Renin, angiotensin, sodium and organ damage

Minireview: Understanding and targeting inflammatory, hemodynamic and injury markers for cardiorenal protection in type 1 diabetes

The coexistence of cardiovascular disease (CVD) and diabetic kidney disease (DKD) is common in people with type 1 diabetes (T1D) and is strongly associated with an increased risk of morbidity and mortality. Hence, it is imperative to explore robust tools that can accurately reflect the development and progression of cardiorenal complications. Several cardiovascular and kidney biomarkers have been identified to detect at-risk individuals with T1D. The primary aim of this review is to highlight biomarkers of injury, inflammation, or renal hemodynamic changes that may influence T1D susceptibility to CVD and DKD. We will also examine the impact of approved pharmacotherapies for type 2 diabetes, including renin-angiotensin-aldosterone system (RAAS) inhibitors, sodium-glucose cotransporter-2 (SGLT2) inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RAs) on candidate biomarkers for cardiorenal complications in people with T1D and discuss how these changes may potentially mediate kidney and cardiovascular protection. Identifying predictive and prognostic biomarkers for DKD and CVD may highlight potential drug targets to attenuate cardiorenal disease progression, implement novel risk stratification measures in clinical trials, and improve the assessment, diagnosis, and treatment of at-risk individuals with T1D.

The role of Kolaviron, a bioflavonoid from Garcinia kola, in the management of cardiovascular diseases: A systematic review

While the cardiovascular effects of Kolaviron (KV) and Garcinia kola (GK) are documented in the literature, a thorough search through literature revealed a fragmentation of information on the effect of KV and GK on cardiovascular diseases (CVDs). This systematic review aims to evaluate and summarize preclinical or clinical evidence on the effect of KV and GK on CVDs. Using the PRISMA guidelines, a systematic literature search was conducted in five medical databases (PubMed, Cochrane, EMBASE, CINAHL, and Web of Science). Inclusion criteria included both in vivo and in vitro studies related to CVDs. Eligible studies included those in which specific clinical parameters, CVD biomarkers, or voltage-gated channel effects were reported. The quality of the included studies was assessed using a modified Collaborative Approach to Meta-Analysis and Review of Animal Data from the Experimental Studies (CAMARADE) checklist. A total of 22 studies were included in this systematic review. The median and mean values of the included studies' quality scores were 6 and 5.864 ± 0.296, respectively. The results from the quality assessment of included studies validate their suitability, usefulness, and fit. Based on this systematic review, the effect of KV and GK on CVDs can be divided into eight emerging trends: (1) Anti-hypertensive/Blood pressure lowering effect; (2) Lipid profile improvement effect (3) Anti-atherosclerotic effect; (4) Anti-thrombotic effect; (5) Cardioprotection; (6) Vasodilatory effect; (7) Antioxidant effects; and (8) Genetic expression and therapeutic target for cardiovascular dysfunction. From this systematic review, it can be concluded that KV is helpful in managing CVD risk factors such as hypertension and high lipids/cholesterol. Several included studies in this review demonstrated the antihypertensive, lipid improvement, antioxidant, and signaling pathway modulation effects of KV. This potentially makes KV a good therapeutic target for the management of CVDs.

Pharmacological treatment of migraine: Drug classes, mechanisms of action, clinical trials and new treatments

Migraine is the sixth most prevalent disease globally, a major cause of disability, and it imposes an enormous personal and socioeconomic burden. Migraine treatment is often limited by insufficient therapy response, leading to the need for individually adjusted treatment approaches. In this review, we analyse historical and current pharmaceutical development approaches in acute and chronic migraine based on a comprehensive and systematic analysis of Food and Drug Administration (FDA)-approved drugs and those under investigation. The development of migraine therapeutics has significantly intensified during the last 3 years, as shown by our analysis of the trends of drug development between 1970 and 2020. The spectrum of drug targets has expanded considerably, which has been accompanied by an increase in the number of specialised clinical trials. This review highlights the mechanistic implications of FDA-approved and currently investigated drugs and discusses current and future therapeutic options based on identified drug classes of interest.

Effect of free running wheel exercise on renal expression of parathyroid hormone receptor type 1 in spontaneously hypertensive rats

An active lifestyle is generally recommended for hypertensive patients to prevent subsequent end-organ damage. However, experimental data on long-term effects of exercise on hypertension are insufficient and underlying mechanisms are not well understood. This study was aimed to investigate the effect of exercise on renal expression of parathyroid hormone-related protein (PTHrP) and parathyroid hormone receptor type 1 (PTHR1) in spontaneously hypertensive rats (SHR). Twenty-four rats started free running wheel exercise at the age of 1.5 months (pre-hypertensive state) and proceeded for 1.5, 3.0, 6.0, and 10.0 months. Thirty rats kept under standard housing conditions were used as sedentary controls. Kidney function was assessed by measuring plasma creatinine levels and urine albumin-to-creatinine ratios. Renal expression of PTHrP and PTHR1 was analyzed by qRT-PCR and western blot. Renal expression of PTHR1 was markedly increased between the 6th and 10th months in sedentary rats and this increase was significantly lower in SHRs with high physical activity on mRNA (-30%) and protein level (-27%). At the same time, urine albumin-to-creatinine ratio increased (from 65 to 231 mg/g) but somehow lower in exercise performing SHRs (48-196 mg/g). Our data suggest that enhanced exercise, stimulated by allocation of a free running wheel, is associated with lower PTHR1 expression in SHRs and this may contribute to preserved kidney function.

Biochemical Effects of Aqueous Extract of Persea americana (Mill) on the Myocardium of Left Ventricle of High Salt-Fed Adult Wistar Rats

BACKGROUND

The cardioprotective effects of Persea americana extract was investigated on biochemical activities of high salt-fed adult Wistar rats in this study.

METHOD

Forty healthy Wistar rats of both sexes weighing 120 to 150 g were randomly assigned into 8 groups of 5 rats each (groups A, B, C, D, E, F, G, and H). Rats in groups A, F, G, and H were fed with standard laboratory pellets, while groups B, C, D, and E were fed on the high-salt diet for 4 weeks. Concomitantly, daily administration of 50, 100, and 150 mg/kg of the P americana extract were given orally to groups C and F, D and G, and E and H, respectively, while rats in groups A and B were administered distilled water. Blood samples were taken by cardiac puncture; concentration of sodium ion, potassium ion, nitric oxide, and activity of lactate dehydrogenase were determined. One-way analysis of variance was used to analyze data, followed by Student-Newman-Keuls (SNK) test for multiple comparison.

RESULTS

Results revealed that concentration of potassium ion and nitric oxide was significantly lower ( P < .05) in high salt-fed groups. Sodium ion concentration and activity of lactate dehydrogenase were higher in high salt-fed group while P americana prevented biochemical perturbations in other experimental groups.

CONCLUSION

In conclusion, high salt-diet induced biochemical alterations which were significantly protected by oral administration of P americana extract.

Anti-hypertensive Herbs and their Mechanisms of Action: Part I

The use of herbal therapies for treatment and management of cardiovascular diseases (CVDs) is increasing. Plants contain a bounty of phytochemicals that have proven to be protective by reducing the risk of various ailments and diseases. Indeed, accumulating literature provides the scientific evidence and hence reason d'etre for the application of herbal therapy in relation to CVDs. Slowly, but absolutely, herbal remedies are being entrenched into evidence-based medical practice. This is partly due to the supporting clinical trials and epidemiological studies. The rationale for this expanding interest and use of plant based treatments being that a significant proportion of hypertensive patients do not respond to Modern therapeutic medication. Other elements to this equation are the cost of medication, side-effects, accessibility, and availability of drugs. Therefore, we believe it is pertinent to review the literature on the beneficial effects of herbs and their isolated compounds as medication for treatment of hypertension, a prevalent risk factor for CVDs. Our search utilized the PubMed and ScienceDirect databases, and the criterion for inclusion was based on the following keywords and phrases: hypertension, high blood pressure, herbal medicine, complementary and alternative medicine (CAM), nitric oxide, vascular smooth muscle cell (VSMC) proliferation, hydrogen sulfide, nuclear factor kappa-B, oxidative stress, and epigenetics/epigenomics. Each of the aforementioned keywords was co-joined with herb in question, and where possible with its constituent molecule(s). In this first of a two-part review, we provide a brief introduction of hypertension, followed by a discussion of the molecular and cellular mechanisms. We then present and discuss the plants that are most commonly used in the treatment and management of hypertension.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Occipital Artery Function during the Development of 2-Kidney, 1-Clip Hypertension in Rats

This study compared the contractile responses elicited by angiotensin II (AII), arginine vasopressin (AVP), and 5-hydroxytryptamine (5-HT) in isolated occipital arteries (OAs) from sham-operated (SHAM) and 2-kidney, 1-clip (2K-1C) hypertensive rats. OAs were isolated and bisected into proximal segments (closer to the common carotid artery) and distal segments (closer to the nodose ganglion) and mounted separately on myographs. On day 9, 2K-1C rats had higher mean arterial blood pressures, heart rates, and plasma renin concentrations than SHAM rats. The contractile responses to AII were markedly diminished in both proximal and distal segments of OAs from 2K-1C rats as compared to those from SHAM rats. The responses elicited by AVP were substantially greater in distal than in proximal segments of OAs from SHAM rats and that AVP elicited similar responses in OA segments from 2K-1C rats. The responses elicited by 5-HT were similar in proximal and distal segments from SHAM and 2K-1C rats. These results demonstrate that continued exposure to circulating AII and AVP in 2K-1C rats reduces the contractile efficacy of AII but not AVP or 5-HT. The diminished responsiveness to AII may alter the physiological status of OAs in vivo.

Retinoid X receptor agonists inhibit hypertension-induced myocardial hypertrophy by modulating LKB1/AMPK/p70S6K signaling pathway

BACKGROUND

Retinoid X receptor (RXR) has been demonstrated to play an important role in cardiac development and has been implicated in cardiovascular diseases. This study aimed to examine the effects of RXRα agonist bexarotene on pathological left ventricular hypertrophy (LVH) in a spontaneously hypertensive rat (SHR) model and the underlying mechanism.

METHODS

WKY rats served as controls. SHRs were randomized into 3 groups at the age of 4 weeks and were treated (once daily for 12 weeks) with either bexarotene (30 or 100mg/kg body weight) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Neonatal cardiomyocytes were treated with AngII (10(-7) mmol/L) with or without the indicated concentration of RXRα ligand 9-cis-RA. The protein abundances of β-actin, RXRα, LKB1, phospho-LKB1, AMPK, phospho-AMPK, P70S6K, phospho-P70S6K, ACE, and AT1 receptor were measured along with blood pressure, body weight and angiotensin II (Ang II) levels. The effects of LKB1 downregulation by LKB1 small, interfering RNA were examined.

RESULTS

Treatment of SHRs with bexarotene resulted in significant inhibition of LVH without eliminating hypertension. Immunoblot with heart tissue homogenates from SHRs revealed that bexarotene activated the LKB1/AMPK signaling pathway and inhibited p70S6K. However, the increased Ang II levels in SHR serum and heart tissue were not reduced by bexarotene treatment. Treatment of cardiomyocytes with Ang II resulted in significantly reduced LKB1/AMPK activity and increased p70S6K activity. 9-cis-RA antagonized Ang II-induced LKB1/AMPK and p70S6K activation changes in vitro.

CONCLUSIONS

RXR agonists prevent the inhibition of the LKB1/AMPK/p70S6K pathway and regulate protein synthesis to reduce LVH. This antihypertrophic effect of bexarotene is independent of blood pressure.

Protein kinase C-mediated ATP stimulation of Na(+)-ATPase activity in LLC-PK1 cells involves a P2Y2 and/or P2Y4 receptor

ATP-activated P2Y receptors play an important role in renal sodium excretion. The aim of this study was to evaluate the modulation of ATPase-driven sodium reabsorption in the proximal tubule by ATP or adenosine (Ado). LLC-PK1 cells, a model of porcine proximal tubule cells, were used. ATP (10(-6)M) or Ado (10(-6)M) specifically stimulated Na(+)-ATPase activity without any changes in (Na(+)+K(+))-ATPase activity. Our results show that the Ado effect is mediated by its conversion to ATP. Furthermore, it was observed that the effect of ATP was mimicked by UTP, ATPγS and 2-thio-UTP, an agonist of P2Y2 and P2Y4 receptors. In addition, ATP-stimulated Na(+)-ATPase activity involves protein kinase C (PKC). Our results indicate that ATP-induced stimulation of proximal tubule Na(+)-ATPase activity is mediated by a PKC-dependent P2Y2 and/or P2Y4 pathway. These findings provide new perspectives on the role of the effect of P2Y-mediated extracellular ATP on renal sodium handling.

Antioxidants in kidney diseases: the impact of bardoxolone methyl

Drugs targeting the renin-angiotensin-aldosterone system (RAAS) are the mainstay of therapy to retard the progression of proteinuric chronic kidney disease (CKD) such as diabetic nephropathy. However, diabetic nephropathy is still the first cause of end-stage renal disease. New drugs targeted to the pathogenesis and mechanisms of progression of these diseases beyond RAAS inhibition are needed. There is solid experimental evidence of a key role of oxidative stress and its interrelation with inflammation on renal damage. However, randomized and well-powered trials on these agents in CKD are scarce. We now review the biological bases of oxidative stress and its role in kidney diseases, with focus on diabetic nephropathy, as well as the role of the Keap1-Nrf2 pathway and recent clinical trials targeting this pathway with bardoxolone methyl.

Changes in angiotensin receptors expression play a pivotal role in the renal damage observed in spontaneously hypertensive rats

The renal renin-angiotensin system plays a central role in the development of hypertension. The aim of this work was to verify the expression of angiotensin II receptors AT1R and AT2R in the microsomal fraction of renal cortex and correlate this with the development of hypertension and renal damage in spontaneously hypertensive rats (SHR) using Wistar-Kyoto rats (WKY) as controls. AT1R expression increased (126%) and AT2R expression decreased (66%) in 4-wk-old SHR; AT2 expression decreased in 14-wk-old SHR (61%) compared with respective age-matched WKY. These modifications were correlated to the increase in protein kinase C activity and decrease in protein kinase A activity. Four-week-old SHR showed large accumulations of macrophages in kidney glomerulus and the tubulointerstitial area, dense cortical collagen deposition, and arterial proliferative changes in the walls of arterioles and medium-sized vessels. Similar modifications were also observed in 14-wk-old SHR. Four-week-old SHR treated with losartan (30 mg·kg−1·day−1) or hydralazine (15 and 30 mg·kg−1·day−1) by gavage for 10 wk did not develop hypertension. The decrease in AT2R expression and renal damage observed in SHR remained even after treatment with hydralazine. On the other hand, losartan treatment prevented the modifications observed in 14-wk-old SHR, indicating that renal injuries are caused specifically by AT1 rather than an increase in blood pressure. Our results indicate that the imbalance in AT1R and AT2R expression is associated with an inflammatory process that contributes to renal injury in adult SHR and to the development of hypertension.

Salt-induced cardiac hypertrophy and interstitial fibrosis are due to a blood pressure-independent mechanism in Wistar rats

High salt intake is a known cardiovascular risk factor and is associated with cardiac alterations. To better understand this effect, male Wistar rats were fed a normal (NSD: 1.3% NaCl), high 4 (HSD4: 4%), or high 8 (HSD8: 8%) salt diet from weaning until 18 wk of age. The HSD8 group was subdivided into HSD8, HSD8+HZ (15 mg . kg(-1) . d(-1) hydralazine in the drinking water), and HSD8+LOS (20 mg . kg(-1) . d(-1) losartan in the drinking water) groups. The cardiomyocyte diameter was greater in the HSD4 and HSD8 groups than in the HSD8+LOS and NSD groups. Interstitial fibrosis was greater in the HSD4 and HSD8 groups than in the HSD8+HZ and NSD groups. Hydralazine prevented high blood pressure (BP) and fibrosis, but not cardiomyocyte hypertrophy. Losartan prevented high BP and cardiomyocyte hypertrophy, but not fibrosis. Angiotensin II type 1 receptor (AT(1)) protein expression in both ventricles was greater in the HSD8 group than in the NSD group. Losartan, but not hydralazine, prevented this effect. Compared with the NSD group, the binding of an AT(1) conformation-specific antibody that recognizes the activated form of the receptor was lower in both ventricles in all other groups. Losartan further lowered the binding of the anti-AT(1) antibody in both ventricles compared with all other experimental groups. Angiotensin II was greater in both ventricles in all groups compared with the NSD group. Myocardial structural alterations in response to HSD are independent of the effect on BP. Salt-induced cardiomyocyte hypertrophy and interstitial fibrosis possibly are due to different mechanisms. Evidence from the present study suggests that salt-induced AT(1) receptor internalization is probably due to angiotensin II binding.

The RAAS in the pathogenesis and treatment of diabetic nephropathy

Angiotensin II and other components of the renin-angiotensin-aldosterone system (RAAS) have a central role in the pathogenesis and progression of diabetic renal disease. A study in patients with type 1 diabetes and overt nephropathy found that RAAS inhibition with angiotensin-converting-enzyme (ACE) inhibitors was associated with a reduced risk of progression to end-stage renal disease and mortality compared with non-RAAS-inhibiting drugs. Blood-pressure control was similar between groups and proteinuria reduction was responsible for a large part of the renoprotective and cardioprotective effect. ACE inhibitors can also prevent microalbuminuria in patients with type 2 diabetes who are hypertensive and normoalbuminuric; in addition, ACE inhibitors are cardioprotective even in the early stages of diabetic renal disease. Angiotensin-II-receptor blockers (ARBs) are renoprotective (but not cardioprotective) in patients with type 2 diabetes and overt nephropathy or microalbuminuria. Studies have evaluated the renoprotective effect of other RAAS inhibitors, such as aldosterone antagonists and renin inhibitors, administered either alone or in combination with ACE inhibitors or ARBs. An important task for the future will be identifying which combination of agents achieves the best renoprotection (and cardioprotection) at the lowest cost. Such findings will have major implications, particularly in settings where money and facilities are limited and in settings where renal replacement therapy is not available and the prevention of kidney failure is life saving.

Gene expression for the renin system in the myocardium of hypertensive ISIAH rats

The concentration of mRNA for angiotensin-converting enzyme (ACE) and angiotensin type 1A receptor (AT1A) in the myocardium of hypertensive ISIAH rats and normotensive WAG rats was measured by real-time PCR. Gene expression of the angiotensin type 1A receptor in the myocardium of 4-month-old ISIAH rats was lower than in WAG rats. The content of mRNA for angiotensin-converting enzyme in the myocardium of adult ISIAH rats was elevated by 80%. Therefore, the development of myocardial hypertrophy anticipates the increase in enzyme expression in the myocardium. Water deprivation (17 h) was accompanied by a decrease in the concentration of mRNA for angiotensin-converting enzyme in the myocardium of ISIAH rats, which did not differ from that in normotensive animals. Our results suggest that the decrease in cardiac preload and increase in plasma renin activity during dehydration reduce requirements for hyperactivity of the local cardiac renin-angiotensin system.

The mechanism of distinct diurnal variations of renin-angiotensin system in aorta and heart of spontaneously hypertensive rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-beta1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.

Attenuation of angiotensin II-induced vascular dysfunction and hypertension by overexpression of Thioredoxin 2

Reactive oxygen species increase in the cardiovascular system during hypertension and in response to angiotensin II. Because mitochondria contribute to reactive oxygen species generation, we sought to investigate the role of thioredoxin 2, a mitochondria-specific antioxidant enzyme. Mice were created with overexpression of human thioredoxin 2 (Tg(hTrx2) mice) and backcrossed to C57BL/6J mice for > or =6 generations. Twelve-week-old male Tg(hTrx2) or littermate wild-type mice were made hypertensive by infusion of angiotensin II (400 ng/kg per minute) for 14 days using osmotic minipumps. Systolic arterial blood pressure was not different between Tg(hTrx2) and wild-type animals under baseline conditions (101+/-1 respective 102+/-1 mm Hg). The angiotensin II-induced hypertension in wild-type mice (145+/-2 mm Hg) was significantly attenuated in Tg(hTrx2) mice (124+/-1 mm Hg; P<0.001). Aortic endothelium-dependent relaxation was significantly reduced in wild-type mice after angiotensin II infusion but nearly unchanged in transgenic mice. Elevated vascular superoxide and hydrogen peroxide levels, as well as expression of NADPH oxidase subunits in response to angiotensin II infusion, were significantly attenuated in Tg(hTrx2) mice. Mitochondrial superoxide anion levels were augmented after angiotensin II infusion in wild-type mice, and this was blunted in Tg(hTrx2) mice. Angiotensin II infusion significantly increased myocardial superoxide formation, heart weight, and cardiomyocyte size in wild-type but not in Tg(hTrx2) mice. These data indicate a major role for mitochondrial thioredoxin 2 in the development of cardiovascular alterations and hypertension during chronic angiotensin II infusion. Thioredoxin 2 may represent an important therapeutic target for the prevention and treatment of hypertension and oxidative stress.

Hemodynamic and cardiac effects of chronic eprosartan and moxonidine therapy in stroke-prone spontaneously hypertensive rats

The renin-angiotensin and sympathetic nervous systems play critical interlinked roles in the development of left ventricular hypertrophy, fibrosis, and dysfunction. These studies investigated the hemodynamic and cardiac effects of monoblockade and coblockade of renin-angiotensin and sympathetic nervous systems. Stroke-prone spontaneously hypertensive rats (16 weeks old; male; n=12 per group) received the sympatholytic imidazoline compound, moxonidine (2.4 mg/kg per day); the angiotensin-receptor blocker eprosartan (30 mg/kg per day), separately or in combination; or saline vehicle for 8 weeks, SC, via osmotic minipumps. Blood pressure and heart rate were continuously measured by radiotelemetry. After 8 weeks, in vivo cardiac function and structure were measured by transthoracic echocardiography and a Millar conductance catheter, and the rats were then euthanized and blood and heart ventricles collected for various determinations. Compared with vehicle, the subhypotensive dose of moxonidine resulted in lower (P<0.01) heart rate, left ventricular hypertrophy, cardiomyocyte cross-sectional area, interleukin 1 beta, tumor necrosis factor-alpha, and mRNA for natriuretic peptides. Eprosartan reduced pressure (P<0.01), as well as extracellular signal-regulated kinase (ERK) 44 phosphorylation, Bax/Bcl-2, and collagen I/III, and improved left ventricular diastolic function (P<0.03). Combined treatment resulted in greater reductions in blood pressure, heart rate, left ventricular hypertrophy, collagen I/III, and inhibited inducible NO synthase and increased endothelial NO synthase phosphorylation, as well as reduced left ventricular anterior wall thickness, without altering the other parameters. Thus, in advanced hypertension complicated with cardiac fibrosis, sympathetic inhibition and angiotensin II blockade resulted in greater reduction in blood pressure and heart rate, inhibition of inflammation, and improved left ventricular pathology but did not add to the benefits of angiotensin II blockade on cardiac function.

Interleukin-18 stimulates fibronectin expression in primary human cardiac fibroblasts via PI3K-Akt-dependent NF-kappaB activation

Fibronectin (FN), a key component of the extracellular matrix, is upregulated in cardiac tissue during myocardial hypertrophy and failure. Here we show that interleukin (IL)-18, a proinflammatory and pro-hypertrophic cytokine, stimulates FN expression in adult human cardiac fibroblasts (HCF), an effect blocked by either the IL-18BP:Fc chimera or IL-18 neutralizing antibodies. IL-18 stimulated FN promoter-reporter activity in HCF, a response attenuated by mutation of an NF-kappaB binding site in the FN promoter. Overexpression of p65 stimulated FN transcription. IL-18 stimulated in vitro (p65, p50) and in vivo NF-kappaB DNA binding activities, and induced kappaB-dependent reporter gene activity. These effects were inhibited by adenoviral transduction of dominant negative (dn) p65 (Ad.dnp65) and dnIKK2 (Ad.dnIKK2). Investigation of signaling intermediates revealed that IL-18 stimulated PI3 kinase activity (blocked by wortmannin, LY294002, or Ad.dnPI3Kp85), and Akt phosphorylation and kinase activity (blocked by SH-5 or Ad.dnAkt). Furthermore, targeting MyD88, IRAK1, TRAF6, PI3K, Akt, and NF-kappaB by RNA interference or dn expression vectors blunted IL-18 mediated FN transcription and mRNA expression. Conversely, FN stimulated IL-18 expression. These data provide the first evidence that IL-18 and FN stimulate each other's expression in HCF, and suggest a role for IL-18, FN and their crosstalk in myocardial hypertrophy and remodeling, disease states characterized by enhanced FN expression and fibrosis.

Aliskiren, a novel oral renin inhibitor, provides dose-dependent efficacy and placebo-like tolerability in Japanese patients with hypertension

Aliskiren is a novel orally active renin inhibitor for the treatment of hypertension. This study evaluated the antihypertensive efficacy, safety and tolerability of aliskiren in Japanese patients with hypertension. Forty hundred and fifty-five Japanese men and women with a mean sitting diastolic blood pressure of 95-110 mmHg were randomized to receive once-daily double-blind treatment for 8 weeks with aliskiren 75, 150 or 300 mg or placebo. Aliskiren produced significant, dose-dependent reductions in mean sitting diastolic blood pressure (p<0.0005 vs. placebo for each dose) and mean sitting systolic blood pressure (p<0.001 vs. placebo for each dose). The placebo-corrected reductions in mean sitting systolic/diastolic blood pressure were 5.7/4.0, 5.9/4.5 and 11.2/7.5 mmHg in the aliskiren 75, 150 and 300 mg groups, respectively. After 8 weeks' treatment, 27.8%, 47.8%, 48.2% and 63.7% of patients in the placebo and aliskiren 75, 150 and 300 mg groups, respectively, achieved a successful treatment response (diastolic blood pressure <90 mmHg and/or reduced by > or =10 mmHg from baseline; p<0.005 vs. placebo for each dose). Aliskiren treatment was well tolerated, with the incidence of adverse events reported in the active treatment groups (53-55%) being similar to that in the placebo group (50%). This study, which is the first to assess the antihypertensive efficacy and safety of aliskiren in Japanese patients with hypertension, demonstrates that the once-daily oral renin inhibitor aliskiren provides significant, dose-dependent reductions in blood pressure with placebo-like tolerability.

Renal and Vascular Protective Effects of Telmisartan in Patients with Essential Hypertension

It is known that the angiotensin receptor blockers (ARBs) have organ protective effects in patients with heart failure or renal impairment. Several studies have revealed that the ARB telmisartan has an organ protective effect, but there have been few studies directly comparing the effects of telmisartan and calcium antagonists, since most clinical studies on telmisartan have been conducted in treated patients or patients on combination therapy. The present study was conducted to compare the renal and vascular protective effects of telmisartan monotherapy and calcium antagonist monotherapy in untreated hypertensive patients. Forty-three patients with untreated essential hypertension were randomized to receive amlodipine (n=22) or telmisartan (n=21), which were respectively administered at doses of 5 mg and 40 mg once daily in the morning for 24 weeks. The patients were examined before and after treatment to assess changes of renal function, flow-mediated dilation (a parameter of vascular endothelial function), and brachial-ankle pulse wave velocity (baPWV; a parameter of arteriosclerosis). Before treatment, there were no significant differences in these parameters between groups. The decreases of urinary albumin excretion and baPWV, and the increase of flow-mediated dilation were significantly greater in the telmisartan group than the amlodipine group, while the antihypertensive effects were not significantly different between the two groups. In conclusion, these results suggest that telmisartan is more effective at protecting renal function and vascular endothelial function, and at improving arteriosclerosis than the calcium channel blocker in patients with essential hypertension.

Identification of quantitative trait loci for cardiac hypertrophy in two different strains of the spontaneously hypertensive rat

Cardiac hypertrophy and left ventricular hypertrophy are known to be substantially controlled by genetic factors. As an experimental model, we undertook genome-wide screens for cardiac mass in F2 populations bred from the stroke-prone spontaneously hypertensive rats (SHRSP) and normal spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) of a Japanese colony. Two F2 cohorts were independently produced: F2(SHRSP x WKY) (110 male and 110 female rats) and F2(SHR x WKY) (151 male rats). The ratio of heart weight to body weight (Hw/Bw) was evaluated at 12 months of age in F2(SHRSP x WKY) after salt-loading for 7 months, and at around 15 weeks of age in F2(SHR x WKY) who had been fed a normal rat chow diet. Subsequent to an initial screen with 251 markers in F2(SHRSP x WKY) male progeny, 170 and 161 markers were selected and characterized in F2(SHRSP x WKY) female progeny and F2(SHR x WKY) male progeny, respectively. Markers from four chromosomal regions showed suggestive or significant linkage to Hw/Bw. The strongest and the most consistent linkage was found in the vicinity of D3Mgh16 on rat chromosome (RNO) 3 (a maximal log of the odds score reached 4.0 to 6.6 across the F2 populations studied). In the other three regions on RNO6, RNO10 and RNO13, the degree of linkage was more prominent in either males or females. These data provide solid evidence for a "principal" RNO3 quantitative trait loci regulating Hw/Bw in SHRSP and SHR, and also suggest the possible presence of sexual dimorphism in regard to genetic susceptibility for cardiac hypertrophy.

Angiotensin II-Dependent Chronic Hypertension and Cardiac Hypertrophy Are Unaffected by gp91phox-Containing NADPH Oxidase

The gp91phox-containing NADPH oxidase is the major source of reactive oxygen species (ROS) in the cardiovascular system and inactivation of gp91phox has been reported to blunt hypertension and cardiac hypertrophy seen in angiotensin (Ang) II-infused animals. In the current study, we sought to determine the role of gp91phox-derived ROS on cardiovascular outcomes of chronic exposure to Ang II. The gp91phox-deficient mice were crossed with transgenic mice expressing active human renin in the liver (TTRhRen). TTRhRen mice exhibit chronic Ang II–dependent hypertension and frank cardiac hypertrophy by age 10 to 12 weeks. Four genotypes of mice were generated: control, TTRhRen trangenics (TTRhRen), gp91phox-deficient (gp91 − ), and TTRhRen transgenic gp91phox-deficient (TTRhRen/gp91 − ). Eight to 10 mice/group were studied. ROS levels were significantly reduced ( P <0.05) in the heart and aorta of TTRhRen/gp91 − and gp91 − mice compared with control counterparts, and this was associated with reduced cardiac, aortic, and renal NADPH oxidase activity ( P <0.05). Systolic blood pressure (SBP), cardiac mass, and cardiac fibrosis were increased in TTRhRen versus controls. In contrast to its action on ROS generation, gp91phox inactivation had no effect on development of hypertension or cardiac hypertrophy in TTRhRen mice, although interstitial fibrosis was reduced. Cardiac and renal expression of gp91phox homologues, Nox1 and Nox4, was not different between groups. Thus, although eliminating gp91phox-associated ROS production may be important in cardiovascular consequences in acute insult models, it does not prevent the development of hypertension and cardiac hypertrophy in a model in which the endogenous renin-angiotensin system is chronically upregulated.

Renal Artery Dissection after Angiographic Evaluation of Lower Extremities

We describe a case of renovascular hypertension that was caused by renal artery dissection after an angiographic evaluation of the lower extremities. Retention of contrast medium in the affected kidney even 1 day after the procedure caused us to suspect renal artery dissection. Magnetic resonance angiography revealed irregular streaks in the lumen of the affected artery, a sign of dissection. Treatment by a transluminal angioplasty with stent insertion improved renal function and reduced systemic blood pressure with normalization of plasma renin activity. In patients whose systemic blood pressure increases suddenly after any conceivable physical traction on the abdominal aorta, evaluation of the renal arteries should be considered. Appropriate endovascular treatment can preserve renal function and reduce systemic blood pressure.

Efficacy of candesartan in the treatment of migraine in hypertensive patients

Triptans are usually administered for migraine, but cannot be given to patients with malfunctioning cardiac or cerebral vascular systems, which commonly accompany hypertension. This article focuses on 8 cases in which treatment with candesartan was successful in reducing both the incidence and severity of headache in hypertensive patients with migraine. The cases reported in this article showed a mean improvement in Migraine Disability Assessment score from 29.4 to 9 points and in blood pressure from 154.9/90.4 to 129.5/81.9mmHg, suggesting that candesartan is an extremely attractive option for the treatment of migraine. Although recent studies have reported the efficacy of candesartan for treating migraine, there has been no description of its potential advantages over other prophylactic drugs. The present study included patients who could not tolerate triptans for whom triptans were contraindicated, several patients for whom other migraine prophylactic drugs showed little or no effect, and one patient for whom candesartan was prescribed initially for hypertension, but was also found to be therapeutic for migraines. Thus candesartan is considered to be a unique, attractive choice of prophylactic agent for migraine complicated by hypertension.