Effects of local mechanical stimulation on coronary artery endothelial function and angiotensin II type 1 receptor in pressure or flow-overload

Interstitial-fluid shear stresses induced by vertically oscillating head motion lower blood pressure in hypertensive rats and humans

The mechanisms by which physical exercise benefits brain functions are not fully understood. Here, we show that vertically oscillating head motions mimicking mechanical accelerations experienced during fast walking, light jogging or treadmill running at a moderate velocity reduce the blood pressure of rats and human adults with hypertension. In hypertensive rats, shear stresses of less than 1 Pa resulting from interstitial-fluid flow induced by such passive head motions reduced the expression of the angiotensin II type-1 receptor in astrocytes in the rostral ventrolateral medulla, and the resulting antihypertensive effects were abrogated by hydrogel introduction that inhibited interstitial-fluid movement in the medulla. Our findings suggest that oscillatory mechanical interventions could be used to elicit antihypertensive effects.

Hypertrophy of the right ventricle by pulmonary artery banding in rats: a study of structural, functional, and transcriptomics alterations in the right and left ventricles

Introduction: Right ventricular remodeling with subsequent functional impairment can occur in some clinical conditions in adults and children. The triggering factors, molecular mechanisms, and, especially, the evolution over time are still not well known. Left ventricular (LV) changes associated with right ventricular (RV) remodeling are also poorly understood. Objectives: The study aimed to evaluate RV morphological, functional, and gene expression parameters in rats submitted to pulmonary artery banding compared to control rats, with the temporal evolution of these parameters, and to analyze the influence of RV remodeling by pulmonary artery banding in rats and their controls over time on LV geometry, histology, gene expression, and functional performance. Methods: Healthy 6-week-old male Wistar-EPM rats weighing 170-200 g were included. One day after the echocardiogram, depending on the animals undergoing the pulmonary artery banding (PAB) procedure or not (control group), they were then randomly divided into subgroups according to the follow-up time: 72 h, or 2, 4, 6, or 8 weeks. In each subgroup, the following were conducted: a new echocardiogram, a hemodynamic study, the collection of material for morphological analysis (hypertrophy and fibrosis), and molecular biology (gene expression). The results were presented as the mean ± standard deviation of the mean. A two-way ANOVA and Tukey post-test compared the variables of the subgroups and evolution follow-up times. The adopted significance level was 5%. Results: There was no significant difference among the subgroups in the percentage of water in both the lungs and the liver (the percentage of water in the lungs ranged from 76% to 78% and that of the liver ranged from 67% to 71%). The weight of the right chambers was significantly higher in PAB animals in all subgroups (RV PAB weighed from 0.34 to 0.48 g, and control subjects, from 0.17 to 0.20 g; right atrium (RA) with PAB from 0.09 to 0.14 g; and control subjects from 0.02 to 0.03 g). In the RV of PAB animals, there was a significant increase in myocyte nuclear volume (97 μm3-183.6 μm3) compared to control subjects (34.2 μm3-57.2 μm3), which was more intense in subgroups with shorter PAB follow-up time, and the fibrosis percentage (5.9%-10.4% vs. 0.96%-1.18%) was higher as the PAB follow-up time was longer. In the echocardiography result, there was a significant increase in myocardial thickness in all PAB groups (0.09-0.11 cm compared to control subjects-0.04-0.05 cm), but there was no variation in RV diastolic diameter. From 2 to 8 weeks of PAB, the S-wave (S') (0.031 cm/s and 0.040 cm/s), and fractional area change (FAC) (51%-56%), RV systolic function parameters were significantly lower than those of the respective control subjects (0.040 cm/s to 0.050 cm/s and 61%-67%). Furthermore, higher expression of genes related to hypertrophy and extracellular matrix in the initial subgroups and apoptosis genes in the longer follow-up PAB subgroups were observed in RV. On the other hand, LV weight was not different between animals with and without PAB. The nuclear volume of the PAB animals was greater than that of the control subjects (74 μm3-136 μm3; 40.8 μm3-46.9 μm3), and the percentage of fibrosis was significantly higher in the 4- and 8-week PAB groups (1.2% and 2.2%) compared to the control subjects (0.4% and 0.7%). Echocardiography showed that the diastolic diameter and LV myocardial thickness were not different between PAB animals and control subjects. Measurements of isovolumetric relaxation time and E-wave deceleration time at the echocardiography were different between PAB animals and control subjects in all subgroups, but there were no changes in diastolic function in the hemodynamic study. There was also increased expression of genes related to various functions, particularly hypertrophy. Conclusion: 1) Rats submitted to pulmonary artery banding presented RV remodeling compatible with hypertrophy. Such alterations were mediated by increased gene expression and functional alterations, which coincide with the onset of fibrosis. 2) Structural changes of the RV, such as weight, myocardial thickness, myocyte nuclear volume, and degree of fibrosis, were modified according to the time of exposure to pulmonary artery banding and related to variations in gene expression, highlighting the change from an alpha to a beta pattern from early to late follow-up times. 3) The study suggests that the left ventricle developed histological alterations accompanied by gene expression modifications simultaneously with the alterations found in the right ventricle.

Association between AGTR1 A1166C polymorphism and the susceptibility to diabetic nephropathy: Evidence from a meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is a common complication in patients with diabetic mellitus (DM). Growing evidences have demonstrated that the polymorphisms of angiotensin II receptor type 1 (AGTR1) showed significant association with DN onset, but no consensus has been achieved yet. Therefore, we performed this meta-analysis to combine the findings of previous researches for a more comprehensive conclusion.

METHODS

Eligible publications were identified through electronic databases. The intensity of the correlation between AGTR1 A1166C polymorphism and DN susceptibility was evaluated through calculating pooled odds ratios (ORs) with their 95% confidence intervals (95% CIs). Heterogeneity among included studies was examined with Q test. When P-value less than .05, significant heterogeneity presented, random-effects model was used to calculate the pooled ORs, otherwise, the fixed-effects model was used. Stratification analyses were also performed based on ethnicity and the type of DM.

RESULTS

Seventeen eligible articles were finally included in the present meta-analysis. The analysis results showed that AGTR1 A1166C polymorphism was significantly related to increased risk of DN under CC versus AA (OR = 1.723, 95% CI = 1.123-2.644), CC + AC versus AA (OR = 1.179, 95% CI = 1.004-1.383), CC versus AA + AC (OR = 1.662, 95% CI = 1.112-2.486), and C versus A (OR = 1.208, 95% CI = 1.044-1.397) genetic models. Additionally, a similar result was also found in Asian and T2DM (type 2 diabetic mellitus) groups after subgroup analyses of ethnicity and DM type.

CONCLUSION

AGTR1 A1166C polymorphism may increase the susceptibility to DN, especially in Asians and T2DM population.

Nestin upregulation characterizes vascular remodeling secondary to hypertension in the rat

Proliferation and hypertrophy of vascular smooth muscle cells represent hallmark features of vessel remodeling secondary to hypertension. The intermediate filament protein nestin was recently identified in vascular smooth muscle cells and in other cell types directly participated in proliferation. The present study tested the hypothesis that vessel remodeling secondary to hypertension was characterized by nestin upregulation in vascular smooth muscle cells. Two weeks after suprarenal abdominal aorta constriction of adult male Sprague-Dawley rats, elevated mean arterial pressure increased the media area and thickness of the carotid artery and aorta and concomitantly upregulated nestin protein levels. In the normal adult rat carotid artery, nestin immunoreactivity was observed in a subpopulation of vascular smooth muscle cells, and the density significantly increased following suprarenal abdominal aorta constriction. Filamentous nestin was detected in cultured rat carotid artery- and aorta-derived vascular smooth muscle cells and an analogous paradigm observed in human aorta-derived vascular smooth muscle cells. ANG II and EGF treatment of vascular smooth muscle cells stimulated DNA and protein synthesis and increased nestin protein levels. Lentiviral short-hairpin RNA-mediated nestin depletion of carotid artery-derived vascular smooth muscle cells inhibited peptide growth factor-stimulated DNA synthesis, whereas protein synthesis remained intact. These data have demonstrated that vessel remodeling secondary to hypertension was characterized in part by nestin upregulation in vascular smooth muscle cells. The selective role of nestin in peptide growth factor-stimulated DNA synthesis has revealed that the proliferative and hypertrophic responses of vascular smooth muscle cells were mediated by divergent signaling events.

Elevated pressure causes endothelial dysfunction in mouse carotid arteries by increasing local angiotensin signaling

Experiments were performed to determine whether or not acute exposure to elevated pressure would disrupt endothelium-dependent dilatation by increasing local angiotensin II (ANG II) signaling. Vasomotor responses of mouse-isolated carotid arteries were analyzed in a pressure myograph at a control transmural pressure (PTM) of 80 mmHg. Acetylcholine-induced dilatation was reduced by endothelial denudation or by inhibition of nitric oxide synthase (NG-nitro-L-arginine methyl ester, 100 μM). Transient exposure to elevated PTM (150 mmHg, 180 min) inhibited dilatation to acetylcholine but did not affect responses to the nitric oxide donor diethylamine NONOate. Elevated PTM also increased endothelial reactive oxygen species, and the pressure-induced endothelial dysfunction was prevented by the direct antioxidant and NADPH oxidase inhibitor apocynin (100 μM). The increase in endothelial reactive oxygen species in response to elevated PTM was reduced by the ANG II type 1 receptor (AT1R) antagonists losartan (3 μM) or valsartan (1 μM). Indeed, elevated PTM caused marked expression of angiotensinogen, the precursor of ANG II. Inhibition of ANG II signaling, by blocking angiotensin-converting enzyme (1 μM perindoprilat or 10 μM captopril) or blocking AT1Rs prevented the impaired response to acetylcholine in arteries exposed to 150 mmHg but did not affect dilatation to the muscarinic agonist in arteries maintained at 80 mmHg. After the inhibition of ANG II, elevated pressure no longer impaired endothelial dilatation. In arteries treated with perindoprilat to inhibit endogenous formation of the peptide, exogenous ANG II (0.3 μM, 180 min) inhibited dilatation to acetylcholine. Therefore, elevated pressure rapidly impairs endothelium-dependent dilatation by causing ANG expression and enabling ANG II-dependent activation of AT1Rs. These processes may contribute to the pathogenesis of hypertension-induced vascular dysfunction and organ injury.