Vehicle-treated Spontaneously Hypertensive Rats Research Articles

Age-Related Effects of AT1 Receptor Antagonist Losartan on Cognitive Decline in Spontaneously Hypertensive Rats.

Both hypertension and aging are known to increase the vulnerability of the brain to neurovascular damage, resulting in cognitive impairment. The present study investigated the efficacy of the antihypertensive drug losartan on age- and hypertension-associated cognitive decline and the possible mechanism underlying its effect in spontaneously hypertensive rats (SHRs). Losartan was administered (10 mg/kg, i.p. for 19 days) to 3- and 14-month-old SHRs. Age-matched Wistar rats were used as controls. Working memory, short-term object recognition, and spatial memory were assessed using the Y-maze, object recognition test (ORT) and radial arm maze (RAM) test. The expression of markers associated with aging, oxidative stress, and memory-related signaling was assessed in the frontal cortex (FC) and hippocampus. Motor activity measured over 24 h was not different between groups. Middle-aged vehicle-treated SHRs showed poorer performance in spontaneous alternation behavior (SAB) and activity in the first Y-maze test than their younger counterparts, suggesting age-related reduced "decision making" and reactivity in a novel environment. Losartan improved the age- and hypertension-induced decline in short-term recognition and spatial memory measured in the ORT and the second Y-maze test, particularly in the middle-aged rats, but was ineffective in the young adult rats. Changes in memory and age-related markers such as cAMP response element-binding protein (CREB) and amyloid-β1-42 (Aβ1-42) and increased oxidative stress were observed in the hippocampus but not in the FC between young adult and middle-aged vehicle-treated SHRs. Losartan increased CREB expression while reducing Aβ1-42 levels and concomitant oxidative stress in middle-aged SHRs compared with vehicle-treated SHRs. In conclusion, our study highlights the complex interplay between hypertension, aging, and cognitive impairment. It suggests that there is a critical time window for therapeutic intervention with angiotensin II type 1 receptor blockers.

Exploring the potential effect of electroacupuncture on cardiovascular function and lipid profiles in spontaneously hypertensive rats

BackgroundInvestigating the effects of electroacupuncture (EA) treatment on cardiovascular function and aortic lipid profiles in spontaneously hypertensive rats (SHR) constitutes the foundational focus of this study. The overarching goal is to comprehensively elucidate the alterations brought about by EA treatment and to assess its potential as an alternative therapy for hypertension. MethodsConsecutive EA treatments were administered to SHR, and the effects on systolic blood pressure, cardiac function, and hypertension-related neuronal signals were assessed. Aortic lipid profiles in vehicle-treated SHR and EA-treated SHR groups were analyzed using mass spectrometry-based lipid profiling. Additionally, the expression of Cers2 and GNPAT, enzymes involved in the synthesis of specific aortic lipids, was examined. ResultsThe study demonstrated that consecutive EA treatments restored systolic blood pressure, improved cardiovascular function, and normalized hypertension-related neuronal signals in SHR. Analysis of the aortic lipid profiles revealed distinct differences between the vehicle-treated SHR group and the EA-treated SHR group. Specifically, EA treatment significantly altered the levels of aortic sphingomyelin and phospholipids, including very long-chain fatty acyl-ceramides and ether phosphatidylcholines. These changes in aortic lipid profiles correlated significantly with systolic blood pressure and cardiac function indicators. Furthermore, EA treatment significantly altered the expression of Cers2 and GNPAT. ConclusionsThe findings suggest that EA may influence cardiovascular functions and aortic lipid profiles in SHR.

Effects of adolescent methylphenidate administration on methamphetamine conditioned place preference in an animal model of attention-deficit/hyperactivity disorder: Examination of potential sex differences

BackgroundIndividuals with attention-deficit/hyperactivity disorder (ADHD) are more likely to be diagnosed with a substance use disorder; however, the effects of long-term psychostimulant treatment on addiction are mixed. Preclinical studies are useful for further elucidating the relationship between ADHD and addiction-like behaviors, but these studies have focused on male subjects only. The goal of the current study was to determine if early-life administration of methylphenidate (MPH) augments methamphetamine (METH) conditioned place preference (CPP) and/or potentiates reinstatement of CPP in both male and female rats. MethodsMale and female spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) received either MPH (1.5mg/kg; p.o.) or vehicle (1.0ml/kg) during adolescence (postnatal day [PND] ~29–57). Two weeks after cessation of MPH treatment, rats were tested for METH CPP (1.0mg/kg or 2.0mg/kg; s.c.). Rats were then given extinction sessions. Once rats met extinction criteria, they were tested for reinstatement of CPP following a priming injection of METH (0.25mg/kg; s.c.). ResultsAll groups developed METH CPP, except vehicle-treated SHR males and vehicle-treated WKY females conditioned with the higher dose of METH (2.0mg/kg). Female SHRs treated with MPH showed greater reinstatement of METH CPP compared to female SHRs treated with vehicle. Adolescent MPH treatment did not augment the locomotor-stimulant effects of METH in adulthood. ConclusionsThese results demonstrate the importance of considering biological sex when prescribing psychostimulant medications for ADHD as long-term MPH administration may increase the risk of continued drug use in females with ADHD following a period of abstinence.

Inhibition of endoplasmic reticulum stress restores the balance of renal RAS components and lowers blood pressure in the spontaneously hypertensive rats

ABSTRACT Background Endoplasmic reticulum (ER) stress has been shown to play a critical role in the pathogenesis of hypertension. However, the underlying mechanisms for lowering blood pressure (BP) by suppressing ER stress remain unclear. Here, we hypothesized that inhibition of ER stress could restore the balance between RAS components and lower BP in spontaneously hypertensive rats (SHRs). Methods Wistar-Kyoto (WKY) rats and SHRs received vehicle or 4-PBA, an ER stress inhibitor, in the drinking water for 4 weeks. BP was measured by tail-cuff plethysmography, and the expression of RAS components was examined by Western blot. Results Compared with vehicle-treated WKY rats, vehicle-treated SHRs exhibited higher blood pressure and increased renal ER stress and oxidative stress, accompanied by impaired diuresis and natriuresis. Moreover, SHRs had higher ACE and AT1R and lower AT2R, ACE2, and MasR expressions in the kidney. Interestingly, 4-PBA treatment improved impaired diuresis and natriuresis and lowered blood pressure in SHRs, accompanied by reducing ACE and AT1R protein expression and increasing AT2R, ACE2, and MasR expression in the kidneys of SHRs. In addition, these changes were associated with the reduction of ER stress and oxidative stress. Conclusions These results suggest that the imbalance of renal RAS components was associated with increased ER stress in SHRs. Inhibition of ER stress with 4-PBA reversed the imbalance of renal RAS components and restored the impaired diuresis and natriuresis, which, at least in part, explains the blood pressure-lowering effects of 4-PBA in hypertension.

Chronic cyclooxygenase-2 inhibition prevents the worsening of hypertension and endothelial dysfunction induced by ouabain in resistance arteries of spontaneously hypertensive rats

AimPrevious studies raise cyclooxygenase (COX) activation as a possible mechanism involved in the pathophysiology of ouabain-induced hypertension. We hypothesized that inhibition of COX-2 activity might prevent ouabain-induced vascular dysfunction and worsening of hypertension in spontaneously hypertensive rats (SHR). MethodsSHR were exposed to ouabain or vehicle and treated or not with the selective COX-2 inhibitor nimesulide for 5 weeks. Systolic blood pressure was measured by plethysmography. Vascular reactivity by wire myograph and protein expression by Western-blot were assessed in mesenteric resistance arteries (MRA) of groups. Thromboxane A2 (TXA2) production by ELISA was evaluated in MRA supernatants of groups. ResultsNoradrenaline-induced maximal contraction (Emax) was greater in MRA from SHR receiving ouabain than those of vehicle group. In situ inhibition of COX-2, TXA2 synthase, or TP receptor reduced the Emax to noradrenaline in MRA of ouabain to vehicle levels. TXA2 production was higher in ouabain than in vehicle group. Ouabain enhanced expression of cytoplasmic tyrosine kinase Src (c-Src)/ERK1/2/COX-2/TXA2 synthase/TP receptor in SHR MRA, but did not change NFkB/iKB ratio. Anticontractile effect of nitric oxide (NO) was smaller in MRA from ouabain- than vehicle-treated SHR, as well as eNOS and nNOS expression. Nimesulide co-treatment prevented the ouabain-induced worsening of hypertension and noradrenaline MRA hypercontractility in SHR. ConclusionOuabain worsen hypertension and induce MRA hypercontractility in SHR associated with upregulated c-Src/ERK1/2/COX-2/TXA2 synthase/TXA2/TP receptor axis. These effects were prevented by COX-2 inhibition.

Empagliflozin Downregulates Renal NHE3 Activity and NaPi‐2 Expression and Reduces Blood Pressure in Hypertensive Rats

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, also known as gliflozins, can lower blood pressure (BP) and reduce cardiovascular mortality in hypertensive patients with type 2 diabetes. However, the molecular mechanisms underlying the antihypertensive effects of the SGLT2 inhibitors have not been elucidated. This study tested the hypothesis that empagliflozin, an SGLT2 inhibitor, reduces BP of nondiabetic hypertensive rats and that this effect may be associated with altered expression and/or covalent modification of apical sodium transporters in the renal proximal tubule. To this end, spontaneously hypertensive rats (SHR) and normotensive Wistar rats (12-14 weeks of age) were treated for 2 weeks with empagliflozin 10 mg/kg/day or vehicle (water) orally. BP was measured non-invasively (tail-cuff plethysmography) and invasively (arterial catheterization). Proximal tubule Na+/H+ exchanger isoform 3 (NHE3) activity was assessed by in vivo stationary microperfusion. NHE3 phosphorylated at serine 552 (pNHE3-552), total NHE3 and Na+-dependent phosphate cotransporter type II (NaPi-2) expression in the renal cortex were evaluated by immunoblotting. We found that vehicle-treated SHR exhibited a small increase in BP (9±2 mmHg), whereas empagliflozin reduced BP of hypertensive rats (-10±2 mmHg). No changes in BP were observed in Wistar rats. The in vivo stationary microperfusion analyses showed that empagliflozin inhibited the activity of NHE3 in both hypertensive and normotensive rats. Inhibition of NHE3 activity by empagliflozin was not accompanied by differences in the levels of pNHE3-552 or total NHE3 expression in the renal cortex. On the other hand, NaPi-2 expression was upregulated in the renal cortex of vehicle-treated SHR (226±18 vs. 100±5% in vehicle-treated Wistar rats, p< 0.0001), and treatment with empagliflozin significantly reduced it (163±11 vs. 226±18%, p< 0.01). Renal cortical NaPi-2 abundance was not affected by empagliflozin in normotensive rats. These findings demonstrate empagliflozin lowers blood pressure in nondiabetic hypertensive rats. Moreover, it shows that SGLT2 inhibition may reduce proximal tubule sodium reabsorption via inhibition of NHE3 and downregulation of NaPi-2. Future studies are necessary to evaluate the impact of SGLT2 inhibitors in the distal nephron and its association with the antihypertensive effects of the gliflozins.

Therapeutic effects of losartan on prostatic hyperplasia in spontaneously hypertensive rats

AimsWe investigated the therapeutic effects of losartan, an angiotensin II type 1 receptor blocker, on prostatic hyperplasia in spontaneously hypertensive rats (SHRs). Main methodsMale SHRs (age, 36 weeks) were perorally treated with losartan (3 or 10 mg·kg−1) or vehicle once daily for 18 weeks. Age-matched Wistar Kyoto rats (WKYs) were used as vehicle-treated controls (n = 8). The effects of losartan were evaluated by analyzing prostate weight, blood pressure, and prostatic blood flow. The tissue malondialdehyde (MDA), interleukin-6 (IL-6), and basic fibroblast growth factor (bFGF) levels were measured. Histological analysis for the ventral prostate involved hematoxylin and eosin staining and TdT-mediated dUTP nick-end labeling (TUNEL) assay. Key findingsCompared to the vehicle-treated WKYs, the vehicle-treated SHRs had significantly higher prostate weight, prostate weight/body weight ratio (PBR), blood pressure, glandular epithelial area, and tissue MDA, IL-6, and bFGF levels in the ventral prostate and lower prostatic blood flow. Treatment with losartan caused significant recovery of blood flow and decreased PBR and glandular epithelial area as well as tissue MDA, IL-6, and bFGF levels in the SHR ventral prostate without affecting blood pressure. High-dose losartan significantly decreased blood pressure and increased TUNEL-positive cells in the ventral prostate in SHRs. SignificanceChronic losartan treatment could ameliorate prostatic hyperplasia via recovery of reduced prostatic blood flow and induction of apoptosis in the ventral prostate in SHRs. Losartan might have therapeutic effects on not only hypertension but also prostatic hyperplasia in humans.

Protective effects of tadalafil on prostatic hyperplasia in spontaneously hypertensive rats

We investigated the effects of the phosphodiesterase type 5 inhibitor, tadalafil on prostatic hyperplasia in a hypertensive rat model. Twelve-week-old male spontaneously hypertensive rats (SHRs) were orally treated with tadalafil (2 or 10 mg/kg/day) or vehicle for six weeks. Wistar Kyoto (WKY) rats treated with vehicle were used as controls. The effect of tadalafil was evaluated by measuring prostate weight, blood pressure, and prostatic blood flow. The presence of malondialdehyde (MDA), interleukin-6 (IL-6), transforming growth factor-beta1 (TGF-β1), and basic fibroblast growth factor (bFGF) in the ventral prostate were examined. Hematoxylin and eosin staining was performed to assess the morphological change. The prostatic contractility was evaluated by an organ bath experiment. The vehicle-treated SHRs demonstrated a significantly higher prostate weight, prostate weight/body weight ratio (PBR), blood pressure, and tissue levels of MDA, IL-6, TGF-β1, and bFGF, and lower prostatic blood flow compared to the vehicle-treated WKY rats. Moreover, the SHRs showed glandular morphological abnormalities in the ventral prostate compared to the WKY rats. There was no significant difference in potassium chloride or noradrenaline-induced prostatic contractility between the WKY rats and the SHRs. Treatment with tadalafil decreased prostate weight and PBR in a dose-dependent manner, and improved prostatic blood flow and tissue levels of MDA, IL-6, TGF-β1, and bFGF in SHRs, without affecting the blood pressure. Furthermore, tadalafil ameliorated the glandular morphological abnormalities in the SHR ventral prostate. In conclusion, tadalafil could suppress the prostatic hyperplasia via recovery of reduction in prostatic blood flow in SHRs.

Kefir ameliorates hypertension via gut–brain mechanisms in spontaneously hypertensive rats

Hypertension is associated with gut dysbiosis and dysregulation of the gut–brain axis. Previous work has shown that probiotic treatments exert beneficial cardiovascular effects in humans and animal models of hypertension. Coupled with the evidence of elevated sympathetic outflow and chronic inflammation in hypertension, we hypothesized that both peripherally and centrally mediated mechanisms underlie the antihypertensive effects of kefir, a probiotic obtained from the fermentation of milk by kefir grains. Eight-week-old spontaneously hypertensive rats (SHRs) were treated by oral gavage with either vehicle or kefir (0.3 ml/100 g/day; 9 weeks; SHR-Kefir), and age-matched with vehicle-treated Wistar Kyoto rats (WKY). Long-term kefir treatment attenuated mean arterial pressure elevations in SHR-Kefir relative to vehicle-treated SHRs. Peripherally, SHRs exhibited differences in the wall of the jejunum (fewer Paneth cells per crypt of Lieberkϋhn and increased tunica muscularis thickness) and higher serum lipopolysaccharide levels compared to WKY, alterations which were reversed in SHR-Kefir. Centrally, kefir treatment reduced IL-6 and TNF-α protein densities, and abolished the microglial activation observed in the hypothalamic paraventricular nucleus and rostral ventrolateral medulla of SHRs. Taken together, our findings indicate that the antihypertensive effects of long-term kefir treatment occur, at least in part, through improved structural and functional integrity of the intestinal wall and protection against neuroinflammation within cardioregulatory nuclei.

Chronic inhibition of chemokine receptor CXCR2 attenuates cardiac remodeling and dysfunction in spontaneously hypertensive rats

System hypertension is a major risk factor for cardiac hypertrophy and heart failure. Our recent findings reveal that the ablation or inhibition of C-X-C chemokine receptor (CXCR) 2 blocks this process in mice; however, it is not clear whether the pharmacological inhibition of CXCR2 attenuates hypertension and subsequent cardiac remodeling in spontaneously hypertensive rats (SHRs). In the present study, we showed that chemokines (CXCL1 and CXCL2) and CXCR2 were significantly upregulated in SHR hearts compared with Wistar–Kyoto rat (WKY) hearts. Moreover, the administration of CXCR2-specific inhibitor N-(2-hydroxy-4-nitrophenyl)-N′-(2-bromophenyl)-urea (SB225002) in SHRs (at 2 months of age) for an additional 4 months significantly suppressed the elevation of blood pressure, cardiac myocyte hypertrophy, fibrosis, inflammation, and superoxide production and improved heart dysfunction in SHRs compared with vehicle-treated SHRs. SB225002 treatment also reduced established hypertension, cardiac remodeling and contractile dysfunction. Moreover, CXCR2-mediated increases in the recruitment of Mac-2-positive macrophages, proinflammatory cytokines, vascular permeability and ROS production in SHR hearts were markedly attenuated by SB225002. Accordingly, the inhibition of CXCR2 by SB225002 deactivates multiple signaling pathways (AKT/mTOR, ERK1/2, STAT3, calcineurin A, TGF-β/Smad2/3, NF-κB-p65, and NOX). Our results provide new evidence that the chronic blocking of CXCR2 activation attenuates progression of cardiac hypertrophic remodeling and dysfunction in SHRs. These findings may be of value in understanding the benefits of CXCR2 inhibition for hypertensive cardiac hypertrophy and provide further support for the clinical application of CXCR2 inhibitors for the prevention and treatment of heart failure.

Berberine reduces endothelial injury and arterial stiffness in spontaneously hypertensive rats

ABSTRACTBackground: Changes in circulating endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs) are considered as a new perspective reflection of the endothelial injury and repair status. Our previous studies have demonstrated that berberine improved endothelial function and arterial stiffness in healthy subjects. In this study, we further investigated the effects of berberine on regulating the circulating EMPs and EPCs, and preventing endothelial dysfunction and arterial stiffness in spontaneously hypertensive rats (SHRs). Methods: Twenty male SHRs were randomly divided into two groups: Berberine-treated SHR group and vehicle-treated SHR group. The SHR rats were intragastrically treated with physiologic saline, berberine 50 mg/kg.d or vehicle for 4 weeks, respectively. Ten male Wistar-Kyoto (WKY) rats treated with vehicle served as normotensive controls. Tail systolic blood pressure was monitored every 2 weeks. At the end of the study, aortic pulse wave velocity (aPWV) was measured in vivo, and aorta were collected for measurement of endothelium-dependent vasodilation and immunohistological staining of elastic fiber. Peripheral blood was collected for circulating EMP detection and EPC culture. Results: Compared to normotensive rats, hypertensive rats displayed significantly higher circulating CD31+/CD42− MPs, lower number and colony-forming units (CFUs) of EPCs, worse endothelium-dependent vasodilation, and faster aPWV. Berberine treatment in SHRs partly reduced the blood pressure and circulating EMPs, and augmented EPC numbers and CFUs. In addition, berberine preserved arterial elasticity by lowering aPWV and increasing the content of arterial media elastin fiber, and improved endothelial function by maintaining better endothelium-dependent vasodilation. Robust relationship was observed among circulating CD31+/CD42− MPs, EPC numbers and aPWV. Conclusions: Abnormal changes of circulating EMPs and EPCs in SHRs are associated with endothelial dysfunction and arterial stiffness. Berberine may be a novel therapeutic option for the hypertension-related vascular injury in SHRs.

Validation of a preclinical model of heart failure with reduced ejection fraction by a dual angiotensin receptor-neprilysin inhibitor and an angiotensin-converting enzyme inhibitor

Heart failure (HF) patients often suffer from several co-existing diseases and co-morbidities. Among them, hypertension and myocardial infarction (MI) are two of the most frequent causes of HF1. Thus, as expected, experimental induction of MI in Spontaneously Hypertensive Rats (SHR) provokes severe left ventricular dysfunction and is associated with signs of HF2. Therapeutic effects of Angiotensin-converting enzyme inhibitor (ACEi) and Angiotensin receptor-neprilysin inhibitor (ARNi) have been demonstrated in HF patients with reduced ejection fraction (HFrEF). The aim of the present study was to validate the translational value of the HF preclinical model SHR PMI using ARNi (Valsartan/Sacubitril, LCZ696) and ACEi (perindopril) treatments recommended by the ESC guidelines for HFrEF patients. Permanent MI (PMI) was induced by coronary ligation in SHR (8-week-old; N = 30) randomized in three groups: –placebo, LCZ696 (68 mg/kg/d); –Perindopril (1 mg/kg/d); –compared to a sham operated group ( N = 10). Three months post-MI, LV function was assessed by echocardiography and hemodynamic study. HF signs were assessed by LV end-diastolic pressure (LVEDP, mmHg), lung and right ventricle (RV) weights (mg). Two vehicle-treated SHR PMI died during the follow-up, no death was observed in LCZ696 or Perindopril treated groups. Post-MI, both ARNi or ACEi treatments had beneficial effects on the adverse LV remodeling and seemed to prevent the mortality and signs of HF (further studies required to confirm these results). In summary, the SHR PMI model has a good predictive value and can be used as preclinical model for the evaluation of new therapeutic strategy in HFrEF [1] , [2] .

Chronic Treatment With Acetylcholinesterase Inhibitors Attenuates Vascular Dysfunction in Spontaneously Hypertensive Rats.

Acetylcholinesterase inhibition prevents autonomic imbalance, reduces inflammation, and attenuates the development of hypertension. Considering that vascular dysfunction is a crucial feature of arterial hypertension, we investigated the effects of chronic administration of acetylcholinesterase inhibitors-pyridostigmine or donepezil-on vascular reactivity of spontaneously hypertensive rats (SHR). Endothelium-dependent relaxant responses to acetylcholine (ACh) and contractile responses induced by electric field stimulation (EFS) and alpha-adrenergic agonist were studied in mesenteric resistance arteries from SHR and Wistar Kyoto rats. SHR were treated for 16 weeks with vehicle, pyridostigmine (1.5 mg/kg/day) or donepezil (1.4 mg/kg/day). Pyridostigmine and donepezil decreased the vasoconstrictor responses to EFS, which were increased in vehicle-treated SHR. Acetylcholinesterase inhibition increased the modulatory effects of nitric oxide (NO) on SHR vascular reactivity, that is, N(ω)-nitro-(L)-arginine methyl ester (L-NAME) increased EFS-induced contractions and reduced ACh-induced relaxation, with more significant effects in pyridostigmine- and donepezil-treated SHR. The acetylcholinesterase inhibitors also decreased vascular reactive oxygen species levels. This study demonstrates for the first time that long-term administration of acetylcholinesterase inhibitors, pyridostigmine or donepezil, attenuates vascular reactivity dysfunction in SHR by decreasing reactive oxygen species generation and increasing NO bioavailability; possibly via increased endothelial NO synthase activity, and inhibition of NADPH oxidase activity.

Treatment with low dose fasudil for acute ischemic stroke in chronic hypertension

We investigated the effect of Rho kinase inhibition on changes in cerebral blood flow (CBF), brain injury and vascular function after ischemic stroke in spontaneously hypertensive rats (SHR). Changes in core MCA and collateral perfusion were measured by a validated laser Doppler method. Animals underwent 2 h tMCAO and 2 h reperfusion. Fasudil (0.1 mg/kg, i.v.) or vehicle was given at 30 min ischemia (n = 9/group; mean (SD)). Brain injury was determined by 2,3,5-triphenyltetrazolium chloride staining. To determine the effect of fasudil on vascular function, fasudil was given 10 min before reperfusion and parenchymal arterioles studied isolated (n = 6/group; mean(SD)). Collateral perfusion was low in vehicle-treated SHR (−8(32)%) that changed minimally with fasudil (6(24)%, p > 0.05, effect size: 0.47;95% CI−0.49–1.39). Reperfusion CBF was below baseline in vehicle (−27(26)%) and fasudil (−32(25)%, p > 0.05, effect size: 0.19; 95% CI−0.74–1.11) groups, suggesting incomplete reperfusion in both groups. Fasudil had little effect on brain injury volume (28(13)% vs. 36(7)% in vehicle, p > 0.05, effect size: 0.75; 95% CI−0.24–1.66). In isolated parenchymal arterioles, myogenic tone was similar between groups (37(6)% vs. 38(10)% in vehicle, p > 0.05, effect size: 0.09; 95% CI−1.05–1.21). There were no differences with fasudil treatment vs. vehicle in perfusion, brain injury and vascular function that may be related to the low dose that had minimal blood pressure lowering effect.

Abstract 253: The Direct Renin Inhibitor Aliskiren Prevents Endothelial Dysfunction in Spontaneously Hypertensive Rat Aortas

Introduction: Hypertension is a significant medical problem. Aliskiren is a novel anti-hypertensive agent that inhibits renin directly. We tested the hypothesis that aliskiren prevents endothelial dysfunction in spontaneously hypertensive rats (SHRs). Methods: SHRs and age-matched Wistar Kyoto (WKY) rats were randomly divided and subjected to oral administration of aliskiren (10 mg/kg/day) or vehicle for 8 weeks. Blood pressure was monitored bi-weekly by a tail-cuff method. After an initial equilibration period, each ring was contracted by elevated KCl (60 mmol/L) to ensure a level of contractility suitable for subsequent experimentation. To examine endothelium-dependent relaxations in phenylephrine-contracted rings, two consecutive concentration-response curves to acetylcholine (ACh; 3 nmol/L -30 μmol/L) were constructed. In some phenylephrine-contracted rings without intact endothelium, sodium nitroprusside (SNP; 3 nmol/L – 10μmol/L) were applied cumulatively to the bathing solution to test the sensitivity of vascular smooth muscle cells (VSMCs) to NO. Results: Aliskiren reduced systolic blood pressure (SBP) to 155.6 ± 1.87 mmHg as compared to 165.3 ± 3.2 mmHg in vehicle-treated SHRs (n = 7), while chronic aliskiren administration did not affect SBP in WKY rats. SHR aortas with endothelium relaxed less in response to different concentrations of ACh than age-matched WKY rat aortas and ACh failed to cause relaxations of aortic rings without endothelium. By contrast, endothelium-independent relaxations caused by sodium nitroprusside (SNP) were comparable in aortas from SHR and WKY rats. Chronic aliskiren administration improved endothelium-dependent dilatations of aortas from SHRs compared to vehicle-treated SHRs, but this was unaffected in WKY rats. Endothelium-independent relaxations to SNP were not significantly different in aortas from the four treatment groups. Conclusions: Aliksiren reduces blood pressure and improves endothelium-dependent dilatations of SHRs. Figure 1. Effects of 8-week treatment of aliskiren on acetylcholine (ACh)-induced endothelium-dependent dilatations in SHR (A) and WKY (B) aortas. Results are mean ± SEM of 7 experiments. *p&lt;0.05.

Pharmacologically increasing collateral perfusion during acute stroke using a carboxyhemoglobin gas transfer agent (Sanguinate™) in spontaneously hypertensive rats

Similar to patients with chronic hypertension, spontaneously hypertensive rats (SHR) develop fast core progression during middle cerebral artery occlusion (MCAO) resulting in large final infarct volumes. We investigated the effect of Sanguinate™ (SG), a PEGylated carboxyhemoglobin (COHb) gas transfer agent, on changes in collateral and reperfusion cerebral blood flow and brain injury in SHR during 2 h of MCAO. SG (8 mL/kg) or vehicle (n = 6–8/group) was infused i.v. after 30 or 90 min of ischemia with 2 h reperfusion. Multi-site laser Doppler probes simultaneously measured changes in core MCA and collateral flow during ischemia and reperfusion using a validated method. Brain injury was measured using TTC. Animals were anesthetized with choral hydrate. Collateral flow changed little in vehicle-treated SHR during ischemia (−8 ± 9% vs. prior to infusion) whereas flow increased in SG-treated animals (29 ± 10%; p < 0.05). In addition, SG improved reperfusion regardless of time of treatment; however, brain injury was smaller only with early treatment in SHR vs. vehicle (28.8 ± 3.2% vs. 18.8 ± 2.3%; p < 0.05). Limited collateral flow in SHR during MCAO is consistent with small penumbra and large infarction. The ability to increase collateral flow in SHR with SG suggests that this compound may be useful as an adjunct to endovascular therapy and extend the time window for treatment.

Abstract 62: Sanguinate TM Opens Collaterals, Improves Reperfusion and Decreases Infarct in Hypertensive Rats

Background: The PEGylated cell-free carboxyhemoglobin gas exchanger Sanguinate TM (SG) has multiple beneficial actions that may improve stroke outcome including anti-inflammatory, vasodilatory and oxygen delivery capacity. We investigated the ability of SG to improve infarction in spontaneously hypertensive rats (SHR) that are known to have vasoconstricted pial collaterals and poor stroke outcome. Methods: SHR were treated IV with SG (8 ml/kg; n=8) or vehicle (Lactated Ringer’s; n=6) plus tPA (0.9 mg/ml) after 30 min of proximal middle cerebral artery occlusion (MCAO) by filament occlusion. Pial collateral and reperfusion flow were measured for 2 hrs of occlusion and 2 hrs reperfusion using dual laser Doppler probes in the core (Bregma -2mm, lateral +4mm) and collateral (Bregma +2mm, lateral +3mm) territories. Collateral openings (number and duration (min)) were assessed off cerebral blood flow (CBF) tracings, defined as independent of changes in blood pressure (Fig. 1; arrows show openings). Infarction was measured using triphenyltetrazolium chloride (TTC). Animals were anesthetized with chloral hydrate and ventilated to maintain blood gases within normal ranges. Results: Vehicle-treated SHR had incomplete reperfusion and poor collaterals that was improved by SG. During MCAO, SG increased the number of collateral openings from 1.0±0.8 to 3.1±0.8 (p=0.03) and duration of openings from 6.0±5.8 to 35.4±9.8 min (p=0.04; Fig. 2). Reperfusion CBF was -43±6% of baseline in vehicle-treated, but only -7±19% of baseline in SG-treated animals. Improved collateral and reperfusion flow with SG was associated with decreased infarct volume vs. vehicle (28.8±3.2% vs. 18.8±2.3%; p&lt;0.05). The presence of tPA had no effect in either group. Conclusions: Smaller infarction with early SG treatment may be related to its ability to open constricted collaterals in SHR and improve reperfusion. Thus, SG may be able to extend the time window for endovascular or tPA treatment.

Chronic treatment with epigallocatechin gallate reduces motor hyperactivity and affects in vitro tested intestinal motility of spontaneously hypertensive rats

BackgroundGreen tea catechins seem to contribute toward reducing body weight and fat.ObjectiveWe aimed to investigate whether chronic administration of (–)-epigallocatechin-3-gallate (EGCG), the most abundant catechin of green tea, reduces weight gain in spontaneously hypertensive rats (SHR), an animal model of metabolic syndrome, by increasing motor activity and/or by altering gastrointestinal motility.DesignNine-week-old SHR were randomly assigned to two groups and treated by gavage for 3 weeks with vehicle dimethyl sulfoxide or EGCG (200 mg/kg/day). Age-matched Wistar-Kyoto (WKY) control rats were treated with vehicle alone. The effect of chronic administration of EGCG was evaluated on open-field motor activity and on ex vivo colonic and duodenal motility. Moreover, in vitro acute effect of 20-min incubation with EGCG (100 µM) or vehicle was evaluated in colonic and duodenal specimens from untreated WKY rats and SHR.ResultsVehicle-treated SHR were normoglycemic and hyperinsulinemic, and showed a reduction of plasma adiponectin when compared to vehicle-treated WKY rats. In addition, consistent with fasting glucose and insulin values, vehicle-treated SHR were more insulin resistant than age-matched vehicle-treated WKY rats. Chronic treatment for 3 weeks with EGCG improved insulin sensitivity, raised plasma adiponectin levels, and reduced food intake and weight gain in SHR. Vehicle-treated SHR showed increased open-field motor activity (both crossings and rearings) when tested after each week of treatment. The overall hyperactivity of vehicle-treated SHR was significantly reduced to the levels of vehicle-treated WKY rats after 2 and 3 weeks of EGCG treatment. Colonic and duodenal preparations obtained from SHR chronically treated in vivo with EGCG showed reduced responses to carbachol (0.05–5 µM) and increased inhibitory response to electrical field stimulation (EFS, 1–10 Hz, 13 V, 1 msec, 10-sec train duration), respectively. In vitro acute EGCG incubation (100 µM, 20 min) of colonic and duodenum strips obtained from untreated SHR and WKY rats showed a reduced contractile colonic response to a fixed dose of carbachol (1.5 µM) only in SHR with respect to its own vehicle, whereas the inhibitory duodenal response to a fixed EFS frequency (5 Hz) was significantly reduced in both WKY rats and SHR groups with respect to their own vehicle.ConclusionsThese data suggest that EGCG affects body weight gain in rats and this effect seems to be due to the altered intestinal motility and not to increased motor activity.

Augmentation of autophagy by atorvastatin via Akt/mTOR pathway in spontaneously hypertensive rats.

Autophagy is activated in hypertension-induced cardiac hypertrophy. However, the mechanisms and significance of an activated autophagy are not clear. This study was designed to determine the role of atorvastatin (ATO) in cardiac autophagy and associated benefits on cardiac remodeling and left ventricular function in spontaneously hypertensive rats (SHRs). Twenty-eight male SHRs at 8 weeks of age were randomized to treatment with vehicle (saline solution; SHR+V) or ATO (SHR+ATO; 50 mg kg(-1) per day) for 6 or 12 months. Age-matched male Wistar-Kyoto (WKY) rats were used as normotensive controls. Cardiac magnetic resonance was used to evaluate cardiac function and structure. Compared with WKY rats, SHRs showed significant left ventricle (LV) dysfunction, remodeling and increases in cardiomyocyte size, which were all attenuated by 6 and 12 months of ATO treatment. Compared with WKY rats, autophagy was activated in the hearts of SHRs and this effect was amplified by chronic ATO treatment, particularly following 12 months of treatment. Protein expression levels of microtubule-associated protein-1 light chain 3-II and beclin-1, the biomarkers of an activated cardiac autophagy, were significantly elevated in ATO-treated versus vehicle-treated SHRs and control WKY rats. Cardiac Akt and phosphorylated mammalian target of rapamycin (mTOR) expression were also increased in the hearts of SHR versus WKY rats, and this effect was attenuated by ATO treatment. These findings suggest that ATO-mediated improvements in LV function and structure in SHRs may be, in part, through its regulation of cardiac autophagy via the Akt/mTOR pathway.

Resveratrol restored Nrf2 function, reduced renal inflammation, and mitigated hypertension in spontaneously hypertensive rats.

Compelling evidence supports the role of oxidative stress and renal interstitial inflammation in the pathogenesis of hypertension. Resveratrol is a polyphenolic stilbene, which can lower oxidative stress by activating the transcription factor nuclear factor-E2-related factor-2 (Nrf2), the master regulator of numerous genes encoding antioxidant and phase II-detoxifying enzymes and molecules. Given the role of oxidative stress and inflammation in the pathogenesis of hypertension, we conducted this study to test the hypothesis that long-term administration of resveratrol will attenuate renal inflammation and oxidative stress and, hence, progression of hypertension in the young spontaneously hypertensive rats (SHR). SHR and control [Wistar-Kyoto (WKY)] rats were treated for 9 wk with resveratrol or vehicle in their drinking water. Vehicle-treated SHR exhibited renal inflammatory injury and oxidative stress, as evidenced by glomerulosclerosis, tubulointerstitial injury, infiltration of inflammatory cells, and increased levels of renal 8-isoprostane and protein carbonylation. This was associated with reduced antioxidant capacity and downregulations of Nrf2 and phase II antioxidant enzyme glutathione-S-transferase (GST). Resveratrol treatment mitigated renal inflammation and injury, reduced oxidative stress, normalized antioxidant capacity, restored Nrf2 and GST activity, and attenuated the progression of hypertension in SHR. However, resveratrol had no effect on these parameters in WKY rats. In conclusion, development and progression of hypertension in the SHR are associated with inflammation, oxidative stress, and impaired Nrf2-GST activity in the kidney. Long-term administration of resveratrol restores Nrf2 expression, ameliorates inflammation, and attenuates development of hypertension in SHR. Clinical studies are needed to explore efficacy of resveratrol in human hypertension.