Age-matched Spontaneously Hypertensive Rats Research Articles

Parvalbumin interneuron deficiency in the prefrontal and motor cortices of spontaneously hypertensive rats: an attention-deficit hyperactivity disorder animal model insight.

Attention deficit hyperactivity disorder (ADHD) is characterized by impairments in developmental-behavioral inhibition, resulting in impulsivity and hyperactivity. Recent research has underscored cortical inhibition deficiencies in ADHD via the gamma-aminobutyric acid (GABA)ergic system, which is crucial for maintaining excitatory-inhibitory balance in the brain. This study explored postnatal changes in parvalbumin (PV) immunoreactivity, indicating GABAergic interneuron types, in the prefrontal (PFC) and motor (MC) cortices of spontaneously hypertensive rats (SHRs), an ADHD animal model. Examining PV- positive (PV+) cells associated with dopamine D2 receptors (D2) and the impact of dopamine on GABA synthesis, we also investigated changes in the immunoreactivity of D2 and tyrosine hydroxylase (TH). Brain sections from 4- to 10-week-old SHRs and Wistar Kyoto rats (WKYs) were immunohistochemically analyzed, comparing PV+, D2+ cells, and TH+ fiber densities across age-matched SHRs and WKYs in specific PFC/MC regions. The results revealed significantly reduced PV+ cell density in SHRs: prelimbic (~20% less), anterior cingulate (~15% less), primary (~15% less), and secondary motor (~17% less) cortices. PV+ deficits coincided with the upregulation of D2 in prepubertal SHRs and the downregulation of TH predominantly in pubertal/postpubertal SHRs. Reduced PV+ cells in various PFC regions could contribute to inattention/behavioral alterations in ADHD, while MC deficits could manifest as motor hyperactivity. D2 upregulation and TH deficits may impact GABA synthesis, exacerbating behavioral deficits in ADHD. These findings not only shed new light on ADHD pathophysiology but also pave the way for future research endeavors.

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.

Proteomic mapping reveals dysregulated angiogenesis in the cerebral arteries of rats with early-onset hypertension

Hypertension is associated with the presence of vascular abnormalities, including remodeling and rarefaction. These processes play an important role in cerebrovascular disease development; however, the mechanistic changes leading to these diseases are not well characterized. Using data-independent acquisition-based mass spectrometry analysis, here we determined the protein changes in cerebral arteries in pre- and early-onset hypertension from the spontaneously hypertensive rat (SHR), a model that resembles essential hypertension in humans. Our analysis identified 125 proteins with expression levels that were significantly upregulated or downregulated in 12-week-old spontaneously hypertensive rats compared to normotensive Wistar Kyoto rats. Using an angiogenesis enrichment analysis, we further identified a critical imbalance in angiogenic proteins that promoted an anti-angiogenic profile in cerebral arteries at early onset of hypertension. In a comparison to previously published data, we demonstrate that this angiogenic imbalance is not present in mesenteric and renal arteries from age-matched SHRs. Finally, we identified two proteins (Fbln5 and Cdh13), whose expression levels were critically altered in cerebral arteries compared to the other arterial beds. The observation of an angiogenic imbalance in cerebral arteries from the SHR reveals critical protein changes in the cerebrovasculature at the early onset of hypertension and provides novel insights into the early pathology of cerebrovascular disease.

Voiding behavior in awake unrestrained untethered spontaneously hypertensive and Wistar control rats.

The spontaneously hypertensive rat (SHR), a genetic model of high blood pressure, has also been studied as a potential model of overactive bladder. In vivo studies have confirmed the presence of surrogate markers of overactive bladder, including detrusor overactivity, increased urinary frequency, decreased bladder capacity and voided volume (VV), and afferent hypersensitivity to bladder irritation. However, these observations were during awake cystometry using implanted bladder catheters tethered to an infusion pump and artificially filled. We conducted experiments in awake unrestrained untethered age-matched female SHRs and Wistar rats to quantify naïve consumption and voiding behavior and the effect of capsaicin desensitization on consumption and voiding behavior. Food and water consumption, body weight, voiding frequency, and VV were recorded. Rats were placed in metabolism cages for 24 h, up to twice a week, from 17 to 37 wk of age. Compared with Wistar rats, SHRs exhibited decrease in VV and did not exhibit diurnal variation in VV between light and dark periods, suggesting that SHRs may have bladder hypersensitivity. Furthermore, SHRs may also have smaller bladder capacities, as they consumed less water, voided less volume (regardless of light cycle), and had equal urinary frequencies compared with age-matched Wistar rats. We detected no change in SHR voiding behavior following capsaicin desensitization, which was in contrast to a prior awake in vivo cystometry study describing increased VV and micturition interval in SHRs and suggests that C-fiber activity may not contribute to bladder hypersensitivity in SHRs.NEW & NOTEWORTHY We characterized the long-term (20 wk) voiding, defecation, and consumption behavior of age-matched spontaneously hypertensive and Wistar rats without the influence of anesthesia or catheters. Spontaneously hypertensive rats exhibited bladder hypersensitiviy that persisted for the 20-wk duration and was unaffected by capsacin desensitization.

Combined treatment with epoxyeicosatrienoic acid analog and 20-hydroxyeicosatetraenoic acid antagonist provides substantial hypotensive effect in spontaneously hypertensive rats.

The global morbidity and mortality related to hypertension and associated disorders increases continuously and novel therapeutic strategies are still in high demand. Increasing evidence suggests the important role in blood pressure regulation of cytochrome P-450-dependent metabolites of arachidonic acid. Epoxyeicosatrienoic acids (EETs) induce vasodilation and natriuresis, and have renoprotective and anti-inflammatory properties. 20-HETE is an arachidonic acid metabolite with both prohypertensive and antihypertensive activities. To explore the pathophysiological role of arachidonic acid metabolites in more detail, we examined the antihypertensive efficiency of EET-A, a stable analog of 14,15-EET, and of AAA, a novel antagonist of the 20-HETE receptors. Male spontaneously hypertensive rats (SHR) were treated for 5 weeks with EET-A, AAA or the combination; age-matched untreated SHR and normotensive Wistar-Kyoto rats served as controls. EET-A and AAA were administered in drinking water at 10 mg/kg/day each. SBP was measured by telemetry and urine, blood, and tissue samples were collected for relevant analyses. EET-A or AAA given alone had no significant effect on SHR blood pressure. In contrast, combined treatment with AAA and EET-A was significantly antihypertensive, causing a decrease in SBP from 180 ± 3 to 160 ± 5 mmHg (P < 0.05). Additionally, the combined treatment attenuated cardiac hypertrophy, decreased kidney ANG II level, increased natriuresis, and increased the excretion of nitric oxide metabolites. Considering the beneficial impact of the combined treatment with EET-A and AAA on SHR blood pressure and cardiovascular and renal function, we suggest that the treatment is a promising therapeutic strategy for human hypertension.

Huoxue Qianyang decoction ameliorates cardiac remodeling in obese spontaneously hypertensive rats in association with ATF6-CHOP endoplasmic reticulum stress signaling pathway regulation

ObjectiveEndoplasmic reticulum (ER) stress is involved in hypertension related cardiac remodeling. We aimed to evaluate the effects of Huoxue Qianyang (HXQY) decoction on cardiac remodeling in obese spontaneously hypertensive rats (SHRs), and explore its impacts on the activating transcription factor 6 (ATF6)-C/EBP homologous protein (CHOP) ER stress signaling pathway. MethodsTwenty-seven obese SHRs were randomly divided into Obese SHR, Obese SHR + HXQY and Obese SHR + Valsartan groups, and treated with the indicated drugs for 8 weeks. Nine age-matched male SHRs were used as controls. Systolic blood pressure (SBP), body weight (BW), and the left ventricular mass index (LVMI) were measured weekly or at end point. Then, angiotensin II (Ang II), fasting glucose (FPG) and fasting insulin (FIN), total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglyceride (TG) levels were evaluated with commercial kits. Apoptotic cardiomyocytes were detected by the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method. The expression levels of GRP78, ATF6, PERK/pPERK and CHOP were assessed by quantitative PCR and Western blot. ResultsTreatment with HXQY decoction resulted in significantly reduced SBP, BW, LVMI, Ang II, TC and LDL-C levels, as well as the homeostasis model assessment of insulin resistance (HOMA-IR) score in obese SHRs. Apoptosis in heart tissues of obese SHRs was significantly attenuated after HXQY decoction administration, paralleling reduced expression of GRP78, ATF6, PERK/pPERK and CHOP at both mRNA and protein levels. ConclusionCardiac remodeling in obese SHRs is ameliorated by intervention with HXQY decoction in association with inhibited ATF6−CHOP ER stress signaling pathway.

Dronedarone induces regression of coronary artery remodeling related to better global antioxidant status.

Our group previously demonstrated that dronedarone induces regression of left ventricular hypertrophy in spontaneously hypertensive rats (SHRs). We assessed changes in vascular remodeling and oxidative stress following short-term use of this agent. The coronary artery was isolated from 10-month-old male SHRs treated with 100 mg kg-1 dronedarone once daily for 14 days (SHR-D group), and age-matched untreated SHRs were used as hypertensive controls. We analyzed the geometry and composition of the artery and constructed dose-response curves for acetylcholine and serotonin (5-HT). We calculated a global score (OXY-SCORE) from plasma biomarkers of oxidative status: carbonyl levels, thiol levels, reduced glutathione levels, total antioxidant capacity, and superoxide anion scavenging activity. Finally, we analyzed asymmetric dimethylarginine (ADMA) concentrations in plasma. Dronedarone significantly decreased wall thickness (medial and adventitial layer thickness and cell count) and the cross-sectional area of the artery. Dronedarone significantly improved endothelium-dependent relaxation and reduced the contraction induced by 5-HT. The OXY-SCORE was negative in the SHR model group (suggesting an enhanced oxidative status) and was positive in the SHR-D group (suggesting enhanced antioxidant defense). Dronedarone significantly decreased the concentrations of ADMA. We conclude that dronedarone improves coronary artery remodeling in SHRs. The better global antioxidant status after treatment with dronedarone and decreased plasma ADMA levels could contribute to the cardiovascular protective effect of dronedarone.

Impact of moderate- and high-intensity exercise on the endothelial ultrastructure and function in mesenteric arteries from hypertensive rats

Oxidative stress (OS) influences vascular function and structure in spontaneously hypertensive rats (SHRs). It is also responsible for the decreased nitric oxide (NO) bioavailability that influences endothelial vasodilation. The effects of high-intensity exercise on endothelial function and ultrastructure in hypertension remain unknown. Thus, this study investigated the effects of moderate- and high-intensity exercise on hypertension-associated endothelial dysfunction and ultrastructural remodeling. Moderate-intensity (SHR-M) and high-intensity (SHRH) aerobic exercise training groups were compared in age-matched sedentary SHRs (SHRC) and normotensive Wistar–Kyoto rats (WKY-C). The results showed that the endothelial ultrastructure was impaired in the SHR-H and SHR-C groups. Glutathione peroxidase levels were significantly increased in the SHR-M group compared to the SHR-C group. MDA content was higher in the SHR-H group than in the SHR-C group, but the levels of antioxidant enzymes did not increase accordingly. Apocynin scavenging reactive oxygen species (ROS) ameliorated endothelium-dependent vasodilator function in the SHR-H group. However, the SHR-M and WKY-C groups abolished the increased vasodilation induced by apocynin. L-NAME, a NO synthase inhibitor, was applied to isolated mesenteric arteries (MAs) to evaluate NO contribution. Moderate-intensity exercise reversed the decreased NO contribution to MAs in hypertension, and high-intensity exercise aggravated this change. These data suggest that moderate-intensity exercise ameliorated adverse remodeling of the endothelial ultrastructure and function in hypertension by decreasing oxidative stress and increasing NO contribution. However, high-intensity exercise exacerbated all of these changes by increasing OS and ROS contribution, and decreasing NO contribution.

Influence of Age on Anticontractile Effect of Perivascular Adipose Tissue in Normotensive and Hypertensive Rats.

Perivascular adipose tissue (PVAT) and its vasomodulatory effects play an important role in the physiology and pathophysiology of blood vessels. Alterations in PVAT associated with reduction in its anticontractile influence are proven to contribute to vascular dysfunction in hypertension. The aim of this study was to examine whether the changes in PVAT properties could participate in progression of vascular abnormalities in developing spontaneously hypertensive rats (SHR). Normotensive Wistar-Kyoto (WKY) rats and SHR, both in 5th and in 12th week of age, were used. Systolic blood pressure was similar between WKY rats and SHR in 5th week of age; however, in 12th week, it was significantly increased in SHR comparing to WKY rats. The amount of retroperitoneal fat was higher in WKY rats in both age groups, whereas body weight was higher in WKY rats only in 12th week, when compared to age-matched SHR. From isolated superior mesenteric arteries, two ring preparations were prepared for isometric tension recording, one with PVAT intact and other with PVAT removed. In WKY rats as well as in SHR, arterial contractile responses to noradrenaline, applied cumulatively on rings, were significantly inhibited in the presence of intact PVAT. In both age groups, anticontractile effect of PVAT was higher in WKY rats than in SHR. Neurogenic contractions, induced by electrical stimulation of perivascular sympathoadrenergic nerves, were significantly attenuated in the presence of PVAT in WKY mesenteric arteries from both age groups; however, in arteries from SHR, intact PVAT had no influence on this type of contractile responses. The results suggest that in SHR impairment of anticontractile effect of PVAT precedes hypertension and might contribute to its development.

A17051 LONG-TERM TOCOTRIENOL-RICH VITAMIN E SUPPLEMENTATION ACCELERATED THE DEVELOPMENT OF HIGH BLOOD PRESSURE IN SPONTANEOUSLY HYPERTENSIVE RATS

Objectives: This study hypothesized that TRE supplementation from pre-hypertensive stage diminishes renal oxidative stress and therefore prevents the development of hypertension in spontaneously hypertensive rats (SHR). This study aims to determine the effect of early TRE supplementation on (i) systolic blood pressure (SBP), (ii) renal superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and lipid peroxidation levels (TBARS) in SHR. Methods: Pre-hypertensive male SHR aged 4 weeks were given TRE (100 mg/kg body weight/day) via oral gavage for either 2, 4, 6, 8 or 12 weeks (TRE-SHR). Blood pressure and renal oxidant/antioxidant levels were determined at the end of supplementation i.e. at the age of 6, 8, 10, 12 and 16 weeks. SBP was measured using tail-cuff plethysmography. Statistical analysis was performed using one-way ANOVA followed by post-hoc Tukey's test. P < 0.05 was considered as statistically significant. Results: SBP of TRE-SHR was significantly lower at 6 weeks of age, but interestingly, it accelerated and was significantly higher at the age of 12 and 16 weeks compared to that in age-matched untreated SHR. TBARS levels were significantly lower in all the age groups in TRE-SHR. Renal GPx activity was significant higher in 6 weeks old TRE-SHR. No significant differences were evident in renal SOD and CAT activities in all the TRE-SHR groups when compared to those in the non-treated SHR. Conclusion: In conclusion, it appears that TRE supplementation to pre-hypertensive SHR initially delays the rise in systolic blood pressure but when given for a longer duration it increases the rate of increase in blood pressure; suggesting of its potential pro-hypertensive properties.

Neprilysin Inhibition by an Antisense Oligonucleotide (ASO) Ameliorates Kidney Damage in a Salt‐induced Rat Chronic Kidney Disease Model

Neprilysin (NEP) is the key enzyme that degrades natriuretic peptides (NPs), which are the neurohormones contributing to natriuresis, diuresis and blood pressure regulation. NEP inhibition results in enhanced natriuresis and vasodilation by augmenting NP levels, which lead to the reduction of intra‐glomerular pressure and proteinuria in the damaged kidneys. We evaluated the renoprotective effects of a Generation 2.5 NEP antisense oligonucleotide (ASO) in a hypertensive and salt‐induced severe chronic kidney disease (CKD) model. Male, uninephrectomized (UNX) spontaneously hypertensive rats (SHR) were randomized to concurrently receive seven weeks of high salt intake (1% NaCl in drinking water for 5 weeks and then 1.5% for remaining two weeks) and drug treatments (vehicle control, NEP ASO at 20 mg/kg SQ weekly or the small molecule NEP inhibitor AHU377 at 50 mg/kg PO daily). AHU377 (Sacubitril) is the main ingredient of the recently approved heart failure drug Entresto®. Age‐matched SHR naïve (SHR control, normal salt intake) and SHRs with UNX (UnX control, normal salt intake + UnX) served as negative controls. NEP ASO treated rats demonstrated improvements in proteinuria compared to vehicle control or AHU377 treatments1. There were no differences between the treatment groups in blood BUN, creatinine level and creatinine clearance. In the NEP ASO group, kidney qPCR analysis demonstrated marked reductions of NEP expression (&gt;90%) and significantly less inflammation (MCP1, KIM1, NGAL) and fibrosis (ColIa1) relative to control or AHU377 treatments2. Western blot and NEP activity assays of kidney homogenates corroborated the qPCR findings. Meanwhile, NEP ASO and AHU377 treatments restored urinary cGMP/creatinine ratio3 suppressed by salt‐induced kidney damage. Histological examination of the kidney revealed less interstitial fibrosis, eosinophilic casts and glomerulosclerosis with NEP ASO treatment. In summary, in a severe rat CKD model, NEP ASO treatment was effective in blunting disease progression (i.e. less proteinuria, inflammation and fibrosis), which was not observed with the treatment by a small molecular NEP inhibitor AHU377. SHR control UnX control UnX, salt + vehicle UnX, salt + NEP ASO UnX, salt + AHU377 1 MicroAlb/CRE (mg/ml/mg/dL) 0.22 ± 0.04 1.25 ± 0.23 16.2 ± 3.3 2.40 ± 0.80** 26.3 ± 10.1 2 MCP1 gene expression (%) 100 ± 8 121 ± 8 347 ± 48 239 ± 18* 351 ± 31 KIM1 gene expression (%) 100 ± 28 248 ± 47 10,189 ± 2,382 1,430 ± 307* 18,970 ± 12,266 NGAL gene expression (%) 100 ± 7 157 ± 7 1,870 ± 387 463 ± 36** 1,987 ± 794 ColIa1 gene expression (%) 100 ± 10 139 ± 13 753 ± 122 474 ± 28* 752 ± 95 3 Urinary cGMP/CRE (pmol/ml/mg/dL) 33.6 ± 4.6 26.6 ± 2.4 19.5 ± 1.6 26.4 ± 2.2* 34.4 ± 4.2 1(UnX, salt + vehicle) vs. (UnX, salt + NEP ASO): ** p &lt; 0.01 2(UnX, salt + vehicle) vs. (UnX, salt + NEP ASO): * p &lt; 0.05, ** p &lt; 0.01 3(UnX, salt + vehicle) vs. (UnX, salt + NEP ASO): * p &lt; 0.05 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Identification of Novel mRNA Transcripts in the Sympathetic Stellate Ganglia using RNA Sequencing

IntroductionSympathetic hyperactivity is a key feature of human hypertension as well as animal models of disease. In the spontaneously hypertensive rat (SHR), a genetic‐based model of hypertension, dysautonomia occurs prior to increases in blood pressure.AimIn this study, we aimed to establish the genetic changes in post‐ganglionic sympathetic neurons (PGSNs) obtained from SHR rats and to confirm the presence of these transcripts in stellate ganglia from human donor patients.MethodPGSNs were obtained from 16‐week normotensive Wistar rats and age‐matched hypertensive SHR with known sympathetic hyper‐responsiveness. RNA sequencing was used to investigate the transcriptomic changes within the cardiac sympathetic stellate ganglia in disease.ResultsRNAseq data were analysed using a Salmon‐DESeq2 pipeline1,2. We observed 768 differentially expressed mRNA transcripts in SHR compared with Wistar PGSNs, using the Benjamini‐Hochberg adjusted p&lt;0.01 level. Gene ontology (GO) analysis of the rat dataset revealed extracellular ligand‐gated ion channels (GO:0005302) to be the most over‐represented ‘molecular function’ GO group. There were 15 differentially expressed genes in SHR stellate neurons within this group; including nicotinic, purinergic, glutamatergic, serotonergic, GABAergic and glycinergic receptor subunits. The presence of these transcripts was confirmed using qRT‐PCR in stellate ganglia obtained from human and rat.ConclusionRNAseq transcriptomics has revealed differential gene expression profiles in PGSNs obtained from SHR and normotensive Wistar rats. These key transcripts were also present in human stellate ganglia. Taken together, these genes require further investigation for their role in sympathetic hyperactivity and dysautonomias.Support or Funding InformationThis project was funded by the Wellcome Trust OXION initiative (105409/Z/14/Z), the British Heart Foundation, NIH SPARC (OT2OD023848) and new innovator (DP2HL142045) initiatives.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Early signs of cardiac diastolic dysfunction in ovariectomized WKY and SHR female rats

Half of patients with heart failure (HF) have diastolic dysfunction but preserved EF (> 50%; HFpEF). There is no specific treatment. Aging populations, and particularly women, are more widely concerned. Why are women more likely than men to develop HFpEF? Despite possible limitations, small animal models could provide comprehensive approaches to identify/test novel therapeutic targets. Determine whether loss of estrogens could promote diastolic dysfunction in a rat model of menopause induced by bilateral ovariectomy. The spontaneously hypertensive rat (SHR) model was investigated in parallel as a potential positive control. 7-weeks-old female WKY rats were ovariectomized (OVX-WKY, n = 7) and compared to sham (WKY, n = 7) and sex and age-matched SHR rats ( n = 7). They were followed by Doppler echocardiography and Tissue Doppler Imaging (Vevo2100, VisualSonics). After final examination (12 weeks post-surgery), cardiomyocytes were enzymatically isolated. Cell shortening and intracellular Ca 2+ (dye indo-1AM) were measured (IonOptix ® system). Echocardiographic parameters were similar in all 7-week old rats. At week 19, EF was also comparable in all groups and considered as preserved (WKY: 60 ± 7%, OVX-WKY: 58 ± 5%, SHR: 52 ± 6%). Hearts morphology was also comparable. However, increased myocardial performance index (Tei), prolonged isovolumic relaxation time and increased left ventricular filling pressure (E/e’ ratio) suggested diastolic dysfunction both in OVX-WKY and SHR, yet with more marked effects in SHR. Single cell contraction and Ca 2+ cycling were modified both in OVX-WKY and SHR, yet differently between the two groups. Estrogen depletion promoted signs of diastolic dysfunction early. In young SHR females, diastolic dysfunction also developed rapidly, presumably in parallel with onset of hypertension. Ca 2+ cycling alterations are involved, yet differently suggesting distinct and complex mechanisms.

Abstract 208: Excessive Autophagy Contributes to Microvascular Endothelial Dysfunction in Prehypertensive Spontaneously Hypertensive Rats

Autophagy exists in vascular endothelial cells, however, the exact role of autophagy in hypertensive-associated vascular endothelial dysfunction remains largely elusive. We assessed the hypothesis that autophagy is one of the mechanisms of endothelial dysfunction in normotensive spontaneously hypertensive rats (SHRs). Age-matched male SHRs and Wistar Kyoto rats (WKY) aged 4 weeks (young) and 12 weeks (adult) were randomized into 2 groups and treated daily for 2 weeks by a) gavage with vehicle alone (normal saline) or b) intraperitoneally injection of rapamycin (1 mg/kg/day), and the vascular function of their isolated aorta and mesenteric artery was assessed in vitro . Furthermore, human umbilical vein endothelial cells (HUVECs) were incubated serum-starved for 6 h to induce excessive cell autophagy, and then incubated with DMEM containing 10% FBS and a) treated with 10 nmol/L insulin-like growth factor 1 (IGF-1) for 12 h, b) treated with 100 nmol/L Rapamycin for 1 h for 37°C. Compared with WKY, young and adult SHRs showed endothelial dysfunction of the aorta and mesenteric artery, along with decreased phosphorylated (p)-Akt, p-mTOR, and autophagic marker protein p62 and increased LC3 II/I in microvascular but not aortic tissues. Treatment of young SHRs with the mTOR inhibitor rapamycin aggravated the endothelial autophagy and subsequent impaired endothelial function. Moreover, IGF-1 significantly activated Akt/mTOR signaling in HUVECs and reduced autophagic levels, while rapamycin inhibited p-mTOR and increased autophagic levels. In conclusion, mesenteric endothelial dysfunction in prehypertensive SHRs is at least partly attributable to excessive autophagy in vascular tissues, and is likely mediated by the underactive Akt/mTOR signaling pathway; however, autophagy appears not to be responsible for the macrovascular endothelial dysfunction.

Exercise intensity-dependent reverse and adverse remodeling of voltage-gated Ca(2+) channels in mesenteric arteries from spontaneously hypertensive rats.

Exercise can be regarded as a drug for treating hypertension, and the 'dosage' (intensity/volume) is therefore of great importance. L-type voltage-gated Ca(2+) (Cav1.2) channels on the plasma membrane of vascular smooth muscle cells have a pivotal role in modulating the vascular tone, and the upregulation of Cav1.2 channels is a hallmark feature of hypertension. The present study investigated the beneficial and adverse effects of exercise at different intensities on the remodeling of the Cav1.2 channel in mesenteric arteries (MAs) of spontaneously hypertensive rats (SHRs). Moderate- (SHR-M, 18-20 m min(-1)) and high-intensity (SHR-H, 26-28 m min(-1)) aerobic exercise training groups were created for SHRs and lasted for 8 weeks (1 h per day, 5 d per week). Age-matched sedentary SHRs and normotensive Wistar-Kyoto rats (WKY) were used as controls. The mesenteric arterial mechanical and functional properties were evaluated. Moderate-intensity exercise training induced a lower systolic blood pressure and heart rate in these rats compared with sedentary SHRs. BayK 8644 and nifedipine induced vasoconstriction and dose-dependent vasorelaxation, respectively, in the mesenteric arterial rings. Moderate-intensity exercise significantly suppressed the increase in BayK 8644-induced vasoconstriction, tissue sensitivity to nifedipine, Cav1.2 channel current density and Cav1.2 α1C-subunit protein expression in MAs from SHRs. However, high-intensity exercise training aggravated all of these hypertension-associated functional and molecular alterations of Cav1.2 channels. These results indicate that moderate-intensity aerobic training may act as a drug and effectively reverse the remodeling of Cav1.2 channels in hypertension to restore the vascular function in MAs, but that high-intensity exercise exaggerates the adverse remodeling of Cav1.2 channels and worsens the vascular function.

CCL5 Inhibits Elevation of Blood Pressure and Expression of Hypertensive Mediators in Developing Hypertension State Spontaneously Hypertensive Rats

CCL5, a proinflammatory chemokine, has been shown to attenuate angiotensin (Ang) II-induced expression of hypertensive mediators as well as Ang II-induced inhibition of anti-hypertensive mediator expression in vascular smooth muscle cells (VSMCs) of spontaneously hypertensive rats (SHR). In the present study, functional roles of CCL5 on hypertension were examined in developing hypertension state SHR (DHSHR). DHSHR at an age of 8 weeks were injected CCL5 (1.5 μg/kg) subcutaneously twice a day for 3 weeks (SHRi, n=5). Control groups consisted of normal age-matched saline-treated SHR (SHRc, n=5) and normotensive Wistar-Kyoto rats (WKY, n=5). Effect of CCL5 on blood pressure was measured before treatment, weekly during treatment, and 1 day after the final injection. After injecting for 3 weeks, effects of CCL5 on expression of hypertensive mediators were examined in thoracic aorta tissues and VSMCs. Blood pressure in SHRi was maintained without any elevation during the treatment period, whereas blood pressure in SHRc progressively increased with age. Expression of Ang II subtype I receptor was reduced in SHRi thoracic aorta tissues and VSMCs compared to those in SHRc. In addition, expression levels of hypertensive mediators were significantly reduced in SHRi thoracic aorta tissues and VSMCs compared to those in SHRc. In contrast, AMP-activated protein kinase (AMPK) activity and interleukin-10 (IL-10) expression were elevated in SHRi thoracic aorta tissues and VSMCs compared to levels in SHRc. These results suggest that reduction of hypertensive mediators and elevation of antihypertensive mediators by CCL5 treatment promotes maintenance of blood pressure in DHSHR.

Short-term esmolol improves coronary artery remodeling in spontaneously hypertensive rats through increased nitric oxide bioavailability and superoxide dismutase activity.

The aim of this study was to assess the effects of short-term esmolol therapy on coronary artery structure and function and plasma oxidative stress in spontaneously hypertensive rats (SHR). For this purpose, 14-month-old male SHR were treated for 48 hours with esmolol (SHR-E, 300 μg/kg/min). Age-matched untreated male SHR and Wistar Kyoto rats (WKY) were used as hypertensive and normotensive controls, respectively. At the end of intervention we performed a histological study to analyze coronary artery wall width (WW), wall-to-lumen ratio (W/L), and media cross-sectional area (MCSA). Dose-response curves for acetylcholine (ACh) and sodium nitroprusside were constructed. We also assessed several plasma oxidative stress biomarkers, namely, superoxide scavenging activity (SOSA), nitrites, and total antioxidant capacity (TAC). We observed a significant reduction in WW (P < 0.001), W/L (P < 0.05), and MCSA (P < 0.01) and improved endothelium-dependent relaxation (AUCSHR-E = 201.2 ± 33 versus AUCSHR = 97.5 ± 21, P < 0.05) in SHR-E compared with untreated SHR; no differences were observed for WW, MCSA, and endothelium-dependent relaxation by ACh at higher concentrations (10−6 to 10−4 mol/l) for SHR-E with respect to WKY. SOSA (P < 0.001) and nitrite (P < 0.01) values were significantly higher in SHR-E than in untreated SHR; however, TAC did not increase after treatment with esmolol. Esmolol improves early coronary artery remodeling in SHR.

Macrophage migration inhibitory factor in the nucleus of solitary tract decreases blood pressure in SHRs

The macrophage migration inhibitory factor (MIF) is an intracellular inhibitor of the central nervous system actions of angiotensin II on blood pressure. Considering that angiotensin II actions at the nucleus of the solitary tract are important for the maintenance of hypertension in spontaneously hypertensive rats (SHRs), we tested if increased MIF expression in the nucleus of the solitary tract of SHR alters the baseline high blood pressure in these rats. Eight-week-old SHRs or normotensive rats were microinjected with the vector AAV2-CBA-MIF into the nucleus of the solitary tract, resulting in MIF expression predominantly in neurons. Rats also underwent recordings of the mean arterial blood pressure (MAP) and heart rate (via telemetry devices implanted in the abdominal aorta), cardiac- and baroreflex function. Injections of AAV2-CBA-MIF into the nucleus of the solitary tract of SHRs produced significant decreases in the MAP, ranging from 10 to 20 mmHg, compared with age-matched SHRs that had received identical microinjections of the control vector AAV2-CBA-eGFP. This lowered MAP in SHRs was maintained through the end of the experiment at 31 days, and was associated with an improvement in baroreflex function to values observed in normotensive rats. In contrast to SHRs, similar increased MIF expression in the nucleus of the solitary tract of normotensive rats produced no changes in baseline MAP and baroreflex function. These results indicate that an increased expression of MIF within the nucleus of the solitary tract neurons of SHRs lowers blood pressure and restores baroreflex function.

838 Activation of the aldosterone/MR system by aging in spontaneously hypertensive rats

In the present study we hypothesised that age-associated changes in the renal aldosterone/mineralocorticoid receptor (MR) system may differ between normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). In WKY, body mass index (BMI) significantly increased with age. Fat mass accumulation may operate as a confounding factor therefore WKY were submitted to 15% food restriction (WKY-FR) from 5 to 13 and 52 weeks of age. Renal oxidative stress was increased in aged WKY and SHR. Long-term FR significantly reduced the BMI and decreased renal oxidative stress when compared to age-matched WKY and SHR. Aged WKY and SHR had increased MR functionality, which correlated positively with increased plasma aldosterone levels, nuclear MR content and abundance of aldosterone effectors in the renal medulla. In contrast, when compared to aged WKY and SHR, aged WKY-FR had decreased plasma aldosterone levels and decreased activation of the aldosterone/MR system in the renal medulla. Increases in renal oxidative stress and plasma aldosterone in aged WKY, to levels observed in SHR, were not sufficient to result in sustained increases in blood pressure. In conclusion, activation of the aldosterone/MR system is intensified by aging in SHR whereas hyperaldosteronism in WKY is associated with increases in body fat mass.

CD36 overexpression predisposes to arrhythmias but reduces infarct size in spontaneously hypertensive rats: gene expression profile analysis.

CD36 fatty acid translocase plays a key role in supplying heart with its major energy substrate, long-chain fatty acids (FA). Previously, we found that the spontaneously hypertensive rat (SHR) harbors a deletion variant of Cd36 gene that results in reduced transport of long-chain FA into cardiomyocytes and predisposes the SHR to cardiac hypertrophy. In the current study, we analyzed the effects of mutant Cd36 on susceptibility to ischemic ventricular arrhythmias and myocardial infarction in adult SHR-Cd36 transgenic rats with wild-type Cd36 compared with age-matched SHR controls. Using an open-chest model of coronary artery occlusion, we found that SHR-Cd36 transgenic rats showed profound arrhythmogenesis resulting in significantly increased duration of tachyarrhythmias (207 ± 48 s vs. 55 ± 21 s, P < 0.05), total number of premature ventricular complexes (2,623 ± 517 vs. 849 ± 250, P < 0.05) and arrhythmia score (3.86 ± 0.18 vs. 3.13 ± 0.13, P < 0.001). On the other hand, transgenic SHR compared with SHR controls showed significantly reduced infarct size (52.6 ± 4.3% vs. 72.4 ± 2.9% of area at risk, P < 0.001). Similar differences were observed in isolated perfused hearts, and the increased susceptibility of transgenic SHR to arrhythmias was abolished by reserpine, suggesting the involvement of catecholamines. To further search for possible molecular mechanisms of altered ischemic tolerance, we compared gene expression profiles in left ventricles dissected from 6-wk-old transgenic SHR vs. age-matched controls using Illumina-based sequencing. Circadian rhythms and oxidative phosphorylation were identified as the top KEGG pathways, while circadian rhythms, VDR/RXR activation, IGF1 signaling, and HMGB1 signaling were the top IPA canonical pathways potentially important for Cd36-mediated effects on ischemic tolerance. It can be concluded that transgenic expression of Cd36 plays an important role in modulating the incidence and severity of ischemic and reperfusion ventricular arrhythmias and myocardial infarct size induced by coronary artery occlusion. The proarrhythmic effect of Cd36 transgene appears to be dependent on adrenergic stimulation.