Expression of an angiotensin-(1-7)-producing fusion protein in rats induced marked changes in regional vascular resistance

We have described a transgenic rat line which express an Angiotensin-(1-7)-producing fusion protein, the TGR(A1-7)3292. In these rats testis acts as an angiotensin-(1-7) biological pump, increasing its plasma concentration 2.5 fold. In this study we performed hemodynamic measurements in TGR(A1-7)3292 and age-matched Hannover Sprague-Dawley (SD) control rats, using fluorescent microspheres. Urethane-anesthetized TG rats had similar level of baseline blood pressure (99 +/- 3 mmHg) as SD rats (101 +/- 3 mmHg). However, pronounced differences were observed in other hemodynamic measurements. TGR(A1-7)3292 rats presented a significantly increase in stroke volume (0.29 +/- 0.01 ml vs 0.25 +/- 0.01 ml in SD), increased cardiac index (24.6 +/- 0.91 ml/ min.Kg vs 21.9 +/- 0.65 ml/ min.Kg) and decreased total peripheral resistance (3.9 +/- 0.13 mmHg.ml (-1) .min.100g vs 4.5 +/- 0.13 mmHg.ml (-1) .min.100g). The increase in stroke volume in TGR may be partially explained by the small decrease in HR (326 +/- 7.0 beats/ min vs 359 +/- 6.0 beats/ min in SD). Strikingly, TGR(A1-7)3292 rats presented a substantial decrease in the vascular resistance in lung, spleen, kidney, adrenals, brain, testis and brown fat tissue with no significant differences in the left ventricle, mesentery, skin, gastrocnemius muscle and white fat tissue. These results corroborate and extend previous results observed after acute angiotensin-(1-7) infusion, showing that chronic increase in circulating angiotensin-(1-7) produces sustained and important changes in regional and systemic hemodynamics. Moreover our data suggest a physiological role for angiotensin-(1-7) in the tonic control of regional blood flow. Key words: hemodynamic, angiotensin-(1-7), fluorescent microspheres, transgenic rats

Ablation of angiotensin (1-7) receptor Mas in C57Bl/6 mice causes endothelial dysfunction

The Mas gene codes for an angiotensin (1-7) receptor. There is accumulating evidence that Mas is involved in vascular homeostasis. We have recently backcrossed Mas-knockout mice to two different genetic backgrounds, C57Bl/6 and FVB/N. FVB/NMas-deficient mice exhibited elevation in blood pressure (BP) and impaired endothelial function. In the present study, we aimed to address the question whether this phenotype is strain-specific. Therefore, we evaluated endothelial function in C57Bl/6Mas-deficient mice. Similar to FVB/NMas-knockout animals, Mas-deficiency in C57Bl/6 mice leads to endothelial dysfunction evaluated by the acute BP effect of acetylcholine administration. Measurements of nitric oxide (NO) and reactive oxygen species (ROS) and the systems involved in their metabolism revealed an imbalance between these vasoactive factors in C57Bl/6Mas-knockout mice, which may explain the impairment of endothelial function in these animals. However, endothelial dysfunction was less prominent in Mas-deficient mice on a C57Bl/6 background compared to FVB/N. Moreover, C57Bl/6Mas-deficient mice remained normotensive while FVB/N-based animals exhibited elevated BP. The impairment of endothelium-dependent vasodilatory response to acetylcholine in two different mouse strains with Mas deficiency indicates a key role of Mas in endothelial function by its effects on the generation and metabolism of NO and ROS

The ACE2/angiotensin-(1-7)/MAS axis of the renin-angiotensin system: focus on angiotensin-(1-7)

The renin-angiotensin system (RAS) is a key player in the control of the cardiovascular system and hydroelectrolyte balance, with an influence on organs and functions throughout the body. The classical view of this system saw it as a sequence of many enzymatic steps that culminate in the production of a single biologically active metabolite, the octapeptide angiotensin (ANG) II, by the angiotensin converting enzyme (ACE). The past two decades have revealed new functions for some of the intermediate products, beyond their roles as substrates along the classical route. They may be processed in alternative ways by enzymes such as the ACE homolog ACE2. One effect is to establish a second axis through ACE2/ANG-(1-7)/MAS, whose end point is the metabolite ANG-(1-7). ACE2 and other enzymes can form ANG-(1-7) directly or indirectly from either the decapeptide ANG I or from ANG II. In many cases, this second axis appears to counteract or modulate the effects of the classical axis. ANG-(1-7) itself acts on the receptor MAS to influence a range of mechanisms in the heart, kidney, brain, and other tissues. This review highlights the current knowledge about the roles of ANG-(1-7) in physiology and disease, with particular emphasis on the brain

Angiotensin-(1-7) through receptor Mas mediates endothelial nitric oxide synthase activation via akt-dependent pathways

Angiotensin-(1-7) [Ang-(1-7)] causes endothelial-dependent vasodilation mediated, in part, by NO release. However, the molecular mechanisms involved in endothelial NO synthase (eNOS) activation by Ang-(1-7) remain unknown. Using Chinese hamster ovary cells stably transfected with Mas cDNA (Chinese hamster ovary-Mas), we evaluated the underlying mechanisms related to receptor Mas–mediated posttranslational eNOS activation and NO release. We further examined the Ang-(1-7) profile of eNOS activation in human aortic endothelial cells, which constitutively express the Mas receptor. Chinese hamster ovary-Mas cells and human aortic endothelial cell were stimulated with Ang-(1-7; 10−7 mol/L; 1 to 30 minutes) in the absence or presence of A-779 (10−6 mol/L). Additional experiments were performed in the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin (10−6 mol/L). Changes in eNOS (at Ser1177/Thr495 residues) and Akt phosphorylation were evaluated by Western blotting. NO release was measured using both the fluorochrome 2,3-diaminonaphthalene and an NO analyzer. Ang-(1-7) significantly stimulated eNOS activation (reciprocal phosphorylation/dephosphorylation at Ser1177/Thr495) and induced a sustained Akt phosphorylation (P<0.05). Concomitantly, a significant increase in NO release was observed (2-fold increase in relation to control). These effects were blocked by A-779. Wortmannin suppressed eNOS activation in both Chinese hamster ovary-Mas and human aortic endothelial cells. Our findings demonstrate that Ang-(1-7), through Mas, stimulates eNOS activation and NO production via Akt-dependent pathways. These novel data highlight the importance of the Ang-(1-7)/Mas axis as a putative regulator of endot

Endothelial dysfunction and elevated blood pressure in MAS gene-deleted mice

Mas codes for a G protein-coupled receptor that is implicated in angiotensin-(1-7) signaling. We studied the cardiovascular phenotype of Mas-deficient mice backcrossed onto the FVB/N genetic background using telemetry and found that they exhibit higher blood pressures compared with controls. These Mas(-/-) mice also had impaired endothelial function, decreased NO production, and lower endothelial NO synthase expression. Reduced nicotinamide-adenine dinucleotide phosphate oxidase catalytic subunit gp91(phox) protein content determined by Western blotting was higher in Mas(-/-) mice than in controls, whereas superoxide dismutase and catalase activities were reduced. The superoxide dismutase mimetic, Tempol, decreased blood pressure in Mas(-/-) mice but had a minimal effect in control mice. Our results show a major cardiovascular phenotype in Mas(-/-) mice. Mas-deletion results in increased blood pressure, endothelial dysfunction, and an imbalance between NO and reactive oxygen species. Our animals represent a promising model to study angiotensin-(1-7)-mediated cardiovascular effects and to evaluate Mas agonistic compounds as novel cardioprotective and antihypertensive agents based on their beneficial effects on endothelial function

Mechanical strength of thermoplastics and composite thermoplastics welded by laser – a review

Thermoplastic welding is currently well implemented in the market, with several competitive and suitable processes, ranging from simple hot plate to ultrasonic welding. By its side, laser welding of plastics is still in a relatively early stage of research. This process is one of the most recent in the welding of thermoplastics and of great interest in the market. The welding technique is based on heating the thermoplastics by transmitting heat in the form of radiation. This is due to the ability of certain plastics to absorb the beam. Usually, one of the parts to be welded must be transparent and the other opaque to radiation. These two parts are kept under pressure as the laser beams are transmitted through the transparent part. The laser beam is concentrated in the joint area of the opaque part, heating and melting it. There are relatively few scientific studies on the joining of thermoplastics by laser and, in the case of thermoplastic matrix composites, there are even fewer. The main conclusion is that the mechanical strength of a laser welded joint is in the range of 30-50 MPa, a value that is frankly weak when compared to the value that the base material can handle and which is usually more than double for thermoplastics and 10 times for composites. Although the fusion process is contactless, one of the great limitations of laser welding of plastics is the need to exert pressure on the joint, which conditions and complicates the execution of a weld. However, despite everything, it is certain that laser welding presents mechanical strength values superior to those of a bonded connection and the processing time is much shorter, therefore, it is clear the interest on the process.info:eu-repo/semantics/publishedVersio

Short-term cardiovascular physical programme ameliorates arterial stiffness and decreases oxidative stress in women with metabolic syndrome

OBJECTIVE: To evaluate the impact of a short-term cardiovascular physical programme on the metabolic, anthropometric and oxidative stress parameters of women with metabolic syndrome. METHODS: Thirty sedentary female patients, age range 30-60 years, were invited to participate in a 6-week cardiovascular physical programme. The training consisted of 60-min sessions of aerobic and strength exercises performed 3 times a week; a total of 18 sessions. Anthropometric data, functional exercise capacity, general biochemical profile, serum lipid peroxidation, superoxide dismutase and catalase activity in erythrocytes were evaluated according to standardized protocols. Peripheral vascular function was assessed using applanation tonometry. All assessments were performed before and after the training programme. RESULTS: The physical programme proved effective in improving the distance covered in the 6-min walk test and in reducing arterial pressure levels, pulse pressure and the Augmentation Index, without modifying heart rate. The plasma thiobarbituric acid reactive substances levels, indicators of oxidative stress, were significantly decreased after the programme. Superoxide dismutase activity was increased in erythrocyte lysates, with no significant change in catalase activity. Waist circumference was significantly decreased compared with baseline. The distance covered in the 6-min walk test was significantly greater after the short-term cardiovascular training. CONCLUSION: These findings indicate that short-term combined aerobic and strength training may represent an important non-pharmacological approach for treating individuals with metabolic syndrome

Hemodynamic phenotyping of transgenic rats with ubiquitous expression of an angiotensin-(1-7)-producing fusion protein

Activation of the angiotensin (Ang) converting enzyme 2/Ang-(1-7)/MAS receptor pathway of the renin-angiotensin system induces protective mechanisms in different diseases.  Herein, we describe the cardiovascular phenotype of a new transgenic rat line (TG7371) that expresses an Ang-(1-7)-producing fusion protein.  The transgene-specific mRNA and the corresponding protein were shown to be present in all evaluated tissues of TG7371 with the highest expression in aorta and brain.  Plasma Ang-(1-7) levels, measured by radioimmunoassay were similar to control SD rats, however high Ang-(1-7) levels were found in the hypothalamus.  TG7371 showed lower baseline mean arterial pressure, assessed in conscious or anesthetized rats by telemetry or short-term recordings, associated with increased plasma ANP and higher urinary sodium concentration.  Evaluation of regional blood flow and hemodynamic parameters with fluorescent microspheres showed a significant increase in blood flow in different tissues (kidneys, mesentery, muscle, spleen, brown fat, heart and skin), with a resulting decreased total peripheral resistance.  TG7371 rats also presented increased cardiac and global sympathetic tone, increased plasma AVP levels and decreased free water clearance.  Altogether, our data show that expression of an Ang-(1-7)-producing fusion protein induced a hypotensive phenotype due to widespread vasodilation and consequent fall in peripheral resistance.  This phenotype was associated with an increase in ANP together with an increase in AVP and sympathetic drive, which did not fully compensate the lower BP.  Here we present the hemodynamic impact of long-term increase in tissue expression of an Ang-(1-7)-fusion protein and provide a new tool to investigate this peptide in different pathophysiological conditions