The pro-resolving mediator, annexin A1 regulates blood pressure, and age-associated changes in cardiovascular function and remodeling.

Aging is associated with chronic, low-level inflammation which may contribute to cardiovascular pathologies such as hypertension and atherosclerosis. This chronic inflammation may be opposed by endogenous mechanisms to limit inflammation, for example, by the actions of annexin A1 (ANXA1), an endogenous glucocorticoid-regulated protein that has anti-inflammatory and pro-resolving activity. We hypothesized the pro-resolving mediator ANXA1 protects against age-induced changes in blood pressure (BP), cardiovascular structure and function, and cardiac senescence. BP was measured monthly in conscious mature (4-month) and middle-aged (12-month) ANXA1-deficient (ANXA1-/- ) and wild-type C57BL/6 mice. Body composition was measured using EchoMRI, and both cardiac and vascular function using ultrasound imaging. Cardiac hypertrophy, fibrosis and senescence, vascular fibrosis, elastin, and calcification were assessed histologically. Gene expression relevant to structural remodeling, inflammation, and cardiomyocyte senescence were also quantified. In C57BL/6 mice, progression from 4 to 12 months of age did not affect the majority of cardiovascular parameters measured, with the exception of mild cardiac hypertrophy, vascular calcium, and collagen deposition. Interestingly, ANXA1-/- mice exhibited higher BP, regardless of age. Additionally, age progression had a marked impact in ANXA1-/- mice, with markedly augmented vascular remodeling, impaired vascular distensibility, and body composition. Consistent with vascular dysfunction, cardiac dysfunction, and hypertrophy were also evident, together with markers of senescence and inflammation. These findings suggest that endogenous ANXA1 plays a critical role in regulating BP, cardiovascular function, and remodeling and delays cardiac senescence. Our findings support the development of novel ANXA1-based therapies to prevent age-related cardiovascular pathologies.

Cardiovascular characterisation of a novel mouse model that combines hypertension and diabetes co-morbidities.

Epidemiologic data suggest that the prevalence of hypertension in patients with diabetes mellitus is ∼1.5-2.0 times greater than in matched non-diabetic patients. This co-existent disease burden exacerbates cardiac and vascular injury, leading to structural and functional changes to the myocardium, impaired cardiac function and heart failure. Oxidative stress and persistent low-grade inflammation underlie both conditions, and are identified as major contributors to pathological cardiac remodelling. There is an urgent need for effective therapies that specifically target oxidative stress and inflammation to protect against cardiac remodelling. Animal models are a valuable tool for testing emerging therapeutics, however, there is a notable lack of appropriate animal models of co-morbid diabetes and hypertension. In this study, we describe a novel preclinical mouse model combining diabetes and hypertension to investigate cardiac and vascular pathology of co-morbid disease. Type 1 diabetes was induced in spontaneously hypertensive, 8-week old, male Schlager (BPH/2) mice via 5 consecutive, daily injections of streptozotocin (55 mg/kg in citrate buffer; i.p.). Non-diabetic mice received citrate buffer only. After 10 weeks of diabetes induction, cardiac function was assessed by echocardiography prior to post-mortem evaluation of cardiomyocyte hypertrophy, interstitial fibrosis and inflammation by histology, RT-PCR and flow cytometry. We focussed on the oxidative and inflammatory stress pathways that contribute to cardiovascular remodelling. In particular, we demonstrate that markers of inflammation (monocyte chemoattractant protein; MCP-1), oxidative stress (urinary 8-isoprostanes) and fibrosis (connective tissue growth factor; CTGF) are significantly increased, whilst diastolic dysfunction, as indicated by prolonged isovolumic relaxation time (IVRT), is elevated in this diabetic and hypertensive mouse model. In summary, this pre-clinical mouse model provides researchers with a tool to test therapeutic strategies unique to co-morbid diabetes and hypertension, thereby facilitating the emergence of novel therapeutics to combat the cardiovascular consequences of these debilitating co-morbidities.

Taipan Natriuretic Peptides Are Potent and Selective Agonists for the Natriuretic Peptide Receptor A.

Cardiovascular ailments are a major cause of mortality where over 1.3 billion people suffer from hypertension leading to heart-disease related deaths. Snake venoms possess a broad repertoire of natriuretic peptides with therapeutic potential for treating hypertension, congestive heart failure, and related cardiovascular disease. We now describe several taipan (Oxyuranus microlepidotus) natriuretic peptides TNPa-e which stimulated cGMP production through the natriuretic peptide receptor A (NPR-A) with higher potencies for the rat NPR-A (rNPR-A) over human NPR-A (hNPR-A). TNPc and TNPd were the most potent, demonstrating 100- and 560-fold selectivity for rNPR-A over hNPR-A. In vivo studies found that TNPc decreased diastolic and systolic blood pressure (BP) and increased heart rate (HR) in conscious normotensive rabbits, to a level that was similar to that of human atrial natriuretic peptide (hANP). TNPc also enhanced the bradycardia due to cardiac afferent stimulation (Bezold-Jarisch reflex). This indicated that TNPc possesses the ability to lower blood pressure and facilitate cardiac vagal afferent reflexes but unlike hANP does not produce tachycardia. The 3-dimensional structure of TNPc was well defined within the pharmacophoric disulfide ring, displaying two turn-like regions (RMSD = 1.15 Å). Further, its much greater biological stability together with its selectivity and potency will enhance its usefulness as a biological tool.

Endothelium-dependent relaxation is impaired in Schlager hypertensive (BPH/2J) mice by region-specific mechanisms in conductance and resistance arteries.

AIMS: Endothelial dysfunction and arterial stiffness are hallmarks of hypertension, and major risk factors for cardiovascular disease. BPH/2J (Schlager) mice are a genetic model of spontaneous hypertension, but little is known about the vascular pathophysiology of these mice and the region-specific differences between vascular beds. Therefore, this study compared the vascular function and structure of large conductance (aorta and femoral) and resistance (mesenteric) arteries of BPH/2J mice with their normotensive BPN/2J counterparts. MAIN METHODS: Blood pressure was measured in BPH/2J and BPN/3J mice via pre-implanted radiotelemetry probes. At endpoint, vascular function and passive mechanical wall properties were assessed using wire and pressure myography, qPCR and histology. KEY FINDINGS: Mean arterial blood pressure was elevated in BPH/2J mice compared to BPN/3J controls. Endothelium-dependent relaxation to acetylcholine was attenuated in both the aorta and mesenteric arteries of BPH/2J mice, but through different mechanisms. In the aorta, hypertension reduced the contribution of prostanoids. Conversely, in the mesenteric arteries, hypertension reduced the contribution of both nitric oxide and endothelium-dependent hyperpolarization. Hypertension reduced volume compliance in both femoral and mesenteric arteries, but hypertrophic inward remodelling was only observed in the mesenteric arteries of BPH/2J mice. SIGNIFICANCE: This is the first comprehensive investigation of vascular function and structural remodelling in BPH/2J mice. Overall, hypertensive BPH/2J mice exhibited endothelial dysfunction and adverse vascular remodelling in the macro- and microvasculature, underpinned by distinct region-specific mechanisms. This highlights BPH/2J mice as a highly suitable model for evaluating novel therapeutics to treat hypertension-associated vascular dysfunction.

Blood pressure variability: methodological aspects, clinical relevance and practical indications for management - a European Society of Hypertension position paper ∗.

Blood pressure is not a static parameter, but rather undergoes continuous fluctuations over time, as a result of the interaction between environmental and behavioural factors on one side and intrinsic cardiovascular regulatory mechanisms on the other side. Increased blood pressure variability (BPV) may indicate an impaired cardiovascular regulation and may represent a cardiovascular risk factor itself, having been associated with increased all-cause and cardiovascular mortality, stroke, coronary artery disease, heart failure, end-stage renal disease, and dementia incidence. Nonetheless, BPV was considered only a research issue in previous hypertension management guidelines, because the available evidence on its clinical relevance presents several gaps and is based on heterogeneous studies with limited standardization of methods for BPV assessment. The aim of this position paper, with contributions from members of the European Society of Hypertension Working Group on Blood Pressure Monitoring and Cardiovascular Variability and from a number of international experts, is to summarize the available evidence in the field of BPV assessment methodology and clinical applications and to provide practical indications on how to measure and interpret BPV in research and clinical settings based on currently available data. Pending issues and clinical and methodological recommendations supported by available evidence are also reported. The information provided by this paper should contribute to a better standardization of future studies on BPV, but should also provide clinicians with some indications on how BPV can be managed based on currently available data.

Association Between the Gut Microbiome and Their Metabolites With Human Blood Pressure Variability.

BACKGROUND: Blood pressure (BP) variability is an independent risk factor for cardiovascular events. Recent evidence supports a role for the gut microbiota in BP regulation. However, whether the gut microbiome is associated with BP variability is yet to be determined. Here, we aimed to investigate the interplay between the gut microbiome and their metabolites in relation to BP variability. METHODS: Ambulatory BP monitoring was performed in 69 participants from Australia (55.1% women; mean±SD, 59.8±7.26 years; body mass index, 25.2±2.83 kg/m2). These data were used to determine nighttime dipping, morning BP surge (MBPS) and BP variability as SD. The gut microbiome was determined by 16S ribosomal RNA (rRNA) sequencing and metabolite levels by gas chromatography. RESULTS: We identified specific taxa associated with systolic BP variability, nighttime dipping, and MBPS. Notably, Alistipesfinegoldii and Lactobacillus spp. were only present in participants within the normal ranges of BP variability, MBPS and dipping, while Prevotella spp. and Clostridium spp., were found to be present in extreme dippers and the highest quartiles of BP SD and MBPS. There was a negative association between MBPS and microbial α-diversity (r=-0.244, P=0.046). MBPS was also negatively associated with plasma levels of microbial metabolites called short-chain fatty acids (r=-0.305, P=0.020), particularly acetate (r=-0.311, P=0.017). CONCLUSIONS: Gut microbiome diversity, levels of microbial metabolites, and the bacteria Alistipesfinegoldii and Lactobacillus were associated with lower BP variability and Clostridium and Prevotella with higher BP variability. Thus, our findings suggest the gut microbiome and metabolites may be involved in the regulation of BP variability.

Rodent models of hypertension.

Elevated blood pressure (BP), or hypertension, is the main risk factor for cardiovascular disease. As a multifactorial and systemic disease that involves multiple organs and systems, hypertension remains a challenging disease to study. Models of hypertension are invaluable to support the discovery of the specific genetic, cellular and molecular mechanisms underlying essential hypertension, as well as to test new possible treatments to lower BP. Rodent models have proven to be an invaluable tool for advancing the field. In this review, we discuss the strengths and weaknesses of rodent models of hypertension through a systems approach. We highlight the ways how target organs and systems including the kidneys, vasculature, the sympathetic nervous system (SNS), immune system and the gut microbiota influence BP in each rodent model. We also discuss often overlooked hypertensive conditions such as pulmonary hypertension and hypertensive-pregnancy disorders, providing an important resource for researchers. LINKED ARTICLES: This article is part of a themed issue on Preclinical Models for Cardiovascular disease research (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.5/issuetoc.

MicroRNA-132 may be associated with blood pressure and liver steatosis-preliminary observations in obese individuals.

Recent findings in experimental models have shown that the microRNA miR-132 (mir-132) is an important regulator of liver homeostasis and lipid metabolism. We aimed to assess miR-132 expression in liver and fat tissues of obese individuals and examine its association with blood pressure (BP) and hepatic steatosis. We examined obese individuals undergoing bariatric surgery for weight loss (n = 19). Clinical and demographic information was obtained. Quantitative PCR was performed to determine tissue expression of miR-132 in liver and subcutaneous and visceral fat biopsies obtained during bariatric surgery. Liver biopsies were read by a single liver pathologist and graded for steatosis, inflammation and fibrosis. Participants (aged 39 ± 8.1 years) had a body mass index (BMI) of 42 ± 4.5 kg/m2 and presented with 2.2 ± 1.2 metabolic abnormalities. Supine BP was 127 ± 16/74 ± 11 mmHg. Hepatic and visceral fat expression of miR-132 were correlated (r = 0.59, P = 0.033). There was no correlation between subcutaneous and visceral expression of miR-132 (r = -0.31, P = 0.20). Hepatic and visceral fat miR-132 expression were associated with BMI (r = 0.62 and r = 0.68, P = 0.049 respectively) and degree of liver steatosis (r = 0.60 and r = 0.55, P < 0.05, respectively). Subcutaneous fat miRNA-132 expression was correlated to office systolic BP (r = 0.46, P < 0.05), several aspects of 24 h BP (24 h systolic BP: r = 0.52; day systolic BP: r = 0.59, P < 0.05 for all), plasma triglycerides (r = 0.51, P < 0.01) and liver enzymes (ALT: r = -0.52; AST: r = -0.48, P < 0.05 for all). We found an association between miR-132 and markers of cardiovascular and metabolic disease. Reduction of miR-132 may be a target for the regulation of liver lipid homeostasis and control of obesity-related blood pressure.

Deficiency of MicroRNA-181a Results in Transcriptome-Wide Cell-Specific Changes in the Kidney and Increases Blood Pressure.

[Figure: see text].

Renal Deafferentation Prevents Progression of Hypertension and Changes to Sympathetic Reflexes in a Rabbit Model of Chronic Kidney Disease.

[Figure: see text].

The Gut Microbiota and Their Metabolites in Human Arterial Stiffness.

AIM: Gut microbiota-derived metabolites, such as short-chain fatty acids (SCFAs) have vasodilator properties in animal and human ex vivo arteries. However, the role of the gut microbiota and SCFAs in arterial stiffness in humans is still unclear. Here we aimed to determine associations between the gut microbiome, SCFA and their G-protein coupled sensing receptors (GPCRs) in relation to human arterial stiffness. METHODS: Ambulatory arterial stiffness index (AASI) was determined from ambulatory blood pressure (BP) monitoring in 69 participants from regional and metropolitan regions in Australia (55.1% women; mean, 59.8± SD, 7.26 years of age). The gut microbiome was determined by 16S rRNA sequencing, SCFA levels by gas chromatography, and GPCR expression in circulating immune cells by real-time PCR. RESULTS: There was no association between metrics of bacterial α and ß diversity and AASI or AASI quartiles in men and women. We identified two main bacteria taxa that were associated with AASI quartiles: Lactobacillus spp. was only present in the lowest quartile, while Clostridium spp. was present in all quartiles but the lowest. AASI was positively associated with higher levels of plasma, but not faecal, butyrate. Finally, we identified that the expression of GPR43 (FFAR2) and GPR41 (FFAR3) in circulating immune cells were negatively associated with AASI. CONCLUSIONS: Our results suggest that arterial stiffness is associated with lower levels of the metabolite-sensing receptors GPR41/GPR43 in humans, blunting its response to BP-lowering metabolites such as butyrate. The role of Lactobacillus spp. and Clostridium spp., as well as butyrate-sensing receptors GPR41/GPR43, in human arterial stiffness needs to be determined.

Essential Hypertension Is Associated With Changes in Gut Microbial Metabolic Pathways: A Multisite Analysis of Ambulatory Blood Pressure.

[Figure: see text].

Microbial Interventions to Control and Reduce Blood Pressure in Australia (MICRoBIA): rationale and design of a double-blinded randomised cross-over placebo controlled trial.

BACKGROUND: Hypertension is a prevalent chronic disease worldwide that remains poorly controlled. Recent studies support the concept that the gut microbiota is involved in the development of hypertension and that dietary fibre intake may act through the gut microbiota to lower blood pressure (BP). Resistant starch is a type of prebiotic fibre which is metabolised by commensal bacteria in the colon to produce short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate. Previous work in pre-clinical models provides strong evidence that both prebiotic fibre as well as SCFAs (i.e. postbiotics) can prevent the development of hypertension. The aim of this clinical trial is to determine if acetylated and butyrylated modified resistant starch can decrease BP of hypertensive individuals via the modulation of the gut microbiota and release of high levels of SCFAs. METHODS: This is a phase IIa double-blinded, randomised, cross-over, placebo controlled trial. Participants are randomly allocated to receive either a diet containing 40 g/day of the modified resistant starch or placebo (corn starch or regular flour) for 3 weeks on each diet, with a 3-week washout period between the two diets. BP is measured in the office, at home, and using a 24-h ambulatory device. Arterial stiffness is measured using carotid-to-femoral pulse wave velocity. Our primary endpoint is a reduction in ambulatory daytime systolic BP. Secondary endpoints include changes to circulating cytokines, immune markers, and modulation to the gut microbiome. DISCUSSION: The findings of this study will provide the first evidence for the use of a combination of pre- and postbiotics to lower BP in humans. The results are expected at the end of 2021. TRIAL REGISTRATION: Australia and New Zealand Clinical Trial Registry ACTRN12619000916145 . Registered on 1 July 2019.

A spontaneously hypertensive diet-induced atherosclerosis-prone mouse model of metabolic syndrome.

Metabolic Syndrome (MetS) is a complex and multifactorial condition often characterised by obesity, hypertension, hyperlipidaemia, insulin resistance, glucose intolerance and fasting hyperglycaemia. Collectively, MetS can increase the risk of atherosclerotic-cardiovascular disease, which is the leading cause of death worldwide. However, no animal model currently exists to study MetS in the context of atherosclerosis. In this study we developed a pre-clinical mouse model that recapitulates the spectrum of MetS features while developing atherosclerosis. When BPHx mice were placed on a western type diet for 16 weeks, all the classical characteristics of MetS were observed. Comprehensive metabolic analyses and atherosclerotic imaging revealed BPHx mice to be obese and hypertensive, with elevated total plasma cholesterol and triglyceride levels, that accelerated atherosclerosis. Altogether, we demonstrate that the BPHx mouse has all the major components of MetS, and accelerates the development of atherosclerosis.

Leptin and Melanocortin Signaling Mediates Hypertension in Offspring From Female Rabbits Fed a High-Fat Diet During Gestation and Lactation.

Maternal high-fat diet in rabbits leads to hypertension and elevated renal sympathetic nerve activity (RSNA) in adult offspring but whether this is due to adiposity or maternal programming is unclear. We gave intracerebroventricular (ICV) and ventromedial hypothalamus (VMH) administration of leptin-receptor antagonist, α-melanocyte-stimulating hormone (αMSH), melanocortin-receptor antagonist (SHU9119), or insulin-receptor (InsR) antagonist to conscious adult offspring from mothers fed a high-fat diet (mHFD), control diet (mCD), or mCD offspring fed HFD for 10d (mCD10d, to deposit equivalent fat but not during development). mHFD and mCD10d rabbits had higher mean arterial pressure (MAP, +6.4 mmHg, +12.1 mmHg, p < 0.001) and RSNA (+2.3 nu, +3.2 nu, p < 0.01) than mCD, but all had similar plasma leptin. VMH leptin-receptor antagonist reduced MAP (-8.0 ± 3.0 mmHg, p < 0.001) in mCD10d but not in mHFD or mCD group. Intracerebroventricular leptin-receptor antagonist reduced MAP only in mHFD rabbits (p < 0.05). Intracerebroventricular SHU9119 reduced MAP and RSNA in mHFD but only reduced MAP in the mCD10d group. VMH αMSH increased RSNA (+85%, p < 0.001) in mHFD rabbits but ICV αMSH increased RSNA in both mHFD and mCD10d rabbits (+45%, +51%, respectively, p < 0.001). The InsR antagonist had no effect by either route on MAP or RSNA. Hypothalamic leptin receptor and brain-derived neurotrophic factor (BDNF) mRNA were greater in mHFD compared with mCD rabbits and mCD10d rabbits. In conclusion, the higher MAP in mHFD and mCD10d offspring was likely due to greater central leptin signaling at distinct sites within the hypothalamus while enhanced melanocortin contribution was common to both groups suggesting that residual body fat was mainly responsible. However, the effects of SHU9119 and αMSH on RSNA pathways only in mHFD suggest a maternal HFD may program sympatho-excitatory capacity in these offspring and that this may involve increased leptin receptor and BDNF expression.

Blunted natriuretic response to saline loading in sheep with hypertensive kidney disease following radiofrequency catheter-based renal denervation.

Renal sympathetic nerves contribute to renal excretory function during volume expansion. We hypothesized that intact renal innervation is required for excretion of a fluid/electrolyte load in hypertensive chronic kidney disease (CKD) and normotensive healthy settings. Blood pressure, kidney hemodynamic and excretory response to 180 min of isotonic saline loading (0.13 ml/kg/min) were examined in female normotensive (control) and hypertensive CKD sheep at 2 and 11 months after sham (control-intact, CKD-intact) or radiofrequency catheter-based RDN (control-RDN, CKD-RDN) procedure. Basal blood pressure was ~ 7 to 9 mmHg lower at 2, and 11 months in CKD-RDN compared with CKD-intact sheep. Saline loading did not alter glomerular filtration rate in any group. At 2 months, in response to saline loading, total urine and sodium excretion were ~ 40 to 50% less, in control-RDN and CKD-RDN than intact groups. At 11 months, the natriuretic and diuretic response to saline loading were similar between control-intact, control-RDN and CKD-intact groups but sodium excretion was ~ 42% less in CKD-RDN compared with CKD-intact at this time-point. These findings indicate that chronic withdrawal of basal renal sympathetic activity impairs fluid/electrolyte excretion during volume expansion. Clinically, a reduced ability to excrete a saline load following RDN may contribute to disturbances in body fluid balance in hypertensive CKD.

Role of Mineralocorticoid and Angiotensin Type 1 Receptors in the Paraventricular Nucleus in Angiotensin-Induced Hypertension.

The hypothalamic paraventricular nucleus (PVN) is an important site where an interaction between circulating angiotensin (Ang) and mineralocorticoid receptor (MR) activity may modify sympathetic nerve activity (SNA) to influence long-term elevation of blood pressure. We examined in conscious Ang II-treated rabbits, the effects on blood pressure and tonic and reflex renal SNA (RSNA) of microinjecting into the PVN either RU28318 to block MR, losartan to block Ang (AT1) receptors or muscimol to inhibit GABA A receptor agonist actions. Male rabbits received a moderate dose of Ang II (24 ng/kg/min subcutaneously) for 3 months (n = 13) or sham treatment (n = 13). At 3 months, blood pressure increased by +19% in the Ang II group compared to 10% in the sham (P = 0.022) but RSNA was similar. RU28318 lowered blood pressure in both Ang II and shams but had a greater effect on RSNA and heart rate in the Ang II-treated group (P < 0.05). Losartan also lowered RSNA, while muscimol produced sympatho-excitation in both groups. In Ang II-treated rabbits, RU28318 attenuated the blood pressure increase following chemoreceptor stimulation but did not affect responses to air jet stress. In contrast losartan and muscimol reduced blood pressure and RSNA responses to both hypoxia and air jet. While neither RU28318 nor losartan changed the RSNA baroreflex, RU28318 augmented the range of the heart rate baroreflex by 10% in Ang II-treated rabbits. Muscimol, however, augmented the RSNA baroreflex by 11% in sham animals and none of the treatments altered baroreflex sensitivity. In conclusion, 3 months of moderate Ang II treatment promotes activation of reflex RSNA principally via MR activation in the PVN, rather than via activation of AT1 receptors. However, the onset of hypertension is independent of both. Interestingly, the sympatho-excitatory effects of muscimol in both groups suggest that overall, the PVN regulates a tonic sympatho-inhibitory influence on blood pressure control.

Impact of in vitro embryo culture and transfer on blood pressure regulation in the adolescent lamb.

Nutrition during the periconceptional period influences postnatal cardiovascular health. We determined whether in vitro embryo culture and transfer, which are manipulations of the nutritional environment during the periconceptional period, dysregulate postnatal blood pressure and blood pressure regulatory mechanisms. Embryos were either transferred to an intermediate recipient ewe (ET) or cultured in vitro in the absence (IVC) or presence of human serum (IVCHS) and a methyl donor (IVCHS+M) for 6 days. Basal blood pressure was recorded at 19-20 weeks after birth. Mean arterial pressure (MAP) and heart rate (HR) were measured before and after varying doses of phenylephrine (PE). mRNA expression of signaling molecules involved in blood pressure regulation was measured in the renal artery. Basal MAP did not differ between groups. Baroreflex sensitivity, set point, and upper plateau were also maintained in all groups after PE stimulation. Adrenergic receptors alpha-1A (αAR1A), alpha-1B (αAR1B), and angiotensin II receptor type 1 (AT1R) mRNA expression were not different from controls in the renal artery. These results suggest there is no programmed effect of ET or IVC on basal blood pressure or the baroreflex control mechanisms in adolescence, but future studies are required to determine the impact of ET and IVC on these mechanisms later in the life course when developmental programming effects may be unmasked by age.