Role of non-nitric oxide non-prostaglandin endothelium-derived relaxing factor(s) in bradykinin vasodilation

Prenatal hypoxia predisposes vascular functional and structural changes associated with oxidative stress damage and depressive behavior in adult offspring male rats

Intrauterine hypoxia-ischemia (HI) provides a strong stimulus for a developmental origin of both the central nervous system and cardiovascular diseases. This study aimed to investigate vascular functional and structural changes, oxidative stress damage, and behavioral alterations in adult male offspring submitted to HI during pregnancy. The pregnant Wistar rats had a uterine artery clamped for 45 min on the 18th gestational day, submitting the offspring to hypoxic-ischemic conditions. The Sham group passed to the same surgical procedure as the HI rats, without occlusion of the maternal uterine artery, and the controls consisted of non-manipulated healthy animals. After weaning, the male pups were divided into three groups: control, sham, and HI, according to the maternal procedure. At postnatal day 90 (P90), the adult male offspring performed the open field and forced swim tests. In P119, the rats had their blood pressure checked and were euthanized. Prenatal HI induced a depressive behavior in adult male offspring associated with a reduced vasodilator response to acetylcholine in perfused mesenteric arterial bed, and reduced superoxide dismutase and glutathione peroxidase activities in the aorta compared to control and sham groups. Prenatal HI also increased the vasoconstrictor response to norepinephrine, the media thickness, collagen deposition, and the oxidative damage in the aorta from adult male offspring compared to control and sham groups. Our results suggest an association among prenatal HI and adult vascular structural and functional changes, oxidative stress damage, and depressive behavior.

Açaí (Euterpe oleracea Mart.) seed extract improves aerobic exercise performance in rats

The purpose of this study was to examine whether the supplementation with an açai (Euterpe oleracea Mart.) seed extract (ASE) would affect the aerobic exercise performance in rats and correlate with the vascular function, muscle oxidative stress and mitochondrial biogenesis. Male Wistar rats were divided into five groups: Sedentary, Sedentary with chronic supplementation of ASE, Training, Training with chronic (200 mg/Kg/day intragastric gavage for 5 weeks) or acute (30 min before the maximal treadmill stress test (MST) supplementation with ASE. The exercise training was performed on a treadmill (30 min/day; 5 days/week) for 4 weeks. The chronic supplementation with ASE increased the exercise time (58%) and the running distance (129%) in relation to the MST, while the Training group increased 40% and 78% and the Training with acute ASE group increased 30% and 63%, respectively. The training-induced increase of ACh vasodilation was not changed by ASE, but the norepinephrine-induced vasoconstriction was reduced by chronic and acute supplementation with ASE. The increased levels of malondialdehyde in soleus muscle homogenates from the Training group was reduced only by chronic supplementation with ASE. The muscle antioxidant defense, NO₂ levels, and expression of the mitochondrial biogenesis-related proteins (PGC1α, SIRT-1, p-AMPK/AMPK, Nrf-2) were not different between Training and Sedentary groups, but all these parameters were increased in the Training with Chronic ASE compared with the Sedentary groups. In conclusion, chronic supplementation with ASE improves aerobic physical performance by increasing the vascular function, reducing the oxidative stress, and up-regulating the mitochondrial biogenesis key proteins.

Increase in kinins on post-exercise hypotension in normotensive and hypertensive volunteers

Post-exercise hypotension is an important event for blood pressure regulation, especially in hypertensive individuals. Although post-exercise hypotension is a well-known phenomenon, the mechanism responsible is still unclear. The kallikrein-kinin system is involved in blood pressure control, but its role in post-exercise hypotension has not yet been investigated. Thus, the purpose of this study was to investigate the involvement of the vasodilators bradykinin and des-Arg(9)-BK and kallikrein activity in post-exercise hypotension promoted by 35 min of cycle ergometer (CE) or circuit weight-training (CWT) bouts in normotensive and hypertensive individuals. A significant decrease in mean arterial pressure at 45 and 60 min after CE and 45 min after CWT was observed in normotensive individuals. Hypertensive values of mean arterial pressure were significantly reduced at 45 and 60 min after CE and at 60 min after CWT. Before exercise, plasma bradykinin concentrations and kallikrein activity were higher in hypertensive compared to normotensive volunteers. Kinin levels increased in the groups evaluated at the end of the training period and 60 min post-exercise. These data suggest that the kallikrein-kinin system may be involved in post-exercise hypotension in normotensive and hypertensive individuals subjected to CE and CWT bouts.

Potentiation of bradykinin effect by angiotensin-converting enzyme inhibition does not correlate with angiotensin-converting enzyme activity in the rat mesenteric arteries

Angiotensin-converting enzyme (kininase II [ACE]) inhibitors are capable of potentiating bradykinin (BK) effects by enhancing the actions of bradykinin on B(2) receptors independent of blocking its inactivation. To investigate further the importance of ACE kininase activity on BK-induced vasodilation, we investigated the effect of inhibiting ACE, as well as other kininases, on both BK metabolism and vasodilator effect in preparations that exhibit increased ACE activity. Mesenteric arterial beds obtained from 1-kidney, 1-clip hypertensive rats presented augmented ACE and angiotensin I converting activities compared with normotensive rats. The isolated and perfused mesenteric beds were exposed to BK for 15 minutes in the absence or in the presence of kininase inhibitors; then, the perfusate was collected for analysis of the products of BK metabolism by high-performance liquid chromatography. BK was metabolized to the fragments BK(1-8), BK(1-7), and BK(1-5), and the recovery of intact BK was reduced by 47% in the hypertensive group. Recovery of BK was increased in both groups in the presence of a kininase I inhibitor and in the hypertensive group by neutral endopeptidase 24.11 inhibitor; however, ACE inhibition did not affect BK metabolism in both groups. In contrast, only the ACE inhibitor potentiated the vasodilator effect of BK in a mesenteric bed preconstricted with phenylephrine; the increase in BK effect, nevertheless, was not greater in arteries from hypertensive rats that presented an increased ACE activity when compared with those in the normotensive group. These data demonstrated that ACE inhibitor-induced potentiation of BK vasodilator effects is not related to their actions on BK degradation.

Effects of exercise training on the vascular reactivity of the whole kidney circulation in rabbits

Exercise training is known to improve vasodilating mechanisms mediated by endothelium-dependent relaxing factors in the cardiac and skeletal muscle vascular beds. However, the effects of exercise training on visceral vascular reactivity, including the renal circulation, are still unclear. We used the experimental model of the isolated perfused rabbit kidney, which involves both the renal macro- and microcirculation, to test the hypothesis that exercise training improves vasodilator mechanisms in the entire renal circulation. New Zealand White rabbits were pen confined (Sed; n = 24) or treadmill trained (0% grade) for 5 days/wk at a speed of 18 m/min during 60 min over a 12-wk period (ExT; n = 24). Kidneys isolated from Sed and ExT rabbits were continuously perfused in a nonrecirculating system under conditions of constant flow and precontracted with norepinephrine (NE). We assessed the effects of exercise training on renal vascular reactivity using endothelial-dependent [acetylcholine (ACh) and bradykinin (BK)] and -independent [sodium nitroprusside (SNP)] vasodilators. ACh induced marked and dose-related vasodilator responses in kidneys from Sed rabbits, the reduction in perfusion pressure reaching 41 ± 8% ( n = 6; P < 0.05). In the kidneys from ExT rabbits, vasodilation induced by ACh was significantly enhanced to 54 ± 6% ( n = 6; P < 0.05). In contrast, BK-induced renal vasodilation was not enhanced by training [19 ± 8 and 13 ± 4% reduction in perfusion pressure for Sed and ExT rabbits, respectively ( n = 6; P > 0.05)]. Continuous perfusion of isolated kidneys from ExT animals with Nω-nitro-l-arginine methyl ester (l-NAME; 300 μM), an inhibitor of nitric oxide (NO) biosynthesis, completely blunted the additional vasodilation elicited by ACh [reduction in perfusion pressure of 54 ± 6 and 38 ± 5% for ExT and l-NAME + ExT, respectively ( n = 6; P < 0.05)]. On the other hand, l-NAME infusion did not affect ACh-induced vasodilation in Sed animals. Exercise training also increased renal vasodilation induced by SNP [36 ± 7 and 45 ± 10% reduction in perfusion pressure for Sed and ExT rabbits, respectively ( n = 6; P < 0.05)]. It is concluded that exercise training alters the rabbit kidney vascular reactivity, enhancing endothelium-dependent and -independent renal vasodilation. This effect seems to be related not only to an increased bioavailability of NO but also to the enhanced responsiveness of the renal vascular smooth muscle to NO.

Metabolic control of muscle blood flow during exercise in humans

During muscle contraction, several mechanisms regulate blood flow to ensure a close coupling between muscle oxygen delivery and metabolic demand. No single factor has been identified to constitute the primary metabolic regulator, yet there are signal transduction pathways between skeletal muscle and the vasculature that induce vasodilation. A link between muscle metabolic events and microvascular control of blood flow is illustrated by local dilation of terminal arterioles during contraction of muscle fibers and conduction of vasodilation upstream. Endothelial-derived vasodilator mechanisms are known to exert control of muscle vasodilation. Adenosine, nitric oxide (NO), prostacyclin (PGI2), and endothelial-derived hyperpolarization factor (EDHF) are possible mediators of muscle vasodilation during exercise. In humans, adenosine has been shown to contribute to functional hyperemia as blood flow is reduced under nonselective adenosine-receptor blockade. No clear role has been demonstrated for either NO or PGI2(2), based on studies employing selective inhibition of these substances individually, suggesting a redundancy of vasodilator mechanisms. This is supported by recent work demonstrating that combined blockade of NOS and PGI2, and NOS and cytochrome P450, both attenuate exercise-induced hyperemia in humans. Combined vasodilator blockade studies offer the potential to uncover important interactions and compensatory vasodilator responses. The signaling pathways that link metabolic events evoked by muscle contraction to vasodilatory signals in the local vascular bed remains an important area of study.

SR141716A-sensitive enhancement of ET-1 hypotensive effect by chronic NOS inhibition

The present study evaluated the potential mechanism involved in the hypotensive effect induced by ET-1 in rats treated with the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in the drinking water during 7 days. Hypertension developed in the L-NAME-treated rats (164+/-3 versus 112+/-1 mm Hg in untreated control rats), and the hypotensive effect of ET-1 (100 pmol/kg IV) was significantly enhanced compared with control rats (32+/-2% versus 20+/-1% fall in mean arterial pressure). The enhanced ET-1 hypotensive effect in L-NAME-treated rats was abolished by the ETB receptor antagonist BQ-788 but was unaltered by the cyclooxygenase inhibitor diclofenac, the cytochrome P450 inhibitor fluconazole, or the potassium channel blockers apamin, glibenclamide, tetraethylammonium, and 4-aminopyridine. Pretreatment with the cannabinoid CB1 receptor antagonist SR141716A significantly reduced the hypotensive response to ET-1 in L-NAME-treated rats (20+/-1%), although it did not modify the response in untreated control rats (17+/-1%). These findings indicate that in rats under chronic NOS inhibition, the hypotensive effect of ET-1 is unexpectedly enhanced and appears to be mediated by a non-NO/non-prostanoid mechanism and involves an SR141716A-sensitive mechanism triggered by ETB receptor activation.

Cholecalciferol treatment restores the relaxant responses of spontaneously hypertensive rat arteries to bradykinin

The vasodilation and hyperpolarization induced by bradykinin (BK) in the mesenteric vascular bed and mesenteric arteries from spontaneously hypertensive rats (SHR) and from normotensive Wistar rats (NWR), as well as Wistar Kyoto rats (WKY), was investigated before and after prolonged oral treatment with cholecalciferol (125 mg kg(-1) body weight per day) for 3 weeks. The cholecalciferol treatment caused a decrease in the SHR blood pressure, as well as a normalization in the resting potential of the smooth muscle cell membrane of mesenteric arteries and restored their hyperpolarizing response to BK. The concentration-response curves for the vasodilator effect of BK on the mesenteric vascular bed were significantly decreased in SHR and in WKY when compared with NWR. Cholecalciferol treatment improved the maximum responses of the SHR preparation, bringing them to levels similar to those of the NWR preparations, which themselves were unaffected by the treatment. In the presence of apamin, a Ca(2+)-dependent K(+) channel inhibitor, the maximum responses to BK in preparations from NWR or cholecalciferol-treated SHR decreased to values similar to those observed in untreated SHR. Our results indicate that the low responsivity of the SHR resistance vessels to the relaxant effect of BK is due to impaired Ca(2+)-dependent K(+) channels and that reversion of this impairment contributes to the blood pressure reduction caused by the cholecalciferol treatment. However, the mechanism of the low responsivity in WKY remains to be investigated.

P-450 metabolites of arachidonic acid in the control of cardiovascular function

Recent studies have indicated that arachidonic acid is primarily metabolized by cytochrome P-450 (CYP) enzymes in the brain, lung, kidney, and peripheral vasculature to 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) and that these compounds play critical roles in the regulation of renal, pulmonary, and cardiac function and vascular tone. EETs are endothelium-derived vasodilators that hyperpolarize vascular smooth muscle (VSM) cells by activating K(+) channels. 20-HETE is a vasoconstrictor produced in VSM cells that reduces the open-state probability of Ca(2+)-activated K(+) channels. Inhibitors of the formation of 20-HETE block the myogenic response of renal, cerebral, and skeletal muscle arterioles in vitro and autoregulation of renal and cerebral blood flow in vivo. They also block tubuloglomerular feedback responses in vivo and the vasoconstrictor response to elevations in tissue PO(2) both in vivo and in vitro. The formation of 20-HETE in VSM is stimulated by angiotensin II and endothelin and is inhibited by nitric oxide (NO) and carbon monoxide (CO). Blockade of the formation of 20-HETE attenuates the vascular responses to angiotensin II, endothelin, norepinephrine, NO, and CO. In the kidney, EETs and 20-HETE are produced in the proximal tubule and the thick ascending loop of Henle. They regulate Na(+) transport in these nephron segments. 20-HETE also contributes to the mitogenic effects of a variety of growth factors in VSM, renal epithelial, and mesangial cells. The production of EETs and 20-HETE is altered in experimental and genetic models of hypertension, diabetes, uremia, toxemia of pregnancy, and hepatorenal syndrome. Given the importance of this pathway in the control of cardiovascular function, it is likely that CYP metabolites of arachidonic acid contribute to the changes in renal function and vascular tone associated with some of these conditions and that drugs that modify the formation and/or actions of EETs and 20-HETE may have therapeutic benefits.

Potentiation of bradykinin by angiotensin-(1-7) on arterioles of spontaneously hypertensive rats studied in vivo

In the present study, we investigated the potentiating effect of angiotensin-(1-7) [Ang-(1-7)] on bradykinin (BK)-induced vasodilation in the mesenteric vascular bed of anesthetized spontaneously hypertensive rats using intravital microscopy. Topical application of BK and Ang-(1-7) induced vasodilation in mesenteric arterioles. The BK-induced effect, but not acetylcholine, sodium nitroprusside, or histamine responses, was potentiated in the presence of Ang-(1-7). This interaction was abolished by BK-B(2) and Ang-(1-7) antagonists (HOE 140 and A-779, respectively), a K(+) channel blocker (tetraethylammonium), and cyclooxygenase inhibitors (indomethacin and diclofenac); however, nitric oxide synthase inhibition (Nomega-nitro-L-arginine methyl ester) did not modify the Ang-(1-7)-potentiating activity. Long-term angiotensin-converting enzyme (ACE) inhibition increased BK and Ang-(1-7)-induced vasodilation. The BK potentiation by Ang-(1-7) was preserved after ACE inhibition, Ang II type 1 receptor blockade, or the combination of both treatments. The most striking finding of this study was the unexpected observation that the potentiation of BK vasodilation in spontaneously hypertensive rats treated short- or long-term with ACE inhibitors was reverted by the Ang-(1-7) antagonist A-779. Our results unmasked a key role for an Ang-(1-7)-related mechanism in mediating BK potentiation by ACE inhibitors.

State-of-the-Art lecture. Statins and blockers of the renin-angiotensin system: vascular protection beyond their primary mode of action

In addition to their primary mode of action, statins and blockers of the renin-angiotensin system possess common additional properties that are under active investigation. The inhibition of cellular proliferation, the restoration of endothelial activity, the inhibition of platelet reactivity, and an antioxidant potential are only a few examples of shared effects that target the arterial wall. These and other properties may eventually become exploited for the improved treatment of cardiovascular diseases and of other diseases apparently unrelated to the cardiovascular field, including inflammation and cancer. This review analyzes the current knowledge on the pleiotropic properties of these classes of drugs. Direct comparison indicates that study of the associations among these drugs may eventually disclose additive or synergistic effects that, perhaps even at lower dosages, may provide improved vascular protection and a strong alliance against several atherogenic mechanisms.