Standardization of a new non-invasive device for assessment of arterial stiffness in rats: Correlation with age-related arteries' structure.

Pulse wave velocity (PWV) has become a gold standard index to quantify the stiffness of the aorta and is a predictor of cardiovascular events. A recent paper compared the pOpmètreⓇ, a device for measuring the finger-toe PWV, with other techniques and demonstrated its accuracy and validity. However, human devices do not allow the advancement of our knowledge on conditioning mechanisms. Based on its human validation, a new device, pOpetⓇ 1.0 system was designed for estimation of PWV in small animals and this present study aimed to standardize the pOpetⓇ 1.0 for estimation of arterial stiffness in rats, and to confirm its liability and stability as well as the reproducibility of assessments. Therefore several precautions were taken into consideration like as the correct position of the animal and photodiodes according to manufacturers' suggestions. Results indicated that estimation of PWV through the new pOpetⓇ 1.0 device exhibits good internal consistency, stability and objectivity in all tests performed between days and evaluators. Importantly, data suggest for the first time that this new device is able to detect changes in arterial stiffness that are conditioned by age and pressure-related arterial remodeling. • This new pOpetⓇ device is able to detect changes in vessel structure. • This new pOpetⓇ device exhibits good internal consistency, stability and objectivity in all tests performed • Correct position of the animal and photodiodes are crucial to obtain a very stable signal.

Molecular Pathways Involved in Aerobic Exercise Training Enhance Vascular Relaxation.

PURPOSE: The beneficial effects of exercise training on the cardiovascular system are well known. Because our knowledge of exercise-induced vascular function is still limited, we aimed to uncover the molecular mechanisms conditioning the improved vascular relaxation in muscular arteries. METHODS: Male Wistar-Kyoto rats with the same ability to run on a treadmill after maximal exercise tests were allocated to the following two groups: trained (Tr) (treadmill, 50%-60% of maximal capacity, 5 d·wk) and untrained (UnTr). After 13 wk, the femoral arteries were harvested and used for functional, structural, and molecular analyses. RESULTS: Acetylcholine (ACh)-induced relaxation and nitric oxide (NO) production were enhanced in arteries from Tr rats compared with UnTr rats. Tr arteries exhibited reduced microRNA (miRNA)-124a expression (whose target is caveolin-1), increased the density of caveolae aligned along the sarcolemma and reduced ACh-induced relaxation in the presence of methyl-ß-cyclodextrin, which disrupts caveolae. Higher endothelial NO synthase (eNOS) expression with lower miRNA-155 expression and the posttranslational modification of eNOS (phosphorylation of stimulatory Ser1177 and dephosphorylation of inhibitory Thr495) by the PI3-kinase/Akt1/2/3 pathway also contributed to the higher NO production induced by exercise training. Furthermore, increased Cu/Zn- and extracellular-superoxide dismutase expression and enhanced effects of their pharmacological scavenger activity on the ACh-induced response were observed in Tr arteries. CONCLUSIONS: The results of the present study provide a molecular basis for exercise-induced NO bioavailability in healthy femoral arteries. Increased caveolae domain and eNOS expression/activity in Tr arteries are associated with downregulation of miRNA-124a and -155, as well as are involved with higher antioxidant defense, subsequently inducing a favorable endothelium-dependent milieu in Tr arteries.

Maintenance of Blood-Brain Barrier Integrity in Hypertension: A Novel Benefit of Exercise Training for Autonomic Control.

The blood-brain barrier (BBB) is a complex multicellular structure acting as selective barrier controlling the transport of substances between these compartments. Accumulating evidence has shown that chronic hypertension is accompanied by BBB dysfunction, deficient local perfusion and plasma angiotensin II (Ang II) access into the parenchyma of brain areas related to autonomic circulatory control. Knowing that spontaneously hypertensive rats (SHR) exhibit deficient autonomic control and brain Ang II hyperactivity and that exercise training is highly effective in correcting both, we hypothesized that training, by reducing Ang II content, could improve BBB function within autonomic brain areas of the SHR. After confirming the absence of BBB lesion in the pre-hypertensive SHR, but marked fluorescein isothiocyanate dextran (FITC, 10 kD) leakage into the brain parenchyma of the hypothalamic paraventricular nucleus (PVN), nucleus of the solitary tract, and rostral ventrolateral medulla during the established phase of hypertension, adult SHR, and age-matched WKY were submitted to a treadmill training (T) or kept sedentary (S) for 8 weeks. The robust FITC leakage within autonomic areas of the SHR-S was largely reduced and almost normalized since the 2nd week of training (T2). BBB leakage reduction occurred simultaneously and showed strong correlations with both decreased LF/HF ratio to the heart and reduced vasomotor sympathetic activity (power spectral analysis), these effects preceding the appearance of resting bradycardia (T4) and partial pressure fall (T8). In other groups of SHR-T simultaneously infused with icv Ang II or saline (osmotic mini-pumps connected to a lateral ventricle cannula) we proved that decreased local availability of this peptide and reduced microglia activation (IBA1 staining) are crucial mechanisms conditioning the restoration of BBB integrity. Our data also revealed that Ang II-induced BBB lesion was faster within the PVN (T2), suggesting the prominent role of this nucleus in driven hypertension-induced deficits. These original set of data suggest that reduced local Ang II content (and decreased activation of its downstream pathways) is an essential and early-activated mechanism to maintain BBB integrity in trained SHR and uncovers a novel beneficial effect of exercise training to improve autonomic control even in the presence of hypertension.

An interaction of renin-angiotensin and kallikrein-kinin systems contributes to vascular hypertrophy in angiotensin II-induced hypertension: in vivo and in vitro studies.

The kallikrein-kinin and renin-angiotensin systems interact at multiple levels. In the present study, we tested the hypothesis that the B1 kinin receptor (B1R) contributes to vascular hypertrophy in angiotensin II (ANG II)-induced hypertension, through a mechanism involving reactive oxygen species (ROS) generation and extracellular signal-regulated kinase (ERK1/2) activation. Male Wistar rats were infused with vehicle (control rats), 400 ng/Kg/min ANG II (ANG II rats) or 400 ng/Kg/min ANG II plus B1 receptor antagonist, 350 ng/Kg/min des-Arg(9)-Leu(8)-bradykinin (ANGII+DAL rats), via osmotic mini-pumps (14 days) or received ANG II plus losartan (10 mg/Kg, 14 days, gavage - ANG II+LOS rats). After 14 days, ANG II rats exhibited increased systolic arterial pressure [(mmHg) 184 ± 5.9 vs 115 ± 2.3], aortic hypertrophy; increased ROS generation [2-hydroxyethidium/dihydroethidium (EOH/DHE): 21.8 ± 2.7 vs 6.0 ± 1.8] and ERK1/2 phosphorylation (% of control: 218.3 ± 29.4 vs 100 ± 0.25]. B1R expression was increased in aortas from ANG II and ANG II+DAL rats than in aortas from the ANG II+LOS and control groups. B1R antagonism reduced aorta hypertrophy, prevented ROS generation (EOH/DHE: 9.17 ± 3.1) and ERK1/2 phosphorylation (137 ± 20.7%) in ANG II rats. Cultured aortic vascular smooth muscle cells (VSMC) stimulated with low concentrations (0.1 nM) of ANG II plus B1R agonist exhibited increased ROS generation, ERK1/2 phosphorylation, proliferating-cell nuclear antigen expression and [H3]leucine incorporation. At this concentration, neither ANG II nor the B1R agonist produced any effects when tested individually. The ANG II/B1R agonist synergism was inhibited by losartan (AT1 blocker, 10 µM), B1R antagonist (10 µM) and Tiron (superoxide anion scavenger, 10 mM). These data suggest that B1R activation contributes to ANG II-induced aortic hypertrophy. This is associated with activation of redox-regulated ERK1/2 pathway that controls aortic smooth muscle cells growth. Our findings highlight an important cross-talk between the DABK and ANG II in the vascular system and contribute to a better understanding of the mechanisms involved in vascular remodeling in hypertension.

Afferent signaling drives oxytocinergic preautonomic neurons and mediates training-induced plasticity.

We showed previously that oxytocinergic (OTergic) projections from the hypothalamic paraventricular nucleus (PVN) to the dorsal brain stem mediate training-induced heart rate (HR) adjustments and that beneficial effects of training are blocked by sinoaortic denervation (SAD; Exp Physiol 94: 630-640; 1103-1113, 2009). We sought now to determine the combined effect of training and SAD on PVN OTergic neurons in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Rats underwent SAD or sham surgery and were trained (55% of maximal capacity) or kept sedentary for 3 mo. After hemodynamic measurements were taken at rest, rats were deeply anesthetized. Fresh brains were frozen and sliced to isolate the PVN; samples were processed for OT expression (real-time PCR) and fixed brains were processed for OT immunofluorescence. In sham rats, training improved treadmill performance and increased the gain of baroreflex control of HR. Training reduced resting HR (-8%) in both groups, with a fall in blood pressure (-10%) only in SHR rats. These changes were accompanied by marked increases in PVN OT mRNA expression (3.9- and 2.2-fold in WKY and SHR rats, respectively) and peptide density in PVN OTergic neurons (2.6-fold in both groups), with significant correlations between OT content and training-induced resting bradycardia. SAD abolished PVN OT mRNA expression and markedly reduced PVN OT density in WKY and SHR. Training had no effect on HR, PVN OT mRNA, or OT content following SAD. The chronic absence of inputs from baroreceptors and chemoreceptors uncovers the pivotal role of afferent signaling in driving both the plasticity and activity of PVN OTergic neurons, as well as the beneficial effects of training on cardiovascular control.