Animal Models of Hypertension: A Scientific Statement From the American Heart Association

Basic Mechanisms of Brain Injury and Cognitive Decline in Hypertension

Dementia affects almost 50 million adults worldwide, and remains a major cause of death and disability. Hypertension is a leading risk factor for dementia, including Alzheimer disease and Alzheimer disease-related dementias. Although this association is well-established, the mechanisms underlying hypertension-induced cognitive decline remain poorly understood. By exploring the mechanisms mediating the detrimental effects of hypertension on the brain, studies have aimed to provide therapeutic insights and strategies on how to protect the brain from the effects of blood pressure elevation. In this review, we focus on the basic mechanisms contributing to the cerebrovascular adaptions to elevated blood pressure and hypertension-induced microvascular injury. We also assess the cellular mechanisms of neurovascular unit dysfunction, focusing on the premise that cognitive impairment ensues when the dynamic metabolic demands of neurons are not met due to neurovascular uncoupling, and summarize cognitive deficits across various rodent models of hypertension as a resource for investigators. Despite significant advances in antihypertensive therapy, hypertension remains a critical risk factor for cognitive decline, and several questions remain about the development and progression of hypertension-induced cognitive impairment.

Tissue Compliance and Intracranial Pressure Responses to Large Intracerebral Hemorrhage in Young and Aged Spontaneously Hypertensive Rats

BACKGROUND

After a large intracerebral hemorrhage (ICH), the hematoma and swelling cause intracranial pressure (ICP) to increase, sometimes causing brain herniation and death. This is partly countered by widespread tissue compliance, an acute decrease in tissue volume distal to the stroke, at least in young healthy animals. Intracranial compensation dynamics seem to vary with age, but there is no data on old animals or those with hypertension, major factors influencing ICH risk and outcome.

METHODS

We assessed hematoma volume, edema, ICP, and functional deficits in young and aged spontaneously hypertensive rats (SHRs) and young normotensive control strains after collagenase-induced ICH. Macroscopic and microscopic brain volume fractions, such as contralateral hemisphere volume, cortical thickness, and neuronal morphology, were assessed via histological and stereological techniques.

RESULTS

Hematoma volume was 52% larger in young versus aged SHRs; surprisingly, aged SHRs still experienced proportionally worse outcomes following ICH, with 2× greater elevations in edema and ICP relative to bleed volume and 3× the degree of tissue compliance. Aged SHRs also experienced equivalent neurological deficits following ICH compared with their younger counterparts, despite the lack of significant age-related behavioral effects. Importantly, tissue compliance occurred across strains and age groups and was not impaired by hypertension or old age.

CONCLUSIONS

Aged SHRs show considerable capacity for tissue compliance following ICH and seem to rely on such mechanisms more heavily in settings of elevated ICP. Therefore, the ICP compensation response to ICH mass effect varies across the lifespan according to risk factors such as chronic hypertension.

Unraveling the role of galectin-3 in cardiac pathology and physiology

Galectin-3 (Gal-3) is a carbohydrate-binding protein with multiple functions. Gal-3 regulates cell growth, proliferation, and apoptosis by orchestrating cell-cell and cell-matrix interactions. It is implicated in the development and progression of cardiovascular disease, and its expression is increased in patients with heart failure. In atherosclerosis, Gal-3 promotes monocyte recruitment to the arterial wall boosting inflammation and atheroma. In acute myocardial infarction (AMI), the expression of Gal-3 increases in infarcted and remote zones from the beginning of AMI, and plays a critical role in macrophage infiltration, differentiation to M1 phenotype, inflammation and interstitial fibrosis through collagen synthesis. Genetic deficiency of Gal-3 delays wound healing, impairs cardiac remodeling and function after AMI. On the contrary, Gal-3 deficiency shows opposite results with improved remodeling and function in other cardiomyopathies and in hypertension. Pharmacologic inhibition with non-selective inhibitors is also protective in cardiac disease. Finally, we recently showed that Gal-3 participates in normal aging. However, genetic absence of Gal-3 in aged mice exacerbates pathological hypertrophy and increases fibrosis, as opposed to reduced fibrosis shown in cardiac disease. Despite some gaps in understanding its precise mechanisms of action, Gal-3 represents a potential therapeutic target for the treatment of cardiovascular diseases and the management of cardiac aging. In this review, we summarize the current knowledge regarding the role of Gal-3 in the pathophysiology of heart failure, atherosclerosis, hypertension, myocarditis, and ischemic heart disease. Furthermore, we describe the physiological role of Gal-3 in cardiac aging.

Heterogeneous vasomotor responses in segments from Göttingen Minipigs coronary, cerebral, and mesenteric artery: A comparative study

Göttingen Minipigs (GM) are used as an important preclinical model for cardiovascular safety pharmacology and for evaluation of cardiovascular drug targets. To improve the translational value of the GM model, the current study represents a basic characterization of vascular responses to endothelial regulators and sympathetic, parasympathetic, and sensory neurotransmitters in different anatomical origins. The aim of the current comparative and descriptive study is to use myography to characterize the vasomotor responses of coronary artery isolated from GM and compare the responses to those obtained from parallel studies using cerebral and mesenteric arteries. The selected agonists for sympathetic (norepinephrine), parasympathetic (carbachol), sensory (calcitonin gene-related peptide, CGRP), and endothelial pathways (endothelin-1, ET-1, and bradykinin) were used for comparison. Further, the robust nature of the vasomotor responses was evaluated after 24 h of cold storage of vascular tissue mimicking the situation under which human biopsies are often kept before experiments or grafting is feasible. Results show that bradykinin and CGRP consistently dilated, and endothelin consistently contracted artery segments from coronary, cerebral, and mesenteric origin. By comparison, norepinephrine and carbachol, had responses that varied with the anatomical source of the tissues. To support the basic characterization of GM vasomotor responses, we demonstrated the presence of mRNA encoding selected vascular receptors (CGRP- and ETA-receptors) in fresh artery segments. In conclusion, the vasomotor responses of isolated coronary, cerebral, and mesenteric arteries to selected agonists of endothelial, sympathetic, parasympathetic, and sensory pathways are different and the phenotypes are similar to sporadic human findings.

FRESH™ 3D bioprinted cardiac tissue, a bioengineered platform for in vitro pharmacology

There is critical need for a predictive model of human cardiac physiology in drug development to assess compound effects on human tissues. In vitro two-dimensional monolayer cultures of cardiomyocytes provide biochemical and cellular readouts, and in vivo animal models provide information on systemic cardiovascular response. However, there remains a significant gap in these models due to their incomplete recapitulation of adult human cardiovascular physiology. Recent efforts in developing in vitro models from engineered heart tissues have demonstrated potential for bridging this gap using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in three-dimensional tissue structure. Here, we advance this paradigm by implementing FRESH™ 3D bioprinting to build human cardiac tissues in a medium throughput, well-plate format with controlled tissue architecture, tailored cellular composition, and native-like physiological function, specifically in its drug response. We combined hiPSC-CMs, endothelial cells, and fibroblasts in a cellular bioink and FRESH™ 3D bioprinted this mixture in the format of a thin tissue strip stabilized on a tissue fixture. We show that cardiac tissues could be fabricated directly in a 24-well plate format were composed of dense and highly aligned hiPSC-CMs at >600 million cells/mL and, within 14 days, demonstrated reproducible calcium transients and a fast conduction velocity of ∼16 cm/s. Interrogation of these cardiac tissues with the β-adrenergic receptor agonist isoproterenol showed responses consistent with positive chronotropy and inotropy. Treatment with calcium channel blocker verapamil demonstrated responses expected of hiPSC-CM derived cardiac tissues. These results confirm that FRESH™ 3D bioprinted cardiac tissues represent an in vitro platform that provides data on human physiological response.

Translational tissue-engineered vascular grafts: From bench to bedside

Cardiovascular disease is a primary cause of mortality worldwide, and patients often require bypass surgery that utilizes autologous vessels as conduits. However, the limited availability of suitable vessels and the risk of failure and complications have driven the need for alternative solutions. Tissue-engineered vascular grafts (TEVGs) offer a promising solution to these challenges. TEVGs are artificial vascular grafts made of biomaterials and/or vascular cells that can mimic the structure and function of natural blood vessels. The ideal TEVG should possess biocompatibility, biomechanical mechanical properties, and durability for long-term success in vivo. Achieving these characteristics requires a multi-disciplinary approach involving material science, engineering, biology, and clinical translation. Recent advancements in scaffold fabrication have led to the development of TEVGs with improved functional and biomechanical properties. Innovative techniques such as electrospinning, 3D bioprinting, and multi-part microfluidic channel systems have allowed the creation of intricate and customized tubular scaffolds. Nevertheless, multiple obstacles must be overcome to apply these innovations effectively in clinical practice, including the need for standardized preclinical models and cost-effective and scalable manufacturing methods. This review highlights the fundamental approaches required to successfully fabricate functional vascular grafts and the necessary translational methodologies to advance their use in clinical practice.

Adenosine A2A receptors in the rostral ventrolateral medulla participate in blood pressure decrease with electroacupuncture in hypertensive rats

Acupuncture is increasingly used to manage high blood pressure (BP) as a complementary therapy. However, the mechanisms underlying its hypotensive effects remain unclear. Our previous studies have shown that electroacupuncture (EA) at the ST36-37 acupoints, overlying the deep peroneal nerve, attenuates pressor responses through adenosine A2A receptors (A2AR) in the rostral ventrolateral medulla (rVLM). However, it is uncertain whether rVLM A2AR contributes to EA's BP-lowering effect in sustained hypertension. We hypothesized that a course of EA treatment lowers BP, in part, through the activation of adenosine A2AR in the rVLM in hypertensive rats. To mimic essential hypertension in the clinic, we performed EA in conscious Dahl salt-sensitive hypertensive rats (DSHRs). EA (0.1-0.4 mA, 2 Hz) was applied at ST36-37 for 30 min twice weekly for four weeks, while sham-EA was conducted in a similar manner but without electrical input. In hypertensive rats, BP was reduced by EA (n = 14) but neither by sham-EA (n = 14) nor in the absence of needling (n = 8). Following four weeks of eight treatments and then under anesthesia, EA's modulatory effect on elevated BP was reversed by unilateral rVLM microinjection of SCH 58261 (1 mM in 50 nl; an A2AR antagonist; n = 7; P < 0.05) but not the vehicle (n = 5) in EA-treated DSHRs. Activation of rVLM A2AR in DSHRs treated with sham-EA by an A2AR agonist, CGS-21680 (0.4 mM in 50 nl; n = 8), decreased BP. Unilateral administration of SCH 58261 or CGS-21680 into the rVLM did not alter basal BP in Dahl salt-sensitive rats fed a regular diet with normal BP. The A2AR level in the rVLM after EA was increased compared to the sham-EA and untreated DSHRs (n = 5 in each group; all P < 0.05). These data suggest that a 4-week twice weekly EA treatment reduced BP in salt-sensitive hypertensive rats likely through adenosine-mediated A2AR in the rVLM.

Neurochemical alterations of intrinsic cardiac ganglionated nerve plexus caused by arterial hypertension developed during ageing in spontaneously hypertensive and Wistar Kyoto rats

The acknowledged hypothesis of the cause of arterial hypertension is the emerging disbalance in sympathetic and parasympathetic regulations of the cardiovascular system. This disbalance manifests in a disorder of sustainability of endogenous autonomic and sensory neural substances including calcitonin gene-related peptide (CGRP). This study aimed to examine neurochemical alterations of intrinsic cardiac ganglionated nerve plexus (GP) triggered by arterial hypertension during ageing in spontaneously hypertensive rats of juvenile (prehypertensive, 8-9 weeks), adult (early hypertensive, 12-18 weeks) and elderly (persistent hypertensive, 46-60 weeks) age in comparison with the age-matched Wistar-Kyoto rats as controls. Parasympathetic, sympathetic and sensory neural structures of GP were analysed and evaluated morphometrically in tissue sections and whole-mount cardiac preparations. Both the elevated blood pressure and the evident ultrasonic signs of heart failure were identified for spontaneously hypertensive rats and in part for the aged control rats. The amount of adrenergic and immunoreactive to CGRP neural structures was increased in the adult group of spontaneously hypertensive rats along with the significant alterations that occurred during ageing. In conclusion, the revealed chemical alterations of GP support the hypothesis about the possible disbalance of efferent and afferent heart innervation and may be considered as the basis for the emergence and progression of arterial hypertension and perhaps even as a consequence of hypertension in the aged spontaneously hypertensive rats. The determined anatomical changes in the ageing Wistar-Kyoto rats suggest this breed being as inappropriate for its use as control animals for hypertension studies in older animal age.

The Epigenetic Legacy of Maternal Protein Restriction: Renal Ptger1 DNA Methylation Changes in Hypertensive Rat Offspring

Nutrient imbalances during gestation are a risk factor for hypertension in offspring. Although the effects of prenatal nutritional deficiency on the development of hypertension and cardiovascular diseases in adulthood have been extensively documented, its underlying mechanisms remain poorly understood. In this study, we aimed to elucidate the precise role and functional significance of epigenetic modifications in the pathogenesis of hypertension. To this end, we integrated methylome and transcriptome data to identify potential salt-sensitive hypertension genes using the kidneys of stroke-prone spontaneously hypertensive rat (SHRSP) pups exposed to a low-protein diet throughout their fetal life. Maternal protein restriction during gestation led to a positive correlation between DNA hypermethylation of the renal prostaglandin E receptor 1 (Ptger1) CpG island and high mRNA expression of Ptger1 in offspring, which is consistently conserved. Furthermore, post-weaning low-protein or high-protein diets modified the Ptger1 DNA hypermethylation caused by fetal malnutrition. Here, we show that this epigenetic variation in Ptger1 is linked to disease susceptibility established during fetal stages and could be reprogrammed by manipulating the postnatal diet. Thus, our findings clarify the developmental origins connecting the maternal nutritional environment and potential epigenetic biomarkers for offspring hypertension. These findings shed light on hypertension prevention and prospective therapeutic strategies.

Infused juice concentrate of Japanese plum Prunus mume attenuates inflammatory vascular remodeling in a mouse model of hypertension induced by angiotensin II

Fruit from the Prunus mume tree is a traditional food in Japan. Recently, bainiku-ekisu, an infused juice concentrate of Japanese Prunus mume, is attracting attention as a health promoting supplement. Angiotensin II (Ang II) plays a central role in development of hypertension. It has been reported that bainiku-ekisu treatment attenuates the growth-promoting signaling induced by Ang II in vascular smooth muscle cells. However, whether bainiku-ekisu has any effect on an animal model of hypertension remains unknown. Therefore, this study was designed to explore the potential anti-hypertensive benefit of bainiku-ekisu utilizing a mouse model of hypertension with Ang II infusion. Male C57BL/6 mice were infused with Ang II for 2 weeks and given 0.1% bainiku-ekisu containing water or normal water for 2 weeks with blood pressure evaluation. After 2 weeks, mice were euthanized, and the aortas were collected for evaluation of remodeling. Aortic medial hypertrophy was observed in control mice after Ang II infusion, which was attenuated in bainiku-ekisu group with Ang II infusion. Bainiku-ekisu further attenuated aortic induction of collagen producing cells and immune cell infiltration. Development of hypertension induced by Ang II was also prevented by bainiku-ekisu. Echocardiograph indicated protection of Ang II-induced cardiac hypertrophy by bainiku-ekisu. In vascular fibroblasts, bainiku-ekisu attenuated vascular cell adhesion molecule-1 induction, an endoplasmic reticulum stress marker, inositol requiring enzyme-1α phosphorylation, and enhancement in glucose consumption in response to Ang II. In conclusion, Bainiku-ekisu prevented Ang II-induced hypertension and inflammatory vascular remodeling. Potential cardiovascular health benefit to taking bainiku-ekisu should be further studied.

Intestinal Cckbr-specific knockout mouse as a novel model of salt-sensitive hypertension via sodium over-absorption

OBJECTIVES

To investigate the value of CCKBRfl/fl villin-Cre mice as a mouse model of salt-sensitive hypertension (SSH).

METHODS

In the first part, 2-month-old CCKBRfl/fl villin-Cre mice (CKO) and control CCKBRfl/fl mice (WT) were fed with normal diet (0.4% NaCl) or high salt diet (4% NaCl), separately for 6 weeks. In the rescue study, one week of hydrochlorothiazide or saline injection were treated with the CKO mice fed high salt diet. The blood pressure, biochemical indexes, and the expression of small intestinal sodium transporters (NHE3, NKCC1, eNaC) was detected. The organ injury markers (MMP2/MMP9) and the histopathological changes of kidneys were observed, whereas the changes of duodenal sodium absorption were detected by small intestinal perfusion in vivo.

RESULTS

The CCKBRfl/fl villin-Cre mice with high salt intake exhibited high blood pressure, increased duodenal sodium absorption and urinary sodium excretion, and with renal injury. The protein expression of NHE3, NKCC1 and eNaC were also significant increase in the intestine of CKO-HS mice. Treatment with hydrochlorothiazide remarkably attenuated the elevated blood pressure by high salt absorption in the CCKBRfl/fl villin-Cre mice, but no significant histopathological changes were observed.

CONCLUSIONS

These results support a crucial role of intestinal Cckbr deficiency on SSH development and the diuretic antihypertension effect in CCKBRfl/fl villin-Cre mice. The CCKBRfl/fl villin-Cre mice with the high salt intake may serve as a stable model of salt-sensitive hypertensive induced by sodium overloading.

Mouse models of cerebral injury and cognitive impairment in hypertension

Hypertension is a major risk factor for dementia, including both vascular and neurodegenerative etiologies. With the original aim of studying the effect of blood pressure elevation on canonical target organs of hypertension as the heart, the vasculature or the kidneys, several experimental models of hypertension have sprouted during the years. With the more recent interest of understanding the cerebral injury burden caused by hypertension, it is worth understanding how the main models of hypertension or localized cerebral hypertension stand in the field of hypertension-induced cerebral injury and cognitive impairment. With this review we will report main genetic, pharmacological and surgical models of cognitive impairment induced by hypertension, summarizing how each specific category and model can improve our understanding of the complex phenomenon of cognitive loss of vascular etiology.

Diversity of cells and signals in the cardiovascular system

This white paper is the outcome of the seventh UC Davis Cardiovascular Research Symposium on Systems Approach to Understanding Cardiovascular Disease and Arrhythmia. This biannual meeting aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2022 Symposium was 'Cell Diversity in the Cardiovascular System, cell-autonomous and cell-cell signalling'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies, and challenges in examining cell and signal diversity, co-ordination and interrelationships involved in cardiovascular function. This paper originates from the topics of formal presentations and informal discussions from the Symposium, which aimed to develop a holistic view of how the multiple cell types in the cardiovascular system integrate to influence cardiovascular function, disease progression and therapeutic strategies. The first section describes the major cell types (e.g. cardiomyocytes, vascular smooth muscle and endothelial cells, fibroblasts, neurons, immune cells, etc.) and the signals involved in cardiovascular function. The second section emphasizes the complexity at the subcellular, cellular and system levels in the context of cardiovascular development, ageing and disease. Finally, the third section surveys the technological innovations that allow the interrogation of this diversity and advancing our understanding of the integrated cardiovascular function and dysfunction.

Sex- and age-related differences in renal and cardiac injury and senescence in stroke-prone spontaneously hypertensive rats

BACKGROUND

Sex differences play a critical role in the incidence and severity of cardiovascular diseases, whereby men are at a higher risk of developing cardiovascular disease compared to age-matched premenopausal women. Marked sex differences at the cellular and tissue level may contribute to susceptibility to cardiovascular disease and end-organ damage. In this study, we have performed an in-depth histological analysis of sex differences in hypertensive cardiac and renal injury in middle-aged stroke-prone spontaneously hypertensive rats (SHRSPs) to determine the interaction between age, sex and cell senescence.

METHODS

Kidneys, hearts and urine samples were collected from 6.5- and 8-month-old (Mo) male and female SHRSPs. Urine samples were assayed for albumin and creatinine content. Kidneys and hearts were screened for a suite of cellular senescence markers (senescence-associated β-galactosidase, p16^INK4a, p21, γH2AX). Renal and cardiac fibrosis was quantified using Masson's trichrome staining, and glomerular hypertrophy and sclerosis were quantified using Periodic acid-Schiff staining.

RESULTS

Marked renal and cardiac fibrosis, concomitant with albuminuria, were evident in all SHRSPs. These sequelae were differentially affected by age, sex and organ. That is, the level of fibrosis was greater in the kidney than the heart, males had greater levels of fibrosis than females in both the heart and kidney, and even a 6-week increase in age resulted in greater levels of kidney fibrosis in males. The differences in kidney fibrosis were reflected by elevated levels of cellular senescence in the kidney in males but not females. Senescent cell burden was significantly less in cardiac tissue compared to renal tissue and was not affected by age or sex.

CONCLUSIONS

Our study demonstrates a clear sex pattern in age-related progression of renal and cardiac fibrosis and cellular senescence in SHRSP rats. A 6-week time frame was associated with increased indices of cardiac and renal fibrosis and cellular senescence in male SHRSPs. Female SHRSP rats were protected from renal and cardiac damage compared to age-matched males. Thus, the SHRSP is an ideal model to investigate the effects of sex and aging on organ injury over a short timeframe.

Sex differences in blood pressure, free radicals and plasma cholesterol fractions in Ren-2 transgenic rats of various ages

Sex-related cardiovascular differences were observed in humans as well as in experimental animals. Our previous study demonstrated a marked sexual dimorphism in blood pressure (BP) of 9-month-old heterozygous transgenic Ren 2 rats (TGR), in which mouse Ren-2 renin gene was inserted into the genome of normotensive Hannover Sprague-Dawley rats (HanSD). We found significantly elevated BP only in male TGR, whereas BP of TGR females was similar to that of HanSD females. The aim of our present study was to compare BP of 3- and 6-month-old heterozygous TGR with age- and sex-matched HanSD under the same conditions as we measured in 9-month-old rats. We also monitored the amount of oxidative stress marker, thiobarbituric acid-reactive substances (TBARS), and a main intracellular antioxidant, reduced glutathione in the heart, kidneys and liver. We also measured plasma triglycerides and cholesterol levels. We found an increased mean arterial pressure in both female and male 3-month-old TGR (172±17 vs. 187±4 mm Hg, respectively) compared to HanSD (115±5 vs. 133±3 mm Hg, respectively) but there was a marked sexual dimorphism of 6 month-old TGR where only males were hypertensive (145±5 mm Hg) while females became normotensive (123±7 mm Hg). We did not find any relationship between BP values and concentrations of TBARS or glutathione or plasma lipid levels. Our results demonstrated that 6-month-old TGR exhibited a marked sexual BP dimorphism, which was not dependent on the abnormalities in oxidative stress or cholesterol metabolism.

Exploitation of In Vivo-Emulated In Vitro System in Advanced Food Science

Reasonable model construction contributes to the accuracy of experimental results. Multiple in vivo models offer reliable choices for effective evaluation, whereas their applications are hampered due to adverse features including high time-consumption, high cost and ethical contradictions. In vivo-emulated in vitro systems (IVE systems) have experienced rapid development and have been brought into food science for about two decades. IVE systems' flexibly gathers the strengths of in vitro and in vivo models into one, reflecting the results in an efficient, systematic and interacted manner. In this review, we comprehensively reviewed the current research progress of IVE systems based on the literature published in the recent two decades. By categorizing the IVE systems into 2D coculture models, spheroids and organoids, their applications were systematically summarized and typically exemplified. The pros and cons of IVE systems were also thoroughly discussed, drawing attention to present challenges and inspiring potential orientation and future perspectives. The wide applicability and multiple possibilities suggest IVE systems as an effective and persuasive platform in the future of advanced food science.

Short exposure to high salt in drinking solution leads to a cardiovascular phenotype of hypertension without changes in the blood volume of rats

NEW FINDINGS

What is the central question of this study? Is the cardiovascular phenotype of high blood pressure observed in rats salt loaded with 2% NaCl in drinking solution a blood volume-dependent hypertension? What is the main finding and its importance? Animals exposed to 2% NaCl drinking solution develop hypertension, with dominance of sympathetic outflow and high [Na+ ] in the cerebrospinal fluid, but without changes in the blood volume. The phenotype of salt-dependent hypertension might be related to accumulation of [Na+ ] in the cerebrospinal fluid, which makes it an interesting animal model in which to study the neuronal pathways involved in control of the circulation in osmotic challenge conditions.

ABSTRACT

Evidence suggests that hypertension induced by high salt intake is correlated with an autonomic imbalance that favours sympathetic hyperactivity and an increase in vascular resistance, indicating a neurogenic component to this pathology. Although there are several animal models in which to study salt-induced hypertension with prolonged exposure to a high-sodium diet, here we sought to investigate whether the increase in arterial blood pressure of rats subjected to a short exposure to high salt, with 2% NaCl drinking solution instead of water, relies on changes in the circulating blood volume. Male Wistar rats were divided randomly into three groups: euhydrated (EU, n = 10), salt loaded (SL, n = 13) and water deprived (WD, n = 6). The SL rats exhibited a significant increase in mean arterial blood pressure, with a large low-frequency component of systolic arterial blood pressure variability, when compared with the EU group. Circulating blood volume did not differ between SL and EU rats, but it was lower in WD rats. Compared with EU rats, the [Na+ ] in cerebrospinal fluid was higher in SL rats and similar in magnitude to the WD rats. Plasma [Na+ ] did not differ between SL and EU rats, but it was higher in WD rats. Collectively, our data suggest that the hypertension induced by a short exposure to high salt intake closely resembles a neurogenic mechanism, but not a blood volume-dependent mechanism, with cumulative [Na+ ] in the cerebrospinal fluid that could be associated with changes in the neurochemistry of autonomic nuclei, which are highly susceptible to osmotic stress related to high salt consumption.

The co-expression of steroidogenic enzymes with T1R3 during testicular development in the Congjiang Xiang pig

Testosterone is a key crucial hormone synthesized by steroidogenic enzymes that initiate and maintain spermatogenesis and secondary sexual characteristics in adult males. The taste receptor family 1 subunit 3 (T1R3) is reported to be associated with male reproduction. T1R3 can regulate the expressions of steroidogenic enzymes and affect testosterone synthesis. In this study, we addressed the question of whether the expression of steroid synthase was associated with T1R3 and its downstream-tasting molecules during testicular development. The results showed an overall upward trend in testosterone and morphological development in testes from Congjiang Xiang pigs from pre-puberty to sexual maturity. Gene expression levels of testicular steroidogenic acute regulatory protein (StAR), 3β-hydroxysteroid dehydrogenase (3β-HSD), cytochrome P450c17 (CYP17A1) and 17β-hydroxysteroid dehydrogenase (17β-HSD) were increased from pre-puberty to sexual maturity. Protein expression changes of CYP17A1 and 3β-HSD were consistent with mRNA. The relative abundance of tasting molecules (TAS1R3, phospholipase Cβ2, PLCβ2) was increased from pre-puberty to puberty (P < 0.05), with no further significant changes in expression from puberty to sexual maturity. Steroidogenic enzymes (3β-HSD and CYP17A1) were strongly detected in Leydig cells from pre-puberty to sexual maturity, while tasting molecules were localized in Leydig cells and spermatogenic cells. Correlation analysis showed that the genes mentioned above (except for PLCβ2) were positively correlated with testosterone levels and morphological characteristics of the testes at different developmental stages of Congjiang Xiang pigs. These results suggest that steroidogenic enzymes regulate testosterone synthesis and testicular development, and that taste receptor T1R3, but not PLCβ2, may associate with this process.

Angiotensin II Type 1A Receptor Expressed in Smooth Muscle Cells is Required for Hypertensive Vascular Remodeling in Mice Infused With Angiotensin II

BACKGROUND

Ang II (angiotensin II) type 1 (AT1) receptors play a critical role in cardiovascular diseases such as hypertension. Rodents have 2 types of AT1 receptor (AT1A and AT1B) of which knock-in Tagln-mediated smooth muscle AT1A silencing attenuated Ang II-induced hypertension. Although vascular remodeling, a significant contributor to organ damage, occurs concurrently with hypertension in Ang II-infused mice, the contribution of smooth muscle AT1A in this process remains unexplored. Accordingly, it is hypothesized that smooth muscle AT1A receptors exclusively contribute to both medial thickening and adventitial fibrosis regardless of the presence of hypertension.

METHODS

About 1 µg/kg per minute Ang II was infused for 2 weeks in 2 distinct AT1A receptor silenced mice, knock-in Tagln-mediated constitutive smooth muscle AT1A receptor silenced mice, and Myh11-mediated inducible smooth muscle AT1A together with global AT1B silenced mice for evaluation of hypertensive cardiovascular remodeling.

RESULTS

Medial thickness, adventitial collagen deposition, and immune cell infiltration in aorta were increased in control mice but not in both smooth muscle AT1A receptor silenced mice. Coronary arterial perivascular fibrosis in response to Ang II infusion was also attenuated in both AT1A receptor silenced mice. Ang II-induced cardiac hypertrophy was attenuated in constitutive smooth muscle AT1A receptor silenced mice. However, Ang II-induced cardiac hypertrophy and hypertension were not altered in inducible smooth muscle AT1A receptor silenced mice.

CONCLUSIONS

Smooth muscle AT1A receptors mediate Ang II-induced vascular remodeling including medial hypertrophy and inflammatory perivascular fibrosis regardless of the presence of hypertension. Our data suggest an independent etiology of blood pressure elevation and hypertensive vascular remodeling in response to Ang II.

Activation of the Mas receptors by AVE0991 and MrgD receptor using alamandine to limit the deleterious effects of Ang II-induced hypertension

The MrgD receptor agonist, alamandine (ALA) and Mas receptor agonist, AVE0991 have recently been identified as protective components of the renin-angiotensin system. We evaluated the effects of ALA and AVE0991 on cardiovascular function and remodeling in angiotensin (Ang) II-induced hypertension in rats. Sprague Dawley rats were subject to 4-week subcutaneous infusions of Ang II (80 ng/kg/min) or saline after which they were treated with ALA (50 μg/kg), AVE0991 (576 μg/kg), or ALA+AVE0991 during the last 2 weeks. Systolic blood pressure (SBP) and heart rate (HR) values were recorded with tail-cuff plethysmography at 1, 15, and 29 days post-treatment. After euthanization, the heart and thoracic aorta were removed for further analysis and vascular responses. SBP significantly increased in the Ang II group when compared to the control group. Furthermore, Ang II also caused an increase in cardiac and aortic cyclophilin-A (CYP-A), monocyte chemoattractant protein-1 (MCP-1), and cardiomyocyte degeneration but produced a decrease in vascular relaxation. HR, matrix metalloproteinase-2 and -9, NADPH oxidase-4, and lysyl oxidase levels were comparable among groups. ALA, AVE0991, and the drug combination produced antihypertensive effects and alleviated vascular responses. The inflammatory and oxidative stress related to cardiac MCP-1 and CYP-A levels decreased in the Ang II+ALA+AVE0991 group. Vascular but not cardiac angiotensin-converting enzyme-2 levels decreased with Ang II administration but were similar to the Ang II+ALA+AVE0991 group. Our experimental data showed the combination of ALA and AVE0991 was found beneficial in Ang II-induced hypertension in rats by reducing SBP, oxidative stress, inflammation, and improving vascular responses.

Table olive elicits antihypertensive activity in spontaneously hypertensive rats

BACKGROUND

Table olives are a food with a high content of bioactive compounds with cardioprotective properties, such as oleic acid, polyphenols, and pentacyclic triterpenes. Here, we investigate the effect of the intake of table olives on blood pressure (BP) and body weight in spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar Kyoto (WKY) rats. 'Arbequina' table olives (3.85 g kg^-1 ) were administered by gavage to SHR and WKY rats in short-term (1 day) and long-term (7 weeks) experiments. BP was measured by the tail-cuff method, and polyphenols and triterpenes were determined in olives and plasma by liquid chromatography-mass spectrometry.

RESULTS

Administration of 'Arbequina' olives to WKY rats did not exert any change in BP in any of the experiments. However, in SHR, the single dose induced a transient reduction in BP of approximately 15 mmHg, from the second to the tenth hour after the administration. In the long-term assay, a similar decrease was established in the second week and was maintained throughout the experiment. Moreover, the daily administration of olives to rats did not affect their body weight when compared with controls in either the WKY rats or SHR. The determination of polyphenols and triterpenes in plasma indicated that, at the end of the experiment, only maslinic acid, oleanolic acid, hydroxytyrosol, and luteolin were found, all of them being compounds with already described capacity to decrease BP.

CONCLUSION

The results suggest that the daily intake of table olives could decrease BP in hypertension without affecting body weight, indicating that table olives could contribute to improving cardiovascular health. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Zhijing powder manages blood pressure by regulating PI3K/AKT signal pathway in hypertensive rats

Background

Zhijing Powder (ZJP) is a traditional Chinese medicine containing two kinds of Chinese medicine. Those studies analyze the molecular mechanism of ZJP in treating hypertension through network pharmacology, combined with animal experiments.

Methods

First, the effective ingredients and potential targets of the drug were obtained through drug databases, while the targets of disease obtained through disease target databases. The potential targets, cellular bioanalysis and signaling pathways were found in some platforms by analyzing collected targets. Further experiments were conducted to verify the effect and mechanism of drugs on cold and high salt in an induced-hypertension rat model.

Results

There are 17 effective components of centipedes and 10 of scorpions, with 464 drug targets obtained after screening. A total of 1263 hypertension targets were obtained after screening and integration, resulting in a protein-protein interaction network (PPI) with 145 points and 1310 edges. Gene ontology (GO) analysis shows that blood circulation regulation and activation of G protein-coupled receptors are mainly biological processes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis shows that neuroactive ligand-receptor interaction, calcium signaling pathways, PI3K-AKT signaling pathways are the most abundant gene-enriched pathway. Animal experiments indicated that ZJP can reduce blood pressure (BP), affect expression of the PI3K-AKT signaling pathway, and improve oxidative stress in the body.

Conclusion

ZJP ameliorates oxidative stress and reduces BP in hypertensive rats caused by cold stimuli and high salt, revealing its effect on the expression of the PI3K/AKT signaling pathway in the rat aorta.

The association between arterial stiffness and cancer occurrence: Data from Kailuan cohort study

Background

This study aimed to investigate whether increased arterial stiffness, measured by brachial-ankle pulse wave velocity (baPWV) is associated with cancer.

Materials and methods

A total of 45,627 Chinese adults underwent a baPWV examination. The participants were followed up from 1st January 2012 to 31st December 2018. Cox proportional hazards model was used to assess the association between the baPWV values and cancer.

Results

During a total follow-up duration of 172,775.69 person-years, there were 553 new cases of cancer. The subjects in the highest baPWV group showed an increased risk of cancer when compared with the lowest baPWV group as confirmed by multivariate-adjusted hazard ratios (HR = 1.51, 95% CI = 1.14∼2.00) in the entire cohort. Compared with participants in the lowest baPWV group, the HRs (95% CI) for digestive cancer in the second and third groups were 1.55 (1.00∼2.40) and 1.99 (1.19∼3.33), respectively. The Kaplan-Meier analysis demonstrated a significant increase in cancer in participants with a baPWV ≥ 18 m/s (P < 0.001). Compared with the lowest baPWV group, the highest baPWV group showed an increased risk of cancer in men (HR = 1.72, 95% CI = 1.22∼2.43) and those < 60 years (HR = 1.75, 95% CI = 1.20∼2.55), respectively.

Conclusion

Increased arterial stiffness measured by baPWV is associated with cancer occurrence, especially digestive cancer occurrence.

Clinical trial registration

ClinicalTrials.gov, identifier ChiCTR-TNRC-11001489.

Role of blood-borne factors in sympathoexcitation-mediated hypertension: Potential neurally mediated hypertension in preeclampsia

Hypertension remains a threat for society due to its unknown causes, preventing proper management, for the growing number of patients, for its state as a high-risk factor for stroke, cardiac and renal complication and as cause of disability. Data from clinical and animal researches have suggested the important role of many soluble factors in the pathophysiology of hypertension through their neuro-stimulating effects. Central targets of these factors are of molecular, cellular and structural nature. Preeclampsia (PE) is characterized by high level of soluble factors with strong pro-hypertensive activity and includes immune factors such as proinflammatory cytokines (PICs). The potential neural effect of those factors in PE is still poorly understood. Shedding light into the potential central effect of the soluble factors in PE may advance our current comprehension of the pathophysiology of hypertension in PE, which will contribute to better management of the disease. In this paper, we summarized existing data in respect of hypothesis of this review, that is, the existence of the neural component in the pathophysiology of the hypertension in PE. Future studies would address this hypothesis to broaden our understanding of the pathophysiology of hypertension in PE.

In Vitro and In Vivo Antihypertensive Effect of Milk Fermented with Different Strains of Common Starter Lactic Acid Bacteria

Currently, functional dairy products pave a promising way for the prophylaxis of essential hypertension, and the search for new strains capable of producing such products is a constant challenge for scientists around the world. In this study, the antihypertensive properties of milk fermented with several strains of traditional yogurt starters (Lactobacillus delbrueckii strains Lb100 and Lb200; Lactococcus lactis strains dlA, AM1 and MA1; Streptococcus thermophilus strains 159 and 16t) and one strain of non-conventional probiotic starter (Lacticaseibacillus paracasei ABK) were assessed. The in vitro assessment using angiotensin-converting enzyme inhibition assay was performed for all fermentation products, and the best performed products were tested in vivo using Spontaneously Hypertensive Rat (SHR) animal model. In addition, for the best performed products the fatty acid (FA) composition and FA-related nutritional indices were determined. As a result, the milk fermented with two strains (Lb. delbrueckii LB100 and Lc. lactis AM1) demonstrated significant antihypertensive effect during both in vitro and in vivo experiments. Moreover, the milk fermented with Lb. delbrueckii Lb100 demonstrated significantly better FA-related nutritional indexes and lowered total cholesterol in SHRs upon regular consumption. The obtained results can be used in the future to develop new starter cultures producing effective functional antihypertensive dairy products.

Estrogen receptor beta activity contributes to both tumor necrosis factor alpha expression in the hypothalamic paraventricular nucleus and the resistance to hypertension following angiotensin II in female mice

Sex differences in the sensitivity to hypertension and inflammatory processes are well characterized but insufficiently understood. In male mice, tumor necrosis factor alpha (TNFα) in the hypothalamic paraventricular nucleus (PVN) contributes to hypertension following slow-pressor angiotensin II (AngII) infusion. However, the role of PVN TNFα in the response to AngII in female mice is unknown. Using a combination of in situ hybridization, high-resolution electron microscopic immunohistochemistry, spatial-temporal gene silencing, and dihydroethidium microfluorography we investigated the influence of AngII on both blood pressure and PVN TNFα signaling in female mice. We found that chronic (14-day) infusion of AngII in female mice did not impact blood pressure, TNFα levels, the expression of the TNFα type 1 receptor (TNFR1), or the subcellular distribution of TNFR1 in the PVN. However, it was shown that blockade of estrogen receptor β (ERβ), a major hypothalamic estrogen receptor, was accompanied by both elevated PVN TNFα and hypertension following AngII. Further, AngII hypertension following ERβ blockade was attenuated by inhibiting PVN TNFα signaling by local TNFR1 silencing. It was also shown that ERβ blockade in isolated PVN-spinal cord projection neurons (i.e. sympathoexcitatory) heightened TNFα-induced production of NADPH oxidase (NOX2)-mediated reactive oxygen species, molecules that may play a key role in mediating the effect of TNFα in hypertension. These results indicate that ERβ contributes to the reduced sensitivity of female mice to hypothalamic inflammatory cytokine signaling and hypertension in response to AngII.

Hypertension related toxicity of chloroquine explains its failure against COVID-19: Based on rat model

Chloroquine was once thought to be a promising treatment for COVID-19 but it quickly failed due to its inefficiency and association with increased mortality. Further, comorbidities such as hypertension may have contributed this failure. The safety and toxicity of chloroquine at doses required for treating SARS-CoV-2 infection in hypertensive patients remain unknown. Herein, to investigate these effects, we performed a safety evaluation of chloroquine at the approved dose (63 mg/kg) and at a high dose (126 mg/kg) in hypertensive rats. We found that chloroquine increased the mortality of hypertensive rats to 18.2% and 100%, respectively, after 7 days. During the chloroquine exposure period, the bodyweight, feed, and water consumption of hypertensive rats were decreased significantly. In addition, we show that chloroquine induces prolongation of QTc interval, elevation of LDH and CK, and histopathological damage of the myocardium in hypertensive rats. Ocular toxicity was observed in hypertensive rats in the form of hemorrhage in the eyes and retinal damage. Furthermore, we also observed intestinal toxicity in hypertensive rats, which presented as thinning intestinal walls with hemorrhagic contents, and histopathological changes of the jejunum. Hepatotoxicity was also evidenced by elevated ALT, and vacuolization of hepatocytes was also observed. Nephrotoxicity was observed only in high dose chloroquine-treated hypertensive rats, presenting as alterations of urinalysis and renal function. Immune alterations were also found in high-dose chloroquine-treated hypertensive rats with elevation of serum IL-10, IL-1β and GRO, and moderate damage to the spleen. In summary, this study partially explains the reason for the failure of chloroquine as a COVID-19 therapy, and underlines the importance of safety evaluation and medical supervision of chloroquine to avoid patient harm, especially to those with hypertension.

Knockout of the Circadian Clock Protein PER1 (Period1) Exacerbates Hypertension and Increases Kidney Injury in Dahl Salt-Sensitive Rats

BACKGROUND

Circadian rhythms play an essential role in physiological function. The molecular clock that underlies circadian physiological function consists of a core group of transcription factors, including the protein PER1 (Period1). Studies in mice show that PER1 plays a role in the regulation of blood pressure and renal sodium handling; however, the results are dependent on the strain being studied. Using male Dahl salt-sensitive (SS) rats with global knockout of PER1 (SSPer1-/-), we aim to test the hypothesis that PER1 plays a key role in the regulation of salt-sensitive blood pressure.

METHODS

The model was generated using CRISPR/Cas9 and was characterized using radiotelemetry and measures of renal function and circadian rhythm.

RESULTS

SSPer1-/- rats had similar mean arterial pressure when fed a normal 0.4% NaCl diet but developed augmented hypertension after three weeks on a high-salt (4% NaCl) diet. Despite being maintained on a normal 12:12 light:dark cycle, SSPer1-/- rats exhibited desynchrony mean arterial pressure rhythms on a high-salt diet, as evidenced by increased variability in the time of peak mean arterial pressure. SSPer1-/- rats excrete less sodium after three weeks on the high-salt diet. Furthermore, SSPer1-/- rats exhibited decreased creatinine clearance, a measurement of renal function, as well as increased signs of kidney tissue damage. SSPer1-/- rats also exhibited higher plasma aldosterone levels.

CONCLUSIONS

Altogether, our findings demonstrate that loss of PER1 in Dahl SS rats causes an array of deleterious effects, including exacerbation of the development of salt-sensitive hypertension and renal damage.

Endothelial and Vascular Smooth Muscle Dysfunction in Hypertension

The development of essential hypertension involves several factors. Vascular dysfunction, characterized by endothelial dysfunction, low-grade inflammation and structural remodeling, plays an important role in the initiation and maintenance of essential hypertension. Although the mechanistic pathways by which essential hypertension develops are poorly understood, several pharmacological classes available on the clinical settings improve blood pressure by interfering in the cardiac output and/or vascular function. This review is divided in two major sections. The first section depicts the major molecular pathways as renin angiotensin aldosterone system (RAAS), endothelin, nitric oxide signalling pathway and oxidative stress in the development of vascular dysfunction. The second section describes the role of some pharmacological classes such as i) RAAS inhibitors, ii) dual angiotensin receptor-neprilysin inhibitors, iii) endothelin-1 receptor antagonists, iv) soluble guanylate cyclase modulators, v) phosphodiesterase type 5 inhibitors and vi) sodium-glucose cotransporter 2 inhibitors in the context of hypertension. Some classes are already approved in the treatment of hypertension, but others are not yet approved. However, due to their potential benefits these classes were included.

Why Multitarget Vasodilatory (Endo)cannabinoids are Not Effective as Antihypertensive Compounds after Chronic Administration: Comparison of Their Effects on Systemic and Pulmonary Hypertension

Systemic and pulmonary hypertension are multifactorial, high-pressure diseases. The first one is a civilizational condition, and the second one is characterized by a very high mortality rate. Searching for new therapeutic strategies is still an important task. (Endo)cannabinoids, known for their strong vasodilatory properties, have been proposed as possible drugs for different types of hypertension. Unfortunately, our review, in which we summarized all publications found in the PubMed database regarding chronic administration of (endo)cannabinoids in experimental models of systemic and pulmonary hypertension, does not confirm any encouraging suggestions, being based mainly on in vitro and acute in vivo experiments. We considered vasodilator or blood pressure (BP) responses and cardioprotective, anti-oxidative, and the anti-inflammatory effects of particular compounds and their influence on the endocannabinoid system. We found that multitarget (endo)cannabinoids failed to modify higher BP in systemic hypertension since they induced responses leading to decreased and increased BP. In contrast, multitarget cannabidiol and monotarget ligands effectively treated pulmonary and systemic hypertension, respectively. To summarize, based on the available literature, only (endo)cannabinoids with a defined site of action are recommended as potential antihypertensive compounds in systemic hypertension, whereas both mono- and multitarget compounds may be effective in pulmonary hypertension.

Influence of electroacupuncture on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase signaling pathway in spontaneously hypertensive rats

OBJECTIVE

To investigate the influence of electroacupuncture (EA) on ghrelin and the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthase (PI3K/Akt/eNOS) signaling pathway in spontaneously hypertensive rats (SHRs).

METHODS

Eight Wistar-Kyoto rats were used as the healthy blood pressure (BP) control (normal group), and 32 SHRs were randomized into model group, EA group, EA plus ghrelin group (EA + G group), and EA plus PF04628935 group (a potent ghrelin receptor blocker; EA + P group) using a random number table. Rats in the normal group and model group did not receive treatment, but were immobilized for 20 min per day, 5 times a week, for 4 continuous weeks. SHRs in the EA group, EA + G group and EA + P group were immobilized and given EA treatment in 20 min sessions, 5 times per week, for 4 weeks. Additionally, 1 h before EA, SHRs in the EA + G group and EA + P group were intraperitoneally injected with ghrelin or PF04628935, respectively, for 4 weeks. The tail-cuff method was used to measure BP. After the 4-week intervention, the rats were sacrificed by cervical dislocation, and pathological morphology of the abdominal aorta was observed using hematoxylin-eosin (HE) staining. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of ghrelin, nitric oxide (NO), endothelin-1 (ET-1) and thromboxane A2 (TXA2) in the serum. Isolated thoracic aortic ring experiment was performed to evaluate vasorelaxation. Western blot was used to measure the expression of PI3K, Akt, phosphorylated Akt (p-Akt) and eNOS proteins in the abdominal aorta. Further, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to measure the relative levels of mRNA expression for PI3K, Akt and eNOS in the abdominal aorta.

RESULTS

EA significantly reduced the systolic BP (SBP) and diastolic BP (DBP) (P < 0.05). HE staining showed that EA improved the morphology of the vascular endothelium to some extent. Results of ELISA indicated that higher concentrations of ghrelin and NO, and lower concentrations of ET-1 and TXA2 were presented in the EA group (P < 0.05). The isolated thoracic aortic ring experiment demonstrated that the vasodilation capacity of the thoracic aorta increased in the EA group. Results of Western blot and qRT-PCR showed that EA increased the abundance of PI3K, p-Akt/Akt and eNOS proteins, as well as expression levels of PI3K, Akt and eNOS mRNAs (P < 0.05). In the EA + G group, SBP and DBP decreased (P < 0.05), ghrelin concentrations increased (P < 0.05), and the concentrations of ET-1 and TXA2 decreased (P < 0.05), relative to the EA group. In addition, the levels of PI3K and eNOS proteins, the p-Akt/Akt ratio, and the expression of PI3K, Akt and eNOS mRNAs increased significantly in the EA + G group (P < 0.05), while PF04628935 reversed these effects.

CONCLUSION

EA effectively reduced BP and protected the vascular endothelium, and these effects may be linked to promoting the release of ghrelin and activation of the PI3K/Akt/eNOS signaling pathway.

Angiotensin II differentially affects hippocampal glial inflammatory markers in young adult male and female mice

Hypertension is a risk factor for neurodegenerative disorders involving inflammation and inflammatory cytokine-producing brain cells (microglia and astrocytes) in the hippocampus and medial prefrontal cortex (mPFC). Here we investigated the effect of slow-pressor angiotensin II (AngII) on gliosis in the hippocampus and mPFC of young adult (2-mo-old) male and female mice. In males, AngII induced hypertension, and this resulted in an increase in the density of the astrocyte marker glial fibrillary acidic protein (GFAP) in the subgranular hilus and a decrease in the density of the microglial marker ionized calcium binding adapter molecule (Iba-1) in the CA1 region. Females infused with AngII did not show hypertension but, significantly, showed alterations in hippocampal glial activation. Compared with vehicle, AngII-infused female mice had an increased density of Iba-1 in the dentate gyrus and CA2/3a region. Like males, females infused with AngII exhibited decreased Iba-1 in the CA1 region. Neither male nor female mice showed differences in GFAP or Iba-1 in the mPFC following AngII infusion. These results demonstrate that the hippocampus is particularly vulnerable to AngII in young adulthood. Differences in gonadal hormones or the sensitivity to AngII hypertension may account for divergences in GFAP and Iba-1 in males and females.

ROS Suppression by Egg White Hydrolysate in DOCA-Salt Rats—An Alternative Tool against Vascular Dysfunction in Severe Hypertension

This study aimed to evaluate the potential for lowering blood pressure and beneficial effects on mesenteric resistance arteries (MRA) and conductance vessels (aorta) produced by dietary supplementation of an egg white hydrolysate (EWH) in rats with severe hypertension induced by deoxycorticosterone plus salt treatment (DOCA-salt), as well as the underlying mechanisms involved. The DOCA-salt model presented higher blood pressure, which was significantly reduced by EWH. The impaired acetylcholine-induced relaxation and eNOS expression observed in MRA and aorta from DOCA-salt rats was ameliorated by EWH. This effect on vessels (MRA and aorta) was related to the antioxidant effect of EWH, since hydrolysate intake prevented the NF-κB/TNFα inflammatory pathway and NADPH oxidase-induced reactive oxygen species (ROS) generation, as well as the mitochondrial source of ROS in MRA. At the plasma level, EWH blocked the higher ROS and MDA generation by DOCA-salt treatment, without altering the antioxidant marker. In conclusion, EWH demonstrated an antihypertensive effect in a model of severe hypertension. This effect could be related to its endothelium-dependent vasodilator properties mediated by an ameliorated vessel’s redox imbalance and inflammatory state.

Hypertension secondary to nitric oxide depletion produces oxidative imbalance and inflammatory/fibrotic outcomes in the cornea of C57BL/6 mice

Arterial hypertension (AH) leads to oxidative and inflammatory imbalance that contribute to fibrosis development in many target organs. Here, we aimed to highlight the harmful effects of severe AH in the cornea. Our experimental model was established by administration of NG-nitro-L-arginine-methyl-ester (L-NAME) to C57BL/6 mice, which were monitored weekly for arterial blood pressure and intraocular pressure (IOP). Morphological studies of ocular tissues were accompanied by analyses of reactive oxygen species generation, and localization/expression of NAPDH oxidase isoforms (NOX1, NOX2, NOX4) and inflammatory biomarkers (PPARα, PPARγ, IL-1β, IL-6, IL-10, TNF-α, and COX-2). Masson's trichrome and Sirius Red staining were used to explore the fibrotic status of the cornea. The expression of collagen isoforms (COL1α1, COL1α2, COL3α1, COL4α1, COL4α2) and relevant metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) were also quantified to evaluate the participation of collagen metabolism in AH-related corneal damage. Hypertensive animals showed an increase in IOP values, and a thinner cornea compared with normotensive controls. Moreover, AH increased NADPH oxidase activity and reactive oxygen species generation in the cornea, which was accompanied by transcriptional upregulation of NOX isoforms and inflammatory biomarkers, while reducing PPAR expression. L-NAME-treated animals also developed corneal fibrosis with overexpression of collagen isoforms and reduction of factors responsible for collagen degradation. This is the first study reporting structural changes in the cornea and elevated IOP in L-NAME-treated mice. Overexpression of the NADPH oxidase system and collagen deposition might play a substantial role in the pathogenic mechanisms contributing to ocular disturbances in a context of severe hypertension.

Improved method for surgical induction of chronic hypertension in mice

Chronic hypertension can be induced in mice by one-kidney one-clip (1K1C) or two-kidney one-clip surgery, transgenic overexpression of angiotensinogen and renin, administration of deoxycorticosterone acetate-salt, supplying Nitro-L-arginine methyl-ester in the drinking water and Angiotensin-II infusion. Although each model has its own pros and cons, selection of a model that mimics human hypertensive disease accurately is essential to ensure rigor and reproducibility in hypertension research. 1K1C mice represent an efficient, budget-friendly, and translationally capable model; however, their use in preclinical research has remained largely hindered due to concerns about potential technical complexity and lack of reported information regarding procedure-related mortality rates. Here, we describe in detail an improved version of the 1K1C surgery in mice that has zero intraoperative mortality and excellent survival rates in a long-term setting and permits the development of stable chronic hypertension and its target organ complications. Key to this outcome is unilateral nephrectomy 1 week after renal artery clipping to decelerate the blood pressure (BP) increase, which allows the organism to adapt better to the BP rise. The technical and animal welfare improvements presented here may promote the acceptance of the 1K1C model.

Of Mouse and Man: Cross-Species Characterization of Hypertensive Cardiac Remodeling

Hypertension is a major public health concern and poses a significant risk for sudden cardiac death (SCD). However, the characterisation of human tissues tends to be macroscopic, with little appreciation for the quantification of the pathological remodelling responsible for the advancement of the disease. While the components of hypertensive remodelling are well established, the timeline and comparative quantification of pathological changes in hypertension have not been shown before. Here, we sought to identify the phasing of cardiac remodelling with hypertension using post-mortem tissue from SCD patients with early and advanced hypertensive heart disease (HHD). In order to study and quantify the progression of phenotypic changes, human specimens were contrasted to a well-described angiotensin-II-mediated hypertensive mouse model. While cardiomyocyte hypertrophy is an early adaptive response in the mouse that stabilises in established hypertension and declines as the disease progresses, this finding did not translate to the human setting. In contrast, optimising fibrosis quantification methods and applying them to each setting identified perivascular fibrosis as the prevailing possible cause for overall disease progression. Indeed, assessing myocardial inflammation highlights CD45+ inflammatory cell infiltration that precedes fibrosis and is an early-phase event in response to elevated arterial pressures that may underscore perivascular remodelling. Along with aetiology insight, we highlight cross-species comparison for quantification of cardiac remodelling in human hypertension. As such, this platform could assist with the development of therapies specific to the disease phase rather than targeting global components of hypertension, such as blood pressure lowering.

A New Approach for the Development of Multiple Cardiovascular Risk Factors in Two Rat Models of Hypertension

Cardiovascular disease (CVD) is the leading cause of death among non-communicable diseases. There is a lack of valid animal models that mimic associations among multiple cardiovascular risk factors in humans. The present study developed an animal model that uses multiple cardiovascular risk factors—namely, hypertension, hypothyroidism, and a high-fat diet (HFD). Two models of hypertension were used: renovascular hypertension (two-kidney, one clip [2K1C]) and spontaneously hypertensive rats (SHRs). The naive group was composed of normotensive rats. Twelve weeks after surgery to induce renovascular hypertension, rats in the 2K1C and SHR groups underwent thyroidectomy. The HFD was then implemented for 6 weeks. Renal function, serum redox status, biochemical CVD markers, electrocardiographic profile, blood pressure, mesenteric vascular bed reactivity, histopathology, and morphometry were investigated. Both experimental models induced dyslipidemia, renal function impairment, and hepatic steatosis, accompanied by higher levels of different inflammatory markers and serum oxidative stress. These alterations contributed to end-organ damage in all hypertensive rats. Our findings corroborate a viable alternative model that involves multiple cardiovascular risk factors and resembles conditions that are seen in humans. Both models mimicked CVD, but our data show that SHRs exhibit more significant pathophysiological changes.

Sex Differences in Diurnal Sodium Handling During Diet-Induced Obesity in Rats

BACKGROUND

Emerging evidence over the past several years suggests that diurnal control of sodium excretion is sex dependent and involves the renal endothelin system. Given recent awareness of disruptions of circadian function in obesity, we determined whether diet-induced obesity impairs renal handling of an acute salt load at different times of day and whether this varies by sex and is associated with renal endothelin dysfunction.

METHODS

Male and female Sprague-Dawley rats were placed on a high-fat diet for 8 weeks before assessing renal sodium handling and blood pressure.

RESULTS

Male, but not female, rats on high fat had a significantly reduced natriuretic response to acute NaCl injection at the beginning of their active period that was associated with lower endothelin 1 (ET-1) excretion, lower ET-1 mRNA expression in the cortex and outer medulla as well as lower ET_B receptor expression in the outer medulla of the high-fat rats. Obese males also had significantly higher blood pressure (telemetry) that was exacerbated by adding high salt to the diet during the last 2 weeks. While female rats developed hypertension with a high-fat diet, they were not salt sensitive and ET-1 excretion was unchanged.

CONCLUSIONS

These data identify diet-induced obesity as a sex-specific disruptive factor for maintaining proper sodium handling. Although high-fat diets induce hypertension in both sexes, these data reveal that males are at greater risk of salt-dependent hypertension and further suggest that females have more redundant systems that can be productive against salt-sensitive hypertension in at least some circumstances.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Compromised Cortical-Hippocampal Network Function From Transient Hypertension: Linking Mid-Life Hypertension to Late Life Dementia Risk

Mid-life hypertension is a major risk factor for developing dementia later in life. While anti-hypertensive drugs restore normotension, dementia risk remains above baseline suggesting that brain damage sustained during transient hypertension is irreversible. The current study characterized a rat model of transient hypertension with an extended period of normotensive recovery: F344 rats were treated with L-NG-Nitroarginine methyl ester (L-NAME) for 1 month to induce hypertension then allowed up to 4 months of recovery. With respect to cognitive deficits, comparison between 1 month and 4 months of recovery identified initial deficits in spatial memory that resolved by 4 months post-hypertension; contrastingly, loss of cognitive flexibility did not. The specific cells and brain regions underlying these cognitive deficits were investigated. Irreversible structural damage to the brain was observed in both the prefrontal cortex and the hippocampus, with decreased blood vessel density, myelin and neuronal loss. We then measured theta-gamma phase amplitude coupling as a readout for network function, a potential link between the observed cognitive and pathological deficits. Four months after hypertension, we detected decreased theta-gamma phase amplitude coupling within each brain region and a concurrent increase in baseline connectivity between the two regions reflecting an attempt to maintain function that may account for the improvement in spatial memory. Our results demonstrate that connectivity between prefrontal cortex and hippocampus is a vulnerable network affected by transient hypertension which is not rescued over time; thus demonstrating for the first time a mechanistic link between the long-term effects of transient hypertension and dementia risk.

SGLT2 inhibition effect on salt-induced hypertension, RAAS, and Na+ transport in Dahl SS rats

Na+-glucose cotransporter-2 (SGLT2) inhibitors are the new mainstay of treatment for diabetes mellitus and cardiovascular diseases. Despite the remarkable benefits, the molecular mechanisms mediating the effects of SGLT2 inhibitors on water and electrolyte balance are incompletely understood. The goal of this study was to determine whether SGLT2 inhibition alters blood pressure and kidney function via affecting the renin-angiotensin-aldosterone system (RAAS) and Na+ channels/transporters along the nephron in Dahl salt-sensitive rats, a model of salt-induced hypertension. Administration of dapagliflozin (Dapa) at 2 mg/kg/day via drinking water for 3 wk blunted the development of salt-induced hypertension as evidenced by lower blood pressure and a left shift of the pressure natriuresis curve. Urinary flow rate, glucose excretion, and Na+- and Cl--to-creatinine ratios increased in Dapa-treated compared with vehicle-treated rats. To define the contribution of the RAAS, we measured various hormones. Despite apparent effects on Na+- and Cl--to-creatinine ratios, Dapa treatment did not affect RAAS metabolites. Subsequently, we assessed the effects of Dapa on renal Na+ channels and transporters using RT-PCR, Western blot analysis, and patch clamp. Neither mRNA nor protein expression levels of renal transporters (SGLT2, Na+/H+ exchanger isoform 3, Na+-K+-2Cl- cotransporter 2, Na+-Cl- cotransporter, and α-, β-, and γ-epithelial Na+ channel subunits) changed significantly between groups. Furthermore, electrophysiological experiments did not reveal any difference in Dapa treatment on the conductance and activity of epithelial Na+ channels. Our data suggest that SGLT2 inhibition in a nondiabetic model of salt-sensitive hypertension blunts the development of salt-induced hypertension by causing glucosuria and natriuresis without changes in the RAAS or the expression or activity of the main Na+ channels and transporters.NEW & NOTEWORTHY The present study indicates that Na+-glucose cotransporter-2 (SGLT2) inhibition in a nondiabetic model of salt-sensitive hypertension blunts the development and magnitude of salt-induced hypertension. Chronic inhibition of SGLT2 increases glucose and Na+ excretion without secondary effects on the expression and function of other Na+ transporters and channels along the nephron and hormone levels in the renin-angiotensin-aldosterone system. These data provide novel insights into the effects of SGLT2 inhibitors and their potential use in hypertension.

Investigating the effect of Fenofibrate on biomarkers of vascular inflammation in L-NAME induced hypertensive rats

This study aims to evaluate the impact of fenofibrate on the levels of (IL-6, hsCRP, Lp-PLA2, sCD40L, and cystatin C) in hypertensive rats. Twenty-four rats were divided into two groups each of twelve. The first group served as the normotensive group, while the second group was regarded as the hypertensive group. Each group was further divided into two subgroups (control and treated). The control subgroups only received a placebo and the treated subgroups were given fenofibrate 30 mg/kg daily orally by gastric gavage for 4 weeks. The level of hsCRP, IL6, and Lp-PLA2 significantly increased, but sCD40L and cystatin C levels were not changed in hypertensive rats. Fenofibrate has significantly reduced the levels of hsCRP and Lp-LPA2 in hypertensive rats while IL6 and sCD40s have not been changed in both groups. In conclusion, Fenofibrate has revealed a pleiotropic anti-inflammatory effect by reducing the level of hsCRP and Lp-LPA2 in hypertensive rats.

Cross-Talk between CB1, AT1, AT2 and Mas Receptors Responsible for Blood Pressure Control in the Paraventricular Nucleus of Hypothalamus in Conscious Spontaneously Hypertensive Rats and Their Normotensive Controls

We have previously shown that in urethane-anaesthetized rats, intravenous injection of the angiotensin II (Ang II) AT1 receptor antagonist losartan reversed the pressor effect of the cannabinoid CB1 receptor agonist CP55940 given in the paraventricular nucleus of hypothalamus (PVN). The aim of our study was to determine the potential interactions in the PVN between CB1 receptors and AT1 and AT2 receptors for Ang II and Mas receptors for Ang 1-7 in blood pressure regulation in conscious spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats. The pressor effects of Ang II, Ang 1-7 and CP55940 microinjected into the PVN were stronger in SHRs than in WKYs. Increases in blood pressure in response to Ang II were strongly inhibited by antagonists of AT1 (losartan), AT2 (PD123319) and CB1 (AM251) receptors, to Ang 1-7 by a Mas antagonist (A-779) and AM251 and to CP55940 by losartan, PD123319 and A-779. Higher (AT1 and CB1) and lower (AT2 and Mas) receptor expression in the PVN of SHR compared to WKY may partially explain the above differences. In conclusion, blood pressure control in the PVN depends on the mutual interaction of CB1, AT1, AT2 and Mas receptors in conscious spontaneously hypertensive rats and their normotensive controls.

Estrogen Metabolite 2-Methoxyestradiol Attenuates Blood Pressure in Hypertensive Rats by Downregulating Angiotensin Type 1 Receptor

The therapeutic potential of 2-Methoxyestradiol (2ME2) is evident in cardiovascular disease. Our laboratory has previously demonstrated the mechanism involved in the 2ME2 regulation of angiotensin type 1 receptor (AT1R) in vitro. However, 2ME2 regulation of angiotensin receptors and its effects on blood pressure (BP) and resting heart rate (RHR) are uncertain. In this study, male and female Wistar-Kyoto (WKY) rats infused with angiotensin II (65 ng/min) and male spontaneously hypertensive rats (SHR) were surgically implanted with telemetric probes to continuously assess arterial BP and RHR. In both male and female WKY rats, 2ME2 treatment (20 mg/kg/day for 2 weeks) resulted in a significant reduction of Ang II-induced systolic, diastolic, and mean arterial BP. Moreover, significant weight loss and RHR were indicated in all groups. In a separate set of experiments, prolonged 2ME2 exposure in male SHR (20 mg/kg/day for 5 weeks) displayed a significant reduction in diastolic and mean arterial BP along with RHR. We also found downregulation of angiotensin receptors and angiotensinogen (AGT) in the kidney and liver and a reduction of plasma Ang II levels. Collectively, we demonstrate that 2ME2 attenuated BP and RHR in hypertensive rats involves downregulation of angiotensin receptors and body weight loss.

Cardiology in Rabbits and Rodents-Common Cardiac Diseases, Therapeutic Options, and Limitations

Information about heart diseases and their treatment is still sparce for rabbits and rodents. Dilated cardiomyopathy seems to occur more frequently in rabbits, whereas in guinea pigs pericardial effusion is often diagnosed. There are still no available therapeutic studies for heart diseases in rabbits and rodents, and treatment is often extrapolated from dogs and cats. Consideration should be given to the off-label use of drugs, mostly not licensed in the species mentioned in this article.

Role of thioredoxin-interacting protein in mediating endothelial dysfunction in hypertension

Excessive oxidative stress is a major causative factor of endothelial dysfunction in hypertension. As an endogenous pro-oxidant, thioredoxin-interacting protein (TXNIP) contributes to oxidative damage in various tissues. The present study aimed to investigate the role of TXNIP in mediating endothelial dysfunction in hypertension. In vivo, an experimental model of acquired hypertension was established with two-kidney, one-clip (2K1C) surgery. The expression of TXNIP in the vascular endothelial cells of multiple vessels was significantly increased in hypertensive rats compared with sham-operated rats. Resveratrol, a TXNIP inhibitor, suppressed vascular oxidative damage and increased the expression and activity of eNOS in the aorta of hypertensive rats. Notably, impaired endothelium-dependent vasodilation was effectively improved by TXNIP inhibition in hypertensive rats. In vitro, we observed that Ang II increased the expression of TXNIP in primary human aortic endothelial cells (HAECs) and that TXNIP knockdown by RNA interference alleviated cellular oxidative stress damage and mitigated the impaired eNOS activation and intracellular nitric oxide (NO) production observed in Ang II-treated HAECs. However, inhibiting thioredoxin (TRX) with PX-12 completely blunted the protective effect of silencing TXNIP. In addition, TXNIP knockdown facilitated TRX expression and promoted TRX nuclear translocation to further activate AP1 and REF1. TRX overexpression exhibited favorable effects on eNOS/NO homeostasis in Ang II-treated HAECs. Thus, TXNIP contributes to oxidative stress and endothelial dysfunction in hypertension, and these effects are dependent on the antioxidant capacity of TRX, suggesting that targeting TXNIP may be a novel strategy for antihypertensive therapy.