2K1C Rats Research Articles

Acute inhibition of nicotinamide adenine dinucleotide phosphate oxidase in the commissural nucleus of the solitary tract reduces arterial pressure and renal sympathetic nerve activity in renovascular hypertension.

A growing body of evidence suggests that oxidative stress plays a role in the pathophysiology of hypertension. However, the involvement of the reactive oxygen species (ROS) in the commissural nucleus of the solitary tract (commNTS) in development the of hypertension remains unclear. We evaluated the hemodynamic and sympathetic responses to acute inhibition of NADPH oxidase in the commNTS in renovascular hypertensive rats. Under anesthesia, male Holtzman rats were implanted with a silver clip around the left renal artery to induce 2-kidney 1-clip (2K1C) hypertension. After six weeks, these rats were anesthetized and instrumented for recording mean arterial pressure (MAP), renal blood flow (RBF), renal vascular resistance (RVR), and renal sympathetic nerve activity (RSNA) during baseline and after injection of apocynin (nicotinamide adenine dinucleotide phosphate oxidase inhibitor), NSC 23766 (RAC inhibitor) or saline into the commNTS. Apocynin into the commNTS decreased MAP, RSNA, and RVR in 2K1C rats. NSC 23766 into the commNTS decreased MAP and RSNA, without changing RVR in 2K1C rats. These results demonstrate that the formation of ROS in the commNTS is important to maintain sympathoexcitation and hypertension in 2K1C rats and suggest that NADPH oxidase in the commNTS could be a potential target for therapeutics in renovascular hypertension.

No benefit of HIF prolyl hydroxylase inhibition for hypertensive renal damage in renovascular hypertensive rats.

Introduction: We previously reported that malignant hypertension is associated with impaired capillary density of target organs. Here, we tested the hypothesis that stabilization of hypoxia-inducible factor (HIF) in a modified "preconditioning" approach prevents the development of malignant hypertension. To stabilize HIF, we employed pharmacological inhibition of HIF prolyl hydroxylases (PHD), that profoundly affect HIF metabolism. Methods: Two-kidney, one-clip renovascular hypertension (2K1C) was induced in rats; controls were sham operated. 2K1C rats received either intermittent injections of the PHD inhibitor ICA (2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetate) or placebo. Thirty-five days after clipping, the frequency of malignant hypertension was assessed (based on weight loss and the occurrence of characteristic vascular lesions). In addition, kidney injury was compared between all ICA treated versus all placebo treated 2K1C, regardless of the occurrence of malignant hypertension. HIF stabilization was evaluated by immunohistochemistry, and HIF target gene expression by RT-PCR. Results: Blood pressure was elevated to the same degree in ICA- and placebo-treated 2K1C compared to control rats. ICA treatment did not affect the frequency of malignant hypertension or the extent of kidney tissue fibrosis, inflammation, or capillary density. There was a trend towards higher mortality and worse kidney function in ICA-treated 2K1C rats. ICA increased the number of HIF-1α-positive renal tubular cell nuclei and induced several HIF-1 target genes. In contrast, expression of HIF-2α protein as well as HIF-2 target genes were markedly enhanced by 2K1C hypertension, irrespective of ICA treatment. Discussion: We conclude that intermittent PHD inhibition did not ameliorate severe renovascular hypertension in rats. We speculate that the unexpected strong renal accumulation of HIF-2α in renovascular hypertension, which could not be further augmented by ICA, may contribute to the lack of a benefit from PHD inhibition.

Comparative Analysis of Hypertensive Tubulopathy in Animal Models of Hypertension and Its Relevance to Human Pathology.

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats. Mouse models, SHR, and the nonclipped kidney in 2K1C rats had no regular signs of hypertensive tubulopathy. Histopathology in animals was mild and limited to variations in the volume density of tubular lumen and epithelium, interstitial space, and interstitial collagen. Affected kidneys in animals demonstrated lesion values that are significantly different compared with healthy controls but correspond to mild damage if compared with hypertensive humans. The most substantial human-like hypertensive tubulopathy was detected in the clipped kidney of 2K1C rats. For the first time, our study demonstrated the regular presence of chronic progressive nephropathy (CPN) in relatively young mice and rats with induced hypertension. Because CPN may confound the assessment of rodent models of hypertension, proliferative markers should be used to verify nonhypertensive tubulopathy.

Influence of Intestinal Barrier on Alleviating an Increase in Blood Pressure by Sodium Alginate Intake in 2-Kidney, 1-Clip Renovascular Hypertensive Rats.

Sodium alginate (SALG) is a substance derived from brown seaweed that has been shown to reduce blood pressure (BP). However, its effects on renovascular hypertension caused by 2-kidney, 1-clip (2K1C) are not yet clear. Previous research suggests that hypertensive rats have increased intestinal permeability, and that SALG improves the gut barrier in inflammatory bowel disease mouse models. Therefore, the goal of this study was to determine whether the antihypertensive effects of SALG involve the intestinal barrier in 2K1C rats. Rats were fed either a 1.0% SALG diet or a control diet for six weeks after being subjected to 2K1C surgery or a sham operation. The systolic BP was measured weekly, and the mean arterial BP was measured at the end of the study. Intestinal samples were taken for analysis, and plasma lipopolysaccharide (LPS) levels were measured. The results showed that BP in 2K1C rats was significantly higher than in SHAM rats when fed CTL, but not when fed SALG. The gut barrier in 2K1C rats was improved by SALG intake. Plasma LPS levels also differed depending on the animal model and diet. In conclusion, dietary SALG may alleviate 2K1C renovascular hypertension by altering the gut barrier.

Chronic administration of catalase inhibitor attenuates hypertension in renovascular hypertensive rats

AimsReactive oxygen species like hydrogen peroxide (H2O2) are produced endogenously and may participate in intra- and extracellular signaling, including modulation of angiotensin II responses. In the present study, we investigated the effects of chronic subcutaneous (sc) administration of the catalase inhibitor 3-amino-1,2,4-triazole (ATZ) on arterial pressure, autonomic modulation of arterial pressure, hypothalamic expression of AT1 receptors and neuroinflammatory markers and fluid balance in 2-kidney, 1clip (2K1C) renovascular hypertensive rats. Materials and methodsMale Holtzman rats with a clip occluding partially the left renal artery and chronic sc injections of ATZ were used. Key findingsSubcutaneous injections of ATZ (600 mg/kg of body weight/day) for 9 days in 2K1C rats reduced arterial pressure (137 ± 8, vs. saline: 182 ± 8 mmHg). ATZ also reduced the sympathetic modulation and enhanced the parasympathetic modulation of pulse interval, reducing the sympatho-vagal balance. Additionally, ATZ reduced mRNA expression for interleukins 6 and IL-1β, tumor necrosis factor-α, AT1 receptor (0.77 ± 0.06, vs. saline: 1.47 ± 0.26 fold change), NOX 2 (0.85 ± 0.13, vs. saline: 1.75 ± 0.15 fold change) and the marker of microglial activation, CD 11 (0.47 ± 0.07, vs. saline, 1.34 ± 0.15 fold change) in the hypothalamus of 2K1C rats. Daily water and food intake and renal excretion were only slightly modified by ATZ. SignificanceThe results suggest that the increase of endogenous H2O2 availability with chronic treatment with ATZ had an anti-hypertensive effect in 2K1C hypertensive rats. This effect depends on decreased activity of sympathetic pressor mechanisms and mRNA expression of AT1 receptors and neuroinflammatory markers possibly due to reduced angiotensin II action.

Integrated network pharmacology and molecular docking analyses of the mechanisms underlying the antihypertensive effects of lotusine

Hypertension is a modifiable cardiovascular risk factor and cause of death worldwide. Lotusine, an alkaloid extracted from a plant used in traditional Chinese Medicine, has shown anti-hypertensive effects. However, its therapeutic efficacy requires further investigation. We adopted integrated network pharmacology and molecular docking approaches with the aim of investigating lotusine's antihypertensive effects and mechanisms of action in rat models. After identifying the optimal intravenous dosage, we observed the effects of lotusine administration on two-kidney, one-clip (2K1C) rats and spontaneously hypertensive rats (SHRs). Based on network pharmacology and molecular docking analyses, we measured renal sympathetic nerve activity (RSNA) to evaluate lotusine's effect. Finally, an abdominal aortic coarctation (AAC) model was established to evaluate lotusine's long-term effects. The network pharmacology analysis identified 21 intersection targets; of these, 17 were also implicated by the neuroactive live receiver interaction. Further integrated analysis showed high lotusine affinity for the cholinergic receptor nicotinic alpha 2 subunit, adrenoceptor beta 2, and adrenoceptor alpha 1B. Blood pressure of the 2K1C rats and SHRs decreased after treatment with 2.0 and 4.0 mg/kg of lotusine (P < 0.001 versus saline control). We also observed RSNA decreases consistent with the network pharmacology and molecular docking analysis results. Results from the AAC rat model indicated that myocardial hypertrophy was decreased with lotusine administration, demonstrated by echocardiography and hematoxylin and eosin and Masson staining. This study provides insights into the antihypertensive effects and underlying mechanisms of lotusine; lotusine may exert long-term protective effects against myocardial hypertrophy caused by elevated blood pressure.

S-51-6: RENOVASCULAR HYPERTENSION AND BRAIN: ROLE OF THE RENIN-ANGIOTENSIN SYSTEM AND SODIUM

Renovascular hypertension is a type of secondary hypertension. Renovascular hypertensive 2-kidney, 1-clip (2K1C) rats have an increased activity of the renin-angiotensin system, and it is an experimental model to study renovascular hypertension. Renovascular hypertensive 2K1C rats have an imbalance of RAS components in the brain, an impairment of the baroreflex and they present an increase in daily intake of hypertonic NaCl solution. Therefore, we focused on studying: 1) the effects of overexpression of RAS components in the in the nucleus of the solitary tract (NTS), a brainstem area involved with cardiovascular control, 2) the brain mechanisms involved with the sodium appetite (operationally defined as an ingestion of hypertonic NaCl solution) in 2K1C rats. In adult Holtzman rats, the left renal artery was partially occluded by a silver clip with an opening of 0.2 mm to induce 2K1C. The experiments started after 6 weeks (hypertension plateau). We observed that increasing angiotensin type 2 receptor (AT2R) expression in the NTS attenuated the development of renovascular hypertension and also reversed the impairment of the baroreflex observed in 2K1C rats. Furthermore, an observed decrease in mRNA levels of angiotensin-converting enzyme 2 in the NTS of 2K1C rats was restored to control levels after viral-mediated increases in AT2R at this site. Virally mediated blockade of an intracellular pathway activated by angiotensin II (ANG II) acting in type 1 receptor (AT1R) in the NTS attenuated the development of renovascular hypertension and also reversed the impairment of the baroreflex. Daily 0.3 M NaCl intake transiently increased from the 2nd to the 5th week after 2K1C surgery. On the 6th week, in spite of comparable daily 0.3 M NaCl intake between 2K1C and sham rats, water deprivation (used to induce sodium appetite) produced a greater increase 0.3 M NaCl intake in 2K1C rats. Moreover, this intake is totally blocked by central AT1R and mineralocorticoid receptor antagonism. These data demonstrated that ANG II acting in the AT1R in the NTS is involved with the development of hypertension and baroreflex impairment in 2K1C and that AT2 overexpression at the same site can counteract these effects. In addition, the results demonstrated the participation of ANG II and aldosterone acting centrally in the enhanced sodium intake in water deprived 2K1C rats.

Crataeva nurvala Bark (Capparidaceae) Extract Modulates Oxidative Stress-Related Gene Expression, Restores Antioxidant Enzymes, and Prevents Oxidative Stress in the Kidney and Heart of 2K1C Rats.

Crataeva nurvala is a medicinal plant, which contains a wide range of polyphenolic and bioactive compounds. The aim of the study was to evaluate the renal-protective activity of Crataeva nurvala in two-kidney, one-clip (2K1C) rats. In this study, the ethanol extract of Crataeva nurvala bark at a dose of 100 mg/kg was orally used to treat 2K1C rats for four weeks. At the end of the experiment, all rats were sacrificed and tissue samples were collected for further biochemical and histological assessments. This investigation showed that Crataeva nurvala treatment prevented the kidney dysfunction in 2K1C rats. Uric acid and creatinine concentration and CK-MB activities increased in 2K1C rats which were normalized by Crataeva nurvala. 2K1C rats also showed increased oxidative stress, depicted by the elevated level of MDA, NO, and APOP in plasma and tissues. Oxidative stress parameters declined in 2K1C rats by the treatment of Crataeva nurvala. These results could be attributed to the restoration of antioxidant enzyme activities such as catalase and SOD. Crataeva nurvala extracts also upregulated antioxidant gene expression in the kidneys of 2K1C rats. Moreover, several anti-inflammatory genes were suppressed by Crataeva nurvala treatment in 2K1C rats. Furthermore, fibrosis and collagen deposition in the kidneys were also lowered by the treatment of the Crataeva nurvala extract. The experimental data suggest that the Crataeva nurvala extract protected renal damage and oxidative stress, probably by restoring antioxidant enzymes activities in 2K1C rats.

Dracocephalum moldavica L. Extract ameliorates intestinal inflammation by regulating gut microbiota and repairing the intestinal barrier in 2k1c rats

When used in ethnomedicine, Dracocephalum moldavica L. (DML) and its bioactive extract protect against several diseases caused by inflammation and oxidative stress. However, the effect of DML on intestinal inflammation in hypertension has not been thoroughly investigated. This study focused on the effects of DML extract on intestinal inflammation in two-kidney, one clip (2K1C) rats. Male Wistar rats were divided into three groups with daily intragastric administration of either saline (control group and model group) or DML extract (treatment group, 50 mg/kg per day) for 4 weeks. In the model and treatment groups, 2K1C hypertension was induced by clipping the left renal artery. The profiles of stool microbiota, the levels of short-chain fatty acids (SCFAs), the integrity of the gut barrier, oxidative stress biomarkers and inflammatory factors were analyzed in rats supplemented with or without DML extract. This study revealed the alleviation of high blood pressure in 2K1C rats treated with DML extract. The DML extract attenuated gut microbiota dysbiosis in the 2K1C rats by increasing the abundance of the genus Lactobacillus and by decreasing the abundance of Papillibacter, Desulfovibrio and Anaerobiospirillum genera. Treatment with the DML extract increased the levels of SCFAs and repaired the intestinal barrier, it reduced the release of oxidative stress biomarkers and inflammatory factors and suppressed the expression of TLR4 and NF-?B mRNAs. We conclude that the DML extract may alleviate intestinal inflammation by adjusting the profile of gut microbiota and enhancing the intestinal barrier.

PS-B10-8: BLOCKADE OF AT1 RECEPTORS RESTORE P2/P1 WITHOUT CHANGING INTRACRANIAL PRESSURE IN RENOVASCULAR HYPERTENSIVE RATS WITH 0.3 M NACL AD LIBITUM

Objective: Renovascular hypertension is characterized by activation of the renin angiotensin aldosterone system, elevated sympathetic nerve activity and sodium appetite behavior. The association of increased sodium intake and hypertension can worsen the injury to end organs. We tested the effects of AT1 receptors blockade (losartan, 10 mg/kg iv) on mean arterial pressure (MAP), intracranial pressure (ICP) and P2/P1 ratio (index of brain compliance) in 2K1C rats with 0.3 M NaCl ad libitum. Design and Methods: Male Holtzman rats (150 tp 180 g) with water and food ad libitum received a silver clip around the left renal artery to induce 2K1C or no clip (SHAM surgery) resulting 3 groups: SHAM (n = 9), 2K1C (n = 9) and 2K1C/Na (n = 7), which had an additional bottle of 0.3 M NaCl ad libitum. Six weeks after the renal surgery, MAP and ICP were recorded under urethane anesthesia (1.2 g/kg iv) and the P2/P1 was calculated offline from the waveform. Saline (0.2 ml/rat) was used as control injection before losartan. Results: In SHAM rats, ICP and P2/P1 were not changed by losartan (7.8 ± 1.1 and 0.88 ± 0.02; vs. saline: 7.9 ± 1.1 and 0.83 ± 0.01 mmHg, respectively), while MAP was decreased (104 ± 5, vs. saline: 120 ± 3 mmHg, p &lt; 0.05). In 2K1C, MAP, ICP and P2/P1 values were greater than SHAM (respectively, 196 ± 6, 14.7 ± 2.7 and 1.1 ± 0.03 mmHg, vs. SHAM; p &lt; 0.05) and all of them were decreased by losartan pre-treatment (137 ± 6, 8.6 ± 1.3 and 0.87 ± 0.05 mmHg, vs. saline, respectively). In 2K1C-Na MAP and P2/P1 were greater than in SHAM (186 ± 7 and 1.15 ± 0.06 mmHg, vs sham p &lt; 0.05) and were decreased by losartan (162 ± 8 and 0.87 ± 0.02 mmHg, vs. saline; p &lt; 0.05), although the decrease in MAP after losartan was lesser than the observed in 2K1C rats (p &lt; 0.05). In 2K1C-Na rats, ICP was not different from SHAM (10.8 ± 1.2, vs. SHAM: 7.8 ± 1.1 mmHg, p &gt; 0.05) and losartan had no effect on ICP (10.3 ± 1.7, vs. saline: 10.8 ± 1.2 mmHg, p &gt; 0.05). Conclusion: Even without a change in ICP, AT1 blockade in 2K1C-Na was effective in restoring P2/P1 ratio, suggesting a beneficial effect on brain compliance in this situation.

S-44-2: ANTIHYPERTENSIVE EFFECT OF GALANGIN IN RENAL ARTERY STENOSIS-INDUCED HYPERTENSIVE RATS

Background: Galangin is a natural flavonoid found in honey and Alpinia officinarum. Several reports have suggested the anti-mutagenic, antioxidant, anti-proliferative, and apoptotic effects. However, the antihypertensive effect of galangin in renovascular hypertension has not been investigated. Aims: This study aims to investigate the effect of galangin on blood pressure and cardiac changes in renovascular hypertension. Methods: Male Sprague Dawley rats (180–220 g) were induced hypertension by clipping the left renal artery, 2-kidney-1-clip (2K-1C). After 3 weeks of the induction period, galangin (30 and 60 mg/kg) and losartan (10 mg/kg) were given to the rats for 4 weeks (n = 8/group). Blood pressure and cardiac function were evaluated at the end of the experimental day. The level of angiotensin-converting enzyme (ACE) activity, angiotensin II, and oxidative stress markers were assessed in the plasma and cardiac tissue of rats. The protein expression of angiotensin II receptor type 1 (AT1R), transforming growth factor-beta 1 (TGF- β 1) and collagen type I (Col I) were determined in cardiac tissue. Statistical analysis was carried out by one-way ANOVA followed by Tukey post hoc test. A p value less than 0.05 was considered statistically significant. Results: Hypertension and cardiac dysfunction and hypertrophy were observed in 2K-1C rats compared to the sham-operated rats (p &lt; 0.05). Treatment with galangin (30 and 60 mg/kg) decreased high blood pressure and improved cardiac function as well as alleviated left ventricular hypertrophy in 2K-1C hypertensive rats (p &lt; 0.05). This result was related with the reduction of systemic ACE activity and angiotensin II levels in 2K-1C hypertensive rats that were treated with galangin (p &lt; 0.05). Moreover, the expression of AT1R, TGF- β 1 and Col I in cardiac tissue was modulated by treatment with galangin (p &lt; 0.05). Additionally, galangin showed anti-oxidative effects as it reduced the production of superoxide and malondialdehyde levels in cardiac tissue of rats (p &lt; 0.05). Conclusion: Galangin exhibited an antihypertensive effect and alleviated cardiac alteration in renovascular hypertensive rats. The underlying mechanism might be related to its inhibitory effects on renin-angiotensin system and anti-oxidative properties renal artery stenosis-induced hypertensive rats. Furthermore, the beneficial effect of galangin on heart might mediate the suppression of AT1R, TGF- β 1 and Col I pathway.

Quercetin decreases cardiac hypertrophic mediators and maladaptive coronary arterial remodeling in renovascular hypertensive rats without improving cardiac function.

Oxidative stress and MMP activity are found in the hearts and arteries in hypertension and contribute to the resulting hypertrophy and dysfunction. Quercetin is a flavonoid that reduces MMP-2 activity and ameliorates hypertrophic vascular remodeling of hypertension. The hypothesis is that treatment of hypertensive rats with quercetin ameliorates coronary maladaptive remodeling and decreases hypertrophic cardiac dysfunction by decreasing oxidative stress and MMP activity. Male Sprague-Dawley two-kidney, one-clip (2K1C) and Sham rats were treated with quercetin (10mg/kg/day) or its vehicle for 8weeks by gavage. Rats were analyzed at 10weeks of hypertension. Systolic blood pressure (SBP) was examined by tail-cuff plethysmography. Cardiac left ventricles were used to determine MMP activity by in situ zymography and oxidative stress by dihydroethidium. Immunofluorescence was performed to detect transforming growth factor (TGF)-β and nuclear factor kappa B (NFkB). Morphological analyses of heart and coronary arteries were done by H&E and picrosirius red, and cardiac function was measured by Langendorff. SBP was increased in 2K1C rats, and quercetin did not reduce it. However, quercetin decreased both oxidative stress and TGF-β in the left ventricles of 2K1C rats. Quercetin also decreased the accentuated MMP activity in left ventricles and coronary arteries of 2K1C rats. Quercetin ameliorated hypertension-induced coronary arterial hypertrophic remodeling, although it did not reduce cardiac hypertrophic remodeling and dysfunction. Quercetin decreases cardiac oxidative stress and TGF-β and MMP activity in addition to improving coronary remodeling, yet does not ameliorate cardiac dysfunction in 2K1C rats.

Effects of intrarenal angiotensin 1-7 infusion on renal haemodynamic and excretory function in anaesthetised two-kidney one-clip and deoxycorticosterone acetate-salt hypertensive rats.

What is the central question of this study? Are renal functional responses to intrarenal angiotensin 1-7 (Ang (1-7)) infusion dependent on the level of the endogenous renin-angiotensin system (RAS) in the two-kidney one-clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt animal models of hypertension? What is the main finding and its importance? The renal actions of Ang (1-7) are dependent on the relative endogenous levels of each arm of the classical angiotensin II-angiotensin II type 1 receptor (AT1 R) axis and those of the Ang (1-7)-Mas receptor axis. These findings support the hypothesis that a balance exists between the intrarenal classical and novel arms of the RAS, and in particular the relative abundance of AT1 R to Mas receptor, which may to a large extent determine the renal excretory response to Ang (1-7) infusion. This study investigated the action of angiotensin 1-7 (Ang (1-7)) on renal haemodynamic and excretory function in the two-kidney one-clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt rat models of hypertension, in which the endogenous renin-angiotensin system (RAS) activity was likely to be raised or lowered, respectively. Rats were anaesthetised and prepared for the measurement of mean arterial pressure and kidney function during renal interstitial infusion of Ang (1-7) or saline. Kidney tissue concentrations of angiotensin II (Ang II) and Ang (1-7) were determined. Intrarenal infusion of Ang (1-7) into the clipped kidney of 2K1C rats increased urine flow (UV), absolute (UNa V) and fractional sodium (FENa ) excretions by 110%, 214% and 147%, respectively. Renal Ang II concentrations of the clipped kidney were increased with no major changes in Ang (1-7) concentration. By contrast, Ang (1-7) infusion decreased UV, UNa V, and FENa by 27%, 24% and 21%, respectively in the non-clipped kidney in which tissue Ang (1-7) concentrations were increased, but renal Ang II concentrations were unchanged compared to sham animals. Ang (1-7) infusion in DOCA-salt rats had minimal effects on glomerular filtration rate but significantly decreased UV, UNa V and FENa by ∼30%. Renal Ang (1-7) concentrations were higher and Ang II concentrations were lower in DOCA-salt rats compared to sham rats. These findings demonstrate that the intrarenal infusion of exogenous Ang (1-7) elicits different renal excretory responses the magnitude of which is dependent on the balance between the endogenous renal Ang II-AT1 receptor axis and Ang (1-7)-Mas receptor axis.

Differential effects of estrogen receptors in the rostral ventrolateral medulla in Goldblatt hypertension

Previous studies have shown that 17β-estradiol plays a cardioprotective role in the central nervous system (CNS) of male rats. The aim of the present study was to determine the influence of 17β-estradiol on sympathetic vasomotor activity and blood pressure in a renovascular hypertensive Goldblatt two-kidney one-clip (2K-1C) male rat model. We also determined the influence of angiotensin II AT1 receptor on the expression of estrogen receptors (ERα, ERβ, and G protein-coupled ER (GPER)) in the rostral ventrolateral medulla (RVLM) of Goldblatt rats. Experiments were performed in Goldblatt and age-matched control rats six weeks after clipping of renal artery to induce hypertension. Microinjection of 17β-estradiol into the RVLM led to a greater reduction in mean arterial pressure and renal sympathetic nerve activity in controls than in 2K-1C rats. Microinjection of the GPER agonist G-1 into the RVLM led to a significantly greater increase in mean arterial pressure and renal sympathetic nerve activity in 2K-1C rats. Expression levels of estrogen receptors GPER and ERα, but not ERβ, were significantly higher in the RVLM of 2K-1C rats than in that of the control rats. Chronic treatment with losartan significantly reduced the expression levels of estrogen receptors in the RVLM of 2K-1C rats. Taken altogether, the data suggest that the imbalance of actions between ERα and GPER, particularly with the predominance of GPER in the RVLM, contributes to sympathetic overactivation in male rats with Goldblatt hypertension. AT1-Angiotensin II receptor in the RVLM upregulated estrogen receptor expression in male Goldblatt rats.

Abstract 075: The Kidney-OVLT Neuroaxis Mediates Neurogenic Hypertension And Polydipsia In 2-Kidney, 1-Clip Rats

Renal afferent nerves mediate activation of the sympathetic nervous system and hypertension in rats with unilateral renal artery stenosis (2K1C-HTN). However, the central neural structures that mediate this response are unclear. The organum vasculosum of the lamina terminalis (OVLT), has also been implicated in the regulation of mean arterial pressure (MAP) and sympathetic activity in preclinical models of hypertension. We tested the hypothesis that afferent renal nerves and the OVLT share a common neural pathway required for the development of 2K1C-HTN. Two experiments were conducted. 1: Male rats (n=5-9) were implanted with telemeters to measure MAP. 1-week later they received a clip on the left renal artery and were subjected to afferent renal denervation (ARDN) by periaxonal capsaicin (2K1C-ARDN) or sham (2K1C-sham) treatment of the clipped kidney. 2: Male rats (n=6-8) were subjected to lesioning of the OVLT (OVLTx) or sham operation. 1-week later telemeters were implanted and 7 days later the left renal artery was stenosed by application of a silver clip. In both experiments, MAP was measured continuously for 6 weeks, and water intake (WI) was measured once a week. Neurogenic pressor activity (NPA) was assessed by measuring the peak MAP response to ganglionic blockade. EXPT 1 Results: At the end of the protocol, MAP was 165±5 mmHg in 2K1C-sham compared to 131±10mmHg in 2K-1C-ARDN rats (p&lt;0.001). WI increased in 2K1C-sham rats peaking at 110±13 ml/day at week 2. In contrast, WI was markedly reduced in 2K1C-ARDN rats at this same time point (41±3 ml/day). NPA was increased in 2K1C-sham (-50 ± 4 mmHg) but was reduced in 2K1C-ARDN (-25 ± 3 mmHg) rats (p&lt;0.05). EXPT 2 Results: At end of the protocol MAP was 162±6 mmHg in sham-2K1C rats compared to 135±8 mmHg in OVLTx-2K1C rats (p&lt;0.001). WI peaked at 74±9 ml/day in sham lesion-2K1C compared to 52±9 ml/day in OVLTx-2K1C rats at week 2 (p&lt;0.05). NPA was increased in sham-2K1C rats (-51 ± 3 mmHg) but was reduced in OVLTx-2K1C rats (-31 ± 4 mmHg) (p&lt;0.05). Since both ARDN and OVLTx attenuated MAP, WI, and NPA similarly in 2K1C rats, we hypothesize that afferent renal nerves and the OVLT are linked in a common neural pathway required for the development of hypertension following renal artery stenosis.

Cardiorenal dysfunction and hypertrophy induced by renal artery occlusion are normalized by galangin treatment in rats.

Galangin is a polyphenolic compound found in Alpinia officinarum and propolis. This study investigated the effect of galangin on blood pressure, the renin angiotensin system (RAS), cardiac and kidney alterations and oxidative stress in two-kidney one-clipped (2K-1C) hypertensive rats. Hypertension was induced in male Sprague Dawley rats (180-220g), and the rats were given galangin (30 and 60mg/kg) and losartan (10mg/kg) for 4 weeks (n=8/group). Galangin decreased hypertension and cardiac dysfunction and hypertrophy, which was related to the reducing circulation angiotensin converting enzyme (ACE) activity and angiotensin II concentration (p<0.05). These effects were consistent with the reduced overexpression of angiotensin II receptor type 1 (AT1R), transforming growth factor beta 1 (TGF-β1) and collagen type I (Col I) protein in cardiac tissue (p<0.05). Additionally, renal artery occlusion, procedure-induced kidney dysfunction and fibrosis were attenuated in the galangin-treated group. Galangin treatment normalized the overexpression of AT1R and NADPH oxidase 4 (Nox-4) protein and normalized the downregulation of nuclear factor-erythroid Factor 2-related Factor 2 (Nrf-2) and haem oxygenase 1 (HO-1) in 2K-1C rats (p<0.05). Galangin exhibited antioxidative effects, as it reduced systemic and tissue oxidative stress markers and increased catalase activity in 2K-1C rats (p<0.05). In conclusion, galangin attenuated hypertension, renin-angiotensin system activation, cardiorenal damage and oxidative stress induced by renal artery stenosis in rats. These effects might be associated with modulation of the expression of AT1R, TGF-β1 and Col I protein in the heart as well as AT1R/Nox-4 and Nrf-2/HO-1 protein in renal tissue in hypertensive rats.

Wnt/β-catenin signaling in the adrenal glands of rats in various types of experimental hypertension.

Wnt/β-catenin signaling plays a key role in maintaining homeostasis, which is disturbed in hypertension. Taking into account the lack of literature describing changes in the Wnt/β-catenin pathway in the adrenal glands under conditions of elevated arterial pressure, here we compare the expression of WNT4, WNT10A, β-catenin, and GSK-3β in the adrenal glands of hypertensive rats of various etiologies. The studies were carried out on the adrenal glands of rats with spontaneous hypertension (SHR), renalvascular (2K1C), and deoxycorticosterone acetate (DOCA)-salt. Immunohistochemical and PCR methods were used to identify the molecular components of the canonical signaling pathway and to evaluate gene expression. Immunoreactivity and expression of WNT4, WNT10A, β-catenin, and GSK-3β in adrenals of SHR was decreased, compared to control rats. In adrenals of 2K1C rats, intensity of immunohistochemical reaction and expression of WNT4 and β-catenin was lower, while immunoreactivity and expression of WNT10A and GSK-3β were higher, compared to normotensive animals. Significantly stronger immunoreaction and expression of WNT4, β-catenin and GSK-3β but weaker immunoreactivity and expression of WNT10A were noted in adrenals in DOCA-salt rats, compared to control rats. In conclusion, our data provide new molecular information indicating that the canonical WNT pathway is disrupted in the adrenal glands of hypertensive rats. They show that the dysregulation of the WNT pathway depends on the etiology of hypertension.

Nobiletin resolves left ventricular and renal changes in 2K-1C hypertensive rats

This study investigated the effects of nobiletin on cardiorenal changes and the underlying mechanisms involved in two-kidney, one-clip (2K-1C) hypertension. 2K-1C rats were treated with nobiletin (15 or 30 mg/kg/day) or losartan (10 mg/kg/day) for 4 weeks (n = 8/group). Nobiletin (30 mg/kg) reduced high levels of blood pressure and circulating angiotensin II and angiotensin-converting enzyme activity in 2K-1C rats. Left ventricular (LV) dysfunction and remodelling in 2K-1C rats were alleviated in the nobiletin-treated group (P < 0.05). Nobiletin reduced the upregulation of Ang II type I receptor (AT1R)/JAK (Janus kinase)/STAT (signal transducer and activator of transcription) protein expression in cardiac tissue of 2K-1C rats (P < 0.05). The reduction in kidney function, and accumulation of renal fibrosis in 2K-1C rats were alleviated by nobiletin (P < 0.05). Overexpression of AT1R and NADPH oxidase 4 (Nox4) protein in nonclipped kidney tissue was suppressed in the nobiletin-treated group (P < 0.05). The elevations in oxidative stress parameters and the reductions in antioxidant enzymes were attenuated in 2K-1C rats treated with nobiletin (P < 0.05). In summary, nobiletin had renin-angiotensin system inhibitory and antioxidant effects and attenuated LV dysfunction and remodelling via restoration of the AT1R/JAK/STAT pathway. Nobiletin also resolved renal damage that was related to modulation of the AT1R/Nox4 cascade in 2K-1C hypertension.

Oral Administration of Garcinia dulcis Flower Extract Lowers Arterial Blood Pressure of 2-kidneys-1-clip Renovascular Hypertensive Rat

The hexane insoluble fraction of the Garcinia dulcis (GD) flower extract comprises mainly camboginol and morelloflavone which possess potent in vivo and in vitro antioxidant properties. This study aimed to evaluate the effects of 4-week oral administration of GD flower extract on the arterial blood pressure (ABP) and the excretory function of the kidney in the 2-kidneys-1-clip (2K1C) renovascular hypertensive rats (total=12) compared to sham operated (SO) normotensive Wistar rats (total=12). Four weeks after hypertensive-induced surgery, either 50 mg/kg BW GD flower extract or vehicle was orally administered to the 2K1C or SO groups (n=6/group) daily for four weeks. ABP and the renal excretory function were studied in anesthetized rats, and expression of endothelial nitric oxide synthase (eNOS) mRNA in the isolated thoracic aorta were measured. In the 2K1C rats, GD flower extract significantly decreased ABP while increased significantly eNOS mRNA levels. GD flower extract did not exert a diuretic effect in either SO and 2K1C rats since there was no change in observed urine excretion, but it did tend to attenuated the renal tubular damage caused by renovascular hypertension. GD flower extract was anti-hypertensive in this model of renovascular hypertension and problably acts via the endothelial nitric oxide signaling pathway.

Borneol reduces sympathetic vasomotor hyperactivity and restores depressed baroreflex sensitivity in rats with renovascular hypertension.

Borneol is a bicyclic monoterpene that has long been used in traditional Chinese medicine to increase blood-brain barrier permeability and has shown promising cardiovascular effects. The present study aimed to evaluate the effect of borneol on vascular tone, blood pressure, autonomic function, and baroreflex sensitivity in normotensive and hypertensive rats. A combination of in vitro and in vivo assays was performed in 2-kidneys-1-clip hypertensive rats (2K1C) and their controls (sham). We assessed the in vivo effect of oral treatment with borneol on blood pressure, heart rate, autonomic function, and baroreflex sensitivity in sham and 2K1C rats. Additionally, the vasorelaxant effect of borneol in the superior mesenteric artery isolated from rats and its mechanism of action were evaluated. Oral administration of borneol (125 mg/kg/day) reduced blood pressure, sympathetic vasomotor hyperactivity, and serum oxidative stress and improved baroreflex sensitivity in 2K1C rats. In vessel preparations, borneol induced endothelium-independent vasodilatation after precontraction with phenylephrine or KCl (60 mM). There was no difference in the vascular effect induced by borneol in either the 2K1C or the sham group. In addition, borneol antagonized the contractions induced by CaCl2 and reversed (S)-(-)-Bay K 8644-induced contraction. These data suggest that borneol presents antihypertensive effects in 2K1C rats, which is associated with its ability to improve autonomic impairment and baroreflex dysfunction. The borneol-induced relaxation in the superior mesenteric artery involves L-type Ca2+ channel blockade. This vascular action associated with the antioxidant effect induced by borneol may be responsible, at least in part, for the in vivo effects induced by this monoterpene.