Normotensive Animals Research Articles

Evaluation of the Canonical Wnt Signaling Pathway in the Hearts of Hypertensive Rats of Various Etiologies.

Wnt/β-catenin signaling dysregulation is associated with the pathogenesis of many human diseases, including hypertension and heart disease. The aim of this study was to immunohistochemically evaluate and compare the expression of the Fzd8, WNT1, GSK-3β, and β-catenin genes in the hearts of rats with spontaneous hypertension (SHRs) and deoxycorticosterone acetate (DOCA)-salt-induced hypertension. The myocardial expression of Fzd8, WNT1, GSK-3β, and β-catenin was detected by immunohistochemistry, and the gene expression was assessed with a real-time PCR method. In SHRs, the immunoreactivity of Fzd8, WNT1, GSK-3β, and β-catenin was attenuated in comparison to that in normotensive animals. In DOCA-salt-induced hypertension, the immunoreactivity of Fzd8, WNT1, GSK-3β, and β-catenin was enhanced. In SHRs, decreases in the expression of the genes encoding Fzd8, WNT1, GSK-3β, and β-catenin were observed compared to the control group. Increased expression of the genes encoding Fzd8, WNT1, GSK-3β, and β-catenin was demonstrated in the hearts of rats with DOCA-salt-induced hypertension. Wnt signaling may play an essential role in the pathogenesis of arterial hypertension and the accompanying heart damage. The obtained results may constitute the basis for further research aimed at better understanding the role of the Wnt/β-catenin pathway in the functioning of the heart.

Proteomic profiling of renal tissue of normo- and hypertensive rats with the renalase peptide RP220 as an affinity ligand.

Renalase (RNLS) is a recently discovered protein that plays an important role in the regulation of blood pressure by acting inside and outside cells. Intracellular RNLS is a FAD-dependent oxidoreductase that oxidizes isomeric forms of β-NAD(P)H. Extracellular renalase lacking its N-terminal peptide and cofactor FAD exerts various protective effects via non-catalytic mechanisms. Certain experimental evidence exists in the literature that the RP220 peptide (a 20-mer peptide corresponding to the amino acid sequence RNLS 220-239) reproduces a number of non-catalytic effects of this protein, acting on receptor proteins of the plasma membrane. The possibility of interaction of this peptide with intracellular proteins has not been studied. Taking into consideration the known role of RNLS as a possible antihypertensive factor, the aim of this study was to perform proteomic profiling of the kidneys of normotensive and hypertensive rats using RP220 as an affinity ligand. Proteomic (semi-quantitative) identification revealed changes in the relative content of about 200 individual proteins in the kidneys of hypertensive rats bound to the affinity sorbent as compared to the kidneys of normotensive animals. Increased binding of SHR renal proteins to RP220 over the normotensive control was found for proteins involved in the development of cardiovascular pathology. Decreased binding of the kidney proteins from hypertensive animals to RP220 was noted for components of the ubiquitin-proteasome system, ribosomes, and cytoskeleton.

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

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

A digoxin derivative that potently reduces intraocular pressure: efficacy and mechanism of action in different animal models.

Glaucoma is a blinding disease. Reduction of intraocular pressure (IOP) is the mainstay of treatment, but current drugs show side effects or become progressively ineffective, highlighting the need for novel compounds. We have synthesized a family of perhydro-1,4-oxazepine derivatives of digoxin, the selective inhibitor of Na,K-ATPase. The cyclobutyl derivative (DcB) displays strong selectivity for the human α2 isoform and potently reduces IOP in rabbits. These observations appeared consistent with a hypothesis that in ciliary epithelium DcB inhibits the α2 isoform of Na,K-ATPase, which is expressed strongly in nonpigmented cells, reducing aqueous humor (AH) inflow. This paper extends assessment of efficacy and mechanism of action of DcB using an ocular hypertensive nonhuman primate model (OHT-NHP) (Macaca fascicularis). In OHT-NHP, DcB potently lowers IOP, in both acute (24 h) and extended (7-10 days) settings, accompanied by increased aqueous humor flow rate (AFR). By contrast, ocular normotensive animals (ONT-NHP) are poorly responsive to DcB, if at all. The mechanism of action of DcB has been analyzed using isolated porcine ciliary epithelium and perfused enucleated eyes to study AH inflow and AH outflow facility, respectively. 1) DcB significantly stimulates AH inflow although prior addition of 8-Br-cAMP, which raises AH inflow, precludes additional effects of DcB. 2) DcB significantly increases AH outflow facility via the trabecular meshwork (TM). Taken together, the data indicate that the original hypothesis on the mechanism of action must be revised. In the OHT-NHP, and presumably other species, DcB lowers IOP by increasing AH outflow facility rather than by decreasing AH inflow.NEW & NOTEWORTHY When applied topically, a cyclobutyl derivative of digoxin (DcB) potently reduces intraocular pressure in an ocular hypertensive nonhuman primate model (Macaca fascicularis), associated with increased aqueous humor (AH) flow rate (AFR). The mechanism of action of DcB involves increased AH outflow facility as detected in enucleated perfused porcine eyes and, in parallel, increased (AH) inflow as detected in isolated porcine ciliary epithelium. DcB might have potential as a drug for the treatment of open-angle human glaucoma.

Endothelial cell Orai1 is essential for endothelium-dependent contraction of mouse carotid arteries in normotensive and hypertensive mice.

Endothelium-dependent contraction (EDC) exists in blood vessels of normotensive animals, but is exaggerated in hypertension. An early signal in EDC is cytosolic Ca2+ rise in endothelial cells. In this study we investigated the functional role of Orai1, a major endothelial cell Ca2+ entry channel, in EDC. Hypertension model was established in WT mice by intake of L-NNA in the drinking water (0.5 g/L) for 4 weeks or osmotic pump delivery of Ang II (1.5 mg·kg-1·d-1) for 2 weeks. In TRPC5 KO mice, the concentration of L-NNA and Ang II were increased to 1 g/L or 2 mg·kg-1·d-1, respectively. Arterial segments were prepared from carotid arteries and aortas, andEDC was elicited by acetylcholine in the presence of Nω-nitro-L-arginine methyl ester. We showed that low concentration of acetylcholine (3-30 nM) initiated relaxation in phenylephrine-precontracted carotid arteries of both normotensive and hypertensive mice, while high concentration of acetylcholine (0.1-2 μM) induced contraction. Application of selective Orai1 inhibitors AnCoA4 (100 μM) or YM58483 (400 nM) had no effect on ACh-induced relaxation but markedly reduced acetylcholine-induced EDC. We found that EDC was increased in hypertensive mice compared with that of normotensive mice, which was associated with increased Orai1 expression in endothelial cells of hypertensive mice. Compared to TRPC5 and TRPV4, which were also involved in EDC, endothelial cell Orai1 had relatively greater contribution to EDC than either TRPC5 or TRPV4 alone. We identified COX-2, followed by PGF2α, PGD2 and PGE2 as the downstream signals of Orai1/TRPC5/TRPV4. In conclusion, Orai1 coordinates together with TRPC5 and TRPV4 in endothelial cells to regulate EDC responses. This study demonstrates a novel function of Orai1 in EDC in both normotensive and hypertensive mice, thus providing a general scheme about the control of EDC by Ca2+-permeable channels.

The Dual Cardiovascular Effect of Centrally Administered Clonidine: A Comparative Study between Pentobarbital- and Ketamine/Xylazine-Anesthetized Rats

The administration of the α2-adrenergic receptor agonist clonidine via intracerebroventricular route produces hypotension in pentobarbital-anesthetized rats and pressor responses in conscious normotensive rats. We explored the impact of different anesthetics on the central nervous system-dependent cardiovascular effects of clonidine. Normotensive male Wistar rats with guide cannulas previously implanted in the cerebroventricular system were anesthetized with pentobarbital or ketamine/xylazine and prepared for blood pressure measurement. The animals received intracerebroventricular injections of 10 μg clonidine or 0.6 μg dexmedetomidine, and the effects on the systolic, diastolic, mean arterial pressure, and heart rate were evaluated. The influence of 5 μg yohimbine, a selective α2-adrenergic receptor antagonist, was also assessed. The i.c.v. microinjection of clonidine decreased all three components of systemic arterial pressure and the heart rate of pentobarbital-anesthetized rats. On the other hand, clonidine increased the blood pressure and generated a less intense reduction in the heart rate of ketamine/xylazine-anesthetized rats. The pressor and bradycardic effects of clonidine in ketamine/xylazine-anesthetized animals were reproduced by dexmedetomidine, a more selective α2-adrenergic receptor agonist. Notably, the previous intracerebroventricular injection of yohimbine significantly inhibited the hypertensive effect of clonidine and dexmedetomidine. This study discloses that while normotensive rats anesthetized with pentobarbital show hypotensive responses, the stimulation of α2-adrenergic receptors increases the blood pressure in rats under ketamine/xylazine-induced anesthesia, reproducing the effects seen in conscious normotensive animals. Recognizing the mechanisms involved in these differences may allow us to understand better the final effects of clonidine and other α2-adrenergic receptor agonists in the central nervous system, contributing to the repurposing of these drugs.

Comparative proteomic analysis of renal tissue of normotensive and hypertensive rats.

Comparative proteomic analysis of kidney tissue from normotensive (WKY) and spontaneously hypertensive (SHR) rats revealed quantitative and qualitative changes in renal proteins. The number of renal proteins specific for WKY rats (blood pressure 110-120 mm Hg) was 13-16. There were 20-24 renal proteins specific for SHR (blood pressure 180 mm Hg and more). The total number of identified renal proteins common for both rat strains included 972-975 proteins. A pairwise comparison of all possible (SHR-WKY) variants identified 8 proteins specific only for normotensive (WKY) animals, and 7 proteins specific only for hypertensive ones (SHR). Taking into consideration their biological roles, the lack of some enzyme proteins in hypertensive rats (for example, biliverdin reductase A) reduces the production of molecules exhibiting antihypertensive properties, while the appearance of others (e.g. betaine-homocysteine S-methyltransferase 2, septin 2, etc.) can be interpreted as a compensatory reaction. Renal proteins with altered relative content (with more than 2.5-fold change) accounted for no more than 5% of all identified proteins. Among the proteins with an increased relative content in hypertensive animals, the largest group consisted of proteins involved in the processes of energy generation and carbohydrate metabolism, as well as antioxidant and protective proteins. In the context of the development of hypertension, the identified relative changes can apparently be considered compensatory. Among the proteins with the most pronounced decrease in the relative content in hypertensive rats, the dramatic reduction in acyl-CoA medium-chain synthetase-3 (ACSM3) appears to make an important contribution to the development of renal pathology in these animals.

Meta-analysis of experimental studies of the effect of melatonin monotherapy on hemodynamic parameters in normotensive and hypertensive rats

Objective. The purpose of the work is to use a meta-analysis to investigate the effect of melatonin monotherapy on the hemodynamic parameters of normotensive and hypertensive rats.Design and methods. For our metaanalysis, we selected 39 publications, of which 28 studied the effect of melatonin monotherapy on hemodynamic parameters in normotensive rats, 12 in SHR rats, 7 in rats with fructose-induced hypertension, 3 in rats with L-NAME-induced hypertension. Meta-analysis of study results was conducted using the statistical program Review Manager 5.3 (Cochrane Library).Results. Our meta-analysis showed that melatonin has a dose-dependent hypotensive and bradycardic effect with a single intravenous administration. The hypotensive effect of chronic administration of melatonin will increase with the duration of therapy. Moreover, the hypotensive effect of melatonin is significantly higher in hypertensive animals compared to normotensive ones. Long-term therapy with melatonin reduced blood pressure levels in normotensive animals by no more than 2 mm Hg, and in hypertensive rats by an average of 20–30 mm Hg.Conclusions. As a result, since melatonin demonstrates a good hypotensive effect in various models of experimental hypertension, it is advisable to continue clinical studies of the possibility of using melatonin in the treatment of hypertension, which should focus on monotherapy, dose selection, various methods of increasing bioavailability and prolonging the effect.

Abstract 005: Renal Macrophages From Losartan Treated Mice Transfer The Hypertension

The immune system participates in the Angiotensin II (AngII)-dependent hypertension (HTN). Dendritic Cells (DCs)-CD11c + and macrophages (Mo) are abundant in the kidney. However, new subpopulations of CD11c + cells with Mo characteristics (F4/80 + ) have been described. Recently, studies have shown that type-1 AngII receptor (AT 1 R) in CD11c + cells could have a protective effect on HTN in contrast to the pro-hypertensive effects of AT 1 R activation in other cells. Here, our goal was to evaluate whether renal Mo (rMo) modify their phenotype during AngII-induced inflammatory kidney damage, and whether their transfer to normotensive animals promotes HTN in an AT 1 R-dependent manner. Male C57BI/6 mice (10 weeks, n=6) were infused with AngII (490 ng/kg/min), AngII+Losartan (LOS; 20mg/kg/d, in drinking water), or vehicle (Vh) for 14-days. Systolic blood pressure (SBP) was measured by plethysmography. Renal DCs (rDCs, CD11c + F4/80 - ) and rMo (CD11c + F4/80 + ) were evaluated by flow cytometry and isolated at 14-days for the transfer to normotensive mice, which were followed for 7-days (n=4-5). Finally, rDCs and rMo were stimulated in vitro with AngII (100nM, 24h) to analyze the mRNAs abundance of AT 1 R. All data are presented by mean±standard deviation.LOS prevented the SBP rise (AngII+LOS=110.3±11.1 vs. AngII=134.7±6.9 mmHg; p<0.01) and the increase of rDCs population (AngII+LOS=12.8±2.0% vs. AngII=16.5±0.6%; p<0.01) induced by AngII, without changing rMo population. The rMo transfer from AngII mice did not induce HTN in normotensive animals after 24h (basal=106.8±2.3 vs. 112.4±4.9 mmHg; ns), compared to rDCs (Basal=110.0±8.3 vs. 132.0±14.3 mmHg; p<0.05). However, the rMo from AngII+LOS mice increased SBP in healthy animals compared to their baseline (basal=109±5.6 vs. 123±8.0 mmHg; p<0.05). This effect was not observed by rDCs transfer (basal=109±2.9 vs. 113±7.0 mmHg; ns). Finally, the rMo from AngII mice showed an increase in the AT 1 R mRNA abundance (p<0.05), compared to Vh rMo, however, AngII in vitro treatment did not modify the mRNA levels.The in vivo AT 1 R antagonism may have a differential effect on rMo, transferring HTN to normotensive mice. These findings suggest that subpopulations of renal CD11c + cells have a differential role in HTN.Fondecyt 1231909

Role of Brain Endothelin Receptor Type B (ETB) in the Regulation of Tyrosine Hydroxylase in the Olfactory Bulb of DOCA-Salt Hypertensive Rats.

We previously reported that endothelins (ETs) regulate tyrosine hydroxylase (TH) activity and expression in the olfactory bulb (OB) of normotensive and hypertensive animals. Applying an ET receptor type A (ETA) antagonist to the brain suggested that endogenous ETs bind to ET receptor type B (ETB) to elicit effects. The aim of the present work was to evaluate the role of central ETB stimulation on the regulation of blood pressure (BP) and the catecholaminergic system in the OB of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. DOCA-salt hypertensive rats were infused for 7 days with cerebrospinal fluid or IRL-1620 (ETB receptor agonist) through a cannula placed in the lateral brain ventricle. Systolic BP (SBP) and heart rate were recorded by plethysmography. The expression of TH and its phosphorylated forms in the OB were determined by immunoblotting, TH activity by a radioenzymatic assay, and TH mRNA by quantitative real-time polymerase chain reaction. Chronic administration of IRL-1620 decreased SBP in hypertensive rats but not in normotensive animals. Furthermore, the blockade of ETB receptors also decreased TH-mRNA in DOCA-salt rats, but it did not modify TH activity or protein expression. These findings suggest that brain ETs through the activation of ETB receptors contribute to SBP regulation in DOCA-salt hypertension. However, the catecholaminergic system in the OB does not appear to be conclusively involved although mRNA TH was reduced. Present and previous findings suggest that in this salt-sensitive animal model of hypertension, the OB contributes to chronic BP elevation.

AT1R BLOCKADE PROMOTES TRANSFER OF HYPERTENSION BY RENAL CD11C+F4/80+ MACROPHAGES

Objective: The immune system participates in arterial hypertension (AHT) induced by Angiotensin II (AngII). dendritic cells (DCs)-CD11c+ and macrophages (Mo) are abundant in the kidney. However, new subpopulations of CD11c+ cells with Mo characteristics have been described, presenting an F4/80+ phenotype. Additionally, recent studies have shown a controversial role of the type 1 AngII receptor (AT1R) in CD11c+ cells. In this context, it is unknown whether Mo CD11c+-F4/80+ modifies their phenotype during AngII-induced inflammatory kidney damage, and whether this promotes AHT in an AT1R-dependent manner. The goal was evaluate whether renal Mo CD11c+-F4/80+ (rMo) modify their phenotype in AHT by AngII and determine whether their transfer to normotensive animals promotes AHT in an AT1R-dependent manner. Design and method: Male C57BI/6 mice (8 - 10 weeks, n = 6) were infused with AngII (490 ng/kg/min), AngII+Losartan (LOS; 20mg/kg/day, in drinking water), or vehicle for 14 -days. Systolic blood pressure (SBP) was measured by photoplestimography, DCs-CD11c+-F4/80- and rMo infiltrate were evaluated in cortex and medulla by flow cytometry. These cells were isolated and transferred to normotensive recipients, whose SBP was measured for 7-days (n = 3 - 5). Finally, the rMo were stimulated in vitro with AngII (100nM-24h) to analyze the abundance of mRNAs (Nox2, Sgk1, ENaC and AT1R; qRT-PCR). The data correspond to the mean ± standard deviation. Results: AngII increased SBP (AngII 134.7 ± 6.9 vs. Vehicle (Vh) 114.5 ± 7.8mmHg;p < 0.001) and promoted DCs-CD11c+F4/80- (AngII = 45.6 ± 11.9% vs. Vh = 31.7 ± 6.7%; p < 0.05) and Mo-CD11c+F4/80+ (AngII = 66.1 ± 8.4% vs. Vh = 55.6 ± 5.1%; p < 0.05) infiltration in renal medulla, and that was prevented by LOS (p < 0.05). We did not observe statistical differences in cortex. Interestingly, rMo transfer from AngII animals did not induce AHT in healthy recipient animals after 24h (Basal = 106.8 ± 2.3 vs.112.4 ± 4.9 mmHg;ns), compared to DCs-CD11c+-F4/80- (Basal = 110.0 ± 8.3 vs.132.0 ± 14.3mmHg;p < 0.05). However, the rMo of AngII+LOS animals increased SBP healthy recipients with respect to their baseline (basal = 109 ± 5.6 vs. 123 ± 8.0mmHg;p < 0.05). The rMo and DCs of hypertensive animals showed an increase in the abundance of AT1R (p < 0.05) compared to vehicle rMo. Conclusions: Pharmacological blockade of AT1R in vivo would have a differential effect on rMo, transferring AHT to normotensive animals. These findings suggest that subpopulations of renal CD11c+ cells have a differential role in AHT.

Impact of Intratracheal Administration of Polyethylene Glycol-Coated Silver Nanoparticles on the Heart of Normotensive and Hypertensive Mice.

Silver nanoparticles are widely used in various industrial and biomedical applications; however, little is known about their potential cardiotoxicity after pulmonary exposure, particularly in hypertensive subjects. We assessed the cardiotoxicity of polyethylene glycol (PEG)-coated AgNPs in hypertensive (HT) mice. Saline (control) or PEG-AgNPs (0.5 mg/kg) were intratracheally (i.t.) instilled four times (on days 7, 14, 21, and 28 post-angiotensin II or vehicle [saline] infusion). On day 29, various cardiovascular parameters were evaluated. Systolic blood pressure and heart rate were higher in PEG-AgNPs-treated HT mice than in saline-treated HT or PEG-AgNPs-treated normotensive mice. The heart histology of PEG-AgNPs-treated HT mice had comparatively larger cardiomyocyte damage with fibrosis and inflammatory cells when compared with saline-treated HT mice. Similarly, the relative heart weight and the activities of lactate dehydrogenase and creatine kinase-MB and the concentration of brain natriuretic peptide concentration were significantly augmented in heart homogenates of HT mice treated with PEG-AgNPs compared with HT mice treated with saline or normotensive animals exposed to PEG-AgNPs. Similarly, the concentrations of endothelin-1, P-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 in heart homogenates were significantly higher than in the other two groups when HT mice were exposed to PEG-AgNPs. Markers of inflammation and oxidative and nitrosative stress were significantly elevated in heart homogenates of HT mice given PEG-AgNPs compared with HT mice treated with saline or normotensive animals exposed to PEG-AgNPs. The hearts of HT mice exposed to PEG-AgNPs had significantly increased DNA damage than those of HT mice treated with saline or normotensive mice treated with AgNPs. In conclusion, the cardiac injury caused by PEG-AgNPs was aggravated in hypertensive mice. The cardiotoxicity of PEG-AgNPs in HT mice highlights the importance of an in-depth assessment of their toxicity before using them in clinical settings, particularly in patients with pre-existing cardiovascular diseases.

Altered autonomic control or coronary artery blood flow by the aortic body chemoreceptors in conscious normotensive and hypertensive sheep

Peripheral arterial chemoreceptors monitor the chemical composition of the blood. While, the carotid bodies located at the bifurcation of the common carotid arteries have been extensively studied. The physiological role of the aortic bodies located in the walls of the aortic arch remains relatively under-studied, and its role in hypertension is unexplored.We hypothesized that activation of the aortic bodies would increase coronary blood flow in the normotensive state and that the parasympathetic nerves to the heart would mediate this.Experiments were conducted in conscious and anesthetized ewes instrumented to record arterial pressure, coronary blood flow, and cardiac output. Two groups of animals were studied, one made hypertensive using a 2 kidney one-clip model (HTN. n=6) and a sham-clipped normotensive group (Con. n=6). Unilateral renal clipping increased resting mean arterial pressure (Con: 84±5 vs HTN 115±6 mmHg). The aortic body chemoreceptors were stimulated by a bolus infusion of potassium cyanide (KCN; 10-30 μg/kg) into the left ventricle.Activation of the aortic bodies in the normotensive and hypertensive animals resulted in a significant increase in coronary blood flow ( P<0.05, 2-way ANOVA, interaction effect), which was not different between groups. In normotensive sheep, the aortic body chemoreflex-mediated coronary vasodilation was attenuated by atropine infusion. Interestingly, the coronary vasodilation in hypertensive animals was not altered by the blockade of muscarinic receptors but was attenuated after propranolol infusion ( P<0.05, interaction effect). Bilateral vagotomy is not possible in conscious animals; under anesthesia, the coronary blood flow response to aortic body stimulation was significantly attenuated in normotensive sheep. Neither atropine nor propranolol affected the aortic body chemoreflex meditated changes in either group's blood pressure, heart rate, or cardiac output. This data suggests that the aortic bodies play an important role in modulating coronary blood flow and that their effector mechanism is altered in hypertension. Many patients with hypertension are on beta-blockers. Our finding indicates that the aortic bodies modulate coronary blood flow via a beta-adrenergic mechanism in hypertension, which may have important implications for regulating coronary blood flow during exertion in hypertensive patients. Work is supported by the Health Research Council (HRC) of New Zealand. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Hypotensive Effects of Arginase Inhibition by L-Norvaline in Genetic Models of Normotensive and Hypertensive Rats.

The main effect of arginase inhibition after administration of L-norvaline is a decrease in BP. At the same time, norvaline causes various side effects in normotensive and hypertensive animals. In our experiments, L-norvaline was administered intraperitoneally (30 mg/kg) for 7 days to normotensive WAG rats (Wistar Albino Glaxo) and hypertensive ISIAH rats (Inherited, Stress-Induced Arterial Hypertension). In ISIAH rats, BP decrease was accompanied by an increase in diuresis, while in WAG rats, diuresis remained unchanged or little changed. At the same time, hypertensive rats demonstrated an increase of catecholamine content in the adrenal glands, while in normotensive animals, it was decreased. The differences in the effects of norvaline can be associated with different mechanisms of BP maintenance in normotensive and hypertensive animals. Normally, BP is maintained by the regulatory influences of the nitric oxide system. In hypertension, this system is weakened, and the hypotensive effects are probably achieved via increased diuresis.

Influence of Butyrate on Impaired Gene Expression in Colon from Patients with High Blood Pressure.

Hypertension (HTN) is associated with gut dysbiosis and the depletion of butyrate-producing bacteria in animal models and people. Furthermore, fecal material transfer from donor hypertensive patients increases blood pressure in normotensive recipient animals and ameliorates HTN-associated pathophysiology. These observations have implications in the impaired interactions between the gut and gut microbiota in HTN. Although this concept is supported in animal models, little is known about human HTN. Therefore, our objective for this study was to compare gene expression with transcriptomics and its potential to influence microbiota in subjects with normal and high blood pressure (HBP). Colon samples from reference subjects with normal blood pressure (REF) and HBP were used for RNA-seq to analyze their transcriptomes. We observed the significant downregulation of gene sets governing immune responses (e.g., SGK1 and OASL), gut epithelial function (e.g., KRT20 and SLC9A3R1), gut microbiota (e.g., PPARG and CIDEC) and genes associated with cardiovascular and gut diseases (e.g., PLAUR and NLN) in HBP subjects; the expression of genes within these pathways correlated with blood pressure. Potential drug targets in the gut epithelium were identified using the Drug Gene International Database for possible use in HTN. They include peroxisome proliferator-activated receptor gamma (PPRG), active serum/glucocorticoid regulated kinase 1 (SGK1) and 3 beta-hydroxysteroid isomerase type II inhibitor (HSD3B). Finally, butyrate, a microbiota-derived short-chain fatty acid, restored the disrupted expression of certain functional genes in colonic organoids from HBP subjects. Patients with HBP exhibit a unique transcriptome that could underlie impaired gut-microbiota interactions. Targeting these interactions could provide a promising new therapeutic intervention for hypertension management.

Hypertension contributes to exacerbated osteoarthritis pathophysiology in rats in a sex-dependent manner

BackgroundHypertension is a common comorbidity of osteoarthritis (OA) with known autonomic dysregulation; thus, the autonomic nervous system may provide a shared underlying mechanism. The objective of this study was to examine the role of the autonomic nervous system in a preclinical model of OA and hypertension.MethodsExperiments were conducted in spontaneously hypertensive rats and a normotensive control strain, including male and female rats. OA was surgically induced via medial meniscus transection with skin incision used as a sham control (n = 7–8/strain/sex/surgery). Tactile sensitivity, anxiety-related behavior, and serum corticosterone were measured at baseline then bi-weekly across 8 weeks. At weeks 9–10, cardiovascular responses to a chemical vagal nerve agonist were determined to indirectly evaluate vagus nerve function. The joint structure was assessed via grading of histological sections.ResultsIn males, OA resulted in thinner cartilage in both hypertensive (OA vs. non-OA p < 0.001) and normotensive (OA vs. non-OA p < 0.001). Only females with comorbid hypertension and OA displayed thinner cartilage (p = 0.013). Male hypertensive OA animals had increased calcified subchondral bone compared to normotensive OA animals (p = 0.043) while female hypertensive OA animals had increased calcified subchondral bone compared to hypertensive sham animals (p < 0.001). All MCLT+MMT groups developed low-grade synovitis; interestingly, hypertensive OA females had higher synovitis scores than normotensive OA females (p = 0.046). Additionally, hypertension led to larger drops in blood pressure with vagal activation in both OA (hypertensive vs. normotensive p = 0.018) and sham (hypertensive vs. normotensive p < 0.001) male animals. In females, this trend held true only in OA animals (normotensive vs. hypertensive p = 0.005).ConclusionThese data provide preliminary evidence that hypertension influences OA progression and encourages further study into the autonomic nervous system as a possible mechanism.

PS-BPB04-5: SELECTIVE ACTIVATION OF GLUTAMATERGIC NEURONS WITHIN THE SFO EVOKES A PRESSOR RESPONSE THAT IS DEPENDENT ON THE PVN

Objective: An overactive glutamatergic projection from the subfornical organ (SFO) to the paraventricular nucleus (PVN) is associated with the development of hypertension. Despite this, the functional relationship of this pathway under normotensive conditions remains poorly defined within the literature. Without this knowledge, it remains unknown if a dysfunction of this pathway is the underlying cause of hypertension or rather simply a consequence of the underlying hypertensive disease pathology. As such, the aim of this study is to identify the short-term function of the SFO and PVN pathway under normotensive conditions. Design and Methods: An optogenetic viral vector (pAAV-CaMKIIa-hChR2 (H134R)-EYFP) was microinjected into the SFO of Lewis rats (n = 5). Three weeks later, rats were anaesthetised and instrumented to record blood pressure and sympathetic nerve activity, administer intravenous drugs and to photo-stimulate glutamatergic SFO neurons. Results: Photostimulation of glutamatergic SFO neurons produced a pressor response that was abolished by inhibition of neuronal transmission within the PVN (9 ± 1mmHg vs 3 ± 1mmHg peak change from baseline, baseline vs PVN inhibition, n = 2 rats, 3 replicates per rat). In a separate cohort (n = 3 rats, 5 replicates per rat), we determined if the pressor response elicited was dependant on the sympathetic nervous system and/or the release of the vasoactive hormone vasopressin. Blockade of sympathetic vasomotor outflow attenuated the pressor response by 76%, whereas combined inhibition of sympathetic outflow and vasopressin 1a receptors attenuated the pressor response by 88%. Finally, photostimulation of glutamatergic SFO neurons led to a peak increase in sympathetic nerve activity (n = 2) that was abolished by phenylephrine administration, suggesting that the neuronal circuitry underpinning this response is barosensitive. Conclusions: This study demonstrates that the pressor response elicited by glutamatergic SFO neurons is dependent on the PVN and is largely mediated by the sympathetic nervous system via barosensitive neuronal circuitry. Chronic activation of this pathway will be undertaken to determine if an overactivation of this neuronal pathway induces hypertension in normotensive animals.

A peptide fraction from hardened common beans (Phaseolus vulgaris) induces endothelium-dependent antihypertensive and renal effects in rats

Beans reached the research spotlight as a source of bioactive compounds capable of modulating different functions. Recently, we reported antioxidant and oxidonitrergic effect of a low molecular weight peptide fraction (<3 kDa) from hardened bean (Phaseolus vulgaris) in vitro and ex vivo, which necessitate further in vivo assessments. This work aimed to evaluate the hypotensive effect and the involved physiological mechanisms of the hardened common bean peptide (Phaseolus vulgaris) in normotensive (Wistar) and hypertensive (SHR) animals. Bean flour was combined with a solution containing acetonitrile, water and formic acid (25: 24: 1). Protein extract (PV3) was fractioned (3 kDa membrane). We assessed PV3 effects on renal function and hemodynamics of wistar (WT–normotensive) and spontaneously hypertensive rats (SHR) and measured systemic arterial pressure and flow in aortic and renal beds. The potential endothelial and oxidonitrergic involvements were tested in isolated renal artery rings. As results, we found that PV3: I) decreased food consumption in SHR, increased water intake and urinary volume in WT, increased glomerular filtration rate in WT and SHR, caused natriuresis in SHR; II) caused NO- and endothelium-dependent vasorelaxation in renal artery rings; III) reduced arterial pressure and resistance in aortic and renal vascular beds; IV) caused antihypertensive effects in a dose-dependent manner. Current findings support PV3 as a source of bioactive peptides and raise the potential of composing nutraceutical formulations to treat renal and cardiovascular diseases.

Prophylactic Treatment with Hydrogen Sulphide Can Prevent Renal Ischemia-Reperfusion Injury in L-NAME Induced Hypertensive Rats with Cisplatin-Induced Acute Renal Failure.

(Background and Objectives): Renal ischemia perfusion injury is one of the major issues in kidney transplant. The aim of the study was to investigate the hypothesis that prophylactic treatment-with a hydrogen sulphide donor to an acute renal failure case of hypertensive rats-can minimize the ischemia reperfusion injury of the kidney which is beneficial for kidney transplant. To check this hypothesis, the present study was designed to investigate the effect of chronic administration of a hydrogen sulphide (H2S) donor and sodium hydrosulfide (NaHS) on nuclear factor kappa B (NF-kB) and inter cellular adhesion molecule-1 (ICAM-1) concentration in non-renal failure (NRF) and acute renal failure (ARF) rats in the ischemia-reperfusion injury (IRI) model of the kidney in both normotensive WKY and hypertensive rats (L-nitro arginine methyl ester (L-NAME-induced); (Materials and Methods): A total number of 48 Sprague-Dawley rats were recruited into eight groups each consisting of six animals. Each of these eight groups was used to measure systemic and renal parameters, H2S, antioxidant parameters in plasma, plasma concentration of NF-kB and ICAM-1 and renal cortical blood pressure. ARF was induced by single intraperitoneal (i.p.) cisplatin injection (5 mg/kg). Hypertension was induced by oral administration of L-NAME in drinking water for four weeks at 40 mg/kg/day. NaHS was administered (i.p) at 56 µmol/kg for five weeks while dL-propargylglycine (PAG), a H2S generation inhibitor, was administered as a single intra-peritoneal injection (50 mg/kg). An acute surgical experiment was performed for the induction of renal ischemia for 30 min by renal artery clamping followed by reperfusion for three hours; (Results): Chronic administration of NaHS attenuated the severity of ARF in both normotensive and hypertensive animals (L-NAME) along with lowering the blood pressure in hypertensive groups. NaHS improved the oxidative stress parameters such as total superoxide dismutase (T-SOD), glutathione (GSH) and reduced the malondialdehyde (MDA) concentration along with reduction of NF-kB and ICAM-1 following renal IRI; Conclusions: These findings demonstrate that H2S not only reduced the severity of cisplatin induced ARF but also reduced the severity of renal IRI by upregulating antioxidants along with decreased concentrations of NF-kB and ICAM-1 in normotensive and L-NAME induced hypertensive rats.

Abstract 10254: Renal CD11c + F4/80 - Dendritic Cells, but Not Renal CD11c + F4/80 + Macrophages, Transfer the Hypertension From Angiotensin II-mice

Introduction: Immune system participates in Angiotensin II (AngII)-hypertension (HTN). Previously, it was shown that dendritic cells (DCs)-CD11c + are required for HTN development. However, new CD11c + cell subpopulations, presenting macrophages (Mφ) characteristics (F4/80 + ), have been described. Since renal DCs and Mφ share several markers, their participation in AngII-HTN remains under discussion. Our objective was to analyze whether renal DCs-CD11c + F4/80 - or/and CD11c + F4/80 + (Mφ) modify their phenotype in the AngII-HTN, and to determine if they promote HTN by transferring this phenotype to normotensive animals. Methods: Male C57BI/6 mice (8-10 weeks-old, n=6) were infused with AngII (490 ng/kg/min) by 14-days. We measured systolic blood pressure (SBP), and renal DCs-CD11c + F4/80 - and Mφ-CD11c + F4/80 + infiltrations were evaluated by flow cytometry. In addition, these cells were isolated at 14-days and transferred to normotensive mice (n=4-5) for SBP measurements. Finally, renal Mφ-CD11c + F4/80 + from HTN mice were stimulated in vitro with AngII (100nM-24h) to analyze the mRNAs abundance of Nox2 , Sgk1 , ENaC and AT 1 R , by qRT-PCR. Results: AngII increased SBP (AngII 134.7±6.9 vs. Vehicle (Vh) 114.5±7.8mmHg; p&lt;0.001) and promoted the infiltration of DCs-CD11c + F4/80 - (AngII=45.6±11.9% vs. Vh=31.7±6.7%; p&lt;0.05) and Mφ-CD11c + F4/80 + (AngII=66.1±8.4% vs. Vh=55.6±5.1%; p&lt;0.05) in renal medulla. No statistical differences we observed in the renal cortex. Interestingly, the adoptive transfer of renal Mφ-CD11c + F4/80 + (1x10 6 -cells) from AngII animals to healthy recipient mice did not transfer HTN after 24h (baseline=106.8.0±2.3 vs. 112.4±4.5mmHg; ns), compared to DCs-CD11c + F4/80 - (baseline=110.0±8.3 vs. 132.0±14.3mmHg; p&lt;0.05). Finally, renal Mφ-CD11c + -F4/80 + purified from HTN animals and re-stimulated in vitro with AngII did not show changes in the mRNA levels evaluated (p&gt;0.05). Conclusions: The AngII-HTN promotes a differentiated infiltration of DCs-CD11c + F4/80 - and Mφ-CD11c + F4/80 + in renal medulla. However, only renal DCs, and not renal Mφ, acquire the ability to transfer HTN, suggesting that renal CD11c + cell subpopulations may have a differential role in AngII-HTN.Supported by Fondecyt-ANID #1201251 and #3201016