The Triad Na+ Activated Na+ Channel (Nax)-Salt Inducible KINASE (SIK) and (Na+ + K+)-ATPase: Targeting the Villains to Treat Salt Resistant and Sensitive Hypertension.

The Na+-activated Na+ channel (Nax) and salt-inducible kinase (SIK) are stimulated by increases in local Na+ concentration, affecting (Na+ + K+)-ATPase activity. To test the hypothesis that the triad Nax/SIK/(Na+ + K+)-ATPase contributes to kidney injury and salt-sensitive hypertension (HTN), uninephrectomized male Wistar rats (200 g; n = 20) were randomly divided into 4 groups based on a salt diet (normal salt diet; NSD-0.5% NaCl-or high-salt diet; HSD-4% NaCl) and subcutaneous administration of saline (0.9% NaCl) or deoxycorticosterone acetate (DOCA, 8 mg/kg), as follows: Control (CTRL), CTRL-Salt, DOCA, and DOCA-Salt, respectively. After 28 days, the following were measured: kidney function, blood pressure, (Na+ + K+)-ATPase and SIK1 kidney activities, and Nax and SIK1 renal expression levels. SIK isoforms in kidneys of CTRL rats were present in the glomerulus and tubular epithelia; they were not altered by HSD and/or HTN. CTRL-Salt rats remained normotensive but presented slight kidney function decay. HSD rats displayed augmentation of the Nax/SIK/(Na+ + K+)-ATPase pathway. HTN, kidney injury, and kidney function decay were present in all DOCA rats; these were aggravated by HSD. DOCA rats presented unaltered (Na+ + K+)-ATPase activity, diminished total SIK activity, and augmented SIK1 and Nax content in the kidney cortex. DOCA-Salt rats expressed SIK1 activity and downregulation in (Na+ + K+)-ATPase activity in the kidney cortex despite augmented Nax content. The data of this study indicate that the (Na+ + K+)-ATPase activity response to SIK is attenuated in rats under HSD, independent of HTN, as a mechanism contributing to kidney injury and salt-sensitive HTN.

Bioactive Peptides from Ruditapes philippinarum Attenuate Hypertension and Cardiorenal Damage in Deoxycorticosterone Acetate-Salt Hypertensive Rats.

Hypertension is a common disease that affects human health and can lead to damage to the heart, kidneys, and other important organs. In this study, we investigated the regulatory effects of bioactive peptides derived from Ruditapes philippinarum (RPP) on hypertension and organ protection in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We found that RPPs exhibited significant blood pressure-lowering properties. Furthermore, the results showed that RPPs positively influenced vascular remodeling and effectively maintained a balanced water-sodium equilibrium. Meanwhile, RPPs demonstrated anti-inflammatory potential by reducing the serum levels of inflammatory cytokines (TNF-α, IL-2, and IL-6). Moreover, we observed the strong antioxidant activity of RPPs, which played a critical role in reducing oxidative stress and alleviating hypertension-induced damage to the aorta, heart, and kidneys. Additionally, our study explored the regulatory effects of RPPs on the gut microbiota, suggesting a possible correlation between their antihypertensive effects and the modulation of gut microbiota. Our previous studies have demonstrated that RPPs can significantly reduce blood pressure in SHR rats. This suggests that RPPs can significantly improve both essential hypertension and DOAC-salt-induced secondary hypertension and can ameliorate cardiorenal damage caused by hypertension. These findings further support the possibility of RPPs as an active ingredient in functional anti-hypertensive foods.

Further evidence against the role renal medullary perfusion in short-term control of arterial pressure in normotensive and mildly or overtly hypertensive rats.

Earlier evidence from studies of rat hypertension models undermines the widespread view that the rate of renal medullary blood flow (MBF) is critical in control of arterial pressure (MAP). Here, we examined the role of MBF in rats that were normotensive, with modest short-lasting pressure elevation, or with overt established hypertension. The groups studied were anaesthetised Sprague-Dawley rats: (1) normotensive, (2) with acute i.v. norepinephrine-induced MAP elevation, and (3) with hypertension induced by unilateral nephrectomy followed by administration of deoxycorticosterone-acetate (DOCA) and 1% NaCl drinking fluid for 3 weeks. MBF was measured (laser-Doppler probe) and selectively increased using 4-h renal medullary infusion of bradykinin. MAP, renal excretion parameters and post-experiment medullary tissue osmolality and sodium concentration were determined. In the three experimental groups, baseline MAP was 117, 151 and 171 mmHg, respectively. Intramedullary bradykinin increased MBF by 45%, 65% and 70%, respectively, but this was not associated with a change in MAP. In normotensive rats a significant decrease in medullary tissue sodium was seen. The intramedullary bradykinin specifically increased renal excretion of water, sodium and total solutes in norepinephrine-treated rats but not in the two other groups. As previously shown in models of rat hypertension, in the normotensive rats and those with acute mild pressure elevation (resembling labile borderline human hypertension), 4-h renal medullary hyperperfusion failed to decrease MAP. Nor did it decrease in DOCA-salt model mimicking low-renin human hypertension. Evidently, within the 4-h observation, medullary perfusion was not a critical determinant of MAP in normotensive and hypertensive rats.

Probiotic Bifidobacterium breve prevents DOCA-salt hypertension.

Many probiotics that affect gut microbial ecology have been shown to produce beneficial effects on renin-angiotensin-dependent rodent models and human hypertension. We hypothesized that Bifidobacterium breve CECT7263 (BFM) would attenuate hypertension in deoxycorticosterone acetate (DOCA)-salt rats, a renin-independent model of hypertension. Rats were randomly divided into five groups: control, DOCA-salt, treated DOCA-salt-BFM, treated DOCA-salt-butyrate, and treated DOCA-salt-acetate, for 5 weeks. BFM prevented the increase in systolic blood pressure, cardiac weight, and renal damage induced by DOCA-salt. BFM increased acetate-producing bacterial population and gut acetate levels, improved colonic integrity, normalized endotoxemia, plasma trimethylamine (TMA) levels, and restored the Th17 and Treg content in mesenteric lymph nodes and aorta. Furthermore, BFM improved nitric oxide-dependent vasorelaxation induced by acetylcholine in aortic rings and reduced NADPH oxidase activity in DOCA-salt animals. These protective effects were mimicked by acetate, but not by butyrate supplementation. These data demonstrate that BFM induces changes in gut microbiota linked with attenuation of endothelial dysfunction and increase in blood pressure in this low-renin form of hypertension. These beneficial effects seem to be mediated by increased acetate and reduced TMA production by gut microbiota, thus, improving gut integrity and restoring Th17/Tregs polarization and endotoxemia.

DOCA-salt hypertension and the role of the OVLT-sympathetic-gut microbiome axis.

Hypertension is a multifaceted condition influenced by genetic and environmental factors and estimated to cause 9.4 million deaths globally every year. Recently, there has been growing interest in understanding the gut microbe-host interaction in the maintenance of health or disease states, but relatively few studies have shown an association between the gut microbiome and specific types of hypertension. The deoxycorticosterone acetate (DOCA)-salt model of hypertension in rats is known to have a neurogenic component linked to increased sympathetic nervous system activity. As such, our lab has recently shown the hypertensive response in DOCA treated rats requires an intact organum vasculosum of the lamina terminalis (OVLT), a central hypothalamic circumventricular organ. Currently, we hypothesize the OVLT mediates changes in the gut microbiome associated with concomitant hypertension. Herein, we report that the hypertensive effects of DOCA-salt treatment were significantly attenuated throughout the 24-hour day/night cycle in OLVT lesioned rats on days 1, 3, and 9-21 of DOCA treatment compared with sham rats. Increased blood pressure (BP) in DOCA-salt treated rats was accompanied by specific changes in regional gut microbial populations yet was mitigated and offset by lesion of the OVLT. Furthermore, bacterial populations in OVLT-lesioned rats with attenuated hypertension more closely resembled those in normal control rats. We conclude that DOCA-salt hypertension is associated with specific microbiome changes in the gut, and the attenuated hypertensive effects of DOCA-salt in OVLT-lesioned rats is mediated in part through counteracting changes in these bacterial populations.

Grape Extract from Chardonnay Seeds Restores Deoxycorticosterone Acetate-Salt-Induced Endothelial Dysfunction and Hypertension in Rats.

Grape extract (GE), which contains various polyphenolic compounds, exerts protective effects against lifestyle-related diseases, such as diabetes and hypertension. We pharmacologically investigated whether dietary supplements with an extract from Chardonnay exerted antihypertensive effects in deoxycorticosterone acetate (DOCA)-salt-induced hypertensive rats. GE increased nitric oxide (NO) production by activating the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in cultured endothelial cells and induced vasorelaxation in the aorta and mesenteric artery via the same pathway. The development and progression of hypertension by the DOCA-salt treatment was significantly inhibited in GE-fed rats. Reduced vasoreactive responses to acetylcholine in the aorta of DOCA-salt rats were significantly ameliorated by the GE diet. Dietary GE supplements slightly diminished vascular superoxide anion production induced by the DOCA-salt treatment. On the other hand, dietary GE supplements had no effect on the progression of hypertension in rats in which NO synthase was pharmacologically and chronically suppressed. In addition, the oral administration of GE for 5 d in healthy rats enhanced endothelial NO synthase (eNOS) gene expression and vascular reactivity to acetylcholine in the aorta. Thus, GE has endothelium-dependent vasorelaxant properties that are mediated by the activation of endothelial NO synthase via the PI3K/Akt pathway, and this mechanism is conducive to the antihypertensive effects of GE observed in DOCA-salt-treated rats.

Chronic Cannabidiol Administration Fails to Diminish Blood Pressure in Rats with Primary and Secondary Hypertension Despite Its Effects on Cardiac and Plasma Endocannabinoid System, Oxidative Stress and Lipid Metabolism.

We investigated the influence of cannabidiol (CBD) on blood pressure (BP) and heart rate (HR) in spontaneously (SHR) and deoxycorticosterone (DOCA-salt) hypertensive rats. Hypertension was connected with increases in cardiac and plasma markers of lipid peroxidation in both models, whereas cardiac endocannabinoid levels decreased in SHR and increased in DOCA-salt. CBD (10 mg/kg once a day for 2 weeks) did not modify BP and HR in hypertension but counteracted pro-oxidant effects. Moreover, it decreased cardiac or plasma levels of anandamide, 2-arachidonoylglycerol and oleoyl ethanolamide in DOCA-salt and inhibited the activity of fatty acid amide hydrolase (FAAH) in both models. In the respective normotensive control rats, CBD increased lipid peroxidation, free fatty acid levels and FAAH activity. In conclusion, chronic CBD administration does not possess antihypertensive activity in a model of primary and secondary (DOCA-salt) hypertension, despite its antioxidant effect. The latter may be direct rather than based on the endocannabinoid system. The unexpected CBD-related increase in lipid peroxidation in normotensive controls may lead to untoward effects; thus, caution should be kept if CBD is used therapeutically.

Genetic ablation and pharmacological inhibition of immunosubunit ß5i attenuates cardiac remodeling in deoxycorticosterone-acetate (DOCA)-salt hypertensive mice.

Hypertensive cardiac remodeling is a major cause of heart failure. The immunoproteasome is an inducible form of the proteasome and its catalytic subunit ß5i (also named LMP7) is involved in angiotensin II-induced atrial fibrillation; however, its role in deoxycorticosterone-acetate (DOCA)-salt-induced cardiac remodeling remains unclear. C57BL/6 J wild-type (WT) and ß5i knockout (ß5i KO) mice were subjected to uninephrectomy (sham) and DOCA-salt treatment for three weeks. Cardiac function, fibrosis, and inflammation were evaluated by echocardiography and histological analysis. Protein and gene expression levels were analyzed by quantitative real-time PCR and immunoblotting. Our results showed that after 21 days of DOCA-salt treatment, ß5i expression and chymotrypsin-like activity were the most significantly increased factors in the heart compared with the sham control. Moreover, DOCA-salt-induced elevation of blood pressure, adverse cardiac function, chamber and myocyte hypertrophy, interstitial fibrosis, oxidative stress, and inflammation were markedly attenuated in ß5i KO mice. These findings were verified in ß5i inhibitor PR-957-treated mice. Moreover, blocking of PTEN (the gene of phosphate and tensin homolog deleted on chromosome ten) markedly attenuated the inhibitory effect of ß5i knockout on DOCA-salt-induced cardiac remodeling. Mechanistically, DOCA-salt stress upregulated the expression of ß5i, which promoted the degradation of PTEN and the activation of downstream signals (AKT/mTOR, TGF-ß1/Smad2/3, NOX, and NF-κB), which ultimately led to cardiac hypertrophic remodeling. This study provides new evidence of the critical role of ß5i in DOCA-salt-induced cardiac remodeling through the regulation of PTEN stability, and indicates that the inhibition of ß5i may be a promising therapeutic target for the treatment of hypertensive heart diseases.

Upregulation of Tumor Susceptibility Gene 101 (TSG101) by mechanical stress in podocytes.

Elevated mechanical stress in glomerular hypertension is thought to damage podocytes, the loss of which leads to development of glomerulosclerosis. Applying cDNA array analysis to mechanically stressed podocytes, we have recently identified TSG101 as a stretch-induced candidate gene among others. TSG101, which is part of the ESCRT-I complex, is involved in multivesicular body (MVB) formation. Here we demonstrate that TSG101 mRNA is strongly upregulated in conditionally immortalized mouse podocytes by cyclic mechanical stress. Differentiation of podocytes does not affect TSG101 mRNA levels. TSG101 immunofluorescence is distributed in a vesicular pattern in podocytes, the staining intensity being enhanced by mechanical stress. In DOCA/salt treated rats, a model of glomerular hypertension, glomerular TSG101 mRNA levels are elevated, and an increased number of MVBs is observed by electron microscopy in podocyte processes. Our data demonstrate that mechanical stress upregulates TSG101 in podocytes, suggesting that glomerular hypertension enhances sorting of cell surface proteins and their ligands into the degradative pathway in podocytes.

Cardiac Ablation of SOCS3 Aggravates DOCA-Salt-Induced Hypertrophic Remodeling by Activation of Gp130-Dependent Signaling in Mice.

BACKGROUND/AIMS: Cardiac remodeling is a critical pathogenetic process leading to heart failure. Suppressor of cytokine signaling-3 (SOCS3) is demonstrated as a key negative regulator of the gp130 receptor to inhibit cardiac hypertrophy. However, the role of SOCS3 in deoxycorticosterone-acetate (DOCA)-salt-induced cardiac remodeling remains unclear. METHODS: Cardiac-specific SOCS3 knockout (SOCS3cKO) and wild-type (WT) C57BL/6J mice were subjected to uninephrectomy and DOCA-salt for 3 weeks. The effect of SOCS3 on cardiac remodeling and inflammation was evaluated by histological analysis. Gene and protein levels were measured by real-time PCR and immunoblotting analysis. RESULTS: After DOCA-salt treatment, the expression of SOCS3, activation of gp130/JAK/STAT3, cardiac dysfunction and fibrosis in DOCA-salt mice were significantly elevated, which were markedly attenuated by eplerenone, a specific mineralocorticoid receptor (MR) blocker. Moreover, DOCA-salt-induced cardiac dysfunction, hypertrophy, fibrosis and inflammation were aggravated in SOCS3cKO mice, but were significantly reduced in AAV9-SOCS3-injected mice. These effects were mostly associated with activation of gp130/STAT3/AKT/ERK1/2, TGF-ß/Smad2/3 and NF-κB signaling pathways. CONCLUSIONS: Our data demonstrate that loss of SOCS3 in cardiomyocytes promotes DOCA-salt-induced cardiac remodeling and inflammation, and it may be a novel potential therapeutic target for hypertensive heart disease.

Lesion of the OVLT markedly attenuates chronic DOCA-salt hypertension in rats.

Lesions of the anteroventral third ventricle (AV3V region) are known to prevent many forms of experimental hypertension, including mineralocorticoid [deoxycorticosterone acetate (DOCA)-salt] hypertension in the rat. However, AV3V lesions include the organum vasculosum of the lamina terminalis (OVLT), portions of the median preoptic nucleus, and efferent fibers from the subfornical organ (SFO), thereby limiting the ability to define the individual contribution of these structures to the prevention of experimental hypertension. Having previously reported that the SFO does not play a significant role in the development of DOCA-salt hypertension, the present study was designed to test the hypothesis that the OVLT is necessary for DOCA-salt hypertension in the rat. In uninephrectomized OVLT-lesioned (OVLTx; n = 6) and sham-operated ( n = 4) Sprague-Dawley rats consuming a 0.1% NaCl diet and 0.9% NaCl drinking solution, 24-h mean arterial pressure (MAP) was recorded telemetrically 5 days before and 21 days after DOCA implantation (100 mg sc per rat). No differences in control MAP were observed between groups. The chronic pressor response to DOCA was attenuated in OVLTx rats such that MAP increased to 133 ± 3 mmHg in sham-operated rats by day 21 of DOCA compared with 120 ± 4 mmHg (means ± SE) in OVLTx rats. These results support the hypothesis that the OVLT is an important brain site of action for the pathogenesis of DOCA-salt hypertension in the rat.

Angiotensin generation in the brain: a re-evaluation.

The existence of a so-called brain renin-angiotensin system (RAS) is controversial. Given the presence of the blood-brain barrier, angiotensin generation in the brain, if occurring, should depend on local synthesis of renin and angiotensinogen. Yet, although initially brain-selective expression of intracellular renin was reported, data in intracellular renin knockout animals argue against a role for this renin in angiotensin generation. Moreover, renin levels in brain tissue at most represented renin in trapped blood. Additionally, in neurogenic hypertension brain prorenin up-regulation has been claimed, which would generate angiotensin following its binding to the (pro)renin receptor. However, recent studies reported no evidence for prorenin expression in the brain, nor for its selective up-regulation in neurogenic hypertension, and the (pro)renin receptor rather displays RAS-unrelated functions. Finally, although angiotensinogen mRNA is detectable in the brain, brain angiotensinogen protein levels are low, and even these low levels might be an overestimation due to assay artefacts. Taken together, independent angiotensin generation in the brain is unlikely. Indeed, brain angiotensin levels are extremely low, with angiotensin (Ang) I levels corresponding to the small amounts of Ang I in trapped blood plasma, and Ang II levels at most representing Ang II bound to (vascular) brain Ang II type 1 receptors. This review concludes with a unifying concept proposing the blood origin of angiotensin in the brain, possibly resulting in increased levels following blood-brain barrier disruption (e.g. due to hypertension), and suggesting that interfering with either intracellular renin or the (pro)renin receptor has consequences in an RAS-independent manner.

Hypertension and chronic inhibition of endocannabinoid degradation modify the endocannabinoid system and redox balance in rat heart and plasma.

The interaction between the endocannabinoid and ROS signaling systems has been demonstrated in different organs. Inhibitors of fatty acid amide hydrolase (FAAH), the key enzyme responsible for degradation of the endocannabinoid anandamide, are postulated to possess anti-hypertensive potential. Here, we compared the effects of hypertension and chronic FAAH inhibition by URB597 on the endocannabinoid system and redox balance in spontaneously hypertensive rats (SHR) and hypertensive deoxycorticosterone acetate (DOCA)-salt rats. Enhanced oxidative stress and lipid peroxidation were found in both hypertension models. Hypertension affected cardiac and plasma endocannabinoid systems in a model-dependent manner: anandamide and 2-arachidonoylglycerol levels decreased in SHR and increased in DOCA-salt. Cardiac CB1 receptor expression increased in both models while higher CB2 receptor expression was only in DOCA-salt. URB597 increased endocannabinoid levels in both models but produced the partial reduction of oxidative stress in DOCA-salt but not in SHR. Notably, URB597 decreased antioxidant defense and increased lipid peroxidation products in normotension. Therefore, the therapeutic potential of FAAH inhibitors should be interpreted cautiously.

(-)-Epicatechin Reduces Blood Pressure and Improves Left Ventricular Function and Compliance in Deoxycorticosterone Acetate-Salt Hypertensive Rats.

(−)-Epicatechin (E) is a flavanol found in green tea and cocoa and has been shown to attenuate tumour necrosis factor alpha (TNF-α)-mediated inflammation, improve nitric oxide levels, promote endothelial nitric oxide synthase (eNOS) activation and inhibit NADPH oxidase. This study investigated the effect of 28 days of low epicatechin dosing (1 mg/kg/day) on the cardiovascular function of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Wistar rats (n = 120, 8 weeks of age) underwent uninephrectomy and were randomised into four groups (uninephrectomy (UNX), UNX + E, DOCA, DOCA + E). DOCA and DOCA + E rats received 1% NaCl drinking water along with subcutaneous injections of 25 mg deoxycorticosterone-acetate (in 0.4 mL of dimethylformamide) every fourth day. UNX + E and DOCA + E rats received 1 mg/kg/day of epicatechin by oral gavage. Single-cell micro-electrode electrophysiology, Langendorff isolated-heart assessment and isolated aorta and mesenteric organ baths were used to assess cardiovascular parameters. Serum malondialdehyde concentration was used as a marker of oxidative stress. Myocardial stiffness was increased and left ventricular compliance significantly diminished in the DOCA control group, and these changes were attenuated by epicatechin treatment (p < 0.05). Additionally, the DOCA + E rats showed significantly reduced blood pressure and malondialdehyde concentrations; however, there was no improvement in left ventricular hypertrophy, electrophysiology or vascular function. This study demonstrates the ability of epicatechin to reduce blood pressure, prevent myocardial stiffening and preserve cardiac compliance in hypertrophied DOCA-salt rat hearts.

DOCA-Salt Hypertension: an Update.

Hypertension is a multifaceted disease that is involved in ∼40% of cardiovascular mortalities and is the result of both genetic and environmental factors. Because of its complexity, hypertension has been studied by using various models and approaches, each of which tends to focus on individual organs or tissues to isolate the most critical and treatable causes of hypertension and the related damage to end-organs. Animal models of hypertension have ranged from Goldblatt's kidney clip models in which the origin of the disease is clearly renal to animals that spontaneously develop hypertension either through targeted genetic manipulations, such as the TGR(mRen2)27, or selective breeding resulting in more enigmatic origins, as exemplified by the spontaneously hypertensive rat (SHR). These two genetically derived models simulate the less-common human primary hypertension in which research has been able to define a Mendelian linkage. Several models are more neurogenic or endocrine in nature and illustrate that crosstalk between the nervous system and hormones can cause a significant rise in blood pressure (BP). This review will examine one of these neurogenic models of hypertension, i.e., the deoxycorticosterone acetate (DOCA), reduced renal mass, and high-salt diet (DOCA-salt) rodent model, one of the most common experimental models used today. Although the DOCA-salt model is mainly believed to be neurogenic and has been shown to impact the central and peripheral nervous systems, it also significantly involves many other body organs.

Structure-based optimization of cyclopropyl urea derivatives as potent soluble epoxide hydrolase inhibitors for potential decrease of renal injury without hypotensive action.

Epoxyeicosatrienoic acids (EETs) are known to have beneficial pharmacological effects on various cardiovascular events. However, EETs are biologically metabolized by soluble epoxide hydrolase (sEH) to less active metabolites. In our search for potent sEH inhibitors, we optimized a series of cyclopropyl urea derivatives and identified compound 38 as a potent sEH inhibitor with minimal CYP inhibition and good oral absorption in rats. Administration of 38 to DOCA-salt rats suppressed urinary albumin and MCP-1 excretion without affecting systolic blood pressure.

Urine metabolic profile in rats with arterial hypertension of different genesis.

The diversity of pathogenetic mechanisms underlying arterial hypertension leads to the necessity to devise a personalized approach to the diagnosis and treatment of the disease. Metabolomics is one of the promising methods for personalized medicine, as it provides a comprehensive understanding of the physiological processes occurring in the body. The metabolome is a set of low-molecular substances available for detection in a sample and representing intermediate and final products of cell metabolism. Changes in the content and ratio of metabolites in the sample mark the corresponding pathogenetic mechanisms by highlighting them, which is especially important for such a multifactorial disease as arterial hypertension. To identify metabolomic markers for hypertensive conditions of different origins, three forms of arterial hypertension (AH) were studied: rats with hereditary AH (ISIAH rat strain); rats with AH induced by L-NAME administration (a model of endothelial dysfunction with impaired NO production); rats with AH caused by the administration of deoxycorticosterone in combination with salt loading (hormone-dependent form - DOCA-salt AH). WAG rats were used as normotensive controls. 24-hour urine samples were collected from all animals and analyzed by quantitative NMR spectroscopy for metabolic profiling. Then, potential metabolomic markers for the studied forms of hypertensive conditions were identified using multivariate statistics. Analysis of the data obtained showed that hereditary stress-induced arterial hypertension in ISIAH rats was characterized by a decrease in the following urine metabolites: nicotinamide and 1-methylnicotinamide (markers of inflammatory processes), N- acetylglutamate (nitric oxide cycle), isobutyrate and methyl acetoacetate (gut microbiota). Pharmacologically induced forms of hypertension (the L-NAME and DOCA+NaCl groups) do not share metabolomic markers with hereditary AH. They are differentiated by N,N-dimethylglycine (both groups), choline (the L-NAME group) and 1-methylnicotinamide (the group of rats with DOCA-salt hypertension).

Role of the median preoptic nucleus in the development of chronic deoxycorticosterone acetate (DOCA)-salt hypertension.

We have previously reported that the subfornical organ (SFO) does not contribute to the chronic hypertensive response to DOCA-salt in rats, and yet the organum vasculosum of the lamina terminalis (OVLT) plays a significant role in the development of deoxycorticosterone acetate (DOCA)-salt hypertension. Since efferent fibers of the OVLT project to and through the median preoptic nucleus (MnPO), the present study was designed to test the hypothesis that the MnPO is necessary for DOCA-salt hypertension in the rat. Male Sprague-Dawley rats underwent SHAM (MnPOsham; n = 5) or electrolytic lesion of the MnPO (MnPOx; n = 7) followed by subsequent unilateral nephrectomy and telemetry instrumentation. After recovery and during the experimental protocol, rats consumed a 0.1% NaCl diet and 0.9% NaCl drinking solution. Mean arterial pressure (MAP) was recorded telemetrically 5 days before and 21 days after DOCA implantation (100 mg/rat; SQ). The chronic pressor response to DOCA was attenuated in MnPOx rats by Day 11 of treatment and continued such that MAP increased 25 ± 3 mmHg in MnPOsham rats by Day 21 of DOCA compared to 14 ± 3 mmHg in MnPOx rats. These results support the hypothesis that the MnPO is an important brain site of action and necessary for the full development of DOCA-salt hypertension in the rat.

Cell-specific transcriptome changes in the hypothalamic arcuate nucleus in a mouse deoxycorticosterone acetate-salt model of hypertension.

A common preclinical model of hypertension characterized by low circulating renin is the "deoxycorticosterone acetate (DOCA)-salt" model, which influences blood pressure and metabolism through mechanisms involving the angiotensin II type 1 receptor (AT1R) in the brain. More specifically, AT1R within Agouti-related peptide (AgRP) neurons of the arcuate nucleus of the hypothalamus (ARC) has been implicated in selected effects of DOCA-salt. In addition, microglia have been implicated in the cerebrovascular effects of DOCA-salt and angiotensin II. To characterize DOCA-salt effects upon the transcriptomes of individual cell types within the ARC, we used single-nucleus RNA sequencing (snRNAseq) to examine this region from male C57BL/6J mice that underwent sham or DOCA-salt treatment. Thirty-two unique primary cell type clusters were identified. Sub-clustering of neuropeptide-related clusters resulted in identification of three distinct AgRP subclusters. DOCA-salt treatment caused subtype-specific changes in gene expression patterns associated with AT1R and G protein signaling, neurotransmitter uptake, synapse functions, and hormone secretion. In addition, two primary cell type clusters were identified as resting versus activated microglia, and multiple distinct subtypes of activated microglia were suggested by sub-cluster analysis. While DOCA-salt had no overall effect on total microglial density within the ARC, DOCA-salt appeared to cause a redistribution of the relative abundance of activated microglia subtypes. These data provide novel insights into cell-specific molecular changes occurring within the ARC during DOCA-salt treatment, and prompt increased investigation of the physiological and pathophysiological significance of distinct subtypes of neuronal and glial cell types.

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

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.