Sandra Crestani

Antihypertensive effects of isoquercitrin and extracts from Tropaeolum majus L.: Evidence for the inhibition of angiotensin converting enzyme

AIM OF THE STUDY Previous studies have shown that the extracts obtained from Tropaeolum majus L. exhibit pronounced diuretic properties. In the present study, we assessed whether the hypotensive and/or antihypertensive mechanism of hydroethanolic extract (HETM), semi-purified fraction (TMLR) obtained from T. majus and the flavonoids isoquercitrin (ISQ) and kaempferol (KPF) can be mediated by their interaction with angiotensin converting enzyme (ACE). METHODS AND METHODS Firstly, to evaluate changes in mean arterial pressure (MAP), different groups of normotensive and spontaneously hypertensive rats (SHR) were orally and intraduodenally treated with HETM (10-300 mg/kg) and TMLR (12.5-100mg/kg) and intravenously treated with ISQ and KPF being later anesthetized with ketamine (100mg/kg) and xylazine (20mg/kg). The left femoral vein and the right carotid artery were isolated, and polyethylene catheters were inserted for ISQ and KPF (0.5-4 mg/kg) administration and blood pressure recording, respectively. The plasmatic ACE activity was evaluated to indirect fluorimetry, in serum samples after orally treatment with HETM, TMLR, ISQ and KPF. RESULTS The oral administration of the HETM and its TMLR significantly reduced, in a dose-dependent manner, the MAP in both normotensive and SHR. In addition, these preparations significantly decreased the MAP for up to 3h after the administration of the extract. Additionally, the intravenous administration of ISQ, but not KPF, decreased MAP in rats. Otherwise, neither the extracts nor ISQ affected the heart rate. The oral administration of the HETM, TMLR or ISQ reduced ACE activity in serum samples at 90 min after administration. Finally, the intravenous administration of ISQ caused a significant reduction in the hypertensive response to angiotensin I, but not angiotensin II in normotensive rats. CONCLUSION Our results show that the hypotensive effects caused by the HETM, as well as by its TMLR, may be associated with the high levels of the flavonoid ISQ found in this plant. In addition, ISQ-induced hypotension in rats is an event dependent on the inhibition of angiotensin II generation by ACE.

A potent and nitric oxide-dependent hypotensive effect induced in rats by semi-purified fractions from Maytenus ilicifolia.

The aim of this study is to investigate whether extracts and semi-purified fractions obtained from Maytenus ilicifolia leaves have vascular effects in vivo.We tested the ethanolic supernatant of the infusion (ESI), and the ethanolic supernatant of the aqueous extract (ESAE) on the mean arterial pressure (MAP) and heart rate(HR) of anesthetized rats. Intravenous injection of ESAE caused a dose-dependent effect at 10, 20 and 30 mg/kg, reducing MAP by as much as 52.6 +/- 5.5 mmHg. Only the highest dose of ESAE (30 mg/kg) caused a significant reduction in HR during its hypotensive effect. The effect of ESAE was unchanged by atropine,propranolol, or bilateral vagotomy, but was significantly reduced (80%) in animals continuously infused with L-NAME. In addition, methylene blue and ODQ, as well as the potassium channel blockers tetraethylammonium,4-aminopyridine, and glibenclamide, impaired ESAE-induced hypotension. The ethyl acetate fraction(EAF) obtained from ESAE had a potency at least two times greater than ESAE in MAP, without causing any significant change in HR. The hypotension induced by EAF was circumvented by L-NAME, methylene blue andODQ, strongly reduced by tetraethylammonium and 4-aminopyridine (but not by glibenclamide), and abolished by association of these three potassium channel blockers. Chemical investigation revealed that flavonols, mainly catechin and epicatechin, as well as flavonol glycosides (mono- to triglycosides), and tannins, are the main components of this fraction. Our results demonstrate that preparations obtained from M. ilicifolia present a potent hypotensive effect in vivo, an event predominantly dependent on the nitricoxide/guanylate cyclase pathway.

Activation of muscarinic receptors by a hydroalcoholic extract of Dicksonia sellowiana Presl. HooK (Dicksoniaceae) induces vascular relaxation and hypotension in rats

Dicksonia sellowiana (Presl.) Hook is a native plant from the Central and South Americas that contain high levels of polyphenols, antioxidant compounds involved in protection against inflammation, cancer and cardiovascular risk. A phytomedicinal preparation obtained from aerial parts of D. sellowiana is currently under clinical evaluation in Brazil against asthma, and has been associated with several other beneficial effects. This study demonstrates that a hydroalcoholic extract obtained from D. sellowiana leaves (HEDS) fully relax, in a concentration-dependent manner, rat aortic rings precontracted with phenylephrine. Moreover, administration of HEDS (10, 20 and 40 mg/kg, i.v.) in anaesthetized rats resulted in a strong but reversible hypotension. Aortic relaxation induced by HEDS was abolished by endothelium removal, by incubation of the nitric oxide synthase inhibitor L-NAME, or the soluble guanylate cyclase inhibitor ODQ. In addition, this effect was partially inhibited by indomethacin (a cyclooxygenase inhibitor) and KT 5730 (a PKA inhibitor). The potassium channels blockade by either tetraethylammonium or charybdotoxin also resulted in a potent inhibition of HEDS-induced aortic relaxation, whereas apamine only slightly reduced it. In addition HEDS-induced relaxation was unchanged by 4-amynopiridine and glibenclamide. The selective muscarinic receptor antagonist atropine counteracted both aortic relaxation and blood pressure reduction generated by HEDS. Experiments using HPLC revealed the presence of high amounts of phenolic compounds in this extract. Taken together, our results reveal that the D. sellowiana possess substances with both in vivo and in vitro activities and that the vascular effect of HEDS involves activation of muscarinic receptors, stimulation of the nitric oxide pathway and opening of calcium-activated potassium channels.

Screening for in vivo (anti)estrogenic and (anti)androgenic activities of Tropaeolum majus L. and its effect on uterine contractility.

ETHNOPHARMACOLOGICAL RELEVANCE Tropaeolum majus L. (Tropaeolaceae) is a medicinal herb popularly used in Brazil for treatment of inflammatory and cardiovascular diseases. Despite some published data on its efficacy, there are still few toxicological data describing the safety of this plant. The aim of this study was to evaluate the (anti)estrogenic and (anti)androgenic activity of the hydroethanolic extract obtained from Tropaeolum majus L. (HETM), as well as its possible effects on uterine contractility. MATERIALS AND METHODS Three experimental protocols were performed, (a) uterotrophic assay, (b) Hershberger assay and (c) an ex vivo test to investigate the effects of maternal administration of HETM on uterine contractility at the end of pregnancy. In all protocols three doses of the HETM were administered to Wistar rats: 3, 30 and 300mg/kg. RESULTS In vivo tests for detection of (anti)androgenic and (anti)estrogenic activities did not show any significant alterations. Similarly, no alterations were observed on uterine contractility induced by oxytocin and arachidonic acid. CONCLUSIONS HETM was unable to produce (anti)estrogenic or (anti)androgenic activities in the short-term in vivo screening assays performed. In addition, there was no evidence that HETM can affect uterine contractility following gestational exposure of rats.

Vasorelaxant and hypotensive effects of the extract and the isolated flavonoid rutin obtained from Polygala paniculata L.

Objectives  This study aimed to investigate the in‐vitro and in‐vivo cardiovascular effects of the crude hydroalcoholic extract from Polygala paniculata (HEPP) in rats.

High-Salt Intake Augments the Activity of the RhoA/ROCK Pathway and Reduces Intracellular Calcium in Arteries From Rats

BACKGROUND We investigated the influence of salt overconsumption on the functionality of the RhoA/Rho‐associated kinase (ROCK) pathway and calcium regulation in arteries. METHODS The aorta and small mesenteric arteries from rats fed a chow containing 2%, 4%, or 8% NaCl were evaluated in organ baths for the activity of the RhoA/ROCK pathway and intracellular calcium mobilization. Components of these pathways and intracellular calcium levels were also assessed in samples from 4% NaCl group. RESULTS In arteries from animals fed regular chow, the ROCK inhibitor Y‐27632 reduced the responses to phenylephrine, even when the smallest concentrations (1 and 3 &mgr;M) were tested. However, only higher concentrations of Y‐27632 (10 and 50 &mgr;M) reduced phenylephrine‐induced contraction in vessels from high‐salt groups. Immunoblotting revealed augmented phosphorylation of the myosin phosphatase targeting subunit 1 and increased amounts of RhoA in the membrane fraction of aorta homogenates from the 4% NaCl group. Under calcium‐free solution, vessels from NaCl groups presented reduced contractile responses to phenylephrine and caffeine, compared with the regular chow group. Moreover, decreased intracellular calcium at rest and after stimulation with ATP were found in aortic smooth muscle cells from 4% NaCl‐fed rats, which also showed diminished levels of SERCA2 and SERCA3, but not of IP3 and ryanodine receptors, or STIM1 and Orai1 proteins. CONCLUSIONS Arteries from rats subjected to high‐salt intake are unable to properly regulate intracellular calcium levels and present augmented activity of the calcium sensitization pathway RhoA/ROCK. These changes may precede the development of vascular diseases induced by high‐salt intake.

The Role Erectile Dysfunction Plays in Cardiovascular Diseases

Erectile dysfunction (ED) is defined as the persistent inability to maintain or achieve a penile erection sufficient for satisfactory sexual performance (1-2). ED is a very common condition in middle-aged men (3). According to the National Institute of Health (NIH) this physiological disorder affects 30 million men in the United States (US) (2). The outlook for 2025 is scary because this number is expected to grow to approximately 322 million (4). Although ED is directly associated with aging (5), its etiology is considered multifactorial. Both conditions, ED and aging, share a variety of risk factors such as atherosclerosis, sedentary lifestyle, abnormal lipids, diabetes, smoking, metabolic syndrome and hypertension (2, 6-7). In addition, ED is considered an important marker of cardiovascular disease (CVD) (8). Studies over the last decade suggest vascular changes as a common factor between ED and CVD (1, 7, 9). Also, the most important vascular alteration mentioned in these pathologies cited above is endothelial dysfunction. According to several authors, endothelial and smooth muscle dysfunction are crucial factors involved in systemic and peripheral vascular diseases, especially ED (10). In this chapter we will discuss the association between the main CVD and ED.