Vascular structure and oxidative stress in salt-loaded spontaneously hypertensive rats: effects of losartan and atenolol

Effects of Long-Term Intervention with Losartan, Aspirin and Atorvastatin on Vascular Remodeling in Juvenile Spontaneously Hypertensive Rats

Hypertension in adolescents is associated with adverse cardiac and vascular events. In addition to lowering blood pressure, it is not clear whether pharmacological therapy in early life can improve vascular remodeling. This study aimed to evaluate the effects of long-term administration of losartan, aspirin, and atorvastatin on vascular remodeling in juvenile spontaneously hypertensive rats (SHRs). Losartan, aspirin, and atorvastatin were administered via gavage at doses of 20, 10, and 10 mg/kg/day, respectively, on SHRs aged 6-22 weeks. Paraffin sections of the blood vessels were stained with hematoxylin-eosin (H&E) and Sirius Red to evaluate the changes in the vascular structure and the accumulation of different types of collagen. The plasma levels of renin, angiotensin II (Ang II), aldosterone (ALD), endothelin-1 (ET-1), interleukin-6 (IL-6), and neutrophil elastase (NE) were determined using ELISA kits. After the 16-week treatment with losartan, aspirin, and atorvastatin, the wall thickness of the thoracic aorta and carotid artery decreased. The integrity of the elastic fibers in the tunica media was maintained in an orderly manner, and collagen deposition in the adventitia was retarded. The plasma levels of renin, ALD, ET-1, IL-6, and NE in the SHRs also decreased. These findings suggest that losartan, aspirin, and atorvastatin could improve vascular remodeling beyond their antihypertensive, anti-inflammatory, and lipid-lowering effects. Many aspects of the protection provided by pharmacological therapy are important for the prevention of cardiovascular diseases in adults and older adults.

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.

Increased arterial pressure in mice with overexpression of the ADHD candidate gene calcyon in forebrain

The link between blood pressure (BP) and cerebral function is well established. However, it is not clear whether a common mechanism could underlie the relationship between elevated BP and cognitive deficits. The expression of calcyon, a gene abundant in catecholaminergic and hypothalamic nuclei along with other forebrain regions, is increased in the brain of the spontaneously hypertensive rat (SHR) which is a widely accepted animal model of essential hypertension and attention deficit hyperactivity disorder (ADHD). Previous studies demonstrated that mice with up-regulation of calcyon in forebrain (CalOE) exhibit deficits in working memory. To date, there is no evidence directly connecting calcyon to BP regulation. Here, we investigated whether forebrain up-regulation of calcyon alters BP using radiotelemetry. We found that CalOE mice exhibited higher mean arterial pressure (MAP) compared to tTA controls. Plasma norepinephrine levels were significantly higher in CalOE mice compared to tTA controls. Silencing the transgene with doxycycline normalized BP in CalOE mice, whereas challenging the mice with 4% high salt diet for 12 days exacerbated the MAP differences between CalOE and tTA mice. High salt diet challenge also increased proteinuria and urinary thiobarbituric acid reactive substances (TBARs) in tTA and CalOE; and the increases were more prominent in CalOE mice. Taken together, our data suggest that upregulation of calcyon in forebrain could increase BP via alterations in noradrenergic transmission and increased oxidative stress during high salt challenge. Overall, this study reveals that calcyon could be a novel neural regulator of BP raising the possibility that it could play a role in the development of vascular abnormalities.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Transient Receptor Potential Melastatin 4 (TRPM4) Contributes to High Salt Diet-Mediated Early-Stage Endothelial Injury

Background/Aims: The present study investigated whether the transient receptor potential melastatin 4 (TRPM4) channel plays a role in high salt diet (HSD)-induced endothelial injuries. Methods: Western blotting and immunofluorescence were used to examine TRPM4 expression in the mesenteric endothelium of Dahl salt-sensitive (SS) rats fed a HSD. The MTT, TUNEL, and transwell assays were used to evaluate the cell viability, cell apoptosis, and cell migration, respectively, of human umbilical vein endothelial cells (HUVECs). Enzyme-linked immunosorbent assays were used to determine the concentrations of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion protein 1 (VCAM-1), and E-selectin. Carboxy-H2DCFDA, a membrane-permeable reactive oxygen species (ROS)-sensitive fluorescent probe, was used to detect intracellular ROS levels. Results: TRPM4 was mainly expressed near the plasma membrane of mesenteric artery endothelial cells, and its expression level increased in SS hypertensive rats fed a HSD. Its protein expression was significantly upregulated upon treatment with exogenous hydrogen peroxide (H2O2) and aldosterone in cultured HUVECs. Cell viability decreased upon treatment with both agents in a concentration-dependent manner, which could be partially reversed by 9-phenanthrol, a specific TRPM4 inhibitor. Exogenous H2O2 induced apoptosis, enhanced cell migration, and increased the release of adhesion molecules, including ICAM-1, VCAM-1, and E-selectin, all of which were significantly attenuated upon treatment with 9-phenanthrol. Aldosterone and H2O2 induced the accumulation of intracellular ROS, which was significantly inhibited by 9-phenanthrol, suggesting that oxidative stress is one of the mechanisms underlying aldosterone-induced endothelial injury. Conclusions: Given the fact that oxidative stress and high levels of circulating aldosterone are present in hypertensive patients, we suggest that the upregulation of TRPM4 in the vascular endothelium may be involved in endothelial injuries caused by these stimuli.

Mediterranean diets supplemented with virgin olive oil and nuts enhance plasmatic antioxidant capabilities and decrease xanthine oxidase activity in people with metabolic syndrome: The PREDIMED study

SCOPE

This study assessed plasmatic antioxidant capabilities and xanthine oxidase (XOX) activity in metabolic syndrome patients after 5 years intervention with Mediterranean diet (MeDiet) supplemented with extra-virgin olive oil or with nuts or with low-fat diet (the PREDIMED [PREvención con Dieta MEDiterránea] study).

METHODS AND RESULTS

Seventy-five participants were randomly selected. Daily energy and nutrient intake were assessed with a validated 137-item food frequency questionnaire, and adherence to the MeDiet was assessed using a 14-item questionnaire. Catalase, superoxide dismutase (SOD), myeloperoxidase, XOX activities and protein levels, and protein carbonyl derivatives, nitrotyrosine, nitrite and nitrate levels were determined in overnight fasting venous blood samples. The plasma activity and protein levels of SOD and catalase were significantly higher and XOX activity was lower in MeDiet supplemented with extra-virgin olive oil and MeDiet supplemented with nuts than in the control group. Participants in both MeDiet groups showed higher plasma nitrate levels than in the control group. Adherence to the MeDiet showed a positive correlation with SOD and catalase plasma antioxidant activities.

CONCLUSION

A MeDiet enriched with either virgin olive oil or nuts enhances the plasma antioxidant capabilities and decreases XOX activity in patients with the metabolic syndrome but we did not observe changes in myeloperoxidase or markers of oxidative damage.

Hsp90β is involved in the development of high salt-diet-induced nephropathy via interaction with various signalling proteins

A high-salt diet often leads to a local intrarenal increase in renal hypoxia and oxidative stress, which are responsible for an excess production of pathogenic substances. Here, Wistar Kyoto/spontaneous hypertensive (WKY/SHR) rats fed a high-salt diet developed severe proteinuria, resulting from pronounced renal inflammation, fibrosis and tubular epithelial cell apoptosis. All these were mainly non-pressure-related effects. Hsp90β, TGF-β, HIF-1α, TNF-α, IL-6 and MCP-1 were shown to be highly expressed in response to salt loading. Next, we found that Hsp90β might play the key role in non-pressure-related effects of salt loading through a series of cellular signalling events, including the NF-κB, p38 activation and Bcl-2 inactivation. Hsp90β was previously proven to regulate the upstream mediators in multiple cellular signalling cascades through stabilizing and maintaining their activities. In our study, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) or Hsp90β knockdown dramatically alleviated the high-salt-diet-induced proteinuria and renal damage without altering blood pressure significantly, when it reversed activations of NF-κB, mTOR and p38 signalling cascades. Meanwhile, Co-IP results demonstrated that Hsp90β could interact with and stabilize TAK1, AMPKα, IKKα/β, HIF-1α and Raptor, whereas Hsp90β inhibition disrupted this process. In addition, Hsp90β inhibition-mediated renal improvements also accompanied the reduction of renal oxidative stress. In conclusion, salt loading indeed exhibited non-pressure-related impacts on proteinuria and renal dysfunction in WKY/SHR rats. Hsp90β inhibition caused the destabilization of upstream mediators in various pathogenic signalling events, thereby effectively ameliorating this nephropathy owing to renal hypoxia and oxidative stress.

Salt, Angiotensin II, Superoxide, and Endothelial Function

Proper function of the vascular endothelium is essential for cardiovascular health, in large part due to its antiproliferative, antihypertrophic, and anti-inflammatory properties. Crucial to the protective role of the endothelium is the production and liberation of nitric oxide (NO), which not only acts as a potent vasodilator, but also reduces levels of reactive oxygen species, including superoxide anion (O2•-). Superoxide anion is highly injurious to the vasculature because it not only scavenges NO molecules, but has other damaging effects, including direct oxidative disruption of normal signaling mechanisms in the endothelium and vascular smooth muscle cells. The renin-angiotensin system plays a crucial role in the maintenance of normal blood pressure. This function is mediated via the peptide hormone angiotensin II (ANG II), which maintains normal blood volume by regulating Na+ excretion. However, elevation of ANG II above normal levels increases O2•- production, promotes oxidative stress and endothelial dysfunction, and plays a major role in multiple disease conditions. Elevated dietary salt intake also leads to oxidant stress and endothelial dysfunction, but these occur in the face of salt-induced ANG II suppression and reduced levels of circulating ANG II. While the effects of abnormally high levels of ANG II have been extensively studied, far less is known regarding the mechanisms of oxidant stress and endothelial dysfunction occurring in response to chronic exposure to abnormally low levels of ANG II. The current article focuses on the mechanisms and consequences of this less well understood relationship among salt, superoxide, and endothelial function.

Central hemodynamics, vascular stiffness, and nocturia in patients with type 2 diabetes

Recently, studies have shown that the presence of nocturia may not be a benign condition and related with systemic illness and mortality. Elevated blood pressure (BP) was another factor related with nocturia. Type 2 diabetes mellitus (T2DM) is also associated with nocturia. It is now clear that, apart from peripheral BP, central hemodynamic parameters are important for cardiovascular prognosis. However, no previous study in the literature examined the relationship between nocturia and central hemodynamic parameters in patients with T2DM. The current study was designed to examine these relationships. Nocturia was defined as two or more voids per night. Central hemodynamic parameters were assessed from ambulatory BP measurements. In addition to routine biochemistry, 24-h urine collection was performed to measure protein, albumin, and sodium excretion. 158 patients (52.3%) had T2DM and 144 (47.7%) did not have T2DM (control group). The presence of T2DM was independently related with nocturia. Both in whole group and in T2DM patients, most of the hemodynamic parameters are higher in patients with nocturia compared to patients without nocturia. Among patients with T2DM, nocturia was associated with augmentation index and pulse wave velocity. In conclusion, central hemodynamic parameters and markers of vascular stiffness may be related with nocturia in patients with T2DM.

Sodium Excretion and Cardiovascular Structure and Function in the Nonhypertensive Population: The Korean Genome and Epidemiology Study

BACKGROUND

The effect of sodium intake on the cardiovascular system remains controversial. The purpose of this study is to investigate the relation between sodium intake and cardiovascular structure and function in the nonhypertensive population.

METHODS

We performed a cross-sectional analysis in 1,586 nonhypertensive subjects who participated in the Korean Genome Epidemiology Study (2007-2008). Sodium intake was assessed by estimating the 24-hour urinary sodium excretion from a spot urine sample. Changes in cardiovascular structure and function were assessed by using tissue Doppler echocardiography, the carotid intima-media thickness (CIMT), and the brachial-ankle pulse wave velocity (baPWV).

RESULTS

Systolic and diastolic blood pressures increased with increasing tertiles of estimated 24-hour urinary sodium excretion. In multivariate analyses adjusting for covariates, there were stepwise decreases in the baPWV (P = 0.003) and CIMT (P = 0.001) values as the estimated 24-hour urinary sodium excretion increased, whereas no significant differences in left ventricular (LV) structural and functional parameters were observed across the tertiles of estimated 24-hour urinary sodium excretion. Multiple linear regression analyses revealed that the estimated 24-hour urinary sodium excretion was independently and inversely associated with baPWV (P < 0.001) and CIMT (P = 0.001), but not with LV parameters.

CONCLUSIONS

In the nonhypertensive population, urinary sodium excretion was inversely related to baPWV and CIMT. However, there were no associations between urinary sodium excretion and LV structure or function.

The relationship between central hemodynamics, morning blood pressure surge, glycemic control and sodium intake in patients with type 2 diabetes and essential hypertension

AIMS

The current study aimed to investigate the relationship between morning blood pressure surge (MBPS), hemodynamic parameters, glycemic control and 24-h urinary sodium excretion (USE) in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

MBPS and central hemodynamic parameters were assessed from ambulatory blood pressure measurements. In addition to routine biochemistry, 24h urine collection was performed to measure protein, albumin and sodium excretion.

RESULTS

There were 146 (38%) patients with T2DM and 238 (72%) patients without T2DM (control group). Patients with T2DM had statistically higher MBPS compared with patients without T2DM (P<0.0001). In patients with T2DM, MBPS was correlated with HbA1c (rho=0.311, P<0.0001), 24h urinary sodium excretion (USE) (rho=0.292, P=0.004) and various hemodynamic parameters. Additionally, regression analysis showed that being male (P=0.006), the presence of coronary artery disease (P=0.023), HbA1c (P=0.012), and 24h USE (P=0.001) were independently related with log MBPS in T2DM patients.

CONCLUSION

This study demonstrated that T2DM was an independent risk factor for increased MBPS and MBPS was associated with central hemodynamic parameters. Additionally poor glycemic control and sodium intake were associated with worse MBPS in T2DM.

Effects of Valsartan vs Amlodipin on renal function in salt loaded spontaneously hypertensive rats

The goal of this study was to compare the effects of valsartan and amlodipin on the systolic blood pressure and parameters specific to the renal function in salt loaded spontaneously hypertensive rats (SHR). 32 male SHR were used at age of 20 weeks and body weight ranging between 265-300 g. From 8 weeks of age tab water was replaced with a solution of NaCl (1%) given ad libitum. Rats were divided into 2 groups: valsartan treated group SHRVAL (n=16) in which valsartan was given at a dose of 10 mg/kg b. w. and amlodipine treated group SHRAMLO (n=16) in which amlodipine was given at a dose of 5 mg/kg b. w. For a period of 12 weeks we have evaluated the effect of the investigated drugs on systolic blood pressure, body weight and renal function tests. In salt loaded rats amlodipine was more effective in reducing the systolic blood pressure in contrast to valsartan who had more pronounced effect on renal parameters most evident in proteinuria. Since both treatment groups have different mechanism of action a combination therapy may be beneficial in improving renal function in SHR rats.

Release from glomerular overload by the addition of low-dose thiazide in patients with angiotensin receptor blocker-resistant hypertension

BACKGROUND/AIMS

This multicenter, prospective, observational study assessed the renoprotective effects of losartan/thiazide combination therapy in terms of lowering the estimated glomerular filtration rate (eGFR).

METHODS

Adult patients with angiotensin receptor blocker (ARB)-resistant essential hypertension (n = 104) were enrolled and switched to combination therapy with losartan (50 mg/day) and hydrochlorothiazide (12.5 mg/day).

RESULTS

eGFR values declined significantly during the first 3 months, and changes in eGFR were assessed according to tertiles of the eGFR decrease ratio at 3 months. Only the high eGFR decrease (1st tertile) group showed significantly greater decreases in baseline eGFR and albumin-to-creatinine ratio (ACR) during the first 3 months. Additionally, the assessment according to tertiles of the baseline eGFR showed a signifcant decrease in eGFR and ACR during the first 3 months in the high baseline eGFR (1st tertile) group, but not in the moderate (2nd tertile) and low baseline eGFR (3rd tertile) groups.

CONCLUSION

The present results revealed that losartan/thiazide combination therapy attenuated glomerular overload, indicating that this therapy may provide glomerular protection in patients with an elevated GFR without causing prolonged damage to renal function.

H(2)S inhibits hyperglycemia-induced intrarenal renin-angiotensin system activation via attenuation of reactive oxygen species generation

Decrease in endogenous hydrogen sulfide (H₂S) was reported to participate in the pathogenesis of diabetic nephropathy (DN). This study is aimed at exploring the relationship between the abnormalities in H₂S metabolism, hyperglycemia-induced oxidative stress and the activation of intrarenal renin-angiotensin system (RAS). Cultured renal mesangial cells (MCs) and streptozotocin (STZ) induced diabetic rats were used for the studies. The expressions of angiotensinogen (AGT), angiotensin converting enzyme (ACE), angiotensin II (Ang II) type I receptor (AT1), transforming growth factor-β1 (TGF-β1) and collagen IV were measured by real time PCR and Western blot. Reactive oxygen species (ROS) production was assessed by fluorescent probe assays. Cell proliferation was analyzed by 5'-bromo-2'-deoxyuridine incorporation assay. Ang II concentration was measured by an enzyme immunoassay. AGT, ACE and AT1 receptor mRNA levels and Ang II concentration were increased in high glucose (HG) -treated MCs, the cell proliferation rate and the production of TGF-β1 and of collagen IV productions were also increased. The NADPH oxidase inhibitor diphenylenechloride iodonium (DPI) was able to reverse the HG-induced RAS activation and the changes in cell proliferation and collagen synthesis. Supplementation of H₂S attenuated HG-induced elevations in ROS and RAS activation. Blockade on H₂S biosynthesis from cystathione-γ-lyase (CSE) by DL-propargylglycine (PPG) resulted in effects similar to that of HG treatment. In STZ-induced diabetic rats, the changes in RAS were also reversed by H₂S supplementation without affecting blood glucose concentration. These data suggested that the decrease in H₂S under hyperglycemic condition leads to an imbalance between oxidative and reductive species. The increased oxidative species results in intrarenal RAS activation, which, in turn, contributes to the pathogenesis of renal dysfunction.

Salt loading in canola oil fed SHRSP rats induces endothelial dysfunction

This study aimed to determine if 50 days of canola oil intake in the absence or presence of salt loading affects: (1) antioxidant and oxidative stress markers, (2) aortic mRNA of NADPH oxidase (NOX) subunits and superoxide dismutase (SOD) isoforms and (3) endothelial function in SHRSP rats. SHRSP rats were fed a diet containing 10 wt/wt% soybean oil or 10 wt/wt% canola oil, and given tap water or water containing 1% NaCl for 50 days. Without salt, canola oil significantly increased RBC SOD, plasma cholesterol and triglycerides, aortic p22^phox, NOX2 and CuZn-SOD mRNA, and decreased RBC glutathione peroxidase activity. With salt, canola oil reduced RBC SOD and catalase activity, LDL-C, and p22^phox mRNA compared with canola oil alone, whereas plasma malondialdehyde (MDA) was reduced and RBC MDA and LDL-C were higher. With salt, the canola oil group had significantly reduced endothelium-dependent vasodilating responses to ACh and contractile responses to norepinephrine compared with the canola oil group without salt and to the WKY rats. These results indicate that ingestion of canola oil increases O₂⁻ generation, and that canola oil ingestion in combination with salt leads to endothelial dysfunction in the SHRSP model.

Sympathoinhibitory effects of telmisartan through the reduction of oxidative stress in the rostral ventrolateral medulla of obesity-induced hypertensive rats

OBJECTIVES

Sympathetic nervous system (SNS) activity is critically involved in the development and progression of obesity-induced hypertension. Angiotensin II type 1 receptor (AT1R)-induced oxidative stress in the rostral ventrolateral medulla (RVLM), a vasomotor center in the brainstem, activates the SNS in hypertensive rats. The aim of the present study was to determine whether oral administration of an AT1R blocker (ARB) inhibits SNS activity via antioxidative effects in the RVLM of rats with dietary-induced obesity.

METHODS AND RESULTS

Obesity-prone rats fed a high-fat diet were divided into groups treated with either telmisartan obesity-prone (TLM-OP), or losartan obesity-prone (LOS-OP), or vehicle obesity-prone (VEH-OP). SBP, SNS activity, and oxidative stress in the RVLM were significantly higher in obesity-prone rats than in obesity-resistant rats. Body weight, visceral fat, blood glucose, serum insulin, and plasma adiponectin concentrations were significantly lower in TLM-OP and LOS-OP than in VEH-OP, and plasma adiponectin concentrations were significantly higher in TLM-OP than in LOS-OP. Although SBP was reduced to similar levels both in TLM-OP and LOS-OP, both oxidative stress in the RVLM and SNS activity were significantly lower in TLM-OP than in LOS-OP or VEH-OP.

CONCLUSION

Orally administered telmisartan inhibited SNS activity through antioxidative effects via AT1R blockade in the RVLM of obesity-prone rats. AT1R and oxidative stress in the RVLM might be novel treatment targets for obesity-induced hypertension through sympathoinhibition, and telmisartan might be preferable for obesity-induced hypertension.

Combination therapy with losartan and pioglitazone additively reduces renal oxidative and nitrative stress induced by chronic high fat, sucrose, and sodium intake

We recently showed that combination therapy with losartan and pioglitazone provided synergistic effects compared with monotherapy in improving lesions of renal structure and function in Sprague-Dawley rats fed with a high-fat, high-sodium diet and 20% sucrose solution. This study was designed to explore the underlying mechanisms of additive renoprotection provided by combination therapy. Losartan, pioglitazone, and their combination were orally administered for 8 weeks. The increased level of renal malondialdehyde and expression of nicotinamide adenine dinucleotide phosphate oxidase subunit p47^phox and nitrotyrosine as well as the decreased total superoxide dismutase activity and copper, zinc-superoxide dismutase expression were tangible evidence for the presence of oxidative and nitrative stress in the kidney of model rats. Treatment with both drugs, individually and in combination, improved these abnormal changes. Combination therapy showed synergistic effects in reducing malondialdehyde level, p47^phox, and nitrotyrosine expression to almost the normal level compared with monotherapy. All these results suggest that the additive renoprotection provided by combination therapy might be attributed to a further reduction of oxidative and nitrative stress.

Angiotensin II receptor type 1 blockade decreases CTGF/CCN2-mediated damage and fibrosis in normal and dystrophic skeletal muscles

Connective tissue growth factor (CTGF/CCN-2) is mainly involved in the induction of extracellular matrix (ECM) proteins. The levels of CTGF correlate with the degree and severity of fibrosis in many tissues, including dystrophic skeletal muscle. The CTGF overexpression in tibialis anterior skeletal muscle using an adenoviral vector reproduced many of the features observed in dystrophic muscles including muscle damage and regeneration, fibrotic response and decrease in the skeletal muscle strength. The renin-angiotensin system is involved in the genesis and progression of fibrotic diseases through its main fibrotic components angiotensin-II and its transducer receptor AT-1. The use of AT-1 receptor blockers (ARB) has been shown to decrease fibrosis. In this paper, we show the effect of AT-1 receptor blockade on CTGF-dependent biological activity in skeletal muscle cells as well as the response to CTGF overexpression in normal skeletal muscle. Our results show that in myoblasts ARB decreased CTGF-mediated increase of ECM protein levels, extracellular signal regulated kinases 1/2 (ERK-1/2) phosphorylation and stress fibres formation. In tibialis anterior muscle overexpressing CTGF using an adenovirus, ARB treatment decreased CTGF-mediated increase of ECM molecules, α-SMA and ERK-1/2 phosphorylation levels. Quite remarkable, ARB was able to prevent the loss of contractile force of tibialis anterior muscles overexpressing CTGF. Finally, we show that ARB decreased the levels of fibrotic proteins, CTGF and ERK-1/2 phosphorylation augmented in a dystrophic skeletal muscle from mdx mice. We propose that ARB is a novel pharmacological tool that can be used to decrease the fibrosis induced by CTGF in skeletal muscle associated with muscular dystrophies.

Clinical neuroprotective drugs for treatment and prevention of stroke

Stroke is an enormous public health problem with an imperative need for more effective therapies. In therapies for ischemic stroke, tissue plasminogen activators, antiplatelet agents and anticoagulants are used mainly for their antithrombotic effects. However, free radical scavengers, minocycline and growth factors have shown neuroprotective effects in the treatment of stroke, while antihypertensive drugs, lipid-lowering drugs and hypoglycemic drugs have shown beneficial effects for the prevention of stroke. In the present review, we evaluate the treatment and prevention of stroke in light of clinical studies and discuss new anti-stroke effects other than the main effects of drugs, focusing on optimal pharmacotherapy.

Oxidative stress, Noxs, and hypertension: experimental evidence and clinical controversies

Reactive oxygen species (ROS) are signaling molecules that influence many physiological processes. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in chronic diseases including hypertension. Although oxidative stress may not be the sole cause of hypertension, it amplifies blood pressure elevation in the presence of other prohypertensive factors (salt, renin-angiotensin system, sympathetic hyperactivity). A major source for cardiovascular ROS is a family of non-phagocytic NADPH oxidases (Nox1, Nox2, Nox4, Nox5). Other sources of ROS involve mitochondrial electron transport enzymes, xanthine oxidase, and uncoupled nitric oxide synthase. Although evidence from experimental and animal studies supports a role for oxidative stress in the pathogenesis of hypertension, there is still no convincing proof that oxidative stress is a cause of human hypertension. However, what is clear is that oxidative stress is important in the molecular mechanisms associated with cardiovascular and renal injury in hypertension and that hypertension itself can contribute to oxidative stress. The present review addresses the putative function of ROS in the pathogenesis of hypertension and focuses on the role of Noxs in ROS generation in vessels and the kidney. Implications of oxidative stress in human hypertension are discussed, and clinical uncertainties are highlighted.

Valsartan-induced improvement in insulin sensitivity is not paralleled by changes in microvascular function in individuals with impaired glucose metabolism

BACKGROUND

Individuals with impaired glucose metabolism (IGM) are at high risk of developing type 2 diabetes (T2DM). The renin-angiotensin system (RAS) is activated in insulin-resistant states and its inhibition resulted in delayed onset of T2DM. The underlying mechanisms may include improvement in microvascular structure and function, which may increase glucose and insulin delivery to insulin-sensitive tissues. We hypothesized that functional and structural capillary density is impaired in insulin-resistant individuals with IGM and that treatment with the angiotensin-receptor blocker valsartan (VAL) will improve insulin sensitivity and microvascular function.

METHODS

In this randomized controlled trial, individuals with IGM (n = 48) underwent a hyperinsulinaemic-euglycaemic clamp to assess insulin sensitivity (M-value) and capillaroscopy to examine baseline skin capillary density (BCD), capillary density after arterial occlusion (PRH) and capillary density during venous occlusion (VEN) before and after 26 weeks of VAL or placebo (PLB). Sixteen BMI-matched individuals with normal glucose metabolism (NGM) served as controls.

RESULTS

Individuals with IGM were more insulin resistant (P < 0.001) and had impaired microvascular function compared with those with NGM (all P < 0.01). Univariate associations were found for microvascular function (BCD, PRH, VEN) and M-value (all P < 0.005). The relations were independent of age, sex and BMI. VAL improved insulin sensitivity (P = 0.034) and lowered blood pressure as compared with PLB, whereas microvascular function remained unchanged.

CONCLUSION

In insulin-resistant individuals with IGM, impaired functional and structural capillary density was inversely associated with insulin sensitivity. VAL improved insulin sensitivity without affecting the functional and structural capillary density, indicating that other mechanisms may be stronger determinants in the VAL-mediated insulin-sensitizing effect.

The effect of short-term canola oil ingestion on oxidative stress in the vasculature of stroke-prone spontaneously hypertensive rats

Background

This study aimed to determine if 25 days of canola oil intake in the absence of excess dietary salt or together with salt loading affects antioxidant and oxidative stress markers in the circulation. A further aim was to determine the mRNA expression of NADPH oxidase subunits and superoxide dismutase (SOD) isoforms in the aorta of stroke-prone spontaneously hypertensive (SHRSP) rats.

Methods

Male SHRSP rats, were fed a defatted control diet containing 10% wt/wt soybean oil or a defatted treatment diet containing 10% wt/wt canola oil, and given tap water or water containing 1% NaCl. Blood was collected at the end of study for analysis of red blood cell (RBC) antioxidant enzymes, RBC and plasma malondialdehyde (MDA), plasma 8-isoprostane and plasma lipids. The aorta was removed and the mRNA expression of NOX2, p22^phox, CuZn-SOD, Mn-SOD and EC-SOD were determined.

Results

In the absence of salt, canola oil reduced RBC SOD and glutathione peroxidase, and increased total cholesterol and LDL cholesterol compared with soybean oil. RBC glutathione peroxidase activity was significantly lower in both the salt loaded groups compared to the soybean oil only group. In addition, RBC MDA and plasma HDL cholesterol were significantly higher in both the salt loaded groups compared to the no salt groups. Plasma MDA concentration was higher and LDL cholesterol concentration lower in the canola oil group loaded with salt compared to the canola oil group without salt. The mRNA expression of NADPH oxidase subunits and SOD isoforms were significantly reduced in the canola oil group with salt compared to canola oil group without salt.

Conclusion

In conclusion, these results indicate that canola oil reduces antioxidant status and increases plasma lipids, which are risk factors for cardiovascular disease. However, canola oil in combination with salt intake increased MDA, a marker of lipid peroxidation and decreased NAPDH oxidase subunits and aortic SOD gene expression.

Association of central hemodynamics with estimated 24-h urinary sodium in patients with hypertension

OBJECTIVE

High salt intake is known to be the most pivotal environmental factor in the pathogenesis of hypertension. However, the association of high sodium intake with central hemodynamics in hypertensive individuals has not been well defined. Here, we determined the association of estimated 24-h urine sodium and potassium excretion estimated from a spot urine analysis with parameters of central pulse wave analysis in 515 hypertensive individuals.

METHODS

Fasting spot urine samples were obtained in the early morning after the first void, and estimated 24-h urine sodium and potassium excretion were estimated from measurement of urine sodium, potassium and creatinine. Central hemodynamics and arterial stiffness parameters were assessed via pulse wave analysis of the radial artery.

RESULTS

The estimated 24-h sodium and potassium excretion values were 150 ± 40 and 49 ± 10 mEq, respectively. There was a step-wise decrease in pulse pressure amplification with increasing estimated 24-h urine sodium excretion. Multiple linear regression analyses revealed that both estimated 24-h urine sodium excretion and sodium/potassium ratio were independently associated with increases in central pulse pressure, augmented aortic pressure and augmentation index and were inversely associated with pulse pressure amplification.

CONCLUSION

The estimated 24-h urinary sodium excretion is independently associated with central hemodynamics. This may provide the basis for prospective interventional studies of epidemiologic scale to determine the potential beneficial effects of reduced salt consumption on central hemodynamics.

Down-regulation of DDAH2 and eNOS induces endothelial dysfunction in sinoaortic-denervated rats

The aim of present study was to investigate whether downregulation of dimethylarginine dimethylaminohydrolase (DDAH2) and endothelial nitric oxide synthase (eNOS) induced endothelial dysfunction in sinoaortic-denervated (SAD) rats. SAD rats exhibited significantly higher blood pressure (BP) variability and markedly lower baroreflex sensitivity. However, there was no significant difference in BP between SAD rats and sham-operated rats. In SAD rats, ultrastructural analysis revealed that endothelial cells were degenerated and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) study showed that apoptotic aortic endothelial cells increased. Circulating angiotensinII (AngII), asymmetric dimethylarginine (ADMA) and malondialdehyde (MDA) levels in SAD rats were similar to sham-operated rats, but aortic AngII and MDA levels locally increased. Endothelium-mediated relaxation of thoracic aorta isolated from SAD rats was impaired compared to sham-operated rats, whereas the sodium nitroprusside-induced relaxation was quite similar. Western blotting results showed that DDAH2 and eNOS expressions decreased significantly in the aortae of SAD rats. Treatment of primary cultured rat aortic endothelial cells with AngII (1 μM) resulted in a marked reduction of DDAH2 and eNOS expressions, and coadministration of losartan (1 μM), an AT(1) receptor antagonist, abolished the effect. In conclusion, downregulation of DDAH2 and eNOS induced endothelial dysfunction in SAD rats. DDAH2 and eNOS may be the potential targets for treatment of endothelial dysfunction.

The role of oxidative stress in the pathophysiology of hypertension

Hypertension is considered to be the most important risk factor in the development of cardiovascular disease. An increasing body of evidence suggests that oxidative stress, which results in an excessive generation of reactive oxygen species (ROS), has a key role in the pathogenesis of hypertension. The modulation of the vasomotor system involves ROS as mediators of vasoconstriction induced by angiotensin II, endothelin-1 and urotensin-II, among others. The bioavailability of nitric oxide (NO), which is a major vasodilator, is highly dependent on the redox status. Under physiological conditions, low concentrations of intracellular ROS have an important role in the normal redox signaling maintaining vascular function and integrity. However, under pathophysiological conditions, increased levels of ROS contribute to vascular dysfunction and remodeling through oxidative damage. In human hypertension, an increase in the production of superoxide anions and hydrogen peroxide, a decrease in NO synthesis and a reduction in antioxidant bioavailability have been observed. In turn, antioxidants are reducing agents that can neutralize these oxidative and otherwise damaging biomolecules. The use of antioxidant vitamins, such as vitamins C and E, has gained considerable interest as protecting agents against vascular endothelial damage. Available data support the role of these vitamins as effective antioxidants that can counteract ROS effects. This review discusses the mechanisms involved in ROS generation, the role of oxidative stress in the pathogenesis of vascular damage in hypertension, and the possible therapeutic strategies that could prevent or treat this disorder.