systolic (SAP), diastolic (DAP), andmean (MAP) arterial pressure were recorded. Control SHR (SHAM) was notexposed to PER. Results: Five weeks old control SHR (SHAM) did not have installed arterialhypertension. However, when the SHR were submitted to PER, they alreadyexhibited a higher arterial pressure at five weeks, when compared to the SHAMgroup (SAP PER 150±4 vs. SHAM 124±3 mmHg, n=8, p≤0.001; DAP PER 103±5 vs. SHAM 85±5 mmHg, n=8, p≤0.05; MAP PER 119±4 vs. SHAM 98±4 mmHg,n=8, p ≤0.01). Nevertheless, the stimulation of the CSN prevented this increasein blood pressure in the five weeks old SHR submitted to PER (PAS SHR PERstim. 130±4 vs. SHAM 124±3 mmHg; PAD SHR PER stim. 84±3 vs. SHAM 85±5mmHg; PAM SHR PER stim. 99±4 vs. SHAM 98±4 mmHg, n=8, p>0, 05). Conclusion: PER accelerated the onset of arterial hypertension in SHR withinfive weeks. However, the activation of the baroreceptor and chemoreceptor reflexes through the electrical stimulation of the CSN in SHR exposed to PERdelayed the onset of arterial hypertension.

Red Quinoa Hydrolysates with Antioxidant Properties Improve Cardiovascular Health in Spontaneously Hypertensive Rats.

In recent years, quinoa has been postulated as an emerging crop for the production of functional foods. Quinoa has been used to obtain plant protein hydrolysates with in vitro biological activity. The aim of the present study was to evaluate the beneficial effect of red quinoa hydrolysate (QrH) on oxidative stress and cardiovascular health in an in vivo experimental model of hypertension (HTN) in the spontaneously hypertensive rat (SHR). The oral administration of QrH at 1000 mg/kg/day (QrHH) showed a significant reduction in SBP from baseline (-9.8 ± 4.5 mm Hg; p < 0.05) in SHR. The mechanical stimulation thresholds did not change during the study QrH groups, whereas in the case of SHR control and SHR vitamin C, a significant reduction was observed (p < 0.05). The SHR QrHH exhibited higher antioxidant capacity in the kidney than the other experimental groups (p < 0.05). The SHR QrHH group showed an increase in reduced glutathione levels in the liver compared to the SHR control group (p < 0.05). In relation to lipid peroxidation, SHR QrHH exhibited a significant decrease in plasma, kidney and heart malondialdehyde (MDA) values compared to the SHR control group (p < 0.05). The results obtained revealed the in vivo antioxidant effect of QrH and its ability to ameliorate HTN and its associated complications.

Spontaneously hypertensive rats vs. Wistar Kyoto and Wistar rats: An assessment of anxiety, motor activity, memory performance, and seizure susceptibility

Spontaneously hypertensive rats (SHRs) are widely accepted for modeling essential hypertension and Attention deficit hyperactivity disorder (ADHD). However, data concerning central nervous system changes associated with behavioral responses of this strain and usage of Wistar Kyoto (WKY) rats as controls are confounding. The objective of the present study was to assess the impact of anxiety and motor activity on the cognitive responses of SHRs compared to Wistar and WKY rats. In addition, the role of brain-derived neurotrophic factor (BDNF) in the hippocampus on cognitive behavior and seizure susceptibility in the three strains was evaluated. In Experiment#1, SHR demonstrated impulsive responses in the novelty suppression feeding test accompanied by impaired spatial working and associative memory in the Y maze and object recognition test compared with the Wistar rat but not WKY rats. In addition, the WKY rats exhibited diminished activity compared to Wistar rats in an actimeter. In Experiment#2, the seizure susceptibility was assessed by 3-min electroencephalographic (EEG) recording after two consecutive injections of pentylenetetrazol (PTZ) (20+40 mg/kg). The WKY rats were more vulnerable to rhythmic metrazol activity (RMA) than the Wistar rats. In contrast, Wistar rats were more prone to generalized tonic-clonic seizures (GTCS) than WKY rats and SHRs. Control SHR had lower BDNF expression in the hippocampus compared to Wistar rats. However, while the BDNF levels were elevated in the Wistar and WKY rats after PTZ injection, no change in this signaling molecule was observed in the SHR in the seizure condition. The results suggest Wistar rats as a more appropriate control of SHR than WKY rats for studying memory responses mediated by BDNF in the hippocampus. The higher vulnerability to seizures in Wistar and WKY rats compared to SHR might be linked to PTZ-induced decreased expression of BDNF in the hippocampus.

Exercise-induced angiogenesis is attenuated by captopril but maintained under perindopril treatment in hypertensive rats.

Angiogenesis is an important exercise-induced response to improve blood flow and decrease vascular resistance in spontaneously hypertensive rats (SHR), but some antihypertensive drugs attenuate this effect. This study compared the effects of captopril and perindopril on exercise-induced cardiac and skeletal muscle angiogenesis. Forty-eight Wistar rats and 48 SHR underwent 60 days of aerobic training or were kept sedentary. During the last 45 days, rats were treated with captopril, perindopril or water (Control). Blood pressure (BP) measurements were taken and histological samples from the tibialis anterior (TA) and left ventricle (LV) muscles were analyzed for capillary density (CD) and vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR-2) and endothelial nitric oxide synthase (eNOS) protein level. Exercise increased vessel density in Wistar rats due to higher VEGFR-2 (+17%) and eNOS (+31%) protein level. Captopril and perindopril attenuated exercise-induced angiogenesis in Wistar rats, but the attenuation was small in the perindopril group, and this response was mediated by higher eNOS levels in the Per group compared to the Cap group. Exercise increased myocardial CD in Wistar rats in all groups and treatment did not attenuate it. Both exercise and pharmacological treatment reduced BP of SHR similarly. Rarefaction was found in TA of SHR compared to Wistar, due to lower levels of VEGF (-26%) and eNOS (-27%) and treatment did not avoid this response. Exercise prevented these reductions in control SHR. While rats treated with perindopril showed angiogenesis in the TA muscle after training, those rats treated with captopril showed attenuated angiogenesis (-18%). This response was also mediated by lower eNOS levels in Cap group compared with Per and control group. Myocardial CD was reduced in all sedentary hypertensive compared with Wistar and training restored the number of vessels compared with sedentary SHR. In conclusion, taken into account only the aspect of vessel growth, since both pharmacological treatments reduced BP in SHR, the result of the present study suggests that perindopril could be a drug of choice over captopril for hypertensive practitioners of aerobic physical exercises, especially considering that it does not attenuate angiogenesis induced by aerobic physical training in skeletal and cardiac muscles.

Periodontitis accelerates the development of arterial hypertension in spontaneously hypertensive rats (SHR)

Objectives: Arterial hypertension and the inflammatory process are pathophysiologically associated. Of note, it is well understood that periodontitis is an inflammatory morbidity, epidemiologically related to cardiovascular mortality, particularly with the risk of developing arterial hypertension. Considering that in Spontaneously Hypertensive Rats (SHR) the elevation of arterial pressure starts from the 7th week of age, this study aimed to evaluate whether periodontitis accelerates the onset of arterial hypertension, for instance, in 5-week-old SHR. Methods: Induction of periodontitis was started in 3-week-old SHR and maintained for 2 weeks through the ligation of the left first molar with a silk suture, followed by the Porphyromonas gingivalis (strain W83) administration, p.o., 3 times a week. The femoral artery of 5-week-old SHR was cannulated, and 24 hours later, with the animals awakened, the systolic (SAP), diastolic (DAP), and mean (MAP) arterial pressures were recorded. Results: 5-week-old control SHR (SHAM) did not have installed arterial hypertension, while SHR with periodontitis (PER) exhibited a higher arterial pressure when compared to the SHAM group (SAP PER: 150±4 vs. SAP SHAM: 124±3 mmHg, n=8, p≤0.001; DAP PER: 103±5 vs. DAP SHAM: 85±5 mmHg, n=8, p≤0.05; MAP PER: 119±4 vs. MAP SHAM 98±4 mmHg n=8, p ≤0.01). Conclusion: The differences observed in the pressure values between the groups studied demonstrate that periodontitis accelerates the development of hypertension in SHR. Funding Sources: Fundação de Amparo à Pesquisa do Estados de São Paulo - FAPESP, Process 2021/08622-7 and 2020/06043-7. Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq, Process 306994/2021-6 and 423999/2021-4. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The sustainable antihypertensive and target organ damage protective effect of transcranial focused ultrasound stimulation in spontaneously hypertensive rats.

In this study, we aimed to investigate the sustainable antihypertensive effects and protection against target organ damage caused by low-intensity focused ultrasound (LIFU) stimulation and the underlying mechanism in spontaneously hypertensive rats (SHRs) model. SHRs were treated with ultrasound stimulation of the ventrolateral periaqueductal gray (VlPAG) for 20 min every day for 2 months. Systolic blood pressure (SBP) was compared among normotensive Wistar-Kyoto rats, SHR control group, SHR Sham group, and SHR LIFU stimulation group. Cardiac ultrasound imaging and hematoxylin-eosin and Masson staining of the heart and kidney were performed to assess target organ damage. The c-fos immunofluorescence analysis and plasma levels of angiotensin II, aldosterone, hydrocortisone, and endothelin-1 were measured to investigate the neurohumoral and organ systems involved. We found that SBP was reduced from 172 ± 4.2 mmHg to 141 ± 2.1 mmHg after 1 month of LIFU stimulation, P < 0.01. The next month of treatment can maintain the rat's blood pressure at 146 ± 4.2 mmHg at the end of the experiment. LIFU stimulation reverses left ventricular hypertrophy and improves heart and kidney function. Furthermore, LIFU stimulation enhanced the neural activity from the VLPAG to the caudal ventrolateral medulla and reduced the plasma levels of ANGII and Aldo. We concluded that LIFU stimulation has a sustainable antihypertensive effect and protects against target organ damage by activating antihypertensive neural pathways from VLPAG to the caudal ventrolateral medulla and further inhibiting the renin-angiotensin system (RAS) activity, thereby supporting a novel and noninvasive alternative therapy to treat hypertension.

Effect of blood flow-restricted resistance training on myocardial fibrosis in early spontaneously hypertensive rats.

The purpose of this study was to explore the effect of blood flow-restricted resistance training on myocardial fibrosis in early spontaneously hypertensive rats (SHRs). Four-week-old male Wistar-Kyoto rats and SHRs were randomly divided into the following groups: normal group (WKY), SHR control (SHR-SED) group, high-intensity resistance training (HIRT) group, low- and medium-intensity resistance training (LMIRT) group, and blood flow-restricted low- and medium-resistance training (BFRT) group. Body weight, hemodynamics, cardiac function, myocardial morphology and fibrosis, and the expression levels of transforming growth factor-beta1-Smad (TGFβ-1-Smad) pathway-related proteins in the myocardium were assessed. (1) BFRT lowered blood pressure significantly, decreased left ventricular wall thickness, and improved cardiac function. At the same time, BFRT was superior to traditional resistance training in lowering diastolic blood pressure, and was superior to HIRT in improving left ventricular compliance, reducing heart rate, and reducing left ventricular posterior wall and left ventricular mass (P < 0.05). (2) BFRT decreased collagen I and collagen fiber area in the myocardium, increased the collagen III area, and decreased the collagen I/III ratio (P < 0.05). BFRT produced a better proportion of myocardial collagen fibers than did traditional resistance training (P < 0.05). (3) In the myocardium of the BFRT group compared to the traditional resistance training group, the expression of TGFβ-1, Smad2/3/4, p-Smad2/3, CTGF, and TIMP1 was significantly downregulated, MMP2 and TIMP2 were significantly upregulated, the MMP/TIMP ratio significantly increased, and TGFβ-1 expression significantly decreased (P < 0.05). BFRT inhibited the TGFβ-1-Smad pathway in the myocardium, downregulated the expression of CTGF, and regulated the balance between MMPs and TIMPs, thereby reducing myocardial fibrosis in SHR, and improving cardiac morphology and function. BFRT also lowered blood pressure, and achieved an effect of early prevention and treatment of hypertension. At the same time, BFRT was superior to traditional resistance training in reducing diastolic blood pressure and adjusting the proportion of myocardial collagen fibers.

S-12-3: BENEFICIAL EFFECTS OF EMPAGLIFLOZIN ON METABOLIC PARAMETERS AND DIASTOLIC FUNCTION IN SPONTANEOUSLY HYPERTENSIVE RATS FED A HIGH-FAT DIET

Objective: Non-alcoholic fatty liver disease (NAFLD) is a multifactorial pathological syndrome characterized by lipid accumulation in hepatocytes. This can lead to non-alcoholic steatohepatitis (NASH) which can progress to liver fibrosis, cirrhosis and liver cancer. Unfortunately, the pathogenesis of NAFLD is still unknown. However, current studies suggest that gliflozins, primarily antidiabetics, could have beneficial effects on liver metabolism. The aim of this study was therefore to examine whether empagliflozin (10 mg.kg-1.day-1 in drinking fluid) will have beneficial effects. Design and methods: NAFLD was induced by eight weeks of high-fat diet feeding (60% protein) in adult (6-month-old) spontaneously hypertensive rats (SHR). Control SHR were fed a standard diet. Then, the animals were either untreated or treated with empagliflozin for eight weeks. The evaluation of renal function (metabolic cages) and oral glucose tolerance (OGT) test were performed before the start of the treatment and at the end of the study. Cardiac function evaluated by echocardiography as well as metabolic parameters in serum and in liver were determined at the end of the experiment. Results: High-fat diet feeding increased body weight and visceral adiposity. Moreover, it worsened insulin resistance (evaluated as OGT test). In addition, it induced increase in triglycerides and cholesterol levels. Although it had no effect on renal function, it substantially deteriorated not only systolic but also diastolic function of the heart in SHR rats. Empagliflozin had no effect on body weight or visceral fat deposition but improved insulin sensitivity (OGT test) and several metabolic parameters (plasma insulin, non-esterified fatty acids, uric acid and HDL-cholesterol). Moreover, it had beneficial effects on systolic (fractional shortening) and especially diastolic (PWTd, RWT, and E/A ratio) function. Conclusions: Our results demonstrated that the treatment with empagliflozin had beneficial hepatoprotective and cardioprotective actions in hypertensive rats with experimentally induced non-alcoholic liver fatty disease.

Effects of Taxifolin in Spontaneously Hypertensive Rats with a Focus on Erythrocyte Quality.

Oxidative stress and multiple erythrocyte abnormalities have been observed in hypertension. We focused on the effects of angiotensin-converting enzyme 2 (ACE2) inhibition by MLN-4760 inhibitor on angiotensin peptides, oxidative stress parameters, and selected erythrocyte quality markers in spontaneously hypertensive rats (SHR). We also investigated the potential effects of polyphenolic antioxidant taxifolin when applied in vivo and in vitro following its incubation with erythrocytes. SHRs were divided into four groups: control, taxifolin-treated, MLN-4760-treated, and MLN-4760 with taxifolin. MLN-4760 administration increased the blood pressure rise independent of taxifolin treatment, whereas taxifolin decreased it in control SHRs. Body weight gain was also higher in ACE2-inhibited animals and normalized after taxifolin treatment. However, taxifolin did not induce any change in angiotensin peptide concentrations nor a clear antioxidant effect. We documented an increase in Na,K-ATPase enzyme activity in erythrocyte membranes of ACE2-inhibited SHRs after taxifolin treatment. In conclusion, ACE2 inhibition deteriorated some selected RBC properties in SHRs. Although taxifolin treatment did not improve oxidative stress markers, our data confirmed the blood pressure-lowering potential, anti-obesogenic effect, and some "erythroprotective" effects of this compound in both control and ACE2-inhibited SHRs. In vitro investigations documenting different effects of taxifolin on erythrocyte properties from control and ACE2-inhibited SHRs accentuated the irreplaceability of in vivo studies.

Aerobic exercise improves renal fibrosis in spontaneously hypertensive rats

Objective: To study the effects of aerobic exercise training on renal fibrosis in spontaneously hypertensive rats (SHR), and to explore the protective effect of exercise on renal damage in hypertensive rats. Methods: Eight-week-old male SHR and Wistar Kyoto rats of the same age (WKY) were randomly divided into 4 groups (n=6): sedentary WKY control group (WKY-S), sedentary SHR control group (SHR-S), low-intensity exercise group (SHR-L) and medium-intensity exercise group (SHR-M). SHR-L group and SHR-M group were set at a slope of 0° at 14 m/min (35% of the maximum aerobic speed) and 20 m/min (50% of the maximum aerobic speed), running on a sports treadmill for 14 weeks, 5 times a week, and 60 min each time. WKY-S and SHR-S groups were kept quietly. Blood pressure was measured 72 hours after exercise training. And the serum levels of creatinine (Scr) and BUN were detected. The morphology of renal tissue was observed by hematoxylin and eosin (HE) staining. The collagen deposition of renal tissue was observed by Masson staining, and the renal collagen volume fraction (CVF) was calculated. Results: Compared with WKY-S group, blood pressure, serum Scr and BUN, kidney CVF levels and AngⅡ, AT1R, TGF-β, α-SMA, CTGF expressions in SHR-S group were increased significantly (P＜0.05). Compared with SHR-S group, blood pressure, serum Scr and BUN, kidney CVF level and AngⅡ, AT1R, TGF-β, α-SMA, CTGF expressions in SHR-L and SHR-M groups were decreased significantly (P＜0.05) and the decreasing trend was more obvious in SHR-M group (P＜0.05). Conclusion: Aerobic exercise can improve renal fibrosis and renal function in spontaneously hypertensive rats by inhibiting the AngⅡ-AT1R-TGF-β pathway.

Effects of moderate-continuous and high-intensity interval aerobic training on cardiac function of spontaneously hypertensive rats.

The aim of this study was to verify the effects of moderate-intensity continuous (MICT) and high-intensity interval (HIIT) aerobic training on cardiac morphology and function and the mechanical properties of single cardiomyocytes in spontaneously hypertensive rats (SHR) in the compensated phase of hypertension. Sixteen-week-old male SHR and normotensive Wistar (WIS) rats were allocated to six groups of six animals each: SHR CONT or WIS CONT (control); SHR MICT or WIS MICT (underwent MICT, 30 min/day, five days per week for eight weeks); and SHR HIIT or WIS HIIT (underwent HIIT, 30 min/day, five days per week for eight weeks). Total exercise time until fatigue and maximum running speed were determined using a maximal running test before and after the experimental period. Systolic (SAP), diastolic (DAP), and mean (MAP) blood pressures were measured using tail plethysmography before and after the experimental period. Echocardiographic evaluations were performed at the end of the experimental period. The rats were euthanized after in vivo assessments, and left ventricular myocytes were isolated to evaluate global intracellular Ca2+ transient ([Ca2+]i) and contractile function. Cellular measurements were performed at basal temperature (~37°C) at 3, 5, and 7 Hz. The results showed that both training programs increased total exercise time until fatigue and, consequently, maximum running speed. In hypertensive rats, MICT decreased SAP, DAP, MAP, interventricular septal thickness during systole and diastole, and the contraction amplitude at 5 Hz. HIIT increased heart weight and left ventricular wall thickness during systole and diastole and reduced SAP, MAP, and the time to peak [Ca2+]i at all pacing frequencies. In conclusion, both aerobic training protocols promoted beneficial adaptations to cardiac morphology, function, and mechanical properties of single cardiomyocytes in SHR.

Chemogenetic inhibition of Phox2-expressing neurons in the commissural NTS decreases blood pressure in anesthetized spontaneously hypertensive rats

Interruption of the activity of neurons in the commissural portion of the nucleus of the solitary tract (cNTS) decreases blood pressure (BP) in experimental models of hypertension, such as the spontaneously hypertensive (SH) rat. To examine whether PHOX2B expressing cNTS neurons are involved in maintaining the elevated BP, we used replication-deficient viruses with a modified Phox2 binding site promoter to express the inhibitory chemogenetic allatostatin receptor or green fluorescent protein in the cNTS. Following administration of allatostatin, we observed a depressor and bradycardic response in anesthetized SH rats that expressed the allatostatin receptor. Injection of allatostatin did not affect BP or heart rate (HR) in control SH rats expressing green fluorescent protein in the cNTS. Immunohistochemistry showed that the majority of transduced cNTS neurons were PHOX2B-immunoreactive and some also expressed tyrosine hydroxylase. We conclude that in anesthetized SH rat, the Phox2B expressing cNTS neurons maintain elevated BP.

Sacubitril/Valsartan Improves Sexual Function and Fibrosis of the Clitoral and Vaginal Tissues in Female Spontaneously Hypertensive Rats.

:Female sexual dysfunction is common in hypertension. The effects of sacubitril/valsartan (SAC/VAL) as a potential therapy for hypertension and heart failure have not been studied in relation to sexual function and genital fibrosis in female spontaneously hypertensive rats (SHRs). Thirty female SHRs were administered VAL, SAC/VAL, or saline. Ten normotensive female Wistar–Kyoto (WKY) rats were included in the control group. We assessed estrous cyclicity and sexual behavior in the female rats. In addition, the morphology of clitoral and vaginal tissues was evaluated by histological analyses. Western blotting and enzyme-linked immunosorbent assays were used to assess the levels of fibrotic markers in vaginal and clitoral tissues. Furthermore, the protein levels of phosphatase and tensin homolog deleted from chromosome 10 (PTEN), phosphoinositide-3-kinase (PI3K), and AKT expression were measured by Western blotting. SAC/VAL treatment improved hypertension-induced sexual dysfunction, exhibited as a prolonged estrus phase, increased receptivity and proceptive events, and decreased aggressive events, compared with those of VAL treatment and control SHRs without treatments. In addition, SAC/VAL-treated SHRs had lower levels of fibrotic markers, estradiol, and estrogen receptor α/β than the levels of VAL-treated SHRs or SHRs without treatment. Moreover, SAC/VAL decreased p-PTEN expression and increased p-PI3K and p-AKT expression at the protein level compared with those in VAL treatment alone. VAL and SAC/VAL treatments have significantly increased sexual receptivity and proceptivity, decreased aggressiveness, and improved the fibrosis of vaginal and clitoral tissues in female SHRs. However, SAC/VAL treatment shows more effective results compared with VAL treatment, which may be related to the PTEN/PI3K/AKT pathway.