Two-kidney, one clip and one-kidney, one clip hypertension in mice

(Pro)renin Receptor Blockade Prevents Increases in Systolic Blood Pressure, Sodium Retention, and αENaC Protein Expression in the Kidney of 2K1C Goldblatt Mice

Physiological control of blood pressure (BP) and extracellular fluid volume is mediated by the action of the renin-angiotensin system (RAS). The presence of RAS components throughout the nephron has been widely discussed. The (pro)renin receptor (PRR) is a member of the RAS widely expressed in the body of humans and rodents. In the kidney, PRR is expressed in mesangial cells, renal vasculature, and tubules of the proximal and distal nephron. Binding of the PRR to renin and prorenin promotes angiotensin (Ang) I-mediated sodium (Na+) reabsorption via the epithelial sodium channel (ENaC). The Goldblatt 2-kidney 1-clip (2K1C) is a model of experimental renovascular hypertension that displays activation of systemic and intrarenal RAS. We use the 2K1C hypertension mouse model for 7 days to evaluate the role of the PRR on renal αENaC expression, Na+ reabsorption, and BP using pharmacological systemic blockade of the PRR with PRO20 peptide. Mice undergoing or not to 2K1C surgery (0.13 mm clip internal gap) were chronically infused with PRO20 and compared to sham (control) mice to assess changes in systolic BP (SBP) and diastolic BP (DBP), intrarenal angiotensin-converting enzyme (ACE) activity, Ang II, and renal αENaC expression and natriuretic responses after a saline challenge. Renal artery obstruction increased SBP and DBP, intrarenal ACE activity, Ang II levels, Na+ retention, and αENaC expression in both kidneys. PRO20 prevented the increases in SBP, DBP, attenuated Na+ retention, and blunted intrarenal Ang II and αENaC levels in non-clipped kidneys of 2K1C mice. Chronic infusion of the PRR for 7 days prevents hypertensive responses in part due to impaired αENaC upregulation and intrarenal Ang II formation in the early phase of the development of renovascular hypertension in 2K1C Goldblatt mice.

Acute kidney injury in paediatric kidney transplant recipients

Acute kidney injury (AKI) in paediatric kidney transplant recipients is common. Infection including urinary tract infection (UTI) and rejection are the most common causes in children. Surgical complications often cause AKI early post-transplant, whereas BK polyomavirus nephropathy rarely occurs in the first month post-transplant. Understanding kidney physiology helps to appreciate the sensitivity of the allograft to AKI, more so than native kidneys. Although the cause of AKI is often multi-factorial, there may be an underlying process that is treatable. Eliciting the aetiology, in this regard, is of paramount importance. Pre-renal and post-renal causes of allograft dysfunction are important to distinguish from intrinsic kidney disease. Clinical information and examination of fluid balance, urine dipstick testing, blood tests, bladder and kidney transplant ultrasound, and kidney transplant biopsy remain vital assessment tools in narrowing the differential diagnosis. A careful prescribed and recreational drug history is always warranted as many drugs including supplements are nephrotoxic. Additional causes such as allograft rejection, recurrent disease, and calcineurin inhibitor toxicity need to be considered in cases of allograft dysfunction, which would not affect the native kidneys. Early detection and assessment of AKI is crucial in promoting recovery. Significant progress has been made in specific pathologies over the last 20 years, which has improved kidney allograft survival rates considerably. Research into identifying AKI biomarkers to assist early diagnosis, before the serum creatinine rises, is ongoing.

Salt-sensitive hypertension in GR mutant rats is associated with altered plasma polyunsaturated fatty acid levels and aortic vascular reactivity

In humans, glucocorticoid resistance is attributed to mutations in the glucocorticoid receptor (GR). Most of these mutations result in decreased ligand binding, transactivation, and/or translocation, albeit with normal protein abundances. However, there is no clear genotype‒phenotype relationship between the severity or age at disease presentation and the degree of functional loss of the receptor. Previously, we documented that a GR+/- rat line developed clinical features of glucocorticoid resistance, namely, hypercortisolemia, adrenal hyperplasia, and salt-sensitive hypertension. In this study, we analyzed the GR+/em4 rat model heterozygously mutant for the deletion of exon 3, which encompasses the second zinc finger, including the domains of DNA binding, dimerization, and nuclear localization signals. On a standard diet, mutant rats exhibited a trend toward increased corticosterone levels and a normal systolic blood pressure and heart rate but presented with adrenal hyperplasia. They exhibited increased adrenal soluble epoxide hydroxylase (sEH), favoring an increase in less active polyunsaturated fatty acids. Indeed, a significant increase in nonactive omega-3 and omega-6 polyunsaturated fatty acids, such as 5(6)-DiHETrE or 9(10)-DiHOME, was observed with advanced age (10 versus 5 weeks old) and following a switch to a high-salt diet accompanied by salt-sensitive hypertension. In thoracic aortas, a reduced soluble epoxide hydrolase (sEH) protein abundance resulted in altered vascular reactivity upon a standard diet, which was blunted upon a high-salt diet. In conclusion, mutations in the GR affecting the ligand-binding domain as well as the dimerization domain resulted in deregulated GR signaling, favoring salt-sensitive hypertension in the absence of obvious mineralocorticoid excess.

Investigating the Interplay between Cardiovascular and Neurodegenerative Disease

Neurological diseases, including neurodegenerative diseases (NDDs), are the primary cause of disability worldwide and the second leading cause of death. The chronic nature of these conditions and the lack of disease-modifying therapies highlight the urgent need for developing effective therapies. To accomplish this, effective models of NDDs are required to increase our understanding of underlying pathophysiology and for evaluating treatment efficacy. Traditionally, models of NDDs have focused on the central nervous system (CNS). However, evidence points to a relationship between systemic factors and the development of NDDs. Cardiovascular disease and related risk factors have been shown to modify the cerebral vasculature and the risk of developing Alzheimer's disease. These findings, combined with reports of changes to vascular density and blood-brain barrier integrity in other NDDs, such as Huntington's disease and Parkinson's disease, suggest that cardiovascular health may be predictive of brain function. To evaluate this, we explore evidence for disruptions to the circulatory system in murine models of NDDs, evidence of disruptions to the CNS in cardiovascular disease models and summarize models combining cardiovascular disruption with models of NDDs. In this study, we aim to increase our understanding of cardiovascular disease and neurodegeneration interactions across multiple disease states and evaluate the utility of combining model systems.

Role of plasmacytoid dendritic cells in vascular dysfunction in mice with renovascular hypertension

Endothelial dysfunction and inflammation are clinically significant risk factors for cardiovascular diseases in hypertension. Although immune cells play a role in hypertension, the impact of plasmacytoid dendritic cells in established renovascular hypertension-induced cardiovascular complications is not fully understood. We investigated plasmacytoid dendritic cells' contribution to arterial endothelial dysfunction and inflammation in renovascular hypertension. A two-kidney one-clip (2K1C) model for four weeks in both male and female mice was used to induce renovascular hypertension. We treated mice with or without anti-PDCA-1 antibodies for one week to deplete the plasmacytoid dendritic cells. Renovascular hypertension causes cardiac hypertrophy, lung edema, and microvascular endothelial dysfunction associated with inflammation induction in mice. Moreover, renovascular hypertension affects the profile of immune cells, including dendritic cells and macrophages, with variations between male and female mice. Interestingly, the depletion of plasmacytoid dendritic cells significantly reduces blood pressure, cardiac hypertrophy, lung edema, inflammation, and oxidative stress and improves microvascular endothelial function via the endoplasmic reticulum (ER) stress, autophagy, and mTOR-dependent mechanisms. Plasmacytoid dendritic cells significantly contribute to the development of cardiovascular complications in renovascular hypertension by modulating immune cells, inflammation, oxidative stress, and ER stress.

Apelin-13: a novel approach to suppressing renin production in RVHT

Renovascular hypertension (RVHT) is characterized by renal artery stenosis and overactivated renin-angiotensin system (RAS). Apelin, known for its negative modulation of RAS, has protective effects against cardiovascular diseases. The role and mechanisms of the primary active form of apelin, apelin-13, in RVHT are unclear. In this study, male Sprague-Dawley rats were divided into control, two-kidney one-clip (2K1C) model, and 2K1C with apelin-13 treatment groups. Renin expression was analyzed using immunohistochemistry and molecular techniques. Full-length (pro)renin receptor (fPRR) and soluble PRR (sPRR) levels were assessed via Western blotting, and cAMP levels were measured using ELISA. Plasma renin content, plasma renin activity (PRA), angiotensin II (ANG II), and sPRR levels were determined by ELISA. Human Calu-6 and mouse As4.1 cells were used to investigate renin production mechanisms. The 2K1C model exhibited increased systolic blood pressure, plasma renin content, PRA, sPRR, and ANG II levels, while apelin-13 treatment reduced these elevations. Apelin-13 inhibited cAMP production, renin mRNA expression, protein synthesis, and PRR/sPRR protein expression in renal tissue. In Calu-6 cells, cAMP-induced fPRR and site-1 protease (S1P)-derived sPRR expression, which was blocked by cAMP-responsive element-binding protein (CREB) inhibition. Apelin-13 suppressed cAMP elevation, CREB phosphorylation, fPRR/sPRR protein expression, and renin production. Recombinant sPRR (sPRR-His) stimulated renin production, which was inhibited by the PRR decoy peptide PRO20 and S1P inhibitor PF429242. These findings suggest that apelin-13 inhibits plasma renin expression through the cAMP/PKA/sPRR pathway, providing a potential therapeutic approach for RVHT. Understanding the regulation of renin production is crucial for developing effective treatments.NEW & NOTEWORTHY Our research elucidated that apelin-13 inhibits renin production through the cAMP/PKA/soluble (pro)renin receptor pathway, presenting a promising therapeutic approach for renovascular hypertension (RVHT) by targeting renin expression mechanisms. These findings underscore the potential of apelin-13 as a novel strategy to address RVHT.

Long non-coding RNAs in cardiac hypertrophy and heart failure: functions, mechanisms and clinical prospects

The surge in reports describing non-coding RNAs (ncRNAs) has focused attention on their possible biological roles and effects on development and disease. ncRNAs have been touted as previously uncharacterized regulators of gene expression and cellular processes, possibly working to fine-tune these functions. The sheer number of ncRNAs identified has outpaced the capacity to characterize each molecule thoroughly and to reliably establish its clinical relevance; it has, nonetheless, created excitement about their potential as molecular targets for novel therapeutic approaches to treat human disease. In this Review, we focus on one category of ncRNAs - long non-coding RNAs - and their expression, functions and molecular mechanisms in cardiac hypertrophy and heart failure. We further discuss the prospects for this specific class of ncRNAs as novel targets for the diagnosis and treatment of these conditions.

Establishment of a novel mouse model of renal artery coiling-based chronic hypoperfusion-related kidney injury

Renal artery stenosis-induced chronic renal ischemia is an important cause of renal dysfunction, especially in older adults, and its incidence is currently increasing. To elucidate the mechanisms underlying chronic renal hypoperfusion-induced kidney damage, we developed a novel mouse model of renal artery coiling-based chronic hypoperfusion-related kidney injury. This model exhibits decreased renal blood flow and function, atrophy, and parenchymal injury in the coiled kidney, along with compensatory hypertrophy in the non-coiled kidney, without chronic hypertension. The availability of this mouse model, which can develop renal ischemia without genetic modification, will enhance kidney disease research by serving as a new tool to investigate the effects of acquired factors (e.g., obesity and aging) and genetic factors on renal artery stenosis-related renal parenchymal damage.

Mitochondria-Derived Reactive Oxygen Species Contribute to Synergistic Interaction of Diabetes and Hypertension in Causing Chronic Kidney Injury

Diabetes (DM) and hypertension (HTN) are major risk factors for chronic kidney injury, together accounting for >70% of end-stage renal disease. The combination of DM and HTN significantly accelerates development of renal injury; however, the underlying mechanisms of this synergy are still poorly understood. This study assessed whether mitochondria (MT) dysfunction is essential in developing renal injury in a rat model with combined DM and HTN. Type 1 DM was induced in Wistar rats by streptozotocin (STZ). HTN was induced six weeks later by inter-renal aorta constriction between the renal arteries, so that right kidneys were exposed to HTN while left kidneys were exposed to normotension. Kidneys exposed to DM or HTN alone had only mild glomerular injury and urinary albumin excretion (UAE). In contrast, kidneys exposed to DM plus 8 weeks HTN had significantly increased UAE and glomerular structural damage with reduced glomerular filtration rate. Marked increases in MT-derived reactive oxygen species (ROS) were also observed in right kidneys exposed to HTN+DM. We further tested whether treatment with MT-targeted antioxidant (MitoTEMPO) after the onset of HTN attenuates renal injury in rats with DM+HTN. Results show that kidneys in DM+AC+MitoTEMPO rats had lower UAE, less glomerular damage, and preserved MT function compared to untreated DM+AC rats. Our studies indicate that MT-derived ROS play a major role in promoting kidney dysfunction when DM is combined with HTN. Preserving MT function might be a potential therapeutic approach to halt the development of renal injury when DM coexists with HTN.

Crosstalk between cytotoxic CD8+ T cells and stressed cardiomyocytes triggers development of interstitial cardiac fibrosis in hypertensive mouse hearts

Aims

Cardiac fibrosis is central to heart failure (HF), especially HF with preserved ejection fraction (HFpEF), often caused by hypertension. Despite fibrosis causing diastolic dysfunction and impaired electrical conduction, responsible for arrhythmia-induced sudden cardiac death, the mechanisms are poorly defined and effective therapies are lacking. Here we show that crosstalk between cardiac cytotoxic memory CD8+ T cells and overly stressed cardiomyocytes is essential for development of non-ischemic hypertensive cardiac fibrosis.

Methods and results

CD8 T cell depletion in hypertensive mice, strongly attenuated CF, reduced cardiac apoptosis and improved ventricular relaxation. Interaction between cytotoxic memory CD8+ T cells and overly stressed cardiomyocytes is highly dependent on the CD8+ T cells expressing the innate stress-sensing receptor NKG2D and stressed cardiomyocytes expressing the NKG2D activating ligand RAE-1. The interaction between NKG2D and RAE-1 results in CD8+ T cell activation, release of perforin, cardiomyocyte apoptosis, increased numbers of TGF-β1 expressing macrophages and fibrosis. Deleting NKG2D or perforin from CD8+ T cells greatly attenuates these effects. Activation of the cytoplasmic DNA-STING-TBK1-IRF3 signaling pathway in overly stressed cardiomyocytes is responsible for elevating RAE-1 and MCP-1, a macrophage attracting chemokine. Inhibiting STING activation greatly attenuates cardiomyocyte RAE-1 expression, the cardiomyocyte apoptosis, TGF-β1 and fibrosis.

Conclusion

Our data highlight a novel pathway by which CD8 T cells contribute to an early triggering mechanism in CF development; preventing CD8+ T cell activation by inhibiting the cardiomyocyte RAE-1-CD8+ T cell-NKG2D axis holds promise for novel therapeutic strategies to limit hypertensive cardiac fibrosis.

Renomedullary exosomes produce antihypertensive effects in reversible two-kidney one-clip renovascular hypertensive mice

The rapid fall in blood pressure following unclipping of the stenotic renal artery in the Goldblatt two-kidney one-clip (2K1C) model of renovascular hypertension is proposed to be due to release of renomedullary vasodepressor lipids, but the mechanism has remained unclear. In this study, we hypothesized that the hypotensive response to unclipping is mediated by exosomes released from the renal medulla. In male C57BL6/J mice made hypertensive by the 2K1C surgery, unclipping of the renal artery after 10 days decreased mean arterial pressure (MAP) by 23 mmHg one hr after unclipping. This effect was accompanied by a 556% increase in the concentration of exosomes in plasma as observed by nanoparticle tracking analysis. Immunohistochemical analysis of exosome markers, CD63 and AnnexinII, showed increased staining in interstitial cells of the inner medulla of stenotic but not contralateral control kidney of clipped 2K1C mice. Treatment with rapamycin, an inducer of exosome release, blunted the hypertensive response to clipping, whereas GW-4869, an exosome biosynthesis inhibitor, prevented both the clipping-induced increase in inner medullary exosome marker staining and the unclipping-induced fall in MAP. Plasma exosomes isolated from unclipped 2K1C mice showed elevated neutral lipid content compared to sham mouse exosomes by flow cytometric analysis after Nile red staining. Exosomes from 2K1C but not sham control mice exerted potent MAP-lowering and diuretic-natriuretic effects in both 2K1C and angiotensin II-infused hypertensive mice. These results are consistent with increased renomedullary synthesis and release of exosomes with elevated antihypertensive neutral lipids in response to increased renal perfusion pressure.

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

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

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.

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

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

Exercise Normalized the Hippocampal Renin-Angiotensin System and Restored Spatial Memory Function, Neurogenesis, and Blood-Brain Barrier Permeability in the 2K1C-Hypertensive Mouse

Hypertension is associated with blood-brain barrier alteration and brain function decline. Previously, we established the 2-kidney,1-clip (2K1C) hypertensive mice model by renin-angiotensin system (RAS) stimulating. We found that 2K1C-induced hypertension would impair hippocampus-related memory function and decrease adult hippocampal neurogenesis. Even though large studies have investigated the mechanism of hypertension affecting brain function, there remains a lack of efficient ways to halt this vicious effect. The previous study indicated that running exercise ameliorates neurogenesis and spatial memory function in aging mice. Moreover, studies showed that exercise could normalize RAS activity, which might be associated with neurogenesis impairment. Thus, we hypothesize that running exercise could ameliorate neurogenesis and spatial memory function impairment in the 2K1C-hypertension mice. In this study, we performed 2K1C surgery on eight-weeks-old C57BL/6 mice and put them on treadmill exercise one month after the surgery. The results indicate that running exercise improves the spatial memory and neurogenesis impairment of the 2K1C-mice. Moreover, running exercise normalized the activated RAS and blood-brain barrier leakage of the hippocampus, although the blood pressure was not decreased. In conclusion, running exercise could halt hypertension-induced brain impairment through RAS normalization.

Salubrious effects of ulinastatin and quercetin alone or in combination in endothelial dysfunction and vascular dementia

BACKGROUND

Vascular dementia is the second most prevalent form of dementia. Hypertension is the leading risk factor for endothelial dysfunction and the progression of dementia that is of vascular origin. This study investigates the role of ulinastatin (UTI) and quercetin alone as well as in combination in hypertension-induced endothelial dysfunction and vascular dementia (VaD).

METHOD

Two-kidney one-clip (2K1C) renovascular model was set up to induce hypertension in the Albino Wistar rats (males). Rats were assessed for mean arterial blood pressure, behavioral function (Morris water maze, attention set-shifting tests), vascular endothelial function, and biochemical levels (aortic superoxide anion and serum nitrite/nitrate), as well as brains' thiobarbituric acid reactive species-TBARS, reduced glutathione-GSH, interleukin-6, 10, tumor necrosis factor-TNF-α and acetylcholinesterase-AChE). UTI (10,000 U/kg, ip) and quercetin (60 mg/kg) were used alone and in combination for treatment. Donepezil (0.5 mg/kg) was used as a positive control.

RESULTS

2K1C rats showed impairment in learning, memory, executive functioning, and reversal learning. These rats further showed endothelial dysfunction as well as an increase in mean arterial blood pressure, brains' oxidative stress, inflammation, and AChE-activity. Treatment with UTI and quercetin alone as well in combination significantly attenuated the 2K1C model induced impairments in the behavioural, biochemical, and endothelial parameters.

CONCLUSION

2K1C renovascular hypertension-induced impairment in behavioural, biochemical, and endothelial parameters were attenuated by the treatment with UTI and quercetin alone as well as in combination. Therefore, the utility of these agents might be studied further to understand their full potential in hypertension-induced VaD.

Comparative analysis of hypertensive nephrosclerosis in animal models of hypertension and its relevance to human pathology. Glomerulopathy

Current research on hypertension utilizes more than fifty animal models that rely mainly on stable increases in systolic blood pressure. In experimental hypertension, grading or scoring of glomerulopathy in the majority of studies is based on a wide range of opinion-based histological changes that do not necessarily comply with lesional descriptors for glomerular injury that are well-established in clinical pathology. Here, we provide a critical appraisal of experimental hypertensive glomerulopathy with the same approach used to assess hypertensive glomerulopathy in humans. Four hypertensive models with varying pathogenesis were analyzed–chronic angiotensin II infused mice, mice expressing active human renin in the liver (TTRhRen), spontaneously hypertensive rats (SHR), and Goldblatt two-kidney one-clip rats (2K1C). Analysis of glomerulopathy utilized the same criteria applied in humans–hyalinosis, focal segmental glomerulosclerosis (FSGS), ischemic, hypertrophic and solidified glomeruli, or global glomerulosclerosis (GGS). Data from animal models were compared to human reference values. Kidneys in TTRhRen mice, SHR and the nonclipped kidneys in 2K1C rats had no sign of hyalinosis, FSGS or GGS. Glomerulopathy in these groups was limited to variations in mesangial and capillary compartment volumes, with mild increases in collagen deposition. Histopathology in angiotensin II infused mice corresponded to mesangioproliferative glomerulonephritis, but not hypertensive glomerulosclerosis. The number of nephrons was significantly reduced in TTRhRen mice and SHR, but did not correlate with severity of glomerulopathy. The most substantial human-like glomerulosclerotic lesions, including FSGS, ischemic obsolescent glomeruli and GGS, were found in the clipped kidneys of 2K1C rats. The comparison of affected kidneys to healthy control in animals produces lesion values that are numerically impressive but correspond to mild damage if compared to humans. Animal studies should be standardized by employing the criteria and classifications established in human pathology to make experimental and human data fully comparable for comprehensive analysis and model improvements.

Salt-Sensitive Hypertension in GR+/- Rats Is Accompanied with Dysregulation in Adrenal Soluble Epoxide Hydrolase and Polyunsaturated Fatty Acid Pathways

Mutations within the glucocorticoid receptor (GR) gene locus lead to glucocorticoid resistance which is characterized by several clinical symptoms such as adrenal gland hyperplasia and salt-sensitive hypertension, although the underlying mechanisms are still unknown. We studied GR haploinsufficient (GR^+/−) Sprague Dawley rats which, on a standard diet, showed significantly increased plasma aldosterone and corticosterone levels and an adrenocortex hyperplasia accompanied by a normal systolic blood pressure. Following a high salt diet, these rats developed salt-sensitive hypertension and maintained elevated enzyme-soluble epoxide hydrolase (sEH) in adrenal glands, while sEH was significantly decreased in wild-type rats. Furthermore, GR^+/− rats showed dysregulation of the equilibrated linoleic and arachidonic acid pathways, with a significant increase of less active metabolites such as 8,9-DiHETrE. In Sprague Dawley rats, GR haploinsufficiency induced steroid disturbances, which provoked hypertension only in combination with high salt intake, which was accompanied by disturbances in sEH and fatty acid metabolism. Our results suggest that sEH inhibition could be a potential target to treat hypertension in patients with GR haploinsufficiency.

Piezo1 initiates platelet hyperreactivity and accelerates thrombosis in hypertension

BACKGROUND

Thrombosis is the pathological basis of cardiovascular and cerebrovascular diseases, which seriously threaten human life and health. Among them, nearly half of cardiovascular disease patients suffer from severe hypertension complications. Hypertension is thought to cause abnormal platelet activation and increases the risk of thrombosis, but the related mechanism is still vague.

OBJECTIVES

This study hypothesized that the abnormal hemodynamics of blood under hypertension might affect platelet function and accelerate thrombosis by activating mechanoreceptor Piezo1.

METHODS

To assess the activation effect of hypertension on mechanoreceptor Piezo1, we injected Piezo1 agonist Yoda1 and antagonist GsMTx-4 through the tail vein, then examined the platelet activation status and thrombosis.

RESULTS

Our results displayed that antagonist GsMTx-4 effectively inhibited calcium influx caused by hypertension and agonist Yoda1. Antithrombotic studies proved that the inhibition of Piezo1 effectively inhibited arterial thrombosis and reduced the infarct size of stroke in hypertensive mice.

CONCLUSIONS

Our study explains the activation of mechanoreceptor Piezo1 under hypertension is the key to abnormal platelet activation and thrombosis while providing novel platelet intervention strategies to prevent thrombosis.

Chronic Blockade of NMDAR Subunit 2A in the Hypothalamic Paraventricular Nucleus Alleviates Hypertension Through Suppression of MEK/ERK/CREB Pathway

BACKGROUND

N-Methyl-d-aspartate receptor (NMDAR) in the hypothalamic paraventricular nucleus (PVN) plays critical roles in regulating sympathetic outflow. Studies showed that acute application of the antagonists of NMDAR or its subunits would reduce sympathetic nerve discharges. However, little is known about the effect of long-term management of NMDAR in hypertensive animals.

METHODS

PEAQX, the specific antagonist of NMDAR subunit 2A (GluN2A) was injected into both sides of the PVN of two-kidney, one-clip (2K1C) renal hypertensive rats and control (normotensive rats) for 3 weeks.

RESULTS

Three weeks of PEAQX infusion significantly reduced the blood pressure of the 2K1C rats. It managed to resume the balance between excitatory and inhibitory neural transmitters, reduce the level of proinflammatory cytokines and reactive oxygen species in the PVN, and reduce the level of norepinephrine in plasma of the 2K1C rats. PEAQX administration also largely reduced the transcription and translation levels of GluN2A and changed the expression levels of NMDAR subunits 1 and 2B (GluN1 and GluN2B). In addition, NMDAR was known to function through activating the extracellular regulated protein kinases (ERK) or phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathways. In our study, we found that in the PVN of 2K1C rats treated with PEAQX, the phosphorylation levels of mitogen-activated protein kinase kinase (MEK), ERK1/2, and cAMP-response element-binding protein (CREB) significantly reduced, while the phosphorylation level of PI3K did not change significantly.

CONCLUSIONS

Chronic blockade of GluN2A alleviates hypertension through suppression of MEK/ERK/CREB pathway.

Nrf1 Knock-Down in the Hypothalamic Paraventricular Nucleus Alleviates Hypertension Through Intervention of Superoxide Production-Removal Balance and Mitochondrial Function

Oxidative stress in the hypothalamic paraventricular nucleus (PVN) contributes greatly to the development of hypertension. The recombinant nuclear respiratory factor 1 (Nrf1) regulates the transcription of several genes related to mitochondrial respiratory chain function or antioxidant expression, and thus may be involved in the pathogenesis of hypertension. Here we show that in the two-kidney, one-clip (2K1C) hypertensive rats the transcription level of Nrf1 was elevated comparing to the normotensive controls. Knocking down of Nrf1 in the PVN of 2K1C rats can significantly reduce their blood pressure and level of plasma norepinephrine (NE). Analysis revealed significant reduction of superoxide production level in both whole cell and mitochondria, along with up-regulation of superoxide dismutase 1 (Cu/Zn-SOD), NAD(P)H: quinone oxidoreductase 1 (NQO1), thioredoxin-dependent peroxiredoxin 3 (Prdx3), cytochrome c (Cyt-c) and glutathione synthesis rate-limiting enzyme (glutamyl-cysteine ligase catalytic subunit (Gclc) and modifier subunit (Gclm)), and down-regulation of cytochrome c oxidase subunit VI c (Cox6c) transcription after Nrf1 knock-down. In addition, the reduced ATP production and elevated mitochondrial membrane potential in the PVN of 2K1C rats were reinstated with Nrf1 knock-down, together with restored expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (Tfam), coiled-coil myosin-like BCL2-interacting protein (Beclin1), and Mitofusin 1 (Mfn1), which are related to the mitochondrial biogenesis, fusion, and autophagy. Together, the results indicate that the PVN Nrf1 is associated with the development of 2K1C-induced hypertension, and Nrf1 knock-down in the PVN can alleviate hypertension through intervention of mitochondrial function and restorement of the production-removal balance of superoxide.

A new approach to identifying hypertension-associated genes in the mesenteric artery of spontaneously hypertensive rats and stroke-prone spontaneously hypertensive rats

Supplemental Digital Content is available in the text

Objective:

Hypertension is one of the most prevalent diseases in humans who live a modern lifestyle. Alongside more effective care, clarification of the genetic background of hypertension is urgently required. Gene expression in mesenteric resistance arteries of spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP) and two types of renal hypertensive Wistar Kyoto rats (WKY), two kidneys and one clip renal hypertensive rat (2K1C) and one kidney and one clip renal hypertensive rat (1K1C), was compared using DNA microarrays.

Methods:

We used a simultaneous equation and comparative selection method to identify genes associated with hypertension using the Reactome analysis tool and GenBank database.

Results:

The expression of 298 genes was altered between SHR and WKY (44 upregulated and 254 downregulated), while the expression of 290 genes was altered between SHRSP and WKY (83 upregulated and 207 downregulated). For SHRSP versus SHR, the expression of 60 genes was altered (36 upregulated and 24 downregulated). Several genes expressed in SHR and SHRSP were also expressed in the renovascular hypertensive 2K1C and 1K1C rats, indicative of the existence of hyper-renin and/or hypervolemic pathophysiological changes in SHR and SHRSP.

Conclusion:

The overexpression of Kcnq1, Crlf1, Alb and Xirp1 and the inhibition of Galr2, Kcnh1, Ache, Chrm2 and Slc5a7 expression may indicate that a relationship exists between these genes and the cause and/or worsening of hypertension in SHR and SHRSP.

Excessive dietary salt promotes aortic stiffness in murine renovascular hypertension

Renovascular hypertension is characterized by activation of the renin-angiotensin-aldosterone system, blunted natriuretic responses, and elevated sympathetic nerve activity. Excess dietary salt intake exaggerates arterial blood pressure (ABP) in multiple models of experimental hypertension. The present study tested whether a high-salt diet exaggerated ABP and vascular dysfunction in a 2-kidney, 1-clip (2K1C) murine model. Male C57BL/6J mice (8-12 wk) were randomly assigned, and fed a 0.1% or 4.0% NaCl diet, and instrumented with telemetry units to measure ABP. Then, the 2K1C model was produced by placing a cuff around the right renal artery. Systolic, diastolic, and mean ABP were significantly higher in mice fed 4.0% vs. 0.1% NaCl at 1 wk but not after 3 wk. Interestingly, 2K1C hypertension progressively increased arterial pulse pressure in both groups; however, the magnitude was significantly greater in mice fed 4.0% vs. 0.1% NaCl at 3 wk. Moreover, pulse wave velocity was significantly greater in 2K1C mice fed 4.0% vs. 0.1% NaCl diet or sham-operated mice fed either diet. Histological assessment of aortas indicated no structural differences among groups. Finally, endothelium-dependent vasodilation was significantly and selectively attenuated in the aorta but not mesenteric arteries of 2K1C mice fed 4.0% NaCl vs. 0.1% NaCl or sham-operated control mice. The findings suggest that dietary salt loading transiently exaggerates 2K1C renovascular hypertension but promotes chronic aortic stiffness and selective aortic vascular dysfunction.NEW & NOTEWORTHY High dietary salt exaggerates hypertension in multiple experimental models. Here we demonstrate that a high-salt diet produces a greater increase in arterial blood pressure at 1 wk after induction of 2-kidney, 1-clip (2K1C) hypertension but not at 3 wk. Interestingly, 2K1C mice fed a high-salt diet displayed an exaggerated pulse pressure, elevated pulse wave velocity, and reduced endothelium-dependent vasodilation of the aorta but not mesenteric arteries. These findings suggest that dietary salt may interact with underlying cardiovascular disease to promote selective vascular dysfunction and aortic stiffness.

Morphological and Functional Characteristics of Animal Models of Myocardial Fibrosis Induced by Pressure Overload

Myocardial fibrosis is characterized by excessive deposition of myocardial interstitial collagen, abnormal distribution, and excessive proliferation of fibroblasts. According to the researches in recent years, myocardial fibrosis, as the pathological basis of various cardiovascular diseases, has been proven to be a core determinant in ventricular remodeling. Pressure load is one of the causes of myocardial fibrosis. In experimental models of pressure-overload-induced myocardial fibrosis, significant increase in left ventricular parameters such as interventricular septal thickness and left ventricular posterior wall thickness and the decrease of ejection fraction are some of the manifestations of cardiac damage. These morphological and functional changes have a serious impact on the maintenance of physiological functions. Therefore, establishing a suitable myocardial fibrosis model is the basis of its pathogenesis research. This paper will discuss the methods of establishing myocardial fibrosis model and compare the advantages and disadvantages of the models in order to provide a strong basis for establishing a myocardial fibrosis model.

Renal Chemerin Expression is Induced in Models of Hypertensive Nephropathy and Glomerulonephritis and Correlates with Markers of Inflammation and Fibrosis

Chemerin and its receptor, chemokine-like receptor 1 (CmklR1), are associated with chemotaxis, inflammation, and endothelial function, especially in metabolic syndrome, coronary heart disease, and hypertension. In humans, circulating chemerin levels and renal function show an inverse relation. So far, little is known about the potential role of chemerin in hypertensive nephropathy and renal inflammation. Therefore, we determined systemic and renal chemerin levels in 2-kidney-1-clip (2k1c) hypertensive and Thy1.1 nephritic rats, respectively, to explore the correlation between chemerin and markers of renal inflammation and fibrosis. Immunohistochemistry revealed a model-specific induction of chemerin expression at the corresponding site of renal damage (tubular vs. glomerular). In both models, renal expression of chemerin (RT-PCR, Western blot) was increased and correlated positively with markers of inflammation and fibrosis. In contrast, circulating chemerin levels remained unchanged. Taken together, these findings demonstrate that renal chemerin expression is associated with processes of inflammation and fibrosis-related to renal damage. However, its use as circulating biomarker of renal inflammation seems to be limited in our rat models.

Hypertension and Its Impact on Stroke Recovery: From a Vascular to a Parenchymal Overview

Hypertension is the first modifiable vascular risk factor accounting for 10.4 million deaths worldwide; it is strongly and independently associated with the risk of stroke and is related to worse prognosis. In addition, hypertension seems to be a key player in the implementation of vascular cognitive impairment. Long-term hypertension, complicated or not by the occurrence of ischemic stroke, is often reviewed on its vascular side, and parenchymal consequences are put aside. Here, we sought to review the impact of isolated hypertension or hypertension associated to stroke on brain atrophy, neuron connectivity and neurogenesis, and phenotype modification of microglia and astrocytes. Finally, we discuss the impact of antihypertensive therapies on cell responses to hypertension and functional recovery. This attractive topic remains a focus of continued investigation and stresses the relevance of including this vascular risk factor in preclinical investigations of stroke outcome.

Renovascular Hypertension Aggravates Atherosclerosis in Cholesterol-Fed Rabbits

BACKGROUND

Hypertension is a major risk factor for atherosclerotic disease. However, it is still not clear whether mechanical stress caused by hypertension directly affects the atherosclerotic development in the aorta and coronary arteries.

OBJECTIVES AND METHODS

We generated a hypertensive (HTN) rabbit model by surgical removal of the left kidney and partial ligation of the right renal artery. After a 16-week cholesterol diet, we compared aortic and coronary atherosclerosis of HTN rabbits with those of normotensive rabbits.

RESULTS

Hypertension did not affect lipid and apolipoprotein levels in plasma but led to a 3.0-fold increase in aortic atherosclerosis and a 1.7-fold increase in coronary atherosclerosis compared with control rabbits. Enhanced atherosclerosis in HTN rabbits was caused by significant increases in macrophages and smooth muscle cells in the lesions. Furthermore, oxidized LDL contents in the lesions were significantly increased in HTN rabbits. In addition, HTN rabbits exhibited prominent hyaline arteriolosclerosis in coronary arterioles.

CONCLUSIONS

These results indicate that hyper tension not only enhances atherosclerosis in large arteries including the aorta and coronary arteries but also affects hyaline arteriolosclerosis in small arteries.

Inhibition of the Hypoxia-Inducible Factor 1α-Induced Cardiospecific HERNA1 Enhance-Templated RNA Protects From Heart Disease

Supplemental Digital Content is available in the text.

Background:

Enhancers are genomic regulatory elements conferring spatiotemporal and signal-dependent control of gene expression. Recent evidence suggests that enhancers can generate noncoding enhancer RNAs, but their (patho)biological functions remain largely elusive.

Methods:

We performed chromatin immunoprecipitation–coupled sequencing of histone marks combined with RNA sequencing of left ventricular biopsies from experimental and genetic mouse models of human cardiac hypertrophy to identify transcripts revealing enhancer localization, conservation with the human genome, and hypoxia-inducible factor 1α dependence. The most promising candidate, hypoxia-inducible enhancer RNA (HERNA)1, was further examined by investigating its capacity to modulate neighboring coding gene expression by binding to their gene promoters by using chromatin isolation by RNA purification and λN–BoxB tethering–based reporter assays. The role of HERNA1 and its neighboring genes for pathological stress–induced growth and contractile dysfunction, and the therapeutic potential of HERNA1 inhibition was studied in gapmer-mediated loss-of-function studies in vitro using human induced pluripotent stem cell–derived cardiomyocytes and various in vivo models of human pathological cardiac hypertrophy.

Results:

HERNA1 is robustly induced on pathological stress. Production of HERNA1 is initiated by direct hypoxia-inducible factor 1α binding to a hypoxia-response element in the histoneH3-lysine27acetylation marks–enriched promoter of the enhancer and confers hypoxia responsiveness to nearby genes including synaptotagmin XVII, a member of the family of membrane-trafficking and Ca²⁺-sensing proteins and SMG1, encoding a phosphatidylinositol 3-kinase–related kinase. Consequently, a substrate of SMG1, ATP-dependent RNA helicase upframeshift 1, is hyperphoshorylated in a HERNA1- and SMG1-dependent manner. In vitro and in vivo inactivation of SMG1 and SYT17 revealed overlapping and distinct roles in modulating cardiac hypertrophy. Finally, in vivo administration of antisense oligonucleotides targeting HERNA1 protected mice from stress-induced pathological hypertrophy. The inhibition of HERNA1 postdisease development reversed left ventricular growth and dysfunction, resulting in increased overall survival.

Conclusions:

HERNA1 is a novel heart-specific noncoding RNA with key regulatory functions in modulating the growth, metabolic, and contractile gene program in disease, and reveals a molecular target amenable to therapeutic exploitation.

Frontline Science: Targeted expression of a dominant-negative high mobility group A1 transgene improves outcome in sepsis

High mobility group (HMG) proteins are a family of architectural transcription factors, with HMGA1 playing a role in the regulation of genes involved in promoting systemic inflammatory responses. We speculated that blocking HMGA1-mediated pathways might improve outcomes from sepsis. To investigate HMGA1 further, we developed genetically modified mice expressing a dominant negative (dn) form of HMGA1 targeted to the vasculature. In dnHMGA1 transgenic (Tg) mice, endogenous HMGA1 is present, but its function is decreased due to the mutant transgene. These mice allowed us to specifically study the importance of HMGA1 not only during a purely pro-inflammatory insult of endotoxemia, but also during microbial sepsis induced by implantation of a bacterial-laden fibrin clot into the peritoneum. We found that the dnHMGA1 transgene was only present in Tg and not wild-type (WT) littermate mice, and the mutant transgene was able to interact with transcription factors (such as NF-κB), but was not able to bind DNA. Tg mice exhibited a blunted hypotensive response to endotoxemia, and less mortality in microbial sepsis. Moreover, Tg mice had a reduced inflammatory response during sepsis, with decreased macrophage and neutrophil infiltration into tissues, which was associated with reduced expression of monocyte chemotactic protein-1 and macrophage inflammatory protein-2. Collectively, these data suggest that targeted expression of a dnHMGA1 transgene is able to improve outcomes in models of endotoxin exposure and microbial sepsis, in part by modulating the immune response and suggest a novel modifiable pathway to target therapeutics in sepsis.

The long noncoding RNA Wisper controls cardiac fibrosis and remodeling

Long noncoding RNAs (lncRNAs) are emerging as powerful regulators of cardiac development and disease. However, our understanding of the importance of these molecules in cardiac fibrosis is limited. Using an integrated genomic screen, we identified Wisper (Wisp2 super-enhancer-associated RNA) as a cardiac fibroblast-enriched lncRNA that regulates cardiac fibrosis after injury. Wisper expression was correlated with cardiac fibrosis both in a murine model of myocardial infarction (MI) and in heart tissue from human patients suffering from aortic stenosis. Loss-of-function approaches in vitro using modified antisense oligonucleotides (ASOs) demonstrated that Wisper is a specific regulator of cardiac fibroblast proliferation, migration, and survival. Accordingly, ASO-mediated silencing of Wisper in vivo attenuated MI-induced fibrosis and cardiac dysfunction. Functionally, Wisper regulates cardiac fibroblast gene expression programs critical for cell identity, extracellular matrix deposition, proliferation, and survival. In addition, its association with TIA1-related protein allows it to control the expression of a profibrotic form of lysyl hydroxylase 2, implicated in collagen cross-linking and stabilization of the matrix. Together, our findings identify Wisper as a cardiac fibroblast-enriched super-enhancer-associated lncRNA that represents an attractive therapeutic target to reduce the pathological development of cardiac fibrosis in response to MI and prevent adverse remodeling in the damaged heart.

Hypertension Accelerates Alzheimer's Disease-Related Pathologies in Pigs and 3xTg Mice

Epidemiological studies suggest there is an association between midlife hypertension and increased risk of late-life Alzheimer’s disease (AD). However, whether hypertension accelerates the onset of AD or is a distinct disease that becomes more prevalent with age (comorbidity) remains unclear. This study aimed to test the possible relationship between hypertension and AD pathogenesis. Two animal models were used in this study. For the first model, 7-month-old Lanyu-miniature-pigs were given the abdominal aortic constriction operation to induce hypertension and their AD-related pathologies were assessed at 1, 2, and 3 months after the operation. The results showed that hypertension was detected since 1 month after the operation in the pigs. Levels of Aβ, amyloid precursor protein, RAGE, phosphorylated tau and activated GSK3β in the hippocampi increased at 3 months after the operation. For the second model, 3xTg mice at the ages of 2, 5, and 7 months were subjected to the “two-kidney-one-clip” operation to induce hypertension. One month after the operation, blood pressure was significantly increased in the 3xTg mice in any age. Aβ, amyloid plaque load, and phosphorylated tau levels increased in the operated mice. Furthermore, the operation also induced shrinkage in the dendritic arbor of hippocampal dentate gyrus granule neurons, leakage in the blood-brain barrier, activation in microglia, and impairment in the hippocampus-dependent learning and memory in the 3xTg mice. In conclusion, hypertension accelerates the onset of AD. Blood pressure control during midlife may delay the onset of AD.

Effective prediction of preeclampsia by measuring serum angiotensin II, urinary angiotensinogen and urinary transforming growth factor β1

The aim of the current study was to analyze serum angiotensin II (Ang II), urinary angiotensinogen (AGT) and urinary transforming growth factor β1 (TGFβ1) levels in relation to the clinical manifestation of preeclampsia, and to explore the effects of circulating and renal renin angiotensin system (RAS) in preeclampsia patients. An enzyme-linked immunosorbent assay was used to evaluate serum Ang II, urinary AGT and urinary TGFβ1 in preeclampsia, pregnancy-induced hypertension and normotensive pregnancy patients. The correlation between urinary AGT and serum Ang II, urinary TGFβ1, blood pressure and urinary albumin/creatinine ratio (ACR) were then analyzed. Receiver operating characteristic (ROC) curves were also constructed. Negative correlations were observed between urinary AGT and blood pressure, and urinary AGT and ACR, whereas positive correlations were found between urinary AGT and serum Ang II, and urinary AFT and TGFβ1. Moreover, the area under the curve (AUC) of AGT was 0.841 [95% confidence interval (CI): 0.742–0.940, P<0.001], which was significantly higher than that of serum Ang II or urinary TGFβ1 (P<0.001). The optimal cut-off value of urinary AGT at 193 ng/l showed a high diagnostic value in preeclampsia. The AUC of combined serum Ang II, urinary AGT and urinary TGFβ1 was 0.918 (95% CI: 0.845–0.990, P<0.001), with a sensitivity of 83.9% and a specificity of 89.7%. Decreased levels of urinary AGT in preeclampsia patients suggested that local renal RAS was suppressed, and this was associated with hypertension and proteinuria. A high value preeclampsia diagnosis could be achieved by measuring urinary AGT or a combination of urinary AGT, serum Ang II and urinary TGFβ1.

Low-sodium diet induces atherogenesis regardless of lowering blood pressure in hypertensive hyperlipidemic mice

This study investigated the influence of sodium restriction and antihypertensive drugs on atherogenesis utilizing hypertensive (H) low-density lipoprotein-receptor knockout mice treated or not with losartan (Los) or hydralazine (Hyd) and fed low-sodium (LS) or normal-sodium (NS) chow. Despite reducing the blood pressure (BP) of H-LS mice, the LS diet caused arterial lipid infiltration due to increased plasma total cholesterol (TC) and triglycerides (TG). Los and Hyd reduced the BP of H-LS mice, and Los effectively prevented arterial injury, likely by reducing plasma TG and nonesterified fatty acids. Aortic lipid infiltration was lower in Los-treated H-LS mice (H-LS+Los) than in normotensive (N)-LS and H-LS mice. Aortic angiotensin II type 1 (AT1) receptor content was greater in H-NS than H-LS mice and in H-LS+Hyd than H-LS+Los mice. Carboxymethyl-lysine (CML) and receptor for advanced glycation end products (RAGE) immunostaining was greater in H-LS than H-NS mice. CML and RAGE levels were lower in LS animals treated with antihypertensive drugs, and Hyd enhanced the AT1 receptor level. Hyd also increased the gene expression of F4/80 but not tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-10, intercellular adhesion molecule-1 or cluster of differentiation 66. The novelty of the current study is that in a murine model of simultaneous hypertension and hyperlipidemia, the pleiotropic effect of chronic, severe sodium restriction elicited aortic damage even with reduced BP. These negative effects on the arterial wall were reduced by AT1 receptor antagonism, demonstrating the influence of angiotensin II in atherogenesis induced by a severely LS diet.

Applications and Limitations of Mouse Models for Understanding Human Atherosclerosis

Most of the biological understanding of mechanisms underlying coronary artery disease (CAD) derives from studies of mouse models. The identification of multiple CAD loci and strong candidate genes in large human genome-wide association studies (GWASs) presented an opportunity to examine the relevance of mouse models for the human disease. We comprehensively reviewed the mouse literature, including 827 literature-derived genes, and compared it to human data. First, we observed striking concordance of risk factors for atherosclerosis in mice and humans. Second, there was highly significant overlap of mouse genes with human genes identified by GWASs. In particular, of the 46 genes with strong association signals in CAD GWASs that were studied in mouse models, all but one exhibited consistent effects on atherosclerosis-related phenotypes. Third, we compared 178 CAD-associated pathways derived from human GWASs with 263 from mouse studies and observed that the majority were consistent between the species.

Chrysanthemum morifolium extract improves hypertension-induced cardiac hypertrophy in rats by reduction of blood pressure and inhibition of myocardial hypoxia inducible factor-1alpha expression

CONTEXT

Chrysanthemum morifolium Ramat. (Asteraceae) extract (CME) possesses a vasodilator effect in vitro. However, the use of polyphenol-rich CME in the treatment of hypertension-induced cardiac hypertrophy has not been reported.

OBJECTIVE

We investigated the effect of polyphenol-rich CME on hypertension-induced cardiac hypertrophy in rats and its possible mechanism of action.

MATERIALS AND METHODS

The Sprague-Dawley rat model with cardiac hypertrophy was induced by renovascular hypertension. The blood pressure, cardiac weight index, free fatty acids (FFA) in serum and myocardium, and protein expressions of myocardial hypoxia inducible factor-1α (HIF-1α), peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase-1a (CPT-1a), pyruvate dehydrogenase kinase-4 (PDK-4) and glucose transporter-4 (GLUT-4) were measured after treating hypertensive rats with polyphenol-rich CME of anthodia 75-150 mg/kg once daily for 4 weeks. A myocardial histological examination was also conducted.

RESULTS

After CME treatment, the blood pressure, cardiac weight and cardiac weight index decreased by 5.7-9.6%, 9.2-18.4% and 10.9-20.1%, respectively, and the cardiomyocyte cross-sectional area also decreased by 8.3-30.4%. The CME treatment simultaneously decreased the FFA in serum and myocardium and protein expressions of myocardial HIF-1α and GLUT-4, and increased the protein expressions of myocardial PPARα, CPT-1a and PDK-4, especially in the CME 150 mg/kg group (p < 0.05 or p < 0.01).

DISCUSSION AND CONCLUSION

Polyphenol-rich CME may alleviate hypertensive cardiac hypertrophy in rats. Its mechanisms may be related to the reduction of blood pressure and amelioration of the myocardial energy metabolism. The latter may be attributed to the inhibition of HIF-1α expression and subsequent modulation of PPARα-mediated CPT-1a, PDK-4 and GLUT-4 expressions.

Animal models for the study of primary and secondary hypertension in humans

Hypertension is a significant cause of morbidity and mortality worldwide. It is defined as systolic and diastolic blood pressures (SBP/DBP) >140 and 90 mmHg, respectively. Individuals with an SBP between 120 and 139, or DBP between 80 and 89 mmHg, are said to exhibit pre-hypertension. Hypertension can have primary or secondary causes. Primary or essential hypertension is a multifactorial disease caused by interacting environmental and polygenic factors. Secondary causes are renovascular hypertension, renal disease, endocrine disorders and other medical conditions. The aim of the present review article was to examine the different animal models that have been generated for studying the molecular and physiological mechanisms underlying hypertension. Their advantages, disadvantages and limitations will be discussed.

Prior renovascular hypertension does not predispose to atherosclerosis in mice

BACKGROUND

Hypertension is a major risk factor for development of atherosclerotic cardiovascular disease (ASCVD). Although lowering blood pressure with antihypertensive drugs reduces the increased risk of ASCVD, residual increased risk still remains, suggesting that hypertension may cause chronic changes that promote atherosclerosis. Thus, we tested the hypothesis that hypertension increases the susceptibility to atherosclerosis in mice even after a period of re-established normotension.

METHODS

We used the 2-kidney, 1-clip (2K1C) technique to induce angiotensin-driven renovascular hypertension, and overexpression of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene to cause severe hypercholesterolemia and atherosclerosis.

RESULTS

First, we performed 2K1C (n = 8) or sham surgery (n = 9) in PCSK9 transgenic mice before they were fed a high fat diet for 14 weeks. As expected, 2K1C did not affect cholesterol levels, but induced cardiac hypertrophy and significantly increased the atherosclerotic lesion area compared to sham mice (1.8 fold, p < 0.01). Next, we performed 2K1C (n = 13) or sham surgery (n = 14) in wild-type mice but removed the clipped/sham-operated kidney after 10 weeks to eliminate hypertension, and subsequently induced hypercholesterolemia by way of adeno-associated virus-mediated hepatic gene transfer of PCSK9 combined with high-fat diet. After 14 weeks of hypercholesterolemia, atherosclerotic lesion areas were not significantly different in mice with or without prior 2K1C hypertension (0.95 fold, p = 0.35).

CONCLUSION

Renovascular hypertension in mice does not induce pro-atherogenic changes that persist beyond the hypertensive phase. These results indicate that hypertension only promotes atherogenesis when coinciding temporally with hypercholesterolemia.

Effects of Restoration of Blood Flow on the Development of Aortic Atherosclerosis in ApoE-/- Mice With Unilateral Renal Artery Stenosis

Background

Chronic unilateral renal artery stenosis (RAS) causes accelerated atherosclerosis in apolipoprotein E–deficient (ApoE^−/−) mice, but effects of restoration of renal blood flow on aortic atherosclerosis are unknown.

Methods and Results

Male ApoE^−/− mice underwent sham surgery (n=16) or had partial ligation of the right renal artery (n=41) with the ligature being removed 4 days later (D4LR; n=6), 8 days later (D8LR; n=11), or left in place for 90 days (chronic RAS; n=24). Ligature removal at 4 or 8 days resulted in improved renal blood flow, decreased plasma angiotensin II levels, a return of systolic blood pressure to baseline, and increased plasma levels of neutrophil gelatinase associated lipocalin. Chronic RAS resulted in increased lipid staining in the aortic arch (33.2% [24.4, 47.5] vs 11.6% [6.1, 14.2]; P<0.05) and descending thoracic aorta (10.2% [6.4, 25.9] vs 4.9% [2.8, 7.8]; P<0.05), compared to sham surgery. There was an increased amount of aortic arch lipid staining in the D8LR group (22.7% [22.1, 32.7]), compared to sham‐surgery, but less than observed with chronic RAS. Lipid staining in the aortic arch was not increased in the D4LR group, and lipid staining in the descending aorta was not increased in either the D8LR or D4LR groups. There was less macrophage expression in infrarenal aortic atheroma in the D4LR and D8LR groups compared to the chronic RAS group.

Conclusions

Restoration of renal blood flow at either 4 or 8 days after unilateral RAS had a beneficial effect on systolic blood pressure, aortic lipid deposition, and atheroma inflammation.

Hypertension impairs hippocampus-related adult neurogenesis, CA1 neuron dendritic arborization and long-term memory

Hypertension is associated with neurodegenerative diseases and cognitive impairment. Several studies using spontaneous hypertensive rats to study the effect of hypertension on memory performance and adult hippocampal neurogenesis have reached inconsistent conclusions. The contradictory findings may be related to the genetic variability of spontaneous hypertensive rats due to the conventional breeding practices. The objective of this study is to examine the effect of hypertension on hippocampal structure and function in isogenic mice. Hypertension was induced by the '2 kidneys, 1 clip' method (2K1C) which constricted one of the two renal arteries. The blood pressures of 2K1C mice were higher than the sham group on post-operation day 7 and remained high up to day 28. Mice with 2K1C-induced hypertension had impaired long-term, but not short-term, memory. Dendritic complexity of CA1 neurons and hippocampal neurogenesis were reduced by 2K1C-induced hypertension on post-operation day 28. Furthermore, 2K1C decreased the levels of hippocampal brain-derived neurotrophic factor, while blood vessel density and activation status of astrocytes and microglia were not affected. In conclusion, hypertension impairs hippocampus-associated long-term memory, dendritic arborization and neurogenesis, which may be caused by down-regulation of brain-derived neurotrophic factor signaling pathways.

Melatonin attenuates hypertension-induced renal injury partially through inhibiting oxidative stress in rats

The aim of the present study was to investigate the protective effects of melatonin (MLT) on hypertension-induced renal injury and identify its mechanism of action. Twenty-four healthy male Wistar rats were divided into a sham control group (n=8), which was subjected to sham operation and received vehicle treatment (physiological saline intraperitoneally at 0.1 ml/100 g), a vehicle group (n=8), which was subjected to occlusion of the left renal artery and vehicle treatment, and the MLT group (n=8), which was subjected to occlusion of the left renal artery and treated with MLT (10 mg/kg/day). Pathological features of the renal tissues were determined using hematoxylin and eosin staining and Masson staining. Urine protein, serum creatinine (Scr), superoxide dismutase (SOD) and malondialdehyde (MDA) were determined. Immunohistochemical analysis was performed to determine the expression of heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, reverse transcription polymerase chain reaction was conducted to determine the mRNA expression of HO-1, ICAM-1, eNOS and iNOS. A marked decrease in blood pressure was noticed in the MLT group at week 4 compared with that of the vehicle group (P<0.01). Furthermore, MLT treatment attenuated the infiltration of inflammatory cells and oedema/atrophy of renal tubules. MLT attenuated hypertension-induced increases in urine protein excretion, serum creatinine and MDA as well as decreases in SOD activity in renal tissues. Furthermore, MLT attenuated hypertension-induced increases in iNOS and ICAM-1 as well as decreases in eNOS and HO-1 expression at the mRNA and protein level. In conclusion, the results of the present study indicated that MLT had protective roles in hypertension-induced renal injury. Its mechanism of action is, at least in part, associated with the inhibition of oxidative stress.

Factors regulating the renal circulation in spontaneously hypertensive rats

Hypertension is one of the leading causes of health morbidity and mortality which are linked to many life threatening diseases such as stroke heart problems and renal dysfunction.

The integrity of renal microcirculation is crucial to maintaining the clearance and the excretory function in the normotensive and hypertensive conditions. Furthermore, any alteration in the renal function is involved in the pathophysiology of hypertension.

The aim of this review is to provide a brief discussion of some factors that regulate renal haemodynamics in spontaneously hypertensive rats, an animal model of hypertension, and how these factors are linked to the disease.

Animal Models in Cardiovascular Research: Hypertension and Atherosclerosis

Hypertension and atherosclerosis are among the most common causes of mortality in both developed and developing countries. Experimental animal models of hypertension and atherosclerosis have become a valuable tool for providing information on etiology, pathophysiology, and complications of the disease and on the efficacy and mechanism of action of various drugs and compounds used in treatment. An animal model has been developed to study hypertension and atherosclerosis for several reasons. Compared to human models, an animal model is easily manageable, as compounding effects of dietary and environmental factors can be controlled. Blood vessels and cardiac tissue samples can be taken for detailed experimental and biomolecular examination. Choice of animal model is often determined by the research aim, as well as financial and technical factors. A thorough understanding of the animal models used and complete analysis must be validated so that the data can be extrapolated to humans. In conclusion, animal models for hypertension and atherosclerosis are invaluable in improving our understanding of cardiovascular disease and developing new pharmacological therapies.

Calcitonin gene-related peptide (CGRP) receptors are important to maintain cerebrovascular reactivity in chronic hypertension

Cerebral blood flow autoregulation (CA) shifts to higher blood pressures in chronic hypertensive patients, which increases their risk for brain damage. Although cerebral vascular smooth muscle cells express the potent vasodilatatory peptides calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) and their receptors (calcitonin receptor-like receptor (Calclr), receptor-modifying proteins (RAMP) 1 and 2), their contribution to CA during chronic hypertension is poorly understood. Here we report that chronic (10 weeks) hypertensive (one-kidney-one-clip-method) mice overexpressing the Calclr in smooth muscle cells (CLR-tg), which increases the natural sensitivity of the brain vasculature to CGRP and AM show significantly better blood pressure drop-induced cerebrovascular reactivity than wt controls. Compared to sham mice, this was paralleled by increased cerebral CGRP-binding sites (receptor autoradiography), significantly in CLR-tg but not wt mice. AM-binding sites remained unchanged. Whereas hypertension did not alter RAMP-1 expression (droplet digital (dd) PCR) in either mouse line, RAMP-2 expression dropped significantly in both mouse lines by about 65%. Moreover, in wt only Calclr expression was reduced by about 70% parallel to an increase of smooth muscle actin (Acta2) expression. Thus, chronic hypertension induces a stoichiometric shift between CGRP and AM receptors in favor of the CGRP receptor. However, the parallel reduction of Calclr expression observed in wt mice but not CLR-tg mice appears to be a key mechanism in chronic hypertension impairing cerebrovascular reactivity.

Deficient prolylcarboxypeptidase gene and protein expression in left ventricles of spontaneously hypertensive rats (SHR)

Prolylcarboxypeptidase (PRCP), an endothelial cell membrane serine peptidase that inactivates angiotensin II and activates pre-kallikrein, is thought to have anti-hypertensive and anti-proliferative roles in cardiovascular homeostasis. We hypothesized that PRCP function may be altered in heart tissue under conditions that predispose to left ventricle hypertrophy (LVH) in rats. We therefore used real-time PCR and western-blotting to examine the mRNA and protein expression of PRCP in the hearts of spontaneously hypertensive rats (SHR) at pre-hypertensive (5-week-old) and hypertensive (16-week-old) stages compared with age-matched hypertensive (2 kidney-1 clip; 2K-1C) rats and normotensive Wistar rats. PRCP mRNA expression was significantly reduced in hearts of 5- and 16-week-old SHR compared with age-matched Wistar controls, 2K-1C hypertensive rats and sham-operated normotensive rats. There were no significant differences in the PRCP mRNA and protein expression levels in hearts from hypertensive renovascular and sham-operated normotensive rats. Prolonged treatment of SHR with the AT1 receptor antagonist losartan (40 mg/kg, gavage for 8 weeks) reduced the left ventricular weight/body weight ratio (LVW/BW), as well as the mRNA expression of collagen type 1, collagen type 3 and MMP9 in left ventricular tissue, without affecting PRCP gene and protein expression. Our results suggest that diminished PRCP gene and protein expression might be constitutionally involved in the SHR phenotype. In addition, since neither the development of arterial hypertension in the 2K-1C model nor its successful treatment in SHR altered PRCP gene and protein expression in heart tissue, it appears unlikely that PRCP function is regulated by the renin-angiotensin system or by afterload conditions.

Inhibition of phosphodiesterase 5 restores endothelial function in renovascular hypertension

Background

The clipping of an artery supplying one of the two kidneys (2K1C) activates the renin-angiotensin (Ang) system (RAS), resulting in hypertension and endothelial dysfunction. Recently, we demonstrated the intrarenal beneficial effects of sildenafil on the high levels of Ang II and reactive oxygen species (ROS) and on high blood pressure (BP) in 2K1C mice. Thus, in the present study, we tested the hypothesis that sildenafil improves endothelial function in hypertensive 2K1C mice by improving the NO/ROS balance.

Methods

2K1C hypertension was induced in C57BL/6 mice. Two weeks later, they were treated with sildenafil (40 mg/kg/day, via oral) or vehicle for 2 weeks and compared with sham mice. At the end of the treatment, the levels of plasma and intrarenal Ang peptides were measured. Endothelial function and ROS production were assessed in mesenteric arterial bed (MAB).

Results

The 2K1C mice exhibited normal plasma levels of Ang I, II and 1–7, whereas the intrarenal Ang I and II were increased (~35% and ~140%) compared with the Sham mice. Sildenafil normalized the intrarenal Ang I and II and increased the plasma (~45%) and intrarenal (+15%) Ang 1–7. The 2K1C mice exhibited endothelial dysfunction, primarily due to increased ROS and decreased NO productions by endothelial cells, which were ameliorated by treatment with sildenafil.

Conclusion

These data suggest that the effects of sildenafil on endothelial dysfunction in 2K1C mice may be due to interaction with RAS and restoring NO/ROS balance in the endothelial cells from MAB. Thus, sildenafil is a promising candidate drug for the treatment of hypertension accompanied by endothelial dysfunction and kidney disease.

Sympathoactivation and rho-kinase-dependent baroreflex function in experimental renovascular hypertension with reduced kidney mass

BACKGROUND

Dysregulation of the autonomic nervous system is frequent in subjects with cardiovascular disease. The contribution of different forms of renovascular hypertension and the mechanisms contributing to autonomic dysfunction in hypertension are incompletely understood. Here, murine models of renovascular hypertension with preserved (2-kidneys-1 clip, 2K1C) and reduced (1-kidney-1 clip, 1K1C) kidney mass were studied with regard to autonomic nervous system regulation (sympathetic tone: power-spectral analysis of systolic blood pressure; parasympathetic tone: power-spectral analysis of heart rate) and baroreflex sensitivity of heart rate by spontaneous, concomitant changes of systolic blood pressure and pulse interval. Involvement of the renin-angiotensin system and the rho-kinase pathway were determined by application of inhibitors.

RESULTS

C57BL6N mice (6 to 11) with reduced kidney mass (1K1C) or with preserved kidney mass (2K1C) developed a similar degree of hypertension. In comparison to control mice, both models presented with a significantly increased sympathetic tone and lower baroreflex sensitivity of heart rate. However, only 2K1C animals had a lower parasympathetic tone, whereas urinary norepinephrine excretion was reduced in the 1K1C model. Rho kinase inhibition given to a subset of 1K1C and 2K1C animals improved baroreflex sensitivity of heart rate selectively in the 1K1C model. Rho kinase inhibition had no additional effects on autonomic nervous system in either model of renovascular hypertension and did not change the blood pressure. Blockade of AT1 receptors (in 2K1C animals) normalized the sympathetic tone, decreased resting heart rate, improved baroreflex sensitivity of heart rate and parasympathetic tone.

CONCLUSIONS

Regardless of residual renal mass, blood pressure and sympathetic tone are increased, whereas baroreflex sensitivity is depressed in murine models of renovascular hypertension. Reduced norepinephrine excretion and/or degradation might contribute to sympathoactivation in renovascular hypertension with reduced renal mass (1K1C). Overall, the study helps to direct research to optimize medical therapy of hypertension.

Animal models of atherosclerosis and magnetic resonance imaging for monitoring plaque progression

Atherosclerosis, the main cause of heart attack and stroke, is the leading cause of death in most modern countries. Preventing clinical events depends on a better understanding of the mechanism of atherosclerotic plaque destabilization. Our knowledge on the characteristics of vulnerable plaques in humans has grown past decades. Histological studies have provided a precise definition of high-risk lesions and novel imaging methods for human atherosclerotic plaque characterization have made significant progress. However the pathological mechanisms leading from stable lesions to the formation of vulnerable plaques remain uncertain and the related clinical events are unpredictable. An animal model mimicking human plaque destablization is required as well as an in vivo imaging method to assess and monitor atherosclerosis progression. Magnetic resonance imaging (MRI) is increasingly used for in vivo assessment of atherosclerotic plaques in the human carotids. MRI provides well-characterized morphological and functional features of human atherosclerotic plaque which can be also assessed in animal models. This review summarizes the most common species used as animal models for experimental atherosclerosis, the techniques to induce atherosclerosis and to obtain vulnerable plaques, together with the role of MRI for monitoring atherosclerotic plaques in animals.

Phosphodiesterase 5 attenuates the vasodilatory response in renovascular hypertension

NO/cGMP signaling plays an important role in vascular relaxation and regulation of blood pressure. The key enzyme in the cascade, the NO-stimulated cGMP-forming guanylyl cyclase exists in two enzymatically indistinguishable isoforms (NO-GC1, NO-GC2) with NO-GC1 being the major NO-GC in the vasculature. Here, we studied the NO/cGMP pathway in renal resistance arteries of NO-GC1 KO mice and its role in renovascular hypertension induced by the 2-kidney-1-clip-operation (2K1C). In the NO-GC1 KOs, relaxation of renal vasculature as determined in isolated perfused kidneys was reduced in accordance with the marked reduction of cGMP-forming activity (80%). Noteworthy, increased eNOS-catalyzed NO formation was detected in kidneys of NO-GC1 KOs. Upon the 2K1C operation, NO-GC1 KO mice developed hypertension but the increase in blood pressures was not any higher than in WT. Conversely, operated WT mice showed a reduction of cGMP-dependent relaxation of renal vessels, which was not found in the NO-GC1 KOs. The reduced relaxation in operated WT mice was restored by sildenafil indicating that enhanced PDE5-catalyzed cGMP degradation most likely accounts for the attenuated vascular responsiveness. PDE5 activation depends on allosteric binding of cGMP. Because cGMP levels are lower, the 2K1C-induced vascular changes do not occur in the NO-GC1 KOs. In support of a higher PDE5 activity, sildenafil reduced blood pressure more efficiently in operated WT than NO-GC1 KO mice. All together our data suggest that within renovascular hypertension, cGMP-based PDE5 activation terminates NO/cGMP signaling thereby providing a new molecular basis for further pharmacological interventions.