Antihypertensive Effect In Spontaneously Hypertensive Rats Research Articles

NO-cGMP-K+ Channels Pathways Participate in the Antihypertensive Effects of Attalea phalerata Martius ex Spreng Oil-Loaded Nanocapsules.

Attalea phalerata Martius ex Spreng is a palm tree that is widely distributed in the Central-West region of Brazil. In this study, we investigated whether the oil-loaded nanocapsules of A. phalerata (APON) have acute and long-lasting antihypertensive effects in male spontaneously hypertensive rats (SHR), as well as explored the underlying molecular mechanisms. APON was prepared using the interfacial polymer deposition method. The particle size, polydispersity index, and zeta potential were investigated using dynamic and electrophoretic light scattering. The antihypertensive effects of APON (administered at doses of 1, 3, and 10 mg/kg) were evaluated after acute intraduodenal administration and after 7 days of oral treatment. To investigate the molecular pathways involved, we used pharmacological antagonists and inhibitors that target prostaglandin/cyclic adenosine monophosphate, nitric oxide/cyclic guanosine monophosphate, and potassium channels. Both acute and prolonged administration of APON (at doses of 3 and 10 mg/kg) resulted in a significant reduction in systolic, diastolic, and mean arterial pressure. Prior treatment with a non-selective nitric oxide synthase inhibitor (Nω-nitro-L-arginine methyl ester), guanylyl cyclase inhibitor (methylene blue), or non-selective calcium-sensitive K+ channel blocker (tetraethylammonium) abolished the antihypertensive effects of APON. Our study showed that A. phalerata oil-loaded nanocapsules have a significant antihypertensive effect in SHR after both short-term and long-term (7-day) use. This effect seems to rely on the vascular endothelium function and involves the NO-cGMP-K+ channel pathway. This research suggests a new direction for future studies to definitively prove the therapeutic benefits of APON in treating cardiovascular disease.

Asprosin contributes to vascular remodeling in hypertensive rats via superoxide signaling.

Proliferation and migration of vascular smooth muscle cells (VSMCs) contribute to vascular remodeling. Asprosin, a newly discovered protein hormone, is involved in metabolic diseases. Little is known about the roles of asprosin in cardiovascular diseases. This study focused on the role and mechanism of asprosin on VSMC proliferation and migration, and vascular remodeling in a rat model of hypertension. VSMCs were obtained from the aortic media of 8-week-old male Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Asprosin was upregulated in the VSMCs of SHR. For in vitro studies, asprosin promoted VSMC proliferation and migration of WKY and SHR, and increased Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) activity, NOX1/2/4 protein expressions and superoxide production. Knockdown of asprosin inhibited the proliferation, migration, NOX activity, NOX1/2 expressions and superoxide production in the VSMCs of SHR. The roles of asprosin in promoting VSMC proliferation and migration were not affected by hydrogen peroxide scavenger, but attenuated by superoxide scavenger, selective NOX1 or NOX2 inhibitor. Toll-like receptor 4 (TLR4) was upregulated in SHR, TLR4 knockdown inhibited asprosin overexpression-induced proliferation, migration and oxidative stress in VSMCs of WKY and SHR. Asprosin was upregulated in arteries of SHR, and knockdown of asprosin in vivo not only attenuated oxidative stress and vascular remodeling in aorta and mesentery artery, but also caused a subsequent persistent antihypertensive effect in SHR. Asprosin promotes VSMC proliferation and migration via NOX-mediated superoxide production. Inhibition of endogenous asprosin expression attenuates VSMC proliferation and migration, and vascular remodeling of SHR.

Blood Pressure-Lowering Effect of Wine Lees Phenolic Compounds Is Mediated by Endothelial-Derived Factors: Role of Sirtuin 1.

The antihypertensive effect of wine lees powder (WLPW) from a Cabernet grape variety was related to its high content in flavanols and anthocyanins compounds. This study investigates the involvement of endothelial-derived factors and SIRT1 in its bioactivity. Spontaneously hypertensive rats (SHR) were orally administered water or WLPW (125 mg/kg bw). Posteriorly, both groups were intraperitoneally administered saline, Nω-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor, indomethacin, a prostacyclin synthesis inhibitor, or sirtinol, an inhibitor of sirtuins. Blood pressure (BP) was recorded before and 6 h after WLPW administration. In an additional experiment, SHR were administered water or WLPW and endothelial expressions of eNos, Sirt1, Nox4, and Et1 were determined. The BP-lowering properties of WLPW were abolished by L-NAME and partially reduced by indomethacin, demonstrating that WLPW antihypertensive effect was mediated by changes in NO availability, although prostacyclin also contributed to this activity. Moreover, BP-lowering effect was reduced by sirtinol, indicating that WLPW decreased BP in a SIRT1-dependent manner. Furthermore, WLPW upregulated eNos and Sirt1 and downregulated Nox4 and Et1 endothelial gene expression. These results evidence the vasoprotective effect of WLPW and show that its antihypertensive effect in SHR is endothelium dependent and mediated by SIRT1.

Antihypertensive Effects of Virgin Olive Oil (Unfiltered) Low Molecular Weight Peptides with ACE Inhibitory Activity in Spontaneously Hypertensive Rats

The low molecular weight peptide composition of virgin olive oil (VOO) is mostly unknown. We hypothesised that unfiltered VOO could possess low molecular weight peptides with antihypertensive activity. We produced unfiltered VOO and obtained a water-soluble peptide extract from it. The peptides were separated by size-exclusion using fast protein liquid chromatography, and the low molecular weight fraction was analysed by nanoscale liquid chromatography-Orbitrap coupled with tandem mass spectrometry and de novo sequencing. We selected 23 peptide sequences containing between 6 and 9 amino acids and molecular masses ranging 698–1017 Da. Those peptides were chemically synthesised and their angiotensin-converting enzyme (ACE) inhibitory activity was studied in vitro. Seven peptides showed a strong activity, with half maximal inhibitory concentration (IC50) <10 µm. The antihypertensive effects of the four most active synthesised ACE inhibitor peptides were studied in spontaneously hypertensive rats (SHR). Acute oral administration of synthetic peptides RDGGYCC and CCGNAVPQ showed antihypertensive activity in SHR. We conclude that unfiltered VOO naturally contains low molecular weight peptides with specific ACE inhibitory activity and antihypertensive effects in SHR.

Egg white protein hydrolysate reduces blood pressure, improves vascular relaxation and modifies aortic angiotensin II receptors expression in spontaneously hypertensive rats

Angiotensin converting enzyme (ACE) inhibitory peptides from egg have demonstrated reduction of blood pressure (BP) in vivo. In this study we evaluated the effects of egg white hydrolysate (EWH) prepared by thermolysin and pepsin in spontaneously hypertensive rats (SHRs). Fourteen to sixteen week old SHRs were implanted with telemetry devices. After recovery, the rats were divided randomly into three groups: untreated, EWH low dose (250 mg/kg BW), and EWH high dose (1000 mg/kg BW) for 12 days. BP showed a significant reduction in the EWH high dose group compared to untreated controls. BP reduction was associated with enhanced ex vivo vasodilation reduced oxidative/nitrosative stress, reduced angiotensin converting enzyme and angiotensin II type 1 receptor expression, while enhanced angiotensin II type 2 receptor expression. Circulating level of angiotensin II was unaffected. Thus, EWH exerted anti-hypertensive effects in SHRs through multiple mechanisms of vascular relaxation and RAS modulation.

Effects of long-term intake of Antarctic krill oils on artery blood pressure in spontaneously hypertensive rats.

In recent years, there has been a noticeable increase in research on krill oil (KO) for its health benefits. However, the action of KO in lowering blood pressure (BP) has not been studied yet. Therefore the aim of this study was to assess the ability of long-term KO supplementation to lower systolic BP (SBP) in spontaneously hypertensive rats (SHRs) and Sprague Dawley (SD) rats. Compared with the blank control (BC) SHRs administered edible soybean oil, the high-dose (500 mg kg-1 body weight (BW)) KO-supplemented SHRs in the 2nd, 3rd, 4th and 5th weeks following oral administration, the mid-dose (100 mg kg-1 BW) KO-supplemented SHRs in the 4th and 5th weeks following oral administration and the low-dose (20 mg kg-1 BW) KO-supplemented SHRs in the 5th week following oral administration showed significantly lower SBP (P < 0.05). However, supplementation of KO had no significant effect on the SBP of healthy SD rats. Meanwhile, 5 weeks of KO administration significantly increased the serum levels of nitric oxide (NO) and total NO synthase of SHRs (P < 0.05). KO has an antihypertensive effect in SHRs that is associated with an NO-related mechanism. © 2016 Society of Chemical Industry.

Anti-hypertensive property of a nickel-piperazine/NO donor in spontaneously hypertensive rats

The nickel-piperazine/NO donor compound, Ni(PipNONO)Cl, belonging to the family of compounds labelled as ⿿metal-nonoates⿿, due to its promising vasodilating activity, has been considered as a potential drug candidate in anti-hypertensive therapy.Drug efficacy has been evaluated in spontaneously hypertensive rats (SHR) in comparison with normotensive animals (C57BL/6 mice and WKY rats). In normotensive animals the metal-nonoate maintained blood pressure at basal level both following acute administration and after 30 days of treatment. In SHR, Ni(PipNONO)Cl reduced blood pressure in the dose range of 3⿿10mg/kg. When compared with a commercial NONOate, DETA/NO, used at the same doses, Ni(PipNONO)Cl was more active in reducing blood pressure in SHR than DETA/NO in the first two weeks, while the effect of the two molecules was similar in the third and fourth week. The degradation and control compound Ni(Pip)Cl2 had no effect on blood pressure and heart rate in same animal models. Remarkably, the blood pressure reduction induced by the new NO-donor Ni(PipNONO)Cl does not evoke changes in the heart rate and tolerance. Considering the mechanisms of vascular protection, 30 days of administration of Ni(PipNONO)Cl improved endothelial function in SHR by upregulating endothelial NO synthase (eNOS) through increased eNOS protein levels and downregulated Caveolin-1 (Cav-1), and by increasing superoxide dismutase 1 (SOD1) protein level in aortae.In cultured endothelial cells Ni(PipNONO)Cl restored the cell functions (cytoskeletal protein expression, migration and proliferation) altered by the inflammatory mediator interleukin-1β (IL-1β), impairing the endothelial to mesenchimal transition.In conclusion, Ni(PipNONO)Cl maintained unaltered blood pressure in normotensive mice and rats, and it exerted anti-hypertensive effect in SHR through the restoration of vascular endothelial protective functions.

Evidences of antihypertensive potential of extract from Solanum capsicoides All. in spontaneously hypertensive rats

BackgroundSolanum capsicoides All. is morphologically similar to Solanum sisymbriifolium Lam. which is used in folk medicine in South America for antihypertensive and diuretics purposes. This similarity has led to species identification errors, which therefore may result in errors by patients. PurposeTo evaluate the antihypertensive and diuretics potential of the methanol extract from Solanum capsicoides All. (MeOH–Sc), in vitro and in vivo, in spontaneously hypertensive rats (SHR). MethodsInitial experiments were performed in rat mesenteric artery to evaluate the in vitro vascular effect of MeOH–Sc and its fractions, in addition to the mechanisms involved during the observed effect. Mean arterial pressure (MAP) and heart rate (HR) were recorded in non-anesthetised hypertensive and normotensive rats. In another set of experiments, MeOH–Sc was administered for 21 consecutive days. Daily body weight measurements were conducted and MAP, HR and urinary volume were measured every 5 days. The mesenteric artery from treated animals was tested for phenylephrine and sodium nitroprussiate (SNP) sensitivity. ResultsInitially, MeOH–Sc and fractions relaxed phenylephrine-induced contractions in mesenteric artery rings. The vasorelaxant effect was not changed in the presence of a blocker of eNOS (L-NAME) in rings with an intact endothelium. In denuded-endothelium rings, the vasorelaxant response was significantly reduced in the presence of a cAMP inhibitor (SQ 22536 10µM) in SHR but not in Wistar Kyoto rats (WKY). However, in the presence of a cGMP inhibitor (ODQ 10µM), a curve shift to the right was observed in WKY animals, but not in SHR. Intravenous bolus injections of MeOH–Sc into non-anesthetised SHR and WKY, induced hypotension that was associated with an increase in HR. A significant antihypertensive effect was observed in animals that received MeOH–Sc orally for 21 days, which also prevented the development of cardiac hypertrophy. Urine volume from animals treated with MeOH–Sc significantly increased. Finally, MeOH–Sc induced beneficial changes in vascular responsiveness. ConclusionMeOH–Sc has a potential antihypertensive effect in SHR.

Physico-chemical properties, antioxidant activities and antihypertensive effects of walnut protein and its hydrolysate.

Some food proteins hydrolysates are found to possess multiple health effects. In this study, walnut protein (WP) was enzymatically hydrolysed by alcalase and trypsin under optimal conditions. The physico-chemical properties, antioxidant and angiotensin-converting enzyme (ACE) inhibitory activities of WP, alcalase-generated walnut protein hydrolysate (AWPH) and trypsin-generated walnut protein hydrolysate (TWPH) were comparatively studied. Stability properties of the walnut protein hydrolysate (WPH) and the antihypertensive activity in spontaneously hypertensive rats (SHRs) were also investigated. The WPH showed higher physico-chemical properties, antioxidant activities, ACE inhibitory activity and stability against thermal treatment and gastrointestinal digestion than WP. The results of antihypertensive effects in SHRs showed that the most potent decrease of AWPH and TWPH in the systolic blood pressure occurred at 4 h (-26 mmHg) and 6 h (-30 mmHg) after administration. The study indicated that the WPH could significantly decrease the systolic blood pressure (P < 0.05). The WPH exhibited high physico-chemical properties, potent inhibitory activities and high stability. TWPH was more effective than AWPH in the detected properties. The results would be helpful for the comprehensive utilisation of the walnut resources. © 2015 Society of Chemical Industry.

A Novel ACE Inhibitory Peptide Ala-His-Leu-Leu Lowering Blood Pressure in Spontaneously Hypertensive Rats.

Ala-His-Leu-Leu (AHLL) was isolated and purified from the loach (Misgurnus anguillicaudatus) hydrolysate in our previous study. The aim of this study was to investigate the antihypertensive effects of angiotensin-I-converting enzyme (ACE) inhibitory peptide AHLL in spontaneously hypertensive rats (SHRs). AHLL showed good antihypertensive effects in SHRs during the long-term oral administration and no allergic reactions or coughing were observed. After 2 months of oral administration of AHLL, the body weight growth was normal. The decrements in systolic blood pressure of the high dose (5 mg/kg bw) and the low dose of AHLL (1 mg/kg bw) treatment groups were 22.1 and 5.0 mmHg at week 8, respectively. Compared to the control group, the concentrations of triglyceride and sodium in serum were reduced significantly in the high-dose group after 2 months. The ACE activity of kidney and lung decreased significantly, which indicated that AHLL exerted an antihypertensive effect on kidney and lung and they were the target sites of AHLL. These results strongly supported the in vivo antihypertensive mechanism of AHLL.

Antihypertensive Effect of a Combination of Uracil and Glycerol Derived from Lactobacillus plantarum Strain TWK10-Fermented Soy Milk.

We previously demonstrated that angiotensin-converting enzyme (ACE) could be inhibited by soy milk that had been fermented with the Lactobacillus plantarum strain TWK10, suggesting great potential for the development of antihypertensive products. In this work, the bioactive ACE inhibitors in TWK10-fermented soy milk water extracts were isolated, and a combination of uracil and glycerol (CUG) was identified as one of the ACE inhibitors. We then examined the physiological effects of CUG treatment in short-term and long-term studies using spontaneously hypertensive rats (SHRs) as an experimental model. The results revealed that the fermented soy milk extracts and CUG decreased blood pressure by 11.97 ± 3.71 to 19.54 ± 9.54 mmHg, 8 h after oral administration, and exhibited antihypertensive effects in SHRs in a long-term study. In addition, CUG was shown to decrease blood pressure by suppressing either the renin activity or the ACE activity and, thus, decreasing the downstream vasoconstricting peptide angiotensin II and the hormone aldosterone. CUG also promoted nitric oxide production, resulting in vasodilation and further improvement to hypertension. This important finding suggests that TWK10-fermented soy milk and its functional ingredients, uracil and glycerol, exhibit antihypertensive effects via multiple pathways and provide a healthier and more natural antihypertensive functional food.

Efficacy and Safety ofGwakhyangjeonggi-SanRetention Enema in Normal Rats and Spontaneously Hypertensive Rats

The purpose of this study is to establish a protocol of retention-enema experiments and evaluate the antihypertensive effect and the safety of Gwakhyangjeonggi-san retention enema. Normal and spontaneously hypertensive rats (SHRs) were divided into treatment and control groups, respectively. We applied the Gwakhyangjeonggi-san extract by decoction and 0.9% NaCl in each group, estimated the blood pressure and body weight, and performed HPLC analysis. ALT, AST, BUN, and creatinine were examined. The systolic blood pressure within each group in normal rats differed significantly in time effect, and so did the diastolic blood pressure in the treatment group of normal rats. The systolic, diastolic, and mean blood pressure showed significant differences in group effect in the treatment group of the SHRs. The time effect of the body weight in both groups of normal rats differed significantly, so did group × time and time effects in both groups of SHRs. AST, ALT, BUN, and creatinine showed no significant difference between groups. We concluded that the Gwakhyangjeonggi-san retention enema has a hypotensive effect in normal rats within the regular range of blood pressure, but an antihypertensive effect in SHRs. Also, the intervention is safe and does not affect the liver and kidney functions in normal rats.

Antihypertensive effect of formononetin through regulating the expressions of eNOS, 5-HT2A/1B receptors and α1-adrenoceptors in spontaneously rat arteries

One of the main pathological changes of hypertension is the dysfunction of blood vessels. We have found in our previous study that formononetin, one kind of phytoestrogens, has an acute antihypertensive effect. Therefore, we hypothesized that formononetin might produce a chronic antihypertensive effect through regulating the expressions of contractile receptors and endothelial nitric oxide synthase (eNOS) in artery. The present study was conducted to verify this effect. Male spontaneously hypertensive rats (SHRs) were divided into two groups, orally administrated formononetin (50mg/kg per day) and Tween 80 vehicle, respectively, for 8 weeks. The blood pressure was measured by tail-cuff method. Isometric tension of arterial rings was recorded by a myograph system. The mRNA and protein expression in arteries was determined with quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. Results showed that the systolic blood pressure of SHRs decreased significantly in formononetin group compared to Tween 80 group. The vasoconstriction induced by phenylephrine or 5-hydroxytryptamine (5-HT) in the mesenteric artery segments in formononetin group was decreased, and the relaxation induced by acetylcholine was increased compared with that in Tween 80 group. In the mesenteric arteries of the formononetin-treated SHRs, the expressions of α1-adrenoceptors and 5-HT2A/1B receptors at both mRNA and protein levels decreased, while the mRNA and protein expressions of eNOS increased. In conclusion, formononetin has a chronic antihypertensive effect in SHRs. The antihypertensive mechanism may be associated with the down-regulation of α1-adrenoceptors and 5-HT2A/1B receptors, and the up-regulation of eNOS expression in arteries.

Antihypertensive profile of 2-thienyl-3,4-methylenedioxybenzoylhydrazone is mediated by activation of the A2A adenosine receptor

Several N-acylhydrazone derivatives synthesized from safrole have been found to promote intense vasodilation and antihypertensive activity. The present work describes the synthesis and antihypertensive profile of 2-thienyl-3,4-methylenedioxybenzoylhydrazone (LASSBio-1027), a new analogue of the lead compound 3,4-methylenedioxybenzoyl-2-thienylhydrazone. Thoracic aortas from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were prepared for isometric tension recording. Noninvasive blood pressure measurements were made during 14 days of intraperitoneal (10 mg/kg) or oral (20 mg/kg) administration of LASSBio-1027. LASSBio-1027 exhibited partially endothelium-dependent vasorelaxant activity, which was attenuated in the presence of l-NAME, glibenclamide, or ZM 241385. LASSBio-1027 exhibited an antihypertensive effect in SHR during 14 days of intraperitoneal or oral administration, but did not induce a hypotensive effect in normotensive WKY rats. LASSBio-1027-induced vascular relaxation of aortas from WKY rats was mediated by the activation of A2A adenosine receptors. Docking studies and binding assays suggested that LASSBio-1027 has affinity for A2A and A3 adenosine receptors. This new N-acylhydrazone derivative represents a potential strategy for the treatment of arterial hypertension.

Acute effect of whey peptides upon blood pressure of hypertensive rats, and relationship with their angiotensin‐converting enzyme inhibitory activity

The aim of this study was to investigate the antihypertensive effect of a peptide fraction (PepC) obtained from a whey protein concentrate following hydrolysis by Cynara cardunculus, as well as of its fraction with MW below 3 kDa (PepCF). Both these concentrates encompassed peptides that exhibited potent in vitro inhibition of angiotensin-converting enzyme (ACE): two were released from α-lactalbumin--KGYGGVSLPEW and DKVGINYW, and one from β-lactoglobulin--DAQSAPLRVY. Upon oral administration, by gastric intubation, of 400 mg/kg body weight (bw) of those peptide concentrates, or 5 mg/kg bw of the corresponding synthetic peptides, to 12 wk-old spontaneously hypertensive rats (SHR), the systolic and diastolic blood pressures were monitored by the tail-cuff method--before, and 2, 4, 6, 8 and 24 h afterwards. Water and zofenopril (5 mg/kg bw)--a known ACE-inhibitor, were used as negative and positive controls, respectively. Acute administration of PepC, PepCF, KGYGGVSLPEW, DKVGINYW and DAQSAPLRVY caused antihypertensive effects in SHR; the maximum effect occurred by 4 h and 6 h after administration of the peptide concentrates and the synthetic peptides, respectively. PepC and KGYGGVSLPEW also showed ACE-inhibitory activity in vivo: the pressor effect of angiotensin I was significantly lower, and the response to bradykinin increased when the rats were pre-treated with either product. Our results strongly suggest that PepC will be effective as nutraceutical ingredient for the formulation of functional foods aimed at hypertension control.

The antihypertensive effect of ethyl acetate extract of radish leaves in spontaneously hypertensive rats.

Radish (Raphanus sativus L.) is a cruciferous vegetable, and its leaves have antioxidant and anticancer properties. This study was conducted to evaluate the effects of ethyl acetate extracts from radish leaves on hypertension in 11-week-old spontaneously hypertensive rats (SHRs). The SHRs were randomly divided into 3 groups of 6 rats each on the basis of initial systolic blood pressure (SBP) and were treated with oral administration of radish leaf extract (0, 30, or 90 mg/kg body weight [bw], respectively) for 5 weeks. Six Wistar rats were used as normotensive controls. The amount of the radish leaf extract had no effect on body weight. The SBP of the SHRs showed a decreasing trend with the consumption of the radish leaf extract. In the third week, the SBP of the group fed 90 mg extract/kg bw reduced from 214 mmHg to 166 mmHg and was significantly lower than that of the normotensive and hypertensive controls. The extract did not show a significant effect on the angiotensin-converting enzyme (ACE) activity in the serum, kidney, and lung. The extract increased the concentration of NO in serum and the activities of antioxidant enzymes such as glutathione peroxidase and catalase in red blood cells (RBCs). The serum concentrations of Na+ and K+ were not significantly different between all groups. However, the fecal concentrations of Na+ and K+ increased; the fecal concentrations of Na+ and K+ for the normotensive and hypertensive controls were not different. Urinary excretion of Na+ was higher in the normotensive Wistar rats than in the SHRs, while that of K+ was not significantly different. These findings indicate that consumption of radish leaves might have had antihypertensive effects in SHRs by increasing the serum concentration of NO and fecal concentration of Na+ and enhancing antioxidant activities.

Antihypertensive Mechanism of a Peptide‐Enriched Soy Sauce‐Like Seasoning: The Active Constituents and Its Suppressive Effect on Renin–Angiotensin–Aldosterone System

We previously reported that a peptide-enriched soy sauce-like seasoning called fermented soybean seasoning (FSS) demonstrated antihypertensive effects both in spontaneously hypertensive rats (SHR) and Dahl salt-sensitive rats. Angiotensin I-converting enzyme (ACE) inhibitory substances (9 kinds of dipeptides and a nicotianamine) were identified from FSS. In the present study, we clarified the mechanisms underlying the antihypertensive effects of FSS in SHR. FSS was divided into the nicotianamine fraction and the peptide fraction. The peptide fraction was found to exert a more prevalent antihypertensive effect than the nicotianamine fraction in SHR. Among the peptides, we identified Gly-Tyr and Ser-Tyr as the 2 primary substances in FSS that contributed to the antihypertensive effect in SHR. These peptides were neither degraded by acid nor gastrointestinal proteases, and were absorbed into the circulating blood. FSS (2000 mg/kg) exerted ACE inhibitory activity in the lung of rats and provided a decrease (P= 0.0067) in the level of serum aldosterone after a single oral administration in SHR, resulting in the antihypertensive effect. The antihypertensive mechanism was found to be similar to therapeutic ACE inhibitors and other food-derived ACE inhibitory peptides, which are in wide use and are recognized as safe.

Antihypertensive effect of a bovine lactoferrin pepsin hydrolysate: Identification of novel active peptides

The potential of bovine lactoferrin (LF) as a source of antihypertensive peptides has been examined. For this purpose, LF pepsin hydrolysate with molecular mass lower than 3kDa (LFH<3kDa) was prepared and orally administered to spontaneously hypertensive rats (SHR), resulting in reduced systolic blood pressure in a significant and maintained manner up to 24h after administration. LFH<3kDa was further fractionated by semi-preparative high performance liquid chromatography (HPLC) and 38 peptides, contained in the active fractions, were identified by using an ion trap mass spectrometer. Based on the peptide abundance, a total of 11 peptides were chemically synthesized and their ACE inhibitory activity tested. Only three of them, corresponding to peptides of sequences LIWKL, RPYL and LNNSRAP exerted in vitro inhibitory effects on angiotensin I converting enzyme (ACE) activity and had a 50% inhibitory concentration (IC50) of 0.47, 56.5 and 105.3μM, respectively. The three peptides also showed antihypertensive effects in SHR and remarkably the effect of LIWKL remained significant for up to 24h post-administration, similarly LFH<3kDa and the captopril control. The two most potent in vitro inhibitory peptides showed ex vivo inhibitory effect on ACE-dependent vasoconstriction as well. In conclusion, three novel LF-derived peptides and a pepsin LFH<3kDa lowered blood pressure and exhibit potential as orally effective antihypertensive compounds.

Novel antihypertensive hexa- and heptapeptides with ACE-inhibiting properties: From the in vitro ACE assay to the spontaneously hypertensive rat

Bioactive ACE inhibiting peptides are gaining interest in hypertension treatment. We have designed and screened six synthetic heptapeptides (PACEI48 to PACEI53) based on two hexapeptide leads (PACEI32 and PACEI34) to improve ACE inhibitory properties and assess their antihypertensive effects. ACE activity was assayed in vitro and ex vivo. Selected peptides were administered to spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats. In vitro cytotoxicity was assessed with the MTT reduction test. The six heptapeptides at low micromolar concentration produced different degrees of in vitro inhibition of ACE activity using the synthetic substrate HHL or the natural substrate angiotensin I; and ex vivo inhibition of ACE-dependent, angiotensin I-induced vasoconstriction, but not angiotensin II-induced vasoconstriction. Oral administration of the hexapeptide PACEI32L, and the heptapeptides PACEI50L and PACEI52L, induced reductions in systolic blood pressure lasting up to 3h in SHRs but not in WKY rats. Intravenous injection of PACEI32L and PACEI50L, but not PACEI52L, induced acute transient reductions in mean blood pressure of SHRs. d-Amino acid peptides showed five-fold less ACE inhibitory potency, no inhibitory effect on angiotensin I-induced vasoconstriction, and antihypertensive effect in SHRs after i.v. injection, but not after oral administration. The toxicity of peptides to reduce the viability of cultured cells was in the millimolar range. In conclusion, we have obtained novel rationally designed heptapeptides with improved ACE inhibitory properties when compared to lead hexapeptides. One selected hexapeptide and two heptapeptides show oral antihypertensive effects in SHRs and appear safe in cytotoxicity assays.

The antihypertensive effect of ethyl acetate extract from red raspberry fruit in hypertensive rats

Objectives:To evaluate the antihypertensive effect of Xinjiang red raspberry fruit ethyl acetate extract (EER) on spontaneously hypertensive rats (SHR) and its possible mechanism from antioxidant perspective.Materials and Methods:The SHR rats were randomly divided into 3 groups, and treated with EER low dose (EERL, 100 mg/kg/d), high dose (EERH, 200 mg/kg/d), and water (SHR) through gastric gavage daily for 5 weeks. Another 8 age-matched male Wistar–Kyoto rats were used as normotensive group (WKY). The systolic blood pressure (SBP) was measured by noninvasive tail-cuff method once a week. At the end of the treatment, blood samples were collected and serum concentrations of nitric oxide (NO), superoxide dismutase (SOD), malondialchehyche (MDA), and plasma endothelin (ET) were determined.Results:Treatment of SHR rats with EER lowered the blood pressure compared with that treated with water (SHR), and the high dose showed more significant reduction in blood pressure. Treatment of SHR rats with EER increased serum NO and SOD levels and lowered ET and MDA levels. As compared with control group, NO levels were increased significantly in EERL (P < 0.01), SOD was elevated more significantly in both EERL and EERH (P < 0.01); MDA was decreased significantly in EERH group (P < 0.05), whereas plasma ET decreased more significantly in the EERH group (P < 0.05).Conclusions:The red raspberry extracts demonstrated a dose-dependent antihypertensive effects in SHR and this may be related to increased NO activation and improved vascular endothelial dysfunction via antioxidation. These results confirmed that raspberries rich in polyphenols have potential cardiovascular protective effects.