Increased Aortic NADPH Oxidase Activity in Rats With Genetically High Angiotensin-Converting Enzyme Levels

d-Allulose Ameliorates Hyperglycemia Through IRE1α Sulfonation-RIDD-Sirt1 Decay Axis in the Skeletal Muscle

Aims: The skeletal muscle maintains glucose disposal via insulin signaling and glucose transport. The progression of diabetes and insulin resistance is critically influenced by endoplasmic reticulum (ER) stress. d-Allulose, a low-calorie sugar substitute, has shown crucial physiological activities under conditions involving hyperglycemia and insulin resistance. However, the molecular mechanisms of d-allulose in the progression of diabetes have not been fully elucidated. Here, we evaluated the effect of d-allulose on hyperglycemia-associated ER stress responses in human skeletal myoblasts (HSkM) and db/db diabetic and high-fat diet-fed mice. Results: d-allulose effectively controlled glycemic markers such as insulin and hemoglobin A1c (HbA1c), showing anti-diabetic effects by inhibiting the disruption of insulin receptor substrate (IRS)-1 tyrosine phosphorylation and glucose transporter 4 (GLUT4) expression, in which the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt) pathway is involved. The levels of glucose dysmetabolism-based NADPH oxidase, such as NADPH-dependent oxidoreductase (Nox) 4, were highly increased, and their interaction with IRE1α and the resultant sulfonation-regulated IRE1-dependent decay (RIDD)-Sirt1 decay were also highly increased under diabetic conditions, which were controlled with d-allulose treatment. Skeletal muscle cells grown with a high glucose medium supplemented with d-allulose showed controlled IRE1α sulfonation-RIDD-Sirt1 decay, in which Nox4 was involved. Innovation and Conclusion: The study observations indicate that d-allulose contributes to the muscular glucose disposal in the diabetic state where ER-localized Nox4-induced IRE1α sulfonation results in the decay of Sirt1, a core factor for controlling glucose metabolism. Antioxid. Redox Signal. 37, 229-245.

GABA and Fermented Curcuma longa L. Extract Enriched with GABA Ameliorate Obesity through Nox4-IRE1α Sulfonation-RIDD-SIRT1 Decay Axis in High-Fat Diet-Induced Obese Mice

Gamma-aminobutyric acid (GABA) is a natural amino acid with antioxidant activity and is often considered to have therapeutic potential against obesity. Obesity has long been linked to ROS and ER stress, but the effect of GABA on the ROS-associated ER stress axis has not been thoroughly explored. Thus, in this study, the effect of GABA and fermented Curcuma longa L. extract enriched with GABA (FCLL-GABA) on the ROS-related ER stress axis and inositol-requiring transmembrane kinase/endoribonuclease 1α (IRE1α) sulfonation were examined with the HFD model to determine the underlying anti-obesity mechanism. Here, GABA and FCLL-GABA supplementations significantly inhibited the weight gain in HFD fed mice. The GABA and FCLL-GABA supplementation lowered the expressions of adipogenic transcription factors such as PPAR-γ, C/EBPα, FAS, and SREBP-1c in white adipose tissue (WAT) and liver from HFD-fed mice. The enhanced hyper-nutrient dysmetabolism-based NADPH oxidase (Nox) 4 and the resultant IRE1α sulfonation-RIDD-SIRT1 decay under HFD conditions were controlled with GABA and FCLL-GABA. Notably, GABA and FCLL-GABA administration significantly increased AMPK and sirtuin 1 (SIRT1) levels in WAT of HFD-fed mice. These significant observations indicate that ER-localized Nox4-induced IRE1α sulfonation results in the decay of SIRT1 as a novel mechanism behind the positive implications of GABA on obesity. Moreover, the investigation lays a firm foundation for the development of FCLL-GABA as a functional ingredient.

Novel canine isocitrate dehydrogenase 1 mutation Y208C attenuates dimerization ability

Isocitrate dehydrogenase 1 (IDH1) mutations are common in gliomas, acute myeloid leukemia, and chondrosarcoma. The mutation ‘hotspot’ is a single arginine residue, R132. The R132H mutant of IDH1 produces the 2-hydroxyglutarate (2-HG) carcinogen from α-ketoglutarate (α-KG). The reduction of α-KG induces the accumulation of hypoxia-inducible factor-1α subunit (HIF-1α) in the cytosol, which is a predisposing factor for carcinogenesis. R132H is the most common IDH1 mutation in humans, but mutations at the R132 residue can also occur in tumor tissues of dogs. The current study reported the discovery of a novel Tyr208Cys (Y208C) mutation in canine IDH1 (cIDH1), which was isolated from 2 of 45 canine chondrosarcoma cases. As the genomic DNA isolated from chondrosarcoma tissue was mutated, but that isolated from blood was not, Y208C mutations were considered to be spontaneous somatic mutations. The isocitrate dehydrogenase activity of the Y208C mutant was attenuated compared with that of wild-type (WT) cIDH1, but the attenuation of Y208C was less intense than that of the R132H mutation. The induction of HIF-1α response element activity and cell retention of HIF-1α were not increased by Y208C overexpression. In silico and cell biological analysis of IDH1 dimerization revealed that the Y208C mutation, but not the R132H mutation, attenuated binding activity with WT cIDH1. These data suggested that the attenuation of dimerization by the Y208C mutation may cause tumorigenesis through different mechanisms other than via 2-HG production by the IDH1 R132 mutation.

Rho-kinase pathway activation and apoptosis in circulating leucocytes in patients with heart failure with reduced ejection fraction

Background

Increased Rho‐kinase activity in circulating leucocytes is observed in heart failure with reduced ejection fraction (HFrEF). However, there is little information in HFrEF regarding other Rho‐kinase pathway components an on the relationship between Rho‐kinase and apoptosis. Here, Rho‐kinase activation levels and phosphorylation of major downstream molecules and apoptosis levels were measured for the first time both in HFrEF patients and healthy individuals.

Methods

Cross‐sectional study comparing HFrEF patients (n = 20) and healthy controls (n = 19). Rho‐kinase activity in circulating leucocytes (peripheral blood mononuclear cells, PBMCs) was determined by myosin light chain phosphatase 1 (MYPT1) and ezrin‐radixin‐moesin (ERM) phosphorylation. Rho‐kinase cascade proteins phosphorylation p38‐MAPK, myosin light chain‐2, JAK and JNK were also analysed along with apoptosis.

Results

MYPT1 and ERM phosphorylation were significantly elevated in HFrEF patients, (3.9‐ and 4.8‐fold higher than in controls, respectively). JAK phosphorylation was significantly increased by 300% over controls. Phosphorylation of downstream molecules p38‐MAPK and myosin light chain‐2 was significantly higher by 360% and 490%, respectively, while JNK phosphorylation was reduced by 60%. Catecholamine and angiotensin II levels were significantly higher in HFrEF patients, while angiotensin‐(1‐9) levels were lower. Apoptosis in circulating leucocytes was significantly increased in HFrEF patients by 2.8‐fold compared with controls and significantly correlated with Rho‐kinase activation.

Conclusion

Rho‐kinase pathway is activated in PMBCs from HFrEF patients despite optimal treatment, and it is closely associated with neurohormonal activation and with apoptosis. ROCK cascade inhibition might induce clinical benefits in HFrEF patients, and its assessment in PMBCs could be useful to evaluate reverse remodelling and disease regression.

Angiotensin-(1-9) reduces cardiovascular and renal inflammation in experimental renin-independent hypertension

Hypertension-induced cardiovascular and renal damage can be mediated by activation of the renin-angiotensin-aldosterone system. There are different factors beyond renin-angiotensin-aldosterone system involved in hypertension and renal damage. Inflammation has emerged as an important mediator of hypertension and cardiovascular and kidney damage. Angiotensin-(1-9), a peptide of the renin-angiotensin system, counter-regulates both the physiological and pathological actions of angiotensin II. Recent data has shown that angiotensin-(1-9) protects the heart and blood vessels from adverse cardiovascular remodeling in experimental models of hypertension and/or heart failure and reduces cardiac fibrosis in stroke-prone, spontaneously hypertensive rats. These effects are mediated by the angiotensin II type 2 receptor (AT2R). However, it remains unknown whether angiotensin-(1-9) also has an anti-inflammatory effect. In the present study, we investigate whether angiotensin-(1-9) reduces inflammation and fibrosis in the heart, arteries, and kidney in a DOCA-salt hypertensive model and explore the mechanisms underlying the amelioration of end-organ damage. DOCA-salt hypertensive rats received: a) vehicle, b) angiotensin-(1-9), c) PD123319 (AT2R blocker), d) angiotensin-(1-9) plus A779 (a Mas receptor blocker) or e) angiotensin-(1-9) plus PD123319, and sham rats were used as a control. Our results showed that angiotensin-(1-9) decreased hypertension and increased vasodilation in DOCA-salt hypertensive rats. These actions were partially inhibited by PD123319. Moreover, angiotensin-(1-9) decreased diuresis, fibrosis, and inflammation. These beneficial effects were not mediated by Mas or AT2R blockers. We concluded that angiotensin-(1-9) protects against volume overload-induced hypertensive cardiovascular and kidney damage by decreasing inflammation in the heart, aortic wall, and kidney, through mechanisms independent of the Mas or AT2R.

Puerarin-7-O-glucuronide, a water-soluble puerarin metabolite, prevents angiotensin II-induced cardiomyocyte hypertrophy by reducing oxidative stress

This study aimed to investigate the anti-oxidant and anti-hypertrophic effects of puerarin-7-O-glucuronide, a water-soluble puerarin metabolite. The anti-oxidant effects of puerarin-7-O-glucuronide were assessed by measurement of intracellular superoxide levels, total superoxide dismutase (SOD) activity, total anti-oxidant capacity, and glutathione (GSH)/glutathione disulfide (GSSG) ratio in cultured neonatal rat cardiomyocytes (NRCMs) stimulated with the xanthine oxidase (XO)/xanthine (X) system or angiotensin II. The activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and expression of NADPH oxidase subunits p22^phox and p47^phox were determined. The anti-hypertrophic effects of puerarin-7-O-glucuronide in angiotensin II-challenged NRCMs were characterized by changes in cell morphology and expression of hypertrophic genes. In the pharmacokinetic study, the plasma concentration of puerarin-7-O-glucuronide was determined by rapid resolution-liquid chromatography-tandem mass spectrometry (RR-LC-MS/MS). Puerarin-7-O-glucuronide prevented XO/X-induced increase in intracellular superoxide production and decreases in total SOD activity, GSH/GSSG ratio, and total anti-oxidant capacity. Puerarin-7-O-glucuronide also reversed angiotensin II-induced increases in intracellular superoxide production and NADPH oxidase activity and decreases in total SOD activity. These anti-oxidant effects of puerarin-7-O-glucuronide were accompanied by downregulation of p22^phox and p47^phox. Furthermore, puerarin-7-O-glucuronide prevented angiotensin II-induced increases in cell surface area and perimeter, as well as changes in Nppa, Myh7, and Myh6. In the pharmacokinetic study, puerarin-7-O-glucuronide was cleared with a half-life of 0.94 h after intravenous administration. Puerarin could be detected in rat plasma, albeit in low concentration, as early as 5 min after intravenous administration of puerarin-7-O-glucuronide. These anti-oxidant and anti-hypertrophic properties of puerarin-7-O-glucuronide were similar to those of its parent compound puerarin. These results support the development of puerarin-7-O-glucuronide as a novel pharmaceutical agent for therapeutic application.

Phytanic acid activates NADPH oxidase through transactivation of epidermal growth factor receptor in vascular smooth muscle cells

BACKGROUND

Phytanic acid (PA) has been implicated in development of cancer and its defective metabolism is known to cause life-threatening conditions, such as Refsum disease, in children. To explore molecular mechanisms of phytanic acid-induced cellular pathology, we investigated its effect on NADPH oxidase (NOX) and epidermal growth factor receptor (EGFR) in rat aortic smooth muscle cells (RASMC).

METHODS

Smooth muscle cells were isolated from rat aortae using enzymic digestion with collagenase and elastase. Cultured RASMC were treated with varying concentrations (0.5-10 μg/ml) of phytanic acid in the presence/absence of fetal bovine serum (FBS) and/or EGFR inhibitor, AG1478. Following treatment with experimental agents, NOX activity was assayed in RASMC cultures by luminescence method. Gene expression of NOX-1 and p47phox was assessed using RT-PCR. NOX-1, p47phox and, total EGFR protein and its phosphorylated form were measured by Western blotting.

RESULTS

Treatment of RASMC with supraphysiological concentrations (>2.5 μg/ml) of PA significantly (p < 0.01) increased the NOX activity. PA also significantly increased gene/protein expression of NOX-1 and p47phox whereas p22phox and p67phox remained unaffected. Interestingly, PA (2.5-10 μg/ml) markedly (2-3 folds) increased the total and phosphorylated EGFR. Treatment of cells with EGFR inhibitor, AG1478, significantly blocked the PA-induced enhancement of NOX activity.

CONCLUSIONS

Our findings that PA transactivates EGFR and induces NOX activity in vascular smooth muscle cells provide new insights into molecular mechanisms of PA's role in cancer and Refsum disease.

NADPH oxidase is implicated in the pathogenesis of oxidative phosphorylation dysfunction in mice fed a high-fat diet

The aim of this study was to evaluate the role of NADPH oxidase (NADPHox) in the pathogenesis of oxidative phosphorylation (OXPHOS) dysfunction as found in mice fed a high-fat diet (HFD). C57BL/6J mice were distributed in four groups: WT/SCD: six wild-type (WT) mice fed a standard chow diet (SCD); WT/HFD, six WT mice fed a HFD; NOX2(-/-)/SCD, six NADPHox-deficient mice on a SCD; (4) NOX2(-/-)/HFD, six NADPHox-deficient mice on a HFD. After 32 weeks, we studied the liver for: histology; OXPHOS complex activity; fully assembled OXPHOS complexes and their subunits; gene expression of OXPHOS subunits; oxidative and nitrosative stress; and oxidative DNA damage. In the liver of WT/HFD mice, we found a significant decreased in the activity of all OXPHOS complexes, in fully assembled complexes, in the amount of OXPHOS subunits, and in gene expression of mitochondrial DNA-encoded subunits. 8-hydroxy-2'-deoxyguanosine was only increased in mitochondrial DNA. The liver of NOX(-/-)/HFD mice showed mild steatosis but no non-alcoholic steatohepatitis (NASH) lesions were found. OXPHOS activity, OXPHOS subunits, and assembly of subunits into OXPHOS complexes were normal in these mice. We conclude that this study shows that NADPH deficiency protects mice from developing OXPHOS dysfunction and NASH caused by a HFD.

Simultaneous Rho kinase inhibition in circulating leukocytes and in cardiovascular tissue in rats with high angiotensin converting enzyme levels

BACKGROUND

The small guanosine triphosphatase RhoA and its direct target Rho kinase (ROCK) play important roles in cardiovascular pathophysiology. Activated ROCK phosphorylates intracellular proteins with detrimental effects on cardiovascular remodeling. Increased ROCK activity in circulating leukocytes is observed in hypertension and in heart failure, but its relationship with ROCK activation in the myocardium and vessels is unknown. We hypothesized that ROCK activation and phosphorylation/activation of some of its key downstream molecules in the heart and arterial wall are reflected in circulating leukocytes.

METHODS

Phosphorylation of MYPT1, ERM and p38-MAPK and levels of p65-NF-κB were determined in the left ventricle (LV), aortic wall and circulating leukocytes in rats with high (Brown Norway, BN) and low (Lewis) angiotensin converting enzyme. A group of BN rats received the ROCK inhibitor fasudil (7days).

RESULTS

Compared to Lewis rats, in the BN group phosphorylated levels of MYPT1, ERM and p38-MAPK and levels of p65-NF-κB were increased (P<0.05) in the LV (67%, 92%, 52% and 98%, respectively); in the aortic wall (57%, 51%, 68% and 66%, respectively) and in circulating leukocytes (61%, 72%, 49% and 105%, respectively). Fasudil reduced all these levels to those observed in Lewis rats. Phosphorylated MYPT1, ERM, and p38-MAPK and levels of p65-NF-κB in circulating leukocytes were significantly correlated with their respective LV and aortic wall levels (excepting p65-NF-κB in aorta).

CONCLUSION

ROCK activity in circulating leukocytes reflects activation of this signaling pathway in the myocardium and aortic wall in this model, and supports its value as a potential cardiovascular remodeling marker.

Arsenic causes aortic dysfunction and systemic hypertension in rats: Augmentation of angiotensin II signaling

The groundwater pollutant arsenic can cause various cardiovascular disorders. Angiotensin II, a potent vasoconstrictor, plays an important role in vascular dysfunction by promoting changes in endothelial function, vascular reactivity, tissue remodeling and oxidative stress. We investigated whether modulation of angiotensin II signaling and redox homeostasis could be a mechanism contributing to arsenic-induced vascular disorder. Rats were exposed to arsenic at 25, 50 and 100ppm of sodium arsenite through drinking water consecutively for 90 days. Blood pressure was recorded weekly. On the 91st day, the rats were sacrificed for blood collection and isolation of thoracic aorta. Angiotensin converting enzyme and angiotensin II levels were assessed in plasma. Aortic reactivity to angiotensin II was assessed in organ-bath system. Western blot of AT1 receptors and G protein (Gαq/11), ELISA of signal transducers of MAP kinase pathway and reactive oxygen species (ROS) generation were assessed in aorta. Arsenic caused concentration-dependent increase in systolic, diastolic and mean arterial blood pressure from the 10th, 8th and 7th week onwards, respectively. Arsenic caused concentration-dependent enhancement of the angiotensin II-induced aortic contractile response. Arsenic also caused concentration-dependent increase in the plasma levels of angiotensin II and angiotensin converting enzyme and the expression of aortic AT1 receptor and Gαq/11 proteins. Arsenic increased aortic protein kinase C activity and the concentrations of protein tyrosine kinase, extracellular signal-regulated kinase-1/2 and vascular endothelial growth factor. Further, arsenic increased aortic mRNA expression of Nox2, Nox4 and p22phox, NADPH oxidase activity and ROS generation. The results suggest that arsenic-mediated enhancement of angiotensin II signaling could be an important mechanism in the arsenic-induced vascular disorder, where ROS could augment the angiotensin II signaling through activation of MAP kinase pathway.

In vitro treatment of HepG2 cells with saturated fatty acids reproduces mitochondrial dysfunction found in nonalcoholic steatohepatitis

Activity of the oxidative phosphorylation system (OXPHOS) is decreased in humans and mice with nonalcoholic steatohepatitis. Nitro-oxidative stress seems to be involved in its pathogenesis. The aim of this study was to determine whether fatty acids are implicated in the pathogenesis of this mitochondrial defect. In HepG2 cells, we analyzed the effect of saturated (palmitic and stearic acids) and monounsaturated (oleic acid) fatty acids on: OXPHOS activity; levels of protein expression of OXPHOS complexes and their subunits; gene expression and half-life of OXPHOS complexes; nitro-oxidative stress; and NADPH oxidase gene expression and activity. We also studied the effects of inhibiting or silencing NADPH oxidase on the palmitic-acid-induced nitro-oxidative stress and subsequent OXPHOS inhibition. Exposure of cultured HepG2 cells to saturated fatty acids resulted in a significant decrease in the OXPHOS activity. This effect was prevented in the presence of a mimic of manganese superoxide dismutase. Palmitic acid reduced the amount of both fully-assembled OXPHOS complexes and of complex subunits. This reduction was due mainly to an accelerated degradation of these subunits, which was associated with a 3-tyrosine nitration of mitochondrial proteins. Pretreatment of cells with uric acid, an antiperoxynitrite agent, prevented protein degradation induced by palmitic acid. A reduced gene expression also contributed to decrease mitochondrial DNA (mtDNA)-encoded subunits. Saturated fatty acids induced oxidative stress and caused mtDNA oxidative damage. This effect was prevented by inhibiting NADPH oxidase. These acids activated NADPH oxidase gene expression and increased NADPH oxidase activity. Silencing this oxidase abrogated totally the inhibitory effect of palmitic acid on OXPHOS complex activity. We conclude that saturated fatty acids caused nitro-oxidative stress, reduced OXPHOS complex half-life and activity, and decreased gene expression of mtDNA-encoded subunits. These effects were mediated by activation of NADPH oxidase. That is, these acids reproduced mitochondrial dysfunction found in humans and animals with nonalcoholic steatohepatitis.

Angiotensin-(1-9) reverses experimental hypertension and cardiovascular damage by inhibition of the angiotensin converting enzyme/Ang II axis

BACKGROUND

Little is known about the biological effects of angiotensin-(1-9), but available evidence shows that angiotensin-(1-9) has beneficial effects in preventing/ameliorating cardiovascular remodeling.

OBJECTIVE

In this study, we evaluated whether angiotensin-(1-9) decreases hypertension and reverses experimental cardiovascular damage in the rat.

METHODS AND RESULTS

Angiotensin-(1-9) (600  ng/kg per min for 2 weeks) reduced already-established hypertension in rats with early high blood pressure induced by angiotensin II infusion or renal artery clipping. Angiotensin-(1-9) also improved cardiac (assessed by echocardiography) and endothelial function in small-diameter mesenteric arteries, cardiac and aortic wall hypertrophy, fibrosis, oxidative stress, collagen and transforming growth factor type β - 1 protein expression (assessed by western blot). The beneficial effect of angiotensin-(1-9) was blunted by coadministration of the angiotensin type 2(AT2) receptor blocker PD123319 (36  ng/kg per min) but not by coadministration of the Mas receptor blocker A779 (100  ng/kg per min). Angiotensin-(1-9) treatment also decreased circulating levels of Ang II, angiotensin-converting enzyme activity and oxidative stress in aorta and left ventricle. Whereas, Ang-(1-9) increased endothelial nitric oxide synthase mRNA levels in aorta as well as plasma nitrate levels.

CONCLUSION

Angiotensin-(1-9) reduces hypertension, ameliorates structural alterations (hypertrophy and fibrosis), oxidative stress in the heart and aorta and improves cardiac and endothelial function in hypertensive rats. These effects were mediated by the AT2 receptor but not by the angiotensin-(1-7)/Mas receptor axis.

High-fat diet decreases activity of the oxidative phosphorylation complexes and causes nonalcoholic steatohepatitis in mice

Nonalcoholic fatty liver disease (NAFLD) is the most frequent histological finding in individuals with abnormal liver-function tests in the Western countries. In previous studies, we have shown that oxidative phosphorylation (OXPHOS) is decreased in individuals with NAFLD, but the cause of this mitochondrial dysfunction remains uncertain. The aims of this study were to determine whether feeding mice a high-fat diet (HFD) induces any change in the activity of OXPHOS, and to investigate the mechanisms involved in the pathogenesis of this defect. To that end, 30 mice were distributed between five groups: control mice fed a standard diet, and mice on a HFD and treated with saline solution, melatonin (an antioxidant), MnTBAP (a superoxide dismutase analog) or uric acid (a scavenger of peroxynitrite) for 28 weeks intraperitoneously. In the liver of these mice, we studied histology, activity and assembly of OXPHOS complexes, levels of subunits of these complexes, gene expression of these subunits, oxidative and nitrosative stress, and oxidative DNA damage. In HFD-fed mice, we found nonalcoholic steatohepatitis, increased gene expression of TNFα, IFNγ, MCP-1, caspase-3, TGFβ1 and collagen α1(I), and increased levels of 3-tyrosine nitrated proteins. The activity and assembly of all OXPHOS complexes was decreased to about 50–60%. The amount of all studied OXPHOS subunits was markedly decreased, particularly the mitochondrial-DNA-encoded subunits. Gene expression of mitochondrial-DNA-encoded subunits was decreased to about 60% of control. There was oxidative damage to mitochondrial DNA but not to genomic DNA. Treatment of HFD-fed mice with melatonin, MnTBAP or uric acid prevented all changes observed in untreated HFD-fed mice. We conclude that a HFD decreased OXPHOS enzymatic activity owing to a decreased amount of fully assembled complexes caused by a reduced synthesis of their subunits. Antioxidants and antiperoxynitrites prevented all of these changes, suggesting that nitro-oxidative stress played a key role in the pathogenesis of these alterations. Treatment with these agents might prevent the development of NAFLD in humans.

Atorvastatin ameliorates arsenic-induced hypertension and enhancement of vascular redox signaling in rats

Chronic arsenic exposure has been linked to elevated blood pressure and cardiovascular diseases, while statins reduce the incidence of cardiovascular disease predominantly by their low density lipoprotein-lowering effect. Besides, statins have other beneficial effects, including antioxidant and anti-inflammatory activities. We evaluated whether atorvastatin, a widely used statin, can ameliorate arsenic-induced increase in blood pressure and alteration in lipid profile and also whether the amelioration could relate to altered NO and ROS signaling. Rats were exposed to sodium arsenite (100ppm) through drinking water for 90 consecutive days. Atorvastatin (10mg/kg bw, orally) was administered once daily during the last 30days of arsenic exposure. On the 91st day, blood was collected for lipid profile. Western blot of iNOS and eNOS protein, NO and 3-nitrotyrosine production, Nox-4 and p22Phox mRNA expression, Nox activity, ROS generation, lipid peroxidation and antioxidants were evaluated in thoracic aorta. Arsenic increased systolic, diastolic and mean arterial blood pressure, while it decreased HDL-C and increased LDL-C, total cholesterol and triglycerides in serum. Arsenic down-regulated eNOS and up-regulated iNOS protein expression and increased basal NO and 3-nitrotyrosine level. Arsenic increased aortic Nox-4 and p22Phox mRNA expression, Nox activity, ROS generation and lipid peroxidation. Further, arsenic decreased the activities of superoxide dismutase, catalase, and glutathione peroxidase and depleted aortic GSH content. Atorvastatin regularized blood pressure, improved lipid profile and attenuated arsenic-mediated redox alterations. The results demonstrate that atorvastatin has the potential to ameliorate arsenic-induced hypertension by improving lipid profile, aortic NO signaling and restoring vascular redox homeostasis.

Central angiotensin-(1-7) improves vagal function independent of blood pressure in hypertensive (mRen2)27 rats

Hypertensive transgenic (mRen2)27 rats with overexpression of the mRen2 gene have impaired baroreflex sensitivity for heart rate control and high nicotinamide adenine dinucleotide phosphate oxidase and kinase-to-phosphatase signaling activity in medullary tissue compared with normotensive Hannover Sprague-Dawley control rats. They also exhibit insulin resistance at a young age. To determine whether blocking angiotensin II actions, supplementing angiotensin-(1-7), or scavenging reactive oxygen species in brain differentially alters mean arterial pressure, baroreflex sensitivity, or metabolic function, while altering medullary signaling pathways in these animals, we compared intracerebroventricular infusions of the angiotensin II type 1 receptor antagonist candesartan (4 μg/5 μL/h), angiotensin-(1-7) (0.1 μg/5 μL/h), a reactive oxygen species scavenger tempol (25 μg/5 μL/h), or artificial cerebrospinal fluid (5 μL/h) for 2 weeks. Mean arterial pressure was reduced in candesartan-treated rats without significantly improving the vagal components of baroreflex function or heart rate variability. In contrast, angiotensin-(1-7) treatment significantly improved the vagal components of baroreflex function and heart rate variability at a dose that did not significantly lower mean arterial pressure. Tempol significantly reduced nicotinamide adenine dinucleotide phosphate oxidase activity in brain dorsal medullary tissue but had no effect on mean arterial pressure or autonomic function. Candesartan tended to reduce fat mass, but none of the treatments significantly altered indices of metabolic function or mitogen-activated protein kinase signaling pathways in dorsal medulla. Although additional dose response studies are necessary to determine the potential maximal effectiveness of each treatment, the current findings demonstrate that blood pressure and baroreflex function can be essentially normalized independently of medullary nicotinamide adenine dinucleotide phosphate oxidase or mitogen-activated protein kinase in hypertensive (mRen2)27 rats.

Differences in oxidative stress status and expression of MKP-1 in dorsal medulla of transgenic rats with altered brain renin-angiotensin system

ANG II-stimulated production of reactive oxygen species (ROS) through NADPH oxidase is suggested to activate MAPK pathways, which are implicated in neurally mediated pressor effects of ANG II. Emerging evidence suggests that ANG-(1-7) up regulates MAPK phosphatases to reduce MAPK signaling and attenuate actions of ANG II. Whether angiotensin peptides participate in long-term regulation of these systems in the brain is not known. Therefore, we determined tissue and mitochondrial ROS, as well as expression and activity of MAPK phosphatase-1 (MKP-1) in brain dorsal medullary tissue of hypertensive transgenic (mRen2)27 rats exhibiting higher ANG II/ANG-(1-7) tone or hypotensive transgenic rats with targeted decreased glial expression of angiotensinogen, ASrAOGEN (AS) exhibiting lower ANG II/ANG-(1-7) tone compared with normotensive Sprague-Dawley (SD) rats that serve as the control strain. Transgenic (mRen2)27 rats showed higher medullary tissue NADPH oxidase activity and dihydroethidium fluorescence in isolated mitochondria vs. SD or AS rats. Mitochondrial uncoupling protein 2 was lower in AS and unchanged in (mRen2)27 compared with SD rats. MKP-1 mRNA and protein expression were higher in AS and unchanged in (mRen2)27 compared with SD rats. AS rats also had lower phosphorylated ERK1/2 and JNK consistent with higher MKP-1 activity. Thus, an altered brain renin-angiotensin system influences oxidative stress status and regulates MKP-1 expression. However, there is a dissociation between these effects and the hemodynamic profiles. Higher ROS was associated with hypertension in (mRen2)27 and normal MKP-1, whereas the higher MKP-1 was associated with hypotension in AS, where ROS was normal relative to SD rats.

Cross-talk between the cellular redox state and the circadian system in Neurospora

The circadian system is composed of a number of feedback loops, and multiple feedback loops in the form of oscillators help to maintain stable rhythms. The filamentous fungus Neurospora crassa exhibits a circadian rhythm during asexual spore formation (conidiation banding) and has a major feedback loop that includes the FREQUENCY (FRQ)/WHITE COLLAR (WC) -1 and -2 oscillator (FWO). A mutation in superoxide dismutase (sod)-1, an antioxidant gene, causes a robust and stable circadian rhythm compared with that of wild-type (Wt). However, the mechanisms underlying the functions of reactive oxygen species (ROS) remain unknown. Here, we show that cellular ROS concentrations change in a circadian manner (ROS oscillation), and the amplitudes of ROS oscillation increase with each cycle and then become steady (ROS homeostasis). The ROS oscillation and homeostasis are produced by the ROS-destroying catalases (CATs) and ROS-generating NADPH oxidase (NOX). cat-1 is also induced by illumination, and it reduces ROS levels. Although ROS oscillation persists in the absence of frq, wc-1 or wc-2, its homeostasis is altered. Furthermore, genetic and biochemical evidence reveals that ROS concentration regulates the transcriptional function of WCC and a higher ROS concentration enhances conidiation banding. These findings suggest that the circadian system engages in cross-talk with the cellular redox state via ROS-regulatory factors.

Rho kinase inhibition activates the homologous angiotensin-converting enzyme-angiotensin-(1-9) axis in experimental hypertension

BACKGROUND

Angiotensin II (Ang II) levels depend on renin, angiotensin-converting enzyme (ACE), and on the homologous angiotensin-converting enzyme (ACE2). Increased ACE and Ang II levels are associated with higher Rho kinase activity. However, the relationship between Rho kinase activation and ACE2 in hypertension is unknown.

OBJECTIVE

The role of the Rho kinase signaling pathway in both enzymatic activity and aortic gene expression of ACE2 in deoxycorticosterone acetate (DOCA) hypertensive rats was assessed in the present study.

METHODS AND RESULTS

Compared with sham animals, Rho kinase activity was higher by 400% (P<0.05) in the aortic wall of the DOCA hypertensive rats. In addition to blood pressure reduction, the specific Rho kinase inhibitor fasudil reduced aortic Rho kinase activity to levels observed in the sham control group and increased ACE2 enzymatic activity (by 83% in plasma and by 52% in the aortic wall, P<0.05), ACE2, and endothelial nitric oxide synthase (eNOS) aortic mRNA levels (by 340 and 40%, respectively, P<0.05) with respect to the untreated hypertensive DOCA rats. Fasudil also increased significantly plasma levels of Ang-(1-9) in normotensive and in the hypertensive rats. Aortic mRNA and protein levels of transforming growth factor-β1 (TGF-β1), plasminogen activator inhibitor 1 (PAI-1), and monocyte chemoattractant protein 1 (MCP-1) were significantly (P<0.05) higher in the untreated DOCA rats and were normalized by fasudil administration.

CONCLUSION

In experimental hypertension, Rho-associated, coiled-coil containing protein kinase (ROCK) inhibition reduces blood pressure and increases ACE2 levels and activity. At the same time, ROCK inhibition reduces angiotensin II and increases Ang-(1-9) plasma levels. Fasudil also increases vascular eNOS mRNA levels and reduces aortic overexpression of the remodeling promotion proteins TGF-β1, PAI-1, and MCP-1. This effect might additionally contribute to the antihypertensive and antiremodeling effects of ROCK inhibition in hypertension.

Inhibition of bilirubin metabolism induces moderate hyperbilirubinemia and attenuates ANG II-dependent hypertension in mice

Population studies indicate that moderate hyperbilirubinemia is associated with reduced incidence of cardiovascular diseases, including hypertension. Despite this correlative evidence, no studies have directly tested the hypothesis that moderate increases in plasma bilirubin levels can attenuate the development of hypertension. This hypothesis was tested by treating mice with Indinavir, a drug that competes with bilirubin for metabolism by UDP-glucuronosyltransferase 1A1 (UGT1A1). Treatment of mice with Indinavir (500 mg x kg(-1) x day(-1), gavage) resulted in a twofold increase in plasma unconjugated bilirubin levels. Next, we determined the effect of Indinavir-induced changes in plasma bilirubin on the development of ANG II-dependent hypertension. Moderate hyperbilirubinemia was induced 3 days before the implantation of an osmotic minipump that delivered ANG II at a rate of 1 microg x kg(-1) x min(-1). ANG II infusion increased mean arterial pressure (MAP) by 20 mmHg in control mice but by only 6 mmHg in mice treated with Indinavir (n = 6). Similar to Indinavir treatment, direct infusion of bilirubin (37.2 mg x kg(-1) x day(-1) i.v.) resulted in a twofold increase in plasma bilirubin levels and also attenuated the development of ANG II-dependent hypertension. Moderate hyperbilirubinemia resulted in an increase in plasma nitrate/nitrite levels, which averaged 36 +/- 2 vs. 50 +/- 7 microM in ANG II vehicle vs. Indinavir-treated mice (n = 5). Moderate hyperbilirubinemia resulted in attenuation of vascular oxidative stress as determined by dihydroethidium staining of aortic segments. These results indicate that moderate hyperbilirubinemia prevents ANG II-dependent hypertension by a mechanism that may involve decreases in vascular oxidative stress.

Effect of renin inhibition and AT1R blockade on myocardial remodeling in the transgenic Ren2 rat

Angiotensin II (Ang II) stimulation of the Ang type 1 receptor (AT(1)R) facilitates myocardial remodeling through NADPH oxidase-mediated generation of oxidative stress. Components of the renin-angiotensin system constitute an autocrine/paracrine unit in the myocardium, including renin, which is the rate-limiting step in the generation of Ang II. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo renin inhibition and/or AT(1)R blockade in a rodent model of chronically elevated tissue Ang II levels, the transgenic (mRen2)27 rat (Ren2). The Ren2 overexpresses the mouse renin transgene with resultant hypertension, insulin resistance, and cardiovascular damage. Young (6- to 7-wk-old) heterozygous (+/-) male Ren2 and age-matched Sprague-Dawley rats were treated with the renin inhibitor aliskiren, which has high preferential affinity for human and mouse renin, an AT(1)R blocker, irbesartan, or placebo for 3 wk. Myocardial NADPH oxidase activity and immunostaining for NADPH oxidase subunits and 3-nitrotyrosine were evaluated and remodeling changes assessed by light and transmission electron microscopy. Blood pressure, myocardial NADPH oxidase activity and subunit immunostaining, 3-nitrotyrosine, perivascular fibrosis, mitochondrial content, and markers of activity were significantly increased in Ren2 compared with SD littermates. Both renin inhibition and blockade of the AT(1)R significantly attenuated cardiac functional and structural alterations, although irbesartan treatment resulted in greater reductions of both blood pressure and markers of oxidative stress. Collectively, these data suggest that both reduce changes driven, in part, by Ang II-mediated increases in NADPH oxidase and, in part, increases in blood pressure.

Angiotensin-(1-7) prevents activation of NADPH oxidase and renal vascular dysfunction in diabetic hypertensive rats

BACKGROUND/AIM

We examined the influence of chronic treatment with angiotensin-(1-7) [Ang-(1-7)] on renox (renal NADPH oxidase, NOX-4) and the development of renal dysfunction in streptozotocin-treated spontaneously hypertensive rats (diabetic SHR).

METHODS

Mean arterial pressure, urinary protein and vascular responsiveness of the isolated renal artery to vasoactive agonists were studied in vehicle- or Ang-(1-7)-treated SHR and diabetic SHR.

RESULTS

Ang-(1-7) decreased the elevated levels of renal NADPH oxidase (NOX) activity and attenuated the activation of NOX-4 gene expression in the diabetic SHR kidney. Ang-(1-7) treatment increased sodium excretion but did not affect mean arterial pressure in diabetic SHR. There was a significant increase in urinary protein (266 +/- 22 mg/24 h) in the diabetic compared to control SHR (112 +/- 13 mg/24 h) and treatment of diabetic SHR with Ang-(1-7) reduced the degree of proteinuria (185 +/- 23 mg/24 h, p < 0.05). Ang-(1-7) treatment also attenuated the diabetes-induced increase in renal vascular responsiveness to endothelin-1, norepinephrine, and angiotensin II in SHR, but significantly increased the vasodilation of the renal artery of SHR and diabetic SHR to the vasodilator agonists.

CONCLUSION

These results suggest that treatment with Ang-(1-7) constitutes a potential therapeutic strategy to alleviate NOX-mediated oxidative stress and to reduce renal dysfunction in diabetic hypertensive rats.

Rho kinase activation and gene expression related to vascular remodeling in normotensive rats with high angiotensin I converting enzyme levels

The RhoA/Rho kinase (ROCK) pathway is a new mechanism of remodeling and vasoconstriction. Few data are available regarding ROCK activation when angiotensin I-converting enzyme is high and blood pressure is normal. We hypothesized that ROCK is activated in the vascular wall in normotensive rats with genetically high angiotensin I-converting enzyme levels, and it causes increased vascular expression of genes promoting vascular remodeling and also oxidative stress. Aortic ROCK activation, mRNA and protein levels (of monocyte chemoattractant protein-1, transforming growth factor [TGF]-beta(1), and plasminogen activator inhibitor-1 [PAI-1]), NADPH oxidase activity, and O(2)(*-) production were measured in normotensive rats with genetically high (Brown Norway [BN]) and low (Lewis) angiotensin-I-converting enzyme levels and in BN rats treated with the ROCK antagonist fasudil (100 mg/kg per day) for 7 days. ROCK activation was 12-fold higher in BN versus Lewis rats (P<0.05) and was reduced with fasudil by 100% (P<0.05). Aortic TGF-beta1, PAI-1, and monocyte chemoattractant protein-1 mRNA levels were higher in BN versus Lewis rats by 300%, 180%, and 1000%, respectively (P<0.05). Aortic TGF-beta1, PAI-1, and monocyte chemoattractant protein-1 protein levels were higher in BN versus Lewis rats (P<0,05). Fasudil reduced TGF-beta1 and PAI-1 mRNA and TGF-beta1, PAI-1, and monocyte chemoattractant protein-1 protein aortic levels to those observed in Lewis rats. Aortic reduced nicotinamide-adenine dinucleotide phosphate oxidase activity and (*)O(2)(-) production were increased by 88% and 300%, respectively, in BN rats (P<0.05) and normalized by fasudil. In conclusion, ROCK is significantly activated in the aortic wall in normotensive rats with genetically high angiotensin-I-converting enzyme and angiotensin II, and it causes activation of genes that promote vascular remodeling and also increases vascular oxidative stress.

Contribution of different Nox homologues to cardiac remodeling in two-kidney two-clip renovascular hypertensive rats: effect of valsartan

Growing evidences have shown that hypertension, cardiac hypertrophy and fibrosis were associated with an overactivity of NAD(P)H oxidase. It is unknown, however, which isoform of NAD(P)H oxidase yields O(2)*(-) formation in heart and aorta in two-kidney, two-clip (2K2C) hypertensive rats in vivo and thus is responsible for the development of cardiac remodeling. We examined the pathological change of NAD(P)H oxidase homologues and tested the effect of valsartan on the cardiac remodeling in 2K2C renovascular hypertensive rats. Four weeks after male Sprague-Dawley rats accepted 2K2C or sham operation, 2K2C hypertensive (>160 mmHg) rats were divided into vehicle-treated (2K2C) and valsartan (30 mg kg(-1) per day, for 6 weeks)-treated (2K2C+Val) groups, which were compared with sham-operated controls (Sham). At week 10, 2K2C hypertensive rats showed increased serum level of angiotensin II (Ang II), MDA and blood pressure (BP), obvious cardiac hypertrophy and fibrosis, increased O(2)*(-) production and NAD(P)H oxidase activity and expression in aorta and heart. The heart in 2K2C hypertensive rats preferred to use NADH as substrate while the aorta used both NADH and NADPH. Valsartan treatment decreased BP, ameliorated cardiac hypertrophy and fibrosis, decreased O(2)*(-) production and NAD(P)H oxidase activity in aorta and heart. Nox2 and Nox4 protein expression increased in heart, while Nox1 and Nox4 increased in aorta in 2K2C hypertensive rats, which were all normalized after valsartan treatment. In conclusion, these data indicate that different Nox expression might account for substrate preference and the formation of O(2)*(-) by NAD(P)H oxidase resulting from elevated Ang II in the 2K2C model contributes to the development of renovascular hypertension and subsequent cardiac remodeling.

Sustained activation of Rac1 in hepatic stellate cells promotes liver injury and fibrosis in mice

Rac, a small, GTP-binding protein in the Rho family, regulates several cellular functions, including the activation of NADPH oxidase, a major intracellular producer of reactive oxygen species (ROS). Hepatic stellate cells (HSCs) isolated from mice that are genetically deficient in NADPH oxidase produce less ROS, and their activation during chronic liver injury is abrogated, resulting in decreased liver fibrosis. Therefore, we hypothesized that HSC ROS production and activation would be enhanced, and fibrosis worsened, by increasing Rac expression in HSCs. To achieve this, we used transgenic mice that express constitutively active human Rac1 under the control of the alpha-smooth muscle actin (alpha-sma) promoter, because alpha-sma expression is induced spontaneously during HSC activation. Transgene expression was upregulated progressively during culture of primary Rac-transgenic HSCs, and this increased HSC ROS production as well as expression of activation markers and collagen. Similarly, Rac mice treated with carbon tetrachloride (CCl(4)) accumulated greater numbers of activated HSCs and had more liver damage, hepatocyte apoptosis, and liver fibrosis-as well as higher mortality-than CCl(4)-treated wild-type mice. In conclusion, sustained activation of Rac in HSCs perpetuates their activation and exacerbates toxin-induced liver injury and fibrosis, prompting speculation that Rac may be a therapeutic target in patients with cirrhosis.