Spontaneously Hypertensive Rats Hearts Research Articles

High-Density Lipoprotein Signaling via Sphingosine-1-Phosphate Receptors Safeguards Spontaneously Hypertensive Rats against Myocardial Ischemia/Reperfusion Injury.

High-density lipoprotein (HDL) protects against ischemia/reperfusion (I/R) injury via signaling through scavenger-receptor class B type-I (SR-BI) and sphingosine-1-phosphate receptors (S1PRs). We recently reported that HDL protects the hearts of spontaneously hypertensive rats (SHRs) against I/R injury in an SR-BI-dependent manner. In this study, we examined the role of S1PRs in HDL-induced protection against myocardial I/R injury in hypertensive rats. Hearts from Wistar Kyoto rats (WKYs) and SHRs were subjected to I/R injury using a modified Langendorff system. The hearts were treated with or without HDL in the presence or absence of a receptor- or kinase-specific antagonist. Cardiac hemodynamics and infarct size were measured. Target proteins were analyzed by immunoblotting and ELISA, and nitrite levels were measured using Greis reagent. HDL protected the hearts of WKYs and SHRs against I/R injury. HDL, however, was more protective in WKYs. HDL protection in SHRs required lipid uptake via SR-BI and S1PR1 and S1PR3 but not S1PR2. The hearts from SHRs expressed significantly lower levels of S1PR3 than the hearts from WKYs. HDL differentially activated mediators of the SAFE and RISK pathways in WKYs and SHRs and resulted in nitric oxide generation. Blockage of these pathways abrogated HDL effects. HDL protects against myocardial I/R injury in normotensive and hypertensive rats, albeit to varying degrees. HDL protection in hearts from hypertensive rodents involved SR-BI-mediated lipid uptake coupled with signaling through S1PR1 and S1PR3. The extent of HDL-induced cardiac protection is directly proportional to S1PR3 expression levels. Mechanistically, the safeguarding effects of HDL involved activation of the SAFE and RISK pathways and the generation of nitric oxide.

Transcriptome and proteome analyses reveal that upregulation of GSTM2 by allisartan improves cardiac remodeling and dysfunction in hypertensive rats.

Long-term hypertension can lead to hypertensive heart disease, which ultimately progresses to heart failure. As an angiotensin receptor blocker antihypertensive drug, allisartan can control blood pressure, and improve cardiac remodeling and cardiac dysfunction caused by hypertension. The aim of the present study was to investigate the protective effects of allisartan on the heart of spontaneously hypertensive rats (SHRs) and the underlying mechanisms. SHRs were used as an animal model of hypertensive heart disease and were treated with allisartan orally at a dose of 25 mg/kg/day. The blood pressure levels of the rats were continuously monitored, their body and heart weights were measured, and their cardiac structure and function were evaluated using echocardiography. Wheat germ agglutinin staining and Masson trichrome staining were employed to assess the morphology of the myocardial tissue. In addition, transcriptome and proteome analyses were performed using the Solexa/Illumina sequencing platform and tandem mass tag technology, respectively. Immunofluorescence co-localization was conducted to analyze Nrf2 nuclear translocation, and TUNEL was performed to detect the levels of cell apoptosis. The protein expression levels of pro-collagen I, collagen III, phosphorylated (p)-AKT, AKT, p-PI3K and PI3K, and the mRNA expression levels of Col1a1 and Col3a1 were determined by western blotting and reverse transcription-quantitative PCR, respectively. Allisartan lowered blood pressure, attenuated cardiac remodeling and improved cardiac function in SHRs. In addition, allisartan alleviated cardiomyocyte hypertrophy and cardiac fibrosis. Allisartan also significantly affected the 'pentose phosphate pathway', 'fatty acid elongation', 'valine, leucine and isoleucine degradation', 'glutathione metabolism', and 'amino sugar and nucleotide sugar metabolism' pathways in the hearts of SHRs, and upregulated the expression levels of GSTM2. Furthermore, allisartan activated the PI3K-AKT-Nrf2 signaling pathway and inhibited cardiomyocyte apoptosis. In conclusion, the present study demonstrated that allisartan can effectively control blood pressure in SHRs, and improves cardiac remodeling and cardiac dysfunction. Allisartan may also upregulate the expression levels of GSTM2 in the hearts of SHRs and significantly affect glutathione metabolism, as determined by transcriptome and proteome analyses. The cardioprotective effect of allisartan may be mediated through activation of the PI3K-AKT-Nrf2 signaling pathway, upregulation of GSTM2 expression and reduction of cardiomyocyte apoptosis in SHRs.

99mTc-HFAPi imaging identifies early myocardial fibrosis in the hypertensive heart.

This study aimed to explore whether 99mTc-radiolabeled fibroblast activation protein inhibitor (99mTc-HFAPi) imaging can detect early myocardial fibrosis in the hypertensive heart. In the experimental model, spontaneously hypertensive rats (SHRs) and age-matched Wistar Kyoto rats (WKYs) were randomly divided into three groups (8, 16, and 28 weeks). The animals underwent 99mTc-HFAPi imaging and echocardiography. Autoradiography and histological analyses were performed in the left ventricle. The mRNA and protein expression level of the fibroblast activation protein (FAP) and collagen I were measured using quantitative PCR and western blot. In the clinical investigation, a total of 106 patients with essential hypertension and 20 gender-matched healthy controls underwent 99mTc-HFAPi imaging and echocardiography. In-vivo and in-vitro autographic images demonstrated diffusely enhanced 99mTc-HFAPi uptake in the SHR heart starting at week 8, before irreversible collagen deposition. The mRNA and protein levels of FAP in SHRs began to increase from week 8, whereas changes in collagen I levels were not detected until week 28. In the clinical investigation, even in hypertensive patients with normal diastolic indicators, normal left ventricular geometry, and normal global longitudinal strain (GLS), the prevalence of increased 99mTc-HFAPi uptake reached 34, 41, and 20%, respectively, indicating that early fibrogenesis precedes structural and functional myocardial abnormalities. In hypertension, 99mTc-HFAPi imaging can detect early fibrotic process before myocardial functional and structural changes.

Quinapril treatment curtails decline of global longitudinal strain and mechanical function in hypertensive rats.

Left ventricular (LV) global longitudinal strain (GLS) has been proposed as an early imaging biomarker of cardiac mechanical dysfunction. To assess the impact of angiotensin-converting enzyme (ACE) inhibitor treatment of hypertensive heart disease on LV GLS and mechanical function. The spontaneously hypertensive rat (SHR) model of hypertensive heart disease (n = 38) was studied. A subset of SHRs received quinapril (TSHR, n = 16) from 3 months (mo). Wistar Kyoto rats (WKY, n = 13) were used as controls. Tagged cardiac MRI was performed using a 4.7 T Varian preclinical scanner. The SHRs had significantly lower LV ejection fraction (EF) than the WKYs at 3 mo (53.0 ± 1.7% vs. 69.6 ± 2.1%, P < 0.05), 14 mo (57.0 ± 2.5% vs. 74.4 ± 2.9%, P < 0.05) and 24 mo (50.1 ± 2.4% vs. 67.0 ± 2.0%, P < 0.01). At 24 mo, ACE inhibitor treatment was associated with significantly greater LV EF in TSHRs compared to untreated SHRs (64.2 ± 3.4% vs. 50.1 ± 2.4%, P < 0.01). Peak GLS magnitude was significantly lower in SHRs hearts compared with WKYs at 14 months (7.5% ± 0.4% vs. 9.9 ± 0.8%, P < 0.05). At 24 months, Peak GLS magnitude was significantly lower in SHRs compared with both WKYs (6.5 ± 0.4% vs. 9.7 ± 1.0%, P < 0.01) and TSHRs (6.5 ± 0.4% vs. 9.6 ± 0.6%, P < 0.05). ACE inhibitor treatment curtails the decline in global longitudinal strain in hypertensive rats, with the treatment group exhibiting significantly greater LV EF and GLS magnitude at 24 mo compared with untreated SHRs.

TESTOSTERONE INDUCES POSTMENOPAUSAL HYPERTENSIVE HYPERTROPHY THROUGH INHIBITING THE ACTIVATION OF AMPK- FOXO1/MURF1 SIGNALING PATHWAY

Objective: It has been found that relative elevated level of testosterone could exacerbates postmenopausal hypertensive left ventricular hypertrophy(PM-HTN-LVH), but the mechanisms responsible are unknown. Moreover, MuRF1, a muscle-specific E3 ubiquitin ligase in the ubiquitination process, was newly identified as a negative regulatory factor of myocardial and muscle tissue in exerting a protective functions on the cardiomyocyte hypertrophy. There are little study to certify whether MuRF1 took part in testosterone-induced PM-HTN-LVH. Design and method: Femal spontaneously hypertensive rats (SHR) were ovariectomized (OVX group) or sham-operated (Sham group) at 12 weeks and then the OVX group were intramuscularly injected the testosterone (T 2.85 mg/kg/ quaque omni die im) (OVX+T group) or vehicle (OVX+ vehicle group) for 4 weeks. Futher, Cultured cardiomyocytes were respectively stimulated with different concentration gradients of testosterone for 24h, then measured the expression of myosin heavy chain (MHC) and MuRF1, as well as the phosphorylation levels of AMPK(p-AMPK) and Forkhead box O 1 (p-FOXO1), were separately measured using western blot. Results: After 4 weeks of testosterone supplementation, SHR heart exhibited significant increments in the heart weight/tibial length and the levels of IVST, LVPWT, LVM and the expression of MHC, and have a lower expression of the MuRF1, p-AMPK and p-FOXO1 in the OVX+T group, compared with OVX group and Sham group. Moreover, the expression level of p-AMPK and p-FOXO1 in the heart were at least twice as many as gastrocnemius muscle among the three group, but the MuRF1 was equivalent between heart and gastrocnemius muscle. In vivo, after the treatment of different gradients of testosterone for 24h, the protein expression of MHC showed an S-shaped growth trend and MuRF1, p-AMPK and p-FOXO1 presented with reverse S-shaped reduction along with increasing of testosterone concentration, peaking at 10-6M testosterone. Conclusions: The present study demonstrates that testosterone induces PM-HTN-LVH by modulating the atrophy related AMPK-FOXO1/MuRF1 signaling pathway in vitro and vivo. Increased the heart expression of MuRF1 by activation of AMPK may reverse testosterone-mediated PM-HTN-LVH, which might cause little change of MuRF1 expression in the skeletal muscle resulting in the muscle atrophy.

Progressive Cardiac Metabolic Defects Accompany Diastolic and Severe Systolic Dysfunction in Spontaneously Hypertensive Rat Hearts.

Background Cardiac metabolic abnormalities are present in heart failure. Few studies have followed metabolic changes accompanying diastolic and systolic heart failure in the same model. We examined metabolic changes during the development of diastolic and severe systolic dysfunction in spontaneously hypertensive rats (SHR). Methods and Results We serially measured myocardial glucose uptake rates with dynamic 2-[18F] fluoro-2-deoxy-d-glucose positron emission tomography in vivo in 9-, 12-, and 18-month-old SHR and Wistar Kyoto rats. Cardiac magnetic resonance imaging determined systolic function(ejection fraction) and diastolic function (isovolumetric relaxation time) and left ventricular mass in the same rats. Cardiac metabolomics was performed at 12 and 18 months in separate rats. At 12 months, SHR hearts, compared with Wistar Kyoto hearts, demonstrated increased isovolumetric relaxation time and slightly reduced ejection fraction indicating diastolic and mild systolic dysfunction, respectively, and higher (versus 9-month-old SHR decreasing) 2-[18F] fluoro-2-deoxy-d-glucose uptake rates (Ki). At 18 months, only few SHR hearts maintained similar abnormalities as 12-month-old SHR, while most exhibited severe systolic dysfunction, worsening diastolic function, and markedly reduced 2-[18F] fluoro-2-deoxy-d-glucose uptake rates. Left ventricular mass normalized to body weight was elevated in SHR, more pronounced with severe systolic dysfunction. Cardiac metabolite changes differed between SHR hearts at 12 and 18 months, indicating progressive defects in fatty acid, glucose, branched chain amino acid, and ketone body metabolism. Conclusions Diastolic and severe systolic dysfunction in SHR are associated with decreasing cardiac glucose uptake, and progressive abnormalities in metabolite profiles. Whether and which metabolic changes trigger progressive heart failure needs to be established.

Prolonged Ca2+ release refractoriness and T-tubule disruption as determinants of increased propensity to cardiac alternans in the hypertensive heart disease.

Cardiac alternans is a dynamical phenomenon linked to the genesis of severe arrhythmias and sudden cardiac death. It has been proposed that alternans is caused by alterations in Ca2+ handling by the sarcoplasmic reticulum (SR), in both the SR Ca2+ uptake and release processes. The hypertrophic myocardium is particularly prone to alternans, but the precise mechanisms underlying its increased vulnerability are not known. Mechanical alternans (intact hearts) and Ca2+ alternans (cardiac myocytes) were studied in spontaneously hypertensive rats (SHR) during the first year of age after the onset of hypertension and compared with age-matched normotensive rats. Subcellular Ca2+ alternans, T-tubule organization, SR Ca2+ uptake, and Ca2+ release refractoriness were measured. The increased susceptibility of SHR to high-frequency-induced mechanical and Ca2+ alternans appeared when the hypertrophy developed, associated with an adverse remodeling of the T-tubule network (6 mo). At the subcellular level, Ca2+ discordant alternans was also observed. From 6 mo of age, SHR myocytes showed a prolongation of Ca2+ release refractoriness without alterations in the capacity of SR Ca2+ removal, measured by the frequency-dependent acceleration of relaxation. Sensitizing SR Ca2+ release channels (RyR2) by a low dose of caffeine or by an increase in extracellular Ca2+ concentration, shortened refractoriness of SR Ca2+ release, and reduced alternans in SHR hearts. The tuning of SR Ca2+ release refractoriness is a crucial target to prevent cardiac alternans in a hypertrophic myocardium with an adverse T-tubule remodeling.

Human Omentin-1 Administration Ameliorates Hypertensive Complications without Affecting Hypertension in Spontaneously Hypertensive Rats.

Hypertension is one of the major risk factors for cardiovascular diseases and is caused by various abnormalities including the contractility of blood vessels. Spontaneously hypertensive rats (SHR), whose systemic blood pressure increases with aging, are a frequently used animal model for investigating essential hypertension and related complications in humans due to the damage of several organs. Human omentin-1 is an adipocytokine consisting of 313 amino acids. Serum omentin-1 levels decreased in hypertensive patients compared with normotensive controls. Furthermore, omentin-1 knockout mice showed elevated blood pressure and impaired endothelial vasodilation. Taken together, we hypothesized that adipocytokine, human omentin-1 may improve the hypertension and its complications including heart and renal failure in the aged SHR (65-68-weeks-old). SHR were subcutaneously administered with human omentin-1 (18 μg/kg/day, 2 weeks). Human omentin-1 had no effect on body weight, heart rate, and systolic blood pressure in SHR. The measurement of isometric contraction revealed that human omentin-1 had no influence on the enhanced vasocontractile or impaired vasodilator responses in the isolated thoracic aorta from SHR. On the other hand, human omentin-1 tended to improve left ventricular diastolic failure and renal failure in SHR. In summary, human omentin-1 tended to improve hypertensive complications (heart and renal failure), while it had no influence on the severe hypertension in the aged SHR. The further study of human omentin-1 may lead to the development of therapeutic agents for hypertensive complications.

Comparative analysis of intracardiac neural structures in the aged rats with essential hypertension.

Persistent arterial hypertension initiates cardiac autonomic imbalance and alters cardiac tissues. Previous studies have shown that neural component contributes to arterial hypertension etiology, maintenance, and progression and leads to brain damage, peripheral neuropathy, and remodeling of intrinsic cardiac neural plexus. Recently, significant structural changes of the intracardiac neural plexus were demonstrated in young prehypertensive and adult hypertensive spontaneously hypertensive rats (SHR), yet structural alterations of intracardiac neural plexus that occur in the aged SHR remain undetermined. Thus, we analyzed the impact of uncontrolled arterial hypertension in old (48-52 weeks) SHR and the age-matched Wistar-Kyoto rats (WKY). Intrinsic cardiac neural plexus was examined using a combination of immunofluorescence confocal microscopy and transmission electron microscopy in cardiac sections and whole-mount preparations. Our findings demonstrate that structural changes of intrinsic cardiac neural plexus caused by arterial hypertension are heterogeneous and may support recent physiological implications about cardiac denervation occurring together with the hyperinnervation of the SHR heart. We conclude that arterial hypertension leads to (i) the decrease of the neuronal body area, the thickness of atrial nerves, the number of myelinated nerve fibers, unmyelinated axon area and cumulative axon area in the nerve, and the density of myocardial nerve fibers, and (ii) the increase in myelinated nerve fiber area and density of neuronal bodies within epicardiac ganglia. Despite neuropathic alterations of myelinated fibers were exposed within intracardiac nerves of both groups, SHR and WKY, we consider that the determined significant changes in structure of intrinsic cardiac neural plexus were predisposed by arterial hypertension.

Inhibition of Rho/ROCK signaling pathway participates in the cardiac protection of exercise training in spontaneously hypertensive rats

Exercise training (ExT) is capable of improving the heart function of spontaneously hypertensive rats (SHRs), but the underlying molecular mechanisms remain elusive. This study was aimed to investigate whether inhibition of RhoA/ROCK signaling pathway contributes to the cardiac protection by low-intensity ExT in SHRs. The results demonstrated that, compared with Wistar-Kyoto (WKY) rats, SHRs obviously exhibited higher blood pressure, increased heart weight index and thickness of left ventricular wall, decreased left ventricular function, damaged myocardial construction, and increased collagen fiber of left ventricle (P < 0.05 or P < 0.01). Meanwhile, the mRNA and protein expression levels of RhoA and ROCK in the heart of SHRs were significantly increased, compared with those of WKY rats (P < 0.05 or P < 0.01). Interestingly, the pathological changes of heart aforementioned were all improved in SHR-ExT rats compared with SHR-Sed rats (P < 0.05 or P < 0.01), indicating the cardiac protection of exercise training. In addition, the cardiac protective effect of exercise training could be blocked by LPA, an activator of Rho/ROCK signaling, and the protective effect in SHR rats could be mimicked by Fasudil, an inhibitor of Rho/ROCK signaling. The results strongly suggest that low-intensity ExT can protect heart against structure and function through inhibiting Rho/ROCK signaling pathway in hypertensive rats.

Alterations of Lipid Metabolism in the Heart in Spontaneously Hypertensive Rats Precedes Left Ventricular Hypertrophy and Cardiac Dysfunction.

Disturbances in cardiac lipid metabolism are associated with the development of cardiac hypertrophy and heart failure. Spontaneously hypertensive rats (SHRs), a genetic model of primary hypertension and pathological left ventricular (LV) hypertrophy, have high levels of diacylglycerols in cardiomyocytes early in development. However, the exact effect of lipids and pathways that are involved in their metabolism on the development of cardiac dysfunction in SHRs is unknown. Therefore, we used SHRs and Wistar Kyoto (WKY) rats at 6 and 18 weeks of age to analyze the impact of perturbations of processes that are involved in lipid synthesis and degradation in the development of LV hypertrophy in SHRs with age. Triglyceride levels were higher, whereas free fatty acid (FA) content was lower in the LV in SHRs compared with WKY rats. The expression of de novo FA synthesis proteins was lower in cardiomyocytes in SHRs compared with corresponding WKY controls. The higher expression of genes that are involved in TG synthesis in 6-week-old SHRs may explain the higher TG content in these rats. Adenosine monophosphate-activated protein kinase phosphorylation and peroxisome proliferator-activated receptor α protein content were lower in cardiomyocytes in 18-week-old SHRs, suggesting a lower rate of β-oxidation. The decreased protein content of α/β-hydrolase domain-containing 5, adipose triglyceride lipase (ATGL) activator, and increased content of G0/G1 switch protein 2, ATGL inhibitor, indicating a lower rate of lipolysis in the heart in SHRs. In conclusion, the present study showed that the development of LV hypertrophy and myocardial dysfunction in SHRs is associated with triglyceride accumulation, attributable to a lower rate of lipolysis and β-oxidation in cardiomyocytes.

Spontaneously hypertensive rats manifest deficits in emotional response to 22-kHz and 50-kHz ultrasonic playback

Many symptoms used routinely for human psychiatric diagnosis cannot be directly observed in animals which cannot describe their internal states. However, the ultrasonic vocalizations (USV) rodents use to communicate their emotional states can be measured. USV have therefore become a particularly useful tool in brain disease models. Spontaneously hypertensive rats (SHR) are considered an animal model of attention deficit hyperactivity disorder (ADHD) and schizophrenia. However, the specifics of SHR's behavior have not been fully described and there is very little data on their USV. Recently, we developed a communication model, in which Wistar rats are exposed to pre-recorded playbacks of aversive (22-kHz) or appetitive (50-kHz) USV, and their vocal responses depend on the extent of prior fear conditioning (0, 1, 6 or 10 shocks). Here, we investigated SHR's behavior and heart rate (HR) in our communication model, in comparison to Wistar rats employed as controls. In general, SHR emitted typical USV categories, however, they contained more short 22-kHz and less 50-kHz USV overall. Moreover, fewer SHR, in comparison with Wistar rats, emitted long 22-kHz USV after fear conditioning. SHR did not show a 50-kHz playback-induced HR increase, while they showed a profound 22-kHz playback-induced HR decrease. Finally, the number of previously delivered conditioning shocks appeared to have no effect on the investigated vocal, locomotor and HR responses of SHR. The phenomena observed in SHR are potentially attributable to deficits in emotional perception and processing. A lower number of 50-kHz USV emitted by SHR may reflect observations of speech impairments in human patients and further supports the usefulness of SHR to model ADHD and schizophrenia.

SPONTANEOUSLY HYPERTENSIVE RATS EXHIBIT ENHANCED CARDIAC CONNEXIN-43 AND REDUCED PRO-FIBROTIC MARKERS IN RESPONSE TO COLD ACCLIMATION

We have previously shown that down-regulation of myocardial gap junction channel protein, connexin-43 (Cx43), and up-regulation of extracellular matrix (ECM) proteins in hearts of spontaneously hypertensive rats (SHR) promote occurrence of lethal arrhythmia. Cold acclimation has a potential for reducing cardiovascular risk, especially in setting of various pathological conditions, but there is a gap of knowledge concern the heart response to adaptive thermogenesis. The purpose of the study is to explore myocardial Cx43 and ECM proteins in genetically hairless strain of SHR (SHRM) that represents rewarding model of increased adaptive thermogenesis.Adult hairless males and females SHRM strain that harbors mutated desmoglein-4 gene and their wild type SHR were housed at standard 22 C (that is below thermo-neutrality for these animals) and 12:12 hour light: dark cycle. WKY control rats were used as reference normotensive strain. Heart samples of the left ventricular tissue from euthanatized rats were used for the proteomics of Cx43, protein kinases, which phosphorylates Cx43, and for ECM markers TGF-, SMAD2/3, MMP-2, collagen-1. Immunofluorescence detection of Cx43 was performed to examine its myocardial topology.Cx43 protein and its phosphorylated status was reduced in males and females SHR vs WKY rat hearts. In contrast, adaptive thermogenesis resulted in increased both parameters in SHRM regardless the sex. Moreover, pathological topology of Cx43 attributed to its enhanced localization at lateral sides of the cardiomyocytes in SHR was attenuated in SHRM. In addition, there were gentle differences in protein levels of PKA, PKG, PKC, MAPK, Akt between SHR and SHRM. Protein level of TGF- and SMAD 2/3 were increased in SHR compare to WKY rat hearts but decreased in SHRM unlike collagen-1 that was not altered in SHRM compare to SHR.Findings revealed beneficial up-regulation of myocardial Cx43 along with down-regulation of extracellular matrix proteins in response of hairless SHR to increased thermogenesis.

High Density Lipoprotein Reduces Blood Pressure and Protects Spontaneously Hypertensive Rats Against Myocardial Ischemia-Reperfusion Injury in an SR-BI Dependent Manner.

BackgroundHypertension is a key risk factor in the development of cardiovascular diseases. Elevation in blood pressure alters high density lipoprotein (HDL) function and composition. The exact role of HDL in cardiovascular complications observed in hypertension is however not clearly understood. HDL protected against myocardial ischemia/reperfusion (I/R) injury in normotensive rats. Nonetheless, it's not clear if restoration of HDL function and/or composition protects against myocardial I/R injury in spontaneously hypertensive rats (SHR).ObjectivesIn this study we tested the effect of HDL treatment on I/R injury in Wistar Kyoto rats (WKY) and SHR and investigated the possible underlying mechanism(s).MethodsHDL (900 ng/kg/min) or vehicle were continuously administered to 11-week old WKY and SHR for 1 week (chronic treatment). Blood pressure was measured before and after treatment. Hearts were subjected to I/R injury using a modified Langendorff system. Another set of rats were treated with HDL administered at reperfusion (acute treatment) in the presence or absence of scavenger receptor class B type-I (SR-BI) blocking antibody. Cardiac hemodynamics were computed and cardiac enzyme release and infarct size were measured. Total cholesterol (TC) and HDL-cholesterol (HDL-C) were enzymatically assayed. Markers of autophagy and inflammation were detected by immunoblotting and ELISA, respectively.ResultsHDL treatment did not increase TC or HDL-C levels in SHR or WKY, yet it significantly (P < 0.01) reduced systolic and diastolic blood pressure in SHR. Chronic and acute HDL treatment significantly (P < 0.05) protected WKY and SHR against myocardial I/R injury. Chronic HDL treatment was significantly (P < 0.05) more protective in SHR whereas acute HDL treatment induced significantly (P < 0.05) greater protection in WKY. The extent of HDL induced protection was proportional to the expression levels of cardiac SR-BI and blockage of SR-BI completely abolished HDL mediated protection in SHR. Chronic HDL treatment significantly (P < 0.05) reduced markers of autophagy and inflammation in hypertensive rats.ConclusionsWe demonstrate a novel anti-hypertensive and a cardioprotective effect of HDL against myocardial I/R injury in SHR, the magnitude of which is directly related to the expression levels of cardiac SR-BI. Mechanistically, chronic HDL treatment protected SHR hearts by reducing autophagy and inflammation.

Cardioprotective effects of the proline-rich oligopeptide Bj-PRO-7a in spontaneously hypertensive rats.

The proline-rich oligopeptide from Bothrops jararaca snake venom, Bj-PRO-7a, promotes acute effects in blood pressure in hypertensive animals. However, the cardiac effects of this heptapeptide are completely unknown. Thus, we sought to evaluate whether the Bj-PRO-7a could protect against cardiac remodelling in spontaneously hypertensive rats (SHR). SHR were treated with Bj-PRO-7a (71nmol/kg/day, s.c.) or saline for 28days. Wistar rats were used as control. Systolic blood pressure (SBP) and heart rate (HR) were measured by tail-cuff plethysmography. Cardiomyocyte diameter and interstitial and perivascular fibrosis of the left ventricle (LV) were evaluated using Picrosirius staining. Immunofluorescence was used to detect collagen I and III. Fibroblast proliferation was assessed by immunohistochemistry to detect proliferating cell nuclear antigen (PCNA). Protein expression was assessed by western blot. The superoxide dismutase and catalase activities and the concentration of lipid peroxidation products were evaluated in the LV. The SBP and HR were not different between treated and non-treated SHR at the end of the treatment. However, Bj-PRO-7a attenuated the cardiomyocyte hypertrophy, deposition of interstitial and perivascular fibrosis and collagen I, and positive PCNA-labelled fibroblasts. This peptide also reduced the increased levels of TBARS, expression and activity of catalase, and activity of SOD in LV from SHR. Also, the Bj-PRO-7a increased the expression of metalloproteinases-2 in SHR hearts. These findings demonstrate that the Bj-PRO-7a reduced the pathological cardiac remodelling in a pressure-independent manner in hypertensive rats through mechanisms mediated by oxidative stress regulation.

Artificial light at night suppresses the expression of sarco/endoplasmic reticulum Ca2+ -ATPase in the left ventricle of the heart in normotensive and hypertensive rats.

What is the central question of this study? Artificial light at night decreases blood pressure and heart rate in rats. Are these changes in heart rate accompanied by changes in protein expression in the heart's left ventricle? What is the main finding and its importance? Five weeks of artificial light at night affected protein expression in the heart's left ventricle in normotensive and hypertensive rats. Artificial light at night decreased expression of the sarco/endoplasmic reticulum Ca2+ -ATPase, angiotensin II receptor type 1 and endothelin-1. Artificial light at night (ALAN) affects the circadian rhythm of the heart rate in normotensive Wistar rats (WT) and spontaneously hypertensive rats (SHR) through the autonomic nervous system, which regulates the heart's activity through calcium handling, an important regulator in heart contractility. We analysed the expression of the sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA2) and other selected regulatory proteins involved in the regulation of heart contractility, angiotensin II receptor type 1 (AT1 R), endothelin-1 (ET-1) and tyrosine hydroxylase (TH), in the left ventricle of the heart in WT and SHR after 2 and 5weeks of ALAN with intensity 1-2lx. Expression of SERCA2 was decreased in WT (control: 0.53±0.07; ALAN: 0.46±0.10) and SHR (control: 0.72±0.18; ALAN: 0.56±0.21) after 5weeks of ALAN (P=0.067). Expression of AT1 R was significantly decreased in WT (control: 0.51±0.27; ALAN: 0.34±0.20) and SHR (control: 0.38±0.07; ALAN: 0.23±0.09) after 2weeks of ALAN (P=0.028) and in SHR after 5weeks of ALAN. Expression of ET-1 was decreased in WT (control: 0.51±0.27; ALAN: 0.28±0.12) and SHR (control: 0.54±0.10; ALAN: 0.35±0.23) after 5weeks of ALAN (P=0.015). ALAN did not affect the expression of TH in WT or SHR. In conclusion, ALAN suppressed the expression of SERCA2, AT1 R and ET-1, which are important for the regulation of heart contractility, in a strain-dependent pattern in both WT and SHR.

CIHH protects the heart against left ventricular remodelling and myocardial fibrosis by balancing the renin-angiotensin system in SHR

AimThe aim of our study was to clarify the cardioprotection of chronic intermittent hypobaric hypoxia (CIHH) and the underlying mechanism in spontaneously hypertensive rats (SHR). Main methodsAdult male rats were divided into normal blood pressure Wistar-Kyoto rats (WKY) control (WKY-CON), WKY rats with CIHH treatment (WKY-CIHH), SHR control (SHR-CON) and SHR with CIHH treatment (SHR-CIHH) groups. SHR-CIHH and WKY-CIHH rats were subjected to hypobaric hypoxia simulating 4000-m altitude for 35 days, 5 h per day. Arterial blood pressure and cardiac function parameters, including ejection fraction, fractional shortening and left ventricular (LV) wall thickness, were evaluated. Cardiac pathomorphology and myocardial fibrosis were determined. The expression of angiotensin-converting enzyme (ACE), ACE2, Ang II, Ang1-7, AT1 receptor, Mas receptor, IL-6, TNF-α，IL-10, SOD and MDA were assayed in myocardium. Key findingsCIHH significantly decreased arterial blood pressure, alleviated LV hypertrophy, and improved cardiovascular function in SHR (P < 0.05–0.01). Also, CIHH protected SHR heart against morphological changes and fibrosis. In addition, CIHH significantly down-regulated the ACE/Ang II/AT1 receptor axis and up-regulated the ACE2/Ang1–7/Mas axis of renin-angiotensin system (RAS) in SHR (P < 0.05–0.01). CIHH significantly reduced IL-6, TNF-α, and MDA levels, but increased IL-10 and SOD in SHR myocardium (P < 0.05–0.01). SignificanceThe CIHH treatment protected the heart of SHR against LV remodelling and myocardial fibrosis, which might be carried out through a balance in the ACE/Ang II/AT1 axis and the ACE2/Ang1–7/Mas axis of the RAS to reduce inflammation, and inhibit oxidative stress.

Relaxin increased blood pressure and sympathetic activity in paraventricular nucleus of hypertensive rats via enhancing oxidative stress

Relaxin, an ovarian polypeptide hormone, is found in the hypothalamic paraventricular nucleus (PVN) which is an important central integrative site for the control of blood pressure and sympathetic outflow. The aim of this study was to determine if superoxide anions modulate the effects of relaxin in the PVN. Experiments were performed in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Relaxin mRNA and protein, and its receptor, relaxin family peptide receptor 1 (RXFP1) levels in PVN were 3.24, 3.17, and 3.64 times higher in SHRs than in WKY rats, respectively. Microinjection of relaxin-2 into the PVN dose-dependently increased mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA) and heart rate (HR) in both WKY rats and SHRs, although the effects on MAP (16.87 ± 1.99 vs. 8.97 ± 1.48 mm Hg in 100 nmol), RSNA (22.60 ± 2.15 vs. 11.77 ± 1.43 % in 100 nmol) and HR (22.85 ± 3.13 vs. 12.62 ± 2.83 beats/min in 100 nmol) were greater in SHRs. Oxidative stress level was enhanced after relaxin-2 microinjection into the PVN. Pretreatment with superoxide anion scavengers or NADPH oxidase inhibitor blocked, and superoxide dismutase inhibitor potentiated the effects of relaxin-2 on MAP, RSNA and HR. RXFP1 knockdown significantly attenuated the blood pressure of SHRs, and inhibited the increases of atrial natriuretic peptide, brain natriuretic peptide, collagen I, collagen III and fibronectin in the heart of SHRs. These results demonstrated that relaxin is expressed in the PVN, and contributes to hypertension and sympathetic overdrive via oxidative stress. Down-regulation of RXFP1 in the PVN could attenuate hypertension and cardiac remodeling.

Ketogenic diet aggravates cardiac remodeling in adult spontaneously hypertensive rats

BackgroundKetogenic diet (KD) has been proposed to be an effective lifestyle intervention in metabolic syndrome. However, the effects of KD on cardiac remodeling have not been investigated. Our aim was to investigate the effects and the underling mechanisms of KD on cardiac remodeling in spontaneously hypertensive rats (SHRs).Methods10-week-old spontaneously hypertensive rats were subjected to normal diet or ketogenic diet for 4 weeks. Then, their blood pressure and cardiac remodeling were assessed. Cardiac fibroblasts were isolated from 1- to 3-day-old neonatal pups. The cells were then cultured with ketone body with or without TGF-β to investigate the mechanism in vitro.Results4 weeks of KD feeding aggravated interstitial fibrosis and cardiac remodeling in SHRs. More interestingly, ketogenic diet feeding increased the activity of mammalian target of rapamyoin (mTOR) complex 2 pathway in the heart of SHRs. In addition, β-hydroxybutyrate strengthened the progression of TGF-β-induced fibrosis in isolated cardiac fibroblasts. mTOR inhibition reversed this effect, indicating that ketone body contributes to cardiac fibroblasts via mTOR pathway.ConclusionsThese data suggest that ketogenic diet may lead to adverse effects on the remodeling in the hypertensive heart, and they underscore the necessity to fully evaluate its reliability before clinical use.

3D imaging and morphometry of the heart capillary system in spontaneously hypertensive rats and normotensive controls

Systemic arterial hypertension is a highly prevalent chronic disease associated with hypertensive cardiomyopathy. One important feature of this condition is remodelling of intramural small coronary arteries and arterioles. Here, we investigated the implications of this remodelling in the downstream vascular organization, in particular at the capillary level. We used Spontaneously Hypertensive Rats (SHR) exhibiting many features of the human hypertensive cardiomyopathy. We generated 3D high-resolution mesoscopic reconstructions of the entire network of SHR hearts combining gel-based fluorescent labelling of coronaries with a CLARITY-based tissue clearing protocol. We performed morphometric quantification of the capillary network over time to assess capillary diameter, linear density, and angular dispersion. In SHRs, we found significant remodelling of the capillary network density and dispersion. SHR capillary density is increased in both ventricles and at all ages, including before the onset of systemic hypertension. This result suggests that remodelling occurs independently from the onset of systemic hypertension and left ventricular hypertrophy. On the contrary, capillary angular dispersion increases with time in SHR. Consistently, our multicolor imaging underlined a strong correlation between vascular dispersion and cellular disarray. Together our data show that 3D high-resolution reconstruction of the capillary network can unveil anatomic signatures in both physiological and pathological cardiac conditions, thus offering a reliable method for integrated quantitative analyses.