Chronic inhibition of NO synthesis per se promotes structural intimal remodeling of the rat aorta

Parboiled Germinated Brown Rice Improves Cardiac Structure and Gene Expression in Hypertensive Rats

Hypertension leads to oxidative stress, inflammation, and fibrosis. The suppression of these indicators may be one treatment approach. Parboiled germinated brown rice (PGBR), obtained by steaming germinated Jasmine rice, reduces oxidative stress and inflammation in vivo. PGBR contains more bioactive compounds than brown rice (BR) and white rice (WR). Anti-hypertensive benefits of PGBR have been predicted, but research is lacking. The anti-hypertensive effects of PGBR were investigated in the downstream gene network of hypertension pathogenesis, including the renin-angiotensin system, fibrosis, oxidative stress production, and antioxidant enzymes in N-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. To strengthen our findings, the cardiac structure was also studied. PGBR-exposed rats showed significant reductions in systolic blood pressure (SBP) compared to the hypertensive group. WR did not reduce SBP because of the loss of bioactive compounds during intensive milling. PGBR also reduced the expression of the angiotensin type 1 receptor (AT1R), transforming growth factor-β (TGF-β), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX4), which contribute to the renin-angiotensin system, fibrosis, and oxidative stress production, respectively. Losartan (Los, an anti-hypertensive drug)-treated rats also exhibited similar gene expression, implying that PGBR may reduce hypertension using the same downstream target as Los. Our data also indicated that PGBR reduced cardiac lesions, such as the cardiomyopathy induced by L-NAME. This is the first report on the anti-hypertensive effects of PGBR in vivo by the suppression of the renin response, fibrosis, and improved cardiac structure.

Monocyte Low-Density Lipoprotein Receptor-Related Protein 1 (LRP1) Expression Correlates with cIMT in Mexican Hypertensive Patients

Fundamento

A hipertensão arterial (HTA) representa um grande fator de risco de morbidade e mortalidade cardiovascular. Ainda não se sabe que mecanismos moleculares específicos estão associados ao desenvolvimento de hipertensão essencial.

Objetivo

Neste trabalho, analisamos a associação entre expressão mRNA de monócito LRP1, expressão de proteína LRP1, e espessura íntima-média de carótida (EIMC) de pacientes com hipertensão essencial.

Métodos

A expressão mRNA de monócito LRP1 e os níveis de proteína e EIMC foram quantificados em 200 indivíduos mexicanos, sendo 91 normotensos (NT) e 109 hipertensos (HT) A significância estatística foi definida em p < 0,05.

Resultados

O grupo de pacientes HT tinha EIMC maior altamente significativa em comparação com os pacientes NT (p = 0,002), e isso está relacionado ao aumento na expressão mRNA de LRP1 (6,54 versus. 2,87) (p = 0,002) e expressão de proteína LRP1 (17,83 versus 6,25), respectivamente (p = 0,001). Essas diferenças foram mantidas mesmo quando dividimos nossos grupos de estudo, levando em consideração apenas aqueles que apresentavam dislipidemia na expressão de mRNA (p = 0,041) e de proteínas (p < 0,001). Também se identificou que a indução de LRP1 mediada por LRP1 em monócitos em de maneira dependente de dose e tempo, com diferença significativa em NT versus HT (0,195 ± 0,09 versus 0,226 ± 0,12, p = 0,046).

Conclusão

Foi encontrado um aumento em EIMC em indivíduos com hipertensão, associada a expressões de proteína LRP1 e mRNA mais altas em monócitos, independente da presença de dislipidemia em pacientes HT. Esses resultados que a upregulation de LRP1 em monócitos de pacientes hipertensos mexicanos poderia estar envolvida na diminuição da EIMC. (Arq Bras Cardiol. 2021; 116(1):56-65)

Structural alterations in rat myocardium induced by chronic l-arginine and l-NAME supplementation

Structural changes affecting cardiomyocyte function may contribute to the pathophysiological remodeling underlying cardiac function impairment. Recent reports have shown that endogenous nitric oxide (NO) plays an important role in this process. In order to examine the role of NO in cardiomyocyte remodeling, male rats were acclimated to room temperature (22 ± 1 °C) or cold (4 ± 1 °C) and treated with 2.25% l-arginine·HCl or 0.01% l-NAME (Nω-nitro-l-arginine methyl ester)·HCl for 45 days. Untreated groups served as controls. Right heart ventricles were routinely prepared for light microscopic examination. Stereological estimations of volume densities of cardiomyocytes, surrounding blood vessels and connective tissue, as well as the morphometric measurements of cardiomyocyte diameters were performed. Tissue sections were also analyzed for structural alterations. We observed that both l-arginine and l-NAME supplementation induced cardiomyocyte hypertrophy, regardless of ambient temperature. However, cardiomyocyte hypertrophy was associated with fibrosis and extra collagen deposition only in the l-NAME treated group. Taken together, our results suggest that NO has a modulatory role in right heart ventricle remodeling by coordinating hypertrophy of cardiomyocytes and fibrous tissue preventing cardiac fibrosis.

Cardioprotective role of tadalafil against cisplatin-induced cardiovascular damage in rats

The present study investigated the possible cardioprotective effect of tadalafil (Tad) on cisplatin (CDDP)-induced cardiac and vascular damages in rats. A total number of seventy two healthy male albino rats initially weighting between 200 and 220 g were used and randomly divided into four groups,18 rats in each. The control group received no treatment; CDDP group received a single dose of CDDP (4 mg/kg) intraperitoneal (i.p.) per week for 4 weeks the duration of the experiment; Tad group received 0.4 mg/kg BW Tad i.p. daily and Tad +CDDP group received 0.4 mg/kg BW Tad i.p. +4 mg/kg BW CDDP i.p. The results showed that Tad was able to decrease blood pressure, heart rate, levels of serum cardiac troponin (cTn-I), malondialdehyde (MDA) and increased levels of reduced glutathione (GSH) and nitric oxide (NO) in the heart homogenate sample from CDDP treated rats. Semi-quantitative analysis showed that Tad was able to decrease the histopathological scores of cardiac muscular hyalinzation and fibrosis in three sacrifices in CDDP treated rats. CDDP treated rats showed significantly increased thickening in wall of aorta with an irregular luminal layer of endothelial cell linings in three sacrifices when it was compared to other groups. Moreover, immunohistochemical labeling of α- smooth muscle actin (α-SMA) in aorta revealed significant lower scores in Tad +CDDP group when they were compared to CDDP group. In conclusion, Tad alone did not induce any harmful effects on blood pressure, selective antioxidant, peroxidation markers or cardiac histology, in addition, Tad has a cardio-protective role against CDDP.

Oral administration of veratric acid, a constituent of vegetables and fruits, prevents cardiovascular remodelling in hypertensive rats: a functional evaluation

In our previous studies, veratric acid (VA) shows beneficial effect on hypertension and its associated dyslipidaemia. In continuation, this study was designed to investigate the effect of VA, one of the major benzoic acid derivatives from vegetables and fruits, on cardiovascular remodelling in hypertensive rats, primarily assessed by functional studies using Langendorff isolated heart system and organ bath system. Hypertension was induced in male albino Wistar rats by oral administration of N ω -nitro-l-arginine methyl ester hydrochloride (l-NAME) (40 mg/kg body weight (b.w.)) in drinking water for 4 weeks. VA was orally administered at a dose of 40 mg/kg b.w. l-NAME-treated rats showed impaired cardiac ventricular and vascular function, evaluated by Langendorff isolated heart system and organ bath studies, respectively; a significant increase in the lipid peroxidation products such as thiobarbituric acid-reactive substances and lipid hydroperoxides in aorta; and a significant decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase and levels of GSH, vitamin C and vitamin E in aorta. Fibrotic remodelling of the aorta and heart were assessed by Masson's Trichrome staining and Van Gieson's staining, respectively. In addition, l-NAME rats showed increased heart fibronectin expression assessed by immunohistochemical analysis. VA supplementation throughout the experimental period significantly normalised cardiovascular function, oxidative stress, antioxidant status and fibrotic remodelling of tissues. These results of the present study conclude that VA acts as a protective agent against hypertension-associated cardiovascular remodelling.

Effect of aliskiren, telmisartan and torsemide on cardiac dysfunction in l-nitro arginine methyl ester (l-NAME) induced hypertension in rats

Comparative study of cardio protective effect of aliskiren, telmisartan, and torsemide was carried out on l-nitro arginine methyl ester (l-NAME) induced hypertension in rats. The three drugs were given daily for 8 weeks simultaneously with l-NAME, with a control group for each drug and l-NAME. The degree of protection was assessed by measurement of systolic blood pressure and heart rate of animals every two weeks. At the end of the experimental period blood sampling was carried out for estimation of the level of NO2 (-)/NO3 (-). After which animals were sacrificed for heart dissection to detect collagen types I and III gene expression. Histopathological study was done to evaluate the extension of collagen deposits. The study revealed that the three drugs decreased blood pressure significantly compared to l-NAME. There was no significant difference between aliskiren and telmisartan in all measurements, but there was significant decrease in measurements of both aliskiren and telmisartan treated groups compared to torsemide starting from 4th week. There were insignificant changes in pulse rate values between the three l-NAME treated groups through the experiment. The three drugs significantly increased NO compared to l-NAME. Collagen I and III gene expression was significantly decreased by the three drugs but the highest percentage of inhibition was with telmisartan compared to l-NAME. Comparing the percentage inhibition of cardiac fibrosis, there was insignificant difference between telmisartan and torsemide treated groups while both were superior to aliskiren. In conclusion, further experimental studies are required to elucidate the potential cardioprotective mechanisms of aliskiren, telmisartan and torsemide, and assess their efficacy in treatment of heart failure.

Vanillic acid: a potential inhibitor of cardiac and aortic wall remodeling in l-NAME induced hypertension through upregulation of endothelial nitric oxide synthase

The objective of the present study is to investigate the effects of vanillic acid on blood pressure, cardiac marker enzymes, left ventricular function and endothelial nitric oxide synthase (eNOS) expression in N(ω)-nitro-l-arginine methyl ester hydrochloride (l-NAME) induced hypertension in male albino Wistar rats. In hypertensive rats, mean arterial pressure (MAP), heart rate, cardiac marker enzymes and organ weight were increased. Impaired left ventricular function and decreased aortic eNOS expression was also observed in hypertensive rats. Moreover, treatment with vanillic acid exhibited beneficial effect on blood pressure, left ventricular function and cardiac marker enzymes. In addition, treatment with vanillic acid on hypertensive rats had upregulated eNOS expression and showed beneficial effects evidenced by histopathology and ultrastructural observations of aorta. In conclusion, vanillic acid has enough potential to normalize hypertension and left ventricular function in l-NAME induced hypertensive rats. With additional studies, vanillic acid might be used as a functional drug or as an adjuvant in the management of hypertension.

Rosuvastatin prevents proteinuria and renal inflammation in nitric oxide-deficient rats

OBJECTIVE

The aim of the present study was to assess the effects of rosuvastatin on renal injury and inflammation in a model of nitric oxide deficiency.

METHODS

Male Wistar rats were randomly divided into four groups (n = 10/group) and treated for 28 days with saline (CTRL); 30 mg/kg/day L-NAME (L-name); L-NAME and 20 mg/kg/day rosuvastatin (L-name+ROS-20); or L-NAME and 2 mg/kg/day rosuvastatin (L-name+ROS-2). Systolic blood pressure was measured by plethysmography in the central artery of the tail. The serum total cholesterol, triglycerides, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, creatinine, nitric oxide, interleukin-6, and tumor necrosis factor alpha levels were analyzed. Urine samples were taken to measure the albumin: urinary creatinine ratio. Kidneys were sectioned and stained with hematoxylin/eosin and Masson's trichrome. Immunohistochemical analysis of the renal tissue was performed to detect macrophage infiltration of the glomeruli.

RESULTS

The systolic blood pressure was elevated in the L-name but not the L-name+rosuvastatin-20 and L-name+rosuvastatin-2 groups. The L-name group had a significantly reduced nitric oxide level and an increased interleukin-6 and tumor necrosis factor alpha level, albumin: urinary creatinine ratio and number of macrophages in the renal glomeruli. Rosuvastatin increased the nitric oxide level in the L-name+rosuvastatin-2 group and reduced the interleukin-6 and tumor necrosis factor alpha levels, glomerular macrophage number and albumin:urinary creatinine ratio in the L-name+rosuvastatin-20 and L-name+rosuvastatin-2 groups.

CONCLUSION

Rosuvastatin treatment reduced glomerular damage due to improvement in the inflammatory pattern independent of the systolic blood pressure and serum lipid level. These effects may lead to improvements in the treatment of kidney disease.

Melatonin interactions with blood pressure and vascular function during L-NAME-induced hypertension

The mechanisms responsible for the antihypertensive effect of melatonin are not completely understood. To elucidate the possible role of the nitric oxide (NO) pathway in the hemodynamic actions of melatonin, the effects of this indolamine on vascular function during hypertension induced by the NO-synthase (NOS) inhibitor, N(omega)-nitro-L-arginine-methyl ester (L-NAME) were investigated. Four groups of male adult Wistar rats were employed: control, L-NAME (40 mg/kg), melatonin (10 mg/kg) and L-NAME + melatonin for 5 wks. Systolic and diastolic blood pressure were measured invasively in the carotid artery. Conjugated dienes concentration (an oxidative load marker), NOS RNA expression and its activity and RNA expression of cyclooxygenase-(COX)-1 and COX-2 were determined in the aorta. Acetylcholine-induced responses and their NO-mediated component were evaluated in femoral and mesenteric artery. Moreover, endothelium-derived constricting factor (EDCF)-dependent vasoconstriction and inner diameter were determined in the femoral artery. Chronic L-NAME treatment induced hypertension, elevated the oxidative load and inhibited NOS activity. Moreover, impaired NO-dependent relaxation, augmented EDCF-constriction, increased COX-2 expression and reduced arterial inner diameter were observed. Melatonin added to L-NAME treatment completely prevented elevation of the oxidative load in the aorta. However, melatonin was not able to prevent NOS activity decline, elevation of COX-2 expression or the impairment of vascular responses (except moderate improvement in relaxation of small mesenteric arteries) and it exerted only slight antihypertensive effect. In conclusion, in addition to the reduction of the oxidative load, the restoration of the NO pathway seems to play an important role in the antihypertensive effect of melatonin.

Can eccentric arterial plaques alone cause flow stagnation points and favour thrombus incorporation?

We have used an experimental model of aorta stenosis, with a Plexiglas plug, simulating a stable atheromatous plaque that promotes local turbulence and thrombosis. With animal survival of more than 24 h, we followed the partial fibrinolysis of the thrombus as well as its posterior organization and incorporation to the arterial wall as a neointima for up to 30 days. The mushroom plug form permitted the development of recirculation and stasis areas around it, favouring this evolution. Despite noted limitations, this study demonstrates that thrombus incorporation can contribute to plaque extension, as it can promote recirculation and stasis areas.

Proteomic analysis permits the identification of new biomarkers of arterial wall remodeling in hypertension

Hypertension represents one of the main risk factors for vascular diseases. Genetic susceptibility may influence the rate of its development and the associated vascular remodeling. To explore markers of hypertension-related morbidity, we have used surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry to study changes in proteins released by the aorta of two rat strains with different susceptibilities to hypertension. Fischer and Brown Norway (BN) rats were divided into a control group and a group receiving low-dose N(Omega)-nitro-L-arginine methyl ester (L-NAME), a hypertensive drug, interfering with endothelial function. In spite of a significant elevation of blood pressure in both strains in response to L-NAME, BN rats exhibited a lower vascular remodeling in response to hypertension. Proteomic analysis of secreted aortic proteins by SELDI-TOF MS allowed detection of four mass-to-charge ratio (m/z) peaks whose corresponding proteins were identified as ubiquitin, smooth muscle (SM) 22alpha, thymosin beta4, and C-terminal fragment of filamin A, differentially secreted in Fischer rats in response to L-NAME. We have confirmed a strain-dependent difference in susceptibility to L-NAME-induced hypertension between BN and Fischer rats. The greater susceptibility of Fischer rats is associated with aortic wall hypertrophic remodeling, reflected by increased aortic secretion of four identified biomarkers. Similar variations in one of them, SM22alpha, also were observed in plasma, suggesting that this marker could be used to assess vascular damage induced by hypertension.

Regression of left ventricular hypertrophy and aortic remodelling in NO-deficient hypertensive rats: effect of L-arginine and spironolactone

AIM

We investigated, whether the substrate for nitric oxide (NO) formation -L-arginine - and the aldosterone receptor antagonist - spironolactone - are able to reverse alterations of the left ventricle (LV) and aorta in N(omega)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension.

METHODS

Six groups of male adult Wistar rats were investigated: controls after 4 and 7 weeks of experiment, rats treated with L-NAME for 4 weeks and three recovery groups: spontaneous-reversion (4 weeks L-NAME + 3 weeks placebo), spironolactone-induced reversion (4 weeks L-NAME + 3 weeks spironolactone) and L-arginine-induced reversion (4 weeks L-NAME+ 3 weeks L-arginine). Blood pressure was measured by tail-cuff plethysmography. Relative weight of the LV, myocardial fibrosis (based upon histomorphometry and hydroxyproline determination) and conjugated dienes in the LV and aortic cross-sectional area, inner diameter and wall thickness were determined. NO-synthase activity was investigated in the LV and aorta.

RESULTS

L-NAME administration induced hypertension, left ventricular hypertrophy (LVH), LV fibrosis, aortic thickening and diminution of NO-synthase activity in the LV and aorta. Reduction in blood pressure and regression of LVH were observed in all recovery groups, yet reduction in LV fibrosis and aortic thickening were not. NO-synthase activity was restored only in the L-arginine and spironolactone group.

CONCLUSION

In our study, the reversion of hypertension and LVH was not dependent on the restoration of NO-synthase activity. Moreover, LV fibrosis and aortic remodelling seem to be more resistant to conditions resulting in regression of LVH. Preserved level of fibrosis in the initial period of LVH regression might result in loss of structural homogeneity and possible functional alterations of the LV.

Regression of L-NAME-induced hypertension: the role of nitric oxide and endothelium-derived constricting factor

N(G)-Nitro-L-arginine-methyl ester (L-NAME)-induced hypertension is a well established model of experimental hypertension. Although regression experiments are effective at approximating a clinical setting the reversal of already established L-NAME hypertension has not been intensively researched. We investigated whether spontaneous regression of L-NAME hypertension after discontinuing the drug administration was associated with recovery of endothelial dysfunction. Special attention was devoted to NO signaling and endothelium-derived constricting factor (EDCF) formation in various parts of the vascular tree. Male adult Wistar rats were divided into 4 groups: an L-NAME (5 weeks), a spontaneous recovery (5 weeks L-NAME + 3 weeks of recovery) and two age-matched control groups (a 5- and 8-week control group). The NO-mediated and EDCF-mediated components of acetylcholine-induced responses were evaluated in preconstricted small mesenteric and femoral arteries. The activity, mRNA and protein expression of NO synthase together with the mRNA expression of cyclooxygenase were determined in the aorta. L-NAME administration caused hypertension, impaired NO signaling (as indicated by the reduced NO component of acetylcholine-induced relaxation and decreased NO synthase activity) in all arteries investigated and reduced the inner diameter of the femoral artery. Moreover, we observed enhanced cyclooxygenase-dependent EDCF formation in the femoral arteries and enhanced cyclooxygenase-2 expression in the aortas of L-NAME-treated rats. During spontaneous recovery a functional restoration of NO signaling took place in all parts of the vascular tree. However, the increases in systolic blood pressure, EDCF formation, and cyclooxygenase expression and the reduction in femoral artery diameter were not completely restored. We conclude that impaired NO signaling was improved after the cessation of L-NAME administration. However, persisting arterial structural alterations and enhanced EDCF formation may decelerate blood pressure reduction even after the restoration of NO synthase activity.

Aorta remodeling responses to distinct atherogenic stimuli: hypertension, hypercholesterolemia and turbulent flow/low wall shear stress

This review is based on recently published data from our laboratory. We investigated the role of hypertension and laminar flow, hypercholesterolemia and laminar flow and turbulent blood flow/low wall shear stress, and turbulent blood flow/low wall shear stress associated with hypercholesterolemia on aorta remodeling of rats feeding normal diet or hypercholesterolemic diet. Our findings suggest that increased circumferential wall tension due to hypertension plays a key role in the remodeling through biomechanical effects on oxidative stress and increased TGF-beta expression; the remodeling observed in the presence of hypercholesterolemia could be initiated by oxidative stress that is involved in several processes of atherogenesis and this remodeling is more pronounced in the presence of turbulent blood flow/low wall shear stress.

Turbulent blood flow plays an essential localizing role in the development of atherosclerotic lesions in experimentally induced hypercholesterolaemia in rats

Taking into account that atherosclerosis is a focal disease and high levels of plasma cholesterol are closely correlated with its pathogenesis, it is a challenge to explain how equal concentrations of cholesterol bathing the endothelium can produce local, rather than global, effects on arteries. The focal distribution of atherosclerotic lesions has been considered to be dependent, at least in part, on hydrodynamic factors. The present study was carried out to further test the hypothesis that these forces are an important localizing factor in rats feeding a hypercholesterolaemic diet and submitted to infra-diaphragmatic aortic constriction. These animals develop a normotensive prestenotic region with laminar blood flow that serves as control for a normotensive poststenotic region with turbulent blood flow. Our findings clearly demonstrated that the combination of turbulent blood flow and low wall shear stress (WSS) in the presence of hypercholesterolaemia and oxidative stress creates conditions to the formation of focally distributed incipient atherosclerotic lesions observed in the poststenotic segment. In contrast, only diffuse fatty streaks could be observed in the normotensive prestenotic segment with laminar blood flow and normal WSS in the presence of hypercholesterolaemia and oxidative stress. Although haemodynamic forces are not by themselves responsible for the pathogenesis of atherosclerosis, they prime the local vascular wall in which the lesion develop. Further studies are required to establish how haemodynamic forces are detected and transduced into chemical signalling by the cells of the artery wall and then converted into pathophysiologically relevant phenotypic changes.

Circumferential wall tension due to hypertension plays a pivotal role in aorta remodelling

The present study was carried out to investigate the role of hypertension in the genesis and localization of intimal lesions and medial remodelling found in the prestenotic segment in relation to a severe stenosis of the abdominal aorta just below the diaphragm. Male young rats were divided randomly into operated group, animals submitted to surgical abdominal aorta stenosis, and sham-operated group, a control group of animals submitted to sham operation to simulate abdominal aorta stenosis. Aortas in the hypertensive prestenotic segment with increased circumferential wall tension associated with normal tensile stress, laminar flow/normal wall shear stress were characterized by enlarged heterogeneous endothelial cells elongated in the direction of the blood flow, diffusely distributed conspicuous neointimal plaques and medial thickening. The immunohistochemical analysis revealed an increased expression of eNOS, iNOS, nitrotyrosine and transforming growth factor-beta (TGF-beta) in endothelial cells and/or smooth muscle cells in this segment. Our findings suggest that increased circumferential wall tension due to hypertension plays a pivotal role in the remodelling of the prestenotic segment through biomechanical effects on oxidative stress and increased TGF-beta expression. Further studies are needed to clarify the intrinsic pathogenetic mechanism of focal distribution of the neointimal plaques in the hypertensive segment.

Turbulent flow/low wall shear stress and stretch differentially affect aorta remodeling in rats

OBJECTIVE

The present investigation was carried out to evaluate the relationship between local hemodynamic forces and intimal and medial remodeling in the proximal and distal segments of the arterial walls of rats in relation to severe infradiaphragmatic stenosis of the aorta.

METHODS

Young male rats were divided randomly into an operated group, animals submitted to surgical abdominal aorta stenosis, and a sham-operated group, a control group of animals submitted to sham operation to simulate abdominal aorta stenosis.

RESULTS AND CONCLUSIONS

Constricted aortas showed two distinct adaptive remodeling responses to hemodynamic stimuli induced by infradiaphragmatic coarctation. The first is remodeling in the hypertensive prestenotic segment with increased circumferential wall tension (CWT), associated with normal tensile stress, laminar flow/normal wall shear stress characterized by enlarged heterogeneous endothelial cells, elongated in the direction of the blood flow, diffusely distributed neointimal plaques, appearing as discrete bulging towards the vascular lumen and medial thickening. Our findings suggest that increased CWT caused by hypertension play a pivotal role in the remodeling of the prestenotic segment through biomechanical effects on oxidative stress and increased expression of transforming growth factor beta. The second is remodeling in the normotensive poststenotic segment with turbulent flow/low wall shear stress and normal CWT and tensile stress characterized by groups of endothelial cells with phenotypic alterations and focally distributed neointimal plaques, similar but many of them larger than those found in the prestenotic segments. Further studies are needed to determine how the mechanical forces of turbulent flow/low shear stress are detected and transduced into chemical signaling by the cells of the artery walls and then converted into pathophysiologically relevant phenotypic changes.

L-arginine fails to protect against myocardial remodelling in L-NAME-induced hypertension

BACKGROUND

We investigated whether the substrate for nitric oxide synthesis L-arginine is able to modify hypertension and left ventricular hypertrophy development induced by chronic blockade of nitric oxide synthase activity by NG-nitro-L-arginine-methyl ester (L-NAME).

MATERIAL AND METHODS

Four groups of rats were investigated: control, L-arginine 1.5 g kg-1, L-NAME 40 mg kg-1, and L-NAME +L-arginine in corresponding doses. Systolic blood pressure was measured by non-invasive tail-cuff plethysmography each week. After 4 weeks, the animals were sacrificed and hydroxyproline and coenzyme Q9 and Q10 concentrations in the left ventricle, and nitric oxide synthase activity in the left ventricle, kidney and brain were investigated.

RESULTS

In the L-NAME group, nitric oxide synthase activity was decreased in the left ventricle, kidney and brain, and hypertension, left ventricular hypertrophy and fibrosis developed. Heart remodelling was associated with the decrease of coenzyme Q9 and Q10 concentrations in the left ventricle. Simultaneous treatment with L-NAME and L-arginine prevented nitric oxide synthase activity diminution in the left ventricle but not in the kidney and brain, and completely failed to prevent hypertension, left ventricular hypertrophy and fibrosis. Nevertheless, l-arginine prevented the diminution of coenzyme Q9 and Q10 concentrations in the left ventricle.

CONCLUSIONS

We conclude that L-arginine failed to prevent hypertension, left ventricular hypertrophy and fibrosis development despite restoration of nitric oxide synthase activity in the left ventricle. However, L-arginine prevented the diminution of coenzyme Q levels in the left ventricle.

Effect of simvastatin on remodeling of the left ventricle and aorta in L-NAME-induced hypertension

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been shown to prevent or reverse hypertrophy of the LV in several models of left ventricular hypertrophy. The aim of the present study was to determine whether treatment with simvastatin can prevent hypertension, reduction of tissue nitric oxide synthase activity and left ventricular (LV) remodeling in NG-nitro-L-arginine methyl ester(L-NAME)-induced hypertension. Four groups of rats were investigated: control, simvastatin (10 mg/kg), L-NAME (40 mg/kg) and L-NAME + simvastatin (in corresponding doses). Animals were sacrificed and studied after 6 weeks of treatment. The decrease of NO-synthase activity in the LV, kidney and brain was associated with hypertension, LV hypertrophy and fibrosis development and remodeling of the aorta in the L-NAME group. Simvastatin attenuated the inhibition of NO-synthase activity in kidney and brain, partly prevented hypertension development and reduced the concentration of coenzyme Q in the LV. Nevertheless, myocardial hypertrophy, fibrosis and enhancement of DNA concentration in the LV, and remodeling of the aorta were not prevented by simultaneous simvastatin treatment in the L-NAME treated animals. We conclude that the HMG-CoA reductase inhibitor simvastatin improved nitric oxide production and partially prevented hypertension development, without preventing remodeling of the left ventricle and aorta in NO-deficient hypertension.

Nitric oxide synthase 3-dependent vascular remodeling and circulatory dysfunction in cirrhosis

Vascular remodeling is an active process that consists in important modifications in the vessel wall. Endothelium-derived nitric oxide (NO) plays a major role in this phenomenon. We assessed wall thickness (WT), total wall area (TWA), lumen diameter, and total nuclei number/cross-section (TN) in cirrhotic rats with ascites and in control rats. A second group of cirrhotic rats received the NO synthesis inhibitor, L-NAME, or vehicle daily for 11 weeks and systemic hemodynamics, arterial compliance, aortic NO synthase 3 (NOS3) protein expression, and vascular morphology were analyzed. Cirrhotic vessels showed a significant reduction in WT, TWA, and TN as compared to control vessels. Long-term inhibition of NOS activity in cirrhotic rats resulted in a significant increase in WT, TWA, and TN as compared to cirrhotic rats receiving vehicle. NOS3 protein abundance was higher in aortic vessels of nontreated cirrhotic animals than in controls. This difference was abolished by chronic treatment with L-NAME. NOS inhibition in cirrhotic rats resulted in higher arterial pressure and peripheral resistance and lower arterial compliance than cirrhotic rats receiving vehicle. Therefore, vascular remodeling in cirrhosis with ascites is a generalized process with significant functional consequences that can be negatively modulated by long-term inhibition of NOS activity.

Chronic inhibition of nitric oxide synthase induces hypertension and cardiomyocyte mitochondrial and myocardial collagen remodelling in the absence of hypertrophy

OBJECTIVES

To evaluate the morphometric and ultrastructural alterations of the heart produced by long-term inhibition of nitric oxide (NO) synthase with N(omega)-nitro-l-arginine methyl ester (l-NAME) and to examine whether the changes are caused by l-NAME-induced hypertension or a lack of NO.

METHODS

Male Wistar rats were divided randomly into three sets: control group, standard diet/l-NAME-treated group, and standard diet/l-NAME + captopril-treated group.

RESULTS

Chronic inhibition of NO synthesis with l-NAME given for 4 weeks promoted a time-dependent hypertensive response which was not accompanied by an increase in cardiac mass, myocellular hypertrophy or other evidence of myocyte damage. However, this response was associated with left ventricular cardiomyocyte mitochondrial remodelling and discrete interstitial fibrosis in both the left and right ventricles. The remodelling was characterized by an increase in the number and size of mitochondria. Importantly, systolic pressure overload did not result in left ventricle decompensation. The concomitant treatment with l-NAME and captopril abolished the development of hypertension and left ventricular cardiomyocyte subcellular remodelling, but not the discrete interstitial fibrosis in the left and right ventricle.

CONCLUSIONS

The present study suggests that, in the l-NAME model of hypertension, decreased NO production could be an important means of controlling cardiovascular hypertensive stress by regulating mitochondrial biogenesis and function in the tissue. On the other hand, discrete interstitial ventricular myocardial fibrosis observed in l-NAME-treated rats, either hypertensive or rendered normotensive with captopril, clearly indicates that this response depends on a process associated with NO insufficiency.